Fin-based aircraft flap and design method thereof

Abstract

The invention discloses an aircraft flap based on fins and a design method thereof, and belongs to the technical field of aircraft design. The problems that in the prior art, a traditional aircraft flap and a design method thereof are poor in noise reduction effect and difficult to maintain are solved. The invention provides an aircraft flap based on fins. The aircraft flap comprises a main wing, a trailing edge inner side flap, a trailing edge outer side flap and a fin-shaped structure. The trailing edge inner side flap and the trailing edge outer side flap are connected with the main wing, and the fin-shaped structure is installed in the side edge of the trailing edge outer side flap, so that the side edge of the flap forms a fin-shaped ventilation structure; the fin-shaped structure is composed of fins, the outer contour surface curvature of the fin-shaped structure is kept consistent with the surface curvature of an original flap, and the spanwise length of the fins is linearly distributed. The method effectively achieves the effect of reducing the noise of the machine body, and can be applied to noise reduction flap design.

Description

Technical Field

[0001] The present invention relates to a fin-based aircraft flap and its design method, belonging to the technical field of aircraft design. Background Art

[0002] Currently, the problem of aerodynamic noise is one of the key issues in the development of large airliners, which is directly related to whether large airliners can obtain airworthiness certification; most large airliners adopt a lift augmentation configuration with trailing-edge flaps. While meeting the lift-to-drag ratio characteristics and suppressing stall during takeoff and landing phases, the aerodynamic noise generated increases the overall noise level of large airliners, and the side-edge noise of the trailing-edge flap accounts for a large proportion of the fuselage noise. The high-intensity side-edge vortex pair formed by the pressure difference between the upper and lower surfaces of the side edge of the flap, due to its own instability and its interaction with the solid wall, induces unsteady pressure pulsation, resulting in an increase in the noise level; therefore, there is an urgent need to develop an efficient and stable noise control method to solve the side-edge noise problem of the flap.

[0003] In the prior art, the side-edge noise reduction technology of the flap is mainly divided into two categories: active control and passive control. The core idea of both is to eliminate or weaken the side-edge vortex structure of the flap. The active control method controls the vortex structure by injecting energy into the flow field, including blowing control, plasma, etc. The passive control technology reduces noise by changing and modifying the side-edge configuration. The methods mainly include: side-edge flap end plates, adding porous materials, continuous linear methods, and perturbation flow vanes, etc.; however, the noise reduction effect of the active control technology is limited, and at the same time, additional driving mechanisms or storage spaces are required, while the side-edge flap end plates and continuous linear methods will increase the extra weight and manufacturing difficulty of the aircraft, and adding porous materials and perturbation flow vane methods will affect the aerodynamic performance of the aircraft and are not easy to maintain.

[0004] In summary, a fin-based aircraft flap and its design method are needed. Summary of the Invention

[0005] A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify the key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is only to present certain concepts in a simplified form as a prelude to the more detailed description to be discussed later.

[0006] In view of this, to solve the problem that the traditional aircraft flap and its design method in the prior art have poor noise reduction effect and are difficult to maintain, the present invention provides a fin-based aircraft flap and its design method.

[0007] The first technical solution is as follows: A fin-based aircraft flap includes a main wing, an inner trailing-edge flap, an outer trailing-edge flap, and a fin-like structure; The inner trailing-edge flap and the outer trailing-edge flap are connected to the main wing, and the fin structure is installed inside the side edge of the outer trailing-edge flap, so that the side edge of the flap forms a fin-shaped ventilation structure; The fin structure is composed of fin sheets.

[0008] Furthermore, the curvature of the outer contour surface of the fin structure is consistent with the curvature of the original flap surface, and the spanwise length of the fin sheets is linearly distributed.

[0009] Technical solution two is as follows: A fin-based aircraft flap and its design method, which is used to design a fin-based aircraft flap described in technical solution one, and includes the following steps: S1. Determine the chordwise installation length and installation position of the fin sheets according to the chord length of the airfoil at the end face of the outer trailing-edge flap; S2. Determine the maximum spanwise length of the fin sheets at the trailing edge of the flap and the maximum spanwise length of the fin sheets at the leading edge of the flap according to the thickness of the airfoil at the end face of the outer trailing-edge flap, and complete the design of the fin-based flap.

[0010] Furthermore, in S1, the chordwise distance between the leading edge point of the airfoil and the starting installation position of the fin sheet is expressed as: ; where is the chord length of the airfoil at the end face of the outer trailing-edge flap; The chordwise distance between the trailing edge point of the airfoil and the termination installation position of the fin sheet is expressed as: ; The chordwise installation length of the fin sheet is expressed as: .

