大气压共面介质阻挡放电等离子体射流的形成机理

发布时间：2018-09-12 13:58

【摘要】：大气压等离子体射流(APPJ)具有操作简单、无需真空腔体、电子温度高、气体温度低等优点,被广泛用于材料表面处理、环境治理和生物医学领域。对APPJ的产生机理的理解是应用开拓、工艺优化和控制的基础。本文从实验和数值模拟两个方面对大气压共面介质阻挡放电(DBD)等离子体射流的形成和发展机理进行了研究。研究分为三部分:首先,实验研究了氦气大气压共面DBD等离子体射流的基本特性,得到放电电压、气流量、电极宽度、介质管径和长度、异型介质管和外部气体环境等放电条件对射流特性的影响。结果表明,电极之间DBD的特性影响APPJ的形成和发展;形成射流需要适当的He气流通道;但射流本身与气流方向无关。其次,利用可控的外加电场、磁场和金属管对氦气大气压共面DBD等离子体射流的发展进行干预,研究了射流在外加电、磁场中的行为。发现射流路径在电场、磁场中发生明显的偏转,射流长度减小,并出现径向展宽或分离现象。外加浮置金属管可以阻挡射流的传播,但较高电压下射流也能够穿过金属管;在金属管施加正电压有利于射流发展,而负电压则阻挡射流传播;维持射流传播的电场从管内指向管外,大致为~10kV/cm量级,使电子崩由管外朝向管内发展。最后,利用二维流体模型模拟研究了氦气DBD等离子体射流的发展过程。结果表明,DBD电极外的射流产生源于DBD形成后瞬时阴极附近空间正离子电荷及其产生的向外的轴向电场,它同时也是射流初始头部。电子在强电场作用下被加速,导致气体的电离和激发,形成向外的射流;电子迁移后,在空间集聚的正离子电荷形成新的射流头部并产生轴向电场,使射流继续向外发展,直至电场减弱至击穿电场以下。在阴极外,介质壁对射流的影响很小。DBD射流类似于单电极正电晕的“正流注”放电,它从介质管内向外发展。
[Abstract]:Atmospheric pressure plasma jet (APPJ) has many advantages such as simple operation, no vacuum chamber, high electron temperature and low gas temperature. It is widely used in material surface treatment, environmental treatment and biomedicine. Understanding the production mechanism of APPJ is the basis of application development, process optimization and control. In this paper, the formation and development mechanism of coplanar dielectric barrier discharge (DBD) plasma jet at atmospheric pressure is studied in terms of both experimental and numerical simulation. The research is divided into three parts: firstly, the basic characteristics of helium coplanar DBD plasma jet at atmospheric pressure are studied experimentally. The discharge voltage, gas flow rate, electrode width, diameter and length of dielectric tube are obtained. The influence of discharge conditions such as the abnormal dielectric tube and the external gas environment on the jet characteristics. The results show that the characteristics of DBD between electrodes affect the formation and development of APPJ, and the formation of jet requires a proper He airflow channel, but the jet itself is independent of the direction of the flow. Secondly, the development of helium coplanar DBD plasma jet is interfered with by using controllable applied electric field, magnetic field and metal tube, and the behavior of the jet in external charging and magnetic field is studied. It is found that the jet path deflects obviously in the electric field and the magnetic field, and the jet length decreases, and the radial broadening or separation occurs. The external floating metal tube can prevent the jet from propagating, but the jet can also pass through the metal tube at higher voltage, the positive voltage applied in the metal tube is conducive to the development of the jet, while the negative voltage prevents the jet from propagating. The electric field which keeps the jet propagating from the inside of the tube to the outside of the tube is about 10 kV / cm, which makes the electron avalanche develop from the outside of the tube to the inside of the tube. Finally, the development process of helium DBD plasma jet is simulated with a two-dimensional fluid model. The results show that the jet generation outside the DBD electrode originates from the spatial positive ion charge near the instantaneous cathode and its outward axial electric field after the formation of the DBD, which is also the initial head of the jet. Electrons are accelerated under the action of a strong electric field, resulting in the ionization and excitation of the gas and the formation of an outward jet. After the electron migrates, the positive ion charge gathered in the space forms a new jet head and produces an axial electric field, so that the jet continues to develop outwards. Until the electric field weakens below the breakdown field. Outside the cathode, the influence of the dielectric wall on the jet is very small. DBD jet is similar to the "positive current" discharge of the single electrode positive corona, and it develops from the inside to the outside of the dielectric tube.
【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O358;O53

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