不同通风风速下地下环道火羽流特性研究

Study on Characteristics of Fire Plumes in Underground Loop under Different Ventilation Velocities

地下环形受限空间因其复杂的结构特征具有较大火灾危险,保障其安全运营需要针对其结构特征设计适合防排烟方式,而确定最佳排烟风速是防排烟设计基础.以某典型地下环道为研究对象,利用数值模拟结合理论分析,研究了地下环道内不同通风风速、不同火源位置耦合作用下火羽流蔓延特性,针对不同火源位置在2.5~3.5 m/s风速范围内设置9个典型火灾场景,定量分析了羽流温度场、浓度场、烟气层高度变化规律.研究表明:主干隧道羽流特性几乎不受风速影响,支路隧道次之,增加风速对提高交叉口隧道火灾安全性最明显;综合考虑经济因素,建议主干隧道、支路隧道、交叉路口隧道机械通风风速分别设置为2.5 m/s、3.0 m/s、3.5 m/s.研究结果可为环形受限空间火灾防治提供理论支撑和技术参考,是对地下空间火灾防控理论的有益探索.

The complex structure of an underground annular confined space cases a serious fire risk.In order to ensure its safe operation,it is necessary to design a smoke control method based on its structural characteristics,in which the determination of the best smoke exhaust speed is the basis of smoke control design.In this paper,a typical underground loop is taken as the research object,numerical simulation and theoretical analysis are carried out to study the propagation characteristics of fire plume under the coupling of different ventilation velocities and different fire source locations in the underground loop.Nine typical fire scenes are set based on different fire source locations in the wind velocity range of 2.5-3.5 m/s,and the temperature field,concentration field and the height of the smoke layer are quantitatively analyzed.Results show that the plume characteristics of the main tunnel are almost unaffected by the wind velocity,and those of the branch tunnel are less affected.The increase of wind speed is most effective in improving the safety against intersection tunnel fires.The comprehensive consideration of economic factors suggests that the mechanical ventilation wind velocities of the main tunnel,branch tunnel and intersection tunnel should set as 2.5,3.0 and 3.5 m/s,respectively.The research results can provide theoretical support and technical reference for the prevention and control of fires in an annular confined space,which is a useful exploration for the theory of fire prevention and control in an underground space.