Design & Manufacturing of Press Fabrics for Improved...
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Transcript of Design & Manufacturing of Press Fabrics for Improved...
Design & Manufacturingof Press Fabrics for
Improved Dewatering
Chad A. Hume & Dr. David W. Rosen
George W. Woodruff School of Mechanical EngineeringRenewable Bioproducts InstituteGeorgia Institute of Technology
RBI Dewatering Project
• Press Fabric DesignGoal: Design features, such as holes and grooves, for inner layer of multi-layer fabric to:
– Facilitate dewatering
– Prevent/reduce rewetting
• Inner Layer ManufacturingGoal: Develop 2D and 3D ink-jet printing testbeds to fabricate designed inner layers using high viscosity fluids such as thermoplastic polyurethane (TPU)
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Agenda 2020 Drier Web Roadmap
• High Priority R&D Area– Next-generation nip/press design for single-direction
flow – eliminate rewet
• High Priority Projects– Develop adaptive felt materials or structures that have
high permeability at high nip-loads and low permeability at low loads
– Identify or develop a membrane that will support unidirectional or preferential flow of water away from the fiber web
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Outline
• Press Fabric Introduction
• Press Fabric Flow Modeling
– Passive
– Active
• Inkjet Printing
– Prototyping
– High viscosity droplet generator
– Process modeling
• Conclusions
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Paper Machine Overview
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Increasing Dry Solids
1% 20% 50% 95%
𝑑. 𝑠.
=𝑚𝑓𝑖𝑏𝑒𝑟
𝑚𝑓𝑖𝑏𝑒𝑟 +𝑚𝑤𝑎𝑡𝑒𝑟
Recent trends and directions
• Non-woven bases– Research observed better pressure uniformity,
higher solids, less marking, and less rewet
• Inclusion of polymer membranes and layers
• New manufacturing techniques– Additive manufacturing can build optimized geometry
for polymer layer7
Outline
• Press Fabric Designs
• Press Fabric Flow Modeling
– Passive
– Active
• Inkjet Printing
– Prototyping
– High viscosity droplet generator
– Process modeling
• Conclusions
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Press Fabric Design
• Focus on barrier layer
• FEA & CFD to simulate
deformation and flow
• Various designs are studied including woven, nonwoven, conical, etc., as well as “active” geometries
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Data Available
• Stream Lines
• Velocity/Pressure
• Pressure Drop
– This is related to flow resistance
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3D Results
• Can we design a hole that opens for forward flow and closes to prevent rewet
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• 145% increase in resistance to back flow
Outline
• Press Fabric Designs
• Press Fabric Flow Modeling
– Passive
– Active
• Inkjet Printing
– Prototyping
– High viscosity droplet generator
– Process modeling
• Conclusions
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Inkjet Printing – 3D Printing
• High Resolution
• Fast
• Scalable – just add more nozzles
• Multiple materials
• $15-20B industry and growing
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Fabric Prototyping
• Prototype fabric designs were fabricated using the Stratasys Connex to explore both passive and active designs
•
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Georgia Tech Inkjet System
• Print high viscosity (>100cP) and complex fluids (non-Newtonian, suspensions/colloids)
• Ultrasonic droplet generation technology– New approach to printing. Excite at resonant frequency +
acoustic focusing in nozzle causes ejection of droplet.
– Easily scaled for printing repeated patterns.
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4 mm droplets
Droplet Modeling
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• Efficiently model how different machine parameters and material affect print quality
Closure
• 1st order approximation for how hole design affects flow.
• Promising new design to facilitate unidirectional flow. Investigating variants.
• Inkjet printing proposed as manufacturing process with high viscosity materials
• Developing process simulation to predict as-fabricated geometries
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Design & Manufacturingof Press Fabrics for
Improved Dewatering
Chad A. Hume & Dr. David W. Rosen
George W. Woodruff School of Mechanical EngineeringRenewable Bioproducts InstituteGeorgia Institute of Technology
Pressing Overview: Basic Physics
• Water movement occurs only with pressure differential• Pressure must be higher in the sheet than felt• If hydraulic pressure exists, saturation must exist at least
locally– There must be a continuum of fluid
• To move fluid:– Voids must exist in the felt, or– Voids must exist beyond the felt, or– Water must flow in MD or CD, or– Sheet explodes (Crushing)
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Flow Modeling: 2D and 3D
• 2D Simulations
• 3D Simulations
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3D Results
• Investigation of passive geometries
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Summary
• 1st order approximation for how hole design affects flow
• Various designs tested and one proposed which improves through flow and resists backflow
• Phase 2:
– How can we manufacture these membranes?
– Inkjet Printing!
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