Corona Discharge System Research Articles

Experimental study on enhancing electrostatic charging of nonwoven filter media through novel electrode configurations

The COVID-19 pandemic has underscored the urgent need for efficient particle filtration to tackle public health challenges. This study compares the electrostatic charging capabilities of two types of electrodes: conventional Metal Lamellar Electrodes (MLE) and Modified Lamellar Plate Electrodes (MLPE) with PMMA insulation, in their role of charging nonwoven polypropylene filter media. Experimental analysis unequivocally demonstrates the superiority of MLPE in promoting effective electrostatic charge, as influenced by applied high voltage and inter-electrode distance, resulting in a significant enhancement in fine particle filtration. Numerical simulations of the electric field conducted using the COMSOL software and employing the Finite Element Method (FEM) validate these findings. FEM discretizes the domain into small finite elements and applies Laplace's equation in charge-free regions, providing a comprehensive understanding of the behavior of dual-electrode corona discharge systems. These simulations indicate higher field intensities for MLPE compared to MLE.By integrating experimental and numerical analyses, this study sheds light on the potential benefits of MLPE for air filtration systems, offering a noteworthy advancement in the control of airborne infections and reduction of environmental health risks. This research lays the groundwork for the development of more efficient and durable filtration systems, meeting the increasing demands for public health protection.The findings of this study suggest that the adoption of MLPE could significantly contribute to improving indoor air quality and mitigating the transmission of respiratory diseases. MLPE may also find utility in industrial filtration and air purification in sensitive work environments. Ultimately, this research sets the stage for the development of more efficient and sustainable filtration systems, addressing the growing needs for public health protection.

Combined control of PM and NOx emissions by corona discharge

This work investigates the potential of corona discharge to control particulate matter and NOx emissions from small-scale biomass combustion. The electrostatic precipitator (ESP) was designed and used to suppress emissions from a 15-kW heating unit. The ESP was operated at different power modes at both polarities and demonstrated the capability to reduce NOx emissions with a removal efficiency of 78 % while PM concentration was reduced to a magnitude of particle content in ambient air. The efficiency of ESP was evaluated considering the technological parameters, namely the reduced electric field, Nt-product, and specific input energy. The growth in NOx abatement was observed when the energy input exceeded 1 J/L for both polarities and Nt-product exceeded 4.5 × 108 s/cm3/1 × 109 s/cm3 for negative/positive corona. The results of this work may contribute to understanding the processes in corona discharge and optimising corona discharge systems for various applications.

TEM and zeta potential titration as suitable techniques for investigating the joining of modified ceramic surfaces

Transmission Electron Microscopy (TEM-EDS) and Zeta potential titration of ceramic surfaces allowed researchers to go inside their adhesion mechanism when joined with an adhesive. The case study concerned the plasma Corona treatment to improve the joint strength between SiC surfaces joined with an epoxy adhesive. The formidable mechanical and chemical properties inherent to silicon carbide pose challenges in applying conventional methods like mechanical machining and wet etching for surface texturing. Exploring alternative strategies, plasma Corona treatment which is an Atmospheric Pressure Plasmas (APPs) process emerges as a potential solution. The mechanism of chemical interaction and mechanical interlocking between plasma-treated surfaces and the epoxy adhesive used for the joining was never explored in detail and proven. The presence of layers with different crystallographic natures and chemical compositions was assessed by TEM-EDS: an amorphous silica layer was produced by the corona activation treatment and it created a mechanical anchoring system when penetrated by the adhesive. The zeta potential titration as a function of pH evidenced that untreated SiC had a surface with amphoteric functional groups, while the Corona treatment induced the formation of surface functional groups (OH) with a strong acidic behavior on SiC. The investigated epoxy adhesive exposed a prevalence of basic amino groups. Zeta potential titration curves highlighted the chemical interaction between the treated SiC surfaces and the epoxy adhesive: the large electrostatic attraction between the OH groups of the treated SiC and the amino groups of the epoxy adhesive had a role in the mechanical strength of the joining. TEM and Zeta potential titration can be proposed as suitable techniques to evaluate the effectiveness of the plasma corona discharge system in modifying the surface of SiC and to solidify its standing in comparison to other established surface modification techniques to improve SiC-based joints.

