高海拔大纵坡铁路隧道火灾特性数值模拟研究

Numerical Simulation of Fire Characteristics of Railway Tunnels with High-altitude and Large Longitudinal Slope

为深入分析高海拔大纵坡铁路隧道的火灾特性,进而为高海拔铁路隧道防灾救援工作提供基础依据。文章采用FDS对铁路隧道火灾场景进行数值模拟,研究火灾规模为20MW时,不同海拔高度铁路隧道的烟气扩散规律以及疏散通道2 m特征高度和隧道拱顶温度场的纵向分布规律。研究结果表明:火灾规模相同时,随着海拔的升高,火灾烟气纵向一维蔓延速度加快,对于火源上游v=0.00003h+2.27,对于火源下游v=0.00006h+3.4312。大纵坡的设置能抑制火灾烟流向上游扩散,上游特征高度的温度场受影响程度小,使得火源上游特征高度的温度场在安全疏散时间内满足限值要求。火源下游约120 m距离范围内,随着海拔的升高,拱顶纵向温度也随之升高;而在120 m范围以外,则随海拔的升高而降低。大纵坡铁路隧道火灾发生时拱顶最高温度点向下游偏移,且最高温度随着海拔的升高而增大t=0.0365h+443.98。

In order to deeply analyze the fire characteristics of railway tunnels with high altitude and large longitudinal slope,and provide the basis for disaster prevention and rescue work of railway tunnels with high altitude.In this paper,FDS is used to simulate the fire scenario of railway tunnels.The smoke flow law of railway tunnels at different altitudes and the longitudinal distribution law of 2 m characteristic height of evacuation passage and temperature field at tunnel vault are studied when the fire scale is 20 MW.The results show that when the scale of fire is the same,with the increase of altitude,the vertical one-dimensional spread speed of fire smoke acceleratec,for the upstream of fire source v=0.00003 h+2.27,for the downstream of fire source v=0.00006 h+3.4312.The installation of large longitudinal slope can restrain the spread of fire smoke upstream,and the temperature field of upstream characteristic height is less affected,which makes the temperature field at upstream characteristic height of fire source meet the limit requirement in safe evacuation time.Within the range of 120 m downstream of the tunnel fire source,the longitudinal temperature of the vault increases with the increase of altitude,while outside the range of 120 m,it decreases with the increase of altitude.The highest temperature point of vault of railway tunnel with large longitudinal slope shifts downstream when fire occurs,and the highest temperature increases with the increase of altitude t=0.0365 h+443.98.