Stall flutter prediction techniques for fan and compressor blades

A review is presented of stall Butter prediction methodology including empirical, analytical, and semi-empirical approaches, Because of the lack of accurate and efficient unsteady aerodynamic models for stall Butter predictions, interim semiempirical methods are developed to assist turbomachinery designers during the development of current advanced fan and compressor designs for both military and commercial applications. A semiempirical approach that builds on an empirical stall Butter database combined with a classical Bat plate linearized unsteady aerodynamic model that accounts for chordwise deformations has been developed. This model is shown to provide good correlations when compared to isolated airfoil and cascade data for standard configurations, When applied to low aspect ratio fans, this approach provided excellent correlations with experimental results.