Studies On Plasma Characteristics Of Pulsed Surface Dielectric Barrier Discharge And Its De-icing Process

Icing on wind turbine blades and aircraft wings can cause serious problems.Surface dielectric barrier discharge(SDBD)as a new de-icing technology increases the interest of scholars due to its advantages of low energy consumption,short response time and excellent prospects.However,the plasma process,the discharge mode transition and the physical effect of SDBD and its de-icing process should be investigated deeply.Based on these conditions,the plasma characteristics of pulsed SDBD and its de-icing process are studied by combining experiment and numerical simulation.The main contents and conclusions are as follows:1.The study on the plasma characteristics of two-electrode pulsed surface streamer discharge.The formation process of surface streamer discharge,evolution of different discharge phases and influence of residual surface charges on sequential pulses discharge are analyzed by experiment and numerical simulation.Experimental results show that single positive pulse discharge is composed of the primary streamer corresponding to the positive current and the secondary streamer corresponding to the negative current.In the sequential pulses discharge,the increase of residual surface charges decrease the deposited energy and luminous intensity of primary streamer.But they enhance the deposited energy and luminous intensity of secondary streamer.Numerical simulation shows that positive current is composed of electron current and the negative current is composed of ion current.Pre-charging on the dielectric surface is utilized to replace the residual surface charges,which can inhibit the expansion of primary streamer and reduces the intensity of primary streamer.But it is beneficial for the formation of reverse electric field and the enhancement of the secondary streamer intensity.2.The study on the plasma characteristics of three-electrode pulsed surface streamer discharge.The surface streamer evolution,energy of different discharge phase and surface temperature of actutor are analyzed by plasma diagnostics.The mechanisms for the formation and propagation of different streamer pahses are analyzed by numerical simulation.Electrical and thermal properties show that the three-electrode pulsed surface streamer discahrge can induce stronger deposited energy and higher surface temperature compared with the two-electrode pulsed surface streamer discahrge.Spatial-temporal resolved streamer developing images display that the three-electrode pulsed surface streamer discahrge not only contains the primary and secondary streamers,but also forms a new discharge process(transitional streamer)with relatively uniform streamer morphology and unclear propagation direction in the ionization channel after the primary streamer reaches to the second grounded electrode.In the sequential pulses discharge,it is shown that the transitional streamer concentrates in the HV electrode region due to the residual surface charges left by the previous pulse discharge.Based on the numerical model,it is founded that the cathode layer with an enhanced reduced electric filed is formed on the second grounded electrode surface when the primary streamer approaches the second grounded electrode due to a large number of positive ions accumulated in the primary streamer head.The second grounded electrode carries away the charge generated by discharge,which can decrease the charges accumulation on the dielectric surface and enhance the electric field of the transitional streamer.3.The study on the plasma characteristics of three-electrode pulsed surface spark discharge.The discharge mode transition,electron temperature and electron density are diagnosed.Formation and propagation of shock wave are studied by numerical simulation.Optical-electrical characteristic show that two discharge modes of surface streamer and surface spark discharge can be observed in the three-electrode sequential pulsed SDBD.According to the spatial-temporal evolution of the discharge process,the single pulse surface spark discharge is composed of the primary streamer,transitional streamer and spark discharge phase.Based on the optical emission spectrum,the maximum electron temperature of 5.04 eV appears at the initial phase of the spark discharge,and gradually decreased with time.Electron density is calculated to be about 4.30-7.06×10¹⁷ cm^-3.Schlieren system and High Mach Fluid model exhibit that the temperature can rise extremely to 4000 K the shock wave can be formed in the discharge area due to the rapid release of the pulsed energy through the surface spark discharge.4.The study on the plasma characteristics of pulsed SDBD for de-icing process.Different discharge modes are utilized to remove different morphologies of ice.And the interaction of between droplets with surface streamer is studied by numerical simulation.Experimental results show that the three-electrode pulsed surface streamer discharge shows a better performance on removing mixed ice than that of the two-electrode pulsed surface streamer discharge.The high speed camera and numerical simulation show that the droplet exhibits the characteristics of dielectric and causes a 'blocking' phenomenon during the pulsed surface streamer discharge.Experimental results show that the three-electrode pulsed surface spark discharge can induce the ice-breaking of actuator.Ice-breaking can be divided into three discharge stages of corona discharge,streamer discharge and surface spark charge.Finally,surface spark discharge is formed in the discharge gap and induces strong shock wave to break the covered glaze ice.The pulsed surface spark discharge in ice-breaking mainly consists of streamer discharge and spark discharge.Based on the optical emission spectrum,the electron density is calculated to be about 3.07×10¹⁷ cm^-3.