the forming and densification of fibre mats in twin-wire formers: modelling
DESCRIPTION
Vinicius Lobosco, Bo Norman & Sören Östlund. The Forming and Densification of Fibre Mats in Twin-Wire Formers: Modelling. Outline. Background on forming Model Results Conclusion Future Work. Schematic Papermachine. A. Flaks. A Modern Forming Section. Blades improve formation - PowerPoint PPT PresentationTRANSCRIPT
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The Forming and Densification of Fibre Mats in
Twin-Wire Formers: Modelling
Vinicius Lobosco, Bo Norman & Sören Östlund
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Outline
● Background on forming● Model● Results● Conclusion● Future Work
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A. Flaks
Schematic Papermachine
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● Blades improve formation● Mats start on the roll
A Modern Forming Section
Norman & Fellers
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Dewatering Mechanisms
ThickeningFiltration
Parker, 1972
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Outline
● Background on forming● Model● Results● Conclusion● Future Work
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Present Available Models● Incompressible
– Zhao & Kerekes– Roshanzamir et al.– Holmqvist
● Elastic– Martinez– Zahrai et al.
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Experimental Material Behaviour
● Vomhoff & Schmidt– Permanent
deformation– Hysteresis
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Mathematical Model
● Balance Equations:– Mass;– Momentum
● Transfer Equations● Constitutive Equations
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Assumptions
● Continuum● Intertial effect neglected● Wire gives no resistance● Symmetry● Darcyan flow● No interface resistance
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Mathematical Model 2
● Convective-diffusive time-dependent equation● Finite Element Method (FEM)
Variation = Convection + Diffusion
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Outline
● Background on forming● Model● Results● Conclusion● Future Work
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Results 1● Filtration● Dryness● Unbeaten
Kraft pulp – CSF 718
● 10 kPa – 20 ms
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Results 2● Dryness● Beaten kraft
pulp CSF 598● 10 kPa – 20 ms
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Results 3● Thickning● Blade forming ● Three
haversinus pulses 15 kPa 2 ms with 2 ms interval
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Results 4● Contours of
Structural stress
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Results 5
● Material response from the different elements and the experimental data (Vomhoff & Schmidt)
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Results 6
● Diminishing returns● Average solids
content vs. applied stress
● No improvement after 15 kPa
Ave
rage
fina
l sol
ids c
onte
nt
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Conclusions
● Demonstrates considerable dryness gradient effects.
● Demontrates dryness relaxation effects.● Needs more data on unloading of webs.● Available to the industry.● Will be of large interest in modelling of twin-wire
roll and blade forming.
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Future Work● Numerical
– Streamline diffusion– Moving Finite Elements (Yi Liu – C4)
● Physical Model– Hysteresis operator– Wire and interface resistance
● Generalisation– Couple with Holmqvist's blade pressure model
● Validate– Filtration and papermachine (e.g. Euro-FEX)
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Acknowledgements
● CPDC for the funds that made this project possible
● Hannes Vomhoff for making his experimental data available.
● Raul Tempone (NADA – KTH) for the support regarding the numerical method