室外风作用下竖井结构内火灾烟气运动规律研究

Movement of fire smoke under external wind in shaft structure

室外风是影响高层(超高层)建筑火灾蔓延的主要因素。通过数值模拟六个不同火灾场景温度场、能见度及CO浓度场变化过程,定量总结了不同风向、风速条件下侧向全开竖井结构内烟气运动规律。模拟结果发现,迎面风作用下,竖井内会产生较高滞止压力,中性面位置上升,上部烟气加速向竖井下部蔓延,下部烟气通过开口排出;背面风作用下,中性面位置下降,竖井顶部、侧面及开口面会形成空气动力阴影区且呈负压,火灾烟气从开口向外蔓延;侧向风作用下,竖井开口产生切向力封闭作用,火灾烟气主要在竖井结构内蔓延。一定速度室外风能够较强改变竖井内烟气蔓延规律,建议在进行高层(超高层)建筑设计时,参考当地常年主导风向进行外窗位置设计。

External wind is one of the major factors that influence the spread of fire in high-rise （super high-rise） buildings. By numerical simulation for the temperature field, visibility and CO concentration field at six different fire scenarios, this paper quantitatively investigates the movement behaviors of smoke in the side full open type shaft structure under different wind direction and velocity conditions. It is found that under adverse wind, stagnation pressure will be generated in the shaft, with the rise of neutral surface position, and the top smoke will spread towards the bottom of shaft at a high speed and move out from the opening at the bottom. Under favorable wind, the neutral surface position will descend, with formation of an air power shadow zone at the top, side and opening of the shaft, being of negative pressure. In this case the fire smoke will spread from the opening. Under side wind, tangential force closure will form at the opening of the shaft, and the fire smoke mainly spreads in the shaft structure. External air has a significant role in the spread of smoke in the shaft at a certain velocity. It is recommended that the design of external window position in high-rise （super high-rise） buildings should refer to local perennial prevailing wind direction.