Simplified radiation and soot models for buoyant diffusion flames: Quantitative investigation of fuel mixing effects

Simplified radiation and soot models were proposed to provide a simple yet effective method predicting flame radiation and soot characteristics for buoyant diffusion flames. To explore the quantitative effects of fuel mixing and validate the proposed models, LII measurement of soot distribution and multi-point measurement of radiation flux were conducted for different fuel mixtures and different mixing ratios. Characteristic length scales, including the height of soot inception, the height of maximum soot volume fraction and the height of soot oxidation in the soot distributions, were determined by the fuel type and mixing ratio, and resulted in different maximum soot volume fractions. The axial distribution of soot volume fraction, maximum soot volume fraction, soot volume and soot yield can be predicted by the simplified soot model based on the critical mixture fractions. The probability density function of axial soot volume fraction can be described by an exponential function related to the non-sooty probability and maximum soot volume fraction. In addition, flame radiation power presents a linear correlation with soot volume, and flame radiation fraction of buoyant diffusion flame of fuel mixtures presents a linear relationship with the maximum soot volume fraction, which is in agreement with the simplified radiation model proposed in this work.