Noise reduction structure, power propulsion system and noise reduction method

Abstract

This invention relates to a noise reduction structure, a propulsion system, and a noise reduction method. The propulsion system includes a first wall and a second wall, with a radial space between the first and second walls forming an airflow channel. The noise reduction structure includes multiple noise reduction units, each including: a groove formed on at least one surface of the first or second wall, recessed from the surface; this surface provides the wall of the airflow channel; and a porous medium layer covering at least the entire contour of the groove.

Description

Technical Field

[0001] This invention relates to a noise reduction structure, a power propulsion system, and a noise reduction method. Background Technology

[0002] Propulsion systems, such as those commonly used in civil aircraft engines, exert noise radiation on airports during takeoff and landing. This is constrained by the stringent requirements of the International Civil Aviation Organization (ICAO). The latest airworthiness noise regulations require new civil aircraft to adopt the more stringent Stage 5 noise airworthiness standards, which further reduce the cumulative noise margin by 7 dB compared to Stage 4. Low-noise design that balances aerodynamic efficiency and lightweight design is becoming increasingly important in the design phase of next-generation aircraft engine products.

[0003] Aircraft engines are the primary source of noise in aircraft. To achieve superior thrust performance, modern aircraft engines have increasingly larger bypass ratios, leading to larger fan sizes. Due to their large size and high rotational speed, fan noise dominates the overall engine noise. Therefore, reducing fan noise is crucial in aircraft noise reduction design.

[0004] To address these issues, existing solutions typically involve covering the inner walls of the air intake and bypass duct with acoustic liners. The working principle of these liners is to absorb and dissipate sound waves along their propagation path, thereby reducing noise. Currently, perforated honeycomb acoustic liners are widely used in commercial aircraft engines. These liners mainly consist of a perforated panel, a honeycomb core, and a rigid backplate, and can be viewed as an arrangement of numerous Helmholtz resonant cavities. The size of the resonant cavity determines its resonant frequency; therefore, sound waves of a specific frequency entering the honeycomb core through the small holes in the panel will resonate, converting sound energy into heat energy, thus achieving noise reduction.

[0005] However, due to the need for weight reduction, modern civil turbofan engine designs are trending towards increased bypass ratios and shorter nacelle lengths. This results in shorter spacing between adjacent blade rows within the duct, further limiting the available space for acoustic liner coverage. Since the sound absorption performance of the acoustic liner is positively correlated with its coverage area, existing acoustic liner covering methods struggle to meet both the engine's weight reduction requirements and increasingly stringent noise compliance standards. Meanwhile, traditional honeycomb perforated panel acoustic liners, employing frequency resonance, are effective at reducing single-tone noise. However, fan noise includes both single-tone and broadband noise, exhibiting multi-target characteristics, and traditional honeycomb perforated panel acoustic liner configurations perform poorly in suppressing multi-frequency noise.

[0006] In summary, there is a need in this field for a noise reduction method and a noise reduction mechanism that can achieve more efficient broadband noise reduction under the conditions of limited space and weight. Summary of the Invention

[0007] One object of the present invention is to provide a noise reduction structure.

[0008] Another object of the present invention is to provide a power propulsion system.

[0009] Another object of the present invention is to provide a noise reduction method.

[0010] According to a first aspect of the present invention, a noise reduction structure is used in a propulsion system, wherein the propulsion system includes: a first wall and a second wall, the radial space between the first wall and the second wall forming an airflow channel of the propulsion system, the noise reduction structure includes a plurality of noise reduction units, each of the noise reduction units including: a groove formed on at least one surface of the first wall and the second wall, recessed from the surface; the surface provides the wall of the airflow channel; and a porous medium layer covering at least the entire contour of the groove.

[0011] In one or more embodiments of the noise reduction structure, the noise reduction unit is distributed axially to include the upstream and / or downstream of the rotor blade corresponding to the airflow channel; and a plurality of the noise reduction units are distributed circumferentially.

[0012] In one or more embodiments of the noise reduction structure, the outline of the groove includes an arc shape, a square shape, a trapezoidal shape, and a star shape.

