Sino-German-Workshop, Oct , Shanghai, China 1 New possibilities for velocity measurements in metallic melts S. Eckert, G. Gerbeth, F. Stefani Department Magnetohydrodynamics, Forschungszentrum Rossendorf P.O. Box , D Dresden, Germany, Sino-German Workshop on Electromagnetic Processing of Materials Oct , Shanghai, China

Sino-German-Workshop, Oct , Shanghai, China 2  Knowledge about the flow field and the transport properties of the flow 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

Sino-German-Workshop, Oct , Shanghai, China 3 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 Current situation

Sino-German-Workshop, Oct , Shanghai, China 4Goals 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

Sino-German-Workshop, Oct , Shanghai, China 5 Data of interest flow rate local velocity fluctuations, turbulence level flow pattern (velocity profiles, 3D-structure)

Sino-German-Workshop, Oct , Shanghai, China 6 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 techniques

Sino-German-Workshop, Oct , Shanghai, China 7 Ultrasound Doppler Velocimetry (UDV) Takeda (1987, 1991) Commercial instrument standard transducers (T max = 150°C) Measurement of instantaneous velocity profiles

Sino-German-Workshop, Oct , Shanghai, China 8 Pulse-echo method: information about the position  time of flight measurement information about velocity  Doppler relation (c - sound velocity, f D - Doppler frequency, f 0 - ultrasound frequency) UDV – Measuring principle

Sino-German-Workshop, Oct , Shanghai, China 9 UDV in liquid metals – problems High temperature Acoustic coupling Transmission of ultrasonic energy through interfaces (channel walls) Wetting conditions Availability of reflecting particles

Sino-German-Workshop, Oct , Shanghai, China 10 Concept of an integrated probe I

Sino-German-Workshop, Oct , Shanghai, China 11 Concept 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

Sino-German-Workshop, Oct , Shanghai, China 12 UDV in bubbly flows – PbBi Typical velocity signal of a single rising bubble Further details: see presentation of Ch. Zhang

Sino-German-Workshop, Oct , Shanghai, China 13 (a) (b) PbBi, 250 °C, single orifice: d o = 0.5 mm, (a) Q g = 0.04 cm 3 /s, (b) Q g = 1.2 cm 3 /s UDV in bubbly flows – PbBi

Sino-German-Workshop, Oct , Shanghai, China 14 UDV – Flows driven by RMF/TMF

Sino-German-Workshop, Oct , Shanghai, China 15 Vertical velocity Streamfunction UDV – Flow driven by RMF

Sino-German-Workshop, Oct , Shanghai, China 16 Vertical velocity Streamfunction UDV – Flow driven by TMF

Sino-German-Workshop, Oct , Shanghai, China 17 UDV – Flow driven by RMF/TMF

Sino-German-Workshop, Oct , Shanghai, China 18 Rectangular alumina crucible (130  80 mm 2 ) 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-up

Sino-German-Workshop, Oct , Shanghai, China 19 UDV 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

Sino-German-Workshop, Oct , Shanghai, China 20 An existing flow field will modify an applied magnetic field: B=B 0 +b, b~R m B 0 (R m =µ  Lv) e.g. the magnetic field measured outside the melt contains information about the flow field Rm ~  b ~ O(  T) Example: crystal growth configuration (Czochralski method) Contactless Inductive Flow Tomography (CIFT)

Sino-German-Workshop, Oct , Shanghai, China 21 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

Sino-German-Workshop, Oct , Shanghai, China 22 CIFT - 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

Sino-German-Workshop, Oct , Shanghai, China 23 Lid with stirrer and motor Vessel, electronic equipment CIFT - Experiment

Sino-German-Workshop, Oct , Shanghai, China 24 CIFT - Results Induced magnetic field for transverse primary field Induced magnetic field for axial primary field Reconstructed velocity field

Sino-German-Workshop, Oct , Shanghai, China 25 CIFT - Results

Sino-German-Workshop, Oct , Shanghai, China 26Conclusions 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)