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

Abstract

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.