Hollow fan blade cavity structure and design method considering bird strike resistance

Abstract

The present invention discloses a hollow fan blade cavity structure and a design method thereof considering bird strike resistance. The blade cavity structure comprises a skin (1), an internal reinforcing rib (2), a blade tip (3), a blade leading edge (4), a blade trailing edge (5), a blade root (6) and a tenon (7). The internal reinforcing rib (2) comprises a main rib (8) and a secondary rib (9). The blade cavity structure is a rotating structure centered on a rotating shaft. Two main ribs (8) are arranged in the middle of the internal reinforcing rib (2) and simultaneously connect the blade tip (3) and the blade root (6). The secondary rib (9) is distributed inside the internal reinforcing rib (2) and simultaneously connects the main rib (8), the blade leading edge (4), the blade trailing edge (5), the blade tip (3) and the blade root (6). The present invention takes into account the bird strike position and movement process during the bird strike impact process, can achieve full utilization of materials, and effectively reduce the mass of the hollow fan blade.

Description

Technical Field

[0001] The present invention relates to the field of aviation, and in particular to a hollow fan blade cavity structure considering bird strike resistance performance and a design method thereof. Background Art

[0002] With the rapid development of the aviation industry in recent years and the continuous increase in air traffic, the risk of bird strikes is increasing. Once a bird strikes an aircraft engine, the consequences are extremely serious. Furthermore, improvements in aircraft engine design have also put forward new requirements for engine lightweighting. As one of the most important components of an aircraft engine, fan blades are one of the most important components of an aircraft engine. Considering the bird strike resistance of hollow fan blades in their lightweight design is of great significance to aircraft engine safety.

[0003] Currently, hollow fan blades are primarily manufactured using a superplastic forming and diffusion welding process. Due to processing limitations, the hollow configuration is typically a "W" shape. This hollow configuration is simple and uniform, with internal reinforcement plates extending from the blade root to the tip. However, when a bird strikes a blade, the threat level varies depending on the blade position. This configuration cannot adjust to changes in the bird's motion and impact force, resulting in redundant filling of the cavity reinforcement plate material. Summary of the Invention

[0004] In response to the above-mentioned deficiencies in the prior art, the present invention provides a hollow fan blade cavity structure and a design method that take into account bird strike resistance, which solves the problem that current hollow fan blades fail to fully consider the influence of bird strike position and movement process, and the overall uniformity of the cavity rib structure causes material redundancy.

[0005] In order to achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is: a hollow fan blade cavity structure considering anti-bird strike performance, the blade cavity structure including a skin, internal reinforcing ribs, a blade tip, a blade leading edge, a blade trailing edge, a blade root and a tenon, the internal reinforcing ribs including main ribs and secondary ribs, the blade cavity structure is a rotating structure with the rotating shaft as the center, the skin is laid on the surface of the structure, the two main ribs are arranged in the middle of the internal reinforcing ribs, and at the same time connect the blade tip and the blade root, the secondary ribs are distributed inside the internal reinforcing ribs, and at the same time connect the main ribs, the blade leading edge, the blade trailing edge, the blade tip and the blade root, the blade leading edge is the front area of ​​the blade rotation direction, the blade trailing edge is the rear area of ​​the blade rotation direction, the blade tip is the area of ​​the blade away from the rotating shaft, the blade root is the area of ​​the blade close to the rotating shaft, and is connected to the tenon.

[0006] The beneficial effect of the above scheme is: through the above technical scheme, the cavity structure of the hollow fan blade is adjusted according to the changes in bird strike movement and impact force, which can fully utilize the material and effectively reduce the quality of the hollow fan blade.

[0007] Furthermore, the main reinforcement and the secondary reinforcement are unevenly distributed.

[0008] The beneficial effect of the above further solution is: through the above technical solution, since the degree of threat to different parts of the blade is different when a bird hits the blade, if the main reinforcement and secondary reinforcement are evenly distributed, redundancy of the reinforcement plate material will be caused.

[0009] Furthermore, the ribs at the leading edge of the blade are thicker than the ribs at the trailing edge of the blade.

[0010] The beneficial effect of the above further scheme is that when a bird strikes, the leading edge of the blade is the first to be impacted, which is more dangerous, so the ribs are relatively thick. The trailing edge of the blade mainly bears the impact force of the bird in the later stage of the impact and bears less load, so the ribs are relatively thin to prevent the blade from vibrating and failing.