[0013] In one or more embodiments of the noise reduction structure, the porous dielectric layer is made of a metallic material, including metal foam and metal mesh.

[0014] In one or more embodiments of the noise reduction structure, the porous dielectric layer also covers the wall between adjacent noise reduction units.

[0015] According to a second aspect of the present invention, a power propulsion system includes a noise reduction structure as described in the first aspect.

[0016] In one or more embodiments of the propulsion system, the propulsion system includes a turbofan engine, and the noise reduction structure is disposed on the inner surface of the fan casing, the inner wall of the inlet nacelle, the outer bypass duct outlet wall, and / or the fan hub surface of the turbofan engine.

[0017] In one or more embodiments of the power propulsion system, the noise reduction unit and the first and / or second wall surface on which it is located are integrally formed.

[0018] According to a third aspect of the present invention, a noise reduction method is provided, wherein the propulsion system includes: a first wall and a second wall, the radial space between the first wall and the second wall constituting an airflow channel for the propulsion system, and the noise reduction method includes:

[0019] A noise reduction structure is directly disposed on the surface of the first wall and / or the second wall. The noise reduction structure includes a plurality of noise reduction units. Each noise reduction unit includes: a groove formed on the surface of at least one of the first wall and the second wall, recessed from the surface; the surface provides the wall surface of the airflow channel; and a porous medium layer that at least covers the surface of the contour line of the groove.

[0020] In one or more embodiments of the noise reduction method, the noise reduction structure is set to be located upstream and / or downstream of the rotor blade corresponding to the airflow channel in the axial distribution range; and a plurality of noise reduction units are distributed in the circumferential direction such that the noise reduction units are offset from the axial region corresponding to the rotor blade.

[0021] In one or more embodiments of the noise reduction method, the noise reduction unit is configured to directly contact the airflow of the airflow channel as a wall surface, and a soundless lining is provided on the surface of the first wall and the second wall.

[0022] In one or more embodiments of the noise reduction method, different noise reduction units are constructed at different axial positions, including a first noise reduction unit and a second noise reduction unit. The acoustic impedance value, groove shape, size and / or number of axially distributed grooves of the porous dielectric layer of the first noise reduction unit and the second noise reduction unit are different.

[0023] The beneficial effects of this invention include, but are not limited to, that compared to noise reduction solutions that involve placing sound liners on the engine wall, the noise reduction structure and method employed in this invention not only achieve noise reduction but also meet the requirement of weight reduction, and further improve the noise reduction effect. The principle is that, compared to the flat wall configuration formed by placing sound liners, the groove structure significantly increases the contact area between the sound-absorbing material and the sound field, thereby achieving greater sound energy dissipation. Simultaneously, sound waves undergo irregular scattering within the groove, and each scattering increases the number of contacts with the sound-absorbing material. Furthermore, due to the porous dielectric material covering the surface of the groove, micro-scale cavities of different sizes exist within the material, which can dissipate sound waves of different frequencies, thus possessing broadband sound absorption characteristics compared to current sound liner solutions. Attached Figure Description

[0024] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0025] Figure 1 This is a schematic diagram of existing noise reduction solutions for gas turbine engines.

[0026] Figure 2 This is a schematic diagram of the structure of a propulsion system from an external perspective, according to one embodiment.

[0027] Figure 3 This is a cross-sectional view of a propulsion system according to an embodiment.

[0028] Figures 4A to 4D These are schematic diagrams of the noise reduction units in the noise reduction structures of the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment, respectively.

[0029] Figure 5A , Figure 5B , Figure 5C The sound pressure cloud maps are calculated based on the sound propagation numerical values ​​of the wall surface without noise reduction, the wall surface with sound lining, and the noise reduction structure of the first embodiment, respectively.

