Fluid Mechanics and Acoustics Laboratory - UMR 5509

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Laboratoire de Mécanique des Fluides et d’Acoustique

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Home > Teams > Turbomachinery Team > T2 - Aéroelasticité et Aéroacoustique

Analysis and modelisation of non-synchronous aeroelastic phenomena in an axial multistage compressor

Theme 2 - Aéroélasticité et Couplage Acoustique
Period 23/01/2017-22/01/2020
Contact(s) AUBERT Stéphane
PhD student FIQUET Anne-lise
Partners Safran Helicopter Engines

Significant Non-Synchronous-Blade vibrations have been observed in an experimental multi-stage high-speed compressor setup at part-speed conditions. High amplitude acoustic modes, propagating around the circumference and originating in a highly loaded downstream stage have been observed in coherence with the structural vibration mode.
In order to understand the occurring phenomena, a detailed numerical study has been carried out to reproduce the mechanism. Unsteady full annulus RANS simulations of the whole setup have been performed using the solver elsA. The results revealed the development of propagating acoustic modes which are partially trapped in the annulus and are in resonance with an aerodynamic disturbance in the relevant rotor. The results indicate that the aerodynamic disturbance, which is identified as a separation of the blade boundary layer which adapts its frequency and phase to a propagating acoustic wave whose circumferential wave number is determined by acoustic propagation conditions.
Furthermore, the simulations clearly show the mechanism behind the modulation of the propagating wave with the rotor blades, leading to a change of circumferential wave numbers while passing the blade row.
This phenomenon is highly relevant to modern compressor designs, since the appearance of the axially propagating acoustic waves can excite blade vibrations if they coincide with a structural eigenmode, as observed in the presented experiments.

Figure 1 : Frequency spectra of unsteady wall pressure measurment at leading-edge of Stator-2 in the stationary frame of reference ((a) blue curve) and frequency spectra of magnet-coil signal in Rotor-2 in the relative frame of reference ((b) red curve)

Figure 2 : Unsteady non-synchronous entropy fluctuation for one time instant at 80% of channel height at operating point where non-synchronous phenomena is observed (URANS full-annulus simulation)

Documents and associated publications

Fiquet, A., Brandstetter, C., Aubert, S., and Philit, M. "Non-Engine Order oscillations in an axial multi-stage compressor." ISUAAAT17-087, September 2018, Oxford, UK

Fiquet, A., Brandstetter, C., Aubert, S., and Philit, M. (October 9, 2019). "Non-Synchronous Aeroacoustic Interaction in an Axial Multi-Stage Compressor." ASME. J. Turbomach. October 2019; 141(10): 101013. https://doi.org/10.1115/1.4044675

Fiquet, A., Vercoutter, A., Buffaz, N., Brandstetter, C. and Aubert, S. "Acoustic Resonance in an axial multi-stage compressor leading to non-synchronous blade vibration" ASME TurboExpo 2020