节点文献
基于流体—化学反应混合模型的空气放电机理及特性研究
Research of the Mechanism and Characteristics in Air Discharge Based on the Fluid-Chemical Reaction Hybrid Model
【作者】 刘兴华；
【导师】 何为；
【作者基本信息】 重庆大学 ， 电气工程， 2012， 博士
【摘要】 随着我国“十二五”期间特高压交、直流输电网络建设的全面展开，特高压交、直流输电线路的电晕放电机理、外绝缘安全等问题的研究得到了高度重视。国家科技部也于2011年3月增补了相关的“973”课题，开展特高压交、直流输电系统电磁与绝缘特性的基础问题研究，目的是争取在特高压绝缘与电磁特性技术领域取得突破，为获得可靠、经济的特高压输电线路和电力设备外绝缘设计提供技术支撑。特高压交、直流输电线的电晕放电属于空气放电的一种，国内外对空气放电特性开展了大量研究，得到了诸如电晕起始场强、合成电场、电晕损耗的许多半物理、半经验公式，也开展了温度、湿度和高海拔等对空气放电影响规律研究，取得了一些研究成果。但是，对关键的空气放电微观基础理论研究甚少。空气放电的机理研究涉及到多学科交叉，目前由于大气压下空气放电受探针技术的制约，使得空气放电通过试验诊断难度较大。因此，借助有限的试验结果采用数值模拟方法研究空气放电的机理不仅能节约成本，还能控制和优化空气放电的过程，从而为高压输电线路和电力设备外绝缘设计提供理论支持。目前，在空气放电的机理研究中，多数是采用单一的理论模型模拟其微观物理过程，缺乏空气放电中粒子之间全面的化学反应过程。因此，本文提出了基于流体-化学反应的空气放电混合数值模型，即从粒子之间的化学反应角度对空气放电的微观物理过程以及其特征量进行研究。提出了能够表征空气放电微观物理过程的特征量，并分析研究了高海拔气压、放电间距和放电电压等主要因素对空气放电特征量的影响规律。同时，本文搭建了大气压下空气放电观察测量装置，分析空气放电的发展特性，并且利用试验测得的结果验证了混合数值模型的正确性。论文的研究结果为高压输电线的电晕放电提供了理论与数值方法，具有重要的理论意义与工程价值。论文的主要研究内容及取得的成果如下：1）提出了基于流体-化学反应的空气放电混合数值模型，推导了数值模型的数学物理控制方程、边界条件以及初始值的计算方法。提出了一种改进的空气放电输运参数的计算方法，即首先建立一维模型，通过求解Boltzman方程计算得到空气放电中电子能量分布函数，进而获得空气放电中电子迁移率、电子扩散系数和电子反应系数等输运参数。2）基于本论文提出的混合数值模型，对低气压下不同电极结构的空气放电进行了仿真模拟。研究了空气放电过程中的粒子种类及化学反应类型，并通过与现有文献的试验结果进行验证。确定能够反映空气放电的12种基本粒子以及它们之间的27种化学反应类型。进而探讨了低气压下空气放电基本微观物理过程的特征量以及空气放电特征量随气压的变化规律。3）针对特高压输电线附近空气放电的特点，在混合数值模型中引入光电离项，研究了大气压下空气放电微观物理过程，分析确定了能够表征大气压下空气放电微观物理过程的特征量。结果表明：粒子种类、粒子密度、电子温度、电场以及能量分布是反映空气放电过程的重要特征量。它们的变化与空气放电微观物理过程具有直接关系，与输电线路电晕放电起始电压、自持和消散过程以及发光现象紧密相关。4）研究了高海拔气压、放电间距和放电电压等主要因素对空气放电特征量的影响，从而揭示了外界因素对空气放电微观物理过程的具体影响规律。结果表明：高海拔气压主要通过影响电子平均自由程和电子漂移速率来影响空气放电的宏观特性；放电电压和放电间距的改变则会带来电场分布的迅速改变，从而对空气放电发展过程影响较大。5）搭建了棒-板电极空气放电观察测量平台，并开展大气压下相关试验。通过发光图片、紫外成像仪分析研究了电晕放电从起晕到稳定的发展过程。测量放电电压-电流特性曲线、放电电流波形并与仿真结果进行比较，验证了流体-化学反应混合模型的准确性。
【Abstract】 To satisfy the increasing demand on the power electricity in China, more and moreultra-high-voltage (UHV) transmission lines will be built in next five years. With theincrease of the voltage rating, many new problems arise, including the corona discharge,insulation and manufacture of UHV electrical equipment. To solve the problem in UHVpower transmission engineering, Chinese Ministry of Science and Technologysupplemented an extra973project regarding the electromagnetic environment andinsulation of UHV transmission line in2011, which aimed at solving the newengineering problem arising in the UHV power transmission engineering and finallypromote the safety operation of UHV transmission line.The corona generated on UHV transmission line is a kind of air discharge. Thephysical mechanism of air discharge research is interdisciplinary. At present, it is verydifficult to diagnose the progress of air discharge by laboratory test due to the restrictionof the probe techniques. Therefore, with the limited test results, to study air dischargemechanism by the numerical simulation method can not only save high cost, but alsocan control and optimize the process of air discharge. The achievement in the study onmechanism of corona discharge can offer theatrical tools for the outer insulation designof UHV electrical equipment.At present, most research of air discharge just utilized a single theory and model ofair discharge microscopic physical process. It is short of comprehensive considerationof chemical reaction process in air discharge process. Therefore, this paper establishedmixed numerical air discharge model based on fluid-chemical reaction hybrid model tostudy microscopic physical process