sino-german-workshop, oct. 11-13 2004, shanghai, china 1 new possibilities for velocity measurements...

1Sino-German-Workshop, Oct. 11-13 2004, Shanghai, China

New possibilities for velocity New possibilities for velocity measurements in metallic meltsmeasurements in metallic melts

S. Eckert, G. Gerbeth, F. Stefani

Department Magnetohydrodynamics, Forschungszentrum Rossendorf P.O. Box 510119, D-01314 Dresden, Germany, http://www.fz-rossendorf.de/FWS/FWSH

E-mail: s.eckert@fz-rossendorf.de

Sino-German Workshopon Electromagnetic Processing of Materials

Oct. 11-13, Shanghai, China

2Sino-German-Workshop, Oct. 11-13 2004, Shanghai, China

Knowledge about the flow field and the transport

properties of the flow

Why do we need flow measurements in metallic melts ?Why do we need flow measurements in metallic melts ?

Optimisation of products, technologies and facilities

• better understanding of the process• validation of CFD models• on-line control and monitoring

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Commercial measuring techniques Commercial measuring techniques for liquid metal flows are almost for liquid metal flows are almost not available !not available !

Reasons– properties of the fluid (opaqueness, heat conductivity,..)

– high temperatures

– chemical reactivity

– interfacial effects

– external electromagnetic fields

Current situationCurrent situation

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GoalsGoals

• to develop measuring techniques for liquid metal flows at moderate temperatures

model experiments (T 300°C)

• to extend the range of application towards higher temperatures

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Data of interestData of interest

• flow rate

• local velocity

• fluctuations, turbulence level

• flow pattern (velocity profiles, 3D-structure)

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• Local probes (invasive)

• Electric Potential Probe (EPP, Vives Probe)

• Mechano-Optical Probe (MOP)

• Ultrasonic methods (non-invasive, but need contact)

• Ultrasound Doppler Velocimetry (UDV)

• Inductive methods (contact-less)

• Inductive Flowmeter (IFM)

• Contactless Inductive Flow Tomography (CIFT)

• X-ray radioscopy

• Local probes (invasive)

• Electric Potential Probe (EPP, Vives Probe)

• Mechano-Optical Probe (MOP)

• Ultrasonic methods (non-invasive, but need contact)

• Ultrasound Doppler Velocimetry (UDV)

• Inductive methods (contact-less)

• Inductive Flowmeter (IFM)

• Contactless Inductive Flow Tomography (CIFT)

• X-ray radioscopy

List of measuring techniquesList of measuring techniques

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Ultrasound Doppler Velocimetry (UDV)Ultrasound Doppler Velocimetry (UDV)

• Takeda (1987, 1991)

• Commercial instrument

• standard transducers

(Tmax = 150°C)

• Measurement of instantaneous velocity profiles

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UDV in liquid metals – problemsUDV in liquid metals – problems

• High temperature

• Acoustic coupling

• Transmission of ultrasonic energy through

interfaces (channel walls)

• Wetting conditions

• Availability of reflecting particles

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Concept of an integrated probe IConcept of an integrated probe I

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Concept of an integrated probe IIConcept of an integrated probe II

• Collaboration with the University Nishni-Novgorod (Russia)• Piezoelectric transducer coupled on an acoustic wave guide

made of stainless steel• Stainless steel foil (0.1 mm) wrapped axially around a capillary

tube: length 200 mm, outer diameter 7.5 mm

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UDV – Flows driven by RMF/TMFUDV – Flows driven by RMF/TMF

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Vertical velocity Streamfunction

UDV – Flow driven by RMFUDV – Flow driven by RMF

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Vertical velocity Streamfunction

UDV – Flow driven by TMFUDV – Flow driven by TMF

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UDV – Flow driven by RMF/TMFUDV – Flow driven by RMF/TMF

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• Rectangular alumina crucible (130 80 mm2)

• melt depth 40 mm

• inductive heater

• melt temperature:

620°C (CuSn), 750°C (Al)

• installation of the integrated sensor at the free surface of the melt

• Doppler angle 35°

UDV in CuSn/Al – Experimental Set-upUDV in CuSn/Al – Experimental Set-up

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UDV in CuSn/Al – ResultsUDV in CuSn/Al – Results

Profiles obtained at two positions: • different signs• similarity of shape and

amplitude

Velocity signal obtained in liquid

aluminium by up-and-down moving

of the sensor by hand

10.0 12.5 15.0 17.5 20.0 22.5 25.0-60

-40

-20

0

20

40

60

velo

city

[mm

/s]

time [s]

70 75 80 85 90 95 100-200

-100

0

100

200

position 1 position 2

velo

city

[m

m/s

]

measuring depth [mm]

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• An existing flow field will modify an applied magnetic field:

B=B0+b, b~Rm B0 (Rm=µLv)

e.g. the magnetic field measured outside the melt contains information about the flow field

• Rm ~ 10-3 b ~ O(T)Example: crystal growth configuration

(Czochralski method)

Contactless Inductive Flow Tomography (CIFT)

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SV sr

srSdsdV

rr

rBrurotrB 3

00

'

'')'(

4'

)'()'(

4)(

SV ss

ssSdsdV

rs

rBrudivs 3

'

'')'(

2

1

'

)'()'(

2

1)(

• Bio-Savart‘s law

• inverse method to reconstruct the velocity field • additional requirements:

– mass conservation (div u = 0)– Tichonov regularization (keeps the mean quadratic

curvature of the velocity field finite)

CIFT - Basics

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CIFT - ExperimentCIFT - Experiment

• Cylinder filled with InGaSn

(D = 180 mm , H = 180 mm)

• Magnetic field: two pairs of Helmholtz coils 10mT

• 48 Hall sensors

(KSY44-Infineon, resolution 1 T)

• Mechanical stirrer (2000rpm)

max. velocity ~ 1 m/s

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Lid with stirrer and motor

Vessel, electronic equipment

CIFT - ExperimentCIFT - Experiment

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CIFT - ResultsCIFT - Results

Induced magnetic fieldfor transverse primaryfield

Induced magnetic fieldfor axial primary field

Reconstructed velocity field

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CIFT - ResultsCIFT - Results

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ConclusionsConclusions

• Several measuring techniques exist to determine the velocity field in metallic melts

• Successful investigations are under progress to extend the application range towards higher temperatures

• Promising new developments:– Ultrasound Doppler Velocimetry (UDV)– Contactless Inductive Flow Tomography (CIFT)