屏蔽气体流速对同轴双管式氦气大气压等离子体射流粒子分布的影响

Effect of flow rate of shielding gas on distribution of particles in coaxial double-tube helium atmospheric pressure plasma jet

在大气压等离子体射流应用中,环境气体对射流流出物的影响不可忽视,尤其是在某些对环境粒子高度敏感的特定场景中.同轴双管式射流装置可用于抑制射流流出物与环境气体之间的相互扩散,从而控制射流流出物的化学性质.本文对同轴双管式氦气大气压等离子体射流在不同屏蔽气体流速下的放电特性和化学性质进行了数值仿真研究,并通过实验光学图像对仿真模型加以验证.结果表明,相比于没有屏蔽气体的情况,在高流速条件下放电得到增强,而在低流速下放电较弱;随着流速的增加,空间中的粒子数均随之增加,这可以归因于由屏蔽气体流速增加而产生的更宽的主放电通道.此外,不同浓度轮廓线上的离子径向通量受到流速的影响也存在很大差异.本研究进一步揭示了不同的放电位置对氮氧粒子产生的影响,加深了关于屏蔽气体流速影响等离子体射流放电行为的认识,并可能为等离子体射流的进一步应用开辟新的机会.

In the application of atmospheric pressure plasma jet,the influence of ambient gas cannot be ignored,especially in some specific scenarios which are highly sensitive to ambient particles.Coaxial double-tube plasma jet device is a promising method of controlling the chemical properties of jet effluent by restraining the mutual diffusion between jet effluent and ambient gas.In this work,the discharge characteristics and chemical properties of coaxial double-tube helium atmospheric pressure plasma jet at different flow rates of shielding gas are studied numerically,and the model is validated by experimental optical images.The results illustrate the enhanced discharge at the high flow rate,the weaker discharge at the low flow rate,and discharge behaviors without shielding gas as well.With the increase of shielded gas flow rate,the particle density increases in the discharge space,which can be attributed to the wider main discharge channel caused by the increase of shielding gas flow rate.In addition,the analysis shows the great difference in ion fluxes affected by the flow rate of the SG between the contour lines of different helium mole fractions.This study further reveals that different discharge positions have a great influence on the generation of nitrogen and oxygen particles,thus deepening the understanding of influence of shielding gas flow rate on discharge behavior,and may open up new opportunities for the further application of plasma jet.