[0011] Furthermore, the blade root and tenon connection parts are locally reinforced through grid design and material filling.

[0012] The beneficial effect of the above further solution is that the connection portion between the blade root and the tenon is locally strengthened, which can effectively prevent the blade root from breaking.

[0013] In addition, the present invention also adopts a technical solution: a design method for a hollow fan blade cavity structure considering bird strike resistance, the method comprising the following steps:

[0014] S1: Perform high-precision nonlinear simulation analysis on the bird impact process of fan blades, selecting different bird impact positions as impact points for bird impact simulation;

[0015] S2: The time history curve of the impact force during the impact process is obtained based on the bird strike simulation, showing the impact force on the fan blades at any time;

[0016] S3: Based on the bird's motion position on the blade and the blade's response, for n conditions of bird impact at different blade heights, the impact force at m typical moments is selected as the external load through the time history curve of the impact force;

[0017] S4: With the goal of minimizing strain energy, the blade volume as a constraint, and the impact force external load at m typical moments as the load, a multi-condition topology optimization design of the fan blade is performed;

[0018] S5: Delete the low-density units of the fan blade finite element model, retain the high-density units, reconstruct the fan blade model, and determine whether the reconstructed model after topology optimization is consistent with the configuration of the bird strike simulation in S1. If the blade configuration is consistent, the optimization process has converged and the optimization design is ended. If the blade configuration is inconsistent, the optimization process has not converged. Return the reconstructed model to S1 for high-precision nonlinear simulation analysis until the optimization process converges, completing the design of the hollow fan blade cavity structure.

[0019] The beneficial effect of the above scheme is: through the above technical scheme, taking into account the bird strike position and movement process during the bird strike impact, the impact force equivalence is used to convert the nonlinear impact problem into static topology optimization, thereby realizing the improvement of bird strike resistance performance during the fan blade design stage.

[0020] Furthermore, the multi-condition topology optimization design in S4 introduces the maximum size control and reinforcement feature control methods, including the following formulas:

[0021]

[0022] Among them, f(x) is the objective function of structural flexibility, is the weight of the blade response at time t of the j-th impact condition, is the stiffness matrix, x i is the density of the fan blade finite element model element, f * (x i ) is the density function of the fan blade finite element model element, is the displacement field of the fan blade at time t for the j-th impact condition, and the superscript T is the transpose of the matrix;

[0023]

[0024] Where i is the finite element model unit number, l is the number of finite element model unit numbers, v is the volume of each unit in the finite element model, V frac is the volume fraction of the blade, v0 is the initial volume of each unit in the finite element model;

[0025]

[0026] in, is the magnitude of the impact force on the fan blade at time t in the j-th impact condition;

[0027]

[0028] Among them, Ω r (y) is the yth maximum size control area, Ω is the maximum size control area variable, is any symbol, ∈ is a symbol;

[0029] 0 <x min ≤x i ≤1

[0030] Among them, x min is the minimum value of the unit density of the fan blade finite element model.

[0031] The beneficial effect of the above further solution is: through the above technical solution, the fan blades are subjected to multi-working condition topology optimization, and maximum size control is introduced to obtain a rib-shaped cavity layout and prevent material accumulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a cavity structure diagram of a hollow fan blade considering bird strike resistance.

[0033] Among them: 1. Skin; 2. Internal reinforcement ribs; 3. Blade tip; 4. Blade leading edge; 5. Blade trailing edge; 6. Blade root; 7. Tenon; 8. Main reinforcement; 9. Secondary reinforcement.

[0034] Figure 2 The figure is a flow chart of a design method for a hollow fan blade cavity structure considering bird strike resistance. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1, as Figure 1 As shown, a hollow fan blade cavity structure considering bird strike resistance performance is shown, the blade cavity structure includes a skin 1, internal reinforcing ribs 2, a blade tip 3, a blade leading edge 4, a blade trailing edge 5, a blade root 6 and a tenon 7, the internal reinforcing ribs 2 include main ribs 8 and secondary ribs 9, the blade cavity structure is a rotating structure with the rotating shaft as the center, the skin 1 is laid on the surface of the structure, the two main ribs 8 are arranged in the middle of the internal reinforcing ribs 2, and at the same time connect the blade tip 3 and the blade root 6, the secondary ribs 9 are distributed inside the internal reinforcing ribs 2, and at the same time connect the main ribs 8, the blade leading edge 4, the blade trailing edge 5, the blade tip 3 and the blade root 6, the blade leading edge 4 is the front area of ​​the blade rotation direction, the blade trailing edge 5 is the rear area of ​​the blade rotation direction, the blade tip 3 is the area of ​​the blade away from the rotating shaft, the blade root 6 is the area of ​​the blade close to the rotating shaft, and is connected to the tenon 7.

