Numerical Simulation Study Of Electric Spark Ignition Process With Lean Mixture

For higher thermal efficiency and lower exhaust emissions,the leanburn spark-ignition engines have a bright future but are limited by the high cycle-by-cycle variations and low flame developing speed.The formation and development of the initial flame kernel has an important influence on the cycle-by-cycle variations of the lean-burn engines.So,it is necessary to carry out a detailed simulation study of the ignition process.In this paper,a Lagrangian ignition model is developed,which includes circuit sub model(breakdown voltage,breakdown energy,discharge current and gap voltage),kernel development sub model(kernel radius,mass and temperature)and combustion model.The results show that the ignition model developed in this paper can predict the development of initial flame kernel radius well.Combined with the experiment and simulation,the influence factors of the development of the initial fire kernel are analyzed,and the influence of the ignition strategies on the development of the initial fire kernel is studied with and without the initial flow field.By paralleling the ignition coils and controlling the charge and discharge process of each coil separately,different ignition strategies can be achieved,such as single coil discharge,four coils discharge in parallel,sequential discharge and continuous discharge.By changing the ignition strategy,the ignition energy can be changed.Experiments and simulations both show that increasing ignition energy can promote the development of the initial core.The Lagrangian ignition model developed in this paper can predict the development of the initial flame kernel under different conditions,and provide support for the study of the mechanism of the subsequent ignition process affecting the engine load cycle-by-cycle variations.