Amplitude Of Applied Voltage Research Articles

Simulation of the pulsed streamer discharge in water considering the effect of hydrostatic pressure

Streamer discharge is a very complex multi-scale and multi-physics coupling process, and there is no accurate model that can describe its development. In this paper, a two-dimensional axisymmetric fluid model is established in COMSOL to simulate and study the effects of the applied voltage amplitude, the discharge gap distance, the rising edge of pulse voltage, and hydrostatic pressure on the development of the positive streamer discharge at a needle-plate electrode in water under a nanosecond pulse voltage. The results show that increasing the voltage amplitude, decreasing the pulse rise time, and narrowing the discharge gap all increase the electric field strength of the streamer, thereby affecting the electron density of the plasma channel, among which changing the discharge gap has the greatest effect on the electron density. And under the gap of 3 mm, the peak electron density can reach 3.76 × 1023 m−3; if the discharge gap is narrowed to 1 mm, the peak electron density is reduced to 1.20 × 1023 m−3. In addition, hydrostatic pressure and water molecule spacing are closely linked. Increasing the hydrostatic pressure decreases the electric field strength and the peak electron density in the plasma channel, and its effect on the peak electron density saturates with increasing hydrostatic pressure.

Deformation theory and nonlinear dynamic behavior of PVC gel actuators

Polyvinyl chloride (PVC) gel generates complex nonlinear vibration behavior under an alternating current voltage excitation, which has potential application as a dynamic electromechanical actuator. However, there are few studies on the deformation theory of PVC gel actuators, especially the dynamic nonlinear response theory. In this paper, a complex dynamic model is established according to the electrodeformation mechanism of PVC film, and the nonlinear dynamic behavior of the actuator is numerically studied by a differential equation. The effects of applied voltage amplitude, voltage frequency, dibutyl adipate content, mechanical tension, and bias voltage on the dynamic properties of PVC film were analyzed under the condition of equal biaxial tension. The variation of amplitude and the generation and disappearance of the beat frequency during vibration are analyzed by using time-domain characteristics. The degree of PVC actuator nonlinearity as well as vibration stability and periodicity is also reflected based on the phase path and Poincare map. Finally, the law of influence of external condition parameters on the dynamic response of the PVC actuator is obtained.

Emergence of chaos in an electroactive artificial muscle PVC gel under state-varying electromechanical parameters

The deformation mechanism of artificial muscle materials based on the natural method has always been one of the frontier topics in the field of biophysics. Electroactive PVC gel is a composite material that mimics the response of natural muscles, making it highly advantageous for various bionic mechanical applications. The existing literature primarily focuses on enhancing the performance and exploring applications of PVC gel, with particular emphasis on optimizing its ability to simulate muscle deformation. However, the existing literature lacks research on the theoretical mechanism and modeling of large deformation, particularly regarding the investigation of nonlinear dynamic behavior under state-varying electromechanical parameters. The present research establishes a novel theoretical model for PVC gel and investigates its dynamic response to voltage, mechanical force, and inertia force. Firstly, the electromechanical constitutive model of PVC gel actuator was elucidated, and the nonlinear dynamics control equation of PVC gel actuator was established based on the Gent model. Secondly, we investigate the vibration characteristics of PVC gel material by analyzing four key parameters: size, tensile strength, applied voltage amplitude, and excitation frequency. Through this analysis, we determine the relevant parameters and operational range of the PVC gel actuator when subjected to voltage excitation. Meanwhile, the phase trajectories and Poincaré maps were generated based on the control equation calculation results to investigate the vibration stability and chaotic characteristics of the PVC gel actuator under electromechanical coupling conditions. The deformation of PVC gel is influenced by various nonlinear factors, wherein the alteration in frequency induces harmonic, subharmonic, and super-harmonic resonance phenomena within the frequency response. By revising the size, voltage, and frequency of these three factors, with particular emphasis on regulating the frequency, chaotic behavior in the PVC gel will be facilitated. Finally, the bifurcation analysis of the electromechanical vibration behavior of the PVC gel actuator was carried out, and the stability of the PVC gel vibration was further quantitatively determined by the Lyapunov exponent.

