Pre-Stall Instability Distribution Over a Transonic Compressor Rotor
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Authors
Gannon, A.J.
Hobson, G.V.
Subjects
transonic compressor
near-stall operation
nonaxisymmetric flows
near-stall operation
nonaxisymmetric flows
Advisors
Date of Issue
2009-05
Date
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Abstract
An investigation of the behavior of a transonic compressor rotor when operating close to
stall is presented. The specific areas of interest are the behavior and location of lowfrequency
instabilities close to stall. In running close to stall, compressors can begin to
exhibit nonperiodic flow between the blade passages even when appearing to be operating
in a stable steady-state condition. The data from the current rotor clearly show that
low-frequency instabilities were present during steady-state operation when stall was
approached. These frequencies are not geometrically fixed to the rotor and typically
appear at 0.3–0.8 of the rotor speed. The presence of these low-frequency instabilities is
known and detection is reasonably commonplace; however, attempts to quantify the location
and strength of these instabilities as stall is approached have proved difficult. In
the current test fast response pressure sensors were positioned in the case-wall; upstream,
downstream, and over the rotor blade tips. Simultaneous data from the sensors
were taken at successive steady-state settings with each being closer to stall. A time
domain analysis of the data investigates the magnitude of the instabilities and their
transient effect on the relative inlet flow angle. The data are also presented in the frequency
domain to show the development and distribution of the instabilities over the
rotor as stall was approached. Initially the instabilities appeared within the rotor row and
extended downstream but at operation closer to stall they began to protrude upstream as
well. The greatest amplitude of the instabilities was within the blade row in the complex
flow region that contains phenomena such as the tip-vortex/normal-shock interaction and
the shock/boundary-layer interaction. In addition as stall is approached the growth of the
instabilities is nonlinear and not confined to one frequency.
Type
Article
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Sponsors
Funder
The present study was part of the compressor research program sponsored by the Propulsion and Power Department of the Naval Air Warfare Centre, Patuxent River, MD with Ravi Ravindranath as the technical monitor.
Format
Citation
Journal of Fluids Engineering, Volume 131, May 2009.
Distribution Statement
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.