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SCIENCE CHINA Technological Sciences, Volume 60 , Issue 8 : 1144-1159(2017) https://doi.org/10.1007/s11431-016-0218-5

Aerodynamic/mechanism optimization of a variable camber Fowler flap for general aviation aircraft

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  • ReceivedMar 22, 2016
  • AcceptedOct 31, 2016
  • PublishedDec 8, 2016

Abstract

A conventional Fowler flap is designed to improve the take-off and landing performances of an aircraft. Because the flight states of general aviation aircraft vary significantly. A Fowler flap with a double-sliding track has been designed, which is capable of changing airfoil camber while cruising and climbing as well as meeting low-speed performance requirements. The aerodynamic characteristics of the variable camber Fowler flap were studied by computational simulation, and cambering was found to be beneficial for improving the lift-to-drag ratio when the lift coefficient was larger than the critical value, below which decambering was more effective; this critical value differed somewhat under different conditions. Taking the mechanism into account, the take-off and landing configurations were optimized on the basis of the GA (W)-1 airfoil with a 30% chord Fowler flap. Compared with reference configuration, the maximum lift coefficient of optimized take-off configuration was increased by 6.6% as well as the stalling angle and the lift-to-drag ratio were increased by 1.3° and 7.58%, respectively. Moreover, the maximum lift coefficient of the optimized landing configuration was increased by 6.3%, and the stalling angle was increased by 1.1°; however, the nose-down pitching moment of both configurations increased. Similar results were attained on a general aviation aircraft wing/body combination. A 3D model of the variable-camber Fowler flap driving mechanism was established in a computer-aided design system, and the results showed that all design configurations could be achieved by the double-sliding track.


References

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  • Figure 1

    VCW using deflected flap and drooped spoiler on B787.

  • Figure 2

    B777 PIP drooped aileron.

  • Figure 3

    Sketch of a certain type of general aviation aircraft (unit: m). (a) Top view; (b) isometric view.

  • Figure 4

    View of the computational grid.

  • Figure 5

    Experimental and computational lift coefficient versus AOA for 30P30N.

  • Figure 6

    Experimental and computational pressure distribution for 30P30N (α = 8°).

  • Figure 7

    VC flap for GA (W)-1. (a) VC motion of flap; (b) some details of VC flap.

  • Figure 8

    (Color online) Effects of variable camber on aerodynamic characteristics in climb conditions. (a) Cl as a function of AOA and flap deflection; (b) L/D as a function of AOA and flap deflection; (c) Cm as a function of Cl and flap deflection; (d) increment of L/D as a function of Cl and flap deflection.

  • Figure 9

    (Color online) Effects of variable camber on the pressure coefficient distribution in climb conditions at α = 0°.

  • Figure 10

    (Color online) Effects of variable camber upon aerodynamic characteristics in cruise conditions. (a) Cl as a function of AOA and flap deflection; (b) L/D as a function of AOA and flap deflection; (c) Cm as a function of Cl and flap deflection; (d) increment of L/D as a function of Cl and flap deflection.

  • Figure 11

    (Color online) Effects of variable camber upon pressure coefficient distribution in cruise conditions at α = 0°.

  • Figure 12

    (Color online) Half-models of the VCWB and surface mesh. (a) Decambering; (b) clean; (c) cambering.

  • Figure 13

    Far-field boundary set of the VCWB flow field, Rec = 11×106, Ma = 0.313.

  • Figure 14

    Aerodynamic characteristics of VCWB in cruise conditions. (a) CL as a function of AOA and flap deflection; (b) L/D as a function of CL and flap deflection; (c) CM as a function of AOA and flap deflection; (d) delta L/D as a function of CL and flap deflection.

  • Figure 15

    Surface streamlines and pressure distributions on the VCWB at typical AOAs. (a) δflap = +3°, α = 0°; (b) δflap = 0°, α = 0°; (c) δflap = –3°, α = 0°; (d) δflap = +3°, α = 8°; (e) δflap = 0°, α = 8°; (f) δflap= –3°, α = 8°.

  • Figure 16

    The illustration of the VC flap.

  • Figure 17

    Optimization flow module.

  • Figure 18

    (Color online) Selection of candidate optimal configurations. (a) K8-takeoffvs Cl11-landing; (b) Cl11-takeoffvs Cl11-landing; (c) weight vs Cl11-landing.

  • Figure 19

    (Color online) Comparison of the optimized and referenced configurations (denoted as Config.X). (a) Take-off configurations; (b) landing configurations.

