铸件在凝固过程中的传热和自然对流计算

论文中以流函数、涡度和温度为基本变量,建立了铸件凝固时的传热和自然对流的数学模型。控制方程采用半隐式有限差分在固定网格上求解。在模型建立过程中,着重讨论了潜热的处理和固液相区(界面)速度条件。对于潜热处理,采用了基于合金平衡相图的比热焓法;对于固液相区(界面)速度条件,提出了一种新的、基于固相率进行修正的处理方法。另外还探讨了将本文提出的解法应用于复杂几何条件的可能性。最后,通过对一个典型例子进行计算,对自然对流对铸件凝固的影响作了深入的讨论。

HEAT TRANSFER AND NATURAL CONVECTION COMPUTATION FOR THE SOLIDIFICATION PROCESS OF CASTINGS

A mathematical model using stream function, vorticity and cemperature as basic varibles is developed to represent the heat transfer and natural convection in the solidification prooess of castings. The solutions of the governing equations are carried out by means of a semi-implicit finite difference scheme based on fixed grid methodology. Consideration is given to the latent heat evolution and velocity conditiion in the liquid-solid phase zone(inte-rface).A specific enthalpy method associated with the alloy equilibrium phase diagram is employed to account for the latent heat of phase change. A new revision approach according to solid fraction is proposed for the treatment of the zero velocity condition as liquid region turns to solid. Moreover, the possibility of applying the present model to the problems of irregular geometries is discussed. In the last part of the paper, a tpyical freezing problem is solved, and the influence of natural convection on the solidification of castings is analysed in detail.