Large-eddy simulation of premixed turbulent combustion using a level-set approach

In the present study, we have formulated the G equation concept for large-eddy simulation (LES) of premixed turbulent combustion. The developed model for the subgrid burning velocity is shown to correctly reflect Damköhler's limits for large- and small-scale turbulence. From the discussion of the regime diagram for turbulent premixed combustion, it is shown that given a particular configuration of flow parameters, changes in the LES filter width result in changes along constant Karlovitz number lines. The Karlovitz number is chosen as the horizontal axis to construct a new regime diagram for LES of premixed turbulent combustion, where changes in the filter width are represented by vertical lines. In addition, some new regimes appear in the new diagram, which are related to the numerical treatment. An important conclusion is that changes in the filter width cannot result in changes of the combustion regime among the corrugated flamelets, thin reaction zones, and broken reaction zones regimes. This is a consistency requirement for the model, since the choice of the filter width cannot change the fundamental combustion mode. With decreasing filter width, changes from corrugated to wrinkled flamelets, or in general to a laminar regime, are possible. In applying the model in a numerical simulation of a turbulent Bunsen burner experiment, it is shown that the results predict the mean flame front location, and thereby the turbulent burning velocity, and the influence of the heat release on the flow field in good agreement with experimental data.