Fuel Mixing Effects on Flame Temperature and Soot Formation of Coflow Diffusion Flames.

Abstract

Effects of fuel mixing were investigated on flame height and flame temperature of coflow diffusion flames which were closely related to soot formation inside the flame. Four kinds of fuels with different sooting tendencies and transport properties (CH4, C3H8, C2H4, C2H2) were diluted by nitrogen and used as component fuel gases. Main results obtained are as follows : (1) Flame tip temperature is a good measure to qualitatively estimate the intensity of soot formation inside the flame. (2) Addition of nitrogen to the fuel has both effects of dilution and soot suppression, and at a certain addition rate the flame tip temperature attains a maximum value due to their competitive action. (3) There exists a significant correlation between soot formation and adiabatic flame temperature and when soot formation is vigorous, factors increasing this temperature promote soot formation. (4) Effects of Lewis number and preferential diffusion should be taken into account for effective suppression of soot formation by mixing of fuels with different transport properties.