Experiments on the burning of cross piles of wood

Abstract

Experiments have been performed in which geometrically scaled, unenclosed, cross piles of wood were burned under controlled conditions. For sticks of square cross section ranging in size from 0.16 to 9.15 centimeters, the typical weight-time curve illustrated the three characteristic stages: ignition, active combustion, and decay. For the active combustion stage, the maximum rate of burning (rate of weight loss) was determined and all the test data were correlated in terms of a porosity factor involving the vent area of the pile and the exposed surface area of the sticks. The correlation between the scaled rate of burning and the porosity factor may be simply considered in terms of three regions: a. Diffusion-limited combustion, in which the scaled rate of burning is very nearly proportional to the porosity factor, b. free combustion, in which the scaled rate of burning is independent of the porosity factor, and c. nonsustained combustion, in which the openness of the pile prevents the maintenance of combustion. Similarity considerations of flame height and radiant intensity data indicate that a simple model may adequately describe the natural convection burning of cross piles of wood of the type and size range investigated.