Fuel Property Effects on Particulates In Spark Ignition Engines

This paper focuses on particulate emissions from direct injection spark ignition engines running on controlled ethanol-gasoline splash-blended fuels. Study objectives include understanding the relationship between ethanol concentration and particulate emissions, as well as assessing the impact of distillation characteristics and aromatic content of the base fuel. Model year 2011 vehicles equipped with GM Ecotec, Ford EcoBoost, and Chrysler PentaStar engines were evaluated on FTP75 and US06 drive cycles. Both gravimetric and particle number data were recorded with the vehicles running on controlled splash-blended fuels with a range of ethanol concentrations. A high T90 commercial gasoline served as a template in defining a consistent gasoline fraction that was used in preparing many of the ethanol blends. A controlled gasoline was used to avoid distillation and aromatic content variability seen in commercial blends.

Test results show major reductions in both particulate mass and number with ethanol concentrations as low as 10%. Ethanol is believed to promote faster evaporation of wetted walls in situations of fuel-jet impingement, while also providing additional oxygen in fuel-rich diffusion flames. Fuel properties, including distillation characteristics and aromatic content, were shown to impact particulate emissions. Ethanol was shown to be highly effective in reducing particulate emissions caused by the presence of high boiling point aromatics in the gasoline fraction.