Abstract Downward flame spread over insulation materials by restriction of parallel glass curtain wall is an important potential scenario in modern underground building fire accidents. Meanwhile, considering the continuous challenge of research efforts in low pressure fire behavior, experimental investigation was conducted for the individual and coupling effects of pressure and curtain wall spacing on flexible polyurethane (FPU) downward flame spreading characteristics. Three pressures (70/85/100 kPa) below or near atmospheric pressure, and six kinds of spacings (4.5/6.0/8.5/11.0/14.0 cm and non-curtain wall) were applied to give a phenomenological study on the complicated variations of pyrolysis front, melting and dripping process, burning rate, flame spread velocity, flame height and pulsation frequency. First, evolution of vertex angle in pyrolysis front was observed to be stable and insensitive to both ambient pressure and interlayer spacing. Also, three dripping formations of molten fuel were found, and enhanced by decreasing pressure and spacing. Second, comprehensive understandings of coupling effects on burning rate, spread velocity and various heat transfer components were performed and formulated with semi-quantitative correlations theoretically. Finally, nonmonotonic tendencies of spacing vs. flame height or pulsation frequency were interpreted based on classical fluid and fire dynamic theory. This work could be valuable for fire hazardous analysis of modern building under sub-atmospheric environment.

中文翻译：

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次大气压对地下建筑平行玻璃幕墙结构典型保温材料向下火焰蔓延的影响

摘要 平行玻璃幕墙限制下火焰在保温材料上蔓延是现代地下建筑火灾事故的重要潜在场景。同时，考虑到低压火灾行为研究工作的持续挑战，对压力和幕墙间距对柔性聚氨酯（FPU）向下火焰蔓延特性的单独和耦合影响进行了实验研究。使用低于或接近大气压的三种压力（70/85/100 kPa）和六种间距（4.5/6.0/8.5/11.0/14.0 cm和非幕墙），对复杂变化的现象进行了现象学研究。热解前沿、熔化和滴落过程、燃烧速率、火焰蔓延速度、火焰高度和脉动频率。第一的，观察到热解前沿中顶角的演变是稳定的，并且对环境压力和层间距都不敏感。此外，还发现了三种熔融燃料滴落形成，并通过降低压力和间距而增强。其次，对燃烧速率、传播速度和各种传热成分的耦合效应进行了全面的理解，并在理论上用半定量相关性进行了表述。最后，基于经典流体和火灾动力学理论解释了间距与火焰高度或脉动频率的非单调趋势。这项工作对亚大气环境下现代建筑的火灾危险性分析具有重要意义。发现了三种熔融燃料滴落形成，并通过降低压力和间距来增强。其次，对燃烧速率、传播速度和各种传热成分的耦合效应进行了全面的理解，并在理论上用半定量相关性进行了表述。最后，基于经典流体和火灾动力学理论解释了间距与火焰高度或脉动频率的非单调趋势。这项工作对亚大气环境下现代建筑的火灾危险性分析具有重要意义。发现了三种熔融燃料滴落形成，并通过降低压力和间距来增强。其次，对燃烧速率、传播速度和各种传热成分的耦合效应进行了全面的理解，并在理论上用半定量相关性进行了表述。最后，基于经典流体和火灾动力学理论解释了间距与火焰高度或脉动频率的非单调趋势。这项工作对亚大气环境下现代建筑的火灾危险性分析具有重要意义。基于经典流体和火灾动力学理论解释了间距与火焰高度或脉动频率的非单调趋势。这项工作对亚大气环境下现代建筑的火灾危险性分析具有重要意义。基于经典流体和火灾动力学理论解释了间距与火焰高度或脉动频率的非单调趋势。这项工作对亚大气环境下现代建筑的火灾危险性分析具有重要意义。