Intelligent computer simulation tools for HV circuit breakers and issues related to simulation
Intelligent simulation tools are developed within the Integrated Simulation and Evaluation Environment using Visual Studio C++ and object oriented programming. Such an environment should result in huge savings in time and cost for switchgear manufacturers. Conventional k-epsilon turbulence model has been modified to take into account of steep radial temperature gradient at the arc edge with much improved results. Investigations of computational convergence and the effects of initial conditions show that solutions independent of initial arc conditions with sufficient accuracy can be achieved with the Liverpool arc model.
The development of PC based CAD tools for auto-expansion circuit breaker design
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 the design of auto-expansion circuit breakers. The model takes account of radiation transport, arc radiation induced inner wall ablation, turbulence enhanced momentum and energy transport and the moving parts of the breaker. With the aid of the PC based PHOENICS, a commercial general purpose computational fluid dynamics (CFD) package, the conservation equations for the gas and arc together with the relevant Maxwell's equations can be solved. The temperature, velocity and electric fields within the breaker can easily be visualised and the thermal interruption capability predicted. The effects of changing design parameters can be simulated in detail, thus reducing the number of short-circuit tests. Results are verified by available tests.
Numerical simulations of argon plasma jets flowing into cold air
Computational results and comparisons with experimental data are presented for simulations of axisymmetric turbulent argon plasma jets flowing into a cold air environment. The calculations were performed using the LAVA code [J. D. Rarnshaw and C. H. Chang,Plasma Chem. Plasma Process.12, 299 (1992)], and were designed to simulate experiments performed by Brossa and Pfender (Plasma Chem. Plasma Process.8, 75 (1988)) (BP) and by Finckeet al (private communication, 1992] (FSH). To our knowledge, these are the first such simulations in which multicomponent diffusion and interactions between dissociation and ionization of different species are consistently, accounted for. Turbulence effects were represented by a standardκ-ɛ model, both with and without an axisymmetric jet correction term and for several different choices of the turbulent Prandil and Schmidt numbers Prt and Scl. Simulations were performed for one FSH experiment and two BP experiments at different values of torch powerP and argon flow rateW. The inflow profiles in the FSH simulations were adjusted to matchP,W, and the experimental data slightly downstream of the torch exit as closely as possible. The same profile shapes were then used to matchP andW for the BP simulations, for which data near the torch exit were not available. Swirl was neglected except in one of the FSH calculations, where it was found to have negligible effect, as expected. Best results were obtained with the axisymmetric jet correction term omitted and with Prt = Scl = 0.7. Agreement with the experimental data was then lair overall, but still showed systematic deviations and cannot be regarded as fully satisfactory. Possible reasons for the discrepancies are discussed.