AC Arc Discharge Research Articles

Numerical Evaluation of Melting and Breaking Conditions of Strands due to AC Arc Discharge Generated between Wires in 66kV Overhead Transmission Line

Numerical Evaluation of Melting and Breaking Conditions of Strands due to AC Arc Discharge Generated between Wires in 66kV Overhead Transmission Line

AC flashover characteristics and arc development process of glaze ice-covered insulators in natural environment

Ice accretion on the insulators can reduces the creepage distance to a certain extent as low as the dry arc distance, which may cause flashover trip and subsequent blackout. Extensive research on insulator icing has been carried out in a controlled-climate room. Due to great differences in environmental parameters between laboratory simulation and field tests, icing characteristics and discharge development of ice-covered insulator obtained in the laboratory cannot veritably reflect natural icing law and arc propagation process. Consequently, in the present study the glaze-icing on energized insulators was investigated on site, and the mechanism of icicle growth on the insulator energized with different voltage levels was revealed. Meanwhile, AC flashover performances and arc discharge development of ice-coated insulators for the two test conditions were compared and discussed. Results show that for a weak electric field, icicle firstly grows vertically, and then bends to the axis of the insulator when its length reaches to a certain level. Nevertheless, icicle develops towards the axis at the beginning under a high electric field. AC flashover voltage of ice-accreted insulators increases exponentially with an increasing applied voltage, while the relation of flashover voltage and ice weight fits well with a negative power function. Icing flashover voltage of the insulators obtained in natural environment is 14%～21% higher than that in the chamber. Compared with the flashover in the laboratory, during the discharge of the insulators naturally covered with ice, arc extinction-reignition and floating phenomena are more significant, and the ice-melting is more severe.

Study on the Analysis of Restrike Pattern and Radial Spectrum of AC Arc Discharge based on the Electrode Material

In this study, we designed and fabricated a system based on IEC-62606 and UL-1699 such that stable arc discharge could be produced. AC arc discharge was performed to interpret the restrike pattern and radiation spectrum according to the electrode material. In the voltage waveform analysis of flat copper electrodes, it was analyzed that the accompaniment cycle of the negative waveform was more unstable than the half cycle of the positive waveform. We observed that the radiation spectrum of copper electrodes occurred in the ultraviolet and visible light regions. Moreover, the voltage waveform of the carbon electrode was found to be similar to the pattern produced by the copper electrode. However, we observed that the restrike generated at the half cycle of the negative waveform was produced relatively faster. The radio spectra were strongest near 589 nm, 671 nm, and 766 nm. AC arc discharges using copper electrodes and carbon electrodes were found to be between the arc-discharge patterns of copper electrodes and carbon electrodes. It has been proven that depending on the material of the electrode, there are differences in voltage list like, current patterns, and radiated spectra bands.

Applicability of CNT as support candidate for thiophene hydrodesulfurization and 1-octene hydrogenation catalyst

The application of carbon nanotubes (CNT) as a support candidate for hydrotreating catalysts for FCC (fluid catalytic cracking) gasoline was researched in the microreactor with a fixed bed at experimental conditions. The CNT synthesized using the AC arc discharge method was functionalized by chemical treatment with nitric acid. Scanning electron spectroscopy (SEM), X-ray diffraction (XRD) and X-photoelectron spectroscopy (XPS) of the functionalized CNT show that during the functionalization of it, HNO3 impurities unwanted for further application were removed and carbon nanostructures haveoxidized, and therefore they have oxide functional groups attached to those walls. At all the conditions observed, the Ni-Mo/CNT catalysts and Co-Mo-0.25 catalyst showed better hydrodesulfurization activities in comparison with the conventional Ni-Mo/γ-Al2O3. As shown in the XRD analysis, the Ni–W/CNT catalysts showed lowest thiophene hydrodesulfurization activity in the temperature range observed, but they showed very good hydrogenation activity on model compounds used.Catalytic performance tests of different catalysts showed that good applicability of the CNT as support candidate for the hydrotreating catalysts. It also was experimentally demonstrated that the Ni-Mo/CNT and Co-Mo/CNT can be the best hydrotreating catalysts.

