Aircraft landing gear noise reduction device and method with miniature metal wire wound on surface

Abstract

The invention relates to the field of aviation noise control, and provides an aircraft landing gear noise reduction device and method based on micro metal wire spiral winding. The device part comprises a metal wire and a metal wire fixing buckle, the metal wire is fixed through the metal wire fixing buckle, and meanwhile the size and material parameters of the metal wire are designed in a targeted mode. In the method part, the designed metal wire is wound on a cylindrical bluff body part, possibly generating vortex shedding and vortex-fixing interference, on the nose gear in a spiral winding manner, and the two ends and the axial interval position of the metal wire are fixed through the metal wire fixing buckles, so that the metal wire is ensured to be fastened. Therefore, through the wound metal wires, single-frequency noise in the over-top direction caused by falling of a towing rod vortex can be effectively eliminated, broadband noise is reduced, and the noise control capability of an airplane is improved. The method is suitable for various civil aircraft types, and has the advantages of being simple in structure, remarkable in noise reduction effect, high in practicability, high in adaptability and the like.

Description

Technical Field

[0001] This invention relates to the field of aviation noise control, and more specifically, to an aircraft landing gear noise reduction device and method based on micro-wire surface winding. Background Technology

[0002] With the rapid development of the civil aviation industry, aircraft noise has received increasing attention. Landing gear, as one of the main sources of noise in modern large passenger aircraft, has a significant impact on airworthiness certification and market competitiveness due to its noise reduction technology. Currently, various landing gear noise reduction methods exist, including optimizing the landing gear shape, adding baffles, and using passive or active noise control technologies. However, these methods still have limitations in terms of noise reduction effectiveness, adaptability, and economy. For example, while streamlined design can reduce some aerodynamic noise, it limits the structural strength and stability of the landing gear; ordinary fairing designs, although altering airflow patterns, easily affect the functions of the landing gear's telescopic mechanism and introduce significant aerodynamic drag and additional weight, resulting in low economic efficiency; active noise control technology is costly and structurally complex, making large-scale application difficult. Therefore, researching an efficient, lightweight, highly adaptable landing gear noise reduction technology that does not affect the original functions of the landing gear is of great significance. Summary of the Invention

[0003] To address the problems in the prior art, this invention provides a novel landing gear noise reduction device and method based on micro-wire surface winding, which can eliminate single-frequency noise and reduce broadband noise caused by vortex shedding of blunt body components without changing the landing gear's own configuration or affecting its structural function.

[0004] This invention discloses a noise reduction device for aircraft landing gear with micro-wires wound on its surface. The device comprises metal wires and fixing clips for securing the wires. The method includes three parts: selecting the wire winding position, winding the wires, and securing the wires.

[0005] The metal wire is positioned on a cylindrical blunt component on the nose landing gear where vortex shedding and vortex-structure interference may occur.

[0006] The metal wire is wound in a spiral manner, and there is no gap between the metal wire and the cylindrical blunt body component.

[0007] The metal wire is fixed by fixing both ends of the metal wire with fasteners, and by fixing it at intervals of 5 times the pitch along the axial direction of the cylindrical blunt body component.

[0008] By breaking down large eddy structures in the flow field with metal wires, large eddies are broken down into smaller eddies, promoting the transition from laminar to turbulent flow, reducing eddy shedding noise generated when airflow passes around blunt components such as landing gear trailing bars, and converting noise from low frequency to high frequency.

[0009] The advantages of this invention are:

[0010] 1. The present invention relates to an aircraft landing gear noise reduction device with micro-metal wires wound on the surface. The device is designed with micro-metal wires and wire fixing buckles. The method involves winding the micro-metal wires in a spiral manner onto a cylindrical blunt part on the front landing gear, thereby effectively reducing aerodynamic noise.

