Arc Temperature Research Articles

Cu/W Electrode Ablation and Its Influence on Free-Burning Arcs in SF₆ Alternatives

A free-burning arc experiment was performed in a gas mixture composed of CO2/O2/C5F10O (85%/10%/5%). An optical emission spectroscopy (OES) diagnostic was developed to obtain spatially resolved arc spectra at a high frame rate. Spectral measurements are compared with simulated spectra to estimate arc parameters including temperature and composition. These techniques are used to characterize the arc and its associated electrode jets over a range of conditions, in order to study the influence of ablated Cu/W on arc characteristics. The observed spectra indicate that the ablation of the contact tip primarily occurs through vaporization rather than the expulsion of droplets. The metal vapor content of the arc is investigated as the arc driving current is varied, and a transition threshold for increased ablation at electrode current densities above 50 A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula> is determined. The expansion angle of the electrode jet is estimated from the concentration of metal vapor in the arcing region at different axial positions, using a basic conical expansion model. The dependence of the measured voltage on the arc composition is examined, and a positive correlation between Cu content and arc voltage is identified. This trend is attributed to the higher emissivity of the metal vapor, which suppresses the central arc temperature and increases its resistivity.

Energy Balance Model for Providing Mechanistic Insights Into HTV and LSR Performance in Inclined Plane Tests

Silicone rubber (SR) is widely used in external insulation. However, the utilization of either high-temperature vulcanized (HTV) SR or liquid SR (LSR) remains controversial in China because of their differences in tracking and erosion resistance and aging resistance due to various amounts of nonreinforcing fillers. Here, the tracking and erosion behaviors of HTV and LSR during the inclined plane test (IPT) are captured and compared for a detailed comprehension of the difference between the two materials. The results revealed that LSR was easily carbonized and formed electrical tracks initially. Then, the carbonization slowed because of developing a protective ceramic layer. The relatively stable ceramic layer resulted in less frequent rapid erosion but increased the average arc burning time. An energy balance model of dry-band arcing (DBA) was established to evaluate DBA’s energy dissipation and absorption. Then, the emission spectra of DBA were collected to analyze the arc temperature and resistance more accurately. The energy input from the system is dissipated primarily through heating and evaporation of the liquid film, with radiant energy only accounting for a minuscule fraction. In different erosion states, the power absorbed by the surface of samples is different. LSR shows an average absorption power of 19.9 W in the initial carbonization state, which is higher than that of HTV (16.5 W). The average absorption power in the fast erosion state is the same for both samples at about 30 W. The absorption power at 20–25 W is considered the threshold range of relatively stable erosion.

Experimental study of the effect of argon on the restrike characteristics of nitrogen arc

The arc restrike process is a typical mode of operation within a direct current arc plasma torch. By using a transfer arc device with a planar anode parallel to the gas flow direction, the effect of argon addition on the disappearance of downstream old arc roots, the overall arc downstream movement process and the generation of upstream new arc roots of the nitrogen arc restrike process is experimentally investigated. The experimental results show that for pure nitrogen arc, the restrike frequency is very high and the old arc root disappears very quickly. The addition of argon will significantly decrease the temperature of the arc root and prolong the coexistence time of the old and new arc roots. This phenomenon is caused by the rapid decay of charged particle density in the nitrogen arc, because the recombination process of charged particles in the nitrogen arc is faster than that in the argon arc. The breakdown field strength at the upstream location where the new arc root occurs is calculated by combining the measurements of arc voltage, arc grayscale image and temperature. The results show that as the percentage of argon increases, the boundary layer thickness becomes thinner and the critical electric field strength required for arc breakdown decreases, leading to the generation of new arc roots more likely to occur toward the upstream location. This study improves the understanding of the effect of argon on the nitrogen arc restrike process.

Development of Tungsten Electrode for TIG Welding

Tungsten Inert Gas (TIG) welding process is mostly applied to high alloy steel pipes including stainless steels because of superior welding quality and gap bridge-ability than other welding processes. However, it has poor productivity due to low welding speed and deposition rate. In order to improve TIG welding productivity, high performance TIG welding with higher arc temperature, automation and high deposition rate system including hot wire have been developed. Higher arc temperature and longer welding time damage tungsten electrodes of TIG welding. It causes welding defect such as tungsten inclusion and short replacement cycle of tungsten electrodes. Various types of tungsten electrodes containing rare earth metal oxides (thorium, lanthanum, cerium, etc) were introduced to improve electrode erosion resistance and arc stability. In this study, their operation characteristics, arc starting performance, tip development, and electrode consumption were reviewed.

