magnetohydrodynamic flow in the helium- cooled lead ... · liquid metal magnetohydrodynamics (mhd)...

KIT – University of the State of Baden-Wuerttemberg and

National Research Center of the Helmholtz Association

L. Bühler, S. Horanyi, C. Mistrangelo

www.kit.edu

Magnetohydrodynamic flow in the helium-cooled lead-lithium test blanket for ITER.

Mock-up experiments, comparison with numerical simulations and further requirements on the way to ITER

International Workshop on Liquid Metal Breeder Blankets

Madrid, September 23-24, 2010

Helium cooled lead lithium blanket

Mock-up experiments

Numerical simulations

Summary & conclusions


International Workshop on Liquid Metal Breeder Blanket, Sept. 23-24, 2010, Madrid

International Thermonuclear Experimental Reactor

Test blanket

module

(TBM)

Blanket

Radiation shielding

Breeding of tritium6Li + n He + T + energy

Cooling of the first wall

Conversion of nuclear power

Heat removal

Requirements can be

accomplished with

Li-containing liquids as

breeder and coolant

Liquid metal flows in fusion blankets

Magnetic confinement of plasma

Liquid metal magnetohydrodynamics (MHD)



el.magn. force

viscous force

el.magn. force

inertia force

inertia force

viscous force

Bjvvvv

2

2

11

Hap

tN

Bvj

NHaRe /2

Conservation of

Momentum

Mass & Charge

Ohm‘s law

0

2

u

LBN

222 BL

Ha

0,0 jv

Magnetohydrodynamic equations

Lorentz force

Induced electric field

Dimensionless groups

Interaction parameter

Hartmann number

Reynolds number

N ≈ 105

Ha ≈ 104

Fusion (ITER)



HCLL

Helium Cooled Lead Lithium Blanket



HCLL is a Separately-cooled blanket

Liquid metal is used only as breeder

Heat is removed by helium

HCLL blanket features

Modular concept

Stiffening plates form a grid of

rectangular cells breeder units (BU)

He inlet pipe

and manifold

216 mm stiffening plates

(grid)

first wall (FW)

breeder units (BU)

tor

pol

rad




PbLi

first wall

(FW)

He inlet pipe

and manifold

back plate

(BP)

PbLi inlet

gap

cooling plates

(CP)

B

tor

pol

rad

Blanket MHD issues

Gap at BP Change of cross-section

Expansion along B lines

Rectangular High aspect ratio

ducts Leak of currents




PbLi

first wall

(FW)

He inlet pipe

and manifold

back plate

(BP)

PbLi inlet

gap

cooling plates

(CP)stiffening

plates (SP)B

tor

pol

rad


Blanket MHD issues





Gap at FW Inertia effects



PbLi

first wall

(FW)

He inlet pipe

and manifold

PbLi inlet

gap

cooling plates

(CP)

B

back plate

(BP)

tor

pol

rad stiffening

plates (SP)

Blanket MHD issues









tor

pol

rad

first wall

(FW)

He inlet pipe

and manifold

PbLi inlet pipe

cooling plates

(CP)stiffening

plates (SP)

back plate

(BP)

B

Blanket MHD issues






Manifolds High velocity

Long path

Circular pipes




tor

pol

rad

first wall

(FW)

He inlet pipe

and manifold

PbLi inlet pipe

cooling plates

(CP)stiffening

plates (SP)

back plate

(BP)

B

Flow distribution

(corrosion, tritium permeation)

Pressure drop

Blanket MHD issues






Manifolds High velocity

Long path

Circular pipes

Electric flow coupling




MHD model experiments for

ITER test blanket module

HCLL mock-up experiments



1

3

4

2

1

3

4

2

Back plate

Manifolds

First wall

Cooling plates

Stiffening plates

pol (y)

rad (x)

tor (z) B

NaK

Flow scheme

Objectives

Measurements of pressure

and electric potential

Comparison with theory

Scaling laws for pressure


Mock-up scaled 1:2 compared to original TBM (4 breeder units)

Model fluid: sodium potassium alloy NaK = 2.88 106 1/m



rad (x)

tor,B

pol (y)

L (tor) [mm] 45

a (pol) [mm] 409

b (rad) [mm] 173

B max [T] 2.1

Q [m3/h] 0 25

0.015 0.026

Ha 0 5500

N 10 105

2L

a

Manufactured mock-up

b

Experiment features

L

tc ww

Mock-up scaled 1:2 compared to original TBM (4 breeder units)

