火灾时隧道截面形状对临界风速和烟气分布影响的数值研究

Numerical studies on the critical velocity and smoke distribution affected by tunnel cross-section geometry in tunnel fire

模拟分析了某地铁实际工程中三种区间隧道断面(单线盾构圆形断面、单跨矩形断面和双跨矩形断面)对临界风速的影响,结果表明单线盾构圆形隧道的临界风速最大,双跨矩形隧道对应的临界风速最小.拟合得出了纵向通风速度和逆流层长度的变化关系式,计算得出了10 MW火灾强度下三种隧道的临界风速,并在临界风速条件下对三种截面形状隧道对烟气的温度和浓度分布的影响进行了模拟分析,验证了拟合得出的通风速度和逆流层长度变化关系式的准确性,为地铁区间隧道火灾烟气扩散控制和通风系统设计提供了一定的参考依据.

Three different cross-sectional geometry tunnels in actual project （single-track shield tunnel, singlespan rectangular tunnel and double-span rectangular tunnel） which have the same heights and maximal widths affecting the critical velocity are simulated and analyzed. The results show that the single-track shield cross-sections have the maximal critical velocity and the double-span rectangular cross-sections have the minimal critical velocity of the three tunnels. The corrections of longitudinal ventilation with backing up distances are obtained. The critical velocities are computed of the three tunnels from the corrections. The temperature and smoke distributions affected by tunnel geometry are simulated and analyzed at the computed critical velocity, which validates the veracity of the obtained corrections. The results can provide theory instructions for subway tunnel smoke control and the design of longitudinal ventilation systems.