The heat dissipation by the multi-needle electrode structure ionic wind generator

Ionic wind generated by atmospheric pressure discharge can be used for propulsion, heat dissipation, food drying, which shows the unique advantages of no mechanical parts and fast response. However, the wind speed and the energy efficiency of ionic wind generator are very low, which limit its application. In this paper, an ionic wind generator, constructed with needle-net electrode structure and powered by high-voltage positive dielectric current (DC) power supply, is built for cooling of a metal oxide semiconductor field effect transistor (MOSFET). The energy efficiency and wind speed of the ionic wind generator are optimized by adjusting the electrode structure and applied voltage amplitude. The results show that when the discharge spacing is fixed at 10 mm and the optimal needle spacing is 17.5 mm with 6 needles at 14 kV, the ionic wind velocity can reach a maximum value 3.20 m s−1 and the energy efficiency is 1.90%. Under optimal experimental conditions, the heat dissipation performance of MOSFET is significantly enhanced compared to using only a heat sink. With cooling by the ionic wind generator, the MOSFET junction temperature can be lowered by about 29 °C after 240 s operation.

Degradation and transformation of carbamazepine in aqueous medium under non-thermal plasma oxidation process

Carbamazepine (CBZ) is a pharmaceutical compound detected in various water resources. With a view to removing this contaminant, the applicability of non-thermal plasma (NTP) oxidation process has been widely tested in recent years. This study utilized NTP from a dielectric barrier discharge reactor in the treatment of CBZ. NTP on the surface of a water sample containing 25 mg.L−1 of CBZ resulted in a removal efficiency of over 90% with an energy yield of 0.19 g. (kWh)−1. On the other hand, a rapid reduction in pH and an increase of conductivity and nitrate/nitrite ions concentration were observed during the degradation. The applied voltage amplitude significantly affected the removal efficiency and the energy yield as the degradation efficiency was 55%, 70%, and 72% respectively with an applied voltage of 8, 10, and 12 kV. The water matrices containing inorganic anions such as chloride and carbonate ions reduced the removal efficiency by scavenging the reactive species. Accordingly, a reduction in the removal efficiency was observed in tap water. The high-resolution mass spectrometry (HRMS) results revealed that both reactive oxygen and nitrogen species take part in the reaction process which yields many intermediate products including aromatic nitro-products. This study concluded that NTP can effectively degrade CBZ in both pure and tap water, but special attention must be paid to changes in the water quality parameters (pH, conductivity, and nitrate/nitrite ions) and the fate of nitro products.

Comparisons of the acoustic radiation force of ultrasonic standing waves in half-wavelength and quarter-wavelength micro-resonators of cylindrical geometry

Ultrasonic standing waves with specific wavelengths generated in the multi-layered micro-resonators were numerically and experimentally analyzed. Using a three-dimensional scanning fluorescence microscope, the acoustophoretic motion of fluorescent microparticles within the micro-resonators was carefully and accurately measured. The manufactured micro-resonators were validated by comparing the location of the acoustic pressure nodal plane and the average energy density curves derived from numerical and experimental results. Results confirmed that the acoustic radiation force of the induced ultrasonic standing waves drives the microparticles vertically within the micro-resonators and their average energy density increases as the sinusoidal voltage applied to the piezoelectric transducer increases. Semi-empirical correlations were developed for the average energy density, based on experimental results for a wide range of the applied voltage amplitudes. The correlations were in good agreement, within less than 20 % of the experimental values measured for both the half-wavelength and quarter-wavelength micro-resonators.

In operando cryo-STEM of pulse-induced charge density wave switching in TaS2

The charge density wave material 1T-TaS2 exhibits a pulse-induced insulator-to-metal transition, which shows promise for next-generation electronics such as memristive memory and neuromorphic hardware. However, the rational design of TaS2 devices is hindered by a poor understanding of the switching mechanism, the pulse-induced phase, and the influence of material defects. Here, we operate a 2-terminal TaS2 device within a scanning transmission electron microscope at cryogenic temperature, and directly visualize the changing charge density wave structure with nanoscale spatial resolution and down to 300 μs temporal resolution. We show that the pulse-induced transition is driven by Joule heating, and that the pulse-induced state corresponds to the nearly commensurate and incommensurate charge density wave phases, depending on the applied voltage amplitude. With our in operando cryogenic electron microscopy experiments, we directly correlate the charge density wave structure with the device resistance, and show that dislocations significantly impact device performance. This work resolves fundamental questions of resistive switching in TaS2 devices, critical for engineering reliable and scalable TaS2 electronics.

