Negative Corona Discharge Research Articles

Negative corona discharge mechanism in C4F7N–CO2 and C4F7N–N2 mixtures

Due to their good dielectric properties and low global warming potential, C4F7N–CO2 and C4F7N–N2 mixtures have shown promising potential to replace SF6 in high voltage gas insulated equipment. However, during manufacturing, installation, and transportation of power equipment, burs and metal particles can be inevitably left inside, and they can cause corona discharge. Fundamental investigation of the corona discharge mechanism is essential to monitor partial discharge signals in environmentally friendly power equipment. This paper applies the fluid model to investigate the discharge mechanism of C4F7N–CO2 and C4F7N–N2 mixtures in negative point-plane corona discharge. A 2D axisymmetric model combines the drift-diffusion equations for electrons, positive ions, and negative ions and Poisson’s equation to study the process of dynamics. The gas is a mixture of C4F7N (5%, 7%, or 13%) and CO2 or N2 (95%, 93%, or 87%). The rise time of the first discharge pulse in C4F7N–CO2 and C4F7N–N2 mixtures is about 0.1 ns. The interval time between the first and the second pulse in the 5% C4F7N–95%CO2 mixture is about 1.5 times longer than that in the 5% C4F7N–95% N2 mixture. When the C4F7N content is 7% and 13%, the interval time between the first and second pulses in C4F7N–CO2 mixtures is about 2 and 3 times longer than those in C4F7N–N2 mixtures, respectively. The suppression regions in C4F7N–CO2 mixtures are larger than those in corresponding C4F7N–N2 mixtures. The total number of electrons, positive ions, and negative ions in C4F7N–CO2 mixtures is higher than that in C4F7N–N2 mixtures, while the reduced electric field in C4F7N–CO2 mixtures is smaller than that in C4F7N–N2 mixtures.

Simulation of Negative and Positive Corona Discharges in Air for Investigation of Electromagnetic Waves Propagation

Corona discharge, as one of the partial discharge (PD) modes, emits electromagnetic (EM) waves in the ultrahigh frequency (UHF) range. In order to study the behavior of the EM waves emitted from a PD source, a comprehensive PD source modeling method should be employed that takes into account the essential processes involved in the formation of that. In this article, a drift- and diffusion-based model is presented to simulate the corona discharges in the positive and negative voltages to investigate the differences between these two types of corona and their characteristics in terms of the EM waves’ propagation. This modeling tool includes ionization, attachment, and photoionization source terms as necessary phenomena to form the discharge. The results are analyzed for both types of coronas in the UHF range, and the differences between them are shown. Experimentally measured corona discharges using a high-frequency current transformers (HFCTs) and a monopole antenna probes are compared with the simulation current signals in the time and frequency domains, with promising results in terms of rise time and amplitude of the signal.

The microscopic principle and traits on pulsed discharge of negative corona

A systematic investigation of the dynamical behaviors and traits of negative corona discharge in pure oxygen is performed and the microscopic physical mechanism of the discharge is studied. In the meantime, a new dynamical model is presented, which can predict different discharge phases including steady-state discharge and periodic discharge of saw-tooth pulses. The change in the discharge outputs with time is analyzed comprehensively using the nonlinear dynamics method, and the Trichel pulsed oscillation and the dynamical characteristics are described. In addition, the positive ions impacting the cathode and the negative ions can be treated as feedback signals for maintaining pulsed discharge at the constant external excitation. It is found that the gas pressure levels significantly affect the discharge behaviors and the pulsed characteristics of charged particles and glow radiation. In particular, the microscopic mechanism of gas pressure level influencing the negative corona discharge is discovered. Meanwhile, the pulsed characteristics of the discharge outputs are studied, and an explanation of the microscopic formation mechanism of the symmetrical and asymmetrical jagged pulses of diverse outputs is given. It is revealed that the mass, migration speed, and migration time of various particles have a great influence on discharge behaviors.

