隧道断面突变对纵向排烟效果的影响研究

Effect on the longitudinal smoke control in tunnel with the sudden change of the cross-section

通过FDS数值模拟,以30 MW设计火灾为例,对相关规范推荐的两个临界风速值3.2 m/s和4.0 m/s对隧道内有突然加宽或加宽加高断面时纵向排烟的实际控烟效果进行了分析。研究结果表明:两个临界风速都不能完全控制烟气回流。3.2m/s临界风速由于风速较小,火源上游烟气层高度低,不利于人员逃生;而4.0m/s的临界风速尽管仍有烟气回流,但由于加宽加高隧道的蓄烟作用,火源上游的烟气层高度有所提高,人员的逃生环境有较大的改善。对于此种类型的隧道,要想达到良好的控烟效果,需加大临界风速。

Considering the effect of longitudinal ventilation sys tern on the smoke control in the tunnel with the sudden change of the cross-section, and taking 30 MW fire as an example, the smoke control effects of two critical velocities of 3. 2 m/s and 4.0 m/s which are recommended in the relative design guides were studied by FDS. It is found that both of these two critical values cannot prevent the smoke backlayer. The velocity of 3.2 m/s is too small that the length of the backlayer is long, and the smoke layer is low at the upstream of the fire. This is dan ger for the occupant evacuation. The smoke control effect can be improved when the critical velocity is increased to 4.0 m/s, the evacuation environment at the upstream of the fire is im proved based on the higher smoke layer height. The results showed that the critical velocity should be increased in order to get much better smoke control effects for these kinds of tun nels.