Structural and Aerodynamic Considerations of an Active Piezoelectric Trailing-Edge Tab on a ...

277 Pages·2013·10.57 MB·English

by  Gabriel Jon Murray

The Pennsylvania State University
The Graduate School
STRUCTURAL AND AERODYNAMIC CONSIDERATIONS OF AN
ACTIVE PIEZOELECTRIC TRAILING-EDGE TAB ON A
HELICOPTER ROTOR
A Dissertation in
Aerospace Engineering
by
Gabriel Jon Murray
c 2013 Gabriel Jon Murray
(cid:13)
Submitted in Partial Fulfillment
of the Requirements
for the Degree of
Doctor of Philosophy
May 2013
The dissertation of Gabriel Jon Murray was reviewed and approved by the fol-
∗
lowing:
Farhan Gandhi
Professor of Aerospace Engineering
Dissertation Advisor, Chair of Committee
Edward Smith
Professor of Aerospace Engineering
Joseph Horn
Professor of Aerospace Engineering
Timothy Miller
Senior Research Associate
George A. Lesieutre
Professor of Aerospace Engineering
Head of the Department of Aerospace Engineering
Signatures are on file in the Graduate School.
∗
Abstract
Rotorcrafthaveauniqueabilitynottypicallysharedwiththeirfixed-wingbrethren,
namely the ability to hover, maintaining position over a fixed point on the Earth
in a zero-wind environment. The rotation of the rotorcraft’s wings (rotor blades)
allows them to experience apparent wind, even if the rotorcraft is not moving
relative to the surrounding air. However, this ability comes at a cost, namely
a more complex operating condition for the rotor. One of the consequences of
this complex environment is increased noise and vibrations compared to airplanes.
Research has been focused on this issue for some time, considering myriad methods
of achieving noise and vibration reduction.
Thisdissertationisconcernedwithanactivetabforuseonarotorcraftfornoise
and vibration reduction. The tab is located at the trailing edge of the airfoil. The
tab consists of a shim sandwiched by layers of the piezoelectric actuators, macro
fibercomposites, ofvaryinglength. Thisconfigurationissimilartoabimorph. The
modus operandi is similar to that of a trailing edge flap. The actuators deform the
tab, bending it to achieve a tip displacement. This provides a change in the lift,
moment, and drag coefficients of the airfoil. By actuating the system at 3/rev to
5/rev, reductions in noise and vibration can be realized. The system was examined
and designed around using the UH-60 Blackhawk as the model rotorcraft. The tab
is envisioned to operate between 65% to 85% of the main rotor span. The tab’s
chordwise dimensions considered were 20% and 15% of the blade chord.
In order to assess the potential of the tab to change the lift and moment coeffi-
cients of the airfoil-tab system, a steady computational fluid dynamics study was
conducted. The results were generated via the University of Maryland’s Transonic
Unsteady Navier-Stokes code. Various tab deflection angles, Mach numbers, and
angle-of-attack values were computed. These results were compared to a trailing
edge flap of similar size. The comparison shows that the tab produces lift and mo-
ment increments similar to that of the trailing edge flap. The moment increment
iii
of the tab is consistently larger than the moment increment of the trailing edge
flap. The 15% chord tab produces a smaller increment in lift and moment for a
given tip deflection than the 20% chord tab. The longer tab has a lift coefficient
on average 1.18 times the shorter tab and a moment increment 1.15 times that of
the shorter tab.
The design of the tab—composed of both active piezoelectric actuators and
passive materials—was conducted using finite element analysis. The objectives
were to maximize the tip deflection due to the actuators, while minimizing the
deformation due to inertial and aerodynamic forces and loads. The inertial loads
(acceleration terms) come from both blade motion, such as flapping and pitch,
as well as the rotation of the rotor (centrifugal force). All of these previously
mentioned terms cause the tab to undergo undesirable deflections. The original
concept consisted of a bimorph configuration with a single layer of macro fiber
composite the entire length of the 20% chord tab. The final design has three,
tapered actuator layers on either side of a shim. Also, the length of the tab was
reduced to 15% of the chord. A multitude of designs were compared via their
performance objectives as well as how the design variables changed performances
relative to the objectives. The result of this detailed analysis was the selection of
several configurations that were investigated in detail.
With several designs selected, they formed the basis to build a prototype tab.
This prototype was based on a 15% chord tab. Due to the available commercial
actuatorlengths, atwolayersystemwasultimatelybuilt. Thetabtipdisplacement
was measured with both static and harmonic inputs. Various input voltages, both
with and without a DC offset, were tested, up to -500 V to 1500 V. The input
frequency was varied between 0 Hz to 17.2 Hz. Also, a frequency response of
the tab was generated. High voltage static tip displacement compares well with
the expected result. The first bending natural frequency was measured at 138
Hz and compares well with the computed range of 135 Hz to 142 Hz, depending
on bond layer thickness. The results of dynamic inputs uncovered an unexpected
reduction in tip displacement of 60% to 65% of the static result, for high voltages.