Removal of Mixed Volatile Organic Compounds of Benzene, Toluene, and Xylene in a Multistage Corona Discharge System under Excess Air

Removal of Mixed Volatile Organic Compounds of Benzene, Toluene, and Xylene in a Multistage Corona Discharge System under Excess Air

Trichel pulse characteristics and mechanism of negative corona discharge in sub-millimeter gaps

A negative corona discharge system of a needle-plate electrode suitable for sub-millimeter gaps is established to investigate Trichel pulse characteristics of negative corona discharge, in which an optical acquisition system is especially applied to timely observe a discharging corona. Electrostatics–hydrodynamics coupling simulations of air discharging in 100 μm-gaped needle-plate electrodes are performed to elucidate the micro-physical process of negative corona discharge. The impact ionization coefficient used for simulations and the experimentally recorded images of discharge corona are combined to characterize the active region of secondary electron emission. Dynamical distribution and transport of the charged particles are analyzed from multiphysics simulations to explain the microscopic mechanism for various stages of Trichel pulses. Even though the corona front near the plate electrode maintains a high rate of collision ionization and secondary electron excitation, the needle tip corona has not reached the threshold electric field of electron avalanche required for glow discharge, as manifested by discharge sawtooth waves comprised of corona and glow components. The amplitude and frequency of Trichel pulses increase, respectively, with impact ionization and secondary electron emission, which is evidently dependent on attachment coefficient and anion mobility. A higher attachment coefficient will lead to a significant reduction in amplitude of Trichel pulses. The present study provides a theoretical basis and experimental verification for micrometer discharges, which is the key point of insulation protections in microelectromechanical systems.

Efficacy of cold atmospheric plasma for inactivation of viruses on raspberries

In this study, the effectiveness of cold atmospheric plasma (CAP) in inactivating murine norovirus (MNV/human norovirus surrogate) and hepatitis A virus (HAV) on aerosol-inoculated dark red Willamette raspberries was explored. Pulsed positive corona discharge system fed by synthetic air was used for the production of CAP. Raspberries were treated for 1, 3, 5, 7, and 10 min at 25 W. Application of CAP enabled a 4 log10 infectivity reduction in <5 min for MNV and approximately 10 min for HAV (from starting level of 6.91 and 7.84 log10 PFU/mL, respectively). Viral genome copies reduction of 3.18 log10 for MNV and 4.32 for HAV were found from starting level of 5.76 and 6.47 log10 gc/μL, respectively. CAP treatment did not result in significant degradation of fruit color, an important quality attribute. The study demonstrated CAP as an efficient post-harvest decontamination method to reduce viral load in raspberries without significantly affecting its quality parameters. Industrial relevanceDue to the fast-processing paces required in the raspberry industry, it is difficult to assure the complete microbiological safety of this fruit. Cold atmospheric plasma is a practical, environmentally-friendly, non-thermal tool for the effective reduction of microbial pathogens. The model developed in this study demonstrated that CAP treatment of fresh raspberries not only inactivated hazardous enteric viruses in a short time (10 min) but also unaffected fruit color stability. The simplicity of described CAP design and low-cost inputs (air and electricity) enable the commercial application of inexpensive plasma chambers for continuous surface decontamination of large volumes of raspberries without bringing processing to a standstill.

Surface modification of SiC to improve joint strength via a Corona plasma treatment

The high mechanical and chemical properties of SiC make it difficult to texture and modify its surface using such conventional methods as mechanical machining and wet etching. Among possible alternative strategies, Atmospheric Pressure Plasmas (APPs) could be used, cutting cost and time, but much still has to be understood about their feasibility for the surface treatment of ceramic materials.In this work, the effectiveness of a commercial corona discharge system in modifying the surface of SiC has been evaluated, focusing on its positive effect on the joint strength of adhesively bonded plasma-treated SiC.The objective of the study has been to observe the surface changes, in terms of chemical composition and texture, that take place as a result of exposure to corona plasma and to compare the obtained results with previous studies on laser and low-pressure plasma textured SiC samples. These very first results, derived from characterization and mechanical testing, suggest that this approach could be a promising alternative.

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.

