Comparison of multiple diagnostic techniques to study soot formation and morphology in a diffusion flame

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• 作者：Mohammad Reza Kholghy^a ; Yashar Afarin^a ; Anton D Sediako^a ; Javier Barba^b ; Magí ; n Lapuerta^b ; Carson Chu^a ; Jason Weingarten^a ; Bobby Borshanpour^a ; Victor Chernov^a ; Murray J Thomson^a ; ^{murray.thomson@utoronto.ca} ; ^{mr.kholghy@mail.utoronto.ca}
• 关键词：Laser induced incandescence ; Laser extinction ; Soot spectral emission spectroscopy ; Rapid thermocouple insertion ; Thermophoretic sampling particle densitometry
• 刊名：Combustion and Flame
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：176
• 期：Complete
• 页码：567-583
• 全文大小：5054 K
• 卷排序：176

文摘

Different non-intrusive optical and intrusive non optical diagnostic methods are used to measure flame and soot properties in a laminar coflow diffusion flame in order to compare and analyze the sensitivity of each technique to soot particles with different age and morphology. Flame temperature is measured using rapid thermocouple insertion (RTI) method and also by measuring soot spectral emissions (SSE). Soot volume fraction (fv) is measured quantitatively with laser extinction (LE), time resolved laser induced incandescent (TiRe-LII) and SSE methods and qualitatively from the transmission electron microscope (TEM) images of the thermophoretically sampled soot particles. Particle internal/aggregate nanostructure, and primary particle diameter are also analyzed based on TEM images from the sampled particles and TiRe-LII. It is shown that the optical methods are only sensitive to mature soot particles with solid appearance and cannot detect either temperature or fv in regions where liquid like nascent soot particles are dominant. fv measured by LE and TiRe-LII agree well while the values measured by SSE are lower. This discrepancy is attributed to the high sensitivity of fv measured by SSE to the measured temperature values. Temperature profiles measured by SSE are considerably higher than the values measured by RTI. It is shown that not considering the change of the surface emissivity of the thermocouple junction due to particle deposition for estimating radiation loss in regions where nascent or mature soot particles are dominant contributes to this discrepancy. Primary particle sizes measured based on TEM images and TiRe-LII agree reasonably well. Soot aggregate fractal dimension is shown to decrease as the soot particles age and become more mature.