ABSTRACT
Understanding the behavior of the oscillations of the jets into the mold of thin slab funnel is essential to ensure a constant supply of liquid steel, improve control of the flow patterns and consequently increase plant productivity and the final product quality. To achieve this, we conducted a study of the effect of the internal design of the nozzle on the fluid dynamics of the mold, trying to determine the origin of the oscillations of the jets. Use of mathematical and physical simulation was done to study these phenomena.
For the mathematical modeling it resorts to the fundamental equations, the RSM turbulence model and VOF multiphase model. The governing equations are discretized and solved by iteration-segregated implicit method implemented in FLUENT®.
The results of the mathematical simulation are showing that even for a nozzle designs with a stable operational performance, the oscillations of the jets remain present and become more intense for high casting speeds and deeper nozzle. The analysis of each of the simulated nozzles show that the internal geometry causes flow disturbances in areas where the internal cross-sectional areas change, generating high and low dynamic pressures and promoting a tendency for the liquid steel to exit preferably by one of the ports. A delicate balance of forces, in the order of micro-scales, was found and is given on the tip of the internal bifurcation of the nozzle. This balance is related to the fluctuating speeds and the ferrostatic pressure. If this balance is broken the oscillations are more severe, causing permanent changes in the mass flow rate from one port to another. In addition, it was found that there is continuous formation of a vortex path which is generated from the separation of the boundary layer on the splitter ports, a phenomenon that intensifies the periodic oscillation of the jets
Keywords
Nozzle design; mathematical simulation; funnel thin slab caster; jet oscillations; turbulence
