A review of mainly the past two years is undertaken of the industrial applications of pulsed power. Repetitively operated pulsed power generators with a moderate peak power have been developed for industrial applications. These generators are reliable and have low maintenance. Development of the pulsed power generators helps promote industrial applications of pulsed power for such things as food processing, medical treatment, water treatment, exhaust gas treatment, ozone generation, engine ignition, ion implantation and others. Here, industrial applications of pulsed power are classified by application for biological effects, for pulsed streamer discharges in gases, for pulsed discharges in liquid or liquid- mixture, and for material processing.

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Industrial Applications of Pulsed Power Technology

We simulate short positive and negative streamers in air at standard temperature and pressure. First, double-headed streamers in homogeneous electric fields of 50 kV cm^(−1) are briefly studied, and then we analyse streamers that emerge from needle electrodes with voltages of 10–20 kV in more detail. The streamer velocity at a given streamer length depends only weakly on the initial ionization seed, except in the case of negative streamers in homogeneous fields. We characterize the streamer evolution by length, velocity, head radius, head charge and maximal field enhancement. We show that the velocity of positive streamers is determined mainly by their radius and in quantitative agreement with recent experimental results both for radius and velocity. The velocity of negative streamers is dominated by electron drift in the enhanced field; in the low local fields of the present simulations, it is little influenced by photo-ionization. Initially it is puzzling that negative streamers can be slower than positive ones under similar conditions, both in experiment and in simulation, as negative streamer fronts always move at least with the electron drift velocity in the local field. We argue that this drift motion broadens the streamer head, decreases the field enhancement and ultimately leads to slower propagation or even extinction of the negative streamer.

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Positive and negative streamers in ambient air: modelling evolution and velocities

Positive and negative streamers are studied in ambient air at 1 bar; they emerge from a needle electrode placed 40mm above a planar electrode. The amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses have rise times of 30 ns or shorter. Diameters, velocities and energies of the streamers are measured. Two regimes are identified; a low voltage regime where only positive streamers appear and a high voltage regime where both positive and
negative streamers exist. Below 5 kV, no streamers emerge. In the range from 5 to 40 kV, positive streamers form, while the negative discharges only form a glowing cloud at the
electrode tip, but no streamers. For 5–20 kV, diameters and velocities of the positive streamers have the minimal values of d = 0.2mm and v ≈ 10^5 ms^(−1). For 20–40 kV, their diameters increase by a factor of 6 while the voltage increases only by a factor of 2. Above the transition value of 40 kV, streamers of both polarities form; they strongly resemble each other, though the positive ones propagate further; their diameters continue to increase with applied voltage. For 96 kV, positive streamers attain diameters of 3mm and velocities of 4 × 10^6 ms^(−1); negative streamers are about 20% slower and thinner. An empirical fit formula for the relation between velocity v and diameter d is v = 0.5d^2 mm^(−1) ns^(−1) for both polarities. Streamers of both polarities dissipate energies of the order of several millijoules per streamer while crossing the gap.

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Positive and negative streamers in ambient air: measuring diameter, velocity and dissipated energy

Plasma-catalytic removal of toluene over CeO2-MnOx catalysts in an atmosphere dielectric barrier discharge

A review of air filtration technologies for sustainable and healthy building ventilation

Removal of dilute VOCs in air by post-plasma catalysis over Ag-based composite oxide catalysts

Streamer properties such as their velocity, diameter, intensity and density, can be obtained by analysis of temporal and spatial resolved ICCD imaging. In this paper, experimental results on streamer generation and propagation as a function of several high-voltage pulse and reactor parameters are described. Experiments were performed on a large scale wire–plate reactor in ambient air. The set-up allows for independent variation of the parameters over wide ranges. The minimum gate time of the ICCD camera is 5 ns, allowing for a high temporal resolution. The camera can be triggered with a precision of 1 ns. Both negative and positive polarity pulses are investigated. The most important conclusions are as follows. (1) The streamer velocity ((0.5–2.5) × 106 m s−1) increases if the applied electric field and/or the voltage rise rate is increased. (2) The same is true regarding the velocity ((0.2–1.2) × 105 m s−1) with which the streamer diameter (0.7–3.0 mm) increases during propagation. (3) Typical properties (velocity, diameter, etc) of negative and positive polarity streamers vary less than 25%, especially when the applied electric field is high. (4) As long as the dc bias voltage is below the dc corona onset value it does not have a separate effect on the visual streamer properties. Only the total voltage (peak voltage + dc) is of importance. (5) A simple model was used to determine the electric field in the secondary streamer channel. It was found that in the light emitting part of the secondary streamer the electric field is approximately 21.5 kV cm−1. In the remainder (dark part) of the channel the electric field is around 6.5 kV cm−1. This paper shows mainly experimental findings. Not all observed relations and phenomena could be explained. This is partly caused by the fact that current theoretical and numerical models are not yet able to describe the experimental situation as used during this study.

