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Erschienen in:
2019 | OriginalPaper | Buchkapitel
Residual Modal Unbalance Evaluation Method by Mode Shape Weighted Optimization
verfasst von : Max L’vov, Bernd Lacombe, Ulrich Ehehalt
Erschienen in: Proceedings of the 10th International Conference on Rotor Dynamics – IFToMM
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Abstract
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.
The paper presents the Mode Shape Weighted Optimization Method for evaluating residual modal unbalances. This method allows considering all vibration amplitudes for all bearings and all resonance and service speeds at the same time. The method relies on the knowledge of mode shapes and takes advantage of their low dependency on support system properties. It allows evaluation of modal unbalances for modes below and above service speed. The optimization algorithm calculates the residual unbalance vector (compensation unbalance) in one step. Finally, the residual modal unbalance values are obtained by weighting the compensation unbalance vector with the corresponding mode shape.
The Mode Shape Weighted Optimization Method allows for higher quality control of turbo-generator components and ensures comparability between different balancing facilities. Numerical and experimental investigations are presented to prove the suitability of the method.