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

Principal Investigator: Angela Violi, University of Michigan, avioli(at)umich.edu
Faculty: Jason Martz, University of Michigan
Post-Doc: Paolo Elvati, University of Michigan
Student: Doohyun Kim, University of Michigan
Government: Peter Schihl, Nickholas Johnson, U.S. Army TARDEC
Industry: Justin Kollien, Detroit Diesel/Daimler

JP-8 has replaced diesel fuel 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.

The current work represents a combined approach, employing both engine experiments and comprehensive, high fidelity JP-8 computational fluid dynamics (CFD) combustion modeling. In our previous experimental work, JP-8 was compared with DF-2, and the resulting impact on combustion, performance and emissions were analyzed. Further experiments are proposed to characterize the impact of JP-8 of diesel combustion, performance and emissions. The previous modeling work identified preliminary chemical kinetic mechanisms along with the need for multicomponent surrogate fuel capability for the use of realistic JP-8 surrogates. Computational studies and visualization of fundamental aspects of combustion and emission formation, both spatially and temporally will be used to provide 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 JP-8 spray and combustion, using state-of-the-art chemical kinetics.
  • Develop new chemical kinetic schemes and surrogate composition(s) in order to better simulate combustion with JP-8 fuels of varying CN.
  • Perform engine experiments to further assess the impact of JP-8 fuel variation, including CN. Perform engine experiments with both real and surrogate JP-8 compositions to assess the performance of the JP-8 surrogates relative to the real fuels.
  • 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.