A new RMF stirrer design to reduce mixing time

Abstract

The goal of this study is to develop an FPGA-based new rotating magnetic field (RMF) stirrer system that would reduce mixing time. To achieve this goal, it has been suggested that, unlike the literature, the mixing process is performed not only by a single magnetic fish rotating at the center but also by multiple magnetic fish rotating at symmetric positions. As the first step within such scope, ANSYS Maxwell® simulation software was used to design a stirrer core capable of realizing said proposition. The design was subsequently manufactured, and RST coils were wound. Being completed by the manufacturing of the electronic circuit to drive the coils, RST phases of the stirrer system were fed by PWM voltage with a phase difference of 120◦. The myRIO® embedded system made use of the FPGA structure to control phases sequentially, generate PWM signals, and define the increment range for phase frequency. The ARM microprocessor structure of the myRIO® embedded system was utilized in the system for Adaptive control method. Programming of the myRIO® embedded system was achieved through the developed graphic-based LabVIEW® software. When the system was driven at 100% duty cycle, the magnetic force provided by the stator caused four magnetic fish with a 90◦ angle to each other to act as rotors, with two of the reciprocal magnetic fish rotating clockwise while the other two rotating counterclockwise. This enabled the mixing process to be more homogeneous and to be completed in a shorter period of time. Findings suggest that mixing time for water has been reduced by 35% in average. Experimental results on the structure, control and effects on reduction of mixing time of the RMF stirrer system developed within the scope of the study has been discussed in detail.