Sensitivity analysis for objectives of power, efficiency, heat loss, and working fluid cost based on input parameters in the Stirling engine

The Stirling engine is a combustion engine that converts mechanical work into electricity. Stirling engine needs a working fluid to work and usually, air, helium, hydrogen, nitrogen, etc. are used. Among the mentioned operating fluids, only air is free, but unfortunately, it has lower power and efficiency compared to other working fluids. It is expected that the desired power and efficiency can be obtained at a lower cost by combining two working fluids such as air and helium. However, to check this issue, it is needed to analyze the sensitivity of different input parameters on the outputs. Therefore, in this study, the non-ideal thermodynamic model was investigated, and the results of the presented model were validated by experiments, and then with the help of Design Expert software, 1260 designs were considered. Finally, the effect of changes in input parameters such as the speed, gas injection pressure, temperature, and helium percentage on outputs such as power, efficiency, heat loss, and cost were investigated. It was found that the cost was only a function of the gas injection pressure and the percentage of the fluid composition. Moreover, the results showed that with the increase of the temperature, pressure, speed, and percentage of helium, the power increased by 189%, 178%, 82%, and 54%, respectively. With increasing the temperature, speed, and pressure, efficiency increased by 42%, decreased by 23%, and decreased by 17%, respectively. With the increase in the temperature, speed, and pressure, the heat loss increased by 85%, 71%, and 357%, respectively.