FORWARD AND BACKWARD PRECESSION OF A VERTICAL ANISOTROPICALLY SUPPORTED ROTOR

This paper presents the analytical and experimental study of a vertica l, overhung imbalanced rotor supported by flexible, anisotropic bearin gs. The results show that existence of imbalance and shaft bow causes the synchronous forced precession of the rotor to be forward (below th e first value of split balance resonance and above the second value of the split balance resonance) or backward (between the two values of t he split resonance). This phenomenon is classical. The new result cons ists of exploring the existence of forward precession of the inboard a nd midspan rotor sections while the outboard disk is precessing backwa rd. The sensitivity analysis shows which system parameters are mainly responsible for this apparently bizarre phenomenon. (C) 1996 Academic Press Limited