The impact of oxygenated fuels on diesel combustion and emissions

The reduction of particulate matter emissions from compression-ignition engines has become a strong topic, due to increasingly stringent emission standards and health concerns. Oxygenated fuels can be used to reduce particulate emissions; however, the impact of modifying the chemical and physical properties of diesel fuel by adding oxygenates has not been well researched. In this experimental study, the impact of oxygenated fuels on diesel combustion and emissions has been evaluated. Particulate matter, hydrocarbon, carbon monoxide and NO_x emissions were measured for the oxygenated blends. In-cylinder pressure measurements were obtained, from which heat release rates were determined.; Several glycol ethers, as well as methyl soyate, were evaluated at 2 wt.% and 4 wt.% oxygen blend levels. The results indicated that particulate matter emission reductions varied for the oxygenates evaluated. Monoglyme and diglyme were most effective in reducing particulate matter emissions. Heat release results revealed a substantial reduction in heat release rate during the premixed stage for the triglyme blends, suggesting that the difficulty in volatilizing triglyme in the premix chamber may have led to less combustion during the early stages of combustion.; A mixture of 20 wt.% monoglyme and 80 wt.% diglyme was also evaluated as an oxygenating agent, at blend levels up to 14 wt% oxygen. Particulate matter reductions were dependent upon the amount of oxygen blended; however, the trend was not linear. As oxygen content increased, further reductions in particulate matter were less pronounced. The results also suggested that the impact of oxygenates may vary across the range of diesel engines in service. Heat release data indicated that a shift in heat release from the premixed to the mixing-controlled stage occurred. This was most apparent at low speed and load conditions, where the premixed stage of combustion provides the highest rate of heat release.; Monoglyme and diglyme were substituted with n-heptane and n-dodecane, two linear alkanes with similar volatility, to evaluate the impact of modifying several chemical and physical properties on diesel combustion and emissions. The results suggested that oxygen content was primarily responsible for the particulate matter reductions observed.