Low-noise mounting device and noise reduction structural design method thereof

Abstract

The application provides a low-noise mounting device and a noise reduction structure design method thereof, and relates to the technical field of aviation noise control. The low-noise mounting device noise reduction structure design method comprises the following steps: obtaining unsteady pressure fluctuation data of a calculation model surface; wherein the calculation model has the main structure characteristics of the low-noise mounting device; obtaining the maximum unsteady pressure fluctuation amplitude position of the calculation model surface according to the unsteady pressure fluctuation data, and expanding and dividing multiple acoustic processing areas from the maximum position as the center; calculating each acoustic processing area to obtain the corresponding target frequency; and selecting an acoustic impedance matching structure according to the target frequency, so that the acoustic structure with specific frequency characteristics can be designed for different acoustic processing areas, thereby realizing the precise control of the mounting device on multi-frequency noise, and further helping to achieve the ideal noise reduction effect on the body mounting effect noise, especially the mounting effect noise of the open rotor engine.

Description

Technical Field

[0001] This invention relates to the field of aviation noise control technology, and more specifically, to a low-noise installation device and its noise reduction structure design method. Background Technology

[0002] Airframe mounting effect noise is an important topic in aero-engine noise research, specifically referring to the additional noise generated by the engine's position, mounting method, and interaction with surrounding airflow when mounted on an aircraft fuselage (such as a wing or fuselage). As a revolutionary ultra-high bypass ratio propulsion system, the open rotary engine exhibits significantly different noise characteristics compared to traditional turbofan engines. These differences are mainly reflected in the following aspects: First, the open rotary engine employs a rotor-plus-rotor or rotor-plus-stator design, resulting in strong unsteady aerodynamic interference between the leading and trailing blades, leading to unique discrete frequency noise; second, due to the lack of a casing structure in traditional engines, its noise radiation exhibits omnidirectional characteristics, resulting in a more complex noise spectrum distribution; third, the aerodynamic coupling effect between the engine and its mounting structure is more significant, easily generating additional broadband noise.

[0003] Studies have shown that the installation effect noise of open rotor engines can be 3-5 dB higher than that of conventional engines. This is mainly due to: 1) the direct impact of the propfan wake on the mounting structure; 2) the disturbance of the incoming flow by the mounting structure leading to rotor inflow distortion; and 3) the secondary interference between the wake of the mounting structure and the rotor blades. These factors not only increase the overall noise level but may also induce specific tonal noise components. Currently, research on the control of installation effect noise in open rotor engines is still relatively limited. Traditional engine noise control generally employs methods such as laying porous sound-absorbing materials with a single structure, like acoustic liner, on the mounting structure. The basic unit resonant cavity structure is as follows: Figure 1 As shown, the quantitative relationship between its geometric dimensions and resonant frequency is described by the following formula.

[0004]

[0005] In the formula, c is the speed of sound, S is the cross-sectional area of ​​the neck, l is the length of the neck, d is the diameter of the neck, and V is the volume of the cavity.

[0006] However, this method has significant technical limitations: on the one hand, porous materials typically only have a significant noise suppression effect on specific frequency bands, with lower noise reduction efficiency in other frequency ranges; on the other hand, the complex aerodynamic interference between the open rotor blades and the mounting structure generates broadband noise, the spectral characteristics of which vary significantly with the relative position of the mounting structure wall in space; furthermore, indiscriminately covering a single structure with sound-absorbing material results in material waste and no noise reduction benefit. Therefore, it is currently difficult to achieve ideal noise reduction results. Summary of the Invention

[0007] The purpose of this invention is to provide a noise reduction structure design method for a low-noise installation device, which can improve the technical problem in the prior art that it is difficult to achieve ideal noise reduction effect for the installation effect noise of the machine body, especially the installation effect noise of the open rotor engine.

[0008] The present invention also aims to provide a low-noise mounting device that can improve the technical problem in the prior art that it is difficult to achieve ideal noise reduction for the mounting effect noise of the machine body, especially the mounting effect noise of the open rotor engine.

[0009] The embodiments of the present invention can be implemented in the following ways:

[0010] A method for designing a noise reduction structure for a low-noise installation device, the method comprising:

[0011] Obtain unsteady pressure pulsation data on the surface of the computational model; wherein, the computational model has the main structural features of a low-noise installation device;

[0012] Based on the unsteady pressure pulsation data, the maximum unsteady pressure pulsation amplitude on the surface of the calculation model is obtained, and multiple acoustic processing areas are divided outward from the maximum value as the center.