[0037] The main ribs 8 and secondary ribs 9 are unevenly distributed. The ribs at the leading edge 4 of the blade are thicker than those at the trailing edge 5 of the blade. The connection between the blade root 6 and the tenon 7 is locally reinforced through grid design and material filling.

[0038] Example 2, as Figure 2As shown, a design method for a hollow fan blade cavity structure considering bird strike resistance performance includes the following steps:

[0039] S1: Perform high-precision nonlinear simulation analysis on the bird impact process of fan blades, selecting different bird impact positions as impact points for bird impact simulation;

[0040] S2: The time history curve of the impact force during the impact process is obtained based on the bird strike simulation, showing the impact force on the fan blades at any time;

[0041] S3: Based on the bird's motion position on the blade and the blade's response, for n conditions of bird impact at different blade heights, the impact force at m typical moments is selected as the external load through the time history curve of the impact force;

[0042] S4: With the goal of minimizing strain energy, the blade volume as a constraint, and the impact force external load at m typical moments as the load, a multi-condition topology optimization design of the fan blade is performed;

[0043] S5: Delete the low-density units of the fan blade finite element model, retain the high-density units, reconstruct the fan blade model, and determine whether the reconstructed model after topology optimization is consistent with the configuration of the bird strike simulation in S1. If the blade configuration is consistent, the optimization process has converged and the optimization design is ended. If the blade configuration is inconsistent, the optimization process has not converged. Return the reconstructed model to S1 for high-precision nonlinear simulation analysis until the optimization process converges, completing the design of the hollow fan blade cavity structure.

[0044] The multi-condition topology optimization design in S4 introduces the maximum size control and reinforcement feature control methods, including the following formulas:

[0045]

[0046] Among them, f(x) is the objective function of structural flexibility, is the weight of the blade response at time t of the j-th impact condition, is the stiffness matrix, x i is the density of the fan blade finite element model element, f * (x i ) is the density function of the fan blade finite element model element, is the displacement field of the fan blade at time t for the j-th impact condition, and the superscript T is the transpose of the matrix;

[0047]

[0048] Where i is the finite element model unit number, l is the number of finite element model unit numbers, v is the volume of each unit in the finite element model, V fracis the volume fraction of the blade, v0 is the initial volume of each unit in the finite element model;

[0049]

[0050] in, is the magnitude of the impact force on the fan blade at time t in the j-th impact condition;

[0051]

[0052] Among them, Ω r (y) is the yth maximum size control area, Ω is the maximum size control area variable, is any symbol, ∈ is a symbol;

[0053] 0 <x min ≤x i ≤1

[0054] Among them, x min is the minimum value of the unit density of the fan blade finite element model.

[0055] In one embodiment of the present invention, a high-precision nonlinear simulation analysis is performed on the process of a bird striking a fan blade, wherein, in order to fully consider the dangerous working conditions faced by the blade during actual operation, different bird strike positions are selected as impact points for bird strike simulation; after the impact dynamics calculation is completed, a time history curve of the impact force during the impact process can be obtained, which shows the magnitude of the impact force on the fan blade at any time; according to the movement position of the bird on the blade and the response of the blade, for n working conditions of bird strikes with different blade heights, the impact force at m typical moments is selected as the external load; with the goal of minimizing strain energy and the blade volume as a constraint, multiple impact Using force as the load, the fan blades underwent multi-condition topology optimization. During the optimization process, a maximum size control was introduced to achieve a ribbed cavity layout and prevent material accumulation. After topology optimization was completed, the low-density elements of the finite element model were deleted, while the high-density elements were retained. The fan blades were remodeled to determine whether the optimized configuration was consistent with the configuration simulated in the bird strike in S1. If the blade configuration was inconsistent, the optimization process was considered unconverged and the updated configuration was returned to step S1 for multi-condition nonlinear dynamic analysis. If the blade configuration was consistent, the optimization was considered converged, and the final configuration was obtained, ending the optimization process. After optimization, the hollow ratio of the hollow fan blades reached 43%.

