Influence of fuel volatility on particulate matter emissions from a production DISI engine

Abstract

An investigation into the influence of fuel volatility on the resultant particulate matter (PM) emissions from a DISI engine is reported. Testing was performed at a steady-state highway cruise condition to investigate phenomena leading to seasonal changes in PM emissions observed in published roadside studies. Fuel volatility, which varies with season was the prime focus of the investigation, with a secondary goal of investigating the influence of ethanol blended fuels at the varied volatility levels. In tests with both surrogate and commercial fuels, high volatility fuels presented elevated emissions of both particle number (PN) and gravimetric mass emissions. Furthermore, the effect of 10% ethanol match-blending was investigated at both the high and low volatility conditions. Inclusion of ethanol in match-blended high volatility fuels was found to result in no significant change in PM emissions versus the neat fuel complement, while a considerable enhancement of PM emissions resulted from ethanol match-blending in low volatility fuels. Evidence from the literature, changes in the measured PN concentrations & size distributions over the length of a test, and post-run imaging of the fuel injector face, all suggest that an increase in intensity of flash-boiling conditions & fuel wetting of the injector tip drive the observed changes for the test conditions and engine architecture used in this study.