Effect of thermodynamic-dynamic parameters on the oscillation and performance of a free piston Stirling engine

This paper presents an analysis of the oscillation and parametric performance of a gamma-type free piston Stirling engine using a thermodynamic-dynamic nonlinear model. Firstly, the concept of oscillation and impact cylinder points is defined and a method for determining the stable oscillation zone of the free piston Stirling engine is proposed. Besides, the effects of various thermodynamic parameters on the system's performance, such as charging pressure, hot-end and cold-end temperatures, and dynamic parameters (such as the masses and spring stiffness of the displacer and piston), are investigated. The oscillation zone takes on a "V" shape when the piston and displacer masses or stiffness, and hot-end temperature and displacer stiffness, are varied. Finally, the output power and operating frequency of the impact cylinder line are determined. The results show that maximum output power and operating frequency of 75.36 W at 58.21 Hz or 76.73 W at 58.61 Hz are achieved at the "V" bottom when either the piston and displacer masses are adjusted or their stiffness properties are varied. Additionally, consistent output power and operating frequency of 125.35 W and 75.08 Hz, and 104.63 W and 68.59 Hz, are obtained regardless of changes in both displacer mass and stiffness.