Thermoacoustic hysteresis of a free-piston Stirling electric generator

Abstract

A panorama of thermoacoustic hysteresis of a free piston Stirling electric generator (FPSG) was studied, where a thermoacoustic networks approach was proposed to model the corresponding process. Of the featuring nonlinear phenomena inherent in an FPSG, thermoacoustic hysteresis occurs during the onset and damping evolvement, representing irreversibility and pertinent loss characteristics to some degree. In order to unveil the underlying mechanism, onset and damping experiments were conducted, on a lab-developed 5 kW FPSG prototype, under multiple operating conditions. The experimental results show that the damping temperature is significantly higher than the onset temperature, and dynamic parameters all experience a similar hysteresis curve against heating block temperature. It is found that larger initial heating power leads to higher onset temperature, while charge pressure exerts an opposite impact. So far, as the electric load resistance is concerned, the larger one leads to both lower onset and damping temperature. Based on the experiments, a frequency-domain thermoacoustic networks model was developed and validated, with a maximum deviation within 2.79% in onset temperature and −0.96% in onset frequency at various load resistance. Although the dynamic damping process is not reproduced in the current model, it provides a good way to predict the onset characteristics promptly.