In order to better match the working conditions of the organic Rankine cycle (ORC) system for vehicle engine waste heat recovery, this paper aims to study the performance of the free piston expander-linear generator (FPE-LG) under variable operation conditions using a simulation model based on Matlab/Simulink software. Firstly, the effect of the mass of the free piston assembly (FPA) and internal resistance of the linear generator (LG) on the electromagnetic force, motion characteristics and output performance are discussed and analyzed. Secondly, the effect of the changing intake pressure and exhaust back pressure on the performance of the FPE-LG are investigated. The velocity reaches the maximum of 3.12 m/s when the intake pressure, operation frequency, external load resistance, mass of the FPA and the internal resistance of LG are 3 bar, 5 Hz, 9 Î©, 0.59 kg and 14.7 Î©, respectively. This study can provide a useful guidance for the application of the FPE-LG in the actual ORC system.
Keywords Organic Rankine cycle; Free piston expander-linear generator; Motion characteristics; Variable operation conditions; Output performance