Wu Zeqi, Liu Kunpeng, Yang Jinyi, Shao Lin, Qin Hengjie, Wei Xiaoge
College of Building Environment Engineering, Zhengzhou University of Light Industry, Zhengzhou, 450001, China.
Zhengzhou Key Laboratory of Electric Power Fire Safety, Zhengzhou University of Light Industry, Zhengzhou, 450001, China.
Sci Rep. 2024 Aug 22;14(1):19567. doi: 10.1038/s41598-024-70557-6.
The ceiling structure in a long-narrow space has a significant impact on the thickness of the fire smoke layer. This paper mainly studies the influence of the height of the ceiling structure on the thickness of the smoke layer before the ceiling structure. Firstly, a theoretical analysis is conducted on the relationship between the critical thickness that affects the smoke flow state and the smoke layer thickness directly below the ceiling structure, and a formula for calculating the smoke layer thickness under gradient flow conditions is derived. Then a small-scale experimental platform was built to study the deviation of actual fire smoke relative to theoretical calculations. Experimental results show that due to the smoke cannot maintain gradient flow when crossing the ceiling structure, there is difference with theoretical calculations in the smoke layer thickness directly below the ceiling structure and some distance before the ceiling structure (which may be of greater concern for personnel evacuation). The gradient flow coefficient and thickness coefficient are defined to represent the above differences. After analysis, it was found that the gradient flow coefficient and thickness coefficient showed different linear variation patterns when the height of the ceiling structure was longer than 35 cm or shorter than 30 cm. Through numerical analysis, this study suggests that the main reason for the change in this linear pattern is whether the potential energy conversed from kinetic energy of the thin layer close to the ceiling structure can directly make the smoke to cross the ceiling structure. The research conclusions of this paper can assist in the engineering design of building smoke control and personnel evacuation.
狭长空间中的顶棚结构对火灾烟层厚度有显著影响。本文主要研究顶棚结构高度对顶棚结构前方烟层厚度的影响。首先，对影响烟流状态的临界厚度与顶棚结构正下方烟层厚度之间的关系进行理论分析，推导了梯度流条件下烟层厚度的计算公式。然后搭建小型实验平台，研究实际火灾烟气相对于理论计算的偏差。实验结果表明，由于烟气穿过顶棚结构时无法保持梯度流，顶棚结构正下方及顶棚结构前方一定距离处（人员疏散可能更关注此处）的烟层厚度与理论计算存在差异。定义梯度流系数和厚度系数来表征上述差异。分析发现，当顶棚结构高度大于35 cm或小于30 cm时，梯度流系数和厚度系数呈现不同的线性变化规律。通过数值分析，本研究认为这种线性规律变化的主要原因是靠近顶棚结构的薄层动能转化的势能能否直接使烟气穿过顶棚结构。本文的研究结论可为建筑防烟和人员疏散的工程设计提供参考。
