Performance study of helium-air hybrid Stirling engine under parameters effect of temperature, pressure, rotational speed and working fluid composition

The Stirling engine is an external combustion engine that works with different thermal energies such as solar energy, biomass, fossil fuels, etc. The purpose of this study is to investigate various parameters to increase the performance of the helium-air hybrid Stirling engine. In this study, by three thermo-dynamics models, including isothermal, ideal adiabatic, and non-ideal adiabatic, a simulation was done for the Gama-type Stirling engine and their results were compared to experimental data. After determining the superior model, the effect of combining two helium and air gases at different percentages, the speed, the temperature, and the pressure was investigated and the sensitivity analysis of these parameters was performed, using the MINITAB software and the regression analysis. Obtained results of the sensitivity analysis showed when the percentage of helium from 0% to 35%, the power increases, and then by increasing the percentage of helium from 35% to 75%, the power is constant and from 75% to 100% the power starts to increase again. In total, by increasing the percentage of helium from zero to 100%, the power will increase by 42%. It was also found that by increasing the percentage of helium from zero to 100%, the efficiency will increase by 95%, and by increasing the percentage of helium from 0 to 100%, heat loss will be reduced by 35%.