Negative Corona Research Articles

Application End Evaluation of Electrostatic Precipitation for Control PM and NOx Emissions from Small-Scale Combustions

Electrostatic precipitators (ESPs) have shown promise in reducing particulate matter (PM) emissions, but their potential for simultaneous NOx reduction in small-scale combustion systems remains underexplored. This study focuses on using non-thermal plasma generated in a corona discharge to reduce PM and NOx emissions from small-scale combustion. ESP was specifically designed for a commercially available 15 kW boiler with wood pellet combustion and used with both positive and negative discharge polarity to control emissions without any chemical additives. ESP performance was evaluated across a range of specific input energies (SIE) in terms of particle mass and number concentrations and NOx concentrations obtained by continuous gas analysis. ESP ensured the reduction in PM concentrations from 48 mg/m3 to the magnitude of PM content in the ambient air. The highest precipitation efficiency was observed for particles in the 20–200 nm range. Concurrently, NOx emissions were reduced by up to 78%, from 178 mg/m3 to 39 mg/m3. These results were achieved at specific input energies of 36 for positive and 48 J/L for negative corona, which is significantly lower than those reported for many existing separate PM and NOx control systems. This study demonstrates the potential of ESPs as a compact, energy-efficient solution for simultaneous PM and NOx removal in small-scale combustion systems, offering promising implications for improving air pollution control technologies for small-scale combustion systems.

Theory of stability of self-sustaining dc discharges at inception with application to negative corona

Theory of stability of self-sustaining dc discharges at inception with application to negative corona

Simulation study of the effect of electrode polarity on microscale corona discharge characteristics

Abstract The occurrence and application scenarios of micro-scale corona discharge are diverse, and the effect of micro-scale corona discharge mechanism and needle electrode polarity on corona discharge characteristics is still unclear. This paper establishes a microscale simulation model of pin-plate DC positive and negative corona fluid chemical reactions. The phenomenon of positive and negative corona discharge is being investigated. The internal discharge mechanism is analyzed from the microscopic point of view. Results demonstrate that positive corona discharge generates space charges that reduce the electric field strength between the needle electrode and amplify it between the plate electrodes. In contrast, negative corona discharge exhibits the opposite effect. The number of charged particles produced by microscale negative corona discharge is larger than that produced by positive corona, and the discharge phenomenon is more intense than that of positive corona. Under the simulation conditions in this paper, the ionization reaction rate of micro-scale positive and negative corona rises rapidly at the initial discharge. It will gradually remain stable after experiencing an upward pulse. The pulse peak value generated by micro-scale negative corona discharge is much higher than that of positive corona, and the pulse width of negative corona discharge is about half smaller than that of positive corona, which can reach a stable corona discharge state faster.

Conic Cross-Sectional Electrodes and Their Influence on Negative Corona Discharge and Trichel Pulse Characteristics

Conic Cross-Sectional Electrodes and Their Influence on Negative Corona Discharge and Trichel Pulse Characteristics

Study on the treatment of oil production wastewater by corona discharge coupling Fenton reagent

As the main by-product of oil production, oil production wastewater has the characteristics of high organic content and poor biodegradability, which makes the low temperature plasma wastewater treatment technology get new development. The Ground electrode atomization negative corona discharge（GEANCD） technology increases the discharge current on the basis of traditional corona discharge, but the uneven atomization of liquid is a key challenge at present, which will have a great impact on the degradation of wastewater pollutants. In this study, the GEANCD reactor was redesigned and a self-developed spiral wire hole electrode (SWHE) was used to replace the conventional wire electrode (WE). The discharge characteristics of the reactor under the two electrode structures were investigated and the optimal discharge parameters were determined. Under the optimum discharge parameters, the treatment effect of the two electrode structures with or without coupling Fenton reagent on oil production wastewater was also compared. The experimental results show that under the optimal discharge parameters of flow rate of 25 mL/min, plate electrode distance of 50 mm and discharge voltage of 14 kV, the reactor equipped with SWHE has higher discharge current, and the treatment effect of oil production wastewater is better when coupled with Fenton reagent.

