Study on low nitrogen oxide and low smoke emissions in a heavy-duty engine fuelled with dimethyl ether

Abstract

The objective of the study presented here was to examine the possibility of simultaneously reducing soot and nitrogen oxide (NOx) emissions from a heavy-duty diesel engine fuelled with dimethyl ether (DME). The experiments show that low NOx emissions and smoke opacity can be achieved at engine loads of 10–40 per cent and 1400 r/min using a high level of exhaust gas recirculation (EGR). However, combustion in these conditions is incomplete, which results in increases in the amounts of unburned hydrocarbons and carbon monoxide. The φ–T map shows that the soot emission region of DME is smaller than that of diesel, and the NO emission region is almost the same as that of diesel. This is because of the high oxygen content of DME which is 34.8 mass%. The adiabatic flame temperature does not cross the NO and soot emission regions when about 40 per cent EGR is used. It was confirmed that the engine fuelled with DME can result in low NOx and low smoke emissions at EGR levels up to 40 per cent.