Generalized modal balancing for non-isotropic rotor systems

Abstract

This paper primarily aims at the new generalized modal balancing for non-isotropic rotor systems. The method is based on the derived unbalance modal responses from the complete modal analysis for non-isotropic rotor systems. We found, from investigating the modal configuration to be balanced, that the isotropic and asymmetric rotor systems appear a single 1X harmonic, whereas the anisotropic and general rotor systems appear duel and multiple harmonics, respectively. Furthermore, for the asymmetric and general rotor systems, each harmonic is combined with the multiple modal parameters. The peculiar feature for balancing the non-isotropic rotor systems is that the additional right eigenvector and counter excitation in stator to cancel the anisotropy are required to suppress effectively the total residual response. In this process, the concept of the dominant balancing mode is drawn from the definition of the major harmonic. Also it is suggested that the balancing performance is dependent upon the degree of accuracy of the unbalance modal response that is approximated by the dominant mode at a critical speed. The numerical simulations of the simple general rotor model with one balancing plane are performed to demonstrate the theoretical findings and effectiveness of the proposed method for non-isotropic rotor systems.