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The design and fabrication of morphing airfoils using MFC (Micro-Fiber Composite) actuators. The research focuses on changing the upper wing surface of the airfoil by implementing MFC actuators and evaluating their aerodynamic performance compared to other control techniques such as steady jet injection and DBD plasma actuation. The document also explores the advantages and disadvantages of using MFC actuators for airfoil shaping.
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c : Model chord CD : Drag Coefficient CD0 : Zero-Lift Drag Coefficient CL : Lift Coefficient D : Drag Force I : Current L : Lift Force l : Local coordinate tangent to the airfoil surface M : Mach number N : Normal Force n : Local coordinate normal to the airfoil surface P : Actuation Power p : Pressure q : Dynamic Pressure Re : Reynolds Number St : Strouhal number s : Model span (width) u : Free-stream velocity U∞ : Free-stream Velocity V : Voltage x : Stream-wise coordinate of the wind tunnel y : Span-wise coordinate of the wind tunnel z : Vertical coordinate of the wind tunnel
Greek letters: α : Angle of attack of the airfoil ρ : Air density μ : Dynamic Viscosity
Symbols: ∞ : free-stream conditions
Abbreviation: DBD: Dielectric Barrier Discharge EAP: Electroactive Polymer LE: Leading Edge NUS: National University of Singapore PZT: Piezoelectricity SMA: Shape Memory Alloy TE: Trailing Edge
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This project may not have been successful without the help and guidance of the following
persons:
Once again, I would wish to express my utmost gratitude and appreciation for the great deal of support and assistance received from the above persons during the course of the project. I had indeed learnt and gained invaluable knowledge from all of them.
Cheers!
12 th^ of January, 2012
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REFERENCES g) … ……………………………………………………………...... 134
H) APPENDIXES i) Sm
Appendix A Macro Fiber Composite 145
Appendix B CAD Drawing of the Test Section and Models Components
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Figure 2.1: History of Aircraft Morphing Technologies [14]. ............................................... 8
Figure 2.2: Classification of various types of wing designs. ............................................... 12
Figure 2.3: Wing Sweep Method [25]. ................................................................................ 13
Figure 2.4: Different wing sweep designs (a) Unswept, (b) back Swept, (c) forward swept, (d) variable swept, and (e) oblique Swept [27].................................... 14
Figure 2.5: Different Types of Swept Wing Aircrafts. ........................................................ 15
Figure 2.6: Spanwise method [25]. ...................................................................................... 16
Figure 2.7: RK Fighter prototypes developed by G.I Bakashev: (a) RK [31] (b) RK-I [33]. ................................................................................................................. 16
Figure 2.8: Variable-span wing system with (a) Ball bearings (b) Center structure and mechanism details [34]. .................................................................................. 17
Figure 2.9: Variable-span wing mounted on the UAV prototype [34]. ............................... 17
Figure 2.10: Chord length extends [27]. .............................................................................. 19
Figure 2.11: Dihedral wing aircraft [25]. ............................................................................. 20
Figure 2.12: (a) Dihedral wing (b) Anhedral wing [27]. ..................................................... 20
Figure 2.13: Low-Wing Aircraft (a) High-Wing Aircraft (b) [39]. ..................................... 21
Figure 2.14: MiG 105-11 [40]. ............................................................................................ 21
Figure 2.15: Boeing 737 (Left) [41] Harrier (Right) [42].................................................... 22
Figure 2.16: Angle of incidence of an airplane wing on an airplane [44]. .......................... 23
Figure 2.17: (a) Gull shape (b) Invert-Gull change shape [27]............................................ 24
Figure 2.18: Gull wing Göppingen Gö 3 Minimoa [47]. .................................................... 25
Figure 2.19: Inverted gull wing (a) F4U Corsair [48] (b) Junkers Ju 87 [49] .................... 25
Figure 2.20: The frontal views of three morphing configurations with a variable angle gull-wing mechanism (a) Unmorphed (b) Gull shape (c) Inverted gull shape [50]. ....................................................................................................... 26
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Figure 3.3: Small, open-loop, subsonic wind tunnel of the NUS Temasek. Laboratories. ................................................................................................... 73
