Effect Of Corona Discharge Research Articles

Surface degradation of epoxy resin exposed to corona discharge under bipolar square wave field: From phenomenon to the insights

The unavoidable corona discharge induced by distorted field is detrimental to the safety of power equipment, especially the equipment with high voltage magnitude and high frequency. In this paper, the degradation morphology, residual components, lifetime of endurance, partial discharge characteristics, and evolution of surface traps of epoxy insulation under bipolar square wave field is investigated. The results show that degraded zone exhibits as three layers with round pits and channel-like ravines on the surface of epoxy resin exposed to corona discharge. It is demonstrated that more oxygen element during corona discharge while more carbon element during breakdown appeared, and nano-Al2O3 fillers migrates to the discharged zone. The maximum temperature and number of emitted phonons increase with voltage amplitude and frequency in power law and exponential form, respectively, corresponding to the fitting function of endurance lifetime. The emitted light is concentrated on the near ultraviolet (UV) and infrared ray (IR) band, indicating the energy pooling and thermal effect of corona discharge, which interprets the distinct degradation behavior of samples under sinusoidal and bipolar square wave voltage. The effect of space charge and thermal conductivity should be considered simultaneously in the degradation of epoxy insulation under bipolar square wave field due to polarity reversal and high frequency, which is proved by the disparate behavior of EP/nano-Al2O3 composites resistance to corona discharge and the breakdown moment at falling edge of bipolar square wave voltage. This work may contribute to the advancement of resistance to corona discharge degradation in equipment with high power density, high voltage amplitude and high frequency.

Coupling effect of electric field and corona discharge on combustion and soot formation of ethylene jet flame

The coupling of electric field (E-field) and corona discharge is designed to adjust the appearance and soot formation of the ethylene jet flame. The temperature and content of soot are measured by the improved two-color pyrometry (TCP). Experiments indicate that the flame is stretched and deflected laterally under the coupling field. The maximum temperature of soot and the proportion of high temperature zone in the flame increase, and oxidation rate of soot increases. The flame is more stable under the coupling of reverse E-field and corona discharge. From the non-coupled field to the coupling field of 100 kV/m and −100 kV/m, the temperature proportion of the flame in the range of 1700 K–1800 K increases from 0 to 44.2 % and 54.8 % respectively, and the peak oxidation rates of soot also increase by 204 % and 219 % respectively. The E-field in the coupling field accounts for the main influence. The high voltage side of the flame is affected by the ionic wind generated by corona discharge, and the amount of soot generated under the high coupling field is less than that on the left side.

Enhancing fine particle removal by electrostatic precipitation from flue gas with a high PM concentration: Effect of various electrode configurations

Particle pollution has hazardous effects on air quality and human health, especially fine particle. However, the highly efficient removal of fine particles is an unsolved problem in electrostatic precipitators (ESPs). In this study, a transparent ESP was designed to investigate the effect of fine particles on the corona discharge performance and the role of ionic wind in particle migration. And five types of typical discharge electrodes were applied. The results showed that the presence of fine particles could weaken the corona current produced by electrode discharge. Among these electrodes, the spike electrode can reduce the adverse effect of the particle space charge. The maximum ionic wind velocity around the electrode tips and within the near-plate region could reached 5.67 m/s and 5.00 m/s under an applied voltage of 30 kV, respectively. Combining the effects of corona discharge and ionic wind, the collection efficiencies of fine particles decreased in the following order: spike electrode (medium needle) > spike electrode (longest needle) > arista electrode > spike electrode (shortest needle) > sawtooth electrode. In general, spike electrode discharge has better performance for particle charging and particle collection efficiency and is suitable for fine particle removal in ESPs. In addition, electrode configuration/arrangement optimization methods were proposed to enhance fine particle removal in ESPs.

Water Microdroplets in Air: A Hitherto Unnoticed Natural Source of Nitrogen Oxides.

