433594 Simulations of an Unwound Paste Extruder Flight

Thursday, November 12, 2015: 2:15 PM
252A/B (Salt Palace Convention Center)
Matthew Pruitt1, Matthew Brown1, Brandon Ennis2 and Bryan J. Ennis2, (1)Chemical Engineering, The University of Tennessee at Chattanooga, Chattanooga, TN, (2)Department of Civil & Chemical Engineering, University of Tennessee at Chattanooga, Chattanooga, TN

Simulations of an Unwound Paste Extruder Flight

Matthew Pruitt, Matthew Brown, Brandon Ennis, Bryan J. Ennis*

Department of Chemical Engineering, The University of Tennessee at Chattanooga

*Corresponding author, bryan-j-ennis@utc.edu

Paste extrusion is widely used in processing (food, pharmaceuticals, catalysts).  As a matter of design, pressure is developed within the screw (screw characteristic), which then allows extrusion of the paste at the die (die characteristic).  There have been few advances, either analytically or modelling since Benbow & Bridgwater [2].  In this and related work [1,3], analytical expressions for the rise in flight pressure with axial position, based on an unwound flight model have been developed, as a variant of the Janssen equation and originally based on the work of Darnell and Mol [4]. Here, feed pressure is amplified by sliding friction of barrel conveying pastes through a flight channel forward to the die face, leading the extrusion of strings of compacted paste, or extrudate. 

This work revisits unwound flight models using finite element methods. In particular, arbitrary Lagrangian/Eulerian methods are employed through LS-DYNA. The impact of various material models (both plastic and geotechnical: Mohr-Coulombic, Federal Highway Administration (FHWA) Soil Model, and Drucker-Prager) on the development of flight pressure is explored, as well as the impact of both flight and barrel friction.  Model validation also occurs through approximate analytical solution of the unwound flight, modified Janssen equations.

Keywords: Paste Extrusion, Screw Extrusion, Material Modeling, Finite Element

References:

[1] A.S. Burbidge, J. Bridgwater.” The single screw extrusion of pastes”. Chem. Eng. Sci. Pg 2531–2543. 1995.

[2] Benbow, John and Bridgwater, John. “Paste Flow and Extrusion.” University of Birmingham,

Oxford. Clarendon Press. 1993.

[3]  Botten, A.J., Burbride, A.S., and Blackburn, S. “A model to predict the pressure development in single screw extrusion.” University of Birmingham. Journal of Materials Processing Technology 135. 2002.

 [4] Darnell, W.H. and Mol, E.A.J. “Solids Conveying in Extruders.” SPE Journal. April 1956.


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