Numerical study of nonlinear stability boundaries for orifice-compensated hole-entry hybrid journal bearings

Abstract

A high-performance and finite-length bearing system requires that the shaft can be stabilized even under a strong perturbation. The linear stability theory neglects the effects of nonlinear forces and the initial point of the shaft. Therefore, the stability of the bearing system is largely determined by the rotating speed of the shaft. In the present numerical investigation, the nonlinear forces and initial point of the shaft are accounted for to obtain the nonlinear stability boundary. The objective of this study is extended to orifice-compensated and hole-entry hybrid journal bearings with finite length. The critical rotating speed and the shaft center trajectory are acquired by solving Reynolds equation using the finite element method. By identifying the states of the orbits (stable or unstable), the nonlinear stability boundaries can be obtained. Results show that for the hybrid bearing system under the nonlinear conditions, the critical speed is a determinant factor while the initial location is another key factor. The shaft can be unstable if the initial point is outside of the stability boundary, although the speed is lower than the critical speed. There exists an obvious transitional region between the stable and unstable condition when the speed approaches the critical speed.

Multi-Physics Fields Based Nonlinear Dynamic Behavior Analysis of Air Bearing Motorized Spindle

“…To the ABMS, however, the influence of Electromagnetic factors on the dynamic behavior of the ABMS system is not understood clearly. It had been pointed out the existence of stability boundary of air journal bearing, and the stability boundary varying with rotating speed is also investigated [27,28]. To the ABMS, however, the influence of Electromagnetic factors to the stability of the system may not be ignored.…”

Stability analysis of long hydrodynamic journal bearings based on the journal center trajectory

“…Smolík et al [5] investigated the threshold speed and threshold curve of nonlinear hydrodynamic bearings by applying a short bearing approximation. Kushare and Sharma [6] displayed the nonlinear stability of hybrid journal bearings with valve restrictors lubricated using non-Newtonian fluids, and Li et al [7] illustrated the nonlinear stability boundaries of hybrid journal bearings with orifice restrictors. Lin et al investigated the effects of surface topography [8] and non-Newtonian lubricants [9] on the stability boundary of short journal bearings.…”