大气压微波等离子体射流装置放电特性研究

基于同轴传输线结构设计了两种不同喷嘴结构的大气压微波等离子体射流(MW-APPJ)装置，其工作频率2.45 GHz，工作气体为氩气，分别研究了两种不同喷嘴结构对等离子体放电特性产生的影响。仿真结果表明，MW-APPJ在气体喷嘴处会产生高强度的电场，经过优化结构，实现在频率2.45 GHz下，喷嘴处的场强满足氩气电离的击穿场强阈值要求。同时，利用多物理场耦合仿真软件对装置的气流分布进行了稳态模拟，并通过实验对比分析了两种喷嘴结构下大气压氩等离子体射流的基本特性。实验结果表明，不同的喷嘴结构会影响等离子体装置的反射系数随输入功率的变化规律，但并不影响等离子体射流长度随输入功率的变化规律和反射功率随进气流量的变化规律；同时，在大气压下，稳态微波等离子体射流呈现出类金属性，等离子体中的电子只能在很薄的区域中吸收微波能量，因而造成微波的反射功率较大。

Design and study of atmospheric pressure microwave plasma jet

Two atmospheric pressure microwave plasma jet (MW-APPJ) devices with different nozzle structures are designed which are based on the coaxial transmission line structure. The frequency is 2.45 GHz and working gas is argon. What's more, the effects of two different nozzle structures on the characteristics of plasma discharge have been studied. Based on the electromagnetic field simulation results, the MW-APPJ generates a high-intensity electric field at the nozzle. After optimizing the structure, the field strength at the nozzle have reached the breakdown field strength required for argon ionization under the frequency of 2.45 GHz. Meanwhile, the simulation of the argon flow distribution was carried out under steady-state using multi-physics coupling simulation software. In addition, the basic characteristics of the atmospheric pressure argon plasma jet under the two nozzle structures were compared and analyzed through experiments. The experimental results show that different nozzle structures can affect the variation of reflection parameter with input power, but do not affect the variation of plasma jet length with input power and the variation of reflected power with inlet flow; at the same time, under atmospheric pressure, the steady-state microwave plasma jet exhibits metal-like property and the electrons in the plasma can only absorb microwave energy in a very thin area, which causes large reflected power of the microwave.