Transcript FLOWCOMAG

Flow Control by Tailored Magnetic Fields
(FLOWCOMAG)
April 1-2, 2004
Jointly organized by:
In frame of:
Forschungszentrum Rossendorf (FZR)
TU Dresden
Collaborative Research Centre SFB 609
(supported by DFG)
Some introductory remarks
G. Gerbeth
Context, Basic Ideas, Some Examples
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FLOWCOMAG
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Context
Basic
-
and applied studies on Magnetohydrodynamics (MHD):
20 years tradition at FZR
10 years tradition at TU Dresden (TUD)
Local network in Dresden (IFW, Uni Freiberg, FhG, MPI)
Traditional cooperation and Twinning Agreement with
Institute of Physics Riga (Latvia)
Since 2002:
Collaborative Research Centre SFB 609 at TUD
supported by DFG
supposed to last 11 years with ~ 1.3 Mio €/a
Forschungszentrum
Rossendorf
FLOWCOMAG
SFB 609
Context
Electrically conducting fluids:
liquid metals, semiconductor melts,
electrolytes
 
 
MHD = NSE + Lorentz Force f L ( r , t )  j  B
  

where j   ( E  v  B)

Volume force f L :
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- nice tool to play with the flow
- can be arranged as needed
- contactless action, perfectly controllable
- several applications, industrial requests
FLOWCOMAG
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Basic Idea: Tailored magnetic field systems
Up to now: Forward Strategy –
Known magnetic field actions:
DC fields:
AC-fields, low frequency:
AC-fields, high frequency:
What are the changes if some
magnetic field is applied?
Flow damping
stirring and pumping
Heating and melting, levitation
 MHD Catalogue
Necessary: Transition to inverse approach
1) Which flow is desirable?
2) Which Lorentz force can provide this?
3) How to make this Lorentz force?
Note: flow field often not the goal, just some intermediate agent
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FLOWCOMAG
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Basic Idea: Tailored magnetic field systems
Why now?
1) Strong request from applied side for smart solutions with low effort
(Tesla cost money!)
2) powerful community for optimization, control theory, inverse strategies
3) new computer capabilities
4) MHD catalogue is well filled
5) new level of velocity measuring techniques for liquid metal MHD flows
(liquid metal model experiments up to T  400°C)
6) new level of experimental tools for superposition of AC and DC magnetic
fields
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Velocity measuring technique (example)
400
350
velocity [mm/s]
PbBi bubbly flow at T  270°C
bubble
300
250
200
150
liquid velocity
100
50
0
75
100
125
150
175
200
depth [mm]
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FLOWCOMAG
SFB 609
225
MULTIMAG
Experimental platform for combined AC and DC magnetic fields
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FLOWCOMAG
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Examples for partly going the inverse way
1) Industrial Cz-growth of single Si crystals
2) Float-zone crystal growth
3) Industrial Al investment casting
4) Melt extraction of metallic fibers
5) Seawater flows
6) Electromagnetic levitation
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FLOWCOMAG
SFB 609
Industrial Cz-growth of single Si crystals
Goals:
- larger diameters (200  300)
- stable growth process
- homogeneous oxygen
distribution
Solution:
AC fields for flow driving,
DC fields for reduction of fluctuations
Combined fields installed at Wacker Siltronic
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Float-zone crystal growth
Solution: secondary coil with phase
shift acting as a pump
Usual HF heater gives
double-vortex in molten zone
Concave phase boundary is
bad
Goal: modified flow field in
order to change the solidliquid phase boundary
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Realization at
IFW Dresden
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Float-zone crystal growth
The principle action of such a two-phase stirrer
Model experiments demonstration
Single coil
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double coil
upwards pumping
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double coil
downwards pumping
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Industrial Al investment casting
Magnetic control
of the filling
process
Material: Al-Si-alloys
Problem: high velocities lead to entrapment
of oxides and gas bubbles
Solution: Magnetic brake by
a) DC field
 done
b) AC pump
 in progress
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FLOWCOMAG
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Melt extraction of metallic fibers
Magnetic stabilization of:
Real process:
steel fibers
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+
the free surface (global DC field)
the meniscus oscillations
(ferromagnetic edge)
Model experiment
with SnPb
FLOWCOMAG
Results: red – no magnet
green – with magnetic control
SFB 609
Electromagnetic levitation
Principle
Pronounced rotations and oscillations
Goal:
Stabilization of the probe
Solution:
Superimposed DC field
no strong field needed, but careful spatial design
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FLOWCOMAG
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Electromagnetic levitation
DC-current added to
the levitating coil
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DC-field provided by
permanent magnets
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Summary

Flow control by magnetic fields: nice tool to
modify velocity fields

inverse approach: challenging task

Several industrial requests, short bridge to
applications

Closer relation between communities of
optimization/control and MHD very attractive

Right time for FLOWCOMAG
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FLOWCOMAG
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