Electrostatic elimination of charged particles by DC-type bipolar electrostatic eliminator

The electrostatic eliminator is widely used to prevent silos from explosions caused by the electrostatic discharge of charged particles. However, electrostatic accidents still happen occasionally. This study investigated charge elimination characteristics of the DC-type bipolar electrostatic eliminator under different configurations of the applied voltages, air velocities, and initial charge densities of particles for helping improve the charge elimination efficiency. The results show that the unipolar corona discharge will lead to reverse charging of particles, while the bipolar corona discharge at a suitable configuration can neutralize the charged particles completely. The upper and lower ionizers in the bipolar electrostatic eliminator should be applied with positive and negative voltages, respectively, and the positive voltage should be greater than the negative one. The suitable configuration of the electrostatic eliminator is insensitive to air velocity due to the simultaneous increase of the charging capability of positive and negative corona discharges with increasing the air velocity. This electrostatic eliminator can neutralize the charged particles with a net negative charge even in the presence of positively charged particles in the mixture. Furthermore, the performance of this electrostatic eliminator on a full-scale silo was examined using a light intensifier to observe the electrostatic discharge inside the silo. The proposed electrostatic eliminator was found to be effective in eliminating the electrostatic discharge in the silo.

Study and Numerical Simulation of Negative and Positive Corona Discharge: A Review

Two models to describe the phenomenon of corona discharge are presented: the first is known as the plasma model which with plasma chemistry defines the volumetric and surface reactions among charge carriers such as electrons, positive, and negative ions. This model uses Poisson's equation and a formulation of the space-charge density to calculate the electric field necessary to solve the species transport equations. Besides, only the plasma model determines the density of the charge carriers. The second is a simplified model which describes the corona discharge in terms of current conservation coupled with Poisson's equation. This model does not have any connection with the attributes of plasma chemistry. Both models propose solutions for the electric potential and space charge density distribution from the corona electrode to the ground electrode.

An Application of Corona-Treated and Chemically Modified Poly(D-Lactic Acid) Films as Benzydamine Hydrochloride Carriers

In the present article, chitosan and casein polyelectrolyte multilayers (PEMs) deposited on poly(D-lactic acid) (PDLA) substrates are investigated. PDLA substrates are modified both physically under negative corona discharge and chemically with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> -ethyl- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N ^\prime $ </tex-math></inline-formula> -(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC). The substrates modified by a combination of corona discharge and chemical modification are also studied. The topology of the multilayers is studied with AFM. The electret properties of the substrates obtained are investigated. The dependencies of the normalized surface potential on the storage time are studied. A layer-by-layer (LbL) deposition technique is used for multilayer deposition on the substrates. PEMs with eight layers are obtained. Benzydamine hydrochloride (Benz) is immobilized in the resulting PEMs. Drug loading efficiency and drug release from PDLA multilayers are studied. The results of PDLA multilayers demonstrate that the chemical modification of the PDLA substrates increases the amount of Benz loaded in the multilayers. The combination of corona treatment and chemical modification results in lower amounts of loaded drugs in both combination cases, when compared with only chemically modified samples.

Effect of Room’s Temperature and Electrode Gap on Current of Negative Corona Discharge in Rod-Plane Electrode Configuration

The stable corona discharge is widely used in filtration and electrostatic separation in recent years, and several models have been used by researchers to analyze one of its most important properties which is the current-voltage characteristic. The aim of this paper is to investigate the influence of ambient temperature and electrodes’ gap on negative DC discharge using rod-plane geometry, and the Townsend formula was found to be most appropriate model (I=K.V.(V-V0)). The experimental results show that for the same voltage level applied to the high voltage electrode, the discharge current rises with increasing temperature and decreases as the electrodes’ gap increases. Using curve fitting, it was proven that the geometric factor K is proportional to temperature and to the power of the distance between electrodes independently, and the threshold voltage V0 is proportional to the product of the temperature reciprocal and the power of the inter-electrode spacing. From these results, a new modified Townsend formula by introducing the air temperature and the distance between electrodes is proposed to calculate the discharge current with an accuracy of ±10%.

