高储能密度液体介质脉冲绝缘特性研究

发布时间：2018-06-25 10:09

本文选题：介质击穿 + 储能密度　；参考：《国防科学技术大学》2014年硕士论文

【摘要】：由于液体介质具有较高的储能密度、较好的自愈性等优点,被广泛应用在高功率脉冲设备的脉冲形成线中作储能介质,但实际上工程用液体难以同时满足高电阻率、高介电常数及高击穿强度等要求。为此,本文研究了水基混合液电阻率贮存易失效的问题,进行了高储能型液体介质的微秒脉冲击穿研究,并开展了加添加剂、施加压力和纳米粉体掺杂对液体脉冲绝缘特性影响的研究。这些研究对改善液体介质储能特性和脉冲功率装置的紧凑小型化具有一定指导意义,本文的主要研究内容和结果如下。首先,针对以去离子水为代表的极性液体电阻率保持时间不长的问题,采用25%体积分数的乙醇/水和乙二醇/水混合液,分别开展了电阻率保持实验研究。发现混合液的电阻率在保持时会下降,且下降过程基本可分为三个阶段:快速下降、缓慢下降和恒定阶段。电阻率的变化过程基本是一个电化学平衡过程,空气和不锈钢会导致水基混合液电阻率下降较快,通过除气和采用PET塑料密闭保持可减缓下降。如采用工业试样保持一个月后,不锈钢试件中液体电阻率下降为保持初始值的6.1%,而PET塑料试件中液体电阻率下降为保持初始值的26%。其次,尽管水基混合液经过一定处理能延长其电阻率保持时间,但相对碳酸丙烯酯而言化学稳定性稍差,因此开展了碳酸丙烯酯及其与碳酸乙烯酯混合液的脉冲绝缘特性的研究,并研究了施加机械压力对其脉冲击穿的影响。碳酸丙烯酯固有电阻率可达10 MΩ·cm以上,露天保持两周后仍有6 MΩ·cm。其平均击穿强度为398.5 k V/cm,添加碳酸乙烯酯还可进一步提高其介电常数和储能密度。加压能有效改善碳酸丙烯酯的脉冲绝缘特性,当静压从1 bar上升到11 bar时,有效时间从1.24μs上升到2.79μs;归一化击穿场强从480.3 k V/cm上升到887.3 k V/cm;储能密度提高3.4倍,从0.65 MJ/m~3上升为2.2 MJ/m~3。最后,对低介电常数的弱极性液体进行了研究,本文以蓖麻油为基质油,开展了添加钛酸钡纳米粉体改性对其介电常数和脉冲绝缘特性影响的研究。改性效果因添加纳米粉体的粒径和浓度不同而不同。其中,介电常数随所添加纳米粉体的浓度提高而增大,最大能提高4倍;当纳米粉体粒径100 nm,质量分数为6%时,得到最佳改性效果,击穿场强提高到1.55 MV/cm,是原油的1.25倍;储能密度提高到0.67 MJ/m~3,是原油的1.6倍。添加的纳米粉体浓度存在最优值,在一定范围内,随纳米粉体浓度的增大击穿场强先提高后下降。
[Abstract]:Because liquid medium has the advantages of high energy storage density and good self-healing, it is widely used as energy storage medium in pulse forming line of high power pulse equipment, but in fact, it is difficult for engineering liquid to satisfy the high resistivity at the same time. High dielectric constant and high breakdown strength. Therefore, in this paper, the problem that the resistivity of aqueous mixture is easy to fail in storage is studied, the microsecond pulse breakdown of high energy storage liquid medium is studied, and the additive is added. The effect of pressure and nano-powder doping on the properties of liquid pulse insulation is studied. These studies have a certain guiding significance for improving the energy storage characteristics of liquid media and the compact miniaturization of pulse power devices. The main contents and results of this paper are as follows. Firstly, in order to solve the problem that the resistivity retention time of the polar liquid represented by deionized water is not long, 25% volume fraction of ethanol / water and ethylene glycol / water mixture were used to carry out the experimental study of resistivity retention. It is found that the resistivity of the mixture decreases when it is kept, and the decline process can be basically divided into three stages: rapid descent, slow descent and constant phase. The change process of resistivity is basically an electrochemical equilibrium process. Air and stainless steel can cause the resistivity of aqueous mixture to decrease more quickly, which can be slowed down by degassing and keeping PET plastic sealed. If the industrial specimen is used for one month, the resistivity of the liquid in the stainless steel specimen decreases to 6.1 percent of the initial value, while the liquid resistivity in the PET plastic specimen decreases to 26 percent of the initial value. Secondly, although the water-base mixture can prolong the retention time of resistivity, the chemical stability of the aqueous mixture is slightly worse than that of propylene carbonate. Therefore, the pulse insulation characteristics of propylene carbonate and its mixture with ethylene carbonate were studied, and the effect of mechanical pressure on the pulse breakdown was studied. The inherent resistivity of propylene carbonate can reach more than 10 M 惟 cm, and there is still 6 M 惟 cm in the open air after two weeks. The average breakdown strength is 398.5 kV / cm, and the dielectric constant and energy storage density can be further improved by adding ethylene carbonate. When the static pressure increased from 1 bar to 11 bar, the effective time increased from 1.24 渭 s to 2.79 渭 s, the normalized breakdown field strength increased from 480.3 kV / cm to 887.3 kV / cm, and the energy storage density increased 3.4-fold, from 0.65 MJ / m3 to 2.2 MJ / mm3. Finally, the weak polar liquid with low dielectric constant was studied. In this paper, the effects of adding barium titanate nano-powder on the dielectric constant and pulse insulation characteristics of castor oil were studied. The effect of modification varies with the particle size and concentration of nano-powder. The dielectric constant increases by 4 times with the increase of the concentration of nano-powder, and the best modification effect is obtained when the particle size is 100 nm and the mass fraction is 6. The breakdown field strength is increased to 1.55 MV / cm, which is 1.25 times of that of crude oil. The energy storage density increased to 0.67 MJ / m ~ (3), 1.6 times that of crude oil. In a certain range, the breakdown field strength increases firstly and then decreases with the increase of the concentration of nano-powder.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM21

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