A5003655937- Vacuum and Plasma Arcs
- Electrical Fault Detection and Protection
- Welding Techniques and Residual Stresses
- Diamond and Carbon-based Materials Research
- Plasma Diagnostics and Applications
- Combustion and Detonation Processes
- Gas Dynamics and Kinetic Theory
- Lightning and Electromagnetic Phenomena
- Metal and Thin Film Mechanics
- High voltage insulation and dielectric phenomena
- Electrostatic Discharge in Electronics
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Power Transformer Diagnostics and Insulation
- Quantum chaos and dynamical systems
- Thermal Analysis in Power Transmission
- Electromagnetic Launch and Propulsion Technology
- Quantum many-body systems
- Space Satellite Systems and Control
- Theoretical and Computational Physics
- Petri Nets in System Modeling
- Engineering Applied Research
- Induction Heating and Inverter Technology
- Control and Stability of Dynamical Systems
- Energy and Environmental Systems
Celestica (Brasil)
2024
Hangzhou Dianzi University
2023
University of Liverpool
2002-2016
University of California, Santa Barbara
2014-2016
University of Cambridge
1976
PC-based arc modeling taking account of the effects nozzle ablation and mixing process PTFE vapor with SF/sub 6/ has been carried out for a full-scale auto-expansion circuit breaker moving contact. An equation to calculate concentration in mixture is introduced together overall mass, momentum, energy conservation equations mixture. The thermodynamic transport properties 6/-PTFE calculated by theory are given. empirical relationship between radiation reabsorption factor relevant arcing...
The arc conservation equations based on laminar flow and the boundary layer assumption have been solved for a 2 kA DC nitrogen burning in supersonic nozzle at stagnation pressure of 23 atm. An approximate radiation transport model is used to account emission absorption radiation. computed results are good agreement with experiments. A hybrid approach (i.e. combination integral differential methods) predict presence arc. It has found that isothermal external provides best between calculated...
Progress in the physics of high-power arcs has been largely due to a blend detailed experimental and theoretical investigations aimed at explaining electrical behaviour discharge terms fundamental physical processes. In case collision-dominated, high-pressure important role radiative energy transfer, including strong self-absorption, established through study cylindrically symmetric, uncontaminated arc plasmas. As result, an insight gained into additional complications produced naturally...
The conservation equations of turbulent gas-blast nozzle arcs based on local thermal equilibrium and boundary layer assumptions have been solved numerically. A Prandtl mixing length model turbulence has adopted because its simplicity success when applied to rounded jets. investigation is aimed at an understanding the arc in a circuit-breaker, where key problem behaviour during current-zero period. Emphasis placed quantitative analysis turbulence-enhanced cooling influence dominant energy...
In circuit breakers, arc heaters and welding apparatus, metal vapor resulting from electrode erosion is inevitably injected into the plasma. The then burns in a mixture of working gas (SF/sub 6/ case breakers) vapor, whose properties are substantially different those pure SF/sub 6/. present work computational investigation effects on behavior supersonic nozzle under dc conditions. electrodes treated as coupled system. plasma assumed to be local thermodynamic equilibrium (LTE). thin non-LTE...
A comparative study of the two most popular turbulence models, Prandtl mixing length model and K-epsilon model, has been carried out for turbulent SF6 arcs burning in a supersonic nozzle under direct current conditions. The computed radial temperature profiles are compared with those measured previously by Leseberg Pietsch at currents 100 A, 600 1800 respectively. It found that parameters dependent upon arcing while applicable all investigated. For nozzle, consideration range applicability...
Three radiation models, the semi-empirical model based on net emission coefficients (Zhang et al 1987 J. Phys. D: Appl. 20 386–79), five-band P1 (Eby 1998 31 1578–88), and method of partial characteristics (Aubrecht Lowke 1994 27 2066–73; Sevast'yanenko 1979 Eng. 36 138–48), are used to calculate transfer in an SF6 nozzle arc. The temperature distributions computed by three models compared with measurements Leseberg Pietsch (1981 Proc. 4th Int. Symp. Switching Arc Phenomena (Lodz, Poland) pp...
It is shown that the arc model based on laminar flow cannot predict satisfactorily voltage of an air burning in a supersonic nozzle. The Prandtl mixing length (PML) and modified k-epsilon turbulence (MKE) are used to introduce enhanced momentum energy transport. Arc voltages predicted by these two models good agreement with experiments at stagnation pressure (P0) 10 bar. MKE for P0 = 13 bar 7 better than those PML. therefore preferred nozzle arc. There peaks ρCP 4000 K 7000 due,...
It is shown that, with the current understanding of basic arc physics, CAD tools based on a mathematical model encompassing all important physical processes can be developed to aid design auto-expansion circuit breakers. The takes account radiation transport, induced inner wall ablation, turbulence enhanced momentum and energy transport moving parts breaker. With PC PHOENICS, commercial general purpose computational fluid dynamics (CFD) package, conservation equations for gas together...
The transport and thermodynamic properties of a copper-nitrogen (Cu-N) mixture are calculated for temperatures between 2000 28000K pressures 1 10 atmospheres. results show that, compared with the electrical conductivity pure nitrogen, small concentration copper vapour can greatly enhance at below about 8000K. internal energy enthalpy per unit mass reduced by 1/2 2/3 when X is increased from 0 to 1, where ratio total number density all species that nitrogen species. Changes in electron...
