Mixing is an important technique for improving product quality in various manufacturing processes. Various mixers are used in the mixing processes of many fields including iron works, food industry, cosmetics and construction.
Among various types of mixers, a twin spiral mixer has the advantage of small volume and continuous mixing. In a twin spiral mixer, the left and right spiral wings attached to two axes rotating in opposite directions alternately work by advancing the material in one direction. First, the left spiral wing rotates and contacts material particles, advancing them and sending some of them toward the right spiral wing. The right spiral wing then approaches the position where it can contact the particles. Next, the left spiral wing releases the particles, and the right spiral wing comes into contact with them, advancing them and sending some toward the left spiral wing. Thus, in the twin spiral mixer, mixing is achieved by a simple cross action of the spiral wings that send some particles toward each other. From this mixing principle, the mixing degree in the twin spiral mixer is determined by the number of wings that interact with particles. In addition, due to the single mode of mixing, the attainable mixing degree is not high, and therefore, the length of the mixer must be long inevitably to increase the mixing degree.
Generally, various methods of structural and working parameters optimization have been widely used to improve the performance of machines and equipment. However, these methods are not sufficient to fundamentally change the performance characteristics and they have certain limitations. In the twin spiral mixer, it is also difficult to achieve the improvement in the mixing degree by optimizing the structural parameters, since the mixing process is realized by a simple cross action of the spiral wings.
Ri Song, a researcher at the Faculty of Mining Engineering, evaluated the mixing degree by simulating the mixing process of a twin spiral mixer by DEM (discrete element method) and then, based on this, he proposed a plan of increasing the mixing degree by installing inverse spiral wings at regular intervals in a twin spiral mixer to change the mixing mode.
Comparing the mixing degree for the conventional twin spiral mixer and the twin spiral mixer with inverse spiral wings, it was 0.779 7 for the conventional mode, 0.801 3 for the 2:1 mode, 0.81 for the 3:1 mode and 0.790 7 for the 4:1 mode, which means the 3:1 mode was the best, and the outputs from simulations were 89.1W, 429.7W, 287.8W and 151.5W, respectively.
You can find more details in his paper “Study on improving the mixing degree of a twin spiral mixer by changing the mixing mode using inverse spiral wings” in “Journal of the Brazilian Society of Mechanical Sciences and Engineering” (SCI).