倾斜隧道火灾烟气非对称蔓延行为及诱导、卷吸空气机理研究

Smoke is an important reason for the casualties in tunnel fires. We found that the smoke generation mechanism and smoke propagation behaviors in inclined tunnel fires were different with that in horizontal tunnel fires. Theoretical analyses, brine-water technique combined with image processing, tunnel fire experiments are employed to study the asymmetric smoke propagation behavior and the mechanism of driving and entraining air in inclined tunnel fires..(1) The asymmetric propagation behavior of the smoke at both sides of the fire under the coupling effect between the stack effect and the static pressure of the head of the ceiling-jet is investigated. The mathematical models of the propagation velocity of the head of the ceiling-jet, the back-layering length upstream the fire and the thickness of the smoke layer downstream the fire are proposed..(2) The mechanisms of driving and entraining ambient flow in different flow regimes are analyzed. For the bidirectional stratified flow regime, the models for estimating the entrainments through the head of the ceiling-jet and the smoke layer interface are proposed. For the unidirectional flow regime, the model for calculating the volume flow rate of the ambient air entering the inclined tunnel under stack effect is proposed..The smoke behaviors at both sides of the fire should be treated differently. The findings are helpful for further understanding the smoke propagation characteristics in inclined tunnel fires. The prediction models proposed in the present study can be used to calculate the smoke flow rate and guide the engineering design, which breaks the conventional way of estimating the smoke flow rate only by classic plume theory.

烟气是导致隧道火灾人员伤亡的重要原因，我们发现倾斜隧道具有不同于水平隧道的火灾烟气生成机制与蔓延行为。本项目拟通过理论分析、盐水实验结合图像处理、火灾烟气实验等手段，研究倾斜隧道火源两侧烟气非对称蔓延行为及诱导、卷吸环境空气的机理：.(1) 探究烟囱效应和顶棚射流头部静压耦合作用下火源两侧烟气非对称蔓延行为，建立火源两侧顶棚射流头部蔓延速度、火源上游烟气逆流长度和下游烟气层厚度预测模型；.(2) 搞清不同流动模式下烟气诱导、卷吸空气的机理；对于双向分层流动，建立顶棚射流头部及烟气分界面卷吸空气量的预测模型；对于全断面单向流动，建立烟囱效应诱导空气量的预测模型。.本项目提出差异化地看待火源两侧烟气行为特征，研究成果有助于深化对倾斜隧道火灾烟气蔓延特性的认识；建立的诱导、卷吸空气量预测模型突破只用经典火羽流卷吸理论计算烟气量的定式思维，可更准确地量化倾斜隧道火灾烟气生成量，指导工程设计。

高温有毒烟气是导致隧道火灾人员伤亡的重要原因。在烟囱效应作用下，倾斜隧道具有不同于水平隧道的火灾烟气生成机制与蔓延行为。本项目综合利用理论分析、模型实验和数值模拟等手段，系统研究了隧道坡度、火源位置及火源功率对烟气层化厚度、蔓延速度、逆流长度及烟气流量的影响。（1）揭示了倾斜隧道火源上游烟气逆流长度影响因素，建立了瞬态最大逆流长度和稳态逆流长度预测模型。（2）分析了倾斜隧道火灾烟气顶棚射流瞬态蔓延加速现象，建立了顶棚射流头部最大蔓延速度预测模型，并将其与稳态时烟气蔓延速度进行了对比。（3）提出了影响烟气温度/密度分层特性的无量纲参数，建立了火源下游烟气自然蔓延层化厚度预测模型。（4）揭示了不同烟气分层条件下倾斜隧道火灾烟气流量变化规律，提出了烟气总流量计算模型。（5）分析了下坡倾斜隧道纵向排烟可能存在的流动不确定性，指出了确保排烟达到预期效果需要采取的措施。. 本项目圆满完成了既定的研究目标和成果指标。相关研究成果已发表高水平论文8篇，其中Building and Environment与Tunnelling and Underground Space Technology等JCR一区SCI论文7篇。培养毕业博士研究生1名，硕士研究生2名。参加国内及国际学术会议9次。本项目的研究成果具有明确的工程应用前景，能够为设计隧道火灾通风系统和组织应急救援提供科学依据和数据支撑。