Spectral modeling of thermal radiation in oxy-fuel pulverized coal flames
Thermal radiation through gases and particle matter is the dominant mode of heat transfer in pulverized coal fired boilers. The Oxyflame subproject C3 aims to develop efficient models to accurately calculate the radiation heat transfer in oxy-fuel combustion systems. For this purpose, the “Full-Spectrum Correlated-k” model is further developed to include non-grey radiation properties of coal and ash particles in real-sized oxy-fuel boilers.
Another important issue is the influence of turbulent fluctuations on the radiation field, since small variations in temperature strongly alter the emission of radiation. Based on the LES simulation results, conducted by subproject C2, the influence of different averaging approaches of the wavenumber, spatial, angular and time space on the radiative source terms and wall heat fluxes is thoroughly investigated.
In the LES context, a fast solution of the radiative transfer equation is crucial to reduce the computational effort for designing real boilers. Herein, the focus is led on the further development of the Mean-Flux-Scheme as an efficient spatial discretization scheme with high accuracy. Very accurate radiation models and experimental results after the flame front are used to validate the improved models.