[0011] 2. The aircraft landing gear noise reduction method using micro-wires wound around its surface, as described in this invention, employs a simple hardware structure. The noise reduction method is highly feasible and adaptable, and does not affect the landing gear's structure or function. Compared to adding additional fairings or altering the shape of landing gear components, directly winding micro-wires does not affect the landing gear's retraction and extension functions. Furthermore, the selected wire material has a low density, providing a large coverage area while maintaining extremely low mass. This improves noise reduction while having minimal impact on the aircraft's overall weight, aerodynamic performance, and fuel economy. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the metal wire and metal fixing buckle structure in the aircraft landing gear noise reduction device with micro-metal wire wound on the surface of the present invention.

[0013] Figure 2 This is a block diagram illustrating the noise reduction method for aircraft landing gear with micro-metal wires wound on the surface according to the present invention;

[0014] Figure 3 This is a schematic diagram of the wire end fixing method in the aircraft landing gear noise reduction method of the present invention, which involves winding micro-metal wires on the surface of the metal wires.

[0015] Figure 4 This is a schematic diagram of the actual nose landing gear structure of the B737-400;

[0016] Figure 5 A schematic diagram of the spirally wound metal wire for the tow bar of the B737-400's front landing gear.

[0017] Figure 6 This image shows the noise reduction effect after metal wire is wrapped around the tow bar of the B737-400's front landing gear. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings.

[0019] The present invention relates to a noise reduction device and method for aircraft landing gear with micro-metal wires wound on the surface. Based on the noise reduction principle of microstructure on the surface of blunt body parts, the device mainly reduces the noise intensity during the take-off and landing of aircraft landing gear by winding micro-metal wires on the cylindrical blunt body parts in the existing nose landing gear and relying on the spiral structure of the micro-metal wires to disrupt the flow field of the blunt body parts.

[0020] In the present invention, a noise reduction device and method for aircraft landing gear with micro-wires wound on the surface, the device includes a metal wire 1 and a metal wire fixing clip 2, such as... Figure 1 As shown.

[0021] The metal wire 1 is a micro-metal wire. The cross-sectional diameter D of the metal wire 1 is a key parameter. If it is too thick, it will increase the weight or affect the airflow. If it is too thin, the strength will not be sufficient. Therefore, in this invention, the cross-sectional diameter D of the metal wire 1 must meet the following requirements: 0.5mm≤D≤1.2mm.

[0022] The material for wire 1 needs to be selected based on compatibility, taking into account the environment in which the landing gear components are located (e.g., high humidity in the ocean, electromagnetic interference, weight reduction requirements). Specifically:

[0023] (1) Austenitic stainless steel: grade 304 / 316L; tensile strength ≥500 MPa; temperature range: -200°C~800°C; suitable for highly corrosive environments in marine / high humidity areas.

[0024] (2) Titanium alloy (Ti-6Al-4V): density 4.43 g / cm³; elastic modulus 110 GPa; excellent fatigue resistance, suitable for aviation scenarios with high weight reduction requirements and fatigue resistance.

[0025] (3) Aluminum alloy (7075-T6): density 2.81 g / cm³; conductivity 30% IACS; tensile strength ≥570MPa; suitable for lightweight low-speed landing gear design.

[0026] (4) Copper-nickel alloy (Monel 400): Excellent resistance to salt spray corrosion; strength 550-750 MPa; resistivity 48 μΩ·cm; suitable for high conductivity requirements, such as electromagnetic shielding composite noise reduction and other scenarios.

[0027] The surface of metal wire 1 is coated with a high-temperature resistant primer (temperature resistance ≥300°C) to prevent electrochemical corrosion between the metal wire and the substrate. At the same time, a diamond-like carbon coating is also applied to the outer layer of the primer of metal wire 1, with a roughness Ra≤1.6 μm. A larger roughness will cause additional noise.

[0028] After the dimensions and materials of wire 1 are designed, material verification is required. The tensile strength of wire 1 is confirmed to be ≥500 MPa by tensile test (ASTM E8 standard), and its fatigue life (>10^7 cycles) is verified by vibration table test.

