CN116238682A - Wing tip winglet for an aircraft and aircraft equipped with such a wing tip winglet - Google Patents

Abstract

The invention relates to a winglet (9) for an aircraft, comprising: a first control section (L1) located in the base region of the winglet (9); a third control section (L3) located in the tip region of the winglet (9); and a second control section (L2) located between the first control section (L1) and the third control section (L3). The second control section (L2) is a flow control section which is provided with a winglet slit (11) along at least a part of the spanwise direction of the winglet (9), while the first control section (L1) and the third control section (L3) are non-flow control sections. By means of the aerodynamic shape of the wing tip winglet for the aircraft, the winglet flow separation in the low-speed large-attack angle state can be delayed without designing a complex structure, and the flight resistance in the high-speed cruising state can be reduced.

Description

Wing tip winglet for an aircraft and aircraft equipped with such a wing tip winglet

Technical Field

The invention relates to the field of aerodynamic shape optimization design of civil aircrafts, in particular to an aerodynamic shape design of a wing tip winglet for an aircrafts, and particularly relates to a wing tip winglet with a slit. The invention also relates to an aircraft equipped with the wing tip winglet.

Background

For a typical long range aircraft, fuel consumption is about 22% of its direct cost. Drag reduction can directly reduce the operating costs of airlines, typically about 0.2% for long range aircraft per 1% reduction in drag.

During the actual flight of civil aircraft, the winglet functions to reduce the induced drag. At cruise Mach numbers, there are higher suction peaks on the upper surface of the winglet due to the airfoil and twist profile of the winglet itself. Meanwhile, in a low-speed large attack angle state, the upper wash effect of the wing leading edge lift-increasing device enables the winglet stall attack angle to be 1-2 degrees earlier than that of a clean wing. Thus, the winglet surfaces are prone to flow separation, which can adversely affect the handling efficiency of the aileron, and in severe cases even jeopardize the flight safety of the whole aircraft. In view of the high-low speed co-design requirements, it is particularly important to study the flow control technology of the winglet.

Currently, various improvements are made in the industry for flow control technology for winglets.

In U.S. patent No. 8387923B2 entitled "method for increasing lift and reducing drag of an aerodynamic surface (Method for increasing the lift of aerodynamic surfaces and for reducing the drag)" filed by the applicant's alarnia aerospace industry company in 2008, 3 and 10, a method of increasing lift and drag reduction on an aerodynamic surface is disclosed. The method is innovative in that a passive control mode is adopted, an opening is formed in the upper surface of the main wing, air is pumped into the air bag on the lower surface, and the air bag blows compressed air to the upper surface of the wing trailing edge flap, so that the effect of increasing the lift of the aircraft is achieved. The method is not only suitable for drag reduction of the aircraft, but also effective for drag reduction of ground vehicles. The patent adopts the form of active blowing, namely, a blowing bag is arranged under the air suction port. When the trailing edge flap is deflected downwards, the air compressed in the air-blowing bladder blows on the leading edge of the flap, which is mainly aimed at increasing the lift of the high-lift device of the aircraft.

In U.S. patent application US20040155157A1 entitled "wing tip Winglet (Winglet)" filed by applicant Robert m.bray at 12 th of 2002, a series of flow control approaches to improve airfoil lift and steering stability are proposed for wing tip winglets. The flow control means employed in this patent application are primarily directed to active blowing and suction by means of upper and lower surface switches, i.e. valve mechanisms that can be opened or closed when needed.

However, the concept of the above design is still focused on adding an auxiliary mechanism to actively adjust the air flow, and the disadvantage is obvious, that is, the number of components is increased, resulting in complex structure and increased cost, and the design is often limited by various weather conditions, so that the expected efficiency at the beginning of the design is difficult to achieve.

For this reason, there is a need for improvements in the aerodynamic profile of a winglet for an aircraft to delay winglet flow separation at low speeds and large angles of attack and to reduce drag at high speeds of cruise without increasing structural complexity and cost.

Disclosure of Invention

The invention aims to provide a wing tip winglet for an aircraft, which can delay the flow separation of the winglet in a low-speed large-attack angle state and reduce the flight resistance in a high-speed cruising state by virtue of the aerodynamic appearance of the wing tip winglet without designing a complex structure.

