The Generalized Untwist Problem of Rotating Blades: A Coupled Aeroelastic Formulation

The untwist of rotating blades in turbomachines treated so far in the literatare simply as a pure elasticity problem is generalized and formulated rigorously as a problem of aeroelasticity by variational principles (VPs) and generalized VP(GVP). It takes into account not only the centrifugal force, but also the aeroelastic interaction between blades and the flow as well as the elastic distortion of the cross section shape of blades, assuming the material to be linearly elastic but nonisotropic. Thus, a new rigorous theoretical basis for the finite element analysis of blade untwist in turbomachine design is provided. Nomenclature Aboundary surface or its area Astrain energy density AIinlet, outlet and hub/casing annuli A2uupstream periodic boundary surface: A2 = A2,, + A2u + A2. (Fig.1)