Parameters Of Corona Discharge Research Articles

Air Pulsed-Corona discharges for degradation of emerging pharmaceutical pollutants in water and toxicity by-products control

The present study, based a tip-to-plane pulsed corona setup, examined the effects of tip-water distance, radius of curvature of electrode tip, and pulse voltage on the production of liquid-phase RONS used an indicator of degradation performance. Measurements of long-lived RONS species (nitrates, nitrites and H2O2) in deionized water were specifically analyzed. The optimum conditions were used for the removal of a high concentration (500 mg/L) of 4-acetaminophen (i.e. paracetamol) with study of oxidation by-products and their toxicity. The results showed that optimum RONS production in the liquid phase occurred for a short gap distance (4 mm), a tip curvature radius of 100 μm and a pulsed voltage of 10 kV and 10 kHz corresponding to an energetic corona spark regime which is characterized by optical emission spectroscopic measurements. Using these optimal corona discharge parameters, the study showed that after 30 min of exposure to the air plasma, 60 % removal efficiency was achieved at an initial paracetamol concentration of 500 mg/L based on HPLC-DAD sample analysis. GC–MS and LC-MS analysis of treated samples enabled us to identify and characterize two new by-products not previously identified in the literature: N-(4-(4-hydroxyphenylamino) phenyl) acetamide (m/z: 242) and N-(4-aminophenyl) acetamide (m/z: 150), most of which were nitrogen compounds. Further analysis of the toxicity of these by-products to the human cell line (HEK-293) demonstrated that the treated water was not toxic.Overall, these results show that the CDP system is one of the best techniques for treating highly polluted wastewater.

Evolution of Negative Corona in the Discharge-Current Limitation Mode: Transition from the Pulsed-Periodic Mode to Steady-State Burning

The evolution of burning modes of a weak-current corona discharge in a diode filled with atmospheric air, having a pointed cathode and a flat anode, has been investigated. A theoretical description is performed in terms of an axisymmetric multifluid plasma model, including the kinetics of 9 types of particles and 25 plasma-chemical reactions. A discharge in a gap 10 mm long, with a needle-like cathode having a tip curvature radius of 100 μm, a source voltage of 8 kV, a ballast capacitance of 100 pF and a circuit ballast resistance of 1 MΩ, is described in detail. It is shown, both experimentally and theoretically, that the discharge has a lifetime of 180 μs and occurs in four clearly different stages under these conditions: (1) dark breakdown delay phase (0–20 μs); (2) Trichel pulse phase with a variable on–off time ratio and quasi-steady-state corona current component (20–80 μs); and (3) intermediate phase of monotonically rising weak current (80–130 μs), which ends with a vibrational transition to the (4) steady-state phase (130–180 μs), having a typical structure of glow discharge. The tendencies to a change in the corona discharge parameters with a variation in the feed voltage are analyzed. The results of theoretical calculations are in good agreement with the experimental data.

Influence of Unipolar Corona Discharge Parameters on the Efficiency of Separation of Oil–Water Emulsions by Cellulose Acetate Membranes

Influence of Unipolar Corona Discharge Parameters on the Efficiency of Separation of Oil–Water Emulsions by Cellulose Acetate Membranes

Influence of Magnetic Field on Characteristics of Corona Discharge in Wire-Cylinder Electrodes Configuration

The behavior of corona discharge was investigated in wire–cylinder electrodes under the effect of a crossed magnetic field. Townsend’s formula was used commonly with a modified empirical formula to evaluate the different parameters of corona discharge in positive and negative discharge. By using a least-squares fitting, the dimensional constants A, K, and the exponent n displayed a significant dependence on the applied magnetic field. An improvement of pre-breakdown has been achieved by using a crossed magnetic field. For both polarities, while the magnetic field is present, breakdown voltage VB and corona inception voltage V0 increased, whereas the corona current decreases. In addition, the corona inception voltage was greater in positive corona in the absence of a magnetic field, while the opposite occurred regarding the crossed magnetic field. Furthermore, the breakdown streamer demonstrated significant triggering in the negative corona by applying the magnetic field.