Oil–water interface dynamics and electrical breakdown in pulsed electric field

The motion of immiscible liquids and electrical breakdown at the interface of two horizontal layers of conducting water and transformer oil are studied under vertically oriented nonuniform pulsed electric field. The interface profile is tracked during experiments and shows the appearance and growth of a water cone inside the oil. After the water cone reaches the high voltage electrode located in the oil, three scenarios are observed depending on water conductivity and pulsed voltage amplitude: electrical current flows over the water without plasma formation; plasma onset occurs due to thermal breakdown in the water at the moment the cone tip touches the sphere; plasma onset occurs due to breakdown through a swarm of small water drops atomized from the cone tip under the action of electrical forces. From experiments and numerical simulations, the breakdown time is determined depending on applied voltage amplitude; the oil–water interface behavior in the electric field is analysed; and the electrical force distribution is studied. The experiment and simulation results show good agreement.

Study of coaxial-dual-gap dielectric barrier discharge based on capillary: discharge characteristics and Escherichia Coli decontamination.

The medical capillary catheters occupy a high proportion of medical diagnosis, monitoring and treatment devices, and will cause serious cross-infection without being disinfected adequately. This paper presents a new plasma structure for efficient inactivation of harmful microorganisms in medical capillaries. An innovative coaxial-dual-gap dielectric barrier discharge (CDG-DBD) reactor powered by nanosecond-pulsed power supply was designed for disinfection of Escherichia Coli (E. coli) inside and outside medical capillary catheters in this work. Atmospheric helium plasma (AHP) and atmospheric air plasma (AAP) were successfully obtained inside and outside capillary (0.6mm inner diameter and 1.0mm outer diameter), respectively. The electrical and optical characteristics of AHP and AAP were investigated. As the threshold of applied voltage amplitude (Uamp) was below 7.0kV, only one helium glow discharge was generated inside the capillary at the rising and falling stages of pulse voltage. As the Uamp exceeded the threshold, two helium glow discharges were generated that further caused generation of air discharge. Under the Uamp of 9.0kV, the production of AHP lowered the breakdown voltage in air gap, resulting in the formation of high-volume and uniform AAP, which was conducive to the realization of full inactivation. The inactivation rates of E. coli reached 98.13% and 99.99% by 2min AHP and 0.5min AAP treatment, respectively. The electrical stress of AHP and the reactive oxygen and nitrogen species (RONS) produced by AAP were contributed to the inactivation of E. coli. The results of SEM show that plasma treatment can destroy the cellular structure of E.coli.

Non-thermal plasma actuator mechanism in interaction with fluid flow structure for aeronautical flow control

Plasma actuators generated by surface dielectric barrier discharge are developed for controlling flow in aeronautics applications. This research studies the simulation of cold plasma discharge at atmospheric pressure coupled with compressible fluid dynamics using COMSOL Multiphysics 5.4. Modeling of dielectric barrier discharge in air at high voltages is carried out in two dimensions. The development of electric field and space charge density are discussed in several cases to determine the discharge regime. Non-thermal plasma generates tangential ionic winds at the surface during corona discharge. The results are validated by the experimental results of the literature. The maximum electric wind velocity above the actuator grows linearly with the applied voltage, and simultaneously, the horizontal extension of the discharge grows with the applied voltage. The induced electrohydrodynamic force augments with the applied voltage amplitude, reaching saturation at higher voltages. Moreover, as the voltage rises, the discharge becomes filamentary, inducing a higher number of streamer pulses. Hence, the power consumption discharge increases abruptly as the voltage rises. In addition, the efficiency increases at higher voltage amplitudes and with the dielectric thickness. Our findings give a clear description of physical atmospheric plasma parameters in the surface discharge mechanism and the efficiency of the actuator plasma.

