High-subsonic winglet design method based on circulation distribution and supercritical airfoils

Abstract

This invention proposes a design method for high-subsonic winglets based on circulation distribution and supercritical airfoils. The method includes the following steps: S1, designing a smooth and continuous winglet based on the extension of the main wing surface; S2, designing the circulation distribution along the spanwise coordinates after wing deployment, making the lift or circulation distribution approximately elliptical, but slightly concentrated inward to reduce the root bending moment; S3, designing a supercritical airfoil at the upward curve of the winglet, optimizing the curvature distribution of the upper surface of the airfoil, and eliminating strong shock waves. This invention reduces aircraft aerodynamic drag and structural weight by designing a reasonable load distribution, while avoiding shock waves and separation problems caused by aerodynamic interference at the wingtip.

Description

Technical Field

[0001] This invention belongs to the field of aircraft aerodynamic design and relates to a design method for high subsonic winglets of supercritical airfoils. Background Technology

[0002] Aircraft wing design is a critical technology that significantly impacts an aircraft's aerodynamics, load, and weight. Winglets, as an integral part of the wing, also have a significant influence. Traditional winglets often have noticeable bends or structural branches at the wingtip, resulting in structural discontinuity and aerodynamic interference, causing localized airflow separation at the wingtip. For high-subsonic aircraft, this is even more likely to lead to strong shock waves, generating significant shock wave drag and disrupting the optimal circulation distribution, thus inducing drag. The widespread application of composite material technology has made it increasingly easier to manufacture lightweight, high-strength, smooth curved surfaces, thereby reducing the cost and weight of designing and manufacturing smooth, continuous winglets. This not only saves weight but also improves aerodynamic efficiency. Designing a reasonable spanwise lift distribution (i.e., circulation distribution, which is proportional to lift) is key to increasing lift, reducing drag, and reducing weight. Furthermore, for subsonic and supersonic mixed flow problems, the modification of supercritical airfoils and the design of twist angle distribution are also crucial factors. Summary of the Invention

[0003] The purpose of this invention is:

[0004] A design method for high subsonic winglets based on circulation distribution and supercritical airfoils is proposed to improve the aerodynamic efficiency of aircraft and maintain a small wing root bending moment to reduce structural weight.

[0005] The technical solution of this invention is:

[0006] A design method for high subsonic winglets based on circulation distribution and supercritical airfoils, used to obtain a reasonable aerodynamic shape for winglets, is characterized by the following design steps:

[0007] (1) Based on the main wing surface extension, a smooth and continuous wingtip winglet is designed, including continuous airfoil, chord length, twist, anhedral, and sweep distribution;

[0008] (2) The computer wing includes the spanwise coordinates of the curved, upturned winglets when unfolded to the plane;

[0009] (3) Calculate the pressure distribution of the computer wing using computational fluid dynamics numerical calculation methods;

[0010] (4) Obtain the circulation of different sections of the wing from the pressure distribution, then draw the circulation distribution along the spanwise coordinates after the wing is deployed, and compare it with the elliptical distribution.

[0011] (5) Based on the difference between the circulation distribution and the ellipse, adjust the design parameters in the first step and repeat the above process to make the circulation distribution of the wing close to the ellipse, but slightly concentrated inward to reduce the wing root bending moment.

[0012] (6) At the point where the wingtip bends upward, a large supersonic airflow will occur due to component interference and end with a strong shock wave. It is necessary to apply a unique supercritical airfoil design method at this point to optimize the curvature distribution of the upper surface of the airfoil in order to eliminate the strong shock wave.

[0013] (7) Redo the computational fluid dynamics numerical calculations until the pressure distribution of the wing is close to the contour lines of equal percentage chord length.

[0014] (8) Based on the influence of airfoil changes on lift, adjust the parameters in the first step appropriately so that the pressure distribution and circulation distribution of the wing meet the requirements.

[0015] The advantages and beneficial effects of this invention are:

[0016] The present invention provides a high subsonic winglet design method based on circulation distribution and supercritical airfoil. By designing a reasonable load distribution, it reduces the aerodynamic drag and structural weight of the aircraft, while avoiding shock waves and separation problems caused by aerodynamic interference at the wingtip. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is an example of a smooth, continuous winglet designed using this method.

[0019] Figure 2 The process involves drawing the circulation distribution of the wing after it has been deployed during the design phase and comparing it with an ellipse.

[0020] Figure 3 The comparison shows the pressure distribution after the shock wave, which is easily generated at the upward bend of the wingtip winglet, is eliminated by supercritical airfoil modification.

[0021] Figure 4 A comparison of the modified supercritical airfoil at the wingtip bend with the original airfoil. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] A design method for high subsonic winglets based on circulation distribution and supercritical airfoils, used to obtain a reasonable aerodynamic shape for winglets, is characterized by the following design steps:

[0025] (1) Based on the main wing surface extension, a smooth and continuous wingtip winglet is designed, including continuous airfoil, chord length, twist, anhedral, and sweep distribution;

[0026] (2) The computer wing includes the curved, upturned winglets, and its spanwise coordinates when deployed to the plane (see...). Figure 2 (The upturned wingtips unfold), meaning that the length of the curve along the span is the same as the straight length after unfolding:

[0027]

[0028] (1) In the formula, s is the curve length, which is also the spanwise coordinate after unfolding, and dy is the spanwise coordinate infinitesimal element.

[0029] dz is a vertical coordinate infinitesimal element.

