Fire Safety Science Digital Archive

A methodology and a model are presented for the calculation of radiation distribution from fires. Extensive application of the model is discussed with regard to turbulent buoyant jet fires wherein radiation is controlled by soot and the flame size is such that it produces optically thin conditions. The local soot concentration is modeled, according to previous results, to be 1) proportional to the inverse smoke-point heat release rate, Y,- ll& and 2) a function of the local mixture fraction and temperature. The local volumetric emissive power is averaged over the turbulent fluctuations to obtain the radiation losses for optically thin flame situations. Combustion is modeled, in a standard way, by an ensemble of laminar flamelets whose chemical composition of species is known from state relationships. The combustion model is an integral model that has been validated by extensive data from turbulent buoyant jet flames whereas the radiation model is validated here by comparison with propane turbulent jet flames; this comparison allows the determination of a proportionality coefficient for the soot concentration and radiation term. The generality and soundness of the model has been determined by applying it to predict the jet flame radiation from another fuel, propylene (while maintaining the same proportionality constant for the soot as for the propane). Preliminary results and favorable comparisons with experiments are also shown for pool fires of diameter up to 1 m. The proposed methodology and the model can be applied to an arbitrary burning material whose laminar smoke-point heat release rate has been measured in laboratory experiments.