Evaluation of fluctuating anisotropy of particles in CFB combustor using second-order moment method

The second-order moment (SOM) method is developed to describe the fluctuating anisotropy of particles in coal combustion process. Large-eddy simulation (LES) is employed for turbulence of gas phase. The LES-SOM model is coupled with chemical kinetics for coal combustion simulations and the anisotropy characteristic of particles is analyzed in circulating fluidized bed (CFB). The simulation results reveal that the molar fractions of gas species with the SOM model considering fluctuating anisotropy of particles are in better agreement with experimental data than those with the KTGF model. The distribution of the SOM of particles is evaluated. It is found that the SOM of particles is enhanced towards the wall. With the increasing particles concentration, the SOM of particles is sharply increased at first, reaches the maximum, and then gradually decreases. The SOM for coal particles is relatively lower compared to desulfurizer particles, while the fluctuating anisotropy for coal particles is larger. The Reynolds stresses of particles are also investigated. It is found that the Reynolds stresses of particles are one order of magnitude greater than the second-order moment of particles.