Transient Two-phase Flow in a Slide-gate Nozzle and Mold ...ccc.illinois.edu/s/2014_Presentations/03_Cho-SM_Two_Phase... · CCC Annual Report UIUC, August 20, 2014 Transient Two-phase

CCC Annual ReportUIUC, August 20, 2014

Transient Two-phase Flow in

a Slide-gate Nozzle and Mold with

Double-ruler EMBr

POSTECH: Seong-Mook Cho and Seon-Hyo KimUIUC: Brian G. Thomas

Department of Mechanical Science & Engineering

University of Illinois at Urbana-Champaign

Pohang University of Science and Technology • Department of Materials Science and Engineering • Seong-Mook Cho • 2/34

Slide-gate and Double-ruler EMBr in Continuous Slab Casting

Middle plate

SEN

OR

IR

Towardsright NF

Towardsleft NF

<Schematic of continuous steel slab casting>

<Slide-gate middle plate on SEN>

Slide-gate produces asymmetric open area for flowing molten steel

Double-ruler EMBr locates magnet rulers at two regions: just above the port and below nozzle port

Upper ruler

Lower ruler


Research Scope Previous works

- Quantified transient two-phase (molten steel-argon) flow in slide-gatenozzle and mold without EMBr, using LES coupled with DPM model andnail board tests

- Investigated effects of double-ruler EMBr on single-phase (molten steel)flow in slide-gate nozzle and mold using standard model and nailboard tests

Objectives to- Gain insight of effects of double-ruler EMBr on transient two-phase flow in

slide-gate nozzle and mold- Develop and validate LES coupled with DPM and MHD to predict two-

phase flow considering EMBr effect- Compare steady-state standard model and LES to predict transient

flow variations in the mold Methodologies

- Plant Experiments: nail board tests, eddy-current sensor measurements- Computational Models: standard model, LES coupled with DPM and

MHD model

εk −

εk −

εk −


Process ConditionsCaster Dimensions

Nozzle bore diameter (inner/outer) 90 mm (at UTN top) to 80 mm (at bottom well) /160 mm (at UTN top) to 140 mm (at SEN bottom)

Nozzle bottom well depth 19 mm

Nozzle port area 80 mm (width) 85 mm (height)Nozzle port angle

*2008: 52 to 35 down degree step angle at the top, 45 down degree angle at the bottom

*2010: 35 down degree angle at both top and bottom

Mold thickness 250 mmMold width 1300 mm

Domain length 4648 mm (mold region: 3000 mm (below mold top))

Process ConditionsSteel flow rate 552.5 LPM (3.9 tonne/min)Casting speed 1.70 m/min (28.3 mm/sec)

Argon gas flow rate & volume fraction9.2 SLPM (1 atm, 273 K); 33.0 LPM (1.87 atm, 1827 K) & 5.6 % (hot)

Submerged depth of nozzle 164 mm

Meniscus level below mold top 103 mm

EMBr current (both coils) EMBr off: 0 A EMBr on: 300 A

×


Plant Measurements: Nail Board Tests (2013 CCC Report)

<Time-averaged surface velocity> <Surface velocity fluctuation>

~50% fluctuation of mean velocity

<Time-averaged surface level> <Surface level fluctuation>

~8 mm

<Slag motion without EMBr>

<Slag motion with EMBr>

k: coefficient of slag motion

k=slope


Plant Measurements: Eddy Current Sensor Measurement (2013 CCC Report)

AVG level: ~103 mm

<Surface level by time>

<Power spectrum of level variation>

With EMBr, surface level fluctuation at quarter point (located midway between SEN and NF) is reduced by ~33%: 0.6 mm (Without EMBr) and 0.4 mm (With EMBr)

~0.03 Hz (~35 sec)


Governing Equations

Molten steel flow field: Large Eddy Simulation (LES)

Argon gas bubble motion: Discrete Phase Model (DPM)

Electromagnetic force induced by EMBr: Magneto-Hydro-Dynamics (MHD) model

( ) mass shell,ii

Sρux

=∂∂

( ) ( ) ( ) iL,imom,Ar,i mom,shell,i

j

j

it

ji

*

jij

i FSSx

u

x

uμμ

xx

puρu

xρu

t+++

∂∂

+∂∂+

∂∂+

∂∂−=

∂∂+

∂∂

iradient,pressure_giss,virtual_maibuoyancy,idrag,iAr, FFFF

dt

du+++=

( ) ( )iAr,i2ArAr

Didrag, uu

dρ

ReμC

4

3F −⋅=

μ

uuρdRe ArAr −

=

( )

