Surface Corona Discharge Research Articles

A Numerical Simulation Study on DC Positive Corona Discharge Characteristics at the Conductor’s Tip Defect

For investigating the relationship between the surface corona discharge of a DC wire and other influencing factors, a hybrid numerical model based on a fluid-chemical reaction was proposed to simulate the discharge process at the tip defect of the wire. Under different defect geometries and gas pressures achieved via simulation, the microscopic process of the reaction and movement of electrons and heavy particles during a positive corona discharge was studied, and characteristic parameters such as corona inception voltage and discharge current were analyzed. Furthermore, through the corona cage test, for a specific electrode configuration, corona inception voltages under different pressures were compared and verified, which showed that the model was reasonable. The results showed that the maximum electron density of the streamer head was about 1 × 1020 m−3, the rise time of the pulse current was about 10 ns, and the decay time was about 300–500 ns. The corona inception voltage decreased with an increase in the tip height and decreases in the tip curvature radius, conductor radius, and background air pressure; the amplitude of the pulse current increased with increases in the wire radius and curvature radius of the defect tip and decreases in tip height and background air pressure. The experimental results are consistent with the simulation results, which verifies the reasonability of the model.

Device for Polarization of Polymer Films in the Field of a Barrier Type Surface Corona Discharge

Device for Polarization of Polymer Films in the Field of a Barrier Type Surface Corona Discharge

Degradation of glyphosate in water by the application of surface corona discharges.

Glyphosate (GLP) is one of the most widely applied herbicides, and is found ubiquitously in the environment. The removal of glyphosate from waste water and soil is challenging and can be achieved with chemical or biological methods, which, nevertheless, suffer from different disadvantages. The application of a physical plasma for the removal of GLP in water was examined by the application of surface corona discharges in a wire-to-cylinder setup filled with argon. The plasma was ignited at the liquid surface without any additives. By applying a photometric method, GLP was detected after derivatisation with fluorenyl methoxycarbonyl chloride, whereas phosphate was determined with ammonium molybdate. A GLP degradation rate of 90.8% could be achieved within a treatment time of 30 minutes with an estimated energy efficiency of 0.32 g/kWh.

Influence of Corona Discharge on CaSO4 Solubility of Silicone Rubber Insulator Surface

Some studies have shown that the operating state of silicone rubber insulators is not only affected by surface corona discharge, but also different due to the surface covered with different pollutants, but few studies have linked the two. In this paper, by designing the corona discharge test of silicone rubber insulator, the output of nitric acid from its surface product was calculated, and the concentration of nitric acid under different air humidity was obtained. The solubility test of slightly dissolved salt calcium sulfate in nitric acid solution at 293.15K and 333.15K was designed to obtain the solubility of calcium sulfate at different concentrations of nitric acid at two temperatures. Finally, a quantitative analysis of the solubility of calcium sulfate on the surface of insulator FXBW-10/70 in nitric acid solution shows that the surface contamination of insulator with good hydrophobicity may be completely dissolved by nitric acid solution, but the surface of insulator with loss of hydrophobicity cannot be completely dissolved by nitric acid. This study provides a theoretical basis for the dissolution characteristics of silicon rubber insulator corona discharge on its surface soluble salt composition and provides a new idea for the influence of insulator corona discharge on its electrical properties.

Surface Plasmas Versus Volume Plasma: Energy Deposition and Ozone Generation in Air and Oxygen

The energy deposition and the ozone generation in a shielded sliding discharge were compared with those of a simple surface discharge and a pulsed corona discharge in atmospheric pressure air and oxygen. All discharges were generated by applying 160 ns, high voltage pulses. Under the same conditions, the highest energy deposition per pulse was obtained with the shielded sliding discharge. The energy deposition was lower by a factor of four for the surface discharge plasma and by an order of magnitude for the pulsed corona discharge plasma. Replacing air with the more electronegative oxygen caused a decrease in the deposited energy due to electron attachment. The threshold voltage for plasma formation in oxygen in a shielded sliding discharge was approximately 5 kV, three times less than that of the surface discharge (≥15 kV) and four times less than that of the pulsed corona discharge (≥20 kV). A new finding of this study is that, whereas the decrease in energy in the pulsed corona discharge was ≥50 %, and that of the simple surface discharge ≥40 %, it was negligible in the shielded sliding discharge. Since the ozone generation scales with energy density, the results show that plasma reactors based on the nanosecond sliding discharge principle have major advantages in compactness, ignition voltage, and in the use of oxygen, rather than air, compared to surface discharges and corona discharges.

