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2019 (published: 11.06.2019)
Home > Issue > Determination of geometrical parameters of the turns of a twin-screw extruder press for the production of vegetable oils
Determination of geometrical parameters of the turns of a twin-screw extruder press for the production of vegetable oils
A new method of obtaining ecologically pure edible vegetable oils was investigated, i.e. pressing in a press-extruder with two synchronously rotating screws. Its advantages include good mixing of the material, self-cleaning screws, short residence time, and good sealing of the product in the channel. The aim of the study was to determine the throughput of the turns of the extruder based on 3D modeling of equivalent dimensions of rectangular channels formed by turns of a twin-screw press. We used the methods of mathematical modeling hydrodynamics for a two-dimensional field of plane-parallel stationary Couette flow velocity potential, which makes it possible to use the extraction in capillary-porous bodies in the extraction of edible vegetable oils. It was determined that the obtained numerical solution is characterized by the absence of oscillations, which is characteristic of a theoretical dependence. It is provedthat an analytical solution using hyperbolic functions results in the accumulation of rounding errors when using a significant number of terms of this series. The presence of hyperbolic functions in the analytical solution results in a significant computational error, which is expressed in the oscillation of the solution near the fixed boundary of the region of solution existence. As a result of the research, an estimate of the channel capacity was obtained taking into account the output device resistances. The main conclusion is the use of the integral characteristics of the turns to determine the transporting capacity of the extruder part of the press taking into account the modulus of the velocity gradient of the layered flow in the screw channel, the effective viscosity of the material, and the hydraulic interaction of the turns based on the continuity of the flow of the viscous-plastic material in the turns channels. As a result, the flow-pressure characteristics of the extruder part were determined and an iterative algorithm was proposed that allows predicting the hydraulic forces developed by the press according to the geometrical parameters of the turns and the rheology of the material during the press operation.
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Keywords: edible vegetable oils; hydrodynamics of laminar flows; viscous fluid; biphasic mixture; mathematical model; pressing; screw press; extrusion.
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