Transient Discharge Research Articles

The influence of electric circuit parameters on NOx generation by transient spark discharge

Nitrogen fixation, production of NO and NO2 from N2 and O2 in air, has been investigated with transient spark self-pulsing DC discharges. NO production is boosted by the addition of capacitors and an inductor to the electrical circuit which drives the discharge. The quantity of NO produced per joule of electrical input energy is doubled, though the quantity of NO2 produced drops. The yield of NO is also increased because the modified circuit enables higher discharge currents to be used. NO concentrations as high as 2000 ppm were obtained with input energy densities of around 300 J per liter of input gas, whilst NO2 concentrations were around 150 ppm. This simple modification of the driving circuit may have potential for optimizing the plasma chemistry with other input gas mixtures and for scaling up nitrogen fixation from air.

Temporal evolution characteristics of the excited species in a pulsed needle-water discharge: effect of voltage and frequency

Transient spark discharge has broad application prospects due to its excellent performance in generating reactive oxygen species, but there is currently limited research on transient excited species, which are important precursors for the formation of these species. In this paper, we obtained a transient spark discharge with a needle-water electrode configuration, and then developed an optical detection system based on a photomultiplier to measure the temporal evolution of four excited species. It is observed that N2 (C) is produced mainly in the streamer phase, while H (n = 3), O (3p), and OH (A) are produced mainly in the spark phase, which results from the difference in threshold energy and pathway for generating different species. To investigate the variation mechanism of peak time and peak intensity during the evolution process, the gas temperature T g, electron density n e, and electron excitation temperature T exc were calculated by using the optical emission spectroscopy under different pulse voltage and pulse repetition frequency conditions. The results indicate that the discharge conditions influence the physical parameters of T g, n e, and T exc as well as the output voltage waveform, and then they jointly determine the evolution characteristics of excited species. These insights contribute to understanding the characteristics of excited species which affect the formation of reactive species by influencing the chemical chain reaction in the transient spark discharge.

Transient discharge performance of high-temperature latent storage system integrated with supercritical CO2 Brayton cycle: A combined analytical and numerical study

In this article, a generalized robust analytical model is developed to evaluate the discharge performance of a high-temperature latent heat storage (HT-LHS) system coupled with the supercritical CO2 (sCO2) recompression Brayton cycle. During discharging, the release of thermal energy from metallic phase change medium (PCM) based HT-LHS is the input to the sCO2 cycle. The thermal efficiency of sCO2 recompression cycle is observed to be significantly larger (> 50 %) than the conventional Rankine cycle at higher operating temperature (700–750 °C). The thermal efficiency increases with turbine input temperature for all split ratios and is maximized at a split ratio of 0.75. Turbine inlet pressure and air temperature are identified as the most and least sensitive parameters to affect the cycle efficiency. The average effectiveness of the LHS considering only conduction is compared with combined conduction and convection in PCM during discharging. The combined effect increases the average effectiveness of LHS maximum by 26.8 %. The analytical model is developed by eliminating two traditional assumptions considered so far in deriving analytical model. The derived dimensionless governing equations are solved using a Python routine to obtain the discharge performance (ε = 0.61,Q = 797.48 kW, ro = 138.61 mm) of LHS.

Identification of corona discharges based on wavelet scalogram images with deep convolutional neural networks

This paper presents a new wavelet-based approach to automate the identification of positive and negative DC corona discharge current pulses. Two electrode systems with variable gap spacings formed corona discharges, and two commercial sensors (a high-frequency current transformer (HFCT) and a shunt resistor) captured transient corona discharge currents. The proposed method employs a continuous wavelet transform to generate time-frequency representations of corona discharge pulse currents, called scalogram images. The effects of sampling interval, data acquisition time, data shifting, and external noise components in the signals on the scalogram images were examined. The well-known pre-trained convolutional neural network models, AlexNet, MobileNet, and ShuffleNet, were tailored, and their ensemble structure was generated to discriminate scalogram images of discharge pulses. A framework was constructed to increase the generalization ability of the study. The results demonstrate that the scalogram images are robust candidates for corona discharge identification.

