Effect of charge dilution on gaseous and particulate emissions from a diesel engine fueled with biodiesel and biodiesel blended with methanol and ethanol

In this study, the effect of intake charge dilution with carbon dioxide on the combustion and emission characteristics of a 4-cylinder direct-injection diesel engine fueled with biodiesel, ethanol-biodiesel and methanol-biodiesel were investigated. With increase of intake CO2 concentration, CO, HC, particulate mass concentration, particle number concentration and geometric diameter (GMD) of all fuels increased while NOx decreased obviously. After addition of methanol and ethanol in biodiesel, the NOx, particulate mass concentration and particle number concentration decreased at each intake CO2 concentration, compared with biodiesel. Moreover, as the intake CO2 concentration increased from 2% to 5.6%, particulate mass concentration of the alcohol-biodiesel blends remained almost unchanged. It means that the combination of alcohol-biodiesel blends with intake charge dilution could reduce the NOx emission and maintains particulate mass concentration at a relatively low level.