Study of combustion and emission characteristics of diesel fuel/water emulsion (1st report, Effects of atomization condition)

Abstract

Emulsion fuel is regarded as one of the possible fuels for reducing the emissions of pollutants from combustion systems. This study investigated the effect of droplet size on combustion and emission characteristics for both pure diesel and emulsion fuel in preheated ambient air. A burner equipped with a twin fluid atomizer was used to vary Sauter mean droplet diameter (SMD) of spray. Water percentage of 5 and 10 vol% in W/O emulsion fuel was used. Experimental results show that both emulsion fuel had lower EICO₂ than diesel fuel. This result shows combustion efficiency of emulsion fuel was lower than that of diesel fuel. As the preheated ambient air temperature T_Ambi was increased to 473 K, combustion efficiency of emulsion fuels was improved. In emulsion fuel combustion, NO emission was lower than pure diesel fuel combustion. The vaporization of water in emulsion fuels reduced local flame temperature and thus reduced the NO formation. Smaller fuel droplet SMD had higher NO emission for pure diesel fuel. However, NO emission had no dependence on fuel droplet SMD for emulsion fuel. Emulsion fuels also had lower flame luminance as compared with diesel fuel alone. This is caused by lower soot emission of emulsion fuels.