Study On The Effect Of Smoke Prevention And Exhaust In Subway Transfer Station Fire With Water Mist Curtain And Air Vents In Platform Screen Door Area

In recent years,the number of urban population in China has increased dramatically.The traffic jam is becoming more and more serious.Traffic pressure of modern cities have been greatly relieved by subway because of its characteristics of saving land,large passenger transport,high efficiency and convenience.Although the subway has brought great convenience to people’s travel,the internal structure of the station is complex and the space is closed,therefore,there are many kinds of safety accidents,especially fire accidents.When the fire occurs,the poisonous and harmful smoke can spread in the subway confined space.The smoke can do great harm for people’s body,and even threaten people’s lives.Therefore,the subway smoke prevention and exhaust work is particularly important.It is necessary for us to study the smoke prevention and exhaust effect of the smoke prevention and exhaust system in case of subway station fire,so as to provide theoretical basis and reference suggestions for the optimization design of the smoke prevention and exhaust system and the safe evacuation of people in case of subway station fire.In this paper,the full-scale model for a cross subway transfer station in Xi’an is constructed by using Pyrosim.This paper includes two aspects: smoke prevention and smoke exhaust.The characteristics of fire smoke such as the smoke spread,temperature,carbon monoxide volume fraction,soot visibility were compared under different working conditions when the platform fire occurs.According to the analysis of smoke characteristics,the design parameters of the best smoke prevention and exhaust effect were obtained.Water mist curtain was set at the stairway and the smoke prevention effect of the water mist screen was compared under three different characteristic parameters,such as the spray flow,blow head latitude angel and particle size.And then the characteristic parameters of the fine mist curtain was obtained when the best smoke prevention effect is achieved.In this paper,the smoke exhaust effect of the platform fire was studied by opening the air vents above the platform screen door.The smoke exhaust effect of the air vents under different opening positions and numbers was compared under the two conditions of only opening the platform smoke exhaust system and the tunnel smoke exhaust system was combined with the platform smoke exhaust system.And then the opening parameters of the fine air vents were obtained when the best smoke exhaust effect was achieved.The main conclusions are as follows:(1)The water mist curtain has the effect of smoke suppression and cooling.The results show that in case of fire in the center of island platform floor,setting water mist curtain at the stairway can prevent smoke from spreading to the upper floor,reduce the temperature and carbon monoxide volume fraction at the stairway,improve the soot visibility of the stairway,enhance the smoke prevention effect of the platform,and ensure the safe evacuation of personnel.(2)The smoke prevention effect of the platform is related to the characteristic parameters of the water mist curtain.The results show that the larger the spray flow,the smaller the blow head latitude angel and the smaller the particle size bring better smoke prevention effect.In this paper,when the spray flow of the water mist curtain at the staircase is 12L/min,the blow head latitude angel is 30°,and the particle size is 100μm,the stairway temperature and carbon monoxide volume fraction are the lowest and the soot visibility is the highest.(3)The air vents opening in the area of platform screen door can improve the smoke exhaust effect of platform.The results show that when the fire occurs in the center of island platform,the opening of air vents in the area above the platform screen door can achieve the space connection between the platform and the tunnel.The air vents helps the platform to exhaust high temperature and toxic smoke,reduce the temperature and carbon monoxide volume fraction of the platform,improve the soot visibility of the platform,and enhance the smoke exhaust effect of the platform.(4)The smoke exhaust effect of the platform is related to the opening position and quantity of the air vents.The results show that when the fire occurs in the center of the island platform floor,when only the platform smoke exhaust system is turned on,18 air vents far away from the fire source have the best smoke exhaust effect.When the tunnel smoke exhaust system is combined with the platform smoke exhaust system,18 air vents near the fire source have the best smoke exhaust effect.