随机粗糙表面对非牛顿磁流体轴承润滑性能的影响 *

Effectsof Random Surface Roughnesson Lubrication Performanceof Journal Bearing Lubricatedwith Non-New

关键词:  磁流体轴承  应力偶  粗糙表面  随机广义雷诺方程  润滑特性

Key words:  Magnetic fluid bearing  Couple stress  Surface roughness  Stochastic generalized Reynolds

摘要:

为了研究应力偶效应和粗糙表面形貌效应对磁流体轴承润滑性能的双重影响，首先采用蒙特卡罗方法对具有高斯分布的随机粗糙表面进行表征，并与扫描电子显微镜下实际加工表面形貌图进行对比，同时基于 Christensen随机模型和 Stokes微连续理论，推导出随机广义非牛顿雷诺方程，通过有限差分法对微尺度条件下磁流体轴承进行数值模拟，分析横向和纵向粗糙模型下不同参数对磁流体轴承润滑特性的影响。结果表明:实际的工程粗糙表面具有各向异性；不同粗糙模型对承载性能的影响趋势与宽径比有关，当粗糙度参数为 0.3，轴承宽径比为 0.5时，纵向粗糙模型将使最大无量纲压力提升 3.9％，而横向模型将会削弱压力水平；当宽径比增至 2.0时，横向粗糙模型将使其提升 5.7％，从而改善承载性能；动力参数、磁力系数以及应力偶参数的增加均能不同程度地增强液膜压力水平，其中后两者的增加将会使粗糙模型的影响效应显著增强，同时承载力增大且偏位角减小；当应力偶参数从 0.2增至 0.5时，粗糙模型对承载力的影响趋势随宽径比变化的分界点从 1.70增至 1.95。

Abstract:

In order to study the effects of couple stress and rough surface morphology effect on the lubrica.tion performance of magnetic fluid bearing，the Monte-Carlo method was used to characterize the random surface roughness with Gaussian distribution，and compared with the actual surface morphology under scanning electron. ic microscope，the stochastic generalized Reynolds equation was deduced by the Christensen’s stochastic model and Stokes micro-continum theory，the finite difference method was used to simulate the magnetic fluid bearing under the micro-scale condition，and the effects of different parameters on the lubrication characteristics underthe transverse and longitudinal rough models were analyzed. The results show that the actual rough surface of theproject has anisotropy，the influence of different rough models on the load carrying performance is related to the aspect ratio，when the roughness parameter is 0.3，and the aspect ratio is 0.5，the longitudinal rough model will increase the maximum dimensionless pressure by 3.9%，while the transverse model will weaken the pressure lev. el. When the aspect ratio increased to 2.0，the transverse rough model will increase it by 5.7%，thus improving the load carrying performance. The increase of the dynamic parameters，magnetic coefficient and couple stress pa. equation；Lubrication performance rameters can increase the pressure level in different degrees，and the increase of the latter two will significantly increase the effect of the rough models，while the bearing capacity increases and attitude angle decreases. Whenthe couple stress parameter increases from 0.2 to 0.5，the demarcation point between the bearing capacity withthe change of aspect ratio in the rough model will increase from 1.70 to 1.95.