Effect of Unbalance on the Dynamic Response of a Flexible Rotor Supported on Porous Oil Journal Bearings
The present study deals with non-dimensional dynamic analysis of a flexible rotor with a rigid disk under unbalance excitation mounted on porous oil journal bearings at the two ends. The system equation of motion is obtained by finite element formulation of Timoshenko Beam and the disk and the oil-film forces are calculated from the solution of the modified Reynolds equation simultaneously with Darcy’s equation. The system equation of motion is then solved by Wilson-θ method. The effect of unbalance on the rotor-bearing system can be observed from the waterfall diagram of the rotor vibration. It has been observed that when the operating speed is low, the major cause of rotor vibration is the unbalance, but at higher operating speeds, oil-whirl phenomenon takes over as a major cause of vibration. The simulation is carried out for different rotor-bearing parameters. The method developed here can also be used to obtain journal centre trajectories and responses at different nodal points of the rotor.
KeywordsTimoshenko beam Porous hydrodynamic bearing Unbalance response Oil-whirl Oil-whip