Fire Safety Science Digital Archive

A physical model is proposed to describe the steady propagation of a planar fire front through a uniform, horizontal, porous fuel bed: The model.assumes that there is no ambient wind and the bed is thermally-thin. In the present model, the mechanisms of preheating of unburned fuel contain radiation from the flame; radiation and conduction through the fuel bed due to the non-uniform temperature distribution of unburned fuel. The cooling mechanisms including radiative cooling from the upper surface of fuel bed and convective cooling induced by the flame are also considered. A simple formula is obtained to relate the rate of spread (ROS) with the major influential factors . The model is tested against laboratory fires. If the convective cooling coefficient is constant in variable situation, the predicted ROS is about 1.5 times the measured value and the predicted temperature distribution of unburned fuel differs from the observed values, too. Adjusting the convective cooling coefficient properly would give better predictions for both ROS and the temperature distribution.