低压下高温导线电流过载喷射着火研究

以聚全氟乙丙烯(FEP)高温阻燃材料为绝缘层的电缆电线,在航天器中有着较广泛的应用,但是关于它们短路过载引起的着火却少有研究。通过低压实验舱模拟微重力下的弱浮力环境,对过载电流下的FEP高温导线的着火现象进行了研究。实验结果表明,由于FEP导线热容高,热解过程中,会在绝缘层与线芯之间积聚热解气体,形成气泡,随后气泡破裂发生喷射着火现象;随着环境压力的增大,FEP热解气泡的宽度逐渐增加,而气泡高度逐渐减小;实验段导线中间位置所受拉伸应力最大,喷射着火发生在中间位置的概率最高;相同氧气浓度下,着火能量随着压力的增加而逐渐降低,而增加氧气浓度则会使着火能量降低。

Bursting ignition of high-temperature electric wire with overload current in sub-atmospheric pressure

Fluorinated ethylene propylene (FEP) is often used for the wire coating materials for practical applications in spacecraft, but its bursting ignition mechanism was scarcely investigated. In this paper, a weakly-buoyance environment was created in a sub-atmospheric cabin and the FEP wire ignition experiment with a large continuous constant current was conducted inside the cabin. The experimental and theoretical analyses showed that the formation of the bubble is caused by the large heat capacity of FEP insulation, where the pyrolysis gases between core and insulation layer accumulate gradually. It is also found that with the increase of air pressure, the bubble has lower height and broader width, and in the center of the wire, the expansion stress is higher, so the bubble bursting occurs at the center with higher probability. Finally, with the increasing air pressure, ignition energy decreases, and a higher oxygen concentration also causes the decrease of ignition energy.