Structural design method for improving the flutter boundary of diamond-shaped back-flying wing and diamond-shaped back-flying wing

Abstract

The present invention belongs to the field of aircraft manufacturing, and specifically relates to a structural design method for improving the flutter boundary of a diamond-shaped back-flappable wing and a diamond-shaped back-flappable wing. The structural design method includes establishing a preliminary structure of the diamond-shaped back-flappable wing; performing load analysis and flutter characteristic calculation; performing optimization to obtain an optimized structure; establishing an evaluation standard to perform numerical evaluation on the optimized structure; performing a wind tunnel test to verify the flutter boundary of the optimized structure and determine the final structure. The diamond-shaped back-flappable wing is based on a carbon fiber composite material structure, and aims to improve the flutter boundary of the wing. By locally applying steel, the weight distribution, structural strength and stiffness of the diamond-shaped back-flappable wing are optimized, and finally a diamond-shaped back-flappable wing structure coupled with a carbon fiber composite material and a small amount of steel is established. The structural design method for improving the flutter boundary of the diamond-shaped back-flappable wing and the diamond-shaped back-flappable wing of the present invention can significantly improve the flutter boundary of the diamond-shaped back-flappable wing, and have engineering practical value.

Description

Technical Field

[0001] The invention belongs to the field of aircraft manufacturing, and in particular relates to a structural design method for improving the flutter boundary of a diamond back-bounce wing and a diamond back-bounce wing. Background Art

[0002] In order to reduce the structural weight, composite materials are widely used in the design of aircraft wing structures. However, the structural stiffness of composite materials is relatively small compared to that of all-metal materials, which causes the aircraft to face a greater risk of flutter. Taking into account the two conflicting requirements of lighter structural weight and larger flutter margin is one of the major challenges in the design of modern aircraft wing surfaces. At present, the method of increasing the relative thickness of the wing surface is usually used to enhance the wing surface stiffness, but this will bring a large increase in drag, which restricts the gliding ability of the aircraft.

[0003] The diamond back wing is a combined wing that is connected by hinges with two wing strips with relatively large aspect ratios on the front wing and the rear wing. It has good high lift-to-drag ratio characteristics. At the same time, the diamond back wing is a high-lift aerodynamic layout form of the foldable variant cruise aircraft and is an important way to achieve glide range extension.

[0004] The study found that the application of carbon fiber composite materials in the diamond-back wing structure can greatly reduce the weight of the wing structure. However, due to the large aspect ratio and small relative thickness of the diamond-back wing, the diamond-back wing structure made of all carbon fiber composite materials has low strength, resulting in a small flutter boundary, which seriously restricts the flight performance of the aircraft. Unfortunately, the method of increasing the relative thickness of the wing surface cannot overcome the constraint problem of the small design space of the diamond-back wing.

[0005] Currently, there is an urgent need to develop a structural design method for improving the flutter boundary of the diamond back wing and a diamond back wing. Summary of the invention

[0006] One technical problem to be solved by the present invention is to provide a structural design method for improving the flutter boundary of the diamond back-flying wing. Another technical problem to be solved by the present invention is to provide a diamond back-flying wing. By overcoming the defects of the prior art, the contradiction between the requirements of the diamond back-flying wing for lighter structural weight and larger flutter boundary, as well as the technical difficulties of thin airfoil and small design space are solved.

[0007] The structural design method for improving the flutter boundary of a diamond-shaped back-flying wing of the present invention is characterized by comprising the following steps:

[0008] S10. Establish the preliminary structure of the diamond-shaped back bomb wing;

[0009] According to the overall design requirements and preliminary strength requirements of the diamond back wing, determine the appearance parameters of the diamond back wing and the all-carbon fiber composite material structural frame of the diamond back wing;

[0010] The external parameters of the diamond-shaped back wing include the front wing half span L 1 , rear wing half span L 2 , front wing chord length C 1 , rear wing chord length C 2 , front wing sweep angle and rear wing sweep angle;

[0011] The diamond-back wing’s all-carbon fiber composite structural framework includes skin thickness, internal spar structure, and foam filler distribution;

[0012] S20. Perform load analysis and flutter characteristic calculation;

[0013] The wing surface load analysis and strength and stiffness verification of the all-carbon fiber composite material structural frame of the diamond-shaped back-bomb wing are carried out to determine the strength and stiffness boundaries of the diamond-shaped back-bomb wing within the flight envelope; the flutter characteristics are calculated to determine the flutter boundaries of the diamond-shaped back-bomb wing;

[0014] S30. Optimize to obtain an optimized structure;

