Influence of different alternative fuels on particle emission from a turbocharged common-rail Diesel engine

Influence of alternative fuels on diesel engine exhaust particle emission was investigated using an ultra-low sulfur diesel fuel as a baseline fuel where two biodiesels (canola & tallow), Fischer-Tropsch and bioethanol were used as alternative fuel. Both the biodiesels coming from canola and tallow feedstocks, as well as F-T were used as 100% to run the engine where up to 40% energy substitution by ethanol was achieved without any sacrifice of engine power output. It was found that up to 30% ethanol substitution reduced both particulate mass (PM) and particle number (PN) emission consistently for all load settings at 2000 rpm, highest 59% reduction in PM and 70% reduction in PN observed at 100% load. As previously suggested the possible mechanism for the observed reduction is the oxidation of particulate matter by OH radicals which are in excess with ethanol fumigation. For 40% ethanol substitution some inconsistency was observed for PM emission at different loads but consistent reduction was found for PN. Condensation of unburned/partially burned hydrocarbons that later condense on existing soot might be responsible for this, as the maximum increase of PM was observed at quarter load where low in cylinder temperature favour to nucleation of unburned hydrocarbons. PM emission was also reduced in case of using 100% FT, and 100% biodiesel and the highest 90% reduction in PM was observed for biodiesel at 100% load with almost no difference between the two biodiesels itself. On the other side a considerable difference was observed between canola and tallow biodiesel in case of PN emission. Canola biodiesel increased PN, due to the presence of the nucleation mode, for almost an order of magnitude for all load and speed settings where no such increase was observed for tallow biodiesel. (C) 2013 The authors, Published by Elsevier Ltd.