Studies On Facade Flame Behavior Ejected From A Top-hung Window Of Fire Compartment Under No Wind And Normal Wind

With the acceleration of urbanization,more and more(super)high-rise buildings with comprehensive structures and functions have been built in cities,which is accompanied with great fire risks.Fires in high-rise buldings bring great challenges to fire safety.Once a fire occurs,with the increasing of burning rate inside the compartment,it will develop from well-ventilaed condition to under-ventilated condition.For under-ventilated condition,the unburnt gas inside the compartment spreads out from the window and burns outside the compartment forming facade flame.The external facade flame ejected from the window is an important fundamental urban fire safety problem,which has a significant effect on the urban/building fire spread.Previous studies on the flame ejecting behavior from a window of compartment fires are mainly focused on fully opened windows.One or two windows were considered in these studies with various boundary conditions,including horizontal eave,sloping facing wall,side walls,reduced atmosphere pressure at high altitude,normal-and sideward wind,etc.However,there is still no study for the effect of top-hung window on the fire behaivors of compartment fires.Due to the effect of top-hung window,the air supply and flame ejecting behavior are completely different from those of fully opened windows,which remains to be explored.Therefore,this thesis presents an experimental study on the characteristic parameters of flame ejecting behavior of compartment fires with a top-hung window under no wind and normal wind.For the flame ejecting behavior of compertment fires with a top-hung window under no wind condition,a model is develop by assuming that there are two symmetrical virtual rectangular fire sources on both sides of the window.The ventilation factor and characteristic length of the virtual rectangular fire source perpendicular to the facade wall,which including the effect of the opening angle of the window are derived.The evolution behaviors of critical heat release rate of flame ejection,temperature inside the compartment,facade flame height and the maximum facade flame depth under various opening angles of the top-hung window are revealed,and theretical models are proposed.For the flame ejecting behavior of compertment fires with a top-hung window under normal wind condition,the evolution behaviors of critical heat release rate of flame ejection and facade flame height are revealed.The characteristic length of the virtual rectangular fire source parallel to the facade wall,which including the effect of the opening angle of the window,is proposed.Based on the analysis of the wind Froude number and the ratio of air entrainment between normal wind condition and no wind condition,theretical model of facade flame height for comprtment fires with a top-hung window under normal wind condition is established.