Friction Induced Rotor Whirl—A Study in Stability

Of deep concern to designers of high speed, close clearance rotating machinery is that type of self-excited rotor whirl induced by rubbing friction between rotor and stator. Since the probability of transient or continuous rubbing is high, it is important to determine whether the consequent whirl will be sustained, whether it will decay, or whether it will increase destructively. This paper develops, for a simple flexible overhung rotor, an analysis showing that regimes of stability, dependent upon damping and stiffness characteristics, do indeed exist. A stability chart is computed for the selected model and this may be used to determine whether a specific disturbance deflection will decay, grow, or remain constant during the disturbance or after its removal.