Ionization processes of negative corona discharge. Part 2. Theory. Comparison with experiment

The purpose of the research is a theoretical analysis of ionization processes in the air, which are initiated by a high-voltage field generated by the negative needle-flat electrode electrode system. Methods. Fe, Cu, Al electrodes are used. Calculations are carried out using the methods of quantum mechanics and mathematical physics. Results. The processes of cold and thermoelectron emission of electrons, enhanced by an external high-voltage field (Schottky emission), are analyzed. The conditions under which the generation of charges from the cathode surface due to plasma-chemical reactions and the capture of surface electrons by electronegative oxygen molecules are decisive are investigated. Based on the PE theory, a theory of injection of negative ions from the cathode into an electronegative gas is constructed and the theory is compared with experiment. It has been shown that at small radii of curvature of needle tips, when E ≥ 106 V/cm, the generation of charges is due to cold emission of electrons. In average fields E ≈ 105 V/cm, electron emission is due to the Schottky effect. In fields E ≈ 104 V/cm and below, injection is caused by electrochemical processes and PE capture. A theory has been developed for PEs that appear at electric field intensities on the electrode of the order of several tens of kV/cm, that is, on flat and slightly curved negative electrodes. The capture of PE by electron-withdrawing molecules causes an injection current and, as a consequence, the ignition of a corona discharge. Analytical expressions for the surface density as a function of the local electric field strength, as well as an expression for the injection current, are obtained. The agreement between theory and experiment is satisfactory. Conclusion. An analysis of the development of CR on negative needles is given. A theory of PE at the cathode in strong electric fields was developed. Based on the results of measuring dark negative current-voltage characteristics, it is possible to determine the patterns of surface processes involving electronic transitions, in particular, determine the concentration of PE and injection currents.

Investigation into negative corona discharge in steam jets and distribution characteristics of charged steam jets

Electricity provides a wide range of benefits for plant growth, and the electric field created by a charged steam jet exhibits significant potential for application in this field. This study investigates the electrical characteristics of charged steam jets, including the corona-discharge process, distribution of electric fields, and deposition currents. By installing a needle-ring electrode near the steam-jet exit, high-potential charged steam is generated within a confined space through the corona charging of droplets in the steam. The humid environment inside the steam jet considerably reduces the corona current compared with that of air. The outlet current is identified as a critical factor for assessing the charged steam-jet behaviour, with a higher outlet current indicating a stronger electric field and deposition current. The configuration of the electrode and the steam operational conditions, particularly the latter, affect the outlet current. Experimental results highlight the different electrical distribution characteristics of wet and saturated steam jets. Notably, the distributions of electric field and deposition currents, along with the depositional droplets and absolute-humidity increments exhibit asymmetry above and below the steam jet. This paper presents a discussion on the formation, development, and dissipative processes of charged droplets and an analysis into their possible movement trajectories under various forces. Generally, the asymmetric distribution of charged steam jets is caused by the asymmetric distribution of charged droplets or water-cluster molecules, which becomes more pronounced as one departs further from the steam-jet exit.

Negative corona discharge strategy for efficient quantum dot light-emitting diodes.

In colloid quantum dot light-emitting diodes (QLEDs), the control of interface states between ZnO and quantum dots (QDs) plays a vital role. We present a straightforward and efficient method using a negative corona discharge to modify the QD film, creating a dipole moment at the interface of QDs and magnesium-doped ZnO (ZnMgO) for balanced charge carrier distribution within the QDs. This process boosts external quantum efficiencies in red, green, and blue QLEDs to 17.71%, 14.53%, and 9.04% respectively. Notably, optimized devices exhibit significant enhancements, especially at lower brightness levels (1000 to 10,000 cd·m-2), vital for applications in mobile displays, TV screens, and indoor lighting.

