@article{garcia_kim_vinod_sahoo_wax_kim_fang_narayanaswamy_wu_jiang_2024, title={Carbon nanofibers/liquid metal composites for high temperature laser ultrasound}, volume={138}, ISSN={["1874-9968"]}, url={https://doi.org/10.1016/j.ultras.2024.107245}, DOI={10.1016/j.ultras.2024.107245}, abstractNote={As the demand for clean energy becomes greater worldwide, there will also be an increasing demand for next generation nuclear power plants that incorporate advanced sensors and monitoring equipment. A major challenge posed by nuclear power plants is that, during normal operation, the reactor compartment is subjected to high operating temperatures and radiation flux. Diagnostic sensors monitoring such structures are also subject to temperatures reaching hundreds of degrees Celsius, which puts them at risk for heat degradation. In this work, the ability of carbon nanofibers to work in conjunction with a liquid metal as a photoacoustic transmitter was demonstrated at high temperatures. Fields metal, a Bi-In-Sn eutectic, and gallium are compared as acoustic mediums. Fields metal was shown experimentally to have superior performance over gallium and other reference cases. Under stimulation from a low fluence 6 ns pulse laser at 6 mJ/cm2 with 532 nm green light, the Fields metal transducer transmitted a 200 kHz longitudinal wave with amplitude >5.5 times that generated by a gallium transducer at 300 °C. Each high temperature test was conducted from a hot to cold progression, beginning as high as 300 °C, and then cooling down to 100 °C. Each test shows increasing signal amplitude of the liquid metal transducers as temperature decreases. Carbon nanofibers show a strong improvement over previously used candle-soot nanoparticles in both their ability to produce strong acoustic signals and absorb higher laser fluences up to 12 mJ/cm2.}, journal={ULTRASONICS}, author={Garcia, Nicholas and Kim, Howuk and Vinod, Kaushik and Sahoo, Abinash and Wax, Michael and Kim, Taeyang and Fang, Tiegang and Narayanaswamy, Venkat and Wu, Huaiyu and Jiang, Xiaoning}, year={2024}, month={Mar} }
 @article{wang_liu_feng_maes_fang_cui_yi_somers_yao_2024, title={Effects of oxygen enrichment on diesel spray flame soot formation in O<sub>2</sub>/Ar atmosphere}, volume={260}, ISSN={["1556-2921"]}, url={https://doi.org/10.1016/j.combustflame.2023.113244}, DOI={10.1016/j.combustflame.2023.113244}, abstractNote={In this study, diesel spray combustion at oxygen-enriched conditions (oxygen volume fraction of 21–70 %) with argon dilution is experimentally investigated in a constant-volume combustion chamber. Optical diagnostics are employed to study flame development, stabilization, and soot formation at oxygen-enriched conditions. To further verify the experimental observations, two-stage Lagrangian simulations are used to analyze the effects of oxygen on the formation and oxidation of soot precursors, polycyclic aromatic hydrocarbons. Results show that replacing nitrogen in air by argon leads to a 50 % reduction of the flame lift-off length, an increased soot flame temperature by 300 K, and higher soot concentrations. Flame morphology and structure still follow the classic conventional diesel combustion model in the oxygen range of 21–40 %, while changes are observed when oxygen levels are higher than 50 %. The width and length of the soot flame are shortened, and chemiluminescence from intermediate species like CO dominates the flame natural luminosity at the spray head, where the flame temperature reaches near 3000 K. Soot reduction mechanisms at high-degree oxygen-enrichment conditions are investigated. The intrinsic mixing-limited combustion of diesel sprays leads to unavoidable fuel-rich areas locally, but the shortened flame lift-off length and sufficient oxygen supply confines soot-forming conditions to a smaller, upstream region. The residence time of fuel parcels in this confined soot-forming area is shortened due to the larger local spray velocity. Thereafter, fuel parcels enter a high-temperature fuel-lean region, where the formed soot is oxidized rapidly.}, journal={COMBUSTION AND FLAME}, author={Wang, Yu and Liu, Haifeng and Feng, Lei and Maes, Noud and Fang, Tiegang and Cui, Yanqing and Yi, Wentao and Somers, Bart and Yao, Mingfa}, year={2024}, month={Feb} }
 @article{kiryaman_vinod_fang_denhartog_2024, title={Effects of yarn properties on aerosol filtration performance of single jersey fabrics}, volume={1}, ISSN={["1746-7748"]}, url={https://doi.org/10.1177/00405175231221297}, DOI={10.1177/00405175231221297}, abstractNote={ A pandemic caused by airborne pathogens raises a great need for N95 respirators and surgical masks. Subsequently, the risk of undersupply becomes a primary challenge requiring the prioritization of those masks for healthcare workers. Health agencies recommend wearing cloth masks in low-risk groups to reduce the demand. Unlike N95 respirators and surgical masks, cloth masks can be made from various fabrics, and their filtration performance becomes material-dependent. However, the existing literature presents limited and contradictory results on the property-performance relationship of fabrics used for cloth masks. Thus, the fundamental parameters determining the effectiveness of the fabrics remain unknown. Herein, we investigated the effects of yarn properties and multilayering on the filtration performance of single jersey fabrics. The fabrics performed up to 45% particle filtration efficiency, with the range of air permeability from 110–330 ft3/min/ft2. The results revealed that while the structural differences associated with the yarn choice had a smaller impact on the particle filtration efficiency of the fabrics compared to air permeability, their effects were great enough to yield statistically significant differences between the fabrics. In addition, our findings demonstrated that multilayering effectively improved the filtration performance of fabrics but resulted in a greater increase in airflow resistance than particle filtration efficiency. To limit the tradeoff between air permeability and particle filtration efficiency, yarn properties should be considered in the material selection of multilayer masks. We anticipate that our work will be a starting point for a guide on cloth masks with minimal filtration and breathability requirements. }, journal={TEXTILE RESEARCH JOURNAL}, author={Kiryaman, Didem and Vinod, Kaushik N. and Fang, Tiegang and Denhartog, Emiel}, year={2024}, month={Jan} }
 @article{vinod_gore_fang_2024, title={Experimental Combustion and Flame Characterization of a Chemical Looping-Based Oxidative Dehydrogenation Byproduct Fuel Mixture Containing High CO<sub>2</sub> Dilution}, volume={146}, ISSN={["1528-8994"]}, DOI={10.1115/1.4065402}, abstractNote={Abstract This study investigates the combustion performance of CO2 rich fuel mixtures containing ethane and methane as active species using a constant volume combustion chamber. This fuel is obtained as byproducts of a chemical looping based oxidative dehydrogenation (Cl-ODH) process ethylene production. The byproduct gas mixture has 40.79% CO2, 39.49% ethane, and 4.88% methane by weight with other minor compounds. After initial combustion modelling, the gas fuel mixture was reduced to just the major species: CO2, ethane, and methane. The mixture was then tested for flammability limits and combustion performance under spark-ignition conditions. Effects of ambient conditions and stoichiometry like temperatures between 300 to 400 K with initial pressures from 1 to 10 bar were tested. The fuel mixture showed an overall reduced flame velocity compared to gasoline. Instability in combustion was believed to be caused by the dissociation of ethane under elevated conditions. At higher pressures, the flame produces lower cumulative heat release. Simulations were also performed using a model tuned to replicate the operations of the combustion chamber used in the experiments. Heat release and unburnt fuel mass data were calculated to identify the discrepancies in the combustion completeness at elevated pressures. The effects of CO2 quenching the flame coupled with the increased dissociation of the fuel species can lead to up to more than 75% of the fuel mixture being unburnt. Data from this study was used to modify a small-scale spark-ignition engine to use this fuel and produce usable energy.}, number={8}, journal={JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Vinod, Kaushik Nonavinakere and Gore, Matt and Fang, Tiegang}, year={2024}, month={Aug} }
 @article{garcia_kim_vinod_kim_fang_jiang_2023, title={A Bi-In-Sn eutectic multi-layer high temperature ultrasound transmitter with candle-soot nanoparticles for improved photoacoustic efficiency}, volume={12487}, ISBN={["978-1-5106-6081-6"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2658480}, abstractNote={There is a growing need for non-invasive structural health monitoring in extreme environments. For nuclear power plants, pressure and temperature sensing under hazardous environment plays an important role for coolant system safety and stability management. Current sensing methods are intrusive, and suffer from degradation in the plant environment, limited life cycle, and complicated repair and replacement procedures. In this paper, we present an advanced Bi-In-Sn liquid metal (LM) transducer with the addition of candle-soot nanoparticles (CSNP) for improved photoacoustic efficiency and a metallic stencil for control of the liquid metal layer thickness. The sensitivity of the liquid metal candle-soot nanoparticle (LM-CSNP) ultrasound transmitter was characterized under 2 mJ/cm2 at 65 °C, and 6 mJ/cm2 at 100 °C —300 °C. Compared with existing LM transmitter, the newly presented transmitter showed a sensitivity 6.6 times stronger than previously reported LM only transmitter.}, journal={NONDESTRUCTIVE CHARACTERIZATION AND MONITORING OF ADVANCED MATERIALS, AEROSPACE, CIVIL INFRASTRUCTURE, AND TRANSPORTATION XVII}, author={Garcia, Nicholas and Kim, Ho-Wuk and Vinod, Kaushik and Kim, Taeyang and Fang, Tiegang and Jiang, Xiaoning}, year={2023} }
 @article{gore_vinod_fang_2023, title={Experimental Investigation of Gaseous Mixtures of Ethane, Methane, and Carbon Dioxide as an Alternative to Conventional Fuel in Spark Ignition Engines}, volume={145}, ISSN={["1528-8994"]}, DOI={10.1115/1.4055201}, abstractNote={Abstract}, number={3}, journal={JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Gore, Matthew and Vinod, Kaushik Nonavinakere and Fang, Tiegang}, year={2023}, month={Mar} }
 @article{vinod_gore_liu_fang_2023, title={Experimental characterization of ammonia, methane, and gasoline fuel mixtures in small scale spark ignited engines}, volume={16}, ISSN={["2666-352X"]}, url={https://doi.org/10.1016/j.jaecs.2023.100205}, DOI={10.1016/j.jaecs.2023.100205}, abstractNote={In this study, gaseous anhydrous ammonia is blended with fuels like gasoline and methane and tested in an instrumented, low-technology single cylinder carbureted engine. In-cylinder pressure and emissions are monitored with the various mixtures and their performance is then compared with pure gasoline. With the addition of ammonia, the stability of combustion inside the combustion chamber was affected. But with the addition of a combustion modifier, the overall variability was reduced. At higher substitutions of ammonia, Initial results show an increase in indicated thermal efficiency of the engine. There is also a substantial decrease in the heat release rate (HRR) of the engine when substituting gasoline with ammonia. With the addition of methane, the change in the fuel reactivity helped improve HRR. Increasing ammonia substitution also resulted in an increase in indicated efficiency when compared to pure gasoline by approximately 12% with 50% substitution of ammonia in gasoline. Adding ammonia to the fuel mixtures also showed an initial reduction in unburnt hydrocarbon emission, followed by a sudden increase with further increasing concentration, suggesting incomplete combustion of the fuel mixture. The addition of methane with gasoline also showed a reduction in overall NOx emissions. Furthermore, methane was also tested as the main fuel with ammonia substitution of up to 50%. This ammonia and methane blend also showed comparable results to the gasoline, ammonia, and methane blends tested. From the emissions data, the catalyzing effects of ammonia were also seen with some cases showing varying trends with increasing ammonia substitution. Results from this study can be used to design small-scale engine based power generation systems that need very little modifications to accept ammonia based mixed fuels. Furthermore, this study lays the groundwork for using fuels blends with methane sourced using carbon neutral technologies and ammonia to power engine based systems.}, journal={APPLICATIONS IN ENERGY AND COMBUSTION SCIENCE}, author={Vinod, Kaushik Nonavinakere and Gore, Matt and Liu, Hanzhang and Fang, Tiegang}, year={2023}, month={Dec} }
 @article{vinod_fang_2023, title={Experimental characterization of spark ignited ammonia combustion under elevated oxygen concentrations}, volume={39}, ISSN={["1873-2704"]}, url={https://doi.org/10.1016/j.proci.2022.08.007}, DOI={10.1016/j.proci.2022.08.007}, abstractNote={Due to its nature as a carbon free fuel and carrying hydrogen energy ammonia has received a lot of attention recently to be used as an alternative to fossil fuel in gas turbine and internal combustion engines. However, several barriers such as long ignition delay, slow flame speed, and low reactivity need to be overcome before its practical applications in engines. One potential approach to improve the ignition can be achieved by using oxygen enriched combustion. In this study, oxygen-enriched combustion of ammonia is tested in a constant volume combustion chamber to understand its combustion characteristics like flame velocity and heat release rates. With the help of high speed Schlieren imaging, an ammonia-oxygen flame is studied inside the combustion chamber. The influence of a wide range of oxygen concentrations from 15 to 40% are tested along with equivalence ratios ranging from 0.9 to 1.15. Ammonia when ignited at an oxygen concentration of 40% with an equivalence ratio of ϕ= 1.1 at 10 bar has a maximum flame velocity of 112.7 cm/s. Reduced oxygen concentration also negatively affects the flame velocity, introducing instabilities and causing the flame to develop asymmetrically due to buoyancy effects inside the combustion chamber. Heat release rate (HRR) curves show that increasing the oxygen concentration from 21 to 35% of the mixture can help reduce the ignition delays. Peak HRR data shows increased sensitivity to air fuel ratios with increased oxygen concentrations in the ambient gas. HRR also shows an overall positive dependence on the oxygen concentration in the ambient gas.}, number={4}, journal={PROCEEDINGS OF THE COMBUSTION INSTITUTE}, author={Vinod, Kaushik Nonavinakere and Fang, Tiegang}, year={2023}, pages={4319–4326} }
 @article{wang_ajayi_vinod_xu_fang_2023, title={Impact and wetting of polysilazane droplets on a metal surface}, volume={677}, ISSN={["1873-4359"]}, url={https://doi.org/10.1016/j.colsurfa.2023.132328}, DOI={10.1016/j.colsurfa.2023.132328}, abstractNote={Spray coating with liquid polymers is a crucial step in producing polymer-derived ceramic (PDC) coatings before curing the precursor. However, the interactions between polymer droplets and target surfaces during the spray coating process have not been adequately characterized in existing literature. This experimental study aims to comprehensively examine the previously unknown droplet impact dynamics for a specific ceramic precursor, Polysilazane, on Inconel surfaces. The diameter of Polysilazane droplets was kept constant, while their impact velocity was varied to achieve different impact conditions. The same parameter range was also explored with water, water-glycerol, and ethanol droplets for comparison purposes. High-speed videos were captured to observe the instantaneous impact process, while low-speed videos were recorded at specific instances to document the gradual wetting process at later stages. The investigation revealed unique spreading dynamics of Polysilazane droplets, including smooth contact angle variation during the transition from impact to lateral spreading, absence of delayed wetting, no formation of wavy structures on the droplet interface during spreading, and no retraction process within the studied conditions (Weber number up to 1200). Conversely, Polysilazane displayed similarities in the normalized spreading curves with other liquids. Additionally, the maximum spread factor of Polysilazane could be well predicted using existing universal scaling models designed for different liquid types. Lastly, Polysilazane exhibited a distinctive post-impact wetting process that persisted for an extended duration. The wetting dynamics of Polysilazane could be effectively described by an empirical exponential law originally developed for partial wetting systems.}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Wang, Fujun and Ajayi, Tosin and Vinod, Kaushik Nonavinakere and Xu, Chengying and Fang, Tiegang}, year={2023}, month={Nov} }
 @article{kim_balagopal_kerrigan_garcia_chow_bourham_fang_jiang_2023, title={Noninvasive liquid level sensing with laser generated ultrasonic waves}, volume={130}, ISSN={0041-624X}, url={http://dx.doi.org/10.1016/j.ultras.2023.106926}, DOI={10.1016/j.ultras.2023.106926}, abstractNote={This article proposes a noninvasive liquid level sensing technique using laser-generated ultrasound waves for nuclear power plant applications. Liquid level sensors play an important role of managing the coolant system safely and stably in the plant structure. Current sensing techniques are mostly intrusive, performing inside the fluidic structure, which is disadvantageous in terms of the regular maintenance of the plant system. Furthermore, typical intrusive sensors do not perform stably under varying environmental conditions such as temperature and radiation. In this study, sensing units are attached to the outer surface of a liquid vessel to capture guided ultrasound waves in a nonintrusive manner. The signal intensity of the guided wave dissipates when the signal interacts with the internal liquid media. The sensing mechanism is mathematically expressed as an index value to correlate the liquid level with the sensor signal. For the acoustic wave generation, laser-generated ultrasound was adopted instead of using typical contact type transducers. Following the simulation validation of the proposed concept, the performance of the developed sensor was confirmed through experimental results under elevated liquid temperature conditions. The nonlinear multivariable regression exhibited the best-fit to the datasets measured under the variable liquid level and temperature conditions.}, journal={Ultrasonics}, publisher={Elsevier BV}, author={Kim, Howuk and Balagopal, Bharat and Kerrigan, Sean and Garcia, Nicholas and Chow, Mo-Yuen and Bourham, Mohamed and Fang, Tiegang and Jiang, Xiaoning}, year={2023}, month={Apr}, pages={106926} }
 @article{cui_liu_wen_feng_ming_zheng_fang_xu_bai_yao_2022, title={Optical diagnostics of misfire in partially premixed combustion under low load conditions}, volume={329}, ISSN={["1873-7153"]}, DOI={10.1016/j.fuel.2022.125432}, abstractNote={• Fuel-tracer PLIF is used to quantify the equivalence ratio and temperature. • Misfire of PPC is due to synergistic effect of equivalent ratio and temperature. • In high direct injection pressure, the misfire is due to excessive premixing. • In late direct injection timing, the misfire is due to thermodynamic environment. • Misfire region most likely appears when the equivalence ratio is lower than 0.49. To clarify the misfire mechanism is important for stabilizing combustion in partially premixed combustion (PPC) under low load. Fuel-tracer planar laser-induced fluorescence (PLIF), formaldehyde PLIF, flame and OH* natural luminosity imaging were utilized to qualify the local equivalence ratio, low-temperature reaction and the high-temperature flame features in an optical engine. Results show that in high direct injection (DI) pressure (1000 bar), due to excessive premixing, the local equivalence ratio in the initial timing of the high temperature heat release (HTHR) is low. Although the auto-ignition flame kernels are formed in high DI pressure, they cannot stably develop, resulting in misfire during the flame development process. In late DI timing (-5 crank angle degree after top dead center, °CA ADTC), since the whole heat release process occurs in the expansion stroke, the in-cylinder temperature and pressure continue decreasing. Although the local equivalence ratio in some regions is high enough, the in-cylinder thermodynamic environment does not support the generation of more auto-ignition flame kernels, thus a small amount of auto-ignition flame kernels can only develop through flame propagation. In short, the misfire of PPC occurs in regions where the equivalence ratio is low or the in-cylinder thermodynamic environment does not further support flame development. Therefore, the trade-off relationship between equivalence ratio and temperature determines the formation of auto-ignition kernels. The local equivalence ratio and temperature distribution near the initial timing of HTHR is the key factor to ensure the subsequent stable combustion. Taking the ambient pressure of 18 bar as an example, the boundary condition where the autoignition kernels are most likely formed or the charge is most likely ignited by the nearby flame kernels is in the range of 0.53–0.62 for equivalence ratio and 740–757 K for temperature. The misfire region most likely appears when the equivalence ratio is lower than 0.49. It can be concluded that the misfire of PPC results from the synergistic effect of local equivalent ratio and temperature. The controlling parameters of injection pressure and injection timing are actually optimizing the suitable combinations of equivalence ratio and temperature to stabilize combustion.}, journal={FUEL}, author={Cui, Yanqing and Liu, Haifeng and Wen, Mingsheng and Feng, Lei and Ming, Zhenyang and Zheng, Zunqing and Fang, Tiegang and Xu, Leilei and Bai, Xue-Song and Yao, Mingfa}, year={2022}, month={Dec} }
 @article{kim_sriram_fang_kelley_park_2021, title={An eco-friendly approach for blending of fast-pyrolysis bio-oil in petroleum-derived fuel by controlling ash content of loblolly pine}, volume={179}, ISSN={["1879-0682"]}, DOI={10.1016/j.renene.2021.08.033}, abstractNote={This paper describes the effect of the ash content in biomass on the distribution of pyrolysis products and the miscibility of bio-oil in diesel. Ash content of loblolly pine wood (0.5 wt %, 1.1 wt %, and 1.5 wt %) was systematically varied by impregnating the wood with potassium carbonate solution. Variation in the ash content did not create a significant change in the chemical composition of the impregnated biomass. However, the response to a variety of thermal treatments changed significantly. The volatile matter content decreased from 88.3% to 78.2%, while the bio-oil yield declined from 45.7% to 29.9% as the ash content increased. Although the total organic yield decreased with increased biomass ash content, the total concentration of phenolic monomers increased from 2.8 mg/g to 20.2 mg/g, and bio-oil miscibility with a commercial diesel fuel increased from 6.7% to 13.4% based on wet bio-oil. The miscibility of guaiacol and 4-methyl guaiacol in diesel was higher than that of catechol, due to the lower polar and hydrogen bonding contribution. Test in a diesel engine showed a simultaneous reduction of HC and NOx emissions using diesel extracts.}, journal={RENEWABLE ENERGY}, author={Kim, Hoyong and Sriram, Subash and Fang, Tiegang and Kelley, Stephen and Park, Sunkyu}, year={2021}, month={Dec}, pages={2063–2070} }
 @article{wang_vinod_fang_2021, title={Compression ignition and spark assisted ignition of direct injected PRF65 spray}, volume={291}, ISSN={["1873-7153"]}, DOI={10.1016/j.fuel.2020.120123}, abstractNote={In this study the spark assisted compression ignition combustion (SACI) developments were investigated using PRF65 (low octane fuel), a mixture of 65% isooctane (by volume) and 35% n-heptane (by volume) with a RON of 65. Characteristics like the cumulative heat release (CHR) and the peak heat release rates (HRR) were studied pressure data from experiments conducted in a constant volume combustion chamber (CVCC) for more precise control of the tested conditions. Spray flame images were also studied using high speed imaging systems to understand the effect of the conditions tested in the luminosity of the flame. Experiments were performed to understand the effects of oxygen concentration and ambient temperatures. Results show that the heat release rate increases initially and then decreases with the increase in the ambient temperature and the peak heat release rate appears around 650 K to 700 K. The peak heat release rate timing is advanced with the increase of the ambient temperature or oxygen level. Flame luminosity was also found to increases with the increase in ambient temperature. Under a low ambient temperature, the oxygen level plays a major role in affecting the peak heat release rate. Under lower oxygen levels, the flame becomes darker, the ignition delay becomes longer, and the combustion process takes more time to complete. A well timed spark timing was found to advance the peak HRR and shorten ignition delay, but this effect becomes minor when the temperature increases.}, journal={FUEL}, author={Wang, Libing and Vinod, Kaushik Nonavinakere and Fang, Tiegang}, year={2021}, month={May} }
 @article{wang_gallardo_michielsen_fang_2021, title={Fundamental study of porcine drip bloodstains on fabrics: Blood droplet impact and wicking dynamics}, volume={318}, ISSN={["1872-6283"]}, DOI={10.1016/j.forsciint.2020.110614}, abstractNote={The underlying physics in bloodstain formation on fabrics is not well understood, despite its importance in bloodstain pattern analysis (BPA). This paper presents a fundamental study of the formation of drip bloodstains on fabrics, by focusing on blood droplet impact and wicking dynamics. The bloodstains were created on plain woven fabric by the perpendicular impact of a single blood drop with seven different impact velocities. The whole droplet impact and wicking processes were captured by multiple cameras. Fabric properties were characterized in detail at different levels. The bloodstain formation process was classified into distinct stages, including the inertial impact, initial absorption, first wicking and second wicking stages. The subsequent wicking process greatly alters the impact-induced bloodstains, in terms of bloodstain area. The dimensionless impact-induced stain factor (βi,e) is strongly dependent on the impact velocity while the final stain factor (βf,e) after the second wicking stage is not. The contribution of the subsequent wicking in altering the stain factor (or stain area) is quantified and found to decrease with increasing impact velocity. The blood wicking dynamics on the fabric in the majority of the first wicking stage can be well described by a simple scaling: (βe-βi,e)/βi,e=C[t-ti/ti]1/2, where ti marks the end of the inertial impact stage. The wicking coefficient C, which represents the influence of droplet impact on the subsequent droplet wicking, is found to scale as C∼We-0.34. In the end, brief comments are provided regarding (1) the influence of the evaporation on the blood drop post-impact wicking dynamics and (2) the shape of bloodstains formed on fabrics, with a few suggested research directions for future work.}, journal={FORENSIC SCIENCE INTERNATIONAL}, author={Wang, Fujun and Gallardo, Vanessa and Michielsen, Stephen and Fang, Tiegang}, year={2021}, month={Jan} }
 @article{kim_kim_garcia_fang_jiang_2021, title={Liquid metallic laser ultrasound transducer for high-temperature applications}, volume={118}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0046052}, DOI={10.1063/5.0046052}, abstractNote={This study aims to investigate a laser ultrasound (LUS) transducer for high-temperature (>100 °C) applications. For decades, many researchers have investigated efficient LUS transducers, yet studies on laser ultrasound transducers capable of performing at the high-temperature condition are rarely found in the literature. Most current LUS transducers still utilize a polymer-based composite material, that is, not stable at varying temperature conditions. This study introduces a liquid metallic (LM) LUS transducer that utilizes field's metal, which has a high thermal expansion (∼3 × 10−4 K−1). We hypothesized that such a high thermal expansion of the liquid metal can effectively produce laser-generated ultrasound waves, substituting for conventional polymer-based transducers. A numerical simulation predicted that the LM LUS transducer would produce higher LUS intensity (∼22 dB) than that without the LUS transducer. Experiment results confirmed that the LM transducer effectively intensifies the ultrasound wave signals, obtaining a signal-to-noise gain over 30 dB. Moreover, the transducer was found capable of transmitting detectable wave packets in relatively high-temperature conditions (∼400 °C), while conventional candle soot nanoparticle-polydimethylsiloxane could not perform stably at these elevated temperatures. The investigations introduced in this article are scientifically significant since we demonstrated the engineering feasibility of liquid metallic materials for LUS transducers.}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Kim, Howuk and Kim, Kyunghoon and Garcia, Nicholas and Fang, Tiegang and Jiang, Xiaoning}, year={2021}, month={May} }
 @article{wang_vinod_fang_2021, title={Spark effects on compression ignition of PRF95 direct injection spray in a constant volume combustion chamber}, volume={129}, ISSN={["1879-2286"]}, DOI={10.1016/j.expthermflusci.2021.110456}, abstractNote={In this study, spark assisted compression ignition (SACI) combustion was investigated using PRF95 (a low reactivity high octane reference fuel of common commercial gasoline), a mixture of 95% isooctane (by volume) and 5% n-heptane (by volume) with a RON of 95 and compared with pure compression-ignition without spark. Characteristics like the cumulative heat release (CHR) and the heat release rates (HRR) were studied using pressure data from experiments conducted in a constant volume combustion chamber (CVCC). The combustion process was visualized with a high speed imaging technique. Tests were conducted to understand the effects of ambient oxygen concentration and temperatures on the heat release and combustion flame developments while controlling other factors. From the experiments it is evident that the peak heat release rate increases initially and then decreases with the increase in the ambient temperature and the highest peak heat release rate appears around 650–700 K. The peak heat release rate timing decreases with the increase of the ambient temperature or oxygen level. Under a low ambient temperature, the oxygen level plays a major role in affecting the peak heat release rate. Under lower oxygen levels, the flame becomes weaker, the ignition delay becomes longer, and the combustion process takes more time to complete. Proper spark timing can help advance the peak HRR and shorten ignition delay, but this effect becomes minor when the ambient temperature increases. For the current high octane low reactivity fuel, auto-ignition can be achieved for all the investigated ambient temperature and oxygen levels. But it is noticed that a spark is necessary for low ambient oxygen and low ambient temperature to achieve proper combustion.}, journal={EXPERIMENTAL THERMAL AND FLUID SCIENCE}, author={Wang, Libing and Vinod, Kaushik Nonavinakere and Fang, Tiegang}, year={2021}, month={Nov} }
