Search

One possibility for onboard electricity generation in a hybrid vehicle is a free piston engine incorporating an integrated linear generator. This paper presents the modelling and development of the linear engine generator concept, where a linear electrical machine is physically integrated within a free piston engine. Details and results of a multi-physics simulation of this concept are given, with a focus on the design of the electric machine. It is shown that a short translator design can result in the highest power density. This also gives the opportunity for integrating the electric machine physically within the compressor. Details of a prototype demonstrator of the resulting generator-compressor are given.

In this study, a linear synchronous machine is compared with a linear transverse flux machine. Both machines have been designed and built with the intention of being used as the power take off in a free piston engine. As both topologies are cylindrical, it is not possible to construct either using just flat laminations and so alternative methods are described and demonstrated. Despite the difference in topology and specification, the machines are compared on a common base in terms of rated force and suitability for use as a generator. Experience gained during the manufacture of two prototypes is described.

the aim of this paper is to investigate the integration of a tubular linear electrical machine with a linear free-piston combustion engine in order to create a single integrated free piston engine generator. The performance of the engine when coupled to a long and short translator electrical machine is discussed. To simulate the dynamic performance of the overall system, an integrated thermodynamic, mechanical and electromagnetic model is required. LMS Amesim software is used to model the thermodynamic engine and electromechanical finite element analysis is used for the electrical machine. The overall performance of an engine coupled to electrical machines with varying translator length is investigated. The performance of such a tubular generator is demonstrated by measurements on a 7-pole/6-slot prototype machine. The short translator generator design appears to perform better in terms of performance and capital cost, based on the dynamic simulation results of the system.

Free-piston engines have the potential to offer a compact machine capable of delivering electrical power. In this work, the design and modelling of a linear tubular generator are presented and used to investigate the effect of the electrical machine design on engine performance. A cogging-force-reduction technique is presented and used as a case study to demonstrate the importance of the integrated design.

In a free piston engine, the translator of a linear generator is coupled directly to the moving cylinder of a thermodynamic engine. For a linear machine to have a constant active area, either the translator or the stator must be oversized. The length of the translator effects its mass, which in turn effects the engine performance. This paper investigates the effect of translator length on the overall power density of a free piston engine coupled to a cylindrical permanent magnet machine.