Influence of Varying O_2 and CO_2 Concentration on Soot Formation and Oxidation

摘要

The influence of oxygen and carbon dioxide concentration on soot was studied by laser diagnostics and TEM(Transmission Electron Microscopy) Photograph in axisymmetric coflowing non-premixed flame. Combined LII(Laser Induced Incandescence), TIRE-LII(Time Resolved LII), and elastic scattering methods were used to measure soot volume fraction, primary particle size and number concentration in laminar non-premixed flames. Soot was also directly sampled with thermophoretic method, then soot morphology was analyzed by TEM Photography. When we make a comparison between the soot distribution observed by laser diagnostics and that of TEM analysis, soot diameter and number concentration reveal agreement. Using carbon dioxide as diluents instead of nitrogen in coflow, primary particle size and soot volume fraction abruptly decrease while number concentration increase. As the oxygen concentration in coflow increases, soot inception and primary particle size increase, however the soot containing area in flame becomes small because the soot oxidation rate increase due to higher temperature and higher oxygen fraction.