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The effect of ethanol blended diesel fuels on brake specific fuel consumption (BSFC), brake specific energy consumption (BSEC), smoke and NOx emissions has been investigated in a direct-injection diesel engine. Unregulated emissions including formaldehyde, acetaldehyde and unburned ethanol emissions are also analyzed. The results indicate that with the increase of ethanol in the blends, smoke reduces significantly, BSEC improves slightly and combustion duration decreases. However, the rate of heat release increases. Ignition delays. BSFC, NOx, acetaldehyde and unburned ethanol emissions increase. The maximum acetaldehyde emissions reached up to 100 ppm at low load. Compared to a gasoline engine using ethanol blended gasoline fuels, unburned ethanol emissions of the diesel engine are higher than those of the gasoline engine at the same ethanol concentrations and similar loads.

Homogeneous charge combustion and emissions of ethanol ignited by pilot diesel fuel were investigated on a two-cylinder diesel engine. The results show that emissions depend on loads and ethanol volume fraction. At low loads, ethanol has little effects on smoke. With the increase of ethanol, NOx decreases, but CO emissions increase. At high loads, smoke emissions reduce greatly with increasing ethanol, but NOx and total hydrocarbon (THC) emissions increase. With the increase of ethanol, ignition delays, combustion duration shortens. The maximum rates of heat release for the fuel containing 10 vol% ethanol (E10) and 30 vol% ethanol (E30) increase. Brake specific energy consumption (BSEC) of E10 and E30 is improved slightly only at full loads. Compared to smoke emissions obtained on the same engine using ethanol blended diesel fuels, the tendency of smoke reduction is similar to that of homogeneous charge combustion of ethanol at the same operating conditions.