Study on breakdown voltage and minimum ignition energy of sparking system for free-piston linear generator

This paper is aimed at studying the breakdown voltage and minimum ignition energy of sparking system for the free-piston linear generator (FPLG). Combing the ignition characteristics and demands specifically for the FPLG system, the breakdown voltage and conduction duration of the primary coil are determined theoretically with the Townsend and Paschen Laws. A computational fluid dynamics (CFD) mode is developed to investigate the in-cylinder pressure and temperature at various igniting moments. The theoretical minimum ignition energy is determined with the laminar combustion theory, which contributes to the design and optimization of the sparking system. The effects of the ignition points and initial in-cylinder temperature on the breakdown voltage and minimum ignition energy are analyzed. The results show that advanced ignition contributes to decreasing the breakdown voltage and the conduction duration of the primary coil, meanwhile has no negative influence on the minimum ignition energy. However, rising initial in-cylinder temperature lowers the breakdown voltage, shortens the conduction duration of the primary coil and reduces the minimum ignition energy.