Study Of Morphology Of Soot In Laminar Premixed Ethylene Flame With Different Methane Doping Ratios

As soot can make negative effects to the environment and human health and the technology of synthesis in flames has been concerned in many fields,the research of soot produced by combustion has become more and more important.However,the mechanism of formation of soot is not clear at present while the study of morphology of soot has become a significant role in the research of soot particles because it can influence many properties of soot.So based on the most accepted theory named HACA mechanism which has been proved by many experiments,morphology of soot in laminar premixed ethylene flame with methane doping was researched in this paper,and the results were used to support the SMPS test which was based on the sphere assumption to support the mechanism of soot formatin as well.First,a combustion system which can generate different kinds of stable BSS flame and a TSPD system which had excel dynamic response and high repeated accuracy were stablished after investigation,then four kinds of flames which have the same flame temperature,equivalent ratio and flow velocity but have different mix ratio of methane were designed to be sampled from 3 heights above burner each,and after observed in TEM and AFM,the samples were analyzed by ImageJ.The results reveal that,the same as the SMPS experiment,few methane doping may strengthen soot tendency in ethylene flame while much methane doping may weaken the tendency in turn,this phenomenon is caused by the change of content of PAHs which is effected by mix ratio.At the same time,the geometrical parameter of soot such as circularity,sphericity and fractal dimension were calculated,it can be learned from the analysis that methane doping couldn’t influence these parameters as they were controlled by the process after nucleation.We can find that as the particle diameter and area of soot increase,the fractal dimension reduces which means that the structures of soot become looser.Finally,the study shows that even the very small particles are not spherical as all of them are fractal,which means agglomeration is always existing during the whole soot formation.