 @article{du_zang_mohan_idoughi_sim_fang_wonka_heidrich_roberts_2021, title={Study of spray structure from non-flash to flash boiling conditions with space-time tomography}, volume={38}, ISSN={["1873-2704"]}, url={https://doi.org/10.1016/j.proci.2020.06.171}, DOI={10.1016/j.proci.2020.06.171}, abstractNote={Flash boiling and plume interaction are common phenomena occurring in gasoline direct injection (GDI) spray at throttling and low load engine conditions. Combined with optical engines and low-pressure vessels, several optical techniques, such as backlight imaging, Mie-scattering, and laser sheet imaging have been employed to study the flash boiling morphology. However, in the 2D images resulting from these techniques (projection views or planar imaging), the 3D information is lost. Those methods are then incapable of providing satisfactory information, especially for the study of multi-plume interaction in flash boiling spray, since multi-plume interaction is not a 2D event. This paper reports the implementation of a 4D tomographic reconstruction method from multi-view diffused back illumination (DBI) images, used for the first time in spray characterization. This cost-effective and time-saving method with a simple experimental setup clarifies the 3D spray structure and fuel trajectory change from non-flashing conditions to flare flash conditions, and quantifies the 3D characteristics of individual plumes in non-flash conditions.}, number={2}, journal={PROCEEDINGS OF THE COMBUSTION INSTITUTE}, publisher={Elsevier BV}, author={Du, Jianguo and Zang, Guangming and Mohan, Balaji and Idoughi, Ramzi and Sim, Jaeheon and Fang, Tiegang and Wonka, Peter and Heidrich, Wolfgang and Roberts, William L.}, year={2021}, pages={3223–3231} }
 @article{du_mohan_sim_fang_roberts_2021, title={Study of spray structure under flash boiling conditions using 2phase-SLIPI}, volume={62}, ISSN={["1432-1114"]}, DOI={10.1007/s00348-020-03123-1}, abstractNote={In gasoline engines, including conventional gasoline direct injection (GDI) engines and newly developed gasoline compression ignition (GCI) engines, flash boiling of the spray occurs during throttling or low load operations. Superheated fuel that is injected into the cylinder, where the gas pressure is lower than the fuel’s saturation vapor pressure, experiences a fast phase change. Plume interaction and spray collapse can occur as a consequence of flash boiling. The structure of flashing spray has not been well elucidated experimentally because of strong multiple-scattering effects in conventional laser sheet imaging due to illumination of out-of-laser-plane droplets. Here, the structured laser illumination planar imaging (SLIPI) is implemented for the first time to study flash boiling sprays. Both front-view and side-view cross-sections are examined to reveal spray behaviors during collapsing events. A comparison of the reconstructed 3D spray volume by SLIPI and conventional laser sheet imaging clearly shows the advantage of SLIPI in resolving the inner structure of the collapsed spray. The near-nozzle region on the injector axis is found to be hollow, indicating that spray collapsing occurs a bit downstream of the nozzle instead of immediately at the nozzle. This observation could not be obtained by conventional laser sheet imaging nor by diffused back illumination (DBI) techniques. In this work, the central tip observed in the 2D DBI image at Rp = 0.1 case has been proven to be not a ’central jet on injector axis’ formed due to radial collapse, but a longer projection on the image caused by stronger adjacent plume circumferential interactions.}, number={1}, journal={EXPERIMENTS IN FLUIDS}, author={Du, Jianguo and Mohan, Balaji and Sim, Jaeheon and Fang, Tiegang and Roberts, William L.}, year={2021}, month={Jan} }
 @article{du_mohan_sim_fang_chang_roberts_2020, title={A comprehensive study of spray and combustion characteristics of a prototype injector for gasoline compression ignition (GCI) application}, volume={277}, ISSN={["1873-7153"]}, url={https://doi.org/10.1016/j.fuel.2020.118144}, DOI={10.1016/j.fuel.2020.118144}, abstractNote={In this study, the spray and combustion characteristics of high reactivity gasoline (HRG) fuel of RON 77 were tested and compared with E10 certification fuel under the gasoline compression ignition (GCI) engine conditions using a high-pressure multi-hole GCI engine injector. A comprehensive characterization in terms of the rate of injection, spray morphology under flash boiling conditions, penetration lengths under both nonevaporative and evaporative conditions, and ignition delay at reactive conditions was performed. It was found that both the high reactivity gasoline and E10 certification fuel exhibit very similar characteristics. The ignition delay times were found to be very similar between both the fuels tested under ambient temperatures higher than 800 K. This work further serves as an extensive database to validate and calibrate the spray models, combustion models and reaction mechanisms for computational fluid dynamics (CFD) driven development of GCI engines.}, journal={FUEL}, publisher={Elsevier BV}, author={Du, Jianguo and Mohan, Balaji and Sim, Jaeheon and Fang, Tiegang and Chang, Junseok and Roberts, William L.}, year={2020}, month={Oct} }
 @article{du_mohan_sim_fang_roberts_2020, title={Auto-ignition characteristics of high-reactivity gasoline fuel using a gasoline multi-hole injector}, volume={112}, ISSN={["1879-2286"]}, DOI={10.1016/j.expthermflusci.2019.109993}, abstractNote={Gasoline compression ignition (GCI) engines have proven to be a highly efficient engine technology with reduced emissions. The high efficiency and reduced emissions of GCI engines heavily rely on the stratification of the fuel being injected directly into the cylinder through multi-hole injectors. Therefore, it is critical to understand the fuel stratification and auto-ignition behaviors of the fuels used in GCI engines. Thus, in this work, the auto-ignition characteristics of high-reactivity and low carbon gasoline fuel (RON 77) were studied in an optically accessible constant volume chamber. A customized high-pressure gasoline multi-hole injector was used. Reactive tests were performed at two different ambient pressures (20 and 30 bar), three different ambient temperatures (800, 900, and 1000 K), three different oxygen concentrations (10, 15 and 21%) and three different injection pressures (100, 300 and 450 bar). The auto-ignition of fuel was achieved with varying ignition delay based on the experimental conditions tested. It was found that the operating conditions profoundly influences the diffusion and partially-premixed combustion mode. For high ambient pressures, temperatures, oxygen concentrations, injection pressure, and combinations, diffusion combustion mode was observed, and partially premixed combustion mode was observed at lower ambient pressures, temperatures, oxygen concentrations, injection pressures, and their combinations.}, journal={EXPERIMENTAL THERMAL AND FLUID SCIENCE}, author={Du, Jianguo and Mohan, Balaji and Sim, Jaeheon and Fang, Tiegang and Roberts, William L.}, year={2020}, month={Apr} }
 @article{du_mohan_sim_fang_chang_roberts_2020, title={INFLUENCE OF FLASH BOILING ON SPRAY MORPHOLOGY USING A PROTOTYPE INJECTOR FOR GASOLINE COMPRESSION IGNITION (GCI) APPLICATION}, volume={30}, ISSN={["1936-2684"]}, DOI={10.1615/AtomizSpr.2020034561}, abstractNote={Flash boiling occurs with gasoline direct injection spray at throttling, and low-load engine conditions leading to plume interactions and sprays collapse under low ambient densities. The change of fuel trajectory compared with the injector's initial design could leave an adverse effect on spray combustion quality, although flash boiling has the potential of achieving better atomization. Thus, studies on the plume to plume interactions and spray collapse processes are of high importance. Researches have mostly been carried out focusing on the plume interactions in the liquid phase, while in the flash boiling condition, the vapor phase of fuel is nonnegligible. This work focusses on the plume to plume interactions considering both the vapor and liquid phase of the fuel under specific throttling conditions in gasoline compression ignition (GCI) engines using a high-pressure wide spray angle prototype injector. The experiments were carried out at a wide range of pressure ratio (Rp) conditions (Rp = 0.05 to 1.4). Simultaneous front view and side view shadowgraph techniques were implemented to visualize the liquid & vapor phase of the fuel spray. Similarly, simultaneous front view Mie scattering and side view diffused backlit illumination (DBI) techniques were implemented to visualize the liquid phase of the fuel spray. Due to the line of sight plume overlapping at the side view, the difference in spray morphology obtained by DBI and shadowgraph is not apparent. However, the front view comparison shows that, in the transition regime, the plume to plume interactions in the vapor phase are more evident than that in the liquid phase. This work reveals that the front view techniques could be an excellent way to study multiplume interactions during flash boiling phenomena.}, number={5}, journal={ATOMIZATION AND SPRAYS}, author={Du, Jianguo and Mohan, Balaji and Sim, Jaeheon and Fang, Tiegang and Chang, Junseok and Roberts, William L.}, year={2020}, pages={351–369} }
 @article{fang_wang_2020, title={Momentum and heat transfer of a special case of the unsteady stagnation-point flow}, volume={41}, ISSN={["1573-2754"]}, DOI={10.1007/s10483-020-2556-9}, number={1}, journal={APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION}, author={Fang, T. G. and Wang, F. J.}, year={2020}, month={Jan}, pages={51–82} }
 @article{wang_fang_2020, title={Retraction dynamics of water droplets after impacting upon solid surfaces from hydrophilic to superhydrophobic}, volume={5}, ISSN={["2469-990X"]}, url={https://doi.org/10.1103/PhysRevFluids.5.033604}, DOI={10.1103/PhysRevFluids.5.033604}, abstractNote={The retraction dynamics of water droplets impacting on surfaces with different wettabilities is studied. Three modes of droplet retractions can be classified as inertial, capillary, and spherical-cap. A new model is proposed to predict the inertial-mode retraction rate of water droplets on different surfaces. The scaling of retraction curves is revised to reveal the similarity behavior of droplet retraction dynamics.}, number={3}, journal={PHYSICAL REVIEW FLUIDS}, author={Wang, Fujun and Fang, Tiegang}, year={2020}, month={Mar} }
 @article{wang_wu_badra_roberts_fang_2020, title={Soot characteristics of high-reactivity gasoline under compression-ignition conditions using a gasoline direct injection (GDI) piezoelectric fuel injector}, volume={265}, ISSN={["1873-7153"]}, DOI={10.1016/j.fuel.2019.116931}, abstractNote={Gasoline compression ignition (GCI) engine technology has become one of the promising alternative solutions to achieve better fuel economy and meet emission requirement. Higher reactivity gasoline-like fuels are more desirable in GCI engines. This study investigates the soot processes under autoignition combustion of high-reactivity gasoline (HRG) with an outwardly opening piezo gasoline direct injection (GDI) fuel injector. HRG fuels are mixtures of refinery streams with RON of 50–80 and they can potentially yield better fuel economy and emissions in GCI engines. Five ambient oxygen concentrations varying from 10% to 21% and three different ambient temperature combinations were selected to simulate various ambient environments. A two-color pyrometry was applied to measure flame temperature and soot concentration (i.e., KL factor). In general, HRG flame temperatures range from 1500 to 2400 K under selected conditions. HRG flames have relatively low KL factor for all selected experiment conditions. High KL factors are only observed at the flame periphery where flame temperatures are lower than 1800 K. Accumulated KL factor was calculated to evaluate overall soot amount. Flames at 800 K ambient temperature always have the highest accumulated KL factor. The soot and soot temperature trade-off were also discussed. The desired condition needs to approach a moderate soot temperature with a relative low integrated KL factor level. The conditions of 800 K with 15% O2, 1000 K with 10% O2 and 1000 K with 12% O2 shows better results. The findings can help facilitate the application of high reactivity gasoline fuels in next generation clean combustion engines.}, journal={FUEL}, author={Wang, Libing and Wu, Zengyang and Badra, Jihad A. and Roberts, William L. and Fang, Tiegang}, year={2020}, month={Apr} }
 @article{du_mohan_sim_fang_roberts_2020, title={Study of spray collapse phenomenon at flash boiling conditions using simultaneous front and side view imaging}, volume={147}, ISSN={["1879-2189"]}, DOI={10.1016/j.ijheatmasstransfer.2019.118824}, abstractNote={Flash boiling has become a topic of interest to researchers due to its potential of achieving good fuel atomization and negative influence on GDI engine emissions when spray collapses and spray-wall impingement exists. Under flash boiling conditions, the accompanying spray collapse phenomenon and plume interaction are not clearly elucidated. Simultaneous side view diffused back illumination (DBI) and front view Mie-scattering were implemented in this work to capture transient plume to plume interaction of iso-octane fuel spray from a 10 hole gasoline direct injection (GDI) injector at flash boiling conditions. Fuel temperature and ambient gas pressure were varied in a wide range to cover collapse, transitional and non-flashing regimes. Two new criteria named ‘spray collapse percentage’, defined based on the front view Mie-scattering technique and ‘optical thickness’ based on the side view DBI technique, were developed for classification of different spray regimes. These two criteria distinguish the collapsing and transitional regimes well from the non-collapsing regime compared to other criteria used in the literature.}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Du, Jianguo and Mohan, Balaji and Sim, Jaeheon and Fang, Tiegang and Roberts, William L.}, year={2020}, month={Feb} }
 @article{wang_wu_ahmed_badra_sarathy_roberts_fang_2019, title={Auto-ignition of direct injection spray of light naphtha, primary reference fuels, gasoline and gasoline surrogate}, volume={170}, ISSN={["1873-6785"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85059141893&partnerID=MN8TOARS}, DOI={10.1016/j.energy.2018.12.144}, abstractNote={In this work, the spray and auto-ignition characteristics of light naphtha (LN), primary reference fuels (PRF65, PRF95), Haltermann gasoline (CARB LEVIII, 10 vol% ethanol), and a gasoline surrogate were studied in an optically accessible constant volume combustion chamber. An outwardly opening hollow cone piezoelectric gasoline direct injection fuel injector was used. Five ambient temperatures from 650 to 950 K with a 75 K step were selected with a fixed ambient density of 3.5 kg/m3, similar to the Spray G density defined by the engine combustion network (ECN). Fuel auto-ignition was achieved with varying ignition delays for the five investigated fuels depending on the selected experimental conditions. Results show that the auto-ignition locations are randomly distributed in the combustion chamber. Differences in ignition delay times among the five fuels are more significant when the ambient temperature is lower than 750 K. When the ambient temperature is lower than 750 K, PRF95 always has the longest ignition delay and LN has the shortest. Ignition delays of the five fuels are almost identical when the ambient temperature exceeds 750 K. Meanwhile, the five fuels have a similar spray front penetration length and spray angles before the occurrence of auto-ignition under all the investigated conditions.}, journal={ENERGY}, author={Wang, Libing and Wu, Zengyang and Ahmed, Ahfaz and Badra, Jihad A. and Sarathy, S. Mani and Roberts, William L. and Fang, Tiegang}, year={2019}, month={Mar}, pages={375–390} }
 @article{wang_vinod_fang_2019, title={Effects of fuels on flash boiling spray from a GDI hollow cone piezoelectric injector}, volume={257}, ISSN={["1873-7153"]}, url={https://doi.org/10.1016/j.fuel.2019.116080}, DOI={10.1016/j.fuel.2019.116080}, abstractNote={Flash-boiling of fuel sprays can have a significant effect on spray formation and its characteristics due to bubble nucleation, growth, and phase change, producing explosive-like atomization and complex spray structures. In this work, experiments were conducted to study the spray of both pure substance fuels (pure isooctane, pure ethanol) and multicomponent fuels (50/50 mixture of isooctane and ethanol, commercial gasoline), under flash boiling conditions and non-flash boiling conditions. Under different temperature and ambient pressure, different superheated degrees can be achieved for the fuels. Pure substances have a single vapor pressure curve, while mixtures do not have a single boiling point at a given pressure, and a two-phase region exists for multicomponent fuel. Under the same conditions, ethanol has higher superheated degree compared to isooctane, but the heat of vaporization for ethanol is also much higher. This contributes to the fact that less boiling is observed in the ethanol spray with longer penetration in several cases. Mixture 50/50 shows a good average of isooctane and ethanol for spray penetration and spray front plume ratio analysis. Gasoline, due to its low initial boiling point and wide range of components, has the widest plume ratio distribution and smallest gradient, as well as complex peak penetration velocity distribution. The results also imply that adding low boiling point (preferably with low heat of vaporization as well) additive or component to high boiling point fuel can facilitate flash boiling, fuel vaporization and mixing.}, journal={FUEL}, publisher={Elsevier BV}, author={Wang, Libing and Vinod, Kaushik Nonavinakere and Fang, Tiegang}, year={2019}, month={Dec} }
 @article{du_mohan_sim_fang_roberts_2019, title={Experimental and analytical study on liquid and vapor penetration of high-reactivity gasoline using a high-pressure gasoline multi-hole injector}, volume={163}, ISSN={["1359-4311"]}, DOI={10.1016/j.applthermaleng.2019.114187}, abstractNote={Spray penetration length is an important parameter which is of great interest to both experimentalists and modelers. As it affects engine efficiency and emissions, measurement and prediction of spray penetration can significantly benefit engine optimization under various operating conditions. In this study, penetration length was investigated in a pre-burn constant volume combustion chamber using a gasoline multi-hole injector with high reactivity gasoline-like fuel designed explicitly for gasoline compression ignition (GCI) engines. Diffused back illumination (DBI) and shadowgraph were implemented for liquid and vapor phase penetration measurements, respectively. Different pre-burn gas mixtures are compared to investigate the influence of ambient gas properties on gasoline spray penetration under evaporating conditions. The liquid penetration under the gas composition of higher molecular weight tends to be longer. However, the vapor penetration showed insignificant effect under different gas compositions. Ambient gas temperature and gas composition were found to be an essential parameter for liquid phase penetration. Pressure difference was found to affect the vapor penetration length while its influence on liquid phase steady state penetration length at high ambient gas temperature is marginal. Statistical analysis was performed for both liquid and vapor phase penetration lengths, and a prediction model was developed with good agreement to the data under all test conditions.}, journal={APPLIED THERMAL ENGINEERING}, author={Du, Jianguo and Mohan, Balaji and Sim, Jaeheon and Fang, Tiegang and Roberts, William L.}, year={2019}, month={Dec} }
 @article{wang_wang_fang_2019, title={Flash boiling hollow cone spray from a GDI injector under different conditions}, volume={118}, ISSN={["1879-3533"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85066876915&partnerID=MN8TOARS}, DOI={10.1016/j.ijmultiphaseflow.2019.05.009}, abstractNote={Good spray atomization facilitates fuel evaporation in a gasoline engine, thus contributing to higher fuel efficiency and lower emissions. During certain operations of a gasoline direct injection (GDI) engine, the combination of increased fuel temperature and sub-atmospheric cylinder pressure during injection can lead to flash boiling condition, which promotes droplet breakup and evaporation. In this study, experiments were carried out to study the flash boiling and non-flash boiling spray of a hollow cone GDI piezoelectric injector. By the combination of different temperature and ambient pressure, different superheat degrees (Tf-Tb) and different ambient-to-saturation pressure ratios (Pa/Ps) can be achieved. For a hollow cone injector, the flash boiling spray can cause the cone shape spray to expand, both inwards and outwards. The axisymmetric inward expansion would converge together and form a fast developing plume shape, and the transition point for plume front to appear is around 0.5 for Pa/Ps ratio. When Pa/Ps is larger than 0.5, the spray development is dominated by the injection momentum and the effect of boiling is minor. When Pa/Ps is reduced to below 0.5, the flash boiling effect takes place and changed the spray dynamics. The peak penetration velocity starts increasing rapidly with the superheated degree only, and a good linear relationship exists between plume ratio and the log(Pa/Ps). The spray axial penetration result at a certain time frame shows three regimes: Pa/Ps > 0.5, 0.1 < Pa/Ps < 0.5 and Pa/Ps < 0.1. When Pa/Ps is less than 0.1, flare flash boiling happens and the original spray shape is hardly maintained due to the micro-explosion, meantime the spray axial penetration further increases at a reduced rate. While cases with similar Pa/Ps value can exhibit similar penetration character, cases with similar Tf-Tb value can show some difference.}, journal={INTERNATIONAL JOURNAL OF MULTIPHASE FLOW}, author={Wang, Libing and Wang, Fujun and Fang, Tiegang}, year={2019}, month={Sep}, pages={50–63} }
 @article{wang_lowrie_ngaile_fang_2019, title={High injection pressure diesel sprays from a piezoelectric fuel injector}, volume={152}, ISSN={["1359-4311"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85062213294&partnerID=MN8TOARS}, DOI={10.1016/j.applthermaleng.2019.02.095}, abstractNote={Increasing injection pressure can increase combustion efficiency in direct injection (DI) diesel engines attributing to enhanced atomization. In this paper, a high pressure experimental setup was built to generate ultra-high fuel pressure. An intensification unit was used to magnify the pressure by about 10 times. Preliminary testing of the high pressure system produced a peak pressure of about 8700 bar. Due to the pressure limitation of the commercially available diesel fuel system, the maximum pressure tested in a practical piezoelectric fuel injector was 2500 bar. A high-speed imaging technique was used to visualize the fuel injection events and spray images were taken by a high speed camera for quantitative analysis. A Schlieren technique was used to visualize the shock waves generated during spray penetration. The near nozzle early stage spray development was also studied using a long distance microscope and an intensified charge coupled device (ICCD) camera. Results show that the spray penetration velocity increases with the increase of the injection pressure, while a higher injection pressure leads to a later opening of the piezoelectric injector. The spray angle first has a large value, then remains relatively steady throughout the injection process. Schlieren results clearly demonstrate detached shock waves during the spray penetration. The near nozzle results show that during the very early stage the spray penetration is quite linear for different injection pressures and the spray angle also appears to be very large at the beginning, which is consistent with the high-speed imaging results. Both high-speed imaging and near nozzle results were compared with published empirical equations. The high-speed imaging result shows a good match with the linear stage of empirical equation, while near nozzle result shows lower penetration velocity, indicating that there exists a very short “acceleration stage” for spray development at the starting moment of fuel injection.}, journal={APPLIED THERMAL ENGINEERING}, author={Wang, Libing and Lowrie, James and Ngaile, Gracious and Fang, Tiegang}, year={2019}, month={Apr}, pages={807–824} }
 @article{du_mohan_sim_fang_roberts_2019, title={Macroscopic non-reacting spray characterization of gasoline compression ignition fuels in a constant volume chamber}, volume={255}, ISSN={["1873-7153"]}, url={https://doi.org/10.1016/j.fuel.2019.115818}, DOI={10.1016/j.fuel.2019.115818}, abstractNote={Recently, gasoline compression ignition (GCI) engines have become a topic of interest due to its benefits in high thermal efficiency and low emissions. Combustion in GCI engines is highly governed by the fuel stratification which is strongly associated with the spray characteristics like penetration length. Researchers have proposed both theoretical, and regression models for liquid penetration length of diesel and gasoline direct injection (GDI) spray at non-evaporating conditions. However, there are no models for gasoline sprays at elevated ambient gas temperatures, pressures, and injection pressures in literature. This research gap needs to be bridged, as it is crucial for GCI engine technology. In this study, penetration length was investigated using a high-pressure custom-made multi-hole gasoline injector. High reactivity low carbon fuel (RON 77), designed explicitly for GCI engines, and E10 certification fuel (RON 91) were used and compared. Diffused back illumination (DBI) and shadowgraph were implemented for liquid and vapor phase penetration measurement, respectively. It was found that the spray characteristics of high reactivity fuel were similar to E10 certification fuel under non-reacting conditions. Statistical analysis was performed for both liquid and vapor phase penetration lengths, and empirical models were developed with good agreements to the experimental data under high ambient gas pressure and temperature relevant to GCI engine operating conditions using GCI fuels at higher injection pressures. A ‘separation point’ was defined for the liquid phase after which it reaches a steady state, and it was demonstrated to be different from the ‘breakup time’ found in the literature.}, journal={FUEL}, publisher={Elsevier BV}, author={Du, Jianguo and Mohan, Balaji and Sim, Jaeheon and Fang, Tiegang and Roberts, William L.}, year={2019}, month={Nov} }
 @article{wang_yang_wang_zhu_fang_2019, title={Maximum Spread of Droplet Impacting onto Solid Surfaces with Different Wettabilities: Adopting a Rim-Lamella Shape}, volume={35}, ISSN={["0743-7463"]}, url={https://doi.org/10.1021/acs.langmuir.8b03748}, DOI={10.1021/acs.langmuir.8b03748}, abstractNote={Experimental and theoretical investigations are presented for the maximum spread factor (βm) of an impacting droplet onto solid surfaces with contact angle hysteresis. Experiments were conducted with deionized water on six surfaces with different wettabilities. The examined Weber number ( We) falls between 10-1 and 103. A new energetic model adopting a rim-lamella shape is proposed to better represent the droplet shape at the maximum spread. The dynamic contact angle at the maximum spread (θβm) is introduced in the model to account for the curvature of the surrounding rim induced by surface wettabilities. A lamella-rim thickness ratio κ ≈ AWe- B ( A, B > 0) is utilized successfully to depict the droplet shape at different We in a unifying manner. Comprehensive evaluations of the model demonstrate that the theoretical prediction can well recover the features of the experimental observations. The L2-error analysis demonstrates the improvement of the proposed model in predicting βm for a wide range of We = 10-1 to 103: the calculated errors are smaller than 8% for all six surfaces. Moreover, the proposed model can also be applied to predict energy conversion/dissipation during the droplet spreading process and the effects of surface wettability on βm in a reasonable manner. The variation of the percentage of the surface energy and viscous dissipation is consistent with that in previous simulations. The weakness of the current model for predicting βm at extremely low Weber number ( We < 1) is also explained.}, number={8}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Wang, Fujun and Yang, Lei and Wang, Libing and Zhu, Yong and Fang, Tiegang}, year={2019}, month={Feb}, pages={3204–3214} }
 @article{londhe_luo_park_kelley_fang_2019, title={Testing of anisole and methyl acetate as additives to diesel and biodiesel fuels in a compression ignition engine}, volume={246}, ISSN={["1873-7153"]}, url={https://doi.org/10.1016/j.fuel.2019.02.079}, DOI={10.1016/j.fuel.2019.02.079}, abstractNote={This paper investigates the effects of anisole and methyl acetate (as fuel additives) on the performance and emission characteristics of a compression-ignition (i.e., diesel) engine. Anisole and methyl acetate can be obtained from methylation of phenol and acetic acid, respectively. Phenol and acetic acid are compounds which are abundant in bio-oil derived from pyrolysis of wood and is thus renewable in nature. Using methyl acetate as a diesel fuel additive in compression-ignition engines has rarely been reported in the literature. The objective of the current work is to provide testing results of methyl acetate and perform comparisons with anisole as fuel additives for both diesel and biodiesel fuels. The effects of loads, additive type, and base fuels were tested. The tested loads include 0, 1.26, 2.52, and 3.78 bar brake mean effective pressure (BMEP) and the base fuels include No.2 diesel and biodiesel from waste cooking oil. The additive concentrations were kept at 10% by volume. Engine performance, exhaust emissions, and in-cylinder combustion were measured and analyzed. For diesel-anisole (DA) blends, it was seen that the blends were comparable to diesel in terms of performance but with slightly higher fuel consumption rates. HC and CO emissions reduced slightly, however, NOx and soot concentration increased. Diesel-methyl acetate (DM) blends were comparable to diesel in terms of performance with a slight increase in the fuel consumption rates. HC and CO emissions decreased with added methyl acetates. NOx and soot concentration increased. Both anisole and methyl acetate of 10% by volume in biodiesel were tested and it was observed that both blends were slightly better than pure biodiesel in terms of performance. HC and CO emissions reduced for both blends. NOx and soot concentration however increased as compared to pure biodiesel. From the experiments, it is believed that both anisole and methyl acetate can be used as suitable additives to diesel and biodiesel in terms of performance; however, the emissions of NOx and soot can pose a challenge.}, journal={FUEL}, publisher={Elsevier BV}, author={Londhe, Himanshu and Luo, Guanqun and Park, Sunkyu and Kelley, Stephen S. and Fang, Tiegang}, year={2019}, month={Jun}, pages={79–92} }
 @article{fang_wang_2019, title={Unsteady Liquid Film Flow with a Prescribed Free-Surface Velocity}, volume={36}, ISSN={["1741-3540"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85063432348&partnerID=MN8TOARS}, DOI={10.1088/0256-307X/36/1/014701}, abstractNote={A liquid film flow over a flat plate is investigated by prescribing the unsteady interface velocity. With this prescribed surface velocity, the governing Navier–Stokes (NS) equations are transformed into a similarity ordinary differential equation, which is solved numerically. The flow characteristics is controlled by an unsteadiness parameter S and the flow direction parameter Λ. The results show that solutions only exist for a certain range of the unsteadiness parameter, i.e., S ⩽ 1 for Λ = −1 and S ⩽ − 2.815877 for Λ = 1. In the solution domain, the dimensionless liquid film thickness β decreases with S for both the cases. The wall shear stress increases with the decrease of S for Λ = −1. However, for Λ = −1 the shear stress magnitude first decreases and then increases with the decrease of S. There are no zero crossing points for the velocity profiles for both the cases. The profiles of velocity stay either positive or negative all the time, except for the wall zero velocity. Consequently, the vertical velocity becomes a monotonic function. To maintain the prescribed velocity, mass transpiration is generally needed, but for the shrinking film case it is possible to have an impermeable wall. The results are also an exact solution to the full NS equations.}, number={1}, journal={CHINESE PHYSICS LETTERS}, author={Fang, Tiegang and Wang, Fujun}, year={2019}, month={Jan} }
