浸入式水口内壁特征对边界层流场结构和氧化铝夹杂物运动行为的影响

Effect of submerged entry nozzle wall surface morphologies on boundary layer structure and alumina inclusions transport

铝镇静钢液浇注过程中,浸入式水口耐材内壁特征受到钢液侵蚀和夹杂物聚集影响,从近光滑壁面逐渐向多孔耐火材料壁面和含结瘤物的粗糙结瘤壁面转变,壁面形貌的变化影响边界层流场结构和氧化铝夹杂物的输运.采用物理模拟的方法在浸入式水口模型内壁镶嵌多孔耐火材料结构和含结瘤物耐材壁面结构,结合粒子图像测速技术研究不同特征壁面附近流场边界层.使用MATLAB耦合流场测速结果和氧化铝夹杂物运动数学模型,研究了不同特征壁面的流场边界层中氧化铝夹杂物的运动轨迹.使用象限分析法确定了浸入式水口边界层流场存在上抛和下扫事件.氧化铝夹杂物位于下扫事件区域时,朝向壁面运动,粒径为1μm的氧化铝夹杂物在下扫事件中运动轨迹更接近壁面,增加了沉积的可能性;氧化铝夹杂物位于上抛事件区域时,远离壁面运动.多孔耐火材料壁面和结瘤壁面边界层内氧化铝夹杂物运动幅度大于光滑壁面边界层流场内氧化铝夹杂物运动幅度.壁面状态由近光滑壁面转变为多孔耐火材料和结瘤壁面时,流场边界层中下扫事件平面占比由10.17%增加到39.77%,上抛事件平面占比由32.96%减小到9.24%;同时,流场边界层中下扫事件发生的概率由25.83%增加到28.24%,这将加速氧化铝夹杂物在多孔耐火材料和结瘤壁面的沉积进程.

During the Al-killed steel continuous casting process,the molten steel corrosion and the accumulation of alumina inclusion deposits affect the submerged entry nozzle(SEN)wall surface,including the surface morphologies of the smooth wall,porous refractory wall,and clogged wall.The SEN wall surface morphology affects the boundary layer structure and alumina inclusions transport.In this study,a physical modeling method was adopted,and the surface morphologies simulation was realized by filling up the natural porous refractory material and inserting the real clog material in the polymethyl methacrylate SEN model.The velocity in the boundary layer was measured using the particle image velocimetry(PIV)technology,and the alumina inclusions transport path in the boundary layer was calculated by MATLAB software.The MATLAB codes combined the velocity data from the PIV measurement results and the inclusion transport equation.The four-quadrant analysis showed that sweep and ejection events existed in the boundary layer.The fluctuations of the velocity and the turbulent kinetic energy in the normal direction were increased in the porous refractory and the clogged wall boundary layer when the sweep and ejection events existed.The transport of the alumina inclusions with a diameter of 1-15μm was affected by the ejection and the sweep events.The alumina inclusions moved toward the boundary in the sweep event.During the sweep event,the transport path of alumina inclusions with 1μm diameter was close to the boundary;the alumina inclusions were more easily attached to the boundary.The alumina inclusions escaped from the boundary in the ejection event.In the porous refractory and the clogged walls,the alumina inclusion transport path in the normal direction was increased.When the SEN wall’s morphologies changed from smooth wall to porous refractory wall and clogged wall,the sweep event area proportion increased from 10.17%to 39.77%,and the ejection event area proportion decreased from 32.96%to 9.24%.Moreover,the sweep event’s probability increased from 25.83%to 28.24%when the morphologies of the SEN wall changed from smooth wall to porous refractory wall and clogged wall,which will increase the alumina inclusion deposition rate in the porous refractory wall and the clogged wall boundary.