The Impact of Fuel Ethanol Content on Particulate Emissions from Light-Duty Vehicles Featuring Spark Ignition Engines

Ethanol has long been a fuel of considerable interest for use as an automotive fuel in spark ignition (SI) internal combustion engines. In recent years, concerns over oil supplies, sustainability and geopolitical factors have lead multiple jurisdictions to mandate the blending of ethanol into standard gasoline. The impact of blend ethanol content on gaseous emissions has been widely studied; particulate matter emissions have received somewhat less attention, despite these emissions being regulated in the USA. Currently, in the EU particulate matter emissions from SI engines are partially regulated - only vehicles featuring direct injection SI engines are subject to emissions limits. A range of experiments was conducted to determine the impact of fuel ethanol content on the emissions of solid pollutants from Euro 5 passenger cars. All testing was conducted in BOSMAL's climate-controlled test facility, with tests performed at multiple ambient temperatures, including the two temperatures specified in EU legislation (+ 25 degrees C, -7 degrees C). Gravimetric (filter) and particle counting methods were used to quantify emissions, as well as particle size distribution profiles. A range of vehicles were tested, featuring both direct injection and port fuel injection SI engines. Where applicable, all testing was carried out in accordance with the demands of EU regulations; the New European Driving Cycle was used for all tests. Overall, results indicated the impact of ethanol content on exhaust emissions of particle mass to be relatively modest. Particle number and size distribution showed somewhat greater sensitivity to fuel ethanol content, highlighting their utility as research metrics. The implications of these observations and increasing pressure to switch to more sustainable energy sources for automotive propulsion are discussed.