Global Flame Radiation Model

A global model for the radiation from buoyant turbulent diffusion flames shows how the radiant fraction can be obtained from the fuel's laminar flame smoke-point value. The model considers the separate roles of soot and gaseous radiation as well as the effects of incompleteness of combustion and radiant heat loss on the flame temperature. The soot absorption coefficient for the buoyant turbulent diffusion flames is shown to be almost inversely proportional to the fuel's smoke-point and proportional to the turbulent flame macro-scale flow time. The predicted radiant fractions are in excellent agreement with experiment for fuels covering a wide range of flame sootiness. However, the predicted global flame temperatures seem somewhat low. By employing simple, yet accurate, curve-fit formulas for the soot and gaseous emissivities, the model is self-contained and can be easily evaluated using spread-sheet software.