Soot Formation in the Buoyancy-Dominated Ethene Diffusion Flame

摘要

A sampling technique, based on the phenomenon of thermophoresis is used here, inorder to study the soot morphology within a buoyancy-dominated ethene diffusion flame. The buoyancy-dominated flame has a fuel flow rate of 50 cc/s and a co-annular air flow of 107 cc/s. Soot morphologies at each sampling location are obtained on carbon-coated grids through a fast probe drive mechanism, and they are analyzed under a transmission electron microscope. These observations, coupled with temperature measurements at various heights of the buoyancy-dominated flame, leads to a basic understanding of particle inception region, surface growth, aggregate formation, oxidation process, aggregate size and primary particle size within the flame. Change in soot morphology is studied both in the vertical and radial axes of the flame. The intense particle inception region, characterized by a large concentration of liquid-like microdroplets, is contained within the low part of the flame. These microdroplets form on the fuel side of the flame front where the temperature is the highest. Since there is very little evidence of oxidation taking place within the buoyancy-dominated flame, it is concluded that most of the soot formed in the flame is released into the surroundings. Observations being made here have been compared to similar soot morphology studies previously made on laminar ethene diffusion flames, both non-sooting and sooting, and laser diagnostic tests.