[0015] Improve the strength and rigidity of the diamond-shaped back wing by replacing the carbon fiber composite structure in the root area of ​​the front and rear wings with steel; the size of the wing root replacement area is the optimization parameter;

[0016] Improve the flutter boundary of the front wing, adopt passive flutter suppression technology, add steel as counterweight inside the leading edge of the front wing, and adjust the mass distribution of the front wing; the size of the front wing counterweight is the optimization parameter;

[0017] Improve the rear wing flutter boundary. In view of the fact that the rear wing surface in the preliminary structure of the diamond-shaped back-flapped wing is thinner than the front wing surface, and has lower strength and stiffness, strengthen the rear wing structure and place a steel main beam inside the all-carbon fiber composite material of the rear wing; the position and size of the steel main beam are the optimization parameters:

[0018] After optimization, the optimized structure of the diamond back wing was obtained. The optimized parameters included the wing root replacement area, front wing counterweight, and the position and size of the steel main beam.

[0019] S40. Establish evaluation criteria and perform numerical evaluation on the optimized structure;

[0020] The evaluation criteria are established as follows:

[0021] The weight gain of the optimized structure does not exceed 5% of the weight of the all-carbon fiber composite material;

[0022] The structural strength of the optimized structure meets the overall design requirements and initial strength requirements of the pre-set diamond-shaped back bomb wing;

[0023] The flutter boundary of the optimized structure exceeds the flight envelope of the aircraft, ensuring that flutter does not occur within the flight envelope of the aircraft;

[0024] The optimized structure of the diamond back-elastic wing is evaluated by a numerical simulation method. If the optimized structure of the diamond back-elastic wing meets the evaluation criteria, the next step is entered; otherwise, the process returns to S20 and iterates repeatedly until the evaluation criteria are met.

[0025] S50. Conduct wind tunnel tests to check and optimize the flutter boundary of the structure and determine the final structure;

[0026] A wind tunnel test model of the diamond back-flying wing is processed according to the optimized structure to check the flutter boundary of the aircraft; if the flutter boundary of the aircraft exceeds the flight envelope, the optimized structure is determined to be the final structure of the diamond back-flying wing, otherwise, return to S20 and repeat the iteration until the flutter boundary requirements are met.

[0027] The diamond-shaped back-elastic wing of the present invention comprises two groups of wing surfaces, a front wing and a rear wing; the front wing comprises two front elastic wings that are symmetrical on both sides, and the wing roots of the two front elastic wings are hinged and fixed; the rear wing comprises two rear elastic wings that are symmetrical on both sides, and the wing roots of the two rear elastic wings are hinged and fixed; the front wing is swept back, and the rear wing is swept forward; the front elastic wings are respectively hinged with the corresponding rear elastic wings, and the wing tips of the front elastic wings extend out of the wing tips of the corresponding rear elastic wings;

[0028] The front and rear wings are covered with carbon fiber composite skins;

[0029] The wing roots of the two front wings are the front wing replacement areas, the front wing leading edge counterweights are arranged at the wing tip leading edges of the front wings, and the remaining front wings are the front wing composite material areas; a carbon fiber composite material wing spar is arranged in the front wing composite material area; and the cavity of the front wing is filled with foam fillers;

[0030] The wing roots of the two rear winglets are the rear wing replacement area, and the remaining rear winglets are the rear wing composite material area; the rear wing main beam is arranged in the rear wing composite material area, and the rear wing main beam includes a steel main beam, a main beam covering the steel main beam, and a composite material force transmission area, and the steel main beam is a rectangular beam; the cavity of the rear wing is filled with foam filler;

[0031] The half span of the front wing displacement area is l 1 , l 1 ≤15% L 1 ; The half span of the rear wing replacement area is l 2 , l 2 ≤15% L 2 ;

[0032] The width of the front wing leading edge counterweight is b1 , Changwei l p1 , b 1 ≤18% C 1 , l p1 ≤20% L 1 ;

[0033] The thickness of the rear wing is t ; The coordinate starting point of the steel main beam is ( x 2 , y 2 ), the width of the steel main beam is b 2 , Houwei h 2 ; 25% C 2 ≤ x 2 ≤35% C 2 , 0≤ y 2 ≤10% t , 10% C 2 ≤ b 2 ≤25% C 2 , 15% t ≤ h 2 ≤40% t .

