S. Men, C. Resagk, H. Brauer,

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2D Measurements of Magnetic Field near the
Interface between Two Fluids Carrying an
Electrical Current

• S. Men, C. Resagk, H. Brauer,
• M. Ziolkowski, M. Kuilekov
• Ilmenau University of Technology

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Outline

• Motivation
• Theoretical Model
• Experimental Setup
• Results and Discussion
• Summary and outlook

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Motivation
Several MHD applications in processing of
materials Aluminum reduction, steel/iron making,
glass melting, crystal growth, etc. require deep
knowledge of behaviors of the surface/interface
of electrically conducting fluids.

• the use of probes is difficult or even
  impossible (limited access and hostile
  environment).
• necessary to develop appropriate methods for
  cell diagnosis.

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Magnetic Field Tomography (MFT)
Construct a highly simplified aluminium reduction
cell to investigate a MFT system

• Build up a magnetic sensor system to detect weak
  magnetic field (nT)
• Develop optical techniques to observe interface
  displacement
• Identify the main interface shape features by
  means of MFT.

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Theoretical Model
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Experimental Setup
CCD camera
Two-fluid cell KOH GaInSn
Light sheet laser
Pneumatic shaker
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2D fluxgate sensor-FXM 205
Specifications Measuring range 100µT Output
voltage 18.5mV/µT Noise
?30pT/?Hz Bandwidth(-3dB) DC to
1.25kHz Linearity ?
0.25 Orthogonality ?1 Operating temp
-4085C Zero drift ?100nT/K Supply
voltage 5V 0.1V DC Supply current
?5mA eff Output impedance lt1k? Dimensions
sensor ?2mm?15mm
electronics 26mm
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Results and discussion
Optical measurement of interface oscillation
Mode 11 fshaker7.2-7.6Hz
Mode 21 fshaker9.3-9.6Hz
fshaker7.3Hz, Idc1.0A, A10.17mm
fshaker9.4Hz, Idc1.0A, A8.28mm
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Simulation of interface oscillation
mode 11, A10mm
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Simulation of interface oscillation
mode 21, A8.0mm
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Schematic of data acquisition and processing
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Magnetic field measurements
Signals of eight Bz and Br at fshaker7.3Hz,
z57.5mm
Peak at 3.65Hz ? Subharmonic at interface
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Contour line of mode 11 at 1.0A, fshaker7.3Hz
Forward calculation
Measurements
Bz
Bz
Br
Br
A9.5-10.5mm
A10.0mm
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Mode 21 at fshaker9.4Hz, Idc1.0A
Forward calculation
Measurement
A8.0mm
A7.5-8.5mm
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Flow chart of interface reconstruction
Interface mode ?mn, A
Extract current density
FEM3D
Biot-Savart law
Magnetid flux density In sensor positions
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Reconstructed interface
mode 21
mode 11
10
-10
CF?12
CF? 16
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Summary and outlook

1. A sensor ring consisting of eight 2D sensors is
   suitable to measure the magnetic field near the
   oscillating interface between two electrically
   conducting fluids for modes m?2, n?3.
2. Forward calculation by FEM3D based on the optical
   measurement is consistent well with the
   experimental results.
3. Evolutionary algorithm is effective for the
   magnetic field tomography to reconstruct a
   non-axisymmetric interface of a low mode.
4. Better experimental results (smaller
   reconstruction error) can be expected when more
   sensors in one ring and/or more sensor rings are
   applied.
5. A rectangular cell whose shape is similar to an
   aluminium reduction cell will be investigated a
   little later.

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Thank you for your attention!