Report on a Study of Noise Generation by a Rotating Blade Row in an Infinite Annulus.
Interim scientific rept. 7 Jul 69-31 Mar 71,
CORNELL AERONAUTICAL LAB INC BUFFALO N Y
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Discrete-tone noise generation by high-speed fans and compressors has been studied by applying existing theories for the flow through a rotating blade row in an infinitely long annulus. McCunes analysis for the linearized, three-dimensional, compressible flow through a nonlifting blade row and its recent extension to lifting blades have both been used to find the acoustic disturbances produced by such flows. These analyses contain the cutoff condition for the duct acoustic modes, including the effect of through flow, and relate the amplitudes of the propagating modes to the blade thickness and loading. In the present work these relationships have been evaluated for some specific thickness and loading distributions to find the pressure and velocity fields away from the blade row. Methods have been developed to calculate the sound intensity flux upstream and downstream of the blade row and results are presented which demonstrate the influence of blade geometry and operating conditions on noise generation. Author
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