CFD Modelling of the Flow Inside an LC Refiner
Transcript of CFD Modelling of the Flow Inside an LC Refiner
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CFD Modelling of the Flow Inside an LC Refiner
Dariusz Asendrych, Grzegorz KondoraCzęstochowa Univ. of Technology, Poland
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 1
A joint meeting
COST Action FP1005Fibre suspension flow modelling - a key for innovation
& competitiveness in the pulp & paper industry
ERCOFTAC SIG 43Fibre suspension flows
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� Introduction / Motivation
� Numerical model� Simplified / full geometry � Boundary conditions� Governing equations
� Results
Outline
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 2
� Results
� Simplified geometry - Diverging grooves� Full geometry - General flow pattern
� Summary / Perspectives
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plate disc refiner Geometry – assumptions
simplified
• neglected housing ⇒ axisymmetric outlet (instead of point outlet)
• neglected axial part of inlet, radial inlet applied
LC refiner
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 3
applied• periodicity of discs geometry - single-
segment (30 degrees of angular extent -1/12)
full
• 12 segments• housing• single-pipe outlet
typical refiner filling
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Boundary conditions
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 4
� simplified filling
� inlet - VELOCITY INLET
� outlet - PRESSURE OUTLET
�PERIODIC B.C.
�INTERFACE for sliding meshes
• geometry and mesh - GAMBIT
• mesh: 6 / 24 mln cells
• FLUENT 6.3 / 13
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• pulp suspension treated as a single-phase continuum (N-S, continuity)
• flow character assumed to be laminar (confirmed by simulation results)
• pulp modelled as either Newtonian or non-Newtonian fluid
Governing equations
UUUU 2p
t∇+∇−=∇⋅+
∂∂
ρµ
ρ
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 5
• fibre-fibre and fibre-wall interactions are neglected - main goal was to analyze the LC refining hydraulics
or
0=∇U
t∂ ρρ
( )γf=µwhere - rate of deformation tensorγ
const=μ
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softwood pulp, Cm = 4%, fibre lenght = 1400 µm, diameter = 26 µm
Newtonian fluid - constant apparent viscosity
Pulp material properties
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 6
ln(l/d) = 3,986 ln(µr) = 5,91 µr = 370
µpulp = µr · µwater = 370 · 0,001003 = 0,371 Pa·s
source:Radoslavova, Silvy, Roux, 1996,,TAPPI Paper makers Conf., Philadelphia
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reverse flows in stator disc
⇓
enhanced internalcirculation
General flow pattern
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 7
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αdiv = 0.0 deg
αdiv = 0.25 deg
Diverging grooves
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 8
αdiv = 0.50 deg
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intensification of reverse flow
Diverging grooves
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Diverging grooves
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 10
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Diverging grooves
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 11
• mass flux exiting stator grows
• power consumption decreases
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Full refiner
simulation
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 12
Full refiner
simulation
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•• housinghousing includedincluded
•• pipepipe outletoutlet
•• 12 12 segmentssegments
outlet pipe
outlet
Full refiner geometry model
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 13
collectoroutlet pipe
inlet
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Velocity magnitude
rotor
stator
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 14
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Pressure distribution
p[bar]
7
6
5
rotor
stator
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4
3
2
1
0
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Pressure distribution
5
4
3
2
p[bar]
5
r*
0
1
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1
r* [-]
5
4
3
2
1
p[bar]
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Pressure distribution
p[bar]
7
6
5
gap
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 17
4
3
2
1
0
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LC refiner flow model - Fox et al.
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 18
Fox, T.S., Brodkey, R.S. Nissan, A.H., 1979, TAPPI J., 62 (3)
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Pressure distribution - CFD vs Fox et al.
exit region
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 19
0 1 2 3 4 5 6 7 [bar]
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Mass flux at filling outlet
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 20
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Mass flux at filling outlet
full refiner single-segment refiner
2
1
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0
-1
-2
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Flow reversals in stator
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 22
full refiner
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Simplified geometry model
• qualitative agreement with experimental observation - adequate numerical model
• divergent grooves:
� modified pressure distribution and enhanced flow reversals
� no energy penalty - improved flow quality
Summary / Perspectives
Full geometry model
• circulation / exit regions - analogy to Fox et al.
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 23
• circulation / exit regions - analogy to Fox et al.
• existence of the backflows in the stator
• mass flow rate distributions stongly non-uniform and rotor position dependent
General
• no fibres included...
• CFD can really help - useful tool in process optimisation
• time consuming simulations
• ongoing simulations / data processing for varying conditions
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Thank You for Your Attention
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 24