A first aspect of the invention relates to a wing tip winglet for an aircraft, comprising:

a first control section located in a base region of the winglet;

a third control section located in a tip region of the wing tip winglet; and

a second control section located between the first control section and the third control section, and

wherein the second control section is a flow control section that is split with a winglet slit along at least a portion of the spanwise direction of the winglet, and the first control section and the third control section are non-flow control sections.

In the above technical solutions, the terms "first", "second" and "third" in the "first", "second" and "third" control sections are added for the purpose of distinguishing only, and are not limiting in any direction and spatial arrangement of the control sections.

The term "flow control section" refers to an area of the winglet that is slotted by design to provide control of the airflow therethrough, while the term "non-flow control section" refers to an area of the winglet that is not designed to provide control of the airflow other than the flow control section.

In a preferred embodiment, the length of the winglet slit in the spanwise direction may be no less than 30% to 80%, preferably 50%, of the total length of the winglet in the spanwise direction.

And under the condition that the small wing slit penetrates through the whole second control section along the spanwise direction, the length of the small wing slit along the spanwise direction is the spanwise length of the second control section. That is, in the above case, the spanwise length of the second control segment is not less than 30% to 80% of the sum of the spanwise lengths of the first, second, and third control segments. The inventors found through experiments that it is the most preferred that the length of the winglet slit in the spanwise direction is not less than 50% of the total length of the winglet in the spanwise direction.

In another preferred embodiment, the width of the winglet slot may be designed to have a first width at the slot in the lower surface of the winglet and a third width at the slot in the upper surface of the winglet, the width decreasing monotonically from the lower surface of the winglet towards the upper surface of the winglet.

More preferably, the ratio of the first width to the third width may be greater than 1.1.

Since the width of the winglet slit is different in each cross section of the winglet and the width is monotonically decreasing from the lower surface of the winglet to the lower surface of the winglet upper wing, the term "first width" defines the width of the winglet slit at the slit of the lower surface of the winglet, i.e., the maximum width of the winglet slit; the term "third width" defines the width of the winglet slit at the slit in the upper surface of the winglet, i.e., the minimum width of the winglet slit.

In yet another preferred embodiment, the first and second slit shape control surfaces of the winglet slit may be spaced apart to form an S-shaped tapered curved space.

At this time, the first slit shape control surface and the second slit shape control surface of the winglet slit are both S-shaped curved surfaces, which are spaced apart from each other to constitute a tapered curved surface space therebetween.

More preferably, the first tangent line of the winglet slit at the lower surface of the winglet and the lower surface of the winglet may form a leading edge inflow angle θ1, the second tangent line of the winglet slit at the upper surface of the winglet and the upper surface of the winglet may form a trailing edge outflow angle θ2, and both the leading edge inflow angle θ1 and the trailing edge outflow angle θ2 are less than 45 °.

In an alternative embodiment, the first and second slit shape control surfaces of the winglet slit are spaced apart to form a trapezoidal tapered space.

The degree of taper of the sectional area of the trapezoidal tapered space is linear compared to the S-shaped tapered curved surface space.

More preferably, the winglet slot and the lower surface of the winglet may form a leading edge inflow angle θ1, and the winglet slot and the upper surface of the winglet may form a trailing edge outflow angle θ2, with both the leading edge inflow angle θ1 and the trailing edge outflow angle θ2 being less than 45 °.

In yet another preferred embodiment, the start of the slot of the winglet slot in the upper surface of the winglet may be in the range of 5% to 30% of the local chord and the width of the winglet slot may be in the range of 0.5% to 3% of the local chord.

More preferably, the slot start position of the winglet slot at the lower surface of the winglet may be in the range of 5% to 30% of the local chord length, and the width of the winglet slot may be in the range of 0.5% to 3% of the local chord length, the slot start position of the lower surface of the winglet being more forward than the slot start position of the upper surface of the winglet, i.e. closer to the nose of the aircraft.

