Understanding and Modeling of Backdraft Phenomena Occurred in Fires of Highly Insulated and Air-Tightened Houses

这项研究是为了了解火灾中的回燃现象。在高0.85m、宽0.82m、长1.05m的实材舱内进行了实验研究。测定了实际木材的质量热解速率和室内上下层的O_2、CO_2、CO和THC（总烃）。绘制了精确的温度分布图。通过一种新型耐火玻璃侧壁观察了木材热解产物引起的回燃现象。在高度绝热和低通风条件下，在三分之一刻度室中的实验结果可以允许以下结论：当火焰几乎耗尽了上层的氧气后，火焰失去了活性，出现了飘浮或幽灵般的火焰。火焰在后墙和洞口之间慢慢移动。2.突然，洞口的火焰消失了。它自己熄灭了。3.就在火灾自行熄灭后，在隔室中没有可见的火焰，但观察到恒定的质量热解速率。木材的阴燃成为主要反应。在第一次回燃发生之前，观察到一个相对较长的，约10分钟的阴燃期。4.在第一次回流后，在开口附近形成了持续的火焰，持续了大约三分钟。这种火焰可能会在报告的回燃火灾中杀死消防队员。5.观察到的回流火焰从天花板附近开始，然后迅速蔓延到地板和开口。6.在第二次和第三次回燃发生之前观察到第二次和第三次阴燃期。但它们的周期变得很短，分别为40秒和19秒。7.木材的自然着火可能在我们实验中回燃的发生中起着重要的作用。

This research is carried out to understand backdraft phenomena in fires. Backdraft phenomena was observed experimentally, Experiments were carried out in a 0.85 m high, 0.82 m wide, 1.05 m long compartment by using actual wood. The mass pyrolysis rate of actual wood, and O_2, CO_2, CO and THC (Total Hydrocarbons) in the upper and lower layers in the compartment were measured. Precise temperature distribution maps were made. Backdraft and its related phenomena caused by pyrolyzates from wood were observed through the side wall made of a newly developed refractory glass. The results obtained from experiments in a one third scale compartment under highly insulated and low-ventilation conditions may allow the following conclusions : l. After the fire had consumed almost all the oxygen in the upper layer, the flame lost its activeness and a drifting or ghosting flame occurred. The flame moved slowly between the rear wall and the opening. 2. Suddenly, the flame at the opening disappeared. It self-extinguished. 3. Just after the self-extinguishment of the fire, there were no visible flames in the compartment but a constant mass pyrolysis rate was observed. Smoldering of the wood became main reaction. A relatively long, about ten minutes, smoldering period was observed before a first backdraft occurred. 4. After the first backdraft, a persistent flame was formed near the opening and lasted about three minutes. This kind of flame might killed firefighters in the reported backdraft fires. 5. The observed backdraft flame started from near the ceiling and then rapidly spread to the floor and the opening. 6. Second and third smoldering period were observed before second and third backdraft occurred. But their period became very short, forty and nineteen seconds respectively. 7. Spontaneous ignition of wood may play an important role in an occurrence of backdraft in our experiments.