Study On The Sprinkler Prevention And Control Of Building Window Fire Overflow And Its Engineering Application

At present,in order to achieve better building facade effects,more and more highrise buildings in China adopt glass curtain walls.However,glass curtain walls and glass windows tend to rupture under fire conditions and form channels for flame to spread to the outdoor.The purposes of this thesis are to study the feasibility of cooling protection using the sprinkling system to cool the glass curtain walls or glass windows,to investigate the cooling protection behaviors,and to propose key parameters for engineering application,finally forming an economical and efficient protection cooling system which could effectively reduce the possibility of window glass breakage in fires and the subsequent risk of upward spill flame.In this thesis,full-scale spilling fire experiments were carried out in a 12 m high,three-story experimental facility and a 12-storey fire test tower with a total height of 39.6 m.The indoor fire spilling behaviors were analyzed in detail,and the influence of fire source location and the feasibility of using sprinkler system to suppress spilling fire was investigated;based on the full-scale test results,the feasibility and accuracy of CFD simulation method were further verified.CFD simulations were carried out to study the protective cooling performance of a single window sprinkler and multiple sprinklers,and to quantify the influence of sprinkler spacing on the protection effect,which provide data support for engineering application.Finally,by considering the existing problems of automatic sprinkler system and protective cooling system in relevant engineering standards and specifications of China,parameters of cooling protection sprinkling system on exterior window protection were designed for engineering application,and from the system application level,an engineering application scheme of window glass cooling protection system was proposed.The protective performance of the system was tested by conducting fire experiments in a real building.The related research outcomes were applied to two typical super high-rise building projects in Chengdu,i.e.,the "Global Gathering" integrated commercial project and the 2#block project of Qinhuangsi Project in Zhonghai.The specific research contents include:(1)Full-scale experiments were carried out to study the influence of indoor fire source positions on fire spilling behavior,and the protection effect on window glass by using different types of window sprinklers.It was found that the classical spill fire model failed to accurately predict the spilling behaviors in full-scale fire experiments,and it is not sufficient to predict the fire spilling phenomenon only by using the critical heat release rate in the classical model;the setting distance and working pressure of glass sprinkler,conventional fast response sprinkler and water curtain sprinkler for effective protection of spilling fire were obtained,and two typical modes of window glass breakage under sprinkler protection conditions in real fires were revealed.This study found that in addition to the sprinkler type,working pressure and installation methods,the glass frame presented a critical influence on the final protection effect;when the installation spacing of window sprinklers is less than 1.6 m,the fireproof partition formed by sprinklers and tempered glasses showed good protective performance in rooms with single and double window glazing.(2)By conducting reconstruction simulation of full-scale experiment scenarios,it was found that the CFD modelling can not only accurately simulate the thickness and temperature of the smoke gas layer above the room during the steady fire stage,but can also effectively simulate the water distribution patterns of both window sprinkler and the conventional sprinkler,as well as the indoor gas temperature after the sprinkler is activated;CFD simulations were conducted to study the glass cooling behaviors under different fire powers and sprinkler spacing,from which a sprinkler installation spacing was found under the worst fire scenario(the automatic fire extinguishing system failed to respond).Results show that when the power of fire source was set to 2MW,4MW and 6MW,the reduction rate of incident heat flux produced by the water film on a single window sprinkler can reach 54%-59%.Moreover,there was no significant difference between the window center and the window edge,the breakage risk of a single window with one single sprinkler remained at the top edge of the window;when the distance between the sprinklers was 2.8 m,a large area between the two sprinklers was not under protection,the risk of window breakage is quite large alongside the rising of the glass temperature.When the sprinkler spacing was reduced to less than 1.6 m,the glass surface temperature stayed near 100℃,which was 67.8%lower than the temperatures from the scenarios without protection.(3)In the view of the lack of specific technical requirements for cooling protection of external wall glass in China’s current standards,this thesis developed the design requirements and engineering application schemes of external window cooling protection system from a system application level,the requirements and schemes were applied in two super-tall building projects.According to the experimental research and numerical simulation analysis,the specific parameters of sprinkler spacing and minimum spraying intensity of the window cooling protection system were proposed;two schemes with independent pump and shared pump for the cooling protection systems on exterior window were compared and analyzed comprehensively.Full scale fire experiments was carried out to verify the shared pump scheme which was recommended under premise of ensuring the safety and stability of water supply.The external window cooling protection system and its key parameters proposed in this thesis have been applied to two real super high-rise building projects,which provide scientific evidence for the design of external window cooling protection system and the revision of national standards and regulations,playing an important exemplary role on the application and implementation of the external window cooling protection system on the glazing facade of(super)high-rise buildings.