Radiation Modelling in Non-Luminous Nonpremixed Turbulent Flames

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Abstract
A finite-rate chemistry model for nonpremixed turbulent combustion, based on the stretched laminar flamelet (slf) approach, is extended to account for radiative heat transfer in non-luminous flames, in the optically thin limit. The model is applied to a methane/air flame, and results in greatly improved predictions of mean temperature, and of its probability density function. Mean carbon monoxide concentration predictions are instead shown to be somewhat deteriorated. The model is further tested to reproduce radiative heat flux levels; solutions obtained by determining the average heat flux divergence by full convolution with the pdT, and by the simpler but less fundamentally correct ‘mean-property’ method, are compared, and show a significant gap. A formulation to deal with non-unity Lewis number flames is proposed; the model holds potential for further extension.