水下铁路隧道V形坡对烟气竞争效应的影响

分析V形坡水下铁路隧道内火灾时烟气流动过程中受到的火风压和空气阻力,采用火灾动力学模拟软件对不同火源功率、不同隧道坡度下V形坡隧道内不同火源位置下烟气蔓延特性进行模拟,研究火源功率、V形坡坡度和火源位置对水下铁路隧道内烟气竞争效应的影响。结果表明:V形坡隧道内的烟气从隧道近火源侧端口流出,空气从隧道另一侧端口进入,两侧坡度对烟气蔓延存在竞争效应;火源位于V形坡隧道左侧时,火源上游烟气层与隧道顶板平行,火源下游与变坡点间的烟气层与水平地面平行,当烟气经过隧道变坡点时烟气层不再与水平地面平行;在竞争效应的作用下,火源下游的烟气逆流长度随火源距变坡点距离的增大呈现出减小、然后保持不变、再略有增大3个阶段;随着隧道坡度的增大,烟气逆流长度逐渐缩短,稳定区的范围逐渐增大,而火源功率对烟气逆流长度的影响逐渐减弱。

Influence of V-Shaped Slope of Underwater Railway Tunnel on Smoke Competition Effect

The fire pressure and air resistance caused by the smoke flow during a fire in the V-shaped underwater railway tunnel were analyzed.The fire dynamics simulation software was used to simulate smoke spreading characteristics under different heat release rates and tunnel slopes at different fire source locations in the V-shaped tunnel so as to study the influence of the heat release rate of fire source,the gradient of the V-shaped slope and fire location on the smoke competition effect in underwater railway tunnel.Results show that the smoke in the V-shaped slope tunnel flows out of the tunnel from the side near fire source and the air enters from the other side of the tunnel,and the slopes on both sides have competitive effects on smoke spreading.When the fire source is located on the left side of the V-shaped slope tunnel,the upstream smoke layer of fire source is parallel to the roof of tunnel,and the smoke layer between the downstream of fire source and the slope changing point is parallel to the level ground,which is no longer parallel to the level ground when the smoke passes through the slope changing point of the tunnel.Under the effect of competition,the back-layering length of the smoke at the downstream of fire source experiences three stages,namely,first decreases then remains unchanged and finally increases slightly,with the increase of the distance between the fire source and the slope changing point.With the increase of tunnel slope,the back-layering length of smoke decreases gradually and the range of stable region increases gradually,and the influence of heat release rate on the back-layering length of smoke weakens gradually.