Aeroelastic vibration analysis of a 1.5 stage compressor

Abstract

Aeroelastic vibration problems are commonly found in modern compressors operating in off-design conditions. Large amplitude vibration could lead to high cycle fatigue (HCF) of blade and usually occurs in front stages of axial compressors. In this study, the influence of tip gap size on aeroelastic stability is analyzed in a 1.5 stage compressor with an in-house fluid-structure interaction code. A three-dimensional unstructured finite-volume compressible flow solver is applied in the fluid domain and a structure dynamic solver with the modal superimposition method for blade motion is used in the structure domain. Rotor tip clearances of 1%, 2% and 3% of tip axial chord at maximum rotor loading conditions at off-design speeds are analyzed for aeroelastic stability. The tip leakage flow and vortex structure can be seen near the blade tip region at a larger tip gap size. The aeroelastic stability of rotor blade at different tip gap sizes is mainly influenced by the 1st torsion mode, and the variation of aerodynamic damping is not monotonous. The intensity of the tip vortex and shock wave are the key factors affecting the aeroelastic stability of rotor when tip gap size increases. Keywords: Aeroelastic vibration problems, Axial compressors, Tip gap size, Aeroelastic stability, Tip vortex, Shock wave