Water microdroplets are widespread in the atmosphere. We report a striking observation that micron-sized water droplets obtained from zero-volt spray sources (sonic spray, humidifier, spray bottle, steamer, etc.) spontaneously generate nitrogen oxides. The mechanistic investigation through the development of custom-designed sampling sources combined with mass spectrometry and isotope labeling experiments confirmed that air nitrogen reacts with the water at the air-water interface, fixing molecular nitrogen to its oxides (NO, NO2, and N2O) and acids (HNO2 and HNO3) at trace levels without any catalyst. These reactions are attributed to the consequence of an experimentally detected feeble corona discharge (breakdown of air) at the air-water interface, likely driven by the high intrinsic electric field at the surface of water microdroplets. The extent of this corona discharge effect varies depending on the pH, salinity/impurity, size, speed, and lifetime of microdroplets in the air. Thus, this study discloses that the air-water interface of microdroplets breaks the strong chemical bond of nitrogen (N2), producing nitrogen oxides in the environment, while lightning strikes and microbial processes in soil are considered their dominant natural sources. As nitrogen oxides are toxic air pollutants, their spontaneous formation at the air-water interface should have important implications in atmospheric reactions, requiring further investigations.

The effects of corona discharge from a cold plasma source on the physicochemical properties and shelf-life of milk

Milk is a nutrient-rich food and a risk source of foodborne pathogens, yet traditional thermal processing/pasteurization can affect its nutritional value. However, recently, consumer demand for healthy, fresh, and safe “green process” foods has increased, so emerging non-thermal food cold plasma (CP) technology has largely addressed consumer demands for safe and healthy foods by effectively eliminating pathogens from milk. In this study, we examined CP treatment duration (0, 1, 5, and 10 min) and membrane filtration (MF) effects on whole and skim milk with respect to milk characteristics, microbial growth, and xanthine oxidase activity over a 0– 15-day storage period. This study revealed that the shelf life of whole milk and MF skimmed milk with CP10 min amounted to 15 days and that the TPC was <6 log colony forming units (CFU/mL), while titratable acidity was <0.18% in compliance with regulatory standards, with insignificant color changes. Additionally, pH and lipid oxidation values in CP and MF groups were positively correlated with storage time (p < 0.05). Thus, CP treatment released free lipids into milk, with minor oxidative reactions. Critically, no significant effects were observed in terms of nutritional value and xanthine oxidase activity. Hence, we provide valuable processing insights for dairy manufacturers and show that CP10 min treatment positively impacted total plate count (TPC) and thermo-resistant bacteria. Our goal is to reduce the heat load on milk without compromising nutritional quality while maintaining food safety.

Study of the influence of corona discharge on the efficiency of oxidation of organic impurities using ozone

Purification of air containing volatile organic compounds is an important task in many industries. This article examines the effect of corona discharge on the efficiency of the oxidation of organic mixtures. As a result of our research, we found that the consumption of ozone for the oxidation of various components of the mixture is approximately the same. This means that other particles, including water vapor, also take part in oxidation reactions.

Numerical study of electrohydrodynamic atomization considering liquid wetting and corona discharge effects

In this paper, the behavior of the cone-jet mode of fluid by electrohydrodynamic atomization (electrospray) is numerically simulated and investigated with the effect of liquid wetting and corona discharge effects. The simulation was performed with contact angle condition to fit the Taylor cone shape by experiments. Experimental data are provided to verify and validate the numerical method, followed by additional analyses on the effects of electrical conductivity, surface tension, flow rate, and fluid viscosity on the electrospray characteristics, including spray current and jet diameter. Numerical results by simulations are in reasonable agreement with experiments and consistent with the literature. Analyses on different contact angles suggest potentially major impacts of this factor on the cone-jet mode in high voltage and low flow rate circumstances. Furthermore, the influence of corona discharge on electrospray is also investigated by both electrospray–corona simulation and experiment using a high-speed camera, yielding a significant improvement in the numerical prediction for Taylor cone formation. Numerical results indicate that liquid wetting on capillary nozzles would be a vital factor for the Taylor cone formation in numerical electrospray–corona discharge studies.

