Mixing Characteristics of an Axial-Flow Rotor: Experimental and Numerical Study

In the metallurgical industry, various types of rotors are used for the injection and distribution of gas and for homogenizing molten metal. In the present work, the liquid-gas two-phase flow around an axial type impeller is studied in a water model, in order to analyze the bubble break-up and coalescence and metal mixing. Details like primary and secondary vortex structure, gas flooding between the blades and gas dispersion are recorded by using high speed photography.A mathematical model that takes into account the combined effect of bubble break-up and coalescence is implemented in the commercial computational fluid dynamics (CFD) software FLUENT. In the proposed work, the impeller is explicitly described in three dimensions using Multiple Reference Frame Model. Dispersed gas and bubbles dynamics in the turbulent water are modeled using an Eulerian-Eulerian approach with dispersed k-epsilon turbulent model. The model predicts spatial distribution of gas hold-up, average bubble size and flow structure. Good qualitative agreement between physical model and simulation is achieved when comparing the bubble size distribution, flow structure and mixing.