Optimizing energy storage properties under moderate electric fields in Na0.5Bi0.5TiO3-based ceramics via configuration entropy modulation

Lead-free ceramic capacitors with large energy storage density and efficiency synchronously under moderate electric fields is a challenging. In this work, a pathway of configuration entropy modulation (ΔSconfig) overcomes this challenge. The (1-x)(Na0.5Bi0.47La0.03)0.94Ba0.06TiO3-xSr(Sn0.2Ti0.2Al0.2Ta0.2Hf0.2)O3 ceramics were successfully synthesized. With the system ΔSconfig increases from 0.98 R to 1.79 R. The 0.85 NBLBT-0.15 SSTATH ceramic obtains a large recoverable energy density (Wrec = 4.28J/cm3) and ultra-high efficiency (η = 92.6%) under 260 kV/cm. The implementation of prominent energy storage performance can be attributed to the refinement of grain and domain size, and the increase of band gap and activation energy, which caused by the increase in ΔSconfig. More critically, the same composition also possesses great frequency (1–100 Hz) and thermal (20–140 °C) stability of energy storage performance as well as the high power density of PD ∼ 36.19 MW/cm3 and transient discharge rate of t0.9–44 ns at 120 kV/cm. This work shows that the regulation of ΔSconfig is an effective strategy to achieve outstanding energy storage properties under moderate electric fields.

Nonlinear charge-voltage relationships in electric double layer capacitors performing under constant load resistance

Nonlinear charge-voltage relationships in electrochemical double layer capacitors (EDLCs) performing under constant load resistance, are analyzed. Three commercial EDLCs with nominal capacitances in the range from 0.1 to 1 F and maximum voltage 5 V, are selected. The time evolution of the electric current obtained during the discharge through a resistor of an EDLC, which is initially charged at a constant potential, is gathered and the electric charge is determined from the area of the current-time curve. Evolution with the electric potential of the stationary charge stored in the EDLCs is interpreted by means of a fitting which leads to a polynomial model for the capacitance. The study of the nonlinear dependence with voltage of the charge allows us to deepen in understanding the differences between integral and differential capacitances of an EDLC, as well as consider the role played by the capacitance at the zero-voltage limit. The model is validated by means of the simulation of the equivalent circuit constituted by the series combination of the equivalent series resistance (ESR) and the differential capacitance in the PSpice® program, and the theoretical and experimental comparison of the charge-voltage curves obtained during the transient discharge of the different EDLCs.

Epileptic Amnesia as an Alzheimer’s Disease Mimic (P2-6.004)

<h3>Objective:</h3> To present a case of amnestic dementia that was caused as a result of mesial temporal lobe epilepsy. <h3>Background:</h3> Memory impairments have been reported as a result of mesial temporal lobe epilepsy. Dementia as a result of long term uncontrolled seizures has been reported. Here we report a patient presenting for evaluation of dementia - diagnosed with uncontrolled mesial temporal lobe epilepsy. <h3>Design/Methods:</h3> A 76 year old male presented to the cognitive clinic for evaluation of amnestic problems that started approximately 4 years prior. The patient reported problems with both long-term and short-term memory–such as details of family vacations, weddings, names of acquaintances. He additionally reported mild word finding abnormalities and spatial difficulty. Neuropsychological testing revealed problems in non contextual verbal learning and memory. The patient notably reported stereotyped events which also started around 4 years prior.–which he described as getting a sense of deja vu followed by tingling in all 4 limbs, nausea and a changed sense of smell. These events occurred around 10 times a month. MRI brain performed 4 years prior had revealed some small vessel ischemic changes and diffuse volume loss. An EEG obtained at the time had been unremarkable. Repeat MRI brain was significant for left hippocampal atrophy with bilateral hippocampal T2 signal hyperintensities. Ambulatory EEG monitoring was significant for transient epileptiform discharges. Lumbar puncture was unremarkable with tau /amyloid profiles not consistent with Alzheimer9s pathology. The patient was started on Levetiracetam with cessation of his episodes of deja vu, tingling and nausea. <h3>Results:</h3> NA <h3>Conclusions:</h3> Uncontrolled mesial temporal lobe epilepsy can result in hippocampal atrophy and cause amnestic problems. Epilepsy should be a diagnostic consideration in patients who present for evaluation of dementia. <b>Disclosure:</b> Dr. Philip has nothing to disclose. Dr. Chabrashvili has nothing to disclose.