[0011] Furthermore, in S2, the maximum spanwise length of the fin sheets at the trailing edge of the flap is expressed as: ; where is the maximum thickness of the airfoil at the end face of the outer trailing-edge flap; The maximum spanwise length of the fin sheets at the leading edge of the flap is expressed as: .

[0012] The beneficial effects of the present invention are as follows: The present invention proposes a fin-based aircraft flap and its design method. On the basis of a conventional wing, fins are installed to replace the flap side edge, so that the flap side edge forms a fin-shaped ventilation structure. The fins help to suppress the generation and development of large-scale vortex structures at the side edge, achieving the effect of reducing the aircraft noise. The fin-shaped structure has the characteristics of not interfering with the retraction and extension of the flap, and does not lose the aerodynamic performance of the lift-increasing device, which has more engineering practical value. Specifically: (1) According to the noise generation mechanism of the flap side edge, the high-strength side-edge vortex pair structure is its main noise source. By adopting a fin-shaped ventilation structure, the flap side edge is designed in a hollowed-out form, effectively decomposing the large-scale vortex structure into small-scale vortex structures, suppressing the formation and development of the side-edge vortex pair, and weakening the vorticity intensity of the side-edge vortex, so as to achieve the purpose of reducing noise; (2) The outer surface profile of the fin-shaped structure designed by the present invention has the same sectional curvature as the original wing. In addition, the chordwise installation length of the fin and the maximum spanwise length of the fin are both related to the airfoil size of the flap side-edge end face and the size of the flap side-edge vortex, that is, it maximally ensures that the aerodynamic shape is consistent with the original shape. Therefore, the fin-based aircraft flap can reduce noise while having good aerodynamic performance; (3) Compared with the active control method, the present invention adopts passive control, that is, there is no need to inject external energy into the flow field and there is no additional driving structure, which is easier to implement in engineering. Compared with other passive control measures, the fin-shaped structure is installed inside the flap side edge, without generating additional weight and saving more material costs. In addition, the flap with the fin-shaped structure can be freely retracted and extended during takeoff, landing and cruise stages, which has more applicability and feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a schematic structural diagram of a fin-based aircraft flap configuration; Figure 2 is a sectional view taken along line A-A of the fin-based aircraft flap configuration; Figure 3 is a schematic sectional view of the fin-shaped structure; Figure 4 is a schematic overall view of the fin-shaped structure; Figure 5 is a schematic diagram of the comparison of the aerodynamic performance of the aircraft; Figure 6 is a schematic diagram of the comparison of the vorticity characteristics between the basic configuration and the fin-based aircraft flap configuration. Among them, (a) is a schematic diagram of the vorticity characteristics of the basic configuration, and (b) is a schematic diagram of the vorticity characteristics of the fin-based aircraft flap configuration; Figure 7Schematic diagram for comparison of spectral curves of observation points. (a) Schematic diagram of the spectral curve of the near-field observation point, and (b) Schematic diagram of the spectral curve of the far-field observation point; Figure 8 Schematic flow chart of a design method for a fin-based aircraft flap.

[0014] Reference numerals: 1. Aircraft; 2. Fuselage; 3. Wing; 4. Engine; 5. Inboard leading-edge slat; 6. Outboard leading-edge slat; 7. Main wing; 8. Inboard trailing-edge flap; 9. Outboard trailing-edge flap; 10. First slide rail; 11. Second slide rail; 12. Hanger; 13. Fin structure; 14. Fin. Detailed implementation manners

[0015] In order to make the technical solutions and advantages in the embodiments of the present invention clearer and more understandable, the following further describes the exemplary embodiments of the present invention in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than an exhaustive list of all embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0016] Embodiment 1: Refer to Figures 1 - 8 This embodiment is described in detail. A fin-based aircraft flap includes a main wing 7, an inboard trailing-edge flap 8, an outboard trailing-edge flap 9, and a fin structure 13; The inboard trailing-edge flap 8 and the outboard trailing-edge flap 9 are connected to the main wing 7, and the fin structure 13 is installed inside the side edge of the outboard trailing-edge flap 9, so that a fin-shaped ventilation structure is formed at the side edge of the flap; The fin structure 13 is composed of fins 14.

