某过江隧道变截面段火灾烟气流动及逃生分析

Research on Smoke Movement and Rescue of Tunnel Fire in Varying Cross-section Portion of a Tunnel Under River

针对某城市过江隧道中出现的多匝道变截面段,首先利用FDS大涡模拟方法,对上行及下行线在不同工况下的烟气羽流进行模拟;然后结合经验公式计算的主隧道段临界风速,分析了3m/s纵向通风风速下烟气羽流随时间变化情况,以及不同的坡度、纵向通风风速下,隧道变截面段的火灾烟气回流长度变化;最后,结合理论计算的逃生时间,对隧道变截面段火灾控制风速进行了分析。得到了在纵向应急通风时,控制变截面段烟气回流及保证逃生安全所需的主隧道临界风速比用修正的Heselden﹠Kennedy公式计算所得值大,需要对变截面段火灾通风系统进行特定模拟分析,以满足其烟气控制要求,研究结果对各种隧道变截面段的火灾烟气和逃生分析有一定的参考价值。

Firstly, a numerical model of tunnel fire in varying cross-section and multi-strand ramp portion of an urban traffic tunnel under river was developed to simulate smoke movement of different condition of upline and downline by large eddy simulation in FDS. And then, smoke propogation over time with 3m/s velocity of longitudinal ventilation was studied.The influence of variable slope, velocity of longitudinal ventilation on the back-layering length in the model was also investigated, conbining with the critical velocity in primary tunnel calculated by empirical formula. Finally, the control velocity of tunnel fire in varying cross-section tunnel was studied conbining with theoretical escape time. It was found that the control velocity got from simulation in primary tunnel which prevents smoke from flowing back and propogation in the varying cross-section tunnel was lager than that was calculated by theory. So it is necessary to simulate and analyze on fire ventilation system of varying cross-section tunnel particularly to meet the demands of control on smoke propogation.The results of this research will provide reference to further study on tunnel fire in varying cross-section tunnel.