Particulate matter emission from different combustion modes in a 2/4 stroke switchable direct injection gasoline engine

Direct injection gasoline engines are staging a come-back because of its potential for improved fuel economy through principally the engine down-sizing by boosting or 2-stroke operation, and possibly stratified charge combustion or Controlled Auto Ignition (CAI) at part load operations. Due to the limited time available for complete fuel evaporation and the mixing of fuel and air mixture, locally fuel rich mixture or even liquid fuel can be present during the combustion process. This causes significant increase in Particulate Matter (PM) emissions from direct injection gasoline engines compared to the conventional port fuel injection gasoline engines, which are of major concerns because of its health implications. In this paper, the PM emissions of different combustion modes were measured from a unique direct injection gasoline engine that could be operated in both spark ignition and CAI combustion modes in either 4-stroke and 2-stroke cycle. In addition, ethanol and gasoline mixtures, E15 and E85, as well as gasoline, were used. PM emissions was sampled directly from the exhaust pipe and DMA. The effects of operating the engine using 2 and 4 strokes SI, CAI, E15 and E85 on PM emissions are presented and analysed.