| A comprehensive modeling approach for simulating flamelet premixed combustion is formulated. The subgrid version of the linear eddy mixing model is refined and used to model flame wrinkling by the fine scale eddies. The advection of the flame by the larger eddies is modeled using a Lagrangian volume tracking scheme. The subgrid model and the advection scheme are independently validated and coupled effectively to produce a two-scale modeling approach. The resulting approach is free of any empiricisms, needs no calibration and fits into the large eddy simulation framework which is used to model the fluid dynamics. The new modeling approach is used to study premixed flames stabilized by stagnating turbulence and turbulent wakes. The results for the stagnation flames predicted using the proposed approach compare better with experimental results than the results obtained using more conventional modeling approaches. Simulations also show that the flamelet nature of combustion, which is not often captured by most approaches, is well captured by the present approach. The simulations of wake stabilized flames suffer from inaccuracies in modeling flame-wall interactions. However, these simulations show that the numerical scheme used to capture the flame evolution has a very significant effect on the predictions of flame structure and its interaction with turbulence in flows dominated by large scale vortex structures. Specifically, the thin-flame model proposed here predicts that the heat release due to combustion weakens the Kelvin-Helmholtz instability and the related von-Karman instability in the near wakes. Such weakening is, however, not predicted by the more conventional methods. The method proposed here has some inherent limitations. Possible ways to overcome these limitations are proposed. |