It is suspected that the actuator suffers from a time-dependent response, with
quick initial displacement followed by a slow creeping to the final displacement
value. This phenomena has also been observed in the literature, although it is not
prevalent.
Using the experiment as a guide to quantify the time-dependent behavior, the
overall viability of the system is discussed. The maximum dynamic tip deflection
(accounting for time-dependent behavior) of a 15% chord tab is 4 . The tab is able
◦
to generate lift coefficient increments up to 0.413 and moment increments of -0.068
for positive tab deflections. Deflections due to aerodynamic loads range from 0.3
◦
to 2 . Deflections due to blade motions are less than 0.5 and due to the centrifugal
◦ ◦
iv
force, 0.78 . This system can be stiffened, reducing the dynamic tip deflection to
◦
3.25 andlimitingtheaerodynamicresponseto1 . Overall, bydesigningthetabto
◦ ◦
modest deflections, moderate reductions in vibration are possible, but are limited
by actuator authority.
v
Table of Contents
List of Figures xi
List of Tables xix
List of Symbols xxiii
Acknowledgments xxvi
Chapter 1
Introduction 1
1.1 Background and Motivation . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Actuators and Smart Materials . . . . . . . . . . . . . . . . . . . . 5
1.3 Individual Blade Control . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.1 US/German MOU on helicopter aeromechanics . . . . . . . 8
1.3.2 Deutsches Zentrum fu¨r Luft- und Raumfahrt (DLR) . . . . . 9
1.3.3 ZF Luftfarhrttechnik . . . . . . . . . . . . . . . . . . . . . . 9
1.3.4 University of Maryland . . . . . . . . . . . . . . . . . . . . . 10
1.4 Trailing Edge Flap . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4.1 University of Maryland . . . . . . . . . . . . . . . . . . . . . 11
1.4.2 Massachusetts Institute of Technology . . . . . . . . . . . . 18
1.4.3 McDonnell-Douglas and Boeing companies . . . . . . . . . . 21
1.4.4 US Army Aviation RD&E Center . . . . . . . . . . . . . . . 23
1.4.5 University of Michigan . . . . . . . . . . . . . . . . . . . . . 25
1.4.6 Advanced Technology Institute of Commuter-helicopter . . . 27
1.4.7 Eurocopter . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
1.4.8 The Pennsylvania State University . . . . . . . . . . . . . . 30
vi
´
1.4.9 Office National d’ Etudes et de Recherches A´erospatiales
(ONERA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.4.10 Royal Institute of Technology (Sweden) and Technion . . . . 33
1.4.11 Japan Aerospace Exploration Agency (JAXA) . . . . . . . . 33
1.4.12 Seoul National University . . . . . . . . . . . . . . . . . . . 34
1.4.13 US Army Research, Development, and Engineering Com-
mand (ARMDEC) . . . . . . . . . . . . . . . . . . . . . . . 34
1.4.14 Non-piezoelectric driven flaps . . . . . . . . . . . . . . . . . 35
1.5 Variable Camber . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
1.6 Blade Twist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
1.7 Active Gurney Flap . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
1.8 Trailing Edge Tab and Variable Chord . . . . . . . . . . . . . . . . 39
1.8.1 National Aerospace Laboratory of Japan/JAXA . . . . . . . 39
1.8.2 Western Michigan University . . . . . . . . . . . . . . . . . . 41
1.8.3 EADS/Eurocopter . . . . . . . . . . . . . . . . . . . . . . . 41
1.8.4 Technical University of Denmark . . . . . . . . . . . . . . . 44
1.8.5 The Pennsylvania State University . . . . . . . . . . . . . . 45
1.9 Multiple Morphing Device Helicopter Performance Analysis . . . . . 49
1.10 Concept and research objectives . . . . . . . . . . . . . . . . . . . . 50
1.10.1 Organization structure of dissertation . . . . . . . . . . . . . 52
Chapter 2
Steady Aerodynamic Study of Tab 54
2.1 Analysis Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
2.2 Aerodynamic Coefficient Results and Discussion: 0.20c tab . . . . . 56
2.2.1 Lift coefficient and increment for Mach number=0.4 . . . . . 57
2.2.2 Moment coefficient and increment for Mach number=0.4 . . 58
2.2.3 Drag coefficient and increment for Mach number=0.4 . . . . 59
2.2.4 Lift coefficient increment per unit drag for Mach number=0.4 61
2.2.5 Moment coefficient increment per unit drag for Mach num-
ber=0.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
2.2.6 Lift coefficient and increment for Mach number=0.6 . . . . . 64
2.2.7 Moment coefficient and increment for Mach number=0.6 . . 67
2.2.8 Drag coefficient and increment for Mach Number=0.6 . . . . 69
2.2.9 Lift coefficient increment per unit drag for Mach number=0.6 70
2.2.10 Moment coefficient increment per unit drag for Mach num-
ber=0.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
2.2.11 Lift coefficient and increment for Mach number=0.8 . . . . . 72
2.2.12 Moment coefficient and increment for Mach number=0.8 . . 75
