MODELING OF HEAT LOSS TO THE SPARK PLUG DURING EARLY FLAME GROWTH IN A SPARK IGNITION ENGINE

摘要

The effect of heat loss to the spark plug during the early flame growth was investigated by modeling flame initiation and early flame propagation around the spark plug. Flame size at initiation following spark breakdown was modeled by solving the one dimensional shock flow equation. Subsequent flame propagation was modeled by thermodynamic energy balance supplemented by submodels for flame speed and turbulence. The purpose of this study was to both qualitatively and quantitatively investigate the effect of heat transfer and spark energy on early flame propagation under changing engine variables of speed, load and fuel/air ratios. Results show that contact area varies appreciably when flame direction and velocities are changed leading to considerable difference in heat loss power. Further, existing flow velocities around spark plug cause a variation in the overall thermal diffusion process in its flame growth.