The term "local chord" refers to the chord measured at any longitudinal section of the wing tip winglet. Since the winglet extends obliquely from the wing, the local chord length on any one of the longitudinal sections is different, and thus each longitudinal section has a corresponding 'local chord length'.

Since the terms "first width" and "third width" define the maximum and minimum width of the winglet slit, respectively, it can be considered that "the width of the winglet slit is in the range of 0.5% to 3% of the local chord length" corresponds to the width of the winglet slit varying in the range of 0.5% to 3% of the local chord length, or that 0.5% of the local chord length is the lower limit value of the minimum width of the winglet slit and that 3% of the local chord length is the upper limit value of the maximum width of the winglet slit.

A second aspect of the invention relates to an aircraft provided with a winglet according to the first aspect.

The wing tip winglet for an aircraft according to the invention can obtain the following advantages by forming a winglet slot on at least a part of a section of the wing tip winglet:

(i) Under the low-speed large attack angle state, the low-momentum airflow in the boundary layer on the upper surface of the winglet of the wing tip is exchanged or balanced with the high-momentum airflow induced by the slotting of the winglet, so that the airflow in the boundary layer increases the momentum in the flowing direction, and the separation characteristic of the winglet of the wing tip is improved;

(ii) In the high-speed cruising state, the suction peak value of the leading edge of the winglet is reduced, thereby reducing cruising resistance.

Drawings

In order to further illustrate the technical effects of the winglet for an aircraft according to the invention, the invention will be described in detail below with reference to the accompanying drawings and to the detailed description, in which:

FIG. 1 is an overall schematic of a large aircraft equipped with wing-mounted cranes;

FIG. 2 is a side view of a wing tip winglet for the aircraft shown in FIG. 1, showing the slotted position of the wing tip winglet;

FIG. 3A is a schematic longitudinal section through a first embodiment of a winglet according to the invention, the longitudinal section being perpendicular to the ground on which the aircraft is placed, the circle in the figure showing in an enlarged manner the leading edge inflow angle and the trailing edge outflow angle;

FIG. 3B is a schematic longitudinal cross-section of a second embodiment of a winglet according to the invention, the longitudinal cross-section being perpendicular to the ground on which the aircraft is placed, and the circled portion of the figure showing in an enlarged manner the leading edge inflow angle and the trailing edge outflow angle;

FIG. 4 shows the change in aerodynamic properties of a wing tip winglet before and after modification according to the invention, wherein the dashed line shows the aerodynamic properties before modification and the solid line shows the aerodynamic properties after modification;

FIGS. 5A and 5B illustrate the change in the gradient of the airflow through the surface boundary layer of the winglet before and after modification at an incoming flow angle of attack of 16;

FIGS. 6A and 6B illustrate the change in airflow gradient through the surface boundary layer of the winglet before and after modification at an incoming flow angle of attack of 17; and

figures 7A and 7B show the change in the gradient of the airflow through the surface boundary layer of the winglet before and after modification at an angle of attack of 18 deg. for incoming flow.

Reference numerals

1. Aircraft with a plurality of aircraft body

2. Machine head

3. Fuselage body

4. Rear body

5. Vertical horizontal tail

6. Hanging device

7. Engine with a motor

8. Wing

9. Wing tip winglet

11. Small wing slotting

12. First dividing line

13. Second separation line

14. First slit shape control surface

15. Second slit shape control surface

16. Wing tip winglet upper surface

17. Lower surface of wing tip winglet

L1 first control section

L2 second control section

L3 third control section

D1 First width of

D2 Second width of

D3 Third width

θ1 leading edge inflow angle

θ2 trailing edge outflow angle

Detailed Description

The design of the profile of a winglet for an aircraft according to the invention and its technical effects are described below with reference to the accompanying drawings.

It should be understood that the embodiments described in this specification are intended to cover only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art without making any inventive effort, are intended to be within the scope of the present invention based on the embodiments described in the specification.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms "comprising" and "having" and any variations thereof in the description of the invention and the claims and the foregoing description of the drawings are intended to cover non-exclusive inclusions. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It will be understood that, based on the same orientation, in the description of the present invention, the orientation or positional relationship indicated by the terms "spanwise," "upper," "lower," "front," "rear," etc. are based on the orientation shown in the drawings or the direction of flight of the aircraft, merely to facilitate description of the present invention and simplify description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the invention.

