渐强环形热流作用下的阻燃电缆细观膨胀与引燃机理研究
发布时间：2018-08-02 11:49
【摘要】：用于电力输送、信息传递的电线电缆在工业化、信息化社会中广泛使用,我国每年均有大量电线电缆生产并投入使用。由于电缆护套层、绝缘层的制备材料多为有机聚合物,携带着大量的火灾荷载,以致相互连通的电缆一旦因电弧、短路等电气故障发生火灾,其释放的毒气和热量将严重危害人们的健康,并且电缆火灾还具有极强的蔓延性。随着防火要求的提高,对于一些重要场所(如核电站),已经明确要求其使用阻燃型电缆,而典型阻燃PVC电缆在受热时释放出大量气体,整体表现出剧烈的膨胀、发泡效应,膨胀形成的多孔炭层具有隔热、隔氧作用,致使引燃过程变得更为复杂。本课题针对电缆这类柱形结构可燃物,以变热流火场环境为研究背景,基于自制环形加热实验平台,开展了二次函数增长型热流(t2热源)加热条件下0.1m长电缆膨胀-点燃实验及lm长电缆火焰蔓延实验,以研究阻燃电缆在受热中材料膨胀、破裂、相变及内外层传热对点燃和火蔓延行为的影响机理,及变热流复杂火源环境下材料的热解和临界点燃特征。同时,为了从微观层面解析电缆材料详细化学热解、膨胀及自燃等反应动力学过程,本文对电缆护套(PVC)和绝缘(XLPE)材料进行了热重分析实验。0.1m长电缆实验表明,阻燃PVC护套电缆在着火前的受热变形过程包含了5个明显的特征阶段,依次为:惰性阶段、波动阶段、膨胀阶段、收缩阶段和稳定阶段,这5个阶段对YJV双层电缆的点燃行为有重要影响。同时,根据多种功率下0.1m长电缆的点燃结果,分析了变热流辐射热源下热流积分与点燃时间的关系,以及阻燃电缆在加热中自发着火的临界温度及热流判据。lm长电缆实验研究发现,在50%电加热功率下该阻燃电缆出现明显的双阶段燃烧过程,这两个阶段分别由外护套和绝缘层的燃烧主导,并且随着加热功率的增大,两个阶段逐渐融合成一个阶段燃烧过程。最后,通过对PVC和XLPE材料进行TG-DTG分析,得到了两种材料在受热时的热解动力学过程和参数,并从反应机理上解释了 ZR-YJV阻燃电缆在中尺寸实验中受热膨胀及点燃特殊行为规律。
[Abstract]:Wires and cables used in power transmission and information transmission are widely used in the industrialized and information society. A large number of wires and cables are produced and put into use in China every year. Because of the cable sheath layer, the insulating layer is mostly made of organic polymer, carrying a large amount of fire load, so that once the cable is connected by electrical faults such as arc, short circuit, fire occurs. The gas and heat released will seriously endanger people's health, and the cable fire is highly contagious. With the improvement of fire resistance requirements, some important places (such as nuclear power stations) have been explicitly required to use flame retardant cables, while typical flame retardant PVC cables release a large amount of gas when heated, showing a violent expansion and foaming effect. The porous carbon layer formed by expansion has the function of heat insulation and oxygen insulation, which makes the ignition process more complicated. This paper aims at the combustible material of cylindrical structure such as cable, taking the environment of variable heat flux fire as the research background, based on the self-made annular heating experimental platform. In order to study the material expansion and rupture of flame retardant cable under the condition of quadratic function growth heat flux (T2) heating, the expansion igniting experiment of 0.1 m long cable and flame spread test of lm long cable were carried out. The influence mechanism of phase transition and heat transfer inside and outside layer on ignition and fire propagation behavior, and the pyrolysis and critical ignition characteristics of materials under the condition of complex heat flux. At the same time, in order to analyze the chemical pyrolysis, expansion and spontaneous combustion of cable material from microcosmic level, the thermogravimetric analysis experiment of cable sheath (PVC) and insulating (XLPE) material was carried out. The process of thermal deformation of flame-retardant PVC sheathed cables before ignition includes five distinct stages: inertia stage, fluctuating stage, intumescent stage, shrinkage stage and stable stage. These five stages have important influence on the igniting behavior of YJV double layer cable. At the same time, according to the igniting result of 0.1m long cable under various power, the relationship between heat flux integral and ignition time under variable heat flux radiation heat source is analyzed. The experimental study on the critical temperature and heat flux criterion of spontaneous ignition of flame retardant cable during heating. The experimental results show that the flame retardant cable has an obvious two-stage combustion process under 50% electric heating power. The two stages are dominated by the outer sheath and the insulation layer, respectively. With the increase of heating power, the two stages are gradually merged into one stage combustion process. Finally, through the TG-DTG analysis of PVC and XLPE materials, the pyrolysis kinetics and parameters of the two materials were obtained, and the special behavior of thermal expansion and ignition of ZR-YJV flame-retardant cable was explained from the reaction mechanism.
【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】：TM247
本文编号：2159333
[Abstract]:Wires and cables used in power transmission and information transmission are widely used in the industrialized and information society. A large number of wires and cables are produced and put into use in China every year. Because of the cable sheath layer, the insulating layer is mostly made of organic polymer, carrying a large amount of fire load, so that once the cable is connected by electrical faults such as arc, short circuit, fire occurs. The gas and heat released will seriously endanger people's health, and the cable fire is highly contagious. With the improvement of fire resistance requirements, some important places (such as nuclear power stations) have been explicitly required to use flame retardant cables, while typical flame retardant PVC cables release a large amount of gas when heated, showing a violent expansion and foaming effect. The porous carbon layer formed by expansion has the function of heat insulation and oxygen insulation, which makes the ignition process more complicated. This paper aims at the combustible material of cylindrical structure such as cable, taking the environment of variable heat flux fire as the research background, based on the self-made annular heating experimental platform. In order to study the material expansion and rupture of flame retardant cable under the condition of quadratic function growth heat flux (T2) heating, the expansion igniting experiment of 0.1 m long cable and flame spread test of lm long cable were carried out. The influence mechanism of phase transition and heat transfer inside and outside layer on ignition and fire propagation behavior, and the pyrolysis and critical ignition characteristics of materials under the condition of complex heat flux. At the same time, in order to analyze the chemical pyrolysis, expansion and spontaneous combustion of cable material from microcosmic level, the thermogravimetric analysis experiment of cable sheath (PVC) and insulating (XLPE) material was carried out. The process of thermal deformation of flame-retardant PVC sheathed cables before ignition includes five distinct stages: inertia stage, fluctuating stage, intumescent stage, shrinkage stage and stable stage. These five stages have important influence on the igniting behavior of YJV double layer cable. At the same time, according to the igniting result of 0.1m long cable under various power, the relationship between heat flux integral and ignition time under variable heat flux radiation heat source is analyzed. The experimental study on the critical temperature and heat flux criterion of spontaneous ignition of flame retardant cable during heating. The experimental results show that the flame retardant cable has an obvious two-stage combustion process under 50% electric heating power. The two stages are dominated by the outer sheath and the insulation layer, respectively. With the increase of heating power, the two stages are gradually merged into one stage combustion process. Finally, through the TG-DTG analysis of PVC and XLPE materials, the pyrolysis kinetics and parameters of the two materials were obtained, and the special behavior of thermal expansion and ignition of ZR-YJV flame-retardant cable was explained from the reaction mechanism.
【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】：TM247
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