正极性直流驱动大气压氦气等离子体射流的传播机制:氦气–空气混合层的影响

Propagation Mechanism of a Positive DC Driven Atmospheric Pressure Helium Plasma Jet: Influences of He-air Mixing Layer

氦气等离子体射流在生物医学、材料处理等诸多领域具备广阔的应用前景。该文通过二维等离子体流体仿真模型,研究正极性直流驱动等离子体射流阴极导向传播的物理机制,并进一步探讨氦气–空气混合层以及放电通道内混合少量空气杂质对放电的影响。仿真结果与实验观测结果较好地吻合,并进一步表明:氦气–空气混合层内电子能量分布导致的电子碰撞电离速率变化是形成阴极导向流柱和空心截面电离波结构的本质原因;潘宁电离能够促进放电,但是对形成流柱和电离波结构不具有决定性影响;放电核心通道内少量的N2/O2杂质对放电存在通过潘宁电离促进放电,以及通过分子激发耗散能量和O2吸附电子抑制放电这两种竞争性作用。

Helium atmospheric pressure plasma jets(He APPJs) have promising applications in many fields such as biomedicine and material processing. In this contribution, a 2-dimensional fluid model was constructed to study the physical mechanism of the cathode-directed propagation of a positive DC driven He APPJ. Influence of helium-air mixing layer and a small amount of air impurities in the discharge channel on the discharges was highlighted. The simulation results were in good agreement with the experimental observations, and it further showed that the change of electron collision ionization rate caused by the electron energy distribution in the He-air mixing layer played an essential role in the formation of cathode-directed streamer and the hollow-section ionization wave structure. Penning ionization can promote the discharge, but it has no decisive effect on the formation of the streamer and the ionization wave structure. A small amount of N2/O2 impurities in the discharge core channel show two competing effects of promoting the discharge via Panning ionization, or inhibiting the discharge via energy dissipation to molecule excitation and electron attachment to O2.