Combustion Behavior and Fuel Economy of Modern Heavy-Duty Diesel Engine Using JP8 and Alternative Fuels

Work began in 2011 and was completed in 2015.

JP-8 has replaced diesel fuel (DF-2) as the single battlefield fuel used by the military in the diesel engines of nearly all tactical ground vehicles. Using JP-8 in diesel engines offers significant benefits, such as less fouling of the fuel injection system and potentially lower soot emissions, and thus an attenuated visual signature. However, JP-8 has lower volumetric calorific value than diesel, which translates to higher fuel consumption and shorter range. In addition, the cetane number (CN) of JP-8 is highly variable. JP-8 ignition delays increase when the cetane number of JP-8 is lower than that of DF-2, potentially leading to misfire and a compromise in the ability of an engine to start reliably. Also the high volatility and low cetane number of JP-8 translates to more vigorous combustion, resulting in knocking and potential damage to the piston.

This work represented a combined approach, employing both engine experiments and comprehensive, high fidelity JP-8 computational fluid dynamics (CFD) combustion modeling. Experiments were conducted to characterize the impact of JP-8 of diesel combustion, performance and emissions. Computational studies and visualization of fundamental aspects of combustion and emission formation, both spatially and temporally provided further insight into the engine experiments, yielding valuable insights into the impact of using JP-8 as a fuel in military diesel engines.

The overarching goals of the project can be summarized as follows:

• Develop the framework for the CFD modeling of spray and combustion, using state-of-the-art chemical kinetics for JP-8 and JP-8 alternative fuels.
• Develop new chemical kinetic schemes and surrogate composition(s) in order to better simulate combustion with JP-8 and JP-8 alternative fuels of varying CN. Develop a reduced kinetic mechanism suitable for CFD application.
• Perform engine experiments to further assess the impact of JP-8 and JP-8 alternative fuel variations, including CN.
• Understand the impact of JP-8’s physical properties and chemical reactivity on the combustion, performance and emission characteristics of compression ignition engines through modeling and engine experiments.

Publications:

• Doohyun Kim, Jason Martz, Andrew Abdul-Nour, Xin Yu, Marcis Jansons, Angela Violi, A six-component surrogate for emulating the physical and chemical characteristics of conventional and alternative jet fuels and their blends, Combustion and Flame, v179, 2017, pp. 86-94
• Dongil Kang, Vickey Kalaskar, Doohyun Kim, Jason Martz, Angela Violi, André Boehman, Experimental study of autoignition characteristics of Jet-A surrogates and their validation in a motored engine and a constant-volume combustion chamber, Fuel, v184, 2016, pp. 565-580. doi:10.1016/j.fuel.2016.07.009
• Doohyun Kim, Jason Martz, Angela Violi, Effects of fuel physical properties on direct injection spray and ignition behavior, Fuel Volume 180, 2016, pp. 481-496.
• Ph.D. Dissertation by Doohyun Kim, “Conventional and Alternative Jet Fuels for Diesel Combustion: Surrogate Development and Insights into the Effect of Fuel Properties on Ignition”, University of Michigan, 2016. http://hdl.handle.net/2027.42/120818
• Yu, X., Luo, X., Jansons, M., Kim, D. et al., “A Fuel Surrogate Validation Approach Using a JP-8 Fueled Optically Accessible Compression Ignition Engine”, SAE Int. J. Fuels Lubr. 8(1):119-134, 2015. doi:10.4271/2015-01-0906
• Doohyun Kim, Jason Martz, Angela Violi, A surrogate for emulating the physical and chemical properties of conventional jet fuel, Combustion and Flame 161 (2014) 1489~1498
• Doohyun Kim, Jason Martz, Angela Violi, “A surrogate for emulating the physical and chemical properties of conventional jet fuel”, Combustion and Flame, Vol. 161, No. 6, , pp. 1489–1498, June 2014. doi:10.1016/j.combustflame.2013.12.015
• Doohyun Kim, Jason Martz, Angela Violi, “A surrogate for emulating the physical and chemical properties of jet fuel”, The 8th U.S. National Combustion Meeting (2013), Paper # 070IC-0269