Predicting particulate matter emissions from spray guided gasoline direct injection spark ignition engines

An index, linking fuel composition with Particulate Matter (PM) emissions (PN index) has been developed and is here evaluated with model fuels in a single cylinder, optical access, Spray Guided Direct Injection (SGDI) engine; the model fuels having independent control of the double bond content and volatility, as used in the index This index is investigated on three different engines: a single cylinder research engine, a V8 engine recently available in the market, and a current production supercharged V6 engine. A number of market gasolines have been tested across all three engines and all of the results follow the trends predicted by the PN index. Imaging of in-cylinder sprays shows the composition of model fuels affects the mixture homogeneity and their PM emissions; in particular the lack of a light-end in the model fuel composition can lead to misleadingly low PN emissions due to improved mixture preparation unrepresentative of market fuels. The index has been investigated in a Jaguar Land Rover V6 engine with five different fuels over a simulated NEDC and the results show the index trends are followed. Emissions have been evaluated from two fuels representing the EU5 reference-fuel specification that have been developed using the PN index to give a difference in PM emissions. The results from these fuels show that a difference in PN emissions of around a factor of two can be seen at both stoichiometric and rich conditions, for two fuels representative of the EU5 reference-fuel specification. This follows trends predicted by the PN index. This has important implications for policy makers and EU legislation, where PN emissions from gasoline vehicles will be regulated for the first time, as batch to batch variations in fuel composition would result in differing test results under the current legislation