Abstract Theoretical and experimental works have been carried out to clarify the effect of core material on the extinction characteristics of the flame spreading over electric wires. Additionally, an attempt has been made to explain previous experimental results (Takahashi et al., 2013 [1] ) which found that Limiting Oxygen Concentration (LOC) of copper (Cu) wire is higher than that of nickel-chrome (NiCr) wire. A theoretical model is developed to discuss the heat loss mechanism in the unburned zone ahead of the gas-phase preheat zone and its validity is confirmed by measured temperature profiles along Cu, iron (Fe), and NiCr wires insulated by low-density polyethylene (LDPE). The theoretical analysis reveals that the flame spread rate is a crucial value to assess the extinction characteristics of the flame spreading over electric wires because it controls heat loss in the unburned zone. The reduction of the flame spread rate increases heat loss in the unburned zone and induces the quenching extinction as a result of extended thermal diffusion length along the electric wire. It is also found that a highly conductive wire increases heat loss rather than poorly conductive wire even under the same flame spread rate. Such characteristics are well described by a newly introduced parameter, ηf, which is a dimensionless flame spread rate derived by the present study. By using ηf, previous experimental findings [1] are successfully explained.

中文翻译：

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线芯在熄灭细电线上蔓延的相对火焰中的作用

摘要 为了阐明芯材对火焰在电线上蔓延的熄灭特性的影响，已经进行了理论和实验工作。此外，已尝试解释之前的实验结果（Takahashi 等人，2013 [1]），该结果发现铜 (Cu) 线的极限氧浓度 (LOC) 高于镍铬 (NiCr) 线. 开发了一个理论模型来讨论气相预热区之前未燃区的热损失机制，其有效性通过沿用低密度聚乙烯绝缘的 Cu、铁 (Fe) 和 NiCr 线测量的温度分布得到证实。低密度聚乙烯）。理论分析表明，火焰蔓延速度是评估火焰在电线上蔓延的熄灭特性的关键值，因为它控制着未燃区的热损失。火焰蔓延速度的降低增加了未燃区的热损失，并由于沿电线的热扩散长度延长而导致淬火熄灭。还发现，即使在相同的火焰蔓延速率下，高导电性线材会增加热损失，而不是导电性差的线材。新引入的参数 ηf 很好地描述了这些特性，该参数是由本研究得出的无量纲火焰蔓延率。通过使用 ηf，成功地解释了先前的实验结果 [1]。火焰蔓延速度的降低增加了未燃区的热损失，并由于沿电线的热扩散长度延长而导致淬火熄灭。还发现，即使在相同的火焰蔓延速率下，高导电性线材会增加热损失，而不是导电性差的线材。新引入的参数 ηf 很好地描述了这些特性，该参数是由本研究得出的无量纲火焰蔓延率。通过使用 ηf，成功地解释了先前的实验结果 [1]。火焰蔓延速度的降低增加了未燃区的热损失，并由于沿电线的热扩散长度延长而导致淬火熄灭。还发现，即使在相同的火焰蔓延速率下，高导电性线材会增加热损失，而不是导电性差的线材。新引入的参数 ηf 很好地描述了这些特性，该参数是由本研究得出的无量纲火焰蔓延率。通过使用 ηf，成功地解释了先前的实验结果 [1]。新引入的参数 ηf 很好地描述了这些特性，该参数是由本研究得出的无量纲火焰蔓延率。通过使用 ηf，成功地解释了先前的实验结果 [1]。新引入的参数 ηf 很好地描述了这些特性，该参数是由本研究得出的无量纲火焰蔓延率。通过使用 ηf，成功地解释了先前的实验结果 [1]。