MODELING OF LOCAL EXTINCTION IN TURBULENT FLAMES

The Eddy Dissipation Concept (EDC), proposed by Magnussen (1985), adva nces the concept that the reactants are homogeneously mixed within the fine eddy structures of turbulence and that the fine structures may t herefore be regarded as perfectly stirred reactors (PSRs). To understa nd more fully the extent to which such a subgrid scale stirred reactor concept could be applied within the context of a computational fluid dynamics (CFD) calculation to model local or global extinction phenome na: (1) Various kinetic mechanisms are investigated with respect to CP U penalty and predictive accuracy in comparisons with stirred reactor lean blowout (LBO) data and (2) a simplified time-scale comparison, ex tracted from the EDC model and applied locally in a fast-chemistry CFD computation, is evaluated with respect to its capabilities to predict attached and lifted flames. Comparisons of kinetic mechanisms with PS R lean blowout data indicate severe discrepancies in the predictions w ith the data and with each other Possible explanations are delineated and discussed. Comparisons of the attached and lifted flame prediction s with experimental data are presented for some benchscale burner case s. The model is only moderately successful in predicting lifted flames and fails completely in the attached flame case. Possible explanation s and research avenues are reviewed and discussed.