Noise Due to Interaction of Boundary Layer Turbulence with a Compressor or a Propulser Rotor.

摘要

The radiated sound due to a compressor or propulsor rotating blade row was investigated under various operating conditions and inflows. The propulsor was operated in air with different blade space-to-chord ratios, different flow coefficients and differing turbulence (non-isotropic) inflows. The inflows ingested are: (1) the natural boundary layer on the hub and annulus wall, (2) a tripped boundary layer on the hub, and (3) a fully developed boundary layer on the hub. The turbulence properties were also altered by placing a grid at the inlet. The mean velocity profiles, turbulence intensities, length scales, and energy spectra of the inflow were measured, as well as near and far-field acoustic spectra. A parametric investigation of the effect of inflow characteristics on the radiated sound has been made. Several length scales were found to exist simultaneously. The noise due to small scale turbulence seems to depend on, i.e., turbulence velocity normal to the blade divided by the axial length scale. The long eddies are also responsible for discrete tone production. (Author)