[0030] Partial reference numerals in the attached figures:

[0031] 100-Power Propulsion System

[0032] 101-First Wall

[0033] 102-Second wall

[0034] 1000-Airflow Channel

[0035] 1003 - Fan casing inner surface

[0036] 1004 - Intake nacelle inner wall

[0037] 1005 - Outer duct outlet wall

[0038] 1006-Fan Hub Surface

[0039] 10000-Acoustic Liner

[0040] 10-Noise Reduction Structure

[0041] 1001-Noise Reduction Unit

[0042] 1-groove

[0043] 2-Porous media layer. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0045] Furthermore, this application uses specific terms to describe embodiments of the application, such as "an embodiment," "one embodiment," and / or "some embodiments," which refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0046] The noise reduction structure and method described in the following embodiments are applied to gas turbine engines, specifically turbofan engines, but are not limited thereto. They are applicable to any propulsion system, including those with fans, blades, or propfans, and are not limited to gas turbine engines. For example, they can be hybrid propulsion systems including gas turbine engines, or pure electric propulsion systems with fans, blades, or propfans. As long as the goal is to reduce fan noise and / or compressor intake noise, the noise reduction structure described in this case can be applied.

[0047] Existing solutions such as Figure 1 As shown, the fan of the gas turbine engine includes fan rotor blades 18 and fan stator blades 20. Acoustic liners 10000 can be provided on the inner wall 1004 of the intake nacelle and the inner surface 1003 of the fan casing to absorb and attenuate the sound energy of single-tone noise, while widening the sound absorption frequency band as much as possible to take into account the wide frequency range.

[0048] However, the inventors discovered that using acoustic liner components for noise reduction was detrimental to engine weight reduction, and the wideband noise reduction performance of the acoustic liner components was also insufficient.

[0049] Based on the above, the inventors have developed a novel noise reduction structure, a power propulsion system, and a noise reduction method. Compared to noise reduction solutions that involve placing sound liners on the engine wall, the noise reduction structure and method employed in this invention simultaneously meet the requirements for weight reduction while achieving better noise reduction, and further enhance the noise reduction effect. The principle lies in the fact that, compared to the flat wall configuration formed by using sound liners, the groove structure significantly increases the contact area between the sound-absorbing material and the sound field, thereby achieving greater sound energy dissipation. Simultaneously, sound waves undergo irregular scattering within the grooves, with each scattering increasing the number of contacts with the sound-absorbing material. Furthermore, due to the porous dielectric material covering the surface of the grooves, micro-cavities of different scales exist within the material, which can dissipate sound waves of different frequencies, thus possessing broadband sound absorption characteristics compared to current sound liner solutions.

[0050] refer to Figure 2 as well as Figure 3As shown, in some embodiments, the turbofan engine may include an intake duct 15, a noise reduction structure 10, a fan hub 17, fan rotor blades 18, a nacelle 19, fan stator blades 20, low-pressure compressor blades 21, high-pressure compressor blades 22, turbine blades 23, an exhaust pipe 24, and an outer bypass duct 25. The noise reduction structure 10 may be provided on the inner surface 1003 of the fan casing, the inner wall 1004 of the intake duct nacelle, the outlet wall 1005 of the outer bypass duct, and / or the surface 1006 of the fan hub to reduce fan-induced noise.

[0051] refer to Figure 2 , Figure 3 as well as Figures 4A to 4D As shown, the noise reduction structure 10 includes a plurality of noise reduction units 1001, each noise reduction unit 1001 including: a groove 1 and a porous medium layer 2. The groove 1 is formed on the surface of at least one of the first wall surface 101 and the second wall surface 102, and is recessed from the surface; the surface provides the wall surface of the airflow channel 1000; the porous medium layer 2 covers at least the surface of the contour line of the groove 1.

[0052] In the propulsion system, the radial space between the first wall 101 and the second wall 102 constitutes the specific structure of the airflow channel 1000 of the propulsion system. For example, the air intake channel is formed by the inner wall 1004 of the air intake nacelle and the fan hub surface 1006. For example, the outer bypass is formed by the inner surface 1003 of the fan casing and the outer bypass outlet wall 1005, but this is not a limitation.