 @article{fang_wang_gao_2019, title={Unsteady magnetohydrodynamic stagnation point flowclosed-form analytical solutions}, volume={40}, ISSN={["1573-2754"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85059591627&partnerID=MN8TOARS}, DOI={10.1007/s10483-019-2463-7}, number={4}, journal={APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION}, author={Fang, T. G. and Wang, F. J. and Gao, Bo}, year={2019}, month={Apr}, pages={449–464} }
 @inproceedings{wang_wang_roberts_fang_2018, title={Compression-ignition of gdi sprays in a constant volume combustion chamber}, volume={2018-March}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85049218975&partnerID=MN8TOARS}, booktitle={2018 Spring Technical Meeting of the Eastern States Section of the Combustion Institute, ESSCI 2018}, author={Wang, L. and Wang, F. and Roberts, W.L. and Fang, T.}, year={2018} }
 @article{chang_zhang_kim_huang_bagal_chang_fang_wu_jiang_2018, title={Evaluation of Photoacoustic Transduction Efficiency of Candle Soot Nanocomposite Transmitters}, volume={17}, ISSN={["1941-0085"]}, url={https://doi.org/10.1109/TNANO.2018.2845703}, DOI={10.1109/TNANO.2018.2845703}, abstractNote={Candle soot nanoparticles (CSNP) and polydimethyl-siloxane (PDMS) composite has shown the highly efficient photoacoustic transduction owing to their high light absorption coefficient and low interfacial thermal resistance. In this study, we report the effect of candle soot structure and thickness on the photoacoustic transduction efficiency. Optical properties of the CSNP/PDMS nanocomposites were characterized through both experimental measurements and finite difference time domain analysis in the visible wavelength range, indicating that the carbon volume fraction and thickness of CS/PDMS composite are highly relevant with light absorption. With a low laser energy input ( <inline-formula><tex-math notation="LaTeX">$< {\text{1 mJ/pulse}}$</tex-math></inline-formula>), the CS/PDMS composite with 2.15 <italic>μ</italic>m thickness exerts an output pressure of 3.78 MPa and a conversion efficiency of <inline-formula><tex-math notation="LaTeX">${\text{9.69}}\,\times \,{\text{10}}^{- 3}$</tex-math> </inline-formula>, which is two orders of magnitude higher than previously reported results.}, number={5}, journal={IEEE TRANSACTIONS ON NANOTECHNOLOGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Chang, Wei-Yi and Zhang, Xu A. and Kim, Jinwook and Huang, Wenbin and Bagal, Abhijeet and Chang, Chih-Hao and Fang, Tiegang and Wu, Hanchang Felix and Jiang, Xiaoning}, year={2018}, month={Sep}, pages={985–993} }
 @article{wu_wang_badra_roberts_fang_2018, title={GDI fuel sprays of light naphtha, PRF95 and gasoline using a piezoelectric injector under different ambient pressures}, volume={223}, ISSN={0016-2361}, url={http://dx.doi.org/10.1016/J.FUEL.2018.03.009}, DOI={10.1016/J.FUEL.2018.03.009}, abstractNote={This study investigates fuel sprays of light naphtha (LN), primary reference fuel (PRF) and gasoline under different ambient pressures with an outwardly opening piezo gasoline direct injection (GDI) fuel injector. The tested gasoline fuel (regular grade with up to 10% ethanol, E10) was obtained by mixing fuels with AKI (the average of the research octane number (RON) and the motor octane number (MON)) of 87 from three local gas stations. Primary reference fuel (PRF) is commonly used as gasoline surrogate fuel and is blended by iso-octane and n-heptane. PRF95 is the blend of 95% iso-octane and 5% n-heptane by volume. LN fuel was provided by Saudi Aramco Oil Company. Five different ambient pressure conditions varied from 1 bar to 10 bar were tested. The spray was visualized by applying a Mie-scattering technique and a high-speed camera was employed to capture the spray images. The spray structure, spray angle, spray penetration length and spray front fluctuation were analyzed and compared among three fuels. Spray images show that a clear filamentary hollow-cone spray structure is formed for all three fuels at atmospheric conditions, and toroidal recirculation vortexes are observed at the downstream spray edges. A higher ambient pressure leads to a stronger vortex located closer to the injector outlet. Generally speaking, larger spray angles are found under higher ambient pressure conditions for all three fuels. Gasoline fuel always has the largest spray angle for each ambient pressure, while PRF95 has the smallest at most time. For each fuel, the spray front penetration length and spray front penetration velocity decrease with increasing ambient pressure. LN, PRF95 and gasoline show similar penetration length and velocity under the tested conditions. A two-stage spray front fluctuation pattern is observed for all three fuels. Stage one begins from the start of the injection and ends at 450–500 μs after the start of the injection trigger (ASOIT) with a slow fluctuation increase for all ambient conditions. After Stage one, the spray front fluctuation increases rapidly to a certain level and then becomes stable in Stage two.}, journal={Fuel}, publisher={Elsevier BV}, author={Wu, Zengyang and Wang, Libing and Badra, Jihad A. and Roberts, William L. and Fang, Tiegang}, year={2018}, month={Jul}, pages={294–311} }
 @article{fang_wang_gao_2018, title={Liquid film flow over an unsteady moving surface with a new stretching velocity}, volume={30}, ISSN={["1089-7666"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85053521143&partnerID=MN8TOARS}, DOI={10.1063/1.5046479}, abstractNote={In this paper, the liquid film flow over an unsteady moving surface is investigated by considering a new surface moving velocity Uw = Ax/t. With this prescribed surface velocity, the governing Navier-Stokes (NS) equations are transformed into a similarity ordinary differential equation, which is solved numerically for both two-dimensional and axisymmetric flow configurations. The results are an exact solution to the full NS equations. The flow characteristics are controlled by a wall moving parameter, namely, A. It is found that solutions only exist for a certain range of the wall moving parameter, i.e., A ≥ −1/2 for the two dimensional case and A ≥ −1/4 for the axisymmetric case. The dimensionless liquid film thickness (β) first increases with the increase in A in the solution domain, and then, it reaches a peak of βm = 1.3864 at A = 0.90 for the two-dimensional case and βm = 1.5836 at A = 0.53 for the axisymmetric case. For both flow configurations, the liquid film thickness increases with time and there exists flow reversal for a positive value of A. These new solutions can not only provide an exact solution to the NS equations but also be used to explain the liquid film flow occurring in practical applications.}, number={9}, journal={PHYSICS OF FLUIDS}, author={Fang, Tiegang and Wang, Fujun and Gao, Bo}, year={2018}, month={Sep} }
 @article{wang_fang_2018, title={Post-impact drop vibration on a hydrophilic surface}, volume={98}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85049309226&partnerID=MN8TOARS}, DOI={10.1016/j.expthermflusci.2018.06.013}, abstractNote={Post-impact drop vibration on a hydrophilic surface has been studied experimentally in terms of the oscillation of spread and thickness factors. Water droplets were dropped from a piezoelectric droplet generator onto a smooth aluminum surface. Three different regimes featuring different oscillatory behaviors were classified based on Weber number. Quantitative characterization of the drop vibration was conducted for Regime I with We<30. Mobile contact line (MCL) and pinned contact line (PCL) vibrations were differentiated for the first time in analyzing the post-impact drop vibration. A time-frequency analysis shows that the transition from MCL vibration to PCL vibration features a tiny shift to a higher oscillation frequency. The normalized oscillation frequency can be well scaled by Ω∼We-1/2 as shown from the classical models. A new, empirical, unifying model was developed to account for the contact line movement in order to incorporate both MCL and PCL vibrations. The hysteresis-induced force at the three-phase contact line was found to alternate the equilibrium position of the vibrating drop with time, and thus making the oscillatory behavior nonlinear. It can be derived from the unifying model that the oscillation frequency should also scale as Ω∼We-1/2 and the damping factor should scale as ζ∼Re-1, which are validated by the presented experimental results. Finally, the good scaling of the damping factor indicates that the major damping mechanism, for both MCL and PCL vibrations, should originate from the viscous dissipation.}, journal={Experimental Thermal and Fluid Science}, author={Wang, F. and Fang, T.}, year={2018}, pages={420–428} }
 @inproceedings{wu_wang_badra_roberts_fang_2018, title={Soot characteristics of light naphtha in a constant volume combustion chamber using two-color pyrometry}, volume={2018-March}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85049233110&partnerID=MN8TOARS}, booktitle={2018 Spring Technical Meeting of the Eastern States Section of the Combustion Institute, ESSCI 2018}, author={Wu, Z. and Wang, L. and Badra, J.A. and Roberts, W.L. and Fang, T.}, year={2018} }
 @article{pantokratoras_fang_2018, title={THE FALKNER-SKAN FLOW WITH VARIABLE VISCOSITY AND NONLINEAR ROSSELAND THERMAL RADIATION}, volume={49}, ISSN={["2162-6561"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85045892222&partnerID=MN8TOARS}, DOI={10.1615/heattransres.2018019655}, number={6}, journal={HEAT TRANSFER RESEARCH}, author={Pantokratoras, Asterios and Fang, Tiegang}, year={2018}, pages={569–582} }
 @article{fang_wang_2018, title={Viscous Slip MHD Flow over a Moving Sheet with an Arbitrary Surface Velocity}, volume={35}, ISSN={["1741-3540"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85058153057&partnerID=MN8TOARS}, DOI={10.1088/0256-307X/35/10/104701}, abstractNote={The magnetohydrodynamic (MHD) flow induced by a stretching or shrinking sheet under slip conditions is studied.Analytical solutions based on the boundary layer assumption are obtained in a closed form and can be applied to a flow configuration with any arbitrary velocity distributions. Seven typical sheet velocity profiles are employed as illustrating examples. The solutions to the slip MHD flow are derived from the general solution and discussed in detail. Different from self-similar boundary layer flows, the flows studied in this work have solutions in explicit analytical forms. However, the current flows require special mass transfer at the wall, which is determined by the moving velocity of the sheet. The effects of the slip parameter, the mass transfer at the wall, and the magnetic field on the flow are also demonstrated.}, number={10}, journal={CHINESE PHYSICS LETTERS}, author={Fang, Tiegang and Wang, Fujun}, year={2018}, month={Oct} }
 @article{wang_badra_roberts_fang_2017, title={Characteristics of spray from a GDI fuel injector for naphtha and surrogate fuels}, volume={190}, ISSN={["1873-7153"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84996565995&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2016.11.015}, abstractNote={Characterization of the spray angle, penetration, and droplet size distribution is important to analyze the spray and atomization quality. In this paper, the spray structure development and atomization characterization of two naphtha fuels, namely light naphtha (LN) and whole naphtha (WN) and two reference fuel surrogates, i.e. toluene primary reference fuel (TPRF) and primary reference fuel (PRF) were investigated using a gasoline direct injection (GDI) fuel injector. The experimental setup included a fuel injection system, a high-speed imaging system, and a droplet size measurement system. Spray images were taken by using a high-speed camera for spray angle and penetration analysis. Sauter mean diameter, Dv(10), Dv(50), Dv(90), and particle size distribution were measured using a laser diffraction technique. Results show that the injection process is very consistent for different runs and the time averaged spray angles during the measuring period are 103.45°, 102.84°, 102.46° and 107.61° for LN, WN, TPRF and PRF, respectively. The spray front remains relatively flat during the early stage of the fuel injection process. The peak penetration velocities are 80 m/s, 75 m/s, 75 m/s and 79 m/s for LN, WN, TPRF and PRF, respectively. Then velocities decrease until the end of the injection and stay relatively stable. The transient particle size and the time-averaged particle size were also analyzed and discussed. The concentration weighted average value generally shows higher values than the arithmetic average results. The average data for WN is usually the second smallest except for Dv90, of which WN is the biggest. Generally the arithmetic average particle sizes of PRF are usually the smallest, and the sizes does not change much with the measuring locations. For droplet size distribution results, LN and WN show bimodal distributions for all the locations while TPRF and PRF shows both bimodal and single peak distribution patterns. The results imply that droplet size distribution is skewed to the larger side for locations close the axis and is skewed to the smaller side for distance away from the axis.}, journal={FUEL}, author={Wang, Libing and Badra, Jihad A. and Roberts, William L. and Fang, Tiegang}, year={2017}, month={Feb}, pages={113–128} }
 @article{jing_wu_roberts_fang_2017, title={Effects of Fuel Quantity on Soot Formation Process for Biomass-Based Renewable Diesel Fuel Combustion}, volume={139}, ISSN={["1528-8919"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85020430438&partnerID=MN8TOARS}, DOI={10.1115/1.4036292}, abstractNote={Soot formation process was investigated for biomass-based renewable diesel fuel, such as biomass to liquid (BTL), and conventional diesel combustion under varied fuel quantities injected into a constant volume combustion chamber. Soot measurement was implemented by two-color pyrometry under quiescent type diesel engine conditions (1000 K and 21% O2 concentration). Different fuel quantities, which correspond to different injection widths from 0.5 ms to 2 ms under constant injection pressure (1000 bar), were used to simulate different loads in engines. For a given fuel, soot temperature and KL factor show a different trend at initial stage for different fuel quantities, where a higher soot temperature can be found in a small fuel quantity case. but a higher KL factor is observed in a large fuel quantity case generally. Another difference occurs at the end of combustion due to the termination of fuel injection. Additionally, BTL flame has a lower soot temperature, especially under a larger fuel quantity (2 ms injection width). Meanwhile, average soot level is lower for BTL flame, especially under a lower fuel quantity (0.5 ms injection width). BTL shows an overall low sooting behavior with low soot temperature compared to diesel; however, trade-off between soot level and soot temperature needs to be carefully selected when different loads are used.}, number={10}, journal={JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME}, author={Jing, Wei and Wu, Zengyang and Roberts, William L. and Fang, Tiegang}, year={2017}, month={Oct} }
 @article{li_ogunkoya_fang_willoughby_rojas_2016, title={Carboxymethylated lignins with low surface tension toward low viscosity and highly stable emulsions of crude bitumen and refined oils}, volume={482}, ISSN={["1095-7103"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84979781362&partnerID=MN8TOARS}, DOI={10.1016/j.jcis.2016.07.063}, abstractNote={Kraft and organosolv lignins were subjected to carboxymethylation to produce fractions that were soluble in water, displayed a minimum surface tension as low as 34mN/m (25°C) and a critical aggregation concentration of ∼1.5wt%. The carboxymethylated lignins (CML), which were characterized in terms of their degree of substitution ((31)P NMR), elemental composition, and molecular weight (GPC), were found suitable in the formulation of emulsions with bitumens of ultra-high viscosity, such as those from the Canadian oil sands. Remarkably, the interfacial features of the CML enabled fuel emulsions that were synthesized in a very broad range of internal phase content (30-70%). Cryo-replica transmission electron microscopy, which was used here the first time to assess the morphology of the lignin-based emulsions, revealed the droplets of the emulsion stabilized with the modified lignin. The observed drop size (diameters<2μm) was confirmed by light scattering, which revealed a normal size distribution. Such characteristics led to stable emulsified systems that are amenable for a wide range of applications. Emulsification with CML afforded bitumen emulsions with very high colloidal stability (no change was noted for over one month) and with a strong shear thinning behavior. Both features indicate excellent prospects for storage, transport and spraying, which are relevant in operations for power generation, which also take advantage of the high heating value of the emulsion components. The ability of CML to stabilize emulsions and to contribute in their combustion was tested with light fuels (kerosene, diesel, and jet fuel) after formulation of high internal phase systems (70% oil) that enabled operation of a fuel engine. A significant finding is that under certain conditions and compared to the respective pure fuel, combustion of the O/W emulsions stabilized by CML presented lower NOx and CO emissions and maintained a relatively high combustion efficiency. The results highlight the possibilities in high volume application for lignin biomacromolecules.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Li, Shuai and Ogunkoya, Dolanimi and Fang, Tiegang and Willoughby, Julie and Rojas, Orlando J.}, year={2016}, month={Nov}, pages={27–38} }
 @inproceedings{jing_wu_roberts_fang_2016, title={Effects of fuel quantity on soot formation process for biomass-based renewable diesel fuel combustion}, DOI={10.1115/icef2016-9380}, abstractNote={Soot formation process was investigated for biomass-based renewable diesel fuel, such as biomass to liquid (BTL), and conventional diesel combustion under varied fuel quantities injected into a constant volume combustion chamber. Soot measurement was implemented by two-color pyrometry under quiescent type diesel engine conditions (1000 K and 21% O2 concentration). Different fuel quantities, which correspond to different injection widths from 0.5 ms to 2 ms under constant injection pressure (1000 bar), were used to simulate different loads in engines. For a given fuel, soot temperature and KL factor show a different trend at initial stage for different fuel quantities, where a higher soot temperature can be found in a small fuel quantity case but a higher KL factor is observed in a large fuel quantity case generally. Another difference occurs at the end of combustion due to the termination of fuel injection. Additionally, BTL flame has a lower soot temperature, especially under a larger fuel quantity (2 ms injection width). Meanwhile, average soot level is lower for BTL flame, especially under a lower fuel quantity (0.5 ms injection width). BTL shows an overall low sooting behavior with low soot temperature compared to diesel, however, trade-off between soot level and soot temperature needs to be carefully selected when different loads are used.}, booktitle={Proceedings of the ASME Internal Combustion Engine Division Fall Technical Conference (ICEF)}, author={Jing, W. and Wu, Z. Y. and Roberts, W. L. and Fang, Tiegang}, year={2016} }
 @inproceedings{jing_wu_roberts_fang_2016, title={Effects of fuel quantity on soot formation process for biomass-based renewable diesel fuel combustion}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85012013277&partnerID=MN8TOARS}, DOI={10.1115/ICEF20169380}, booktitle={ASME 2016 Internal Combustion Engine Fall Technical Conference, ICEF 2016}, author={Jing, W. and Wu, Z. and Roberts, W.L. and Fang, T.}, year={2016} }
 @article{wu_jing_zhang_roberts_fang_2016, title={Narrow band flame emission from dieseline and diesel spray combustion in a constant volume combustion chamber}, volume={185}, ISSN={["1873-7153"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84982090895&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2016.08.022}, abstractNote={In this paper, spray combustion of diesel (No. 2) and diesel-gasoline blend (dieseline: 80% diesel and 20% gasoline by volume) were investigated in an optically accessible constant volume combustion chamber. Effects of ambient conditions on flame emissions were studied. Ambient oxygen concentration was varied from 12% to 21% and three ambient temperatures were selected: 800 K, 1000 K and 1200 K. An intensified CCD camera coupled with bandpass filters was employed to capture the quasi-steady state flame emissions at 430 nm and 470 nm bands. Under non-sooting conditions, the narrow-band flame emissions at 430 nm and 470 nm can be used as indicators of CH∗ (methylidyne) and HCHO∗ (formaldehyde), respectively. The lift-off length was measured by imaging the OH∗ chemiluminescence at 310 nm. Flame emission structure and intensity distribution were compared between dieseline and diesel at wavelength bands. Flame emission images show that both narrow band emissions become shorter, thinner and stronger with higher oxygen concentration and higher ambient temperature for both fuels. Areas of weak intensity are observed at the flame periphery and the upstream for both fuels under all ambient conditions. Average flame emission intensity and area were calculated for 430 nm and 470 nm narrow-band emissions. At a lower ambient temperature the average intensity increases with increasing ambient oxygen concentration. However, at the 1200 K ambient temperature condition, the average intensity is not increasing monotonically for both fuels. For most of the conditions, diesel has a stronger average flame emission intensity than dieseline for the 430 nm band, and similar phenomena can be observed for the 470 nm band with 800 K and 1200 K ambient temperatures. However, for the 1000 K ambient temperature cases, dieseline has stronger average flame emission intensities than diesel for all oxygen concentrations at 470 nm band. Flame emissions for the two bands have a smaller average emission area under higher ambient oxygen concentration and temperature for both fuels, while dieseline has a slightly larger average flame emission area than diesel for most cases. The experimental findings were further analyzed and discussed based on an empirical model of the distributions of air and fuel. Both experiment results and theoretical model show that dieseline has wider 430 nm and 470 nm band emissions than diesel under all conditions.}, journal={FUEL}, author={Wu, Zengyang and Jing, Wei and Zhang, Weibo and Roberts, William L. and Fang, Tiegang}, year={2016}, month={Dec}, pages={829–846} }
 @article{bohon_fang_2016, title={Performance and emission testing of a bi-fuel outboard spark-ignition engine}, volume={17}, ISSN={["2041-3149"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84966648727&partnerID=MN8TOARS}, DOI={10.1177/1468087415597095}, abstractNote={ With the increasing concern about the future availability of gasoline and continuously stringent engine emission regulatory standards, the need for an alternative to gasoline as a primary engine fuel is becoming increasingly important. One proposed alternative is to use natural gas due to its availability, low cost, and generally reduced engine emissions. However, due to volumetric efficiency losses, the conversion of a standard spark-ignition engine originally operating on gasoline to run on natural gas has been shown to produce considerable power reductions. Additionally, improperly tuned natural gas conversion kits could potentially increase certain emissions’ quantities compared to gasoline. This work reports the results of an experiment designed to characterize the performance and emissions of a commonly used gasoline outboard boat motor converted to run on natural gas. Reported are the comparisons between gasoline and natural gas for the widely used engine operating parameters for gauging engine performance related to power output and harmful emissions, including oxides of nitrogen, unburned hydrocarbons, and carbon monoxide, for comparison of the two test fuels. The results indicate that operation on natural gas greatly reduces harmful hydrocarbon and carbon monoxide emissions at the cost of reduced engine power output and potentially increased oxides of nitrogen emissions. }, number={5}, journal={INTERNATIONAL JOURNAL OF ENGINE RESEARCH}, author={Bohon, Steven and Fang, Tiegang}, year={2016}, month={Jun}, pages={576–592} }
 @article{steinmetz_fang_roberts_2016, title={Soot particle size measurements in ethylene diffusion flames at elevated pressures}, volume={169}, ISSN={["1556-2921"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84964931690&partnerID=MN8TOARS}, DOI={10.1016/j.combustflame.2016.02.034}, abstractNote={Soot particle size is investigated in laminar nitrogen-diluted ethylene coflow diffusion flames at 4, 8, 12 and 16 atm. Line of sight attenuation and scattering are used to measure two-dimensional soot volume fraction and particle size fields for the first time at elevated pressures. Soot volume fraction dependence on pressure is consistent with the observations of similar studies, scaling approximately with the square of pressure. Scattering intensity is analyzed through Rayleigh and Rayleigh–Debye–Gans polydisperse fractal aggregate theories to provide two estimates of particle size. An increase in overall particle sizes with pressure is found, consistent with similar one-dimensional studies. Particle diameters in the annulus of the flame increase faster with pressure than those on centerline. Contrary to previous studies, the dependence of particle size on pressure was found to taper off between 8 and 12 atm, with little observed growth beyond 12 atm. The measurements provide additional data for one of the International Sooting Flame (ISF) workshop's target pressurized flames.}, journal={COMBUSTION AND FLAME}, author={Steinmetz, Scott A. and Fang, Tiegang and Roberts, William L.}, year={2016}, month={Jul}, pages={85–93} }
 @article{jing_wu_roberts_fang_2016, title={Spray combustion of biomass-based renewable diesel fuel using multiple injection strategy in a constant volume combustion chamber}, volume={181}, ISSN={["1873-7153"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84969269086&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2016.05.039}, abstractNote={Effect of a two-injection strategy associated with a pilot injection on the spray combustion process was investigated under conventional diesel combustion conditions (1000 K and 21% O2 concentration) for a biomass-based renewable diesel fuel, i.e., biomass to liquid (BTL), and a regular No. 2 diesel in a constant volume combustion chamber using multiband flame measurement and two-color pyrometry. The spray combustion flame structure was visualized by using multiband flame measurement to show features of soot formation, high temperature and low temperature reactions, which can be characterized by the narrow-band emissions of radicals or intermediate species such as OH, HCHO, and CH. The objective of this study was to identify the details of multiple injection combustion, including a pilot and a main injection, and to provide further insights on how the two injections interact. For comparison, three injection strategies were considered for both fuels including a two-injection strategy (Case TI), single injection strategy A (Case SA), and single injection strategy B (Case SB). Multiband flame results show a strong interaction, indicated by OH∗ emissions between the pilot injection and the main injection for Case TI while very weak connection is found for the narrow-band emissions acquired through filters with centerlines of 430 nm and 470 nm. A faster flame development is found for the main injection of Case TI compared to Cases SA and SB, which could be due to the high temperature environment and large air entrainment from the pilot injection. A lower soot level is observed for the BTL flame compared to the diesel flame for all three injection types. Case TI has a lower soot level compared to Cases SA and SB for the BTL fuel, while the diesel fuel maintains a similar soot level among all three injection strategies. Soot temperature of Case TI is lower for both fuels, especially for diesel. Based on these results, it is expected that the two-injection strategy could be effective in reducing soot and NOx (due to lower combustion temperature) simultaneously compared to either of the single injection strategies.}, journal={FUEL}, author={Jing, Wei and Wu, Zengyang and Roberts, William L. and Fang, Tiegang}, year={2016}, month={Oct}, pages={718–728} }
 @article{fang_he_2016, title={Steady Viscous Flow Between Two Porous Disks With Stretching Motion}, volume={138}, ISSN={["1528-901X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84939865333&partnerID=MN8TOARS}, DOI={10.1115/1.4030805}, abstractNote={In this work, an exact solution to the steady-state Navier–Stokes (NS) equations is presented for viscous flows between two stretchable disks with mass transpiration effects. The governing momentum equations were converted into an ordinary differential equation by a similarity transformation technique. The similarity equation was solved numerically and the effects of Reynolds number and the mass transpiration parameter were investigated. At very low Reynolds numbers (i.e., R → 0), a creeping flow was observed with a parabolic radial velocity profile and a cubic function profile for the vertical velocity. With the increase of the Reynolds number, the flow shows a boundary layer behavior near the wall with a constant velocity core flow in the centerline region between the two disks for mass suction or lower mass injection. The effects of the mass transpiration on the flow are quite different and interesting. With strong suction, the radial profiles also show boundary layer type characteristics with a core flow. But for large mass injection, the radial velocity approaches to a linear profile under higher Reynolds number. These results are a rare case of an exact solution to the NS equations and are useful as a benchmark problem for the validation of three-dimensional (3D) numerical computation code.}, number={1}, journal={JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME}, author={Fang, Tiegang and He, Xin}, year={2016}, month={Jan} }
 @article{wang_zhao_bagal_dandley_oldham_fang_parsons_chang_2016, title={Wicking Enhancement in Three-Dimensional Hierarchical Nanostructures}, volume={32}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84982307197&partnerID=MN8TOARS}, DOI={10.1021/acs.langmuir.6b01864}, abstractNote={Wicking, the absorption of liquid into narrow spaces without the assistance of external forces, has drawn much attention due to its potential applications in many engineering fields. Increasing surface roughness using micro/nanostructures can improve capillary action to enhance wicking. However, reducing the structure length scale can also result in significant viscous forces to impede wicking. In this work, we demonstrate enhanced wicking dynamics by using nanostructures with three-dimensional (3D) hierarchical features to increase the surface area while mitigating the obstruction of liquid flow. The proposed structures were engineered using a combination of interference lithography and hydrothermal synthesis of ZnO nanowires, where structures at two length scales were independently designed to control wicking behavior. The fabricated hierarchical 3D structures were tested for water and ethanol wicking properties, demonstrating improved wicking dynamics with intermediate nanowire lengths. The experimental data agree with the derived fluid model based on the balance of capillary and vicious forces. The hierarchical wicking structures can be potentially used in applications in water harvesting surfaces, microfluidics, and integrated heat exchangers.}, number={32}, journal={LANGMUIR}, author={Wang, Zhiting and Zhao, Junjie and Bagal, Abhijeet and Dandley, Erinn C. and Oldham, Christopher J. and Fang, Tiegang and Parsons, Gregory N. and Chang, Chih-Hao}, year={2016}, month={Aug}, pages={8029–8033} }
