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Radiation heat transfer in flames depends strongly on local quantities such as pressure, temperature and concentration of participating species. In the present study, 3D numerical calculations of radiative heat transfer together with the reacting flow field are compared to detailed measurements of the velocity, temperature and spectral radiation field of a model combustor. The geometry of the combustion chamber (dch = 0.5m), the flame configuration (type-II swirling, diffusion flame) and the highly turbulent flow conditions resemble the characteristics of industrial combustors. The concentrations of CO2, H2O, CO, CH4, NO, NOx, O2 and H2 as well as local mean temperatures and their fluctuations were recorded at 300 locations at 14 axial planes. The radiation intensity incident on the wall was measured spectrally and time resolved at 11 axial planes within the spectral range of 1.4 to 5.4 μm. For numerically solving the reacting flow field, spectral methods for calculating the radiative heat transfer were coupled to fluid mechanical methods for calculating the reacting flow. The agreement between numerical prediction and measurements for the reacting flow field as well as for the radiative heat transfer is reasonably good. The numerical computations show that radiative transfer is of major importance. The temperature in the hot reaction zone was found to be lowered by approximately 400 K by radiative losses.

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