Fibre orientation and related head-box optimization systems
Fibre orientation and related head-box optimization systems
Fibre orientation and related head-box optimization systems
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<strong>Fibre</strong> Orientation <strong>and</strong> Related<br />
Head<strong>box</strong> Optimization Systems<br />
Jari Hämäläinen<br />
Centre of Computational ti Engineering i <strong>and</strong> Integrated t Design (CEID)<br />
Lappeenranta University of Technology (LUT)<br />
Lappeenranta, Finl<strong>and</strong>
<strong>Fibre</strong> Orientation<br />
−<br />
−<br />
−<br />
Basic fibrous structure of the paper sheet is<br />
formed at the wet end of a paper machine -<br />
<strong>head</strong><strong>box</strong> <strong>and</strong> forming section<br />
<strong>Fibre</strong> <strong>orientation</strong> (angle <strong>and</strong> anisotropy)<br />
determines the dimensional stability of the paper<br />
Velocity gradients align fibres whereas turbulence<br />
makes <strong>orientation</strong> more r<strong>and</strong>om<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
2
<strong>Fibre</strong> Orientation, its Anisotropy<br />
<strong>and</strong> dCDA Angle Profile<br />
−<br />
<strong>Fibre</strong> <strong>orientation</strong> distribution in each location<br />
−<br />
The average fibre <strong>orientation</strong> angle profile in cross<br />
direction (CD) of a paper machine<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
3
Modelling of <strong>Fibre</strong> Orientation<br />
Probability bilit Distribution ib ti (FOPD)<br />
J/W=0.9<br />
(drag)<br />
J/W=1.0<br />
(“tasaperä”)<br />
J/W=1.1<br />
1<br />
(rush)<br />
J=Jet speed<br />
W=wire speed<br />
Niskanen, Hämäläinen (2011), NPPRJ (in press)<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid 4
CFD-based Optimization for<br />
<strong>Fibre</strong> Orientation ti Angle Profiles<br />
−<br />
−<br />
−<br />
−<br />
Optimal shape design of the tapered <strong>head</strong>er to get<br />
even flow distribution<br />
Optimal control of the slice opening to avoid CD<br />
velocities in the jet<br />
Based on depth-averaged NS equations<br />
Software tools developed to industry<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
5
HOC Software<br />
Step 1. Identification<br />
Step 2. Correction<br />
Input:<br />
Measured fiber<br />
<strong>orientation</strong> profile<br />
Result:<br />
Optimized<br />
fiber <strong>orientation</strong><br />
HOC correction:<br />
Slice opening<br />
correction<br />
HOC identification:<br />
The corresponding<br />
flow conditions<br />
Input:<br />
The flow conditions<br />
from Step 1.<br />
Tammenoja (2009), Results Pulp&Paper (Metso publication)<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
6
HOC Software<br />
Et Extremely Fast tCFDMdl<br />
Model<br />
Step 1: identification<br />
Step 2: correction<br />
CFD model inside HOC software:<br />
− 2D, laminar, depth-averaged<br />
− 5 000 elements (stabilized FEM)<br />
− CPU time is 5 seconds<br />
3D CFD (ANSYS-CFX):<br />
− 3D, turbulent, free jet<br />
− 2-3 million cells<br />
− CPU time is 1 hour<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
7
HOC Software<br />
Mill Example A<br />
[°]<br />
Orienta ation angle<br />
12.0<br />
10.0<br />
8.0<br />
6.0<br />
4.0<br />
2.0<br />
0.0<br />
-2.0<br />
-4.0<br />
-6.0<br />
-8.0 80<br />
-10.0<br />
-12.0<br />
Before <strong>optimization</strong><br />
After <strong>optimization</strong><br />
CD position<br />
• Max‐Min <strong>orientation</strong> range = 20 degrees before <strong>optimization</strong><br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
8
HOC Software<br />
Mill example B<br />
8,0<br />
Before <strong>optimization</strong><br />
After <strong>optimization</strong><br />
6,0<br />
Orientation<br />
n angle [° °]<br />
40 4,0<br />
2,0<br />
0,0<br />
-2,0<br />
-4,0<br />
-6,0<br />
-8,0<br />
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1<br />
Normalized CD position<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
9
More than 50 paper machine<br />
<strong>head</strong><strong>box</strong>es optimized i so far<br />
Avikainen, Hämäläinen, Tarvainen (2010), NPPRJ, 25(4)<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
10
Mod del complexity<br />
Conclusion: Different Modelling<br />
Approaches for Different Purposes<br />
<strong>Fibre</strong><br />
<strong>orientation</strong><br />
− One-phase model (pure water)<br />
− Meter-scale phenomena in<br />
<strong>head</strong><strong>box</strong><br />
− Routine CFD analyses<br />
Flocculation<br />
− Rheological model (effective medium)<br />
− Head losses in pipes, stock<br />
preparation processes, MC,..<br />
− No large concentration variations<br />
−<br />
−<br />
Passive scalar (one-way coupling)<br />
− Dilute suspensions<br />
− <strong>Fibre</strong> <strong>orientation</strong> probability distr.<br />
Two-phase flow (two-way coupling)<br />
− Carrying phase (water) <strong>and</strong><br />
dispersed phase (fibres or flocs)<br />
h<strong>and</strong>led separately<br />
− Concentration variations, slip<br />
velocity between the phases,...<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid 11<br />
"Model reality"
References e e <strong>and</strong> Acknowledgements<br />
e −<br />
−<br />
−<br />
<strong>Fibre</strong> Orientation Probability Distribution (FOPD) modelling<br />
− Doctoral theses by T. Hämäläinen (2008) <strong>and</strong> H. Niskanen (2011)<br />
− Niskanen et al., IJMF (2011)<br />
− Hämäläinen et al., J.Eng.Math. (2011)<br />
− Niskanen, Hämäläinen, NPPRJ (in press)<br />
− Other authors from KTH, UBC, etc.<br />
CFD-based Optimization<br />
− Hämäläinen et al. in “Optimization <strong>and</strong> Computational Fluid<br />
Dynamics”, Thevenin, Janiga (2008)<br />
− Avikainen et al., NPPRJ (2010)<br />
Acknowledgements<br />
− CFD-based <strong>optimization</strong> software tools have been developed since<br />
1995 at University of Jyväskylä, VTT, Metso (Valmet) <strong>and</strong> Numerola<br />
− Thanks to Paper Physics Group at University of Eastern Finl<strong>and</strong>,<br />
Kuopio for the results of FOPD modelling in 2004-20112011<br />
Nancy, 13-14 October, 2011 www.lut.fi/ceid<br />
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