The cold flow and the arc, under direct currents burning in nozzle of arcing device used Benenson (1980 Final Report General Electric Co. (Schenectady, NY) Project 246–2) with fixed stagnation pressure, have been investigated computationally using five models; laminar model, Prandtl mixing length standard k-epsilon model its two variants, Chen–Kim renormalization group model. For flow, computational results are almost same for different models apart from regions close to electrodes. There is...
A residual plasma at 3000 K and under diatomic equilibrium is left inside an axially blown gas blast SF/sub 6/ circuit breaker after the thermal extinction of arc. The breakdown such a depends on electron generation loss mechanisms. Altogether six ionization chemical reactions relevant to time scale have been taken into account. It has found that critical field strength for proportional pressure equal 2.0 V/(m.Pa). This in agreement with experimental results.
The effects of arc-shock interaction on the behaviour an SF6 arc burning in a supersonic nozzle during current zero period are numerically investigated for experimental conditions Frind and Rich. Prandtl mixing length model is used to simulate turbulent arc. adverse pressure gradient associated with shock causes flow separation which leads formation vortices broadening cross-section. Compared absence arc, centre moves upstream broadened. When linearly ramped down towards zero, point axis...
Boundary layer type conservation equations have been used to investigate the zero current behaviour of an axisymmetric SF6 arc burning in a supersonic nozzle. The theoretical model is based on local thermal equilibrium (LTE) and laminar flow. Arc are solved for ramp before voltage after zero. Emphasis has given relative importance various energy transport processes during period. Although there large discrepancy between theory measurements, results this paper considered significant that they...
Supersonic nozzles are commonly used in modern high voltage circuit breakers. The thermodynamic and electrical behavior of arcs burning such is closely related to the nozzle geometry pressures at inlet exit. Computational investigation has been carried out on thermal interruption capability a supersonic different stagnation exit pressure ratios (referred as ratios). critical rate rise recovery (RRRV), which most important parameter determining breaker, was predicted for five three pressures....
Recent experimental results (Smith et. al., 1980 and New land 1982) indicate that nozzle wall ablation can occur even before the arcing current reaches its thermal blocking limit. The is caused by intense arc radiation. evaporated material forms an layer which reduces effective flow area for quenching gas. A theoretical model established to study complicated interaction between layer, external gas arc. It has been found arcs burning in affinely related nozzles behaviour controlled two...
A detailed analysis of the experimental results from an orifice flow arc during quasisteady period following a peak current 3 kA is presented. The velocity profile gas has been derived experimentally measured temperature and axial radial pressure distributions. It shown that total electric power dissipated in column can be adequately taken into account without necessarily introducing possible effects turbulence. also yields indication local energy balance. simplified model, based on integral...
A steady state nozzle arc model based on the boundary layer integral method is established and scaling laws are derived. For affinely related nozzles, solution uniquely determined by a coefficient N, which to stagnation conditions, current, dimensions of nozzle. Tests have been performed arcs in air using two geometricaly similar nozzles at three pressures. good agreement between theory experiment obtained indicates that circuit-breaker can be scaled. To avoid clogging, nominal current...
A simplified arc model based on the integral method is used to study behavior in a supersonic nozzle. Emphasis placed energy balance of overall arc, which extends thennal boundary. Similarity rules for aerodynamic and electrical quantities are established, quantitative definition current zero period given. Computations have been done two nozzle geometries. The geometry plays role shaping thereby affecting axial electric field distribution. Performance curves terms critical rate rise recovery...
For pt.II see ibid., vol.7, p.2232 (1974). The energy equation for the core of axisymmetric electric arcs is de- rived in terms radial integrals. formulation includes to describe diffusive heat flux at boundary and work done against viscous stress there. When shape factors derived Part I are evaluated a number different arc situations from known differential solutions, they correlate well non-dimensional form flux. This result suggests that behaviour can be predicted accurately by overall...
The present work (part II) forms the second part of an investigation into behaviour SF6 nozzle arc. It is concerned with aerodynamic and electrical a transient arc under current ramp specified by rate decay (di/dt) before zero voltage (dV/dt) after zero. five flow models used in I [1] for cold gas DC arcs have been applied to study at three stagnation pressures (P0) two values di/dt ramp, representing wide range arcing conditions. An analysis physical mechanisms encompassed each model given...
The conservation equations of high-pressure arc near the flow stagnation point have been solved for a current ramp before zero (di/dt), and an electrical field (dE/dt) after zero. analysis is based on laminar local thermal equilibrium. Two arc-quenching gases, sulphur-hexafluoride (SF/sub 6/) nitrogen (N/sub 2/), investigated. relative importance radiation, convection, conduction under wide range discharge conditions discussed. Before computed temperature in fair agreement with experimental...
For pt.I see ibid., vol.24, p.490 (1996). A mathematical model of arc behavior in an SF/sub 6/ puffer gas-blast circuit breaker the high current phase was reported a previous paper. This is extended to zero region by solving full partial differential are conservation equations taking account both turbulent and radiation effects. The critical RRRV for can therefore be calculated based on whole arcing history. predicted values compared with experimental results Noeske et al. (1983), good...