Investigation of a high efficient free piston linear generator with variable stroke and variable compression ratio

Abstract

Chemical energy can be converted to electricity with very high efficiencies by means of a free piston linear generator, which allows a variable stoke 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 also well suited for the HCCI-combustion process. Emissions and the consumption can be noticeable reduced. Calculations based on the NEDC indicate significat fuel savings for a compact car. Because of the non-existing mechanical coupling, cylinder cut-off can be practised 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. The examinations contain the gas exchange in two-stroke mode and the influence of the variable stoke and compression ratio on the combustion process. A sophisticated adaptive control scheme is presented which controls the whole system. The paper gives the actual status of the hardware development.