不同燃烧状态飞火颗粒自由燃烧规律研究

飞火是开放空间中大尺度火灾非连续性蔓延的主要形式。本文通过不同热流下的木质飞火颗粒自由燃烧实验,揭示不同燃烧状态飞火颗粒的结构变形、质量损失及温度分布的变化规律。研究表明,颗粒结构变形受材料化学反应机制和热机械力作用共同影响;颗粒燃烧反应易造成热解气体的内部积聚,以致内压激增、诱发喷射或喷溅细小颗粒的现象;阴燃过程颗粒表面温度变化较小但持续时间很长,明火状态的颗粒持续高温并且温度与质量变化剧烈。

Free Combustion of Firebrands in Different Combustion States

Spotting ignition by lofted firebrands,or pieces of burning wood,is the main mechanism of a discontinuous fire spread.This work experimentally studied the radiation ignition of wooden disc particles in different heat flux,to uncover the time-independent structural deformation,mass loss and temperature distribution.The experimental results indicate that the structural deformation of the particles is the interaction of the chemical reaction and the thermo-mechanical effects.The internal reaction of the particles increases the internal pressure of the pyrolysis gas so that it can lead to the surge of the internal pressure and the occurrence of various injection or splashing in different combustion states.Compared with the smoldering process with a lower surface temperature and shorter burning duration,the flaming process is accompanied by the continuous high surface temperature,and the extreme variation of mass loss and temperature.