Oil Whirl of Flexible Rotors

Abstract

The equations for a flexible rotor in journal bearings are set up and solved, extending the method previously used by Hummel and Cameron. It is shown that if w is the natural elastic frequency of the rotor, A the resonant oil frequency for an infinitely stiff but otherwise identical rotor, then the combined frequency s is given by l/ s2 = 1/Λ2 + 1/ w2. This resonant frequency will usually occur when it equals 1/2 the shaft rotational frequency The frequency calculated by the method given here is applied to a number of cases of large turbines and alternators and found to give quite satisfactory results