EXPERIMENTAL INVESTIGATION OF AN AIRFOIL WITH CO-FLOW

89 Pages·2005·2.03 MB·English

EXPERIMENTAL INVESTIGATION OF AN AIRFOIL
WITH CO-FLOW JET FLOW CONTROL

By

ADAM JOSEPH WELLS

A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2005
Copyright 2005

by

ADAM JOSEPH WELLS
ACKNOWLEDGMENTS
The author expresses special thanks to the supervisory committee chairman, Dr.
Bruce F. Carroll, for his continued guidance, encouragement and devotion. Appreciation
is also due to Dr. Ge-Cheng Zha, whose passion for the co-flow airfoil is contagious.
Gratitude is also addressed to the other supervisory committee members, Dr. Lou
Cattafesta and Dr. William Lear Jr., for their support. The author also wishes to
acknowledge all family and friends that helped make this possible.

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TABLE OF CONTENTS

page
ACKNOWLEDGMENTS.................................................................................................iii
LIST OF TABLES.............................................................................................................vi
LIST OF FIGURES..........................................................................................................vii
ABSTRACT.......................................................................................................................ix
CHAPTER
1 INTRODUCTION........................................................................................................1
2 APPARATUS MODIFICATIONS AND ASSEMBLY..............................................3
Co-Flow Jet Airfoil Description...................................................................................3
Wind Tunnel Modifications..........................................................................................6
Mass Flow Rate Controls............................................................................................10
Balance Modifications................................................................................................13
Calibration of Airfoil..................................................................................................14
Instrumentation and Measurements............................................................................18
Uncertainty Analysis..................................................................................................23
3 PROCEDURE.............................................................................................................27
4 DISCUSSION OF RESULTS....................................................................................30
Different Tests Conducted..........................................................................................30
Improved Lift, Drag and Stall.....................................................................................33
Instability of the Jet....................................................................................................38
Stagnation Point Location...........................................................................................39
PIV Results.................................................................................................................39
Drag Determination From Wake Measurements........................................................54
5 CONCLUSIONS........................................................................................................56
APPENDIX
A DETAILED CALIBRATION PROCEDURE............................................................58
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B LIST OF INSTRUMENTATION AND EQUIPMENT.............................................60
C DETAILED AIRFOIL ASSEMBLY PROCEDURE.................................................62
D DETAILED WINDTUNNEL ASSEMBLY PROCEDURE......................................65
E PIV IMAGES..............................................................................................................68
LIST OF REFERENCES...................................................................................................77
BIOGRAPHICAL SKETCH.............................................................................................79

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LIST OF TABLES
Table page

2-1. Orifice plate 1494 coefficients.................................................................................12
2-2. List of the uncertainties of the measured values......................................................24
2-3. Uncertainty in orifice plate calculation....................................................................25
4-1. Lift and drag test matrix...........................................................................................31
4-2. PIV test matrix.........................................................................................................32
4-3. Ratio of lift with tunnel off to lift with tunnel on.....................................................33
4-4. Comparison between CFJ airfoils and baseline airfoil.............................................35