Techno-economic comparative assessment of the ultrasound, electrostatic and microwave supported coalescence of binary water droplets in crude oil

In this study, comparative assessment of the technical performance, energy usage and economic impact of ultrasound, electrostatics and microwave on the coalescence of binary water droplets in crude oil was conducted. The effect of different oil properties such as crude oil viscosity (10.6–106 mPa s) and interfacial tension (IFT) (20–250 mN/m) on the coalescence time and energy consumption was examined. In addition, operation conditions such as inlet emulsion flow velocity (10–100 mm/s), electric field type, ultrasound frequency and applied voltage amplitude (0–30 kV) were evaluated. The numerical models showed good agreement with experimental findings in the literature. Moreover, the process time of the dewatering process increased with rising inlet flow velocities. The elevation of the coalescence time with velocity can be attributed to the increasing effect of flow disturbance, and the reduction of the emulsion residence time. As regards the IFT, the coalescence time reduced as the IFT was increased. This can be associated with the improved stability of emulsions formed at lowered IFT. As the maximum droplet size is directly proportional to the IFT, lowering the IFT reduces the peak diameter of the droplets that are present in the emulsion. Moreover, the coalescence time followed the order: ultrasound < microwave < electrostatics approaches under varying IFT. The coalescence energy increased from ∼15 J, ∼90 J and ∼25 mJ to ∼61 J, ∼235 J and ∼26 mJ for microwave, electrostatics and ultrasound techniques, respectively, as the viscosity was raised from 10.6 to 106 mPa s. Ultrasound coalescence showed significant energy and economic savings in comparison to microwave and electro-coalescence. Hence, ultrasound coalescence would be a potential method for standalone or integrated demulsification over the two other techniques. However, there are indications that beyond a viscosity of 300 mPa s, the effect of ultrasound becomes weak with significant hindrance to droplet movement and accumulation. This analysis provides fundamental insights on the comparative behavior of the three emulsion separation techniques.

Developing characteristics of the positive streamer in water with microsecond pulse voltage

Underwater discharge is the typical method used to generate plasma in a liquid phase environment and is employed in many engineering applications. This study analyzes the formation and development process of the positive streamer in water under microsecond voltage. The effects of voltage amplitude, liquid conductivity, and the presence of bubbles on the underwater discharge characteristics are analyzed by establishing a two-dimensional finite element simulation model of a needle-plate gap. The simulation results show that the electron density of the streamer in water can reach 1023 m−3, and as the applied voltage amplitude increases, the development speed of the streamer increases and the head of the stream bifurcates. Moreover, when the conductivity of the water is high, the development speed of the streamer and the density of charged particles increase. Furthermore, the presence of bubbles significantly impacts the development of the discharge morphology, causing the channel to have multiple bifurcations.

Partial Discharge Measurement and Analysis of Transformer Under Oscillating Lightning Impulse Voltage

Oscillating lightning impulse (OLI) voltage is recommended for on-site testing due to its high generation efficiency. In this article, partial discharge (PD) characteristics under field impulse voltage waveforms are investigated. The experiment is carried out on a scaled transformer model with a protrusion defect inside as the PD source. Both oscillating and standard lightning impulse (SLI) voltages are acquired as test waveforms. Main discharges and reverse discharges are detected simultaneously under both OLI and SLI voltage. The increasing applied voltage amplitude advances the main discharge and enlarges its amplitude, and it also prolongs the duration of the reverse discharge and increases the number. The amplitude of main discharge is related to the PD voltage, while that of reverse discharge depends on the dynamic variation of the impulse voltage. Since OLI voltage contains multiple rising edges during the oscillation period, more PDs are excited. A disruptive effect (DE) model is extended for the PD analysis to show the oscillation effect on the PD distribution. The OLI test with PD measurement performed on a 220-kV transformer proves that PD detection during impulse voltage withstand test reflects more detailed information that can be used for early diagnosis of power transformers.