Effects of ambient humidity and thermal aging on properties of Nomex insulation in mining dry‐type transformer

Temperature and humidity are the main factors that cause the decomposition of Nomex paper widely used as turn-to-turn insulation material of mining dry-type transformers. In this study, for understanding the effect of ambient humidity and thermal aging on the properties of Nomex paper, specimens with the initial moisture content of 7% were aged in the oven for 168, 504, 672 h at 180°C, respectively. After thermal aging, corona discharge experiments of unaged and aged specimens with different aging degrees were carried out at different relative humidity (RH) levels from 10 to 70%. The characteristic parameters of corona discharge, such as the average discharge amplitude and the number of discharges, were measured. Then, the surface conductivity and the surface potential decay rate were measured. The morphology and attenuated total internal reflectance Fourier transform infrared spectroscopy were also analysed for explaining the difference of properties between unaged and aged specimens. The experiment results indicate that the average discharge amplitude decreases with the increase of RH or the deepening of the aging degree of specimens, but the number of discharges shows the reversal tendency. The changes in the physical structure and chemical composition, which is induced by the hydrolysis reaction of Nomex paper, accelerate the surface potential decay and increase the surface conductivity.

Effect of Unipolar Corona Discharge Parameters on the Surface Characteristics of Polysulfonamide Membranes and Their Separation Efficiency for Water-in-Oil Emulsions

Ultrafiltration polysulfonamide (PSA) membranes with a molecular weight cutoff of 100 kDa have been treated in a unipolar corona discharge field in an air atmosphere at varying voltage (5, 15, 25, and 35 kV) and corona discharge treatment times (1, 3, and 5 min). Using instrumental methods of analysis, it has been revealed that the treatment leads to changes in the surface structure of the membrane, namely, an increase in the roughness and hydrophilicity and, as a consequence, in the flux and separation efficiency for a model water-in-oil emulsion. It has been found that the maximum efficiency (89.3%) is exhibited by a PSA membrane treated with a corona discharge at a voltage of 35 kV for 5 min.

Application of PI/MWCNT Nanocomposite for AC Corona Discharge Reduction

Electric-field (E-field) and radio influence voltage (RIV) from high voltage transmission line occur due to corona discharge. In this proposed work, the effect of corona discharge on aluminum conductor steel reinforced (ACSR) conductor was deeply investigated and mitigated by coating the polyimide/multiwalled carbon nanotubes (PI/MWCNTs) on the surface of the conductor. Bare and coated ACSR panther conductors were tested for E-field on the surface of the conductor, corona inception voltage (CIV), corona extinction voltage (CEV), and RIV. PI/MWCNT was synthesized and characterized by X-ray diffraction, thermogravimetric analysis, and permittivity and conductivity tests. The impact of MWCNT on corona discharge parameters were realized by loading it in different weight percentages as 1 wt%, 3 wt%, and 10 wt% in PI. It has been observed from the measured value (as per the standard IEC 60060-2) that the E-field was reduced by 8%-23%, RIV was suppressed with a difference of 7-18 dB, and CIV/CEV was improved for nanocomposite coated conductor. To comprehend the reason for the E-field and RIV suppression, permittivity and conductivity tests were performed as per the standard ASTM D5568. Lightning impulse voltage test was also conducted on plane-plane electrode configuration and affirmed that PI/MWCNT material has the capability to withstand lightning discharge plasma.

DC negative corona discharge characteristics in air flowing transversely and longitudinally through a needle-plate electrode gap

The electrical characteristics of a steady-state DC negative corona discharge in air flowing transversely or longitudinally in relation to the needle-to-plate (or mesh) electrode axis were experimentally investigated. The velocity of air flowing into the corona discharge chamber was limited to a range from 0 to 6 m/s, typical of electrostatic precipitators, gas ionisation sensors and EHD pumps. The investigations showed that in this airflow velocity range three discharge current modes of the DC negative corona could exist: the Trichel-pulse corona mode, the ‘Trichel pulses superimposed on the steady current (or DC) component’ mode and the steady glow (the steady current or DC) corona mode, regardless of the airflow direction. The average corona discharge current, which is a macroscopic corona discharge parameter, was almost not affected by the airflow. However, both microscopic corona discharge parameters: the electric charge and the repetition frequency of Trichel pulses were influenced by the airflow. The transverse airflow caused an increase in the electric charge and a decrease in the repetition rate of Trichel pulses, the both by about 25% at a velocity of 6 m/s. In the case of longitudinal airflow the average corona current slightly increased when the airflow was directed towards the mesh and decreased when the airflow was directed towards the needle tip. Similarly as in the case of transverse airflow, the electric charge and the repetition frequency of Trichel pulses were affected by the longitudinal airflow. The electric charge and the repetition frequency of Trichel pulses increased and decreased, respectively, with growing airflow in the direction towards the needle electrode. The airflow growing in the direction towards the mesh electrode produced the opposite effect - the electric charge and the repetition frequency of Trichel pulses decreased and increased, respectively. The opposite behaviours of the electric charge and the repetition frequency of Trichel pulses with growing airflow velocity could explain the weak dependence of the negative corona average current on transverse or longitudinal airflow. Therefore, the independence of the negative corona average current of the airflow cannot be considered as sufficient proof that the airflow (up to 6 m/s) does not affect the negative corona parameters.

