ABSTRACT
Within the engineering design strategies of U.S. steam turbine generator manufacturers, the peak ground acceleration and displacement levels of recorded earthquakes were long judged sufficiently low to preclude bearing damage to large steam turbine generator sets. However, rotor-bearing research investigations in the earthquake active country of Japan sensitized the author to investigate the potential for the triggering of a large amplitude nonlinear vibration limit cycle at operating speeds below the linear oil-whip vibration threshold speed. Accordingly, using time-transient simulations, the author conducted an extensive parametric study on rotor-bearing vibration response to earthquake ground motions. The results of those simulations show conclusively that under large but realistic ground motion amplitudes, the rotor vibration can be triggered to part ways with the static equilibrium centered linear vibration transient solution, morphing into a sustained stable large amplitude nonlinear limit cycle with journal vibration amplitudes virtually filling up the entire bearing radial clearances. This confirmed and considerably extended the prior warning contained in the publications by Japanese large rotating machinery researchers.
