High-voltage Discharge Research Articles

Phosphorylation of Maize Starch Enhanced with High-Voltage Electrical Discharge (HVED) Instead of Thermal Treatment.

The aim of this research was to explore the use of a high-voltage electrical treatment (HVED) as a substitute for heating during the phosphorylation of maize starch. Starch was treated with HVED, phosphorylated with Na2HPO4 or Na5P3O10 with and without thermal treatment and phosphorylated in combination with HVED prior to and after the chemical modification. When starch was phosphorylated with Na2HPO4, HVED was more efficient in catalyzing reaction (3.89 mg P/kg for 30 min HVED in relation to 0.43 mg P/kg for thermal treatment), whereas with Na5P3O10 similar P content was achieved as with thermal treatment (0.76 P/kg for 30 min HVED in relation to 0.86 mg P/kg). The order of HVED and chemical reactions did not have a marked effect on phosphorous content. In combination with Na2HPO4, HVED pre-treatment had a more pronounced effect on the solubility and water absorption, whereas post-treatment was favoured with Na5P3O10. Mean diameter was increased by all treatments, where HVED had a marked effect. Enthalpy of gelatinization ranged from 11.76 J/g for starch treated with Na5P3O10 and 10 min-HVED to 13.58 J/g for Na5P3O10 treated sample. G′ and G″ increased after both thermally and HVED enhanced phosphorylations, with a slightly more pronounced effect of the HVED.

Experimental study of atmospheric pressure single-pulse nanosecond discharge in pin-to-pin configuration

We present an experimental study of nanosecond high-voltage discharges in a pin-to-pin electrode configuration at atmospheric conditions operating in a single-pulse mode (no memory effects). Discharge parameters were measured using microwave Rayleigh scattering, laser Rayleigh scattering, optical emission spectroscopy enhanced with a nanosecond probing pulse, and fast photography. Spark and corona discharge regimes were studied for electrode gap sizes of 2–10 mm and a discharge pulse duration of 90 ns. The spark regime was observed for gaps <6 mm using discharge pulse energies of 0.6–1 mJ per mm of the gap length. Higher electron number densities, total electron number per gap length, discharge currents, and gas temperatures were observed for smaller electrode gaps and larger pulse energies, reaching maximal values of about 7.5 × 1015 cm−3, 3.5 × 1011 electrons/mm, 22 A, and 4000 K (at 10 μs after the discharge), respectively, for a 2 mm gap and 1 mJ/mm discharge pulse energy. An initial breakdown was followed by a secondary breakdown occurring about 30–70 ns later and was associated with ignition of a cathode spot and transition to a cathodic arc. A majority of the discharge pulse energy was deposited into the gas before the secondary breakdown (85%–89%). The electron number density after the ns-discharge pulse decayed with a characteristic time scale of 150 ns governed by dissociative recombination and electron attachment to oxygen mechanisms. For the corona regime, substantially lower pulse energies (∼0.1 mJ/mm), peak conduction current (1–2 A), electron numbers (3–5 × 1010 electrons per mm), and gas temperatures (360 K) were observed.

Transport Mechanism of Enhanced Performance in an Amorphous/Monoclinic Mixed-Phase Ga2O3 Solar-Blind Deep Ultraviolet Photodetector

Recently, as an emerging material, ultrawide bandgap Ga2O3 has been investigated extensively in solar-blind deep-ultraviolet (DUV) photodetectors (PDs). High sensitivity and signal-to-noise ratio of PDs are essential for the detection of solar-blind DUV signals; however, such factors are often not mutually compatible. In the present study, an amorphous/monoclinic homogeneous mixed-phase structure was demonstrated to be significantly beneficial in enhancing the comprehensive performance of Ga2O3 solar-blind DUV PDs, especially with respect to sensitivity and the signal-to-noise ratio. Further experimental and theoretical findings provide insights on the transport mechanism of enhanced performance in the mixed-phase Ga2O3 solar-blind DUV PD. For effectively separating the photogenerated carriers, a type-II band alignment between amorphous and crystalline Ga2O3 can be exploited. Furthermore, the change of the barrier height of the mixed-phase interface also has a significant impact on the transport properties of the mixed-phase Ga2O3 PD. Additionally, the potential applications of mixed-phase Ga2O3 PD in high-voltage corona discharge were explored, and clear and stable corona discharge signals were obtained. The results of the present study may promote understanding of DUV photoelectronic devices with various mixed-phase Ga2O3 materials and provide an efficient approach for promoting comprehensive performance in future solar-blind detection applications.

