Study On Smoke Control Effect Of Air Curtain And Mechanical Smoke Exhaust In Tunnel

With the rapid development of highway tunnel construction in China,the transportation distance is greatly reduced,and the convenient and fast operation demand is realized.Tunnel traffic makes it very convenient for people to travel,but the occurrence of tunnel fire not only causes casualties,but also may seriously damage the tunnel structure.To control the spread of smoke,and at the same time ensure that people can escape safely from the tunnel.this paper proposes a smoke control method combining mechanical smoke exhaust and Counter-blowing air curtain,which controls the smoke in the middle of two air curtains,and uses the smoke exhaust fan to discharge the smoke.Taking Zhong nan shan tunnel in Qin ling Mountains as the research object,this paper uses FDS fire simulation software to analyze the effect and parameter optimization of the combination of mechanical smoke exhaust and Counter-blowing air curtain in tunnel smoke control.The specific research contents are as follows:Through theoretical analysis,the main factors include jet angle,velocity and nozzle width that affect the smoke control efficiency of air curtain.Using FDS numerical simulation software,the orthogonal experiments of 16 working conditions with three factors and four levels are analyzed.The results show that the best combination level of air curtain as follows:the air supply speed of air curtain is 7 m/s,the air supply angle is 0°and the width of air supply outlet is 0.3 m.FDS numerical simulation software is used to compare the temperature,visibility,CO concentration at 65m away from the fire source between ordinary tunnel and the combination of mechanical smoke exhaust and counter-blowing air curtain,and the distribution of temperature,CO concentration and visibility at different heights along the tunnel,which fully shows that the latter can effectively control the smoke spread.FDS was used to simulate the effect of different air curtain spacing on smoke control.By comparing and analyzing the distribution of temperature,CO concentration and visibility at different heights in different longitudinal positions of the tunnel,combined with the project cost,it is suggested that the distance between two air curtains should be the distance between two adjacent crosswalks,that is,250 m.FDS is used to simulate the influence of different smoke exhaust velocity on the smoke control effect of tunnel,then analyze the distribution of temperature,CO concentration and visibility at different positions and heights in the longitudinal direction of tunnel.It is concluded that the air curtain can control the spread of smoke to the protection area when the smoke exhaust of the fan in the tunnel is greater than 20 m~3/s per unit time.Combined with the visibility requirements of people escaping,it is suggested to increase the unit time exhaust volume of fan to 40 m~3/s at the initial stage of fire,and then reduce the unit time exhaust volume of smoke exhaust fan to 20 m~3/s after all people escape.Finally,the simulation of evacuation is carried out by Pathfinder software.The results show that the combination of mechanical smoke exhaust and Counter-blowing air curtain can make people escape safely.