Resonant Blade Vibrations Caused by Low-Engine-Order Harmonics

This paper studies changes from one compressor stage to another stage of the large-scale flowfield defects associated with low-engine-order harmonics. Using numerical analysis of a typical compressor operating regime, the authors have found that each stage linearly transforms the flowfield. This transformation is not affected by boundary layers of blades, casing, and hub due to their small scales. Thus, simplified rotor and stator aerodynamic grids can be used to calculate large-scale flowfield defects. Taking these features into account, the authors have calculated the blade resonant response to the incoming flowfield defect of an industrial compressor. Experimental data from engine full-scale tests, in which the resonance with second engine order harmonics has been observed, validate the calculated resonant amplitude.