Transcript Flow control by magnetic fields

Flow Control
by Tailored Magnetic Fields
Context, Basic Ideas, Some Examples
Sino-German Workshop
on Electromagnetic Processing of Materials (EPM)
Shanghai University, Oct. 11-13, 2004
G. Gerbeth
Forschungszentrum Rossendorf (FZR), Dresden, Germany
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
Introduction: Sino-German Workshop on EPM
Magnetic Fields:
Contactless influence on Processes and Materials
Attractive R&D topic for the future
Powerful research programs in China and Germany:
 Cooperation between Chinese and German teams
(serious basis exists already)
 Exchange of students, Ph.D.’s, postdoc’s
 Joint R&D projects, joint industrial projects (?)
Support by Sino-German Center for Research Promotion
(founded by NSFC and DFG)
is gratefully acknowledged
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
Introduction: MHD in Dresden (Germany)
Basic
-
and applied studies on Magnetohydrodynamics (MHD):
20 years tradition at FZR
10 years tradition at Dresden University (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
“Electromagnetic flow control in metallurgy, crystal
growth and electrochemistry”
supported by DFG
supposed to last 11 years with ~ 1.7 Mio €/a
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
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 :
- nice tool to play with the flow
- can be arranged as needed
- contactless action, perfectly controllable
- several applications, industrial requests
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
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
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
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
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
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
225
depth [mm]
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
MULTIMAG
Experimental platform for combined AC and DC magnetic fields
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
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
 Dr. Eckert
4) Melt extraction of metallic fibers
5) Seawater flows
6) Electromagnetic levitation
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
 Dr. Priede
Forschungszentrum
Rossendorf
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
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
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Float-zone crystal growth
Goal:
modified flow field in order to
change the solid-liquid phase
boundary
Usual HF heater gives doublevortex in molten zone
Concave phase boundary is bad
for the growth of single crystals
of intermetallic compounds
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
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Float-zone crystal growth
Solution: secondary coil with phase shift acting as a pump
Realization at
IFW Dresden
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Parameters to adjust:
Current amplitude and frequency,
vertical distance between coils,
C1, R1
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Float-zone crystal growth
The principle action of such a two-phase stirrer
Model experiments demonstration
Single coil
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
double coil
upwards pumping
double coil
downwards pumping
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Float-zone crystal growth
Numerical simulations: electromagnetic fields, flow, temperature field
Example: Variation of the vertical distance of the coils
h = 1 mm
h = 3 mm
h = 5 mm
Optimum: distance  crystal radius
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
Float-zone crystal growth
Growth of NiSi5
Pumping action of the double inductor:
downwards
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
upwards
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Float-zone crystal growth
Standard float-zone
with double inductor
Ni95Si5
HoNi2B2C
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Fe87.5Si12.5
YNi2B2C
Forschungszentrum
Rossendorf
Melt extraction of metallic fibres
Extraction of steel fibers
in an open industrial facility
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
Melt extraction of metallic fibres
Principle of the process
• rapid quenching
• almost all materials
(intermetallics, too)
• Diameter > 100 mikron
• Too broad distribution of fibre
diameters
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
Melt extraction of metallic fibers
Magnetic stabilization of:
Model experiment
with SnPb
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
+
the free surface (global DC field)
the meniscus oscillations
(ferromagnetic edge)
Results: red – no magnet
green – with magnetic control
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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
Essential tools:
 numerical simulations
 new class of velocity measuring techniques for
liquid metals
 „cold“ model experiments
Attractive basis in China and Germany

Right time for a Sino-German Workshop
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf
Outlook for 2005

Joint 15th Riga and 6th PAMIR International
Conference on
Fundamental and Applied MHD
Riga (Latvia), June 27 – July 1, 2005
http://www.ipul.lv/pamir

German-Chinese Workshop in Dresden:
to be discussed
Sino-German Workshop on EPM
Shanghai, Oct. 11-12, 2004
Forschungszentrum
Rossendorf