Study On Fire Smoke Characteristics Of Metro Tunnel With Slope And The Intermediate Shaft

The subway tunnel is a long and narrow underground space that often the two ends of the tunnel link with outside.If the subway train is on fire and can not travel to the next station,the personnel must be evacuated.However,due to the limited space inside the tunnel,the high temperature smoke will spread rapidly along the tunnel,which will have an important impact on the safety of personnel and the tunnel.Longitudinal ventilation is the most common form of ventilation in subway tunnel at present,although there are many studies on the subway tunnel fire,but the research on subway tunnel fire smoke characteristics of slope and the intermediate shaft is relatively little.However,the actual subway tunnel is usually has slope,and the existence of the slope will have an important influence on the tunnel in the gas flow,temperature distribution and concentration of CO,if the subway tunnel is longer,in order to avoid the phenomenon of the train track in the tunnel,it must set the middle air shaft to ensure the normal ventilation in the tunnel,effectively eliminate of smoke,and the safety of people.Therefore this article will focus on the detail of smoke spread,temperature distribution and CO distribution when the longitudinal ventilation tunnel in different slope and the intermediate shaft existed.In this paper,the 1:10 scale experiment model is used to validate the simulation results.Through the comparative analysis of the horizontal tunnel of the temperature distribution of the tunnel ceiling and the height of the human eye,the natural ventilation and the critical wind speed ventilation is studied,and the reliability of the full scale simulation results is obtained.Then at the natural ventilation and longitudinal ventilation conditions,the horizontal tunnel,different slope tunnel and the tunnel that exists the intermediate air shaft in different slopes are studied.The results shows :(1)For the subway tunnel without intermediate air shaft,in natural ventilation,with the increase of slope,the phenomenon of smoke recirculation is more and more obvious.The distribution of temperature and CO concentration is similar to that of the horizontal tunnel at 1%,and the slope is increased to a single distribution at the center of fire when the slope increased to 2%.(2)For the subway tunnel without intermediate air shaft,in longitudinal ventilation,the critical wind speed of horizontal tunnel is 3.5m/s.When the slope of uphill tunnel is 1%,2% and 3%,the critical wind speed is 3.5m/s,3.6 m/s and 3.7 m/s,respectively.When the slope of downhill tunnel is 1%,2% and 3%,the critical wind speed is 3.3m/s,3.2 m/s and 2.9 m/s,respectively.(3)For the subway tunnel without intermediate air shaft,under the critical wind speed,the temperature at the height of the human eye of uphill tunnel is characterized by "U" type,and the temperature at the height of the human eye of downhill tunnel is characterized by "n" type.In the middle shaft case,the ceiling temperature is "2 peak" type distribution in critical speed,and the temperature distribution at the height of human eye features in critical speed is "3 peak" type,the CO concentration along the tunnel tends to be the same,with the increase of simulation time.