大跨沉管隧道重点排烟系统设计常见问题的探讨

Discussion on the Common Problems of the Single Point Smoke Extraction for Large-span Immersed Tunnel

为了分析隧道重点排烟产烟量修正、隧道排烟口防吸穿的最大风速以及隧道排烟系统响应时间等相关疑难问题,利用NFPA规范相关算法对某大跨沉管隧道50 MW火灾进行计算。结果表明,隧道重点排烟量应考虑狭长型羽流修正系数,50 MW火灾排烟风量修正系数约是1.60~2.1;隧道防吸穿风速与隧道排烟口的布置方式及风口大小有关,大跨隧道的排烟宜采用顶部排烟方案,排烟口间距按照4H控制,排烟口宜按2.0 m×1.0 m设计,每个车道均布置一个,火灾时宜开启火灾点附近5组排烟口同时排烟;系统按照火灾报警确认后60 s启动可以保证烟气层高度2 m以上,满足人员疏散要求。

In order to analyze some difficult problems such as correction of smoke production for the design of the single point smoke extraction, the maximum wind speed of smoke vent against plug-holing and response time of tunnel smoke control system. The algorithm of the NFPA code standard was used to calculate taking a 50 MW fire in a large span immersed tunnel as an example. The study shows that the smoke flow rate of the tunnel should consider the narrow plume correction coefficient, and the 50MW fire smoke exhaust air correction coefficient is about 1. 60 ~ 2. 1. The maximum wind speed of smoke vent against plug-holing tunnel is related to the layout of the tunnel exhaust inlet and the size of the inlet. The smoke exhaust scheme for the large-span tunnel should be used. The distance between the exhaust ports should be controlled by 4H, and the exhaust ports should be designed according to 2 m x1 m. Five groups of exhaust outlets near the fire point should be opened at the same time. The system can ensure the heightof the smoke layer above 2 m after the fire alarm is confirmed by 60 s which provides a possible evacuationenvironment.