Estimation of discharge magnitude of composite insulator surface corona discharge based on ultraviolet imaging method

Ultraviolet (UV) imaging is a non-contact discharge detection method, in this study, a method, which considers the two factors of observation distance and imager's gain, of estimating the apparent discharge magnitude on composite insulator was proposed. According to the discharge UV image feature, the discharge emitted radiation regions in UV images were extracted with digital image processing algorithm, and then the emitted radiation area parameter was defined. In laboratory, the relationship of emitted radiation area to apparent discharge magnitude, imager's gain and observation distance were studied respectively. Research shows that emitted radiation area increases with the enhancement of discharge intensity, but it has non-linear characteristic; in the gain range of 50 to 80%, emitted radiation area to gain has approximate exponential function relation, when the gain is 50, 60, 70 and 80% respectively, the emitted radiation area to the observation distance has approximate power function relation. Based on the above research, an adaptive neuro-fuzzy inference system (ANFIS) model was established and realized the estimation of apparent discharge magnitude, test shows that it has high prediction accuracy.

Electric and Spectroscopic Analysis of Surface Corona Discharges in Ambient Air and Comparison With Volume Corona Discharges

This paper is firstly devoted to experimental electrical analysis of a dc surface corona discharge in ambient air at atmospheric pressure and room temperature. The surface corona discharge is established between a positive pin and a grounded plate electrode, set on the same side of an insulating plate made either in polymethyl methacrylate (PMMA) or in polytetrafluoroethylen (PTFE). The interelectrode distance, the tip radius of the pin, the applied voltage to the pin, and the nature of the dielectric have been parameterized, and discharge currents are analyzed. It is shown for instance that the surface corona discharge can be ignited over a PMMA dielectric for an applied voltage 20% lower than the PTFE case. This is coherent with calculations of electric fields which are, in the pin region, 25% higher over PMMA than over PTFE. Electrical characteristics of dc surface corona discharge are then compared with those obtained in the case of volume corona discharges generated in the same ambient atmospheric air by using the same positive pin in front of a copper cathode plane. It is observed for the same conditions (applied voltage, gap distance, and tip radius) that the surface corona discharge develops with a higher discharge current even if the UV-visible spectra of both surface and corona discharges remain quasi-similar. This better electric efficiency of surface corona discharge in comparison to volume corona is confirmed from calculations of electric fields and corresponding production rates of certain active species near the pin using multiterm Boltzmann equation solution and literature electron-molecule collision cross sections for electrons impacts with ambient air.

Methods for remote monitoring and defectoscopy systems for electrical machine high-voltage insulation by using an optical radiation

Experimental results applied to an electron-optical system sensitive to the ultraviolet (UV) and visual spectra are presented. This system makes it possible to detect defects in electrical equipment at the stage of its being created and to estimate equipment reliability. The idea of the diagnostic technique is to record the electromagnetic radiation in the ultraviolet spectrum band if surface partial discharge and corona discharges appear.

A DC corona discharge on a flat plate to induce air movement

This paper describes a DC surface corona discharge designed to modify the airflow around a flat plate. The electrode configuration consisted of two thin copper layers placed on each side of the plate's attack edge. Discharge optical measurements with a photomultiplier tube indicated that the light emitted by the plasma is pulsating at a frequency that increases with applied voltage. Moreover, with voltage higher than a threshold value, the electric discharge changes regime with brighter pulses. This discharge also induced an “ionic wind” whose velocity was measured with a pressure sensing probe (up to 1 m/s). Experiments with the particle image velocimetry system in a subsonic wind tunnel showed that this discharge can reduce the separated airflow on the flat plate for a flow of 14 m/s (Reynolds number of 187,000).

Control of separated flows with the ionic wind generated by a DC corona discharge

This paper describes the investigation of a DC surface corona discharge established on a rounded edge of a dielectric material. The ionic wind induced by the discharge was measured with the Particle Image Velocimetry system. A physical induced flow model is proposed to interpret the shape of the velocity field. Experiments on a flat plate and a NACA 0015 were performed in a subsonic wind tunnel. They showed that the flow induced by this discharge acted close to the wall and modified the fully detached flow on the airfoil up to Re = 267,000 and 17.5° by a combined effect of the discharge and a Reynolds effect.