[0029] The wire fastener 2 is used to fix the wire 1 after it has been wound. The wire fastener 2 has a U-shaped structure, with a U-shaped groove for the wire 1 to pass through; the width of the U-shaped groove is equal to the diameter D of the wire 1 plus 0.1 mm. The wire fastener 2 has outward-curved fixing surfaces at both ends. These outward-curved fixing surfaces are arc-shaped and are designed to match the outer wall surface of the component to which the wire 1 is wound, ensuring a tight fit between the outward-curved fixing surfaces and the outer wall surface of the component to which the wire 1 is wound.

[0030] By spirally winding and fixing the aforementioned metal wire 1 onto a specific component of the nose landing gear according to the aircraft landing gear noise reduction method of micro-metal wire surface winding proposed in this invention, the noise intensity during the take-off and landing of the aircraft landing gear can be effectively reduced.

[0031] The present invention relates to a method for noise reduction of aircraft landing gear by winding micro-metal wires on the surface, specifically comprising three parts: selecting the winding position of the metal wire 1, the winding method of the metal wire 1, and the fixing method of the metal wire 1. Figure 2 As shown, specifically:

[0032] A. Selection of the winding position of metal wire 1.

[0033] The metal wire 1 is wound on cylindrical blunt body components on the nose landing gear. This includes not only typical cylindrical blunt body structures such as the nose landing gear trailing bar, but also parts of the nose landing gear such as the torque link and main strut that may cause vortex shedding and vortex-structure interference.

[0034] B. Method for winding metal wire 1.

[0035] Metal wire 1 is spirally wound onto the cylindrical blunt part, aiming to cover the entire cylindrical blunt part as much as possible. The spiral winding pitch parameter is 10-100 times the diameter D of the metal wire. If the pitch is too small, it will cause flow blockage; if it is too large, it will lose its effect on controlling airflow and vortex. The specific pitch parameter needs to be optimized in conjunction with CFD. Based on the CFD (Computational Fluid Dynamics) simulation results, the diameter-to-pitch ratio (D / P) of metal wire 1 is adjusted. For example, for a towing rod (diameter of about 20mm), a metal wire with D=1mm and pitch P=10mm (D / P=1:10) is selected.

[0036] C. Fixing method

[0037] Prefabricate wire fixing clips 2 according to the shape of the cylindrical blunt body component, so that the two sides of the wire fixing clips can fit tightly against the outer wall of the cylindrical blunt body component. After the wire 1 is wound, tighten both ends of the wire 1 to ensure that there is no gap between the wire 1 and the surface of the cylindrical blunt body component; then install the wire fixing clips 2 at both ends of the wire 1 to fix both ends of the wire 1, and install one wire fixing clip 2 every 5 times the thread pitch along the axial direction of the cylindrical blunt body component (e.g., 200 mm intervals if the thread pitch is 40 mm) to further fix the wire 1.

[0038] When fixing both ends of the metal wire 1, place the metal wire 1 into the U-shaped groove of the metal wire fixing clip 2, and then fix the metal wire clip 2. Simultaneously, the end of the metal wire 1 has a 5mm portion extending out of the metal wire fixing clip 2. This portion can be further bent 180° and welded to the outer wall of the U-shaped portion of the metal wire fixing clip 2 to further ensure the tension of the metal wire 1. Figure 3 As shown.

[0039] By using the aforementioned device and method, metal wires are wound around the parts of the nose landing gear that may generate vortex shedding and vortex-structure interference, which can destroy the large vortex structure in the flow field, breaking the large vortices into small vortices, promoting the transition from laminar to turbulent flow, reducing the vortex shedding noise generated when the airflow passes around blunt parts such as the landing gear trailing bar, and converting the noise from low frequency to high frequency. Since the high-frequency sound emitted by the small vortices is easily absorbed by the environment, the device has a significant suppression effect on both single-frequency noise and broadband noise. Experiments show that the noise can be reduced by 8-15 dB at the single-frequency noise location that varies with wind speed in the direction of landing gear overhead, the pure tone noise peak completely disappears, and the mid-to-high frequency broadband noise above 1000 Hz is also reduced to a certain extent.

