JP-8 is the primary aircraft fuel used by the United States Air Force. Today, the Single Battlefield Fuel policy mandates the use of JP-8 in ground vehicles in battlefield with compression ignition engines. However, the cetane number (CN) variation of jet fuels causes problems with optimal combustion phasing, cold start, misfire, durability and noise in compression ignition engines. Recently, computational fluid dynamic (CFD) modeling studies from Dr.Violi's research group at University of Michigan developed two accurate JP-8 surrogates (UM I, UM II), capturing the CN and property variations in the various types of jet fuels that can be used in Army ground vehicles, but these surrogates are not validated on any practical combustion platforms. Therefore, to provide validation experiments to compare elementary ignition behavior, a modified Cooperative Fuel Research (CFR) engine was tested where various equivalence ratios, compression ratios, and fuel and air intake temperature were employed, focusing on the chemical portion of the ignition delay of the surrogate fuel formulations in comparison with a practical JP-8 fuel (POSF-4658). Our group investigated the elementary ignition limit behavior including the percentage of low temperature heat release (%LTHR) the critical compression ratio (CCR) and the critical equivalence ratio (?crit) of each surrogate single compound, the UM surrogate JP-8 mixtures and the practical JP-8 fuel. Furthermore, condensed exhaust trapping and subsequent detailed chemical analysis highlighted the reaction pathways for a particular molecule. This study is intended to provide an intermediate step to validate simulations based on the surrogate fuel representation of JP-8 and the kinetic model to describe its combustion, contributing not only by supporting the ongoing work of Dr.Violi's research group on surrogate fuels development, but also by building a predictive engine simulation capability, resulting in the development of robust and efficient vehicle powertrains fueled with JP-8.

Reaction pathway and elementary ignition behavior of surrogates for JP-8 and alternative JP-8 fuels

247th National Meeting (2014)

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