Effects of Flame Lift-Off and Flame Temperature on Soot Formation in Oxygenated Fuel Sprays 2003-01-0073

Considering the bell-shaped temperature dependence of soot particle formation, the control of flame temperature has a possibility to drastically suppress of soot formation. Furthermore, oxygenated fuels are very effective on soot reduction, and the use of these kinds of fuels has a potentiality for smokeless diesel combustion. In this paper, the effects of flame lift-off and flame temperature on soot formation in oxygenated fuel sprays were experimentally investigated using a constant volume combustion vessel which simulated diesel engine conditions. The diffusion flame lift-off length was measured in order to estimate the amount of the oxygen entrained upstream of the flame lift-off length in the fuel jet. This was determined from time-averaged OH chemiluminescence imaging technique. Also, the flame temperature and soot concentration were simultaneously evaluated by means of two-color method. Measurements were obtained at various ambient gas temperatures, oxygen concentrations and injection pressure drops across nozzle orifice. The experimental results showed that the soot formation inside a burning diesel jet has the significant relation with the flame lift-off length and flame temperature. The oxygenated fuels have a large potentiality for smokeless diesel combustion based on the control of the flame temperature as well as that of the mixture formation process.