Modeling And Experimental Verification Of Free Piston Linear Engine System

Free-piston linear generator(FPLG)is a kind of energy conversion equipment which couples free-piston engine(FPE)and linear motor.Its superior dynamic performance and economy make it a hot spot of current research.Because most of the research is oriented to the development of test prototype,the optimization of physical parameters of system structure,or the influence between permanent magnet linear generator and system is not fully taken into account in system modeling,but the research of permanent magnet linear generator lays more emphasis on motor body than on its application in FPLG system.Aiming at a compressed air-driven opposed free piston generator system,this paper considers fully the relationship and influence of its linear reciprocating motion,friction force,hydrodynamics and electromagnetic characteristics of permanent magnet linear generator,and establishes the simulation model of the system through the software of MATLAB/Simulink.The piston displacement,velocity,acceleration,thrust,pressure,generator voltage and their relationship are simulated and analyzed,and the motion characteristics of the system and the relationship between the influencing factors are obtained.A free piston linear engine system test platform was built.The reliability of the model and the accuracy of the analysis method were verified by comparing and analyzing the test data and simulation results.On this basis,the effects of piston group mass,intake and exhaust position on piston motion characteristics and different pressure on output voltage amplitude,waveform distortion and motor efficiency of permanent magnet linear generator are further studied.The results show that with the increase of pressure,the displacement,velocity and frequency of piston motion increase,while with the increase of piston mass,the maximum displacement increases,and the peak velocity and frequency decrease;with the decrease of the left or the increase of the right intake and exhaust position,the maximum displacement and peak velocity increase,frequency decrease,while the upper and lower stop points change slightly.Finally,the piston pressure and intake position at the highest efficiency of the generator are given.The experimental results verify the feasibility of the working principle of the free piston linear engine system,and provide reference and guidance for the follow-up research.