Determination of adequate regenerator for a Gamma-type Stirling engine

•A Gamma-Stirling engine is investigated to optimize its operation.•A stainless steel of a porosity of 85% was used as material for the regenerator.•Asymmetry of heat transfer inside regenerator’s consumes a part of produced energy.•Central composite rotatable design was adopted to minimize this phenomenon.•The heating temperature is a most significant factor in the study. This paper deals with an optimization of the Stirling engine regenerator’s. Firstly, different materials are experimented (Stainless Steel, Copper, aluminum and Monel 400). The engine performances and the state of each material after 15h of use are considered. The Stainless steel was the material that best satisfies these two conditions. Five regenerators in stainless steel with different porosities were manufactured and experimented (95%, 90%, 85%, 80% and 75%). Porosity that gives the best trade-off between maximizing the engine brake power, maximizing the heat transfer and minimizing the pressure drops, was retained. Thus, the regenerator in stainless steel with porosity of 85% was considered as the most suitable matrix maximizing the Stirling engine performances and minimizing heat and friction losses.