介质阻挡均匀大气压氮气放电特性研究

Characteristics of dielectric barrier homogenous dischargeat at mospheric pressure in nitrogen

基于一维流体力学模型,对介质阻挡均匀大气压氮气放电特性进行了数值计算研究.模型中考虑了氮气中主要的电离、激发过程,所包含的粒子种类为e,N2,N2+,N4+,N2(a1∑u-),N2(A3∑u+).模拟结果显示,氮中的放电具有低气压下汤生放电的特性.放电电流幅度较小,放电过程中气体电压变化缓慢,电子密度远低于离子密度,而且最大值出现在阳极,电子不能在放电间隙中被俘获,不存在中性等离子体区,气体中的电场趋于线性变化.亚稳态N2(A3∑u+)和N2(a1∑u+)在整个放电空间都具有非常高的密度,比电子密度高三个量级以上,亚稳态密度的最大值出现在阳极,这样的分布决定了放电的空间结构.放电所需的种子电子主要由亚稳态之间潘宁电离提供,这种机理使放电的电离水平较低,导致氮气中的放电只能是汤生放电.随着放电参数的变化,多电流峰放电也可在氮气中获得.

On the basis of one-dimensional fluid model, the characteristics of a homogeneous discharge at atmospheric pressure in nitrogen are numerically investigated. The primary processes of excitation and ionization in N2 are considered. The species included in the model are the electron e, N2 in the ground state, two ions N^2＋ , N^4＋ and two metastable states N2 （a^1 ∑^-u ）, N2 （A^3 ∑^＋u ）. The simulation results show that the discharge in N2 appears mostly as a low-pressure Townsend discharge. The amplitude of discharge current is small and the gas voltage changes slowly in the breakdown phase. The electron density is much lower than that of ions and its maximum value occurs at the anode. Electrons are not trapped in the gas gap. There is no quasineutral plasma domain. The densities of metastable states N2 （a^1∑^-u ） and N2 （A^3 ∑^＋u ） are at least three order higher than that of electron. The maximum metastable densities are located close to the anode, which determines the space structure of N2 discharge. Seed electrons needed in discharge are mainly provided by Penning ionizations between metastable molecules. This regime results in a low ionization level, which makes the discharge in N2 being close to a Townsend discharge. When changing discharge conditions properly, multiple-peak discharge can be obtained in N2.