Basic Characteristics of In-Liquid Plasma Jet and Electrode Damage

The most progress towards a practical method of fusing municipal waste incineration ash has been in the use of a plasma jet that employs arc discharge, a form of thermal plasma. However, a remaining problem is that stable plasma generation is prevented by melting of the nozzle of the plasma-jet torch by the high-temperature plasma flow. With the objective of developing high-speed fusion treatment for waste materials using an in-liquid plasma jet, basic research was conducted on plasma stability and the durability of plasma-jet torches, including electrodes and nozzles. Basic plasma jet characteristics such as the discharge voltage, current, and power value at the time of plasma jet generation were investigated experimentally. The relationship between the temperature distribution near the tip of a plasma jet torch and electrode damage was investigated by fluid-heat coupled analysis using the finite element method.

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Lowtemperature plasma generator for effective processing of materials

Ferrous Metallurgy Bulletin of Scientific Technical and Economic Information ◽

10.32339/0135-5910-2021-5-587-592 ◽

2021 ◽

Vol 77 (5) ◽

pp. 587-592

Author(s):

M. Kh. Gadzhiev ◽

A. S. Tyuftyaev ◽

Yu. M. Kulikov ◽

M. A. Sargsyan ◽

D. I. Yusupov ◽

...

Keyword(s):

Low Temperature ◽

Flow Rate ◽

Gas Flow ◽

Arc Discharge ◽

Plasma Jet ◽

Plasma Generator ◽

Low Temperature Plasma ◽

Temperature Plasma ◽

High Enthalpy ◽

High Resource

Low-temperature plasma is used in metallurgy for steel alloying by nitrogen, deoxidization of magnetic alloys, obtaining of steels with particularly low carbon content, metal cleaning of nonmetallic inclusions, desulfurization and other refining processes. The wide application of those technologies is restrained by absence of reliable generators of low-temperature plasma (GLP) with sufficient resource of continuous operation. As a result of studies, a universal generator of high-enthalpy plasma jet of various working gases was created. The generator has expanding channel of the output electrode with an efficiency of ~60 % for argon working gas and ~80% for nitrogen and air. It was shown that the developed generator of low-temperature plasma ensures formation of a weakly diverging (2α = 12°) plasma jet with a diameter D = 5–12 mm, an enthalpy of 5–50 kJ/g and a mass average temperature of 5–10 kK, at a full electric power of the arc discharge of 5–50 kW and a plasma-forming gas flow rate of 1–3 g/s. Results of the study of propane additions to the plasma-forming gas effect on the state of cathodes with inserts made of pure tungsten, lanthanum tungsten, and hafnium presented. It was shown that a small propane addition (1%) to the plasma-forming gas, results in reducing effect of the insert material. Study of the GLP operation at arc current 100A with addition to the working gas nitrogen maximum possible volume of propane, which don’t disturb stability of arc showed that for the developed plasma generator at the nitrogen flow rate ~0,45 g/s, the propane flow rate was ~0,33 g/s (not more than ~73 % of the plasma-forming gas). The created high-resource GLP with changeable electrodes enables to obtain at the exit a high-enthalpy plasma flow of various gases (argon, nitrogen, air) and can be a prototype of more powerful plasmotrons of various technological application, in particular for plasma metallurgy.

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Formation of High Crystallinity Silicon Films by High Speed Scanning of Melting Region Formed by Atmospheric Pressure DC Arc Discharge Micro-Thermal-Plasma-Jet and Its Application to Thin Film Transistor Fabrication

Applied Physics Express ◽

10.1143/apex.3.061401 ◽

2010 ◽

Vol 3 (6) ◽

pp. 061401 ◽

Cited By ~ 11

Author(s):

Shohei Hayashi ◽

Seiichiro Higashi ◽

Hideki Murakami ◽

Seiichi Miyazaki

Keyword(s):

Thin Film ◽

Thermal Plasma ◽

Atmospheric Pressure ◽

High Speed ◽

Arc Discharge ◽

Thin Film Transistor ◽

Plasma Jet ◽

High Crystallinity ◽

Transistor Fabrication ◽

Dc Arc

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Experimental Study and Numerical Simulation on Propagation Properties of a Plasma Jet in a Cylindrical Liquid Chamber

Journal of Applied Mechanics ◽

10.1115/1.4023316 ◽

2013 ◽

Vol 80 (3) ◽

Cited By ~ 3

Author(s):

Yonggang Yu ◽

Qi Zhang ◽

Na Zhao ◽

Dongyao Liu

Keyword(s):

