Prediction of self-absorption in opposed flow diffusion and partially premixed flames using a weighted sum of gray gases model (WSGGM)-based spectral model

A weighted sum of gray gases model (WSGGM)-based low-resolution spectral model for calculating radiation transfer in combustion gases is applied to estimate self-absorption of radiation energy in one-dimensional opposed-flow flames. Development of such a model is necessary in order to enable detailed chemistry-radiation interaction calculations including self-absorption. A database of band model parameters which can be applied to various one-dimensional opposed-flow diffusion and partially premixed flames is created. This in-situ flame property-based database is necessary for the application of the WSGGM to real flames, since previously developed databases were only for homogeneous and isothermal radiation paths. For the validation of the model and database, low-resolution spectral intensities leaving the flat flame in a direction normal to the fuel exit plane are calculated and compared with the results of a narrow-band model based on the Curtis-Godson approximation. Good agreement has been found between them. The resulting radiation model is coupled to the OPPDIF code to calculate the self-absorption of radiant energy and compared with the results of an optically thin calculation and the results of a discrete ordinates calculation in conjunction with the statistical narrow-band model. Significant self-absorption of radiation is found for the flames considered here, particularly on the fuel side of the reaction zone. However, the self-absorption does not have significant effects on the flame structure in this case. Even in the cases of low-velocity diffusion flame and a partially premixed flame having a low equivalence ratio, the effects of self-absorption of radiation on the flame temperature and the production of minor species are not significant.