Numerical analysis of knock during HCCI in a high compression ratio methanol engine based on LES with detailed chemical kinetics

In this study, knock during HCCI (homogeneous charge compression ignition) was studied based on LES (large eddy simulation) with methanol chemical kinetics (84-reaction, 21-species) in a high compression ratio methanol engine. The non-knocking and knocking combustion of SI (spark ignition) and HCCI engines were compared. The results showed that the auto-ignition spots were initially occurred near the combustion chamber wall. The knocking combustion burnt faster during HCCI than SI methanol engine. The HCO reaction rate was different from SI engine, it had two obvious peaks, one was positive peak, and another was negative peak. Compared with the SI methanol engine, in addition to the concentration of HCO, the concentrations of the other intermediate products and species such as CO, OH, CH2O, H2O2, HO2 were increased significantly; the reaction rates of CH2O, H2O2, and HO2 had negative peaks, and whose values were several times higher than SI methanol engine. (C) 2015 Elsevier Ltd. All rights reserved.