Residual Modal Unbalance Evaluation Method by Mode Shape Weighted Optimization

In order to allow for good vibration performance of turbo machinery, high speed balancing of individual turbo-generator components in the balance facility is performed. High speed balance quality of a rotor with flexible behavior can be expressed in terms of residual vibration or residual modal unbalance. The traditionally used residual vibration method has the disadvantage that the balance quality significantly depends on bearing and support types, measuring system and other factors. Residual modal unbalances have very little sensitivity to these factors and can hence be used for direct comparison of the results from different balancing facilities. It also permits setting universal limits for a rotor frame-size that apply to all balancing facilities.