Floating ring bearings have been widely used, over the last decades, in rotors of automotive turbochargers because of their improved damping behavior and their good emergency-operating capabilities. They also offer a cost-effective design and have good assembly properties. Nevertheless, rotors with floating ring bearings show vibration effects of nonlinear nature induced by self-excited oscillations originating from the bearing oil films (oil whirl/whip phenomena) and may exhibit various nonlinear vibration effects which may cause damage to the rotor. In order to investigate these dynamic phenomena, this paper has developed a nonlinear model of a perfectly balanced rigid rotor supported by two identical floating ring bearings with consideration of their vibration behavior mainly governed by fluid dynamics. The dimensionless hydrodynamic forces of floating ring bearings have been derived based on the short bearing theory and the half Sommerfeld solution. Using the numerical continuation approach, different bifurcations are detected when a control parameter, the journal speed, is varied. Depending on the system’s physical parameters, the rotor can show stable or unstable limit cycles which themselves may collapse beyond a certain rotor speed to exhibit a fold bifurcation. Bifurcation analysis is performed to investigate the occurring instabilities and nonlinear phenomena. Such results explain the instabilities characteristics of the floating ring bearing in high-speed applications. It has also been found that the selection of the bearing modulus plays an important role in the characterization of the rotor stability threshold speed and bifurcation sequences. An understanding of the system’s nonlinear behavior serves as the basis for new and rational criteria for the design and the safe operation of rotating machines.

在过去的几十年中，浮动环轴承已广泛应用于汽车涡轮增压器的转子中，因为它们具有改进的阻尼性能和良好的紧急操作能力。它们还提供具有成本效益的设计并具有良好的装配性能。然而，带有浮动环轴承的转子表现出由源自轴承油膜的自激振荡引起的非线性性质的振动效应（油涡/鞭状现象），并且可能表现出可能导致转子损坏的各种非线性振动效应。为了研究这些动态现象，本文开发了一个完美平衡刚性转子的非线性模型，该模型由两个相同的浮环轴承支撑，并考虑到它们的振动行为主要受流体动力学影响。浮环轴承的无量纲流体动力是根据短轴承理论和半索末菲解推导出来的。使用数值连续法，当控制参数（轴颈速度）变化时，可以检测到不同的分岔。根据系统的物理参数，转子可以表现出稳定或不稳定的极限循环，这些极限循环本身可能会在超过某个转子速度时坍塌，从而出现折叠分叉。执行分岔分析以研究发生的不稳定性和非线性现象。这样的结果解释了浮动环轴承在高速应用中的不稳定性特征。还发现轴承模数的选择在转子稳定性阈值速度和分叉序列的表征中起着重要作用。对系统非线性行为的理解是为旋转机器的设计和安全运行制定新的合理标准的基础。