Modelling of Inclusion Motion and Flow Patterns in Swirling Flow Tundishes with Symmetrical and Asymmetrical Structures

Swirling flow tundish (SFT) has recently been developed as a new type of tundish. Its key mechanism is forming swirling flow to enhance inclusion removal from steel for high quality slab casting. This is achieved by guiding the liquid steel into the tundish through the tangential inlet of a cylindrical swirling chamber (SC). This can restrain and alleviate the turbulence of the impact zone. SC has been settled into two types of tundishes-originally symmetrical and asymmetrical. To understand the fundamentals, physical and mathematical modellings of this new process have been conducted in this work. Physical modellings are carried out with the utilization of an asymmetrical one-strand 1 : 2.5 and a symmetrical two-strand 1 : 3 scale models. The internal flow is measured by digital particle image velocimetry (DPIV). Numerical modelling is carried out in line with the physical modelling to examine the details of the flow patterns and rotational effect caused by the SC. The trajectories of non-metallic inclusion particles are also studied by discrete phase model (DPM) within the commercial CFD package environment, FLUENT. The mathematical model proposed is validated by comparing the predicted and measured residence time distribution and velocity fields. The results show that both originally symmetrical and asymmetrical flow fields have been changed to asymmetrical ones after setting SC into it. And the results show that the flow is slower behind the dam and weir. Examinations of the trajectories of inclusion particles suggest that the inclusion removal capacity of the SFT is higher than the tundish with a turbulence inhibitor (TI). From the separation ratio results, it can be seen that SFT has higher ability to remove small inclusion particles than a tundish with TI, which is of great significance especially for production of high-quality steel.