Leading edge slat and aircraft comprising leading edge slat

Abstract

A leading edge slat, having an upper surface, a lower surface, and side end surfaces. The upper surface defines a leading edge of the slat and a trailing edge of the slat; the leading edge of the slat and the trailing edge of the slat define a slat plane; the profile of each side end surface is defined by a side edge of the upper surface and a side edge of the lower surface; at least one of the side end surfaces comprises a first portion and a second portion, wherein the first portion extends from the leading edge of the slat, and the second portion is a continuous convex curved portion extending between the first portion and the trailing edge of the slat. An aircraft comprises the leading edge slat. The leading edge slat can delay flow separation and increase the maximum lift coefficient.

Description

A leading-edge slat and an aircraft including such a leading-edge slat. Technical Field

[0001] This invention relates to the field of aircraft structural design, and more specifically to a leading-edge slat. The invention also relates to aircraft incorporating such a leading-edge slat. Background Technology

[0002] During takeoff, various parameters affect an aircraft's speed. Among these parameters, the maximum lift coefficient is a key parameter for low-speed performance. Increasing the maximum lift coefficient allows the aircraft to take off and land at lower speeds, reducing the need for longer runways.

[0003] Modern large aircraft typically employ wing structural lift enhancement devices such as leading-edge slats and trailing-edge flaps to increase the maximum lift coefficient during low-speed flight. When the leading-edge slats open, airflow passes through the slats and adheres to the upper surface of the fixed wing, injecting energy into the upper surface flow, thereby delaying flow separation and increasing the maximum lift coefficient.

[0004] Existing leading-edge slats typically employ a planar or near-planar design at their end faces. However, when such leading-edge slats open, pressure differentials cause upward-washing vortices (i.e., vortices deflecting upwards around the slat) to form on both sides of the slat's end faces, also known as "slat end face vortices." These vortices extend downstream, passing over discontinuous steps on the fixed wing created by the slat opening. These fixed-wing steps are often located near separation-sensitive areas such as the wing-fuselage transition zone, behind the nacelle, and at the wingtip. In these situations, the upward induction of the end face vortices can easily trigger flow separation, causing the entire aircraft to stall earlier and limiting the improvement of the maximum lift coefficient.

[0005] Since the existing leading-edge slat design is not conducive to the shedding of end-face vortices from the slats, which has an adverse effect on the downstream flow, it is currently desirable to design a slat shape that can minimize the upwashing effect of end-face vortices on the fixed-wing step position. Summary of the Invention

[0006] To address the problem that existing leading-edge slats limit the maximum lift coefficient of aircraft due to end-face vortices, this invention proposes a novel leading-edge slat. By establishing a curved transition shape from the slat end-face to the trailing edge, the novel aerodynamic shape allows the slat end-face vortices to detach earlier after the slat is deployed, effectively reducing the induction of end-face vortices on the fixed wing step and adjacent areas. Furthermore, the curved shape allows the slat to maintain a large chord length at the end-face transition position, ultimately suppressing separation and increasing the maximum lift coefficient.

[0007] Specifically, the leading edge slat has an upper wing surface, a lower wing surface, and a side end face. The upper wing surface defines the leading edge and trailing edge of the slat, and the leading edge and trailing edge of the slat define the slat plane. The profile of the side end face is defined by the side edge of the upper wing surface and the side edge of the lower wing surface. The side end face includes a first part and a second part. The first part extends from the leading edge of the slat, and the second part is a continuous convex curved surface portion that extends between the first part and the trailing edge of the slat.

[0008] In one embodiment of the present invention, the outer end face of the side end face includes a first portion and a second portion.

[0009] In a preferred embodiment, the first part is a planar portion.

[0010] In one embodiment, the first portion is perpendicular to the slat plane.

[0011] In one embodiment, the second portion is perpendicular to the slat plane.

[0012] Optionally, the second part extends at least 20% of the chord length of the slat in the chord direction.

[0013] In one embodiment, the first portion and the second portion are continuous at their junction. The continuous shape between the first portion and the second portion improves the effect of suppressing flow separation.

[0014] In one embodiment, the second portion is continuous with the slat leading edge at their junction. The continuous profile between the second portion and the slat leading edge improves the effect of suppressing flow separation.

[0015] The present invention also relates to an aircraft comprising a leading-edge slat as described above.

[0016] Additional features and advantages of the leading-edge slats described herein will be set forth in the detailed description below, and will be recognized by those skilled in the art either by the following description or by practice of the embodiments described herein, including the detailed description below and the accompanying drawings. Attached Figure Description

[0017] With reference to the above objectives, the technical features of the present invention are clearly described in the following claims, and its advantages will be apparent from the following detailed description with reference to the accompanying drawings, which illustrate preferred embodiments of the invention by way of example, without limiting the scope of the inventive concept.

