Investigation of the chemical kinetics process of diesel combustion in a compression ignition engine using the large eddy simulation approach

Abstract

This work investigated the chemical kinetics processes of diesel combustion under compression ignition combustion conditions using the large eddy simulation approach. An overall reasonable agreement with the experimental combustion results was obtained. To further investigate the combustion details, a data-processing method was adopted to calculate and identify the representative reactions for the species consumption and heat release in each computational cell. It was found that during the initial ignition period, the combustion domain was primarily composed of three combustion regions, including the upstream exothermic region (Region 1), upstream endothermic region (Region 2), and downstream exothermic region (Region 3). The exothermic heat release in Region 1 and endothermic heat release in Region 2 were both dominated by the reaction C7H15O2-2 = C7H15-2 + O2, while Region 3 was dominated by the reaction HCO + O2 = CO + HO2, which laid the foundation for the further intense heat release process. The exhaust gas recirculation (EGR) has a significant effect on the heat release feature during the diffusion combustion process. For the high EGR case, the endothermic heat release was dominated by the reactions OH + H2 = H + H2O and C2H3(+M) = C2H2 + H(+M), rather than by the reaction C7H15O2-2 = C7H15-2 + O2 as at the low EGR rate.