In-Situ Measurement of Soot Volume Fraction and Temperature in Axisymmetric Soot-Laden Flames Using TR-GSVD Algorithm

Abstract

To investigate soot formation and oxidation mechanism in combustion processes, determination of soot volume fraction (SVF) and temperature distributions in laminar co-flow axisymmetric soot-laden flames are still crucially important. This study provides a convenient and low-cost solution with a new inversion algorithm for in-situ measurements of SVF and temperature in axisymmetric soot-laden flames. The measurement instrumentation combines an industrial color camera and a tablet computer for in-situ measurements of SVF and temperature in three kinds of experimental flames. Based on the flame image processing, the Tikhonov regularization coupled with a generalized singular value decomposition (TR-GSVD) algorithm is proposed to do the inversion process. Comparing with common inversion algorithms, the TR-GSVD algorithm provides more accurate results. The measurement results show that the reduction in fuel flow of normal diffusion flame would result in higher temperature and lower SVF through the combined effect of radiant heat loss and fuel pyrolysis. The decrease of the equivalent ratio of partially premixed flame leads SVF to increase first and then decrease, and temperature to rise continuously, which is caused by the effect of fuel pyrolysis and the competition of soot formation and oxidation. For inverse diffusion flame, an increase in oxidant flow and a decrease in fuel flow lead to higher SVF and temperature, which is believed to be caused by the reduction of overall equivalence ratio. The detailed explanation is that the enhanced exothermic reactions lead to the temperature rise, and both the temperature and fuel pyrolysis affect soot formation.