Dynamic response of a dual-opposed free-piston Stirling generator

Abstract

As a type of distributed power generation device, free-piston Stirling generator (FPSG) is characterised by compactness, high efficiency, and long life. This work devotes to exploring the dynamic response of a low-vibration dual-opposed FPSG by employing the newly-developed time-domain acoustic-electrical analogy (TDAEA) method. Transient evolutions of self-sustained oscillations are first exhibited, which contains the start-up and steady stages. An exploration on steady-state performance is then conducted, which shows the maximum thermal-to-electric efficiency of 46.6% with an electric power of 3.92 kW, implying its enormous potential in distributed power generation for low-vibration applications due to its dual-opposed configuration. Dynamic response with jump in external load and gradual variation in heating temperature are subsequently investigated in detail. The results indicate that an acute drop in electric resistance leads to an oscillation attenuation, particularly, a short circuit results in an emergency shutdown. With the heating temperature declining gradually, the oscillation attenuates and even stops. Based on these results, some general operating regulation principles for FPSGs are further concluded to avoid the cylinder striking as well as frequent start and stop. This study gives a deeper understanding on the dynamic characteristics of FPSGs, as well as broadens the usage of the TDAEA method.