Study of Discharge under Swirl Flow and Combustion Conditions

Combustion at a high EGR (Exhaust Gas Recirculation) ratio is an effective means for improving the fuel efficiency of a gasoline engine. However, there is a problem that the combustion speed decreases. So, it is necessary to intensify the in-cylinder flow to ensure the combustion speed. The spark discharge generated by the ignition coil is strongly influenced by the in-cylinder flow. It forms an arcuate discharge path along the flow, and may blow off and re-discharge under a strong gas flow. The behavior of spark discharge strongly affects the ignition, and consequently affects the stability of combustion. However, the phenomena in a combustion chamber are very complicated because of various environmental conditions, and the discharge and combustion phenomena under a strong gas flow remain unclear. In this research, in order to study these phenomena, discharge and combustion experiments under flow using a constant volume container were performed. We observed discharge channel and length from the images obtained by high-speed camera, and calculated the discharge resistance from the voltage and current waveforms of the plug, and discussed the results. Also we performed the experiments by changing the flow velocity, Air/Fuel ratio, etc., and evaluated the follow-up property of the discharge to the flow and the change of the current value due to combustion. From these experimental results, the influence of each factor on discharge characteristics was clarified. We will report on the results of the experiments and discussions obtained in these studies and introduce the future prospects.