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

Project completion 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. However, the specifications of JP-8 are much looser than DF-2, resulting in wide variations in composition. This is an important issue when it comes to designing an engine to handle such fuel composition variations in order to ensure reliable operability in all theaters. Previous studies lack detailed fundamental insight into the underlying physical phenomena of the combustion process.

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 CN 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 CN of JP-8 translates to more vigorous combustion, resulting in knocking and potential damage to the piston.

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, Angela Violi, “A surrogate for emulating the physical and chemical properties of jet fuel”, The 8th U.S. National Combustion Meeting, Paper # 070IC-0269
• 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
• 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
• Dongil Kang, Vickey Kalaskar, Doohyun Kim, Jason Martz, Angela Violi, Andre Boehman, “Experimental study of autoignition characteristics of Jet-A surrogates and their validation in a motored engine and a constant volume combustion chamber”, Fuel, Volume 184, Pages 565–580, 15 November 2016. doi:10.1016/j.fuel.2016.07.009
• Doohyun Kim, Jason Martz, Angela Violi, “The effect of liquid fuel properties on liquid penetration length and ignition delay of fuel spray under diesel-relevant conditions”, submitted to Fuel
• Doohyun Kim, Jason Martz, Andrew Abdul-Nour, Xin Yu, Marcis Jansons, Angela Violi, “An inclusive six-component surrogate for emulating the physical and chemical characteristics of conventional and alternative jet fuels and their blends”, submitted to 36th International Symposium on Combustion
• 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