Development of a Performance Analysis Model for Free-Piston Stirling Power Convertor in Space Nuclear Reactor Power Systems

Space nuclear reactor power system (SNRPS) is a priority technical solution to meet the future space power requirement of high-power, low-mass, and long-life. The thermoelectric conversion subsystem is the key component of SNRPS, which greatly affects the performance, quality, and volume of SNRPS. Among all kinds of proposed thermoelectric conversion technologies, the free-piston Stirling power converter (FPSPC) has become a preferred conversion technology for small-scale advanced SNPRS due to its moderate waste heat emission temperature and high conversion efficiency, mainly composed of a linear alternator and free-piston Stirling engine (FPSE). For studying the performance of FPSPC, a quasi-steady flow thermodynamic cycle analysis model considering parasitic heat losses has been developed for FPSE. And then the performance analysis model for FPSPC has been established by coupling the thermodynamic cycle analysis model with the mechanical motion model of the piston and volt-ampere characteristic model of the linear alternator. Furthermore, the analysis model was compared and validated by the GPU-3 Stirling engine’s experimental data. The performance parameters of Component Test Power Converter (CTPT) FPSPC designed by NASA for SNRPS were also analyzed. The results show that the amplitudes position of CTPC displacer and piston are 15.1 mm and 11.2 mm, respectively. The corresponding average electric power output of CTPC is 17.316 kW. The input thermal power to the CTPT heater is 66.1 kW, leading to the converter efficiency of 26.2%. The average current and voltage of the CTPC alternator are 86.38 A and 193.15 V, respectively. Among all kinds of parasitic energy losses, the regenerator heat loss accounts for the largest proportion, with an average of about 12.7 kW. The effects of cooler and heater temperature on the performance of CTPC FPSPC were also studied.