[0040] Based on the final noise reduction results, wind tunnel tests can be used to optimize parameters and dynamically adjust adaptability to further improve noise reduction performance, making it both effective in noise reduction and lightweight. Specifically, if wind tunnel tests show insufficient noise reduction in local areas (such as the trailing edge of the main support), the winding density in that area can be increased (the pitch can be reduced by 20%).

[0041] For scenarios with high requirements for high-frequency noise suppression, "double helix winding" can also be used. This involves winding a metal wire with the same structural parameters, material, and winding parameters on the basis of the original threaded metal wire, with the two metal wires spaced apart by half a pitch, thereby further breaking up the vortex structure.

[0042] Example:

[0043] Applying the apparatus and method of this invention to the nose landing gear of a B737-400, the structural diagram of which is shown below. Figure 4 As shown, metal wire 1 is wrapped around the tow bar 3 of the front landing gear of this model for noise reduction. Figure 5 As shown, specifically:

[0044] Step 1: Select 304 stainless steel wire with a diameter of 0.8mm or aluminum alloy wire with a diameter of 1mm, suitable for the aerospace environment. The surface of wire 1 is coated with an electroplated zinc-nickel alloy (usually containing 12%-15% nickel), a coating commonly used in aerospace steel components.

[0045] Step Two: Based on the spiral winding method of the prefabricated metal wire 1 in the tow bar 3 structure, with a pitch P designed to be 4cm and a spiral structure whose diameter varies with the outer diameter of the blunt body component, the metal wire 1 is spirally wound onto the tow bar 3 to ensure its stability and durability under high-intensity airflow. When winding the metal wire 1, first, the starting end of the metal wire is passed through the first metal wire fixing clip 2 and pre-tightened with an M3 hexagonal screw. The end of the metal wire 1 is then bent 180 degrees and welded to the metal wire fixing clip 2. Subsequently, the metal wire 1 is wound with a constant tension (20-30N) at a 30° spiral angle, ensuring uniform spacing between each turn (pitch tolerance ±1mm). Each time the winding reaches the installation position of the metal wire fixing clip 2, the metal wire 1 is pressed into the U-shaped groove of the metal wire fixing clip 2 and secured with screws to prevent loosening under airflow impact. Finally, the end of the micro-metal wire at the last clip is bent 180 degrees and welded to the metal wire fixing clip 2, completing the winding and fixing of the metal wire 1. Finally, check the tightness of the entire wire winding and verify the consistency of the pitch (error <2%) using a non-contact laser rangefinder.

[0046] Step 3: Verify the noise reduction effect through wind tunnel testing. Following well-known standard testing methods in the field of aeroacoustic wind tunnel testing, conduct aeroacoustic wind tunnel measurement tests on the basic configuration and noise reduction configuration of the B737-400 nose landing gear model to obtain overall noise data, noise spectrum characteristics, sound source spatial directivity, and other aeroacoustic characteristics of the current model. Furthermore, measure and analyze noise data under different flight conditions to evaluate the effectiveness of the micro-wire spiral winding noise reduction method with different variables.

[0047] Step 4: Compare the reduction in single-frequency peak value and broadband noise after the basic configuration and the winding of metal wire, such as... Figure 6 As shown, the broadband noise is reduced by about 2dB in the 100-400Hz range, and the single-frequency peak at 232Hz caused by the shedding of the tow bar 3 vortex is reduced by about 10dB. It can be seen that the present invention can effectively reduce landing gear noise while maintaining the integrity of the landing gear structure and the normal operation of its functions, providing reliable technical support for the airworthiness certification of aircraft and the improvement of market competitiveness.

