Effects of Fuel Properties on Particle Number and Particle Mass Emissions from Lean and Stoichiometric Gasoline Direct Injection Engine Operation 2019-01-1183
Engine-out particle size distributions and soot mass emissions were measured from a gasoline direct injection (GDI) engine fueled by seven different gasoline formulations to examine the impact of fuel properties on particle emissions. Additionally, particle size distributions were simultaneously measured downstream of a three-way catalyst wash-coated gasoline particulate filter (GPF) to determine size resolved filtration efficiency. Fuels were blended such that one of the following properties was varied while the others remained the same: volatility, aromatics content, and ethanol content. Stoichiometric, lean homogeneous, and lean stratified combustion modes were studied at four steady-state engine conditions, a constant speed load step, and an engine cold start. The particulate matter (PM) Index was calculated for each fuel as a function of the double bond equivalent and vapor pressure of the fuel components. Fuels with higher PM Indices resulted in higher engine-out PM emissions for engine conditions operating in the stoichiometric combustion mode. The lowest volatility fuel and the highest aromatic content fuel produced the highest PM emissions while the fuels with highest ethanol content and highest volatility produced the lowest emissions at stoichiometric conditions. However, under high-load lean homogeneous operation, the high ethanol content fuel produced significantly higher PM emissions than the other fuels. These results indicate that the PM Index alone is not sufficient to predict PM emissions when using highly oxygenated fuels in lean combustion modes. The GPF reduced the tailpipe particle number concentrations by 80 – 95% and showed evidence of passive regeneration under higher load lean engine conditions (Temp>500°C, Lambda>1.3).
Noah Bock, Joonho Jeon, David Kittelson, William Northrop
Univ. of Minnesota-Twin Cities, Univ of Minnesota-Twin Cities