双层盾构公路隧道侧向重点排烟效果研究

摘 要：利用FDS对某双层盾构公路隧道的侧向重点排烟系统进行了模拟研究，探讨了排烟口面积、间距、排烟口开启方案以及纵向通风对排烟效果的影响。结果表明：在无纵向风的条件下，火灾稳定后排烟口的面积为3~5 m2、排烟口间距为60~100 m时，排烟口的面积和间距对排烟效果的影响很小。随着纵向通风风速的增大和上游排烟口开启数量的增加，隧道侧向排烟系统的排烟效率明显减小。双层隧道上下层排烟口的排烟效率分布规律基本相同，下层隧道的总排烟效率略高一些。本文所研究的双层隧道发生20 MW火灾时，在纵向通风风速2 m/s下，排烟口间距为60 m，排烟口面积为4 m2，上游开启2个排烟口、下游开启4个排烟口时排烟效果更好。

Study on lateral point smoke exhaust efficiency in double-deck shield road tunnel

Abstract: Fluent software was used and the Euler multiphase flow model was used to simulate the along-path resistance, flow velocity and dry powder concentration distribution characteristics of ultra-fine dry powder fire extinguishing agent with a particle size of 18 μm sprayed in a horizontal straight pipe with a diameter of 8 cm. The results show that in the range of flow velocity 25~150 m/s and ultrafine dry powder volume fraction 5%~15%, the resistance along the horizontal straight pipe has a quadratic function relationship with the flow velocity, and a linear function relationship with the dry powder volume fraction. The range of resistance value is 0.003 28~0.259 81 MPa/m. Affected by the friction of the pipe wall, the flow velocity of the two-phase flow on the cross section of the pipe presents a distribution characteristic of fast in the middle and slow in the surrounding area, and the effect of the volume fraction of solid particles on the flow velocity can be ignored. The gas-phase drag force generated by the different velocity distributions on the cross-section leads to the annular distribution of the ultrafine dry powder volume fraction. The gas-phase drag force is related to the initial velocity and has nothing to do with the dry powder volume fraction. When the flow rate is lower than 70 m/s, the ultra-fine dry powder is distributed in a crescent shape, and the volume fraction of the ultra-fine dry powder is the highest at the lower part of the pipeline close to the pipe wall. The volume fraction is the lowest near the pipe wall, and the flow velocity is greater than 70 m/s, which can effectively inhibit the sedimentation of ultra-fine dry powder.