Full-time domain analysis on operating characteristics of free piston Stirling generator

Abstract

Free piston Stirling generator (FPSG) has been focused increasingly as energy conversion device for space nuclear power plants due to its long life and maintenance-free characteristics. For the purpose of predicting the operating characteristics and describing the inherent mechanisms of FPSG, experiments have been conducted based on a 1 kW prototype. Pressure fluctuations, pistons’ displacements, phase angle between displacer and power piston, hot and cold end temperatures, etc. were obtained during the experiments. Moreover, a full-time domain numerical model was proposed based on the physical processes experienced by all components within the generator. The comparisons between numerical results and experimental results showed that the relative errors are within 13.1% for the pistons’ amplitudes, 11.7% for the terminal voltage and 3.6% for the operating frequency. The thermodynamic, kinetic and electrical characteristics of the prototype were further analyzed. Some imperceptible phenomena were revealed, including the transient characteristics of heat absorption and rejection, hysteresis loss on the displacer rod and leakage loss at the balancing orifices. A detailed energy distribution scheme was plotted and it can provide guidance for the design and manufacture of subsequent generators of the same type.