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

Shigeta, Masaya

doi:10.1002/tee.22761

Cited by 30 publications

(30 citation statements)

References 102 publications

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“…Excluding these additional factors, in sophisticated conditions, the fundamental mechanisms of turbulence transition of thermal plasma affecting nanopowders should be elucidated. Those mechanisms were explained in an earlier report [40] under conditions restricted to a 2D axisymmetric frame. However, a turbulent flow actually includes numerous vortices with 3D motions that directly affect nanopowder transport.…”

Section: Introductionmentioning

confidence: 79%

“…Elucidating the correlation between the dynamic behaviour of a plasma flow and the transient formation of a nanopowder distribution is indispensable. The issue has not been addressed to date using steady-state simulations or by experimentation, but it has recently been examined using time-dependent simulations restricted at a 2D axisymmetric frame for a direct-current nontransferred arc plasma jet [40] and a direct-current gas tungsten arc welding condition [41].…”

Section: Introductionmentioning

confidence: 99%

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Simulating Turbulent Thermal Plasma Flows for Nanopowder Fabrication

Shigeta

2020

Plasma Chem Plasma Process

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This article presents descriptions of theoretical models and numerical methods for simulating turbulent thermal plasma flow with nanopowder growth. Turbulence models must express turbulent and laminar states because both states co-exist with thermal plasmas showing large density variation and transport properties. Time-dependent 3D simulations are conducted based on Large Eddy Simulation using a dynamic Smagorinsky model. Results show significant difference depending on temporal and spatial discretization schemes and velocity-pressure coupling algorithms. Simulation results demonstrate that advanced numerical methods with high-order accuracy should be used for long and robust computations capturing steep gradients of nanopowder concentration and plasma temperature and 3D dynamic motions of multiscale vortices, which are turbulent features of thermal plasma flows with low Mach numbers. A thermal plasma jet generates a doublelayer structure of inner high-temperature thick vortex rings and outer low-temperature thin vortex rings near the nozzle exit. Flowing downstream, these vortices interact, deform, and break up. Consequently, plasma transits to a complex thermal flow. The widely spreading distribution of multiscale vortices agrees with experimental observations, which are not simulated using conventional methods. Nanopowder is generated from material vapour by nucleation and condensation at interfacial regions between plasma and cold gas. Those regions include numerous vortices. Therefore, the vortices convey the nanopowder, producing a complex distribution of nanopowder. Simultaneously, the nanopowder diffuses and increases in size, decreasing in number by interparticle coagulation. Cross-correlation analysis suggests that a nanopowder distribution distant from a plasma jet can be controlled through temperature fluctuation control at the upstream plasma fringe.

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Section: Introductionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Simulating Turbulent Thermal Plasma Flows for Nanopowder Fabrication

Shigeta

2020

Plasma Chem Plasma Process

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“…It is noteworthy that a turbulent flow has an eddy diffusion effect on the temperature field and the vapor and nanoparticle distributions [17,28]. Although the present model accompanies no turbulence model, time-dependent eddy motions larger than the grid scale were expressed.…”

Section: Model Descriptionmentioning

confidence: 94%

“…They demonstrated that it obtained almost identical number density and mean diameter as the MOM with a complex description [34]. By extension of their model [33], a model that also expresses nanoparticle transport by convection and diffusion has been proposed as [18,21,28]…”

Section: Model Descriptionmentioning

confidence: 99%

“…Nevertheless, its mathematical formulation might be too intricate for engineering use. To avoid this shortcoming, a more sophisticated model with a lower computational cost was developed for nanoparticle generation with a thermal plasma jet [18,21,28]. This study also adopted the model for arc plasma in a direct-current discharge condition.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Analysis of the Correlation between Arc Plasma Fluctuation and Nanoparticle Growth–Transport under Atmospheric Pressure

2019

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A time-dependent two-dimensional (2D) axisymmetric simulation was conducted for arc plasma with dynamically fluctuating fluid generating iron nanoparticles in a direct-current discharge condition. The nonequilibrium process of simultaneous growth and transport of nanoparticles is simulated using a simple model with a low computational cost. To ascertain fluid dynamic instability and steep gradients in plasma temperature and particle distributions, a highly accurate method is adopted for computation. The core region of the arc plasma is almost stationary, whereas the fringe fluctuates because of fluid dynamic instability between the arc plasma and the shielding gas. In the downstream region, the vapor molecules decrease by condensation. The nanoparticles decrease by coagulation. These results suggest that both of the simultaneous processes make important contributions to particle growth. The fluctuation of nanoparticle number density in a distant region exhibits stronger correlation with the temperature fluctuation at the plasma fringe. The correlation analysis results suggest that the distribution of growing nanoparticles distant from the arc plasma can be controlled via control of temperature fluctuation at the arc plasma fringe.

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Numerical modelling of a direct current non‐transferred thermal plasma torch for optimal performance

Yadav

Karmakar²,

Kar

et al. 2022

Contributions to Plasma Physics

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A laminar steady-state 2D axisymmetric model of a direct current (DC) thermal plasma torch using a magneto-hydrodynamic approach has been developed. The model takes into account the entire torch system comprising the plasma gas injection, the inner region of the torch, and the jet exiting into the ambient environment. Numerical results are obtained for two different power inputs chosen from published experimental data. The temperature predictions at the torch exit are found in good agreement with experimental results. Velocity analysis of the plasma jet has been presented and the impact of electromagnetic force on jet velocity is analysed. The Lorentz force arising due to the coupling of fluid motion and electromagnetic forces shoots up the jet velocity to significantly high values near the cathode tip. Temperature and velocity profiles are in good agreement with the characteristics of a long laminar plasma jet. An operating value of heat transfer coefficient (h) has been suggested for optimal torch operation, thus ensuring a low anode erosion rate and acceptable thermal efficiency. The argon torch has the maximum temperature and longest jet length among the plasma gases considered.

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

Cited by 30 publications

References 102 publications

Simulating Turbulent Thermal Plasma Flows for Nanopowder Fabrication

Simulating Turbulent Thermal Plasma Flows for Nanopowder Fabrication

Numerical Analysis of the Correlation between Arc Plasma Fluctuation and Nanoparticle Growth–Transport under Atmospheric Pressure

Numerical modelling of a direct current non‐transferred thermal plasma torch for optimal performance

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