Nanosecond Pulse Power Supply Research Articles

Influence of dielectric materials on discharge characteristics of coaxial DBD driven by nanosecond pulse voltage

The dielectric material is one of the important influencing factors for the dielectric barrier discharge (DBD) characteristics and its application effects. The glass, quartz, polycarbonate (PC), and polytetrafluoroethylene (PTFE) materials are selected as dielectric materials of a coaxial DBD reactor. A nanosecond (ns) pulse power supply is used to drive the coaxial DBD reactors and the influences of dielectric materials on the optical, electrical, and temperature characteristics of DBDs are recorded. The mechanisms of the effects of the dielectric materials on the DBD characteristics are analysed by equivalent electrical model and heat conduct model. From the observation of the discharge, all of the discharges are in the diffuse mode without filament and the coaxial DBD with glass dielectric barrier are more homogenous. With the electrical analysis, it is found that the glass dielectric barrier with larger relative permittivity compared with the other materials leads to a better discharge uniformity and a higher power deposition in gap. At the same applied voltage, the coaxial DBD reactor with glass dielectric barrier also has the highest energy efficiency, which can reach 70.8% at 24 kV peak applied voltage. The operation temperatures of the coaxial DBD reactors after 900 s discharge with different dielectric materials are compared. The coaxial DBD reactor with glass dielectric barrier has the highest outside wall temperature at 78.0 °C. The reactor with PTFE dielectric barrier has the lowest operation temperature at 58.2 °C. With the heat conduct analysis, the results show that the coaxial DBD reactor with glass dielectric barrier has the highest the inner barrier tube temperature at 137.9 °C and has the lowest heat loss power rate at 29.2% under thermal balance. The reported work provides important reference for the selection of dielectric materials for DBD reactors and for the optimization in the industrial application.

A parametric and compact nanosecond pulsed power generator for liquid phase discharge.

Nanosecond pulsed liquid discharge has attracted significant attention in various applications, in which adjustable parameters and compact volume of nanosecond pulsed power are essential for the convenience of researchers. In this paper, a compact volume (0.6 × 0.8 × 0.4 m3) nanosecond pulsed power supply is built for the liquid discharge with the capacity charging power supply technology. Moreover, a high-frequency induction feed control system is adopted to achieve synchronizations between insulated gate bipolar transistors to realize the adjustable pulse width and frequency. A non-inductive resistor is used to test the properties of the nanosecond pulse power supply, and results show that the rising time of nanosecond pulse power is 100 ns with the pulse width in the range of 4 µs to ∼100 µs, and the output pulse voltage and repetition frequency are 0 kV-20 kV and 1 Hz-300 Hz, respectively. Moreover, the needle-to-needle electrode discharge in the liquid phase is successfully excited by this power supply with different working conditions.

NOx production in plasma reactors by pulsed spark discharges

Nitrogen fertilizers are important for modern agriculture, among which nitric acid is a basic chemical for ammonium nitrate production. Herein, NOx was produced from N2 and O2 using a spark discharge technology with point-to-point and circle-to-plate types of plasma reactors driven by a nano-second pulsed power supply. NOx could be produced with an energy efficiency of 0.09 mol kWh−1 under the gases of 50%/50% N2/O2, while NO2 selectivity increased with increasing energy density. The gas temperatures in the spark channels were estimated using the Gibbs free energy equation. Based on kinetics calculations, the reactions of N with O2 and O with NO were the major reactions for NOx production.

Electrocoagulation with a nanosecond pulse power supply to remove COD from municipal wastewater using iron electrodes

Electrocoagulation with a nanosecond pulse power supply to remove COD from municipal wastewater using iron electrodes

Formation of Nitrogen Oxides by Nanosecond Pulsed Plasma Discharges in Gas–Liquid Reactors

