高储能密度液体介质的脉冲绝缘特性

Applications have stimulated intense interest in pulsed power technology towards high power, long duration, high rep-rate, compact structure and small volume. A compact rep-rate Tesla-type pulsed power generator, because of its compact structure, high energy efficiency and high rep-rate operation, is extensively developed and used in the high-power pulsed technology. But the output power and pulse width is not enough, limited to the energy-storage-density of liquid dielectric. Therefore, it is significant to study the energy-storage characteristics of various liquid dielectrics in microsecond regime and explore the physical mechanism of liquid dielectric breakdown. In this project, the research contents are shown as follows. Firstly, the energy-storage characteristics of various liquid dielectrics, such as castor oil, glycerin, propylene carbonate / ethylene carbonate, are investigated, and the appropriate liquid dielectric is optimally selected. Secondly, the influence of the additive, pressurization and degassing on the excellent liquid dielectric are studied. It is verified that the effect of pressurization on breakdown strength for various liquid dielectrics is carried out. Moreover, the influence of different gas content on breakdown strength of the liquid dielectric is investigated and the explanation for increasing breakdown strength for degassed liquid dielectric is presented. Thirdly, the optimal liquid dielectric is applied in the compact rep-rate pulse generator to improve the pulse generator's energy-storage-density significantly. Fourthly, the physical images of liquid dielectric breakdown are obtained by high speed framing camera, and the spectrum and the intensity of the images are analyzed. And then the physical model of liquid dielectric breakdown is optimized and used to explain a series of experimental phenomena. Finally, the engineering application of liquid dielectric is studied, such as the effect of the temperature on breakdown strength of liquid dielectric. These efforts set a good foundation for the development of high-energy-storage-density liquid dielectric and show a good promising application for the future.

紧凑重频Tesla型脉冲发生器具有结构紧凑、能量效率高、可重频运行的特点，符合高功率、长脉宽、高重频、紧凑化、小型化的发展方向，得到了广泛的发展和应用。但受限于液体介质的储能密度，输出脉宽和功率有限。因此，开展微秒脉冲充电下多种液体介质储能特性的研究，探讨液体介质击穿的物理机制，具有重要的学术和应用价值。本项目研究内容主要包括：开展蓖麻油、甘油、碳酸丙烯酯/碳酸乙烯酯在内的多种液体介质储能特性的研究，优选出适宜液体储能介质；开展潜力型液体介质增加添加剂、加载气压、去除气体的研究，证实加载气压对多种液体介质的普适性，气体含量的影响及其原因；开展优选液体介质应用于紧凑重频脉冲发生器研究，显著提高储能密度；采取光学诊断方法获取液体介质击穿的物理图像，并进行谱图和强度分析，优化液体介质击穿的物理模型，解释一系列实验现象；开展液体介质工程化应用研究，为高储能密度液体介质的应用展示良好的应用前景。

脉冲功率技术的重要发展方向是高功率、长脉冲和轻型紧凑化。液体介质由于具有储能密度高、流动散热性能好、自我恢复性能强、易于成型等方面的特色，因此被广泛地应用于脉冲功率系统关键部件脉冲形成线(Pulse Forming Line, PFL)中作为储能介质。本项目提出了针对高储能密度液体介质开展微秒脉冲绝缘特性研究的技术方案，分别进行脉冲绝缘特性、击穿物理机制以及工程化应用的基础研究，难点是优选出适宜的液体储能介质、获取物理图像提出击穿模型、开展工程化应用实践。项目组通过运用建立的液体介质微秒脉冲击穿试验平台及其击穿测量诊断手段，在微秒脉冲情形下开展了蓖麻油、乙醇、乙二醇、丙三醇、碳酸丙烯酯、去离子水等多种高储能液体介质储能特性的研究，采用Weibull分布统计的方法获取了液体介质击穿概率分布，解决了多种液体介质脉冲绝缘特性分析对比的难题；采用超高速相机HSFC-PRO及其同步触发技术，解决了光学诊断的难题；采用真空注入、分子膜过滤、离子交换的方式，解决了丙三醇应用于紧凑重频Tesla变压器型脉冲功率发生器PFL的绝缘难题。通过解决上述关键技术难题，取得成果如下：基于脉冲击穿试验和统计分析方法，建立了液体介质脉冲击穿的数据库，优选出目前最适宜的液体储能介质是丙三醇，最具潜力的是碳酸丙烯酯，并且在碳酸丙烯酯中添加碳酸乙烯酯、间二甲苯、纳米粒子和加载静压，可提高储能密度1倍；通过分析击穿瞬间流注、冲击波、亚微观断裂面产生、传播、截止的图像，并结合非晶态能带与Griffith张力理论建立了高储能密度液体介质击穿物理模型；通过解决高储能密度液体介质应用于脉冲形成线的净化处理及其绝缘配合难题，开展了高储能形成线型紧凑脉冲功率发生器的实验研究，将丙三醇应用于紧凑脉冲形成线作为储能介质，将脉冲功率发生器的能量密度和输出脉宽分别提高了3倍，从而使得脉冲功率发生器的功率密度提高了3倍，显著提高了脉冲功率发生器的紧凑化程度。总体而言，项目组通过液体介质脉冲储能特性的研究，对高储能密度脉冲电容器的研发提供了有益的指导参考，为液体介质在脉冲电容器的应用方面奠定了坚实的基础，展示出良好的应用前景。