Qualification of the TIC conductor for the in-vessel coils in ASDEX upgrade

ASDEX Upgrade will be evolved by installing a new upper divertor with two in-vessel coils allowing the investigation of alternative magnetic configurations. The in-vessel coils will be bended inside the torus. The co-axial conductor consists of a Tefzel insulated water cooled copper core embedded into a stainless steel protection shield. To test the conductor concept and to qualify the electrical and thermal properties of the Tefzel insulated conductor (TIC), prototype conductors of 3 and 8 m length were used. These conductors undergo electrical and thermal tests accompanied by FEM calculations. The electrical tests include high voltage and partial discharge tests. For thermo-mechanical tests the prototype conductors were fed with up to 13 kA for 5 s. During the test the copper conductor was heated up by 60 K. The Tefzel cladding and the protection tube are warmed up with a delay given by the thermal heat conduction and capacity. The thermo-mechanical behaviour of the TIC during the heating and cooling phase could be confirmed by the FEM-models. As part of the qualification, the conductor was thermally overloaded by a factor of 3, without degradation.The paper presents the electrical and thermal tests as well as the results of the related FEM calculations.

New Express Method of Non-Destructive Controlling of the Porous Structure of Asymmetric Membranes

An important practical and fundamental problem in the production of porous polymer membranes is the study of the porous structure and the detection of "defects" or large pores in the area of ​​the membrane. Known porosimetry methods cannot solve this problem. This work proposes a new non-destructive express method for studying the porous structure of asymmetric polymer membranes in high-intensity electric fields. This method can be successfully implemented on both flat sheet and hollow fiber membranes with a known porous structure. On the example of hollow fiber membranes made of polyacrylonitrile and polysulfone an assessment of the chemical structure effect of the membrane material on the high-voltage discharge currents in a highly inhomogeneous electric field through hollow fiber membranes with a given pore size was made. Under normal conditions and an average intensity of an inhomogeneous electric field E = 5 kV/cm, the results obtained allow us to conclude about a certain practical potential of the developed express method.

Synthesis of titanium dioxide nanoparticle by means of discharge plasma over an aqueous solution under high-pressure gas environment

In this study, the utilization of an electric field generated by the high voltage discharge plasma over a liquid water surface containing glycine compound to synthesize titanium dioxide (TiO2) nanoparticles was demonstrated. The experiments were conducted in a batch-type system with applied voltages ranging from 18.6 − 23.4 kV under various pressurized gases at room temperature. The results indicated that the applied voltages, applied pulse numbers, and pulsed repetition rates had a significant influence on the decomposition reaction of glycine compounds and titanium rod electrode erosion. The ultraviolet − visible (UV − vis) spectra showed that titanium dioxide nanoparticles could be observed in each solution product, and most of them were brookite-type structures. According to the HRTEM images, TiC was also produced as a nanoparticle product. Based on the experimental results, this process is applicable and could result in advanced metal-based nanoparticle synthesis technology.

Recovery of Silver From Waste Crystalline Silicon Photovoltaic Cells by Wire Explosion

To establish an effective recycling process for waste photovoltaic (PV) panels, a wire explosion method using a high-voltage pulsed discharge was used to separate silver (Ag) from an ethylene-vinyl acetate (EVA) copolymer resin sheet. The cell used in the experiment was prepared by removing the aluminum frame and the glass cover plate from the waste PV panel. Ag particle recovery experiments were conducted in water. Electrodes were installed on each copper busbar of the cell. A 40.8- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{F}$ </tex-math></inline-formula> capacitor was charged to a maximum of 15.0 kV and then discharged using a mechanical switch. Wire explosions occurred through the 102 Ag wires connected in parallel between the busbars. The particles recovered after the wire explosion were sieved and then characterized by inductively coupled plasma atomic emission spectroscopy and X-ray fluorescence. Scanning electron microscope and energy dispersive spectroscopy analysis revealed that the majority of separated Ag particles were attached to the silicon particles. The Ag recovery rate was 69% at a charging voltage of 15.0 kV. Higher discharge energies increased the Ag recovery rate; however, the recovered particles had lower Ag concentration. A circuit simulation was performed to analyze the current waveforms and calculate the current distribution. Shadowgraph imaging was used to observe the separation process of Ag particles and the EVA layer by wire explosion during pulse discharge. The shadowgraph images indicated that plasma generation and gas expansion have important roles in the separation process.