https://iopscience.iop.org/article/10.1088/0022-3727/41/23/234001/pdf

Analysis of streamer properties in air as function of pulse and reactor parameters by ICCD photography

For pulsed corona plasma applications, it becomes important to develop pilot systems with large average power and high-energy conversion efficiency Since the beginning of 2000, we have been working on an industrial corona plasma system with tasks of 10-30 kW in average power and higher than 90% of total energy conversion efficiency The pulsed-power source should have the following specifications: rise time of 10-25 ns, pulsewidth of 50-150 ns, pulse repetition rate of up to 1000 pulses per second, peak voltage pulse of 70 kV, peak current of 35 kA, dc bias voltage of 10-35 kV, and energy per pulse of up to 30 J Sixteen parallel wire cylinder reactors are used to match the source Gas and reactor temperatures can be controlled individually with water flow around the outside of those cylinders The system is designed for gaseous oxidation and electrostatic dust precipitation The system has been used for up to 17 kW in average power This paper reports the system in detail, discusses issues related to the matching between the source and the reactor, and presents an example of industrial demonstrations on odor abatement at 1000 m3/h Finally, this paper also gives a general guideline for design of corona plasma systems

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An Industrial Streamer Corona Plasma System for Gas Cleaning

In this article a critical component for pulsed power applications is described: the heavy-duty switch. The design of a coaxial, high repetition rate, large average power, and long lifetime spark-gap switch is discussed. The switch is used with a fail-free LCR trigger circuit. Critical issues for switch design are presented together with experimental results. It is observed that the switch has a good stability, and its lifetime is estimated to be in the order of 1010 shots (∼106C) at 10J∕pulse, 60kV and 100ns pulses. Measurements were performed with 20 and 34kV average switching voltage (100ns pulses, energy per pulse 0.4 and 0.75J, respectively). For up to 450pulses∕s (pps), pre-firing can be prevented by increasing the gap pressure (up to 2.5 and 7bars, respectively), no gas flush is required. Above 450pps, up to 820pps, a forced gas flow of maximal 35Nm3∕h, is required for stable operation. Measurements on the time delay and jitter of the switch demonstrate that these values are influenced by pressure,...

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Long lifetime, triggered, spark-gap switch for repetitive pulsed power applications

The main technical challenges for the treatment of volatile organic compounds (VOCs) with plasma-assisted catalysis in industrial applications are large volume plasma generation under atmospheric pressure, byproduct control, and aerosol collection. To solve these problems, a back corona discharge (BCD) configuration has been designed to evenly generate nonthermal plasma in a honeycomb catalyst. Voltage–current curves, discharge images, and emission spectra have been used to characterize the plasma. Grade particle collection results and flow field visualization in the discharge zones show not only that the particles can be collected efficiently, but also that the pressure drop of the catalyst layer is relatively low. A three-stage plasma-assisted catalysis system, comprising a dielectric barrier discharge (DBD) stage, BCD stage, and catalyst stage, was built to evaluate toluene treatment performance by BCD. The ozone analysis results indicate that BCD enhances the ozone decomposition by collecting aerosols...

Zhen Liu

Papers

Removal of dilute VOCs in air by post-plasma catalysis over Ag-based composite oxide catalysts

Analysis of streamer properties in air as function of pulse and reactor parameters by ICCD photography

An Industrial Streamer Corona Plasma System for Gas Cleaning

Long lifetime, triggered, spark-gap switch for repetitive pulsed power applications

Characteristics of back corona discharge in a honeycomb catalyst and its application for treatment of volatile organic compounds.