flow control by tailored magnetic fields (flowcomag)

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


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


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


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


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


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]


Experimental platform for combined AC and DC magnetic fields

MULTIMAG


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


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


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


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


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


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


Electromagnetic levitation

Principle Pronounced rotations and oscillations

Goal: Stabilization of the probe

Solution: Superimposed DC fieldno strong field needed, but careful spatial design


Electromagnetic levitation

DC-current added to the levitating coil

DC-field provided by permanent magnets


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

flow control by tailored magnetic fields (flowcomag)

Documents