The enhanced aerosol deposition by bipolar corona discharge arrays

The corona discharges provide an efficient way to induce precipitation or eliminate fog by increasing ion density in the open air. In this paper, one bipolar corona discharge array (positive and negative high voltage coupled simultaneously) which can generate high densities of positive and negative ions is developed. The comparison between bipolar corona discharge array and unipolar corona discharge array (positive or negative coupled only) indicates that bipolar corona discharge array can generate ∼3 times higher ion density than unipolar corona discharge array. More charged aerosols are produced through collisions between ions and aerosols. The collision rate between aerosols is increased substantially by the attractive forces between positively and negatively charged aerosols. The deposition of aerosols induced by bipolar discharges is 25.7% higher than that of unipolar discharges at the humidity super-saturation condition. Therefore, the bipolar corona discharge system is a new option for the large scale ion sources used for artificial weather modification.

Investigation of polyelectrolyte multilayers deposited on corona charged composite polylactic acid / poly(ε-caprolactone) substrates

In the present study chitosan and casein polyelectrolyte multilayers (PEMs) deposited on composite polylactic acid (PDLA) / poly(ε-caprolactone) (PEC) substrates were investigated. The substrate’s morphology was investigated using polarized light microscopy and their degree of crystallization was studied by the application of differential scanning calorimetry. The substrates obtained were charged in a corona discharge system, consisting of a corona electrode (needle), a grounded plate electrode, and a metal grid placed between them. Positive or negative 5 kV voltage was applied to the corona electrode. 1 kV voltage of the same polarity as that of the corona electrode was applied to the grid. The dependences of the normalized surface potentials on the storage times of positively and negatively charged substrates were studied. Layer-by-layer (LbL) technique was used for multilayer deposition on the substrates. PEMs with different number of layers (4 or 8) were obtained. A model drug Benzydamine hydrochloride was loaded in the casein layers in order to evaluate the effect of the kind of substrate on the drug immobilization and release. A study of the drug release kinetics in saline buffer was carried out and the amount of the released drug was calculated spectrophotometrically. It was shown that the experimental results fit to the Peppas model with a very good level of correlation and the model parameters differ depending on the used substrate.

Effect of pH and ionic strength of chitosan/casein and casein/chitosan multilayers on curcumin release

In the present paper the effect of pH and ionic strength on the immobilization and release of curcumin from chitosan and casein polyelectrolyte multilayers (PEMs) was investigated. The investigated PEMs were deposited on polylactic acid (PDLA) substrates. The PLA substrates were charged in a corona discharge system, consisting of a corona electrode, a grounded plate electrode and a grid placed between them. The substrate was charged for 1 minute at room temperature. Positive or negative 5kV voltage was applied to the corona electrode and 1 kV voltage with the same polarity was applied to the grid. Chitosan solutions with different pH and ionic strength were prepared. Layer-by-Layer (LbL) deposition technique was used for the multilayer build-up. For the deposition process was ensured that the first deposited layer always possessed an opposite electric charge to that of the substrate. An investigation of the water uptake properties of the deposited PEM multilayers was carried out. Curcumin was immobilized in the resulting casein layers. The release of the immobilized curcumin from the multilayers in saline buffer was investigated and the effects of the different pH and ionic strengths of the chitosan solutions were determined.

Acinetobacter Baumannii Sterilization Using DC Corona Discharge

In this work, a corona discharge system with array electrode was built for the rapid sterilization of a resistant pathogen (Acinetobacter baumannii). The electrical parameters, discharge pattern, ozone generation, and optic emission spectra were used to characterize the corona plasma. The discharge current and power of positive corona were larger than those of negative at the same applied voltage. The G-value of ozone generation of positive corona was about 7.31 times larger than that of negative corona, suggesting that the positive corona has higher energy efficiency. The {A}. baumannii sterilization efficiency of corona plasma was much higher than that of using ozone (at the same ozone concentration level). As for negative corona, 99.99% A. baumannii sterilization efficiency was achieved within 9-min treatment with 50-ppm ozone produced. Moreover, the A. baumannii sterilization efficiency of positive corona was higher than that of negative corona at the same applied voltage or discharge power, confirming that the energy efficiency of sterilization of positive corona was higher than that of negative corona. The optic emission spectra suggested that active species such as excited molecules, ions, and radicals were generated in the corona discharge. The as-produced active species played important roles in the sterilization process.

