Study On The Dynamic Characteristics Of Smoke Transmission In High-rise Building Fires Under Fire Load Spillover Effec

With the continuous advancement of urbanization in China,the contradiction between limited land resources and increasing urban population has become increasingly prominent,and high-rise buildings have become the mainstream at present,and people enjoy the convenience of life brought by high-rise buildings,but also accompanied by a huge fire threat.High-rise buildings are composed of multiple single structures(corridors,shafts,rooms),and their fire smoke flow laws are more complex than single building structures.In this paper,a 1:10 scale scale fire similarity simulation experimental platform is designed and constructed,and the dynamic characteristics of fire smoke transmission inside and outside high-rise buildings are analyzed by combining FDS numerical simulation,mainly in the following two aspects: the influence of different fire source locations on the internal flue gas flow characteristics of high-rise buildings and the analysis of the influencing factors of smoke overflow on the fa?ade of high-rise buildings.Specific research contents include:Considering the randomness of the ignition source location in the actual building fire and the possibility of smoke spreading to the adjacent room,based on the principle of the most unfavorable situation,18 sets of experimental working conditions were designed to carry out small-size similar simulation experiments to explore the influence of different heat release rates and different ignition source locations on the flue gas flow of fire.The results show that the higher the heat release rate,the higher the temperature rise in the flue gas transmission area.When the ignition source is located in the same horizontal position and different fire floors,the chimney effect on the smoke extraction effect is mainly considered,the higher the fire floor,the weakening of the chimney effect intensity,resulting in an increase in the temperature rise of the horizontal corridor and adjacent room;The fire source is located on the same fire floor,when different horizontal positions,the distance between the fire source and the shaft is mainly considered,the closer the horizontal position of the fire source to the shaft,the faster the flue gas can be sucked into the shaft,so that the horizontal corridor and adjacent room temperature appreciation is reduced.After the flue gas flows into the open shaft from the front chamber,the driving force is gradually dominated by the chimney effect,and the heat release rate and the position of the ignition source have an impact on the rise rate of the flue gas plume: the larger the heat release rate,the faster the flue gas plume rise rate;The higher the fire floor,the slower the plume upward rate;The closer the fire chamber is to the shaft,the shorter the plume rise time and the faster the ascent rate.At the same time,the flue gas will continuously exchange heat with the wall during the rise of the shaft,and its temperature will decay exponentially with the increase of height,especially below the neutral surface.Based on the possibility that smoke can also spill from the broken windows of the burning room in the actual fire of high-rise buildings,seven sets of fire scenes are designed,and a full-scale model is constructed by Pyrosim to analyze the effects of different ignition source power,different window aspect ratios and different positive wind speeds on the flue gas overflow.The results show that the change of temperature and CO concentration of the upper adjacent room mainly depends on whether the flue gas is attached to the wall when it spreads along the fa?ade,and the power of the ignition source and the aspect ratio of the window of the burning room are the main influencing factors.When the flue gas spreads upward along the outer fa?ade,the thickness of the flue gas layer gradually increases due to the cold air suction effect,and its overall temperature distribution is attenuated longitudinally,especially from the window of the fire room to 10 m.Different positive wind speeds have different mechanisms on flue gas overflow,and when the wind speed is small,the thermal convection effect is strengthened,resulting in an increasing trend in the measurement parameters such as the temperature of the fa?ade and the upper adjacent room.When the wind speed is large,the mixing of cold air and flue gas intensifies,the temperature of the fa?ade drops sharply,and the measurement parameters of the upper adjacent room are kept at room temperature.