Analysis of electric filters for cleaning the air environment of production premises

RELEVANCE: The problem of hazardous working conditions in Russia attracts attention due to an increase in the proportion of workers exposed to negative impacts on their health. Of particular interest is the analysis of the air environment as the main factor influencing human health. 32.2% of workers in hazardous working conditions are exposed to airborne factors, which leads to occupational diseases. To reduce the harmful effects of the air, it is necessary to clean it from harmful components. A promising device for air purification is an electric precipitator.PURPOSE: The study is aimed at selecting and optimizing electric precipitators for air purification in industrial premises. The goal is to determine the most effective design of an electric precipitator for cleaning the air environment of industrial premises.METHODS: The analysis is carried out on the basis of statistical data, the results of studies of electric precipitators of various designs for cleaning the air from dust, harmful gases and microorganisms. The results are used for comparative analysis.RESULTS: The study reveals that different designs of electrostatic precipitators demonstrate different effectiveness in air purification depending on the type of design. The design of corona electrodes affects ozone generation. It has been established that two-zone electrostatic precipitators with needle corona electrodes on the negative corona can significantly reduce ozone emissions. Wet electrostatic precipitators have regeneration, and the presence of several stages increases the cleaning efficiency. Electrostatic filters do not generate ozone and can be used in explosive low-volume areas.CONCLUSION: The study confirms that the choice of electrostatic precipitator should depend on the specifics of production and the volume of the room. For explosive environments, electrostatic precipitators should be preferred, while for large areas, a wet multi-stage electrostatic precipitator is recommended. Electrostatic precipitators-ozonizers can be effective for air disinfection. Summarizing the results allows us to conclude that it is important to choose the appropriate type of electrostatic precipitator to ensure optimal air conditions for the safety of workers.

Improving lightning protection with corona minimising air terminals

A comprehensive approach to lightning protection is comprised of four key steps, namely protection against direct lightning strikes, dealing with surges and transients, dissipation of lightning currents via earthing and bonding, and protecting people. This paper deals with new research findings associated with direct-strike protection with lightning rods or “air terminals”, namely the effect of accumulated corona space charge around the tips of these components. There is now a great deal of consensus amongst lightning researchers and practitioners that space charge accumulation reduces the efficiency of an air terminal by inhibiting the initiation and development of an upward leader, a critical stage in the lightning attachment process. The paper describes measurements carried out in a high-voltage laboratory to quantify the amount of corona discharge that would be emitted under thunderstorm conditions from a variety of air terminals of different geometries. A unique, previously unreported aspect of these experiments was the corona testing of air terminals under dry and wet conditions. The results of these experiments showed that corona discharge (and hence space charge accumulation) from a standard Franklin rod is substantially higher than from the range of significantly blunter “corona minimising” air terminals that were tested. The previously reported polarity difference in corona characteristics was also observed, i.e., the magnitude of negative corona was larger than positive corona for the same ambient electric field. Differences in corona discharge were also observed under wet and dry conditions, where wet air terminals were found to produce modestly more corona. The paper then addresses the optimisation of air terminals, i.e., minimising corona discharge, for practical lightning protection applications, where the air terminal radius of curvature is tailored to its height and position of installation. Various researchers have made these calculations, the outcomes of which are summarised in this paper. In general, radii of curvature in the range 1–100 mm are required, depending on the installation height and location of the air terminal.

Study on the Process and Transition Mechanism of Different Stages in Positive and Negative Corona

Study on the Process and Transition Mechanism of Different Stages in Positive and Negative Corona

A method for calculating space charge distribution in ultra-high voltage direct current transmission lines based on the transport of diluted species theory

The occurrence of corona discharge in ultra-high-voltage direct current transmission lines results in the generation of space charge, which significantly affects the nearby electromagnetic environment. To investigate the micro-physical mechanisms of discharge and provide better guidance for the calculation of the ground ion current density and total electric field, a method based on the theory of the transport of diluted species is proposed. This method enables the visualization and analysis of the movement process of space charge in air medium, as well as the calculation of the total electric field below the transmission lines. To validate the effectiveness of this algorithm, experimental tests of the total electric field are conducted on actual transmission lines. The experimental results demonstrate that the algorithm not only highlights the evident differences in the transient microscopic processes between positive and negative corona discharges but also accurately calculates the total electric field below the transmission lines. In addition, considering the weather conditions in the Chongqing region, relevant recommendations are provided under the influence of wind speed, aiming to offer protection guidelines for individuals engaged in activities near transmission lines.