Effect of pumping gas on temperature field and pressure in hollow tungsten arc

A hollow tungsten negative pressure arc (HTNA) is a heat source that controls the gas flow inside a tungsten electrode and optimizes the arc output. However, to ensure the widespread applicability of HTNAs, the factors affecting the temperature and pressure distribution of an HTNA should be studied. In this study, the effect of pumping gas on the temperature and pressure distribution of an HTNA is elucidated through experiments and numerical simulations. A double spectral line acquisition system with nine optical transmission fibers was used to obtain the arc light intensity for the temperature calculation and spatial reconstruction. Consequently, a unified numerical model was developed to quantitatively study the physical field distribution under the effect of pumping gas. It was observed that the maximum temperature of the traditional gas tungsten arc (GTA) and hollow tungsten arc (HTA) decreased more than that of the HTNA owing to the effects of pumping gas. By analyzing the current density and flow field, it was concluded that convective heat transfer owing to pumping gas is the primary cause of the temperature difference between the arcs rather than Joule heat. Compared with the effect of the Lorenz force, the arc flow had a more significant effect on the pressure difference between the inner and outer tungsten electrodes. The gas in the arc region flowing into tungsten also affected the arc pressure on the base metal surface. The results of this study are expected to provide guidance for controlling the energy output of the welding arcs.

Research on the electric life evaluation technology of the arc extinguishing chamber of the 550 kV circuit breaker

When the circuit breaker is switched on and off, the phenomenon of arc ablation will occur. Under the action of the electric arc, the surface of the contact is constantly damaged, resulting in deformation and material evaporation. With the increase in the electric arc temperature, the material loss on the contact surface of the circuit breaker increases. In this paper, according to the three major factors affecting the electrical life of the circuit breaker arc extinguishing chamber—the state of the arc contact, the nozzle, and the SF6 gas—the corresponding test detection methods and evaluation methods are proposed. With the continuous accumulation of the breaking current, the effective contact displacement between the arc contacts decreases and the average contact resistance increases. The effective contact displacement decreases exponentially with the increase in the cumulative breaking energy. The content of CF4 can be used not only to characterize the discharge ablation on the surface of the nozzle insulating material but also to characterize the discharge decomposition degree of SF6 in the system by adding carbonaceous compounds. Through the experiment, it is suggested that CF4 should reach 600 µl/l as the threshold for judging whether the arc extinguishing chamber needs maintenance. This method can be extended to the working condition evaluation of the arc extinguishing chamber of other types of the SF6 circuit breaker.

Elucidation of arc coupling mechanism in plasma-MIG hybrid welding process through spectroscopic measurement of 3D distributions of plasma temperature and iron vapor concentration

This study aims to clarify the mechanism of arc coupling phenomenon in plasma-MIG hybrid welding through the tomographically spectroscopic measurement of 3D distributions of plasma temperature and iron vapor concentration. The arc coupling strongly depends on arc current waveforms, so both the cases using DC MIG current and pulse MIG current were performed for the comparison. As a result, in the case using DC MIG current, two arcs were regularly connected, because the high temperature region between two arcs with an enough electrical conductivity was widely formed, retaining the current conduction between arcs. In the case using pulse MIG current, the two arcs were strongly connected only in the upslope duration of pulse MIG current. Both arcs were weakly connected or disconnected in other durations. The arc connection is thought to be governed by the balance between the stiffness and deflection of both arcs. In the case using pulse MIG current, two arcs were not connected in the downslope duration of pulse MIG current, although the pulse MIG current was similar with that in the upslope duration. In the upslope duration, the MIG arc is thought to be constricted because of the thermal pinch effect to increase the current density, which enhances the stiffness of MIG arc to prompt the arc connection. In contrast, the pulse MIG current density becomes lower in the downslope duration, which deflects the MIG arc backward to disconnect the arcs. The plasma current increased by 35 A during the arc connection, which increased the plasma arc temperature below the nozzle by 1000 K. The result implies that the arc coupling affects the distributions of the arc pressure and shear force by plasma arc acting on the keyhole inner wall, governing the keyhole stability as well as the weld pool formation process.

