AC Arc Plasma Research Articles

Review of DC and AC Arc Plasma at High Pressures Above Atmospheric Pressure

Review of DC and AC Arc Plasma at High Pressures Above Atmospheric Pressure

Modelling of Electric Processes in Circuits of Arc Plasma Torches Part 1. Approximations of Static Characteristics of Arc Plasma Torches

The article discusses selected structural and operational properties of DC and AC arc plasma torches. References cited in the article contain generalised analytical expressions identifying experimental current-voltage characteristics of typical arc plasma torches. Values of coefficients in formulas approximating static current-voltage characteristics depend not only on the type and the polarity of the plasma torch but also on values of criterial factors. The study discusses separately DC plasma torches and single-phase AC plasma torches.

Temperature and composition of AC arc plasma of medium voltage distribution networks in the air

AC electric air arcs in medium voltage (MV) distribution networks, including railway catenary, photovoltaic power generation systems, and traditional distribution networks, can cause insulation damage accidents. Although various studies have been performed on the macroscopic characteristics of the MV AC arc in the air, the research on the physical properties of the arc, such as temperature field and particle composition, is relatively lacking. This work deals with diagnosing the temperature and particle composition of the arc under laboratory conditions based on the arc generation and the moiré deflection diagnosis systems. Based on the experimental results, there are three typical stages in developing the MV AC arc: the initial, transition, and stable combustion. The temperature during the stable combustion of the arc is between 1500 and 2100 K, while the fluctuation period is half a power frequency cycle. The particle components of the arc are mainly composed of O2, N2, and O. Different from the DC arc, the AC arc exhibits a zero-crossing extinguishing phenomenon, while the gap temperature is still high after extinguishing the arc, and the insulation has not been fully restored. This research provides a method for diagnosing MV AC arcs in the air under laboratory conditions and initial values for the arc modeling.

Unsteady state analysis of free-burning arcs in a 3-Phase AC plasma torch: comparison between parallel and coplanar electrode configurations

An MHD model with parallel electrode configuration was developed to determine the influence of the electrode configuration on 3-Phase arc discharge behavior. The results obtained with this model were compared to previous results obtained with coplanar graphite electrode configuration. Results show a different arc behavior in both cases. In a parallel electrode configuration, the arcs are not confined within the inter-electrode gap as in coplanar electrode configuration. These results were compared to the arc behavior observed with a high-speed video-camera in a nitrogen atmosphere with a high correlation. The influence of frequency and current was also investigated. By adjusting the electrode configuration, the arc elongation and the dissipated power could be controlled. According to the application, such as plasma-assisted combustion, plasma gasification, plasma spray or for different plasma gases, the electrode configuration could play a key role to improve the discharge or operation. This study gives us a better understanding of 3-Phase AC arc plasma discharge.

Synthesis of structure controlled carbon nanomaterials by AC arc plasma process

Carbon nanoparticles (CNPs) with a controlled structure were synthesized through an attractive method based on the decomposition of methane in arc plasma processing. The effects of argon and methane flow rate, electrode material, and input electronic current on the morphology and CNPs' size were studied. The size and morphology of CNPs were characterized using scanning electron microscopy and transmission electron microscopy. Surface area and microstructure were characterized through BET surface area analysis, X-ray diffraction and Raman spectroscopy. The results showed that the BET surface area and resistivity of the CNPs were decreased with increasing input electronic current.

High Speed Video Camera and Electrical Signal Analyses of Arcs Behavior in a 3-Phase AC Arc Plasma Torch

A 3-phase AC plasma torch has been developed and aims at overcoming some limits of the classical DC torches in terms of efficiency, cost and reliability. However, the arc behavior in 3-phase plasma torch remains poorly explored. This paper is dedicated to the high speed video camera at 100,000 frames per second and electrical signal analyses of arcs behavior in a 3-phase AC arc plasma torch. First, a reference case at 150 A, in nitrogen as working gas, has been deeply analyzed. Afterwards, a parametric study based on current and inter-electrode gap has been carried out. Results show that only one arc can exist at a given time and arcs rotate by switching from a pair of electrodes to another one, following the maximal electrical gap potential. However, a particular “abnormal” arc behavior was sometimes observed. Indeed, the arc motion within the inter-electrode gap increases the heat exchange and stabilizes the 3-phase discharge whereas the system is unbalanced when the arc is in the periphery. The analysis highlights that the arc motion is strongly influenced by the electrode jet velocity and repulsive Lorentz forces. The parametric study shows that the current increases both jet velocity and arc discharge stability. Elsewhere, the increase of the inter-electrode gap can also stabilizes the electrical 3-phase arc discharge. Furthermore, the correlation between arc motion and current waveform is highlighted. This work is likely to open the way toward a better understanding of 3-phase discharges in the perspective of their further optimization.