[0017] Furthermore, the curvature of the outer contour surface of the fin structure 13 is consistent with the curvature of the original flap surface, and the spanwise length of the fins 14 is linearly distributed; Specifically, the upper, lower and side surfaces of the fin-based aircraft flap are in a hollowed-out form, and the side surface of the fin structure 13 and the end surface of the side edge of the flap are in the same vertical plane; The shape of the fins 14 is diverse and can be a cuboid, a cylinder, etc.; Refer to Figure 1 , the aircraft 1 includes a fuselage 2, a wing 3 and an engine 4. The wing 3 includes an inboard leading-edge slat 5, an outboard leading-edge slat 6, a main wing 7, an inboard trailing-edge flap 8, and an outboard trailing-edge flap 9. The inboard leading-edge slat 5 and the outboard leading-edge slat 6 extend and retract along the first slide rail 10 installed on the main wing 7. The inboard trailing-edge flap 8 and the outboard trailing-edge flap 9 extend and retract along the second slide rail 11 installed on the main wing 7. The fin structure 13 composed of fins 14 is installed on one side of the scissors difference of the outboard trailing-edge flap 9, and the engine 4 is installed below the main wing 7 through a hanger 12 that bears the gravity and thrust of the engine; Reference Figure 2 , point C is the leading edge point of the airfoil, point D is the trailing edge point of the airfoil, and points E and F are the midpoints of the airfoil thickness . The chordwise distance between points E and F defines the installation length of the fin structure 13. To avoid loss of the aerodynamic performance of the lift augmentation device, the chordwise distance between point E and point C, that is, the chordwise distance between the leading edge point of the airfoil and the starting installation position of the fin e = 0.15 c = 0.026 m, where m is the unit. The chordwise distance between point F and point D, that is, the chordwise distance between the trailing edge point of the airfoil and the ending installation position of the fin f = 0.15 c = 0.026 m, the chordwise installation length of the fin structure 13 s is 70% of the chord length of the airfoil at the end face of the flap c . Maintaining the original aerodynamic shape at the leading and trailing edges of the outboard trailing edge flap 9 can ensure stable airflow at the leading edge and reliable structure at the trailing edge of the outboard trailing edge flap 9. It should be noted that the chordwise distance between point E and point C e , and the chordwise distance between point F and point D f can be different values. Points E and F are only used to illustrate the starting and ending installation positions of the fin structure 13 and should not be regarded as other restrictions; Reference Figure 3 , the fin structure 13 is composed of a group of small fins 14. It should be understood that the smaller the size of the fins 14 and the smaller the interval between adjacent fins 14, the more air passages formed by the fin structure 13, and the more conducive it is to decomposing large-scale vortex structures into small-scale vortex structures. In this embodiment, l and d are the length and width of the fin 14 respectively, , , q and n are the left-right distance and the up-down distance between the center points of adjacent fins 14 respectively, , . It should be noted that to not change the aerodynamic shape of the lift augmentation device, the outer contour line of the fin structure 13 is consistent with the outer contour line of the original flap; the dashed line is the outer contour line of the original flap; Reference Figure 4 , the fins 14 are placed inside the outboard trailing edge flap 9. The span length h of the fins 14 is specifically: , . The span length h of the fins 14 is positively correlated with the size of the side edge vortex pair, that is, the span length of the fins 14 is shorter on the leading edge side of the flap and longer on the trailing edge side of the flap. In addition, to not affect the aerodynamic performance of the lift augmentation device, in this embodiment, it is defined that takes the value of the maximum thickness of the airfoil at the end face of the outboard trailing edge flap1.5 times of takes a value of It should be noted that the fin structure 13 can be adjusted to other forms according to user needs. For example, a cylindrical fin can be used to form the fin structure. Refer to Figure 5 , based on the fin, the aerodynamic force of the aircraft flap configuration and the basic configuration is not much different, and the fin has little influence on the aerodynamic performance of the aircraft lift augmentation device. Among them, BASE_CL and BASE_CD respectively represent the lift coefficient and drag coefficient of the basic configuration, and FINS_CL and FINS_CD respectively represent the lift coefficient and drag coefficient of the aircraft flap configuration based on the fin. Refer to Figure 6 , the basic configuration has an obvious double-vortex structure, and at about 1 / 2 of the flap chord length, the two vortices merge to form a single-vortex structure. In the aircraft flap configuration based on the fin, the fin 14 decomposes the large-scale vortex structure at the flap side edge into a small-scale vortex structure, effectively suppressing the generation and development of the double-vortex structure at the flap side edge, and significantly reducing the vorticity intensity at the flap side edge. VorticityMagnitude represents the vorticity. Refer to Figure 7 , the fin 14 can reduce the near-field noise in the full frequency range, reduce the acoustic energy of the low-frequency and mid-frequency of the far-field noise, and the noise reduction amount of the total sound pressure level at the far-field observation point is 1 dB in the range of 80 Hz - 20 kHz. BASE is the basic configuration, FINS is the aircraft flap configuration based on the fin, PSD is the power spectral density, with the unit of dB / Hz, and Frequency is the frequency, with the unit of Hz.