( )

( )

( )We8 3

8

ReWe

2065.1

3

We

Re100 Re

6.3

100Re0.49 Re

20.68

0.49Re Re

16C

2.6

0.385

0.643

D

<=

<=

<=

<<=

<=

argonsteel

2

ArAr

σ

uuρdWe

−

−=

iAr

Aribuoyancy, g

ρ

ρ-ρF = ( )iAr,i

Ariss,virtual_ma uu

dt

d

ρ

ρ

2

1F −=

i

ii

Ariradient,pressure_g x

uu

ρ

ρF

∂∂=

( ) ΔtmFFFFS Ari gradient,_ pressurei ss,virtual_mai buoyancy,i drag,i Ar,mom, +++−=

( )bBjF 0L

+×=

( )bBμ

1j 0

+×∇= ( ) ( )( ) ( ) 00

2 B uu bBbμσ

1b u

t

b

∇⋅−∇⋅++∇=∇⋅+∂∂

V

AρuS casting

massshell, −=Mass conservation: Mass/momentum sink terms to account for solidification of the molten steel:

Momentum conservation:

icasting

imom, shell, uV

AρuS −=

Bubble motion equation:

Force equations:

Drag coefficient:

Lorentz force:

Induced current density: Induced magnetic field:


Domain, Mesh, and Boundary Conditions

<Front view> <Side view>

Total cells in the domain: ~1.8 million

Boundary conditions

Inlet0.00938 m/sec, 5.6 % volume fraction of Argon

Outlet0 Pa (gauge pressure), particle escape

SurfaceStationary wall with a no slip shear condition,particle escape

Interfacebetween the molten steel /the steel shell

Stationary wall with a no slip shear condition, molten steelmass/momentum sink,particle reflect

(sec)t 2.94(mm) S =

Inlet

Outlet

Surface

Symmetric plane

0 500 1000 1500 2000 2500 30000

5

10

15

20

25

30

35

Measurement

Sh

ell t

hic

kne

ss (

mm

)

Distance from meniscus (mm)

Steel shell thickness profile:

Half domain (assuming symmetry between NFs, containing the electrically-conducting steel shell region as a solid zone)


Double-ruler EMBr Field: External Magnetic Field

Weaker

Magnetic field applied by the double-ruler EMBr has high peaks in two regions: one centered just above the port and the other below the nozzle port

Inner oval showing region of strong field over 0.13T

Pohang University of Science and Technology • Department of Materials Science and Engineering • Seong-Mook Cho •10/34

Double-ruler EMBr Field: Current Density & Electromagnetic Force

<Induced current density> <Electromagnetic force>

High current density and electromagnetic force are generated in two regions: near the nozzle port and near the NF 600mm below the mold top


Comparison of Time-averaged Mold Flow Patternbetween Standard Model and LES (Single Flow)

Time-averaged ~23 s Time-averaged ~32.3 s

εk −

εk−Standard

LES

EMBr off EMBr on

EMBr off EMBr on

Standard model and LES both predict double-role flow pattern and high surface velocity in the mold without EMBr

Both two models show EMBrproduces less flow up the NF (600 mm below mold top), resulting in slower surface velocity and stronger downward flow along the NF

In EMBr on case, steady-state standard model shows better agreement with LES than EMBr off case

The limited accuracy of this steady-state model is perhaps due to complex transient flow variation (anisotropic variations)

εk −

εk −



Comparison of Mold Flow Fluctuations between Standard Model and LES (Single Flow)

( ) ( ) ( )2'2'2' wvu == ( )2'v ( )2'w( )2'u

εk −RMS velocity

(m/sec)

EMBr off

EMBr on

εk−Standard

LES

LES

εk−Standard

Two models both predict EMBrinduces smaller flow variation towards the top surface LES predicts EMBr is more effective to reduce the variations along mold thickness; same trend with R. Singh et al. result[*]

Steady-standard model well-

predicts isotropic variations however, shows limited accuracy for anisotropic variations

Time-averaged

~23 s

Time-averaged ~32.3 s

εk −

LES is much more appropriate model to predict more complex flow variations induced by two-phase flow

*R. Singh, B. G. Thomas, and S. P. Vanka, Metall. Mater. Trans. B., 2014, vol. 45B, pp. 1098-1115


