Investigation of methyl tertiary butyl ether-diesel combustion and odorous emissions in a direct-injection diesel engine

This study investigated methyl tertiary butyl ether (MTBE)-blended diesel fuel combustion and odorous emissions in a direct-injection diesel engine during and after engine warm-up at idling. A few per cent of MTBE (5 vol %) blended in diesel fuel gives lower formaldehyde (HCHO) and an improved exhaust odour than with neat diesel fuel owing to good mixture formation and combustion for lower boiling point and oxygen (O-2) of the blend. With the 10 and 15 vol % MTBE blends, the very-low-boiling-point MTBE forms an overlean mixture and diminishes the positive effect of the O-2 content of MTBE causing the exhaust odour and odorous emissions to deteriorate. Ignition delay of all MTBE blends is about 1-3 degrees crank angle longer than that of neat diesel fuel depending on the engine running conditions. However, the combustion pressures and temperatures of the 5 vol % MTBE blend are similar to or a very little lower than that of neat diesel fuel. However, the 10 and 15 vol % MTBE blends show considerable decreases in the combustion pressures and temperatures.