Integrated parametric study of a hybrid-stabilized argon–water arc under subsonic, transonic and supersonic plasma flow regimes

Abstract

This paper presents a numerical investigation of characteristics and processes in the worldwide unique type of thermal plasma generator with combined stabilization of arc by argon flow and water vortex, the so-called hybrid-stabilized arc. The arc has been used for spraying of ceramic or metallic particles and for pyrolysis of biomass. The net emission coefficients as well as the partial characteristics methods for radiation losses from the argon–water arc are employed. Calculations for 300–600 A with 22.5–40 standard litres per minute (slm) of argon reveal transition from a transonic plasma flow for 400 A to a supersonic one for 600 A with a maximum Mach number of 1.6 near the exit nozzle of the plasma torch. A comparison with available experimental data near the exit nozzle shows very good agreement for the radial temperature profiles. Radial velocity profiles calculated 2 mm downstream of the nozzle exit show good agreement with the profiles determined from the combination of calculation and experiment (the so-called integrated approach). A recent evaluation of the Mach number from the experimental data for 500 and 600 A confirmed the existence of the supersonic flow regime.

Time-Resolved Emission Spectroscopy Measurements during the Restrike Period in Arc Plasma Torch

“…It is known that temperature distribution in the arc column is generally such that the maximum temperature is in the region between the electrodes from which temperature decreases with approaching to electrodes [20][21][22]. For this torch, we do not have experimental data of this type, but according to numerical models, such dependence along the axis of the torch is also present [23,24]. Such temperature distribution can simply explain the dependence as shown in Figure 6; as the arc attachment moves downstream, the position of measurement gets closer to the centre of the arc where the temperature is higher.…”

Modeling and simulation of a turbulent‐like thermal plasma jet for nanopowder production

“…Large eddy simulation (LES) approaches have been a recent trend for thermal plasma flow simulations [6,[72][73][74][75][76][77][78][79][80][81][82]. LES is a time-dependent approach that deals with dynamic motions of large eddies directly using a grid system and models only turbulence composed of small eddies, unresolved by the grid element size.…”

The Influence of Turbulence on Characteristics of a Hybrid-Stabilized Argon-Water Electric Arc

“…Some of our previous calculations analyzed flow regimes, thermal, electrical characteristics and power losses from the hybrid-stabilized electric arc. (9)(10)(11)(12) Experiments carried out with the hybrid torch show the laminar structure of the plasma flowing out of the discharge chamber just behind the nozzle for currents up to 600 A, i.e., the operational regime of our torch. Our previous calculation demonstrates that the Reynolds number based on the outlet diameter 6 mm reaches in the axial region 13,000 at maximum and decreases to 300 in arc fringes.…”

“…To check possible deviations from the laminar model, we utilized the Large-Eddy Simulation (LES) in the present model and compared our results against the laminar case. In our previous paper (12) we stated that the maximum detected discrepancy between the turbulent and laminar models is below 7% for the relative temperature difference at one point only at the arc axis downstream of the nozzle exit, but this time we studied turbulence in the discharge in greater detail. The domain for numerical calculation is shown in Figure 1 by a red-dashed line and includes the discharge area between the outlet nozzle for argon and the near-outlet region of the hybrid plasma torch.…”