关键词：汽车；发动机；仿真分析
摘 要：We set up one cylinder of CNG engine by using GT-Power software and the compression ratio and the knock are studied.The conclusions are as follows:when the compression ratio increases,the rate of pressure rise of acute burning period increases; The maximum cylinder pressure increases;The maximum temperature decreased slightly and after burning period the temperature increases;The critical knocking compression ratio appears at the full load of 4000rpm conditions; If we only consider it knocking or not,the engine compression ratios can change from 10 to 11.