Investigation of a high efficient free piston linear generator with variable stroke and variable compression ratio: A new approach for free piston engines

Abstract

Chemical energy can be converted to electricity with very high efficiencies by means of a free piston linear generator allowing a variable stroke and a variable compression ratio. Therefore online-downsizing in part-load is possible by reducing the stroke. As a result throttling, wall and friction losses are reduced. The paper describes the concept of the free piston linear generator, which is well suited for the HCCI-combustion process. It is expected that emissions and the fuel-consumption can be noticeable reduced. Calculations based on the NEDC indicate significant fuel savings for a mid-class car. Because of the non-existing mechanical coupling, cylinder cut-off can be realized very easily reducing the consumption of high power cars especially in urban drive cycles. The components linear generator and the gas spring have been built up and tested successfully. Examinations of the combustion process have begun on a fully variable electromagnetic valve-train test stand. A sophisticated adaptive control scheme is presented providing solid controls for the free-piston system. The paper describes the current status of the hardware development. © 2007 WEVA Journal.