Transient three-dimensional radiative heat transfer analysis of a turbulent diffusion flame-with a focus on the effect of angular discretization scheme

Abstract

Radiation modeling is a challenging and computational expensive task for turbulent combustion modeling of various fuels. Radiative intensity varies greatly in the angular direction due to turbulent fluctuations of temperature and species fields. A large number of rays are needed in the discrete ordinates method (DOM) or the finite volume method (FVM) to describe the angular variations. Determining the adequate number of rays is essential for the efficient modeling of radiation heat transfer. For this purpose, the effect of angular scheme on predicting the transient three-dimensional radiation heat transfer of a turbulent diffusion flame is investigated. Results show that a smaller number of rays produce strong ray effects and may generate significant errors for radiative heat flux prediction on surrounding walls, while the angular scheme has negligible influence on the radiative heat source. Transient radiative heat fluxes on different walls are also analyzed in detail, and they show completely different contours with unimodal frequency behavior. Recommendation for radiation modeling strategies is proposed for turbulent combustion modeling.