低压条件下PE和ETFE导线火蔓延实验研究

发布时间：2018-05-31 09:15

本文选题：导线火蔓延 + 低压　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：导线的绝缘层往往是聚合物材料,着火后容易发生持续的火蔓延现象。导线的火蔓延过程中间伴随着绝缘层的熔融滴落现象,这是一个复杂、多相、物理与化学反应的过程,并且给航空航天飞行带来了非常大的火灾安全隐患。此外,由于航空航天器自身环境特殊性,飞机所处的环境压力大约为80千帕,而空间站所处的又是微重力环境,氧浓度一般控制在30%左右,与地面环境有很大的不同。如果仅仅依靠地面常规的实验来判断导线火蔓延的危险性,往往不能准确预测航空航天器实际应用中的环境情况。因此,在地面环境下,建立适宜的实验设备模拟低压条件和高氧浓度空间,意义显得非常重要。本文在总结调研前人对导线火蔓延研究的基础上,选取镍铬合金线芯聚乙烯绝缘层(NiCr-PE)导线,铜芯聚乙烯绝缘层(Cu-PE)导线和镍铬合金乙烯四氟乙烯绝缘层(NiCr-ETFE)导线为研究对象,自主设计了低压实验舱设备和导线火蔓延实验平台,研究了不同压力,不同氧浓度下三种导线的火蔓延速度和火焰形态特点,重点分析了 NiCr-PE导线与Cu-PE导线熔融的熔融滴落过程,揭示了导线火蔓延过程中熔融滴落现象的机制。在理论研究方面,本文参照液滴蒸发燃烧模型,分析了 PE导线熔融滴落的物理过程和传热传质特点,建立了熔融滴落的质量守恒方程,得出了液滴直径(D(t))的增长公式。通过对熔融液滴的受力分析,得出了熔融液滴的理论滴落周期(t0)和临界滴落直径(Dcr)值。在实验研究方面,首先根据不同压力下的PE实验结果,验证了理论t0与Dcr的正确性。然后对比分析了 NiCr-PE导线与Cu-PE导线的火蔓延速度随氧浓度和压力的变化关系的区别,定义了 PE导线熔融滴落上限和滴落下限的概念,得出了不同氧浓度下,两种导线滴落上限和滴落下限的变化规律。最后分析NiCr-PE导线与NiCr-ETFE导线的实验结果,对比了两种绝缘层材料对火蔓延速度与火焰形态的影响。
[Abstract]:The insulation layer of conductor is often polymer material, which is prone to continuous fire spread after fire. The fire spread of conductor is accompanied by the melting and dropping of insulation layer, which is a complex, multiphase, physical and chemical reaction process, and brings great fire safety hazards to aerospace flight. In addition, because of the particularity of the aeronautical and spacecraft environment, the environmental pressure of the aircraft is about 80 KPA, while the space station is in the microgravity environment, the oxygen concentration is generally controlled at about 30%, which is very different from the ground environment. If we only rely on conventional experiments on the ground to judge the danger of wire fire spread, it is often not possible to accurately predict the environmental situation in the practical application of aerospace vehicles. Therefore, it is very important to establish a suitable experimental equipment to simulate the low pressure condition and the high oxygen concentration space in the ground environment. In this paper, on the basis of summarizing the previous researches on the fire spread of conductors, we select Ni-Cr alloy wire core polyethylene insulating layer (NiCr-PE) conductor, copper core polyethylene insulating layer (Cu-PEE) conductor and Ni-Cr alloy ethylene tetrafluoroethylene insulating layer (NiCr-ETFEFE) conductor as research objects. The equipment of the low-pressure experimental cabin and the experimental platform of the traverse fire spread were designed independently. The fire spread velocity and flame shape characteristics of the three kinds of conductors under different pressure and different oxygen concentration were studied. The melting and dropping process of NiCr-PE wire and Cu-PE wire is analyzed emphatically, and the mechanism of melting drop phenomenon in the process of lead fire spreading is revealed. In terms of theoretical research, the physical process and heat and mass transfer characteristics of PE wire melt drop are analyzed with reference to the droplet evaporation combustion model, the mass conservation equation of melt drop is established, and the growth formula of droplet diameter is obtained. The theoretical drop period (t 0) and the critical drop diameter (DCR) of the molten droplet are obtained by analyzing the force of the melt droplet. In terms of experimental research, the correctness of theory t0 and Dcr is verified according to the experimental results of PE under different pressures. Then, the difference between the fire spread velocity of NiCr-PE wire and Cu-PE wire with oxygen concentration and pressure is analyzed, the concepts of upper limit and lower limit of melt drop of PE conductor are defined, and the different oxygen concentration is obtained. The variation of the upper and lower drop limits of the two traverse. Finally, the experimental results of NiCr-PE and NiCr-ETFE conductors are analyzed, and the effects of two kinds of insulating materials on fire propagation speed and flame morphology are compared.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：V328;V244.12

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