Figure 3.4: Force and moment components......................................................................... 76
Figure 3.5: Paint spray on the airfoil model. ....................................................................... 78
Figure 3.6: Schematic diagram of the PIV setup. ................................................................ 79
Figure 4.1: Conceptual design. ............................................................................................ 81
Figure 4.2: Schematics of the first model. ........................................................................... 82
Figure 4.3: Schematic diagram of the conventional method for bonding the MFC actuators to the airfoil skin. ............................................................................. 83
Figure 4.4: After bonding MFC on the stainless steel sheet. ............................................... 84
Figure 4.5: Assembled first MFC airfoil model [101]. ........................................................ 85
Figure 4.6: Lateral view of the airfoil model: a) without actuation (shape similar to the NACA 4415 airfoil); b) with actuation at -500 V (3 mm maximum outward displacement); c) with actuation at 1500 V (5 mm maximum inward displacement). ..................................................................................... 87
Figure 4.7: Comparison of NACA 4415 airfoil [102] and non-actuated model: a) lift coefficient; b) drag coefficient. ....................................................................... 89
Figure 4.8: Aerodynamic characteristics of the airfoil model without and with actuation: a) lift coefficient; b) drag coefficient; c) lift over drag ratio; d) lift-drag polar; e) pitching-moment coefficient about c /4; f) non- dimensional chordwise position of the center of pressure. ............................. 92
Figure 4.9: Flow fields from PIV measurements at U ∞ = 15 m/s and α = -5°: a) no actuation; b) -500 V actuation; c) 1500 V actuation. The color field represents the values of the vorticity, the arrows indicate the local velocity vectors. .............................................................................................. 94
Figure 4.10: Flow fields from PIV measurements at U ∞ = 15 m/s and α ≈ 0°: a) no actuation; b) -500 V actuation; c) 1500 V actuation. The color field represents the values of the vorticity, the arrows indicate the local velocity vectors. .............................................................................................. 95
Figure 4.11: Flow fields from PIV measurements at U ∞ = 15 m/s and α = 15°: a) no actuation; b) -500 V actuation; c) 1500 V actuation. The color field represents the values of the vorticity, the arrows indicate the local velocity vectors. .............................................................................................. 96
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Figure 5.14: Aerodynamic characteristics of the airfoil model with sinusoidal actuation of 200V amplitude and 0V offset a) lift coefficient; b) drag coefficient...................................................................................................... 119
Figure 5.15: Flow fields from PIV measurements at U ∞ = 15 m/s and α = -5°: a) 1000 V actuation; b) no actuation; c) -500 V actuation. The color field represents the values of the vorticity, the arrows indicate the local velocity vectors. ............................................................................................ 123
Figure 5.16: Flow fields from PIV measurements at U ∞ = 15 m/s and α = 0°: a) 1000 V actuation; b) no actuation; c) -500 V actuation. The color field represents the values of the vorticity, the arrows indicate the local velocity vectors. ............................................................................................ 124
Figure 5.17: Flow fields from PIV measurements at U ∞ = 15 m/s and α = 15°: a) 1000 V actuation; b) no actuation; c) -500 V actuation. The color field represents the values of the vorticity, the arrows indicate the local velocity vectors. ............................................................................................ 125
Figure 6.1: Lift coefficient of FX63-137 airfoil model without and with injection of a thin, spanwise jet of 42 m/s close to its leading edge. .................................. 127
Figure 6.2: Aerodynamic characteristics of the airfoil model without and with DBD plasma actuation on the leading-edge upper surface: a) lift coefficient; b) drag coefficient; c) lift over drag ratio; d) lift-drag polar. ............................ 129
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Table 2.1 Summary of various morphing airfoil designs…………………………. 48
Table 2.2 Material properties of composite and MFC (Courtesy of Smart Material Corp., 2005)....…………………………………………………... 63
Table 2.3 Summary of various smart materials…………………………………… 64
j)
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relatively light and flexible aircraft during the earlier days. As aircraft flight evolved,
aircraft were built to carry heavier weights and fly at faster speeds.