Effects of corona discharge on the surface structure, morphology and properties of multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were modified by corona discharge and then heat treated in the air. The influences of corona discharge parameters such as treatment time and processing power were investigated. The results of energy dispersive X-ray analysis (EDX) and thermogravimetric analysis (TGA) indicated the introduction of oxygen-containing functional groups onto the surface of the MWCNTs after heat treatment. The water contact angle tests showed that the hydrophobicity of the MWCNTs was decreased to some extent. The static water contact angle was reduced from 146° to 122° when the time of the corona discharge treatment reached 3 min at the processing power of 200 W. The enhanced thermomechanical and mechanical properties of epoxy nanocomposites filled with the corona discharge treated MWCNTs were observed. The modified MWCNTs conferred better properties on the composites than the pristine MWCNTs because of the improved dispersion of MWCNTs in matrix and the enhanced interfacial interaction between the treated MWCNTs and epoxy.

Flow of nanosize cluster-containing plasma in a magnetron discharge

A magnetron source of silver clusters captured by an argon flow with the quadrupole mass filter is used for the analysis of charged clusters after an orifice of the magnetron chamber, and the size distribution function follows from the analysis of clusters deposited on a silicon substrate by an atomic force microscope. Cluster charge near an orifice results from attachment of ions of a secondary plasma that is a tail of a magnetron plasma, and the cluster charge is mostly positive. The character of passage of a buffer gas flow with metal clusters through an orifice is studied both theoretically and experimentally. Assuming the cone shape of the drift chamber near the orifice, we analyze drift of charged clusters in a buffer gas flow towards the orifice if the electric field inside the drift chamber is created by charged rings on the cone surface. Under experimental conditions, when an equilibrium between the buffer gas flow and cluster flux is violated, a typical voltage of rings and parameters of corona discharge for cluster charging are estimated if the electric field does not allow for clusters to reach walls of the drift chamber. The number density of clusters near the orifice is estimated that increases both due to violation of an equilibrium for the cluster flux inside the buffer gas flow and owing to focusing of the cluster by the electric field that is created by electrodes located near walls and due to diffusion motion of clusters. Processes of cluster charging in the magnetron chamber are analyzed.

Theoretical and experimental investigation of a pulsed ESP

The superiority of hybrid pulsed-power/direct-voltage precipitators over conventional designs is now well accepted. In order to maximise the collection efficiency of these devices, a better knowledge of the free-ion charge density and the variation of the inter-electrode electric field is needed. This paper presents the results of an experimental investigation and a theoretical simulation of negative corona discharge in air, under the application of pulsed energisation to a bench-scale coaxial electrode configuration. The construction of the experimental apparatus developed for the present study is described. Corona space charge injection and collection are quantitatively investigated under controlled operating conditions of applied voltage magnitude and frequency. The experimental results obtained are used to verify a new corona model that provides quantitative information regarding corona space charge magnitude and collection time, and can account for the effect of electrode dimensions. The model also quantifies the interdependence of corona discharge parameters including the magnitude of direct and impulse voltage components, impulse frequency and space charge and electric field distributions. This yields the magnitude of important parameters such as the frequency of applied voltage for maximum collection, and the minimum direct voltage level required to prevent corona ions from flowing back to the corona wire.

Effect of a corona discharge on the gasdynamical flow rate

We have shown experimentally that the application of an electric field to an air stream blowing over a corona point has the additional effect of increasing the air velocity. This result is derived from the interaction of two factors. We have developed a model of the phenomenon which is based on electrostatic and hydrodynamic equations. The model provides an equation which relates the additional air velocity to the basic corona discharge parameters. The resulting function agrees with the experimental results.

Study of base pressure fluctuations behind a cone in supersonic flow

Study of base pressure fluctuations behind a cone in supersonic flow