Modeling of Two-Phase Flow in RH Vacuum Degassing Vessel With the Effect of Rotating Magnetic field

Baokuan LiNortheastern University, China

Fumitaka TsukihashiThe University of Tokyo, Japan

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To promote the removal of non- metallic inclusions of molten steel.

To increase the flow rate of molten steel in RH vacuum degassing vessel.

To prolong the life of RH equipment.

Vacuum

water

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Air

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Research motivation

To concentrate the argon gas bubbles and inclusions in central zone of up-leg of RH vessel by using the centripetal force, which is produced as the result of density difference between gas bubbles or inclusions and molten steel in the swirling flow. Therefore, collisions and coalescences increase.

Swirling flow is produced by the application of rotating magnetic field.

Vacuum

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Air

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Research ideas

Gas distributor

Nozzle distribution

Rotameter

Manometer

Ultrasonic flowmeterRH degassing vessel

Impeller

Water model experiments examine the research ideas

Effect of impeller input power on gas bubbles distribution, Q=0.5 m3/h. (a) 0, (b) 20 W, (c) 25 W and (d) 35 W

(a) (c) (d)(b)

67

89

10

0 5 10

15

20

25

30

35

40

6.944×10-5m3/s

11.111×10-5m3/s

16.667×10-5m3/s

Cir

cula

tion

flo

w r

ate,

10-5

m3 /

s

Input power, W

Effect of plane blade impeller on circulation flow rate of RH vessel

Mathematical model

• To develop a mathematical model for the two-phase turbulent flow in the RH vessel with the rotating magnetic field in the up-leg.

• To analyze the gas bubbles driven circulation flow characteristics in RH degassing vessel with the swirling flow.

( )

( )

V

V V V p F g

02

e

FormulationSpitzer et al. [1]

k turbulence model

= g ( )1 Liq

rr

vBF

rr

vBF mr

)(2

1

)(8

1

20

32220

cossin

sincos

FFF

FFF

ry

rx

)()()()()()(zzyyxxz

wwy

vvvx

uuu eeeslipslipinslipin

)(2gLr rF

Centripetal force and horizontal slip velocity caused by rotating magnetic field

Up-leg

Nozzle

zy

x

Gas jet zone1 2

9

)(222 rR

V gLr

sin,cos rsliprslip Vv Vu

Penetrating velocity and slip velocity

])(lnexp[)lnexp()exp( 2210 ggslip dadaaw

Vertical slip velocity

Horizontal penetrating velocity:

Qg : total argon gas flow rate, n :nozzle number A : cross nozzle inlet area

α : gas volume fraction (at inlet α0)

nA

Qvu g

inin

Boundary conditions and solution method

Flow field

Gas volume fraction

Blackage technique

Volume factor ffor fluid

for solidArea factor f

for fluid

for solid

Free surface and symmetrical sections:Vn

Near wall The wall law function is used to calculate k and

V A

in

e

1

0

1

0

0 0

,

,,

,

,

,

: , ,

Inlet is calculated by Thermodynamic equation of gas

Other sections

:

:

n

in

0

Vacuum

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Schematic of physical model of RH degassing vessel with the rotating magnetic field.

Calculated flow velocities at horizontal sections of RH degassing vessels, (a) up-leg, (b) bottom of vacuum chamber, (c) middle of vacuum chamber, and (d) surface of vacuum chamber.

(a)

(d)(c)

(b)

(a)

(b)(c)(d)

0

0.1

0.2

0.3

0.4

0.5

0.6

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.1 0.2 0.3 0.4 0.50

0.1

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0.5

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0.7

00.1 0.2 0.3 0.4 0.5

Computed gas volume fraction at main sections of RH degassing vessels, (a) no swirling flow (b) with swirling flow.

(a) (b)

0.1

0.2

0.3

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0.5

0.6

0.7

0.8

-0.04 0 0.04

Ver

tica

l vel

ocit

y, m

/s

Diameter of up-leg, m

No swirling flowWith swirling flow0.1

0.2

0.3

0.4

0.5

-0.04 0 0.04

Gas

vol

ume

frac

tion

Diameter of up-leg, m

No swirling flowWith swirling flow

Gas volume distribution of RH degassing vessel

Velocity distribution of RH degassing vessel

CONCLUSIONS

Water model experiments verified that the gas bubbles maybe moved toward the central zone of up-leg of RH vessel in the swirling flow.

The numerical results showed that a swirling flow may be produced and extended into the vacuum chamber in case that rotating magnetic field is applied in up-leg. The maximum of gas volume fraction moves toward the center zone of the up-leg.

The larger circulation flow rate can be obtained in RH degassing vessel with the effect of swirling flow.

Thank you!