 @article{pantokratoras_fang_2015, title={A note on the paper 'Analytical approach to heat andmass transfer in MHD free convection from amoving permeable vertical surface' by A. Asgharian, DD Ganji, S. Soleimani, S. Asgharian, N. Sedaghatyzade and B. Mohammadi, Mathematical Methods in the Applied Sciences, 2011, 34 2209-2217}, volume={38}, ISSN={["1099-1476"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84959295249&partnerID=MN8TOARS}, DOI={10.1002/mma.3310}, abstractNote={The present note presents some errors in the aforementioned paper published in Mathematical Methods in the Applied Sciences. Two errors are found in the definition of the non‐dimensional parameters and correct results are presented for temperature profiles included in figure 10 of the previous paper. Copyright © 2014 John Wiley & Sons, Ltd.}, number={17}, journal={MATHEMATICAL METHODS IN THE APPLIED SCIENCES}, author={Pantokratoras, Asterios and Fang, Tiegang}, year={2015}, month={Nov}, pages={3706–3710} }
 @article{fang_he_2015, title={Boundary layer solutions to a point sink flow inside a cone with mass transpiration and moving wall}, volume={130}, ISSN={["2190-5444"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84923833145&partnerID=MN8TOARS}, DOI={10.1140/epjp/i2015-15021-9}, number={2}, journal={EUROPEAN PHYSICAL JOURNAL PLUS}, author={Fang, Tiegang and He, Xin}, year={2015}, month={Feb} }
 @article{zhang_jing_roberts_fang_2015, title={Effects of Ambient Oxygen Concentration on Soot Temperature and Concentration for Biodiesel and Diesel Spray Combustion}, volume={141}, ISSN={["1943-7897"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84929628830&partnerID=MN8TOARS}, DOI={10.1061/(asce)ey.1943-7897.0000214}, abstractNote={AbstractAmbient oxygen concentration, a key variable directly related to exhaust gas recirculation (EGR) levels in diesel engines, plays a significant role in particulate matter (PM) and nitrogen oxides (NOx) emissions. The utilization of biodiesel in diesel engines has been investigated over the last decades for its renewable characteristics and lower emissions compared to diesel. In an earlier work, we demonstrated that the soot temperature and concentration of biodiesel were lower than diesel under regular diesel engine conditions without EGR. Soot concentration was quantified by a parameter called KL factor. As a continuous effort, this paper presents an experimental investigation of the ambient oxygen concentration on soot temperature and KL factor during biodiesel and diesel spray combustion. The experiment was implemented in a constant volume chamber system, where the ambient oxygen concentration varied from 21 to 10% and the ambient temperature was kept to 1,000 K. A high speed two-color pyrometry...}, number={2}, journal={JOURNAL OF ENERGY ENGINEERING}, author={Zhang, Ji and Jing, Wei and Roberts, William L. and Fang, Tiegang}, year={2015}, month={Jun} }
 @article{ogunkoya_fang_2015, title={Engine performance, combustion, and emissions study of biomass to liquid fuel in a compression-ignition engine}, volume={95}, ISSN={["1879-2227"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84923774817&partnerID=MN8TOARS}, DOI={10.1016/j.enconman.2015.02.041}, abstractNote={In this work, the effects of diesel, biodiesel and biomass to liquid (BTL) fuels are investigated in a single-cylinder diesel engine at a fixed speed (2000 rpm) and three engine loads corresponding to 0 bar, 1.26 bar and 3.77 bar brake mean effective pressure (BMEP). The engine performance, in-cylinder combustion, and exhaust emissions were measured. Results show an increase in indicated work for BTL and biodiesel at 1.26 bar and 3.77 bar BMEP when compared to diesel but a decrease at 0 bar. Lower mechanical efficiency was observed for BTL and biodiesel at 1.26 bar BMEP but all three fuels had roughly the same mechanical efficiency at 3.77 bar BMEP. BTL was found to have the lowest brake specific fuel consumption (BSFC) and the highest brake thermal efficiency (BTE) among the three fuels tested. Combustion profiles for the three fuels were observed to vary depending on the engine load. Biodiesel was seen to have the shortest ignition delay among the three fuels regardless of engine loads. Diesel had the longest ignition delay at 0 bar and 3.77 bar BMEP but had the same ignition delay as BTL at 1.26 bar BMEP. At 1.26 bar and 3.77 bar BMEP, BTL had the lowest HC emissions but highest HC emissions at no load conditions when compared to biodiesel and diesel. When compared to diesel and biodiesel BTL had lower CO and CO2 emissions. At 0 bar and 1.26 bar BMEP, BTL had higher NOx emissions than diesel fuel but lower NOx than biodiesel at no load conditions. At the highest engine load tested, NOx emissions were observed to be highest for diesel fuel but lowest for BTL. At 1.26 bar BMEP, diesel had a higher smoke opacity than BTL and biodiesel. At 3.77 bar BMEP, BTL had the highest smoke opacity with diesel fuel having the lowest opacity. This work also demonstrated the effectiveness of BTL as a renewable alternative fuel with characteristics comparable to regular diesel fuel.}, journal={ENERGY CONVERSION AND MANAGEMENT}, author={Ogunkoya, Dolanimi and Fang, Tiegang}, year={2015}, month={May}, pages={342–351} }
 @article{ogunkoya_roberts_fang_thapaliya_2015, title={Investigation of the effects of renewable diesel fuels on engine performance, combustion, and emissions}, volume={140}, ISSN={["1873-7153"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84908577588&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2014.09.061}, abstractNote={A study was undertaken to investigate renewable fuels in a compression-ignition internal combustion engine. The focus of this study was the effect of newly developed renewable fuels on engine performance, combustion, and emissions. Eight fuels were investigated, and they include diesel, jet fuel, a traditional biodiesel (fatty acid methyl ester: FAME), and five next generation biofuels. These five fuels were derived using a two-step process: hydrolysis of the oil into fatty acids (if necessary) and then a thermo-catalytic process to remove the oxygen via a decarboxylation reaction. The fuels included a fed batch deoxygenation of canola derived fatty acids (DCFA), a fed batch deoxygenation of canola derived fatty acids with varying amounts of H2 used during the deoxygenation process (DCFAH), a continuous deoxygenation of canola derived fatty acids (CDCFA), fed batch deoxygenation of lauric acid (DLA), and a third reaction to isomerize the products of the deoxygenated canola derived fatty acid alkanes (IPCF). Diesel, jet fuel, and biodiesel (FAME) have been used as benchmarks for comparing with the newer renewable fuels. The results of the experiments show slightly lower mechanical efficiency but better brake specific fuel consumption for the new renewable fuels. Results from combustion show shorter ignition delays for most of the renewable (deoxygenated) fuels with the exception of fed batch deoxygenation of lauric acid. Combustion results also show lower peak in-cylinder pressures, reduced rate of increase in cylinder pressure, and lower heat release rates for the renewable fuels. Emission results show an increase in hydrocarbon emissions for renewable deoxygenated fuels, but a general decrease in all other emissions including NOx, greenhouse gases, and soot. Results also demonstrate that isomers of the alkanes resulting from the deoxygenation of the canola derived fatty acids could be a potential replacement to conventional fossil diesel and biodiesel based on the experiments in this work.}, journal={FUEL}, author={Ogunkoya, Dolanimi and Roberts, William L. and Fang, Tiegang and Thapaliya, Nirajan}, year={2015}, month={Jan}, pages={541–554} }
 @article{wang_fang_2015, title={Liquid jet breakup for non-circular orifices under low pressures}, volume={72}, ISSN={["1879-3533"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84924963032&partnerID=MN8TOARS}, DOI={10.1016/j.ijmultiphaseflow.2015.02.015}, abstractNote={This study uses a high-speed visualization technique to investigate the breakup process and flow behavior of low pressure water jets issued from non-circular orifices including square, triangular, and rectangular shapes. These orifices have approximately the same sectional areas. Stability curve and Ohnesorge chart are employed to make a comparison with circular jets discharged from a circular orifice of the same sectional area. The analysis is carried out for gauge pressures varying from 0.1 psi to 70 psi with small pressure steps corresponding to a range from 0.7 kPa to 482.6 kPa in metric units. Axis-switching phenomenon is observed and analyzed through calculating the axis-switching wavelength and oscillation frequency for rectangular jets. It is found that results for circular jets agreed well with classic theory. Non-circular jets demonstrate enhanced instabilities as a whole compared to circular jets. The different behaviors of non-circular jets are reasonably explained by Rayleigh’s oscillation theory. Axis-switching and aspect-ratio effect in rectangular jets is found to slow down the increase of breakup-length in the Rayleigh breakup regime. Square and triangular jets are more susceptible to wind effects and they are more unstable especially at higher pressure conditions. This can be concluded from the shorter breakup-length and narrower transitional region from the Rayleigh regime to the wind-induced regime as compared to the circular and rectangular jets. Axis-switching wavelength of the rectangular jets is found to increase linearly with increasing jet velocity and oscillation frequency decreases correspondingly.}, journal={INTERNATIONAL JOURNAL OF MULTIPHASE FLOW}, author={Wang, Fujun and Fang, Tiegang}, year={2015}, month={Jun}, pages={248–262} }
 @article{jing_wu_zhang_fang_2015, title={Measurements of soot temperature and KL factor for spray combustion of biomass derived renewable fuels}, volume={91}, ISSN={["1873-6785"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84946083894&partnerID=MN8TOARS}, DOI={10.1016/j.energy.2015.08.069}, abstractNote={Soot concentration (KL factor) and soot temperature were measured in a constant volume combustion chamber for a new biomass-based biofuel or BTL (biomass to liquid) fuel and regular No.2 diesel. A high-speed camera was employed coupled with two bandpass filters to implement a two-color thermometry method and measure the soot concentration and temperature simultaneously. Ambient conditions were set as follows: three temperatures of 800 K, 1000 K, and 1200 K and four O2 concentrations of 10%, 15%, 18% and 21%. The soot KL factor and temperature spatial distributions are presented for 1000 K ambient temperature. More soot is seen in the near-wall regions under the low ambient oxygen conditions while high level soot is observed in the upstream and midstream for the conventional combustion mode. An analysis was then conducted for the quasi-steady state. The results show that BTL combustion generates a lower integrated KL factor and soot temperature compared to diesel fuel under all the experimental conditions. Additionally, low ambient temperature with a moderate O2 concentration benefits BTL more than diesel due to a larger reduction in the integrated KL factor without increasing soot temperature significantly. Finally, the characteristics of the two-color results were further discussed and analyzed.}, journal={ENERGY}, author={Jing, Wei and Wu, Zengyang and Zhang, Weibo and Fang, Tiegang}, year={2015}, month={Nov}, pages={758–771} }
 @article{fang_2015, title={New unsteady boundary layers over a long thin cylinder}, volume={50}, ISSN={["1572-9648"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84947046791&partnerID=MN8TOARS}, DOI={10.1007/s11012-015-0177-1}, number={12}, journal={MECCANICA}, author={Fang, Tiegang}, year={2015}, month={Dec}, pages={2907–2918} }
 @article{ogunkoya_li_rojas_fang_2015, title={Performance, combustion, and emissions in a diesel engine operated with fuel-in-water emulsions based on lignin}, volume={154}, ISSN={["1872-9118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84930675094&partnerID=MN8TOARS}, DOI={10.1016/j.apenergy.2015.05.036}, abstractNote={We report for the first time on the use of water-continuous emulsions stabilized by a bio-based macromolecule in a compression-ignition diesel engine and compare their performance, combustion and emissions against the base fuels (diesel, biodiesel, and jet fuel). For this purpose, high internal phase ratio emulsions (70:30 fuel-to-water) were produced by mechanical emulsification using carboxymethylated wood lignin as stabilizer. Combusting experiments were performed with the engine operating at 2000 rpm under three loads (0, 1.26 and 3.26 bar brake mean effective pressure, BMEP). Engine performance, in-cylinder combustion, and exhaust emissions were monitored and compared for the fuels tested. At no load condition and when compared to the respective base (single phase) fuels, an increase in the indicated work was observed for diesel and biodiesel emulsions. Compared to the base fuels, the emulsions resulted in higher engine mechanical efficiency at 1.26 and 3.26 bar BMEP except for jet fuel emulsion at 1.26 bar. Additionally, they displayed a lower brake specific fuel consumption (BSFC), if calculated on the basis of effective fuel content discounting emulsion water, and higher brake thermal efficiency. Compared to the base fuel, the respective emulsions generally presented lower peak in-cylinder pressure, lower heat release rates, and longer ignition delays at 1.26 bar and 3.26 bar BMEP; the opposite effect was observed at no-load conditions. Remarkably, a large reduction of nitrogen oxides (NOx) emissions was noted in the combustion of the fuel emulsions, which was accompanied with a relatively higher carbon monoxide (CO) release at 1.26 and 3.26 bar (at 0 bar BMEP, the emulsions produced less CO emissions). The effect of emulsions on hydrocarbon emissions and smoke opacity depended on the fuel type and the engine load. Overall, it is concluded that while reports on fuel emulsions involve oil-continuous systems, the proposed water-continuous alternative represents an opportunity for diesel engines, whereby the fuel is dispersed as micrometric droplets for improved combustion and reduced emissions. At the same time, the fuel emulsion formulation takes advantage of the surface activity and high calorific value of widely available, inexpensive lignin stabilizers, making the proposed system a viable option towards cleaner or fully bio-based fuels.}, journal={APPLIED ENERGY}, author={Ogunkoya, Dolanimi and Li, Shuai and Rojas, Orlando J. and Fang, Tiegang}, year={2015}, month={Sep}, pages={851–861} }
 @article{sharma_fang_2015, title={Spray and atomization of a common rail fuel injector with non-circular orifices}, volume={153}, ISSN={["1873-7153"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84925622927&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2015.02.119}, abstractNote={This paper presents an experimental study on diesel sprays from non-circular orifices in ambient air. The non-circular geometry includes rectangular, square, and triangular shapes. The obtained spray characteristics were compared with those of a circular orifice. The injection pressures were varied from 300 bar (30 MPa) to 1000 bar (100 MPa). Macroscopic spray characteristics like spray cone angle and spray width were measured using a high speed camera. A laser diffraction technique was used to measure the droplet size, i.e. Sauter mean diameter, of the sprays at different axial locations. Spray behavior was measured from different orientations of the non-circular geometric shapes, including edges and corners. Spray widths measured along the spray length clearly demonstrated the presence of axis-switching phenomenon in high pressure diesel sprays obtained from non-circular orifices even at injection pressures as high as 1000 bar. They also exhibited larger widths and hence, larger surface areas, greater cone angles than sprays from a circular orifice. Thus, sprays from non-circular geometric shapes are expected to achieve better air entrainment and hence, mixing than the circular orifices. Droplet size obtained depended on the location of measurement and injection pressure and different behaviors were observed at different locations. It was noticed that non-circular orifices could induce greater instabilities in the diesel sprays thereby leading to faster atomization. As a result, an improvement in the spray characteristics can be achieved using non-circular geometries. Axis-switching phenomenon is expected to play an important role in improving the spray characteristics and the non-circular geometry may provide a cost effective approach for passively controlling the spray characteristics.}, journal={FUEL}, author={Sharma, Priyesh and Fang, Tiegang}, year={2015}, month={Aug}, pages={416–430} }
 @article{jing_roberts_fang_2015, title={Spray combustion of Jet-A and diesel fuels in a constant volume combustion chamber}, volume={89}, ISSN={["1879-2227"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84908374137&partnerID=MN8TOARS}, DOI={10.1016/j.enconman.2014.10.010}, abstractNote={This work investigates the spray combustion of Jet-A fuel in an optical constant-volume combustion chamber under different ambient initial conditions. Ambient temperature was varied at 800 K, 1000 K, and 1200 K and five different ambient O2 concentrations were used, spanning 10–21%. These ambient conditions can be used to mimic practical diesel engine working conditions under different fuel injection timings and exhaust gas recirculation (EGR) levels. Both transient and quasi-steady state analyses were conducted. The transient analysis focused on the flame development from the beginning to the end of the combustion process, illustrating how the flame structure evolves with time. The quasi-steady state analysis concentrated on the stable flame structure and compared the flame emissions in terms of spatially integrated intensity, flame effective area, and intensity per pixel. The transient analysis was based on measurements using high-speed imaging of both OH∗ chemiluminescence and broadband natural luminosity (NL). For the quasi-steady state analysis, three flame narrow-band emissions (OH∗ at 310 nm, Band A at 430 nm and Band B at 470 nm) were captured using an ICCD camera. Based on the current Jet-A data and diesel data obtained from previous experiments, a comparison between Jet-A and diesel was made in terms of flame development during the transient state and spatially integrated intensity, flame effective area, and intensity per pixel during the quasi-steady state. For the transient results, Jet-A shares a similar flame development trend to diesel, but featuring a narrower region of NL and a wider region of OH∗ with the increase of ambient temperature and O2 concentration. The soot cloud is oxidized more quickly for Jet-A than diesel at the end of combustion, evident by comparing the area of NL, especially under high O2 concentration. The quasi-steady state results suggest that soot is oxidized effectively under high O2 concentration conditions by the wider region of OH∗ in the downstream locations where only OH∗ emission is observed. The intensity of OH∗ is higher for Jet-A than diesel under low O2 concentration but lower under high O2 concentration. The intensity of NL is higher for Jet-A for all the conditions investigated. However, the intensities of Band A and Band B are lower for Jet-A for all these conditions. Based on the imaging of multiple-band flame emissions, the spray flame structures were further analyzed for the two fuels under both low temperature and conventional combustion modes. Conceptual flame structures were proposed to complement the previous conceptual models for spray combustion under different combustion modes.}, journal={ENERGY CONVERSION AND MANAGEMENT}, author={Jing, Wei and Roberts, William L. and Fang, Tiegang}, year={2015}, month={Jan}, pages={525–540} }
 @article{book_snow_long_fang_baldauf_2015, title={Temperature effects on particulate emissions from DPF-equipped diesel trucks operating on conventional and biodiesel fuels}, volume={65}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84942616652&partnerID=MN8TOARS}, DOI={10.1080/10962247.2014.984817}, abstractNote={Emissions tests were conducted on two medium heavy-duty diesel trucks equipped with a particulate filter (DPF), with one vehicle using a NOx absorber and the other a selective catalytic reduction (SCR) system for control of nitrogen oxides (NOx). Both vehicles were tested with two different fuels (ultra-low-sulfur diesel [ULSD] and biodiesel [B20]) and ambient temperatures (70ºF and 20ºF), while the truck with the NOx absorber was also operated at two loads (a heavy weight and a light weight). The test procedure included three driving cycles, a cold start with low transients (CSLT), the federal heavy-duty urban dynamometer driving schedule (UDDS), and a warm start with low transients (WSLT). Particulate matter (PM) emissions were measured second-by-second using an Aethalometer for black carbon (BC) concentrations and an engine exhaust particle sizer (EEPS) for particle count measurements between 5.6 and 560 nm. The DPF/NOx absorber vehicle experienced increased BC and particle number concentrations during cold starts under cold ambient conditions, with concentrations two to three times higher than under warm starts at higher ambient temperatures. The average particle count for the UDDS showed an opposite trend, with an approximately 27% decrease when ambient temperatures decreased from 70ºF to 20ºF. This vehicle experienced decreased emissions when going from ULSD to B20. The DPF/SCR vehicle tested had much lower emissions, with many of the BC and particle number measurements below detectable limits. However, both vehicles did experience elevated emissions caused by DPF regeneration. All regeneration events occurred during the UDDS cycle. Slight increases in emissions were measured during the WSLT cycles after the regeneration. However, the day after a regeneration occurred, both vehicles showed significant increases in particle number and BC for the CSLT drive cycle, with increases from 93 to 1380% for PM number emissions compared with tests following a day with no regeneration. Implications: The use of diesel particulate filters (DPFs) on trucks is becoming more common throughout the world. Understanding how DPFs affect air pollution emissions under varying operating conditions will be critical in implementing effective air quality standards. This study evaluated particulate matter (PM) and black carbon (BC) emissions with two DPF-equipped heavy-duty diesel trucks operating on conventional fuel and a biodiesel fuel blend at varying ambient temperatures, loads, and drive cycles.}, number={6}, journal={Journal of the Air and Waste Management Association}, author={Book, E.K. and Snow, R. and Long, T. and Fang, Tiegang and Baldauf, R.}, year={2015}, pages={751–758} }
 @article{pantokratoras_fang_2014, title={Blasius flow with non-linear Rosseland thermal radiation}, volume={49}, ISSN={["1572-9648"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84901607173&partnerID=MN8TOARS}, DOI={10.1007/s11012-014-9911-3}, number={6}, journal={MECCANICA}, author={Pantokratoras, Asterios and Fang, Tiegang}, year={2014}, month={Jun}, pages={1539–1545} }
 @article{sharma_fang_2014, title={Breakup of liquid jets from non-circular orifices}, volume={55}, ISSN={["1432-1114"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84892389249&partnerID=MN8TOARS}, DOI={10.1007/s00348-014-1666-z}, number={2}, journal={EXPERIMENTS IN FLUIDS}, author={Sharma, Priyesh and Fang, Tiegang}, year={2014}, month={Feb} }
 @article{jing_roberts_fang_2014, title={Comparison of soot formation for diesel and jet-a in a constant volume combustion chamber using two-color pyrometry}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84899540595&partnerID=MN8TOARS}, DOI={10.4271/2014-01-1251}, journal={SAE Technical Papers}, author={Jing, W. and Roberts, W. and Fang, T.}, year={2014} }
 @article{zhang_jing_roberts_fang_2014, title={Corrigendum to “Soot measurements for diesel and biodiesel spray combustion under high temperature highly diluted ambient conditions” [Fuel 135 (2014) 340–351]}, volume={137}, ISSN={0016-2361}, url={http://dx.doi.org/10.1016/J.FUEL.2014.08.052}, DOI={10.1016/J.FUEL.2014.08.052}, journal={Fuel}, publisher={Elsevier BV}, author={Zhang, Ji and Jing, Wei and Roberts, William L. and Fang, Tiegang}, year={2014}, month={Dec}, pages={413} }
 @article{kailasanathan_zhang_fang_roberts_2014, title={EFFECTS OF DILUENTS ON SOOT SURFACE TEMPERATURE AND VOLUME FRACTION IN DILUTED ETHYLENE DIFFUSION FLAMES AT PRESSURE}, volume={186}, ISSN={["1563-521X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84901250746&partnerID=MN8TOARS}, DOI={10.1080/00102202.2013.878710}, abstractNote={Soot surface temperature and volume fraction are measured in ethylene/air coflowing laminar diffusion flames at high pressures, diluted with one of four diluents (argon, helium, nitrogen, and carbon dioxide) using a two-color technique. Both temperature and soot measurements presented are line-of-sight averages. The results aid in understanding the kinetic and thermodynamic behavior of the soot formation and oxidation chemistry with changes in diluents, ultimately leading to possible methods of reducing soot emission from practical combustion hardware. The diluted fuel and coflow exit velocities (top-hat profiles) were matched at all pressures to minimize shear effects. In addition to the velocity-matched flow rates, the mass fluxes were held constant for all pressures. Addition of a diluent has a pronounced effect on both the soot surface temperature and volume fraction, with the helium diluted flame yielding the maximum and carbon dioxide diluted flame yielding minimum soot surface temperature and volume fraction. At low pressures, peak soot volume fraction exists at the tip of the flame, and with an increase in pressure, the location shifts lower to the wings of the flame. Due to the very high diffusivity of helium, significantly higher temperature and volume fraction are measured and explained. Carbon dioxide has the most dramatic soot suppression effect. By comparing the soot yield with previously measured soot precursor concentrations in the same flame, it is clear that the lower soot yield is a result of enhanced oxidation rates rather than a reduction in precursor formation.}, number={6}, journal={COMBUSTION SCIENCE AND TECHNOLOGY}, author={Kailasanathan, Ranjith Kumar Abhinavam and Zhang, Ji and Fang, Tiegang and Roberts, William L.}, year={2014}, pages={815–828} }
 @article{fang_2014, title={Flow and Mass Transfer for an Unsteady Stagnation-Point Flow Over a Moving Wall Considering Blowing Effects}, volume={136}, ISSN={["1528-901X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900014339&partnerID=MN8TOARS}, DOI={10.1115/1.4026665}, abstractNote={In this paper, the flow and mass transfer of a two-dimensional unsteady stagnation-point flow over a moving wall, considering the coupled blowing effect from mass transfer, is studied. Similarity equations are derived and solved in a closed form. The flow solution is an exact solution to the two-dimensional unsteady Navier–Stokes equations. An analytical solution of the boundary layer mass transfer equation is obtained together with the momentum solution. The examples demonstrate the significant impacts of the blowing effects on the flow and mass transfer characteristics. A higher blowing parameter results in a lower wall stress and thicker boundary layers with less mass transfer flux at the wall. The higher wall moving parameters produce higher mass transfer flux and blowing velocity. The Schmidt parameters generate a local maximum for the mass transfer flux and blowing velocity under given wall moving and blowing parameters.}, number={7}, journal={JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME}, author={Fang, Tiegang}, year={2014}, month={Jul} }
 @article{fang_jing_2014, title={Flow, heat, and species transfer over a stretching plate considering coupled Stefan blowing effects from species transfer}, volume={19}, ISSN={["1878-7274"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84897073047&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2014.02.009}, abstractNote={In this paper, we investigate the flow, heat and mass transfer of a viscous fluid flow over a stretching sheet by including the blowing effects of mass transfer under high flux conditions. Mass transfer in this work means species transfer and is different from mass transpiration for permeable walls. The new contribution from this work is, for the first time, to consider the coupled blowing effects from massive species transfer on flow, heat, and species transfer for a stretching plate. Based on the exact solutions of the momentum equations, which are valid for the whole Navier–Stokes equations, the energy and mass transfer equations are solved exactly and the effects of the blowing parameter, the Schmidt number, and the Prandtl number on the flow, heat and mass transfer are presented and discussed. The solution is given in terms of an incomplete Gamma function. It is found the coupled blowing effects due to mass transfer can have significant influences on velocity profiles, drag, heat flux, as well as temperature and concentration profiles. These solutions provide rare results with closed form analytical expressions and can be used as benchmark problem for numerical code validation.}, number={9}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Fang, Tiegang and Jing, Wei}, year={2014}, month={Sep}, pages={3086–3097} }
 @article{fang_2014, title={Magnetohydrodynamic viscous flow over a nonlinearly moving surface: Closed-form solutions}, volume={129}, ISSN={["2190-5444"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84907522318&partnerID=MN8TOARS}, DOI={10.1140/epjp/i2014-14092-4}, number={5}, journal={EUROPEAN PHYSICAL JOURNAL PLUS}, author={Fang, Tiegang}, year={2014}, month={May} }
 @article{archer_fang_ferguson_buckner_2014, title={Multi-Objective Design Optimization of a Variable Geometry Spray Fuel Injector}, volume={136}, ISSN={["1050-0472"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903773146&partnerID=MN8TOARS}, DOI={10.1115/1.4026263}, abstractNote={This paper explores the simulation-based design optimization of a variable geometry spray (VGS) fuel injector. A multi-objective genetic algorithm (MOGA) is interfaced with commercial computational fluid dynamics (CFD) software and high performance computing capabilities to evaluate the spray characteristics of each VGS candidate design. A three-point full factorial experimental design is conducted to identify significant design variables and to better understand possible variable interactions. The Pareto frontier of optimal designs reveals the inherent tradeoff between two performance objectives—actuator stroke and spray angle sensitivity. Analysis of these solutions provides insight into dependencies between design parameters and the performance objectives and is used to assess possible performance gains with respect to initial prototype configurations. These insights provide valuable design information for the continued development of this VGS technology.}, number={4}, journal={JOURNAL OF MECHANICAL DESIGN}, author={Archer, J. R. and Fang, Tiegang and Ferguson, Scott and Buckner, Gregory D.}, year={2014}, month={Apr} }
 @article{fang_el-mistikawy_2014, title={Self-similar flow due to the stretching of a deformable fiber}, volume={129}, ISSN={["2190-5444"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84919884593&partnerID=MN8TOARS}, DOI={10.1140/epjp/i2014-14252-6}, number={11}, journal={EUROPEAN PHYSICAL JOURNAL PLUS}, author={Fang, Tiegang and El-Mistikawy, Tarek M. A.}, year={2014}, month={Nov} }
