Active control of an unsymmetrical rotor system with tilting pad journal bearings

The active hybrid tilting-pad bearing, together with the unsymmetrical flexible rotor and the hydraulic system is modeled and studied in this paper. Then the 8 degrees-of-freedom nonlinear dynamic model of unsymmetrical flexible rotor-bearing system with the effect of gyroscopic moment is formulated. The active lubrications based on injecting pressurized oil into the bearing gap through orifices (machined in the bearing sliding surface) are utilized to suppress the shaft vibrations. A proportional—integral (PI) controller is designed for the active lubricated system and the finite difference method is applied to solve the pressure distribution on each tilting pad surface. Numerical results show that the actively lubricated system presents effective vibration reduction for the unbalance response subjected on the flexible rotor and the proposed PI controller exhibits a commendable performance. The feasibility of putting off rotor-bearing instabilities (phenomena of whirl) by using active lubrication is also investigated, which illustrates clearly one of its most promising applications.