Effect of Arc-anode Attachment on Thermal Plasma Jet
An interaction of plasma flow with an arc-anode attachment in a dc arc plasma torch was investigated. Statistical processing of the photographic images of plasma jet was used for analysis of an effect of the anode attachment on structure and stability of plasma flow. Deflection, flattening and flutter of the plasma jet was found to be caused by disturbing effect of the arc-anode attachment.
Experimental investigation of development of fully turbulent plasma jet generated by hybrid gas-water torch
Thermal plasma jets are characterized by strong interaction with surrounding atmosphere. Such jets in most cases represent fully turbulent flow. Fast transition of the plasma jet generated by the hybrid gas-water torch to turbulent behavior is caused by a strong difference between ambient air density and density of the plasma, which is extremely low due to high jet temperature. Development of the plasma jet characteristics and mixing of the jet fluid with ambient air along the jet were experimentally studied. Several diagnostics methods were applied to enable obtaining the properties of the whole jet. The work considers processes in the plasma jet depending on generation conditions. Arc current and flow rate of the plasma forming gas, which determine properties of the arc and correspondingly of the plasma jet, were varied. The obtained data were applied to analyze heat, mass and momentum transfer in the gas-water jets.
Analysis of the Flow Structure of a Turbulent Thermal Plasma Jet.
Abstract The flow structure of a commercial plasma spray torch operating with argon in atmospheric air has been examined. Conditional mean velocities and turbulence intensity measurements were made in the turbulent plasma jet produced by a swirl-stabilized d.c. arc using laser doppler anemometry. Velocity measurements conditional on fluid originating from plasma jet and from the entrained air were obtained by alternately seeding only the plasma gas and the surrounding air. These results strongly imply that an engulfment-type entrainment mechanism takes place in turbulent plasma jets as opposed to a simple diffusion process. Turbulence measurements indicate that the velocity fluctuations are non-isotropic, contrary to what has been assumed in most numerical work. The swirl number (the ratio of angular to axial momentum) was also measured for the plasma jet and found to be 0.04. The results of this paper should be useful in furthering our understanding of the fluid mechanics in a plasma jet, as well as the momentum and heat transfer to injected plasma spray particles, and as a needed database for future numerical work.