| Traditional fossil fuels are still one of the most important parts of modern energy system,then soot is one common particulate pollutant during the incomplete combustion of fossil fuels.In order to deal with global warming,environmental pollution and other issues,oxy-fuel combustion technology combined with flue gas recirculation has been paid more and more attention by researchers.Therefore,further study of the influence factors of soot formation process in combination with oxy-fuel combustion technology would have great practical significance for rational combustion organization and controlling the formation and emission of soot particles during combustion.Ethylene was used as fuel in this paper,the effects of oxygen concentration and flame structure on soot formation in counterflow and coflow laminar diffusion flames were studied based on the detailed soot model.At the same time,soot formation under different coflow atmosphere situations is also researched.Firstly,in oxygen-enriched counterflow diffusion flames,by changing the stoichiometric mixing fraction Zst under the same adiabatic flame temperature Tad to construct different oxygen concentrations and flame structures,the formation process of soot can be affected.As oxygen concentration increases,the stagnation plane and flame sheet,which are relatively distant from each other first,are close to each other and then gradually separate,and the residence time of the stream flow on the fuel side of the stagnation plane becomes shorter and the residence time on the oxidant side of the stagnation plane becomes longer,so that the soot growth process is weakened and the oxidation process of the soot is enhanced,resulting in a significant reduction of soot formation.At the same Zst,the increase of Tad and oxygen concentration simultaneously promotes the growth and oxidation of soot,and ultimately promote the soot formation.Secondly,based on experiment and simulation of coflow diffusion flame,the effects of O2+N2 and O2+CO2 coflow atmospheres on the soot formation were analyzed.The growth and oxidation of soot were mainly carried out in annular region of the flame rather than at the center of the flame.The increase in oxygen concentration promotes the formation of soot and observes the appearance of“soot wings”at the top area of the flame.Compared with O2+N2,O2+CO2 coflow atmosphere simultaneously reducing the growth and oxidation rate of soot,and ultimately inhibit the formation of soot.Finally,at the same Tad,the increase of Zst also inhibits the growth of soot and exacerbates the oxidation of soot in oxygen-enriched coflow diffusion flames.The formation of soot shows a decreasing trend.When Tad rises with same Zst,the growth of soot is stronger than that of oxidation,and the soot formation is increasing. |
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