A novel spark-plug for improved ignition in engines with gasoline direct injection (GDI)

Gasoline direct injection (GDI) is one of the future engine concepts offering a significant increase in efficiency of automotive engines. In this technique, the gasoline spray is directly injected into the combustion chamber, which yields a strongly inhomogeneous air-gasoline mixture. Hence, it is difficult to maintain reliable ignition using a conventional spark-plug. In this paper, a novel spark-plug based on a coaxial microwave resonator is presented. First, the design of the resonator is described. Then its capability of generating plasma in the pressure range up to 5 bar (3750 torr) is evaluated. Finally, some results of gasoline ignition experiments in a combustion chamber are presented.