| With the rapid development of urban modernization in China,the total number of new buildings is increasing year by year,most of which are high-energy buildings.Polymer materials are used in building facade insulation because of their good thermal insulation effect,low price and light weight,so as to reduce building energy consumption.At the same time,in order to meet the needs of lighting,beauty and building space,most high-rise buildings usually use building curtain walls as enclosure structures.There is a vertical mezzanine channel between the facade of the building and the curtain wall.In this case,once the combustible external wall insulation material is ignited by an open flame or high temperature,the Quillfire flow and toxic smoke generated by the burning of the insulation material will spread to other floors along the curtain wall mezzanine,and the fire will spread from the ignition point to the top floor of the building in a very short time.If the fire is not put out in time,it will cause a large-scale three-dimensional fire,and even the thermal radiation generated by burning will ignite the adjacent buildings,resulting in greater fire safety accidents.Combined with the complex space and high density of people in modern high-rise buildings,once a fire breaks out,it is not only difficult to put out the fire but also difficult for people to escape,thus endangering the safety of people’s lives and property.Therefore,it is very necessary to analyze and study the influence law and mechanism of fire spread of building insulation materials in the confined space of curtain wall interlayer.In this paper,Polyurethane foam（PU）is selected as the experimental material.According to the structural characteristics of high-rise buildings and building curtain walls,and the characteristics of fire in modern building external wall insulation materials,a combustion platform is developed for small-scale experimental simulation.In this paper,the fire spread experiments of polyurethane foam insulation materials are carried out under different curtain wall spacing and different curtain wall inclination angles,and the influence law of building curtain walls on fire spread characteristics of polyurethane foam is discussed and analyzed by combining combustion,hydrodynamics and heat transfer.The experimental results show that under the natural convection condition,whether the curtain wall exists or not,the flame front of polyurethane board in the process of vertical counter-current fire spreading presents a typical inverted"V"shape.Under the condition of changing the curtain wall spacing,the mass loss of polyurethane foam in the process of fire spread is approximately linearly decreasing,which represents that the combustion process is relatively stable.Under the coupling effect of thermal feedback,stack effect and constraint effect in the curtain wall interlayer,the mass loss rate of polyurethane foam decreases with the increase of curtain wall spacing,and reaches the peak at D=4cm.The existence of curtain wall has changed the entrainment mode and intensity of flame to air.In the middle and late stage of fire spreading,the flame height fluctuated within a certain range due to the coupling effect of molten dripping and non-constant flame entrainment.Under the influence of curtain wall-induced stretching effect and stack effect coupling,the average flame height with curtain wall was higher than that without curtain wall.Moreover,the average flame height first increased and then decreased with the increase of curtain wall spacing.When D=8cm,the average flame height reached its peak and increased.At the same time,the existence of curtain wall limits the diffusion of heat,and the reflection of curtain wall and its own thermal radiation strengthen the thermal feedback to the combustion zone,which leads to the radiant heat flux with curtain wall configuration being larger than that without curtain wall,and the peak value of radiant heat flux above polyurethane insulation material is larger than that below it at the same curtain wall spacing.Under the small curtain wall spacing,the heat accumulated in the curtain wall interlayer gradually increases with the spread of fire,the radiation of the curtain wall itself gradually increases with the burning of fire,and the central temperature of the plate gradually increases from top to bottom with the spread of fire.Under the large curtain wall spacing,the curtain wall has little influence on the surface temperature of the plate,and the central temperature of the plate is basically the same.Under different curtain wall inclination angles,the variation law of flame height is similar to that under the condition of changing curtain wall distance.With the increase of curtain wall inclination angle,the average flame height first rises and then falls,and when the curtain wall inclination angle is?=5?,the average flame height reaches the maximum value.In the process of fire spreading,the increase of the inclination angle of the curtain wall weakens the limiting effect of the curtain wall,and accelerates the melting rate of polyurethane insulation board.Under the action of gravity,the random peeling combustion zone drops,and the melting rate increases with the increase of the inclination angle of the curtain wall.The dripping of molten liquid directly reduces the combustion quality and accelerates the fire spreading rate.Therefore,in the process of fire spreading,the fire spreading rate increases with the increase of the inclination angle of the curtain wall,which is consistent with the change law of the melting rate.Drops of molten droplets will form a new ignition source in the unburned area,thus forming the situation that multiple ignition sources spread at the same time,and it is easy to form an up-down three-dimensional fire spread,which will cause great difficulties in fire fighting.By comparison,it is found that under the same inclination angle of curtain wall,because the distance between the upper end of curtain wall and the plate is smaller than that of the lower end,the radiation heat flux at the upper end is larger than that at the lower end,and the radiation heat flux at the same position decreases with the increase of inclination angle of curtain wall under different angles.Due to the influence of air entrainment and combustion adequacy,the near-field temperature law of the upper surface of the plate is that the side temperature is higher than the middle temperature.The experimental results provide reference for the study of solid fire spreading behavior under the building curtain wall configuration,and also provide reference for the fire prevention of building facade and the installation of building curtain wall.Figure[32]table[5]reference[74]... |
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