The Effect of Corona Discharges on Droplets Settlement

To increase the ion density by corona discharge is an efficient way to generate charged nucleus from atmospheric aerosols and induce precipitation or eliminate fog. Here, we compare the brightness of discharge and optical emission spectrum (OES) of positive and negative corona discharges, and find the discharge intensity of the negative corona discharge is stronger than positive corona discharge at the same applied voltage. The combination of aerosols and more ions generated by negative corona discharges can produce numerous charged nucleus, which eventually generates large droplets and enhance precipitation through the short-range attractive force between charged nucleus and aerosols. The excessive condensation of water molecules on the negative electrode should be avoided for the application of large corona discharge systems in the mist-shrouded high mountains or airport.

Application of piezoelectric electrets to an energy-harvesting system

We developed a prototype system with a simple structure for energy-harvesting as humans walk in their daily life, using piezoelectric electrets as piezoelectric-power-generating elements. We prepared a porous poly(tetrafluoroethylene) (p-PTFE) film with a thickness of 12 μm and an average pore size of 0.7 μm sandwiched by two films of tetrafluoroethylene–hexafluoropropylene copolymer (FEP) with a thickness of 6 μm (FEP/p-PTFE/FEP film) as an electret film used for the energy-harvesting device. A corona discharge system used to fabricate an FEP/p-PTFE/FEP film with an area of 20 × 20 cm2 that generates piezoelectricity (electret FEP/p-PTFE/FEP film). The electret FEP/p-PTFE/FEP film had a piezoelectric constant d33 of more than 100 pC/N. Then, we fabricated a multilayer film by stacking the metal foil and the electret FEP/p-PTFE/FEP film without forming wrinkles or streaks. The voltage, current, and power generated by the electret FEP/p-PTFE/FEP multilayer film during an exercise involving a research subject repeatedly stepping on the film placed in the floor were evaluated. The maximum instantaneous generated power was about 4500 μW each time the subject stamped up and down. The energy consumed in transmitting an 8-byte signal using a Bluetooth Low Energy (BLE) device is known to be about 600 μW. Considering the electricity consumption of BLE devices, the above result strongly indicates that the power generated by the electret FEP/p-PTFE/FEP multilayer film has great potential for use in BLE devices.

Influence of Output Parameters of a High Voltage on the Technological Characteristics of Electron-Ion Devices Technologies

The article considers parameters of the influence of a high voltage source (HVS), as a form of the output voltage curve and its influence on the technological parameters of the electron-ion technology (EIT) devices for various purposes, the HVS schematic solutions and their classification. A equivalent circuit a single-zone electrostatic precipitator is developed, differing from the existing ones in that the differential capacitance is moved beyond the key VD, because the volume charge can be neglected until the moment of ignition of the corona discharge when considering the corona-discharge system, i.e. for simplicity, the condition is assumed that volumetric charges are created only by corona discharge. Based on this scheme, an equivalent electrical equivalent circuit for a two-zone electrostatic precipitator was constructed. The analytical expression for calculating the electrical constructive capacity of the most commonly used in the electrostatic precipitator corona-discharge system “a number of wires - a plane,” taking into account the additional electric capacity. The article presents the results of the investigation of the effect of the frequency of the output voltage of the HVS and the additional capacitance of the capacitor bank on the volt-ampere characteristic of the corona-discharge system of the electrostatic precipitator-ozonizer. The analytical expression is shown in general form, describing the volt-ampere characteristic of the electrostatic precipitator, taking into account the shape of the HVS output voltage curve. An analytical expression for determining the ozone concentration at the output of the EIT devices in the general case is also shown.

Numerical investigation of water surface deformation due to corona discharge

A two-phase electrohydrodynamic flow in a corona discharge system of a sharp needle and a water electrode is studied considering free interface deformation. The governing equations were solved using finite volume method implemented in a developed solver using the OpenFOAM platform. Recommendations are given about selection of equivalent electrical properties of water. For a constant electrode-water gap, a 60% increase in the applied voltage results in a 90% enhancement of maximum downward air velocity. Interface deformation depth could reach 2 mm (20% of initial water layer depth), revealing that consideration of deformation in a shallow water layer is very important.

