In-cylinder pressure of a 4-cylinder DI CNG engine was measured by a pressure sensor with spark plug .The maxi-mum in-cylinder pressure ,pressure rise rate ,heat release rate and cylinder temperature at different engine speeds ,loads and ig-nition advance angles were analyzed .The results show that the maximum in-cylinder pressure ,maximum pressure rise rate , maximum heat release rate and maximum cylinder temperature gradually decrease ,the combustion start point delays ,and the heat release rate decreases with the increase of speed at the same load .While the former first four parameters gradually increase with the increase of load at the same speed .In full load of 3 800 r/min ,the maximum in-cylinder pressure ,maximum cylinder pressure rise rate and maximum cylinder temperature gradually increase with the advance of ignition timing .At the angle of 34° ,the engine has the optimal power and fuel economy .%用火花塞式压电压力传感器测量1台4缸缸内直喷CNG发动机缸内压力，分析最大缸内压力、压力升高率、放热率及缸内温度等随转速、负荷和点火提前角的变化。结果表明：负荷一定时，随着转速升高，最大缸内压力、最大缸内压力升高率、最大放热率及缸内最高温度逐渐减小，燃烧始点推迟，放热速率减小；转速一定时，随着负荷增加，最大缸内压力、最大缸内压力升高率、放热率及缸内最高温度逐渐增加；转速为3800 r/min、全负荷时，随着点火提前角增加，最大缸内压力、最大缸内压力升高率及缸内最高温度逐渐增加，点火提前角为34°曲轴转角时发动机动力性及经济性最佳。
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