[0034] The structural design method for improving the flutter boundary of the diamond-back wing of the present invention makes full use of the characteristic of the small weight of the carbon fiber composite material structure. On the basis of the accurate evaluation of the aerodynamic characteristics of the diamond-back wing, the strength and stiffness requirements and flutter characteristics of the diamond-back wing are determined within the flight envelope, and a full carbon fiber composite material structure is established. Without increasing the thickness and shape of the wing, with the goal of improving the flutter boundary of the wing, the weight distribution, structural strength and stiffness of the diamond-back wing are optimized by locally applying steel, and finally a diamond-back wing structure coupled with carbon fiber composite materials and a small amount of steel is established.

[0035] The diamond back-elastic wing of the present invention solves the design problem of the contradiction between the structural lightweight requirement of the diamond back-elastic wing and the requirement for a larger flutter boundary, improves the flutter boundary, and at the same time ensures that the structural weight increase does not exceed 5% compared with the all-carbon fiber composite material, and has engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flow chart of a structural design method for improving the flutter boundary of a diamond-shaped back bomb wing according to the present invention;

[0037] Figure 2 The diamond-shaped back-bounce wing of the present invention;

[0038] Figure 3 It is a schematic diagram of some optimized parameters adopted by the diamond-shaped back-flappable wing of the present invention;

[0039] Figure 4 It is a schematic diagram of the front wing cross-section structure of the diamond-shaped back elastic wing of the present invention;

[0040] Figure 5 It is a schematic diagram of the rear wing cross-section structure of the diamond-shaped back-elastic wing of the present invention;

[0041] Figure 6 This is a diagram showing the flutter boundary enhancement effect of the diamond-shaped back-flying wing of the present invention.

[0042] 1. Front wing composite area; 2. Rear wing composite area; 3. Front wing replacement area; 4. Rear wing replacement area; 5. Front wing leading edge counterweight; 6. Rear wing main beam; 7. Carbon fiber composite skin; 8. Carbon fiber composite wing beam; 9. Foam filling; 10. Steel main beam; 11. Main beam and composite force transmission area. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0044] Example: Figure 1 As shown, the structural design method for improving the flutter boundary of the diamond back wing of this embodiment includes the following steps:

[0045] S10. Establish the preliminary structure of the diamond-shaped back bomb wing;

[0046] According to the overall design requirements and preliminary strength requirements of the diamond back wing, determine the appearance parameters of the diamond back wing and the all-carbon fiber composite material structural frame of the diamond back wing;

[0047] The external parameters of the diamond-shaped back wing include the front wing half span L 1 , rear wing half span L 2 , front wing chord length C 1 , rear wing chord length C 2 , front wing sweep angle and rear wing sweep angle;

[0048] The diamond-back wing’s all-carbon fiber composite structural framework includes skin thickness, internal spar structure, and foam filler distribution;

[0049] S20. Perform load analysis and flutter characteristic calculation;

[0050] The wing surface load analysis and strength and stiffness verification of the all-carbon fiber composite material structural frame of the diamond-shaped back-bomb wing are carried out to determine the strength and stiffness boundaries of the diamond-shaped back-bomb wing within the flight envelope; the flutter characteristics are calculated to determine the flutter boundaries of the diamond-shaped back-bomb wing;

[0051] S30. Optimize to obtain an optimized structure;

[0052] Improve the strength and rigidity of the diamond-shaped back wing by replacing the carbon fiber composite structure in the root area of ​​the front and rear wings with steel; the size of the wing root replacement area is the optimization parameter;

[0053] Improve the flutter boundary of the front wing, adopt passive flutter suppression technology, add steel as counterweight inside the leading edge of the front wing, and adjust the mass distribution of the front wing; the size of the front wing counterweight is the optimization parameter;

[0054] Improve the rear wing flutter boundary. In view of the fact that the rear wing surface in the preliminary structure of the diamond-shaped back-flapped wing is thinner than the front wing surface, and has lower strength and stiffness, strengthen the rear wing structure and place a steel main beam 10 inside the all-carbon fiber composite material of the rear wing; wherein the position and size of the steel main beam 10 are optimization parameters:

[0055] After optimization, the optimized structure of the diamond back wing is obtained, and the optimized parameters include the wing root replacement area, the front wing counterweight, and the position and size of the steel main beam 10;

[0056] S40. Establish evaluation criteria and perform numerical evaluation on the optimized structure;

[0057] The evaluation criteria are established as follows:

[0058] The weight gain of the optimized structure does not exceed 5% of the weight of the all-carbon fiber composite material;

[0059] The structural strength of the optimized structure meets the overall design requirements and initial strength requirements of the pre-set diamond-shaped back bomb wing;

[0060] The flutter boundary of the optimized structure exceeds the flight envelope of the aircraft, ensuring that flutter does not occur within the flight envelope of the aircraft;

[0061] The optimized structure of the diamond back-elastic wing is evaluated by a numerical simulation method. If the optimized structure of the diamond back-elastic wing meets the evaluation criteria, the next step is entered; otherwise, the process returns to S20 and iterates repeatedly until the evaluation criteria are met.

