Numerical-simulation of ac plasma-arc thermodynamics

A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequency range of 10-10(2) Hz which includes most industry ac arc frequencies. (C) 1994 Academic Press, Inc.

Stress-distribution at the rigid circular-arc inclusion end

The elastic plane problem of a rigid co-circular arc inclusion under arbitrary loads is dealt with. Applying Schwarz's reflection principle integrated with the analysis of the singularity of complex stress functions, the general solution of the problem is found and several closed-form solutions to some problems of practical importance are given. Finally, the stress distribution at the arc inclusion end is examined and a comparison is made with that of the rigid line inclusion end to show the effect of curvature.

Impact of cathode evaporation on a free-burning arc

A free-burning, high-intensity argon arc at atmospheric pressure was modelled during the evaporation of copper from the cathode. The effect of cathode evaporation on the temperature, mass flow, current flow and Cu concentration was studied for the entire plasma region. The copper evaporates from the tip of the cathode with an evaporation rate of 1 mg s-1. The copper vapour in the cathode region has a velocity of 210 m s-1 with a mass concentration of above 90% within 0.5 mm from the arc axis. The vapour passes from the cathode toward the anode with a slight diffusion in the argon plasma. Higher temperatures and current densities were calculated in the core of the arc caused by the cathode evaporation.

80 C 146 U.S. Aeroplane carrier "Saratoga" and French cruiser "Joan D'Arc" in Pedro Miguel Lock - Panama Canal - 2/7/28

Leonard Carpenter Panama Canal Collection. Photographs: Views of Panama and the Canal. [Box 1] from the Special Collections & Area Studies Department, George A. Smathers Libraries, University of Florida.

Comparative Observation of DC Arc Plasma Jets and Their Arc Root Behaviors at Reduced Pressure

Experimentally observed, results are presented for the DCarcplasmajets and theirarc-rootbehaviors generated atreduced gas pressure and without or with an' applied magnetic field. Pure argon, argon -hydrogen or argon-nitrogen mixture is used as the plasma-forming gas. A specially designed copper mirror is constructed and used for better observing the arc-root behavior on the anode surface of the DC non-transferred arcplasma torch. It is shown that for the cases without applied magnetic field, the laminar plasmajets are stable and approximately axisymmetrical. The arc-root attachment on the anode surface is completely diffusive when argon is used as the plasma-forming gas, while the arc-root attachment often becomes constrictive when hydrogen or nitrogen is added into the argon. When an external magnetic field is applied, the arcroot tends to rotate along the anode surface of the non-transferred arcplasma torch.