Nongray radiation modelings in eulerian-lagrangian methods for pulverized coal flames

Radiation is an important heat transfer mode in pulverized coal flames. Its modeling is challenged by the treatment of the multiphase mixture and the non-gray effects of participating gases and particles. In this work, the k-distribution methods that can successfully account for gas non-gray effects are applied to a pulverized coal ignition flame, in which the carrier gas is modeled by Eulerian equations while the particles are tracked individually in a Lagrangian framework. Bulk radiative properties from the dispersed particles are assembled to the full-spectrum k-distributions of the carrier gas. The Radiative Transfer Equations are solved by the P1 approximation. Radiative heat losses are fed back to the energy equations of both the carrier gas and the dispersed particles. It is found that radiation causes a 500 K temperature difference. Radiative absorption predicted by the k-distribution methods contributes to a 100 K temperature increase. The absorption is nongray therefore cannot to be captured by gray models.