Importance of Turbulence-Radiation Interactions in Turbulent Diffusion Jet Flames

Abstract

Traditional modeling of radiative transfer in reacting flows has ignored turbulence-radiation interactions (TRI). Radiative fluxes, flux divergences and radiative properties have been based on mean temperature and concentration fields. However, both experimental and theoretical work have suggested that mean radiative quantities may differ significantly from those predictions based on the mean parameters because of their strongly nonlinear dependence on the temperature and concentration fields. The composition PDF method is able to consider many nonlinear interactions rigorously, and the method is used here to study turbulence-radiation interactions. This paper tries to answer two basic questions: (1) whether turbulence-radiation interactions are important in turbulent flames or not; (2) if they are important, then what correlations need to be considered in the simulation to capture them. After conducting many flame simulations, it was observed that, on average, TRI effects account for about 1/3 of the total drop in flame peak temperature caused by radiative heat losses. In addition, this study shows that consideration of the temperature self correlation alone is not sufficient to capture TRI, but that the complete absorption coefficient-Planck function correlation must be considered.

Comparison of Accuracy and Computational Expense of Radiation Models in Simulation of Non-Premixed Turbulent Jet Flames

“…The optically-thin radiation model can result in substantial error due to its neglect of self-absorption, as has been shown by both numerical and experimental studies [3]. The gray medium assumption can also result in large errors as was shown by Li and Modest [4] and Wang et al [5,6]. Nongray radiation modeling has begun to draw attention in combustion simulations [6,5].…”

“…In addition, its convergence is known to slow down for optically thick media where the directional discretization is required to be as fine as the spatial discretization to avoid the ray effects. The P-1 method has so far been the most popular RTE solver within the SHM framework because of its simplicity, fairly good accuracy and its low requirement of computational time [4][5][6]. However, its accuracy is questionable in the presence of directionally inhomogeneous intensity distributions [16].…”

Estudo numérico de escoamentos turbulentos com convecção forçada em cavidades cilíndricas: comparação entre LES e RANS

“…As Interações Turbulência-Radiação (TRI -do inglês: Turbulence Radiation Interactions) têm sido investigadas principalmente no âmbito da modelagem clássica da turbulência, onde decomposições de Reynolds ou Favre são aplicadas as equações governantes e todas as flutuações e quantidades médias devem ser modeladas [12][13][14]. Com exceção do trabalho de Dos Santos et al [8] que observaram que os efeitos de TRI são importantes para escoamentos não-reativos em meios participantes opticamente espessos, tem se afirmado na literatura que os efeitos de TRI podem ser negligenciados para escoamentos não reativos [12,15].…”

Comparisons of Radiative Heat Transfer Calculations in a Jet Diffusion Flame Using Spherical Harmonics and k-Distributions

“…The flame investigated in this paper is a methane-air partially premixed flame derived from Sandia Flame D [28] by artificially quadrupling the jet diameter [29,6]. The velocity is reduced accordingly to retain the Reynolds number (Re ¼ 22400).…”