Fig. 1 is an overall schematic view of a large aircraft equipped with wing-mounted cranes. It can be seen that the aircraft 1 generally consists of a nose 2, a fuselage 3, a rear body 24 and wings 8. A vertical horizontal tail 25 is arranged at the tail end of the rear body 24, a hanging device 6 is arranged below the wing 8, and the engine 7 is accommodated in the hanging device 6. At the distal end of the wing 8 a winglet 9 is mounted. The function of these components is well known to those of ordinary skill in the art and will not be described in detail herein.

Figure 2 shows the slotted position of the winglet 9. As shown in fig. 2, the winglet 9 is divided from base to tip into three sections by a first separation line 12 and a second separation line 13, namely: a first control segment L1 located in the base region of the winglet 9; a second control section L2 located in the middle region of the winglet 9; and a third control section L3 located in the tip region of the wing tip winglet 9. That is, the first separation line 12 separates the base region and the middle region of the wing tip winglet 9, the second separation line 13 separates the middle region and the tip region of the wing tip winglet 9, and the second control section L2 is located between the first control section L1 and the third control section L3.

The second control section L2 is designed such that it is provided with a winglet slit 11 in the spanwise direction of the wing tip winglet 9 to form a flow control section. The first control segment L1 and the third control segment L3 are non-flow control segments.

According to the design concept of the invention, the low-momentum air flow in the boundary layer of the upper surface 16 of the winglet is exchanged or balanced with the high-momentum air flow introduced by the winglet slit 11 by forming the winglet slit 11 on at least a part of the section of the winglet 9, so that the air flow in the boundary layer increases the momentum of the flow direction and improves the separation characteristic of the winglet 11.

In this way, the flow control section has the ability to control the airflow flowing therethrough, reducing the adverse effects of flow separation of the winglet 11, causing the peak suction at the leading edge of the winglet to be reduced, thereby reducing cruise drag and improving the flight conditions of the aircraft.

In the present embodiment, the winglet slit 11 is formed in the entire second control section L2 in the spanwise direction of the wing tip winglet 9. Of course, it is also possible to design the winglet slit 11 to be formed in a part of the section of the second control section L2 in the spanwise direction of the wing tip winglet 9, in case flow control conditions are fulfilled, such variants should all be readily conceivable to a person skilled in the art.

With continued reference to fig. 2, the spanwise length of the winglet slit 11 is not less than 30% to 80% of the total spanwise length of the winglet 11. Since the spanwise length of the winglet slit 11 is the spanwise length of the second control segment L2, in other words, the spanwise length of the second control segment L2 is not less than 30% to 80% of the sum of the spanwise lengths of the first, second and third control segments L1, L2 and L3.

In a preferred embodiment, the length of the winglet slit 11 in the spanwise direction is not less than 50% of the total length of the winglet 11 in the spanwise direction.

Fig. 3A is a schematic longitudinal section of the winglet 9, in which the slotted shape of the winglet 9 is shown. As shown in fig. 3A, the winglet slot 11 has a width that varies from the lower wing tip winglet surface 17 toward the upper wing tip winglet surface 18. More specifically, the width of the winglet slot 11 is designed to have a first width D1 at the slot of the lower wing tip winglet surface 17 and a third width D3 at the slot of the upper wing tip winglet surface 16. Furthermore, a second width D2 is measured along the midline of the longitudinal section of the winglet 9. Obviously, the first width D1, the second width D2, and the third width D3 are each not the same.

In the preferred embodiment shown in fig. 3A, the width described above decreases monotonically from the wing tip winglet lower surface 17 towards the wing tip winglet upper surface 16. That is, the first width D1 is the maximum width of the winglet slit 11, and the third width D3 is the minimum width of the winglet slit 11, and the second width D2 is between the first width D1 and the third width D3. In this embodiment, the ratio of the first width D1 to the third width D3 is greater than 1.1.

