Application of the Network Simulation Method to Flat Dies with Inverted Prelands

Köpplmayr, Thomas; Miethlinger, Jürgen

doi:10.3139/217.2758

Cited by 5 publications

(10 citation statements)

References 11 publications

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“…This section revisits the fundamentals of the modeling approach and highlights the novel features incorporated to include the drag force of the screw. The usefulness of network theory in the flow analysis of extrusion equipment has been demonstrated by several studies [ 5 , 35 , 36 , 37 , 38 , 39 , 40 ].…”

Section: Modelingmentioning

confidence: 99%

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part B. (Superimposed Drag-Pressure Flows in Extrusion)

et al. 2020

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Due to progress in the development of screw designs over recent decades, numerous high-performance screws have become commercially available in single-screw extrusion. While some of these advanced designs have been studied intensively, others have received comparatively less attention. We developed and validated a semi-numerical network-theory-based modeling approach to predicting flows of shear-thinning polymer melts in wave-dispersion screws. In the first part (Part A), we systematically reduced the complexity of the flow analysis by omitting the influence of the screw rotation on the conveying behavior of the wave zone. In this part (Part B), we extended the original theory by considering the drag flow imposed by the screw. Two- and three-dimensional melt-conveying models were combined to predict locally the conveying characteristics of the wave channels in a discretized flow network. Extensive experiments were performed on a laboratory single-screw extruder, using various barrel designs and wave-dispersion screws. The predictions of our semi-numerical modeling approach for the axial pressure profile along the wave-dispersion zone accurately reproduce the experimental data. Removing the need for time-consuming numerical simulations, this modeling approach enables fast analyses of the conveying behavior of wave-dispersion zones, thereby offering a useful tool for design and optimization studies and process troubleshooting.

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Section: Modelingmentioning

confidence: 99%

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part B. (Superimposed Drag-Pressure Flows in Extrusion)

et al. 2020

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“…Two modeling approaches can be distinguished: (i) nodal and (ii) mesh analysis. Replacing the currents with flow rates, the voltages with pressures, and the electrical resistances with flow resistances, network theory has also proven useful in the field of polymer processing, where it has been successfully applied in modeling the flows in extrusion dies [23,24,25,26,27] and in extruders [28,29,30]. The main idea is to reduce the complexity of a multidimensional flow by subdividing the geometry into small passages for which simple analytical flow equations are available, assuming that both geometrical parameters and processing conditions are locally constant.…”

Section: Network Analysismentioning

confidence: 99%

“…This simple analytical equation relates the mass flow rate m˙ and the pressure consumption Δ p via the melt density ρ m , the fluidity Φ, the flow exponent m , the die conductance K ’, and a correction factor f p (defined in Reference [27]). The latter is a function of the aspect ratio of the flow channel and takes the rate-limiting influence of the walls for a Newtonian fluid into account.…”

Section: Network Analysismentioning

confidence: 99%

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part A (Pressure Flows)

et al. 2019

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Wave-dispersion screws have been used industrially in many types of extrusion processes, injection molding, and blow molding. These high-performance screws are constructed by replacing the metering section of a conventional screw with a melt-conveying zone consisting of two or more parallel flow channels that oscillate periodically in-depth over multiple cycles. With the barrier flight between the screw channels being selectively undercut, the molten resin is strategically forced to flow across the secondary flight, assuring repeated cross-channel mixing of the polymer melt. Despite the industrial relevance, very few scientific studies have investigated the flow in wave-dispersion sections in detail. As a result, current screw designs are often based on traditional trial-and-error procedures rather than on the principles of extrusion theory. This study, which was split into two parts, was carried out to systematically address this issue. The research reported here (Part A) was designed to reduce the complexity of the problem, exclusively analyzing the pressure-induced flows of polymer melts in wave sections. Ignoring the influence of the screw rotation on the conveying characteristics of the wave section, the results could be clearly assigned to the governing type of flow mechanism, thereby providing a better understanding of the underlying physics. Experimental studies were performed on a novel extrusion die equipped with a dual wave-channel system with alternating channel depth profiles. A seminumerical modeling approach based on network theory is proposed that locally describes the downchannel and cross-channel flows along the wave channels and accurately predicts the pressure distributions in the flow domain. The solutions of our seminumerical approach were, moreover, compared to the results of three-dimensional non-Newtonian CFD simulations. The results of this study will be extended to real screw designs in Part B, which will include the influence of the screw rotation in the flow analysis.

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“…Network theory originates from the field of electrical engineering [34], but has also proven useful in predicting the flow in extrusion dies [35] and in investigating the pumping behavior of barrier-screws [36]. The main idea is to model the flow in complex geometries by subdividing the system into geometrically simpler, interconnected elements for which analytical equations are available.…”

Section: Modeling and Simulationmentioning

confidence: 99%

“…To this end, the Carreau-Yasuda data are converted into equivalent power-law parameters. On a log-log scale, the power law is a linear function and can be considered as the tangent of the Carreau-Yasuda model at a specific shear rate [35]. It is thus possible to determine the local power-law parameters from the Carreau-Yasuda parameters as follows:npl=(η0−η∞)(ncy−1)(anormaltλtrueγ˙rep)a(1+(anormaltλtrueγ˙rep)a)ncy−1−aaη∞+(η0−η∞)(1+(anormaltλtrueγ˙rep)a)ncy−1−aa K=η∞+(η0−η∞)(1+(anormaltλtrueγ…”

Section: Modeling and Simulationmentioning

confidence: 99%

A Network-Theory-Based Comparative Study of Melt-Conveying Models in Single-Screw Extrusion: A. Isothermal Flow

2018

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In many extrusion processes, the metering section is the rate-controlling part of the screw. In this functional zone, the polymer melt is pressurized and readied to be pumped through the die. We have recently proposed a set of heuristic models for predicting the flow behavior of power-law fluids in two- and three-dimensional metering channels. These novel theories remove the need for numerical simulations and can be implemented easily in practice. Here we present a comparative study designed to validate these new methods against experimental data. Extensive experiments were performed on a well-instrumented laboratory single-screw extruder, using various materials, screw designs, and processing conditions. A network-theory-based simulation routine was written in MATLAB to replicate the flow in the metering zones in silico. The predictions of the three-dimensional heuristic melt-conveying model for the axial pressure profile along the screw are in excellent agreement with the experimental extrusion data. To demonstrate the usefulness of the novel melt-flow theories, we additionally compared the models to a modified Newtonian pumping model known from the literature.

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Application of the Network Simulation Method to Flat Dies with Inverted Prelands

Cited by 5 publications

References 11 publications

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part B. (Superimposed Drag-Pressure Flows in Extrusion)

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part B. (Superimposed Drag-Pressure Flows in Extrusion)

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part A (Pressure Flows)

A Network-Theory-Based Comparative Study of Melt-Conveying Models in Single-Screw Extrusion: A. Isothermal Flow

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