Effects of oxygenated fuels on emissions and carbon composition of fine particles from diesel engine

Acetal (1,1-diethoxyethane) is considered as an alternative to ethanol as bio-derived additive for diesel fuel, which is miscible in diesel fuel. Biodiesel can improve the oxygen content and flash point of the fuel blend of acetal and diesel fuel. Two oxygenated fuels were prepared: a blend of 10% acetal + 90% diesel fuel and 10% acetal + 10% biodiesel + 80% diesel fuel. The emissions of NO_x, HC and PM_2.5 from oxygenated fuels were investigated on a diesel engine bench at five modes according to various loads at two steady speeds and compared with base diesel fuel. Additionally, the carbon compositions of PM_2.5 were analyzed by DRI thermal/optical carbon analyzer. Oxygenated fuels have unconspicuous effect on NO_x emission rate but HC emission rate is observed significantly increased at some modes. The emission rate of PM_2.5 is decreased by using oxygenated fuels and it decreases with the increase of fuel oxygen content. The emission rates of TC (total carbon) and EC (elemental carbon) in PM_2.5 are also decreased by oxygenated fuels. The emission rate of organic carbon (OC) is greatly decreased at modes of higher engine speed. The OC/EC ratios of PM_2.5 from oxygenated fuels are higher than that from base diesel fuel at most modes. The carbon compositions fractions of PM_2.5 from the three test fuels are similar, and OC1 and EC1 are contributed to the most fractions of OC and EC, respectively. Compared with base diesel fuel, oxygenated fuels decrease emission rate of PM_2.5, and have more OC contribution to PM_2.5 but have little effect on carbon composition fractions.