[0018] Figure 1 shows a partial schematic diagram of the leading edge slats of a prior art aircraft.

[0019] Figure 2 shows a schematic diagram of the flow at the leading edge slats of a prior art aircraft.

[0020] Figure 3 shows a partial schematic diagram of the leading edge slats of an aircraft according to an embodiment of the present invention.

[0021] Figure 4 shows a partial schematic diagram of the leading edge slats of an aircraft according to an embodiment of the present invention from different angles.

[0022] Figure 5 shows a top view of the leading edge slats of an aircraft according to an embodiment of the present invention.

[0023] Figure 6 shows a schematic diagram of the flow at the leading edge slat of an aircraft according to an embodiment of the present invention.

[0024] Figure 7 shows a comparison of the maximum lift coefficient results of the leading-edge slats of a prior art aircraft and the leading-edge slats of an aircraft according to an embodiment of the present invention.

[0025] Reference numerals in the attached figures: 1, 1' Upper wing surface; 2, 2' Lower wing surface; 3 Side end face; 4 Leading edge of slat; 5 Trailing edge of slat; 6 First part; 7 Second part; 8 First connecting part; 9 Second connecting part. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention in any way.

[0027] The term “leading edge” as used in this article refers to the edge of the wing that first contacts the incoming airflow, and the straight leading edge of the slat is shown at the bottom of the top view of Figure 5. The term “trailing edge” refers to the edge of the wing that last contacts the airflow, and the straight trailing edge of the slat is shown at the top of the top view of Figure 5.

[0028] The term "slat plane" as used herein describes the plane defined by the leading and trailing edges of the slat. Note that the slat plane is not a specific construction, but is defined merely for the convenience of describing the positions of the subsequent first and second sections.

[0029] The term “outer side” as used in this article is used to describe the side that is away from the fuselage of the aircraft.

[0030] The term “chord length” used in this paper is used to describe the distance from the leading edge to the trailing edge.

[0031] The term "chordal position" used in this article is used to describe a specific location along the wing chord direction.

[0032] The phrase “a portion perpendicular to the slat plane” as described in this article means that the vertical projection of that portion onto the slat plane is a line (not a plane) with endpoints.

[0033] The term “continuous” as used in this paper, unless otherwise defined, always refers to any point at the junction of two parts where the second derivative (curvature tensor) is continuous, i.e., curvature continuous, such that the transition between the two parts is perfectly smooth.

[0034] As used in this paper, the term "convex" refers to a surface that protrudes outward from the aircraft structure relative to the tangential plane formed by its connection.

[0035] This invention relates to a leading-edge slat shape that divides the side end face of the leading-edge slat into a first part and a second part, and designs the second part to be convex to increase the maximum lift coefficient of the aircraft. However, those skilled in the art will understand that this design is not limited to leading-edge slats, but can be applied to any other slat or even other wing structures, provided there is a need for it.

[0036] Referring to Figures 1 and 2, a partial schematic diagram of a leading-edge slat of a prior art aircraft and the flow at the leading-edge slat is shown. The prior art leading-edge slat has an upper wing surface 1, a lower wing surface 2, and a side end surface 3, the profile of which is defined by the side edge of the upper wing surface 1 and the side edge of the lower wing surface 2. The shapes and profiles of the upper wing surface 1 and the lower wing surface 2 are known to those skilled in the art and will not be described further herein.

[0037] As can be seen from Figure 2, in this type of leading-edge slat, vortices usually adhere to the side end face 3, forming an upwash of airflow, which causes flow separation to occur earlier in the downstream fixed wing of this region, reducing the maximum lift coefficient.

[0038] Referring to Figures 3-5, a leading-edge slat according to an embodiment of the present invention is provided to address this problem. As shown, the leading-edge slat has an upper wing surface 1', a lower wing surface 2', and a side end face. The upper wing surface 1' defines a leading edge 4 and a trailing edge 5 of the slat, which define a slat plane. The profile of the side end face is defined by the side edge of the upper wing surface 1' and the side edge of the lower wing surface 2'. Unlike the side end face 3 of the prior art (refer to Figures 1 or 5), in the embodiment of the present invention, the side end face is divided into a first portion 6 and a second portion 7. The first portion 6 extends from the leading edge 4 to a first connecting portion 8, where the first portion 6 intersects with the second portion 7. The second portion 7 extends from the first connecting portion 8 to a second connecting portion 9, where the second portion 7 intersects with the trailing edge 5 of the slat.

[0039] In an embodiment of the invention, the outer end face (i.e., the end face near the wingtip) of the two side faces of the slat has the first portion 6 and the second portion 7 shown. In another embodiment, both side faces of the slat may have the aforementioned first portion and second portion. In yet another embodiment, the inner end face (i.e., the end face near the wing root) of the two side faces of the slat may have the aforementioned first portion and second portion.

