A Reduced Chemical Kinetic Mechanism for Low Temperature Diesel Combustion and Soot Emissions

A reduced diesel surrogate fuel chemical kinetic mechanism of n-heptane/toluene/1-hexene including poly-aromatic hydrocarbons (PAHs) formation was developed for prediction of the diesel combustion process and soot emissions. The proposed mechanism, which includes 60 species and 123 reactions, agrees well with experimental ignition delays in shock tubes. The proposed mechanism was coupled with the KIVA-3V Release 2 computational fluid dynamics (CFD) code to predict the combustion process and soot emissions in constant volume spray chamber and diesel direct injection combustion cases. The simulation results predict the combustion processes for diesel fuel under various conditions well. However, the predicted soot emissions have notable deviations compared to the experimental data when C2H2 or phenanthrene (A(3)) were chosen as precursors in the soot model at lower oxygen concentration conditions. The predicted soot emissions at different oxygen concentrations have better agreement with the experimental data when pyrene (A(4)) was chosen as the soot precursor. Compared to C2H2 or A(3), A(4) is a more suitable precursor for soot predictions in the LTC simulations. The overall results show that the present mechanism can be used to predict the combustion process and soot emissions of low temperature diesel combustion.