Application of the WSGG model for the calculation of gas-soot radiation in a turbulent non-premixed methane-air flame inside a cylindrical combustion chamber

This paper presents a study of the effect of soot on the radiative heat transfer in a turbulent, non-premixed methane-air flame inside a combustion chamber. In this problem, an important aspect to be considered is the steep variation of the radiative properties of the medium, which is treated with the weighted-sum-of-gray-gases (WSGG) model based on the superposition of correlations recently obtained for water vapor, carbon dioxide mixtures and soot. The discrete ordinates method (DOM) is employed for the angular integration of the radiative transfer equation (RTE), taking into account turbulence-radiation interactions (TRI). Calculations indicate that the global contribution of soot to the radiative heat transfer in the chamber was of 8%, which is compatible with methane flames. However, in the region with the highest concentration of soot, it was observed a local increase of 30% in the radiative volumetric source in the medium, and of 25% in the radiative heat flux on the wall. In the second part of the paper, the WSGG model is compared with the line-by-line (LBL) integration using the final temperature and concentrations fields obtained from the global flame calculation, leading to average and maximum normalized errors of 1.2% and 4.8%, respectively, and requiring only 1/7000 of the computation effort of the LBL integration. This result indicates that the WSGG model, in spite of its relative simplicity, can provide accurate results for the spectral integration of the radiative properties of gas-soot mixtures in combustion processes.