Determination of elements in human saliva using arc atomic emission spectrometry with MAÉS

Features of determination of trace elements in saliva samples by atomic emission spectrometry with excitation of the spectrum of the sample dry residue from the end of the carbon electrode in AC arc discharge are studied. The samples were analyzed directly after sampling, additional manipulations (including digestion) were not performed. The spectra of dried residues of the samples were recorded on a spectral device MFS-8, modernized with a MAÉS photodiode array. It was found that experimental distributions of P and Ca contents in saliva samples obey the normal law. Concentrations of Mg, Si, Fe, Ti, Mn, Al, Cu, Zn, and Cr correspond to the log-normal distribution and the geometric mean value should be used in this case as an average value of the concentration. Statistical processing of the results for Cd, Ag, and Pb was not performed, since these elements could not be detected in all the samples. The obtained data on the content of elements in 60 saliva samples of various donors are in satisfactory agreement with the literature data. The overestimated results obtained for Mg, Ca, and P can be attributed to the difference in the sample preparation stage, including preliminary centrifugation and storage of samples at negative temperatures.

Determination of hafnium in zirconium materials

An arc atomic emission technique of hafnium determination in zirconium is developed and tested. The study was carried out on a PGS-2 spectrometer equipped with MAÉS analyzer and information processing software «Atom 3.3». («VMK-Optoélektronika», Novosibirsk). Excitation of spectra of pre-oxidized metal was carried out using a medium-frequency generator «Vesuvius» («VMK-Optoélektronika», Novosibirsk). Analytical line of hafnium was free of spectral overlap with the lines of zirconium. We have set a current of the AC arc discharge (20 A), exposure time (30 sec) and the form of the electrode into which the sample is placed («narrow crater») are selected. The effect of buffering additives (graphite powder, bismuth fluoride) on the intensity of the analyte lines was studied. It is shown that high sensitivity of the analyte is observed for oxidized material without additives. Reduction of the random error attributed to the influence of conditions of spectrum excitation and sample preparation is achieved using the intensity ratio of the analyte line and zirconium as an analytical signal. Recommendations regarding preparation of the samples for calibration are given. The lower limit of the determined concentration is 0.01% with a relative standard deviation in repeatability 3%.

Experimental and theoretical investigation of sensing parameters in carbon nanotube-based DNA sensor.

Nowadays, sensitive biosensors with high selectivity, lower costs and short response time are required for detection of DNA. The most preferred materials in DNA sensor designing are nanomaterials such as carbon and Au nanoparticles, because of their very high surface area and biocompatibility which lead to performance and sensitivity improvements in DNA sensors. Carbon nanomaterials such as carbon nanotubes (CNTs) can be considered as a suitable DNA sensor platform due to their high surface-to-volume ratio, favourable electronic properties and fast electron transfer rate. Therefore, in this study, the CNTs which are synthesised by pulsed AC arc discharge method on a high-density polyethylene substrate are used as conducting channels in a chemiresistor for the electrochemical detection of double stranded DNA. Moreover, the response of the proposed sensor is investigated experimentally and analytically in different temperatures, which confirm good agreement between the presented model and experimental data.

Fabrication of Carbon Nanoparticle Strand under Pulsed Arc Discharge

Nowadays, carbon-based nanomaterial application on nanoelectronic is growing fast. Therefore, the nanoparticle fabrication as a device, needs to be optimized. In the present work, a pulsed AC arc discharge apparatus is fabricated for production of carbon nanoparticles (CNPs)-based device, which is derived from decomposition of methane gas in plasma condition and atmospheric pressure controlled by a bobbling system. The morphological properties and identification of synthesized CNPs are characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and nanofocus techniques. The analysis of obtained images confirms the existence of CNPs (mainly carbon nanotubes CNTs) in this method. Also, pulsed electric field equation and relation between growth time and distance between two electrodes are investigated. Moreover, growth conditions of CNPs and their physical mechanism are discussed. Finally, the current-voltage (I-V) characteristics of synthesized CNPs are examined.

