Detecting mixing barriers in Twin-Screw extruder elements via Lagrangian Coherent Structures

Bauer, Hannes; Khinast, Johannes

doi:10.1016/j.ces.2022.118069

Cited by 7 publications

(2 citation statements)

References 57 publications

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“…However, for certain materials, such as shear-sensitive ones, shear flow fields can induce excessive shear viscosity heating [7] and damage fibrous components [8], significantly compromising material properties. Research indicates that, under similar stretching or shearing rates, extension-dominated flow mixing exerts twice the maximum force on solid particles compared to shear flow mixing [9][10][11]. Consequently, extension-dominated flow mixing offers higher dispersion efficiency and more effective dispersion effects, albeit with greater difficulty in acquisition and control compared to shear flow fields.…”

Section: Introductionmentioning

confidence: 99%

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

Guo,

Liu,

Hao

et al. 2024

Applied Sciences

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The challenge of mixing high-viscosity materials is a common issue encountered in the manufacturing process of food materials. The advantages of the internal meshing screw mixer have led to its adoption in various manufacturing processes, but it has yet to be implemented in the food industry. The paper presents a design method for an internal meshing screw mixer based on kinematic principles. The mixer features a helical chamber created by alternating volumes formed by the stator and rotor, establishing an extension-dominated environment for mixing high-viscosity fluids. A kinematic model based on the internal cycloid principle was established, providing trajectories and equations for key points on the rotor, simulating both its rotation and revolution processes, and revealing the velocity variations at different points on the rotor. Based on the kinematic analysis results, a stator and rotor design method was developed according to relevant functional divisions. To achieve the desired motion effects, transmission and support devices were designed, and the relationship between the transmission device and the internal cycloid surface of the fixed rotor was established. The mixer’s application and mixing effectiveness in the food industry were validated using corn syrup and flour. Experimental results showed that the extensional mixer described in the paper effectively mixed high-viscosity fluids while also efficiently blending fine powders. Slurry viscosity was tested with a rheometer at different speeds with an eccentric rotor mixer. Results showed that viscosity decreased with increasing shear rate, with a more pronounced decrease at higher shear rates. The apparent viscosity trend remained consistent at different speeds, although variations were observed at lower shear rates, especially concerning speed. The non-Newtonian fluid index exhibited minimal variations at different speeds, while the consistency coefficient showed significant fluctuations. The mixing uniformity index of the slurry was used to evaluate the mixing uniformity and dispersion uniformity of this extensional mixer. At different rotational speeds, the density of the slurry changes little. The uniformity index of mixing decreases gradually with the increase of rotational speed, reaching its maximum at 15 r/min. The overall trend of the uniformity index decreases with increasing rotational speed, indicating a decrease in density uniformity. A peak appears at 45 r/min, possibly due to the maximum values of elongation rate and shear rate at this speed. As the rotational speed increases, the residence time of the material in the mixer decreases, which may be the main reason for the decrease in mixing uniformity. These findings provide valuable insights into the design and utilization of extension-dominated screw mixers within the food industry, laying a solid foundation for future research and practical applications in this field.

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Section: Introductionmentioning

confidence: 99%

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

Guo,

Liu,

Hao

et al. 2024

Applied Sciences

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“…Co-rotating twin-screw extruders (TSEs) are widely used in polymer, food, and pharmaceutical industries. − Their main features are that twin screws are symmetrical, are of modular design, and have good conveying and mixing capacity for highly viscous fluids. , The ATSEs are recently developed . They maintain the intermeshing function of the classical (symmetrical) twin screws while providing materials with more stretching and compression due to periodic volume compression in the screw channels.…”

Section: Introductionmentioning

confidence: 99%

Residence Time Distribution in an Asymmetrical Twin-Screw Extruder

Yu,

Zhao,

et al. 2023

Ind. Eng. Chem. Res.

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Residence time distribution (RTD) is an important parameter for characterizing axial conveying and mixing in a twinscrew extruder (TSE). This work studies the RTD and flow patterns in an asymmetrical TSE (ATSE) using a transparent barrel for visualization. The RTD of an aqueous solution of sodium carboxymethyl cellulose is measured by using red fine sand particles as tracers, collecting them by a moving thin film at the die exit, and counting them for further statistical calculation. The effects of the screw configuration, screw speed, and feed rate are considered. When the geometrical dimensions and operating parameters are identical, the mean residence time t ̅ in the ATSE is larger than those in a classical (symmetrical) TSE. This is a signature of backflow occurring in the intermeshing regions through the radial gaps between the low flight and the inner wall of the barrel. It is confirmed by particle image velocimetry. Moreover, a response surface model is developed to quantify the effects of the screw configuration and operating parameters on t ̅ .

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Comparison of mixing mechanism under different rotating directions in a horizontal self-cleaning differential rotating twin-shaft kneader

Cheng¹

2023

Chemical Engineering Journal Advances

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Detecting mixing barriers in Twin-Screw extruder elements via Lagrangian Coherent Structures

Cited by 7 publications

References 57 publications

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

Kinematics-Based Design Method and Experimental Validation of Internal Meshing Screw for High-Viscosity Fluid Mixing

Residence Time Distribution in an Asymmetrical Twin-Screw Extruder

Comparison of mixing mechanism under different rotating directions in a horizontal self-cleaning differential rotating twin-shaft kneader

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