Numerical study of type-I intermittency in an atmospheric-pressure dielectric barrier discharge

Atmospheric-pressure dielectric barrier discharge (AP-DBD) as a complex dissipative dynamical system exhibits rich temporal nonlinear and chaotic behavior. The intermittent chaos in AP-DBD, where the abrupt intensive currents break the regular periodic current oscillations during a discharge process, is studied by numerical simulation. By increasing the control parameter of applied voltage amplitude, random intensive currents occur more frequently, reducing the average laminar length (time interval of regular oscillations). It is found that the average laminar length depending on the control parameter follows the scaling law with an exponent of −0.5, implying a type-I intermittent discharge. This study further supplements and strengthens the nonlinear theory in plasma discharge.

Life Prediction of Dry Reactor Sensor Based on Deep Neural Network

In order to solve the problem of increasing the number and service life of a dry-type air core reactor and frequent interturn insulation faults, this paper proposes a life prediction method of a dry-type reactor sensor based on the deep neural network. On the basis of summarizing the research status of turn-to-turn insulation-related problems, this method studies the switching overvoltage generated in the process of breaking the dry-type air core reactor, the deterioration law of turn-to-turn insulation under the cumulative action of switching overvoltage, the influence of thermal aging on the Switching Overvoltage Withstand characteristics of turn-to-turn insulation, and the electrical aging life of turn-to-turn insulation under the power frequency overvoltage. Based on the deep neural network, the electrical aging life model of turn-to-turn insulation of the dry-type air core reactor under power frequency overvoltage is obtained. The results are as follows: with the increase of the applied voltage amplitude, the deterioration speed of the turn-to-turn insulation of the model sample accelerates. When the applied voltage amplitude reaches a certain value, the maximum discharge amount and pulse discharge power of the partial discharge pulse increase rapidly, and the image coincidence degree reaches 85%. The electric aging life curve of the modified interturn insulation model sample of the dry-type air core reactor has a high correlation with the measured aging life data, and the performance is more than 95%. The research results of this paper lay a practical foundation for further research on the deterioration mechanism of interturn insulation under the combined action of multiple factors and provide theoretical support for the risk and life assessment of the dry-type air core reactor.

Influence of pulse rise time and duty cycle on distribution of transients along the wind turbine step-up transformer windings

A transformer is one of the most important assets in an electric power generation system. Wind turbine step-up transformers have recently seen premature failures due to high-frequency repetitive transients. The high-frequency transients under resonance can severely damage the insulation of the transformer. Thus the paper initially analyses the distribution of transformer frequency response to identify critical resonance frequencies for the two transfer function frequency responses; namely, impedance frequency response and voltage ratio response. Transformer frequency response is compared with transient response to understand the influence of repetitive transient parameters; namely applied voltage amplitude, rise time, and duty cycle, on transient distribution along the transformer winding. Based on three variable experiments, the range of rise time was considered as less than 300 ns and 1000 ns, applied voltage considered was 100 V and 1000 V, and duty cycle considered was 10% and 50%. For the current transformer model, both the experimental and PSCAD simulation results indicated that a duty cycle of 50% and rise time < 300 ns were critically damaging to transformer insulation. The research helps in designing transformer insulation stressed under different transient parameters.

New insights into the mechanism of fluid mixing in the micromixer based on alternating current electric heating with film heaters

In order to solve the problem of difficult mixing of high-conductivity solutions, this paper designs a new mixing method of micromixer based on the alternating current (AC) heating effect. We set up the AC electrode and the film heater at the bottom of the microchannel. Under their joint action, the fluid in the microchannel will be affected by the Joule heat generated internally and the external heat source, so that the fluid disturbance and temperature distribution can be flexibly adjusted. It is characterized by joint numerical simulation. The key structural parameters of the micromixer, such as the electrode width ratio, the size of the film heater and the channel structure, are obtained to influence the performance of the micromixer. At the same time, the influence of the applied voltage amplitude and solution conductivity on the performance of the micromixer is analyzed. The results show that when only AC electrodes are applied, that is, the fluid in the microchannel is only affected by the Joule heat generated inside, the mixing efficiency of the micromixer can reach up to 83%. After we apply the film heater, that is, when in the combined action of an AC electrode and an external heat source, it is observed that the relatively high conductivity is as high as 0.2 S/m, and the mixing efficiency exceeds 90%. The two different fluids are almost completely mixed in the microchannel.

