Incorporation of flamelets generated manifold method in coarse-grained Euler-Lagrange simulations of pulverized coal combustion

Large Eddy Simulations (LES) combined with the Flamelet Generated Manifold (FGM) approach has become popular for modeling turbulent flame/combustion of pulverized coal or biomass. In this paper, we incorporate a coarse-graining discrete element method (CG-DEM) with the FGM-LES for cost-effective Euler–Lagrange (EL) simulations of turbulent coal combustion. This developed method significantly reduces the computational burden in both Eulerian phase (via FGM) and Lagrangian phase (via CG) compared to conventional reactive EL simulations. The study is based on the experiment of the CRIEPI (Central Research Institute of Electric Power Industry) burner, which has been extensively used for model validation in literature. It is shown that the developed model can effectively reduce the computing cost while maintaining a good accuracy in predicting the pulverized coal flow dynamics as well as combustion performance. For this particular case, an optimal coarse-graining factor, the size ratio of coarse-grained parcels to original particles, of 2 is determined. A larger coarse-graining factor will create local concentrated regions of fuel and consequently lead to different combustion behavior.