Abstract
Two-dimensional large eddy simulations of the development of piloted turbulent non-premixed jet flames of methane and air exhibiting significant finite-rate chemistry effects are presented. A partial equilibrium/two-scalar exponential (PDF) combustion submodel is applied at the subgrid scale level. Subgrid scale motions are modelled with a first-order closure employing a prognostic equation for the SGS energy. Statistical independence of the joint PDF scalars is relaxed and the necessary moments are obtained from their full transport equations under simplifying assumptions. Extinction is accounted for by comparing the local turbulent Damkohler number against the ratio of the Gibson scalar scale to the reaction zone thickness in mixture fraction space. The post-extinction regime is modelled via a Lagrangian formulation employing the solution of a transport equation for a mixing progress variable that follows a linear deterministic relaxation to its mean value (IEM). Comparisons between simulations and measurements suggested the ability of the method to calculate adequately the partial extinction and re-ignition phenomena observed in the experiments.
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