Bubbling to Jetting Transition during Argon Injection in Molten Steel

Bubbling to Jetting Transition is of the outmost importance in metallurgical processes given that the flow regime influences the refining rates, the refractory erosion, and the blockage of injection nozzles. Bubbling to jetting transition during subsonic bottom injection of argon in molten steel is studied here. The effect of the molten steel height, the injection velocity, the nozzle diameter, and the molten steel viscosity on the jet height and the bubbling to jetting transition is numerically analyzed using Computational Fluid Dynamics. Five subsonic argon injection velocities are considered: 5, 25, 50, 100 and 150 m/s. Three values of the metal height are taken into account, namely 1.5 m, 2 m and 2.5 m. Besides, three values of the nozzle diameters are considered: 0.001 m, 0.005 m and 0.01 m. Finally, three values of the molten steel viscosity are supposed: 0.0067, 0.1 and 1 kg/(m·s). It is observed that for the argon-molten steel system, the bubbling to jetting transition occurs for an injection velocity less than 25 m/s and that for the range of viscosities considered, the molten steel viscosity does not exert significant influence on the jet height and the bubbling to jetting transition. Due to the jet instability at subsonic velocities, a second transition, namely jetting to bubbling, is appreciated.

SLIP VELOCITY MODEL OF POROUS WALLS ABSORBED BY HYDROPHOBIC NANOPARTICLES SIO_2

According to new slip effects on nanopatterned interfaces, the mechanism of enhancing water injection into hydrophobic nanomaterial SiO2 was proposed. When Hydrophobic Nanoparticles（HNPs）are adsorbed on surfaces of porous walls, hydrophobic nanoparticles layers are formed instead of hydrated layer, and slip effects appear on the pore wall when a driving pressure is applied to the rock cores sample. It makes fluid to move more quickly and the flow capacity increases greatly. Experiments on changing wettability of porous walls were conducted, and the phenomenon that porous walls surfaces were adsorbed by nanoparticles was validated with the Environment Scan Electron Microscopy（ESEM）. The results of displacement experiments show that flowing resistance is greatly reduced, and water-phase effective permeability is increased by 47 % averagely after being treated by nanofluid. These results indicate that the slip effect may occur on nanoparticle film of porous walls. Based on this new mechanism of enhancing water injection about hydrophobic nanomaterial SiO2, a slip velocity model in uniform porous media was introduced, and some formulas for the ratio of slip length to radius, slip length ,stream slip velocity and flux increment were deduced. and calculated results indicate that the ratio of slip length to radius is about 3.54%-6.97%, and the slip length is about 0.024 μ m -0.063 μ m. The proposed model can give a good interpretation for the mechanisms of enhancing water injection with the HNPs.