A semi-detailed chemical kinetic model of a gasoline surrogate fuel for internal combustion engine applications

Abstract

A semidetailed chemical kinetic mechanism (473 species and 1267 reactions) to describe the oxidation of a gasoline surrogate fuel consisting of n-heptane, iso-octane, toluene and diisobutylene (DIB) is developed. The model shows generally good agreement with the experimental ignition delay times measured in shock tubes for not only individual components but also their various mixtures over a wide range of temperatures and pressures. Although both simulations and experiments indicate toluene has a promoting effect on the auto-ignition of iso-octane in a specific region, the effect of toluene addition to isooctane is still not fully resolved. Nonetheless, it is found that the reactions of benzyl radical with allene are not important for the kinetic interactions. The measured laminar burning velocities of a research gasoline fuel, CR-87, can be well reproduced by using a TRF+DIB mixture (C6H5CH3/iC8H18/nC7H16/JC8H16, 45/25/20/10% by liquid volume) as a surrogate. In a homogeneous charge compression ignition (HCCI) engine, the model can capture the shift in resistance to auto-ignition for such TRF+DIB fuel when the operating conditions change. A sensitivity analysis shows the chemical origin of such shift cannot be solely explained based on the extent to which NTC (negative temperature coefficient) behavior is absent. The effect of decreasing the inlet temperature and increasing the inlet pressure is a result of the concerted action of manifold factors.