Modelling and validation of a free piston expander-linear generator for waste heat recovery system

In this study, an air driven free piston expander-linear generator (FPE-LG) test rig and the FPE-LG simulation model based on GT-Suite/Simulink have been established. The simulation model is validated by experimental results. Afterwards, the performance of FPE-LG under different conditions and the influence of intake temperature on FPE-LG are conducted. Since the simulation results are in good agreement with the experiment results, this proves the rationality of the simulation model. When intake pressure and temperature rise, the in-cylinder volume increases. Furthermore, the displacement, velocity and acceleration increase with intake temperature. The peak voltage output of FPE-LG linearly increases when increasing the intake temperature and pressure. The peak voltage output is more sensitive to intake pressure than temperature. The higher the intake pressure is, the more obvious the intake temperature effects the peak voltage output. The maximum voltage output can reach up to 23.6 V. The peak power output demonstrates an initial increasing and then reducing trend with the external load resistance. And the maximum peak power output can reach up to 22.23 W when the external load resistance is 9 Ω and intake temperature is 373 K.