Abstract
Stability of lateral rotordynamic modes is an essential consideration during design and acceptance testing of rotating machinery. Experimental modal analysis (EMA) can be used for assessment but is in practice very difficult in actual operating conditions, principally due to the challenges of quantifying the excitation force. Operational modal analysis (OMA) does not require measurement of excitation forces and therefore presents significant logistical advantages over EMA. The background and theoretical concepts of OMA are presented and its use is demonstrated on a 500 kW centrifugal compressor. Measurements performed during commissioning at first raised suspicion that the stability was marginal. However OMA was used to confirm that the first forward mode of the compressor was actually stable and the measurements were reconciled with the predicted behavior. The results show that the assessment of stability margins of rotating machinery can be measured with OMA using only proximity probe data acquired during normal operation.
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Acknowledgments
The authors thank Lloyd’s Register Consulting for funding the work behind this paper and also for granting the authors permission to write and present it. A special thanks goes to Robert Stronach, Henning Hartmann, Said Lahriri, Stefano Morosi from the Fluid and Machinery Dynamics Teams of Lloyd’s Register Consulting for the active contribution in the analyses and discussions.
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Carden, E.P., Sehlstedt, N., Nielsen, K.K., Lundholm, S., Morosi, S. (2015). Stability Analysis and Assessment of Rotor Trains Using Operational Modal Analysis. In: Pennacchi, P. (eds) Proceedings of the 9th IFToMM International Conference on Rotor Dynamics. Mechanisms and Machine Science, vol 21. Springer, Cham. https://doi.org/10.1007/978-3-319-06590-8_172
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DOI: https://doi.org/10.1007/978-3-319-06590-8_172
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