As shown in fig. 3A, the first slot shape control surface 14 and the second slot shape control surface 15 of the winglet slot 11 may be spaced apart to form an S-shaped tapered curved space, with a first tangent line to the winglet slot 11 at the slot of the winglet lower surface 17 forming a leading edge inflow angle θ1 with the winglet lower surface 17 and a second tangent line to the winglet slot 11 at the slot of the winglet upper surface 16 forming a trailing edge outflow angle θ2 with the winglet upper surface 16. Referring to the enlarged view circled in FIG. 3A, the leading edge inflow angle θ1 and the trailing edge outflow angle θ2 are each less than 45, which helps ensure that the airflow is in the desired direction.

With the above design, the winglet slit 11 is formed as an S-shaped curved slot that gradually tapers from bottom to top, so that the airflow, after passing under the winglet 9 through the winglet slit 11, begins to accelerate due to the narrowing of the flow and eventually becomes a high velocity jet exiting the winglet slit 11 to eliminate the low pressure region of the upper surface 16 of the winglet.

In addition, the winglet slot 11 is in the range of 5% to 30% of the local chord length at the beginning of the slot of the upper surface 16 of the winglet. That is, taking fig. 3A as an example, the winglet slit 11 divides the longitudinal section of the winglet 9 into two parts, namely a leading edge body and a trailing edge body, wherein the start of the slit of the winglet slit 11 at the upper surface 16 of the winglet is approximately 5% to 30% of the local chord length of the winglet 9 from the leading edge body to the trailing edge body.

As regards the width of the winglet slit 11, it is in the range of 0.5% to 3% of the local chord of the wing tip winglet 9. Since the first width D1 defines the maximum width of the winglet slot 11 and the third width D3 defines the minimum width of the winglet slot 11, it is also possible to consider that 0.5% of the local chord length is the lower limit of the third width or the minimum width and 3% of the local chord length is the upper limit of the first width or the maximum width.

Similarly, the winglet slot 11 is in the range of 5% to 30% of the local chord at the beginning of the slot of the winglet lower surface 17, and the width of the winglet slot 11 is in the range of 0.5% to 3% of the local chord. It should be noted that the start of the slot of the lower wing surface 17 is more forward, i.e. closer to the nose, than the start of the slot of the upper wing surface 16.

Another slit shape of the winglet is shown in fig. 3B. It can be seen that unlike the S-shaped tapered curved surface space shown in fig. 3A, the first slit shape control surface 14 and the second slit shape control surface 15 of the winglet slit 11 shown in fig. 3B are spaced apart to constitute a trapezoidal tapered space.

In an alternative embodiment shown in fig. 3B, the measurement of parameters of the winglet slit 11 is further simplified. That is, the winglet slot 11 forms a leading edge inflow angle θ1 with the winglet lower surface 17 and the winglet slot 11 forms a trailing edge outflow angle θ2 with the winglet upper surface 16. Referring to the enlarged schematic view circled in fig. 3B, the leading edge inflow angle θ1 and the trailing edge outflow angle θ2 are both smaller than 45 °. This embodiment, although slightly less effective in flow separation than the embodiment shown in fig. 3A, has been significantly better than the prior art and has significantly less difficulty in processing.

Fig. 4 is a graph of aerodynamic properties of a winglet 9 after the winglet slit 11 has been opened and a graph of the change in the curve with and without the winglet slit 11, the abscissa and ordinate of the graph being the angle of attack of the incoming flow and the lift coefficient, respectively, with the broken line showing the aerodynamic properties of the winglet 9 before modification and the solid line showing the aerodynamic properties of the winglet 9 after modification.

It can be seen that, with an incoming flow angle of attack of less than 15 °, the opening of the winglet slit 11 in the winglet 9 does not substantially change much in the lift coefficient for the airflow flowing through the surface boundary layer of the winglet 9; however, in the range of the incoming flow attack angle being more than 15 degrees and less than 20 degrees, the small wing slit 11 formed on the wing tip small wing 9 can obviously increase the lift coefficient, improve the small wing flow separation and reduce the flight resistance under the high-speed cruising state.