[0056] The present invention adopts a multi-condition optimization design method to fully consider various bird strike conditions and comprehensively improve the bird strike resistance of hollow fan blades; the impact force information at different moments during the bird strike process is selected as the external load, and the hollow configuration can be adjusted according to the changes in the bird's movement position and energy during the bird strike process; the dynamic process is simplified into multiple static optimization processes, greatly improving the feasibility and efficiency of the optimization calculation.

[0057] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the invention.

Claims

1. A design method for a hollow fan blade cavity structure considering bird strike resistance, based on the hollow fan blade cavity structure considering bird strike resistance, wherein the hollow fan blade cavity structure considering bird strike resistance comprises a skin (1), internal reinforcing ribs (2), a blade tip (3), a blade leading edge (4), a blade trailing edge (5), a blade root (6) and a tenon (7), wherein the internal reinforcing ribs (2) comprise a main rib (8) and a secondary rib (9), and the blade cavity structure is a rotating structure with a rotating shaft as the center. The skin (1) is laid on the surface of the structure, and two of the The main rib (8) is arranged in the middle of the internal reinforcing rib (2) and connects the blade tip (3) and the blade root (6). The secondary rib (9) is distributed inside the internal reinforcing rib (2) and connects the main rib (8), the leading edge (4) of the blade, the trailing edge (5) of the blade, the blade tip (3) and the blade root (6). The leading edge (4) of the blade is the front area in the direction of rotation of the blade, the trailing edge (5) of the blade is the rear area in the direction of rotation of the blade, the blade tip (3) is the area of ​​the blade away from the rotation axis, and the blade root (6) is the area of ​​the blade close to the rotation axis and is connected to the tenon (7). The main reinforcement (8) and the secondary reinforcement (9) are unevenly distributed; The ribs at the leading edge (4) of the blade are thicker than the ribs at the trailing edge (5) of the blade; The connection portion between the blade root (6) and the tenon (7) is locally reinforced by grid design and material filling; It is characterized by: The design method of the hollow fan blade cavity structure comprises the following steps: S1: Perform high-precision nonlinear simulation analysis on the bird impact process of fan blades, selecting different bird impact positions as impact points for bird impact simulation; S2: The time history curve of the impact force during the impact process is obtained based on the bird strike simulation, showing the impact force on the fan blades at any time; S3: Based on the bird's motion position on the blade and the blade's response, for n conditions of bird impact at different blade heights, the impact force at m typical moments is selected as the external load through the time history curve of the impact force; S4: With the goal of minimizing strain energy, the blade volume as a constraint, and the impact force external load at m typical moments as the load, a multi-condition topology optimization design of the fan blade is performed; S5: Delete the low-density units of the fan blade finite element model, retain the high-density units, reconstruct the fan blade model, and determine whether the reconstructed model after topology optimization is consistent with the configuration of the bird strike simulation in S1. If the blade configuration is consistent, the optimization process has converged and the optimization design is ended. If the blade configuration is inconsistent, the optimization process has not converged. Return the reconstructed model to S1 for high-precision nonlinear simulation analysis until the optimization process converges, completing the design of the hollow fan blade cavity structure.

2. The method for designing a hollow fan blade cavity structure considering bird strike resistance according to claim 1, characterized in that: The multi-condition topology optimization design in S4 introduces the maximum size control and reinforcement feature control methods, including the following formulas: in, is the objective function of structural flexibility, For the Impact conditions The weight of the blade response at the moment, is the stiffness matrix, is the density of the fan blade finite element model element, is the density function of the fan blade finite element model element, For fan blade Impact conditions Time displacement field, superscript is the transpose of the matrix; in, is the finite element model element number, is the number of finite element model elements, is the volume of each unit in the finite element model, is the volume fraction of the blade, is the initial volume of each element in the finite element model; in, For fan blade Impact conditions The magnitude of the impact force at any moment; in, For the A maximum size control area, is the maximum size control region variable, is any symbol, To belong to the symbol; in, is the minimum value of the unit density of the fan blade finite element model.

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