导线火蔓延行为的研究对于核电站、航空航天、高压氧舱、高海拔等变压环境的防火安全具有指导意义。该文通过自建实验台研究了聚乙烯(PE)导线在40~500 kPa变压环境下的火蔓延及熔融滴落行为, 获得了导线火焰形态、质量损失、火蔓延速度及熔融滴落次数等数据, 采用Fluent软件中流体体积(VOF)法和焓-多孔介质法建立滴落过程模型以模拟导线熔化和动态行为, 分析聚乙烯熔化滴落过程中速度、压力、温度随时间的分布规律。结果表明：1) 当压力值由40 kPa增至500 kPa时, 导线的火焰高度增幅达76%, 火焰宽度降幅为31%; 当氧气体积分数由21%增至30%时, 火焰高度增幅更为明显。此时火蔓延速率和质量损失速率加快。2) 氧气体积分数为21%时, PE导线在40~80 kPa出现熔融滴落现象, 火焰形态稳定; 而当氧气体积分数为30%时, 压力超过60 kPa后则无滴落现象。3) 模拟中PE在被加热4.4 s后熔融液滴开始滴落, 在重力作用下与主体分离, 最大速度约22 cm/s, 此时周围气流呈螺旋运动。研究结果可为变压环境下PE导线火灾发展预测及防控提供实验基础。

Objective: The study of fire spread behavior in wires holds significant importance for guiding fire safety measures in variable pressure environments such as nuclear power plants, aerospace applications, hyperbaric oxygen chambers, and high-altitude areas. Currently, there is a lack of comprehensive research focused on variable pressure environments widely applied in spacecraft, high-altitude regions, nuclear power plants, and civilian hyperbaric oxygen chambers. Therefore, this study investigates the fire spread and molten droplet behavior of polyethylene (PE) wires under variable pressure conditions ranging from 40 to 500kPa using a self-built experimental platform. Methods: This study selected typical thermoplastic PE wires as the research subject and constructed a fire spread experimental platform to investigate the effects of variable pressure conditions (40-500kPa) and oxygen volume fractions of 21% and 30% on fire spread behavior. Simulations were conducted using the solidification/melting model in Fluent software to analyze the melting and dynamic motion of molten material suspended on a metal plate. Results: 1) Within the 40-100kPa range, a low-luminosity blue flame appears at the base of the flame and fades as pressure increases. For an oxygen volume fraction of 21%, the bottom blue flame disappears after 100kPa. For a 30% oxygen volume fraction, it vanishes at 60kPa. At pressures from 100kPa to 500 kPa, the blue region at the bottom of the flame disappears, flame brightness intensifies. The top flame color changes from bright yellow to orange, and soot production increases. Increasing the oxygen volume fraction from 21% to 30% reduces the orange region at the flame's top and decreases black soot in the upper section, reshaping the flame into a more triangular form. During this stage, the fire spread rate and mass loss rate increase significantly; 2) As pressure increases, the flame width of the PE wire decreases. At 500kPa, the flame width measures 2.0 and 2.2cm for oxygen volume fractions of 21% and 30%, respectively. Flame height increases with pressure, peaking at 500kPa. At oxygen volume fractions of 21% and 30%, the maximum flame heights are 3.7 and 4.8cm, respectively; 3) At an oxygen volume fraction of 21%, molten dripping occurs in the 40-80kPa range. However, at an oxygen volume fraction of 30%, molten dripping ceases above 60kPa. Simulations reveal that molten droplets form 4.4s after PE is heated and separate from the main body under gravity with a maximum velocity of approximately 22cm/s. Surrounding airflow exhibits a spiral motion during droplet detachment. Conclusions: This study primarily reveals the fire spread and molten droplet behavior of PE wires under different pressure conditions, providing a foundation for predicting and preventing fire development in PE wires found in variable pressure environments.