and characteristics. The characteristics of physicalprocess which can describe the air discharge microscopic progress are proposed. Themain influence factors (pressure, discharge gap, and discharge voltage) to the process ofair discharge are analyzed. At the same time, an atmospheric pressure corona dischargeobservation system was also set up to analyze the progress properties of air discharge.The measured corona discharge current and current waveform are helpful to validateand improve the numerical model. The results of the research provided theory andnumerical method for high voltage transmission line corona discharge. The maincontents and achievements of the paper are as follows:1) According to the insufficient of transport parameters in air discharge numerical model, a one-dimension model is established. The electron energy distribution functionis obtained by solving two Boltzman equations. Then, the transport parameters such aselectron mobility, diffusion coefficient are gained.2) A hybrid model of air discharge based on fluid-chemical reaction is establishedand the governing equation, boundary condition and computing method of initial valueare deduced. Based on the hybrid model proposed in this paper, a variety of physicalstructure discharge under low pressure is simulated. Compared with experimentalresults of related literatures, the hybrid model adopts12kinds of particles and27kindsof chemical reaction to reflect the basic process of air discharge. Then, the basicdynamic progress of air discharge under low pressure, the microscopic characteristics ofphysical progress and the characteristic features of air discharge changed with pressureare discussed.3) In this paper, the photoionization is introduced into the fluid-chemical reactionhybrid model and the microscopic physics process of air discharge under atmosphericpressure which can be used in UHV transmission line is studied. In addition, thecharacteristics of physical process in atmospheric pressure air discharge are analyzed.The results indicate that the particle density, electron temperature, and the distributionsof electric field and energy are the most important feature in the process of air dischargewhich change with the microscopic processes of air discharge and is closely related totransmission line corona discharge onset, self-sustained and dissipation process andluminescence phenomenon.4) The high altitude air pressure, the discharge gap, discharge voltage are the mainfactors influence the air discharge characteristics, calculation were also conductedreveal the specific influence of external factors on the air discharge microscopicphysical processes. And the results show that the high altitude pressure influences themacroscopic properties of air discharge by changing the electron mean free path andelectron drift. The discharge voltage and discharge gap will bring a rapid change of theelectric field distribution and thus influence the development process of air discharge.5) Verifying tests under atmospheric pressure have been carried out using abar-plate electrode air discharge observation measurement system. The air dischargefrom the onset to stable development process through corona image and ultravioletphotons were observed and analyzed by UV camera respectively. The fluid-chemicalreaction hybrid model was validity by the comparison of discharge voltage-currentcharacteristics and discharge current waveform.