WO2000001578A1 - Aerofoil having improved buffet performance - Google Patents

Aerofoil having improved buffet performance Download PDF

Info

Publication number
WO2000001578A1
WO2000001578A1 PCT/GB1999/001921 GB9901921W WO0001578A1 WO 2000001578 A1 WO2000001578 A1 WO 2000001578A1 GB 9901921 W GB9901921 W GB 9901921W WO 0001578 A1 WO0001578 A1 WO 0001578A1
Authority
WO
WIPO (PCT)
Prior art keywords
bump
aerofoil
section
leading edge
chord
Prior art date
Application number
PCT/GB1999/001921
Other languages
French (fr)
Inventor
John Fulker
Pat Ashill
Original Assignee
The Secretary Of State For Defence
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Secretary Of State For Defence filed Critical The Secretary Of State For Defence
Publication of WO2000001578A1 publication Critical patent/WO2000001578A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C23/00—Influencing air flow over aircraft surfaces, not otherwise provided for
    • B64C23/06—Influencing air flow over aircraft surfaces, not otherwise provided for by generating vortices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C3/00—Wings
    • B64C3/10—Shape of wings
    • B64C3/14—Aerofoil profile
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C3/00—Wings
    • B64C3/10—Shape of wings
    • B64C3/14—Aerofoil profile
    • B64C2003/148—Aerofoil profile comprising protuberances, e.g. for modifying boundary layer flow
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T50/00—Aeronautics or air transport
    • Y02T50/10—Drag reduction

Definitions

  • the invention relates to an aerofoil having improved buffet performance.
  • Patent US 5,433,404 the describes a method of distorting the wing in the region of a shock wave to reduce drag.
  • the underlying principle of this concept is to change the shape of the wing, either with a bump or a ramp, placed so that it produces compression waves upstream of the shock. These compression waves weaken the shock wave in the flow-field, thus reducing wave drag.
  • Some limited benefit was also found with these devices in terms of improved buffet performance but their main purpose was to reduce drag. However the problem with these is that they cause greater drag at the cruise and lift conditions.
  • the invention consists of an aerofoil incorporating a bump profile on the upper surface thereof such that the bump forms causes a discontinuous change in slope of the upper surface and wherein the leading edge of the bump member is located within plus or minus 2% of chord length of the point of maximum curvature of the upper surface.
  • the bump member is located such that the main part of the shock is positioned just upstream of the shape change and thus the shape change is applied just downstream of the shock of the unmodified aerofoil rather than either side of the shock as disclosed in the prior art.
  • the bump may be a fixed feature of the design and is positioned to provide improved buffet performance at Mach numbers at and above the cruise Mach number.
  • the idea might be applied as a retro-fit to enhance buffet performance and reduce the drag of an aircraft which requires a higher lift coefficient than that originally specified (as might happen if the weight of the aircraft increased to carry a greater load than originally projected).
  • Figure 1 shows a schematic figure of a bump which forms part of the upper surface of an aerofoil.
  • Figure 2a and b show figure of a straight edged bump and curved bump respectively when incorporated on the upper surface of an aerofoil.
  • Figure 3 shows the effect of the bump on the lift of the aerofoil.
  • Figure 4 shows the response of the pressure measured just upstream of the trailing edge to changes in lift coefficient.
  • Figure 5 shows the influence of the bump on the drag of the aerofoil
  • Figure 1 shows a preferred embodiment of a bump member 1 which is attached or attachable to the upper surface of the aerofoil.
  • the bump member is positioned on the aerofoil upper surface such that it extends from 55% chord to 70% chord.
  • the bump member has three substantially straight sections 2, 3, and 4.
  • the bump member is positioned such that the first section 2 extends from 55% to 60% chord, the second section 3 of substantially zero gradient which extends from 60 to 65% chord, and a third section 4 of downwardly inclined slope extending to 70% chord.
  • the slope of angle of the bump member at its leading edge ⁇ is 4.4°.
  • the location of the bump member leading edge is very important if it is to reduce buffeting and should be positioned on the upper surface of the aerofoil just downstream of where shock occurs.
  • the invention may comprise of various types of bump members.
  • Such embodiments include curved bump members or bumps which may even comprise an arc of a circle.
  • the main consideration is that there is discontinuous change in slope on the upper surface of the aerofoil provided by the bump member at its leading edge
  • Figures 2a and b show a straight edged bump 5 (as described above) and curved bump 6 respectively when incorporated on the upper surface of an aerofoil 7.
  • the invention extends to aerofoils having integral bump members as well as to bump members which may be retro-fitted.
  • the bump member may also be selectable as disclosed in the US patent 5433404.
  • the length of the bump member can vary from 15 to 25 %.
  • the maximum amplitude of the bump member should be limited to between 0.05 tan 3° to 0.05 tan 6° of wing chord length.
  • the effect of the ramp at the upstream face is to incline the shock with the result that the strength of the shock (measured by the pressure rise through it) is reduced. This reduction in strength is proportional to the angle ⁇ .
  • Figure 3 shows normal force coefficient C (a measure of lift coefficient) against angle of incidence ⁇ at a Mach number of 0.69 and a Reynolds number of 19 x 10 6 , for an aerofoil with (8) and without (9) the bump respectively.
  • the bump allows an increase in maximum lift of about 2%.
  • Figure 4 shows the trailing-edge pressure coefficient C PTE against normal force coefficient C N on an aerofoil with (8) and without (9) the bump respectively and indicates that the bump increases the lift coefficient; which there is a rapid decrease in trailing edge pressure equivalent to about 3%.
  • Figure 5 shows drag coefficient Co against normal force coefficient C N on an aerofoil with (8) and without (9) the bump respectively the influence of the bump on the drag of the aerofoil. It indicates that the shape change reduces the drag by a significant amount for normal force coefficients at the cruise value (0.55 approximately) and above. At lower lift coefficients the bump increases the drag ; however since the aerofoil would not normally operate at such low lift this is not a significant disadvantage.

