分岔隧道内非对称复杂卷吸流场下的火羽流行为与烟气输运特性

地下交通工程存在很多分岔隧道，分岔隧道内由于多洞口卷吸与多路径气流，使其内的流场结构和火灾动力学行为具有不同于一般单点进出口隧道内的演化规律，需要建立新的数学模型来进行描述和表征。本项目针对分岔隧道火灾的火羽流行为和烟气蔓延特性，拟揭示分岔隧道内的流场结构演化规律及复杂流场下的火羽流横向与纵向非对称发展行为和火焰形态特征，建立耦合分岔角度、坡度因素和隧道横截面尺寸影响的非对称火羽流关键参数表征模型；揭示分岔隧道内烟气输运动力学机理及烟气特征参数的分布规律，探明烟气层分流对层化稳定性和特征参数分布的影响机制，建立考虑分岔隧道结构参数、强制通风与多坡度因素影响的特征参数表征模型；明晰分岔隧道内纵向风抑制烟气逆流的动力条件，建立分岔隧道内的烟气逆流长度、临界风速和临界驱动力数学模型。本项目研究可完善现有隧道火灾理论在分岔型隧道上的不足，也可为分岔隧道消防安全设计提供理论支撑。

There are many branched tunnels in underground traffic engineering. The flow field structure and fire dynamics behaviors in the branched tunnel have different evolution laws compared to those in the ordinary single-point entrance and exit tunnels due to the multi hole entrainment and multi path airflow. Therefore, it is urgent to establish new mathematical models to describe and characterize these behaviors in branched tunnel. In this project, aiming at the fire plume behavior and smoke spread characteristics of branched tunnel fires, the flow field evolution law in branched tunnels, the horizontal and vertical asymmetric development behavior of flame plume and flame morphology characteristics under the action of complex flow fields will be studied by carrying out theoretical analysis, experiments and numerical modelling. The mathematical model of asymmetric fire plume parameters considering the random characteristics of bifurcation angle, slope factor and tunnel section size will be established. The dynamics mechanism and characteristic parameters distribution of the smoke propagation in the branched tunnel will be revealed. This project will find out the influencing mechanism of the smoke layer split-flow on the stratification stability and the distribution of characteristic parameters, and establish a mathematical model of smoke characteristic parameter considering the dimensions of the branched tunnel, forced ventilation and the multi-slops factor. The dynamic conditions of the smoke backflow, the mathematical model of the smoke backlayering length, the critical ventilation velocity and the critical driving force will be established to clarify the longitudinal ventilation suppression smoke propagation in the branched tunnel. This project can improve the existing tunnel fire theory in branched tunnels, and provide theoretical support for optimizing the branched tunnel fire safety design.