Compact High-Velocity Atmospheric Pressure Dielectric Barrier Plasma Jet in Ambient Air

摘要

In this paper,a non-thermal atmospheric pressure plasma jet at high streaming velocity operating with ambient air is highlighted.In the present technological approach,the employment of air poses a significant challenge.The high oxygen concentration in air results in a reduced concentration of reactive species in combination with a short species lifetime.The plasma jet assembly presented here contains a special dielectric barrier with a high secondary emission coefficient.In this way,the electron density and in turn the density of reactive species is increased.In addition,the plasma jet assembly is equipped with a short electrode.This leads to a higher voltage across the discharge gap and in turn to an increased density of reactive plasma species.The plasma jet is formed within and emitted by a small conical nozzle.A high-speed gas flow with gas velocity of 340 m/s was achieved at the end of the nozzle.In the jet the concentration of toxic and unwanted neutral plasma species like O_3 or NO_x is significantly reduced because of the shorter residence time within the plasma.The range of short-lived active plasma species is in turn considerably enhanced.The jet efficiency and action range measured through the oxidation of a test surface were determined by measuring the increase of surface tension of a polypropylene substrate via contact angle measurements after plasma treatment.Numerical modeling of the plasma plume indicates that oxygen atoms are in fact the main active species in the plasma plume.