不同坡度隧道火灾自熄现象试验研究

Experimental study on fire self-extinction phenomenon in tunnel with different slopes

为探究不同坡度的隧道火灾自熄特性,以美国Memorial隧道为原型,应用Froude准则建立1∶20缩尺隧道模型,在自然通风条件下使用甲醇燃料进行隧道火灾试验,通过数据测量系统获取试验中风速、温度和氧气体积分数数据。结果表明:坡度为3%和5%的隧道火灾试验均未出现自熄现象;无坡度和坡度为1%的隧道中,除热释放速率(HRR)为2.8 kW外的试验均发生自熄现象,且HRR越大,自熄时间越短;隧道坡度的存在,使得热烟气在浮力作用下形成烟囱效应,坡度越大,烟囱效应越强;坡度为3%和5%的隧道中由于形成较大纵向风速,因而火焰不能自熄,坡度较小的隧道由于火源附近氧气体积分数下降至最低氧气体积分数以下,因而发生自熄现象。

In order to explore self-extinction phenomenon of fire in tunnels with different slopes,with America's Memorial Tunnel as a prototype,a 1/20 reduced-scale model tunnel was constructed based on Froude scaling law and a series of experiments were conducted by using methanol to investigate fire in tunnels under natural ventilation.Then,information of velocity,temperature and oxygen concentration were obtained through data acquisition system.The results show that there is no self-extinction phenomenon in experiments with a slope of 3%and 5%,while it occurs in cases of zero and 1%slope except when heat release rate(HRR)is at 2.8 kW,and the greater HRR is,the shorter self-extinction takes.Existence of tunnel slopes causes hot smoke to form stack effect due to buoyancy,and the larger slope is,the stronger stack effect will be.As tunnels with a slope of 3%and 5%form larger longitudinal wind speed,they restrain self-extinction while in tunnels with a smaller slope,the phenomenon occurs because oxygen concentration near the fire source has fallen to the limit.