Numerical Analysis of Metal Transfer Process in Plasma MIG Welding

In plasma MIG welding, inert gas introduced from the torch nozzle is ionized in the upstream region of the MIG arc, which is termed “plasma”. This study aims to clarify the effect of the plasma on the metal-transfer process in the plasma MIG welding through numerical analysis. As a result, the plasma with a temperature of approximately 10,000 K was found to be formed around the wire tip. The MIG arc temperature around the wire tip was 11,000 K at the maximum, which was lower than that of the conventional MIG welding by approximately 1000 K. This difference was caused by the decreased current density around the wire tip due to the influence of the plasma. The droplet temperature was also decreased by 400 K due to this lower current density. The amount of the metal vapor evaporated from the droplet was decreased compared to that of the conventional MIG welding due to the lower droplet temperature. This might lead to a decrease in fume formation generally known in the plasma MIG welding. In the conventional MIG welding, the arc attachment was concentrated around the wire tip, leading to a higher current density. However, in the plasma MIG welding, the plasma transported to the surrounding of the wire tip increases the electric conductivity in that region, due to the influence of the metal vapor mixture. This leads to the dispersion of the arc attachment toward the wire root. Consequently, the current density in the plasma MIG welding was found to decrease compared with that of the conventional MIG welding. The lower current density in plasma MIG welding decreases the Lorenz force acting on the wire neck, thus delaying droplet detachment to make the droplet diameter larger and the metal transfer frequency smaller. The latter was about 20% of that in the conventional MIG welding.

Fusion enhancement of hollow tungsten arc coaxially assisted by fiber laser

Bead-on-plate experiment was performed on a continuous-mode fiber-laser hollow tungsten coaxial welding platform designed and built by us. The weld bead cross-section was observed by using a optics microscope, and the welding arc image was recorded by using a high-speed camera to track the welding process. The changes in the arc physical field after laser addition were analyzed by conducting numerical simulations to explore the mechanism of increasing the welding depth. The results showed that the coaxial hybrid of fiber laser and hollow tungsten arc can significantly increase the weld depth and thermal efficiency of hybrid arc. When the welding current remained constant at 70 A, the weld penetration increased with an increase in the laser power. However, the growth rate was different under different laser power settings and there were the upper and lower critical values of laser power which were 450 W and 60 W. When the laser power remained constant at 400 W, the weld penetration first increased and then remained constant with an increase in the current, and there was a current critical value of 170 A. The main reasons for the increase in the penetration depth were the increase in the arc temperature, arc pressure and thermal efficiency of hybrid welding.

Spectroscopic analysis of the arc plasma during activating flux tungsten inert gas welding process

A-TIG welding has been widely used in the manufacturing fields of aerospace, pressure vessels and ships as a highly efficient welding method. However, the mechanism of the effect of the activating flux on the arc behavior is still controversial. In this work, the spatial distribution of A-TIG welding arc spectra under the action of three types of active agents (fluorides, oxides and chloride) was studied using a spectral diagnostic method. The distribution characteristics of active agent particles, argon and iron particles in the arc were analyzed as well as the arc electron temperature was calculated using Boltzmann plot method. The experimental results shown that the distribution state of different active particles in the spatial of the arc is different. The influence of different active agents on the arc electron temperature in the spatial area of the arc is inconsistent. Chloride can cause a significant increase in the whole arc temperature. Fluoride can increase the arc electron temperature near the anode area. Oxide has less effect on the overall arc temperature.

A study on surface-temperature measurement by means of a vacuum-arc cathode under different current conditions

Accurate detection and analysis of the cathode surface temperature delivers an important reference value as regards the prediction of electrode life and corrosion degree, a thorough study of the vacuum-breakdown phenomenon, design and application of the vacuum-arc ion source and vacuum switch. In this paper, multispectral true temperature measurement T of the surface temperature field of pulsed vacuum arc cathode materials under different discharge currents is carried out. Firstly, aiming at solving the problem of synchronous imaging measurement of the temperature field across the cathode of pulsed vacuum arc, a multi-wavelength monochromatic image-acquisition optical path is designed, based upon the image acquisition module of a high-speed monochrome camera. Also, multiple monochromatic spectral radiation images of the target are synchronously acquired on the focal plane of the same monochrome camera detector. As a result, the spectral-radiation image information of multiple wavelengths can be obtained in a single exposure time, which greatly shortens the temperature-field image acquisition time. Secondly, based upon the multispectral true-temperature calculation method, high-speed multispectral imaging measurement of the target temperature field is realized. Finally, the two-dimensional true temperature distribution of the cathode temperature field under different current conditions was studied by setting up an experimental platform for measuring the cathode temperature of the vacuum arc under different current conditions.