Characteristics of water volatilization and oxides generation by using positive and negative corona

The physical and chemical properties have significant differences for the positive and negative charged particles generated by discharge. In this work, a positive and negative corona discharge system was established, and two discharge reactors for charged particles restraining and acting were designed by a needle electrode covered with a quartz tube and a plate electrode filled with water. The corona discharges happened within the needle-plate electrodes were excited by a positive and negative high voltage source, and the characteristics of both water volatilization and oxides generation were examined within influence of the distances of both quartz tube inside and outside. The results show that the characteristics of both the water volatilization and oxides generation can be affected by the distances of both quartz tube inside and outside. When the distances of tube inside were increased from 5.00 to 13.00 mm, the water volatilizations decreased under negative corona, and increased firstly and declined immediately under positive corona. The maximum value of the water volatilization appeared in the distances of tube inside with 6.00–8.00 mm. In addition, the concentrations of the HNO x and H2O2 in treated water decreased with increasing the distances of tube inside. Moreover, with increasing the distances of tube outside from 4.00 to 14.00 mm, the change trends of both the water volatilizations and oxides presented the same as the distances of tube inside, and the maximum value of the water volatilization and oxides appeared in the distance of tube outside with about 9.00 mm. Overall, the positive corona can generate more water volatilizations and oxides in water than negative corona, and non H2O2 can be produced by negative corona. The results reflect the difference between positive and negative corona interaction with water, which can provide reference for plasma application.

Coalescence and counterflow of droplets on needle electrode with negative corona discharge

The coalescence of droplets on the discharge electrode surface in high humidity environments has rarely been studied, which may affect discharge characteristics. Meanwhile, directional transport of droplets is of great significance for many applications ranging from fluidic processing to thermal management. Here, corona discharge in a needle-plate electrode is adopted to explore the coalescence rule of droplets attached on the discharge electrode surface in a high-humidity environment, and to realize the counterflow of droplets. The experimental results show that the number of coalesced droplets on the needle electrode surface reaches the maximum under −7.5 kV at relative humidity ∼94% and ambient temperature ∼20 °C. When the applied voltage increases from −6 kV to −11 kV, the droplet moves up 2.76 mm in 5 s. The size of the attached droplet depends on the balance of coalescence and evaporation. The coalescence is mainly attributed to the dielectrophoretic force caused by the high electric field gradient. The evaporation is related to the ionic wind generated by the corona discharge. With regard to the counterflow phenomenon of the droplet, we speculate that the high concentration gradient of positive ions near the needle electrode provides a driving force for the negatively charged droplets. Meanwhile, the electrons and negative ions below the needle tip offer a repulsive force to the droplet. The shape and moving direction of the droplet attached to the needle surface can be manipulated by changing the voltage applied to the needle electrode, which shows the potential application value in realizing the self-cleaning of electrodes, liquid lenses and so on.

High temperature coronas in air and flue gas from LPG combustion: Current-voltage characteristics, ion mobilities and free electrons

Positive and negative corona discharges were studied at atmospheric pressure in a tube-wire geometry with a tube diameter of 150 mm. Current-voltage characteristics (CVCs) were measured both in air and in flue gas produced with a liquefied petroleum gas (LPG) burner, covering temperatures from ambient up to 1073 K. Corona operation was stable over the whole temperature range with positive polarity and up to 973 K with negative polarity. Based on a detailed analysis of the original CVC measurements, new insights on the temperature-dependent mobility of gas ions, on the occurrence of free electrons and on the electronic current contribution are presented. Deviations from the Townsend theory of CVCs can be ascribed to the lifetime-dependency of ion mobility caused by the formation of cluster ions. The contribution from free electrons is found to depend on temperature and tube radius.

Исследование релаксации заряда в короноэлектретах на основе сополимера П(ВДФ-ТФЭ)

Using the method of thermally stimulated depolarization currents, this paper explains the polarization in the field of corona discharge of polyvinylidene fluoride-tetrafluoroethylene (P(VDF-TFE)) copolymer films. It has been determined that to achieve the best electret properties of PVDF, polarization must be carried out in the field of negative corona discharge. It was found that the studied objects have two types of polar structures different in the activation energy and the frequency factor. Using a mix of traditional and numerical methods to analyze the peaks of the thermally stimulated depolarization currents, the parameters of the polar structures of both types found in P(VDF-TFE) were determined.

