DEVELOPMENT AND EXPERIMENTAL VALIDATION OF A MODEL-BASED BALANCING PREDICTION METHOD FOR BOWED ROTOR

Rotor balancing is one of the most discussed topics in the field of rotor-dynamics. It is very important in the industrial practice and sometimes there are very particular cases that cannot be addressed and solved by traditional methods. The rotor model addressed in this paper has been initially presented in a previous work [1], with the aim to introduce a procedure for "predicting the effects of balancing" at rotational speeds that are higher than those possible on balancing machines. In this work, the balancing of the same rotor model is addressed by a maintenance standpoint, considering the case of a rotor showing bending at its neutral axis. This situation may be present, for several reasons, in rotors sent to the Original Equipment Manufacturers (OEMs) for repair/refurbishment after several years of operation, or as consequence of emergency events that may cause local deformation and/or require significant re-machining. To some extent, this situation can still allow for High-Speed Balancing (HSB) of such shafts. Nonetheless the availability of prediction models able to evaluate in a relatively short time the feasibility of HSB, in advance of starting any hardware activity, is of paramount importance to avoid costs and time impacts. In this paper, a procedure to address the feasibility of balancing of an industrial steam turbine rotor, starting from runout measurement of its bowed shape, is presented. Hence, results of several approaches are discussed for identification of their limits of applicability. Eventually the result of an analytical model including the deflected shape of the shaft is compared with HSB runs.