[0053] The surface meaning of the outline of groove 1 here is as follows: Figures 4A to 4D As shown, taking the cross-section of groove 1 as an example, the porous dielectric layer 2 at least covers all the recessed portions of groove 1, such as... Figure 4A The first embodiment shown depicts the outline of the cross-section of the arc 11, with the porous dielectric layer 2 covering the entire arc, as shown. Figure 4B In the second embodiment shown, the outline of the square cross-section 12 is shown, and the porous dielectric layer 2 covers the groove walls and bottom. Figure 4C In the third embodiment shown, the outline of the trapezoidal cross-section 13, the porous dielectric layer 2 covers the groove walls and the bottom of the groove, as shown. Figure 4D In the fourth embodiment shown, the outline of the cross-section of the star 14 is covered by a porous medium layer 2, which includes the protruding portion of the star.

[0054] The porous dielectric material of the porous dielectric layer 2 is generally a metal material, which makes it easy to set in the groove. The porous dielectric layer of the metal material can be in the form of foamed metal, metal mesh, etc. Foamed metal is in the form of foamed aluminum, foamed copper, foamed nickel, foamed alloy, etc. Metal mesh, as the name suggests, is a mesh-like metal film. It can be understood that the porous dielectric material can also be other porous dielectric materials with broadband sound absorption properties. Preferably, in some embodiments, in addition to being set on the surface of the entire outline of the groove 1, the porous dielectric layer 2 can also cover the space between the grooves, that is, the wall surface between adjacent noise reduction units 1001, that is, cover the wall surface of the first wall or the second wall itself.

[0055] The noise reduction unit 1001 is disposed on the first wall surface 101 and / or the second wall surface 102. The noise reduction unit 1001 and the first wall surface 101 and / or the second wall surface 102 are integrally formed parts, and the specific process can be to obtain them integrally by additive manufacturing. This can further simplify the process. For turbofan engines, such as for the manufacturing of the fan casing, it saves the step of setting the sound liner on the inner surface 1003 of the fan casing after the fan casing is completed.

[0056] Continue to refer to Figure 2 as well as Figure 3 As shown, the noise reduction unit 1001 is distributed axially within the upstream and / or downstream region of the rotor blade 1002 corresponding to the airflow channel 1000. The noise reduction unit 1001 is staggered from the axial region corresponding to the blade tip of the rotor blade 1002. This arrangement prevents the interaction between the groove structure and the blade tip from altering the distribution of unsteady forces on the blade surface, which could lead to increased noise. Furthermore, multiple noise reduction units 1001 are evenly distributed circumferentially within a certain axial range. It can be understood that the arrangement of multiple noise reduction units 1001 can be regular or irregular. Sound propagation calculations can be used to equate the porous medium to an impedance soft boundary, and the design can be iteratively optimized to obtain a design scheme with maximum transmission loss. The optimization objective is to maximize the transmission loss of the fan's conductable acoustic modes. The optimized parameters are the impedance value of the porous material applied to the groove wall and the groove gap wall, the shape of the groove, the size of the groove, and the distribution of the groove. Based on the obtained optimal impedance value and the impedance model, the parameters of the porous material are obtained, thereby achieving the design of the sound-absorbing wall.

[0057] The noise reduction structure 10 in the above embodiments has a weight reduction effect and better broadband sound absorption characteristics compared to the acoustic liner solution. Specifically, as shown... Figures 5A to 5CAs shown, a circular pipe of uniform diameter is used to simulate the sound propagation process of fan noise in the air intake. The pipe diameter is 1m, the acoustic impedance boundary length is 1.1m, and its distance from the pipe inlet and outlet is 0.1m. The pipe inlet is the sound source surface, and the sound source incident mode is (5, 1). The pipe outlet is a non-reflective boundary. The background flow is a uniform average flow with a flow velocity of 170m / s, and the flow direction is towards the sound source surface. An impedance boundary is applied at the pipe wall to simulate the sound absorption characteristics of porous media materials, using three configuration examples:

[0058] In Example 1, the admittance of the impedance boundary is 0, which means it is a smooth wall, such as the inner surface 1003 of an existing fan casing.