Modelling the Role of the Inner Electrode Radius on the Oxygen Negative Corona Discharge in Coaxial Electrode Geometry

The charge species plays a vital role in changing the field in direct current discharge (DC). This article introduces a numerical modeling in one dimension of the inner electrode diameter of oxygen-fed negative corona discharge in coaxial electrodes geometry. The properties of negative corona plasma in a concentric cylindrical electrodes (wire-cylinder) were simulated by COMSOL Multiphysics software. Various diameters of negative corona electrode, namely 0.01, 0.025, 0.05, 0.075, and 0.125 mm, were applied, ​​where the diameter of the outer cylindrical electrode was taken as 15 mm. The model was run at atmospheric pressure and the applied negative voltage was -10 KV. Moreover, oxygen gas was used to fill the inter-electrodes distance. Furthermore, the spatial distribution of electrons, positive ions, and negative ions as a function of the diameter of negative electrode of the negative corona discharge were investigated. The study also tested the effects of the electrode diameter of the negative corona discharge on ozone generation. The observed decrease in ozone density with the increase in negative electrode diameter was reasonable and consistent with other results provided by researchers in this field.

Self-Organized Fractal Structures on Plasma-Exposed Silver Surface.

Planar fractal microstructure is observed on the silver film treated by positive corona discharge for the first time. Due to the abundant positive ions driven by the electrical field of positive polarity, surface modification is mainly induced by the plasma oxidation effect, resulting in a large scale of dendritic pattern with self-similarity and hierarchy. In contrast, negative ions dominate the plasma-film interaction under negative corona discharge condition, leading to a different surface morphology without fractal characteristics. A growth model based on the modified diffusion-limited aggregation (DLA) theory is proposed to describe the formation of the dendritic fractal structure, whilst the physics behind is attributed to the electric field directed diffusion of the positive ions around the surface roughness. Numerical simulation verifies the high density of the hot spot in the dendritic pattern, which may enable potential applications in fractal photonic metamaterials.

Plasma degradation of trichloroethylene: process optimization and reaction mechanism analysis

In this study, a multi-pin-to-plate negative corona discharge reactor was employed to degrade the hazardous compound trichloroethylene (TCE). The response surface methodology was applied to examine the influence of various process factors (relative humidity (RH), gas flow rate, and discharge power) on the TCE decomposition process, with regard to the TCE removal efficiency, CO2 and CO selectivities. The variance analysis was used to estimate the significance of the single process factors and their interactions. It has been proved that the discharge power had the most influential impact on the TCE removal efficiency, CO2 and CO selectivities and subsequently the gas flow rate, and finally RH. Under the optimal conditions with 20.83% RH, 2 W discharge power and 0.5 l min–1 gas flow rate, the optimal TCE removal efficiency (86.05%), CO2 selectivity (8.62%), and CO selectivity (15.14%) were achieved. In addition, a possible TCE decomposition pathway was proposed based on the investigation of byproducts identified in the exhaust gas of the non-thermal plasma reactor. This work paves the way for control of chlorinated volatile organic compounds.

Effect of transverse airflow on the deflection of negative corona discharge on the Trichel pulse mode at atmospheric pressure

Negative corona discharge can deflect in transverse airflow in pin-to-plane electrodes at atmospheric pressure. In this paper, we investigate the mechanism of Trichel pulse discharge deflection in transverse airflow and give a further understanding of the dynamic process of the deflection through experiments and simulations. In experiments, we quantitatively record the deflection angle by processing the discharge images, and they show that a larger airflow speed will lead to a larger deflection angle. In simulations, the discharge deflection angle is calculated through a 2D fluid model. Besides, the periodic fluctuation of the deflection angle with Trichel pulses is revealed, and this phenomenon can be explained by the alternative dominant effect of airflow or ionization on the net production of positive ions in the vicinity of the tip. When the effect of airflow is dominant, more positive ions will generate away from the center of the tip, which will lead to an increase in the deflection angle. On the other hand, when the effect of ionization prevails, more positive ions will generate near the center because the electric field here is stronger, and the deflection angle will decrease. In addition, if these two effects balance, the deflection angle will reach its maximum or minimum value.

Multi-pulse triboelectric nanogenerator based on micro-gap corona discharge for enhancement of output performance

Triboelectric nanogenerator (TENG), which can convert all forms of mechanical energy into electricity, has been hailed as one of the economical ways to harvest energy. However, the development and application of TENG are limited due to its low output power. Although it is found that the power of TENG can be increased by introducing corona discharge, there are few studies on the influential factors of TENG based on corona discharge. In this paper, the multi-pulse triboelectric nanogenerator (MP-TENG) with enhanced output power is proposed by controlling the negative corona discharge through the integration of TENG and the micro-gap. The experimental results show that Voc, Isc and Qsc are improved 154%, 725% and 3025% respectively. Moreover, the highest power growth rate of 646% can be achieved under a low frequency. The MP-TENG demonstrates a superior output performance that the charging time of 100 μF capacitor to 3.5 V shortens by 1/5 and 12 parallel LED panels (240 lamp beads) can be lit up, which presents a great potential in practical application and plays a guide role in introducing corona discharge into the TENG.

