The emissions and the performance of diethyl succinate in a diesel fuel blend

Abstract

The finite natures of fossil fuels and their contributions to anthropogenic climate change are driving the development of biofuels. However, because of the inherent issues with current biofuels, such as ethanol and biodiesel, innovative replacements are being increasingly sought. Recently, four esters produced from fermentation, namley diethyl succinate, dibutyl succinate, dibutyl fumarate and dibutyl malonate, were reported to have suitable physical properties as a substitute for conventional diesel fuel. Although the physical properties are indicative of the fuel behaviour, the determination of the combustion emissions and the performance of a fuel using controlled engine testing is vital. In this investigation, the engine performance and emissions produced from the most viable fuel, namely diethyl succinate, were examined. Diethyl succinate was blended with diesel in a 20 vol % blend, owing to the low cetane number of diethyl succinate, and the emissions established in pseudo-steady-state conditions using a 2.0 L turbocharged direct-injection EURO 3-compliant light commercial vehicle equipped with a direct-injection common-rail diesel engine. When using the diesel–20 vol % diethyl succinate blend, the fuel demand and the wheel force were higher for the majority of engine speeds than those of diesel, whereas the exhaust gas temperatures were lower. The difference between the exhaust gas temperature for the diesel–20 vol % diethyl succinate blend and that for diesel increased with increasing pedal demand. In comparison with the carbon monoxide emissions from petroleum-derived diesel, the carbon monoxide emissions obtained when using the diesel–20 vol % diethyl succinate blend were reduced, most probably because of more complete combustion due to the increased oxygen content. However, the total hydrocarbon emissions and the mono-nitrogen oxide emissions were shown to increase on using the diethyl succinate blend. Both of these factors were presumably due to the lower cetane number of the fuel, although the increase in the total hydrocarbon emissions was deemed negligible because of the low amount produced by both fuels.