Insulating chitosan/casein multilayers on corona charged polylactic acid substrates

The influence of the structure and physico-chemical properties of chitosan/casein multilayer films on their potential use for drug delivery systems was investigated. The multilayer films were prepared using layer-by-layer self-assembly, whereby chitosan and casein were deposited onto poly(lactic acid) substrates pretreated with either a positive or a negative corona. The corona discharge system consisted of a corona electrode, a grounded plate and a grid. The deposition was studied by ATR FT-IR, AFM, and surface energy measurements. ATR FT-IR spectra proved the formation of polyelectrolyte chitosan — casein complexes. The increasing content of chitosan and casein with increasing number of bilayers was further confirmed by XPS analysis. The surface topography was examined by AFM and the average roughness was evaluated. A comparative analysis of the experimental results was performed and the most appropriate substrate corona treatment for the irreversible binding of the chitosan/casein polyelectrolytes was determined.

Greener corona discharge for enhanced wind generation with a simple dip-coated carbon nanotube decoration

Corona discharge-induced wind (CDIW) has been widely utilized in production lines in the food and semiconductor industries and in indoor devices such as electrostatic precipitators. Some ozone is inevitably emitted, posing serious health risks to respiratory system and lung function of a human being. In this work, a greener corona discharge with enhanced wind generation for a needle-to-cylinder discharge structure is demonstrated using a simple dip-coating method to attach carbon nanotubes (CNTs) to the discharge electrode of a stainless steel needle. Compared with a conventional discharge electrode without CNT decoration, the velocity of the CDIW is greatly enhanced, the onset voltage is lowered, the energy conversion efficiency is greatly improved and the concentration of generated ozone is much reduced, making this easy method of CNT decoration a promising candidate for greener corona discharge systems. In addition, several impact factors for improved performance are discussed mathematically and phenomenologically, providing an insight into the corona discharge and wind generation.

Numerical simulation and experiments on mono-polar negative corona discharge applied in nanocomposites

The corona discharge techniques, which are employed to orient dipoles and built up charges inside functional polymers, can develop important commercial applications of electroactive polymers (EAPs) and electrets for energy storage devices, air filters, electroacoustic and electromechanical transducers. We propose hereby an elective hybrid approach to the point-plane corona modeling in order to obtain more accurate electron flow in unipolar corona discharge system. A coupled system of partial differential equations (PDEs) w.r.t. Navier-stokes equations and hydrodynamic drift diffusion equations described the nature of photo-ionization, where the secondary avalanche in the discharge process was demonstrated. The simulation was verified by comparison with Surface Potential (SP) measurement of the nano-composites after corona polarization. Consequently, the spacial electric potential distribution and initial surface potential could be obtained by the means of finite elements method (FEM), which provided a good numerical approach for the experimental data of electrostatic surface potential. In addition, the influence of nano particle on the charge retain ability of the insulating polymers was also investigated, which could be a guideline for designing an effective poling method on the functional polymers applied in electrical energy storage devices sensors, actuators and transducer etc.

Effect of immobilization conditions on the properties of β-galactosidase immobilized in xanthan/chitosan multilayers

The effect of lactose concentration on the activity of the immobilised enzyme β-galactosidase from Aspergillus niger has been evaluated, considering future applications for the production of galactooligosaccahrides with prebiotic potential. The following enzyme was immobilized in xanthan and chitosan polyelectrolyte multilayers (PEMs) deposited by dip coating method on polylactic acid positively corona charged pads. The pads were charged in a corona discharge system, consisting of a corona electrode (needle), a grounded plate, and a metal grid placed between them. Positive 5 kV voltage was applied to the corona electrode. 1 kV voltage of the same polarity as that of the corona electrode was applied to the grid. The chitosan layers were crosslinked with sodium tripolyphosphate (Na-TPP). The enzyme showed a temperature optimum at 50 °C and a pH optimum at 5.0. The immobilization was carried out over the different adsorption time and optimum conditions were determined. These results give insights for further optimization of transgalactosydase reactions in order to produce galactooligosaccharides with specific structure and having pronounced better prebiotic properties. For the determination of the surface morphology of the investigated samples an atomic force microscope was used and root mean square roughness was obtained.