Dynamic model of the external heat engine of the spacecraft power system

To ensure the possibility of designing modern spacecraft power supply systems based on Stirling engines, computational tools are needed to simulate their work in a wide range of modes, to take into account the influence of the subsystems on each other and on the final characteristics of the propulsion. This paper creates a thermodynamic model of a Stirling free-piston engine, taking into account the hydraulic losses in the elements of the thermal circuit. The model is based on an isothermal approximation. The model was implemented in Matlab. The system of differential equations was integrated using the 4-th order Runge-Kutta method. An objectives database has been prepared for the validation of a mathematical model in the power range from 1 to 50 kW. The article presents the basic equations for the mathematical model and computational schemes, as well as some results of numerical simulation and validation results. The deviations obtained between the calculated and experimental data on the magnitude of the amplitudes and phases of the movement of the pistons do not exceed 8%, which is a fairly good result for models of this class. The model developed can be used in the early stages of spacecraft design for a preliminary assessment of the main indicators of the Stirling engine.