FLAME SPREAD THROUGH RANDOMLY PACKED FUEL PARTICLES

Reproducible small-scale fires were obtained by burning randomly packed wood shavings (popular) under controlled environmental conditions. The rate of linear fire spread over the uniform slab-like fuel bed was measured for each of the pertinent variables over the following ranges: {A table is presented}. A significant increase in the rate of fires spread across the wood shavings was obtained when the relative humidity of the ambient air was decreased, when the fuel particle length was increased, and when the fuel bed voidage was increased. The fuel loading density was found to have no effect on the rate of fire spread over the range investigated. Radiation flux density data obtained from a wide angle view total radiation pyrometer, indicated that the radiation from the burning fuel embers through the fuel bed is significantly greater than that from the overhead flame. Very fine thermocouples inserted into the fuel bed showed that the radiative heating of the unburnt fuel amounts to approximately 40 per cent of the heat required for ignition. © 1969.