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<p>This study presents three-dimensional unsteady computational fluid dynamics simulations, under the assumption of local thermodynamic equilibrium, conducted in OpenFOAM to examine how varying the outlet diameter and throat length of a plasma spray torch affects its internal arc behavior and exit jet characteristics. Voltage and attachment-point temperature diagnostics show a restrike cycle driven by an imbalance between Lorentz and drag forces. These attachment dynamics are consistent across downstream geometries. Outlet observations reveal that Lorentz-driven off-axis motion produces crescent-shaped temperature and velocity fluctuations. When time-averaged, these yield a flat-topped parabolic radial temperature profile with a ~ 15 kK centerline peak and an M-shaped mean velocity with a central dip. The hot-core thickness is geometry-insensitive because the sharp drop in thermal conductivity imposes the conductive bottleneck while elevated kinematic viscosity suppresses shear-layer mixing. In contrast, the velocity responds predictably to geometry: Larger outlets reduce overall jet speed and flatten the core, whereas longer throats increase centerline velocity nearly linearly by extending the acceleration region. These results supply compact, physics-based heat-source and inflow boundary conditions for thermal spray simulations.</p>

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Downstream Geometry Effects on Outlet Jet Characteristics in an Atmospheric Plasma Spray Torch

  • 期刊论文

  • 发表日期：

    2026年5月5日

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  • Byeongryun Jeon,
  • Byeong-Il Min,
  • Anthony B. Murphy,
  • Do Hyun Kim,
  • Hansol Kwon,
  • Yong-jin Kang,
  • Youngjin Park,
  • Yeon Woo Yoo,
  • June Kee Min,
  • Hunkwan Park

摘要

This study presents three-dimensional unsteady computational fluid dynamics simulations, under the assumption of local thermodynamic equilibrium, conducted in OpenFOAM to examine how varying the outlet diameter and throat length of a plasma spray torch affects its internal arc behavior and exit jet characteristics. Voltage and attachment-point temperature diagnostics show a restrike cycle driven by an imbalance between Lorentz and drag forces. These attachment dynamics are consistent across downstream geometries. Outlet observations reveal that Lorentz-driven off-axis motion produces crescent-shaped temperature and velocity fluctuations. When time-averaged, these yield a flat-topped parabolic radial temperature profile with a ~ 15 kK centerline peak and an M-shaped mean velocity with a central dip. The hot-core thickness is geometry-insensitive because the sharp drop in thermal conductivity imposes the conductive bottleneck while elevated kinematic viscosity suppresses shear-layer mixing. In contrast, the velocity responds predictably to geometry: Larger outlets reduce overall jet speed and flatten the core, whereas longer throats increase centerline velocity nearly linearly by extending the acceleration region. These results supply compact, physics-based heat-source and inflow boundary conditions for thermal spray simulations.