【作者】 张战恩；

【导师】 刘和云；

【作者基本信息】 长沙理工大学 ， 工程热物理， 2011， 硕士

【摘要】 随着环境气候的变化,架空导线覆冰事故频繁发生,对高压线、通信线路、电气化铁路的接触线形成了很大的危害。受气候和地形等因素的影响,我国是世界上架空导线覆冰最为严重的国家之一,每年的导线覆冰事故给我国带来巨大的经济损失,已成为电力、通信等行业急需解决的问题。本文首先对国内外架空导线覆冰研究现状进行综述,介绍了现阶段各种导线防、除冰技术的特点和方法,提出了导线覆冰的几个关键问题以及本文主要的工作和安排。其次介绍了架空导线覆冰的基本概念与机理,导线只有在合适的气温(0℃～-10℃)、较高的湿度(85%以上)和适当的风速下才会形成覆冰,覆冰的形式也是多种多样,不同的气象条件下,覆冰类型也不相同,有雨凇、雾凇、湿雪等不同的表观特征,覆冰的物理性质也随之发生变化。再次,对导线覆冰过程中不同气象条件下的收集系数进行实验研究,收集系数反应的是导线捕获空气中过冷液滴的能力,直接影响导线覆冰量的多少。本文通过实验方法,测定在覆冰环境条件下模拟导线收集系数的大小,以及收集系数的影响因素和随实验工况条件变化收集系数的变化规律。接着,通过对导线覆冰表面传热过程的分析,得到导线表面对流换热的理论分析式,以此式为实验原理,在覆冰环境条件下,对导线表面对流换热系数进行实验研究。通过实验,得到对流换热系数随电流、风速、温度等气象参数的变化规律,对流换热系数随风速的增加而增大,随电流增大而增大,环境温度对对流换热基本没有影响。最后,在覆冰环境下,实验得到模拟导线局部对流换热系数的变化情况,局部对流换热系数随空气横掠导线角度呈现先减小、再增大的变化趋势;在此基础上对架空导线局部对流换热与空气横掠旋转圆柱体对流换热进行比较,验证了对流换热实验的可靠性。本文的研究结果对防止导线覆冰有很重要的意义,对导线表面收集系数和对流换热进行了详尽的实验理论研究,为使用临界电流防冰提供理论依据。更多还原

【Abstract】 With the changes of the environment and climate, the electrical transmission lines icing occurs frequently. Atmospheric ice accretion on conductors is becoming one of the major problems in planning and construcing power transmission lines and communications networks. China is one of the countries where ice accretion is very serious affected by climate and terrain. The electrical transmission lines icing causes great economic loss in china every year,it has becoming an urgent problem in power and communications industry.Firstly, the article reviewed the research status of conductor icing at home and abroad,introduced various anti-icing、de-icing technology features and methods and some existing problems about ice accretion. The main content of this article are proposed.Secondly, this article introduced the basic concept and mechanism of icing. ice accretion will be formed only at the right temperature(0℃～-10℃)、humidity(above 85%)and wind velocity. Icing forms are not the same in different weather conditions, such as glaze、rime、wet snow and so on. The apparent characteristics and physical properties of icing are different.Thirdly,the collection coefficient is obtained through a number of experimental tests. The reaction of the collection coefficient is the ability that wires capture the supercooled droplets in the air. Through changing the air temperature, wind speed, droplet diameter and other meteorological parameters, we obtained the law of conductor icing collection coefficient under different meteorological conditions and influencing factors of the collection coefficient.Then, through analysis the heat balance equation of the heated wires and the different characteristics of the heat transfer process in the ice accretion process on overhead transmission wires, the theoretical formula of heat transfer coefficient is obtained. The convection heat transfer is calculated through experimental study in the icing environmental conditions. Ultimately, we obtained that the convective heat transfer coefficient increased with the increasing of wind speed and the current which pass through lines and the air temperature have a little effect.Finally, we obtained the low of local convective heat transfer coefficient through experimental study. The local convective heat transfer coefficient is decreased first and then increased with increasing angle. On this basis, verified the reliability of the experiment compared with the local convection heat transfer when air across rotating cylinder.The results of this article have very important meaning of the mechanism of anti-icing. This article was carried out a detailed experimental and theoretical study about the collection coefficient and the convection heat transfer. The experimental results can be used to provide theoretical support for anti-icing based on the Joule effect.更多还原