沉管隧道侧向集中排烟模式烟雾流动规律研究

为解决海底沉管隧道火灾工况下人员疏散及救援难题，以港珠澳大桥海底沉管隧道为工程依托，在中国首次建立了1：1的侧向集中排烟实体试验平台，基于火源标定试验及理论分析，通过失重法和热辐射法对火源功率进行标定，得到热释放速率随燃烧时间的变化关系曲线。通过沉管隧道侧向集中排烟物理试验以及FDS数值模拟对比分析，得到了油盆火的火灾规模、油量、油盆燃烧面积三者间的对应关系。通过FDS数值模拟计算，得到了火灾峰值功率为50 MW时，在不同纵向诱导风速下，沉管隧道侧向集中排烟模式下烟雾的温度场分布规律、能见度分布规律和烟雾蔓延范围。研究结果表明：火灾峰值功率为50 MW时，随着纵向诱导风速增大，火源附近隧道顶板处的最高温度出现先升高后降低的现象；当纵向风速由1.0 m·s^-1增加到2.5 m·s^-1时，隧道内沿程各点2 m高度处的能见度呈现逐渐提高的现象，且能见度受影响的范围逐渐减小，当纵向诱导风速由2.5 m·s^-1增大至3.5 m·s^-1时，隧道下游2 m高度处的能见度出现逐渐降低现象，且能见度受影响的范围逐渐变大；采用纵向诱导通风+侧向集中排烟模式时，沉管隧道内合理的纵向诱导风速为2.5 m·s^-1。

Research on Flow Behavior of Fumes by Lateral Concentrated Smoke Exhaust of Immersed Tunnel

According to the problems of evacuation and rescue in the immersed tunnel at the seabed under the fire conditions, with the Hong Kong-Zhuhai-Macao Bridge Immersed Tunnel as the support of the project, the physical test platform of the lateral concentrated smoke exhaust with the scale factor of 1:1 was established in the first time domestically. Based on the fire source calibration test and the theoretical analysis, the fire power was calibrated by weightlessness method and heat radiation method, and the relation curve between the heat release rate and the burning time was obtained. Based on lateral concentrated smoke exhaust physical experiments and the FDS numerical simulation comparison test, the relationship among scale of oil basin fire, fuel and burning area of oil basin was obtained. By dint of FDS numerical simulation, the laws of temperature field distribution, laws of visibility distribution and smoke spreading range of the lateral concentrated exhaust of immersed tunnel under the different longitudinal induced wind speeds were obtained, when the peak power of fire was 50 MW. The results show that when the peak power of fire is 50 MW, the maximum temperature at the top of the tunnel near the fire source increases first and then decreases with the increase of the longitudinal induced wind speeds. The visibility of each point of the tunnel at the height of 2 m gradually increases, and the visibility of the involved area gradually decreases when the longitudinal wind speed increases from 1.0 m · s^-1 to 2.5 m · s^-1. And the visibility of the tunnel downstream at the height of 2 m is gradually decreasing, and the involved area gradually becomes larger and large, when the longitudinal wind speeds increase from 2.5 m·s^-1 to 3.5 m·s^-1. The reasonable longitudinal induced wind speed is 2.5 m· s^-1 when the mode of longitudinal induced ventilation and lateral concentrated exhaust is adopted.