Study on the measurement of soot particle size by laser induced incandescence

Soot is very harmful to the human health, which has drawn increasing attention. It has been shown that the toxicity of soot is directly related to the particle size. So it is very important to develop laser-based techniques to rapidly gain soot particle size information. LII (Laser Induced Incandescence) is considered a very promising method for soot measurement, and it can be used to determine soot concentration and particle size. In this paper, LII was used to infer primary particle size of soot at different axis positions in an ethylene/air laminar coflow diffusion flame. The results were compared with those from TEM (Transmission Electron Microscope) image analysis of thermophoretically sampled soot. It was shown that, along the flame axis, the particle diameter first increases and then decreases. Comparing the LII and probe sampling results, the trends agree well but the values differ slightly. Nevertheless, the effectiveness of the LII technique for soot particle sizing is found promising.