大跨径隧道不同车道火灾对侧向集中排烟效率影响研究

Study on the effect of fire in different lanes of long-span tunnels on the efficiency of lateral concentrated smoke exhaust

为探究大跨径隧道不同车道发生火灾时的烟气流动特性及其对侧向集中排烟系统的影响,应用FDS软件探究了大跨径水下隧道火灾特性。首先,研究火源位于不同车道对烟气温度分布特征的影响;然后,分析隧道内烟气流动特征,得到火源位于不同车道时的隧道流场分布情况、烟气蔓延范围;最后,根据数值模拟结果计算不同车道发生火灾时侧向集中排烟系统的排烟效率。结果表明:火源不在隧道中心位置时,两侧的烟气温度分布不对称,近壁面一侧烟气温度高于远离壁面一侧的温度;火源靠近隧道侧壁时,近火源处的烟气将因惯性力的作用而产生涡旋;火源位于不同车道对横向集中排烟的排烟效率影响较大,火源距排烟口的横向距离越远,排烟效果越好,其主要原因是当火源远离排烟口时,烟气在纵向蔓延中不会产生强涡流以及烟气分流现象,从而提高了排烟效率。

In this paper,the FDS fire dynamics simulation software was used to simulate the fire in a large-span underwater tunnel with a fire power of 20 MW.The model used a 0.5 m grid size and the heat release rate of the fire was set to t~2for numerical simulation.The effects of different lane fires on the smoke temperature distribution,flow field distribution,smoke spreading range,and smoke exhaust efficiency were studied by numerical simulation.Through the study of four different lane positions and different smoke exhaust rate combined working conditions,the influencing factors of the smoke exhaust effect were obtained.The results show that when the fire was not in the center of the tunnel,the temperature distribution of the smoke on both sides was asymmetrical,and the temperature of the smoke near the wall was higher than that of the side far away from the wall.When the fire source was close to the side-wall of the tunnel,the smoke near the fire produces a vortex due to the action of inertial force.The produced vortexes changed with different lanes.As the vortex area spreads along the longitudinal direction of the tunnel,the strength of the vortex would have an impact on the smoke exhaust efficiency of the exhaust vent.The farther the horizontal distance between the fire and the exhaust vent is,the better the exhaust effect is.The phenomenon was most obvious when the exhaust rate was 260 m~3/s,the fire moved from a position closer to the far side of the exhaust vent,and the exhaust efficiency was increased from 60.86%to 67.37%,with a growth rate of 10.70%.The main reason was that when the fire was far from the smoke exhaust vent,the smoke would not produce a strong vortex and smoke diversion in the longitudinal spread,thereby improving the smoke exhaust efficiency.