[0030] (3) Calculate the pressure distribution of the computer wing using computational fluid dynamics numerical calculation methods;

[0031] (4) Extract the pressure distribution from a series of cross-sections at different spanwise positions and integrate to obtain the lift force of the cross-section:

[0032] C L =∮pdx (2)

[0033] (2) In the formula, p is the profile pressure and x is the coordinate of the airflow direction in front of the aircraft.

[0034] Since circulation is proportional to lift, the circulation distribution along the unfolded spanwise coordinates can be plotted and compared with the elliptical distribution.

[0035] (5) Based on the difference between the circulation distribution and the ellipse, repeat the above steps and adjust the design parameters in the first step, especially the twist angle, so that the circulation distribution of the wing is close to the ellipse, but slightly concentrated inward to reduce the root bending moment.

[0036] (6) At the point where the wingtip bends upward, a large supersonic airflow will occur due to component interference and end with a strong shock wave. It is necessary to apply a unique supercritical airfoil design method at this point to optimize the curvature distribution of the upper surface of the airfoil in order to eliminate the strong shock wave.

[0037] (7) Recalculate the pressure distribution until the pressure distribution of the wing is close to the contour lines of equal percentage chord length;

[0038] (8) Based on the influence of airfoil changes on lift, adjust the parameters in the first step appropriately so that the pressure distribution and circulation distribution of the wing meet the requirements.

[0039] In an example, for a certain high subsonic aircraft, the method proposed in this invention was used to design winglets, and the steps are as follows:

[0040] (1) Based on the main wing surface extension, design a smooth, continuously upturned winglet, including continuous airfoil, chord length, twist, anhedratio, and sweep distribution, such as... Figure 1 ;

[0041] (2) The computer wing includes the spanwise coordinates of the curved winglets as they unfold to the plane, meaning the length of the curved section at the leading edge of the unfolded wing is the same as the length of the straight section after unfolding. Figure 2 A schematic diagram of the lower geometric deployment; using computational fluid dynamics numerical calculations, the pressure distribution of the wing is calculated; from the pressure distribution, the circulation of the wing at different cross-sections is obtained, and then the circulation distribution along the spanwise coordinates of the deployed wing is plotted and compared with the elliptical distribution; such as Figure 2 The upper circulation distribution diagram shows that, in order to reduce induced drag, it is required to be close to an elliptical distribution. However, in order to reduce the bending moment at the wing root, the load at the wingtip should be slightly smaller and the load at the wing root should be slightly larger.

[0042] (3) At the upward curve of the wingtip, high-speed supersonic airflow will occur due to component interference, ending with a strong shock wave. This aerodynamic interference is related to the continuity of the wingtip's shape change; the more abrupt the turn, the stronger the aerodynamic interference. In this example, the original design already had a smooth and continuous curved surface, which alleviated the problem. However, due to the sensitivity of transonic flow during high-speed flight, a significant shock wave will still occur here (see...). Figure 3 (Left side) A unique supercritical airfoil design method must be applied here to optimize the curvature distribution of the airfoil's upper surface (see...). Figure 4 To eliminate strong shock waves (see...) Figure 3 (Right side)

[0043] It should be noted that the above process operations can be combined to varying degrees. For the sake of brevity, the implementation methods of various combinations will not be elaborated here. Those skilled in the art can flexibly adjust the order of the above operation steps or flexibly combine the above steps according to actual needs.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A design method for high subsonic winglets based on circulation distribution and supercritical airfoils, characterized in that, Includes the following steps: S1, with a smooth and continuous wingtip winglet designed based on the extension of the main wing surface; S2, design the circulation distribution along the spanwise coordinates after the wing is deployed, so that the lift or circulation distribution is close to an ellipse, but slightly concentrated inward to reduce the wing root bending moment; S3 incorporates a supercritical airfoil design at the upturned corner of the wingtip winglet to optimize the curvature distribution of the upper surface of the airfoil and eliminate strong shock waves. Step S2 includes: S21, the computer wing includes the curved winglets at the wingtips, and its spanwise coordinates when deployed to the plane, meaning that its spanwise curved length is the same as its deployed straight length: (1) In the formula, s is the curve length, that is, the spanning coordinate after unfolding, dy is the spanning coordinate element, and dz is the vertical coordinate element. S22, using computational fluid dynamics numerical calculation methods, calculates the pressure distribution of the computer wing; S23, capture the pressure distribution of a series of cross-sections at different spanwise positions: and integrate to obtain the lift force of the cross-section: C L =∮pdx (2) (2) In the formula, p is the profile pressure and x is the coordinate of the airflow direction in front of the aircraft; Since circulation is proportional to lift, the circulation distribution along the unfolded spanwise coordinates can be plotted and compared with the elliptical distribution. S24. Based on the difference between the circulation distribution and the ellipse, repeat the above steps and adjust the design parameters to make the circulation distribution of the wing closer to an ellipse, but slightly concentrated inward to reduce the wing root bending moment.

2. The method according to claim 1, characterized in that, Step S1 includes: The S11 features an upward-curving winglet design, with its shape and aerodynamics continuously varying along the span.

3. The method according to claim 1, characterized in that, Step S11 includes: Design the continuous airfoil, chord, torsion, anhedral, and sweep distribution parameters for the main wing surface.

4. The method according to claim 3, characterized in that, In step S24: Adjust the design parameters to the torsion angle parameters.

5. The method according to claim 4, characterized in that, Step S3 also includes: Based on the effect of airfoil changes on lift, the parameters in step S1 are adjusted appropriately to ensure that the pressure distribution and circulation distribution of the wing meet the requirements.

6. The method according to any one of claims 1-5, wherein: By designing the load distribution, the aerodynamic drag and structural weight of the aircraft are reduced, and shock waves and separation caused by aerodynamic interference at the wingtips are avoided.

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