Liquid Medium ◽

High Speed ◽

Plasma Jet ◽

Flow Region ◽

Discharge Voltage ◽

Main Flow ◽

Camera System ◽

Compression Region ◽

Two Phases ◽

Propagation Properties

A simulator is designed to explore the interactive mechanism of a plasma jet with the liquid medium in the bulk-loaded liquid electrothermal chemical launching process. The properties of the plasma jet expanding in the liquid and the mixing characteristics of the plasma jet with liquid in the cylindrical chamber are studied using a high speed camera system. According to the experimental results, a two-dimensional axisymmetric unsteady compressible flow model has been proposed. The transient characteristics of the jet in flow field have been simulated. The results indicate that, during the expansion of the plasma jet in the liquid medium, there is relatively strong turbulent mixing. The interface between the two phases is not smooth and fluctuates with time stochastically. The higher the discharge voltage is, the stronger the Helmholtz instability effect will be. The Taylor cavity forming during the jet expansion can be divided into three regions: the main flow region, the compression region, and the backflow vortex region. In the main flow region the temperature and velocity of the plasma jet are relatively high and both decrease along the axial and radial direction. The pressure near the Taylor cavity head is high. The high pressure region grows gradually while the pressure value decreases. The calculated axial expansion displacement of the Taylor cavity coincides well with the measured one from experiment.

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Possibility of Humid Municipal Wastes Hygienisation Using Gliding Arc Plasma Reactor

Water ◽

10.3390/w13020194 ◽

2021 ◽

Vol 13 (2) ◽

pp. 194

Author(s):

Joanna Pawłat ◽

Piotr Terebun ◽

Michał Kwiatkowski ◽

Katarzyna Wolny-Koładka

Keyword(s):

Low Temperature ◽

Plasma Treatment ◽

Alternative Fuels ◽

Raw Materials ◽

Arc Discharge ◽

Plasma Reactor ◽

Municipal Waste ◽

Low Temperature Plasma ◽

Temperature Plasma ◽

Gliding Arc

Sterilization of municipal waste for a raw material for the production of refuse-derived fuel and to protect surface and ground waters against biological contamination during transfer and storage creates a lot of problems. This paper evaluates the antimicrobial potential of non-equilibrium plasma in relation to the selected groups of microorganisms found in humid waste. The proposed research is to determine whether mixed municipal waste used for the production of alternative fuels can be sterilized effectively using low-temperature plasma generated in a gliding arc discharge reactor in order to prevent water contamination and health risk for working staff. This work assesses whether plasma treatment of raw materials in several process variants effectively eliminates or reduces the number of selected groups of microorganisms living in mixed municipal waste. The presence of vegetative bacteria and endospores, mold fungi, actinobacteria Escherichia coli, and facultative pathogens, i.e., Staphylococcus spp., Salmonella spp., Shigella spp., Enterococcus faecalis and Clostridium perfringens in the tested material was microbiologically analyzed. It was found that the plasma treatment differently contributes to the elimination of various kinds of microorganisms in the analyzed raw materials. The effectiveness of sterilization depended mainly on the time of raw materials contact with low-temperature plasma. The results are very promising and require further research to optimize the proposed hygienization process.

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High-Speed Video Analysis of the Process Stability in Plasma Spraying

Journal of Thermal Spray Technology ◽

10.1007/s11666-021-01159-1 ◽

2021 ◽

Author(s):

K. Bobzin ◽

M. Öte ◽

M. A. Knoch ◽

I. Alkhasli ◽

H. Heinemann

Keyword(s):

Plasma Spraying ◽

High Speed ◽

Plasma Jet ◽

Plasma Jets ◽

Time Dependent ◽

Acquisition Time ◽

Fast Fourier Transformation ◽

Frequency Spectra ◽

Dependent Signal ◽

The Stability

AbstractIn plasma spraying, instabilities and fluctuations of the plasma jet have a significant influence on the particle in-flight temperatures and velocities, thus affecting the coating properties. This work introduces a new method to analyze the stability of plasma jets using high-speed videography. An approach is presented, which digitally examines the images to determine the size of the plasma jet core. By correlating this jet size with the acquisition time, a time-dependent signal of the plasma jet size is generated. In order to evaluate the stability of the plasma jet, this signal is analyzed by calculating its coefficient of variation cv. The method is validated by measuring the known difference in stability between a single-cathode and a cascaded multi-cathode plasma generator. For this purpose, a design of experiment, covering a variety of parameters, is conducted. To identify the cause of the plasma jet fluctuations, the frequency spectra are obtained and subsequently interpreted by means of the fast Fourier transformation. To quantify the significance of the fluctuations on the particle in-flight properties, a new single numerical parameter is introduced. This parameter is based on the fraction of the time-dependent signal of the plasma jet in the relevant frequency range.

