Research of the homogenization process in the operation of a three-level closed turbine mixer

Abstract

The object of research is a three-level turbine mixer of the closed type, designed and manufactured in full size using a 3D printer.

One of the most problematic places of the fermentation process in a bioreactor is the homogenization of the medium. During mixing, stagnant zones form in most fermenters, in these zones the medium is heterogeneous, warms up worse, receives insufficient air (if the medium is aerobic) and causes the death of cultivated microorganisms. Thus, the final product is not 100 % of the same structure, and, accordingly, quality, which is critical for pharmaceutical products.

In the course of the study, 2 different methods were used, which were designed to confirm or refute each other, namely: the computer simulation method and the experimental method. The experiment consists in manufacturing the developed mixer model and carrying out the mixing process with its use. Mixing is carried out at different velocities, with different types of mixers and using a contrast tracer to visualize the type of formed streams. Graphical modeling consisted of creating a similar experimental model of the mixer and carrying out graphical modeling in the CFX block of the ANSYS program. This method makes it possible to see the created flows from different angles, find the most dynamic zones and study the physics of the process from the inside.

The obtained result shows that a three-level closed turbine mixer shows better homogenization speed results than a typical closed turbine. This is due to the fact that the proposed solution has a number of features, in particular, the cellular structure of the shaft. The proposed computational models in ANSYS make it possible to obtain velocity fields and establish the magnitude and direction of velocity vectors.

A similar technique for evaluating the effectiveness of homogenization can be used in the design of new designs of mechanical mixing devices.