Dry Friction Backward Whirl of Rotors: Theory, Experiments, Results, and Recommendations

This paper presents a theoretical and experimental study into the dry friction backward whirl of rotors. A model is derived that is able to describe the behaviour of a rotor from an excitation up to and including fully established backward whirl. A test rig is presented with which these processes were studied experimentally for a rotor running in conventional (ball-)bearings up to a rotational frequency of 166 Hz (10’000 rpm). Test results are presented and discussed. These results include the whirl behaviour of a rotor in both a very heavy and a stator with compliant mountings and the influence of different system parameters on the whirl behaviour. The numerical predictions are compared to the measured results. Recommendations are given on how to avoid dry friction backward whirl.