2.2.13 Drag coefficient and increment for Mach Number=0.8 . . . . 77
vii
2.2.14 Lift coefficient increment per unit drag for Mach number=0.8 78
2.2.15 Moment coefficient increment per unit drag for Mach num-
ber=0.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
2.3 Comparison of Aerodynamic Coefficients: 0.20c & 0.15c tabs . . . . 82
2.3.1 Comparison of 0.20c & 0.15c for boundary rotor conditions . 82
2.4 Comparison of SC-1094R8 With and Without Tab Extension . . . . 86
Chapter 3
Design and Analysis of Tab 93
3.1 Basic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.1.1 Simple analysis . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.1.2 Analysis using Euler-Bernoulli beam theory . . . . . . . . . 97
3.2 Layered-Actuation Tab . . . . . . . . . . . . . . . . . . . . . . . . . 103
3.2.1 0.2c tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
3.2.2 0.15c tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.2.3 Nondominated set: flapping, aerodynamics, and active dis-
placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
3.3 Spanwise Actuator Variation Tab Design . . . . . . . . . . . . . . . 114
3.4 Selected Configuration . . . . . . . . . . . . . . . . . . . . . . . . . 118
3.4.1 Mode shapes and natural frequencies . . . . . . . . . . . . . 118
3.4.2 Active, aerodynamic, and flapping deflections: 0.15c and
0.2c tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
3.4.3 Rotating environment and blade pitching and flapping an-
gles: 0.15c tab . . . . . . . . . . . . . . . . . . . . . . . . . . 127
3.5 Assessment of Design Achieving Objectives . . . . . . . . . . . . . . 130
Chapter 4
Benchtop Tab Demonstrator 132
4.1 Design of Experimental Tab . . . . . . . . . . . . . . . . . . . . . . 132
4.2 Experimental Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
4.2.1 Testing equipment . . . . . . . . . . . . . . . . . . . . . . . 135
4.2.1.1 Requirements . . . . . . . . . . . . . . . . . . . . . 135
4.2.1.2 Equipment specifications . . . . . . . . . . . . . . . 137
4.2.2 Test specimen . . . . . . . . . . . . . . . . . . . . . . . . . . 140
4.3 Experimental Results and Discussion . . . . . . . . . . . . . . . . . 142
4.3.1 Testing objectives . . . . . . . . . . . . . . . . . . . . . . . . 142
4.3.2 Finite element model of experimental tab . . . . . . . . . . . 145
4.3.3 Testing results and discussion . . . . . . . . . . . . . . . . . 146
4.3.3.1 DC input . . . . . . . . . . . . . . . . . . . . . . . 146
4.3.3.2 Tab frequency response . . . . . . . . . . . . . . . 149
viii
4.3.3.3 Example time trace of output subjected to har-
monic loading . . . . . . . . . . . . . . . . . . . . . 152
4.3.3.4 Harmonic input with DC offset . . . . . . . . . . . 153
4.3.3.5 Harmonic input without DC offset . . . . . . . . . 153
4.3.3.6 Amplifier voltage and current output . . . . . . . . 156
4.3.3.7 Low frequency response . . . . . . . . . . . . . . . 157
4.3.4 High-speed camera results . . . . . . . . . . . . . . . . . . . 158
4.3.5 Exploration of frequency response . . . . . . . . . . . . . . . 161
4.3.6 Tab robustness . . . . . . . . . . . . . . . . . . . . . . . . . 168
Chapter 5
Assessment of Reduced Performance 169
5.1 Impact on Inertial and Aerodynamic Response . . . . . . . . . . . . 169
5.2 Impact on Optimal Designs . . . . . . . . . . . . . . . . . . . . . . 170
5.3 Impact on Active Performance and Viability of Concept . . . . . . . 172
Chapter 6
Conclusion 176
6.1 Steady Aerodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . 177
6.2 Tab and Actuator Design . . . . . . . . . . . . . . . . . . . . . . . . 177
6.3 Benchtop Prototype . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
6.4 Assessment of Reduced Performance . . . . . . . . . . . . . . . . . 182
6.5 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Appendix A
Aerodynamic Coefficient Tables, 0.20c 186
A.1 Lift Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
A.2 Moment Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
A.3 Drag Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
A.4 Increment in Lift Coefficient . . . . . . . . . . . . . . . . . . . . . . 198
A.5 Increment in Moment Coefficient . . . . . . . . . . . . . . . . . . . 203
A.6 Increment in Drag Coefficient . . . . . . . . . . . . . . . . . . . . . 208
Appendix B
Aerodynamic Coefficient Tables, 0.15c 213
B.1 Lift Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
B.2 Moment Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
B.3 Drag Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
B.4 Increment Lift, Moment, and Drag Coefficients . . . . . . . . . . . . 220
ix
Appendix C
CFD Code Used to Generate Tab Pressure Differences 222
C.1 Steady Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
Appendix D
Macro Fiber Composite Properties 226
Appendix E
Effect of Damping on the Tab Response 227
Bibliography 233
x