Importance of Turbulence-Radiation Interactions in Turbulent Reacting Flows

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.

Influence of turbulence–radiation interactions in laboratory-scale methane pool fires

“…This term contributes to the enhancement of flame absorption leading to a reduction in radiant fraction by about 12% (see Table 2). It should be noted that the conclusions drawn from the previous scenarios are consistent with those reported by Li and Modest [14,15] and by Habibi et al [2]in the case of methane jet diffusion flames. Fig.…”

“…The second term, referred to as 'emission TRI', is determined on the basis of local properties only and can be evaluated by using either presumed-pdf approaches [2,6,8e12] or pdf composition methods [3e5, 7,13e16]. Li and Modest [14,15] and Habibi et al [2] isolate and quantify different levels of closure for emission TRI in turbulent methane jet flames and showed that the complete absorption coefficient-Planck function correlation must be considered to obtain a reliable evaluation.…”

Numerical simulations of the radiative transfer in a 2D axisymmetric turbulent non-premixed methane–air flame using up-to-date WSGG and gray-gas models

“…In the present study, the peak temperature dropped ΔT RAD = 130, 131, and 262 K for radiation computed with CR-WSGG, NCR-WSGG and gray-gas, respectively. In similar investigation, Li and Modest [36] found a decrease of ΔT RAD = 145 K for a flame with an optical thickness of 0.474. The flame of the current study has an optical thickness of about 0.43, therefore with a slightly smaller influence of thermal radiation, so the differences between the studies are consistent when CR-and NCRWSGGs were employed.…”

“…These two TRI correlations were found to be the most important in reactive flows [35][36][37]. Decomposition of temperature and absorption coefficient into average and fluctuating components, T =T + T ′ and κ =κ + κ ′ , followed by time averaging, and neglecting higher order terms, κT 4 can be written as [19]:…”

Numerical assessment of the effect of inflow turbulators on the thermal behavior of a combustion chamber

“…, if the mean free path for radiation is much larger than turbulence integral length scale; this assumption was adopted here and in many other studies dealing with TRI based on the timeaveraged form of the RTE [23,27,28]. Additionally, in the present study it was applied the approximation proposed in [23] and [7], in which both absorption coefficient-temperature correlation and temperature self-correlation are considered.…”