Abstract
Free-piston engine coupled with linear generator is a research hotspot in the field of novel vehicle mounted power generation devices. A plate moving-magnet linear generator (PMMLG) is proposed and designed for free-piston engines in this paper. Magnetic circuit of the novel linear generator is analyzed and modeled in detail. The dimensions of a 2 kW prototype with the max stroke of 40 mm and the max electromagnetic force of 800 N is designed by using the derived magnetic circuit model. Static and transient electromagnetic field finite element models with motion solvers are created. Magnetic field distribution, electromagnetic force characteristics, EMF characteristics, coil inductance, generating power and losses of the linear generator are analyzed and compared with two reported prototypes. Computational fluid dynamics model of the PMMLG is established, and the temperature field is analyzed to verify that the air-cooling conditions can ensure long-term stable running of the linear generator without demagnetization. The research results show that the linear generator has the characteristics of low moving mass, low cogging force, high generating efficiency and high response speed.
Highlights
Energy crisis and environmental pollution nowadays are of great concern, which drive the transformation of the automotive industry
The mover of the plate moving-magnet linear generator (PMMLG) needs to be supported by shafts, so it cannot be made very large, but it is very suitable for free-piston engine generator (FPEG)
This paper presents a novel plate moving-magnet linear generator, which is developed for free-piston engines
Summary
Energy crisis and environmental pollution nowadays are of great concern, which drive the transformation of the automotive industry. As an important part of FPEG, the linear generator needs to meet the requirements of low moving mass, low cogging force, high generating efficiency, fast response and high controllability. This is because an increased moving mass will increase the inertia, reduce the operating frequency and increase the response. Yang [14] proposed a moving coil linear generator (MCLG) with the characteristics of low moving mass, fast response, high efficiency, and easy to control, but the power density of the MCLG is low. The moving-coil linear generator is a major research hotspot worldwide because of the characteristics of low moving mass, fast response, high efficiency and so on [16]. Since the main failure form of PM generators is demagnetization of the PM, a computational fluid dynamics (CFD) model of the moving-magnet temperature field will be established, the temperature rise characteristics of the moving-magnet will be studied to verify whether the linear generator can run continuously
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