隧道喷水灭火系统对临界风速的影响研究

Study of the influence of the water suppression system on the critical velocity for tunnel fire

为了研究喷水作用下隧道火灾临界风速的变化规律,采用隧道小尺寸火灾试验的方法,试验测量了不同试验条件下隧道的临界风速,考虑的试验因素包括了火源热释放速率、喷头工作压力、喷头数量和位置。结果表明纵向通风隧道采用喷水灭火系统可以一定程度减小隧道火灾所需要的临界风速,有助于抑制烟气回流。在相同的火源功率下,喷头离火源位置越近,喷头开启数量越多,喷头工作压力越大,对临界风速的减小作用越显著。喷水对临界风速减小的幅度随着火灾热释放速率的增大而逐渐减小。对于实际隧道火灾,火源上游区段喷水流量为10.5L/s可使得6.8、34.2 MW火灾所需的临界风速分别减小29.4%和4.8%。

The aim of this study is to quantify the critical velocity change under the effect of water spray. Small scale tunnel ex- periments are carried out to measure the critical velocity under different experimental conditions, including heat release rate of the fire source, water operation pressure, position and number of the activated nozzles. The results show that water suppres- sion system could benefit the tunnel with longitudinal ventila-tion system to eliminate the backlayering with a lower critical velocity. With the same heat release rate of fire source, the re- duction of the critical velocity increases with the decrease of the distance from the nozzle to fire source, but with increase of the water operation pressure and the nozzle numbers. Additionally, the reduction of the critical velocity is larger in the smaller fire scale. For the full scale tunnel, the reduction of critical velocity is 29.4% and 4.8% for 6.8 MW and 34.2 MW fire respective- ly when the water flow rate is 10.5 L/s in the upstream of the tunnel.