Vibration Control for Rotor Mounted on a Novel Active Bump Type Foil Bearing With Controllable Mechanical Preloads

A novel active bump type foil bearing (ABFB) is put forward aims at demonstrate the feasibility of applying active lubrication control of the aerodynamic gas bearing. The proposed active structure consists of (1) piezoelectric actuators (PZTs) amounted in the bearing housing to produce control forces, (2) flexure hinges machined in the bearing housing to produce pivot for the lever amplifier, (3) lever amplifier machined in the bearing housing to amplify the deformation of PZTs. The mechanical preloads of the ABFB can be actively adjusted by using lever amplifiers which is actuated and controlled by the controlling the driving voltage on PZTs to create variable multiple lobe clearance and realizing the real time shape changing of the lubricate gas film. The static load-deformation test of the ABFB is done to demonstrate that the preload of the bearing is significantly adjusted by changing the driving voltage on PZTs. The lift-off tests versus different driving voltages of the ABFB are done to illustrate that the change of the preloads can significantly affect the drag torque of the ABFB and illustrate the significance of the active control. Rotordynamic tests of the ABFB with different driving voltages have been conducted. Subsynchronous vibrations of the rotor have been suppressed significantly by increasing the driving voltage. The coast-down time increases with the increase of the driving voltage on PZTs. At the rotational speed of 33krpm, the amplitude of the whip motion can be suppressed timely and actively by controlling the driving voltage on PZTs.