Large Eddy Simulation of Premixed Combustion With a Thickened-Flame Approach

A Thickened Flame (TF) modeling approach is combined with a Large Eddy Simulation (LES) methodology to model premixed combustion and the accuracy of these model predictions is evaluated by comparing with the piloted premixed stoichiometric methane-air flame data of Chen et al. [Combust. Flame 107 (1996) 223–226] at a Reynolds number Re = 24,200. In the TF model, the flame front is artificially thickened to resolve it on the computational LES grid. Since the flame front is resolved, the combustion chemistry can be incorporated directly without closure approximations for the reaction rate. The response of the thickened flame to turbulence is taken care of by incorporating an efficiency function in the governing equations. The efficiency function, which is also known as a sub-grid flame wrinkling parameter, is a function of local turbulence and of the premixed flame characteristics, such as laminar flame speed and thickness. Three variants of the TF model are examined: the original Thickened Flame model, the Power-law flame wrinkling model, and the dynamically modified TF model. Reasonable agreement is found when comparing predictions with the experimental data and with computations reported using a probability distribution function (PDF) modeling approach by Lindstedt et al. [Combust. Flame 145 (2006) 495–511] and G-equation approach by Duchamp et al. [Annual Research Briefs, CTR (2000) 105–116].