Abstract

An aerofoil incorporating a bump profile on the upper surface thereof such that the bump forms causes a discontinuous change in slope of the upper surface and wherein the leading edge of the bump member is located within plus or minus 2 % of chord length of the point of maximum curvature of the upper surface.

Description

Aerofoil having improved buffet performance
The invention relates to an aerofoil having improved buffet performance.
Patent US 5,433,404 the describes a method of distorting the wing in the region of a shock wave to reduce drag. The underlying principle of this concept is to change the shape of the wing, either with a bump or a ramp, placed so that it produces compression waves upstream of the shock. These compression waves weaken the shock wave in the flow-field, thus reducing wave drag. Some limited benefit was also found with these devices in terms of improved buffet performance but their main purpose was to reduce drag. However the problem with these is that they cause greater drag at the cruise and lift conditions.
It is an object of the invention to provide an aerofoil having improved resistance to shock buffeting due to shock-induced separation whilst minimising any increase in drag.
It is an object of the invention to improve the buffet performance without causing increased drag at the cruise lift coefficient and Mach number.
The invention consists of an aerofoil incorporating a bump profile on the upper surface thereof such that the bump forms causes a discontinuous change in slope of the upper surface and wherein the leading edge of the bump member is located within plus or minus 2% of chord length of the point of maximum curvature of the upper surface.
The bump member is located such that the main part of the shock is positioned just upstream of the shape change and thus the shape change is applied just downstream of the shock of the unmodified aerofoil rather than either side of the shock as disclosed in the prior art.
The bump may be a fixed feature of the design and is positioned to provide improved buffet performance at Mach numbers at and above the cruise Mach number. Alternatively the idea might be applied as a retro-fit to enhance buffet performance and reduce the drag of an aircraft which requires a higher lift coefficient than that originally specified (as might happen if the weight of the aircraft increased to carry a greater load than originally projected).
By way of example, the invention will now be described with reference to the drawings of which:
Figure 1 shows a schematic figure of a bump which forms part of the upper surface of an aerofoil.
Figure 2a and b show figure of a straight edged bump and curved bump respectively when incorporated on the upper surface of an aerofoil.
Figure 3 shows the effect of the bump on the lift of the aerofoil.
Figure 4 shows the response of the pressure measured just upstream of the trailing edge to changes in lift coefficient.
Figure 5 shows the influence of the bump on the drag of the aerofoil
Figure 1 shows a preferred embodiment of a bump member 1 which is attached or attachable to the upper surface of the aerofoil. The bump member is positioned on the aerofoil upper surface such that it extends from 55% chord to 70% chord. The bump member has three substantially straight sections 2, 3, and 4. The bump member is positioned such that the first section 2 extends from 55% to 60% chord, the second section 3 of substantially zero gradient which extends from 60 to 65% chord, and a third section 4 of downwardly inclined slope extending to 70% chord. The slope of angle of the bump member at its leading edge θ is 4.4°. The location of the bump member leading edge is very important if it is to reduce buffeting and should be positioned on the upper surface of the aerofoil just downstream of where shock occurs.
This is usually within ±1% around the point of maximum curvature, usually downstream of the leading edge at about 10% chord.
