Parametric Study on Arc Behavior of Magnetically Diffused Arc

A model coupling the plasma with a cathode body is applied in the simulation of the diffuse state of a magnetically rotating arc.Four parametric studies are performed:on the external axial magnetic field (AMF),on the cathode shape,on the total current and on the inlet gas velocity.The numerical results show that:the cathode attachment focuses in the center of the cathode tip with zero AMF and gradually shifts off the axis with the increase of AMF;a larger cathode conical angle corresponds to a cathode arc attachment farther away off axis;the maximum values of plasma temperature increase with the total current;the plasma column in front of the cathode tip expands more severely in the axial direction,with a higher inlet speed;the cathode arc attachment shrinks towards the tip as the inlet speed increases.The various results are supposed to be explained by the joint effect of coupled cathode surface heating and plasma rotating flow.     

Analysis of Effects of the Arc Voltage on Arc Discharges in a Cathode Ion Source of Neutral Beam Injector

A hot cathode bucket ion source is used for the EAST(experimental advanced superconducting tokamak)neutral beam injector.The thermal electrons emitted from the surface of the cathode are extracted and accelerated by the electric field formed by the arc voltage,which is applied between the arc chamber of the ion source and the cathode.This paper analyzes the effects of arc voltage on the arc discharge in a hot cathode high current ion source.     

Research of Arc Chamber Optimization Techniques Based on Flow Field and Arc Joint Simulation

The preliminary design of an arc chamber in the 550 kV SF_6 circuit breaker was proposed in accordance with the technical requirements and design experience.The structural optimization was carried out according to the no-load flow field simulation results and verified by no-load pressure measurement.Based on load simulation results such as temperature field variation at the arc area and the tendency of post arc current under different recovery voltage,the second optimal design was completed and its correctness was certificated by a breaking test.Results demonstrate that the interrupting capacity of an arc chamber can be evaluated by the comparison of the gas medium recovery speed and post arc current growth rate.     

Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines,including half-wavelength power transmission lines.In this paper,a lowvoltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera.It was found that the arcing time of the secondary arc rendered a close relationship with its arc length.Through the input and output power energy analysis of the secondary arc,a new critical length criterion for the arcing time was proposed.The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria,and the simulation results were compared with the experimental data.The study showed that the arcing time calculated from the new critical length criterion gave more accurate results,which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines.     

Characteristics of Gliding Arc Discharge Plasma

A gliding arc discharge plasma and its characteristics are described. Analysis of the production principle of the plasma is presented. Some experimental results about two novel types of the gliding arc plasma generator have been obtained. These types of gliding arc plasma axe potentially usable in the chemical industry and environmental engineering.     

Simulation of Magnetically Dispersed Arc Plasma

Magnetically dispersed arc plasma [1] exhibits typically dispersed uniform arc column as well as diffusive cathode root [1,2] and diffusive anode root.In this paper magnetically dispersed arc plasma coupled with solid cathode is numerically simulated by the simplified cathode sheath model of LOWKE [3].The numerical simulation results in argon show that the maximum value of arc root current density on the cathode surface is 3.5×10 7 A/m 2,and the maximum value of energy flux on the cathode surface is 3×10 7 J/m 2,both values are less than the average values of a contracted arc,respectively.     

Analysis of Arc Characteristics and Flow Field in Arc Chamber of High-Voltage SF6 Auto-Expansion Circuit Breaker

A new magnetic hydro-dynamics model for nozzle arc emphasizing the interaction of arc with PTFE （polytetrafluorethylene） vapour is established based on the conservation equations. The interruption of auto-expansion circuit breaker is simulated numerically by finite element method and the influence of PTFE vapour on the arc is analysed with this model. The results reveal that the flow field inside the arc chamber is determined by the arc current, the arcing time, the nozzle arc and the clogging of its thermal boundary. The establishment of quenching pressure relies on both SF6 gas and PTFE vapour that absorbed arc energy in the nozzle. The PTFE vapour leads to an increase in the pressure of nozzle arc obviously, and a decrease in the temperature of arc. But it enhances the temperature of arc at zero current and slows down the decreasing rate of arc temperature as the current decreases.     

