Development of Flexible Rotor Balancing Procedure Using Response Matching Technique

The two main methods used for flexible rotor balancing are Influence Coefficient Method (ICM) and Modal Balancing Method (MBM). ICM relies on experimental trial data with several trial masses installed sequentially on all balancing plains to compute response changes per unit mass, called influence coefficients. MBM requires prior knowledge of mode shape and critical speeds of the rotor to compute orthogonal set of balancing masses for each mode. The objective of this paper is to develop a flexible rotor balancing procedure, wherein FEM model rotor response is matched to the actual rotor response using iterative technique. Unbalance masses, moments, and shaft stiffness are iterated on the model to match experimental response data at three distinct speeds that are below the rotor flexible critical speed. The model rotor is virtually balanced at its flexible critical speed by adding optimized balancing masses iteratively using gradient decent approach. Suitable constraints are placed on the level of residual vibrations. Rotor bow parameters are also incorporated in the model. A parameter called bending parameter is introduced to balance flexible rotor. Experimental rotor mounted on flexible supports is used for the validation of the proposed balancing method.