Parameters of a trigatron-driven low-pulse-repetition-rate TEA CO2 laser preionised by a surface corona discharge

The design of a TEA CO2 laser with UV preionisation by a surface corona discharge is described and the dependences of its average output energy on the gas-flow rate, discharge voltage and pulse repetition rate are presented. The scheme of the electric circuit and the geometry of the pre-ionisation system are considered. The electric circuit is designed to produce only impulse voltage difference between the laser electrodes. The triggering system of the trigatron is used to prevent the appearance of the arc. The dependences of the current, voltage and average output energy on the gas-mixture composition and applied voltages at a low pulse repetition rate are presented. The central output wavelength of the laser was measured with an IR spectrometer. Lasing at two adjacent vibrational–rotational transitions of the CO2 molecule was observed, which demonstrates the possibility of simultaneous lasing at several lines.

Decomposition of volatile organic compounds by a novel electrode system integrating ceramic filter and SPCP method

We developed a new efficient apparatus for gas treatment in which a ceramic filter and SPCP (surface corona discharge induced plasma chemical process) were integrated. In this study, the feasibility of the reactor to decompose volatile organic compounds (VOCs) and performance were evaluated. The efficiency was examined against various conditions of initial concentration of VOCs, as trichloroethylene (TCE), toluene and benzene, and by using variable flow rates of carrier gases (air, nitrogen, and mixture of nitrogen and oxygen or water vapor). TCE was decomposed effectively within the reactor system, especially when the carrier gas contains oxygen or water as an oxygen source, whilst the decomposition efficiency was low with the nitrogen carrier. With a sufficient oxygen source, no organic by-products were detected in the treated gas, and TCE was oxidized to inorganic substances. Toluene and benzene were efficiently decomposed as well. For performance evaluation of such non-thermal plasma reactors for VOC treatment, we proposed a new parameter which is derived with substance based energy density, mSED (J/mol). The new parameter has merit to express the performance with a single parameter for a range of discharge power, flow rates, and initial concentrations of the gas to be treated. With the parameter proposed, the evaluation resulted in a new reactor in this study that has as high a performance as a conventional packed-bed reactor, and their performances are higher than pulse corona (PC), and dielectric barrier discharge reactors.

A novel design of electrodes system for gas treatment integrating ceramic filter and SPCP (surface corona discharge induced plasma chemical process) method

A novel configuration of electrodes system for non-thermal plasma gas treatment was proposed, in which surface corona discharge induced plasma chemical process (SPCP) and a ceramic filter were integrated. The system was characterized by a very simple configuration and a high contact efficiency between gas and discharge plasma. A feasibility of the newly developed apparatus was studied for NO X and soot treatment. NO X as gaseous pollutant was decomposed effectively. Soot suspended in gas as particulate pollutant was captured on the ceramic filter and disappeared with the surface corona discharge treatment on the filter surface. Furthermore, soot and NO X were treated simultaneously. Because soot is removed by oxidization and NO X by reduction, therefore, there is a possibility that they are treated simultaneously and complementarily.

Effect of a plasma actuator on an airflow along an inclined wall: P.I.V. and wall pressure measurements

In this work, we propose to analyse experimentally the ability of a DC surface corona discharge to modify an airflow along an inclined wall. The goal is to fully detach an airflow which is naturally attached along the inclined wall. Two sets of experiments conducted in a wind tunnel up to 10 m/s have been done. First, pressure measurements along the inclined wall have shown a decrease of the pressure downstream the discharge. Next, P.I.V. measurements have shown that the discharge induces a velocity decrease along the inclined wall. Both results are characteristics of a detached airflow.

Sliding discharge in air at atmospheric pressure: electrical properties

Several studies have shown that a surface non-thermal plasma may be used as an electrofluidodynamic actuator for airflow control. For few years, we has been working on this subject, especially in the case of DC corona discharges and AC barrier discharges established at the wall of profiles. The present paper deals with a new type of surface plasma using a sliding discharge. This discharge, excited here by a negative AC voltage with a positive DC component, is created in a three-electrode geometry: one DC positive electrode and two negative AC electrodes at the same voltage. Then a barrier discharge is established between the positive electrode and the first negative one when a surface corona discharge or sliding discharge is generated between the positive electrode and the second negative one. In this preliminary study, the goal is to obtain a stable sliding discharge. Then the electrical properties of this discharge are observed and briefly discussed.

