An aeroelastic stability analysis of a cascade of engine blades coupled only through aerodynamica is developed. The unique feature of the analysis is the direct use of unsteady aerodynamic pressures, rather than lifts and moments, in calculating the susceptibility of a cascade to flutter. The approach developed here is realistic and relevant for analysis of low aspect ratio blades. However, in the calculations presented in this paper, the surface is assumed to be divided into equal elemental areas. The formulation leads to a complex eigenvalue problem, the solution of which determines the susceptibility of the cascade to flutter. The eigenvalues of an assembly of alternately mistuned blades, operating at high reduced frequencies, appear to be very sensitive to the level of mistuned frequencies. The locus of eigenvalues shows a strong tendency to split even for very small percentage differences between the frequencies of the two sets of blades. Further, blades with identical frequencies, but alternately mistuned mode shapes, operating at high reduced frequencies show a tendency towards instability.
Aeroelastic Behavior of Low Aspect Ratio Metal and Composite Blades