超重力场下钢液中夹杂物上浮行为的数值模拟

 超重力技术可以有效提高固液两相间的重力差,在冶金领域,超重力场的引入可以大幅度增加金属熔体中夹杂物的去除效率。基于超重力冶金装置模型,根据动网格与流-固耦合理论,建立了不同重力场下固态夹杂物在钢液中上浮的流体动力学模型。该模型模拟了夹杂物在不同系数的重力场中上浮的运动状态,研究了超重力场中的重力系数与夹杂物尺寸等因素对颗粒上浮和流场分布的影响。模拟结果表明,在重力场系数恒定时,夹杂颗粒经短暂的加速上浮过程后,后续的上浮运动将趋于匀速,夹杂物的上浮速度会随着施加重力场的增大而增长,夹杂物附近的钢液也会被更快地“推开”,从而出现改变流动状态的趋势。尺寸d为1、10 μm的夹杂物颗粒由于其尺寸较小,在施加一定的超重力场后仍满足Stokes上浮模型;尺寸d为100 μm的大尺寸夹杂物则仅在约10倍重力场作用下符合Stokes上浮模型,当施加更大的重力场时,夹杂物附近的流场会由层流流动转变为湍流流动,不再满足Stokes定律。在研究不同系数重力场中夹杂物上浮的模型时发现,当重力场的系数大小随时间变化时,尺寸为1 μm量级的小尺寸夹杂上浮速度的变化幅度与重力场的变化幅度呈正比;而尺寸为10、100 μm的夹杂物在脱离层流流场后,上浮速度与重力场不再呈线性关系。

Numerical simulation of inclusions floating behavior under supergravity field in liquid steel

Supergravity can significantly increase the gravity difference between solid-liquid phases, and the removal rate of inclusions in molten metal can be greatly accelerated. The study was based on the supergravity metallurgy device to establish computational fluid dynamics model of solid inclusions in the liquid steel in different gravity fields, according to the dynamic mesh and flow-solid interaction. The model simulated the floating motion state of inclusions in the gravity fields with different gravity coefficients, and studied the influence of factors such as the supergravity coefficient and size of inclusions on the floating behavior and flow field distribution. The simulation results indicate that the inclusions tend to be steady movement after a short acceleration with the constant gravity coefficient, the extension of supergravity field will cause the increase of floating speed of inclusions and the liquid steel near the inclusions will be “push away” quickly, then the flow state of liquid steel has been changed. Inclusion particles with d=1, 10 μm are still satisfied with the Stokes flow law under the certain supergravity field since the size of particle is small. The large size inclusions of d=100 μm only compliant with the Stoke flow Law when the gravity coefficient is below ten times. With the lager gravity field is applied, the nearby flow field changes from laminar flow to turbulent flow, and the Stokes float law is no longer suited. When studying the model of inclusion floats in gravity fields with different gravity coefficients, it is found that the change of floating velocity for d=1 μm inclusions is directly proportional to the change of gravity coefficient when the coefficient changes with time. After the lager inclusions such as d=10, 100 μm are not consistent with the laminar flow field, the floating velocity is no longer in a linear relationship with the gravity field.