Multi-objective optimization of output power and stability of a free-piston Stirling engine using genetic algorithm

Today, with increasing consumption of non-renewable energy sources, scientists are looking for an alternative for these resources. The Stirling engine is one of the ideas that have recently attracted engineers' attention. The purpose of this study is to optimize the output power and stability of a beta type free-piston Stirling engine. In this regard, at first by deriving the thermodynamic and dynamic equations of the system and combining them, the governing equations are obtained including the nonlinear function of the pressure loss in heat exchangers. The governing nonlinear equations are solved and for the purpose of validation, simulation results obtained in this study are compared with experimental and simulation results presented in the literature. In free-piston Stirling engines, increasing the output power by keeping their stability is very important. Therefore, by performing parametric study, the parameters with more effects on the output power and stability are determined and considered as optimization variables. In order to perform multi-objective optimization of output power and stability of the free-piston Stirling engine, a proper objective function is selected and one of the methods in genetic algorithm is employed using optimization software Modefrontier. Finally, values of variables, before and after optimization and also, percentage of improvements in output power and stability of the free-piston Stirling engine are presented.