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Tiny Cold Atmospheric Plasma Jet for Biomedical Applications

Processes ◽

10.3390/pr9020249 ◽

2021 ◽

Vol 9 (2) ◽

pp. 249

Author(s):

Zhitong Chen ◽

Richard Obenchain ◽

Richard E. Wirz

Keyword(s):

Biomedical Applications ◽

Plasma Jet ◽

Discharge Voltage ◽

Plasma Jets ◽

Atmospheric Plasma ◽

Physical Parameters ◽

Cold Atmospheric Plasma ◽

Water Metal ◽

Plasma Probe ◽

Jet Nozzle

Conventional plasma jets for biomedical applications tend to have several drawbacks, such as high voltages, high gas delivery, large plasma probe volume, and the formation of discharge within the organ. Therefore, it is challenging to employ these jets inside a living organism’s body. Thus, we developed a single-electrode tiny plasma jet and evaluated its use for clinical biomedical applications. We investigated the effect of voltage input and flow rate on the jet length and studied the physical parameters of the plasma jet, including discharge voltage, average gas and subject temperature, and optical emissions via spectroscopy (OES). The interactions between the tiny plasma jet and five subjects (de-ionized (DI) water, metal, cardboard, pork belly, and pork muscle) were studied at distances of 10 mm and 15 mm from the jet nozzle. The results showed that the tiny plasma jet caused no damage or burning of tissues, and the ROS/RNS (reactive oxygen/nitrogen species) intensity increased when the distance was lowered from 15 mm to 10 mm. These initial observations establish the tiny plasma jet device as a potentially useful tool in clinical biomedical applications.

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Bubble Dynamics in a Two-Phase Bubbly Mixture

Volume 7: Fluid Flow, Heat Transfer and Thermal Systems, Parts A and B ◽

10.1115/imece2010-40509 ◽

2010 ◽

Cited By ~ 2

Author(s):

Arvind Jayaprakash ◽

Sowmitra Singh ◽

Georges Chahine

Keyword(s):

Void Fraction ◽

High Speed ◽

Bubble Dynamics ◽

Bubble Radius ◽

Discharge Voltage ◽

Large Bubble ◽

Water Mixture ◽

Two Phase ◽

Mixture Density ◽

Bubbly Medium

The dynamics of a primary relatively large bubble in a water mixture including very fine bubbles is investigated experimentally and the results are provided to several parallel on-going analytical and numerical approaches. The main/primary bubble is produced by an underwater spark discharge from two concentric electrodes placed in the bubbly medium, which is generated using electrolysis. A grid of thin perpendicular wires is used to generate bubble distributions of varying intensities. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the pressure imposed in the container. The size and concentration of the fine bubbles can be controlled by the electrolysis voltage, the length, diameter, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the bubble characteristic quantities such as maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and the mixture is observed using high speed video photography. The void fraction/density of the bubbly mixture in the fluid domain is measured as a function of time and space using image analysis of the high speed movies. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to simple compressible equations employed for spherical bubbles including a modified Gilmore Equation. Suggestions for improvement of the modeling are then presented.

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Design and use of an Efficient Plasma Jet Reactor for High Temperature Gas/Solid Reactions

MRS Proceedings ◽

10.1557/proc-30-133 ◽

1983 ◽

Vol 30 ◽

Cited By ~ 1

Author(s):

F. W. Giacobbe ◽

D. W. Schmerling

Keyword(s):

Carbon Monoxide ◽

High Temperature ◽

Arc Discharge ◽

Plasma Jet ◽

Direct Result ◽

Discharge Region ◽

Plasma Flame ◽

Powdered Carbon ◽

High Yields ◽

Experimental Trials

ABSTRACTA unique and efficient plasma jet reactor has been developed and used to study the high temperature production of carbon monoxide from a reaction between powdered carbon and a pure carbon dioxide plasma. The plasma jet reactor was designed to allow the injection of powdered carbon above the arc discharge region rather than into the plasma flame below the arc discharge region. High yields of carbon monoxide, produced at relatively high efficiencies, were a direct result of this technique. The plasma jet was also designed to enable rapid changing and testing of various anode insertsAverage yields of carbon monoxide in the product gases were as high as 80–87% in selected experimental trials. Carbon monoxide was produced at rates exceeding 15,000 1/hr (at STP) with a power expenditure of 52 Kw.

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