聚氨酯泡沫材料阴燃的点燃过程

Smolder Ignition of Polyurethane Foam

阴燃材料的点燃系指材料在受到外热源加热后,依靠其自身异相氧化反应所放出的热量实现阴燃自维持传播的前期过程,如果导致熄灭则称不能点燃．聚氨酯泡沫材料在受到加热时,热流密度和加热时间是实现点燃的两大因素．在自然对流条件下,热流密度在1．6-6．8 kW／m2之间能实现阴燃材料的点燃．通过积分模型分析,得出了实现点燃的临界表达式．该式表明在一定的外部条件下,点燃成功表现为需要一个确定厚度的初始高温反应区 (炭层)．在不同热流值的实验中,实现点燃的临界炭层厚度大约为40 mm,实验结果与理论分析能够较好吻合．

Smolder ignition is the onset of self-sustained propagation deriving its principal heat from heterogeneous oxidation. The ignition can not be achieved when the elimination of the external heat input causes extinction. While the polyurethane foam is heated, the onset of smoldering is mainly affected by the external heat flux and heating time. With natural convection, it is observed that self-sustained smoldering could only occur in an external heat flux between 1.6 kW/m^2 and 6.8 kW/m^2. The critical expression of the ignition is given by using the integral model. It means that a certain thickness of the initial char is needed to maintain the spread in certain circumstances. The experiments with different heat flux show that the critical char thickness are constant, about 40 ram. The result of the experiments is well consistent to that of the analysis.