A gas–liquid-film flow reactor with a nanosecond pulsed power supply was utilized to produce nitrogen oxides from Ar/N2 mixtures (gas phase) and deionized water (liquid phase). Chemical analysis of the stable products found in both the gas and liquid phases was performed and chemical quenching was incorporated for the liquid phase samples in order to eliminate post plasma reactions. Significant amounts of NO and NO2 in the gas phase and $${\text{NO}}_{2}^{ - }$$ and $${\text{NO}}_{3}^{ - }$$ in the liquid phase were determined using FTIR spectroscopy and ion chromatography, respectively. The production rate of all nitrogen oxides produced increased significantly with N2 concentration while H2O2 formation decreased slightly. The gas temperature of the plasma was approximately 525 K and was unaffected by N2 concentration while the electron density ranged from 1 × 1017 cm−3 in pure Ar to 5.5 × 1017 cm−3 in 28% N2. The role of the $${\cdot {\text{OH}}}$$ in the reaction pathway was assessed by adding CO as a gas phase radical scavenger showing that $${\cdot {\text{OH}}}$$ is essential for conversion of the gas phase NO and NO2 into water soluble $${\text{NO}}_{2}^{ - }$$ and $${\text{NO}}_{3}^{ - }$$ . Conversely, atomic oxygen originating from water is likely responsible for NO and NO2 generation. Experiments with N2/O2/Ar mixtures and air showed a significant increase in NO2 production caused by the additional generation of reactive oxygen species. An overall energy yield for all nitrogen oxides produced in the most efficient case was 50 eV/molecule.

Numerical investigation on the CH4/CO2 nanosecond pulsed dielectric barrier discharge plasma at atmospheric pressure

The excellent non-equilibrium characteristic of the nanosecond pulsed dielectric barrier discharge (NPDBD) plasma can overcome thermodynamically barriers of reactions in the dry reforming of methane (DRM), so that the NPDBD plasma coupled with catalyst provides an attractive alternative to the traditional catalytic method of the DRM. In this work, the one-dimensional fluid model, including 68 species and 276 reactions, is built up to numerically investigate the atmospheric-pressure CH4/CO2 plasma driven by the nanosecond pulsed power supply. Discharge current densities, discharge gap voltages, dissipated power densities, spatial averaged particle densities and spatial distributions of the high-density species, and generating reaction pathways of the significant species in CH4, CO2, and CH4/CO2 NPDBD plasmas at atmospheric pressure are systematically illustrated and discussed. The simulation results should be valuable for optimizations of both existing and emerging DRM approaches using the NPDBD plasma, the plasma-assisted catalyst, and other novel plasma-based fuel reforming technologies.

Nanosecond pulsed plasma discharge over a flowing water film: Characterization of hydrodynamics, electrical, and plasma properties and their effect on hydrogen peroxide generation

A continuously flowing liquid film reactor driven by a variable nanosecond pulsed power supply, where plasma channels generated in argon propagate along the water film, was utilized to assess the effects of output voltage setting, pulse frequency, and gas/liquid flow rate on the generation of H2O2. Increasing the voltage significantly impacted the discharge current, resulting in hotter/denser plasma channels that increased the production rate of hydrogen peroxide but lowered the energy yield. Variation in pulse frequency and gas/liquid flow rates had little impact on electrical and plasma properties, however, the production of H2O2 per pulse decreased with increasing pulse frequency and was shown to be linked to insufficient chemical and/or thermal dissipation of the gas phase between pulses.

An uniform DBD plasma excited by bipolar nanosecond pulse using wire-cylinder electrode configuration in atmospheric air

In this study, a bipolar nanosecond pulsed power supply with 15ns rising time is employed to generate an uniform dielectric barrier discharge using the wire-cylinder electrode configuration in atmospheric air. The images, waveforms of pulse voltage and discharge current, and the optical emission spectra of the discharges are recorded. The rotational and vibrational temperatures of plasma are determined by comparing the simulated spectra with the experimental spectra. The effects of pulse peak voltage, pulse repetition rate and quartz tube diameter on the emission intensities of N2 (C3Πu→B3Πg, 0–0) and N2+B2Σu+→X2Σg+,0–0 and the rotational and vibrational temperatures have been investigated. It is found that the uniform plasma with low gas temperature can be obtained, and the emission intensities of N2 (C3Πu→B3Πg, 0–0) and N2+B2Σu+→X2Σg+,0–0 rise with increasing the pulse peak voltage and pulse repetition rate, while decrease as the increase of quartz tube diameter. In addition, under the condition of 28kV pulse peak voltage, 150Hz pulse repetition rate and 7mm quartz tube diameter, the plasma gas temperature is determined to be 330K. The results also indicate that the plasma gas temperature keep almost constant when increasing the pulse peak voltage and pulse repetition rate but increase with the increase of the quartz tube diameter.

