基于动网格模型的液体动静压轴承刚度阻尼计算方法

Method for Calculating Stiffness and Damping Coefficients of Hybrid Bearings Based on Dynamic Mesh Model

针对雷诺方程不能反映高速油流周向惯性效应、轴颈周向动压效应和静压扩散效应之间的非线性耦合关系及其对三维流场特性的影响,进而导致动静压轴承刚度阻尼的计算精度难以满足高转速精密轴承设计需要之现状,提出基于纳维-斯托克斯方程的动网格计算轴承刚度阻尼新方法。该方法采用自定义程序实现轴颈的旋转速度、位移扰动和速度扰动以及扰动过程中油膜力的计算等功能,成功将轴颈的旋转动边界转换为静边界,有效避免因轴颈旋转引起的网格畸变,并利用弹簧光顺模型更新轴颈受速度扰动和位移扰动引起的油膜网格挤压变形。通过对比研究瞬态和稳态条件下油膜力的变化,界定计算刚度阻尼系数时速度扰动和位移扰动的合理取值范围。利用所提出的方法计算典型轴承的刚度阻尼系数,再现动静压轴承油膜厚度和三维流场压力分布的动态发展过程,并采用影响系数法对该轴承的刚度系数进行试验测试。通过对比试验数据和动网格计算结果发现两者基本吻合,表明所提出的计算方法是有效可行的。

For the reason that Reynolds equation is not suitable for reflecting nonlinear flow mechanics coupled by inertial effect of oil circumferential flow, squeeze effect of the journal, and diffusion effect of oil entry flow, the calculating accuracy of stiffness and damping coefficients can not satisfy optimal design of high speed bearings. A new approach of calculating stiffness and damping coefficients of journal bearings is developed based on Navier-Stokes equation. The changing oil film force, the displacement perturbation, the velocity perturbation and the rotating speed are achieved by usiug user definition function programs. The moving boundary of the journal caused by rotational movement is changed into static boundary for avoiding the grid distortion. The coordination of moving grid caused by displacement perturbation and velocity perturbation is updated by the spring smoothing theoretical model. Comparing oil film force under steady condition with those of transient processes, the value scope of displacement perturbation and velocity perturbation are defined. The stiffness and damping coefficients of a typical bearing are calculated by applying the approach combined with the perturbation theory, and the dynamic development process of oil film thickness and three-dimensional pressure distribution are achieved. Finally, an experiment is used to test the stiffness coefficients of the bearing based on the influence coefficient method, which are substantial in agreement with theoretical analysis. The results show that the numerical method is valid.