Operation Range of Generation Braking Force to Achieve High Efficiency Considering Combustion in a Free-Piston Engine Linear Generator System

Abstract

A linear generator system is expected to realize a highly efficient free-piston generation engine. The efficiency of the system mainly depends on the generation and thermal efficiencies of the engine. The generation efficiency decreases owing to a large braking force on the expansion stroke and a speed reduction at the ends of the stroke. This paper proposes generation control with resonance and output drop that improves the generation efficiency during the expansion stroke. When changing the amount of consumed fuel, the condition to maximize the electricity generation can be achieved by optimizing the ratio of the iron to copper losses. Furthermore, the proposed method improves the combustion performance of the engine by ensuring ideal speed at the combustion start position.