 @article{zhang_jing_roberts_fang_2014, title={Soot measurements for diesel and biodiesel spray combustion under high temperature highly diluted ambient conditions}, volume={135}, ISSN={["1873-7153"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84904957615&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2014.06.071}, abstractNote={This paper presents the soot temperature and KL factor for biodiesel, namely fatty acid methyl ester (FAME) and diesel fuel combustion in a constant volume chamber using a two-color technique. The KL factor is a parameter for soot concentration, where K is an absorption coefficient and proportional to the number density of soot particles, L is the geometric thickness of the flame along the optical detection axis, and KL factor is proportional to soot volume fraction. The main objective is to explore a combustion regime called high-temperature and highly-diluted combustion (HTHDC) and compare it with the conventional and low-temperature combustion (LTC) modes. The three different combustion regimes are implemented under different ambient temperatures (800 K, 1000 K, and 1400 K) and ambient oxygen concentrations (10%, 15%, and 21%). Results are presented in terms of soot temperature and KL factor images, time-resolved pixel-averaged soot temperature, KL factor, and spatially integrated KL factor over the soot area. The time-averaged results for these three regimes are compared for both diesel and biodiesel fuels. Results show complex combined effects of the ambient temperature and oxygen concentration, and that two-color temperature for the HTHDC mode at the 10% oxygen level can actually be lower than the conventional mode. Increasing ambient oxygen and temperature increases soot temperature. Diesel fuel results in higher soot temperature than biodiesel for all three regimes. Results also show that diesel and biodiesel fuels have very different burning and sooting behavior under the three different combustion regimes. For diesel fuel, the HTHDC regime offers better results in terms of lower soot than the conventional and LTC regimes, and the 10% O2, 1400 K ambient condition shows the lowest soot concentration while maintaining a moderate two-color temperature. For biodiesel, the 15% O2, 800 K ambient condition shows some advantages in terms of reducing soot concentration. Based on these results, the practical implementation of this combustion mode is outlined and a feasible option is proposed.}, journal={FUEL}, author={Zhang, Ji and Jing, Wei and Roberts, William L. and Fang, Tiegang}, year={2014}, month={Nov}, pages={340–351} }
 @article{fang_jing_2013, title={Closed-form analytical solutions of flow and heat transfer for an unsteady rear stagnation-point flow}, volume={62}, ISSN={["0017-9310"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875443267&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2013.02.049}, abstractNote={In this paper, flow and heat transfer characteristics of an unsteady rear stagnation-point flow over a moving wall with transpiration are studied. The flow solution is an exact solution to the unsteady Navier–Stokes equations. By ignoring the viscous dissipation terms, analytical solutions of the boundary layer energy equation are obtained for the cases with a constant wall temperature and a prescribed time-dependent wall heat flux. The effects of the controlling parameters on the solution domain, the velocity distribution and the temperature distribution in the fluids are analyzed. With certain given values of the controlling parameters, two solution branches are found for both the flow and the heat transfer problems. These closed-form solutions are rare and can be used as a benchmark problem for numerical code validation.}, number={1}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Fang, Tiegang and Jing, Wei}, year={2013}, month={Jul}, pages={55–62} }
 @inproceedings{jing_roberts_fang_2013, title={Comparison of spray combustion for Jet-A and diesel in a constant volume chamber}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84946237266&partnerID=MN8TOARS}, booktitle={Fall Technical Meeting of the Eastern States Section of the Combustion Institute 2013}, author={Jing, W. and Roberts, W.L. and Fang, T.}, year={2013}, pages={477–482} }
 @article{kailasanathan_yelverton_fang_roberts_2013, title={Effect of diluents on soot precursor formation and temperature in ethylene laminar diffusion flames}, volume={160}, ISSN={["1556-2921"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872855275&partnerID=MN8TOARS}, DOI={10.1016/j.combustflame.2012.11.004}, abstractNote={Soot precursor species concentrations and flame temperature were measured in a diluted laminar co-flow jet diffusion flame at pressures up to eight atmospheres while varying diluent type. The objective of this study was to gain a better understanding of soot production and oxidation mechanisms, which could potentially lead to a reduction in soot emissions from practical combustion devices. Gaseous samples were extracted from the centerline of an ethylene–air laminar diffusion flame, which was diluted individually with four diluents (argon, helium, nitrogen, and carbon dioxide) to manipulate flame temperature and transport properties. The diluted fuel and co-flow exit velocities (top-hat profiles) were matched at all pressures to minimize shear-layer effects, and the mass fluxes were fixed over the pressure range to maintain constant Reynolds number. The flame temperature was measured using a fine gauge R-type thermocouple at pressures up to four atmospheres. Centerline concentration profiles of major non-fuel hydrocarbons collected via extractive sampling with a quartz microprobe and quantification using GC/MS + FID are reported within. The measured hydrocarbon species concentrations are vary dramatically with pressure and diluent, with the helium and carbon dioxide diluted flames yielding the largest and smallest concentrations of soot precursors, respectively. In the case of C2H2 and C6H6, two key soot precursors, helium diluted flames had concentrations more than three times higher compared with the carbon dioxide diluted flame. The peak flame temperature vary with diluents tested, as expected, with carbon dioxide diluted flame being the coolest, with a peak temperature of 1760 K at 1 atm, and the helium diluted flame being the hottest, with a peak temperature of 2140 K. At four atmospheres, the helium diluted flame increased to 2240 K, but the CO2 flame temperature increased more, decreasing the difference to approximately 250 K.}, number={3}, journal={COMBUSTION AND FLAME}, author={Kailasanathan, Ranjith Kumar Abhinavam and Yelverton, Tiffany L. B. and Fang, Tiegang and Roberts, William L.}, year={2013}, month={Mar}, pages={656–670} }
 @article{jing_roberts_fang_2013, title={Effects of Ambient Temperature and Oxygen Concentration on Diesel Spray Combustion Using a Single-Nozzle Injector in a Constant Volume Combustion Chamber}, volume={185}, ISSN={["0010-2202"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84882388541&partnerID=MN8TOARS}, DOI={10.1080/00102202.2013.798315}, abstractNote={This work investigates the effects of ambient conditions on diesel spray combustion in an optically accessible, constant volume chamber using a single-nozzle fuel injector. The ambient O2 concentration was varied between five discrete values from 10% to 21% and three different ambient temperatures (800 K, 1000 K, and 1200 K). These conditions simulate different exhaust gas recirculation (EGR) levels and ambient temperatures in diesel engines. Both conventional diesel combustion and low temperature combustion (LTC) modes were observed under these conditions. A transient analysis and a quasi-steady state analysis are employed in this article. The transient analysis focuses on the flame development from beginning to the end, illustrating how the flame structure changes during this process; the quasi-steady state analysis focuses on the stable flame structure. The transient analysis was conducted using high-speed imaging of both OH* chemiluminescence and natural luminosity (NL). In addition, three different images were acquired using an ICCD camera, corresponding to OH* chemiluminescence, narrow-band flame emission at 430 nm (Band A) and at 470 nm (Band B), and were used to investigate the quasi-steady state combustion process. From the transient analysis, it was found that the NL signal becomes stronger and confined to narrow regions when the temperature and O2 concentration increase during the development of flame. The OH* intensity is much lower for the 10% ambient O2 and 800 K conditions compared to the higher temperatures and O2 levels. This implies the occurrence of LTC under these conditions. Results from the quasi-steady combustion stage indicate that high-temperature reactions effectively oxidize the soot in the downstream locations where only OH* signal is observed. In addition, an area was calculated for each spectral region, and results show that the area of Band A and Band B emissions in these images is larger than the area of OH* emissions at the lower O2 concentrations while the area of OH* emission is larger than the area of Band A and Band B emissions at higher O2 concentrations, for a given ambient temperature. Moreover, the mixture stoichiometry was analyzed using a reformulated definition of excess air ratio for diluted combustion, and this shows that more mixing is required to achieve complete combustion for low ambient oxygen concentration conditions where longer and wider flames are observed. This observation is also verified by the flame length estimated from the NL images.}, number={9}, journal={COMBUSTION SCIENCE AND TECHNOLOGY}, author={Jing, Wei and Roberts, William L. and Fang, Tiegang}, year={2013}, month={Sep}, pages={1378–1399} }
 @article{zhang_jing_roberts_fang_2013, title={Effects of ambient oxygen concentration on biodiesel and diesel spray combustion under simulated engine conditions}, volume={57}, ISSN={["1873-6785"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84880702414&partnerID=MN8TOARS}, DOI={10.1016/j.energy.2013.05.063}, abstractNote={This study investigates the effect of ambient oxygen concentration on biodiesel and diesel spray combustion under simulated compression-ignition engine conditions in a constant-volume chamber. The apparent heat release rate (AHRR) is calculated based on the measured pressure. High-speed imaging of OH* chemiluminescence and natural luminosity (NL) is employed to visualize the combustion process. Temporally and spatially resolved NL and OH* contour plots are obtained. The result indicates that AHRR depends monotonically on the ambient oxygen concentration for both fuels. A lower oxygen concentration yields a slower AHRR increase rate, a lower peak AHRR value, but a higher AHRR value during the burn-out stage when compared with higher ambient oxygen concentration conditions. OH* chemiluminescence and NL contours indicate that biodiesel may experience a longer premixed-combustion duration. The 18% ambient O2 condition works better for biodiesel than diesel in reducing soot luminosity. With 12% O2, diesel combustion is significantly degraded. However, both fuels experience low temperature combustion at 10% O2. These results may imply that biodiesel is able to achieve the desired lower soot production under a moderate oxygen level with higher combustion efficiency, while diesel needs to be burned under very low ambient oxygen concentration for low soot production.}, journal={ENERGY}, author={Zhang, Ji and Jing, Wei and Roberts, William L. and Fang, Tiegang}, year={2013}, month={Aug}, pages={722–732} }
 @article{kailasanathan_book_fang_roberts_2013, title={Hydrocarbon species concentrations in nitrogen diluted ethylene-air laminar jet diffusion flames at elevated pressures}, volume={34}, ISSN={["1873-2704"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877712376&partnerID=MN8TOARS}, DOI={10.1016/j.proci.2012.06.148}, abstractNote={Hydrocarbon species concentrations are measured in a laminar jet diffusion flame at elevated pressures with the objective of better understanding soot production and oxidation mechanisms, which will ultimately lead to a reduction in soot emissions from practical combustion hardware. Samples were extracted from the centerline of an ethylene flame diluted with nitrogen. The diluted fuel and co-axial air top-hat exit velocities were matched and the mass fluxes were held constant at all pressures. This paper reports centerline concentration profiles of major non-fuel hydrocarbons and 5 different PAH species measured via extractive sampling with a quartz microprobe and quantification using GC/MS + FID. The peak concentration of acetylene decreased with increase in pressure, suggesting rapid conversion to heavier compounds, whereas the concentrations of the other major heavier non-fuel hydrocarbons increase with an increase in pressure. The measured peak species concentration as a function of pressure is seen to closely follow a power law function, Pn, where n varies from less than zero for acetylene, propane and diacetylene to greater than unity for the larger PAH species.}, number={1}, journal={PROCEEDINGS OF THE COMBUSTION INSTITUTE}, author={Kailasanathan, Ranjith Kumar Abhinavam and Book, Emily K. and Fang, Tiegang and Roberts, William L.}, year={2013}, pages={1035–1043} }
 @article{jing_fang_2013, title={Note on a New Blackbody Fraction Function Used for Surfaces With a Linear Emissivity in a Wavelength Interval}, volume={135}, ISSN={["1528-8943"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877622228&partnerID=MN8TOARS}, DOI={10.1115/1.4023393}, abstractNote={In this note, a new blackbody radiation fraction function is proposed for calculating the emissive power or total emissivity of a surface that has an emissivity depending linearly on wavelength in a wavelength interval. This new fraction function is expressed as a function of the product of wavelength and temperature and the numerical values are tabulated. Based on the new defined fraction function, the emissive power in a given wavelength interval can be calculated very conveniently combined with the traditional blackbody radiation fraction function. This new function can be used in many practical applications with good accuracy without numerical integration.}, number={5}, journal={JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME}, author={Jing, Wei and Fang, Tiegang}, year={2013}, month={May} }
 @article{pantokratoras_fang_2013, title={Sakiadis flow with nonlinear Rosseland thermal radiation}, volume={87}, ISSN={["1402-4896"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872068683&partnerID=MN8TOARS}, DOI={10.1088/0031-8949/87/01/015703}, abstractNote={In a recent paper by Cortell (2008 Chin. Phys. Lett. 25 1340–2) the effect of radiation on the classical Sakiadis flow along a moving plate in a calm fluid was considered. The results in that paper have been produced using a linearized Rosseland approximation, which is valid only for small temperature differences between the plate and the ambient fluid. In the present work, we extend the above work to a nonlinear Rosseland approximation, which is valid for both small and large temperature differences.}, number={1}, journal={PHYSICA SCRIPTA}, author={Pantokratoras, Asterios and Fang, Tiegang}, year={2013}, month={Jan} }
 @inproceedings{steinmetz_fang_roberts_2013, title={Soot measurements in diluted high pressure laminar ethylene co-flow flames}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84905457491&partnerID=MN8TOARS}, booktitle={Proceedings of the 9th Asia-Pacific Conference on Combustion, ASPACC 2013}, author={Steinmetz, S.A. and Fang, T.G. and Roberts, W.L.}, year={2013} }
 @inproceedings{steinmetz_fang_roberts_2013, title={Soot measurements in high-pressure laminar diffusion flames}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84946216954&partnerID=MN8TOARS}, booktitle={Fall Technical Meeting of the Eastern States Section of the Combustion Institute 2013}, author={Steinmetz, S.A. and Fang, T. and Roberts, W.L.}, year={2013}, pages={318–323} }
 @article{zhang_jing_roberts_fang_2013, title={Soot temperature and KL factor for biodiesel and diesel spray combustion in a constant volume combustion chamber}, volume={107}, ISSN={["1872-9118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875117595&partnerID=MN8TOARS}, DOI={10.1016/j.apenergy.2013.02.023}, abstractNote={This paper presents measurements of the soot temperature and KL factor for biodiesel and diesel combustion in a constant volume chamber using a two-color technique. This technique uses a high-speed camera coupled with two narrowband filters (550 nm and 650 nm, 10 nm FWHM). After calibration, statistical analysis shows that the uncertainty of the two-color temperature is less than 5%, while it is about 50% for the KL factor. This technique is then applied to the spray combustion of biodiesel and diesel fuels under an ambient oxygen concentration of 21% and ambient temperatures of 800, 1000 and 1200 K. The heat release result shows higher energy utilization efficiency for biodiesel compared to diesel under all conditions; meanwhile, diesel shows a higher pressure increase due to its higher heating value. Biodiesel yields a lower temperature inside the flame area, a longer soot lift-off length, and a smaller soot area compared to diesel. Both the KL factor and the total soot with biodiesel are lower than with diesel throughout the entire combustion process, and this difference becomes larger as the ambient temperature decreases. Biodiesel shows approximately 50–100 K lower temperatures than diesel at the quasi-steady stage for 1000 and 1200 K ambient temperature, while diesel shows a lower temperature than biodiesel at 800 K ambient. This result may raise the question of how important the flame temperature is in explaining the higher NOx emissions often observed during biodiesel combustion. Other factors may also play an important role in controlling NOx emissions. Both biodiesel and diesel temperature measurements show a monotonic dependence on the ambient temperature. However, the ambient temperature appears to have a more significant effect on the soot formation and oxidation in diesel combustion, while biodiesel combustion soot characteristics shows relative insensitivity to the ambient temperature.}, journal={APPLIED ENERGY}, author={Zhang, Ji and Jing, Wei and Roberts, William L. and Fang, Tiegang}, year={2013}, month={Jul}, pages={52–65} }
 @article{chen_wang_roberts_fang_2013, title={Spray and atomization of diesel fuel and its alternatives from a single-hole injector using a common rail fuel injection system}, volume={103}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870517496&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2012.08.013}, abstractNote={Fuel spray and atomization characteristics play an important role in the performance of internal combustion engines. As the reserves of petroleum fuel are expected to be depleted within a few decades, finding alternative fuels that are economically viable and sustainable to replace the petroleum fuel has attracted much research attention. In this work, the spray and atomization characteristics were investigated for commercial No. 2 diesel fuel, biodiesel (FAME) derived from waste cooking oil (B100), 20% biodiesel blended diesel fuel (B20), renewable diesel fuel produced in house, and civil aircraft jet fuel (Jet-A). Droplet diameters and particle size distributions were measured by a laser diffraction particle analyzing system and the spray tip penetrations and cone angles were acquired using a high speed imaging technique. All experiments were conducted by employing a common-rail high-pressure fuel injection system with a single-hole nozzle under room temperature and pressure. The experimental results showed that biodiesel and jet fuel had different features compared with diesel. Longer spray tip penetration and larger droplet diameters were observed for B100. The smaller droplet size of the Jet-A were believed to be caused by its relatively lower viscosity and surface tension. B20 showed similar characteristics to diesel but with slightly larger droplet sizes and shorter tip penetration. Renewable diesel fuel showed closer droplet size and spray penetration to Jet-A with both smaller than diesel. As a result, optimizing the trade-off between spray volume and droplet size for different fuels remains a great challenge. However, high-pressure injection helps to optimize the trade-off of spray volume and droplet sizes. Furthermore, it was observed that the smallest droplets were within a region near the injector nozzle tip and grew larger along the axial and radial direction. The variation of droplet diameters became smaller with increasing injection pressure.}, journal={Fuel}, author={Chen, P.-C. and Wang, W.-C. and Roberts, W.L. and Fang, Tiegang}, year={2013}, pages={850–861} }
 @article{yao_fang_2013, title={Spray characteristics of a swirl atomiser in trigger sprayers using water-ethanol mixtures}, volume={91}, ISSN={["0008-4034"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878717947&partnerID=MN8TOARS}, DOI={10.1002/cjce.21821}, abstractNote={Abstract}, number={7}, journal={CANADIAN JOURNAL OF CHEMICAL ENGINEERING}, author={Yao, Shanshan and Fang, Tiegang}, year={2013}, month={Jul}, pages={1312–1324} }
 @article{yao_fang_2012, title={Analytical solutions of laminar swirl decay in a straight pipe}, volume={17}, ISSN={["1007-5704"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84857645070&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2011.11.038}, abstractNote={Abstract In this work, the laminar swirl flow in a straight pipe is revisited and solved analytically by using prescribed axial flow velocity profiles. Based on two axial velocity profiles, namely a slug flow and a developed parabolic velocity profiles, the swirl velocity equation is solved by the separation of variable technique for a rather general inlet swirl velocity distribution, which includes a forced vortex in the core and a free vortex near the wall. The solutions are expressed by the Bessel function for the slug flow and by the generalized Laguerre function for the developed parabolic velocity. Numerical examples are calculated and plotted for different combinations of influential parameters. The effects of the Reynolds number, the pipe axial distance, and the inlet swirl profiles on the swirl velocity distribution and the swirl decay are analyzed. The current results offer analytical equations to estimate the decay rate and the outlet swirl intensity and velocity distribution for the design of swirl flow devices.}, number={8}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Yao, Shanshan and Fang, Tiegang}, year={2012}, month={Aug}, pages={3235–3246} }
 @article{fang_zhang_zhong_2012, title={Boundary layer flow over a stretching sheet with variable thickness}, volume={218}, ISSN={0096-3003}, url={http://dx.doi.org/10.1016/j.amc.2011.12.094}, DOI={10.1016/j.amc.2011.12.094}, abstractNote={In this work, the boundary layers over a continuously stretching sheet with a power law surface velocity were revisited for a sheet with variable thickness. Based on the boundary layer assumptions, the similarity equation governed by two parameters, namely the velocity power index and the wall thickness parameter, was obtained and solved numerically. Theoretical analysis was conducted for special conditions and analytical solutions were derived for the velocity power indices m=-13 and m=-12. Numerical techniques were used to solve the similarity equation for general conditions. Quite different and interesting flow behavior was found for negative power indices. Multiple solutions were obtained for certain wall thickness parameter and velocity power indices. Velocity overshoot near the wall was observed for certain solution branches. It is found that the non-flatness of the stretching surface has significant impacts on the boundary layer development along the wall, on the velocity profiles, and on the shear stress distribution in the fluid. When the velocity power index is less than one, the non-flatness introduces a mass suction effect; while when it is greater than one, the non-flatness leads to a mass injection effect. The results for a non-flat stretching sheet offer quite interesting nonlinear behaviors and further enrich the solution and understanding of boundary layers.}, number={13}, journal={Applied Mathematics and Computation}, publisher={Elsevier BV}, author={Fang, Tiegang and Zhang, Ji and Zhong, Yongfang}, year={2012}, month={Mar}, pages={7241–7252} }
 @misc{fang_2012, title={Comments on "Analytic heat and mass transfer of the mixed hydrodynamic/thermal slip MHD viscous flow over a stretching sheet, International Journal of Mechanical Sciences 53 (2011) 886-896, by M. Turkyilmazoglu"}, volume={55}, ISSN={["0020-7403"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84858334677&partnerID=MN8TOARS}, DOI={10.1016/j.ijmecsci.2011.12.008}, number={1}, journal={INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES}, author={Fang, Tiegang}, year={2012}, month={Feb}, pages={129–129} }
 @article{yao_zhang_fang_2012, title={Effect of viscosities on structure and instability of sprays from a swirl atomizer}, volume={39}, ISSN={["1879-2286"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862819676&partnerID=MN8TOARS}, DOI={10.1016/j.expthermflusci.2012.01.020}, abstractNote={The breakup phenomena of liquid spray sheets and jets are encountered in daily life as well as in various industrial applications. The onset of instability has a direct impact on the downstream spray development, and thus it is necessary to investigate the effect of liquid physical properties on this instability. The present paper focuses on the effects of liquid viscosity on the spray characteristics and instability during the transient operation of a swirl atomizer in a trigger sprayer via experiments. In the experiments, water–glycerol mixtures were used to simulate fluids with a wide range of viscosities. The transient displacement of the dispensing piston was measured. A high-speed digital video camera was used to visualize the near-nozzle spray structure. The digital images of the sprays were further processed in order to analyze the spray angle and the surface waves on the spray cone. By using the spatiotemporal diagrams, the surface wave temporal frequency was also analyzed for fluids with different viscosities. From the experimental results, it is seen that the fluid viscosity plays a critical role in controlling the liquid sheet breakup and atomization. More viscous fluids result in smaller average spray cone angles. The spray cone developed very fast during the early stage for less viscous fluids, while for the most viscous liquid, a very small cone angle with little breakup and atomization was observed. As the liquid viscosity increases, the cone collapses earlier with larger droplets in the end stage. In addition to the spray cone angles, the surface wave temporal frequency was also calculated from the recorded images. The results show that the surface wave temporal frequency depends on the dispensing time and the fluid viscosity, and is almost independent of the location in the near nozzle liquid cone. The results also indicate that the surface wave temporal frequency decreases with time.}, journal={EXPERIMENTAL THERMAL AND FLUID SCIENCE}, author={Yao, Shanshan and Zhang, Ji and Fang, Tiegang}, year={2012}, month={May}, pages={158–166} }
 @article{zhang_jing_fang_2012, title={High speed imaging of OH* chemiluminescence and natural luminosity of low temperature diesel spray combustion}, volume={99}, ISSN={["1873-7153"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862163802&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2012.04.031}, abstractNote={This study focused on spray combustion of ultra low sulfur diesel (ULSD) fuel under low oxygen conditions with low temperature combustion (LTC) mode in an optically accessible constant volume combustion chamber. The ambient oxygen concentration was configured as 10% and 15% to achieve low flame temperature. The ambient gas temperature varied from 800 K to 1200 K. High speed imaging of OH* chemiluminescence and natural luminosity (NL) was used to visualize the instantaneous spray combustion process. The heat release rate was analyzed using the transient combustion pressure and the flame structure was studied based on the combustion images. Results show that a higher oxygen concentration case features a shorter ignition delay and higher heat release rate. The LTC mode can be realized by decreasing the oxygen concentration and ambient temperature simultaneously and it features a longer ignition delay, a slower reaction rate, and apparently lower soot radiation heat loss. The visualization results of NL and OH* show that the high temperature reaction occurs mainly in the mid-stream and downstream of the spray combustion, but not in the region very close to the chamber wall. This study validates the LTC process by showing very weak OH* chemiluminescence signal. The results also indicate that in order to realize LTC mode, it is important to control the ambient oxygen and ambient temperature at the same time. By only reducing the ambient oxygen concentration it may not be effective to suppress soot generation.}, journal={FUEL}, author={Zhang, Ji and Jing, Wei and Fang, Tiegang}, year={2012}, month={Sep}, pages={226–234} }
 @article{fang_yao_zhang_zhong_tao_2012, title={Momentum and heat transfer of the Falkner-Skan flow with algebraic decay: An analytical solution}, volume={17}, ISSN={["1878-7274"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84855241770&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2011.10.021}, abstractNote={In this paper, an analytical solution of the Falkner–Skan equation with mass transfer and wall movement is obtained for a special case, namely a velocity power index of −1/3, with an algebraically decaying velocity profile. The solution is given in a closed form. Under different values of the mass transfer parameter, the wall can be fixed, moving in the same direction as the free stream, or opposite to the free stream (reversal flow near the wall). The thermal boundary layer solution is also presented with a closed form for a prescribed power-law wall temperature, which is expressed by the confluent hypergeometric function of the second kind. The temperature profiles and the wall temperature gradients are plotted. Interesting but complicated variation trends for certain combinations of controlling parameters are observed. Under certain parameter combinations, there exist singular points or poles for the wall temperature gradients, namely wall heat flux. With poles, the temperature profiles can cross the zero temperature line and become negative. From the results, it is also found empirically that under certain given values of the Prandtl number (Pr) and flow controlling parameter (b), the number of times for the temperature profiles crossing the zero line is the same as the number of poles when the wall temperature power index varies between zero and a given value n. The current result provides a new analytical solution for the Falkner–Skan equation with algebraic decay and greatly enriches the understanding of this important equation as well as the heat transfer characteristics for this flow.}, number={6}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Fang, Tiegang and Yao, Shanshan and Zhang, Ji and Zhong, Yongfang and Tao, Hua}, year={2012}, month={Jun}, pages={2476–2488} }
 @article{tie-gang_hua_yong-fang_2012, title={Non-Newtonian Power-Law Fluid Flow over a Shrinking Sheet}, volume={29}, ISSN={["0256-307X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84869077972&partnerID=MN8TOARS}, DOI={10.1088/0256-307x/29/11/114703}, abstractNote={The boundary layer flow of power-law fluids over a shrinking sheet with mass transfer is revisited. Closed-form analytical solutions are found and presented for special cases. One of the presented solutions has an algebraic decay behavior. These analytical solutions might offer valuable insight into the nonlinear boundary layer flow for power-law fluids.}, number={11}, journal={CHINESE PHYSICS LETTERS}, author={Tie-Gang, Fang and Hua, Tao and Yong-Fang, Zhong}, year={2012}, month={Nov} }
