Analysis of Flexible Rotor Whirl and Whip Using a Realistic Hydrodynamic Journal Bearing Model

An analytical method has been developed for the simulation of the transient and steady-state response of flexible rotors supported by realistic incompressible-film hydrodynamic journal bearings. The coupled nonlinear differential equations of rotor motion, formulated as an initial-value problem, are solved in conjunction with a “realistic” Reynolds equation solution which includes finite bearing length, wedge and squeeze films, fluid film cavitation, oil inlet geometry, and eccentricity and tilt (gyroscopics) of the journal. Presented in this paper are some of the results of a numerical and experimental study of rotor whirl using that analytical model. The response of a flexible rotor, for speeds up to the threshold of instability, is demonstrated as a function of disk unbalance and viscous damping. The validity of the analytical model is confirmed by comparison of experimental whirl data with numerical simulations of the response of the test rotor through the critical speed region to the onset of oil whip.