Chaotic Manifold Analysis of Four-Screw Extruders Based on Lagrangian Coherent Structures

Zhu, X.Z.; Tong, Ying; Hu, Yue Xin

doi:10.3390/ma11112272

Cited by 7 publications

(5 citation statements)

References 38 publications

(57 reference statements)

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“…23 There has been a renewed interest in the past few years in chaotic mixing with the single-and multiple-screw extruders. [30][31][32][33][34][35] With the increased degree of freedom in a free-helix extruder per Figure 3, it is possible to make the flow field chaotic by moving the core and helix in a periodic fashion. This is a different approach to that taken by Kim and Kwon, 30,31 who showed that the 3D channel flows could be made chaotic by introducing spatially periodic barriers in the channel to break the cells.…”

Section: Chaotic Mixingmentioning

confidence: 99%

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Chaotic mixing in a free‐helix extruder using a new solution to the biharmonic equation

Campbell

Taylor

Wetzel³

et al. 2022

AIChE Journal

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A recently published approach for modeling the cross flow in an extruder channel using a new solution to the biharmonic equation is utilized in a study of chaotic mixing in a free‐helix single‐screw extruder. This novel extruder was designed and constructed with the screw flight, also referred to as the helix, detached from the screw core. The flight‐helix had straight sides that more closely emulated rectangular channel theory than the nominal sloped sides of a conventional single screw channel. Each of the screw elements could be rotated independently to obtain chaotic motion in the screw channel. Using the new extruder, experimental evidence for the increased mixing of a dye, for both a Dirac and droplet input, with a chaotic flow field relative to the traditional residence time distribution is presented. These experimental results are compared using the new biharmonic equation‐based model. Comparing the experimental chaotic mixing with theoretical calculations was facilitated by a recently published technique for accurately placing the dye in the extruder channel. Because of the ability to periodically rotate only the flight/helix, the chaotic mixing results are minimally confounded by the existence of Moffatt eddies.

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Section: Chaotic Mixingmentioning

confidence: 99%

“…A reported numerical study of chaotic mixing in a rectangular cavity showed that there are mixing windows within the parameter space, where high quality mixing occurs 23 . There has been a renewed interest in the past few years in chaotic mixing with the single‐ and multiple‐screw extruders 30–35 …”

Section: Introductionmentioning

confidence: 99%

Chaotic mixing in a free‐helix extruder using a new solution to the biharmonic equation

Campbell

Taylor

Wetzel³

et al. 2022

AIChE Journal

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“…Multiscrew extruders have more than two screws in the barrel. They have even higher dispersive and distributive mixing performances over twin-screw extruders, owing to more intermeshing zones for a given screw length. , Nevertheless, they are commercially more rare due to mechanical complexities, and are much less documented in the literature.…”

Section: Basic Features Of Screw Extruders As Continuous Reactorsmentioning

confidence: 99%

Intensification of Polymerization Processes by Reactive Extrusion

et al. 2021

Ind. Eng. Chem. Res.

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The unique geometry of screw extruders allows handling very viscous media; thus, they can be used as continuous reactors to conduct polymerization reactions without using any solvents. This is called reactive extrusion polymerization. It is an intensified process as it maximizes reaction rates upon maximizing the concentrations of monomers and an initiator/catalyst (if there is any). It also allows conducting polymerization reactions at higher temperatures, without having to take measures to prevent solvents from evaporating or to work under pressure. However, screw extruders are not suitable for the early stage of polymerization in which the viscosity of the polymerization system may not be high enough for the rotation of the screws to generate a steady flow. A combination of continuously stirred tank reactors and a twin-screw extruder or several in series is preferred for the polymerization process. This review shows how reactive extrusion may intensify different types of polymerization processes under the constraint of no solvents, such as free-radical polymerization, anionic polymerization, ring-opening polymerization, and polycondensation, on one hand; and how challenges are met, on the other hand.

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“…The single-screw extruders are the classic equipment in the processing of polymers [1]. Films, sheets, pipes, and various profiles are produced by the extrusion method.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Polymer Solutions in a Single-Screw Extruder

2019

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Single-screw extruders are the most common equipment used for polymer extrusion. The study of the hydrodynamics of a polymer melts flow in the extruder channel is the basis for modeling and understanding the extrusion process. In general form, the extruder includes a straight section with a screw installed in it. In this study, the three-dimensional mathematical modeling of the polymer solutions flow in the metering zone of a single-screw extruder is performed. The influences of the screw geometry (L/D 2 = 1 . . . 3) on the flow structure and the pressure drop are analyzed under a speed rotation up to 60 rpm. Aqueous solutions of 0.5% polyacrylamide (0.5% PAA) and 1.5% sodium salt of carboxymethyl cellulose (1.5% CMC) are considered as the working fluid. Appl. Sci. 2019, 9, 5423 2 of 12 the helical screw channel is unwound and considered as a flat rectangular channel [4,[17][18][19][20][21][22]. Thus, plane-parallel fluid flow in a channel of infinite width is considered instead of direct 3D modeling. Also, the principle of reversed motion is often used (tube rotation is considered at the fixed screw) [4,[17][18][19][20][21][22]. In all works, polymers are considered as shear-thinning fluid [4,[17][18][19][20][21][22].The main functional zones of the extruder are feeding (solids conveying), melting, and metering. The metering zone is the simplest for modeling in a single-screw extruder, since the flow laws of viscous fluids can be applied to the polymer melt flow [23]. In this zone, the polymer is completely molten [24]. Besides, it is the metering zone that determines the extruder performance [23].Work [4] describes a simple numerical method for solving the problem of the polymer melt flow in the metering zone of the single-screw extruder. The 2D mathematical model takes into account the presence of circulating motion, non-Newtonian behavior of the processed material, and heating of the polymer due to viscous dissipation.In [3,18,19,21,22,25], numerical solutions obtained in a 2D and 3D formulation are approximated by symbolic regression models. The heuristic approach for predicting the main characteristics of the polymer melts flow in the extruder channel is based on genetic programming. Speaking about the evolutionary computation in general, it should be noted that they, like any method using an element of randomness, do not guarantee the detection of a global extremum of the objective function (or optimal solution) for a certain time. Their main advantage is that they allow finding a "better" solution to a difficult task in less time than other methods.In contrast with the standard flat-plate model of the unwound screw channel (2D), this hydrodynamic problem is solved in a three-dimensional formulation in [17,26]. Authors of the papers consider mathematical modeling of the flow in the metering zone of a plasticizing extruder. The objective of the study was the melting of the polymer composition based on polyethylene.Work [27] presents the results of three-dimensional numerical simulation of the polymer mel...

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Chaotic Manifold Analysis of Four-Screw Extruders Based on Lagrangian Coherent Structures

Cited by 7 publications

References 38 publications

Chaotic mixing in a free‐helix extruder using a new solution to the biharmonic equation

Chaotic mixing in a free‐helix extruder using a new solution to the biharmonic equation

Intensification of Polymerization Processes by Reactive Extrusion

Numerical Simulation of Polymer Solutions in a Single-Screw Extruder

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