Characteristic of weld bead using flat wire electrode in GMAW inline during the process: An experimental and numerical analysis

This paper focusses on effect of flat wire electrode on gas metal arc welding (FW-GMAW) inline during the process to improve quality of weld bead. Since the flat wire electrode perimeter has enlarged, the turbulence of the molten droplet characteristics is altered due to the effect of electromagnetic force. To bring out, butt joint welding are proven with use of the flat wire electrode. The experimental results indicated that, the flat wire electrode and their orientations are significantly factors to improve the weld bead dimensions, due to the increased in steady state temperature and heat density. The end result also evident that the depth-to-width (D/W) ratio was improved on an average by 7.7% than regular wire electrode used in GMAW. To validate, a comprehensive numerical model was developed, the result confirmed that the initial arc and steady state temperature are high for FW-GMAW. In addition, improvements in metallurgical and mechanical properties are discussed in this paper.

Characteristics of pantograph‐catenary arc under low air pressure and strong airflow

Pantograph-catenary arc fault is the primary factor threatening the stability of the power transmission for high-speed railway. The motion characteristics of the pantograph-catenary arc under low air pressure and strong airflow is significantly different from the case under atmospheric pressure. In this paper, an experimental platform of pantograph-catenary arc was built to investigate arc root position-time and arc column longitudinal drift height-time characteristic curves under different air pressures and airflow velocites. Via analysing the corresponding results, it can be found that there are different arc root–arc column traction mechanisms at different stages of arc development. The arcing time and arc root stagnation time under low air pressure are significantly longer than the case under atmospheric pressure, resulting in more serious electrode ablation. The arc column longitudinal drift velocity and height are greater with the increase of airflow velocity. Two typical irregular arc motion phenomena—arc root jumping and arc reignition are observed. To clarify the internal mechanism of the above phenomenon, a magnetohydrodynamics (MHD) model of the pantograph-catenary arc was lauched, the influence mechanism of the pantograph-catenary arc temperature and voltage are studied, and the physical process of arc temperature oscillation is analysed. The research results provide theoretical support for arc protection in high-altitude areas.

Modeling of arc in convective shock wave composite system and analysis of its plasma running characteristics

The plasma arc caused by lightning overvoltage can significantly degrade the power grid reliability. Thus, it is essential to design an efficient arc extinguishing system. The modeling and analysis of the plasma arc in an arc extinguishing system can provide an essential theoretical basis for improving and optimizing its structure. However, the precision of the governing equation and boundary value of the plasma arc model chosen in previous studies can be entirely different from the corresponding practical values. This study develops an arc extinguishing system named “convective shock wave complex system.” In order to further optimize its structure and achieve a better arc extinguishing effect, an appropriate model is established to analyze the plasma’s operation characteristics inside the arc extinguishing device while stroking by lightning. Based on the magnetohydrodynamics theory, the COMSOL software is utilized to analyze the temperature of the plasma arc, the flow rate of gas in the cavity, and the conductivity and current density of some monitoring points to comprehensively analyze the plasma’s physical characteristics in the system. Finally, a virtual lightning experiment is utilized to evaluate the simulation results.

Computer Intelligent Numerical Simulation of TIG Welding Using Platy Tungsten Electrode

In order to reveal the law of arc plasma flow and heat transfer in the process of flat tungsten electrode TIG welding as auxiliary heat source for hardfacing of cast iron surface. According to the free burning TIG arc using platy tungsten electrode, A three dimensional (3D) model for tungsten inert gas welding using platy tungsten electrode has been developed. The whole region of platy tungsten TIG arc, namely, platy tungsten cathode, arc plasma and anode surface is treated in a unified numerical model. By using fluent software to do the second development of equations source and solve these equations, the distribution of temperature, velocity and current density are obtained. The simulation results show that the current of flat tungsten electrode is more dispersed, and the heat generation of arc is more dispersed, which leads to the decrease of arc temperature; The current density on the cathode is much higher than that on the anode.

