基于多指标约束的隧道集中排烟量设计模型

利用经典羽流模型计算烟气生成量来设计隧道集中排烟系统的排烟量存在设计量偏小的问题。从火灾烟气控制效果出发,选取排烟效率、烟气蔓延范围、烟气流动速度、人员疏散微环境4个指标,提出一套隧道集中排烟系统的评价指标,构建基于多指标约束的隧道集中排烟量设计模型。通过FDS 5.0对某越江隧道火灾时的各评价指标参数值进行模拟计算,得到该隧道集中排烟系统在20MW火灾时的最适排烟量为140～150 m3/s。研究表明,利用多指标约束的排烟量设计模型可提高隧道集中系统排烟量设计的准确性。

Smoke-extracting rate model for the tunnel-use system based on the multi-index constraints

The given paper is to introduce its development of a newly renovated smoke-extracting rate model for the tunnel-purpose based on the multi-index constraints.Since it has a lot of limiting factors for fire-smoke control,a lot of calculation has to be done to optimize the design in the engineering practice.Traditionally,the problem can be solved by using the classical plume-extraction method.However,since the smoke exhaust rate worked out by using the classical method is rather limited,we prefer to propose a set of suitable evaluation index for the contracted smoke extraction system,which may include theoretical rating evaluation,the smoke-exhaust efficiency evaluation,the smoke spread distance evaluation,that of smoke flowing velocity inside the tunnel,the visibility distribution limit at maximal 2 m height of the tunnel.Our model has been built on the multi-index confining basis.To make our model more practical,we have prepare a simulated model known as FDS 5.0 for the tunnel smoke-extracting system in a cross-river tunnel.In our simulated model,we have laid out eight different exhaust rates at a heat-releasing rate of 20 MW.The results of our simulation have shown that the smoke-exhausting rate can be as high as 140 m3/s based on the likely smoke-exhausting efficiency.And the smoke spread distance and smoke flow velocity should be done between 90.83 m3/s and 150 m3/s,with the smoke flowing velocity in exhaust ports and exhaust duct can be reduced to less than 15 m/s and 10 m/s respectively and the visibility distributions increased greater than 10 m at 2 m tunnel height.If all this can be done,no influence would be brought about to the selection of smoke exhausting rate.In so doing,the optimum exhaust rate of the contracted smoke extraction system in this tunnel can be made to reach 140 m3/s and 150 m3/s at a heat releasing rate of 20 MW.Thus,it can be concluded that the model proposed us proves to be more accurate and effective in improving the smoke extraction in road tunnel design and construction.