水分影响下阴燃传播及气相反应发生的研究

为了解阴燃传播及其反应状态发生变化的特点,采用一半干燥一半加湿的聚氨酯泡沫材料进行实验。在自然对流条件下,阴燃由下到上从干材料传播到湿材料。各次实验中阴燃在干材料部分都保持稳定传播,而湿材料部分所设计的含水率则从8.4%到21.7%。水分的吸热作用使阴燃状态随含水率大小发生极大的变化。在含水率较小时,阴燃仍能继续传播但温度和速度都有所下降;含水率稍大时,阴燃反应受到抑制,在内部有氧气剩余的情况下则会发生气相反应;当含水率进一步增大,阴燃就会熄灭。如果阴燃能传播到材料末端,外界的大量氧气进入阴燃区将使其向明火发生转化。

Study on the Effect of Moisture on Smoldering Propagation and Occurrence of Gas phase Oxidation

Polyurethane foam, whose lower part remained dry and upper part was watered, was used in experiments to study the propagation of smoldering and its variation of reaction. Smoldering spread upward from the dry to the wet in natural convection. In experiments, the moisture contents of the upper samples were from 8.4% to 21.7%, and smoldering kept steady in the lower dry samples. Because of the endothermic evaporation of water, the state of smoldering varied greatly with the moisture content after it reached the sample interface of the dry and the wet. When the moisture content was low, smoldering continued, but its temperature and velocity somewhat decreased. With the increment of moisture content, smoldering reaction was suppressed. And the oxygen, which was not consumed completely by heterogeneous reaction, would react with the combustible gases and led to the occurrence of the gas-phase oxidation. While the moisture content was high enough, smoldering extinguished. In experiments, if smoldering propagated to the end, the transition to flaming combustion would occur for plenty of outer oxygen entering the reaction zone.