[0059] The admittance value of the impedance boundary in Example 2 is 0.0012+0.0012j, and the surface has no grooves, which is to characterize the traditional flat noise reduction wall, that is, for example, the structure in the existing scheme where the acoustic liner 10000 is set on the inner surface 1003 of the fan casing.

[0060] The admittance value of the impedance boundary in Example 3 is the same as that in Example 2, but the surface has a circular groove, i.e. Figure 4A The groove structure shown in the first embodiment is used to simplify the characterization of the noise-reducing wall configuration of the present invention.

[0061] Based on the finite element Helmholtz method, sound propagation was calculated for the example. The sound pressure contour plot results are shown in Figure 4. It can be observed that the impedance wall can dissipate sound energy. Furthermore, the sound field of the grooved noise-reducing wall design is significantly different from that of the flat noise-reducing wall design. The calculated transmission losses for the three configurations are 0dB, 14dB, and 16dB, respectively. Therefore, the grooved noise-reducing wall of this invention has excellent noise reduction effect, and the noise reduction amount is greater than that of the traditional flat wall configuration.

[0062] In summary, the beneficial effects of the above embodiments include, but are not limited to, the noise reduction structure and method adopted in this case, compared with the noise reduction scheme of setting sound liners on the engine wall, meet the requirements of weight reduction while achieving noise reduction effect. Furthermore, due to the porous medium material covering the surface of the groove, there are micro-scale cavities of different sizes inside the material, which can dissipate sound waves of different frequencies, thus possessing broadband sound absorption characteristics compared with the current sound liner solution.

[0063] As described above, this application also provides a noise reduction method for a propulsion system. The propulsion system 100 includes a first wall 101 and a second wall 102, and the radial space between the first wall 101 and the second wall 102 constitutes an airflow channel 1000 of the propulsion system. The noise reduction method includes:

[0064] A noise reduction structure 10 is directly disposed on the surface of the first wall 101 and / or the second wall 102. The noise reduction structure 10 includes a plurality of noise reduction units 1001. Each noise reduction unit 1001 includes: a groove 1, which is formed on the surface of at least one of the first wall 101 and the second wall 102 and is recessed from the surface; the surface provides the wall surface of the airflow channel 1000; and a porous medium layer 2, which at least covers the surface of the contour line of the groove 1.

[0065] Preferably, in some embodiments, the noise reduction structure 10 is axially distributed upstream and / or downstream of the rotor blade 1002 corresponding to the airflow channel 1000; multiple noise reduction units 1001 are distributed circumferentially, such that the noise reduction units 1001 are staggered from the axial regions corresponding to the rotor blade 1002. This is to avoid the risk of increased noise due to the interaction between the groove and the rotor blade tip.

[0066] Preferably, in some embodiments, the noise reduction unit 1001 is configured to directly contact the airflow of the airflow channel as the wall surface of the airflow channel 1000. The surface of the first wall 101 and the second wall 102 is provided with a sound-free liner. It can be understood that the noise reduction effect of the noise reduction structure 10 is better than that of the sound liner. Therefore, the sound-free liner will not affect the noise reduction effect and also realizes the weight reduction of the engine.

[0067] Preferably, in some embodiments, as described above, noise reduction in different frequency bands can be achieved by changing the structure of the grooves and the impedance of the porous dielectric layer. For example, noise reduction units with different sound barriers can be set in regions with different axial lengths, i.e., different noise reduction units 1001 can be structured at different axial positions, including a first noise reduction unit and a second noise reduction unit. The acoustic impedance value of the porous dielectric layer 2, the shape and size of the grooves 1, and / or the number of grooves distributed axially are different between the first noise reduction unit and the second noise reduction unit. The first noise reduction unit and the second noise reduction unit are only used to indicate the structural differences between the noise reduction units and are not limited to two different noise reduction units.

