Abstract: In actuality, wire-confined combustion occurs frequently. Its fire threat is more likely to spread due to ambient wind speed. In this work, the flame spread behavior and characteristics of two types of polyethylene wires (the diameter of the copper core is 6 and 8 mm, respectively, and the thickness of the polyethylene insulation layer is 3 and 2 mm, respectively) under side-confined conditions (the side-confined distance is 10~40 mm) and horizontal wind speed (v=0.2, 0.5, and 0.8 m/s) are studied experimentally. The experimental results reveal that as the wind speed increases, the flame height gradually decreases, and the flame width grow first increases and then decreases. The side-confinement promotes wire burning, but as wind speed increases, this effect eventually weakens. When the horizontal wind speed is low, the heat transfer of the gas phase improves while the heat transmission of the solid phase is reduced. As wind speed increased, the heat transfer mode altered, and heat transfer between the gas and solid phases weakened. This is mostly due to the tilt effect of the flame, which increases thermal radiation and convection in the preheating zone. At the same time, because wind speed lowers the temperature of the gypsum board, the gypsum board's thermal radiation and convection are lowered as well. Furthermore, the horizontal wind alters the "heat source" and "cooling" effects of the copper core. The copper core's "cooling" effect grows as wind speed and diameter increase.

Key words: wire fire, side-confinement, wind speed, flame spread rate, heat transfer

摘要： 电线受限燃烧在现实中非常普遍，在环境风速的作用下，其火灾危害性更容易扩大。本工作通过实验研究了两种尺寸的聚乙烯(PE)电线(铜芯直径分别为6和8 mm，聚乙烯绝缘层的厚度分别为3和2 mm)在侧边受限条件(受限距离为10~40 mm)和水平风速(v=0.2, 0.5, 0.8 m/s)下的火蔓延行为和特性。实验结果表明，随着风速增大，火焰高度逐渐减小，火焰宽度呈先增大后减小的趋势。侧边受限距离对电线燃烧有促进作用，但随着风速增加，这种促进作用逐渐被削弱。水平风速较小的时候，气相热量的传递得到了提升，并减弱了固相热量的传递。随着风速进一步增加，热量传递模式发生了转变，气相和固相热量传递均被削弱。这主要是由于火焰的倾斜效应增加了向预热区的热辐射和热对流；同时，由于风速降低了石膏板的温度，使得石膏板的热辐射和热对流均相应减小。此外，水平风改变了铜芯的“热源”和“冷却”作用，随着风速和铜芯直径增大，铜芯的“冷却”作用增大。

关键词: 电线火灾, 侧边受限, 风速, 火蔓延速度, 热量传递