Temperature and velocity fields in a gas stream exiting a plasma torch. A mathematical model and its experimental verification

McKelliget, J.; Szekely, J.; Vardelle, Michel; Fauchais, Pierre

doi:10.1007/bf00566526

Cited by 82 publications

(24 citation statements)

References 11 publications

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“…In Recent years, 3D modeling work concerning the effects of transverse gas injection from a single injection port on the plasma jet characteristics and the trajectories of injected particles attracted increasing interest (Ref [44][45][46][47][48][49][50][51][52]. The common feature of most of these papers is that assumed 2D temperature and velocity distributions at the outlet of the torch nozzle (or the inlet of the plasma jet region) are employed as boundary conditions for 3D modeling of heat transfer, flow patterns, and particle behavior in the jet region, i.e., only the effect of the carrier gas injection on the 3D characteristics of the plasma jet is included in the modeling work (Ref [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. Using velocity and temperature profiles obtained from modeling of DC arc plasma torches as the starting conditions of plasma jets (Ref 4,53) depends strongly on the ability to model plasma torches.…”

Section: Introductionmentioning

confidence: 99%

“…The 3D heat transfer and flow patterns, as well as the ionization-recombination process, inside a thermal plasma torch also have significant effects on the characteristics of the thermal plasma jet issuing from the exit of the plasma torch and, for example, on the quality of the coatings obtained by plasma spray. Over the past few decades, many papers have been devoted to modeling of the DC arc plasma spray process or to the study of spray-related basic processes based on 2D (axi-symmetrical) assumption with neglecting the effects of the transverse injection of the cold carrier gas on the jet flow field and on particle behavior ( Ref 4,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. But experimental results showed that even a small amount of carrier gas (5% of the main flow) transverse injection, as well as the particles used as the tracers in LDV measurements, may induce a deflection of the plasma jet with a deflection angle as great as 5°, and this 3D effect must be taken into account in the interpretation of the LDV data ( Ref 35).…”

Section: Introductionmentioning

confidence: 99%

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Three Dimensional Modeling of the Plasma Spray Process

Pfender

2007

J Therm Spray Tech

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Results of simulations of three-dimensional (3D) temperature and flow fields inside and outside of a DC arc plasma torch in steady state are presented with transverse particle and carrier gas injection into the plasma jet. The results show that an increase of the gas flow rate at constant current moves the anode arc root further downstream leading to higher enthalpy and velocity at the exit of the torch anode, and stronger mixing effects in the jet region. An increase of the arc current with constant gas flow rate shortens the arc, but increases the enthalpy and velocity at the exit of the torch nozzle, and leads to longer jets. 3D features of the plasma jet due to the 3D starting conditions at the torch exit and, in particular, due to the transverse carrier gas and particle injection, as well as 3D trajectories and heating histories of sprayed particles are also discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Three Dimensional Modeling of the Plasma Spray Process

Pfender

2007

J Therm Spray Tech

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“…Numerous experimental and modeling studies have been performed in past decades concerning the turbulent plasma jet characteristics (e.g. see [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and the references cited therein). The turbulent plasma jets are usually accompanied by large parameter fluctuations (mainly caused by the arc-root fluctuation at torch anode), intense noise emission (noise intensity level may be as high as 120 dB), strong entrainment of ambient gas into the plasma jets and thus with short high-temperature region lengths and steep axial gradients of plasma parameters (e.g.…”

mentioning

confidence: 99%

“…Although many papers have been published concerning the turbulent thermal plasma jet characteristics [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and a number of papers have been published concerning the laminar thermal plasma jet characteristics [6,8,[15][16][17][18][19][20][21][22][23][24][25][26], so far there is no a systematic study that compares carefully the laminar and turbulent thermal plasma jet characteristics. References 6 and 8 compared the predicted characteristics of laminar and turbulent plasma jets, but the comparisons were not sufficient and the conclusion deduced from reference 8 was not consistent with that from reference 6.…”