Claims

1. A method for noise reduction of aircraft landing gear with micro-wires wound on its surface, characterized in that: It includes three parts: selecting the location for wire winding, winding the wire, and fixing the wire. The metal wire is positioned on a cylindrical blunt body component on the nose landing gear where vortex shedding and vortex-structure interference may occur. The metal wire is wound in a spiral manner, and there is no gap between the metal wire and the cylindrical blunt body component; The metal wire is fixed by fixing both ends of the metal wire with fasteners, and by fixing it at intervals of 5 times the pitch along the axial direction of the cylindrical blunt body component. By breaking down large eddy structures in the flow field with metal wires, large eddies are broken down into smaller eddies, promoting the transition from laminar to turbulent flow, reducing eddy shedding noise generated when airflow passes around blunt components such as landing gear trailing bars, and converting noise from low frequency to high frequency.

2. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: The diameter D of the metal wire cross-section satisfies: 0.5mm≤D≤1.2mm.

3. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: The material of the metal wire needs to be selected based on the environment in which the landing gear components are located. Specifically: (1) Austenitic stainless steel: grade 304 / 316L; tensile strength ≥500 MPa; temperature range: -200°C~800°C; suitable for highly corrosive environments in marine / high humidity areas; (2) Titanium alloy (Ti-6Al-4V): density 4.43 g / cm³; elastic modulus 110 GPa; excellent fatigue resistance, suitable for aerospace scenarios with high weight reduction requirements and fatigue resistance; (3) Aluminum alloy (7075-T6): density 2.81 g / cm³; conductivity 30% IACS; tensile strength ≥570 MPa; suitable for lightweight low-speed landing gear design; (4) Copper-nickel alloy (Monel 400): Excellent resistance to salt spray corrosion; strength 550-750 MPa; resistivity 48 μΩ·cm; suitable for high conductivity requirements, such as electromagnetic shielding composite noise reduction and other scenarios.

4. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: The surface of the metal wire is coated with a high-temperature resistant primer; at the same time, a diamond-like coating is also applied to the outer layer of the metal wire primer, with a roughness Ra≤1.6 μm.

5. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: The metal wire needs to undergo material verification. The tensile strength of the metal wire must be confirmed to be ≥500 MPa through tensile testing, and its fatigue life must be verified to be >10^7 cycles through vibration table testing.

6. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: The metal wire is fixed by a metal wire fixing buckle; the metal wire fixing buckle is U-shaped, and the U-shaped groove is used to pass through the metal wire; the width of the U-shaped groove is equal to the diameter D of the metal wire 1 + 0.1mm; the two ends of the metal wire fixing part have outward fixing surfaces, which are arc surfaces, and are designed to match the outer wall surface of the component to which the metal wire is wrapped, so as to ensure that the outward fixing surfaces fit tightly with the outer wall surface of the component to which the metal wire is wrapped.

7. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: The pitch parameter of the spiral winding of the metal wire is 10-100 times the diameter D of the metal wire. The specific ratio of the metal wire diameter to the pitch is adjusted according to the CFD simulation results.

8. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: When the two ends of the metal wire are fixed, a 5mm portion of the metal wire is located outside the fixing component. After bending the metal wire outside the fixing component by 180°, it is fixed to the fixing component.

9. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: Parameter optimization and dynamic adjustment of adaptability are carried out through wind tunnel testing to further optimize noise reduction performance. Specifically, if wind tunnel testing shows that noise reduction is insufficient in a local area, the winding density in that area is increased.

10. The method for noise reduction of aircraft landing gear with micro-wires wound on the surface as described in claim 1, characterized in that: For scenarios with high requirements for high-frequency noise suppression, a double-helix winding method is adopted. On the basis of the original threaded winding metal wire, a metal wire with the same structural parameters, material and winding parameters is wound, and the two metal wires are separated by half a pitch, thereby further breaking up the vortex structure.

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