Explosive Stamping Goals and Objectives Historical Transformation (to the 70th Anniversary of KhAI Scientific School)

The sequence and development the impulse stamping goals and production objectives are described. A new idea development from a primitive “field” technology to modern integrated technologies that allow obtaining unique quality indicators of manufactured parts is shown. The article covers the description of pulse technologies for sheet stamping by the blasting agents explosion and an underwater high-voltage discharge.

Impact of High-Voltage Discharge After-Treatment Technology on Diesel Engine Particulate Matter Composition and Gaseous Emissions.

Diesel particulate matter (DPM) and oxides of nitrogen (NOx) are the emissions from diesel engines (compression ignition engines) of the most concern and are currently strictly regulated. In this work, we present an alternative diesel emission control technique to assist in further emission reduction. An experiment-oriented study on diesel engine emission abatement using low-power, low-frequency, high-voltage discharge (HVD) treatment was carried out in a laboratory-scale reactor with whole diesel engine exhaust gas. A dielectric barrier discharge (DBD) reactor was used in direct contact with diesel exhaust gas at atmospheric temperature with an input energy density between 200 and 400 J/L. An investigation of the direct effect of the high-voltage discharge reactor on the diesel exhaust gas treatment was carried out to characterize both diesel particle and gaseous emissions. The proposed HVD system demonstrated up to 95% particulate matter reduction by mass or 64% reduction by number, and 63% reduction of the diesel soot particle geometrical mean diameter by HVD-generated O3 oxidation. Thermogravimetric analysis revealed the significant change in the diesel soot compositions and oxidation characteristics. HVD-treated particulate matter demonstrated a lower reactivity in comparison to untreated soot. Gas composition analysis indicated the generation of free radicals (e, O, OH, O3, and N) by the HVD system, as mainly indicated by the increase of the NO2/NO ratio and concentration of CO and O2. The pattern of CO2 reduction while CO and O2 increased indicated the dissociation of CO2 by HVD. Free radicals generated by HVD directly affected DeNO, DeNOx, NO2/NO ratio, and CO and CO2 selectivities.

A new direction for obtaining water and hypochlorite solution to fight patho-gens and viruses

The article presents the design of the proposed installation for the treatment and disinfection of various objects, as well as the results of experimental studies on the feasibility of exposure to high-voltage pulsed discharge on water and hypochlorite. Experiments have shown that water and hypochlorite solution subjected to electrohydraulic treatment can effectively fight against bacteria, fungi and viruses. The use of electric pulse technology, due to which various forms of oxygen, hydrogen and hypochlorous acid appear that can damage microbial cells, makes it possible to increase the effectiveness of disinfection of any objects at lower energy costs.

HIGH VOLTAGE BEAM DISCHARGE IN NITROGEN WITH FAST NEUTRAL ATOM REFLECTION FROM TANTALUM CATHODE

The kinetic simulation of high-voltage beam discharge at low pressure of nitrogen is fulfilled. The characteristics of particle flows to the tantalum cathode and back reflection of fast nitrogen atoms are calculated. The reflection coefficient equals tens of percents at voltages up to 100 kV. The generation of fast nitrogen atoms may be used for metals and dielectrics nitriding with implantation effect.

Separation of cathode particles and aluminum current foil in lithium-ion battery by high-voltage pulsed discharge Part II: Prospective life cycle assessment based on experimental data.