The invention however may comprise of various types of bump members. Such embodiments include curved bump members or bumps which may even comprise an arc of a circle. The main consideration is that there is discontinuous change in slope on the upper surface of the aerofoil provided by the bump member at its leading edge
Figures 2a and b show a straight edged bump 5 (as described above) and curved bump 6 respectively when incorporated on the upper surface of an aerofoil 7.
Additionally the invention extends to aerofoils having integral bump members as well as to bump members which may be retro-fitted. The bump member may also be selectable as disclosed in the US patent 5433404.
The length of the bump member can vary from 15 to 25 %. The maximum amplitude of the bump member should be limited to between 0.05 tan 3° to 0.05 tan 6° of wing chord length.
The effect of the ramp at the upstream face is to incline the shock with the result that the strength of the shock (measured by the pressure rise through it) is reduced. This reduction in strength is proportional to the angle θ.
The further consequence is that the separation of the boundary layer at the foot of the shock is delayed to higher angles of incidence, which delays shock-induced separation and buffet.
Figure 3 shows normal force coefficient C (a measure of lift coefficient) against angle of incidence α at a Mach number of 0.69 and a Reynolds number of 19 x 106 , for an aerofoil with (8) and without (9) the bump respectively. The bump allows an increase in maximum lift of about 2%.
Figure 4 shows the trailing-edge pressure coefficient CPTE against normal force coefficient CN on an aerofoil with (8) and without (9) the bump respectively and indicates that the bump increases the lift coefficient; which there is a rapid decrease in trailing edge pressure equivalent to about 3%.
Figure 5 shows drag coefficient Co against normal force coefficient CN on an aerofoil with (8) and without (9) the bump respectively the influence of the bump on the drag of the aerofoil. It indicates that the shape change reduces the drag by a significant amount for normal force coefficients at the cruise value (0.55 approximately) and above. At lower lift coefficients the bump increases the drag ; however since the aerofoil would not normally operate at such low lift this is not a significant disadvantage.

Claims

Claims
1. An aerofoil incorporating a bump profile on the upper surface thereof such that the bump forms causes a discontinuous change in slope of the upper surface and wherein the leading edge of the bump member is located within plus or minus 2% of chord length of the point of maximum curvature of the upper surface.
2. An aerofoil as claimed in claim 1 wherein the leading edge of the bump member is located within plus or minus 1% of chord length of the point of maximum curvature of the upper surface.
3. An aerofoil as claimed in claims 2 or 3 wherein said angle of bump at its leading edge is between 3┬░ and 6┬░.
4. An aerofoil as claimed in claim 3 wherein said angle of bump is 4.4┬░ +/- 0.3┬░
5. An aerofoil as claimed in any preceding claim wherein said bump member has three substantially straight sections, a first section having an upwardly inclined slope, a second section flat of substantially zero gradient, and a third section of downwardly inclined slope
6. An aerofoil as claimed in claim 5 wherein said first section extends from approximately 50%) to 60%) chord line, said second section from 60%> to 65%> chord line, and said third section from 65%o to 70 % chord line, the approximation being +/- 2%.
PCT/GB1999/001921 1998-07-01 1999-06-17 Aerofoil having improved buffet performance WO2000001578A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9814122.9 1998-07-01
GBGB9814122.9A GB9814122D0 (en) 1998-07-01 1998-07-01 Aerofoil having improved buffet performance

Publications (1)

Publication Number Publication Date
WO2000001578A1 true WO2000001578A1 (en) 2000-01-13