Numerical simulation and experimental investigation of transient anode surface temperature in vacuum arc

In this paper, the spatial-temporal evolution of the anode temperature in the vacuum arc during the formation of an anode spot is investigated by numerical simulation and experiments. A transient self-consistent model is established to calculate the arc parameters and the anode temperature. The simulations predict that the maximum anode temperature always occurs after the current peak. Ion density and atom density at the anode side increase significantly during the formation of the anode spot. In the anode spot mode, more evaporated anode material comes into the arc column, leading to higher plasma temperature around the spot. The anode vapor can reduce the energy flux from the plasma to the anode center, providing more uniform anode temperature distribution and correspondingly smoother plasma parameter distributions in the vicinity of the anode center. In addition, a higher Cr fraction in the electrodes can result in a higher anode temperature. Near-infrared spectroscopy and high-speed camera thermography are used to study the anode temperature experimentally in order to verify the simulation results. A reasonable agreement was found.

Modelling of a heavy-current intensively blasted electric arc at atmospheric pressure

The paper deals with intensively blasted electric arc burning in argon in a cylindrical channel of a designed experimental arc heater. The measured values of the arc current, the total voltage between a tungsten cathode and a grounded copper anode, the argon flow rate, and the water flow rates and temperature increments in individual parts of the arc heater characterize the operational conditions, but the parameters of the arc inside remain hidden. The simplified mathematical model has been designed to reveal the arc behavior in the arc heater channel, namely the arc radius and arc temperature development. The model is based on the energy and mass conservation laws and Ohm’s law and utilizes theoretically calculated transport and thermodynamic properties of argon altogether with the measured results as input data. Some simplifying assumptions are applied. A two-zone arrangement with a hot arc zone in the middle and a cold zone near the channel wall is supposed. The arc radius development along the arc heater’s channel is described by Schlichting’s formula for a free beam. Such combinations of three characteristic values of exponent n r, current density j 0 at the cathode tip, and arc temperature T A(s) at the end of the near-cathode layer are sought to enable as close as possible accordance between the computed and experimental data. Thereafter, a slight tuning of these parameters is needed to avoid extreme values of electric field intensity and temperature oscillations near the cathode while not to substantially worsen the reached agreement of measured and computed values. The functionality of the model is demonstrated using four typical sets of experimental data.

Numerical study on instantaneous heat transfer characteristics of AC arc-fault

Studying the heat transfer characteristics of alternating current (AC) arc-fault to electrodes is a key issue in electrical fires. In this paper, an instantaneous heat transfer numerical model of AC arc-fault is developed based on the magneto-hydrodynamic principle. The temperature distribution of the AC arc at the microseconds level and the influence of heat transfer on electrodes at the seconds level when the arc heats are studied. The numerical simulation of the axial temperature of the electrodes is verified by experiments, and the temperature variation in the electrodes at different currents and times is discussed. The results show that the arc temperature varies periodically similar to the current at the microseconds level but it does not go out when the current passes zero. The high-temperature region of electrodes diffuses with the increase in current or time. However, the axial temperature gradient of the electrode decreases with time and increases with current. Furthermore, the range of temperature increase in the electrode position decreases with the increase in current and time, but the electrode position near the arc has a higher initial temperature increase.

Research on active arc-ignition technology as a possible residual-energy-release strategy in electromagnetic rail launch

In order to solve the problem of the original residual energy release strategy being unsuitable for high-energy and fast-firing electromagnetic rail launch, this work has explored the applicability of active arc-ignition technology (AAT). The results obtained from the comparison of launching experiments show that AAT has no influence on the acceleration of the armature and is capable of quickly releasing the residual energy. Based on the theory of magnetohydrodynamics, this work has also made numerical simulation of the muzzle arc, analyzed the influence of AAT on the muzzle arc flow field, electromagnetic (EM) field and temperature field, and evaluated the performance of AAT according to the projectile initial disturbance, the EM impact on guidance devices and the rail ablation. The results show that AAT is now one of the most practicable strategies for residual energy release.

Arc Behavior and Temperature Distribution in Water Thermal Plasma with Mist Generation

Arc Behavior and Temperature Distribution in Water Thermal Plasma with Mist Generation