Investigation of Soot in a Model CFM56 Atmospheric Combustor Using In-Situ Laser-Induced Incandescence Calibration

Abstract

In this work, we investigate qualitative backlight imaging-based spray characteristics and laser-induced incandescence (LII) based quantitative soot volume fraction (SVF) in a CFM56 model combustor with a simplex nozzle at 1 bar, 303 K. The soot volume fraction is quantitatively measured using an in situ extinction-based calibration technique. Soot was detected immediately downstream of the swirler exit and in the shear layer region as observed by other authors. In addition, soot was also detected inside the inner recirculation region which could be due to the spray distribution, geometry, or difference in flame anchoring. The number-averaged soot volume fraction is of the order of 20 ppb which is comparable in magnitude to previously reported combustor measurements. Large eddy simulation (LES) modeling of the experimental setup coupled with the simple two-equation Tesner model has been done using ansysfluent® to study soot formation. The model shows good qualitative agreement with the experimental results although quantitatively it is lower by one order of magnitude. Soot formation occurs in the rich region immediately downstream of the swirler while the second half of the primary zone becomes lean and soot oxidation is more dominant.