Model fluid: sodium potassium alloy NaK = 2.88 106 1/m




Pressure measurements

Magnet

Manifolds

Pressure pipes

Exit pipe

Inlet pipex, rad

z, tor

y, pol Hartmann

wall

Pressure taps



A

C

lB

Pressure taps

BU1

● Selection of characteristic flow paths

● Measurement of pressure differences

BU2

Pressure distribution in the mock-up

p0 = u0 B2L

BU3

BU4

First Wall

Manifolds

Pressure distribution

Inlet pipe and manifold

BU1-BU2

BU3-BU4

Outlet manifold

Ha = 500



A

C

lB

BU1

Pressure taps



BU3


p0 = u0 B2L

First Wall

Manifolds

D E


BU1

Outlet manifold

BU3-BU4

Ha = 500


BU4

BU2



A

C

lB

BU1

Pressure taps



BU3


p0 = u0 B2L

First Wall

Manifolds

D E

GF


BU1-BU2

Outlet manifold

BU3-BU4

Ha = 500


BU4

BU2



A

C

lB

BU1

Pressure taps




p0 = u0 B2L

First Wall

Manifolds

D E

GF


BU1-BU2

Outlet manifold

BU3-BU4

Ha = 500


BU2

L M

NO

BU4

BU3



A

C

lB

BU1

Pressure taps

H

I



L M

NO

D E

GF

BU3

BU4

BU2


p0 = u0 B2L

First Wall

Manifolds


● Inlet manifold (B-C) Outlet manifold (H-I)

● First wall (E-F/M-N)


BU1-BU2

Outlet manifold

BU3-BU4

Ha = 500



A

C

lB

BU1

Pressure taps

H

I



L M

NO

D E

GF

BU3

BU4

BU2


p0 = u0 B2L

First Wall

Manifolds



BU1-BU2

Outlet manifold

BU3-BU4

Ha = 500





A

C

lB

BU1

Pressure taps

H

I



L M

NO

D E

GF

BU3

BU4

BU2


p0 = u0 B2L

First Wall

Manifolds





BU1-BU2

Outlet manifold

BU3-BU4

Ha = 500

pM1pFW

pBPpFW

pM1pM2

p

pBP



A

C

lB

BU1

Pressure taps

● Main pressure drop in manifolds

● All p contributions increase linearly with N -1

● For N -1 0 inertia effects reduce

● Strong inertia effects are present at the FW

H

I

Contributions to the total pressure drop

● Identify critical elements / locations

● Defining scaling laws

L M

NO

E

GF

BU3

BU4

BU2

First Wall

Manifolds

21Re/HaN

pM1pM2

p

pFW

pBP

Ha = 500

D



Ha = 5000● Selection of characteristic flow paths



p0 = u0 B2L


For ITER conditions p is inertialess

A

C

lB

BU1

Pressure taps

H

I

L M

NO

D E

GF

BU3

BU4

BU2

First Wall

Manifolds


BU1-BU2

Outlet manifold

BU3-BU4



Contributions to the total pressure drop

● Identify critical elements / locations

● Defining scaling laws

21Re/HaN

Ha = 5000

For ITER conditions p is inertialess

pM1pM2

p

pFW

pBP

A

C

lB

BU1

Pressure taps

H

I

L M

NO

D E

GF

BU3

BU4

BU2

First Wall

Manifolds



Total pressure drop: correlation

Non-dimensional pressure drop scales as p = p0 + A*N -1 + B*N -1/3

p0

-1 -1/3

2Re/Ha



Electric potential measurements

Potential distribution on mock-up surface; asymptotic theory

According to Ohm’s law, Bvj

with j << 1 x

vy

u

Potential serves for code validation,

physical interpretation as

hydrodynamic streamfunction

Potential sensors

Pressure taps

v Color indicates electric potential on

the walls

circular access tube

poloidal manifold

breeder units

pressure taps

outlet pipe

inlet pipe

manifold

B

2

43

12L

pressure taps

outlet pipe

inlet pipe

manifold

B

2

43

12L

pressure taps

outlet pipe

inlet pipe

manifold

B

2

43

12L

pressure taps

outlet pipe

inlet pipe

manifoldB

2

43

12L



Electric potential measurements

MHD mock-up with instrumentation for potential measurements

According to Ohm’s law, Bvj

with j << 1 x

vy

u

Potential serves for code validation,

physical interpretation as

hydrodynamic streamfunction

Potential sensors

Pressure taps



Measured surface potential

Calculated contours of potential

on the MHD mock-up surface

(cooling plates omitted)

Hartmann wall

Manifolds

rad

tor,B

pol

rad

pol

Back plate

First wallConnecting

gap

A

A

tor,B Stiffening plate (SP)

