Investigation of Rotating Stall in a Single-Stage Axial Compressor Page: 2 of 29
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TECH LIBRARY KAFB, NM
NATIONAL ADVISORY COMMITTEE FOR AERONAU :lE11 111111 1111
TECHNICAL NOTE 3823
INVESTIGATION OF ROTATING STALL IN A
SINGLE-STAGE AXIAL COMPRESSOR
By S. R. Montgomery and J. J. Braun
The rotating-stall characteristics of a single-stage axial-flow
compressor were investigated. The number of stall cells and their propa-
gation velocities were found with and without stator blades. The meas-
ured velocities were compared with those predicted by Stenning's theory
(see NACA TN 35580), assuming the downstream pressure fluctuations to be
negligible, and correlation within 10 percent was obtained at the onset
of stall. It was found that the pressure fluctuations caused by rotating
stall were less downstream of the rotor than upstream; the minimum reduc-
tion across the rotor was 40 percent with stator blades and 75 percent
without stator blades. It was also found that, for the compressor tested,
the stator blades decreased the number of stall cells and tended to induce
rotating stall at larger mass flow rates.
Rotating stall may be defined as a region of separated flow moving
along a blade row. It has been a continuing problem in axial-compressor
development because the resulting vibrations cause severe blade stresses
to be imposed at low-mass-flow operation. If stall frequencies were
predictable, blades could be designed having critical frequencies dif-
ferent from the stall frequency.
Several theories have been put forward for predicting the propa-
gation velocity of a stall cell (refs. 1 to 3). These are all linearized
analyses, with Sears and Marble considering the cascade as an actuator disk
and Stenning, as a cascade of finite width. A further difference in the
theories occurs in connection with the assumption of the downstream flow
field; Sears and Marble considered the wakes to mix in zero length, so
that the flow field is a continuum, while Stenning also considered the
alternative assumption of a series of free jets discharging into a region
of constant pressure.
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Montgomery, S. R. & Braun, J. J. Investigation of Rotating Stall in a Single-Stage Axial Compressor, report, January 1957; (digital.library.unt.edu/ark:/67531/metadc56040/m1/2/: accessed January 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.