Ion current measurement for parameter estimation in small two stroke engines

Reduction of unburned hydrocarbon emissions and fuel economy improvements in two stroke engines, used on small portable tools for gardening or agriculture, rely on good insights into the combustion process and the engine operating parameters. Meaningful information about the engine operating parameters can be retrieved from ion current measurements. This article demonstrates an approach for monitoring the combustion process in two stroke engines by measuring the ion concentration during internal combustion. Especially the estimation of the air-fuel ratio (AFR) and the detection of misfire are made possible by this measurement concept. Due to lack of sensor placement space in these small engines the use of the conventional spark plug is advantageous. The results obtained by the ion measurement concept show that the optimization of the combustion process can be developed through simple means.