Laboratory study on negative spark inception direction and breakdown characteristics in rod–rod air gaps

To better understand the inception direction and breakdown characteristics of negative sparks in rod–rod air gaps, experiments have been carried out with negative 250/2500μs voltage impulses in 0.4m-1.2m air gaps. Three types of air gaps were used including rod-double rods air gaps and two kinds of rod–rod air gaps. Initial angle of spark channel defined as the angle between tangential directions of the initial spark channel to vertical was found to follow Normal distribution in rod–rod air gaps. The average initial angle of negative sparks in rod–rod air gaps is 14°-62° which is larger than that of positive sparks in 0.5m rod-plane air gaps and close to those in 7m-8m rod-plane air gaps. The inception direction and breakdown characteristics of 0.4m-1.2m rod–rod air gaps are influenced by gap distance, grounded rod tip shape and applied voltage amplitude. The negative 50% breakdown voltage increases linearly with gap distance, which is also influenced by gap configuration. As gap distance was elongated, longer upward streamer occurred at conical grounded rod tip resulting in larger attraction and higher striking probability of grounded rod with conical tip; with higher voltage amplitude, the initial angle and striking selectivity of grounded rods become more random.

Effects of the discharge frequency on the dielectric barrier discharge ignition behaviors for lean methane–air mixtures at various pressure values

An experimental study on dielectric barrier discharge (DBD) plasma-assisted ignition was performed through the use of a plug-type DBD electrode at various pressures p up to 500 kPa. The ignition behaviors of lean methane–air mixtures with high-frequency DBD were investigated near the lean limit in a constant volume chamber. Using a high-speed video camera, the plasma formations of the DBD were observed for air and a mixture of the equivalence ratio ϕ=0.3. Plasma spectroscopy was also conducted with an echelle grating and imaging spectrometers. The time-averaged detailed plasma emission spectra from 400 nm to 920 nm and the transient spectrograms in the vicinity of the N2 second positive system (372–382 nm) for ϕ=0.5 were measured. The minimum ignition energy (MIE), minimum discharge duration, and minimum amplitude of the applied voltage were obtained through logistic regression. The results indicated that a plasma emission lifetime became much longer than the discharge time with an application of the high-frequency sinusoidal voltage at high pressure. The longest plasma lifetime was observed at a discharge frequency of 1,180 kHz. The plasma lifetime showed the maximum at a specific pressure. The detailed spectroscopy also showed that continuum spectra at 500 kPa could be fitted to the Planck's curve with temperature above 3000 K at 500 kPa. The profiles of the MIE as a function of pressure exhibited the minimum in the vicinity of 100 kPa. The existence of the optimal frequency for high-efficiency ignition was shown. At the fixed frequency, an increase in the applied voltage amplitude resulted in a decrease in the MIE. In contrast, the effects were saturated over a certain threshold. At 500 kPa, time-resolved plasma spectroscopy showed a rapid local gas heating to the flame temperature over a specific frequency of the applied voltage. This indicated that there was the optimal frequency where the MIE was the minimum.

Large tuning in the electrowetting behaviour on ferroelectric PVDF-HFP/Teflon AF bilayer.

Electrowetting (EW) response on a dielectric depends on its permittivity value, Young contact angle and voltage amplitude. We present a large change in EW contact angle, from 163° to 80°, on the bilayer dielectric made up of ferroelectric PVDF-HFP with a thin layer of fluoropolymer. The thickness values of both layers were separately optimized for high effective capacitance essential for the large EW response. It reveals that the bilayer with ~ 500 nm thick PVDF-HFP layer and ~ 50 nm thin layer of Teflon results in the maximum value of effective dielectric constant, ε ≈ 8. Besides this gain, dc-voltage EW response exhibits hysteresis mainly due to polarization in the ferroelectric layer such that, hysteretic offset voltage was found to depend on the applied voltage amplitude and thickness of the dielectrics. Finally, bilayer was subjected to ac-voltage EW in silicone oil for ambient temperature ranging from − 25 to 70 °C. The consistent EW response in this ambient without any degradation/delamination of polymer surface confirmed the durability of the bilayer on the transparent ITO electrodes.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10853-021-06308-z.