Ionization Processes of Negative Corona Discharge Part 1. Review and Experiment

The purpose of the research is an experimental study of physical processes in the near-electrode zones of negative point electrodes in an electronegative gas (air) under the condition of a high-voltage field.Methods. Video image analysis, current-voltage characteristics measurements, and spectroscopy are used. The current-voltage characteristics of the corona discharge ignition voltage in the environment are measured, the problem of experimental identification of surface charges, the mechanism of negative corona discharge ignition, and the ionic structure of streamers is studied, degradation of electrodes during negative corona discharge, spectrum of corona discharge creation and electromagnetic sound.Results. It is shown that at small radii of curvature of needle electrodes, the development of a negative corona discharge is due to the cold emission of electrons, and on flat and slightly curved negative electrodes, due to the capture of surface electrons by electron-withdrawing molecules. The mechanism of ignition of a corona discharge in an electronegative gas with a negative needle, the structure of streamers from negative needles, the emission spectrum and ethonic degradation of electrodes have been studied.Conclusions. The ignition of a negative corona discharge at small radii of the tips of the pointed needles (ro less than tens of microns) is due to the cold emission of electrons followed by impact ionization of neutral molecules. With slightly curved electrodes, the appearance of a negative corona discharge is due to the capture of surface electrons by electronegative gas molecules with subsequent plasma-chemical reactions. The formation of surface electrons depends on many factors: the presence and structure of oxide films (roughness, defects, etc.), which determine the electron work function and form local fields at the tips of microtips. The appearance of a corona discharge leads to degradation of the corona electrodes, expressed in the spraying of the tips of the points and the melting of the needles. In the dark region of the negative corona discharge (U < U*), photons in the in the ultraviolet spectrum (UV spectrum) are emitted, and when U > U*, in addition to UV photons, photons in the visible region of the spectrum are emitted. Glow fluctuations are caused by the chaotic dynamics of the formation of injection centers (melted tubercles - ectons) on the surface of the corona electrode. The ignition of a corona discharge is accompanied by sound emission with a frequency of about 300 Hz.

Experimental and theoretical study on the influence of bundle number on corona loss characteristics of ultra high voltage corona cage positive/negative DC conductors at high altitude

The corona loss generated by the conductor is one of the important factors in the design of ultra-high voltage (UHV) direct current transmission lines. This article is based on the high-altitude (2200 m) ultra-high voltage corona cage experimental platform built in Xining City, Qinghai Province. For the LGJ400-35 conductor used in the typical ± 800 kV DC transmission lines from Qinghai to Henan Province, positive and negative polarity corona experiments were conducted on LGJ400-35 conductors with 4, 6, 8, and 10 bundle under surface field strength conditions of 14–22 kV/cm. For the first time, corona loss data of bundle conductors in positive/negative polarity ultra-high voltage DC transmission lines were obtained, Fit the prediction formula for corona loss of transmission lines under different bundle numbers and surface electric field strengths of wires. And build a model in COMSOL Multiphysics software for simulation analysis, fitting the correction factor for the impact of wind speed on wire corona loss. The research results in the article can provide data reference and support for the construction of ultra-high voltage direct current transmission lines in high-altitude areas.

Impact of Cathode Geometry on Negative Corona Discharge and Trichel Pulse Characteristics: A Comparative Analysis of Hyperbolic, Elliptic, and Tangent-Circular Needle Shapes

Impact of Cathode Geometry on Negative Corona Discharge and Trichel Pulse Characteristics: A Comparative Analysis of Hyperbolic, Elliptic, and Tangent-Circular Needle Shapes

Interferometer study of radial and axial density evolution and temperature in N2 gas subjected to negative and positive corona discharges

In the present paper, we propose to make an optical diagnosis by laser interferometry to determine experimentally the density of neutral particles in a coronal discharge bathing in a gaseous medium N2. We are particularly interested in the measurement of variation of the optical path and therefore of the index of refraction which allows us to highlight the variation of the density of the neutrals in the discharge, and using a computer treatment (Pearce method) the refractive index of the medium is calculated to determine the spatial distribution of density and temperature (radial and axial) at the core of the corona discharge in two different situations (positive and negative). This optical diagnosis also allowed us to quantitatively determine the phenomenon of depopulation of neutral particles. These quantitative and experimental results are interesting because they allow a good correlation between the theoretical results obtained so far

Cellulose Nanofiber-Based Triboelectric Nanogenerators for Efficient Air Filtration in Harsh Environments.

