Unsteady Flow and Whirl-Inducing Forces in Axial-Flow Compressors: Part I—Experiment

[+] Author and Article Information
A. F. Storace, D. C. Wisler, H.-W. Shin, B. F. Beacher

GE Aircraft Engines Cincinnati, OH 45215

F. F. Ehrich, Z. S. Spakovszky, M. Martinez-Sanchez

Massachusetts Institute of Technology, Cambridge, MA

S. J. Song

Seoul National University, Seoul, Korea

J. Turbomach 123(3), 433-445 (Feb 01, 2000) (13 pages) doi:10.1115/1.1378299 History: Received February 01, 2000
Copyright © 2001 by ASME
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Distribution of tangential blade force for LSRC Offset Rotor Test showing direction of mean and unsteady forces (Fm and Fu) at various circumferential positions; see Appendices B1 and B3a
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Regression plot of cross-axis-force for high compressor loading test point 5 in Fig. 7
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Computed beta coefficients for the LSRC compressor A offset rotor test showing that unsteady forces promote backward whirl over most of the compressor operating range. Test Points 1–6 correspond to those in Fig. 7.
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Models of whirl-inducing forces in turbines and compressors. Net force Fx=Fm+Fu acts perpendicular to the axis of displacement and drives rotor whirl; see Appendix B1.
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Schematic showing cross section of compressor A blading
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LSRC configuration for centerline offset tests showing circumferential variation in rotor tip clearance εR, and stator shroud seal clearance, εs. Looking down on spinning, nonwhirling eccentric rotor with casings moved relative to rotor assembly; see Appendix B2.
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Typical example showing the circumferential variation in unsteady static pressure obtained from a Kulite pressure transducer embedded in a rotor airfoil (96 percent span and 50 percent chord for the large rotor offset): (a) raw data, (b) FFT of raw data, (c) filtered signal.
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The two coordinate systems used to resolve blade forces: (1) blade fixed coordinate (Ttan,R), (blade geometry defined in this system); (2) rotating coordinate (X,Y) (the blade azimuth angle θ is defined in this coordinate system); see Appendix B3
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Overall performance of compressor A showing the effects of variation in axisymmetric clearances relative to baseline performance. Compressors A1–A4 are defined in Table 3 of Appendix A. Data accuracy is identical to that for Fig. 7, therefore data symbols are removed for clarity.
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Overall performance of Compressor A for rotor centerline offset tests relative to baseline performance
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Performance derivatives for compressor A in terms of change in total average clearance from baseline clearance levels
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Performance characteristic for compressors B and C
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(a, b, c) Contours of unsteady static pressure difference on the rotor airfoils at three clearance levels around the circumference for the large centerline offset. Zone A is affected by variation in rotor blade tip clearance and zone B is affected by stator shroud seal clearance. Both zones are affected by any radial flow redistribution; (d) chordwise distribution of measured, steady-state static pressure on rotor airfoil at 80 percent span.
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Circumferential variation of stator airfoil loading for Compressor A showing the effects different levels of rotor tip clearance due to centerline offset. (a–c) 90 percent span; (d–f) 50 percent span; (g–i) 5 percent span. Low, medium, and high compressor loading were obtained at test points 1, 3, and 5, respectively, in Fig. 7.
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Circumferential variation of the unsteady whirl inducing force components and running rotor tip clearance for the large centerline offset of LSRC Compressor A. Zone 1 is for net force increased and zone 2 for net force decreased. Data shown for Test Point 5 in Fig. 7; see Appendix B3a.




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