Effects of Three-Lobe Bearing Geometries on Rigid-Rotor Stability

The stability of a rigid rotor mounted in three-lobe bearings is theoretically studied for which the preload factor, offset factor, and load orientation are systematically varied. Rigid-rotor stability maps are presented. Results indicate that bearings with offset factors of 0.1 or less and moderate preload factors are often more stable than those with larger offset factors. Results also indicate that, for a given preload and load orientation, a particular offset factor exists which produces minimum stability (such bearing geometries should be avoided). Finally, increasing the preload factor was found to increase the rigid-rotor stability.