Bulk synthesis of multi-walled carbon nanotubes by AC arc discharge method

This work proposes the production of multi-walled carbon nanotubes by AC arc discharging of spectroscopically pure graphite electrodes of different shapes, that is, movable cylindrical and stationary rectangular electrode by manual metal arc welding setup. Continuous arc was generated by maintaining the gap of about 3 mm between the electrodes which in turn formed the plasma zone. Vaporization of carbon cations followed by sudden quenching paved the way for formation of carbon nantotubes. Nanotubes produced were deposited on the stationary graphite electrode in the form of soot. Further extraction of the nanoparticles from the soot was performed by conducting series of purification processes which will be discussed in upcoming chapters. Morphology and purity of the extracted nanotubes were investigated by X-ray diffraction, scanning electron microscopy, field-emission scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Following the characterization process, it was observed that the so-produced nanotubes were of different shapes, that is, carbon cone nanotubes, nanocapsules, nanoparticles and branching type and randomly oriented. The length of the nanotubes varied from 231 to 561 nm, whereas diameter was found to be in the range of 14–55 nm.

Production of medically useful nitric monoxide using AC arc discharge

Inhaled nitric monoxide (iNO) is increasingly used as a medical treatment for acute respiratory distress syndrome. A course of the existing nitric monoxide (NO) therapy with gas cylinders could cost up to approximately $15,000 for an average of 30.2 h. Moreover, a gas cylinder containing a mixture of N2 and NO may potentially leak NO. The objective of this study is to develop an efficient and cost-effective on-site iNO generation system. In the present setup, NO was generated by using dry air or mixed oxygen/nitrogen (O2/N2) and an AC power source with an output power level of 5–30 W at atmospheric pressure. The simultaneously produced NO2 was eliminated with an ammonium sulfite ((NH4)2SO3) solution. The effects of the O2/N2 ratio, gas flow rate, discharge gap distance, output energy density and electrode structure on NOx concentration and the NO/NO2 ratio are reported. The concentrations of NO and NO2 reached 62 ppm and 3 ppm, respectively, after absorption and dilution at a gas flow rate of 6 L/min. With the present setup, the AC arc discharge produced NOx at a stable concentration for at least 6 h using dry air.

Atomic Emission Determination of Rare Earth and Trace Elements in Ecological and Geological Samples Using MAES Analyzer

A method of direct simultaneous determination of rare earth (Y, La, Ce, Nd, Sm, Gd, Tb, Ho, Er, Yb, Sc) and trace elements (V, Cr, Ga, Rb, Sr, Zr, Nb, Ag, In, W, Pb), Fe and Mn in sediments and ash of aquatic vegetations of Ivan’kovo Reservoir using atomic emission spectrometry with ac arc discharge is developed. MAES spectrum analyzer (“VMK-Optoelektronika”) and software package “Atom 3.2” are used with a high-resolution (0.003 nm) diffraction spectrograph DFS-13-2 (flat grating 1200 lines/mm), thus providing determination of 11 from 17 rareearth elements within an optical range of 402.71 - 452.64 nm. The detection limits of the method range within 1-3 mg/kg, depending on the element. Spectral overlaping of the molecular bands of CN and analytical lines of Pr, Eu, Dy, Tm, Lu renders determination of these elements impossible.

Spectroanalytical Generators “Sharovaya Molniya”: Upgrading and Diversification

A brief overview of the new electric arc and spark discharge generators of ShM series (“Sharovaya Molniya”) developed at the “VMK-Optoelektro nika company” over a period of 2011 -2016 and designed for atomic-emission spectral analysis is presented. A number of hardware changes that improve characteristics of existing generators are considered. In addition to well-known ShM-40 and ShM-250 generators, lightweight modifications of ShM generators have been developed and manufactured (mainly for the laboratories of educational institutions). “Sharm” arc generators have the same parameters as ShM-40 with an arc current of up to 20 A. “SKAT” spark generators forms a spark discharge of a positive polarity with the parameters similar to those of ShM-250. ShM-20 arc generators form an ac arc discharge (frequency 25 kHz) and dc arc discharge with a current up to 20 A. The generator control system has been upgraded using advanced microcontrollers to extend the capabilities of the devices and improve their performance.

