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Metallurgical and Materials Transactions B

, Volume 47, Issue 5, pp 2732–2743 | Cite as

Microbubble Swarms in a Full-Scale Water Model Tundish

  • Sheng Chang
  • Xiangkun Cao
  • Zongshu Zou
  • Mihaiela Isac
  • Roderick I. L. Guthrie
Article

Abstract

Water modeling, using microbubble swarms, was performed in a full-scale, four-strand, delta-shaped tundish, located at the McGill Metals Processing Centre (MMPC). The objective of the study was to investigate the effectiveness of microbubbles in removing inclusions smaller than 50 μm, applying the principles and conditions previously researched using a smaller scale arrangement. Air was injected into a full-scale model of a ladle shroud (the connecting tube through which liquid steel flows into the tundish below). The model ladle shroud was fitted with twelve, laser-drilled orifices, so as to create microbubbles. The bubbles generated using different gas injection protocols were recorded using a high-speed camera, and the bubble images were postprocessed using the commercial software, ImageJ. With this newly designed ladle shroud, bubble sizes could be reduced dramatically, to as small as a 675 µm average diameter. A three-dimensional, CFD model simulation was developed, using parameters obtained from the corresponding water model experiments, in order to predict the behavior of these microbubbles within the tundish and their potential influence on flow patterns and inclusion float-out capability.

Keywords

Bubble Size Liquid Steel Slide Gate Turbulent Dissipation Rate Inclusion Removal 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

CD

Drag coefficient (−)

db

Diameter of bubble (m)

Fr

Froude number (−)

g

Gravity acceleration (m2/s)

Gk

Generation rate of turbulence kinetic energy (−)

H

Height of liquid bath

I

Turbulence intensity (−)

k

Turbulent kinetic energy (m2/s2)

l

Turbulence length scale (m)

L

Characteristic length (m)

Le

Eddy length scale (m)

l0

Length scale associated with small vortices (m)

\( \dot{m}_{\text{b}} \)

Mass flow rate of bubbles (kg/s)

ni

Number density of inclusions (number/m3)

Ni

Number of inclusions removed per unit time (number/s)

Nb

Number of bubbles (−)

p

Pressure (Pa)

P, PC, PA

Attachment, collision, and adhesion probability between inclusion and bubbles (−)

Qg

Gas flow rate (m3/s)

Rorifice

The radius of the gas injection port (m)

Re

Reynolds number (−)

Stk

Stokes number (−)

tcross

Eddy crossing time (s)

tr

Bubble residence time (s)

Δt

Time step (s)

u, ub

Velocity of fluid flow and bubbles (m/s)

uav, u

Average fluid velocity and the fluctuation of the velocity (m/s)

uair

Velocity of the gas crossing the orifice (m/s)

Vs

Swept volume (m3)

Wec

Critical Weber number (−)

ρ, ρg

Densities of liquid and gas (kg/m3)

ε

Turbulent dissipation rate (m2/s3)

ζ

Normally distributed random number (−)

μeff,μ, μt

Effective viscosity, laminar viscosity, and turbulent viscosity (kg/(m s))

σ

Surface tension (N/m)

τe, τp

Eddy life time and relaxation time (s)

DLS

Dissipative ladle shroud

DPM

Discrete phase model

RTD

Residence time distribution

SEN

Submerged entry nozzle

Notes

Acknowledgments

The authors are indebted to NSERC, and to RTIT for research funding, to the MMPC for giving access to all its research facilities, and to ANSYS Inc. for providing the license of Fluent. The first author is also grateful to the China Scholarship Council for the financial support during his Ph. D studies at McGill.

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2016

Authors and Affiliations

  • Sheng Chang
    • 1
    • 2
  • Xiangkun Cao
    • 2
  • Zongshu Zou
    • 1
  • Mihaiela Isac
    • 2
  • Roderick I. L. Guthrie
    • 2
  1. 1.School of Materials and MetallurgyNortheastern UniversityShenyangP.R. China
  2. 2.McGill Metals Processing CentreMcGill UniversityMontrealCanada

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