Study On Periodic Characteristics And Plasma Impedance Characteristics Of Pulsed Sliding Discharge

Non-equilibrium plasma which has good chemical selectivity and chemical activity because of its high energy electrons and active free radicals has a wide range of applications in industrial and aeronautical fields.As an effective method to produce periodic non-equilibrium plasma at atmospheric pressure,gliding discharge has attracted the attention of researchers both at home and abroad for its simple and compact structure and high concentration of active particles.Compared with the gliding discharge driven by conventional AC/DC power supply,narrow pulse technology can provide higher power density and reduced electric field,and produce active particles with more efficient reaction rate.Therefore,the gliding discharge excited by narrow pulse power supply has a wide application prospect in energy conversion and aerospace ignition.Under the influence of gas flow rate and pulse repetition frequency,the arc development process of gliding discharge presents a relatively unstable change.Therefore,the periodic characteristics and plasma impedance characteristics of gliding discharge are studied in this paper according to the electrical and optical properties.The causes of shortcut events are analyzed,which provides a theoretical basis for the application of gliding discharge.When the voltage is fixed in the circuit,the current characteristics of the circuit are affected by the impedance value.In this paper,the variation of plasma impedance characteristics of microsecond pulse gliding discharge is studied by changing the gas flow rate and pulse repetition rate.The results show that:With the increase of pulse repetition rate,the plasma impedance of gliding arc with unit arc length increases gradually.With the increase of gas flow rate,the plasma impedance of unit arc length increases gradually,however,it is affected by the instability of air flow field.When the gas flow rate is 14L/min,the plasma impedance shows a larger drop.With the help of plasma impedance value and simple calculation,it can be seen that the average electron density of gliding arc plasma decreases grad ually with the increase of pulse repetition rate,and its order of magnitude is about 10¹³ cm^-3.Shortcut event is a special phenomenon in the development of gliding discharge.It is found that when the pulse repetition rate is greater than or equal to 1500Hz,there will be a shortcut event in the process of discharge development.In this paper,the relationship between short-cut events and plasma impedance and discharge power per unit arc length is studied by changing pulse repetition rate.The results show that:When the discharge power on the unit arc length is less than a certain value,the power supplied by the power supply is difficult to meet the power required by the arc channel,which leads to the occurrence of shortcut events.Before or after shortcut events,plasma impedance changes greatly.When the gas flow rate and pulse repetition rate are changed,the gliding period of the gliding discharge fluctuates greatly.In this paper,the characteristics of gliding discharge cycle are analyzed by discharge image.With the increase of gas flow rate,the flow field gradually changes from layer to turbulence,and the rising velocity of gliding arc increases gradually.In the laminar flow state,the gliding arc presents a periodic law,and the gliding discharge changes from periodic to aperiodic under the transition state of the turbulent flow direction of the layer.When the pulse repetition rate is increased,the memory effect can be enhanced,which can restrain the influence of air flow on the periodicity of gliding discharge,and increase the maximum rising height of gliding arc.