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Research Papers

# Axial Transonic Rotor and Stage Behavior Near the Stability Limit

[+] Author and Article Information
Anthony J. Gannon

Department of MAE, Naval Postgraduate School, 700 Dyer Road, RM 245, Monterey, CA 92943ajgannon@nps.edu

Garth V. Hobson

Department of MAE, Naval Postgraduate School, 700 Dyer Road, RM 245, Monterey, CA 92943gvhobson@nps.edu

William L. Davis

Department of MAE, Naval Postgraduate School, 700 Dyer Road, RM 245, Monterey, CA 92943william.l.davis@uscg.mil

J. Turbomach 134(1), 011009 (May 26, 2011) (8 pages) doi:10.1115/1.4003225 History: Received September 01, 2010; Revised September 07, 2010; Published May 26, 2011; Online May 26, 2011

## Abstract

Transient casing pressure data from a transonic rotor and rotor-stator stage measured using high-speed pressure probes embedded in the casewall over the rotor tips are analyzed. Using long data sets sampled at a high frequency, low-frequency (less than once-per-revolution) nonaxisymmetric flow phenomena were detected while operating at steady-state conditions near stall. Both the rotor and stage cases are investigated, and the difference in behavior of a rotor with and without a stator blade row is investigated. Data for both cases over the speed range 70–100% of design and from choke to near the stability limit (stall or surge) are presented. The root mean square power of the low-frequency signal as well as its fraction of the total pressure signal is presented. It was thought that the behavior of these signals as stall was approached could lead to some method of detecting the proximity of stall. For the rotor-only configuration, the strength of these nonaxisymmetric phenomena increased as stall was approached for all speed-lines. However, for the stage configuration, more representative of an operational machine, these were of a lower magnitude and did not exhibit a clearly increasing trend as stall was approached. This would seem to indicate that the stator suppressed these signals somewhat. It is also shown that these nonaxisymmetric phenomena led to a significant variation of the mean relative inlet flow angle into the rotor blade. During stable operation near to stall at 100% speed for the rotor-only case, a 1.9 deg variation of this angle was measured. This compared with a 5.6 deg variation over the entire speed-line. Further, it was observed that while the rotor and stage cases had different stability limits, their peak relative inlet flow angles near stall were similar for both along most speed-lines.

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## Figures

Figure 1

Transonic test rotor-stator stage

Figure 2

Rotor-only and stage stagnation pressure ratios

Figure 3

(a) Rotor-only and (b) stage isentropic efficiencies

Figure 4

Rotor-only and stage rotor-tip relative inlet Mach numbers

Figure 5

Kulite high-speed pressure probe positions

Figure 6

Rotor-only 100% near stall wall pressure contours

Figure 7

Rotor-only 100% speed spectral analysis

Figure 8

Filter performance and band-pass regions

Figure 9

Unfiltered and filtered pressure signal

Figure 10

Filtered pressure signal

Figure 11

Axial Mach number variation

Figure 12

(a) Rotor-only and (b) stage axial Mach number peak variation

Figure 13

(a) Rotor-only and (b) stage comparison of filtered signal magnitude and distribution

Figure 14

(a) Rotor-only and (b) stage low-frequency rms powers

Figure 15

(a) Rotor-only and (b) stage total rms power

Figure 16

(a) Rotor-only and (b) stage low-frequency/total rms nondimensional

Figure 17

Varying relative inlet flow angle

Figure 18

(a) Rotor-only and (b) stage mean-to-max relative inlet angle variation

Figure 19

(a) Rotor-only and (b) stage maximum relative inlet angle

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