Experiments on the Stability of Two Flexible Rotors in Tilting Pad Bearings

Abstract

Two rotors were tested in two sets of five shoe tilting pad bearings. One rotor had three inboard disks while the second rotor had two inboard disks and one overhung disk. Both rotors had two critical speeds below 10 000 RPM. One set of bearings had ball pivots and preload factors of 0.00; the second set had line pivots and preload factors of 0.50. All destablizing mechanisms were eliminated from the systems except for bearing cross coupling coefficients. The first system went unstable at 11 200 RPM while the second went unstable at 10 400 RPM. Both systems went unstable due to whip. Possible causes of the instabilities are discussed.