FUEL MIXING EFFECTS ON FLAME TEMPERATURE AND SOOT FORMATION IN COFLOWDIFFUSION FLAMES

We investigated the effects of fuel mixing on flame height and flame t emperature of coflow diffusion flames which were closely related to so ot formation inside the flame. Four fuels with different sooting tende ncies and transport properties (CH4, C3H8, C2H4, C2H2) were diluted wi th nitrogen and used as component fuel gases for mixing. The main resu lts obtained are as follows: (1) Flame tip temperature is a good quali tative measure of the intensity of soot formation inside the flame. (2 ) Addition of nitrogen to the fuel causes both dilution and soot suppr ession, which lead to the decrease and the increase, respectively, in the flame tip temperature, and at a certain addition rate the flame ti p temperature attains a maximum due to their competitive action. (3) T here exists a strong correlation between the degree of soot formation and adiabatic flame temperature, and when soot formation is vigorous, factors which increase this temperature promote soot formation. (4) Ef fects of Lewis number and preferential diffusion should be taken into account to achieve effective suppression of soot formation by mixing f uels with different transport properties.