The Effect of Inlet Turbulence and Strut Generated Disturbances on Turbomachinery Noise.
Abstract
This thesis presents results of an investigation in which turbomachine rotor sound spectra variations were correlated with aerodynamic measurements of the inlet turbulence, strut wake, and vortex flow strength. Aerodynamic measurements that were made included mean velocity and turbulence intensity profiles, and the axial length scales. Inlet turbulence data indicate that the major effect of the flow contraction appears to be the elongation of atmospheric turbulent eddies from 20 cm to 200 cm. Eddies of this size dominate the generation of blade passing frequency (BPF) noise. Reducing the eddy size by the use of a grid revealed the vortex flow strength to be the second major source of noise at BPF. A doubling of vortex flow strength produced a 6 dB increase in the source pressure level (SPL) of the first BPF. The variation of the SPL with the decay of the strut wake was small. The SPL showed less than a 2 dB change with a doubling of the wake turbulence intensity or the velocity defect. The measured sound spectra were compared with predicted trends from two different analyses. The results of this comparison further supported the conclusion that the strut wake structure was not as effective in producing noise at the vortex strength or the inlet turbulent eddies. A discussion of the relative importance of various sources of noise due to the flow field is given.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 25, 1980
- Accession Number
- ADA098140
Entities
People
- R. Trunzo
Organizations
- Pennsylvania State University