Effects of positive corona on upward leader initiation from tall building by 3D numerical simulation

The initiation of the stable upward leader (SUL) is an important criterion to judge whether a building can be struck by lightning. The corona layer above the tip of a building caused by thunderstorm will affect upward leader initiation; however, there are few studies on the degree of its specific impact. Therefore, based on the established three-dimensional corona discharge model (Guo et al., 2022) and the dynamic critical length criterion of initial streamer as reported by Guo et al. (2020), we establish an SUL initiation model with corona discharge at the tip of the tall building. It is found that the simulated results of our model (considering corona discharge) match well with actual observations. The model is then used to simulate buildings with different height and different peak current of lightning strike (IP). The effect of positive corona discharge at the tip of the building on the initiation of the positive SUL during downward negative cloud-to-ground flash is discussed. The results show the following: 1) for certain IP values, the effect of corona discharge at the tip of the building has a greater effect on taller buildings than shorter ones. 2) For buildings of the same height, as Ip decreases, the effect of corona discharge at the tip of the building becomes greater. For example, for an IP of 20 kA and an Hb of 200 m, at the moment of the SUL initiated from the building, the height of the DL tip above the ground is 550 m when the corona layer is considered in the simulation and is 861 m when which is not considered. The difference between them have reached at 36%.

Three-Dimensional Simulation of Corona Discharge in a Double-Needle System during a Thunderstorm

The effect of corona discharge from buildings or structures on the surrounding atmospheric electric field is very important in the measurement of urban atmospheric electric fields and the early warning of lightning. However, most previous studies were focused on independent buildings, with little research on three-dimensional building groups. Therefore, based on three-dimensional numerical simulation technology, this paper uses a double-needle system to simulate the characteristics of thunderstorm corona discharge from two equal-height buildings separated by a variable distance. The shielding effect of the double-needle system on the ground electric field is evaluated both with and without corona discharge, and the main conclusions are as follows: (1) The larger the distance between the two needles, the closer the peak corona current from each tip of the double-needle system is to that from an independent lightning rod at the same height. When the peak corona current from each tip of the double-needle system equals the peak corona current from an independent lightning rod at the same height to some level of approximation, the distance between the two needle systems is determined by the needle height at this time. (2) If the distance between the two needles is 0.1 m, the corona charge released by the double-needle system is almost equal to that released by an independent lightning rod. The corona charge released by the double-needle system is approximately twice as much as that released by an independent lightning rod when the distance between the two needles is increased to a certain value that increases with the needle height and the time of corona discharge. (3) The greater the value of the time of corona discharge, the stronger the shielding effect of the corona discharge on the ground electric field and the larger the shielding range, but the greater the value of the needle height, the smaller the shielding range. (4) Compared with the shielding effect with no corona discharge, that with corona discharge is greater, but the greater the value of the needle height, the less the enhancement. For example, for corona discharge with a time of 10 s, the needle height is 20 m, and the shielding range is ca. 70 m, which is 8.8 times that without corona discharge; however, for the needle height of 100 m, the shielding range is ca. 150 m, which is only 1.5 times that without corona discharge.

Time Domain Measurement System for Electric Field of Radio Interference Generated by Corona Discharge

When corona discharge occurs around the wire, it will be accompanied by the movement of space charge, and then generate corona discharge effects such as radio interference and audible noise. In order to reveal time domain characteristics of the electric field of radio interference generated by corona discharge, a set of time domain measurement systems for radio interference, including oscillator antenna, sampling resistance, and data acquisition system, is developed. Based on the characteristics of corona-generated radio interference and antenna theory, the size of the antenna, the equivalent circuit model, and the selection of sampling resistance are discussed carefully to satisfy the requirements for the measurement of corona-generated radio interference. To verify the effectiveness of the measurement system, an experimental platform with a single corona source is built, and the time domain waveforms of corona current and radio interference are simultaneously measured. Besides, the attenuation law of radio interference is obtained by using a time domain measurement system. The results show that the amplitude of the measured voltage of radio interference decreases exponentially with distance. The time domain measurement system presented in this paper can lay a solid foundation for the time-domain evaluation of the radio interference level generated by corona discharge.

