Study of Particulate Matter-, NOx- and Hydrocarbon Emissions from a Diesel Engine Fueled with Diesel Oil and Biodiesel with Fumigation of Hydrogen, Methane and Propane

To investigate possibilities for reduction of particulate matter emission from diesel engines, experiments with hydrogen, methane and propane mixed to the inlet air were performed in a Euro 2 Scania diesel engine. The base fuels were marine gas oil (MGO, a diesel oil quality) and biodiesel (80 vol% rape seed methyl ester and 20 vol% soy bean methyl ester). Up to 40 % of the fuel energy was replaced by gas at three different load conditions. The emission of particulate matter (PM) was evaluated through particle mass measurements as well as filter smoke number (FSN) unit. The biodiesel resulted in higher PM emissions at low load, but considerably lower PM emissions at high load compared to MGO. The FSN was much lower for biodiesel than for MGO at all loads. Fumigation was not found to be exclusively advantageous with respect to PM emission. At low load, the PM emission was virtually unaffected by the introduction of hydrogen and propane while the PM emissions increased with methane fumigation. At higher loads noticeable reduction in PM emissions were observed at high gas rates. At 50% load (10 bar BMEP) a reduction of about 60% was obtained when 30% of the fuel energy was replaced by propane. Because of the low density of hydrogen the amount of energy that could be introduced was limited, and only a limited reduction in PM emissions could thus be obtained by hydrogen addition. The NO_x emissions were found to be about 15% higher when the engine was fueled with biodiesel compared to MGO. Fumigation affected the NO_x emission only to a limited extent with the tendency to increase the NO_x emissions with increasing gas rate at high load and reduce or not affect the emissions at low load. Methane and propane fumigation resulted in considerable THC emissions at low load.