A two-lobe Journal Bearing with adjustable Gap Geometry for Vibration Reduction of flexible Rotors

Abstract

Flexible rotors in journal bearings can exhibit large vibration amplitudes during the passage of bending critical speeds.  To reduce these vibrations, a two-lobe journal bearing with adjustable gap geometry is presented. By an adjustment of  the gap height, stiffness and damping properties of the bearing and as a consequence the damping ratio of the rotor  system can be varied during the operation. When the system passes a critical speed in a run-up process, a large gap is  adjusted for higher damping. After the resonance pass through, the gap height is reduced to increase the load  carrying  capacity and to enlarge the stability margin. Investigating the Jeffcott rotor in adjustable journal bearings demonstrates the basic effects. For a validation, a test rig is set up and a related mathematical model is created.  Various experiments are made and compared with numerical results.