Ion current combustion technology for controlled auto-ignition gasoline engines

The use of ionization sensors, by means of a standard spark plug, in gasoline engines is well known. This paper focuses on the use of these sensors for controlled auto-ignition (CAI) gasoline engines, where the air-fuel mixture ignites without the need of a spark. The averaged ion current signals obtained are first observed and compared to the heat release rate and then a method to detect with accuracy the location of the 50 per cent mass fraction burned is described. The variation of emissions is studied and the effects of using a pressure sensor (to calculate the heat release rate) or an ion current sensor are portrayed. Thus it is proved possible to keep the emissions under strict control by using an ion current sensor.