Effect of ozone and oxygen dilution on soot formation in coflow ethylene/oxygen/ozone laminar partially premixed flames

Abstract

Ozone is a prospective additive for enhancing and controlling combustion, due to its extremely oxidizing property. Ozone can enhance laminar burning velocity, broaden the flammability limit and improve flame stability, but the effect of ozone on soot formation in the combustion process of hydrocarbon fuels was not yet clear. Therefore, the soot from ethylene/oxygen/ozone laminar partially premixed flames was investigated. Besides, the response law of soot formation to different dilution gas ratios, and the effect of ozone participation in the reaction was also investigated. This work found that ozone significantly shortened the flame height by 4 mm in the cases of 10 % dilution ratio. The particle size of soot was larger at low and medium flame heights due to ozone involved in combustion. The main reason was that ozone promoteed soot growth. At medium and high flame heights, the larger the percentage of oxygen and ozone, the lower graphitization degree of the soot. The addition of oxygen and ozone both made the I_D/I_G value increase, which indicated the graphitization degree decreased. The soot from high height of the flame with 10 % dilution ratio and the addition of ozone had the largest I_D/I_G value of 0.970, which indicated a very low degree of graphitization. The signal intensity of the oxygen-containing functional groups on the surface of soot at the high flame height was enhanced with the addition of oxygen and ozone to the reaction.