o-26: assembling and test of a halbach array magnet system ... · michael faraday georg simon ohm...
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Authors:
O-26: Assembling and Test of a Halbach Array MagnetSystem for Lorentz Force Velocimetry in Electrolytes
M. Werner* and B. Halbedel
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Part B3 ( Electrolytes“) of the Research Training Group „Lorentz Force Velocimetry and Eddy Current Testing“ ( funded by the DFG„ GRK-1567)
Dipl.-Ing. Michael WernerDepartment of Inorganic-Nonmetallic MaterialsMail: [email protected]: +49 3677 69 3347
Dr.-Ing. Bernd Halbedel
Mail: [email protected]: +49 3677 69 2784
Department of Inorganic-Nonmetallic Materials
LFV: Novel „contactless“ measurement method in electrolytes to providean in-line observation system for glass melts
Vision : Improvement of the process efficiency in electrolytic processes (e.g.glass casting, salt melt cooling) by measuring the flow velocities inclosed channels
Research: - Experiments on salt water under laboratory conditions with highvelocities (~ 5 m/s)
- Later adaption and optimization to a robust system for the harshboundary conditions of real glass melts at lower velocities
Magnet
Fluid Flow
ChannelPrimary magneticfield Eddy currents
Acceleratingforce
Fluid breakingforce
Michael Faraday Isaac NewtonHeinrich Friedrich Emil LenzGeorg Simon Ohm Hendrik Antoon Lorentz
Challenge: Tiny forces (some µN) on magnet systems with masses around1 kg must be detected with highest possible resolution
Task: - Finding the most effective magnet system design- Optimization of the specific geometries of this magnet system
for
- Assembling and characterization of the optimized design
highest forces within the limited mass, to increase loadstep amount on force measurement system
- High Reynolds number (salt water at 5 m/s)- Low magnetic Reynolds number- Low Hartmann number and interactionparameter
- Well defined test channel with plug profileat the inlet
FEM simulation of moving solid bodies,having the same geometry like the channelcross section is possible in a firstapproximation
Optimization can be performed in very shorttime by combination of COMSOL FEM andMATLAB Optimization Toolbox
Reference design / experimental setup:
- Inner cross section: a * b = 50 mm * 50 mm- Length: l = 1500 mm
- Conductivity of the fluid: = 4 S/m- Flow velocity: v = 5 m/s- Minimum gap between poles: > 56 mm- Geometries of magnet system (here standard
system): l, d, h optimization parameters- Magnet system mass limit: m < 1 kg
B
σ
δ
FEM
Standard system(two single magnets with samemagnetization direction):m = 950 g leads to with
l = 38.4 mm, h = 51.9 mm,
d = 31.8 mm
F = 35 µNmax
opt opt
opt
Halbach array combination(without/with triangular shaped endmagnets) m = 950 g, )F = 115 µNmax
Lorentz force can be increased by a factor of three, using Mallinsons method of one sidedfluxes in the same way Halbach did in his arrays (1980).(1973)
Next step:- Further experimental
tests on the channelto prove allsimulations, see alsoPoster P3-19
- Design of magnetsystems based onhigh temperaturesuperconductors
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80 20
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8010
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length l [mm]
height h [mm]
Fo
rce
[μ
N]
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(Nelder-Mead simplex algorithm in MATLAB)
Principle and Response surface for 950 gmagnet material (NdFeB of grade )N52
-20
0
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-40-20
020
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-150
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Length l [mm] / x-direction
Height h [mm] / z-direction
Ma
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etic f
ield
ma
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mT
]
-100
-50
0
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Halbach array system out of 5 single magnets on each side,assembled with a carbon fiber composite bracket. (950 g magnetsand 50 g CFC)Magnetic field was measured and fits perfect to the numericalpredictions.
Numerical investigation of the influence of the fluid profiles on the arisingforces by FLUENT simulation of the experimental test channel:Force decreases with fluid profile change within the channel.