倾斜XPS板材向外多向耦合蔓延燃烧特性研究

Study on characteristics of multi-direction coupling flame spread and combustion after central ignition of inclined XPS sheets

为探究热塑性板材被点火源引燃后向四周火蔓延的行为特征,针对不同倾角的方形挤塑聚苯乙烯(XPS)泡沫板材,开展中心引燃后火焰向不同方向蔓延燃烧的试验,分析火蔓延状态、火蔓延速度和内部温度场随倾斜角度的变化关系。结果表明:XPS材料在受热时产生的收缩行为导致上方预热区接收热量变化,使得倾斜角度大的板材向上火蔓延更困难;当发生向上火蔓延时,蔓延速度随倾角的增大而增大,且速度远大于横向和向下火蔓延速度;向下火蔓延速度随倾斜角度的增大呈先降低后增大的趋势,横向火蔓延受板材倾角影响较小;当材料受热时温升剧烈,则易形成材料向该点处火蔓延,反之,材料受热出现显著收缩而温升较慢,则易熄灭。

For the sake of studying development characteristics of thermoplastic sheets'flame spread after central ignition,a series of experiments were conducted on square XPS foam sheets at different inclination angles,and correlation between flame spread condition,velocity and the internal temperature was analyzed.The results show that the shrinkage after central ignition causes change of energy received in preheated zone,thus making upward flame spread more difficult along sheets with bigger inclination angle.In addition,when inclination angle is getting greater,velocities of upward flame spread increase,which is also greater than those of downward and horizontal flame spread.Besides,velocities of downward flame spread decrease firstly and then increase while horizontal flame spread velocities are less affected by inclination angle.It is also found that flame spread is sustainable if there is a violent temperature rise after heating.On the contrary,it is easy to extinguish if XPS foam shrinks significantly with a slow temperature rise.