含渐缩段卜形分岔合流隧道火灾临界风速研究

为探究“卜”形分岔隧道这一特殊隧道结构对隧道火灾临界风速的影响，运用FDS构建了主路渐缩分岔隧道、主路等宽分岔隧道与直线隧道3种结构的缩尺寸隧道模型，通过数值模拟分析隧道渐缩结构与分岔角度对火灾临界风速的影响。研究表明，对于主路渐缩的分岔隧道，当火源所在位置的局部隧道宽度减小时，所需的临界风量变小。而火源位置确定时，隧道的渐缩结构、分岔角度和分岔结构对临界风速的影响不明显，并提出一种适用于隧道工程渐缩段任意火源位置临界风量的计算公式。对于主路位置的火灾，提出无量纲临界风速与无量纲热释放速率的关系式，与前人直线隧道的变化规律相似，而较高的隧道高度导致临界风速的转折点较大。

Study on fire critical velocity of T-intersecting bifurcation confluence tunnel with tapered section

In order to explore the influence of bifurcated tunnel which has special T-intersecting structure on the critical velocity of tunnel fire, FDS is used to construct the scale tunnel models of three structures: bifurcation tunnel with tapered section, bifurcation tunnel without tapered section and straight tunnel. The influence of tunnel shrinking structure and bifurcation angle on fire critical velocity is analyzed by numerical simulation.Research shows that, for the bifurcation tunnel with tapered section, when the local tunnel width at the location of the fire source decreases, the required critical velocity decreases. When the location of the fire source is determined, the tapered section, bifurcation angle and bifurcation structure of the tunnel have no obvious influence on the critical velocity. And a calculation formula of critical air volume at any fire source position in the shrinking section of tunnel engineering is proposed. For the fire at the main road, the relationship between dimensionless critical velocity and dimensionless heat release rate is proposed, which is similar to the variation law of previous linear tunnels, while the higher tunnel height leads to a larger turning point of critical wind speed.