Multiphase modelling of inclusion removal by bubble adhesion in the submerged entry nozzle with centrifugal swirling flow

Abstract

The most important way to improve the quality of steel is to reduce the number of non-metallic inclusions in the molten steel, which directly affects the quality of the billet. In this paper, a novel swirling flow generator (SFG) is intended to be installed around the inlet of the submerged entry nozzle (SEN) in the tundish to generate a centrifugal swirling flow by utilising gravitational potential energy. The discrete phase model and volume of fluid were adopted to simulate the motion and interaction between bubbles and inclusion particles in a rotating flow field. In the centrifugal swirling flow, collision behaviour between the inclusions and bubbles is considered by a self-developed user-defined function program. Computational fluid dynamics (CFD) simulation results show that the radial pressure gradient is favourable for the inclusion and bubble to move towards the centre, and the more number of blowing ports, the easier the bubbles move to the centre of the SEN, which greatly increases the collision probability between inclusions and bubbles. The application of the SFG could significantly improve the removal efficiency of inclusions. Therefore, it is more advantageous to eliminate the inclusions by injecting air bubbles into the swirling flow field.