Aircraft Design: A Systems Engineering Approach, M. Sadraey, Wiley, Figures

Transcription

1 Aircraft Design: A Systems Engineering Approach, M. Sadraey, Wiley, 2012 Chapter 5 Wing Design Figures 1

2 Identify and prioritize wing design requirements (Performance, stability, producibility, operational requirements, cost, flight safety) Select number of wings Select wing vertical location Select/Design high lift device Select/Determine sweep and dihedral angles (, ) Select or design wing airfoil section Determine other wing parameters (AR, i w, t ) Calculate Lift, Drag, and Pitching moment Requirements Satisfied? Yes No Optimization Calculate b, MAC, C r, C t Figure 5.1. Wing design procedure 2

3 1. Monoplane 2. Biplane 3. triwing Figure 5.2. Three options in number of wings (front view) a. High wing b. Mid wing c. Low wing b. Parasol wing Figure 5.3. Options in vertical wing positions 3

4 1. Cargo aircraft Lockheed Martin C-130J Hercules (high wing) (Courtesy of Antony Osborne) 4

5 2. Passenger aircraft Boeing 767 (low wing) (Courtesy of Anne Deus) 5

6 3. Homebuilt aircraft Pietenpol Air Camper-2 (parasol wing) (Courtesy of Jenny Coffey) 6

7 4. Military aircraft Hawker Sea Hawk FGA6 (mid wing) (Courtesy of Antony Osborne) Figure 5.4. Four aircraft with different wing vertical positions 7

8 x-location of Maximum thickness Thickness Maximum thickness Maximum camber Mean camber line Leading edge radius Leading edge Chord line Trailing edge x-location of Maximum camber Chord Figure 5.5. Airfoil geometric parameters a. Small angle of attack b. Large angle of attack Figure 5.6. Flow around an airfoil 8

9 a. Small angle of attack b. Large angle of attack Figure 5.7. Pressure distribution around an airfoil Trailing edge Flight angle of attacks Pressure center 0.2 Aerodynamic center C m Leading edge -0.1 Pitching moment coefficient o 0 o 4 o 8 o 12 o 16 o 20 o Angle of attack ( ) Figure 5.8. The pressure center movement as a function of angle of attack 9

10 a. The force on pressure center b. Addition of two equal forces c. Force on aerodynamic center Figure 5.9. The movement of resultant force to aerodynamic center V M o L F ac D Figure The aerodynamic lift, drag, pitching moment 10

11 C l C lmax C l i C l o 0 C s (deg) Figure The variations of lift coefficient versus angle of attack C l C l gentle abrupt Figure Stall characteristics 11

12 C m_c/4 + (deg) Figure The variations of pitching moment coefficient versus angle of attack C m_ac + C l Figure The variations of pitching moment coefficient versus lift coefficient 12

13 C d C d min C (C lmin d /C l ) min 0 C l Figure The typical variations of drag coefficient versus lift coefficient C d C dmin 0 C li C ld C l Figure The variations of C l versus C d for a laminar airfoil 13

14 C C l d (C l /C d ) max 0 l Figure The typical variations of lift-to-drag ratio versus angle of attack 14

15 Thick and highly cambered Symmetric Cambered airfoil with deflected high lift device Thin and lightly cambered Supersonic double wedge Figure Five sample airfoil sections 15

16 0.1 y/c a. NACA 1408 airfoil section b. NACA airfoil section y/c y/c c. NACA airfoil section Figure A four-digit, a five-digit and a 6-series airfoil sections [3] c d NACA four digit airfoils NACA five digit airfoils NACA 6-series airfoils c l 16

17 Figure C l -, C m -, and C d -C l graphs of NACA airfoil section [3] 17

18 C t max C lmax fu = c l C dminfu = C m = C l and C d for (C l /C d ) max o = -1.5 s = 12 (t/c) max = 9% Figure The locations of all points of interest of NACA airfoil section (flap-up) [3] C li =

19 Figure Maximum lift coefficient versus ideal lift coefficient for several NACA airfoil sections (Data from [3]) 19

20 Wing zerolift and wave drag coefficient t/c=12% t/c=9% t/c=6% 0.01 t/c=4% Mach number Figure Variation of wing zero-lift and wave drag coefficient versus Mach number for various airfoil thickness ratio. i w Wing chord line at root Figure Wing setting (incidence) angle Fuselage center line 20

21 c l c l i set Figure Wing setting angle corresponds with ideal lift coefficient a. AR = 26.7 b. AR = 15 c. AR = 6.67 d. AR = 3.75 e. AR = 1 Figure Several rectangular wings with the same planform area but different aspect ratio 21

22 C L 2d airfoil (infinite AR) 3d wing (low AR) increasing AR Figure The effect of AR on C L versus angle of attack graph a. Rectangle ( =1) b. Trapezoid 0 < < 1 (straight tapered) c. Triangle (delta) = 0 Figure Wings with various taper ratio 22

23 C L =0 Elliptical lift distribution =1 =0.8 root semispan Figure The typical effect of taper ratio on the lift distribution ac LE C r MAC C t b Figure Mean Aerodynamic Chord and Aerodynamic Center in a straight wing 23

24 C L Front view y/s -b/2 +b/2 Figure Elliptical lift distribution over the wing C L C Lmax C L C Lmax 0 0 root tip root tip a. Non-elliptical (tip stalls before the root) b. Elliptical (root stalls before the tip) Figure Lift distribution over a half wing 24

