Study On Smoke Movement And Mechanical Smoke Exhaust Efficiency Of Underground Transfer Hall

With the development of economy in our country,large space buildings,such as atriums have been more and more popular.Because of the different functional requirements,there is a phenomenon that many large space buildings’ areas always exceed in the design of the fire prevention regulations.When there is a fire happening,the fire smoke control is particularly important.So it is necessary to study the key parameters of the smoke extraction technology.This paper puts the transfer hall as the research object,and references the existing standards,then connects with the domestic and foreign researches to confirm the architectural characteristics and the smoke control means;Then analyzes the feasibility of narrowing the scale model,which is based on the similarity theory to set up a 1:10 scale model of the large space experiment platform,using the top uniform openings,mechanical smoke exhaust;By using FDS simulation software for three different fire power,four kinds of different smoke exhaust quantity,five different smoke exhaust wind speed,five different height of smoke exhaust port and five different experimental condition of filling air volume,to study the distribution of the smoke layer height and visibility;In scale experiment platform to carry out the study,and compares with the results of numerical simulation analysis to verify the correctness of the FDS full size model,and through the experimental results to study the flue gas temperature distribution of the transfer hall;According to the results of experiment and numerical simulation,the research is applied to a practical engineering,and put forward the optimization of underground transfer hall mechanical smoke exhaust.The experimental and simulation results show that:(1)The gas flow is relatively complex,and the flow velocity is uneven distribution.The temperature of smoke rise range is not big.The temperature is not the main risk factors,and the smoke obscuration and toxicity is the major risk factor.(2)Under different fire heat release rate,flue gas temperature increases with the increase of fire power,and the stable final height of smoke layer is directly proportional to fire heat release rate.(3)Under the different smoke exhaust quantity,the overall temperature in the space decreases with the increase of the smoke exhaust rate,and the final stable height of the smoke layer is directly proportional to the smoke exhaust rate.Greater the smoke exhaust rate is,higher the height of the smoke layer is.(4)Under different exhaust wind speed,the overall temperature decreases with the increase of smoke exhaust wind speed.Smoke layer stable final height is directly proportional to the exhaust speed,the greater the smoke exhaust wind speed becomes,the steady smoke layer height is higher,but there is a certain limit,when the wind speed increases to a certain degree,stable height of smoke layer effect will be weakened.(5)Under different exhaust mouth height,steady smoke layer height is directly proportional to the exhaust mouth height first,then becomes inversely proportional relationship.Too high or too low exhaust mouth height for flue gas flow and discharge has larger disturbance.(6)Under the conditions of different air supplement volume,steady smoke layer height is directly proportional to the air supplement volume,the greater the air supplement volume becomes,the higher the steady smoke layer height is,but the gap is smaller.(7)Through the comparison of three kinds of schemes,this paper gives the following suggestions for the optimization of the mechanical smoke extraction solution to transfer hall,which belongs to the project of Shapingba:a)There is not setting up any business(including retail business)in the transfer hall to reduce the dangers of fire;b)Mechanical smoke exhaust system is set up in the transfer hall.Considering with the largest source of strength for the 4 mw fire,and controlling the smoke layer height above 2.6m dangerous height in 20 minutes,the smoke exhaust quantity should be not less than 65000 m3/h,and suggests the smoke wind speed should be not less than 2 m/s,the height of exhaust port recommending layout from the ceiling height of 2～3 m;c)Setting mechanical wind filling system,air volume is set by 50%of smoke exhaust volume;d)The schemes,which are designed by Performance-based design and design organization,are better met the needs of smoke exhaust.