Cathode diameter and operating parameter effects on hafnium cathode evaporation for oxygen plasma cutting arc

Abstract

Abstract. The effects of cathode holder shape on a plasma cutting arc are investigated using a 2-D thermofluid model developed for arc plasma with consideration of hafnium cathode evaporation. The cathode holder shape is defined a convex structure which protrudes from the surface of the cathode holder. Results show that the gas flow near the hafnium cathode is attracted towards to cathode with effect of convex cathode holder. The temperature of cathode surface decreases markedly with the higher protrusion of convex cathode holder by a rapid clockwise rotation of gas flow velocity. The presence of gas flow vortex toward to cathode surface reduces the mass fraction of hafnium vapor on surface cathode. Thus, the amount of mass loss of hafnium evaporation was predicted to decreases significantly with effect of convex cathode holder.Submitted to: J. Phys. D: Appl. Phys.

The 2017 Plasma Roadmap: Low temperature plasma science and technology

“…Further development of diagnostic methods applicable to non-equilibrium regions of the plasma is also required, for example, the 2D timedependent laser-scattering techniques that have been applied to combustion and circuit breaker arcs. Development of methods that allow access to regions that are hidden from view, such as within plasma spraying and cutting torches [128,132], within the kerf in plasma cutting [128,131], and beneath the flux in submerged arc welding [127], would greatly increase our understanding of these approaches. Figure 25 shows two innovative approaches.…”

Electrode Phenomena in Plasma Sources

“…Comparison of the obtained values with the available information on these parameters showed a reasonable agreement. Long et al (2012) studied the evaporation of a hafnium cathode in a plasma cutting arc torch. The total amount of mass loss due to hafnium cathode evaporation was predicted to be enhanced with increasing gas flow rate, gas pressure, and cathode diameter as well.…”

Numerical investigation of the effect of cathode holder shape on hafnium cathode evaporation for an oxygen plasma cutting arc

“…In addition, multiple reports of studies investigating the process parameters related to plasma arc cutting have been published [9]- [14]. Nemchinsky [9] confirmed that swirling the gas enhances the axial gas flow from the cathode.…”

“…The probability of the evaporated atom/ion returning to the cathode is increased by the slowing down of the gas flow near the cathode and thus decreases the net erosion rate. On the other hand, our previous works [13,14] have already used a numerical model for a fundamental study of the effect of various swirl gas angle and process parameters on behaviour of hafnium cathode evaporation in a plasma cutting arc torch. Results have shown that a larger swirl gas angle causes a high-temperature plasma area in front of the cathode surface shrunken in a radial direction.…”

“…The shape of the cathode holder shape was defined a convex structure which protrudes from the surface of the cathode holder. The governing equations for mass, momentum, and energy transfer from the evaporated material in the arc plasma were used to obtain the simulation results which have been set up in the previous works [13,14]. This developmental model incorporates evaporation phenomena of the hafnium cathode and the re-deposition of hafnium vapour on the cathode surface [9].…”