Book Description

This study investigated the effects of turbulence on the spatial distribution of the soot particle and OH fields in turbulent C2H4 air/jet diffusion flames. Measurements obtained using planar laser-induced incandescence (LII) for soot volume fraction and laser-induced fluorescence (LIF) for both OH, and polycyclic aromatic hydrocarbons (PAH) formed the basis for investigating soot formation and destruction processes in these flames. These laser-based techniques were applied to the flame independently as well as simultaneously. Extensive information on the structure of the soot and OH fields was obtained from two-dimensional imaging experiments. Imaging results for soot, OH and PAH indicated three distinct soot formation/oxidation regions; a rapid soot growth region, in which OH and soot particles lie in distinctly different radial locations; a mixing dominated region controlled by large-scale fluid motion; and, finally, a soot oxidation region in which the OH and soot fields overlap spatially, resulting in the rapid oxidation of soot particles. Detailed quantitative analyses including soot volume fraction, OH and soot zone thickness variations, and probabilities distributions for soot and OH were performed. The measurements of soot and OH zone thickness showed that the soot zone thickness varied nearly linearly in the formation region, while approximately a doubling of thickness of the OH zone was evident over the studied Reynolds number range (4000-23000). The probability density function results tor soot, OH, and PAH indicated that OH and PAH are spatially interrelated with respect to soot formation and oxidation processes.