[0062] S50. Conduct wind tunnel tests to check and optimize the flutter boundary of the structure and determine the final structure;

[0063] A wind tunnel test model of the diamond back-flying wing is processed according to the optimized structure to check the flutter boundary of the aircraft; if the flutter boundary of the aircraft exceeds the flight envelope, the optimized structure is determined to be the final structure of the diamond back-flying wing, otherwise, return to S20 and repeat the iteration until the flutter boundary requirements are met.

[0064] like Figure 2~Figure 5 As shown, the diamond-shaped back wing of this embodiment includes two groups of wing surfaces, the front wing and the rear wing; the front wing includes two front wing pieces that are symmetrical on the left and right, and the wing roots of the two front wing pieces are hinged and fixed; the rear wing includes two rear wing pieces that are symmetrical on the left and right, and the wing roots of the two rear wing pieces are hinged and fixed; the front wing is swept back, and the rear wing is swept forward; the front wing is hinged to the corresponding rear wing, and the wing tip of the front wing extends out of the wing tip of the corresponding rear wing;

[0065] The surface of the front wing and the rear wing is covered with a carbon fiber composite material skin 7;

[0066] The wing roots of the two front wings are the front wing replacement area 3, the front wing leading edge counterweight 5 is arranged at the wing tip leading edge of the front wing, and the remaining front wing is the front wing composite material area 1; a carbon fiber composite material spar 8 is arranged in the front wing composite material area 1; and a foam filler 9 is filled in the cavity of the front wing;

[0067] The wing roots of the two rear winglets are the rear wing replacement area 4, and the remaining rear winglets are the rear wing composite material area 2; a rear wing main beam 6 is arranged in the rear wing composite material area 2, and the rear wing main beam 6 includes a steel main beam 10, and a main beam and composite material force transmission area 11 covering the steel main beam 10, and the steel main beam 10 is a rectangular beam; the cavity of the rear winglet is filled with a foam filler 9;

[0068] The half span of the front wing displacement area 3 is l 1 , l 1 ≤15% L 1 ; The half span of the rear wing replacement area 4 is l 2 , l 2 ≤15% L 2 ;

[0069] The width of the front wing leading edge counterweight 5 is b 1 , Changwei l p1 , b 1 ≤18% C 1 , l p1 ≤20% L 1 ;

[0070] The thickness of the rear wing is t ; In the fuselage coordinate system with the leading edge of the wing as the origin, the coordinate starting point of the steel main beam 10 is x 2 , y 2 , the width of the steel main beam 10 is b 2 , Houwei h 2 ; 25% C 2 ≤ x 2 ≤35% C 2 , 0≤ y 2 ≤10% t , 10% C 2 ≤ b 2 ≤25% C 2 , 15% t ≤ h 2 ≤40% t .

[0071] Figure 6 The flutter boundary lifting effect diagram of the diamond back wing of the present invention is given. M is the Mach number, the ordinate H It can be seen that the diamond back-bounce wing of the present invention can significantly improve the flutter boundary and extend the flutter boundary to the full flight envelope, which proves that the structural design method of improving the flutter boundary of the diamond back-bounce wing of the present invention has indeed improved the flutter boundary of the diamond back-bounce wing.

