Abstract The effect of ambient pressure on flame spread and insulation dripping of copper-cored, LDPE-insulated wires exposed to opposed airflows was investigated to increase understanding of electrical wire fire hazards in spacecraft environments. Utilized wire samples consisted of 0.64 mm-diameter copper cores surrounded by 4 mm-outer diameter LDPE insulation sheaths. The wire characteristics were selected for comparison with future experiments planned in the International Space Station (ISS) with similar wires. Environmental pressure was varied from sub-atmospheric (40 kPa) to atmospheric (100 kPa). Wires oriented horizontally were exposed to opposed airflows with speeds of 10 or 20 cm/s. Results showed that flame spread rates increase with pressure and decrease with increasing opposed flow speeds. Melted and burning insulation left behind by flame spread dripped with a frequency that increased with pressure; the total mass dripped decreased with pressure. It was also found that lower flows produced more frequent dripping with less total mass dripped, and higher flows produced the opposite. Coincidingly, as the mass of dripped insulation increased, the flame spread rate decreased. Comparison of present results with those from studies with different wire samples show that the effect of environmental parameters on flame spread and insulation dripping depends strongly on core conductivity and core/insulation diameters. Consequently, care should be taken in extending results obtained from specific wire tests to other wires without justification.

中文翻译：

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降低环境压力和反向气流对 LDPE 绝缘铜线火焰蔓延和滴落的影响

摘要 研究了环境压力对暴露于反向气流的铜芯 LDPE 绝缘电线的火焰蔓延和绝缘滴落的影响，以增加对航天器环境中电线火灾危险的了解。使用的电线样品由 0.64 毫米直径的铜芯组成，周围是 4 毫米外径的 LDPE 绝缘护套。选择导线特性是为了与国际空间站 (ISS) 计划在未来使用类似导线进行的实验进行比较。环境压力从低于大气压 (40 kPa) 到大气压 (100 kPa) 不等。水平定向的电线暴露于速度为 10 或 20 厘米/秒的反向气流中。结果表明，火焰蔓延速度随压力增加而增加，而随着相反流速的增加而减少。火焰蔓延留下的熔化和燃烧的绝缘材料以随压力增加的频率滴落；滴落的总质量随压力而减少。还发现较低的流量产生更频繁的滴落和较少的总滴落质量，而较高的流量产生相反的结果。巧合的是，随着滴下绝缘材料的质量增加，火焰蔓延速度下降。将目前的结果与不同电线样品的研究结果进行比较表明，环境参数对火焰蔓延和绝缘滴落的影响在很大程度上取决于芯线电导率和芯线/绝缘层直径。因此，在没有正当理由的情况下，将特定电线测试的结果扩展到其他电线时应该小心。滴落的总质量随压力而减少。还发现较低的流量产生更频繁的滴落和较少的总滴落质量，而较高的流量产生相反的结果。巧合的是，随着滴下绝缘材料的质量增加，火焰蔓延速度下降。将目前的结果与不同电线样品的研究结果进行比较表明，环境参数对火焰蔓延和绝缘滴落的影响在很大程度上取决于芯线电导率和芯线/绝缘层直径。因此，在没有正当理由的情况下，将特定电线测试的结果扩展到其他电线时应该小心。滴落的总质量随压力而减少。还发现较低的流量产生更频繁的滴落和较少的总滴落质量，而较高的流量产生相反的结果。巧合的是，随着滴下绝缘材料的质量增加，火焰蔓延速度下降。将目前的结果与不同电线样品的研究结果进行比较表明，环境参数对火焰蔓延和绝缘滴落的影响在很大程度上取决于芯线电导率和芯线/绝缘层直径。因此，在没有正当理由的情况下，将特定电线测试的结果扩展到其他电线时应该小心。火焰蔓延速度下降。将目前的结果与不同电线样品的研究结果进行比较表明，环境参数对火焰蔓延和绝缘滴落的影响在很大程度上取决于芯线电导率和芯线/绝缘层直径。因此，在没有正当理由的情况下，将特定电线测试的结果扩展到其他电线时应该小心。火焰蔓延速度下降。将目前的结果与不同电线样品的研究结果进行比较表明，环境参数对火焰蔓延和绝缘滴落的影响在很大程度上取决于芯线导电率和芯线/绝缘层直径。因此，在没有正当理由的情况下，将特定电线测试的结果扩展到其他电线时应该小心。