A Modeling and Experimental Study of Initial Flame Kernel Development and Propagation in SI Engines 2000-01-0960
In spark ignition engines, the mechanism of transferring electrical energy from an ignition system into the mixture in the spark gap is controlled by many aspects. The major parameters of these aspects are inputs of electrical energy, combustion energy release, and heat transfers. Heat caused by combustion energy is transferred to the spark plug, cylinder head, unburned mixture, and others.
This study presents the development and validation of a flame kernel initiation and propagation model in SI engines, and most of the aspects described above are considered during the course of the model development. Furthermore, the model also takes into account the strain rate of the initial kernel and residual gas fraction.
The model is validated by the engine experiments, which are conducted in a constant volume combustion chamber. During the experiments, some test conditions are considered, and these conditions are as follows: air-fuel ratio, electrical characteristics of ignition systems, dwell time and spark plug gap. The velocity of the initial flame kernel development is measured by a laser deflection method.
From the simulation and experiment study, the following results are confirmed: the breakdown energy plays an important role in initial kernel development. As the dwell time is made longer, and the spark plug gap width is extended, the early flame propagation becomes faster.