Dynamic model of a free-piston Stirling engine with four degrees of freedom combined with the thermodynamic submodel

The work presents a dynamic model of the Stirling engine with a free piston, which was combined with a thermodynamic model taking into account isothermal heat exchange in the compression and expansion spaces. On the basis of the performed thermodynamic analysis for the Stirling engine working space, and of the physical model of the system with a free piston, a multidomain simulation model was developed, using the Matlab&Simulink software. On the basis of the derived equations of energy conservation for the thermodynamic model and equations of motion for the mechanical submodel, the influence of the selected thermodynamic and mechanical parameters, including: the influence of the mass of the displacer and piston on the p(V) closed-loop diagram was analysed and the influence of the thermodynamic parameters, including: temperature of the upper heat source on the theoretical work gain and the theoretical work. As a result of the conducted simulations, flow of the working gas mass at the control boundaries and also the curves of the heat fluxes, among other things, were additionally presented. The results presented in this work convey practical information about the thermodynamic and dynamic properties of the simulated object represented by the Stirling engine with a free piston.