Numerical Study on Arc Plasma Behavior During Arc Commutation Process in Direct Current Circuit Breaker

This paper focuses on the numerical investigation of arc plasma behavior during arc commutation process in a medium-voltage direct current circuit breaker(DCCB) contact system.A three-dimensional magneto-hydrodynamic(MHD) model of air arc plasma in the contact system of a DCCB is developed,based on commercial software FLUENT.Coupled electromagnetic and gas dynamic interactions are considered as usual,and a thin layer of nonlinear electrical resistance elements is used to represent the voltage drop of plasma sheath and the formation of new arc root.The distributions of pressure,temperature,gas flow and current density of arc plasma in arc region are calculated.The simulation results indicate that the pressure distribution related to the contact system has a strong effect on the arc commutation process,arising from the change of electrical conductivity in the arc root region.In DCCB contact system,the pressure of arc root region will be concentrated and higher if the space above the moving contact is enclosed,which is not good for arc root commutation.However,when the region is opened,the pressure distribution would be lower and more evenly,which is favorable for the arc root commutation.     

Characteristics of High Voltage Vortex-Stabilized Arc Heaters

Phenomena occurring in a particular vortex-stabilized geometry are discussed. In arc heaters of this type, voltage increases linearly with flow and with size. The level of performance for various sizes is both predictable and fairly constant. Smoke techniques have elucidated re-entrant flow patterns associated with the vortex flow, and windows permit studying the effect of an auxiliary magnetic field on arc rotation. Measurements of effluent fluctuations are reported.     

Numerical Simulation of the Eddy Current Effects on the Arc Splitting Process

This paper focuses on a numerical simulation of the arc plasma behavior in the arc splitting process,considering the eddy currents in the electrodes and the splitter plate.Based on three-dimensional(3D) magneto-hydrodynamic(MHD) theory,a thin layer of nonlinear electrical resistance elements is used in the model to represent the voltage drop of plasma sheath and the formation of new arc root in order to include the arc splitting process in the simulation.In the arcing process,eddy currents in metal parts are generated by a time-varying magnetic field.The arc model is calculated with the time-varying magnetic field term,so that the eddy current effects can be considered.The effect of nonlinear permeability of a ferromagnetic material is also involved in the calculation.Using the simulation results for the temperature,velocity and current density distribution,the arc splitting process is analyzed in detail.The calculated results are compared with the simulation neglecting eddy currents.     

真空弧氘离子源中杂质氕对束流品质的影响

分析了真空弧氘离子源中杂质的主要构成,并着重分析了杂质氕的成因及其对氘离子源性能的影响.对单次脉冲和低重复频率脉冲工作状态下的真空弧氘离子源进行了光谱诊断实验和核反应分析实验,结果表明,氘离子源等离子体中的确含有较多的杂质氕,可对氘离子源的引出束流品质产生较大的危害.并对如何减小杂质氕的影响提出了建议.     

Research on Argon Vacuum Arc Discharge

正Ion source is the kernel part of electromagnetic isotope separator.For the yeilding-type separator the beam current of the ion source need be large,and usually gas discharge is adopted for producing plasma containing enumerous ions,which could form ion beam by extracting electrodes.Gas ion source is one kind of the intense     

Interruption Phenomenon in Intermediate-Frequency Vacuum Arc

In the condition of the 3 mm gap, experiments for 360 Hz intermediate-frequency vacuum arc are carried out in interrupters with the diameters being 41 mm and with the contact materials being CuCr50 and Cu-W-WC alloy respectively. The results indicate that the contacts material is closely related to the breaking capacity of the vacuum interrupters and characteristics of an intermediate-frequency vacuum arc. For contacts with the same diameter, the breaking capacity of CuCr50 is better than that of Cu-W-WC. When the current fails to be interrupted, the arcs overflow the gap and present irregular performances in the first half wave. Consequently a voltage spike appears. More macroscopic metal droplets can be seen in the arc column between CuCr50 contacts because of the lower melting point. It is observed that the droplet emission is much more severe during arc reignition than that in the first half wave. It is much more conspicuous that the high frequency arc voltage noises appear in Cu-W-WC contacts when the vacuum arcs reignite, for higher temperature and stronger electronic emission ability of Cu-W-WC contacts.     

Continuum Radiation from Arc Heated Plasmas

Measurements of the spectral continuum of arc heated nitrogen plasma have been made using high dispersion spectroscopic equipment. These measurements cover a wavelength range of 2700 ? to 44t,000 ? and a temperature range of 9500°K to 12,000°K. The measurements have been compared with a number of theoretical studies of both the spectral and total emissivity. An estimate of the contribution to the continuum of the negative nitrogen ion has been included, and a new value of the effective nuclear charge for Kramers free-free radiation has been measured.     

