Numerical Simulation of Molten Steel with Gas Bubbling in Water Model of Slab Continuous Casting Mold

Gas blowing into molten steel at slide gate during continuous casting can prevent clogging of the submerged entry nozzle. At the same time, however, the liquid flow field is affected by gas flow and sonic of bubbles are even entrapped on the solidified shell to form internal defects in steel products. The gas-liquid two-phase flow was studied with water model to acquire the flow rule for the solution of products quality problem. The water flow in slab continuous casting mold with gas blowing was invested by using numerical simulation, high-speed video camera measurement and image processing. The phenomena of liquid flow without gas blowing and with gas blowing were analyzed comparatively to obtain the movement rule of bubbles and liquid flow. The gas phase affects liquid flow field including the vortex position, surface fluctuation and impact depth of outflow from submerged entry nozzle. On one hand, the increase of gas-liquid ratio will lead to the change of the vortex position intensification of surface fluctuation and shortening of the impact depth due to slower impact velocity. On the other hand, when the liquid flow rate is increased, the bubbles quantity which is trapped down into the lower vortex zone increases with longer traveling distance. The movements of bubbles with different diameters are different in the liquid field. Both the distance in the horizontal direction and penetration depth in the vertical direction extended for smaller bubbles. In the upper vortex zone, most of the bubbles follow 'L' shape movement tracks while their movement rule in the lower vortex zone is complicated and revolves around the vortex center repeatedly. The center at the upper vortex zone is lifted up due to the bubbles buoyancy. The bubbles weaken the turbulence fluctuation of water flow not only in velocity direction but also in its value. The decrement degree of velocity can be observed at the free surface and narrow surface of the mold. The gas-liquid two-phase flow simulated numerically by discrete phase model agrees well with experimental flow fields measured with high-speed video camera.