Accession Number : AD0782165

Title :   Effects of Finite Duct Length and Blade Chord on Noise Generation by a Rotating Blade Row,


Personal Author(s) : Lordi,J. A. ; Homicz,G. F. ; Rehm,R. G.

Report Date : JUN 1974

Pagination or Media Count : 17

Abstract : A theoretical study of discrete-tone noise generation by transonic fan or compressor blade rows is presented. A linearized analysis is made of the three-dimensional disturbance field produced by a rotor located at a finite distance from the open end of an unflanged semi-finite duct. The presence of a uniform mean flow is accounted for and the sound field is related to the blade thickness and loading distributions. The disturbances produced by the blade thickness and loading are obtained by superposition of solutions for rotating sources and dipoles. The solutions for point singularities in the presence of a mean flow are obtained by a transformation of the corresponding solutions in a medium at rest. The transformed problem is solved by extending classical results for the reflection and radiation of acoustic waves from the open end of an unflanged duct to account for sources in the field. (Modified author abstract)

Descriptors :   *Turbofan engines, *Jet engine noise, *Compressor noise, Compressor blades, Turbine blades, Noise pollution, Ducts, Noise reduction, Numerical analysis

Subject Categories : Acoustics
      Jet and Gas Turbine Engines

Distribution Statement : APPROVED FOR PUBLIC RELEASE