 @article{fang_tao_zhong_2012, title={Note on the Unsteady Mixed Boundary Layer in a Porous Medium with Temperature Slip: Exact Solutions}, volume={94}, ISSN={["0169-3913"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84864101663&partnerID=MN8TOARS}, DOI={10.1007/s11242-012-9996-x}, number={1}, journal={TRANSPORT IN POROUS MEDIA}, author={Fang, Tiegang and Tao, Hua and Zhong, Yongfang}, year={2012}, month={Aug}, pages={189–196} }
 @article{fang_zhang_zhong_2012, title={Note on unsteady viscous flow on the outside of an expanding or contracting cylinder}, volume={17}, ISSN={["1007-5704"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862815663&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2011.12.013}, abstractNote={In this paper, the viscous flow on the outside of an expanding or contracting cylinder is studied. The governing Navier–Stokes equations are transformed into a similarity equation, which is solved by a shooting method. The solution is an exact solution to the unsteady Navier–Stokes equations. Results show both trivial and non-trivial solutions. For trivial solutions, there is no axial flow induced during the cylinder expansion or contraction. However, for the non-trivial solutions which only exist for cylinder expansion, an axial flow is generated and its strength increases with the increase in expansion speed.}, number={8}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Fang, Tiegang and Zhang, Ji and Zhong, Yongfang}, year={2012}, month={Aug}, pages={3124–3128} }
 @misc{fang_zhong_2012, title={Reply to "Comment on "Unsteady stagnation-point flow over a plate moving along the direction of flow impingement" by Y. Zhong and T. Fang, Int. J. Heat MassTransfer 54 (2011)3103-3108"}, volume={55}, ISSN={["0017-9310"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-82955163223&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2011.09.040}, number={4}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Fang, Tiegang and Zhong, Yongfang}, year={2012}, month={Jan}, pages={1425–1426} }
 @article{fang_tao_2012, title={Unsteady viscous flow over a rotating stretchable disk with deceleration}, volume={17}, ISSN={["1007-5704"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84864416230&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2012.04.017}, abstractNote={In this work, the laminar unsteady flow over a stretchable rotating disk with deceleration is investigated. The three dimensional Navier–Stokes (NS) equations are reduced into a similarity ordinary differential equation group, which is solved numerically using a shooting method. Mathematically, two solution branches are found for the similarity equations. The lower solution branch may not be physically feasible due to a negative velocity in the circumferential direction. For the physically feasible solution branch, namely the upper solution branch, the fluid behavior is greatly influenced by the disk stretching parameter and the unsteadiness parameter. With disk stretching, the disk can be friction free in both the radial and the circumferential directions, depending on the values of the controlling parameters. The results provide an exact solution to the whole unsteady NS equations with new nonlinear phenomena and multiple solution branches.}, number={12}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Fang, Tiegang and Tao, Hua}, year={2012}, month={Dec}, pages={5064–5072} }
 @article{pantokratoras_fang_2011, title={A note on the Blasius and Sakiadis flow of a non-Newtonian power-law fluid in a constant transverse magnetic field}, volume={218}, ISSN={["0001-5970"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79953028742&partnerID=MN8TOARS}, DOI={10.1007/s00707-010-0406-6}, number={1-2}, journal={ACTA MECHANICA}, author={Pantokratoras, Asterios and Fang, Tiegang}, year={2011}, month={Apr}, pages={187–194} }
 @article{zhang_yao_patel_fang_2011, title={AN EXPERIMENTAL STUDY ON GASOLINE DIRECT-INJECTION SPRAY AND ATOMIZATION CHARACTERISTICS OF ALCOHOL FUELS AND ISOOCTANE}, volume={21}, ISSN={["1936-2684"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84555203802&partnerID=MN8TOARS}, DOI={10.1615/atomizspr.2011003624}, abstractNote={Alcohol fuels such as butanol and ethanol are considered as the alternative or blending fuels to conventional gasoline for fewer emissions and their renewable capability. In this paper the spray structure development and atomization for butanol, ethanol, and isooctane were investigated using a swirl-type inwardly opening gasoline direct-injection (GDI) injector. Two pressures of 7.0 and 10.2 MPa were used for each fuel, and the fuel was injected into a room condition. Transient spray images were taken by using a high-speed camera for visualization and cone angle analysis. Sauter mean diameter (SMD), DV(50), DV(90), and particle size distribution (PSD) were measured using a laser diffraction technique. Results of the transient images clearly show the sac spray at the initial phase (phase 1) and the main spray structure at the developed phase (phase 2). The cone angles at the developed phase for butanol and ethanol are consistently stable, while isooctane presents relatively large fluctuations. The largest cone angle value is observed for ethanol at both injection pressures, while butanol shows the smallest. Higher injection pressure leads to a smaller cone angle for each fuel, among which isooctane shows the largest decrease. In phase 1, isooctane shows a bouncing trend in terms of DV(90), as opposed to butanol and ethanol which show a gradual decrease. In phase 2, all three fuels show consistently smaller droplet size compared to phase 1, suggesting good atomization. A higher injection pressure helps isooctane to reduce the droplet size, meanwhile enabling butanol and ethanol to produce a more uniform PSD, but it does not necessarily induce the droplet size decrease for butanol and ethanol at the current experimental setting.}, number={5}, journal={ATOMIZATION AND SPRAYS}, author={Zhang, Ji and Yao, Shanshan and Patel, Himesh and Fang, Tiegang}, year={2011}, pages={363–374} }
 @article{zhong_fang_wert_2011, title={An adsorption air conditioning system to integrate with the recent development of emission control for heavy-duty vehicles}, volume={36}, ISSN={["1873-6785"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79959378897&partnerID=MN8TOARS}, DOI={10.1016/j.energy.2011.04.032}, abstractNote={The recent development to control the emissions of large diesel engines has provided opportunities for heat-driven cooling methods in vehicles. An adsorption air conditioning system is therefore proposed in this work for heavy-duty truck application. This system is powered by engine waste heat when the engine of a truck is running. When the engine is off, it can be operated by fuel fired heaters, a newly implemented technology to reduce truck idling. Hence, this system can not only reduce engine emissions but also improve the overall energy efficiency. A lumped parameter model of the system using zeolite-water as its working pair is developed, and the adsorption capacity of zeolite is simulated with the linear driving force model. The dynamic performance of the system and a parametric study on adsorbent mass transfer, operating temperatures and cycle operating periods are presented. Alternative working pairs and the potential to commercialize the system are also discussed. This system may be designed to satisfy the cooling requirement for idle reduction of long-haul trucks.}, number={7}, journal={ENERGY}, author={Zhong, Yongfang and Fang, Tiegang and Wert, Kevin L.}, year={2011}, month={Jul}, pages={4125–4135} }
 @article{zhang_fang_zhong_2011, title={Analytical solution of magnetohydrodynamic sink flow}, volume={32}, ISSN={["0253-4827"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80855139343&partnerID=MN8TOARS}, DOI={10.1007/s10483-011-1495-9}, number={10}, journal={APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION}, author={Zhang, Ji and Fang, Tie-gang and Zhong, Yong-fang}, year={2011}, month={Oct}, pages={1221–1230} }
 @article{nadeem_zaheer_fang_2011, title={Effects of thermal radiation on the boundary layer flow of a Jeffrey fluid over an exponentially stretching surface}, volume={57}, ISSN={["1572-9265"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79955881202&partnerID=MN8TOARS}, DOI={10.1007/s11075-010-9423-8}, number={2}, journal={NUMERICAL ALGORITHMS}, author={Nadeem, Sohail and Zaheer, Shehla and Fang, Tiegang}, year={2011}, month={Jun}, pages={187–205} }
 @article{fang_yao_pop_2011, title={Flow and heat transfer over a generalized stretching/shrinking wall problem-Exact solutions of the Navier-Stokes equations}, volume={46}, ISSN={["1878-5638"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80051548371&partnerID=MN8TOARS}, DOI={10.1016/j.ijnonlinmec.2011.04.014}, abstractNote={In this paper, we investigate the steady momentum and heat transfer of a viscous fluid flow over a stretching/shrinking sheet. Exact solutions are presented for the Navier–Stokes equations. The new solutions provide a more general formulation including the linearly stretching and shrinking wall problems as well as the asymptotic suction velocity profiles over a moving plate. Interesting non-linear phenomena are observed in the current results including both exponentially decaying solution and algebraically decaying solution, multiple solutions with infinite number of solutions for the flow field, and velocity overshoot. The energy equation ignoring viscous dissipation is solved exactly and the effects of the mass transfer parameter, the Prandtl number, and the wall stretching/shrinking strength on the temperature profiles and wall heat flux are also presented and discussed. The exact solution of this general flow configuration is a rare case for the Navier–Stokes equation.}, number={9}, journal={INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS}, author={Fang, Tiegang and Yao, Shanshan and Pop, Loan}, year={2011}, month={Nov}, pages={1116–1127} }
 @article{yao_fang_zhong_2011, title={Heat transfer of a generalized stretching/shrinking wall problem with convective boundary conditions}, volume={16}, ISSN={["1878-7274"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77956060446&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2010.05.028}, abstractNote={In this paper, we investigate the heat transfer of a viscous fluid flow over a stretching/shrinking sheet with a convective boundary condition. Based on the exact solutions of the momentum equations, which are valid for the whole Navier–Stokes equations, the energy equation ignoring viscous dissipation is solved exactly and the effects of the mass transfer parameter, the Prandtl number, and the wall stretching/shrinking parameter on the temperature profiles and wall heat flux are presented and discussed. The solution is given as an incomplete Gamma function. It is found the convective boundary conditions results in temperature slip at the wall and this temperature slip is greatly affected by the mass transfer parameter, the Prandtl number, and the wall stretching/shrinking parameters. The temperature profiles in the fluid are also quite different from the prescribed wall temperature cases.}, number={2}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Yao, Shanshan and Fang, Tiegang and Zhong, Yongfang}, year={2011}, month={Feb}, pages={752–760} }
 @article{lien_fang_buckner_2011, title={Hysteretic neural network modeling of spring-coupled piezoelectric actuators}, volume={20}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79956193310&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/20/6/065007}, abstractNote={This paper discusses the development of a high-fidelity, computationally efficient model for spring-coupled piezoelectric stack actuators. The model is based on a hysteretic recurrent neural network (HRNN), and aims to balance computational tractability with physical intuition. Previous work has detailed the development and experimental validation of an HRNN model for unloaded piezoelectric actuators. This paper extends the modeling approach to incorporate coupling with linear springs, and discusses training techniques based on genetic algorithms, which provide advantages over the previously employed Levenberg–Marquardt methods in terms of accuracy and model complexity. The resulting models are computable in real time. Model validity is established by comparison with a rate-dependent threshold-discrete Prandtl–Ishlinskii model.}, number={6}, journal={SMART MATERIALS AND STRUCTURES}, author={Lien, J. P. and Fang, Tiegang and Buckner, Gregory D.}, year={2011}, month={Jun} }
 @article{fang_lee_2011, title={Low sooting combustion of narrow-angle wall-guided sprays in an HSDI diesel engine with retarded injection timings}, volume={90}, ISSN={["0016-2361"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79951942114&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2010.12.031}, abstractNote={An optically accessible single-cylinder high speed direct-injection (HSDI) diesel engine was used to investigate the spray and combustion processes with narrow-angle wall-guided sprays. Influences of injection timings and injection pressure on combustion characteristics and emissions were studied. In-cylinder pressure was measured and used for heat release analysis. High-speed spray and combustion videos were captured. NOx emissions were measured in the exhaust pipe. With significantly retarded post-top dead center (TDC) injections, smokeless combustion was achieved for wall-guided diesel spray. Premixed-combustion was observed from the heat release rates and the combustion images. Natural luminosity was found significantly lower for smokeless combustion case. However, NOx emissions were higher for the low sooting combustion cases. In addition, retarding injection timing lead to more complete combustion with more heat released from the same amount of fuel. Spray images revealed significant fuel impingement for all the conditions and the spray development was controlled and guided by the piston bowl curvature. NOx and natural luminosity trade-off trend was observed for these conditions. However, quite different from conventional diesel combustion, retarding post-TDC injection timing leads to lower natural luminosity and higher NOx emissions for narrow-angle wall-guided spray combustion. For the smokeless combustion case under moderate operating load, both homogeneous combustion and low-luminosity pool fires were observed during combustion process and the latter was due to fuel-piston impingement. The findings in this study could be used to solve the smoke issues associated with narrow-angle injection technique under high load conditions. With narrow-angle injectors, ignition could occur for significantly retarded post-TDC injections, which provides a unique mixing approach for diesel engines.}, number={4}, journal={FUEL}, author={Fang, Tiegang and Lee, Chia-fon F.}, year={2011}, month={Apr}, pages={1449–1456} }
 @article{fang_zhang_2011, title={Note on the Heat Transfer of Flows over a Stretching Wall in Porous Media: Exact Solutions}, volume={86}, ISSN={["1573-1634"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79953180000&partnerID=MN8TOARS}, DOI={10.1007/s11242-010-9640-6}, number={2}, journal={TRANSPORT IN POROUS MEDIA}, author={Fang, Tiegang and Zhang, Ji}, year={2011}, month={Jan}, pages={609–614} }
 @inproceedings{zhang_fang_2011, title={Simultaneous imaging of OH<sup>*</sup> chemiluminescence and flame luminosity of diesel and biodiesel spray combustion}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862580656&partnerID=MN8TOARS}, DOI={10.1115/icef2011-60103}, abstractNote={The research on the spray combustion of diesel and biodiesel is vital to the understanding of emission formation and optimal utilization of fuel. This paper studies the biodiesel and diesel spray combustion in a constant volume chamber under different simulated diesel engine conditions. The ambient temperature at fuel injection varied from 800K to 1200K, while the ambient oxygen concentration was maintained at 21%. Simultaneous high speed imaging of OH* chemiluminescence and flame luminosity was employed to visualize the whole combustion process. Heat release rate was analyzed based on the measured combustion pressure. The apparent heat release rate analysis shows that biodiesel has a shorter ignition delay time than diesel, and biodiesel has a smaller cumulative heat release value due to its lower heating value. The overlaying image of OH* chemiluminescence and flame luminosity clearly identifies the high temperature reaction regions and soot formation regions. The line-of-sight images agree with the published observation that the hydroxyl radical is formed on the lean side of the flame edge. Decreasing ambient temperature greatly reduces the OH* chemiluminescence intensity of the diesel combustion, while the impact is smoother and milder for biodiesel combustion. Biodiesel shows a significantly lower level of flame luminosity than diesel under all conditions. These combined observations lead to a speculation that the soot oxidation process may serve as an important contributor to OH* chemiluminescence intensity for late stage combustion, and biodiesel shows a tendency to produce less soot than diesel under the investigated conditions.}, booktitle={American Society of Mechanical Engineers, Internal Combustion Engine Division (Publication) ICE}, author={Zhang, J. and Fang, Tiegang}, year={2011}, pages={415–421} }
 @inproceedings{zhang_fang_2011, title={Spray combustion of biodiesel and diesel in a constant volume combustion chamber}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79959820861&partnerID=MN8TOARS}, DOI={10.4271/2011-01-1380}, booktitle={SAE 2011 World Congress and Exhibition}, author={Zhang, J. and Fang, T.}, year={2011} }
 @article{zhang_fang_2011, title={Spray combustion of biodiesel and diesel in a constant volume combustion chamber}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877163563&partnerID=MN8TOARS}, journal={SAE Technical Papers}, author={Zhang, J. and Fang, T.}, year={2011} }
 @article{fang_lee_zhang_2011, title={The boundary layers of an unsteady incompressible stagnation-point flow with mass transfer}, volume={46}, ISSN={["0020-7462"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79957829352&partnerID=MN8TOARS}, DOI={10.1016/j.ijnonlinmec.2011.04.007}, abstractNote={In the current work, the boundary layers of an unsteady incompressible stagnation-point flow with mass transfer were further investigated. Similarity transformation technique was used and the similarity equation group was solved using numerical methods. Interesting observation is that there are multiple solutions seen for negative unsteadiness parameters, β. The influences of mass transfer, unsteadiness parameter, and Prandtl numbers on velocity and temperature profiles, wall drag, and wall heat fluxes were investigated and analyzed. The asymptotic behaviors for the similarity equations in limiting situations were theoretically analyzed. It is found that solutions exist for all mass transfer parameters for β≥−1. For a certain mass transfer parameter, there are two solutions when βc<β<0; there is one solution for (β=βc)∪(β≥0); there is no solution for β<βc, where βc is a critical unsteadiness parameter dependent on mass transfer parameter.}, number={7}, journal={INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS}, author={Fang, Tiegang and Lee, Chia-fon F. and Zhang, Ji}, year={2011}, month={Sep}, pages={942–948} }
 @article{aziz_fang_2011, title={Thermal analysis of an annular fin with (a) simultaneously imposed base temperature and base heat flux and (b) fixed base and tip temperatures}, volume={52}, ISSN={["1879-2227"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79952802659&partnerID=MN8TOARS}, DOI={10.1016/j.enconman.2011.02.004}, abstractNote={The performance of an annular fin with uniform thickness losing heat by convection to its surroundings is studied analytically for two sets of boundary conditions: (a) simultaneously prescribed base temperature and base heat flux, (b) specified base and tip temperatures. For (a) analytical expressions are derived for the temperature distribution, the tip heat flow, and the Biot number at the tip. For the fin tip to be insulated, a relationship between the base heat flow, the radii of the fin, and the fin parameter must be satisfied. Based on the base heat flow for the insulated tip, an expression is derived for the tip temperature. For part (b), analytical solutions are presented for the temperature distribution, base heat flow, and tip heat flow. For the adiabatic tip condition, a relation between the tip temperature, the fin parameter, and the radii of the fin must be satisfied. The condition under which the fin tip can be freely exposed to the environment is established. The graphical results provide a comprehensive picture of the thermal performance of the annular fin under both cooling and heating conditions.}, number={7}, journal={ENERGY CONVERSION AND MANAGEMENT}, author={Aziz, Abdul and Fang, Tiegang}, year={2011}, month={Jul}, pages={2467–2478} }
 @article{tie-gang_ji_yong-fang_hua_2011, title={Unsteady Viscous Flow over an Expanding Stretching Cylinder}, volume={28}, ISSN={["0256-307X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-83455233823&partnerID=MN8TOARS}, DOI={10.1088/0256-307x/28/12/124707}, abstractNote={We study the viscous flow over an expanding stretching cylinder. The solution is exact to the Navier—Stokes equations. The stretching velocity of the cylinder is proportional to the axial distance from the origin and decreases with time. There exists a unique solution for the flow with all the studied values of Reynolds number and the unsteadiness parameter. Reversal flows exist for an expanding stretching cylinder. The velocity decays faster for a larger Reynolds number and a more rapidly expanding cylinder.}, number={12}, journal={CHINESE PHYSICS LETTERS}, author={Tie-Gang, Fang and Ji, Zhang and Yong-Fang, Zhong and Hua, Tao}, year={2011}, month={Dec} }
 @article{zhong_fang_2011, title={Unsteady stagnation-point flow over a plate moving along the direction of flow impingement}, volume={54}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79956195087&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2011.04.024}, abstractNote={Unsteady plane and axisymmetric stagnation flow of an incompressible viscous fluid on the body that moves along the oncoming flow with a time-dependent velocity is studied in this work. Similarity solutions for the full Navier–Stokes equations are obtained and the results of the flow velocity, shear stress and stream lines are reported for both plane two dimensional flow and axisymmetric flow. The results show that the features of the similar boundary flow highly depends on a characteristic parameter β. There exists a critical value βc below which no similarity solution to the flow is found. When βc < β < 0, two solution branches exist and different flow patterns appear for each branch. Flow with monophonically growing velocity, reversed flow and flow with S-shaped velocity are obtained for various values of β. The boundary layer thickness of the plane and axisymmetric flows is tabulated, the streamlines of the flow are demonstrated, and the shear stress over the boundary layer is also discussed.}, number={15-16}, journal={International Journal of Heat and Mass Transfer}, author={Zhong, Y. and Fang, Tiegang}, year={2011}, pages={3103–3108} }
 @article{fang_yao_2011, title={Viscous Swirling Flow over a Stretching Cylinder}, volume={28}, ISSN={["0256-307X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-81855177082&partnerID=MN8TOARS}, DOI={10.1088/0256-307x/28/11/114702}, abstractNote={We investigate a viscous flow over a cylinder with stretching and torsional motion. There is an exact solution to the Navier—Stokes equations and there exists a unique solution for all the given values of the flow Reynolds number. The results show that velocity decays faster for a higher Reynolds number and the flow penetrates shallower into the ambient fluid. All the velocity profiles decay algebraically to the ambient zero velocity.}, number={11}, journal={CHINESE PHYSICS LETTERS}, author={Fang, Tiegang and Yao, Shanshan}, year={2011}, month={Nov} }
 @article{fang_zhang_yao_2010, title={A new family of unsteady boundary layers over a stretching surface}, volume={217}, ISSN={["1873-5649"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78650034159&partnerID=MN8TOARS}, DOI={10.1016/j.amc.2010.09.031}, abstractNote={In this paper, a new family of unsteady boundary layers over a stretching flat surface was proposed and studied. This new class of unsteady boundary layers involves the flows over a constant speed stretching surface from a slot, and the slot is moving at a certain speed. Depending on the slot moving parameter, the flow can be treated as a stretching sheet problem or a shrinking sheet problem. Both the momentum and thermal boundary layers were studied. Under special conditions, the solutions reduce to the unsteady Rayleigh problem and the steady Sakiadis stretching sheet problem. Solutions only exist for a certain range of the slot moving parameter, α. Two solutions are found for −53.55° < α < −45°. There are also two solution branches for the thermal boundary layers at any given Prandtl number in this range. Compared with the upper solution branch, the lower solution branch leads to simultaneous reduction in wall drag and heat transfer rate. The results also show that the motion of the slot greatly affects the wall drag and heat transfer characteristics near the wall and the temperature and velocity distributions in the fluids.}, number={8}, journal={APPLIED MATHEMATICS AND COMPUTATION}, author={Fang, Tiegang and Zhang, Ji and Yao, Shanshan}, year={2010}, month={Dec}, pages={3747–3755} }
 @article{aziz_fang_2010, title={Alternative solutions for longitudinal fins of rectangular, trapezoidal, and concave parabolic profiles}, volume={51}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77953915774&partnerID=MN8TOARS}, DOI={10.1016/j.enconman.2010.03.012}, abstractNote={The traditional thermal analysis of fins is based on the assumption of specified thermal boundary conditions at the base and tip of the fin. For situations when the fin base is in contact with a fluid experiencing condensation and the fin is required to remove the energy released by the fluid, the base is subjected to two boundary conditions: a fixed temperature and a fixed heat flux. This paper develops solutions for the temperature distribution in the fins under these conditions. Solutions are provided for rectangular, trapezoidal, and concave parabolic (finite tip thickness). Results illustrating the relationship between the dimensionless heat flux, the fin parameter, and dimensionless tip temperature are provided for all three geometries. The case of convective fin tip is also considered and lead to a relationship between the dimensionless heat flux, the fin parameter, and the Biot number at the tip. The results presented here provide tools that not only complement the traditional analyses but are believed to have more direct relevance for the fin designers.}, number={11}, journal={Energy Conversion and Management}, author={Aziz, A. and Fang, Tiegang}, year={2010}, pages={2188–2194} }
 @article{fang_lee_coverdill_white_2010, title={Effects of injection pressure on low-sooting combustion in an optical hsdi diesel engine using a narrow angle injector}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877184323&partnerID=MN8TOARS}, DOI={10.4271/2010-01-0339}, journal={SAE Technical Papers}, author={Fang, T. and Lee, C.-F. and Coverdill, R. and White, R.}, year={2010} }
 @article{pantokratoras_fang_2010, title={FLOW ADJACENT TO A FLAT PLATE IN A DARCY-BRINKMAN POROUS MEDIUM OSCILLATING WITH ARBITRARY PERIODIC OSCILLATION}, volume={13}, ISSN={["1091-028X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77958600460&partnerID=MN8TOARS}, DOI={10.1615/jpormedia.v13.i8.70}, abstractNote={In this note, an exact solution is presented for the flow produced by a plate oscillating with arbitrary periodic oscillation in a porous medium. The velocity field is composed of a steady state part and a transient part. It is found that the flow depends on the permeability parameter. The velocity profiles and the wave penetration depth are damped in the transverse direction due to the existence of the porous medium. The influence of the porous medium on the oscillation increases with the increase of the permeability parameter.}, number={8}, journal={JOURNAL OF POROUS MEDIA}, author={Pantokratoras, Asterios and Fang, Tiegang}, year={2010}, pages={759–763} }
 @article{zhao_pantokratoras_fang_liao_2010, title={Flow of a Weakly Conducting Fluid in a Channel Filled with a Darcy-Brinkman-Forchheimer Porous Medium}, volume={85}, ISSN={["1573-1634"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77956873895&partnerID=MN8TOARS}, DOI={10.1007/s11242-010-9550-7}, number={1}, journal={TRANSPORT IN POROUS MEDIA}, author={Zhao, B. Q. and Pantokratoras, A. and Fang, T. G. and Liao, S. J.}, year={2010}, month={Oct}, pages={131–142} }
 @article{lien_york_fang_buckner_2010, title={Modeling piezoelectric actuators with Hysteretic Recurrent Neural Networks}, volume={163}, ISSN={["0924-4247"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78049473465&partnerID=MN8TOARS}, DOI={10.1016/j.sna.2010.08.013}, abstractNote={This paper describes the application of Hysteretic Recurrent Neural Networks (HRNNs) to the modeling of polycrystalline piezoelectric actuators. Because piezoelectric materials exhibit voltage/strain relationships that are hysteretic and rate-dependent, the HRNN is composed of neurons with activation functions that incorporate these characteristics. Individual neurons are shown to agree with existing models of ideal single-crystal piezoelectric behavior. The combination of many such neurons into a network allows prediction of the heterogeneous behavior of polycrystalline materials. This model is shown to approximate the strain and polarization of an unloaded commercial stack actuator at multiple loading rates. A comparison is made to a recurrent Radial Basis Function Network model, and the HRNN is demonstrated to more accurately generalize across data sets. The model is further shown to execute on a PC platform at rates over 100 Hz, fast enough to support its application to real-time control.}, number={2}, journal={SENSORS AND ACTUATORS A-PHYSICAL}, author={Lien, J. P. and York, Alexander and Fang, Tiegang and Buckner, Gregory D.}, year={2010}, month={Oct}, pages={516–525} }
 @article{tie-gang_ji_shan-shan_2010, title={Slip Magnetohydrodynamic Viscous Flow over a Permeable Shrinking Sheet}, volume={27}, ISSN={["0256-307X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78651086198&partnerID=MN8TOARS}, DOI={10.1088/0256-307x/27/12/124702}, abstractNote={The magnetohydrodynamic (MHD) flow under slip conditions over a shrinking sheet is solved analytically. The solution is given in a closed form equation and is an exact solution of the full governing Navier-Stokes equations. Interesting solution behavior is observed with multiple solution branches for certain parameter domain. The effects of the mass transfer, slip, and magnetic parameters are discussed.}, number={12}, journal={CHINESE PHYSICS LETTERS}, author={Tie-Gang, Fang and Ji, Zhang and Shan-Shan, Yao}, year={2010}, month={Dec} }
 @article{fang_aziz_2010, title={Viscous Flow with Second-Order Slip Velocity over a Stretching Sheet}, volume={65}, ISSN={["1865-7109"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78649829745&partnerID=MN8TOARS}, DOI={10.1515/zna-2010-1212}, abstractNote={In this paper, viscous flow with a second-order slip condition over a permeable stretching surface is solved analytically. The current work differs from the previous studies in the application of a new second-order slip velocity model. The closed form solution reported is an exact solution of the full governing Navier-Stokes equations. The effects of slip and mass transfer parameters are discussed.}, number={12}, journal={ZEITSCHRIFT FUR NATURFORSCHUNG SECTION A-A JOURNAL OF PHYSICAL SCIENCES}, author={Fang, Tiegang and Aziz, Abdul}, year={2010}, month={Dec}, pages={1087–1092} }
