Vibration of Impellers : 5th report, Measurement of Resonant Vibratory Stresses of an Impeller and Pressure Distribution Due to Aerodynamic Excitation

Volume 7B: Structures and Dynamics

et al. 2013

The phenomenology of rotor-casing setups experiencing contact interactions is still poorly understood, particularly when complex geometries such as centrifugal compressors are involved. Although interaction phenomena have been witnessed and recorded during industrial experiments, the physical understanding of what occurs during these interactions is limited. The usual design approach is to consider possible modal interaction points in a linear framework and move these outside of normal operating conditions by means of minor geometric changes. Based on this linear approach, no information on the severity of these interactions is available to the designer. Besides, a possible interaction point appearing in the linear framework may not produce any harmful interactions, thereby increasing design restrictions. Based on an in-house numerical strategy previously presented, contact interactions for a flexible centrifugal compressor from a helicopter engine and rigid casing setup are investigated. By imposing a small deformation on the casing geometry, blade/casing contact is initiated and subsequent interactions feature complex phenomena that are analyzed. In comparison to previous interaction simulations involving axial compressors, a higher degree of complexity of the numerical simulations stems from a strong curvature of the blade and very significant blade-disk coupling. This coupling presents itself towards the trailing edge where compressor mode shapes indicate a significant component normal to the casing surface. Accordingly, these modes may lead to large amplitude contact forces. Time simulation results are confronted with experimental observations, and the consistency of the behavior of the numerical model with respect to industrial observations is underlined. A frequency domain post-processing of the results reveals specific engine order interactions and frequency spectra are plotted in order to interpret the phenomenon of interest. Such methodology will enable designers to more efficiently discriminate potential critical interaction speeds as compared to the classical linear frequency approach.

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Section: Introductionmentioning

confidence: 99%

Investigation of Rotor-Casing Interactions in the Centrifugal Compressor of a Helicopter Engine

Volume 7B: Structures and Dynamics

et al. 2013

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“…Literature pertaining to the vibration analysis of impellers, and to a larger extent within contact mechanics, is fairly limited. The only available studies deal with modal responses and are detailled in [4,5,6,7]. Recently, the geometry of interest in the presented case study was analyzed in [8].…”

Section: Introductionmentioning

confidence: 99%

A Qualitative Numerical Analysis of Rotor-Casing Interactions in Centrifugal Compressors of Helicopter Engines

Volume 8: 22nd Reliability, Stress Analysis, and Failure Prevention Conference; 25th Conference on Mechanical Vibration and Noi

et al. 2013

“…However, the exploration of interaction phenomena for centrifugal compressors is not yet documented. The only references available deal with numerical [8,9] and experimental [10] modal analysis.…”

Section: Introductionmentioning

confidence: 99%

Rotor-Stator Interaction Scenarios for the Centrifugal Compressor of a Helicopter Engine

Volume 8: 22nd Reliability, Stress Analysis, and Failure Prevention Conference; 25th Conference on Mechanical Vibration and Noi

et al. 2013