  • Figure 20

    (Color online) Comparison of the aerodynamic characteristics of the optimized take-off configurations and Config. X. (a) Lift curves of take-off configurations; (b) lift-drag ratio versus CL of take-off configurations; (c) pitching moment curves of take-off configurations; (d) pressure distribution of take-off configurations.

  • Figure 21

    (Color online) Local streamlines of three take-off configurations at typical AOAs.

  • Figure 22

    (Color online) Comparison of the aerodynamic characteristics of the landing configurations and Config. X. (a) CL curves of landing configurations; (b) L/D versus CL of landing configurations; (c) CM curves of landing configurations; (d) pressure distribution of landing configurations.

  • Figure 23

    (Color online) Local streamlines of three landing configurations at typical AOAs.

  • Figure 24

    (Color online) Half models of the high-lift configuration and surface mesh. (a) Take-off; (b) landing.

  • Figure 25

    (Color online) Computational aerodynamic force of WB high-lift configurations. (a) CL curves of the WB high-lift configurations; (b) L/D versus CL curves of the WB high-lift configurations; (c)L/D versus AOA curves of the WB high-lift configurations; (d) CM versus AOA curves of the WB high-lift configurations.

  • Figure 26

    (Color online) Location of the spanwise stations (unit: millimeter).

  • Figure 27

    (Color online) Cp distributions at the spanwise sections of the WB landing configurations at α = 8°. (a) Station 1; (b) Station 2; (c) Station 3; (d) Station 4.

  • Figure 28

    Cp distributions at spanwise sections of the WB landing configurations at α = 12°. (a) Station 1; (b) Station 2; (c) Station 3; (d) Station 4.

  • Figure 29

    Surface streamlines and pressure distributions on the WB high-lift configurations. (a) Station 1 take-off configuration, α = 8°, top view; (b) landing configuration, α = 8°, top view; (c) take-off configuration, α = 12°, top view; (d) landing configuration, α = 12°, top view.

  • Figure 30

    Double-sliding track mechanism for the VC flap.

  • Figure 31

    Variable cambering by double-sliding track during cruise.

  • Figure 32

    High-lift configurations by double-sliding track for taking off and landing.

  • Table 1   Main parameters of the specified general aviation aircraft

    General parameters

    Wing parameters

    MTOW

    <♥>4650♣kg</♥>

    Aspect ratio

    10

    Payload

    <♥>2250♣kg</♥>

    Area

    <♥>36.9♣m2</♥>

    Maximum range

    <♥>1600♣km</♥>

    Taper ratio

    0.48

    Powerplant

    1100 hp single-engine turboprop

    Sweepback angle at <♥>1/4♣C</♥>

    Incidence angle

    Wing

    high mounted

    Dihedral angle

    Twist angle

    –5°

    at wingtip

  • Table 2   Design point parameters of the specified general aviation aircraft

    Flight status

    Typical Altitude (km)

    Typical Speed

    <♥>(km♣h–1)</♥>

    Reynolds

    number

    Mach

    number

    Climb

    0

    232

    8.8×106

    0.189

    Take-off & landing

    0

    112

    4.3×106

    0.091

    Cruise

    3

    370

    11×106

    0.313

  • Table 3   Input parameters and optimization objectives

    Input parameters

    Optimization objectives

    £ δflap-takeoff £ 30°

    0.9%C £ overlap £ 7.5%C

    1.5%C £ gap £ 4.5%C

    £ δflap-landing £ 12°

    Maximum: K8-takeoff

    Cl8-landing

    Cl11-takeoff

    Cl11-landing

    Minimum: Weight

  • Table 4   Control parameters and lift characteristics of three optimal configurations

    Configurations

    A

    B

    C

    X

    Control parameters

    δflap-takeoff (°)

    17.6

    21.9

    19.2

    20

    Overlap (%C)

    2.03

    2.56

    3.07

    gap (%C)

    3.60

    4.43

    3.74

    δflap-landing (°)

    11.5

    10.9

    11.8

    10

    weight

    46.8

    45.5

    44.7

    Take-off

    Stalling angle (°)

    12.3

    11.6

    11.6

    11.0

    Clmax

    3.22

    3.33

    3.18

    3.02

    L/D at α = 8°

    81.42

    76.62

    77.59

    75.68

    Landing

    Stalling angle (°)

    11.1

    10.5

    10.0

    10.0

    Clmax

    3.56

    3.58

    3.50

    3.35

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