螺旋隧道火灾特性小尺寸实验研究

摘要

To study the characteristics of spiral tunnel fire and prevent people from heat injury, a 1:67 small|scale experimental model of spiral tunnel was established based on Froude Criterion.The temperature distribution regularities and smoke spread characteristics of spiral tunnel fire under different slope and wind velocity were studied by using the model experiment method.The results showed that the high temperature zone in spiral tunnel presents the status of symmetrical distribution with the fire source as middle point under the condition of low slope.With the increase of tunnel slope, the high temperature zone in spiral tunnel gradually extends to downstream, and the temperature under the vault at fire source presents the variation law of increase first, then decrease, and increase again.Regardless of natural ventilation or mechanical longitudinal ventilation, the blown fresh cold air plays a leading role to reduce the tunnel temperature, and the larger the wind velocity, the larger the temperature decreasing amplitude.Along with increasing tunnel slope and natural wind velocity, the fire plume transforms from vertical slender configuration into unstable big|section burning flame.Meanwhile, the increasing slope suppresses the fire smoke backflow and promotes the spread speed of smoke to downstream of fire source, which greatly enhances the effectiveness of smoke exhaust and reduces the harm to personnel.%为探明螺旋隧道火灾特性,防止人员高温伤害,基于Froude准则,搭建比例1∶67的小尺寸螺旋隧道实验模型,采用模型实验方法研究不同坡度和不同风速下螺旋隧道火灾温度分布规律及烟气蔓延特性.研究结果表明:低坡度条件下,螺旋隧道内高温区以火源为中点呈对称分布状态;随着坡度的增加,隧道内高温区逐渐向下游延伸,火源处拱顶下方温度呈现先增大后降低再升高的变化规律;无论是自然风还是机械纵向通风,新鲜冷空气的吹入对隧道温度的降低起到主导作用,且风速越大,温降幅度越大;随着隧道坡度和自然风速的增加,火羽流由竖直狭长型转变为燃烧不稳定的大截面火焰,同时坡度增加抑制了火灾烟气逆流,促进了烟气向火源下游的蔓延速度,大大提高了排烟的有效性,减少人员伤害.