Abstract This work studied flame spread over polyethylene (PE)-insulated wires at high pressure with an emphasis on the effect of ambient pressure. Laboratory simulated wires were used as a tested wire, which consisted of semi-transparent low-density PE (LDPE) tube as an insulation and copper (Cu) rod or stainless-steel (SS) tube as a core. Increasing ambient pressure produced much soot, leading to an intensively yellow luminous flame. Flame spread rate for Cu rod increased with ambient pressure, whereas that for SS tube decreased. A qualitative analysis via a simplified flame spread model shows that the flame heat flux increases with ambient pressure, but consequently the flame heating decreases due to the decreased flame heating length. Therefore, the flame spread rate for SS tube decreased with increasing ambient pressure. For Cu rod, however, the core heating is dominant enough to compensate the decreased flame heating, and thus the ambient pressure positively affected the flame spread. During the flame spread, melted insulations were often dripped down, but it reduced with increasing ambient pressure. For Cu rod, no dripping occurred when further increasing ambient pressure, which indicates that there is the dripping limit at a high-pressure region. These findings should contribute to electrical fire safety in elevated pressure environments.

中文翻译：

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火焰在高压下蔓延到聚乙烯绝缘的铜线和不锈钢线上

摘要 这项工作研究了高压下聚乙烯 (PE) 绝缘电线上的火焰蔓延，重点是环境压力的影响。试验线采用实验室模拟线，以半透明低密度聚乙烯（LDPE）管为绝缘层，铜（Cu）棒或不锈钢（SS）管为芯。增加环境压力会产生大量烟灰，导致强烈的黄色发光火焰。铜棒的火焰蔓延率随环境压力增加而增加，而不锈钢管的火焰蔓延率下降。通过简化的火焰蔓延模型进行的定性分析表明，火焰热通量随着环境压力的增加而增加，但由于火焰加热长度的减少，火焰加热也随之减少。因此，SS 管的火焰蔓延速率随着环境压力的增加而降低。然而，对于铜棒，核心加热足以补偿减少的火焰加热，因此环境压力对火焰蔓延产生积极影响。在火焰蔓延期间，熔化的绝缘材料经常滴落下来，但随着环境压力的增加而减少。对于 Cu 棒，当进一步增加环境压力时没有发生滴落，这表明在高压区存在滴落极限。这些发现应该有助于高压环境中的电气防火安全。这表明在高压区存在滴落极限。这些发现应该有助于高压环境中的电气防火安全。这表明在高压区存在滴落极限。这些发现应该有助于高压环境中的电气防火安全。