Modelling of the heat transfer and fluid flow in a radio-frequency plasma torch with argon-hydrogen as the working gas

Abstract

Modelling results concerning the heat transfer and fluid flow in a radio-frequency plasma torch with argon and hydrogen as the working gas are presented. The diffusion of hydrogen in the gas mixture due to the presence of temperature and concentration gradients within the torch has been modelled by using the combined-diffusion-coefficient approach. Included in the modelling are also the effects of the induced currents appearing in the brass probe for central gas injection on the electromagnetic fields and thus on the plasma flow and heat transfer within the plasma torch. It has been shown that the electrical conductivity of the probe affects the modelling results of the flow field and the temperature distribution in the torch. The flow rate of the central argon flow has substantial effects on the temperature, velocity and concentration fields, especially in the region near the axis of the torch. Computed temperature profiles at a few cross sections of the torch are favourably compared with corresponding experimental data for a typical case.

A three-dimensional investigation of the effects of excitation frequency and sheath gas mixing in an atmospheric-pressure inductively coupled plasma system

“…Similar results have been obtained also by Chen for a different ICP torch configuration [28] and the accumulation of hydrogen in the cold boundary layer of a thermal spray torch was simulated by Ghorui et al [43] using a two-temperature combined diffusion approach. These results are in agreement also with previous investigations by Murphy [42] in which a peak of hydrogen mass fraction has been predicted in the low-temperature fringes of a free burning arc.…”

“…Some works by Tanaka [22,23], Watanabe et al [24,25,26] and other authors [4,27] implemented the second approach, obtaining accurate prediction of species distribution in the torch: as a drawback, in those papers, demixing due to mole fraction and temperature gradients has not been investigated. On the contrary, a combined diffusion approach has been used by Chen [28], but the effects of demixing have not been discussed in detail, although results for the mass fraction of hydrogen shows that it occurs in the near-wall region.…”

Measurement of C2 rotational temperature in Ar-SiH4-CH4 inductively coupled plasma flame with Abel inversion

“…However, numerical analysis involving simple reactions to produce Si particles from SiCl 4 reported by Désilets et al [21] shows that reactants introduced into the plasma have important roles in lowering of temperature. Also, Girshick [22] and Chen et al [23] reported that central gas flow affects the change of temperature in the central region of the plasma, as in our study.…”

“…In the previous study, we assumed that atoms produced by decompositions of the reactant gases were mainly excited in the centre of the plasma while Ar was mainly excited in an off-axis position of the plasma. This assumption is based on various reports by other researchers [18,[20][21][22][23].…”

Calculation and application of combined diffusion coefficients in thermal plasmas

“…The method has been successfully applied to modelling a wide range of phenomena in thermal plasmas. These include demixing in welding arcs 2 3 , plasma torches 4 , arc plasma reactors 5 6 , and inductively-coupled rf plasmas in gas mixtures 7 8 9 10 , mixing of metal vapour in welding arcs 11 12 13 , mixing of air into plasmas 14 15 16 17 18 19 20 21 22 23 , mixing of polymer vapours into the arc in circuit breakers 24 25 26 27 28 29 , and expansion of metal vapour ablated by a laser into the surrounding air 30 .…”