Use of modal weight sets for residual modal unbalance assessment of high speed balance quality of flexible rotors

The paper proposes a rather simple method of residual modal unbalance assessment using modal weight sets. The method works well for evaluation of the first two modes and reasonably well for higher modes as long as there is enough separation between them and there are no overhang modes. Validation was performed based on factory residual vibration limits for at least 50 flexible rotors of different frame-sizes. A relatively good correlation of factory vibration limits and results obtained with weight sets was achieved. These results were in-line with limits set in ISO 1940, ISO 11342 and some OEMs. © M L'vov, E Uryev, 2012