Thermodynamic-Dynamic coupling of a Stirling engine for space exploration

Abstract

As the new space era advances, there is an increasing demand for long-term missions beyond Earth’s orbit, such as on Mars and the Moon. The level of complexity of these missions is higher than conventional missions in terms of duration, particularly the energy demand required. To become viable, power generation systems must have a high power density, that is, high power associated with low mass. From this perspective, dynamic nuclear power generation systems coupled with electric propulsion are considered the most promising systems for deep-space exploration and colonization missions. Thus, to provide valuable information for the development of a dynamic energy conversion system for space, this study carried out thermodynamic modeling of a nuclear-powered Stirling cycle coupled with a dynamic engine model for space purposes. By means of numerical modeling, the constructive parameters of the Stirling engine, such as regenerator efficiency, compression ratio, heat exchanger thermal conductance, engine frequency, piston stroke, and area, are varied to understand the impact of these parameters on the final system performance. The results show that the regenerator efficiency can provide significant gains in the engine efficiency. However, a very high regenerator efficiency reduces the power of the cycle. The engine compression ratio tends to increase the engine efficiency, but a compression ratio above six provides marginal gains for cycle efficiency. From the results obtained, the best parameters yielded a system with a power output of 260.5 kW and a power density of 35.38 kg∙kW-1. This study can serve as a theoretical guideline for the future design of nuclear-powered Stirling engines for space applications, providing insight into the constructive parameters that influence the overall performance of the system.