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Unsteady design-point flow phenomena in transonic compressorsHigh-frequency response probes which had previously been used exclusively in the MIT Blowndown Facility were successfully employed in two conventional steady state axial flow compressor facilities to investigate the unsteady flowfields of highly loaded transonic compressors at design point operation. Laser anemometry measurements taken simultaneously with the high response data were also analyzed. The time averaged high response data of static and total pressure agreed quite well with the conventional steady state instrumentation except for flow angle which showed a large spread in values at all radii regardless of the type of instrumentation used. In addition, the time resolved measurements confirmed earlier test results obtained in the MIT Blowdown Facility for the same compressor. The results of these tests have further revealed that the flowfields of highly loaded transonic compressors are heavily influenced by unsteady flow phenomena. The high response measurements exhibited large variations in the blade to blade flow and in the blade passage flow. The observed unsteadiness in the blade wakes is explained in terms of the rotor blades' shed vorticity in periodic vortex streets. The wakes were modeled as two-dimensional vortex streets with finite size cores. The model fit the data quite well as it was able to reproduce the average wake shape and bi-modal probability density distributions seen in the laser anemometry data. The presence of vortex streets in the blade wakes also explains the large blade to blade fluctuations seen by the high response probes which is simply due to the intermittent sampling of the vortex street as it is swept past a stationary probe.
Document ID
19860021258
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Gertz, J. B. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Epstein, A. H. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Date Acquired
September 5, 2013
Publication Date
August 1, 1986
Subject Category
Aircraft Propulsion And Power
Report/Patent Number
NAS 1.26:176879
NASA-CR-176879
Accession Number
86N30730
Funding Number(s)
CONTRACT_GRANT: NGL-22-009-383
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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