介质阻挡均匀大气压辉光放电数值模拟研究

Numerical simulation of dielectric-barrier-controlled glow discharge at atmospheric pressure

通过数值求解一维电子、离子连续性方程和动量方程 ,以及电流连续性方程 ,计算了氦气介质阻挡大气压辉光放电电子、离子密度和电场在放电空间的时空分布 ,以及放电电流密度和绝缘介质板充电电荷密度随时间的变化 .分析讨论所加电压频率、幅值及介质板性质等对均匀大气压辉光放电性质的影响 .当外加电压频率足够高时 ,大量离子被俘获在放电空间 ,空间电荷场又引起足够多的电子滞留在放电空间 .这些种子电子使得在大气压下发生汤森放电 ,放电空间结构类似于低气压辉光放电 ,即存在明显的阴极位降区、负辉区、法拉第暗区和等离子体正柱区等 .所加电压幅值减小 ,放电电流减小 .绝缘介质层的二次电子发射 ,使放电电流增大 .而介质层越厚 ,放电电流越小 ;介电常数越小 。

The space and time distributions of the electric field and the electron and ion densities, as well as the time evolutions of the discharge current density and the surface charge density of the dielectric layer in He dielectric-barrier-controlled glow discharge at atmospheric pressure are calculated by solving the one-dimensional continuity and momentum equations for electrons and ions, coupled to the current continuity equation. The properties of uniform atmospheric pressure glow discharge under the conditions of different driving frequency, voltage or dielectric layer are discussed and analyzed. When the driving frequency is high enough, a large number of ions are trapped and the induced space charge field makes a great many of electrons stay in the discharge volume. These seed electrons lead to a Townsend discharge at atmosphere pressure. The structure of this discharge is similar to that of low-pressure glow discharge, i.e. there exist four specific regions: the cathode fall, the negative glow, the Faraday dark space and the positive column. The discharge current becomes small with decreasing voltage amplitude applied. The secondary electron emission from the dielectric layer makes the discharge current increase. The thicker the dielectric layer is or the smaller the permittivity, the smaller the discharge current is.