AbstractRecent data from large‐scale turbulent natural gas/air diffusion flames (135‐210 MW) were used to evaluate analysis of flame structure and radiation properties. The conserved‐scalar formalism, in conjunction with the laminar flamelet concept, was used to predict radiative heat fluxes. The narrow‐band model considered the nonluminous gas bands of water vapor, carbon dioxide, methane and carbon monoxide in the 1000‐6000mm wavelength range. Structure predictions were encouraging, with discrepancies for mean temperatures (ca200 K in the hottest portions of the flames) comparable to experimental uncertainties, due to thermocouple errors, flame disturbances from ambient winds and lifting and external expansion effects near the injector. Radiative heat flux predictions were also reasonably good, e.g. predictions based on mean scalar properties were generally 15% lower than the measurements. The findings also suggest that continuum radiation from soot is negligible for the