[0072] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. For those familiar with the art, all features disclosed in the present invention, or steps in all methods or processes disclosed, except for mutually exclusive features and / or steps, can be combined in any way without departing from the principles of the present invention. The present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A structural design method for improving the flutter boundary of a diamond-shaped back-flying wing, characterized in that: The following steps are involved: S10. Establish the preliminary structure of the diamond-shaped back bomb wing; Determine the appearance parameters of the diamond-shaped back-bomb wing and the all-carbon fiber composite material structural frame of the diamond-shaped back-bomb wing; The external parameters of the diamond-shaped back wing include the front wing half span L 1 , rear wing half span L 2 , front wing chord length C 1 , rear wing chord length C 2 , front wing sweep angle and rear wing sweep angle; The diamond-back wing’s all-carbon fiber composite structural framework includes skin thickness, internal spar structure, and foam filler distribution; S20. Perform load analysis and flutter characteristic calculation; The wing surface load analysis and strength and stiffness verification of the all-carbon fiber composite material structural frame of the diamond-shaped back-bomb wing are carried out to determine the strength and stiffness boundaries of the diamond-shaped back-bomb wing within the flight envelope; the flutter characteristics are calculated to determine the flutter boundaries of the diamond-shaped back-bomb wing; S30. Optimize to obtain an optimized structure; Improve the strength and rigidity of the diamond-shaped back wing by replacing the carbon fiber composite structure in the root area of ​​the front and rear wings with steel; the size of the wing root replacement area is the optimization parameter; Improve the flutter boundary of the front wing, adopt passive flutter suppression technology, add steel as counterweight inside the leading edge of the front wing, and adjust the mass distribution of the front wing; the size of the front wing counterweight is the optimization parameter; The rear wing flutter boundary is improved. In view of the fact that the rear wing surface in the preliminary structure of the diamond-shaped back-spring wing is thinner than the front wing surface and has lower strength and stiffness, the rear wing structure is strengthened and a steel main beam (10) is placed inside the full carbon fiber composite material of the rear wing; wherein the position and size of the steel main beam (10) are optimization parameters: After optimization, the optimized structure of the diamond back wing is obtained, and the optimized parameters include the wing root replacement area, the front wing counterweight, and the position and size of the steel main beam (10); S40. Establish evaluation criteria and perform numerical evaluation on the optimized structure; The evaluation criteria are established as follows: The weight gain of the optimized structure does not exceed 5% of the weight of the all-carbon fiber composite material; The structural strength of the optimized structure meets the overall design requirements and initial strength requirements of the pre-set diamond-shaped back bomb wing; The flutter boundary of the optimized structure exceeds the flight envelope of the aircraft, ensuring that flutter does not occur within the flight envelope of the aircraft; The optimized structure of the diamond back-elastic wing is evaluated by a numerical simulation method. If the optimized structure of the diamond back-elastic wing meets the evaluation criteria, the next step is entered; otherwise, the process returns to S20 and iterates repeatedly until the evaluation criteria are met. S50. Conduct wind tunnel tests to check and optimize the flutter boundary of the structure and determine the final structure; A wind tunnel test model of the diamond back-flying wing is processed according to the optimized structure to check the flutter boundary of the aircraft; if the flutter boundary of the aircraft exceeds the flight envelope, the optimized structure is determined to be the final structure of the diamond back-flying wing, otherwise, return to S20 and repeat the iteration until the flutter boundary requirements are met.

2. A diamond-shaped back-bounce wing, which is designed by the structural design method for improving the flutter boundary of the diamond-shaped back-bounce wing according to claim 1, characterized in that: The diamond-shaped back wing comprises two groups of wing surfaces, a front wing and a rear wing; the front wing comprises two front wing pieces that are symmetrical on both sides, and the wing roots of the two front wing pieces are hinged and fixed; the rear wing comprises two rear wing pieces that are symmetrical on both sides, and the wing roots of the two rear wing pieces are hinged and fixed; the front wing is swept back, and the rear wing is swept forward; the front wing is hinged to the corresponding rear wing, and the wing tip of the front wing extends out of the wing tip of the corresponding rear wing; The surfaces of the front wing and the rear wing are covered with carbon fiber composite material skins (7); The wing roots of the two front wings are front wing replacement areas (3), the front wing leading edge counterweights (5) are arranged at the wing tip leading edges of the front wings, and the remaining front wings are front wing composite material areas (1); a carbon fiber composite material spar (8) is arranged in the front wing composite material area (1); and a foam filler (9) is filled in the cavity of the front wing; The wing roots of the two rear winglets are the rear wing replacement area (4), and the remaining rear winglets are the rear wing composite material area (2); a rear wing main beam (6) is arranged in the rear wing composite material area (2), and the rear wing main beam (6) includes a steel main beam (10), and a main beam and composite material force transmission area (11) covering the steel main beam (10), and the steel main beam (10) is a rectangular beam; the cavity of the rear wing is filled with a foam filler (9); The half-span of the front wing displacement area (3) is l 1 , l 1 ≤15% L 1 ; The half-span of the rear wing replacement area (4) is l 2 , l 2 ≤15% L 2 ; The width of the front wing leading edge counterweight (5) is b 1 , Changwei l p1 , b 1 ≤18% C 1 , l p1 ≤20% L 1 ; The thickness of the rear wing is t ; In the fuselage coordinate system with the leading edge of the wing as the origin, the coordinate starting point of the steel main beam (10) is ( x 2 , y 2 ), the width of the steel main beam (10) is b 2 , Houwei h 2 ; 25% C 2 ≤ x 2 ≤35% C 2 , 0≤ y 2 ≤10% t , 10% C 2 ≤ b 2 ≤25% C 2 , 15% t ≤ h 2 ≤40% t .

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