【摘要】：用于電力輸送、信息傳遞的電線電纜在工業(yè)化、信息化社會中廣泛使用,我國每年均有大量電線電纜生產并投入使用。由于電纜護套層、絕緣層的制備材料多為有機聚合物,攜帶著大量的火災荷載,以致相互連通的電纜一旦因電弧、短路等電氣故障發(fā)生火災,其釋放的毒氣和熱量將嚴重危害人們的健康,并且電纜火災還具有極強的蔓延性。隨著防火要求的提高,對于一些重要場所(如核電站),已經明確要求其使用阻燃型電纜,而典型阻燃PVC電纜在受熱時釋放出大量氣體,整體表現出劇烈的膨脹、發(fā)泡效應,膨脹形成的多孔炭層具有隔熱、隔氧作用,致使引燃過程變得更為復雜。本課題針對電纜這類柱形結構可燃物,以變熱流火場環(huán)境為研究背景,基于自制環(huán)形加熱實驗平臺,開展了二次函數增長型熱流(t2熱源)加熱條件下0.1m長電纜膨脹-點燃實驗及l(fā)m長電纜火焰蔓延實驗,以研究阻燃電纜在受熱中材料膨脹、破裂、相變及內外層傳熱對點燃和火蔓延行為的影響機理,及變熱流復雜火源環(huán)境下材料的熱解和臨界點燃特征。同時,為了從微觀層面解析電纜材料詳細化學熱解、膨脹及自燃等反應動力學過程,本文對電纜護套(PVC)和絕緣(XLPE)材料進行了熱重分析實驗。0.1m長電纜實驗表明,阻燃PVC護套電纜在著火前的受熱變形過程包含了5個明顯的特征階段,依次為:惰性階段、波動階段、膨脹階段、收縮階段和穩(wěn)定階段,這5個階段對YJV雙層電纜的點燃行為有重要影響。同時,根據多種功率下0.1m長電纜的點燃結果,分析了變熱流輻射熱源下熱流積分與點燃時間的關系,以及阻燃電纜在加熱中自發(fā)著火的臨界溫度及熱流判據。lm長電纜實驗研究發(fā)現,在50%電加熱功率下該阻燃電纜出現明顯的雙階段燃燒過程,這兩個階段分別由外護套和絕緣層的燃燒主導,并且隨著加熱功率的增大,兩個階段逐漸融合成一個階段燃燒過程。最后,通過對PVC和XLPE材料進行TG-DTG分析,得到了兩種材料在受熱時的熱解動力學過程和參數,并從反應機理上解釋了 ZR-YJV阻燃電纜在中尺寸實驗中受熱膨脹及點燃特殊行為規(guī)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.
【學位授予單位】：中國科學技術大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM247

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本文編號：2159333