风环境下室内火灾自然排烟过程与烟气扩散规律研究

Natural smoke exhaust extracts smoke out from the fire room with self-driving force based on characteristic of building and state difference between inner and outside gas. However, natural smoke exhaust is prone to be affected by surrounding conditions. With surrounding wind, pressure difference between inside and outside, smoke flow across the natural vent and in the fire building will be different from those without surounding winds because of the wind pressure induced by wind. Theoretical analysis, numerical simulation and experimental study are proposed to be carried out to study smoke movement in enclosure fire with natural smoke exhaust under influence of wind. Mechanism of the effect of wind on smoke movement in enclosure fire will be theoretically considered. Distribution of wind pressure, temperature and gas flow in the fire building and across the smoke vent will be simulated and measured with model test in a wind tunnel. Relationships between the gas flow rate through the vents and conditions of surrounding wind, fire, geometric configuration of the building will be summarized. Technique for enhancing the performance of natural ventilation and model evaluating the effect of wind on smoke movement in tipical enclosures under fire will be proposed. Achievements of the study will be used for supporting design of smoke management system, development of enclosure fire models and improvement of building codes.

自然排烟基于建筑结构特点和火灾烟气与环境空气状态差别，利用烟气自身的驱动力将烟气排出室外。自然排烟易受到环境条件改变的影响，在有环境风时，由于风压的存在，排烟口与补气口处压力和气体流动将发生变化，并影响室内烟气的扩散过程。本项目将采用理论分析、数值模拟以及模型实验研究相结合的方法对有风条件下的室内火灾自然排烟和烟气扩散规律开展研究。通过分析环境风对室内火灾烟气扩散和自然排烟的影响机理，模拟、测量环境风作用下建筑内外压力、排烟口处以及室内温度、流速的场分布，获得通风、排烟口气体流率随环境风和火源、建筑几何条件变化的量化规律，提出在有风条件下提高排烟口排烟速率和自然排烟效率的方法以及典型建筑结构环境风对室内烟气蔓延影响程度的评价准则。项目研究成果可为室内火灾模型发展、建筑防排烟系统的设计以及相关规范的完善提供支持。

项目采用理论分析、数值模拟以及模型实验研究相结合的方法对有风条件下的室内火灾自然排烟和烟气扩散规律开展了研究。利用CFD软件对单室和多室火灾条件下的室内外压力分布以及烟气流动扩散规律开展了数值模拟研究。建立了环境风条件下的室内火灾自然排烟模型实验平台，采用激光片光和BN颗粒示踪技术，对环境风下的室内火灾自然排烟过程进行了可视化实验，利用图像处理技术对实验结果进行分析比较，对单室火灾下影响自然排烟效果的因素展开了探讨。数值模拟和模型试验结果表明：对于单室火灾，迎风-背风通风口组合下，补气口与排烟口之间的压差与环境风速的关系可用多项式拟合曲线来表示，其压差值随风速的增大呈抛物线增长。逐步增大排烟口面积时，压差值与烟气排放量均增加，对自然排烟促进作用越显著；逐步增大补气口面积，压差值与烟气排放量均减小，自然排烟效果较差。当环境风速大于2m/s后，烟气流动均过渡到风压主导控制型。房间长度增加，改变开口大小对其排烟效果的影响更明显。迎风-侧风通风口组合下，烟气排放量随环境风速增加而小幅增加。背风-侧风通风口组合下，流动为热压主导控制型，侧风面开口为排烟口，风压作用对其影响最小，其自然排烟效果最差。顶棚排烟时，排烟口流速呈现如下变化趋势：YH组合>BH组合>CH组合。对于廊室结构火灾，无环境风或环境风速较小时，火灾向其它房间蔓延，走廊与其它房间烟气分层明显；当环境风较大时，烟气分层逐渐减弱，最终失效。建筑窗孔面积大小会对建筑内烟气的蔓延产生影响。增大窗孔面积，加速了烟气排放速率，抑制烟气向其他房间蔓延，走道内层化现象减弱。同样室外风速与火源位置下，当排烟窗口位于顶棚时，排烟效果更优，走廊烟气层高度更高。项目的研究成果可为室内火灾模型发展、建筑防排烟系统的设计以及相关规范的完善提供支持。