半固态浆料制备过程的电磁热流体数值模拟

Numerical simulation on electromagnetic,thermal and fluid fields in preparing process of semi-solid slurry

为了优化半固态浆料制备工艺,针对低频电磁搅拌半固态浆料制备系统,建立了电磁热流体数学模型,并在给定的定解条件下,利用ANSYS软件进行了电磁场、流场以及温度场的耦合数值模拟.结果表明,磁感应强度的径向分量大于切向分量,因此,电磁力的切向分量远大于径向分量,并且电磁力随励磁电流强度和频率的增加而增大;浆料速度的切向分量远大于径向分量,边界无滑移使得浆料切向速度近似呈抛物线分布;电磁搅拌使得浆料外半径处的温度梯度加大,而内半径附近出现了等温区,并据此给出了电磁搅拌有助于制备等轴细晶半固态组织的一个物理解释.

In order to optimize the preparation technology of aluminum alloy semi-solid slurry,a coupled mathematical model of electromagnetic, thermal and fluid fields was established for low-frequency electromagnetic stirring semi-solid slurry fabricating system. Under the given initial and boundary conditions,the electromagnetic,fluid and thermal fields were simulated using ANSYS software. The simulation results indicate that the radial component of magnetic flux density is larger than the tangential component,and thus the Lorentz force in tangential direction is larger than that in radical direction. With increasing the intensity and frequency of excitation current,the Lorentz force gets increased. The flow velocity of stirred slurry in tangential direction is significantly larger than that in radial direction,and the radial velocity of the slurry exhibits a near parabolic distribution due to the non-slip of boundary. The electromagnetic stirring increases the temperature gradient at outer radius of the slurry,and the isothermal zone appears near inner radius. Thus,a physical explanation for electromagnetic stirring to be helpful in preparing semi-solid slurry with equiaxed fine grains is given.