New possibilities for velocity measurements in metallic melts
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New possibilities for velocity measurements 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: [email protected]

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New possibilities for velocity measurements 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: [email protected]

Sino-German Workshop

on Electromagnetic Processing of Materials

Oct. 11-13, Shanghai, China


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Why do we need flow measurements in metallic melts ? melts

Knowledge about the flow field and the transport

properties of the flow

Optimisation of products, technologies and facilities

  • better understanding of the process

  • validation of CFD models

  • on-line control and monitoring


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Current situation melts

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

Reasons

  • properties of the fluid (opaqueness, heat conductivity,..)

  • high temperatures

  • chemical reactivity

  • interfacial effects

  • external electromagnetic fields


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Goals melts

  • 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 interest melts

  • flow rate

  • local velocity

  • fluctuations, turbulence level

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


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List of measuring techniques melts

  • 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


  • Ultrasound doppler velocimetry udv l.jpg
    Ultrasound Doppler Velocimetry (UDV) melts

    • Takeda (1987, 1991)

    • Commercial instrument

    • standard transducers

      (Tmax = 150°C)

    • Measurement of instantaneous velocity profiles


    Udv in liquid metals problems l.jpg
    UDV in liquid metals – problems melts

    • High temperature

    • Acoustic coupling

    • Transmission of ultrasonic energy through

      interfaces (channel walls)

    • Wetting conditions

    • Availability of reflecting particles



    Concept of an integrated probe ii l.jpg
    Concept of an integrated probe II melts

    • Collaboration with the University Nishni-Novgorod (Russia)

    • Piezoelectrictransducer 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 – Flow driven by RMF melts

    Streamfunction

    Vertical velocity


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    UDV – Flow driven by TMF melts

    Vertical velocity

    Streamfunction



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    UDV in CuSn/Al – Experimental Set-up melts

    • 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°


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    UDV in CuSn/Al – Results melts

    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


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    Contactless Inductive Flow Tomography (CIFT) melts

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

      B=B0+b,b~Rm B0 (Rm=µLv)

      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)


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    CIFT - Basics melts

    • 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 experiment l.jpg
    CIFT - Experiment melts

    • 48 Hall sensors

      (KSY44-Infineon, resolution 1 T)

    • Mechanical stirrer (2000rpm)

      max. velocity ~ 1 m/s

    • Cylinder filled with InGaSn

      (D = 180 mm , H = 180 mm)

    • Magnetic field: two pairs of Helmholtz coils 10mT


    Cift experiment20 l.jpg
    CIFT - Experiment melts

    Lid with stirrer and motor

    Vessel, electronic equipment


    Cift results l.jpg
    CIFT - Results melts

    Induced magnetic field

    for transverse primary

    field

    Induced magnetic field

    for axial primary field

    Reconstructed velocity field



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    Conclusions melts

    • 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)


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