Transient Swirl Flow in Slide-gate Nozzle (Two-phase Flow)


EMBr off

EMBr on

IR OR

IR OR


EMBroff

EMBron

Clockwise23.4 s(43%)

14.4 s(23%)

Counter clockwise

29.4 s(54%)

46.2 s(74%)

Intermediate1.2 s(3%)

1.8 s(3%)

With EMBr, period of the counter-clockwise swirl flow becomes longer: EMBr makes the flow (from asymmetric open area in the middle plate to nozzle bottom) go down by longer path with imposing electromagnetic force

*19.92s *63.30s

**13.35s **42.21s

*After argon gas injection

**After EMBrapplication

Clockwise Counter clockwise

ClockwiseCounter clockwise

Period of flow directions


Swirl Flow Videos

EMBr off EMBr on

Real flow time ~55.2 s Real flow time ~62.8 s

Swirl in nozzle[*] (Water model experiment)

*Hershey, D. E., B. G. Thomas, and F. M. Najjar, "Turbulent Flow through Bifurcated Nozzles," International Journal for Numerical Methods in Fluids, 17:1, 23-47, 1993.


Nozzle Port Velocity Histories (Two-phase Flow at P1-Nozzle Port)

Intermediate period

10 15 20 25 30 35 40 45 50 55 60 65 700.0

0.5

1.0

1.5

2.0

2.5

3.0

Vel

ocit

y m

agn

itu

de

(m/s

ec)

Time after EMBr application (sec)

P1_nozzle port (EMBr_on) P1_nozzle port (EMBr_on)_0.3s_time-averaging

15 20 25 30 35 40 45 50 55 60 65 700.0

0.5

1.0

1.5

2.0

2.5

3.0V

eloc

ity

mag

nitu

de (

m/s

ec)

Time after gas injection (sec)

P1_nozzle port (EMBr_off) P1_nozzle port (EMBr_off)_0.3s_time-averaging

<EMBr off> <EMBr on>


Jet Velocity Histories (Two-phase Flow at P2-Jet Flow)

15 20 25 30 35 40 45 50 55 60 65 700.0

0.5

1.0

1.5

Vel

ocit

y m

agn

itu

de

(m/s

ec)

Time after argon gas injection (sec)

P2_jet flow (EMBr off) P2_jet flow (EMBr off)_0.3s_time-averaging

10 15 20 25 30 35 40 45 50 55 60 65 700.0

0.5

1.0

1.5

Vel

ocit

y m

agni

tude

(m

/sec

)


P2_jet flow (EMBr_on) P2_jet flow (EMBr_on)_0.3s_time-averaging

Intermediate period

AVG_lag time between P1 and P2 with and without EMBr: ~0.29s



Transient Flow Pattern in the Mold(Two-phase Flow)

Velocity magnitude (m/sec)


EMBr off

EMBr on


*19.92s *63.30s

**13.35s **42.21s

With and without EMBr, double-role pattern is induced in two-phase flow in the mold

Without EMBr, up-and-down wobbling of the jet flow induces variations of velocity magnitude and direction at the surface, and changes the jet flow impingement point on the NF

EMBr makes the slightly thinner jet flow and reduces the wobbling, resulting in more stable surface flow




Avg_lagtime:~3.4s

Avg_lagtime:~4.1s


Mold Flow Videos


EMBr off EMBr on


Velocity Fluctuations & Turbulent Kinetic Energy in the Mold (Two-phase Flow)

Turbulent kinetic energy (m2 /sec2)

++2

'2

'2

' wvu2

1RMS velocity (m/sec)

'u 'v 'w


EMBr off

EMBr onTime-averaged ~62.8 s

++2

'2

'2

' wvu2

1'w'v'u

Two-phaseflow shows more variations in nozzle port and upper-role region than single-phase flow does

EMBr is moreeffective to reduce the variations produced by the jet flow wobbling in upper-role region; especially, casting direction and mold thickness direction


Calculation of Jet Flow Angle

u

v

w

Flow direction

( )ii-1

i vutanα /−=Instantaneous vertical angle:

( )ii-1

i vwtanβ /−=Instantaneous horizontal angle:

along casting direction

along mold width

along mold thickness

Averaged vertical angle:

Averaged horizontal angle:

Vertical angle fluctuation (standard deviation):

Horizontal angle fluctuation (standard deviation):

