隧道火灾模型试验中列车对烟气控制的影响

Influence of Train on Control of Smoke Flow in Small-scale Tunnel Fire Experiment

分别对太行山铁路隧道缩尺模型内有无列车两种工况进行火灾试验,讨论列车阻塞对隧道火灾临界风速的影响,比较有无列车两种工况下临界Froude数,并分析烟气回流长度的影响因素。结果表明:铁路隧道内有列车时控制火灾烟气回流的临界风速明显降低;阻塞比为0.2时的临界风速比无列车时的临界风速减小23%,说明临界风速差异比接近且稍大于隧道阻塞比;计算临界风速时使用的临界Froude数与火灾热释放率相关,不是一个常数。无量纲回流长度与Froude数近似呈线性关系,在相同Froude数下无列车时回流长度明显更长。

Small-scale fire experiments were carried out in the reduced-scale model of the Taihangshan Railway Tunnel under the conditions with and without a model train inside the model tunnel.The critical Froude numbers for preventing smoke backflow in the two different operating conditions are compared with each other.Factors influencing the smoke backlayering lengths are analyzed.The results show that the critical velocity decreases as large as 23% while a model train occupies around 20% of the tunnel cross-section.The decrease rate is slightly larger than the train-tunnel dimension ratio and almost independent of the heat release rate.The critical Froude number is relative to the heat release rate,it is not a constant,but can be divided into two categories,the constant region and linearity region.The dimensionless backlayering length and the Froude number approximate to linear in mutual relations.The smoke backlayering length is significantly larger without model trains when the Froude number remains the same.