Advanced portable healthcare devices with high efficiencies, small pressure drops, and high-temperature resistance are urgently desired in harsh environments with high temperatures, high humidities, and high levels of atmospheric pollution. Triboelectric nanogenerators (TENGs), which serve as energy converters in a revolutionary self-powered sensor device, present a sustainable solution for meeting these requirements. In this work, we developed a porous negative triboelectric material by synthesizing ZIF-8 on the surface of a cellulose/graphene oxide aerogel, grafting it with trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane, and adding a negative corona treatment, and it was combined with a positive triboelectric material to create a cellulose nanofiber-based TENG self-powered filter. The devices achieved a balance between a small pressure drop (53 Pa) and high filtration efficiency (98.97%, 99.65%, and 99.93% for PM0.3, PM0.5, and PM1, respectively), demonstrating robust filtration properties at high temperatures and high humidities. Our work provides a new approach for developing self-powered wearable healthcare devices with excellent air filtration properties.

Effect of high voltage discharge on germination characteristics of vetch seeds at high altitude

High-voltage electrostatic fields and low-temperature plasma technology at atmospheric pressure have an important impact on biological growth promotion. Therefore, a multi-needle-column-plate corona plasma generator is proposed in this paper. The negative corona voltammetry characteristics of multi-needle-plate electrodes and multi-needle-column-plate electrodes with different electrode spacing are investigated experimentally, and the electric field distribution of the device is simulated. The device was also applied to vetch seeds at high altitudes to investigate the effect of discharge on germination and root length. The results show that the introduction of column electrodes can effectively improve the electric field distribution of the device so that the device can provide two modes of high voltage electrostatic field and corona plasma field, and ensure the uniform treatment of seeds when the electrode spacing is 3 cm. The treatment of this device accelerates seed germination and promotes root growth, and is more effective under the combined influence of higher electric field strength, ionic wind generated by the discharge, and the active species than a single factor with a lower electric field, as well as shortening the duration of action. The high voltage electrostatic fields at −3 kV, −6 kV, and −9 kV and the corona discharge plasma fields at −12 kV, −15 kV, and −18 kV can effectively accelerate the germination of vetch seeds as well as promote the root growth under the treatment time of 10 min, 20 min, and 30 min. The optimal conditions were −9 kV for 30 min and −15 kV for 10 min, respectively.

The characteristics of negative corona discharge and radio interference at different altitudes based on coaxial wire–cylinder gap

The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120‒4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable, the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-high-voltage lines.

Investigation of the electret properties of PDLA/PEC porous composite films

In the present paper the influence of both time and low pressure on the surface potential decay of porous composite films of poly(D-lactic acid) and poly(ε-caprolactone) was investigated. The samples were charged in a corona discharge by means of a corona triode system under room conditions. Positive or negative voltage was applied to the corona electrode and voltage of the same polarity as that of the corona electrode was applied to the grid. After charging, the initial surface potential was measured using the method of the vibrating electrode with compensation. Two groups of tests were performed. In the first group, after charging, the electrets were placed into a vacuum chamber where the pressure was reduced step by step in the range from 1000 mbar to 0.1 mbar. At each step the samples were stored for 1 minute. After that the electrets were removed from the vacuum chamber, their surface potential was measured again and the normalized surface potential was calculated. The influence of low pressure was analyzed by the equation that describes processes of desorption from the electret’s surface. In the second group, after charging, the electret surface potential was measured by the time of storage. The possible surface potential decay mechanisms responsible for the electret’s behavior were discussed. It was established that the surface potential decay depends on both corona polarity and type of films. It was shown that the samples charged in a positive corona are more stable than those charged in a negative corona.