The maximum dynamic eccentricity ratio of hydrodynamic rolling hybrid bearings

Hydrodynamic Rolling Hybrid Bearing (HRHB) is dual bearings combination where a hydrodynamic bearing and a rolling bearing with a clearance are assembled coaxially and side by side. The clearance of rolling bearing is a significant parameter for HRHBs. This paper aims to investigate the vibration characteristics of rotor supported by HRHBs to determine the permissible value of clearance of rolling bearing. The maximum dynamic eccentricity ratio is proposed based on the noninterference conditions of rolling bearing and rotor. Then an evaluation method of the maximum dynamic eccentricity ratio is developed. This paper also investigates the effects of the operation parameters such as rotational speed, perturbed force and structure parameters such as bearing span, diameter of rotor, and overhanging length on the maximum dynamic eccentricity ratio. The maximum dynamic eccentricity ratio on the front rolling bearing section is obviously larger than that on the back rolling bearing section. Moreover, the maximum dynamic eccentricity ratio reduces with the increase of the rotational speed and diameter of rotor, but increases with the augmentation of the perturbed force, bearing span, and overhanging length. When the maximum dynamic eccentricity does not go beyond the bound of the radius of the rolling bearing's clearance circle, the rolling bearing does not interfere with the rotor. The paper provides theoretical basis for design of the minimum value of the rolling bearing's clearance in HRHBs.