Vacuum Arcs on Solar Array Surfaces

Arcs on the solar arrays appear to be the most plausible source for the electromagnetic radiation observed with the Arecibo radio telescope. In the laboratory, electrostatic discharges (arcs) on solar array coupons were studied in a simulated geosynchronous equatorial orbit environment. Arc current pulses were recorded with a high time resolution (up to 0.2 ns). Spectral properties of these pulses demonstrated no monotonic behavior but rather separated peaks within the frequency range of 100–1000 MHz. Electromagnetic radiation from these arcs was registered and recorded with a Yagi antenna 8 m distant from the arc site, and a high-speed oscilloscope. Analysis of the spectra resulted in the discovery of well-separated “lines.” Evaluation of arc current spectra and radio-frequency spectra revealed statistically significant patterns in the frequency domain. Measured radio fluxes and theoretical estimates of the power of electromagnetic radiation from arcs on spacecraft solar arrays strongly argue in favor of the arcing hypothesis for the source of this radiation. These results have enabled considerable progress to be made in understanding the physical nature of the generation of electromagnetic radiation by transient vacuum discharges.

Role of Electrode Geometry on the Operational Characteristics of Multiaperture Pseudospark Switch

In the present study comparative analysis for various geometrical parameters has been presented for the operational characteristics in a single gap multiaperture pseudospark switch (PSS). The investigation has been carried out to understand the importance of geometrical parameters on the behavior of the discharge properties of PSS by using 2-D axis-symmetric kinetic simulation tool COMSOL Multiphysics. The primary attention of the study is to show the effect of multiple apertures, baffles, and chicane on the performance of PSS. The analysis has clearly explained the axial, radial, and transient discharge behavior with the penetrating potential in the PSS. It is found that the single gap geometry of PSS with multiaperture, baffle, and chicane has fast switching, higher hold off and higher current carrying capability with long life due to less erosion. In this respect, the analysis has also explained the discharge properties in a single-gap multiaperture PSS with baffles, such as potential penetration inside the PSS for hydrogen gas at different pressures and applied voltages. Along with this, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> characteristics of the same type PSS geometry with baffles and chicane have also been determined by experiment. The obtained results are very much useful for understanding and optimization of the geometrical and operational characteristics of a multiaperture PSS suitable for pulse power applications.

Study on characteristics of acoustic signals generated by different DC discharge modes

Acoustic signals contain rich discharge information. In this study, the acoustic signal characteristics of transient glow, spark, and glow discharges generated through DC pin–pin discharge were investigated. The signals were analyzed in the time, frequency, and time–frequency domains, and the correlation between the electric and the acoustic signal was studied statistically. The results show that glow discharge does not produce measurable sound signals. For the other modes, with a decrease in the discharge gap, the amplitude of the acoustic signal increases sharply with mode transformation, the short-time average energy becomes higher, and the frequency components are more abundant. Meanwhile, the current pulse and sound pressure pulse have a one-to-one relationship in the transient glow and spark regimes, and they are positively correlated in amplitude. A brief theoretical analysis of the mechanism of plasma sound and the trends of signals in different modes is presented. Essentially, the change in the discharge energy is closely related to the sound generation of the plasma.

