In this study, one kind of vegetable methyl ester was added to ethanol-diesel fuel to prevent the separation of ethanol from diesel; thus the ethanol percentage can be up to 30% in volume. More attention was paid to its combustion characteristics, the effects of ethanol on particulate matter (PM) components, SOF (soluble organic fraction), DS (dry soot), and sulfate mass, using different fuel blends in the engine. To understand the effect of ethanol blended diesel fuels on combustion processes and soot formation, images of combustion processes were recorded using a high-speed CCD camera. The results show that with increasing ethanol in the blended fuel, both smoke and PM can be reduced, but the PM decrease is not as efficient as the smoke decrease. The smoke and PM behave differently even for one kind of fuel blend, and it is unreasonable to evaluate the PM emission by the smoke. In addition, under the same condition, increasing ethanol in the fuel blend, the DS emission in PM is reduced significantly, the sulfate emission hardly changes, and the SOF emission in PM is not reduced as expected. The results also indicate that addition of ethanol to diesel fuels the ignition is prolonged, maximum heat release ratio and peak pressure increase, and combustion duration is shortened. In addition, the flame luminosity in the combustion is decreased using blended fuels, which indicates that soot formation in fuel-rich regions is suppressed by the ethanol. (C) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
