Numerical and experimental investigation of stationary and transient flows in tundishes
Since investigations of the real melt flow in the steelworks are not feasible due to the extreme boundary conditions and the lack of optical accessibility, these investigations were carried out in compliance with the characteristic similarities on a reduced water model distributor on a scale of 1:1.7. Laser Doppler anemometry and particle image velocimetry were used as measuring methods. The numerical calculations were performed with the commercial flow solver FLUENT based on the RANS equations.
The numerical and physical simulation of the stationary casting showed that very heterogeneous areas with strong vortices are present in the tundish. The dominant vortex structure is a horseshoe vortex, which lies around the shadow tube beam and is preserved up to the outlet area, where it rests on the tundish base. With regard to flow intensities, the manifold can be divided into three zones, the inlet zone to x/L1 < 0.3, the central zone 0.3 < x/L1 < 0.6 and the outlet zone x/L1 > 0.6. The inlet zone is characterized by a high internal recirculation, which characterizes it as “well-mixed”; in the x-direction, the internal recirculation decreases.
Transient casting is investigated using the ladle change as an example. The results show that with the omission of the input impulse, the vortex intensity in the distributor rapidly decreases. Backflow is completely suppressed so that a piston flow occurs in the manifold. After casting on the new ladle, it takes approx. Δθ = 0.12 until the structures known from stationary casting are restored. The velocities and thus also the backflows in the manifold are considerably higher when casting the new ladle than when stationary casting, but this still has to be quantified.
The comparison between the experimental and numerical investigations carried out for both stationary and transient casting shows that with FLUENT it is possible to reproduce the flow in the continuous casting distributor in a reasonable way. However, it is important to use realistic boundary conditions. In transient casting, this means that even programmed boundary conditions are integrated into the model.
The project was funded by the Deutsche Forschungsgemeinschaft (DFG) under the reference number PF 394/2-1.