Моделирование течения белково-минеральной кормовой смеси в шнековом канале экструдера

Abstract

Выполнено численное моделирование течения белково-минеральной кормовой смеси в канале одношнекового экструдера с учетом особенности течения высоковязкой дисперсной системы, заключающейся в наличии скольжения на границе вязкого подслоя. Получены профили скоростей течения в поперечном сечении шнекового канала в зависимости от его геометрии и физических характеристик экструдируемого продукта. Показано, что учет скольжения на границе вязкого подслоя приводит к тому, что эктрудируемый продукт преимущественно перемещается вблизи гребня шнека.

Within the framework of the joint research of the Republic of Kazakhstan and the Kharkov State University of Food Technology and Trade the proteinmineral fodder additive is were developed, which includes animal and vegetable raw materials. The peculiarity of extrusion technology is that the initial moisture content of raw materials should not exceed 25–30%. As a result, we obtained the highly viscous disperse system, which belongs to the class of non-Newtonian fluids. It is known that the rheological characteristics of non-Newtonian fluids significantly changes the flow pattern in the barrel of an extruder, as a result the calculation of its optimal geometry and productivity is a complex physical and mathematical problem. This paper is devoted the numerical simulation of the flow of proteinmineral fodder additive in a screw channel of extruder with features high-viscosity disperse systems. In this paper we consider a more general case of flow in an auger channel of the extruder that takes into account a two-dimensional flow in the conditions of sliding a high-viscosity dispersed mixture. It is shown that the presence of the slip at the boundary of the viscous sublayer, which are charactering for such disperse systems, leads to the fact that the extruded product is predominantly displaced near the crest of the screw. This fact is illustrated by the obtained profiles of flow velocities in the cross section of the screw channel, depending on its geometry and the physical characteristics of the extruded product. The obtained results will allow further accelerating the design and calculation of the extruder in order to obtain the developed protein-mineral fodder additive, replacing some of the more expensive and technically complex experiments by computer modeling.