Reduced Chemical Kinetic Model of Toluene Reference Fuels for HCCI Combustion

Abstract

We developed a reduced kinetic model for toluene reference fuel (TRF) including 70 species and 196 reactions for homogeneous charge compression ignition (HCCI) combustion. The low temperature reaction scheme for the TRF was based on the existing low-temperature reaction mechanism developed by Tanaka for primary reference fuel (PRF) oxidation. We added skeletal reactions for PRF oxidation to a reduced toluene sub-mechanism. The high-temperature reaction mechanism was mainly from the previous work of Patel and an important TRF reaction [H+O2+M=O+OH+M] was added. Validation of the ignition delay time was performed for single-component, two-component and three-component fuels and the results were satisfactory for HCCI engine conditions. A comparison of various experimental data available in the literature, including shock tube tests and HCCI engine experiments, shows that the present TRF mechanism performs well. A sensitivity analysis at the moment of maximum heat production shows that the reaction of phenol radicals (C6H5) with O2 is more sensitive as the pressure increases. Formaldehyde (HCHO) is a very important intermediate species and should not be neglected.