Structural parameter optimization for free dual-piston linear generator based on impedance matching

This paper presents optimization method for structure parameters of free dual-piston linear generator (FPLG) that base on impedance matching of the generator. The free piston linear generator with dual-piston is composed of combustion chamber, linear generator, and load circuit, which is a thermo-mechanical-electrical nonlinear system with coupling effects. In order to optimize the output performance, this paper study the output characteristics of linear generators, and determine load impedance according to the equivalent circuit. After that, the equivalent stiffness of the combustion chamber is established, and the relevant structure parameters of combustion chamber are designed by iteration optimization. To evaluate the design method of coupled system, a numeric model is developed to simulate multiple cycles of the system. The Matlab/Simulink model is built with the thermodynamic model, thrust force model and dynamic model. In this investigation, the transient process of the system is analyzed, and the optimal structure parameters of FPLG are obtained. After optimization, the output power of the FPLG system was increased by 60%, and the output efficiency of the linear generator reached 93.27%.