Study of knock in a high compression ratio SI methanol engine using LES with detailed chemical kinetics

Methanol as an alternative fuel is considered to be one of the most favorable fuels for internal combustion engines. In this paper, knock in a high compression ratio SI (Spark Ignition) methanol engine was studied by using LES (Large Eddy Simulation) coupled with detailed chemical kinetics. A 21-species, 84-reaction methanol reaction mechanism was adopted to simulate the auto-ignition and combustion process of the methanol/air mixture. The results showed that the end-gas auto-ignition first occurred in the place near the chamber wall because of the higher temperature and pressure. The evolution of OH radicals was essentially the same with the evolution of in-cylinder temperature. OH radicals could be a good temperature indicator. The concentration of HCO radicals was almost negligible during knocking combustion. There existed two effects for CH2O, OH, and H2O2, which were generation and consumption. The reaction intensities of CO, CH2O, H2O2, and OH species were higher than other species during knocking combustion.