Boosting energy-storage performance in lead-free ceramics via polyphase engineering in the superparaelectric state

Dielectric energy storage devices are important components of high-power and pulsed electronic systems. High recoverable energy density (Wrec) and high efficiency (ƞ) are critical parameters for such applications. In this work we propose a strategy of polyphase engineering in the superparaelectric (SPE) state to achieve high-performance energy storage. Through careful engineering of the proportions of rhombic (R) phase and tetragonal (T) phase by a linear dielectric additive, CaTi0.8Hf0.2O3 (CTH), in 0.94Na0.5Bi0.5TiO3-0.06BaTiO3-based ceramics, the SPE state can be shifted to ambient temperature when R/T ≤ 0.16. Thanks to the features of isolated polar nano-domains (PNRs) and the fine P-E hysteresis loop of the SPE state, an ultrahigh Wrec of 8.91 J/cm3 and high ƞ of 78.4% are achieved in our 0.75(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-0.25CaTi0.8Hf0.2O3 sample. The sample was also characterized by excellent temperature and frequency stability, achieving ultra-high power density (178 MW/cm3) and ultra-fast transient discharge time (40 ns). Our work proves that polyphase engineering in the SPE state is a powerful approach to the design of dielectric energy storage materials with high performance.

Influence of a transient spark plasma discharge on producing high molecular masses of chemical products from l-cysteine

Cold atmospheric pressure plasmas are considered a forthcoming method in many research areas. Plasma modification of biomolecules has received much attention in addition to plasma-treated biomaterials. Hence, in this work, we operated a transient spark plasma (TSP) discharge to study its effect on the l-cysteine chemical structure. the TSP was configured in a pin-to-ring electrode arrangement and flowed by Ar gas. We also investigated the effect of two chemicals; dimethyl sulfoxide (DMSO) and hydrogen peroxide (H2O2) by the bubbling method to show how they can change the creation of new chemical bioproducts. Ultraviolet–Visible absorption spectroscopy, Fourier transform infrared spectroscopy and Liquid chromatography–mass spectroscopy were used to investigate any changes in chemical bonds of cysteine structure and to depict the generation of new biomolecules. Based on the displayed results plasma-generated reactive species had a great role in the chemical structure of the cysteine. Entering DMSO and H2O2 into the plasma caused the creation of new products and the heaviest biomolecule was produced by the simultaneous addition of DMSO and H2O2. The results also predicted that some chemical products and amino acids with a higher value molecular masse produced from the polymerization process of cysteine solution. The strong oxidation process is responsible for the heavy chemical compounds.

Study of underwater discharge initiated by a high-voltage preliminary pulse produced by a Marx generator

The results of experimental research on the acoustic and electrical characteristics of underwater spark discharges facilitated by a preliminary discharge are presented. The latter was produced through the application of a short duration high-voltage pulse formed by a Marx generator. The application of this pulse lead to the formation of a low-density region in the form of a streamer which transformed to an oscillating vapor cavity. It was shown that this method provided a breakdown of a significantly increased interelectrode gap for the same charging voltage of the main capacitor and allowed the generation of stronger shocks. The temporal development of transient discharges in a long gap and the relationships between the hydrodynamic and electrical parameters of such discharges are reported and analyzed.

Cold thermal energy storage for milk chilling: A numerical and experimental study

One of the main challenges in small holding dairy production systems is the commencement of cold-chain from the point of milk production. Such systems often rely on pooled milk in a supply chain, with the chilling operations being initiated once substantial quantities of milk (>500 L) are collected. Hence, there is a need to develop an energy efficient and passive thermal storage device for chilling of small volumes of milk. The present study explored a novel approach of developing the phase change materials (PCM) encapsulated inside a spherical module as an immersion cooling device to chill a pool of milk (5 L) held in a vessel. The application of TiO 2 nanoparticles at (0.05–1.00% by wt. ) for developing nanoparticle enhanced water based PCM with improved energy storage was also explored. Transient energy exchange and phase-transition of the PCMs during the milk chilling process was numerically simulated using enthalpy-porosity and volume of fluid model of computational fluid dynamics (CFD). The CFD simulated results were validated through the experimental observations and the flow visualization of the temperature distribution and melting fronts clearly affirmed the rapidity of energy exchange due to the addition of nanoparticles into the PCM. • TiO 2 nanoparticle enhanced phase change materials (PCM) were capsuled inside a portable stainless steel spherical module. • Experimental and numerical transient energy storage (charging) and discharge during passive milk chilling inside a milking vessel were studied. • Nanoparticles accelerated the energy storage, discharge and milk chilling rates significantly. • Studies revealed the scope of deploying TiO 2 nanoparticle enhanced PCM in energy-efficient real-time passive milk chillers.

