A novel approach towards the selection of regenerators for optimal Stirling engine performance based on energy and exergy analyses

Regenerators play a vital role in enhancing the overall performance of Stirling engines. Hence, this paper performed an energy and exergy analysis to elucidate the significance of regenerator characteristics concerning system performance, contributing to the optimal regenerator’s design and selection. The relationship between regenerator structure, regenerator exergy destruction, and output power, thermal efficiency, and exergy efficiency for Stirling engines was established by integrating the thermal model of Stirling engines with a mathematical model of regenerators. In contrast to cross-flow and parallel-flow regenerators, a novel concept of inclined-flow regenerators, featuring a matrix surface inclined in the direction of gas flow, was developed to achieve higher and more balanced engine output power and energy utilization efficiency. A comprehensive investigation was conducted into the effects of matrix structure types and regenerator geometries on the performance of both regenerators and engines. The results reveal that, following structural optimization, Stirling engines equipped with the inclined-flow regenerator demonstrate a substantial 16.6%, 38.3%, and 37.2% increase in power output, thermal efficiency, and exergy efficiency, respectively, compared to those equipped with cross-flow regenerators. In contrast, when compared to engines fitted with parallel-flow regenerators, they experience a 13.5% reduction in power output but achieve remarkable enhancements of 45.4% and 36.7% in thermal and exergy efficiency, respectively. This study introduces new insights into selecting regenerator structures for enhancing the output performance of Stirling engines.