Studies On Soot Formation And Morphology In Ethylene-Oxygen Enriched Laminar Diffusion Flame By Thermophoretic Sampling

Soot formation and emission from fossil fuel combustion systems dramatically affectsthe combustion efficiency, the radiation heat transfer of flame, the environment and humanhealth. Enriched combustion attracts more and more attention from researchers because ofits advantages, such as improving combustion efficiency, separating carbon dioxideeffectively and reducing NOx emission, but now there are few studies about soot formationand emissions in the oxy-fuel combustion field. In the oxy-fuel combustion, soot formationhas different features when the density of oxygen and carbon-dioxide changes. It isimportant to study these features for understanding the process of soot formation andpromoting the development of oxy-fuel combustion. In this dissertation, soot formationfrom the ethylene-oxygen enriched laminar diffusion flame was studied by ThermophoreticSampling Particles Diagnostics, TSPD-TEM.TSPD-TEM included two major parts: experimental method and data processing. Theformer part introduced experimental principle, experimental system and experimentalapparatus of this method. It obtained a TEM image of soot. The latter part based onthermophoresis mechanism, then got the quantitative information from TEM images of sootby image processing and statistical analysis. TSPD-TEM can detect soot morphology,primary soot particle size, fractal dimension and the local soot volume fraction in the flamesimultaneously.The paper got soot morphology and related parameters from different oxygen-enrichedflame and analyzed the effect of the oxygen concentration and carbon dioxide concentrationon soot behavior. The results showed that: with the addition of oxygen, soot nucleation andgrowth strengthened in the bottom of the flame, the primary particle diameter and soot volume fraction increased; in the top of the flame, the addition of oxygen accelerated sootoxidation process, the soot primary particle size and soot volume fraction declined sharply.With the increase of carbon dioxide concentration, the flame temperature is reduced, littlechange occurred in the primary particle diameter, but the soot size and soot volume fractiondecreased, it indicated significant inhibitory effect of carbon dioxide on soot formation.