[0018] Example 2: Refer to Figures 1 - 8 This example is described in detail. A design method for an aircraft flap based on a fin is used to design an aircraft flap based on a fin as described in Example 1, and specifically includes the following steps: S1. Determine the chordwise installation length and installation position of the fin according to the chord length of the airfoil at the end face of the flap on the outer side of the trailing edge. S2. Determine the maximum spanwise length of the fin at the trailing edge of the flap and the maximum spanwise length of the fin at the leading edge of the flap according to the thickness of the airfoil at the end face of the flap on the outer side of the trailing edge, and complete the design of the flap based on the fin.

[0019] Furthermore, in S1, the chordwise distance between the leading edge point of the airfoil and the starting installation position of the fin is expressed as: ; Among them, is the chord length of the airfoil at the end face of the flap on the outer side of the trailing edge; The chordwise distance between the trailing edge point of the airfoil and the termination installation position of the fin is expressed as: ; The chordwise installation length of the fin is expressed as: .

[0020] Furthermore, in the above S2, the maximum spanwise length of the flap trailing-edge fin is expressed as: ; wherein, is the maximum thickness of the airfoil at the end face of the outboard trailing-edge flap; The maximum spanwise length of the flap leading-edge fin is expressed as: .

[0021] Specifically, verified by numerical simulation, when the installation position of the fin 14 takes 0.1 c as the baseline value, it can ensure that the aircraft flap has good aerodynamic performance and reliable structure; Verified by numerical simulation, when the span length of the fin 14 and the maximum thickness of the airfoil at the end face of the flap are in the same order of magnitude, it can ensure that the fin-like structure 13 has the effect of suppressing the noise at the side edge of the flap while having good aerodynamic performance.

[0022] Although the present invention has been described based on a limited number of embodiments, those skilled in the art in this technical field will understand that other embodiments can be envisioned within the scope of the present invention thus described. In addition, it should be noted that the language used in this specification is mainly selected for readability and teaching purposes, rather than for the purpose of explaining or limiting the subject matter of the present invention. Therefore, many modifications and changes are obvious to those of ordinary skill in this technical field without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure of the present invention is illustrative rather than restrictive, and the scope of the present invention is defined by the appended claims.

Claims

1. A fin-based aircraft flap, characterized in that, It includes a main wing (7), an inner trailing-edge flap (8), an outer trailing-edge flap (9) and a fin structure (13); The inner trailing-edge flap (8) and the outer trailing-edge flap (9) are connected to the main wing (7), and the fin structure (13) is installed inside the side edge of the outer trailing-edge flap (9) to form a fin-shaped ventilation structure on the side edge of the flap; The fin structure (13) is composed of fin sheets (14).

2. The fin-based aircraft flap according to claim 1, characterized in that, The curvature of the outer contour surface of the fin structure (13) is consistent with the curvature of the original flap surface, and the spanwise length of the fin sheets (14) is linearly distributed.

3. A design method for a fin-based aircraft flap, characterized in that, A method for designing a fin-based aircraft flap as claimed in claims 1-2, comprising the following steps: S1. Determine the chordwise installation length and installation position of the fin sheets according to the chord length of the airfoil at the end face of the outer trailing-edge flap; S2. Determine the maximum spanwise length of the fin sheets at the trailing edge of the flap and the maximum spanwise length of the fin sheets at the leading edge of the flap according to the thickness of the airfoil at the end face of the outer trailing-edge flap, and complete the design of the fin-based flap.

4. A design method of a fin-based aircraft flap according to claim 3, characterized in that In S1, the chordwise distance between the leading edge point of the airfoil and the starting installation position of the fin is expressed as: ； Wherein, is the chord length of the airfoil at the end face of the outboard trailing edge flap; The chordwise distance between the airfoil trailing edge point and the fin termination installation position It is expressed as: ； Chordwise installation length of the fin Expressed as: 。 5. A design method for a fin-based aircraft flap according to claim 4, characterized in that, In S2, the maximum spanwise length of the flap trailing edge fin is expressed as: ； Wherein, is the maximum thickness of the airfoil at the end face of the outboard trailing-edge flap; The maximum spanwise length of the flap leading-edge fin is expressed as: 。

Images