Research On The Distance Between Outdoor Air Inlet And Smoke Exhaust In High-rise Office Building Based On FDS

Due to the complex internal structure,dense personnel and long vertical evacuation distance of high-rise office buildings,fire in the building will cause huge loss of personnel and property.When a fire occurs,compared with the temperature of the fire site,fire source and other dangerous factors,the fire smoke poses a greater threat to the escape personnel.Therefore,the reasonable design of smoke prevention and exhaust system of high-rise buildings can effectively prevent the back flow of fire smoke,and strive for more escape time for the escape personnel.Combined with practical cases,this paper uses FDS software to establish a60-meter-high,15-story office building for numerical simulation.This high-rise office building is equipped with mechanical smoke control and exhaust system,and the outdoor air inlet and exhaust port of the fan are set on the same facade of the building.A total of 132 working conditions were set,and the fire smoke back flow was investigated by changing the distance between outdoor air inlet and exhaust outlet,and the safe distance between outdoor air inlet and exhaust outlet under different fire source location,fire source power and environmental wind was obtained.The research contents and results are as follows:(1)In the case that there is no ambient wind and the fire source position is the same,two fire scenarios of sprinkler normal opening and sprinkler failure are simulated by changing the power of the fire source.It is found that the fire power has a significant influence on the safety distance between outdoor air intake and smoke exhaust,and the greater the fire power,the greater the safety distance between them.(2)In the absence of ambient wind,fire source locations in the model were set as high level(11-15 floor),middle level(6-10 floor)and low level(1-5 floor)for the same fire source power.By comparing the simulation results,it was found that the fire source location also had a significant impact on outdoor air intake and smoke exhaust.With the decrease of fire source location,the safe distance between outdoor air intake and smoke exhaust gradually becomes larger.(3)Compared with the situation without ambient wind,the safe distance between outdoor air inlet and exhaust port is greatly increased when there is ambient wind and the ambient wind blows from the exhaust port to the air inlet.(4)The fire power under the condition of invariable,fire source location,through environmental wind this factor is added in the numerical model,the simulation showed that,as the wind environment of smoke exhaust mouth blowing when the mechanical pressure air inlet(dangerous wind),outdoor air inlet and exhaust port down--level security spacing of 25 meters and above,the vertical clearance is 6 meters.Above this safe distance,the smoke discharged from the exhaust port can be avoided from returning to the building through the mechanical pressurized inlet.(5)When the outdoor air inlet and smoke outlet of the mechanical smoke control and exhaust system of a high-rise office building are arranged on the same building facade,it is recommended that the safe distance between the outdoor air inlet and smoke outlet be modified from the current "horizontal safe distance 20 meters,vertical safe distance 6 meters" in the Technical standard for smoke management systems in buildings to when the two are arranged horizontally.The minimum distance from the edge shall not be less than 25 meters,and it shall be combined with the local dominant wind direction to avoid setting the smoke exhaust port in the upwind direction of the mechanical pressurized air inlet;In vertical setting,the minimum vertical distance between the two edges shall not be less than 6 meters,and the air inlet of the fan shall be located below the smoke exhaust port.