DC and Pulsed Surface Corona Discharge along a Dielectric Flat Plate in Air: Electrical Properties and Discharge-Induced Ionic Wind

AbstractSeveral studies have shown that a surface corona discharge may be used as an electrohydrodynamic actuator in order to control the airflow around profiles. For a few years, our laboratory has been working on this subject, specifically in the case of a DC corona discharge. The present paper deals with experimental work on DC and pulsed surface non-thermal plasmas produced between two wire electrodes flush mounted on the surface of a PMMA (polymethyl-methacrylate) insulating flat plate. The goal is to optimize the plasma actuator in terms of electro-mechanical efficiency in the absence of an external free airstream. First, electrical properties (such as discharge current versus applied voltage and discharge current versus time) of these different discharges are observed. Secondly, the time-averaged ionic wind induced by DC coronas and pulsed coronas is measured by means of a small diameter tube connected to a micro manometer.

Dependence of the Ultraviolet Intensity and the Density of Electrons Produced by a Surface Corona Discharge for Pre-ionization on the Waveform of Pulsed Voltage

Streamer discharges generated by pulsed power are used for decomposition of harmful gas and liquid. The homogeneous formation of streamer discharges in a large volume in a reactor improves the efficiency of decomposition. To produce streamer discharges homogeneously, the performance of space ionization by a surface corona discharge for pre-ionization has been investigated. The increase of a pulse width from 20 ns to 100 ns brings the increase of about 2 times of ultraviolet intensity and an electron density. For the positive discharge with the pulsed voltage of 6 kV and the rise time of 11 ns, the electron density was increased from 1.2x108 to 2.3x108 cm-3 with the pulse width from 20 to 100 ns (FWHM). As the magnitude of pulsed voltage was increased from 6 to 10 kV, the ultraviolet intensity and the electron density were increased about 3 times. In contrast, the rise time of the pulsed voltage slightly affects the ultraviolet intensity and the electron density. The decrease of the rise time from 30 to 10 ns brings the increase of 5 % of the ultraviolet intensity and 10 % of the electron density.

Experimental Study of the Detachment and the Reattachment of an Airflow Along an Inclined Wall Controlled by a Surface Corona Discharge—Application to a Plane Turbulent Mixing Layer

This paper analyzes experimentally the ability of an electrohydrodynamic actuator to modify the properties of a plane turbulent mixing layer in the wake region of an inclined flat plate (expansion corner). The experiments consists of applying a surface corona discharge established between two electrodes flush mounted on the surface of the test profile. Two cases are investigated. First, one considers the application of the corona to an airflow which is naturally detached at the trailing edge of the test profile and the experiments is repeated with an airflow naturally attached. In this paper, the behavior of the discharge with free air stream up to 35 m/s and measurements by particle image velocimetry for a velocity range from 6 to 16 m/s are presented. The results show that: 1) the discharge regime depends on the free air stream velocity; 2) when the airflow is naturally detached, the corona discharge allows increasing the velocity and the thickness of the mixing layer; 3) when the airflow is naturally attached, it is possible to reduce the velocity and to increase the thickness of the mixing layer; and 4) using a pulse discharge, one observes that the effect of the actuator on the mixing layer is different according to the discharge frequency.

Generation of Thin Surface Plasma Layers for Atmospheric‐Pressure Surface Treatments

AbstractThin layers of atmospheric‐pressure non‐equilibrium plasma can be generated by pulse surface corona discharges and surface barrier discharges developing on the treated surfaces or brought into a close contact with the treated surfaces. Plasma sources based on these discharge types have the potential of meeting the basic on‐line production requirements in the industry and can be useful for a wide range of surface treatments and deposition processes including continuous treatment of textiles. Comparing with atmospheric pressure glow discharge sources, the potential advantages of these plasma sources include their simplicity, robustness, and capability to process in a wide range of working gases. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A hybrid process of EFCM (electrostatic formation of ceramic membrane) and SPCP (surface corona discharge induced plasma chemical process)

A novel method to form a fine particle layer as a hybrid process of electrostatic formation of ceramic membrane (EFCM) and surface corona discharge-induced plasma chemical process (SPCP) was proposed. In this method, particles are synthesized by CVD reaction using surface corona discharge as a source of activation (SPCP). At the same time and same place, the particles imparted monopolar charge and electromigrated onto a substrate ceramic filter to form a particle layer by a DC electrical field. In this study, a TiO 2 fine particle layer was made with this method. The obtained TiO 2 fine particle layer had a unique structure due to EFCM method with a three-dimensional pearl-chain like structure and high prosity. The size of particles generated in the SPCP–CVD reaction was controllable with the concentration of TiCl 4 in reactant gases, and the density of the layer structure could be controlled by the applied DC voltage in the EFCM. It was also confirmed that the obtained TiO 2 particle layer had a photocatalytic activity from the experiments of photocatalytic decomposition of 2,4-dinitrophenol.