NAVAL POSTGRADUATE SCHOOL Monterey, California

THESIS

EXPERIMENTAL INVESTIGATION OF VORTEX SHEDDING IN HIGH REYNOLDS NUMBER FLOW OVER

COMPRESSOR BLADES IN CASCADE

by

Choon Peng, Lim

March 2003

Thesis Advisor: Garth V. Hobson Second Reader: Raymond P. Shreeve

Approved for public release; distribution is unlimited

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4. TITLE AND SUBTITLE: Experimental Investigation of Vortex Shedding in High Reynolds Number Flow Over Compressor Blades in Cascade 6. AUTHOR(S) Choon Peng, Lim

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13. ABSTRACT (maximum 200 words) An investigation of vortex shedding downstream of a cascade of compressor stator blades, at off-design inlet-flow

angles of 35, 33 and 31 degrees and Reynolds numbers, based on chord length, of 625,000, 750,000 and 800,000 is reported. The objective of the study was to characterize the flow and vortex shedding through blade surface pressure

measurements and hot-wire anemometry. Vortex shedding was determined to be a leading edge phenomenon as periodic shedding was only detected on the pressure side of the wake. The relationship between vortex shedding frequency and Reynolds number was nearly linear. The vortex shedding frequency at three incidence angles was observed to be quite similar at lower Reynolds number (i.e. 450,000 and below) but developed into a larger scatter at higher Reynolds number. Similarly, the Strouhal numbers were observed to be fairly consistent (0.22 to 0.24) at low Reynolds number and more scattered (0.18 to 0.25) with increasing Reynolds number. The result obtained was comparable to the experimental results obtained by Roshko[Ref. 14], for vortex shedding behind a circular cylinder.

15. NUMBER OF PAGES 97

14. SUBJECT TERMS Controlled-diffusion, Compressor, Stator, Cascade, Turbomachinery, Hot-wire anemometry, Laser-Doppler velocimetry, Vortex shedding

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NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. 239-18

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Approved for public release; distribution is unlimited

EXPERIMENTAL INVESTIGATION OF VORTEX SHEDDING IN HIGH REYNOLDS NUMBER FLOW OVER COMPRESSOR BLADES IN CASCADE

Choon Peng, Lim Major, Republic of Singapore Air Force

B.E., Mechanical, Nanyang Technological University, 1996

Submitted in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE IN AERONAUTICAL ENGINEERING

from the

NAVAL POSTGRADUATE SCHOOL March 2003

Author: Choon Peng, Lim Approved by: Garth V. Hobson Thesis Advisor Raymond P. Shreeve Second Reader Max F. Platzer Chairman, Department of Aeronautics and Astronautics

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ABSTRACT

An investigation of vortex shedding downstream of a cascade of compressor

stator blades, at off-design inlet-flow angles of 35, 33 and 31 degrees and Reynolds

numbers, based on chord length, of 625,000, 750,000 and 800,000 is reported.

The objective of the study was to characterize the flow and vortex shedding

through blade surface pressure measurements and hot-wire anemometry. Vortex shedding

was determined to be a leading edge phenomenon as periodic shedding was only detected

on the pressure side of the wake. The relationship between vortex shedding frequency

and Reynolds number was nearly linear. The vortex shedding frequency at three

incidence angles was observed to be quite similar at lower Reynolds number (i.e. 450,000

and below) but developed into a larger scatter at higher Reynolds number. Similarly, the

Strouhal numbers were observed to be fairly consistent (0.22 to 0.24) at low Reynolds

number and more scattered (0.18 to 0.25) with increasing Reynolds number. The result

obtained was comparable to the experimental results obtained by Roshko [Ref. 14], for

vortex shedding behind a circular cylinder.

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TABLE OF CONTENTS

I. INTRODUCTION........................................................................................................1 A. BACKGROUND ..............................................................................................1 B. PURPOSE.........................................................................................................3

II. TEST FACILITY AND INSTRUMENTATION......................................................5 A. LOW-SPEED CASCADE WIND TUNNEL .................................................5 B. TEST SECTION ..............................................................................................5 C. INSTRUMENTATION AND DATA ACQUISITION.................................7

1. Pressure Surveys ..................................................................................7 2. Hot-Wire Anemometry........................................................................8 3. LDV Instrumentation and Data Acquisition.....................................9

III. EXPERIMENTAL PROCEDURE...........................................................................11 A. REYNOLDS NUMBER AND INLET-FLOW ANGLE VARIATION ....11 B. PRESSURE MEASUREMENTS .................................................................12 C. HOT-WIRE ANEMOMETRY.....................................................................12

1. IFA 100 and Hot-Wire Calibration..................................................12 2. Hot-Wire Wake Surveys....................................................................13 3. Strouhal Number Survey ..................................................................13

D. LDV MEASUREMENTS..............................................................................14 1. Inlet Guide Vane Adjustment ...........................................................14 2. Particle Seeding..................................................................................14 3. LDV Inlet Surveys..............................................................................14

IV. RESULTS AND DISCUSSION ................................................................................15 A. SURFACE PRESSURE MEASUREMENTS..............................................15 B. WAKE FLOW SURVEYS............................................................................19 C. STROUHAL NUMBER SURVEY...............................................................26

V. CONCLUSIONS AND RECOMMENDATIONS...................................................35 A. CONCLUSIONS ............................................................................................35 B. RECOMMENDATIONS...............................................................................37

APPENDIX A: TABLES OF SCANIVALVE PORTS AND CHANNEL ASSIGNMENTS ........................................................................................................39

APPENDIX B: HOT-WIRE ANEMOMETRY CALIBRATION AND OPERATING PROCEDURES..........................................................................................................41

APPENDIX C: BLADE SURFACE MEASUREMENT OPERATING PROCEDURES..........................................................................................................47

APPENDIX D: LASER-DOPPLER VELOCIMETRY OPERATING PROCEDURES..........................................................................................................49

APPENDIX E: TABULATED DATA FOR HOT-WIRE WAKE SURVEY...................53

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APPENDIX F: FREQUENCY SPECTRUM PLOTS FOR STROUHAL NUMBER SURVEY .....................................................................................................................63

APPENDIX G: LDV INLET-FLOW SURVEY..................................................................75

APPENDIX H: TABULATED DATA FOR L