Investigation of the surface recombination rate in polycrystalline films from the A6B6 compound by the MW-PC method

In this article, the surface recombination rates in polycrystalline CdTe films obtained on oxidized substrates are studied. The results of the corona discharge effect on the CdTe-SiO2–Si-Al structure are presented. In this case, in the static mode, a shift of the short-circuit current spectra to the short-wave region was observed. To analyze the shift of the short-circuit current spectra, the method of microwave probe photoconductivity (MW-PC) was used and non-contact registration of decay transients for excess carriers was carried out. Considering that for CdTe in the wavelength range of about 800–1000 nm, the absorption coefficient increases sharply with the excitation photon energy at the absorption edge. It was found that the surface recombination rate was estimated at 19 ns. It has been determined that the filling of surface traps in CdTe leads to a decrease in the effect of surface recombination.

ЛАБОРАТОРНЫЙ ЭКСПЕРИМЕНТ ПО ИССЛЕДОВАНИЮ ВОЗДЕЙСТВИЯ ИОННОГО ВЕТРА КОРОННОГО РАЗРЯДА НА ТЕПЛЫЙ ТУМАН В ЗАМКНУТОМ ОБЪЕМЕ

The ion wind ability to initiate motions in the originally motionless warm fog inside an enclosed volume is studied. The objective of the study is the experimental check of the possibility to exploit corona discharges for the warm fog modification. The experiment was carried out in a specialized laboratory unit in the Fedorov Institute of Applied Geophysics. The possibility of using the unit to explore the effect of corona discharges on warm fogs is clearly demonstrated.

Assessment of the Effect of Corona Discharge on Synchronous Generator Self-Excitation

The method of operative determination of active power losses (both loading and crown) in alternating current lines has been improved. The proposed technique allows monitoring of active power losses in lines. Based on the comparative analysis of different approximation methods, the most effective method of analytical representation of regression dependences of active power losses on the corona on voltage for different weather conditions is proposed. The validity and reliability of scientific statements, conclusions, and recommendations given in the dissertation are confirmed by the analysis of the results of comparative calculations performed for different models. The efficiency of the developed algorithms and programs was tested on control examples with reference source data, where the results of the calculations were compared with the results obtained by standard programs. The developed technique of operative determination of losses of active power (loading and on a crown) allows one to carry out current monitoring of losses and passive parameters of high-voltage power lines of alternating current. The phenomena of self-excitation of generators connected to unloaded power lines are considered at great length. A physical analysis of the ongoing processes is given, and calculation methods are proposed that have been experimentally tested on a dynamic model. The paper takes into account the effect of the wire corona on the conditions of self-excitation of generators with the necessary developments to prevent this negative phenomenon in the main electrical network. Models and methods have been developed for evaluating the effect of the wire corona on the conditions for the occurrence of self-excitation in ultra-high voltage transmission lines.

Numerical Evaluation of the Effect of Fuel Blending with CO2 and H2 on the Very Early Corona-Discharge Behavior in Spark Ignited Engines

Reducing green-house gases emission from light-duty vehicles is compulsory in order to slow down the climate change. The application of High Frequency Ignition systems based on the Corona discharge effect has shown the potential to extend the dilution limit of engine operating conditions promoting lower temperatures and faster combustion events, thus, higher thermal and indicating efficiency. Furthermore, predicting the behavior of Corona ignition devices against new sustainable fuel blends, including renewable hydrogen and biogas, is crucial in order to deal with the short-intermediate term fleet electric transition. The numerical evaluation of Corona-induced discharge radius and radical species under those conditions can be helpful in order to capture local effects that could be reached only with complex and expensive optical investigations. Using an extended version of the Corona one-dimensional code previously published by the present authors, the simulation of pure methane and different methane–hydrogen blends, and biogas–hydrogen blends mixed with air was performed. Each mixture was simulated both for 10% recirculated exhaust gas dilution and for its corresponding dilute upper limit, which was estimated by means of chemical kinetics simulations integrated with a custom misfire detection criterion.

