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ForschungszentrumRossendorf SFB 609FLOWCOMAG
Flow Control by Tailored Magnetic Fields Flow Control by Tailored Magnetic Fields
(FLOWCOMAG)(FLOWCOMAG)
April 1-2, 2004
Jointly organized by: Forschungszentrum Rossendorf (FZR)TU Dresden
In frame of: Collaborative Research Centre SFB 609 (supported by DFG)
Some introductory remarks
G. Gerbeth
Context, Basic Ideas, Some Examples
ForschungszentrumRossendorf SFB 609FLOWCOMAG
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
Context
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Electrically conducting fluids: liquid metals, semiconductor melts, electrolytes
MHD = NSE + Lorentz Force
where
Context
BjtrfL
),(
)( BvEj
Volume force : - nice tool to play with the flow- can be arranged as needed- contactless action, perfectly controllable- several applications, industrial requests
Lf
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Up to now: Forward Strategy – What are the changes if some magnetic field is applied?
Known magnetic field actions: DC fields: Flow damping AC-fields, low frequency: stirring and pumping AC-fields, high frequency: Heating and melting, levitation
MHD Catalogue
Necessary: Transition to inverse approach1) 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
Basic Idea: Tailored magnetic field systems
ForschungszentrumRossendorf SFB 609FLOWCOMAG
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
Basic Idea: Tailored magnetic field systems
ForschungszentrumRossendorf SFB 609FLOWCOMAG
PbBi bubbly flow at T 270°C
Velocity measuring technique (example)
75 100 125 150 175 200 2250
50
100
150
200
250
300
350
400
bubble
liquid velocity
velo
city
[mm
/s]
depth [mm]
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Experimental platform for combined AC and DC magnetic fields
MULTIMAG
ForschungszentrumRossendorf SFB 609FLOWCOMAG
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
ForschungszentrumRossendorf SFB 609FLOWCOMAG
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
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Float-zone crystal growth
Usual HF heater gives double-vortex in molten zoneConcave phase boundary is
bad
Goal: modified flow field in order to change the solid-liquid phase boundary
Solution: secondary coil with phase shift acting as a pump
Realization at IFW Dresden
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Float-zone crystal growth
The principle action of such a two-phase stirrerModel experiments demonstration
Single coil double coil double coil upwards pumping downwards pumping
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Industrial Al investment casting
Problem: high velocities lead to entrapment of oxides and gas bubbles
Solution: Magnetic brake bya) DC field doneb) AC pump in progress
Magnetic control of the filling
process
Material: Al-Si-alloys
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Melt extraction of metallic fibers
Magnetic stabilization of: the free surface (global DC field) + the meniscus oscillations
(ferromagnetic edge)
Real process: Model experiment Results: red – no magnet steel fibers with SnPb green – with magnetic control
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Electromagnetic levitation
Principle Pronounced rotations and oscillations
Goal: Stabilization of the probe
Solution: Superimposed DC fieldno strong field needed, but careful spatial design
ForschungszentrumRossendorf SFB 609FLOWCOMAG
Electromagnetic levitation
DC-current added to the levitating coil
DC-field provided by permanent magnets
ForschungszentrumRossendorf SFB 609FLOWCOMAG
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