A new correlation between soot sheet width and soot volume fraction in turbulent non-premixed jet flames

Measurements of soot volume fraction (SVF) using planar Laser-Induced Incandescence (LII) were performed in a set of attached turbulent non-premixed jet flames, burning the same mixture of C2H4/H-2/N-2. A novel post processing technique was used to identify and characterize the average width (W-s) and volume fraction of the soot sheets and correlate it with key flame features and parameters. The axial distributions of both W-s and SVF, within those sheets, in all flames are shown to grow with flame length up to the region where soot oxidation becomes significant, with only a secondary dependence on the inflow conditions. Probability density functions (pdfs) of W-s are seen to exhibit far less variation than those of SVF, also indicating the soot structure morphology insensitivity to inflow conditions. The effects of fuel exit strain (OD) and bulk exit Reynolds number (Re-D) on soot sheets are also assessed for three flames, of which two share the same U/D and two share the same Re-D. The variation in U/D at constant Re-D is seen to only affect SVF within the sheets, while a variation in Re-D, at constant UID is shown to have negligible effect on both W-s and SVF, in agreement with previous findings by the authors. Finally, a strong power-law correlation is deduced from joint statistics for W(s )and SVF through all flame locations and for all the flames investigated. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.