Therefore, stronger and stiffer wings need to be developed to accommodate these
requirements. As speed increases, designers had often opted to reduce wingspan, increase
wing thickness and live with the subsequent reduced aerodynamic performance in an
attempt to save weight [ 5 ]. Soon the biomimetic idea of flexible wing warping method
was no longer practical and was replaced with an aileron system introduced in 1910 by
Henry Farman.
Furthermore, the experience learnt from the First World War shown that thicker airfoil
sections were better at creating lift than the thin profiles used at that time. Having a
thicker airfoil section also gives more leeway in designing wings with greater stiffness
and length. Aeronautic engineers continued to develop the path of conventional
engineering principles which could be achieved with the technology available during that
time.
The idea of biomimetic flight was not considered an erroneous approach to aeronautics
but just that it was implemented at a wrong time when technologies was still not advanced
enough to generate adequate lift/drag ratio.
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1.2 Motivation
Many past researches had shown that variable camber wing concept using conventional
high-lift devices were capable of improving the aerodynamic performance of the aircraft
under different flight conditions. However, these systems involve discontinuous or sudden
curvature changes in the airfoil cross-section and also involve complex and bulky
actuation systems such as hydraulic and pneumatic systems and the use of electric motors
etc.
The motivation of this research is to design a morphing wing that improves the
aerodynamics properties of the plane under different flight conditions without
incorporating complex and bulky actuator systems which are used in conventional
variable geometry wings. This concept can be achieved by making use of the state of art
of Macro Fiber Composite (MFC) actuator to control and change the shape profile of the
airfoil. The benefit of this concept is that the wing surface remains continuous to achieve
a seamless flow while having the ability to change its shape with the flexibility to be
optimized for different cruise conditions.
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Chapter 4 will discuss the first MFC airfoil model. This chapter covers the design,
fabrication and assembly process for the model. Experimental results of implementing
MFC actuators on the initial airfoil model will be evaluated.
Chapter 5 will discuss the second MFC airfoil model. This chapter covers the design,
fabrication and assembly process for the second model. Experimental results of
implementing MFC actuators on this airfoil model will be evaluated.
Chapter 6 will compare the aerodynamic performance of an airfoil using MFC actuators
with other control techniques such as steady jet injection and dielectric barrier discharge
(DBD) plasma actuation.
Finally, Chapter 7 wraps up the conclusion drawn from the entire design effort. This
chapter will review the effectiveness of the design and recommendations for further
improvement of the morphing airfoil design will be given.
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Chapter 2 : LITERATURE REVIEW
2.1 Conventional Fixed Wing Design
The conventional idea of an airplane is to have a set of rigid, fixed wings to provide lift
and a combination of ailerons, elevators, and rudder to control roll, pitch, and yaw. In
contemporary conventional aircraft, fixed wings are used and are designed for a single
point in design space representing the most frequent flight conditions that the aircraft will
encounter. These fixed geometry wings are often designed for one mission capability or
are designed as a compromise among several capabilities. Conventional wings are rigid
structures which consist of a discrete number of control surfaces which may be actuated
through input by the pilot in order to achieve a desired flight status. These control surfaces
are typically the flaps, which are employed during landing and takeoff, and the ailerons
which are used to control roll during flight. It is cheaper to manufacture the conventional
design and the controlling of the aircraft mechanism. However, there is always a trade-off
for this design.
The major disadvantage of having fixed geometry wings is that they are usually designed
for one mission capability which often cannot achieve a favorable airframe configuration
for other parts of the mission segments. They can only be optimized for one design point
that is characterized by parameters such as altitude, Mach number and aircraft weight.
Apart from this, the discrete control surfaces deteriorate aerodynamic efficiency by
adding leakage and protuberance drag.
