Investigation Of The Influence Of Surface Discharge Plasma On The Low-pressure Supersonic Gas Flow Field

The surface discharge is one of the most widely used methods to produce the plasma layer of large area. Owing to the economic, efficient and high controllability in the application of plasma control of gas flow, the surface discharge has been paid more and more attention to. And because of the space extendibility of the surface discharge it has a promising application in material processing. In this work, we have investigated the influence of surface discharge on the low-pressure supersonic gas flow field and the influence of the surface discharge plasma on improvement of the hydrophilicity of the non-metal material surface at atmospheric pressure. And the study of plasma control of the low-pressure supersonic gas flow field is based on the background that the disturbance generated by boundary flow transition layer in the cavity of the high-energy chemical oxygen-iodine laser (COIL) will deteriorate the beam quality.Due to the complex components in the background gas and the pressure control range of the chemical oxygen-iodine laser, the discharge phenomena and the electrical characteristics of the low pressure surface discharge plasma in the different working gas and various pressures have been investigated firstly. It is found that the stable discharge in helium can be obtained at the experimental pressure. When O2 is added into the He in ratio of 1:1, the discharge intensity would be decreased and the breakdown voltage rises. And compared to the He, the breakdown voltage of discharge in CO2 is much higher. When O2 is mixted into the CO2, the discharge intensity would be increased and the breakdown voltage would be decreased instead.Considering the real working condition of the COIL, the surface discharge of two coplanar bare electrodes driven by DC power supply has been employed as the actuator and the molecular tagging smoke wire has been used as the characterization method. The feasibility of plasma control of gas flow could be measured by recording the tracks. And it is found that the interaction between plasma and gas flow could be achieved and the cathode space in surface discharge plasma plays a pivotal role in the control of gas flow. What’s more, with the increase of the area of the cathode in surface discharge plasma and the driving voltage, the effect of gas flow control would be improved appreciably.The atmospheric-pressure surface DBD with coplanar electrodes which is driven by the AC has been studied for its application in the improvement of the surface hydrophilicity of the glass and polymer materials. It is shown that the plasma processing alters the surface energy of the thin films made of glass and the PET more effectively than that of the PE thin film. And when the operating frequency of the high voltage AC power supply is 10 kHz, the peak-to-peak value of the output voltage is 10 kV, and the processing time is set at 5 min, the improved hydrophilicity of the inner surface of the PP tube is demonstrated in the obvious capillarity.