This series of papers addresses the recycling of cathode particles and aluminum (Al) foil from positive electrode sheet (PE sheet) dismantled from spent lithium-ion batteries (LIBs) by applying a high-voltage pulsed discharge. As concluded in Part I of the series (Tokoro et al., 2021), cathode particles and Al foil were separated in water based on a single pulsed power application. This separation of LIB components by pulsed discharge was examined by means of prospective life cycle assessment and is expected to have applications in LIB reuse and recycling. The indicators selected were life cycle greenhouse gas (LC-GHG) emissions and life cycle resource consumption potential (LC-RCP). We first completed supplementary experiments to collect redundant data under several scale-up circumstances, and then attempted to quantify the uncertainties from scaling up and progress made in battery technology. When the batch scale of pulsed discharge separation is sufficiently large, the recovery of cathode particles and Al foil from PE sheet by pulsed discharge can reduce both LC-GHG and LC-RCP, in contrast to conventional recycling with roasting processes. Due to technology developments in LIB cathodes, the reuse of positive electrode active materials (PEAM) does not always have lower environmental impacts than the recycling of the raw materials of PEAM in the manufacturing of new LIB cathodes. This study achieved a proof of concept for resource consumption reduction induced by cathode utilization, considering LC-GHG and LC-RCP, by applying high-voltage pulsed discharge separation.

A novel technology of high-voltage pulse discharge for comminution of galena ore

An innovative technology of high-voltage pulse discharge (HVPD) was proposed to investigate the comminution characteristics of galena ore. The optimal experiment parameters were determined as follows: spark gap spacing of 25 mm, pulse number of 120, and voltage of 25 kV. The mass fraction with size <0.074 mm in ground products was improved by the HVPD. Meanwhile, the relative grindability declined with the increase of the grinding time, which indicated that the superiority of HVPD was weakened. The ground products of HVPD were distributed more homogeneously than those of mechanical crushing. The liberation of breakage products was improved by 24.57% via the HVPD. Moreover, the Brunauer–Emmett–Teller (BET) specific surface area, pore volume, and average pore size were increased via the HVPD. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses suggested that obvious grain-boundary breakage and several stomatal traces were observed in the HVPD products.

Thermal Characteristics of All-Film Pulsed Capacitors in Application of Repetitive Pulse Discharge

Temperature rise is one of the major causes for all-film pulsed capacitor (AFPC) failure under high repetitive high-voltage pulse discharge operations. To study the thermal characteristics, a thermal simulation model is established. In this model, the actual operation conditions of capacitors are applied. The practical internal structure and heat production transfer of the AFPC are considered. The validation of the model is proved by the simulation and the experimental results. Based on the finite element method (FEM), the overall temperature field distribution of the AFPC, and the mathematical model between discharge voltage, frequency and temperature rise can be calculated. This model is capable of evaluating the temperature rise characteristics of an AFPC in repetitive high-voltage pulse discharge and can provide certain instructive suggestions for the safe operation and the optimal design of AFPC.

Remote triggering of air-gap discharge by a femtosecond laser filament and postfilament at distances up to 80 m

We experimentally observed laser-induced remote high-voltage discharge triggering between two needle electrodes with half-a-cm spacing. The discharge was initiated by a 744-nm, 90-fs, 6-mJ laser pulse undergoing filamentation in air. For the direct voltage below the self-breakdown threshold, triggering of air-gap discharge was synchronized with a 10-Hz laser repetition rate and occurred between 40 and 80 m of the propagation path. No discharge guiding was observed. The experimentally registered and simulated remote triggering probability was above 80% in the range of 45–60 m from laser output and about 50% in the range of 60–80 m. The probability decreases as the postfilament hot spot diverges with a simultaneous increase in stochastic laser beam wandering.

Application of a Single-phase Five-level Converter for High-voltage and Partial Discharge Tests on Potential Transformers

Application of a Single-phase Five-level Converter for High-voltage and Partial Discharge Tests on Potential Transformers

Cylindrical Vector Beam for Vector Magnetic Field Sensing Based on Magnetic Fluid

Based on the unique polarization characteristic of the cylindrical vector beam, a new-type vector magnetic field sensing technique is proposed. As the cylindrical vector beam passes through a magnetic fluid film, a polarization analyzer is used to detect the polarization state change of the output light after passing through a slit. Based on the birefringence effect, the direction of the magnetic field can be resolved by the direction of the maximum ellipticity, while the magnetic field strength can be obtained by the change of the maximum ellipticity. Both of the magnetic field strength and direction in the X-Y plane could be measured simultaneously. The experimental results show that the direction error is less than 2°, the strength error is less than 10 Gs, and the sensitivity of the strength of magnetic field is 0.12 °/Gs. Therefore, the proposed technique would be promising for two-dimensional magnetic field detection and safety detection, such as high-voltage discharge magnetic field detection.

