Misfire detection and re-ignition control by ion current signal feedback during cold start in two-stage direct-injection engines

Abstract

A misfire detection and re-ignition control device based on an ion current signal is designed, and a method for calculating the threshold level of an ion current integral signal is proposed to judge a misfire event. Based on the combustion cycle control strategy, start-up combustion cycle misfire detection and re-ignition control are investigated in a TSDI-Two Stage Direct Injection gasoline engine using ion current signal feedback. The results show that it is feasible for the ion current integral signal to be used for misfire detection and re-ignition control. In the experiment, when the ion current integral signal is larger than the misfire threshold level (U_misfire>0.5 V), the ion current exists in the combustion chamber, the in-cylinder fuel–air mixture combusts, and the re-ignition event cannot occur. When the ion current integral signal is smaller than the misfire threshold level (U_misfire<0.5 V), the ion current is close to zero, the misfire event occurs, and re-ignition takes place. As far as hydrocarbon emissions are concerned, the level of unburnt hydrocarbons under successful ignition is lowest, the level of unburnt hydrocarbons under successful re-ignition is higher, and the level of unburnt hydrocarbons under unsuccessful ignition and re-ignition is the highest. Hence, the start-up combustion cycle misfire detection and re-ignition control based ion current signal feedback strategy is favorable for reducing unburnt hydrocarbon emissions.