Study of knock in a high compression ratio spark-ignition methanol engine by multi-dimensional simulation

Abstract

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 spark-ignition (SI) methanol engine was studied by using multi-dimensional simulation. Knocking combustion under various engine operating conditions were simulated, and the effects of spark timing, EGR (Exhaust Gas Recirculation) techniques, mixture concentration and combustion chamber shape for suppressing knock in a high compression ratio spark-ignition methanol engine were studied based on the multi-dimensional simulation analysis. The results showed that it could not fully suppress engine knock only by retarding spark timing methods because of the high compression ratio, with the increase of EGR rate, the knock intensity was found to be greatly suppressed and the peak pressure was reduced and postponed. Meanwhile, knock intensity had a maximum point, rich mixture and lean mixture can help reduce knock intensity and the knock occurrence timing was delayed. Finally, in order to reduce engine knock intensity, two feasible new combustion chambers were proposed.