首先,通过分析四冲程发动机等容加热循环、等压加热循环和混合加热循环3个理论循环过程,得出循环热效率和循环平均压力两个指标的影响因素。然后,通过对发动机实际循环过程中进气、压缩、燃烧、膨胀和排气5个过程的研究,以及对柴油机的理论循环和实际循环的差异分析,总结了影响发动机实际循环过程中损失的因素。最后,强调了分析发动机循环过程对提高发动机的热效率具有重要意义。 First of all, by analyzing three theoretical circulation processes such as isothermal heating cycle, isothermal heating cycle and mixed heating cycle of four-stroke engine, the influencing factors of circulating thermal efficiency and circulating average pressure are obtained. Then, by studying the five processes of intake, compression, combustion, expansion and exhaust during the actual cycle of the engine, as well as the difference analysis of the theoretical cycle and the actual cycle of the diesel engine, the factors affecting the actual cycle loss of the engine are summarized . Finally, it is important to analyze the process of engine cycle to improve the thermal efficiency of the engine.