根据朗肯循环发动机尾气余热回收系统中单阀式活塞膨胀机结构特点，建立了其工作过程仿真模型。4种工况下膨胀机缸压试验数据表明，模拟指示功率误差在0.99%-10%，工质水质量流量误差均在3%以内，验证了模型的有效性； 在此基础上，在进口压力5 MPa，进口温度520 ℃，转速1 950 r/min工况下，针对进排气结构参数对膨胀机性能的影响进行分析，得到了膨胀机指示功率、循环质量流量及绝热效率随进气顶杆高度和排气口高度变化的规律。

According to the structural characteristics of piston single valve expander in the waste heat recovery system of Rankine cycle engine, the working process simulation model was established. The test data of expander cylinder pressure under four working conditions shows that the simulated indication power error is between 0.99% and 10% and the water mass flow error is within 3% which verifies the validity of the model. Besides, the influences of inlet and exhaust structural parameters on expander performance are analyzed at inlet pressure of 5 MPa, inlet temperature of 520 °C and speed of 1 950 r/min and the changing laws of indicated power, cyclic mass flow and adiabatic efficiency of expander with the height of intake ejector pin and exhaust port were acquired.