Applications of a multi-point Microwave Discharge Igniter in a multi-cylinder gasoline engine

Abstract

Microwave Discharge Igniter (MDI) is an ignition device that operates based on the microwave resonance phenomenon. Receiving the microwave pulses from a semiconductor generator, the MDI generates non-thermal plasma to enhance the combustion. A new igniter plug consists of multiple MDIs in its structure is developed to achieve leaner operation limit as well as higher dilution limit, which are essential strategies to meet current and future emission regulations. The prototype multi-point MDI plug contains 3 separate MDI port which are all connected and controlled by the semiconductor MW generator. The prototype 3-point MDI is tested in both a single cylinder performance engine and a production multi-cylinder engine. At target conditions of part load and low load, low engine speed, the multi-point MDI performs much better than single MDI and the traditional spark plug in both engines. In the performance engine, the 3-point MDI results in the shortest burn duration especially during the early stages. However, the 3-point MDI exceeds the lean running capability of the production engine when operate as a plug with two active MDI ports and hence the full potential of 3-point MDI currently exceed the current generation of production engines.