Design and analysis of a novel yokeless mover permanent magnet linear generator for free piston engine converter

Abstract

Free piston engine generator (FPEG) is one of the recent solutions by researchers used in hybrid vehicles, which eventually can contribute to the reduction of environmental pollutants from public transports. The purpose of the this work is to introduce a novel dual-stator permanent magnet linear generator with yokeless mover (DSPMLG) to improve the key parameters of the linear generator used in FPEG systems. In this work, an analytical model of the DSPMLG magnetic field is developed to investigate magnetic field flux density distribution and for back-EMF prediction. Then, a two-dimensional (2D) model of the DSPMLG is put forth using the finite element method (FEM) to validate the analytical results. In the next section, 1D modelling and simulation of a two-stroke free-piston engine (FPE) with dual-piston structure is done using Ricardo’s WAVE software. The obtained results are used in the FEM simulation and prototype development in order to accurately evaluate the performance of the introduced generator in the FPEG system. Since the FPE velocity profile distorts the back-EMF, the effect of the velocity profile on back-EMF distortion is investigated using fast Fourier transform. Also, the DSPMLG is optimised for minimum back-EMF distortion, considering the maximum output power. To validate the simulation results, the DSPMLG is developed and the obtained experimental results have proper conformity with the simulation results. Finally, in order to weigh up the effectiveness of the proposed generator, its structure is compared with other reported structures in previous research studies based on the key indicators required for the linear generator used in FPEGs.