Fig. 5A, 6A and 7A show the gradient of the air flow through the surface boundary layer of the winglet 9 without the winglet slit 11 at angles of attack of 16 °, 17 ° and 18 °, respectively, it being seen that with increasing angles of attack, a more pronounced air flow separation occurs at the trailing end of the winglet 9, with a more pronounced adverse effect on the increase in lift coefficient.

Fig. 5B, 6B and 7B show the gradient of the air flow through the surface boundary layer of the winglet 9 provided with the winglet slit 11 at incoming angles of attack of 16 °, 17 ° and 18 °, respectively, it being seen that with increasing incoming angles of attack the air flow separation occurring at the trailing end of the winglet 9 is significantly reduced, thus significantly increasing the lift coefficient, improving the winglet flow separation and reducing the flight resistance at high cruise conditions.

While the design of the wing tip winglet and the principles of operation for an aircraft in accordance with the present invention have been described above in connection with the preferred embodiments and the accompanying drawings, those of ordinary skill in the art will recognize that the above examples are for illustrative purposes only and are not to be construed as limiting the invention. Therefore, the present invention can be modified and changed within the spirit of the claims, and all such modifications and changes fall within the scope of the claims of the present invention.

Claims (11)

1. A winglet (9) for an aircraft, comprising:

-a first control segment (L1) located in a base region of the winglet (9);

-a third control section (L3) located in the tip region of the wing tip winglet (9); and

a second control section (L2) located between the first control section (L1) and the third control section (L3), and

wherein the second control section (L2) is a flow control section provided with a winglet slit (11) along at least a part of the spanwise direction of the winglet (9), and the first control section (L1) and the third control section (L3) are non-flow control sections.

2. The wing tip winglet (9) according to claim 1, characterized in that the length of the winglet slit (11) along the spanwise direction is not less than 30 to 80%, preferably 50%, of the total length of the wing tip winglet (9) along the spanwise direction.

3. The wing tip winglet (9) according to claim 1, characterized in that the width of the winglet slit (11) is designed to have a first width (D1) at the slit of the wing tip winglet lower surface (17) and a third width (D3) at the slit of the wing tip winglet upper surface (16), which width decreases monotonically from the wing tip winglet lower surface (17) towards the wing tip winglet upper surface (17).

4. A wing tip winglet (9) according to claim 3, characterized in that the ratio of the first width (D1) to the third width (D3) is greater than 1.1.

5. A wing tip winglet (9) according to claim 3, characterized in that the first slot shape control surface (14) and the second slot shape control surface (15) of the winglet slot (11) are spaced apart to form an S-shaped tapered curved space.

6. The winglet (9) according to claim 5, wherein a first tangent to the winglet slit (11) at the lower surface (17) of the winglet forms a leading edge inflow angle (θ1) with the lower surface (17) of the winglet, a second tangent to the winglet slit (11) at the upper surface (16) of the winglet forms a trailing edge outflow angle (θ2) with the upper surface (16) of the winglet, and both the leading edge inflow angle (θ1) and the trailing edge outflow angle (θ2) are smaller than 45 °.

7. A wing tip winglet (9) according to claim 3, characterized in that the first slot shape control surface (14) and the second slot shape control surface (15) of the winglet slot (11) are spaced apart to form a trapezoidal tapering space.

8. The winglet (9) according to claim 7, wherein the winglet slot (11) forms a leading edge inflow angle (θ1) with the winglet lower surface (17), the winglet slot (11) forms a trailing edge outflow angle (θ2) with the winglet upper surface (16), and the leading edge inflow angle (θ1) and the trailing edge outflow angle (θ2) are both less than 45 °.

9. A winglet (9) according to claim 3, characterized in that the winglet slit (11) is in the range of 5 to 30% of the local chord at the slit start position of the winglet upper surface (16), the width of the winglet slit (11) being in the range of 0.5 to 3% of the local chord.

10. The winglet (9) according to claim 9, wherein the winglet slot (11) is in the range of 5% to 30% of the local chord at a slot start position of the winglet lower surface (17), the width of the winglet slot (11) being in the range of 0.5% to 3% of the local chord, the slot start position of the winglet lower surface (17) being more forward than the slot start position of the winglet upper surface (16).

11. An aircraft (1) equipped with a winglet (9) according to any of claims 1 to 10.

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