Stiffening plate (SP)

A

A

Contours of measured electric potential on the MHD mock-up surface

Measured electric potential

for Ha = 3000, Re = 1000



Potential measurements

indicate flow distribution

Lines of constant color are streamlines

Fully developed flow conditions along A-A

Hartmann wall

Manifolds

rad

tor,B

pol

rad

pol

Back plate


gap

A

A

Measured electric potential

for Ha = 3000, Re = 1000

Assumption for numerical

calculations

tor,B

Measured surface potential



A

A




Experiments and numerical results

tor

rad pol

SP SP SP

Full electrical coupling

• 4 breeder units

• 24 sub-channels

• 96 boundary layersrad

pol


gap


A-A

B

A

A

CP





Contours of calculated electric

potential on the MHD mock-up

middle plane (AA).tor

rad pol


• 4 breeder units

• 24 sub-channels

• 96 boundary layersrad

pol


gap


A-A

B

A

A

SP SP SP





Comparison of potential profiles along the Hartmann wall

tor

rad pol

Contours of calculated electric

potential on the MHD mock-up

middle plane (AA).


• 4 breeder units

• 24 sub-channels

• 96 boundary layers

A-A

B

SP SP SP

pol

Comparison

Validity of FDF assumption (weak Re - dependence)

Good quality of measuring technique for potential




Comparison

Validity of FDF assumption (weak Re - dependence)

Good quality of measuring technique for potentialComparison of potential profiles along the Hartmann wall

Contours of calculated radial

velocity on the MHD mock-up

middle plane (AA).


• 4 breeder units

• 24 sub-channels


tor

rad pol

u

B

Hartmann wallSP SP SP

pol




Velocity

Uniform velocities in central sub-channels of BUs

Weak effect of cooling plates

Higher velocity at the stiffening plates


• 4 breeder units

• 24 sub-channels


Contours of calculated radial

velocity on the MHD mock-up

middle plane (AA).tor

rad pol

u

B

SP SP SP

2

1

0

-1

-2

u




tor

rad pol

j

Calculated current streamlines

on the MHD mock-up

middle plane (AA).

B

SP SP SP

Current density

Currents cross cooling plates:

Strong electric coupling

through cooling plates

(uniform flow partition)

Current density

In SPs currents flow tangentially:

Weak electric coupling

between BUs

2

1

0

-1

-2

u

2

1

0

-1

-2



Conclusions

HCLL blanket and MHD issues:

Complex 3D MHD flows through geometries with different-cross sections,

large aspect-ratio rectangular ducts, long manifolds, electric flow coupling

Influence on pressure and flow distribution

Methods for MHD flow analysis:

Asymptotic method, numerical simulations, experiments

Application to MHD flow in fusion blankets

Experiments in a mock-up of a HCLL blanket:

Measurements of pressure differences and surface electric potential

for Ha = 05500, N = 10105



Conclusions

Pressure measurements:

- Significant pressure drop along feeding/draining pipes and manifolds

- Pressure in breeder units is practically constant

- Inertia effects can occur at manifolds and first wall gap

Electric potential measurements:

- Overview on flow distribution

- Data for code validation

Numerical results:

- Good comparison with measured distribution in the central cross-section

- Yield insight for better understanding

Weak electric coupling between breeder units

Strong coupling in sub-channels (uniform flow partition)



Further requirements on the way to ITER

Numerical simulation tools required for prediction of MHD flows in ITER

ITER relevant parameters not yet reached, but expected for the next few years

Validation is mandatory

Future experiments should

support ITER TBM design activities (e.g. modified geometry of gaps at the first

wall, influence of helium channels on MHD flow) and operating strategies

(required flow rates and pressure heads, emergency draining time etc)

assess the feasibility of the foreseen measuring techniques in terms of

functionality of single sensors and global integration of instrumentation in the

TBM

study phenomena that cannot be measured in ITER

pay attention to fundamental MHD effects as support for ITER data

understanding




tor

rad pol

j

Calculated current streamlines

on the MHD mock-up

middle plane (AA).

B

SP SP SP

Current density

In cooling plates currents enter

perpendicularly:

Strong electric coupling

through cooling plates

(uniform flow partition)

Current density

In SPs currents flow tangentially:

Weak electric coupling

between BUs

Hartmann wall

2

1

0

-1

-2

u

2

1

0

-1

-2

Re=217

Re=517

Re=974

Ha = 5000

magnetohydrodynamic flow in the helium- cooled lead ... · liquid metal magnetohydrodynamics (mhd)...

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