Aeroelastic Investigation of an Annular Transonic Compressor Cascade: Numerical Sensitivity Study for Validation Purposes

Kurzfassung

The accuracy of flutter or forced response analyses of turbomachinery blade assemblies strongly depends on the correct prediction of the unsteady aerodynamic loads acting on the vibrating blades. This paper presents the aeroelastic numerical results of an annular transonic compressor cascade subjected to harmonic oscillation conditions. The measurements associated were performed in an annular test facility for non-rotating cascades. The aim of this investigation is to get a deeper understanding of the specific characteristics of this test facility as well as improving the flutter prediction procedure and accuracy. For a subsonic and a transonic flow condition, the steady-state blade surface pressure distributions were predicted with two mesh configurations and results were compared to the experimental results. The first configuration omits the geometrical complexity of the experimental model and only models the blade passage. The second mesh configuration includes the cascade’s detailed geometry and cavities. The presence of leakage flows arisen due to the cascade’s slits and cavities are identified and their impact on the main flow field is analyzed and discussed. For the flutter computations, two mesh resolutions were investigated. The global damping predicted with a fine and a coarse mesh was compared, as well as the local pressure amplitudes and phases predicted with both configurations. Results show that even though similar global damping curves are predicted with both mesh resolution, for some IBPAs, local differences exist on the pressure amplitudes and phases. This highlights that only comparing the global damping coefficient, is not sufficient for code validation.