25 C. C L Total lift generated by a half wing C. C L Total lift generated by a half wing Bending moment arm 0 0 root tip root Bending moment arm tip a. Non-elliptical (load is farther from root) b. Elliptical (load is closer to root) Figure Load distribution over a half wing Lift Fuselage Low wing Figure The fuselage contribution to the lift distribution of a low wing configuration 25

26 Lift Wing Flap Flap Figure The flap contribution to the lift distribution 26

27 x Fuselage center line a y y b LE c y C/2 y y d C/4 e y TE Figure Five wings with different sweep angles 27

28 M M cos ( ) Fuselage center line Stagnation streamline (lateral curvature exaggerated) Wing C C/cos ( ) Figure The effective of the sweep angle of the normal Mach number 28

29 C L AR= 7 AR= AR= 7 AR= AR=7 AR=10 AR=10 AR=7 0 o 10 o 20 o 30 o 40 o Sweepback angle (deg) Figure Effect of wing sweepback on ac position for several combinations of AR and 29

30 C L Swept wing Basic unswept wing root tip y/s Figure Typical effect of sweep angle on lift distribution M > 1 Fuselage center line y Wing Oblique shock wave Figure The sweep angle and Mach angle in supersonic flight 30

31 Fuselage center line highly swept inboard low sweep angle outboard Figure Top view of a wing with two sweep angels C r /2 b/2 C r MAC C t b eff Figure Effective wing span in a swept wing 31

32 A C r /2 B C C t /2 C/2 chord line b/2 Figure The wing of Example 5.3( and angles are exaggerated) C r /2 C r /4 A B C C/4 K J I C/2 = 30 L H D b/2=6.325 m TE F L G C t /2 E b eff /2 Figure The top view of the right wing of Example

33 1. Grumman F-14D (Courtesy of Antony Osborne) 33

34 2. Pilatus PC-21 (Courtesy of Antony Osborne) 34

35 3. Fokker 70 (Courtesy of Anne Deus) Figure Sweep angles for three aircraft 35

36 r root tip t a. geometric twist root tip b. Aerodynamic twist Figure Wing twist C L Without twist With twist root b/2 y/s 36

37 Figure The typical effect of a (negative) twist angle on the lift distribution xy plane z z a. Dihedral b. Anhedral Figure Dihedral, anhedral (aircraft front view) xy plane L right Restoring moment L left xy plane z gust xy plane airstream z a. before gust b. after gust Figure The effect of dihedral angle on a disturbance in roll (aircraft front view) 37

38 1. Airbus A330-dihedral (Courtesy of A J Best) 38

39 2. British Aerospace Sea Harrier-anhedral (Courtesy of Jenny Coffey) Figure Two aircraft with different dihedral angles 39

40 Pressure distribution of the wing when HLD deflected C P Pressure distribution of original wing f x/c Figure Example of pressure distribution with the application of a high lift device C l C lmax C m C d C dmin S C li C l without flap deflection with flap deflection Figure Typical effects of high lift device on wing airfoil section features 40

41 9. Kruger flap a. Trailing edge high lift device b. Leading edge high lift device Figure Various types of high lift devices 41

42 Fuselage Center Line C C f b f /2 b/2 a. Top-view of the right wing Leading edge Chord line Trailing edge C f fmax C b. The side-view of the inboard wing (flap deflected) Figure High lift device parameters Fuselage Center Line Flap Aileron Wing tip C b/2 Figure Typical location of the aileron on the wing 42

43 Wing tip Fuselage Center Line C t b/2 Figure Dividing a wing into several sections C L y/s Figure Angles corresponding to each segment in lifting-line theory 43

44 Lift coefficient 0.35 Lift Distribution semi-span Location (m) Figure The lift distribution of the wing in example

45 Fuselage Center Line a. Fence over the wing b. Fence over the wing of General Dynamics F-16XL Figure Example of a stall fence 45

46 1. Panavia Tornado GR4 with its long span flap (Courtesy of Antony Osborne) 46

47 2. Mikoyan-Gurevich MiG-29 with a low AR, and high sweep angle (Courtesy of Antony Osborne) 47

48 3. Piper Super Cub with strut-braced wing (Courtesy of Jenny Coffey) 48

49 4. Sailplane Schleicher ASK-18 with high AR (Courtesy of Akira Uekawa) Figure Four aircraft with various wing characteristics 49

50 Ideal lift coefficient Wing setting angle Figure Airfoil section NACA Ideal lift coefficient 50

51 Lift coefficient 0.7 Lift distribution y/s Figure The lift distribution of the wing (AR = 7, = 0.3, t =0, i w =2 deg) 51

52 Lift coefficient 0.45 Lift distribution y/s Figure The lift distribution of the wing (AR = 7, = 0.8, t =-1.5, i w =1.86 deg) 52

53 C r = 1.78 m MAC = m C t = 1.42 m C f = 0.32 m b f /2 = m b/2 = 5.63 m a. Top view of the right half wing i w = 1.86 deg Horizontal Fuselage Center Line ( fus =0) b. Side view of the aircraft in cruising flight i w = 1.86 deg w = 8.88 deg Fuselage Center Line ( fus =7 deg) fus =7.02 deg Horizontal c. Side view of the aircraft in take-off Figure Wing parameters of Example

54 C l C d Flap down f = 60 deg Flap up Flap up C m C m Re =6,000, (deg) C l Figure Airfoil section NACA