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固体材料火灾的熄灭条件的研究对防火灭火意义重大,然而对其研究较少。向上火蔓延燃烧是火势发展很快的火灾工况,不仅涉及到固体材料已燃区域的裂解燃烧,而且涉及到未燃区域的表面点燃问题。为分析垂直向上燃烧时固体火灾的熄灭条件,本文以火灾模拟软件FDS模拟了从固体可燃物垂直表面以一定速率释出的裂解可燃气的燃烧,得到垂直表面已燃和未燃区域接受到的火焰反馈热通量。模拟结果表明,固体表面受到的火焰反馈热通量随着固体材料裂解速率的增加先迅速增加而后缓慢减小。基于固体裂解所需的能量大于接收到的热通量时固体火灾会逐渐熄灭的理论分析,发现可以根据已燃区域火焰反馈热通量曲线的峰值位置确定近似的固体裂解燃烧熄灭临界质量通量。由该方法确定的熄灭临界质量通量比较准确,且该临界值的大小与固体材料裂解气的燃烧热值的大小成反比。此外,研究发现在固体垂直向上燃烧时,即使已燃区域的材料裂解燃烧处于熄灭的临界条件,也极有可能引起未燃区域被点燃而发生表面过火,导致火势向上蔓延而不能熄灭。
The study of the extinguishing conditions of solid material fire is of great significance to fire prevention and extinguishment, however, its research is less. Burning up and burning up is a fire condition with rapid fire development, which involves not only pyrolysis and combustion of the burned area of solid material, but also the surface ignition of unburned area. In order to analyze the extinguishing condition of solid fire when burning vertically upwards, this paper simulates the combustion of pyrolyzed gas released from the vertical surface of solid combustibles at a certain rate with fire simulation software FDS, Flame feedback heat flux. The simulation results show that the heat flux of flame feedback on the solid surface increases rapidly with the increase of solid material cracking rate and then decreases slowly. Based on the theoretical analysis that the energy required for solid pyrolysis is greater than the solid-state fire extinguished when the heat flux received, it is found that the approximate mass flux of solid pyrolysis combustion quenching can be determined from the peak position of the flame heat flux curve in the burned area . The quench critical mass flux determined by this method is accurate and the magnitude of the critical value is inversely proportional to the magnitude of the calorific value of the pyrolysis gas of the solid material. In addition, the study found that when the vertical combustion of solids, even in the burned area of the material cracking combustion is extinguished critical conditions, it is also very likely to cause unburned area was ignited and the surface over-fire, causing the fire spread upward and can not be extinguished.