Aerodynamic Effects on Mistuned Response of a High-Speed, Low Aspect Ratio Fan

Blade response to an inlet total pressure distortion was measured in a integrally bladed disk, or blisk. Blade-to-blade variations in blade resonant frequencies, know as mistuning, and how these variations are related to vibratory stress amplitude and viscous damping variations were investigated. In addition, a reduced-order analytical model was used to predict the blade resonant stress variations based on the frequency variation measured in the blisk. The measured stress variations were found to be strongly influenced by unsteady aerodynamic coupling. Blade structural mistuning and mechanical coupling through hub motion were determined to have only a minor influence on blade-to-blade stress variations. Stress distribution patterns at resonance and at constant speeds, above and below resonance suggested a relationship between stress variations and unsteady aerodynamics. To support this, aerodynamic damping variations measured at resonance were shown to roughly correspond to stress variations. Experimental results were compared to the predicted variations from the reduced-order model. Results from the model indicated that unsteady aerodynamic coupling played at important role in the mistuned response of the blisk.Air Force Research Lab Wright-Patterson AFB OH Propulsion Directorate is the author of 'Aerodynamic Effects on Mistuned Response of a High-Speed, Low Aspect Ratio Fan' with ISBN 9781423554004 and ISBN 1423554000.