Numerical Simulation Study On Natural Smoke Exhaust Characteristics Of Ultra-thin High Atrium

With the increase of super high-rise buildings,the atrium building has also developed rapidly.Predecessors defined the atrium with a shape factor(A/H^2)less than 0.1 and a height greater than 50 m as ultra-thin High atrium.The internal temperature of the ultra-thin high atrium often presents a stepped distribution,which is one of the important factors affecting the spread of smoke and natural smoke exhaust.Therefore,in this paper,the combination of theoretical analysis and numerical simulation is used to study the smoke spread and natural exhaust characteristics of the ultra-thin high atrium.Investigate and analyze the domestic ultra-thin high atrium buildings,summarize the geometric characteristics of the ultra-thin high atrium,take a hotel in Suzhou as the research object and construct a physical model,determine the simulation parameters and boundary conditions according to the standards and specifications,and determine according to the research content Simulated working conditions of smoke spread and natural smoke exhaust.Combined with the schematic diagram of flue gas flow in the atrium,key parameters such as the chimney effect,the height of the neutral plane,and the pressure of the exhaust vent are analyzed.Using FDS numerical simulation software,the effects of shape factor,fire source power,and temperature gradient on the spread of smoke,the position of plume touching the wall and the maximum height of plume rise were studied.Fix.The research results show that:the filling method of the atrium smoke with a shape factor greater than or equal to 0.10 is settling filling(topping first,then settlement),and the filling method of the atrium smoke when the shape factor is less than 0.10 is spreading filling(first touching the wall,then filling),The final peak);the fire source power has little effect on the position of the plume touching the wall,the maximum height of the plume increases with the increase of the power of the fire source;the position of the flue gas hitting the wall and the maximum rising height both follow the temperature gradient Increasing and decreasing,the temperature gradient will reduce the overall development speed of the plume and cause the plume to spread to both sides in advance.In the part of natural smoke exhaust,the effect of mechanical smoke exhaust and natural smoke exhaust was compared first,and then the effects of indoor and outdoor temperature differences,temperature gradients and the area of exhaust vents and supplementary vents on natural exhaust were analyzed.The research results show that:when the smoke exhaust area is 15%of the atrium floor area,the natural smoke exhaust efficiency is 69.8%,the mechanical exhaust volume is 200,000 m3/h,and the exhaust efficiency is 29.7%;when the indoor and outdoor temperature difference is small,supplementary air Higher temperature will result in more favorable natural smoke exhaust conditions;the greater the power of the fire source,the shorter the time to overcome the reverse chimney effect,the greater the temperature gradient,the smaller the power of the fire source,and the longer the time it takes for the neutral plane to reach a stable value;When designing natural smoke exhaust for the ultra-thin high atrium with a shape factor of less than 0.10,the area of the smoke exhaust port should be controlled at about 25%of the area of the bottom of the atrium,and the area of the air inlet should be controlled at about 70%of the area of the smoke exhaust port.The research of this thesis provides a certain theoretical reference for the design of natural exhaust of such ultra-thin high atrium.