 @article{fang_yao_zhang_aziz_2010, title={Viscous flow over a shrinking sheet with a second order slip flow model}, volume={15}, ISSN={["1878-7274"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-74449090532&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2009.07.017}, abstractNote={In this paper, viscous flow over a shrinking sheet is solved analytically using a newly proposed second order slip flow model. The closed solution is an exact solution of the full governing Navier–Stokes equations. The solution has two branches in a certain range of the parameters. The effects of the two slip parameters and the mass suction parameter on the velocity distribution are presented graphically and discussed. For certain combinations of the slip parameters, the wall drag force can decrease with the increase of mass suction. These results clearly show that the second order slip flow model is necessary to predict the flow characteristics accurately.}, number={7}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Fang, Tiegang and Yao, Shanshan and Zhang, Ji and Aziz, Abdul}, year={2010}, month={Jul}, pages={1831–1842} }
 @article{fang_zhong_2010, title={Viscous flow over a shrinking sheet with an arbitrary surface velocity}, volume={15}, ISSN={["1878-7274"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952744808&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2010.01.034}, abstractNote={In this paper, an analytical solution in a closed form for the boundary layer flow over a shrinking sheet is presented when arbitrary velocity distributions are applied on the shrinking sheet. The solutions with seven typical velocity profiles are derived based on a general closed form expression. Such flow is usually not self-similar and the solution can only be implemented when the mass transfer at the wall is prescribed and determined by the moving velocity of the wall. The characteristics of the flows with the typical velocity distributions are discussed and compared with previous similarity solutions. The flow is observed to have quite different behavior from that of the self-similar flow reported in the literature and the results demonstrate distinctive momentum and energy transport characteristics. Some plots of the stream functions are also illustrated to show the difference in flow field between the shrinking sheet and the stretching sheet. An integral approach to solve boundary layer flow over a shrinking or stretching sheet with uncoupled arbitrary surface velocity and wall mass transfer velocity is outlined and the effectiveness of this approach is discussed.}, number={12}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Fang, Tiegang and Zhong, Yongfang}, year={2010}, month={Dec}, pages={3768–3776} }
 @inproceedings{zhong_wert_fang_2010, title={Waste heat powered adsorption system to provide air conditioning for heavy-duty vehicles}, volume={116}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79952635208&partnerID=MN8TOARS}, number={PART 2}, booktitle={ASHRAE Transactions}, author={Zhong, Y. and Wert, K.L. and Fang, T.}, year={2010}, pages={300–309} }
 @article{pantokratoras_fang_2010, title={cox regression in nested case-control studies with auxiliary covariates}, volume={83}, number={3}, journal={Transport in Porous Media}, author={Pantokratoras, A. and Fang, T. G.}, year={2010}, pages={667–676} }
 @article{fang_coverdill_lee_white_2009, title={Air-fuel mixing and combustion in a small-bore direct injection optically accessible diesel engine using a retarded single injection strategy}, volume={88}, ISSN={["0016-2361"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67651097881&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2009.05.032}, abstractNote={In this paper, the air–fuel mixing and combustion in a small-bore direct injection optical diesel engine were studied for a retarded single injection strategy. The effects of injection pressure and timing were analyzed based on in-cylinder heat release analysis, liquid fuel and vapor fuel imaging by Laser induced exciplex fluorescence technique, and combustion process visualization. NOx emissions were measured in the exhaust pipe. Results show that increasing injection pressure benefits soot reduction while increases NOx emissions. Retarding injection timing leads to simultaneous reduction of soot and NOx emissions with premixed homogeneous charge compression ignition (HCCI) like combustion modes. The vapor distribution in the cylinder is relatively homogeneous, which confirms the observation of premixed combustion in the current studies. The postulated path of these combustion modes were analyzed and discussed on the equivalence ratio-temperature map.}, number={11}, journal={FUEL}, author={Fang, Tiegang and Coverdill, Robert E. and Lee, Chia-fon F. and White, Robert A.}, year={2009}, month={Nov}, pages={2074–2082} }
 @article{fang_lee_2009, title={Bio-diesel effects on combustion processes in an HSDI diesel engine using advanced injection strategies}, volume={32}, ISSN={["1540-7489"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67649256041&partnerID=MN8TOARS}, DOI={10.1016/j.proci.2008.07.031}, abstractNote={An optically accessible single-cylinder high-speed direct-injection (HSDI) diesel engine was used to investigate the combustion process using different fuels including European low sulfur diesel and bio-diesel fuels with advanced multiple injection strategies. Influences of injection timings and fuel types on combustion characteristics and emissions were studied under similar loads. In-cylinder pressure was measured and used for heat release analysis. High-speed combustion videos were captured for all the studied cases using the same frame rate. NOx emissions were measured in the exhaust pipe. Different combustion modes including conventional diesel combustion and low-temperature combustion were observed and confirmed from the heat release rates and the combustion images. Natural luminosity was found consistently lower for bio-diesel than the European low sulfur diesel fuel for all the cases. However, for NOx emissions, under conventional combustion cases such as cases 2 and 3, it was found that bio-diesel leads to increased NOx emissions. Under a certain injection strategy with retarded main injections like case 4 and 5, it is possible to have up to 34% lower NOx emissions for B100 than B0 for case 4 with low-temperature combustion mode. Simultaneous reduction of NOx and natural luminosity was achieved for advanced low-temperature combustion mode. It is hypothesized based on the results that the lower soot generation for bio-diesel fuel is believed due to a lower soot formation rate and a higher soot oxidation rate. The NOx increase problem for bio-diesel fuel can be amended by employing advanced injection strategies with low-temperature combustion modes.}, journal={PROCEEDINGS OF THE COMBUSTION INSTITUTE}, author={Fang, Tiegang and Lee, Chia-fon F.}, year={2009}, pages={2785–2792} }
 @article{fang_lin_foong_lee_2009, title={Biodiesel combustion in an optical HSDI diesel engine under low load premixed combustion conditions}, volume={88}, ISSN={["1873-7153"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67651124927&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2009.02.033}, abstractNote={An optically accessible single-cylinder high-speed direct-injection (HSDI) diesel engine was used to investigate the spray and combustion processes for biodiesel blends under different injection strategies. The experimental results indicated that the heat release rate was dominated by a premixed combustion pattern and the heat release rate peak became smaller with injection timing retardation. The ignition and heat release rate peak occurred later with increasing biodiesel content. Fuel impingement on the wall was observed for all test conditions. The liquid penetration became longer and the fuel impingement was stronger with the increase of biodiesel content. Early and late injection timings result in lower flame luminosity due to improved mixing with longer ignition delay. For all the injection timings, lower soot luminosity was seen for biodiesel blends than pure diesel fuel. Furthermore, NOx emissions were dramatically reduced for premixed combustion mode with retarded post-TDC injection strategies.}, number={11}, journal={FUEL}, author={Fang, Tiegang and Lin, Yuan-Chung and Foong, Tien Mun and Lee, Chia-fon}, year={2009}, month={Nov}, pages={2154–2162} }
 @article{fang_zhang_2009, title={Closed-form exact solutions of MHD viscous flow over a shrinking sheet}, volume={14}, ISSN={1007-5704}, url={http://dx.doi.org/10.1016/j.cnsns.2008.10.005}, DOI={10.1016/j.cnsns.2008.10.005}, abstractNote={In this paper, the magnetohydrodynamic (MHD) flow over a shrinking sheet is solved analytically. The solution is given in a closed-form equation and is an exact solution of the full governing Navier–Stokes equations for the problem. Interesting solution behavior is observed with multiple solution branches for certain parameter domain.}, number={7}, journal={Communications in Nonlinear Science and Numerical Simulation}, publisher={Elsevier BV}, author={Fang, Tiegang and Zhang, Ji}, year={2009}, month={Jul}, pages={2853–2857} }
 @article{fang_coverdill_lee_white_2009, title={Effect of the injection angle on liquid spray development in a high-speed direct-injection optical diesel engine}, volume={223}, ISSN={["0954-4070"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-68849127632&partnerID=MN8TOARS}, DOI={10.1243/09544070JAUTO1221}, abstractNote={ In this paper, the spray development and its interaction with the piston geometry were investigated in a small-bore high-speed direct-injection optical diesel engine. The effects of injection angle, injection timing, injection pressure, and injection fuel quantity were studied. The entire liquid spray cycle was visualized by a background-corrected Mie-scattering technique using a high-speed digital video camera synchronized with a high-repetition-rate copper vapour laser. For some conditions, the initial injection velocity was estimated quantitatively. The results show that the injection angle and injection timing predominantly control the spray interaction with the piston geometry and the resulting air—fuel mixing mode. Narrow-angle injection leads to a significantly different air—fuel mixing process from the traditional wide-angle injector. If properly controlled, the narrow-angle direct-injection technique offers more flexibility on injection timing control with the fuel confined in the central bowl region without wetting the cylinder liner. }, number={D8}, journal={PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING}, author={Fang, T-G and Coverdill, R. E. and Lee, C-F F. and White, R. A.}, year={2009}, month={Aug}, pages={1077–1092} }
 @article{pantokratoras_fang_2009, title={Flow of a Weakly Conducting Fluid in a Channel Filled with a Porous Medium}, volume={83}, ISSN={0169-3913 1573-1634}, url={http://dx.doi.org/10.1007/s11242-009-9470-6}, DOI={10.1007/s11242-009-9470-6}, number={3}, journal={Transport in Porous Media}, publisher={Springer Science and Business Media LLC}, author={Pantokratoras, Asterios and Fang, Tiegang}, year={2009}, month={Sep}, pages={667–676} }
 @article{fang_coverdill_lee_white_2009, title={Influence of injection parameters on the transition from PCCI combustion to diffusion combustion in a small-bore HSDI diesel engine}, volume={10}, ISSN={["1976-3832"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67049172714&partnerID=MN8TOARS}, DOI={10.1007/s12239-009-0033-1}, number={3}, journal={INTERNATIONAL JOURNAL OF AUTOMOTIVE TECHNOLOGY}, author={Fang, T. and Coverdill, R. E. and Lee, C. -F. F. and White, R. A.}, year={2009}, month={Jun}, pages={285–295} }
 @article{fang_coverdill_lee_white_2009, title={Low-temperature combustion within a HSDI diesel engine using multiple-injection strategies}, volume={131}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955321033&partnerID=MN8TOARS}, DOI={10.1115/1.3093999}, abstractNote={Low-temperature compression ignition combustion employing multiple-injection strategies in an optical high-speed direct injection diesel engine was investigated. Heat release characteristics were analyzed. The whole cycle combustion process was visualized by imaging the natural flame luminosity. The NOx emissions were measured in the exhaust pipe. The effects of the pilot injection timing, pilot fuel quantity, main injection timing, operating load, and injection pressure on the combustion and emissions were studied. Low-temperature combustion modes were achieved by using a small pilot injection with an injection timing much earlier than top dead center (TDC) followed by a main injection after TDC. The results were compared with conventional diesel (diffusion) combustion for comparison purposes. A premixed-combustion-dominated heat release rate pattern was seen for all the low-temperature combustion cases, while a typical diffusion flame combustion heat release rate was obtained for the conventional combustion case. A highly luminous flame was observed for the conventional combustion condition while a much less luminous flame was seen for the low-temperature combustion cases. For the higher-load and lower injection pressure cases, liquid fuel being injected into low-temperature premixed flame was observed for certain cases. Compared with the conventional diffusion combustion, simultaneous reductions in soot and NOx were obtained for the low-temperature combustion mode under similar operating loads. For high-load conditions, higher NOx emissions were obtained due to higher in-cylinder temperatures. However, compared with the conventional combustion case, a significant reduction in soot was achieved for the high-load conditions, which shows that increasing injection pressure greatly reduces soot emissions.}, number={6}, journal={Journal of Engineering for Gas Turbines and Power}, author={Fang, T. and Coverdill, R.E. and Lee, C.F. and White, R.A.}, year={2009} }
 @inproceedings{fang_coverdill_lee_white_2009, title={Low-temperature combustion within a HSDI eiesel engine using multiple-injection strategies}, volume={131}, number={6}, booktitle={Journal of Engineering for Gas Turbines and Power}, author={Fang, T. G. and Coverdill, R. E. and Lee, C. F. F. and White, R. A.}, year={2009} }
 @article{fang_zhang_yao_2009, title={Slip MHD viscous flow over a stretching sheet - An exact solution}, volume={14}, ISSN={["1878-7274"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67349181009&partnerID=MN8TOARS}, DOI={10.1016/j.cnsns.2009.02.012}, abstractNote={In this paper, the magnetohydrodynamic (MHD) flow under slip condition over a permeable stretching surface is solved analytically. The solution is given in a closed form equation and is an exact solution of the full governing Navier–Stokes equations. The effects of the slip, the magnetic, and the mass transfer parameters are discussed. Results show that there is only one physical solution for any combination of the slip, the magnetic, and the mass transfer parameters. The velocity and shear stress profiles are greatly influenced by these parameters.}, number={11}, journal={COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION}, author={Fang, Tiegang and Zhang, Ji and Yao, Shanshan}, year={2009}, month={Nov}, pages={3731–3737} }
 @inproceedings{fang_lee_2009, title={Soot visualization in an optical diesel engine fueled with diesel and bio-diesel fuels using multiple injection strategies}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84946563690&partnerID=MN8TOARS}, booktitle={Fall Meeting of the Eastern States Section of the Combustion Institute 2009}, author={Fang, T. and Lee, C.-F.F.}, year={2009}, pages={431–445} }
 @article{fang_zhang_2009, title={Thermal boundary layers over a shrinking sheet: an analytical solution}, volume={209}, ISSN={0001-5970 1619-6937}, url={http://dx.doi.org/10.1007/s00707-009-0183-2}, DOI={10.1007/s00707-009-0183-2}, number={3-4}, journal={Acta Mechanica}, publisher={Springer Science and Business Media LLC}, author={Fang, Tiegang and Zhang, Ji}, year={2009}, month={Jun}, pages={325–343} }
 @article{fang_lee_2009, title={Three-dimensional wall-bounded laminar boundary layer with span-wise cross free stream and moving boundary}, volume={204}, ISSN={["0001-5970"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67349269485&partnerID=MN8TOARS}, DOI={10.1007/s00707-008-0032-8}, number={3-4}, journal={ACTA MECHANICA}, author={Fang, Tiegang and Lee, Chia-fon F.}, year={2009}, month={May}, pages={235–248} }
 @article{fang_zhang_yao_2009, title={Viscous flow over an unsteady shrinking sheet with mass transfer}, volume={26}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-66149140214&partnerID=MN8TOARS}, DOI={10.1088/0256-307x/26/1/014703}, abstractNote={The unsteady viscous flow over a continuously shrinking surface with mass suction is studied. The solution is fortunately an exact solution of the unsteady Navier–Stokes equations. Similarity equations are obtained through the application of similarity transformation techniques. Numerical techniques are used to solve the similarity equations for different values of the mass suction parameters and the unsteadiness parameters. Results show that multiple solutions exist for a certain range of mass suction and unsteadiness parameters. Quite different flow behaviour is observed for an unsteady shrinking sheet from an unsteady stretching sheet.}, number={1}, journal={Chinese Physics Letters}, author={Fang, Tiegang and Zhang, J. and Yao, S.-S.}, year={2009} }
 @article{fang_liang_lee_2008, title={A new solution branch for the Blasius equation-A shrinking sheet problem}, volume={56}, ISSN={["1873-7668"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55649105432&partnerID=MN8TOARS}, DOI={10.1016/j.camwa.2008.07.027}, abstractNote={In this work, a similarity equation of the momentum boundary layer is studied for a moving flat plate with mass transfer in a stationary fluid. The solution is applicable to the practical problem of a shrinking sheet with a constant sheet velocity. Theoretical estimation of the solution domain is obtained. It is shown that the solution only exists with mass suction at the wall surface. The equation with the associated boundary conditions is solved using numerical techniques. Greatly different from the continuously stretching surface problem and the Blasius problem with a free stream, quite complicated behavior is observed in the results. It is seen that there are three different solution zones divided by two critical mass transfer parameters, f01≈1.7028 and f02≈1.7324. When f0<f01, there is no solution for this problem, multiple solutions for f01<f0≤f02, and one solution when (f0=f01)∪(f0>f02). There is a terminating point for the solution domain and the terminating point corresponds to a special algebraically decaying solution for the current problem. The current results provide a new solution branch of the Blasius equation, which is greatly different from the previous study and provide more insight into the understanding of the Blasius equation.}, number={12}, journal={COMPUTERS & MATHEMATICS WITH APPLICATIONS}, author={Fang, Tiegang and Liang, Wei and Lee, Chia-fon F.}, year={2008}, month={Dec}, pages={3088–3095} }
 @article{fang_2008, title={A note on the unsteady boundary layers over a flat plate}, volume={43}, ISSN={["0020-7462"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-53949093932&partnerID=MN8TOARS}, DOI={10.1016/j.ijnonlinmec.2008.06.010}, abstractNote={The unsteady boundary layer over a semi-infinite flat plate was investigated in this paper. The flow involves the unsteady flow over a flat plate with leading edge accretion or ablation. The momentum boundary layer was further analyzed and it was shown that the leading edge ablation had a similar effect to the wall mass injection or upstream wall movement making the fluid blown away from the wall. The thermal boundary layer of the same flow was also studied. Results show that the leading edge accretion or ablation can greatly change the fluid motion and the heat transfer characteristics.}, number={9}, journal={INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS}, author={Fang, Tiegang}, year={2008}, month={Nov}, pages={1007–1011} }
 @article{fang_zhang_2008, title={An exact analytical solution of the Falkner-Skan equation with mass transfer and wall stretching}, volume={43}, ISSN={["0020-7462"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-53949123916&partnerID=MN8TOARS}, DOI={10.1016/j.ijnonlinmec.2008.05.006}, abstractNote={In this paper, an exact analytical solution of the famous Falkner-Skan equation is obtained. The solution involves the boundary layer flow over a moving wall with mass transfer in presence of a free stream with a power-law velocity distribution. Multiple solution branches are observed. The effects of mass transfer and wall stretching are analyzed. Interesting velocity profiles including velocity overshoot and reversal flows are observed in the presence of both mass transfer and wall stretching. These solutions greatly enrich the analytical solution for the celebrated Falkner-Skan equation and the understanding of this important and interesting equation.}, number={9}, journal={INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS}, author={Fang, Tiegang and Zhang, Ji}, year={2008}, month={Nov}, pages={1000–1006} }
 @article{fang_2008, title={Boundary layer flow over a shrinking sheet with power-law velocity}, volume={51}, ISSN={["1879-2189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55549111187&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2008.04.067}, abstractNote={In this work, the boundary layers over a continuously shrinking sheet with a power-law surface velocity and mass transfer were investigated. Based on the boundary layer assumptions, the similarity equations with a controlling parameter β were obtained and solved numerically. Theoretical analysis was conducted for certain special conditions and exact solutions were derived for β = −1 and β = −2 and also for the power index m=-1. Numerical techniques were used to solve the similarity equation for other parameters. Quite different and interesting solution behaviors were found for a shrinking sheet compared with a stretching sheet. Multiple solutions were obtained for certain mass transfer parameter and controlling parameter β. Velocity overshoot near the wall and near the boundary layer edge were observed for certain solution branches. The current results for a power-law shrinking sheet offer quite interesting nonlinear behaviors and greatly enrich the solution and understanding of boundary layers.}, number={25-26}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Fang, Tiegang}, year={2008}, month={Dec}, pages={5838–5843} }
 @article{lin_lee_fang_2008, title={Characterization of particle size distribution from diesel engines fueled with palm-biodiesel blends and paraffinic fuel blends}, volume={42}, ISSN={["1873-2844"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-38749116563&partnerID=MN8TOARS}, DOI={10.1016/j.atmosenv.2007.10.046}, abstractNote={Biodiesels are promoted as alternative fuels and their applications in diesel engines have been investigated by many researchers. However, the particle size distribution emitted from heavy-duty diesel engines fueled with palm-biodiesel blended with premium diesel fuel and paraffinic fuel blended with palm-biodiesel has seldom been addressed. Thus, five test fuels were used in this work to study the particle size distribution: D100 (premium diesel fuel), B100 (100% palm-biodiesel), B20 (20 vol% palm-biodiesel+80 vol% D100), BP9505 (95 vol% paraffinic fuel+5 vol% palm-biodiesel) and BP8020 (80 vol% paraffinic fuel+20 vol% palm-biodiesel). A Micro-Orifice Uniform Deposit Impactor (MOUDI) equipped with aluminum filters was used to collect size-resolved samples. Experimental results indicated that palm-biodiesel blends and paraffinic fuel blends could improve combustion efficiency in diesel engines, but pure palm-biodiesel could cause incomplete combustion. Adding palm-biodiesel to diesel fuel would slightly increase particles with diameter <0.31 μm but paraffinic fuel blends could decrease particles with diameter <1 μm. The mass median diameter of overall particles (MMDo) and σg,o are 0.439 μm and 3.88 for D100; 0.380 μm and 3.24 for B20; 0.465 μm and 4.22 for B100; 1.40 μm and 4.92 for BP9505; 1.46 μm and 2.25 for BP8020. There are more particles with low aerodynamic diameters (diameter <0.31 μm) in the exhaust of D100, B20 and B100 fuels. On the other hand, a greater fraction of particulate matter of BP9505 and BP8020 existed in coarse particles (diameter: 2.5–10 μm). Energy efficiency also increases significantly by 12.3–15.1% with the introduction of paraffinic fuel blends into the engine. Nevertheless, paraffinic fuel blends also reduce the emission of particulate matters by 36.0–38.4%. Carbon monoxide was decreased by 36.8–48.5%. Total hydrocarbon is 39.6–41.7% less than diesel fuel combustion. Nitrogen oxides emission is about 5% lower for paraffinic fuel. These results show that paraffinic fuel can be very competitive and replaced diesel fuels in the future.}, number={6}, journal={ATMOSPHERIC ENVIRONMENT}, author={Lin, Yuan-Chung and Lee, Chia-Fon and Fang, Tiegang}, year={2008}, month={Feb}, pages={1133–1143} }
 @article{fang_coverdill_lee_white_2008, title={Effects of injection angles on combustion processes using multiple injection strategies in an HSDI diesel engine}, volume={87}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-48049084976&partnerID=MN8TOARS}, DOI={10.1016/j.fuel.2008.05.012}, abstractNote={Effects of injection angles and injection pressure on the combustion processes employing multiple injection strategies in a high-speed direct-injection (HSDI) diesel engine are presented in this work. Whole-cycle combustion and liquid spray evolution processes were visualized using a high-speed video camera. NOx emissions were measured in the exhaust pipe. Different heat release patterns are seen for two different injectors with a 70-degree tip and a 150-degree tip. No evidence of fuel-wall impingement is found for the first injection of the 150-degree tip, but for the 70-degree tip, some fuel impinges on the bowl wall and a fuel film is formed. For the second injection, a large amount of fuel deposition is observed for the 70-degree tip. Weak flame is seen for the first injection of the 150-degree tip while two sorts of flames are seen for the first injection of the 70-degree tip including an early weak flame and a late luminous film combustion flame. Ignition occurs near the spray tip in the vicinity of the bowl wall for the second injection events of the 150-degree tip, however, it is near the injector tip in the central region of the bowl for the 70-degree tip. The flame is more homogeneous for the 150-degree tip with higher injection pressure with little soot formation similar to a premixed-charge-compression-ignition (PCCI) combustion. For other cases, liquid fuel is injected into flames showing diffusion flame combustion. More soot luminosity is seen for the 70-degree tip due to significant fuel film deposition on the piston wall with fuel film combustion for both injection events. Lower NOx emissions were obtained for the narrow-angle injector due to the rich air–fuel mixture near the bowl wall during the combustion process. Increasing injection pressure leads to increased NOx emissions for both injection angles because of the relatively leaner and faster combustion process with higher in-cylinder temperature for the increased injection pressure.}, number={15-16}, journal={Fuel}, author={Fang, Tiegang and Coverdill, R.E. and Lee, C.-f.F. and White, R.A.}, year={2008}, pages={3232–3239} }
 @article{fang_2008, title={Energy absorption heating and ignition of energetic solids}, volume={22}, ISSN={["0887-8722"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-42949119175&partnerID=MN8TOARS}, DOI={10.2514/1.32608}, abstractNote={Nomenclature Ka = absorption coefficient, 1/cm k = thermal conductivity,W= cm K q = absorbed radiant flux,W=cm T = temperature, K T0 = initial temperature, K Ts = ignition temperature, K t = time, s ts = ignition time, s X = dimensionless coordinate normal to surface, positive into a sold, x= 1=Ka x = coordinate normal to surface, positive into solid [cm] = thermal diffusivity, cm=s = dimensionless temperature, T T0 = q=kKa s = in-depth absorption parameter or dimensionless ignition temperature, Ts T0 = q=kKa = dimensionless time, t K a s = dimensionless ignition time, ts K 2 a}, number={2}, journal={JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER}, author={Fang, Tiegang}, year={2008}, pages={313–315} }
 @article{fang_2008, title={Flow and heat transfer characteristics of the boundary layers over a stretching surface with a uniform-shear free stream}, volume={51}, ISSN={["0017-9310"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-41649101258&partnerID=MN8TOARS}, DOI={10.1016/j.ijheatmasstransfer.2007.11.013}, abstractNote={In this work, the momentum and thermal boundary layers over a continuously stretching surface with a uniform-shear free stream were investigated. Based on the boundary layer assumptions, the similarity equations were obtained, which were solved numerically. Theoretical analysis was conducted for certain special conditions. The solution domain for the momentum boundary layer was theoretically estimated and compared with the numerical results. It is found that the interaction of uniform-shear free stream and the wall stretching velocity greatly affects the fluid motion and heat transfer characteristics. Dual solutions exist for the stretching parameter γ > γc = −0.596985. There is one solution for γ = γc and no solution for γ < γc. The effects of the Prandtl number, Pr, the temperature power index, m, and the wall stretching parameter, γ, on the heat transfer behaviors were analyzed and discussed. A general exact analytical solution of thermal boundary layers was derived for non-stretching wall condition with γ = 0 and arbitrary values of Pr and γ. Analytical solutions were also given for m=-23 and m = 0 with arbitrary values of Pr and m. Interesting observations were found for negative wall stretching parameter, negative temperature power index, and the lower solution branch.}, number={9-10}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Fang, Tiegang}, year={2008}, month={May}, pages={2199–2213} }
 @article{fang_zhang_2008, title={Flow between two stretchable disks - An exact solution of the Navier-Stokes equations}, volume={35}, ISSN={["0735-1933"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-56349127272&partnerID=MN8TOARS}, DOI={10.1016/j.icheatmasstransfer.2008.04.018}, abstractNote={In this work, an exact solution for the steady state Navier–Stokes equations in cylindrical coordinates is presented by similarity transformation technique. The solution involves the flow between two stretchable infinite disks with accelerated stretching velocity. The similarity equation was solved numerically and the effects of disk stretching parameter and stretching Reynolds number were studied. With the increase of the stretching Reynolds numbers, the fluid begins with a creeping type flow at R = 0 to a typical boundary layer type flow for large Reynolds numbers. The pressure parameter β changes from a positive number to a negative value with the increase of non-zero stretching parameter. The upper wall stretching parameter also greatly affects the velocity distribution between the two disks with a downward net flow for γ ≠ 1. The results are also useful as a benchmark problem for the validation of three-dimensional numerical computation code.}, number={8}, journal={INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER}, author={Fang, Tiegang and Zhang, Ji}, year={2008}, month={Oct}, pages={892–895} }
