Nonlinear Analysis of Stability and Unbalanced Response on Spherical Spiral-Grooved Gas Bearings

This study conducts a nonlinear numerical analysis of the stability and the unbalance response of spherical spiral-grooved bearings (SSGBs) using a nonlinear orbit simulation method. This method is more accurate than the linear method, especially at high bearing loads. Parametric analyses are also performed with respect to nominal clearance and groove depth to optimize groove parameters. Shaft trajectories reflect the nonlinear characters of SSGBs when mass unbalance increases. Fast Fourier transform analyses of rotor orbit responses facilitate identification of the subsynchronous whirling and unbalance response in rotor vibration behavior. Results show that optimum dimensionless groove depths vary for different nominal clearances or rotational speeds. The static performance and stability characteristics of spherical bearings can be significantly influenced by the spiral grooves on the journal surface.