[0040] In one embodiment, the first portion 6 is preferably a planar portion and perpendicular to the slat plane (see Figure 5), thus maintaining a good aerodynamic shape of the slat. However, the invention does not limit the shape profile of the first portion 6. For example, in other embodiments, the first portion 6 can also be a curved portion. Furthermore, the first portion can be continuous with the second portion to jointly form a continuous convex curved surface portion, such that the entire side end face is a convex curved surface (in other words, it appears to have no "planar portion"). In a further embodiment, the first portion 6 can also be inclined relative to the slat plane.

[0041] In an embodiment of the invention, the second portion 7 is a continuous convex curved surface portion that extends between the first portion and the trailing edge of the slat and protrudes outward toward the slat. The second portion 7 may also be perpendicular to the slat plane (see Figure 5). It should be understood that in other variant embodiments, the second portion 7 may also be inclined relative to the slat plane.

[0042] Considering that in the prior art, end face vortex shedding usually occurs at the chord position near the trailing edge, such as the 95%-100% position (defining the leading edge of the slat as the 0% chord position; the trailing edge of the slat as the 100% chord position), Part 7 may extend the chord length of the slat by at least 20%, at least 30%, or at least 40% in the chord direction to satisfy the requirement that the slat end face vortex sheds in advance at the desired position.

[0043] Preferably, the first part 6 and the second part 7 are continuous at the first connecting portion 8, i.e., there is no abrupt change in curvature. Also preferably, the second part 7 is continuous with the leading edge of the slat 4 at the second connecting portion 9. The continuous shape improves the effect of suppressing flow separation.

[0044] As can be seen from Figure 6, in the leading edge slat of the present invention, the slat end face vortex has left the end face in advance, thereby reducing the upwash effect of the end face vortex on the fixed wing step position, which has the effect of delaying stall and improving the maximum lift coefficient of the whole aircraft.

[0045] Figure 7 shows a comparison of the maximum lift coefficient results of a leading-edge slat for a prior art aircraft and a leading-edge slat for an aircraft according to an embodiment of the present invention. The figure represents a leading-edge slat of an embodiment of the present invention; the dashed line represents a leading-edge slat of the prior art; the horizontal axis represents the angle of attack (α, in degrees) at takeoff; and the vertical axis represents the maximum lift coefficient (CL). It can be seen that the maximum lift coefficient of the aircraft is significantly improved at larger angles of attack.

[0046] It should be understood that in other embodiments, the side end face may also have different designs. For example, in some embodiments, the side end face may be divided into a first part, a second part, and a third part, etc.

[0047] This invention proposes a novel leading-edge slat shape. By establishing a curved transition shape from the slat end face to the trailing edge, the novel aerodynamic shape enables the slat end face vortex to detach in advance after the slat is deployed, effectively reducing the induction of end face vortex on the fixed wing step and adjacent area. Moreover, the curved shape allows the slat to maintain a large chord length at the end face transition position, ultimately achieving the effect of suppressing separation and increasing the maximum lift coefficient.

[0048] While the structure of the present invention has been described above with reference to preferred embodiments, those skilled in the art should recognize that the above examples are merely illustrative and should not be construed as limiting the invention. Therefore, modifications and variations can be made to the present invention, all of which will fall within the scope defined by the appended claims.

Claims

1. A leading-edge slat having an upper surface, a lower surface, and a side end face, the upper surface defining a leading edge and a trailing edge of the slat, the leading edge and the trailing edge defining a slat plane, and the profile of the side end face being defined by the side edge of the upper surface and the side edge of the lower surface. Its features are, At least one of the side end faces includes a first portion and a second portion, the first portion extending from the leading edge of the slat, wherein the second portion is a continuous convex curved surface portion extending between the first portion and the trailing edge of the slat.

2. The leading edge slat as described in claim 1, characterized in that, The outer end face of the side end face includes the first part and the second part.

3. The leading edge slat as described in claim 1, characterized in that, The first part and the second part are continuous to form a continuous convex curved surface portion.

4. The leading edge slat as described in claim 1, characterized in that, The first part is a planar part.

5. The leading edge slat as described in claim 1, characterized in that, The first portion is perpendicular to the plane of the slat.

6. The leading-edge slat as claimed in claim 1, characterized in that, The second part is perpendicular to the plane of the slat.

7. The leading edge slat as claimed in claim 1, characterized in that, The second part extends at least 20% of the chord length of the slat in the chord direction.

8. The leading edge slat as claimed in claim 1, characterized in that, The first part and the second part are continuous at their connection point.

9. The leading edge slat as claimed in claim 1, characterized in that, The second part is continuous with the leading edge of the slat at their junction.

10. An aircraft comprising a leading-edge slat as claimed in any one of claims 1-9.

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