隧道火灾集中排烟模式下的排烟效率研究

排烟效率是衡量集中排烟火灾通风方案排烟效果的重要指标。为合理分析排烟效率的变化特性,结合某隧道集中排烟系统设计,借助CFD技术,对设置有排烟道的隧道进行了火灾烟气控制的模拟分析,研究了排烟阀开启个数、开口面积和设置间距对双向排烟和单向排烟两种集中排烟模式下不同排烟阀设置方案中总排烟效率和各个排烟阀的排烟效率的影响。结果表明,集中排烟模式可有效将火灾烟气排出隧道。当排烟阀对称开启时,双向排烟模式下,减少排烟阀开启个数,单个排烟阀的排烟效率升高,但总排烟效率降低;当开口面积较小时,增大面积,总排烟效率升高明显,继续增大开口面积时总排烟效率升高效果减弱;增大间距有利于隧道排烟。单向排烟模式下,当排烟阀开启个数较多或开口面积较大时,距离风机最远的排烟阀排烟效率降低,并出现烟流流出排烟道的现象,排烟阀失效,可考虑在非排烟侧开启少量排烟阀,增大间距,使总排烟效率升高。

Study on smoking exhaust efficiency under central exhaust mode in tunnel fires

The paper is aiming to testing and measuring the effectiveness of smoke-exhausting strategies in the tunnels with the central exhaust system in regard to the smoking-exhaust efficiency.In order to improve our understanding of smoke exhaust mechanism,we have prepared a simulated model by using CFD based on the central exhausting system design of the road tunnel.To be exact,we have studied the effects of the ventilator number,the ventilation area and the design space on the total smoke-exhausting efficiency as well as the efficiency of each ventilator in various ventilation systems under two central exhaust modes of two-way and one-way smoke extraction.In this paper,we have laid out the ventilator numbers of 4,6,8,12,and the ventilation areas of 2.5, 4,6,8,10,with the spaces of 25,50,75,100 taken into full account.The results of our study show that the smoke can be extracted out of a tunnel effectively via the central exhaust system.By using the two-way ventilating mode,when the ventilation outlets are distributed on the both sides of smoke-fire outlet symmetrically,each ventilator tends to work more efficiently,however,the total efficiency of the smoke-exhaust system tends to be lower if the number of ventilator is reduced.In addition,the total efficiency is expected to rise if greater ventilation area and larger space would facilitate the smoke exhaust under the two-way exhaust mode.However,when more exhausting valves are working on or the ventilation area is larger under the one-way exhaust mode,the exhaust valves would likely fail if the smoke in the exhaust valves farthest from the fan flows into the driveway,according to which one possible solution is to open some exhaust valves on the sideway with no fans.In so doing,the total efficiency would be made higher with larger ventilation space.And,in turn,both under the two-way exhaust mode and one-way exhaust mode,the first or second exhaust valves near the fire source should be turned on.The final results should thus be made significant for establishing appropriate design scheme of the exhaust valves in the tunnel-disaster prevention.