Flame behavior from an opening at different elevations on the facade wall of a fire compartment

Abstract This paper investigates flame ejected from opening at different elevations on the facade wall of a fire compartment. Two reduced-scale experimental models are employed consisting of a cubic fire compartment with one opening and a vertical facade wall. Experiments are conducted by varying the height of the opening and at different heat release rates (HRRs). Results show that the distance of the flame base from the bottom of the opening gradually decreases with increasing opening elevation. The external flame height measured from its base increases firstly, reaches the maximum when the opening is located at approximately half height of the fire compartment and subsequently decreases as the opening moves up. Moreover, the increasing elevation of the opening contributes to decreasing mean critical HRR for flame ejection. The above observations are found to be due to the increased deep sinking of the cold inflow while it is mixing and reacting with hot gases, as the vertical elevation of the opening increases, as supported by the additional computational fluid dynamics (CFD) simulation results. This is an important new observation, because whilst having an opening at elevated locations is common in a compartment fire, it has not been accounted for in previous classic models on ejected flame behavior from opening of a fire compartment. By identifying the similarities and differences of facade flame dynamics as the vertical elevation of the opening varies, a new model is proposed and validated for flame height with characteristic length scales to account for the changes in air inflow and critical heat release rate for flame ejection with opening elevations.