The Effect of High-Pressure Arc Discharge Plasma on the Degradation of Chlorpyrifos

A study is conducted to determine the effect of a kind of high-pressure arc discharge plasma on the degradation rate and kinetic equations of chlorpyrifos in different solvents with the treated times and concentrations as variables. The degradation rate was sorted in different solvents as water, methanol, acetone and then acetoacetate. The tendencies of the degradation rates with treated time in water and methanol were optimally fitted with first-order kinetics equations while those in acetone and acetoacetate were fitted with zeroth-order kinetics equations. The difference was attributed to the stronger polarity of water and methanol. The weak correlation of the degradation rates with time was mainly because the high-temperature of the arc discharge tube and the chemically-active species generated by the discharge. The degradation half-life was extended with increase of chlorpyrifos concentration. A degradation half-life less than 3 min was achieved for chlorpyrifos in water and methanol when the initial concentration was less than 300 μg/ml.     

强流双潘宁离子源弧特性研究

针对22cm双潘宁离子源,研究了其弧流与放电调节参数的关系以及二次进气的效果,确定了拉长弧流脉宽、提高弧流强度与稳定性、达成离子源合适工作状态的措施,为获得高品质的弧流提供了依据.离子源弧特性测试研究结果对提高强流离子源的工作性能以实现NBI系统强流准稳态运行有重要的指导意义.     

Three-Dimensional Modelling of a DC Arc in Cross-Flow

A commercial CFD （computational fluid dynamics） code FLUENT was used and modified to model an atmospheric pressure argon arc in a low cross flow by solving the fully coupled conservation equations. Numerical experiments, with an arc current of 100 A to 200 A, an arcing distance of 3 mm to 6 mm, and a cross-flow velocity of 10 m/s to 30 m/s, were carried out. The modelling results show that the arc tends to take the shortest path to the anode when deflected by the cross flow; its anode attachment is farther downstream than the cathode one. Furthermore, due to the low input gas flow imposed in this study, the effect of electromagnetic force is important and it influences the crosscut shape of the arc significantly.     

Characteristics of Atmospheric Pressure Rotating Gliding Arc Plasmas

In this work,a novel direct current (DC) atmospheric pressure rotating gliding arc (RGA) plasma reactor has been developed for plasma-assisted chemical reactions.The influence of the gas composition and the gas flow rate on the arc dynamic behaviour and the formation of reactive species in the N2 and air gliding arc plasmas has been investigated by means of electrical signals,high speed photography,and optical emission spectroscopic diagnostics.Compared to conventional gliding arc reactors with knife-shaped electrodes which generally require a high flow rate (e.g.,10-20 L/min) to maintain a long arc length and reasonable plasma discharge zone,in this RGA system,a lower gas flow rate (e.g.,2 L/min) can also generate a larger effective plasma reaction zone with a longer arc length for chemical reactions.Two different motion patterns can be clearly observed in the N2 and air RGA plasmas.The time-resolved arc voltage signals show that three different arc dynamic modes,the arc restrike mode,takeover mode,and combined modes,can be clearly identified in the RGA plasmas.The occurrence of different motion and arc dynamic modes is strongly dependent on the composition of the working gas and gas flow rate.     

DC Arc Plasma Disposal of Printed Circuit Board

A new solid waste disposal technology setup with DC arc plasma is presented. Being different from conventional combustion or burning such as incineration, it is based on a process called controlled high-temperature pyrolysis, the thermal destruction and recovery process. The results of vitrification of the circuit board is presented. The properties of vitrified product including hardness and leaching test results are presented. The final product (vitrified material) and airemission from the plasma treatment is environmentally acceptable.     

Numerical Modeling of the High-Intensity Transferred Arc with a Water-Cooled Constrictor Tube

Fig.1 Schematic diagram of the high-intensity transferredarc with a water-cooled constrictor tubeFig.2 Computational domain employed in this studyplasma axial-velocities at the upstream boundary (H-Pin Fig. 2) of computational domain.In a recent experimental study of the high-intensitytransferred arc reported by Hartmann and Heberlein[8],a new experimental arrangement has been adopted, i.e.,each water-cooled segment of the constrictor tube isseparated by co-axial boron nitride spacer discs s…