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The Forming and Densification of Fibre Mats in Twin-Wire Formers: Modelling

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

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The Forming and Densification of Fibre Mats in Twin-Wire Formers: Modelling

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  1. Vinicius Lobosco, Bo Norman & Sören Östlund The Forming and Densification of Fibre Mats in Twin-Wire Formers: Modelling

  2. Outline • Background on forming • Model • Results • Conclusion • Future Work

  3. Schematic Papermachine A. Flaks

  4. A Modern Forming Section • Blades improve formation • Mats start on the roll Norman & Fellers

  5. Filtration Thickening Dewatering Mechanisms Parker, 1972

  6. Outline • Background on forming • Model • Results • Conclusion • Future Work

  7. Present Available Models • Incompressible • Zhao & Kerekes • Roshanzamir et al. • Holmqvist • Elastic • Martinez • Zahrai et al.

  8. Experimental Material Behaviour • Vomhoff & Schmidt • Permanent deformation • Hysteresis

  9. Mathematical Model • Balance Equations: • Mass; • Momentum • Transfer Equations • Constitutive Equations

  10. Assumptions • Continuum • Intertial effect neglected • Wire gives no resistance • Symmetry • Darcyan flow • No interface resistance

  11. Mathematical Model 2 • Convective-diffusive time-dependent equation • Finite Element Method (FEM) Variation = Convection + Diffusion

  12. Outline • Background on forming • Model • Results • Conclusion • Future Work

  13. Results 1 • Filtration • Dryness • Unbeaten Kraft pulp – CSF 718 • 10 kPa – 20 ms

  14. Results 2 • Dryness • Beaten kraft pulp CSF 598 • 10 kPa – 20 ms

  15. Results 3 • Thickning • Blade forming • Three haversinus pulses 15 kPa 2 ms with 2 ms interval

  16. Results 4 • Contours of Structural stress

  17. Results 5 • Material response from the different elements and the experimental data (Vomhoff & Schmidt)

  18. Results 6 • Diminishing returns • Average solids content vs. applied stress • No improvement after 15 kPa Average final solids content

  19. 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.

  20. 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)

  21. 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

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