Electrode temperature measurements of multi-phase AC arc by high-speed video camera

The multi-phase AC arc plasma has been applied in the glass melting technology as a promising heat source. The electrode erosion of the multi-phase arc is one of the most important issues to be solved. In the present work, the theory of the two-colour pyrometry by using the high-speed video camera with band-pass filters was applied to the electrode temperature measurements. First, the spectroscopic measurements of the electrode region in the multi-phase arc were conducted to select the appropriate wavelengths of band-pass filters. Then, the electrode temperatures of 2-phase, 6-phase, and 12-phase arcs were measured. The electrode tip temperature and the molten area were evaluated from the obtained 2-dimensional temperature distributions. Results indicated that the increase of the number of the phases leads to the lower tip temperature and the larger molten area. Observation of the multiple arcs further revealed the particular characteristics of the multi-phase arc, such as the periodical arc motion has important role on the electrode molten state.

In-flight particle measurement of glass raw materials in hybrid heating of twelve-phase AC arc with oxygen burner

The high temperature provided by a 12-phase AC arc plasma is beneficial to finish vitrification reaction in milliseconds. Another heating method called “hybrid plasma” combines multi-phase AC arc and oxygen burner are expected to improve glass quality and increase productivity with minimum energy consumption. In this study, recent works on the development of in-flight particle measurement in hybrid plasma system are presented. Two-colour pyrometry offers considerable advantages for measuring particle temperatures in flight. A high-speed camera equipped with a band-pass filter system was applied to measure the in-flight temperatures of glass particles. The intensity recorded by the camera was calibrated using a tungsten halogen lamp. This technique also allows evaluating the fluctuation of the average particle temperature within millisecond in plasma region.

Experimental investigation of in-flight melting by hybrid heating of multi-phase alternating current arc with oxygen burner for alkali-free glass raw materials

An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by hybrid heating of multi-phase AC arc combined with an oxygen burner. A multi-phase AC arc and hybrid plasma were compared to study the in-flight melting efficiency of the granulated raw materials. The effects of the input energy and the primary size of SiO2 in the glass raw materials on the characteristics of the in-flight melted particles were investigated. The reaction rate inside the individual in-flight particles was enhanced with decreasing the primary size of SiO2 particles, resulting in the more effective in-flight melting by the hybrid plasma.

In-Flight Particle Measurement of Alkali-Free Glass Raw Materials in 12-Phase AC Arc Plasma

In-flight particle measurements of the surface temperature and velocity are important for understanding of melting behavior of glass particles during in-flight melting by multi-phase AC arc plasma. However, the use of optical pyrometry for particle surface temperature has inevitable uncertainties due to non-thermal emissions signals from the plasma plume. This work presents spectroscopic measurements of the non-thermal signals which were found to be caused mainly by the plasma emissions scattered by the particles and the radiation emitted by vapor. After that, the accuracy of thermal radiation measurement was estimated and surface temperature of in-flight glass particle was corrected.

High-Speed Observation of AC Arc Plasma Superimposed Pulse Current at Current Zero Point

The use of ac arc plasma involves a problem of instability of the arc plasma at current zero point. A method for stabilizing the transferred-type ac arc plasma has been developed by superimposing a pulse current on an ac current only at each current zero point. In this paper, a high-speed observation of the ac arc plasma is carried out in order to investigate on the stabilization of the ac arc plasma by superimposing a pulse current.

Investigation of In-Flight Melting Behaviour of Granulated Glass Raw Material by Multi-Phase AC Arc Plasma and Hybrid Plasma

An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by twelve-phase AC arc and that combined with an oxygen burner. The particle measurement was carried out to investigate the in-flight melting behavior of glass raw materials during the in-flight melting by twelve-phase AC arc. Obtained results show the mean particle velocity was about 9 m s−1 and mean temperature was about 2600 K. The high vitrification degree achieved within several milliseconds reveals that the new in-flight melting technology of hybrid plasma treating can reduce energy consumption and shorten the glass production cycle.

Ac-driven plasma torch with a well-type cathode working in air and CO2

This work is devoted to the investigation of the discharge characteristics of an ac arc plasma torch with a well-type cathode working in air and CO2. The electrical characteristics, plasma jet image and optical emission profile are investigated by varying the discharge power and the gas flow rate. The dynamic behaviour of arc voltage and current is characterized by smooth-shaped waveforms, regularly iterated with a driving frequency. The moving of arc spot positions is inferred from the measured waveforms, and compared with that observed in dc torches. A simple lifetime test is performed to verify the speculation that the arc spots in ac operation move continuously over a wide region with a very high speed. The result shows that the electrode lifetime can be enhanced by combining the vortex motion of arc gas with the ac driving.

