In this study, the dynamic behavior of three-lobe noncircular hydrodynamic journal bearings lubricated with couple stress fluid is presented. Currently, application of journal bearings with different geometries such as lobed bearings and using non-Newtonian lubricants, including various additives, are the common suggested solutions by tribology researchers to improve the performance of rotor-journal bearing systems. Due to the incompatibility of new lubricant behaviors including polymer chains or other types of suspended particles with considerable size from the classic Navier–Stokes equations, different models such as couple stress fluid theory have been proposed to evaluate their performance. To investigate the self-excited rotor disturbances caused by various factors, like operating in critical speeds, simultaneous solution of governing Reynolds equation of oil lubricant and the rotor motion equations has been done. The result of dynamic analyses using linear and nonlinear approaches indicates the possibility of enhancing the stiffness and damping ability of the three-lobe bearings by strengthening the couple stress properties of lubricant. It is seen from the results that by increasing the couple stress parameter of oil, the type of rotor perturbations in the bearing clearance space changes from divergent oscillations, as a leading cause of collision between the rotor surface and the bearing shell, to limit cycle motion around the rotor stable position or convergent fluctuations to the static equilibrium point. This improvement in the stability range of three-lobe journal bearings using a couple stress lubricant appears in the results of a linear analysis model in terms of increasing the critical mass parameter and decreasing the whirl frequency ratio. In addition, bifurcation diagram results show that using noncircular three-lobe bearings instead of circular types and replacing the Newtonian lubricant with the couple stress fluid improve the dynamic stability of rotor- bearing supports.

在这项研究中，介绍了用耦合应力流体润滑的三叶非圆形流体动力滑动轴承的动态行为。目前，摩擦学研究人员通常建议使用具有不同几何形状的轴颈轴承（例如凸轮轴承）和使用非牛顿润滑剂（包括各种添加剂）来提高转子-轴颈轴承系统的性能。由于新的润滑剂行为不兼容，包括聚合物链或其他类型的悬浮颗粒与经典的 Navier-Stokes 方程相当大，因此提出了不同的模型，如耦合应力流体理论来评估它们的性能。为了研究由各种因素引起的自激转子扰动，例如在临界速度下运行，完成了润滑油的控制雷诺方程和转子运动方程的联立解。使用线性和非线性方法的动态分析结果表明，可以通过加强润滑剂的耦合应力特性来提高三叶轴承的刚度和阻尼能力。从结果可以看出，通过增加油的耦合应力参数，轴承间隙空间中的转子扰动类型由发散振荡转变为转子表面与轴承壳碰撞的主要原因，以限制循环运动围绕转子稳定位置或收敛波动到静态平衡点。使用耦合应力润滑剂的三叶轴颈轴承稳定性范围的这种改进出现在线性分析模型的结果中，即增加临界质量参数和降低涡动频率比。此外，分叉图结果表明，使用非圆形三叶轴承代替圆形轴承并用耦合应力流体代替牛顿润滑剂可以提高转子轴承支架的动态稳定性。