A Numerical Study On The Influence Of Co_2 Addition On Soot Formation In An Ethylene/air Diffusion Flame

摘要

Earlier studies have confirmed that the addition of CO_2 to a diffusion flame suppresses the formation of soot. However, a consensus has not been reached on the fundamental mechanisms of the suppression. In this paper, the influence of CO_2 addition on soot formation in an ethylenelair diffusion flame is investigated by numerical simulation, with focus on the fundamental mechanism of the suppression effect on soot formation. A special strategy is employed to separate the chemical effect from the thermal and dilution effects. The simulation results confirm that the addition of CO_2 suppresses soot formation through not only the thermal and dilution effects, but also the chemical effect. The chemical effect of CO_2 addition is primarily caused by the reduced concentration of radical H due to the reaction CO + OH (←) CO_2 + H, which suppresses the soot inception and surface growth rate. The chemical effect of CO_2 addition has negligible effect on soot oxidation process.