[0068] In summary, the beneficial effects of the noise reduction structure, propulsion system, and noise reduction method described in the above embodiments include, but are not limited to, the fact that, compared to noise reduction schemes that involve placing sound liners on the engine wall, the noise reduction structure and method used in this application not only achieve noise reduction but also meet the requirement of weight reduction and further improve the noise reduction effect. The principle is that, compared to the flat wall configuration formed by placing sound liners, the groove structure significantly increases the contact area between the sound-absorbing material and the sound field, thereby achieving greater sound energy dissipation. Simultaneously, sound waves undergo irregular scattering within the groove, and each scattering increases the number of contacts with the sound-absorbing material. Furthermore, due to the porous dielectric material covering the surface of the groove, micro-cavities of different scales exist within the material, which can dissipate sound waves of different frequencies, thus possessing broadband sound absorption characteristics compared to current sound liner solutions.

[0069] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A noise reducing structure (10) for a power propulsion system (100), wherein The propulsion system (100) includes: a first wall (101) and a second wall (102), the radial space between the first wall (101) and the second wall (102) forming the airflow channel (1000) of the propulsion system, characterized in that the noise reduction structure (10) includes a plurality of noise reduction units (1001), each of the noise reduction units (1001) including: A groove (1) is formed on at least one of the first wall surface (101) and the second wall surface (102), and is recessed from the surface; the surface provides the wall of the airflow channel (1000); and a porous medium layer (2) covers at least the entire outline of the groove (1) surface, wherein the porous medium layer (2) is made of a metallic material, including metal foam and metal mesh.

2. The noise reducing structure (10) of claim 1, wherein The noise reduction unit (1001) is distributed in the axial direction, including the upstream and / or downstream of the rotor blade (18) corresponding to the airflow channel (1000); and a plurality of the noise reduction units (1001) are distributed in the circumferential direction.

3. The noise reducing structure (10) of claim 1, wherein, The outline of the groove (1) includes arc, square, trapezoidal and star shapes.

4. The noise reducing structure (10) of claim 1, wherein, The porous medium layer (2) also covers the wall between adjacent noise reduction units (1001).

5. A power propulsion system (100), characterized by, Includes the noise reduction structure (10) as described in any one of claims 1-4.

6. The power propulsion system (100) of claim 5, characterized in that, The power propulsion system includes a turbofan engine, and the noise reduction structure (10) is disposed on the inner surface (1003) of the fan casing, the inner wall of the air intake nacelle (1004), the outer bypass outlet wall (1005), and / or the fan hub surface (1006) of the turbofan engine.

7. The power propulsion system (100) of claim 5, wherein, The noise reduction unit (1001) is integrally formed with the first wall surface (101) and / or the second wall surface (102) on which it is located.

8. A method for noise reduction for a power propulsion system (100), wherein The propulsion system (100) includes: a first wall (101) and a second wall (102), the radial space between the first wall (101) and the second wall (102) forming the airflow channel (1000) of the propulsion system, characterized in that the noise reduction method includes: A noise reduction structure (10) is directly disposed on the surface of the first wall (101) and / or the second wall (102). The noise reduction structure (10) includes a plurality of noise reduction units (1001). Each noise reduction unit (1001) includes: a groove (1) formed on the surface of at least one of the first wall (101) and the second wall (102) and recessed from the surface; the surface provides the wall of the airflow channel (1000); and a porous medium layer (2) that at least covers the surface of the contour line of the groove (1).

9. The noise reduction method of claim 8, wherein, The noise reduction structure (10) is set in the axial distribution range upstream and / or downstream of the rotor blade (18) corresponding to the airflow channel (1000); a plurality of noise reduction units (1001) are distributed in the circumferential direction, such that the noise reduction unit (1001) is offset from the axial region corresponding to the rotor blade (18).

10. The noise reduction method of claim 8, wherein, The noise reduction unit (1001) is configured to directly contact the airflow of the airflow channel (1000) as the wall surface, and a soundless lining is provided on the surface of the first wall (101) and the second wall (102).

11. The noise reduction method of claim 8, wherein, The noise reduction units (1001) are structured in different axial positions, including a first noise reduction unit and a second noise reduction unit. The acoustic impedance value, the shape and size of the grooves (1) and / or the number of axially distributed grooves of the porous medium layer (2) of the first noise reduction unit and the second noise reduction unit are different.

Images