Simulation of negative corona discharge in atmospheric air: from mode of Trichel pulses to stationary discharge

The paper presents a 2D multi-fluid non-stationary model of a negative corona discharge in atmospheric-pressure air in the needle-to-plane diode. Discharges were simulated in gaps up to 1 cm with an applied voltage in the range of 8-100 kV. The simulation results demonstrate two stages of the discharge evolution: a pulsed-periodic stage called the Trichel pulses mode and a stationary glow discharge mode. The spatio-temporal distributions of the discharge plasma and electric field are shown in detail. Physical mechanism of Trichel pulses formation and transition to the stationary discharge are also revealed. The duration of the Trichel pulse mode gradually decreases with increasing of the applied voltage.

Comparison of the positive and negative modes of corona discharge ion source for direct determination of aspirin in urine by ion mobility spectrometry

Ionization of aspirin (A) in positive and negative modes of a corona discharge (CD) ion source was studied by ion mobility spectrometry (IMS). The IMS spectra showed that aspirin can be both protonated, AH+, and deprotonated, (A-H)-, in positive and negative modes of CD, respectively. Using DFT calculations, it was found that the carbonyl oxygen of COOH group is the most preferred site of protonation with proton affinity of 867.8 kJ mol-1. Also, the calculated ΔG values for deprotonation of aspirin by O2- and O3- were -71.2 and -28.5 kJ mol-1, respectively, indicating its deprotonation is thermodynamically possible. Hydration of AH+ and (A-H)- was studied theoretically and it was found that AH+ and AH+(H2O) are the most abundant species in the ionization region in the presence of 40 ppm of water vapor at 100–200 °C, while (A-H)- is not hydrated in the same condition. The results of measurements in urine showed that urea content of urine interferes with detection of aspirin in positive CD, while urea was not ionized in the negative CD so that aspirin was determined in urine with recovery of 94% in negative CD.

Effects of a negative corona discharge on subsequent positive streamers

Positive streamers can be affected significantly by preceding discharges such as earlier streamers or a corona discharge. In this paper, we primarily discuss the effect of such a corona discharge on subsequent positive streamers with different intervals between them (0/500/990 ms) in air and pure nitrogen at 80 mbar with a repetition frequency of 1 Hz. We found that in air, when the interval time is 500 or 990 ms, a preceding discharge leads to shorter and weaker streamers or even prevents streamer inception altogether. This is likely due to negative ions which have converted to species that are harder to detach. The weaker streamers are also caused by more stable inception clouds which branch out later. When a corona discharge immediately precedes a streamer discharge in air, the streamers become longer, brighter while some branches develop from the side of the electrode instead of its tip. These effects are likely all related to plasma shielding caused by the corona discharge. In nitrogen, inception is primarily caused by electrons instead of negative ions. When the interval time is 500 or 990 ms in this gas, there is nearly no difference between streamers with and without a preceding corona discharge, because the inception time in nitrogen is the formative time that is not sensitive to the initial electron density. For near-zero intervals between corona and streamer discharges in nitrogen, streamers become smoother and thicker which can be attributed to a higher background ionization left by the corona discharge.

Effect of negative ions on decomposition of acetic acid in water using DC corona discharge

AbstractThis study investigates the characteristics of acetic acid decomposition on a negative DC corona discharge over water. The corona discharge is 4 mm away from the water surface. Furthermore, this study explores the mechanisms involved in the chemical reactions of active species during water treatment, using discharged plasma. During processing, oxygen or ozone is supplied to the reactor. The results of experiment and simulation show the same trend on time variation of acetic acid concentration. Therefore, the simulation model that considers the supply of ozone, hydrogen peroxide, and can confirm the change in acetic acid concentration. Our results indicate that negative ions such as can be used for water treatment by DC corona discharge.