Comparison of atmospheric air plasmas excited by high-voltage nanosecond pulsed discharge and sinusoidal alternating current discharge

In this paper, atmospheric pressure air discharge plasma in quartz tube is excited by 15 ns high-voltage nanosecond pulsed discharge (HVNPD) and sinusoidal alternating current discharge (SACD), respectively, and a comparison study of these two kinds of discharges is made through visual imaging, electrical characterization, optical detection of active species, and plasma gas temperature. The peak voltage of the power supplies is kept at 16 kV while the pulse repetition rate of nanosecond pulse power supply is 100 Hz, and the frequency of sinusoidal power supply is 10 kHz. Results show that the HVNPD is uniform while the SACD presents filamentary mode. For exciting the same cycles of discharge, the average energy consumption in HVNPD is about 1/13 of the SACD. However, the chemical active species generated by the HVNPD is about 2–9 times than that excited by the SACD. Meanwhile, the rotational and vibrational temperatures have been obtained via fitting the simulated spectrum of N2 (C3Πu → B3Πg, 0-2) with the measured one, and the results show that the plasma gas temperature in the HVNPD remains close to room temperature whereas the plasma gas temperature in the SACD is about 200 K higher than that in HVNPD in the initial phase and continually increases as discharge exposure time goes on.

Effect of dielectric aging on the behavior of a surface nanosecond pulsed dielectric barrier discharge

In this study, surface Dielectric Barrier Discharge (DBD) actuators powered by a nanosecond pulsed high voltage are investigated. The goal is to experimentally analyze the effect of dielectric aging on the electrical behavior of the discharge and the surface plasma morphology. The used actuator is made of two conducting electrodes separated by a thin dielectric made of polyimide and arranged asymmetrically. The active electrode is connected to a nanosecond pulsed high voltage power supply and the second electrode is grounded and encapsulated inside a dielectric material. The actuator is aged by using the surface DBD supplied continuously during 15 minutes with a voltage pulse of + 10 kV at a frequency of 1 kHz and a pulse width of 250 ns. The experimental results show the existence of two discharges during both rising and falling periods of the voltage for both virgin and aged actuators. After aging, a third discharge current component is observed during the voltage plateau due to the ignition of additional discharges, which enhance the energy per pulse. ICCD camera images indicate that the plasma layer extends further on the dielectric surface in the case of aged actuators. In addition, large and non-localized filaments appear during the voltage plateau after aging due to the non-homogenous positive space charge distribution that intensifies the electric filed locally.

Experimental research of diffuse bi-directional pulsed dielectric barrier discharge plasma

A bi-directional nanosecond pulsed power supply is employed to generate diffuse dielectric barrier discharge in N2 using needle-plate electrode configuration at atmospheric pressure. Both discharge images and optical emission spectra of diffuse bi-directional nanosecond high-voltage pulsed dielectric barrier discharge are successfully recorded under severe electromagnetic interference. The diffuse performance of the discharge at different electrode gap distances is observed. The effects of pulse peak voltage, pulse repetition rate, electrode gap distance, He addition, and O2 addition on the optical emission spectra are investigated. The main physicochemical processes involved are discussed.

The Development of Nanosecond Pulse Power Supply of Electrochemical Micromachining

This paper makes some research on designing and manufacturing a nanosecond pulse power supply of electrochemical micromachining, including DC power supply, waveform generation circuit, rectifier and filter circuit，power amplification and rapid protection circuit. This power supply can generate 5MHz maximum frequency and square wave of 100ns pulse width, stably. The voltage ranges from 0V to 10V, and duty ratio ranges from 0.1 to 0.5, continuously.

