PULSAR achievements: Heat source architecture and Stirling converter

The goal of WP2 is to establish a conceptual design and study of the energy production unit of the PULSAR ASRG, including the heat source and Stirling converter. This design would then be subject to trade-off assessments to define an optimal operating point with the current design limits.

To begin, a review on the state of the art of heat-to-electricity conversion systems and their efficiency for space applications was implemented. The study covered both static and dynamic systems. The different systems are then compared by means of performance indicators, such as efficiencies and Technology Readiness Levels (TRL), alongside an evaluation of the presence and status of European R&D within the respective domains. This analysis confirmed that the dynamic Stirling engine could offer the best compromise in terms of efficiency for the limited thermal power expected for the heat source.

Next, a computer-assisted design of of a heat source was built and parametrized, based on the NASA’s General Purpose Heat Source (GPHS). The parametrization was included to allow implementing dimensional evolutions regarding PULSAR specific requirements, and performing sensitivity studies to anticipate the fact that Europe will probably not have access to the materials developed and used by NASA. Thermal-mechanical calculations for nominal and accidental calculations were performed to map the temperatures in the module (figure). The computed temperature was always below critical values, including in accidental calculations.?

In parallel, a state-of-the art review provides a comprehensive summary of the evolution, operation, and understanding of the free piston Stirling Engine for aerospace application. First, the features of a first thermodynamic cycle were assessed about an optimal operating point estimated by 原子力? 代替エネルギー庁 . To reach the expected performances, a preliminary Stirling converter technology and design was developed. Modelling of this converter implemented the preliminary design specificity (geometry, heat exchangers and regenerator, materials, working gas, thermodynamic parameters, mechanical stability). The design of the heat exchanger of the cold sink was found to be of great importance. The preliminary mechanical design was then established. The design will need to be reviewed as the geometries of the interfaces with the hot and cold sources were not consolidated.

Finally, the design of the PULSAR Stirling engine was optimized, with a focus on achieving the targeted electrical power output while ensuring that the engine operates efficiently and has a prolonged lifespan. Through this detailed analysis and tradeoff process, valuable insights into the design and improvement of Stirling engines were gained, allowing to place confidence in this conversion technology for optimal efficiency.