Study On The Effect Of Smoke Exhaust In Subway Transfer Station Fire With Different Smoke Vent Arrangement And Smoke Exhaust Mode

At present,the rapid increase in the number of urban population in China has brought great pressure on transportation.Urban subways have been used in more and more cities,and have gradually established urban underground transportation network system.However,due to the relatively closed underground environment and the intensive flow of people in the subway station,once a fire occurs,people will often face heavy losses in life and property.In fact,there have been many fire accidents in subway stations around the world.Therefore,research on subway fires has always been the focus of scientific research.The research on subway station fires is mostly about ordinary two-story station mode,but with the increase of underground tracks,in order to meet people’s convenience to travel,subway stations have not only be platforms connecting ground and underground,but also become traffic hub with multiple tracks underground.The subway station has become increasingly huge in space,more complex in structure,more diverse in functions and more common in daily life.However,the existing subway fire design codes do not consider the differences in the structure of different stations in detail,and the given fire protection parameters are also relatively simple.This article takes the subway transfer station as the research object,and studies the influence of smoke exhaust with different smoke vent arrangement and different types of smoke exhaust modes.Using the FDS software,the evacuation indicators such as the spread of smoke,the CO concentration distribution,temperature distribution andthe visibility on the height of the human eye feature layer and the temperature distribution on the ceiling layer under different conditions are calculated and analyzed,and the advantages and disadvantages of each condition are compared.As a result,it is found that the arrangement of the smoke vent "two-side exhaust" and "middle exhaust" are better than the "one-side exhaust" arrangement.When the station hall is large,it can prevent the accumulation of heat and smoke relatively to improve the evacuation environment when a fire occurs.The method of comprehensive smoke extraction and platform air supply can be used to improve the evacuation environment for people.In the event of a fire at the platform floor,with the increase of the intensity of the fire source and the increase of the time of the fire,the smoke influx into the station hall is observed,and this phenomenon first appeared in the surrounding staircase.Beside,it is also found that the structure of the multi-story subway station straddled by stairs helps maintain air pressure balance.The influence of the air supply on adjacent nonflammable layers to the smoke exhaust effect on the fire layer is mainly reflected in the early stage of the fire.