Fibre Orientation and Related Headbox Optimization SystemsHeadbox Optimization Systems

Jari Hämäläinen

C t f C t ti l E i i d I t t d D i (CEID)Centre of Computational Engineering and Integrated Design (CEID)Lappeenranta University of Technology (LUT)Lappeenranta, Finland

Fibre OrientationFibre Orientation

− Basic fibrous structure of the paper sheet is formed at the wet end of a paper machine -headbox and forming section

− Fibre orientation (angle and anisotropy) determines the dimensional stability of the paperdetermines the dimensional stability of the paper

− Velocity gradients align fibres whereas turbulence makes orientation more random

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Fibre Orientation, its Anisotropy d CD A l P filand CD Angle Profile

− Fibre orientation distribution in each location

− The average fibre orientation angle profile in cross direction (CD) of a paper machine

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Modelling of Fibre Orientation P b bilit Di t ib ti (FOPD)Probability Distribution (FOPD)

J/W=0.9(d )(drag)

J/W 1 1J/W=1.1(rush)

J/W=1.0(“tasaperä”)

J=Jet speedW=wire speed

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Niskanen, Hämäläinen (2011), NPPRJ (in press)

CFD-based Optimization for Fib O i t ti A l P filFibre Orientation Angle Profiles

− Optimal shape design of the tapered header to get even flow distribution

− Optimal control of the slice opening to avoid CD velocities in the jet

− Based on depth-averaged NS equations

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− Software tools developed to industry

HOC SoftwareHOC Software

Step 2. CorrectionStep 1. Identification

Input:Measured fiberorientation profile

Result:Optimizedfiber orientation

orientation profile

HOC identification: I t

HOC correction:Slice openingcorrection

HOC identification:The correspondingflow conditions

Input:The flow conditionsfrom Step 1.

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Tammenoja (2009), Results Pulp&Paper (Metso publication)

HOC SoftwareE t l F t CFD M d lExtremely Fast CFD Model

Step 1: identification Step 2: correction

CFD model inside HOC software:− 2D, laminar, depth-averaged− 5 000 elements (stabilized FEM)

3D CFD (ANSYS-CFX):− 3D, turbulent, free jet− 2-3 million cells( )

− CPU time is 5 seconds2 3 million cells

− CPU time is 1 hourNancy, 13-14 October, 2011 7www.lut.fi/ceid

HOC SoftwareMill E l AMill Example A

12 0Before optimization After optimization

6.0

8.0

10.0

12.0

[°]

0.0

2.0

4.0

atio

n an

gle

8 0

-6.0

-4.0

-2.0

Orie

nta

-12.0

-10.0

-8.0

CD positionCD position• Max‐Min orientation range = 20 degrees before optimization

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HOC Software Mill l BMill example B

Before optimization After optimization

4 0

6,0

8,0

°]

Before optimization After optimization

0,0

2,0

4,0

n an

gle

[°

-4,0

-2,0

Orie

ntat

ion

-8,0

-6,0

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

O

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Normalized CD position

More than 50 paper machine h db ti i d fheadboxes optimized so far

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Avikainen, Hämäläinen, Tarvainen (2010), NPPRJ, 25(4)

Conclusion: Different Modelling A h f Diff t PApproaches for Different Purposes

− One-phase model (pure water)− Meter-scale phenomena in

headbox− Routine CFD analyses

− Rheological model (effective medium)del com

plexity

Flocculation g ( )− Head losses in pipes, stock

preparation processes, MC,..− No large concentration variations

Passive scalar (one way coupling)

Mod

Flocculation

− Passive scalar (one-way coupling) − Dilute suspensions− Fibre orientation probability distr.

− Two-phase flow (two-way coupling)

Fibre orientation

p ( y p g)− Carrying phase (water) and

dispersed phase (fibres or flocs) handled separately

− Concentration variations slipConcentration variations, slip velocity between the phases,...

Nancy, 13-14 October, 2011 www.lut.fi/ceid 11"Model reality"

References and Acknowledgementse e e ces a d c o edge e ts

− Fibre Orientation Probability Distribution (FOPD) modelling( ) ( )− Doctoral theses by T. Hämäläinen (2008) and H. Niskanen (2011)

− Niskanen et al., IJMF (2011)− Hämäläinen et al., J.Eng.Math. (2011)− Niskanen Hämäläinen NPPRJ (in press)Niskanen, Hämäläinen, NPPRJ (in press)− Other authors from KTH, UBC, etc.

− CFD-based Optimization− Hämäläinen et al. in “Optimization and Computational Fluid

D i ” Th i J i (2008)Dynamics”, Thevenin, Janiga (2008)− Avikainen et al., NPPRJ (2010)

− AcknowledgementsAcknowledgements− CFD-based optimization software tools have been developed since

1995 at University of Jyväskylä, VTT, Metso (Valmet) and Numerola− Thanks to Paper Physics Group at University of Eastern Finland,

Kuopio for the results of FOPD modelling in 2004 2011Kuopio for the results of FOPD modelling in 2004-2011

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