=

=n

1iiavg α

n

1α

=

=n

1iiavg β

n

1β

( )=

−=n

1iavgiα αα

n

1σ

( )=

−=n

1iavgiβ ββ

n

1σ

<Instantaneous angle histories of two-phase flow without EMBr (at P1)>

15 20 25 30 35 40 45 50 55 60 65 70-90-80-70-60-50-40-30-20-10

0102030405060708090

Ver

tica

l an

gle

(deg

ree)

Time after argon injection (sec)

Point-1 without EMBr

avgα

avgβ

ασ

βσ

45.4

26.1

21.1

5.1

iα

15 20 25 30 35 40 45 50 55 60 65 70-90-80-70-60-50-40-30-20-10

0102030405060708090

Hor

izon

tal a

ngl

e (d

egre

e)


Point-1 without EMBr

iβ


Jet Flow Angle in the Mold (Effect of EMBr on mean and variation)

IR

OR

NFSEN

<Top view: horizontal jet angle>

<Front view: vertical jet angle>

NF

Center line

Surface

IR

OR

NFSEN

NF

SEN

Surface

“EMBr off” “EMBr on” EMBr reduces jet wobbling along both casting direction (vertical angle) and mold

thickness direction (horizontal angle)

21.145.4 ±

22.026.6 ±

13.245.4 ±

17.424.9 ±

26.15.1 ± 22.91.0- ± 18.65.2 ± 21.02.8- ±

<Front view: vertical jet angle>

SEN

avg stdev

Center line

P1 P2

Reduction in angle variation by

EMBr

P1-nozzle

P2-jet

Vertical angle

fluctuation37.4 % 20.9 %

Horizontal angle

fluctuation28.7 % 8.3 %

P1

P2

<Top view: horizontal jet angle>

Horizontal angle fluctuation is slightly larger than vertical angle fluctuation


Transient Surface Flow Pattern (Two-phase Flow)

Time-averaged ~55.2 s Time-averaged ~62.8 s

*19.92s

*63.30s

**13.35s

**42.21s




Decreased jet wobbling by EMBr reduces the surface flow variations along both mold width and thickness; the horizontal velocity fluctuation and the asymmetric flow between IR and OR are suppressed


Surface Flow Videos


EMBr off EMBr on


0 50 100 150 200 250 300 350 400 450 500 550 600 6500.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

Tu

rbu

lent

kin

etic

ene

rgy

(m2/

sec2

)

Distance from mold center (mm)

Without EMBr With EMBr

Velocity Fluctuations & Turbulent Kinetic Energy at the Surface (Two-phase Flow)

<RMS u velocity> <RMS v velocity>

<RMS w velocity> <Turbulent kinetic energy>

0 50 100 150 200 250 300 350 400 450 500 550 600 6500.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

RM

S u

vel

ocit

y (m

/sec

)



0 50 100 150 200 250 300 350 400 450 500 550 600 6500.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

RM

S v

vel

ocit

y (m

/sec

)



0 50 100 150 200 250 300 350 400 450 500 550 600 6500.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

RM

S w

vel

ocit

y (m

/sec

)



offEMBr

'uoffEMBr

'v

offEMBr

'w

onEMBr

'u

onEMBr

'v

onEMBr

'w onEMBr TKE

offEMBr TKE

33.7 %

10.8 %

39.9 %

45.6 %

'u

'v

'w

++2

'2

'2

' wvu2

1

Reduction in Velocity fluctuations & TKE by EMBr

=0.059 m/s

=0.039 m/s

=0.065 m/s

=0.058 m/s

=0.074 m/s

=0.045 m/s

=0.0068 m2/s2

=0.0037 m2/s2

EMBr mainly reduces surface velocity fluctuations along mold thickness (between IR and OR) and casting direction; the swirl flow variations produced by slide-gate can be controlled by the EMBr


Surface Velocity Histories (Two-phase Flow at W/4 at the surface)

15 20 25 30 35 40 45 50 55 60 65 700.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55V

eloc

ity

mag

nit

ud

e (m

/sec

)


Without EMBr

10 15 20 25 30 35 40 45 50 55 60 65 700.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

Vel

ocit

y m

agn

itu

de

(m/s

ec)


With EMBr

Variations of surface velocity magnitude is related to the swirl flow direction in the nozzle bottom with slide-gate

