Visualisation and Analysis of the Flow along the Kneading Block of a Twin-screw Extruder

Carneiro, O. S.; Poulesquen, Arnaud; Covas, J. A.; Vergnes, Bruno

doi:10.3139/217.1708

Cited by 12 publications

(5 citation statements)

References 4 publications

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“…From our calculations, we are able to rank four typical kneading blocks. Our conclusions from the numerical experiences appear to be in very good agreement with global classical interpretation of the flow [37]. It is also in line with guidelines found in reference books.…”

Section: Resultssupporting

confidence: 89%

Parametric Study of the Mixing Efficiency in a Kneading Block Section of a Twin-screw Extruder

Alsteens

Legat

Avalosse³

2004

International Polymer Processing

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Twin-screw extruders are often used to distribute and disperse additives into polymers. The mixing efficiency of the extruders highly depends on the geometry of the kneading blocks of the mixing section. In this paper, the impact of some geometrical parameters, such as the stagger angle and the width of the discs, are investigated by three dimensional time dependent finite element calculations. Results are obtained with the finite element software POLYFLOW. The robustness and the accuracy of the mesh superposition technique is evaluated. It appears that conclusions obtained by the numerical experiments can be used to improve the geometry of the kneading blocks. The mixing efficiency is evaluated by comparing the residence time and the total shear distributions of a large set of virtual particles launched in the flow domain.

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Section: Resultssupporting

confidence: 89%

Parametric Study of the Mixing Efficiency in a Kneading Block Section of a Twin-screw Extruder

Alsteens

Legat

Avalosse³

2004

International Polymer Processing

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“…The study of the melting phenomena in single extruders has a relatively long history. , However, a comprehensive study in the TSE started only recently with Todd . Since then, the study of the melting phenomena in the TSE has attracted much attention. − It was widely accepted that the mechanical energy plays a critical role for the fast melting of polymers in the TSE…”

Section: Introductionmentioning

confidence: 99%

“…An effective viscosity was estimated for the extrusion flow at the initial stage of melting. The existence of solid polymer pellets in the flow significantly increased the viscosity of the flow. − Viscous energy dissipation (VED) could be another key mechanism to generate a significant amount of heat from mechanical energy in the TSE. More recently, Gogos and co-workers , reported that plastic energy dissipation (PED) was the dominant heat source to melt polymers in the TSE.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Melting Mechanism in a Twin-Screw Extruder Using a Pulse Method and Online Measurement

Chen

Sundararaj

Nandakumar

et al. 2004

Ind. Eng. Chem. Res.

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A perturbation (or pulse) method was used to investigate the melting of a polystyrene/polypropylene (PS/PP) blend in a 40-mm twin-screw extruder (TSE). A sliding-barrel technique was used to visualize the melting processes, map the temperature and pressure profiles along the channel, and obtain the residence time distribution (RTD) at different locations in the extruder. Pressure, pulse, and visualization results were used to determine where melting occurred. Three runs with ratios of the flow rate/screw speed (Q/N) varying from 5.0 to 11.3 g/revolution were studied. It was found that the melting of the PS/PP blend in the TSE had three distinct regions. Most of the melting occurred in a narrow transition region (∼50 mm) from the partially filled region to the fully filled region. The location of the transition region was found using four different techniques: visualization, pressure, temperature, and combined pulse/RTD methods. High-speed video of the extrusion processes shows that the solid polymer pellets melted through an “erosion” mechanism. Mechanical energy consumption for melting can be obtained through this perturbation method.

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“…The two flows are described by various process parameters, including screw speed N, shear viscosity η, volume flow rate _ V , pressure gradient p 0 , mechanical drive power per period P=L, and dissipation per period _ Q Diss =L. The volume flow rate _ V is directly linked to the velocity profile in the flow direction v z , as given in Equation (15). The boundary conditions for the velocity are defined by the screw speed and the stationary barrel walls because wall adhesion is assumed.…”

Section: Governing Equationsmentioning

confidence: 99%

“…[14] Twin-screw extrusion modeling, as in the publications mentioned above, has focused mainly on the conveying elements, while kneading blocks have received less attention. The complex flow patterns of kneading blocks, as analyzed by Carneiro, [15,16] pose considerable challenges to these modeling approaches. Szydlowski [17][18][19] was the first to study kneading blocks in detail, of which the geometry is often drastically simplified; for example, Potente [20] replaced the kneading discs with continuous channels and thus modeled kneading blocks as conveying elements.…”

mentioning

confidence: 99%

Modeling melt conveying and power consumption of co‐rotating twin‐screw extruder kneading blocks: Part A. Data generation

Stritzinger

Roland

Berger‐Weber

et al. 2022

Polymer Engineering & Sci

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Mathematical models of polymer melt flow in co‐rotating twin‐screw extruders are crucial to screw design and predict processing characteristics, such as pressure distribution, back‐pressure lengths, degree of filling, melt‐temperature increase, and drive power. Twin‐screw modeling focuses predominantly on conveying elements, and kneading blocks are commonly represented with fictitious continuous flights, which significantly simplifies geometry and ignores considerable leakage flow. This work (Part A) presents a comprehensive analysis of the conveying characteristics and power demands of fully intermeshing co‐rotating twin‐screw extruder kneading blocks that considers the complex three‐dimensional geometry without geometrical simplifications. This analysis comprises the following steps: (1) dimensionless description of the geometry, (2) simplification of the governing equations, (3) formulation of novel dimensionless conveying and power parameters, and (4) a parametric design study with the novel approach of using the characteristic angular screw position, which avoids complex numerical algorithms and drastically reduces the computation required. Our comprehensive parametric design study included 1536 independent design points—a vast amount of data that revealed various effects that are highlighted in this work, including new findings on the interactions between geometry and conveying and power parameters. The obtained results serve, for example, as the basis for screw design, optimizations, scale‐up, and soft sensors.

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Visualisation and Analysis of the Flow along the Kneading Block of a Twin-screw Extruder

Cited by 12 publications

References 4 publications

Parametric Study of the Mixing Efficiency in a Kneading Block Section of a Twin-screw Extruder

Parametric Study of the Mixing Efficiency in a Kneading Block Section of a Twin-screw Extruder

Investigation of the Melting Mechanism in a Twin-Screw Extruder Using a Pulse Method and Online Measurement

Modeling melt conveying and power consumption of co‐rotating twin‐screw extruder kneading blocks: Part A. Data generation

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