| Under the condition of constant injection pressure, the effects of the intake temperature, number of nozzles, injection timing, ignition timing, and methanol temperature on the combustion and emission characteristics of the direct-injection spark-ignition methanol engine during cold-starting are analyzed based on the orthogonal test and combined with numerical simulation. The results show that the injection timing and the number of nozzles have the greatest effect on combustion, followed by intake tem-perature and methanol temperature, and the ignition timing has the least effect. The delay of injection timing and the increase of the number of nozzles significantly reduces the oil film mass on the engine wall, while the increase of the intake temperature and the methanol temperature further promotes the evaporation of the methanol fuel and the consequent increase of the methanol vaporization rate, which accelerates the combustion and reduces the unburned methanol, formaldehyde, and HC emissions. According to the results of extreme variance analysis of orthogonal tests, the oil film mass is significantly reduced to 16.51mg, the methanol vaporization rate is increased to 94.38%, and the combustion efficiency is increased to 84.85% by optimizing the parameters. However, the emissions are not significantly reduced and the NOx emissions are slightly increased by the con-straints of the engine wall temperature. |