Clockwise swirl induces high momentum jet flow, resulting in high surface velocity after lag time (without EMBr: ~3.4s(avg), with EMBr: ~4.1s(avg)). On the other hand, counter clockwise swirl produces lower surface velocity

Intermediate period

Avg_lagtime: ~3.4s Avg_lag time: ~4.1s


Frequency Analysis at the Surface(W/4 at the surface)

0.01 0.1 1 10 1001E-201E-191E-181E-171E-161E-151E-141E-131E-121E-111E-101E-91E-81E-71E-61E-51E-41E-30.01

Pow

er s

pec

tru

m (

m2/

s2)

Frequency (Hz)


~0.054 Hz (~18.5sec)

~0.095 Hz (~10.5 sec)

1E-3 0.01 0.10.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.018EMBr off: EMBr on:

Pow

er s

pec

tru

m(m

m2 )

Frequency(Hz)<Power spectrum of surface level><Power spectrum of surface velocity>

Prediction

Eddy-current measurements

The characteristic frequencies (EMBr off: ~0.054 Hz, EMBr on: ~0.095 Hz) of surface velocity seem to produce similar peaks as the measured surface level fluctuations

The strong maximum peak (~0.03 Hz) at the surface, both with and without EMBr, might be produced by low frequency sloshing between right and left narrow face; the half model of LES fails to capture low peak ( 0.03 Hz) OR this peak would be shown by longer flow time (over 70 s)

~0.057 Hz (~17.5 sec)

~0.096 Hz (~10.4 sec)

~0.03 Hz (~35 sec)

≤


Model Validation with Nail Board Tests:Surface Velocity

0 50 100 150 200 250 300 350 400 450 500 550 600 6500.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45S

urf

ace

velo

city

mag

nit

ud

e (m

/sec

)


Predicted MeasuredWithout EMBr: With EMBr:

0 50 100 150 200 250 300 350 400 450 500 550 600 6500.000.010.020.030.040.050.060.070.080.090.100.110.120.130.140.15

Su

rfac

e ve

loci

ty

mag

nit

ud

e fl

uct

uat

ion

(m

/sec

)


Predicted MeasuredWithout EMBr: With EMBr:

<Surface velocity magnitude> <Surface velocity fluctuation>

The predicted surface velocity magnitude and its fluctuation profiles show remarkable agreement with measurements for both EMBr off and on case

With EMBr, surface flow is slightly slower (by ~17 %) with smaller fluctuations (by ~43 %)

This finding suggests that use of the double-ruler EMBr may help to reduce defects caused by surface flow instability.


Model Validation with Nail Board Tests:Surface Level

Region 1(near SEN: 0~235mm)

Region 2(midway: 235~485mm)

Region 3 (near NF: 485~650 mm)

Without EMBr 0.85 0.74 0.82

With EMBr 0.97 0.63 0.65

<Coefficient (k) of slag motion at the surface regions with and without EMBr>

( )gk)ρ(1ρ

PPH

slagsteel

avgii −−

−=

0 50 100 150 200 250 300 350 400 450 500 550 600 650-8-7-6-5-4-3-2-10123456789

10

Su

rfac

e le

vel h

eigh

t (m

m)


15 sec (prediction) 18 sec (prediction) 21 sec (prediction) 24 sec (prediction) 27 sec (prediction) 30 sec (prediction) Nail board (measurement)

0 50 100 150 200 250 300 350 400 450 500 550 600 650-8-7-6-5-4-3-2-10123456789

10

Su

rfac

e le

vel h

eigh

t (m

m)


11.7 sec (prediction) 14.7 sec (prediction) 17.7 sec (prediction) 20.7 sec (prediction) 23.7 sec (prediction) 26.7 sec (prediction) Nail board (measurement)


New Semi-empirical equation to relate pressure to surface level:

The improved pressure-based surface level prediction agrees with measured surface level profiles with and without EMBr

Predictions are less accurate near SEN without EMBr; perhaps due to low frequency and high amplitude wave motion near SEN

The model might benefit from true free-surface analysis, instead of simple surface-pressure method


Bubbles Distribution in the Mold (1/3 Scale Water Model Experiment)

<35.0 LPM (Water)_0.2 SLPM (Air)> <35.0 LPM (Water)_0.8 SLPM (Argon)>

<35.0 LPM (Water)_1.6 SLPM (Argon)>

With higher gas flow rate, bubbles in the mold are larger

With small gas flow rate, bubbles are carried throughout larger mold region; (because they are small), causing more chance to touch the NF

With high gas flow rate, most bubbles float to the surface near the SEN (because the flow cannot carry bigger bubbles as easily), so less are found near the NF

window

Volume fraction:

0.6 %

Volume fraction:

2.4 %

Volume fraction:

4.6 %


Effect of EMBr on Argon Bubble Distribution in the Mold


- Transient gas distribution changes (agrees with measured) are induced by jet flow wobbling.