Enhancing fine particle separation by hybrid-electrostatic-turbulence coagulation: An experimental and numerical investigation

The electrostatic precipitator(ESP) has low efficiency in removing sub-micron particles. Coagulation technology, as a fine particle pretreatment technology, uses an external effect to agglomerate and grow fine particles, increase the average particle size, and make it easier to remove by subsequent dust removal equipment. However, the coagulation efficiency of a single coagulation technology is limited. Aiming at the particle charging mechanism and coagulation mechanism in the electric/turbulent composite coagulation process of fine particles, this paper uses a combination of numerical simulation and experiment to study the effects of different structural parameters, discharge parameters and flue gas parameters on corona discharge and particle charge. On this basis, the coagulation characteristics of charged particles in the turbulent flow field are studied. The results show that, when the Angle between the tip of the arista electrode is 90°, the corona discharge effect is the best. With the increase of supply voltage and temperature, the charge of particles increases. When the applied positive voltage is 29 kV and negative voltage is −35 kV, the total coagulation coalescence efficiency of fine particles reaches the maximum. The coagulation efficiency increases with the increase of temperature, but decreases with the increase of inlet flow rate.

Thermal phenomena in electrohydrodynamic (EHD) drying

In this work, we explored the effect of AC corona discharge on water evaporation in a strong electric field by using a multipin-dielectric-plate EHD system. Our experiments demonstrated that the AC corona discharge could produce a significant amount of heat because of the Joule and dielectric heating of the dielectric barrier. When the electric field strength was below the ionization point and current density did not exceed 1 mA/m2, the heating was not substantial. At the initial stage of corona discharge with the current density below 10 mA/m2, the cooling effect of evaporation compensated the Joule heating of the dielectric barrier, keeping wet material surface below wet-bulb temperature. With a current density above 10 mA/m2, the AC heating effect became dominant. At 40 kV applied voltage and current density of 38 mA/m2, the temperature of the dielectric increased from 22 °C to 25 °C and the material surface reached wet-bulb temperature. A theoretical model of the relationship between material temperature, electric field strength, discharge current and drying rate in EHD drying was developed and experimentally verified.

Model for 400 kV Transmission Line Power Loss Assessment Using the PMU Measurements

This paper presents an advanced model for monitoring losses on a 400 kV over-head transmission line (OHL) that can be used for measured data verification and loss assessment. Technical losses are unavoidable physical effects of energy transmission and can be reduced to acceptable levels, with a major share of technical losses on transmission lines being Joule losses. However, at 400 kV voltage levels, the influence of the electrical corona discharge effect and current leakage can have significant impact on power loss. This is especially visible in poor weather conditions, such as the appearance of fog, rain and snow. Therefore, loss monitoring is incorporated into exiting business process to provide transmission system operators (TSO) with the measure of losses and the accurate characterization of measured data. This paper presents an advanced model for loss characterization and assessment that uses phasor measurement unit (PMU) measurements and combines them with end-customer measurements. PMU measurements from the algorithm of differential protection are used to detect differential currents and angles, and this paper proposes further usage of these data for determining the corona losses. The collected data are further processed and used to calculate the amount of corona losses and provide accurate loss assessment and estimation. In each step of the model, cross verification of the measured and calculated data is performed in order to finally provide more accurate loss assessment which is incorporated into the current data acquisition and monitoring systems.

