凹型结构下保温材料EPS典型垂直火蔓延特性对比研究

本工作通过自主搭建小尺寸火蔓延的实验平台，研究了凹型结构中保温材料EPS垂直向上和向下火蔓延特性。对比分析了火焰结构特性、火蔓延速度、质量损失速率、火焰温度等参数的变化规律。结果表明，在垂直向上蔓延过程中，EPS出现短暂的停滞现象。一方面由于烟囱效应易形成一个大的浮力压力差，导致火焰不稳定性；另一方面由于凹型结构易于烟气的聚集，导致燃烧不充分。而在垂直向下蔓延过程中，由于逆向烟囱效应的影响，火蔓延速度明显加速。火蔓延过程中质量损失速率，很大程度上受其火焰高度的影响，呈现上下振荡的特性。未燃区域部分，火焰温度经历两个温度峰值，向上蔓延过程中第一个温度峰值大于第二个；而向下蔓延过程中第一个温度峰值小于第二个。这主要是由于火焰结构形态及烟囱效应的方向特点，导致产生两个不同大小的峰值。本研究结果可为实际凹型结构下火蔓延特性研究提供前期理论和参考价值。

Comparative study on typical vertical flame spread characteristics of EPS insulation material under concave structure

The vertical upward and downward flame spread characteristics of insulation material EPS in the concave structure were studied by building a small-scale flame spread experimental platform. The changes of parameters such as flame structure characteristics, flame spread speed, mass loss rate, flame temperature were comparatively analyzed. The research results showed that in the process of vertical upward spreading, EPS appeared stagnant combustion; this was mainly caused by the large gas flow generated by the chimney effect. However, in the process of vertical downward spreading, the flame spread speed was obviously accelerated due to the increase of EPS accumulated in the process of flame spread and the effect of the reverse stack effect. During the upward spreading process, the length of the pyrolysis zone was significantly longer than the pyrolysis zone spreading downwards. At the same time, the flame was basically inclined to both sides of the concave groove, and the molten dripping of the material can be clearly seen, but it was spreading downwards almost no molten spilled liquid. The mass loss rate in the process of flame spread was affected by the flame height to a great extent, which was mainly manifested in two stages: initial oscillation stage and stable oscillation stage. The influence of the stack effect on it was transient and temporary. In the unburned area, the flame temperature experienced two temperature peaks, and the first peak was larger than the second peak in the case of upward spread; while the first peak was smaller than the second peak for downward propagation. This was mainly due to the structure of the flame and the directional characteristics of the chimney effect, resulting in the generation of two different peak sizes. The research results of this work can provide early theoretical and reference value for the study of flame spread characteristics under actual concave structures.