Purpose

An externally-pressurized journal air bearing (AB) with an air-ring (AR), or air-ring bearing (ARB), for a balanced, rigid and light-weight rotor is studied. An elastic structure in the form of an AR is provided between the bearing-bushing and the casing. The ARB is analyzed to determine the dynamic coefficients (DC) at various angular velocities and angular frequencies of vibration of the journal in its range of operation. These DC can then be used to predict the dynamic stability of the rotor ARB system against self-excited (SE) vibration. A numerical simulation procedure is followed to determine the DC.

Methods

The ARB is modeled as a two-degrees of freedom system. During the simulation, the journal follows a prescribed harmonic motion. Self-exciting forces due to flow dynamics inside an ARB induce this motion. Three-dimensional (3-D) flow equations are solved on a moving/deformable grid using ANSYS^®, to compute the pressure (p) distribution in the ARB. Unlike in previous studies, in this study the bushing displacement is determined by the instantaneous p-distribution in the ARB. DC of both AB and AR are determined simultaneously by considering the interaction between the AR and the AB regions through the feed-holes in the bushing.

Results

Time-dependent displacement, velocity, and load-carrying capacity obtained by numerical simulation are used to evaluate the DC.

Conclusion

Incorporation of an AR around an AB can prevent SE vibration due to positive values of direct damping coefficients of AR. A 3-D flow analysis can reveal the realistic nature of flow in an ARB.

中文翻译：

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空气轴承动态系数的确定

目的

研究了带有平衡环，刚性且重量轻的转子的带有空气环（AR）或空气环轴承（ARB）的外压轴颈空气轴承（AB）。在轴承衬套和壳体之间设置有AR形式的弹性结构。对ARB进行分析，以确定轴颈在其工作范围内的各种角速度和振动角频率下的动态系数（DC）。然后，这些DC可以用于预测转子ARB系统针对自激（SE）振动的动态稳定性。遵循数值模拟程序来确定DC。

方法

ARB被建模为两自由度系统。在模拟过程中，轴颈遵循规定的谐波运动。由于ARB内部的流动动力学而产生的自激力会引起这种运动。三维（3-d）流方程使用ANSYS在移动/变形网格解决^®，来计算压力（p在ARB）分布。与以前的研究不同，在这项研究中，套管位移是由ARB中的瞬时p分布确定的。通过考虑AR和AB区域通过衬套中的进料孔的相互作用，可以同时确定AB和AR的DC。

结果

通过数值模拟获得的随时间变化的位移，速度和承载能力可用于评估直流。

结论

由于AR的直接阻尼系数为正值，因此将AB并入AB可以防止SE振动。3-D流量分析可以揭示ARB中流量的真实性。