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confidence: 99%

Comparison of Laminar and Turbulent Thermal Plasma Jet Characteristics—A Modeling Study

Cheng

Chen

Pan

2006

Plasma Chem Plasma Process

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Modeling results are presented to compare the characteristics of laminar and turbulent argon thermal plasma jets issuing into ambient air. The combined-diffusion-coefficient method and the turbulence-enhanced combined-diffusion-coefficient method are employed to treat the diffusion of ambient air into the laminar and turbulent argon plasma jects, respectively. It is shown that since only the molecular diffusion mechanism is involved in the laminar plasma jet, the mass flow rate of ambient air entrained into the laminar plasma jet is comparatively small and less dependent on the jet inlet velocity. On the other hand, since turbulent transport mechanism is dominant in the turbulent plasma jet, the entrainment rate of ambient air into the turbulent plasma jet is about one order of magnitude larger and almost directly proportional to the jet inlet velocity. As a result, the characteristics of laminar plasma jets are quite different from those of turbulent plasma jets. The length of the high-temperature region of the laminar plasma jet is much longer and increases notably with increasing jet inlet velocity or inlet temperature, while the length of the high-temperature region of the turbulent plasma jet is short and less influenced by the jet inlet velocity or inlet temperature. The predicted results are reasonably consistent with available experimental observation by using a DC arc plasma torch at arc currents 80-250 A and argon flow rates (1.8-7.0)×10 −4 kg/s.

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“…Many theoretical analyses and experimental measurements, [6][7][8][9][10][11][12] including some extended numerical simulations which considered two-fluid turbulent mixing 11 and chemical reactions, 12 have been done to find thermal plasma characteristics outside the plasma torch. However, little theoretical work and few experiments have been carried out for thermal plasma jets with shroud gas injection.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of shroud gas effects on air entrainment into thermal plasma jet in ambient atmosphere of normal pressure

Kang

Hong

1999

Journal of Applied Physics

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A numerical analysis of the influence of air entrainment into the plasma jet on the thermal plasma characteristics is performed to provide a design basis for nontransferred plasma torches operated in an ambient air of atmospheric pressure along with shroud gas injection. The assumption of steady-state, axisymmetric, local thermodynamic equilibrium, and optically thin plasma is adopted in a two-dimensional modeling of thermal plasma flow with an annular shroud gas shell. A control volume method and a modified semi-implicit pressure linked equations revised algorithm (known as SIMPLER) are used for solving the governing equations, i.e., the conservation equations of mass, momentum, and energy along with the equations describing the so-called K–ε model for flow turbulent kinetic energy (K) and its dissipation rate (ε), and the mass fraction equations for gas mixing. The two-dimensional distributions of temperature and flow velocity of the thermal plasma jet as well as the air mole fraction mixed with the plasma are found in an exterior jet expanding region outside the torch, and they are compared for the two cases with and without shroud gas injection. As a result of calculations, the flow rate of the injected shroud gas and the location of its injector turn out to be major parameters for controlling ambient air entrainment. The calculations also reveal that the annular injection of shroud gas surrounding the plasma jet reduces air entrainment into the plasma jet remarkably while it does not significantly affect the plasma temperature and velocity. The present numerical modeling suggests the optimum design and operating values of an argon shroud gas injector for minimizing air entrainment into the thermal plasma flame ejected from the nontransferred plasma torch operated at normal pressure in the ambient atmosphere.

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Temperature and velocity fields in a gas stream exiting a plasma torch. A mathematical model and its experimental verification

Cited by 82 publications

References 11 publications

Three Dimensional Modeling of the Plasma Spray Process

Three Dimensional Modeling of the Plasma Spray Process

Comparison of Laminar and Turbulent Thermal Plasma Jet Characteristics—A Modeling Study

Numerical analysis of shroud gas effects on air entrainment into thermal plasma jet in ambient atmosphere of normal pressure

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