Effects of Three-Lobe Bearing Geometries on the Unbalance Response of a Flexible Rotor

Abstract

The synchronous response due to unbalance was studied both theoretically and experimentally for a three-mass rotor mounted in three-lobe and axial-groove bearings. Offset factor, preload factor and load orientation were parametrically varied for the three-lobe bearings. Theoretical predictions indicate that low preload factors (with offset factors of 0.5) result in the smallest critical speed responses. Also, for a preload factor of 0.75, offset factors of approximately 0.65 minimize the critical speed response. Experimental data for peak responses agree within 42 percent (usually much less) of predictions. Reasons for the differences are attributed to the predicted bearing stiffness and damping coefficients.