Study of the AC arc discharge characteristics over polluted insulation surface using optical emission spectroscopy

Flashover of contaminated insulators is one of the major problems for the power distribution. Laboratory experiments have shown that the arc characteristics have great influences on the study of flashover performance of contaminated insulators. In order to investigate the characteristics of AC arc discharge on the polluted insulation surface, an experimental system was designed. The emission spectroscopy of arc discharge was obtained by a CCD spectrometer, and lithium chloride was added in the artificial pollution to introduce lithium as the indicator element in the analysis of arc emission spectroscopy. Arc temperature was obtained by employing the relative line intensities method, and the electron density was determined by analyzing the Stark-broadening values of the profiles. It was indicated that the temperature of partial arc increased with the leakage current value, but electron density of partial arc barely changes with leakage current. Special attention was paid to the influence of gas pressure on the characteristics of partial arc. It was found that both the arc temperature and the electron density of the arc channel increased with pressure in the case of same leakage current.

Analytical investigation of CO2 sensor based on carbon strand

This experimental study attempts to design and develop a novel carbon-based material fabrication method that implements high voltage AC arc discharge. The carbon-based material is to be used in an electric circuit to build up a gas sensing mechanism. After applying a high AC voltage to the graphite electrodes employed in the experiment, an arc ignites between the electrodes as the gas between them is iodized. In the carbon decomposition process, the arc is employed and results in the fabricated carbon strands. Thereafter, carbon monoxide (CO2) in the atmospheric pressure is passed over the electrodes in the Pyrex glass tube chamber where the carbon strand fabrication process takes place. An increment appears in the measured current voltage (I–V) between the two sides of the carbon strand as the carrier concentration of CO2 gas is increased from 200 to 800 ppm. Support vector regression (SVR) algorithm was used for data processing with statistical analysis for errors and quality control.

Arc Contact Ablation: High Speed Camera Visualization

This paper deals with an experimental study of contacts ablation in interaction with an ac arc discharge (half period 10 ms). Images obtained by fast camera are correlated to weight measurements to deduce the mean erosion rate for several types of materials. This paper is completed by thermography measurements to calculate the energy and the mean value of heat flux transferred by the arc to the contacts.

Synthesis of nanocrystalline carbon upon methane pyrolysis in arc discharge

We have studied a carbon material synthesized upon methane pyrolysis in the AC arc discharge using graphite electrodes. Methane was heated by passing through one of the electrodes. Carbon was condensed on the electrodes near the region of arc glow. The synthesized material was analyzed with the help of transmission electron microscopy, X-ray-phase spectroscopy, and Raman scattering spectroscopy. It is found that the synthesized material is a nanocrystalline carbon material composed of closed carbon nanostructures of various forms, carbon nanotubules, and fullerene-like (bulbous) particles. The synthesized material morphology is similar to the structure of the material precipitating onto the cathode in an arc discharge during anode sputtering in an inert gas medium.

Use of single wall carbon nanohorns in polymeric electrolyte fuel cells

Single wall carbon nanohorns (SWNH), produced by AC arc discharge in air, were used as Pt and PtRu supports in polymer electrolyte membrane fuel cells (PEMFC). These electrocatalysts were compared with equivalent electrocatalysts supported on commercial carbon back. The SWNH were characterized by differential thermal analysis (DTA), TEM, SEM, and XRD. The produced SWNH were 84.5 wt% pure, containing 3 wt% of amorphous carbon and 12.5 wt% of graphitic carbon. SWNH were used as electrocatalyst supports and tested in the electrodes of two types of polymer electrolyte fuel cells: H2-fed PEMFC and direct methanol fuel cells (DMFC). The electrocatalyst nanoparticles anchored on both carbon supports were ca. 2.5 nm in diameter obtained by employing ethylene glycol as the reducing agent. The use of SWNH showed catalytic activities 60% higher than using carbon black as the electrocatalyst support in both types of fuel cells.

