Experimental and numerical study of transient compartment fires

This paper reports results of experiments and numerical modeling for fires in small-and medium-scale enclosures in underventilated conditions resulting in flame exhaust to the atmosphere. Delays from ignition to the occurrence of a stable flame outside the enclosure were measured experimentally for three types of fuels (methane, propane, and propylene) with a specified fuel supply rate. Characteristic scales dependent on fuel supply rate, fuel source location, compartment geometry, and vent opening parameters are introduced and used to establish a unified nondimensional dependence of the flame exhaust time on fuel flow rate. For the smallest and largest enclosures used in the experiments, three-dimensional numerical calculations of the dynamics of fire development are performed by large eddy simulation. Calculated reaction rate isosurfaces are presented, which demonstrate the compartment fire evolution and its oscillations after exhaust into the atmosphere. It is shown that the calculation results agree qualitatively with experimental observations and that the flame exhaust times are in good agreement with the experimental correlation.