Excellent Energy-Storage Performance in BNT-SST-LMN Lead-Free Relaxor Ferroelectric Ceramics with High Electrical Homogeneity

Relaxor ferroelectric materials have received increasing attention in pulse power devices due to the high power density and rapid charge–discharge capability. However, challenges exist in relaxor ferroelectric behavior because of their low electric breakdown strength. In this article, a large recoverable energy density of 5.94 J/cm3, together with a high energy efficiency of 86.9%, is achieved synchronously in La(Mg2/3Nb1/3)O3 (LMN) modified Bi0.5Na0.5TiO3-Sr0.7Sm0.2TiO3 (BNT-SST) ceramic. It is suggested that the addition of LMN reduces the grain size and enhances the electrical homogeneity, which boosts the electric breakdown strength of sample ceramics. In addition, in 0.03LMN modified 0.97(BNT-SST) ceramic, a good discharge energy density of 3.9 J/cm3 and a transient discharge time of 65 ns are attained. Meanwhile, the outstanding stability in the temperature range of 20–100 °C and frequency range of 1–100 Hz is observed in the above component. These results indicate that BNT-SST-LMN ceramic has potential as an energy-storage medium.

Similarity solution of subcritical pressure discharges from vessels for arbitrary gases

Based on the Bernoulli’s equation Fischer and Boettcher (2021) developed a model to predict the transient gas discharge from a vessel. Their dimensionless number was able to capture a variation of the molar mass, temperature, vessel volume and opening diameter and showed constant values for these. The influence of the gas, though, could not be completely captured. In this work we improve the model by optimizing the pressure loss coefficient, modifying the dimensionless number and solving the differential equation for determining the pressure over time using the 4th-order Runge-Kutta method. The model was extended to include the influence of the ambient pressure. These improvements lead to the first similarity correlation valid for arbitrary gases. Multiple numerical simulations are performed with ANSYS CFX to verify the similarity model. A grid independence study showed differences below 1 %. The mean deviation between the numerical simulation and the similarity-model is 1.939 %.

Transient CHI System Design Studies for Pegasus-III

Transient coaxial helicity injection (transient CHI), first developed on the Helicity Injected Torus-II (HIT-II) and later on the National Spherical Torus Experiment (NSTX) for implementing solenoid-free plasma current startup capability in a spherical tokamak (ST), is now planned to be tested on the Pegasus-III ST using a novel double-biased configuration. Such a configuration is likely needed for transient CHI deployment in a reactor. The transient CHI system optimization will be studied on Pegasus-III to enable startup toroidal persisting currents at the limits permitted by the external poloidal field coils. A transient CHI discharge is generated by driving injector current along magnetic field lines that connect the inner and outer divertor plates on one end of the ST. Simulations using the Tokamak Simulation Code are used to assess the transient CHI toroidal current generation potential and electrode gap location on the Pegasus-III. While past transient CHI systems have used high-voltage, oil-filled capacitors for driving the injector current, for improved safety, Pegasus-III will use a high-current capacitor bank based on low-voltage electrolytic capacitors. The designed and fabricated system is capable of over 32 kA. The modular design features permit the system to be upgraded to higher currents, as needed, to meet the future needs of the Pegasus-III facility.