Effect of Injection Position on In-Flight Melting Behavior of Granular Alkali-Free Glass Raw Material in 12-Phase AC Arc Plasma

An innovative in-flight glass melting technology with a multi-phase AC arc plasma was developed to save energy and reduce emissions for the glass industry. The effect of the injection position on the in-flight melting behavior of granulated powders was investigated. Results show that the injection position has a strong effect on the melting behavior of alkali-free glass raw material. With the increase in injection distance, the vitrification, decomposition, and particle shrinkage of initial powders are improved. Longer injection distance causes much energy to transfer to particles due to a longer residence time of powder in the high temperature zone. The high vitrification and decomposition degrees indicate that the new in-flight melting technology with 12-phase AC arc can substantially reduce the melting and refining time for glass production.

Plasma pyrolysis of toxic waste

The comparison of technical economic indexes of different waste treatment methods and plasma pyrolysis is presented in the paper. It testifies that plasma technologies are economically expedient for these purposes. Physical prerequisites allowing realizing plasma technologies are presented. Reliable and economical (70–120 Euro per ton of treated product) plasma generation is the basic condition of the technology realization. In this connection, various types of powerful generators of dense plasma (plasmatrons) in the range from 100 kW to 3 MW and temperature of plasma jets from 2000 to 10 000 K, and also physical processes taking place in electric-discharge chambers are examined. Differences between AC and DC electric arc plasma generators are analysed. Temperature in arcs of plasma generators varies from 6000 to 20 000 K, electron concentration is ne∼(1014–1019 cm−3). Specific ware of electrodes in various types of plasma generators intended for long-time operation modes is (10−7–10−4) g C−1. Physicochemical processes in plasma reactors intended for waste treatment and pyrolysis are described.Different types of technological processes on plasma treatment and pyrolysis of waste are analysed. Estimation of present situation of physical investigations and technological developments in this area and predictions for nearest future are included.This article was scheduled to appear in issue 5 of Plasma Phys. Control. Fusion. To access this Special issue please follow this link: http://www.iop.org/EJ/toc/0741-3335/45/5

Effect on transferred ac arc plasma stability of increasing ambient temperature and superimposing pulse at current zero point

The use of alternating current (ac) arc plasma involves a problem of instability of the arc plasma at current zero point. This paper describes the effects of ambient temperature and of superimposing a pulse current on stability of the ac argon arc plasma; the pulse current (10 A) is superimposed on an ac current only at each current zero point. The ac arc plasma is generated between a tungsten electrode of a plasma torch and a copper counter electrode in a chamber. The ac current is 100-500 Arms and the arc plasma length is 40 mm. As the ambient temperature increases from 300 K to 900 K, the stored energy in the arc plasma increases and the required supply voltage to stabilize the arc plasma decreases by about 20% (from 270 to 220 Vrms). Additionally, superimposing a pulse current on an ac current causes the required supply voltage to decrease by about further 20% (from 220 to 180 Vrms).

電流零点パルス重畳法による移行形交流プラズマの安定化

電流零点パルス重畳法による移行形交流プラズマの安定化

Deviations from equilibrium in the 6 3P levels of mercury in an ac arc plasma

Deviations from excitation equilibrium in the Hg 6 3P levels averaged along a radius and in the core of an arc (50 Hz) high-pressure (≈3 atm) mercury arc at 0.5 and 5 ms after the voltage-zero crossing are determined spectroscopically. The results are interpreted in terms of ionization nonequilibrium, overpopulation of the Hg ground state and emission of the resonance radiation.

Time dependence of nonequilibrium in the Hg resonance level in an AC arc plasma

The time-dependent behaviour of the degree of excitation non-equilibrium in the low lying 6 3P 1 resonance level of mercury at the arc core during half a period of a 50-Hz ac mercury arc plasma has been experimentally determined. The population density of this levels is less than the calculated one assuming equilibrium conditions and it exhibits a modulation out of phase with that of the high lying 6 3D 2 level and in phase with the electron temperature.

Resonant-like reabsorption for copper and silver in an AC arc plasma

To measure the line shapes, the authors photographed the spectra with a PGS-2 spectrograph in the third order with single and double ray passage giving the reciprocal linear dispersions of 0.23 and 0.12nm/mm. The line shapes were constructed from the photometric data, the photometry being performed with a slit width of 0.01 mm. To derive the plasma spectra with lower silver concentrations, the authors recorded time-resolved spectra. The intensity was highest at the start of the exposure and then decreased. Data show that on evaporating approximately equal amounts of copper and silver in an arc, one can neglect the effects of reabsorption on the Cu I 327.4 nm and Ag I 338.2 nm lines also.