 @inproceedings{fang_coverdill_lee_white_2008, title={Low temperature combustion within an HSDI diesel engine using multiple injection strategies}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44949247502&partnerID=MN8TOARS}, DOI={10.1115/ICEF2007-1747}, abstractNote={Low Temperature Compression Ignition (LTCI) combustion employing multiple injection strategies in an optical High-Speed Direct Injection (HSDI) diesel engine was investigated in this work. Heat release characteristics were analyzed through the measurement of in-cylinder pressure. The whole cycle combustion process was visualized with a high-speed digital video camera by imaging natural flame luminosity and three-dimensional-like combustion structures were obtained by taking flame images from both the bottom of the optical piston and the side window simultaneously. The NOx emissions were measured in the exhaust pipe. The effects of pilot injection timing, pilot fuel quantity, main injection timing, operating load, and injection pressure on the combustion and emissions were studied. Low temperature combustion mode was achieved by using a small pilot injection with an injection timing much earlier than TDC followed by a main injection after TDC. For comparison, experiment of a diffusion diesel combustion case was also conducted. Premixed-combustion-dominated heat release rate pattern was seen for all the low temperature combustion cases, while a typical diffusion flame combustion heat release rate was obtained for the conventional combustion case. Highly luminous flame was observed for the conventional combustion condition while much less luminous flame was seen for the low temperature combustion cases. For the higher load and lower injection pressure cases, liquid fuel being injected into low temperature premixed flame was observed for certain cases, which was different from the conventional diesel combustion with liquid fuel injected into hot premixed flame. Compared with the conventional diffusion diesel combustion, simultaneous reduction of soot and NOx was obtained for the low temperature combustion mode at both the same and increased injection pressure with similar operating load. For high load conditions, higher NOx emissions were obtained than the low load conditions with the same injection pressure due to a higher in-cylinder temperature under high load conditions with more fuel burned. However, compared with the diffusion combustion mode with a lower load at lower injection pressure, a significant reduction of soot was achieved for the high load conditions, which shows that increasing injection pressure greatly reduce soot emissions.}, booktitle={Proceedings of the 2007 Fall Technical Conference of the ASME Internal Combustion Engine Division}, author={Fang, T. and Coverdill, R.E. and Lee, C.-F.F. and White, R.A.}, year={2008}, pages={343–353} }
 @article{fang_coverdill_lee_white_2008, title={Low temperature premixed combustion within a small bore high speed direct injection (HSDI) optically accessible diesel engine using a retarded single injection}, volume={9}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-53549102483&partnerID=MN8TOARS}, DOI={10.1007/s12239-008-0065-y}, number={5}, journal={International Journal of Automotive Technology}, author={Fang, Tiegang and Coverdill, R.E. and Lee, C.-F.F. and White, R.A.}, year={2008}, pages={551–561} }
 @article{fang_coverdill_lee_while_2008, title={Low-sooting combustion in a small-bore high-speed direct-injection diesel engine using narrow-angle injectors}, volume={222}, ISSN={["0954-4070"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55749097615&partnerID=MN8TOARS}, DOI={10.1243/09544070JAUTO751}, abstractNote={ An optically accessible high-speed direct-injection diesel engine was used to study the effects of injection angles on low-sooting combustion. A digital high-speed camera was employed to capture the entire cycle combustion and spray evolution processes under seven operating conditions including post-top-dead centre (TDC) injection and pre-TDC injection strategies. The nitrogen oxide (NO x) emissions were also measured in the exhaust pipe. In-cylinder pressure data and heat release rate calculations were conducted. All the cases show premixed combustion features. For post-TDC injection cases, a large amount of fuel deposition is seen for a narrower-injection-angle tip, i.e. the 70° tip, and ignition is observed near the injector tip in the centre of the bowl, while for a wider-injection-angle tip, namely a 110° tip, ignition occurs near the spray tip in the vicinity of the bowl wall. The combustion flame is near the bowl wall and at the central region of the bowl for the 70° tip. However, the flame is more distributed and centralized for the 110° tip. Longer spray penetration is found for the pre-TDC injection timing cases. Liquid fuel impinges on the bowl wall or on the piston top and a fuel film is formed. Ignition for all the pre-TDC injection cases occur in a distributed way in the piston bowl. Two different combustion modes are observed for the pre-TDC injection cases including a homogeneous bulky combustion flame at earlier crank angles and a heterogeneous film combustion mode with luminous sooting flame at later crank angles. In terms of soot emissions, NO x emissions, and fuel efficiency, results show that the late post-TDC injection strategy gives the best performance. }, number={D10}, journal={PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING}, author={Fang, T-G and Coverdill, R. E. and Lee, C-F F. and While, R. A.}, year={2008}, month={Oct}, pages={1927–1937} }
 @article{fang_lin_foong_lee_2008, title={Reducing NOx Emissions from a Biodiesel-Fueled Engine by Use of Low-Temperature Combustion}, volume={42}, ISSN={["1520-5851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-57649101964&partnerID=MN8TOARS}, DOI={10.1021/es8001635}, abstractNote={Biodiesel is popularly discussed in many countries due to increased environmental awareness and the limited supply of petroleum. One of the main factors impacting general replacement of diesel by biodiesel is NOx (nitrogen oxides) emissions. Previous studies have shown higher NOx emissions relative to petroleum diesel in traditional direct-injection (DI) diesel engines. In this study, effects of injection timing and different biodiesel blends are studied for low load [2 bar IMEP (indicated mean effective pressure)] conditions. The results show that maximum heat release rate can be reduced by retarding fuel injection. Ignition and peak heat release rate are both delayed for fuels containing more biodiesel. Retarding the injection to post-TDC (top dead center) lowers the peak heat release and flattens the heat release curve. It is observed that low-temperature combustion effectively reduces NOx emissions because less thermal NOx is formed. Although biodiesel combustion produces more NOx for both conventional and late-injection strategies, with the latter leading to a low-temperature combustion mode, the levels of NOx of B20 (20 vol % soy biodiesel and 80 vol % European low-sulfur diesel), B50, and B100 all with post-TDC injection are 68.1%, 66.7%, and 64.4%, respectively, lower than pure European low-sulfur diesel in the conventional injection scenario.}, number={23}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Fang, Tiegang and Lin, Yuan-Chung and Foong, Tien Mun and Lee, Chia-Fon}, year={2008}, month={Dec}, pages={8865–8870} }
 @article{fang_lin_foong_lee_2008, title={Spray and combustion visualization in an optical HSDI diesel engine operated in low-temperature combustion mode with bio-diesel and diesel fuels}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877178240&partnerID=MN8TOARS}, DOI={10.4271/2008-01-1390}, abstractNote={An optically accessible single-cylinder high-speed direct-injection (HSDI) Diesel engine equipped with a Bosch common rail injection system was used to study the spray and combustion processes for European low sulfur diesel, bio-diesel, and their blends at different blending ratio. Influences of injection timing and fuel type on liquid fuel evolution and combustion characteristics were investigated under similar loads. The in-cylinder pressure was measured and the heat release rate was calculated. High-speed Mie-scattering technique was employed to visualize the liquid distribution and evolution. High-speed combustion video was also captured for all the studied cases using the same frame rate. NOx emissions were measured in the exhaust pipe. The experimental results indicated that for all of the conditions the heat release rate was dominated by a premixed combustion pattern and the heat release rate peak became smaller with injection timing retardation for all test fuels. Bio-diesel fuels greatly affected the combustion process and emissions. The ignition and heat release rate peak occurred later with increasing bio-diesel content. Fuel impingement on the wall was observed for all of the conditions. The liquid penetration became longer and the fuel impingement was stronger with the increase of bio-diesel content in the fuel blends. For all the injection timings, lower soot luminosity was seen for bio-diesel blends than pure diesel fuel showing lower soot generation for bio-diesel fuels. However, the influence of bio-diesel blending ratio on the soot generation depended on specific injection strategy. The NOx emissions showed different trends. With conventional injection timing and late injection timing, the NOx emissions consistently increased with the increase of bio-diesel content. But for an early injection strategy, there was a trade-off between ignition delay and oxygen content in affecting the NOx emissions. For this early pre-TDC injection strategy, due to a higher in-cylinder temperature and a longer existence time of this high temperature, the NOx emission was much higher than the other two injection timings. Retarded post-TDC injection timing resulted in simultaneous reduction in soot and NOx emissions. By combining the injection timing optimization with bio-diesel fuel blending ratio, simultaneously reduction of soot and NOx can be realized in practical engines.}, journal={SAE Technical Papers}, author={Fang, T. and Lin, Y.-C. and Foong, T.M. and Lee, C.-F.F.}, year={2008} }
 @article{fang_2007, title={Author's reply to the Comment on “Influences of fluid property variation on the boundary layers of a stretching surface”}, volume={189}, ISSN={0001-5970 1619-6937}, url={http://dx.doi.org/10.1007/s00707-006-0390-z}, DOI={10.1007/s00707-006-0390-z}, number={3-4}, journal={Acta Mechanica}, publisher={Springer Science and Business Media LLC}, author={Fang, T.}, year={2007}, month={Oct}, pages={247–248} }
 @inproceedings{fang_lee_2007, title={Combustion in an optical diesel engine fueled with diesel and bio-diesel fuels using multiple injection strategies}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84946570101&partnerID=MN8TOARS}, booktitle={Fall Technical Meeting of the Eastern States Section of the Combustion Institute 2007 "Chemical and Physical Processes in Combustion"}, author={Fang, T. and Lee, C.-F.F.}, year={2007}, pages={145–158} }
 @article{fang_2007, title={Flow over a stretchable disk}, volume={19}, ISSN={["1070-6631"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-38049083740&partnerID=MN8TOARS}, DOI={10.1063/1.2823572}, abstractNote={In this work, an exact solution for the steady state Navier–Stokes equation in cylindrical coordinates is presented. The solution is an extension of the well-known von Kármán viscous pump problem to the configuration with a stretchable disk with or without rotation. The results also offer new examples for three-dimensional computation code validation.}, number={12}, journal={PHYSICS OF FLUIDS}, author={Fang, Tiegang}, year={2007}, month={Dec} }
 @article{fang_coverdill_lee_white_2007, title={Smokeless combustion within a small-bore HSDI diesel engine using a narrow angle injector}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77954441002&partnerID=MN8TOARS}, DOI={10.4271/2007-01-0203}, journal={SAE Technical Papers}, author={Fang, T. and Coverdill, R.E. and Lee, C.-F.F. and White, R.A.}, year={2007} }
 @article{fang_guo_lee_2006, title={A new iteration method with cubic convergence to solve nonlinear algebraic equations}, volume={175}, ISSN={0096-3003}, url={http://dx.doi.org/10.1016/j.amc.2005.08.020}, DOI={10.1016/j.amc.2005.08.020}, abstractNote={Abstract In this paper, a new iteration scheme is proposed to solve the roots of an algebraic equation f(x) = 0. Given an initial guess, x0, the roots of the equation can be obtained using the following iteration scheme: x n + 1 = x n + - f ′ ( x n ) ± f ′ 2 ( x n ) - 2 f ( x n ) f ″ ( x n ) f ″ ( x n ) . This iteration scheme has unique convergence characteristics different from the well-known Newton’s method. It is shown that this iteration method has cubic local convergence in the neighborhood of the root. Using this scheme, real or complex roots for specific algebraic equations can be found. Because there are two iteration directions, for a given initial guess, two solutions can be found for certain algebraic equations with multiple roots. Examples are presented and compared with other methods.}, number={2}, journal={Applied Mathematics and Computation}, publisher={Elsevier BV}, author={Fang, Tiegang and Guo, Fang and Lee, Chia-fon F.}, year={2006}, month={Apr}, pages={1147–1155} }
 @article{fang_guo_lee_2006, title={A note on the extended Blasius equation}, volume={19}, ISSN={0893-9659}, url={http://dx.doi.org/10.1016/j.aml.2005.08.010}, DOI={10.1016/j.aml.2005.08.010}, abstractNote={In a recent paper, the Blasius equation was extended to a nonlinear equation like af‴+ff″=0 with the prime denoting differentiation with respect to the similarity variable η and a being a constant parameter. The current note will show that the solution of the extended Blasius equation can be obtained from the original Blasius equation solution with a variable transformation technique. The observed phenomena in numerical solutions of previous published work are theoretically analyzed. The equation is also discussed for an arbitrary real parameter or complex parameters. It is further shown that the extended Blasius equation is a special form of the similarity equation of momentum boundary layers over a flat plate with a temperature dependent property.}, number={7}, journal={Applied Mathematics Letters}, publisher={Elsevier BV}, author={Fang, Tiegang and Guo, Fang and Lee, Chia-fon F.}, year={2006}, month={Jul}, pages={613–617} }
 @article{fang_coverdill_lee_white_2006, title={Combustion and soot visualization of Low Temperature Combustion within an HSDI diesel engine using multiple injection strategy}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877211771&partnerID=MN8TOARS}, DOI={10.4271/2006-01-0078}, journal={SAE Technical Papers}, author={Fang, T. and Coverdill, R.E. and Lee, C.-F.F. and White, R.A.}, year={2006} }
 @article{wang_fang_lee_2006, title={Comparisons of computed and measured results for a HSDI diesel engine operating under HCCI mode}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877438217&partnerID=MN8TOARS}, DOI={10.4271/2006-01-1519}, journal={SAE Technical Papers}, author={Wang, R.C. and Fang, T. and Lee, C.-F.F.}, year={2006} }
 @article{fang_lee_2005, title={A moving-wall boundary layer flow of a slightly rarefied gas free stream over a moving flat plate}, volume={18}, ISSN={0893-9659}, url={http://dx.doi.org/10.1016/j.aml.2004.08.006}, DOI={10.1016/j.aml.2004.08.006}, abstractNote={In the current work, the boundary layer flow of a slightly rarefied gas free stream over a moving flat plate is presented and solved numerically. The first-order slip boundary condition is adopted in the derivation. The dimensionless velocity and shear stress profiles are plotted and discussed. A theoretical derivation of the estimated solution domain is developed, which will give a very close estimation to the exact solution domain obtained numerically. The influences of velocity slip at the wall on the velocity and shear stress are also addressed.}, number={5}, journal={Applied Mathematics Letters}, publisher={Elsevier BV}, author={Fang, Tiegang and Lee, Chia-fon F.}, year={2005}, month={May}, pages={487–495} }
 @article{fang_lee_2005, title={Exact solutions of incompressible Couette flow with porous walls for slightly rarefied gases}, volume={42}, ISSN={0947-7411 1432-1181}, url={http://dx.doi.org/10.1007/s00231-005-0009-2}, DOI={10.1007/s00231-005-0009-2}, number={3}, journal={Heat and Mass Transfer}, publisher={Springer Science and Business Media LLC}, author={Fang, Tiegang and Lee, Chia-fon F.}, year={2005}, month={Sep}, pages={255–262} }
 @article{fang_coverdill_lee_white_2005, title={Liquid and vapor fuel distributions within a High Speed Direct Injection (HSDI) diesel engine operating in HCCI and conventional combustion modes}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877425830&partnerID=MN8TOARS}, DOI={10.4271/2005-01-3838}, journal={SAE Technical Papers}, author={Fang, T. and Coverdill, R.E. and Lee, C.-F.F. and White, R.A.}, year={2005} }
 @article{fang_coverdill_lee_white_2005, title={Low temperature combustion within a small bore high speed direct injection (HSDI) diesel engine}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877219266&partnerID=MN8TOARS}, DOI={10.4271/2005-01-0919}, journal={SAE Technical Papers}, author={Fang, T. and Coverdill, R.E. and Lee, C.-F.F. and White, R.A.}, year={2005} }
 @article{fang_2004, title={A note on the incompressible couette flow with porous walls}, volume={31}, ISSN={0735-1933}, url={http://dx.doi.org/10.1016/S0735-1933(03)00199-4}, DOI={10.1016/S0735-1933(03)00199-4}, abstractNote={Analytical solutions play important roles in the understanding of fluid dynamics and heat transfer related problems. Some analytical solutions for incompressible steady/unsteady 2-D problems have been obtained in literature, but only a few of those are found under heat transfer conditions (which brings more complexities into the problem). This paper is focused on the analytical solutions to the basic problem of incompressible unsteady 2-D laminar flows with heat transfer. By using the traveling wave method, fluid dynamic governing equations are developed based on classical Navier–Stokes equations and can be reduced to ordinary differential equations, which provide reliable explanations to the 2-D fluid flows. In this study, a set of analytical solutions to incompressible unsteady 2-D laminar flows with heat transfer are obtained. The results show that both the velocity field and the temperature field take an exponential function form, or a polynomial function form, when traveling wave kind solution is assumed and compared in such fluid flow systems. In addition to heat transfer problem, the effects of boundary input parameters and their categorization and generalization of field forming or field evolutions are also obtained in this study. The current results are also compared with the results of Cai et al. (R. X. Cai, N. Zhang. International Journal of Heat and Mass Transfer, 2002, 45: 2623-2627) and others using different methods. It is found that the current method can cover the results and will also extend the fluid dynamic model into a much wider parameter ranges (and flow situations).}, number={1}, journal={International Communications in Heat and Mass Transfer}, publisher={Elsevier BV}, author={Fang, Tiegang}, year={2004}, month={Jan}, pages={31–41} }
 @article{fang_2004, title={Further Discussion on the Incompressible Pressure—Driven Flow in a Channel with Porous Walls}, volume={31}, ISSN={0735-1933}, url={http://dx.doi.org/10.1016/S0735-1933(04)00030-2}, DOI={10.1016/S0735-1933(04)00030-2}, abstractNote={The unsteady velocity profiles for a pressure-driven Poiseuille flow in a channel with porous walls under mass transfer is analyzed and solved exactly. The steady state temperature distribution with viscous dissipation is also derived and solved exactly. The influences of mass transfer on transient velocity and state steady temperature profiles are presented and discussed. The wall heat transfer characteristics are also analyzed}, number={4}, journal={International Communications in Heat and Mass Transfer}, publisher={Elsevier BV}, author={Fang, Tiegang}, year={2004}, month={May}, pages={487–500} }
 @article{fang_2004, title={Influences of fluid property variation on the boundary layers of a stretching surface}, volume={171}, ISSN={0001-5970 1619-6937}, url={http://dx.doi.org/10.1007/s00707-004-0125-y}, DOI={10.1007/s00707-004-0125-y}, number={1-2}, journal={Acta Mechanica}, publisher={Springer Science and Business Media LLC}, author={Fang, T.}, year={2004}, month={Jul}, pages={105–118} }
 @article{fang_2004, title={Similarity Solutions for Heat Conduction in a Semi-Infinite Medium with Power Law Thermal Conductivity}, volume={31}, ISSN={0735-1933}, url={http://dx.doi.org/10.1016/S0735-1933(04)00029-6}, DOI={10.1016/S0735-1933(04)00029-6}, abstractNote={Similarity transformation technique is applied to a general 1-D heat conduction problem for a semi-infinite media with arbitrary temperature dependent thermal conductivity. The general similarity equation is derived. The attention is paid to a commonly used power law thermal conductivity assumption. The similarity equation is simplified and solved for power law thermal conductivity. The temperature distribution and wall heat fluxes for both wall heating problem and wall cooling problem are solved and discussed for arbitrary power indices}, number={4}, journal={International Communications in Heat and Mass Transfer}, publisher={Elsevier BV}, author={Fang, Tiegang}, year={2004}, month={May}, pages={477–485} }
 @article{mathews_fang_coverdill_lee_white_2004, title={Soot diagnostics using laser-induced incandescence within an optically accessible HSDI diesel engine}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877213195&partnerID=MN8TOARS}, DOI={10.4271/2004-01-1412}, journal={SAE Technical Papers}, author={Mathews, W.S. and Fang, T. and Coverdill, R.E. and Lee, C.-F.F. and White, R.A.}, year={2004} }
 @article{fang_2004, title={The hydromagnetic flow over an oscillating flat plate with arbitrary periodic oscillation}, volume={31}, ISSN={0093-6413}, url={http://dx.doi.org/10.1016/S0093-6413(03)00084-3}, DOI={10.1016/S0093-6413(03)00084-3}, abstractNote={Abstract In this paper, the hydromagnetic flow over a flat plate with arbitrary periodic oscillation is solved exactly. The solution is also applicable for common incompressible viscous flow over a flat plate with arbitrary oscillation. It is found that the penetration of hydromagnetic flow will decrease with increasing non-dimensional magnetic parameter M. The transient part will die away after a certain time for a specific M. The solution will collapse into the steady-state case after a long time. However, for non-hydromagnetic flow, there will be no steady-state solution if the coefficient of the zero-frequency component is not zero.}, number={1}, journal={Mechanics Research Communications}, publisher={Elsevier BV}, author={Fang, Tiegang}, year={2004}, month={Jan}, pages={129–135} }
 @article{fang_2004, title={Unsteady solution of viscous fluid flow in an infinite cylinder with a variable body force}, volume={16}, ISSN={1070-6631 1089-7666}, url={http://dx.doi.org/10.1063/1.1628689}, DOI={10.1063/1.1628689}, abstractNote={In this Brief Communication, the unsteady viscous flow with a variable body force in an infinite cylinder is solved exactly. The solution describes the transient velocity profiles and pressure gradients, which can be used in the application of sedimentation of spherical particles in viscous fluid. The current solution is compared with the previously solved problem between two infinite parallel plates. It is found that, for a similar body force, the central-line velocity of the cylinder will be greater than that of the two-infinite-plate case. But the slip velocity at the wall of cylinder will be smaller than that of the flow between two infinite plates. The transient pressure gradients are also different, resulting in a smaller value for the cylindrical case with a similar body force.}, number={1}, journal={Physics of Fluids}, publisher={AIP Publishing}, author={Fang, Tiegang}, year={2004}, month={Jan}, pages={200–203} }
 @article{fang_2003, title={A new approximation method to evaluate thermal contrast}, volume={44}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037882110&partnerID=MN8TOARS}, DOI={10.1016/S1350-4495(02)00210-4}, abstractNote={A new approximate approach is developed to evaluate the thermal contrast detected by a thermal detector or a quantum detector for a focal plane radiation-detecting instrument. Simple formulas for the detected thermal contrast are obtained. Two terms are included in the thermal contrast. The first term is based on the derivative of emissivity with respect to temperature. The second term is based on the temperature-dependent emissivity. The results can give a more straightforward relationship of these two terms than the previous methods. It is more useful in practical applications than the previous results. The relative error between the current approximation and the previous method is also assessed. It is found that the error will be less than 1% when λT<3000 μm K. Based on the new results, the influences of the two terms are investigated regarding some aspects including lower limit wavelength, wavelength interval of the detector and type of detectors. Although the computed examples are in infrared spectra and room temperature, the analysis and results can be applied to other wavelength and temperature, too. Application to internal combustion engines is also investigated.}, number={3}, journal={Infrared Physics and Technology}, author={Fang, T.}, year={2003}, pages={191–198} }
 @article{fang_2003, title={Further discussion on the optimun temperature of efficiency of production for blackbody radiation}, volume={30}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037257325&partnerID=MN8TOARS}, DOI={10.1016/S0735-1933(03)00006-X}, abstractNote={In this paper, the exact equation governing the optimum temperature of efficiency of blackbody radiation production for a certain wavelength interval is obtained. The new formula is compared with the previous result, and it is found that, under certain condition, the new equation will collapse into the previous theory. The dependence of optimum temperature and the error between the two formulas on lower limit wavelength and bandwidth are also discussed.}, number={1}, journal={International Communications in Heat and Mass Transfer}, author={Fang, T.}, year={2003}, pages={47–52} }
 @article{fang_2003, title={Further study on a moving-wall boundary-layer problem with mass transfer}, volume={163}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0042973084&partnerID=MN8TOARS}, DOI={10.1007/s00707-002-0979-9}, number={3-4}, journal={Acta Mechanica}, author={Fang, T.}, year={2003}, pages={183–188} }
 @article{fang_2003, title={General discussion on displacement law of radiation}, volume={30}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0043068111&partnerID=MN8TOARS}, DOI={10.1016/S0735-1933(03)00111-8}, abstractNote={The Wien's displacement law is generalized to the situations for a certain wavelength interval and non-blackbody radiator. The theory results in a closed form equation. The emissivity distribution can have great influences on the displacement law. The estimated temperature for given wavelengths may largely differ from those based on the Wien's displacement law and extended displacement law for blackbody radiation}, number={5}, journal={International Communications in Heat and Mass Transfer}, author={Fang, T.}, year={2003}, pages={737–743} }
 @article{fang_2003, title={New relationships for temperature sensitivity of radiation}, volume={30}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037353679&partnerID=MN8TOARS}, DOI={10.1016/S0735-1933(03)00028-9}, abstractNote={In this work, the temperature sensitivity of radiation is extended to a certain wavelength interval and is also classified into two categories including the Temperature Sensitivity of Radiators (TSR) and the Temperature Sensitivity of Radiation Detectors (TSRD). Both the exact relationships and the approximated theories are presented. It is found that for a gray-body radiator with temperature-independent emissivity, the TSR is the same as TSRD for an ideal thermal radiation detector. However, there exists difference between an ideal quantum detector and an ideal thermal detector. This extension makes the defined quantity easier to be used in a lot of applications such as the design of industrial furnace and radiation detectors.}, number={2}, journal={International Communications in Heat and Mass Transfer}, author={Fang, T.}, year={2003}, pages={173–184} }
 @article{fang_2003, title={Similarity solutions for a moving-flat plate thermal boundary layer}, volume={163}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0041470273&partnerID=MN8TOARS}, DOI={10.1007/s00707-003-0004-y}, number={3-4}, journal={Acta Mechanica}, author={Fang, T.}, year={2003}, pages={161–172} }
 @article{fang_2002, title={An extension of wien's displacement law for blackbody radiation}, volume={29}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036698919&partnerID=MN8TOARS}, DOI={10.1016/S0735-1933(02)00366-4}, abstractNote={The purpose of this study is to present statistics related to the integration of cloud and rain liquid water and the profiles for different cloud types and regimes. From 2010 to 2012, the CHUVA project collected information regarding cloud and rain characteristics in different precipitation regimes in Brazil. CHUVA had four field campaigns between 2010 and 2011, located in the North, Northeast and Southeast regions of Brazil, covering the semi-arid, Amazon, coastal and mountain regions. The synergy of several instruments allowed us to classify rain events and describe the cloud processes regionally. Microwave radiometers, LiDAR, radar, and disdrometers were employed in this study. The rain type classification was made using vertical profiles of reflectivity (VPR) and polarimetric variables from dual polarization radar (XPOL). The integrated liquid water (ILWC) for non-precipitating clouds was retrieved with a microwave ground-based radiometer using a neural network. For rainy conditions, the profiles from the rain liquid water content (LWCR) and their integrated (ILWR) properties were estimated by Micro Rain Radar (MRR) and XPOL VPRs. For non-precipitating clouds, the ILWC values were larger for the sites in tropical regions, in particular near the coast, than for Southeast Brazil. For rainy cases, distinct LWCR profiles were observed for different rain classifications and regions. The differences are small for low rain rates and a distinction between different rainfall regimes is more evident for high rain rates. Vale and Belém clouds present the deepest layers and largest convective rain rates. The clouds in the Southeast region of Brazil (Vale do Paraíba) and North region (Belém) showed the largest reflectivity in the mixed and glaciated layers, respectively. In contrast, the Northeast coastal site (e.g. Fortaleza) showed larger values in the warm part of the clouds. Several analyses are presented, describing the cloud processes and the differences among the cloud types, rain rates and regions.}, number={6}, journal={International Communications in Heat and Mass Transfer}, author={Fang, T.}, year={2002}, pages={757–761} }
 @article{fang_2002, title={Similarity solution of thermal boundary layers for laminar narrow axisymmetric jets}, volume={23}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036924116&partnerID=MN8TOARS}, DOI={10.1016/S0142-727X(02)00198-4}, abstractNote={In this work, the similarity equation describing the thermal boundary layers of laminar narrow axisymmetric jets is derived based on boundary layer assumptions. The equation is solved exactly. Some properties of the thermal jet are discussed. By introducing new-defined non-dimensional coordinates, the similarity solution results in a "universal" format. The results can also be applied in the boundary layer problem of species diffusion.}, number={6}, journal={International Journal of Heat and Fluid Flow}, author={Fang, T.}, year={2002}, pages={840–843} }
 @article{jansons_lin_fang_rhee_2000, title={Visualization of preflame and combustion reactions in engine cylinders}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877485919&partnerID=MN8TOARS}, DOI={10.4271/2000-01-1800}, journal={SAE Technical Papers}, author={Jansons, M. and Lin, S. and Fang, T. and Rhee, K.T.}, year={2000} }