A diffusive air plasma in bi-directional nanosecond pulsed dielectric barrier discharge

In this study, a diffuse dielectric barrier discharge in air is generated by a bi-directional nanosecond pulsed power supply using a needle–plate electrode configuration at atmospheric pressure. Time-resolved spectra of N2(C 3Πu → B 3Πg, 0–0, 337.1 nm) for both positive and negative pulse discharges are recorded under severe electromagnetic interference. It is found that the lagged time of the photocurrent pulse compared with the voltage pulse in the negative pulse discharge is about 50 times longer than that in the positive pulse discharge at 16 kV pulse peak voltage and becomes shorter with an increase in pulse peak voltage. In addition, the gas temperature of the air plasma is determined to be approximately 395 K by measuring the optical emission spectra of the first negative band of , 0–0, 391.4 nm).

Design and its Experiments of Micro Electrochemical Machining System

A micro Electrochemical Machining (ECM) system has been developed, and macro/micro complex feed mechanism has been presented in order to achieve high-resolution. A nanosecond pulse power supply for micro-ECM has been developed, and the minimum pulse width can reach 50 ns. Complementary chopper circuit has been designed to avoid waveform distortion, which can achieve higher pulse frequency. A series of ECM experiments using the machining system have been carried out, and results of tests have proved that high-resolution spindle, and high frequency, short pulse width power supply help to achieve better quality surface, higher machining accuracy.

Development of Ultra-Short Pulse Power Supply Applicable to Micro-ECM

A nanosecond pulse power supply for micro-ECM (Electrochemical Machining) has been developed, and the minimum pulse on-time is 50 ns. After the influence of ultra-short pulse on micro-ECM was analyzed, complementary chopper circuit was presented to avoid waveform distortion, which can achieve higher pulse frequency. A fast protect circuit was designed, and its response time is less than 5μs, which can avoid damaging workpiece and electrical components by switching off machining voltage and step motor as soon as a short circuit was detected. A series of ECM experiments using the power supply have been carried out, and results of test have proved that high frequency, short pulse width power supply helps to achieve better quality surface, higher machining accuracy.

Experimental research on the localized electrochemical micro-machining

Due to several advantages and wider range of applications, micro-ECM is considered to be one of the most effective advanced future micromachining techniques. An experimental set-up for micro-ECM is constructed, which consists of various components and sub-systems, e.g. mechanical machining unit, nanosecond pulse power supply, circulation system of electrolyte, movement control component and process monitoring component. In addition, this system has the functions of fabricating micro tool electrode and machining status detection. Using the self-developed experimental system, the micro tool-electrode and the micro holes are sequentially machined. Upon the application of ultrashort voltage pulses, micro hole with 20μm diameter is obtained. Experimental results show the potential capability of electrochemical micromachining for better machining accuracy and smaller machining size.

Theoretical and experimental research into electrochemical micro-machining using nanosecond pulses

Based on the principle of electrochemical reactions,the characteristic and mechanism of nanosecond pulses electro-chemical micro-machining are investigated and the theoretical model of micro-electrochemical machining(ECM) is founded.The affections of electrolyte concentration,electrodes gap and pulse parameters on the result of electrochemical micro-mach-ining are discussed.The practical electrochemical machining system is developed.It consists of micro-machining equipment,nanosecond pulse power supply,electrolyte circulating system,movement control component and process monitoring compon-ent.The effects of pulse on-time and voltage on the side gap of electrodes are investigated with experiments.The result of exp-eriments show that decreasing pulse duration and voltage can enhance the localization and improve electrochemical micro-machining accuracy.On the self-developed equipment,tool ele-ctrode and workpiece are sequentially machining in electro-chemical method.Inter-electrode gap is restrained less than 5 μm.A crisscross micro-groove with 30 μm width and the mic-ro-structure with size 20 μm×30 μm×30 μm is produced.The influence of starting point upon forming precision is analyzed.The experimental results prove that micro-ECM can well meet the demand of micro machining.

A high repetition rate nanosecond pulsed power supply for nonthermal plasma generation

The basic principles of high repetition rate nanosecond pulsed power supplies, the design, and the implementation are presented. Voltage pulses of 20-30 kV with a rise time of 30 ns, a pulse duration of 200 ns, a pulse repetition rate of 1-2 kHz, an energy per pulse of 0.5-1 J, and the average power up to 0.5-1 kW have been achieved with total energy conversion efficiency of 90%. The protective circuit against overvoltage and the measurement of high-voltage output are described.