Full-needle geometry: application in a high-voltage corona discharge model with large-scale space

Corona discharge is widely used in many fields, such as drying, temperature control, propulsion, combustion-supporting, etc. In order to solve the problem of the small calculation space of the existing needle electrode discharge model, in the previous work, we proposed a hybrid method based on the combination of hydrodynamic fluid model and ion flow transport equations to study the corona discharge characteristics of the needle electrode in a large-scale space. However, as the voltage increases, the discharge source of the needle electrode changes from a single source (needle tip) to multiple sources (needle tip and needle body). The half-needle geometry used in the hydrodynamic fluid model ignores the needle body, causing the hybrid model to fail to converge under high voltage conditions. Therefore, we propose a full-needle geometry to replace the half-needle geometry in the hydrodynamic fluid model to expand the voltage range of the hybrid model. The calculation results show that the full-needle geometry can converge to the high-voltage hybrid model. The upper limit of the calculated voltage is increased from 20.9 kV to 41 kV, and the research voltage range has been increased by nearly two times. In addition, a needle-ball electrode device was adopted to verify the accuracy of the model. This research not only expands the calculation voltage range of the hybrid model, but also implies the potential of the hybrid model to be used in the multi-source discharge model.

Modeling Nanosecond-Pulsed Spark Discharge and Flame Kernel Evolution

Abstract Dilute combustion, either using exhaust gas recirculation or with excess air, is considered a promising strategy to improve the thermal efficiency of internal combustion engines. However, the dilute air-fuel mixture, especially under intensified turbulence and high-pressure conditions, poses significant challenges for ignitability and combustion stability, which may limit the attainable efficiency benefits. In-depth knowledge of the flame kernel evolution to stabilize ignition and combustion in a challenging environment is crucial for effective engine development and optimization. To date, a comprehensive understanding of ignition processes that result in the development of fully predictive ignition models usable by the automotive industry does not yet exist. Spark-ignition consists of a wide range of physics that includes electrical discharge, plasma evolution, joule-heating of gas, and flame kernel initiation and growth into a self-sustainable flame. In this study, an advanced approach is proposed to model spark-ignition energy deposition and flame kernel growth. To decouple the flame kernel growth from the electrical discharge, a nanosecond-pulsed high-voltage discharge is used to trigger spark-ignition in an optically accessible small ignition test vessel with a quiescent mixture of air and methane. Initial conditions for the flame kernel, including its thermodynamic state and species composition, are derived from a plasma-chemical equilibrium calculation. The geometric shape and dimension of the kernel are characterized using a multi-dimensional thermal plasma solver. The proposed modeling approach is evaluated using a high-fidelity computational fluid dynamics procedure to compare the simulated flame kernel evolution against flame boundaries from companion Schlieren images.

Pulsed Discharge Plasma in High-Pressure Environment for Water Pollutant Degradation and Nanoparticle Synthesis

The application of high-voltage discharge plasma for water pollutant decomposition and the synthesis of nanoparticles under a high-pressure argon gas environment (~4 MPa) was demonstrated. The experiments were carried out in a batch-type system at room temperature with a pulsed DC power supply (15.4 to 18.6 kV) as a discharge plasma source. The results showed that the electrode materials, the pulsed repetition rates, the applied number of pulses, and the applied voltages had a significant effect on the degradation reactions of organic compounds. Furthermore, carbon solid materials from glycine decomposition were generated during the high-voltage discharge plasma treatment under high-pressure conditions, while Raman spectra and the HRTEM images indicated that titanium dioxide with a brookite structure and titanium carbide nanoparticles were also formed under these conditions. It was concluded that this process is applicable in practice and may lead to advanced organic compound decomposition and metal-based nanoparticle synthesis technologies.