Research On The Spread Of Smoke In The Subway Cross Transfer Station

With the development of urban transportation,subway has been widely used in cities of many countries.While bringing convenience to people’s travel,subway also brings hidden dangers to people.Subway stations have high internal tightness,narrow space and high heat flow density.Most of the casualties in fire are caused by smoke poisoning and suffocation.Therefore,how to remove fire smoke quickly and effectively and provide a safer escape environment for subway passengers is very important.In this paper,fire dynamics software FDS and evacuation simulation software Pathfinder are used for numerical simulation of fire and evacuation simulation of an arch "cross" transfer subway station.The specific research contents are as follows:Through the numerical simulation method of fire dynamics software FDS,the influence of five smoke exhaust volumes on the smoke spread,visibility and CO concentration of subway station under the platform independent smoke exhaust mode and combined smoke exhaust mode（opening the platform screen door,enabling the tunnel exhaust fan and combining the platform exhaust fan）is simulated under the fire situation of negative third-floor platform platform.The results show that properly increasing the smoke volume of the platform exhaust system can well control the spread of smoke,improve visibility,CO gas impact on people,but too large smoke volume will not only increase the economic investment of the smoke exhaust system,but also can not effectively and quickly eliminate the smoke volume;Compared with the platform independent smoke exhaust mode,the combined smoke exhaust mode can reduce the smoke volume in the platform area and ensure a safer escape environment for personnel.Through the numerical simulation method of fire dynamics software FDS,the change rule of smoke layer flow state under the action of water spray and the influence of coupling effect of water spray system and smoke exhaust system on smoke flow were simulated in the case of fire at negative three-story platform.The results showed that the spray system can effectively reduce the flue gas temperature near the fire source and the ceiling,almost fire place personnel safety hidden danger,to prevent the high temperature heat damage of subway station structure and material composition,but spray system will make the spray effect in flue gas temperature drop,"smoke congestion" phenomenon,induce the platform area fire smoke sedimentation,As a result,the visibility area less than 10 m at 2 m height of platform and the area with high concentration of CO increase.By means of theoretical analysis and numerical simulation,the problem of smoke penetration in the side smoke exhaust mode of the vaulted station hall on the negative first floor and the influence of smoke outlet location and smoke exhaust volume on the smoke exhaust effect of the vaulted station hall were studied,and the influence of platform air supplement on the mechanical smoke exhaust of the station hall was discussed.The results showed that: When the distance between the smoke outlet and the vault of the station hall is within a certain range,the time when the smoke outlet begins to contact with the smoke removal is similar;The greater the distance between the smoke outlet and the vault of the station hall,the greater the smoke output of the smoke outlet,the more likely the smoke layer near the smoke outlet will be sucked through when the fire occurs,and the best position between the smoke outlet and the vault and the best smoke exhaust air volume can be obtained.It is suggested that mechanical ventilation or screen door should be opened in case of fire on the station floor to provide a safer environment for the station floor.Using Pathfinder evacuation simulation software to the subway station different number evacuate to a safe area safe evacuation time simulation,the necessary of fire simulation software FDS simulation platform under various operating conditions,fire station hall of the available safe egress time is analyzed,through the necessary safety evacuation time and the comparison of the available safe evacuation time,Discuss the number of people safely evacuated.