Influence of blade vibration on part-span rotating stall

Abstract

This paper presents the interaction between blade vibration and part-span rotating stall in a multi-stage high speed compressor. Unsteady aerodynamic and aeroelastic simulations were conducted using URANS CFD. Steady state computations showed short length scale disturbances formed local to the tip of a front stage rotor. Using a full annulus model, these disturbances were shown to coalesce into flow structures rotating around the annulus at approximately 76% of the shaft rotational speed. Natural evolution of the rotating stall did not result in a coherent spatial pattern. Sensitivity studies showed that operating point and tip clearance have significant impact on the developed state of rotating stall. Subsequent analyses carried out with prescribed rotor blade vibration showed a spatial ‘lock-in’ event where the circumferential order of the part-span rotating stall shifted to match that induced by the vibration mode. Moreover, in contrast to its natural form in the absence of vibration, the fully developed rotating stall showed a coherent stall signal. More importantly, it was found that numerical boundary conditions such as mixing plane and sliding planes can significantly influence the outcome of prediction.

UHBR Open-Test-Case Fan ECL5/CATANA: Numerical Investigation Near the Stability Limit Including Aerodynamic Mistuning

“…This can be typically attributed to a loss in stage pressure ratio, depending on the size of the stall cells. Phenomenologically, rotating stall is self-sustained, and can exist without blade vibration, however, Zhao et al [9] reported influence of large vibration amplitudes on the evolution of stall cells. Precursors of rotating stall in form radial vortices are reported further from the stability limit at stable operating conditions [10][11][12][13].…”

Near-Stall Modelling of a Pitching Airfoil at High Incidence, Mach Number and Reduced Frequency

“…In addition to the intrinsic unsteadiness of flow separations, 'external' fluctuations in incidence at near-stall conditions occur when the rotor is vibrating or rotating through distorted inflow conditions. When the compressor is operating close to stall in such conditions, the unsteady aerodynamics are known to alter both its stall behaviour, as reported in numerous publications on inlet distortions [8][9][10], and its aeromechanical behaviour [11][12][13][14]. Even before compressor stall, pre-stall disturbances travel around the circumference, result in asymmetric time-varying loads and can trigger or exacerbate vibrations [15,16].…”