Numerical Simulation Of Interface Transport Behavior On Steel/Slag Melt Droplet

The impact phenomena of the melt droplets exist widely in the steel-making process.Studies on the impact and the coalescence behavior of the melt droplets would not only enrich mass and heat transfer knowledge of the multiphase flow,but also clarify the interface behavior of the melt droplets.More importantly,it would provide the guidance strategy for improving the smelting effect of the steel-making process.The main conclusions were listed as follows:The impact on the dry wall and the wet wall of single/double melt droplet was simulated using the VOF method.The results show that when the melt droplet impacts on the horizontal dry surface,the rebound/breakage phenomena were observed.The spread diameter of the melt droplet increases with the impact speed.When the impact velocity is 2.0m/s,the maximum spreading factor of the droplet is5.24,and the fracture appears at 4.1ms.When the melt droplet impacts on the wet wall,it would splash.Thinner the thickness of the melt film,more obvious splashing jet and higher splashing height.When double melt droplets impact on the wall,the air entrainment in the jet region was found.Smaller the horizontal separating distance,higher jet height.The maximum jet height is 2.63 mm when the horizontal spacing distance is 12 mm.Numerical simulation of the coalescence behavior between two stationary melt droplets was carried out.The results show that the inertial force and the viscous force alternately dominate the coalescence behavior of the melt droplets with the same surface tensions.This leads the melt droplets periodically oscillate and gradually decline.The maximum average velocity in the region reached at 0.023m/s when the surface tension of melt droplet is 1.6.In addition,Marangoni effect was observed during coalescence process of the melt droplet with different surface tensions.Besides,the melt droplets would move forwards due to the surface tension gradient.At the same time,the melt droplet with large surface tension would have a tendency to wrap around the melt droplet with small surface tension.Considering the heat transfer of the melt droplets,numerical simulation of heat transfer process between the melt droplet and the wall was made.The results show that the mainly heat transfer between the melt droplet and the wall appears in the contact zone.Reducing the entrained air would significantly improve the heat transfer efficiency of the melt droplet.Greater the wall temperature difference,the higher the wall heat flux.The spreading properties of the melt droplet correspond to the heat transfer characteristics.Increasing the impact speed significantly enhances the heat transfer effect.The maximum heat flux density is 273kw/m² when the impact velocity is 3m/s.The decarburization model of the melt droplet was established using FLUENT UDF.The gas phase diffusion is dominant during the decarburization process of the melt droplet.There is a vortex region near the downstream of the melt droplet,and the size of the vortex is related to the inlet gas velocity.Increasing the inlet gas velocity,the gas phase temperature,or the CO₂ mole fraction would accelerate the decarburization rate of the melt droplet.The inlet gas flow rate is increased from 0.5m/s to 1.5 m/s when the decarburization rate is increased from 0.15 wt%/s to 0.22wt%/s.When the inlet gas velocity is 1873 K,the decarburization rate is increased by0.07wt%/s.When the CO₂/Ar ratio in the inlet mixture gas is 0.2,the decarburization rate is increased by 0.09 wt%/s.