Upward Laminar Flame Spread Under the Influence of Externally Applied Thermal Radiation

Abstract

Rates of flame spread for the upward laminar propagation of flames over thick vertical sheets of Polymethylmethacrylate (PMMA) were measured under the influence of externally applied thermal radiant fluxes ranging from 0 to 2 W/cms. A previously developed theoretical model for the upward laminar spread of flames over vertical fuel surfaces was extended to account for the additional effect of the external radiation. It is shown that the theoretical predictions agree qualitatively with the experimental measurements and that the temperature of the fuel prior to flame tip arrival plays a critical role in the magnitude of the spread rate. It is found experimentally and predicted theoretically that a correlation in the form of a power law exists between the flame spread rate and the difference between the vaporization temperature of the fuel and its surface temperature prior to flame tip arrival.