- Most bubbles found in upper recirculation region; this trend agrees with the water model measurement

- Predicted bubble spreadingacross top region (differing from measurement) might be due to incorrect assumption of constant bubble size (1mm) vs. (1-5mm with 2.5mm mean)

- With EMBr, more argon bubbles float up to the surface near the SEN wall. In the region 600~1200 mm from the mold top, many bubbles have longer residence time near NF.

Volume fraction: 5.6 %

5.6 % volume fraction


Argon Gas Distribution Videos


EMBr off EMBr on


Summary: Modeling

LES coupled with DPM and MHD model is used to predict transient molten steel-argonflow in slide-gate nozzle and mold with and without EMBr, and the model is validated withnail board tests and eddy-current sensor measurements showing remarkable agreements. Steady-standard model well-predicts isotropic variations, however, shows limited

accuracy for anisotropic variations, especially produced by swirl flow near nozzle port Predicted surface velocity magnitude and its fluctuation profiles show remarkable

agreement with the measurements for both EMBr off and on case The improved pressure-based surface level prediction (new semi-empirical equation to

relate pressure to surface level) agrees with measured surface level profiles with andwithout EMBr Half model of LES predicts the characteristic frequencies of surface velocity fluctuations,

which seem to produce similar peaks as the measured surface level fluctuations. Themeasured strong peak (~0.03 Hz) by an eddy-current sensor at the surface, both with andwithout EMBr, might be produced by low frequency sloshing between right and left narrowface; the model fails to capture the low peak (0.03 Hz) OR this peak would be shown bylonger flow time (over 70 s) LES coupled with DPM shows reasonable match with water model measurements of

argon bubble distribution For better prediction of bubble distribution in the mold, bubble size distribution is needed to

be implemented to transient two-phase flow model

εk −


Summary: Swirl Flow and Its Effect Slide-gate induces swirl flow in nozzle bottom region with clockwise, counter-clockwise, and

intermediate directions. EMBr makes the flow (from asymmetric open area in middle plateto nozzle bottom) go down by longer path with imposing electromagnetic force, resulting inlonger period of the counter-clockwise flow Swirl flow induces jet wobbling showing high jet flow angle fluctuations (vertical and

horizontal angle) in the mold. Both angle fluctuations with EMBr are decreased. EMBr decreases jet wobbling, reducing flow variations produced by slide-gate, including

variations in thickness direction in both jet & top surface, and along NF (in casting direction) Clockwise swirl induces high momentum jet flow, resulting in high surface velocity after

lag time for the jet flow to move toward to surface. On the other hand, counter clockwiseswirl produces lower surface velocity Transient gas distribution changes are induced by jet flow wobbling. With higher gas flow rate, bubbles in the mold are larger and most bubbles float to the

surface near the SEN (because the flow cannot carry bigger bubbles as easily), so less are found near the NF With small gas flow rate, bubbles are carried throughout larger mold region; (because they

are small), causing more chance to touch the NF Most bubbles found in upper recirculation region with and without EMBr With EMBr, more argon bubbles float up to the surface near the SEN wall. In the region

600~1200 mm from the mold top, many bubbles have longer residence time near NF. Thisphenomena may induces more chances for small bubbles to be entrapped by solidifyingsteel shell (13.5~19.1 mm below slab surface).


Acknowledgments

• Continuous Casting Consortium Members(ABB, ArcelorMittal, Baosteel, MagnesitaRefractories, Nippon Steel and Sumitomo Metal Corp., Nucor Steel, Postech/ Posco, Severstal, SSAB, Tata Steel, ANSYS/ Fluent)

• POSCO (Grant No. 4.0004977.01)• Yong-Jin Kim, POSCO for help with the

plant measurements

Documents

Transient Two-phase Flow in a Slide-gate Nozzle and Mold ...ccc.illinois.edu/s/2014_Presentations/03_Cho-SM_Two_Phase... · CCC Annual Report UIUC, August 20, 2014 Transient Two-phase