Spectral radiative effects and turbulence/radiation interaction in a non-luminous turbulent jet diffusion flame

A non-luminous turbulent jet diffusion flame is numerically simulated using a Reynolds stress second-order closure, the steady laminar flamelet model, and different approaches for radiative transfer. The commonly used optically thin approximation is compared with the discrete ordinates method. Calculations using the Planck mean absorption coefficient are compared with computations performed using the spectral line-based weighted-sum-of-gray-gases model. The interaction between turbulence and radiation is simulated, and its influence on the predicted results is investigated. It is shown that the discrete ordinates method and the optically thin approximation yield relatively close results for the present flame if the medium is modelled as gray using the Planck mean absorption coefficient. In both cases, the predicted fraction of radiative heat loss is significantly overestimated. However, if the spectral nature of gaseous radiation is accounted for, the computed radiation loss is closer to the experimental data. The fluctuations of the species have a minor role in the interaction between turbulence and radiation, which is mainly due to the temperature fluctuations. (C) 2003 The Combustion Institute. All rights reserved.