ФОРМУВАННЯ БІПОЛЯРНИХ ІМПУЛЬСНИХ СТРУМІВ У НАВАНТАЖЕННІ ЄМНІСНИХ НАКОПИЧУВАЧІВ ЕНЕРГІЇ ЕЛЕКТРОРОЗРЯДНИХ УСТАНОВОК

A method is proposed for stabilizing the transient discharge processes of capacitive energy storages (CESs) of electric discharge installations (EDIs) to a load whose electrical resistance can vary non-linearly and stochastically. The method is based on the use of one direct voltage generator (DVG) in the EDI, which carries out alternately an oscillatory charge of two CESs to the required voltage, as well as on the introduction of semiconductor switches into the charge circuit and discharge one of these CESs and the developed algorithms for switching them on, according to which bipolar discharge currents are formed alternately in the EDI load, regardless of the nature of the change in its electrical resistance. The frequency and duration of positive and negative discharge-pulse currents in the load can be the same or different, depending on the selected parameters of the elements of discharge circuits of the two CESs. The use of the developed method provides the formation of unipolar modes in the capacitors of each CES, which allows you to choose them for lower voltages, increase their life and reduce cost. In addition, with the same capacitance of the CESs, the total electric charge flowing in the load is practically zero after each even number of discharges. This significantly reduces the effect of electrochemical processes in the load, in particular the electrochemical destruction of the anode of the technological apparatus of the EDI, which inevitably occurs during the formation of unipolar pulse currents. The use of bipolar discharge currents in the EDI load also increases the stability of the discharge modes in the EDI due to the limitation of the duration of possible long aperiodic currents during the discharge of one of the CESs by the beginning of the counter current of the next discharge of the other CES. References 10, figures 3, table 1.

Experimental Study on the Transient Disturbance Characteristics and Influence Factors of Pantograph–Catenary Discharge

The transient electromagnetic disturbance generated by arcing discharge between the pantograph and catenary can pose a significant risk to the safe operation of electrified railways. In order to better comprehend its properties, a pantograph–catenary discharge generating device is designed to simulate the discharge phenomenon with moving electrodes in this experimental investigation. The effects of the applied voltage, the gap distance, and the relative motion between the pantograph and catenary on the time- and frequency-domain features of the discharge current and electromagnetic field are investigated. The variation trends of pulse peak current, rise time, pulse repetition frequency, maximum amplitude, and characteristic frequency in the radiation spectrum are retrieved under varying experimental settings, and the effect mechanisms are derived from the physics of gas discharge. A dynamic discharge test is conducted in this study in order to further understand the effect of electrodes’ relative motion on discharge characteristics. The results indicate that lateral sliding motion of the pantograph along the track has a negligible effect on the transient discharge, whereas a faster vertical approaching motion between the pantograph and catenary generates a larger pulse current peak, a steeper rise front-edge, and a higher radiation intensity.

Experimental and simulated investigation of microdischarge characteristics in a pin-to-pin dielectric barrier discharge (DBD) reactor

Both experimental and simulated studies of microdischarge (MD) are carried out in a dielectric barrier discharge with a pin-to-pin gap of 3.5 mm, ignited by a sinusoidal voltage with a peak voltage of 10 kV and a driving frequency of 5 kHz. Statistical results have shown that the probability of the single current pulse in the positive half-period (HP) reaches 73.6% under these conditions. Experimental results show that great luminous intensity is concentrated on the dielectric surface and the tip of the metal electrode. A 1D plasma fluid model is implemented by coupling the species continuity equations, electron energy density equations, Poisson equation, and Helmholtz equations to analyze the MD dynamics on the microscale. The simulated results are in good qualitative agreement with the experimental results. The simulated results show that the MD dynamics can be divided into three phases: the Townsend phase, the streamer propagation phase, and the discharge decay phase. During the streamer propagation phase, the electric field and electron density increase with the streamer propagation from the anode to the cathode, and their maximal values reach 625.48 Td and 2.31 × 1019 m−3, as well as 790.13 Td and 3.58 × 1019 m−3 in the positive and negative HP, respectively. Furthermore, a transient glow-like discharge is detected around the anode during the same period of streamer propagation. The formation of transient glow-like discharge is attributed to electrons drifting back to the anode, which is driven by the residual voltage in the air gap.