Impact of ethanol blending on particulate emissions from a spark-ignition direct-injection engine

Particulate formation due to combustion of a wide range of ethanol-gasoline blends was investigated in a spark-ignition direct-injection (SIDI) engine. This study is a follow-up to a previous study done by the authors in which particulate formation for ethanol-gasoline blends was examined under fully premixed combustion, eliminating physical effects of the fuel. In this study, fuel was injected directly into the cylinder to investigate how the physical properties of the blended fuels influence particulate formation. The engine was operated at a fixed load, phasing, and equivalence ratio while end of injection timing was varied. The results of this work show that increasing ethanol content leads to a decrease in engine-out particulate in spite of, sometimes significant, changes in fuel properties. However, it was also shown that particulate results can be affected by engine operating history which, if not taken into account, could have implications for research and real world applications.