基于电致伸缩效应的水中纳秒脉冲放电起始机制  

Initiation of nanosecond-pulsed discharge in water:Electrostriction effect

作　　者：李元[1] 李林波 温嘉烨 倪正全 张冠军[1] Li Yuan;Li Lin-Bo;Wen Jia-Ye;Ni Zheng-Quan;Zhang Guan-Jun(State Key Laboratory of Electrical Insulation and Power Equipment,School of Electrical Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学电气工程学院,电力设备电气绝缘国家重点实验室,西安710049

出　　处：《物理学报》2021年第2期354-362,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51607139)资助的课题.

摘　　要：水中纳秒脉冲放电的起始阶段包含了丰富的物理过程,现有实验诊断技术在揭示数纳秒内液体中电荷输运、倍增过程方面还有不少困难,放电起始的机制尚不明确.本文建立了针板电极二维轴对称水中放电物理模型,仿真研究纳秒脉冲导致的水中电致伸缩效应、空化过程和随后的液体电离过程.结果表明,在纳秒脉冲电压作用下,电致伸缩效应可导致针尖附近数微米区域内的液体发生空化,形成大量纳米尺度的空腔;空腔在其表面电致伸缩压强的作用下膨胀,为电子提供了加速空间;高能电子可引发水分子的碰撞电离,使局域液体被快速电离.电致伸缩机制为理解水中纳秒脉冲放电的起始过程提供了新的视角.Underwater nanosecond-pulsed discharges have been widely utilized in numerous industrial applications.The initial stage of nanosecond-pulsed discharge in water contains extremely abundant physical processes,however,it is still difficult to reveal the details of charge transportation and multiplicative process in liquid within several nanoseconds by currently existing experimental diagnostic techniques.Up to now,the initiation mechanism of underwater nanosecond discharge has been still a puzzle.In this paper,we develop a twodimensional axially symmetric underwater discharge model of pin-to-plane,and numerically investigate the electrostriction process,cavitation process,and ionization process in water,induced by nanosecond-pulsed voltage.The negative pressure in water caused by tensile ponderomotive force is calculated.The creation of nanoscale cavities(so-called nanopores)in liquid due to negative pressure is modeled by classical nucleation theory with modified nucleation energy barrier.When estimating the temporal development of nanopore radius,a varying hydrostatic pressure is considered to restrain the unlimited expansion of nanopores.We estimate the electron generation rate by the product of the generation rate of incident electrons and the number density of nanopores.The simulation results show that cavitation occurs in liquid within several microns from pin electrode due to the electrostriction,which results in the formation of a large number of nanopores.The expansion of nanopore,caused by electrostrictive pressure on nanopore surface,provides a sufficient acceleration distance for electrons.The impact ionization of water molecules can be triggered by energetic electrons,leading the local liquid to be ionized rapidly.The effects of nanopores on rapid electron generation in water are discussed.Once nanopores are formed,the electrons can be generated in the following ways:1)Field ionization of water molecules on the nanopore wall continuously provides seed electrons;2)the seed electrons accelerated in nanopo

关 键 词：纳秒脉冲放电 水中放电 电致伸缩 空化 

分 类 号：O461.25[理学—电子物理学]