Aeroelasticity of Fan Blades with Complex Modes
Research into fan blade flutter generally considers structural modes that are pure in either bending or torsion. Reality is often rather different. Real blade modes generally have both bending and torsion components. Moreover, the effect of rotation on large twisted blades induces complex modes, that is modes where the bending and torsion components are not perfectly in-phase.
The aeroelastic stability of complex modes is studied experimentally in a straight cascade wind tunnel in both sub and supersonic flow on a typical fan configuration. Aeroelastic coefficients are measured in the presence of pure plunging and pure pitching as well as complex combinations of these two motions. It is shown that reliable coefficients for complex modes can be obtained by superposition of the coefficients for plunging and pitching. Using the validated principle of superposition, the effect of realistic blade modal parameters on cascade stability is studied.
KeywordsModal Parameter Complex Motion Complex Mode Torsion Component Aeroelastic Stability
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