Self-rewetting carbon nanofluid as working fluid for space and terrestrial heat pipes

Thermal management is very important in modern electronic systems. Recent researches have been dedicated to the study of the heat transfer performances of binary heat transfer fluids with peculiar surface tension properties and in particular to that of “self-rewetting fluids”, i.e., liquids with a surface tension increasing with temperature and concentration. Since in the course of liquid/vapor-phase change, self-rewetting fluids behavior induces a rather strong liquid inflow (caused by both temperature and concentration gradients) from the cold region (where liquid condensates) to the hot evaporator region, this fluids have been proposed and investigated as new heat transfer fluids for advanced heat transfer devices, e.g., heat pipes or heat spreaders for terrestrial and space applications (Savino et al. in Space Technol 25(1):59–61, 2009). The present work is dedicated to the study of the thermophysical properties of a new class of heat transfer fluids based on water/alcohol solutions with suspended carbon nanostructures, in particular single-wall carbon nanohorns (SWNH), synthesized by a homemade apparatus with an AC arc discharge in open air (Mirabile Gattia et al. in Nanotechnology 18:255604, 2007). SWNHs are cone-shaped nanoparticles with diameters between 1 and 5 nm and lengths in the range of 20–100 nm. SWNHs could be found in the form of quite-spherical aggregates with diameters ranging from 20 to 100 nm. The paper also discusses the results of these investigations and laboratory characterization tests of different heat pipes, including reference ordinary heat pipes and innovative pipes filled with self-rewetting fluids and self-rewetting nanofluids. The potential interest of the proposed studies stems from the large number of possible industrial applications, including space technologies and terrestrial applications, such as cooling of electronic components.

Self-Rewetting Fluids with Suspended Carbon Nanostructures

Thermal management is very important in modern electronic systems. Recent researches have been dedicated to the study of the heat transfer performances of binary or multi-component heat transfer fluids with peculiar surface tension properties and in particular to "self-rewetting fluids," i.e., liquids with a surface tension increasing with temperature and concentration. Thermophysical properties like surface tension, wettability and thermal conductivity, at different temperatures, have been measured not only for binary mixtures, but also for a number of ternary aqueous solutions with relatively low freezing point and for nanoparticles suspensions (so called nanofluids). Some of them interestingly exhibit the same anomalous positive surface tension gradient with temperature as binary self-rewetting solutions. Since in the course of liquid/vapour phase change, self-rewetting fluids behaviour induces a rather strong liquid inflow (caused by both temperature and concentration gradients) from the cold region (where liquid condensates) to the hot evaporator region, several interesting applications may be envisaged, e.g., the development of advanced wickless heat pipes for utilization in reduced gravity environments. The present work is dedicated to the study of the thermophysical properties of nanofluids based on water/alcohol solutions with suspended carbon nanostructures, in particular single-wall carbon nanohorns (SWNH), synthesised by an homemade apparatus with an AC arc discharge in open air. The potential interest of the proposed studies stems from the large number of possible industrial applications, including space technologies and terrestrial applications, such as cooling of electronic components.

Stability analysis of multi-phase AC arc discharge for in-flight glass melting

A stable multi-phase AC arc was generated to by transformers at a commercial electric system. The arc discharge behavior and the stability were investigated by the high-speed video camera observation synchronized with the voltage waveform analysis. The effect of the number of phase and the flaming gas addition into the arc region on the arc behavior and the arc stability were studied. Results showed that the re-ignition occurred between adjacent electrodes periodically. Two kinds of the stability analysis methods were introduced. The estimated fluctuation degree showed that an increase of the number of the phase leads to the stable multi-phase AC arc. The deviation of the arc voltage from the average arc voltage was estimated to evaluate the uniformity of the multi-phase AC arc. Although an addition of the oxygen flame into the arc region leads to lower uniformity, the modification of the electrode position can improve the uniformity of the multi-phase AC arc.