Electrical machine design for use in an external combustion free piston engine

摘要

The work is focused on investigating the performance of a linear alternator for use with external combustion — free piston engine. This family of engine can be powered either from renewable sources, scavenging waste energy from other sources of heat, or bespoke combined heat and power plants. Finite element analysis optimisation techniques followed by development of a Matlab/Simulink model were used to investigate the effects of electrical machine inductance and the combined electromagnetic loading of the machine on the resulting force. Cogging force is showed to have the most effect on the resultant force fluctuation, whereas machine inductance has showed its effect at loads exceeding (76 %) of machine rating besides reshaping the resulting force profile. The model also accounts for machine loading and total efficiency variation over mechanical cycle. This enables the system designer to investigate the effect of actual machine model thrust force on the engine performance rather than assuming the electrical machine behaves as a simple damper.