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ID=10834662

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/001921 WO2000001578A1 (en) 1998-07-01 1999-06-17 Aerofoil having improved buffet performance

Country Status (2)

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GB (1) GB9814122D0 (en)
WO (1) WO2000001578A1 (en)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009106872A3 (en) * 2008-02-29 2009-10-22 Airbus Uk Limited Aerodynamic structure with asymmetrical shock bump
WO2009106870A3 (en) * 2008-02-29 2009-10-22 Airbus Uk Limited Shock bump
WO2009106871A3 (en) * 2008-02-29 2009-11-19 Airbus Uk Limited Aerodynamic structure with non-uniformly spaced shock bumps
US7785617B2 (en) 2001-06-22 2010-08-31 The University Of Nottingham Porous matrix comprising cross-linked particles
CN101965291A (en) * 2008-02-29 2011-02-02 空中客车英国有限公司 Shock bump array
CN103224020A (en) * 2013-05-06 2013-07-31 郑志皓 Aircraft wing
US9463870B2 (en) 2008-02-29 2016-10-11 Airbus Operations Limited Aerodynamic structure with series of shock bumps
US10677217B2 (en) 2012-10-03 2020-06-09 General Electric Company Wind turbine and method of operating the same
CN113148110A (en) * 2021-05-28 2021-07-23 西北工业大学 Wing deformation device based on shock wave control bulge and wide-speed-range hypersonic aircraft
CN114104281A (en) * 2021-10-29 2022-03-01 西安交通大学 Mute investigation aircraft

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5433404A (en) 1991-08-01 1995-07-18 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Airfoil with variable geometry expansion surface
GB2296696A (en) * 1994-12-23 1996-07-10 Deutsche Forsch Luft Raumfahrt Deformable aerofoil

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5433404A (en) 1991-08-01 1995-07-18 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Airfoil with variable geometry expansion surface
GB2296696A (en) * 1994-12-23 1996-07-10 Deutsche Forsch Luft Raumfahrt Deformable aerofoil

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7785617B2 (en) 2001-06-22 2010-08-31 The University Of Nottingham Porous matrix comprising cross-linked particles
JP2011513115A (en) * 2008-02-29 2011-04-28 エアバス・ユ―ケ―・リミテッド Shock bump
JP2011513117A (en) * 2008-02-29 2011-04-28 エアバス・ユ―ケ―・リミテッド Aerodynamic structure with asymmetric shock bumps
WO2009106870A3 (en) * 2008-02-29 2009-10-22 Airbus Uk Limited Shock bump
CN101959755A (en) * 2008-02-29 2011-01-26 空中客车英国有限公司 Aerodynamic structure with non-uniformly spaced shock bumps
US8302912B2 (en) 2008-02-29 2012-11-06 Airbus Operations Limited Shock bump
CN101970294A (en) * 2008-02-29 2011-02-09 空中客车英国有限公司 Aerodynamic structure with asymmetrical shock bump
WO2009106871A3 (en) * 2008-02-29 2009-11-19 Airbus Uk Limited Aerodynamic structure with non-uniformly spaced shock bumps
WO2009106872A3 (en) * 2008-02-29 2009-10-22 Airbus Uk Limited Aerodynamic structure with asymmetrical shock bump
CN101965291A (en) * 2008-02-29 2011-02-02 空中客车英国有限公司 Shock bump array
US9896193B2 (en) 2008-02-29 2018-02-20 Airbus Operations Limited Aerodynamic structure with asymmetrical shock bump
US9334045B2 (en) 2008-02-29 2016-05-10 Airbus Operations Limited Aerodynamic structure with non-uniformly spaced shock bumps
US9463870B2 (en) 2008-02-29 2016-10-11 Airbus Operations Limited Aerodynamic structure with series of shock bumps
US10677217B2 (en) 2012-10-03 2020-06-09 General Electric Company Wind turbine and method of operating the same
CN103224020A (en) * 2013-05-06 2013-07-31 郑志皓 Aircraft wing
CN113148110A (en) * 2021-05-28 2021-07-23 西北工业大学 Wing deformation device based on shock wave control bulge and wide-speed-range hypersonic aircraft
CN114104281A (en) * 2021-10-29 2022-03-01 西安交通大学 Mute investigation aircraft

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Publication number Publication date
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