The study herein aims at characterizing the intermittent flaming region of upward current above diffusion flames, and consists of the similarity analysis of the region, derivation of the analytical solution of the basic equations for axisymmetric upward current due to buoyancy with respect to the experimental facts on the region and the determination of experimental constants which are involved in the solution by dimensional analysis and experiments.

As the growth of fire and spread of smoke depend significantly on the behavior of the upward current above fire source in early stages of compartment fire, the characterization of the upward current above fire source is a problem of increasing importance. However, though considerable informations are available on axisymmetric upward current, most of them are almost limited to the region far from fire source. This report analyzes the intermittent flaming region among the near regions to fire source, and derived a mathematical model of this region which enables it to predict the properties of the region at the comparable accuracy to that for the region far from fire source. The report also presents some diagrams for the practical calculation of the useful properties such as mass flow rate in the current and entrainment coefficient at every height in the intermittent region.

* Research Member, Testing & Evaluation Department.