Scientific journal NRU ITMO
Series "Processes and Food Production Equipment"
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March 2021 (published: 25.03.2021)

Number 1(47)

Home > Issue > Influence of the material reverse flow process on the regularities of pressure formation along the length of the screw surface of extruders

UDC 519.68:532.7:541.8:541.182.41

Influence of the material reverse flow process on the regularities of pressure formation along the length of the screw surface of extruders

Pelenko V.V., Verkholantsev A.A., Verboloz A. P., Demchenko V.A., Usmanov I.I., Xia Chenguang

In the present work, the problem of describing the law of increase in the internal screw pressure of a solid material along the length of the screw surface of the extruder is posed and analytically solved, depending not only on the distributed friction forces and concentrated resistance forces of the counter-rotation ribs made on the inner surface of the extruder body, but also taking into account the process of "sluicing" – backflow of material, which significantly affects the formation of the pressure field. The obtained mathematical model allows to substantiate the design and technological parameters of extruders and grinders more correctly. The complexity of the material movement in screw aggregates during its transportation, extrusion, and cutting is caused not only by the complex screw shape of the channel, but also by the influence of a large number of variable technological parameters, structural elements of the mechanism, as well as many factors of a physical, mechanical, and rheodynamic nature. In particular, the processes in two characteristic zones of the screw space, which are fundamentally different in physical conditions, are structured and analytically described by differential calculus methods in the study. The first zone is determined by the absence of the "sluicing" process with an increase in the internal screw pressure from the initial value of Po to the value of Psh, which causes the beginning of the reverse flow of the material. In the second zone of the screw auger, the process of "sluicing" takes place with an increase in pressure from the value of the onset of the reverse current Psh to the pressure Pe of extrusion of the material through the openings of the outlet grinder. In this second zone, the nature of the product flow and the record of the differential equation of material movement change significantly. Based on the obtained mathematical model for the law of pressure distribution along the length of the screw surface, the design and technological characteristics of extruders can be optimized to reduce the energy consumption of materials grinding processes.
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Keywords: mathematical description; differential equation; pressure change law; extrusion; reverse flow; screw surface

DOI 10.17586/2310-1164-2021-14-1-15-24

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