Effects of the initial flame kernel radius and EGR rate on the performance, combustion and emission of high-compression spark-ignition methanol engine

As clean fuel, methanol is considered to be one of the most promising alternative to conventional fuels for internal combustion engines. In this paper, a four-cylinder ignited methanol engine simulation model was built by using a one-dimensional simulation software. The methanol engine was converted from a diesel engine with a compression ratio of 17.5, and the methanol injector was installed in the inlet. Setting the engine speed as 2400 r/min, the effects of the initial flame kernel radius and EGR rate on the performance, combustion and emissions of methanol engine were studied when the throttle opening was 10%, 30%, 50%, 70% and 90%, respectively. The results showed that at any throttle opening, with the increase of EGR rate, the performance of the engine decreased, the in-cylinder combustion deteriorated, the NOx emission decreased significantly, but the HC and CO emission increased. At any throttle opening, the engine performance decreased slightly with the increase of the initial flame kernel radius, and the combustion was optimized. In terms of emission, when the throttle opening was between 10% and 70%, the NOx and CO emission decreased with the increase of the initial flame kernel radius. When the throttle opening was 90%, the NOx and CO emission increased with the increase of the initial flame kernel radius.