An Integrated Balancing Method for Asymmetric Rotor-Bearing Systems: Algebraic Identification, Modal Balancing, and Active Balancing Disks

Purpose The effect of an asymmetric transversal section on the rotor vibration behavior has recently acquired great interest, mainly due to the expansion in the usage of this type of rotor as well as the lack of effective balancing methods. In this work, an integrated method for Balancing Asymmetric Rotor-Bearing Systems is presented. Methods The proposed method consists in using the advantages of the conventional modal balancing (modal masses array) and then combining it with the methodology of parameter algebraic identification; the latter allows identifying both the magnitude as well as the angular position of the unbalance at low rotor speed regardless the nominal speed, preventing the system from operating at a critical speed. The proposed algebraic identifier requires the rotor vibration response as input data, instead of the vibration response produced by trial masses required in the conventional balancing methods. Likewise, the use of active balancing disks (ABDs) is proposed for rotor balancing. Results The identification of the unbalance parameters and their angular position was numerically validated by considering that the rotor operates at (a) constant speed and (b) variable speed at different angular velocities with lineal coast up. The proposed methodology was used to numerically balance a multiple degree-of-freedom rotor with unequal principal moments of inertia of the shaft transverse section and discrete unbalance, achieving a reduction of more than 95% in the vibration amplitude of the rotor in resonance for four vibration modes. The numerical results showed that a single trial balancing run is required to balance the asymmetric rotor-bearing system in situ.