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LIST OF FIGURES
Figure page

2-1. 2-D cross section of CFJ airfoils................................................................................4
2-2. How CFJ0025-131-196 turns into NACA 0025........................................................5
2-3. Unmodified Aerolab wind tunnel...............................................................................6
2-4. Modified Aerolab wind tunnel...................................................................................7
2-5. Hose/clamp attachment to cylinder and balance mechanism. Airfoil is attached
in horizontal position inside tunnel.............................................................................8
2-6. Connection between the balance cylinder and the airfoil..........................................8
2-7. Connection between the suction manifold and the airfoil..........................................9
2-8. Plexiglas box and suction manifold with airfoil located to the left and external
suction connection to the right.................................................................................10
2-9. Normal force calibration curves...............................................................................16
2-10. Axial force calibration curves..................................................................................16
2-11. Lift correction curve.................................................................................................17
2-12. Drag correction curve...............................................................................................18
2-13. Program used in wind tunnel testing........................................................................21
4-1. Lift coefficient verse angle of attack for CFJ0025-065-196....................................34
4-2. Drag polar for CFJ0025-065-196.............................................................................35
4-3. Injection jet coefficients of CFJ0025-065-196.........................................................36
4-4. Lift coefficient verse angle of attack for CFJ0025-131-196....................................37
4-5. Drag polar for CFJ0025-131-196.............................................................................37
4-6. Injection jet coefficients of CFJ0025-131-196.........................................................38
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4-7. Stagnation point location for CFJ0025-065-196 at 20 degrees angle of attack and
A) high and B) low mass flow rates.........................................................................40
4-8. Stagnation point location for CFJ0025-065-196 at 30 degrees angle of attack and
A) high and B) low mass flow rates.........................................................................41
4-9. PIV image of flow over CFJ0025-065-196 A) 40 deg and B) 43 deg......................42
4-10. PIV image of flow over CFJ0025-131-196 A) 36 deg and B) 43 deg......................43
4-11. PIV image of flow over baseline airfoil A) 10 deg and B) 20 deg...........................44
4-12. Velocity profiles of baseline airfoil, CFJ0025-065-196 and CFJ0025-131-196 at
10 degree AOA and various chord locations, A) 5% B) 15% C) 30% D) 50% E)
75% F) 100%............................................................................................................45
4-13. Velocity profiles of baseline airfoil, CFJ0025-065-196 and CFJ0025-131-196
combined into single graph (10 degree AOA).........................................................46
4-14. Positions from where velocity profiles where taken. The arrows designate the
location of the injection and suction slots................................................................47
4-15. Velocity profiles of CFJ0025-065-196 and CFJ 0025-131-196 at 30 degree AOA
and various chord locations, A) 5% B) 15% C) 30% D) 50% E) 75%....................48
4-16. Velocity profiles of CFJ0025-065-196 and CFJ0025-131-196 combined into
single graph (30 degree AOA).................................................................................49
4-17. Velocity profiles of CFJ0025-065-196 at various AOA and chord locations, A)
5% B) 15% C) 30% D) 50% E) 75% F) 100%........................................................49
4-18. Velocity profiles of CFJ0025-065-196 at various AOA combined into single
graph.........................................................................................................................50
4-19. Velocity profiles of CFJ0025-131-196 at various AOA and chord locations, A)
5% B) 15% C) 30% D) 50% E) 75% F) 100%........................................................51
4-20. Velocity profiles of CFJ0025-131-196 at various AOA combined into single
graph.........................................................................................................................52
4-21. Wake profiles of three different airfoil configurations at 0 deg AOA.....................53
4-22. Wake profiles of three different airfoil configurations at 10 deg AOA...................53
4-23. Wake profiles of CFJ airfoils at 30 deg AOA..........................................................54
4-24. Control volume over airfoil......................................................................................55

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Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
EXPERIMENTAL INVESTIGATION OF AN AIRFOIL
WITH CO-FLOW JET FLOW CONTROL
By
Adam Joseph Wells
August 2005
Chair: Bruce F. Carroll
Major Department: Mechanical and Aerospace Engineering
This thesis describes the effort to experimentally verify the high performance
characteristics of the co-flow jet (CFJ) airfoil. The CFJ utilizes tangentially injected air
at the leading edge and tangentially removed air at the trailing edge to increase lift and
stall margin and also decrease drag. The mass flow rates of the injection and suction are
equal, so there is a zero net mass flow rate. The existing MAE subsonic Aerolab wind
tunnel with a one-foot by one-foot test section was modified to accommodate the
injection and suction needed for the CFJ airfoils. The compressor and vacuum systems
were reconfigured so the mass flow rate of air could be measured and controlled. The
sting balance used to hold the airfoil in the test section and gather lift and drag
information was also modified from a previous design.
Two airfoils were tested at the University of Florida. One airfoil had an injection
slot size of 0.65% chord length (chord length was six inches) and the other had an
injection slot size twice as large or 1.31% chord length. Both airfoils had a suction slot
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size of 1.96% chord length. The smaller injection slot size performed superior for
increased lift and stall margin, whereas the larger injection slot size performed superior
for decreased drag. The smaller injection slot airfoil had an increase in maximum lift of
113% to 220% and an increase in stall margin of 100% to 132% when compared to the
baseline airfoil. When the mass flow rate was run at high levels, negative drag (i.e.,
thrust) was measured for both airfoils.
Particle image velocimetry (PIV) was used to quantify the flow field over the
suction surface of the CFJ airfoils. The stagnation point was also studied from the PIV
images. Although the movement due to variations in the mass flow rate could be seen,
the exact location of the stagnation point could not be seen with the current setup because
it lies on the pressure surface of the airfoil. The PIV images also helped in studying the
wake of the airfoils. A wake surplus could be seen in the CFJ airfoils, whereas a
conventional airfoil would have a wake deficit.

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