自由活塞斯特林发动机动力活塞气体作用效应

为了能够深入认识自由活塞斯特林发动机动力活塞的运行特性,找到提高自由活塞斯特林发动机效率的方法,对配气活塞固定不动时的动力活塞的气体作用效应进行了理论分析,并设计了动力活塞的单独运动实验,在此基础上提出了动力活塞自然频率的计算公式。研究了压缩腔压力波超前与滞后动力活塞位移两种情况下动力活塞受到的气体力的作用情况,采用旋转矢量法阐述了气体力的作用机理。当压力波超前或滞后活塞位移小于90°时,一部分气体力发挥了气体弹簧的作用,使系统自然频率增大;当压力波超前或滞后活塞位移大于90°但小于180°时,一部分气体力发挥了惯性力的作用,使系统自然频率减小,且热源温度越高,系统的自然频率越大。利用本实验室的一台自由活塞斯特林发动机进行实验,验证了上述气体力作用的效应与规律,利用此理论计算系统自然频率和实验相差不超过2%,使得斯特林发动机成功启动。

Investigation on Gas Effect of Piston for Free-Piston Stirling Engine

In order to have a deep understanding of the kinematical characteristics of the piston of free-piston Stirling engine and finding the way to increase the efficiency, the effects of gas force are analyzed. During the course of the experiment a new calculation method for natural frequency of piston is proposed. In this paper, the gas force acting on the piston is analyzed in the case of pressure leading or lagging displacement of piston. And the acting mechanism of gas force is stated by means of rotation vector decomposition. The results show that in the case of the pressure wave in advance or delaying the displacement of piston less than 90°, the gas spring and the mechanical spring are parallelarranged, so the natural frequency of the system increases.The gas force is regarded as gas inertia force, so the natural frequency of the piston decreases in the case of the pressure wave in advance or delaying the displacement of piston greater than 90°but less than 180°.The natural frequency of the piston increases with the temperature of the heat source. The above results are verified by an experimental test on a free-piston Stirling engine designed by our laboratory. Through the study, the free-piston Stirling engine has been started-up successfully.