An Undergraduate Experiment to Investigate Air Pollutants Created from Lightning

Chemistry of the environment has been a long-standing and important area of scientific research. Atmospheric chemistry is of particular interest in society due to the impact that rising levels of pollutants are having on the climate. It is well-known that combustion processes create CO and NOx, which leads to the creation of other pollutants, such as ozone and CO2. There are natural processes, such as lightning, that also create a significant amount of pollutant gases. The purpose of this guided and open inquiry laboratory experiment is to provide an opportunity for students to investigate how lightning may produce pollutant gases in the atmosphere. In the guided inquiry experiment, a sealed IR gas cell containing air is exposed to a spark or corona discharge created by an Oudin coil to mimic lightning. IR spectroscopy is used to monitor the reaction progress and identify new species made after exposure to the electrical discharge. Based on the results, students draw conclusions about what types of gases are created in the two different discharge processes and how lightning may contribute to atmospheric pollutants. Students move on to the open inquiry to further investigate aspects of atmospheric gases, where they develop their own hypothesis and methods based on one of the provided suggestions, such as the effect of spark and corona discharge on pure oxygen, nitrogen, or carbon dioxide gases, the kinetics of ozone creation and decay, and the temperature dependence of NO2 dimerization. Although designed for an honors general chemistry course, this experiment can be adapted for second-semester general chemistry, environmental chemistry, analytical, and physical chemistry laboratory courses. Results from these experiments are presented, and the relevant atmospheric chemical processes are discussed. The impact of this experiment on perceived gains in knowledge, the value of inclusion in the curriculum, and the design of the experiment were assessed, and the results are discussed.

Research on fuze microswitch based on corona discharge effect

Abnormal voltages such as electrostatic, constant current, and strong electromagnetic signals can erroneously trigger operation of MEMS pyrotechnics and control systems in a fuze, which may result in casualties. This study designs a solid-state micro-scale switch by combining the corona gas discharge theory of asymmetric electric fields and Peek’s Law. The MEMS switch can be transferred from “off” to “on” through the gas breakdown between the corona electrodes. In the model, one of the two electrodes is spherical and the other flat, so a non-uniform electric field is formed around the electrodes. The theoretical work is as follows. First, the relation among the radius of curvature of the spherical electrode, the discharge gap, and the air breakdown voltage is obtained; to meet the low voltage (30–60 V) required to drive the MEMS switch, the radius of curvature of the spherical electrode needs to be 10–50 μm and the discharge gap between the two electrodes needs to be 9–11 μm. Second, the optimal ratio ε is introduced to parameterize the model. Finally, the corona discharge structural parameters are determined by comparing the theoretical and electric field simulation results. The switch is then fabricated via MEMS processing. A hardware test platform is built and the performing chip tested. It is found that when the electrode gap is 9 μm, the electrostatic voltage is at least 37.3 V, with an error of 2.6% between the actual and theoretical air breakdown voltages. When the electrode gap is 11 μm, the electrostatic voltage is at least 42.3 V, with an error of 10.5% between the actual and theoretical air breakdown voltages. Both cases meet the design requirements.

Density enhancement of nano-sized and submicron-sized water droplets induced by charges released from corona discharge

Corona discharge is widely used as an ionization source in field experiments of weather modification induced by charged particles due to its high efficiency and economy. However, deficient research efforts have been devoted to the effects of corona discharge on the size distribution and evolution of droplets in the humid air. In this paper, the characteristic of water droplets spectrum evolution in humid air with unipolar corona discharge is studied by an electrical low pressure impactor (ELPI) experiment in a 96 m3 cloud chamber. Results show that nano-sized water droplets with diameters from 9 nm to 25 nm grow rapidly because of the inducement of charges released from corona discharge. Additionally, an increase in the concentration of submicron droplets appears at 20 min. To reveal the potential mechanism of the phenomena, the average charge values of charged droplets measured by ELPI are further analyzed. Meanwhile, the relationship between saturated vapor pressure over charged droplet’s surface and its radius is discussed by the modified Kelvin–Thomson equation. Results show that, for the density enhancement of nano-sized droplets, condensational growth induced by charges released from corona discharge dominates significantly. The subsequent increase in the density of submicron-sized droplets is regarded as the break-up of the micron-sized droplets, with the process of evaporation when droplets are approaching the Rayleigh limit in the sub-saturated environment. This research may bring some new perspectives to further study of weather modification and cloud-seeding induced by charged particles, such as by increasing condensed nuclei density, broadening cloud droplets spectrum, and suppressing the evaporation of cloud droplets, etc.