Ignition of combustible forest materials by a radiant energy flux

摘要

The paper reports results of experimental ignition of litter layers consisting of needles ofcedar,pine,and fir-tree,birch leaves.lichen(Cladonia),and moss (Pleurozium shreberi).It is established that the moss is ignited faster than the other combustible forest materials.It is shown that with equal moisture contents,the ignition times of needle litter form different trees are identical within the experimental error,and for litter ofbirch leaves,the ignition time is shorter than forlitter of coniferous trees.This difference if found to be due to differences in the interaction of the radiant flux with litter layers of needles and leaves.Minimum values of the ignition heatpulses for needle and leaf litter layer are estimated for various heat-flux densities.These Values tend to a minimum for a heat-flux density of 0.5-0.8 MW/m~2.