Experimental study on evolution of compartment fire and facade flame through an opening with the fire source attached to a backwall at different elevations

Abstract

This study experimentally investigated the effect of fire source elevation above the floor of a compartment on the evolution of facade flame through the opening. Experiments were conducted employing a 0.5-m cubic compartment with an opening at the centre of one sidewall and an attached facade. A porous propane burner was set inside the compartment and attached to the backwall opposite to the opening. The temperature inside the compartment and the facade flame heights were measured for different openings with burner at various heat release rates and elevations (0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, and 0.40 m) above floor. Results showed that for all burner elevations, the temperature inside the compartment was stratified. The temperatures of both the upper- and lower parts inside compartment first decreased significantly with increasing burner elevation until approximately the height of the opening centre, and then the temperature change was gradual with further increase in burner elevation. The critical heat release rate, when the flame was observed to eject from the opening, generally decreased with increasing burner elevation. The facade flame base elevation above bottom of opening gradually increased first with increasing burner elevation up to approximately the height of opening centre, then changed little at a constant about 0.62 H (H is opening height) with further increase in burner elevation. The facade flame height showed a general increase, although with several transitions with increase in burner elevation. A new characteristic length was proposed concerning the evolutions of temperature inside compartment and the flame base elevation (or flame vertical thickness through the opening), which determines the buoyancy of the hot gas outflow through the opening. The measured facade flame heights at various burner elevations were shown to correlate well to a newly defined non-dimensional excess heat release rate based on the proposed characteristic length.