On-line elimination of oil whip by passive electromagnetic damper

The nonlinear dynamic characteristics (including the trajectories of bearings, frequency spectrum and the factors inducing to oil whip) of a multi-freedom flexible rotor supported on oil journal bearings were numerically studied by variable step-size Newmark integration. The nonlinear oil film forces of the bearings were modeled based on steady short bearing theory. The simulation analysis shows that the complex trajectories disappear and the amplitude of the half frequency vibration distinctly decreases by adding external damping. So experiments were carried out to clarify this phenomenon and demonstrate the feasibility. A test rotor with six disks was equipped on its free end with a passive electromagnetic damper, which worked without contact and with DC current. The power of the damper was turned on when the oil whip of the rotor occurred. It was observed that when the damper was turn on, the complex trajectories of the journal motion disappeared and the rotor-bearing system became stable; when the damper was turned off, the oil whip occurred again.