[0013] The target frequency is calculated for each acoustic processing region.

[0014] An acoustic impedance matching structure is selected based on the target frequency to achieve the noise reduction structure design of the low-noise installation device.

[0015] Optionally, the step of acquiring unsteady pressure pulsation data on the surface of the computational model includes:

[0016] The computational fluid dynamics method is used to perform unsteady flow numerical simulation on the computational model, and the unsteady pressure pulsation data on the surface of the computational model are extracted from the calculation results.

[0017] Optionally, the step of dividing the acoustic processing area outward from the maximum point includes:

[0018] Centered on the maximum point, multiple acoustic processing regions are divided by extending along the flow direction, span direction, or spiral direction.

[0019] Optionally, the step of calculating the corresponding target frequency for each acoustic processing region includes:

[0020] The acoustic power is calculated based on the unsteady surface force of the acoustically processed area.

[0021] The sound power calculation results are processed to obtain the noise energy distribution;

[0022] Select the target frequency from the noise energy distribution.

[0023] Optionally, the selected target frequency is the dominant frequency of the single-tone noise or the peak frequency of the broadband noise in the noise energy distribution.

[0024] Optionally, the step of calculating the acoustic power based on the surface unsteady forces of the acoustically treated area includes:

[0025] The sound power is calculated using the FW-H calculation method, and the integral formula of the FW-H calculation method is as follows:

[0026]

[0027] in, For fluid density; The time derivative of the normal velocity; The distance from the source point to the observation point; This represents the radial component of the Mach number; This is the time derivative of the load in the radial direction; This represents the radial component of the load. dS is the normal component of the load; dS is the unit integral area; S is the integral surface area.

[0028] Optionally, the steps of processing the sound power calculation results to obtain the noise energy distribution include:

[0029] The noise energy distribution is obtained by performing a Discrete Fourier Transform on the sound power calculation results; the Discrete Fourier Transform formula is as follows:

[0030]

[0031] in, For the first in the frequency domain Complex values ​​of each frequency component; is the value of the nth sampling point in the time domain; N is the number of sampling points.

[0032] Optionally, the acoustic impedance matching structure includes a Helmholtz resonant cavity, a porous sound-absorbing structure, and an acoustic metamaterial structure; and / or,

[0033] The acoustic impedance matching structure is formed by: micro-perforation of the wall surface, installation of composite perforated plates, or installation of a combination structure of porous material and steel wire mesh.

[0034] A low-noise installation device includes a main structure and a noise reduction structure. The noise reduction structure is disposed on the surface of the main structure and is obtained according to the noise reduction structure design method of the low-noise installation device described above.

[0035] Optionally, the surface of the main structure on which the noise reduction structure is provided includes at least one of the body surface, the windward side of the suspension, and the side of the suspension.

[0036] The beneficial effects of the low-noise installation device and its noise reduction structure design method provided by the embodiments of the present invention include:

[0037] The embodiments of the present invention provide a noise reduction structure design method for a low-noise installation device. This method involves defining an acoustic treatment area centered on the location of the maximum amplitude of unsteady pressure pulsation, and matching a corresponding acoustic impedance matching structure to the target frequency of the acoustic treatment area. This allows for the design of acoustic structures with specific frequency characteristics for different acoustic treatment areas, thereby achieving precise control of multi-frequency noise in the installation device. This, in turn, helps to achieve ideal noise reduction for installation-effect noise, especially for open rotor engines.

[0038] Embodiments of the present invention also provide a low-noise installation device, which provides a noise reduction structure on the surface of the main structure. The noise reduction structure is designed according to the above-described design method. Therefore, it also has the ability to design acoustic structures with specific frequency characteristics for different acoustic treatment areas, thereby achieving precise control of multi-frequency noise by the installation device. This helps to achieve the beneficial effect of ideal noise reduction for the installation effect noise of the machine body, especially the installation effect noise of the open rotor engine. Attached Figure Description

[0039] The above-described features and advantages of the present invention will be better understood after reading the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related properties or features may have the same or similar reference numerals.

[0040] Figure 1 A schematic diagram of the basic unit resonant cavity structure in the prior art is shown;

[0041] Figure 2 A schematic diagram of the main structure of a low-noise installation device according to one aspect of the present invention is shown;

[0042] Figure 3 A step diagram of a noise reduction structure design method for a low-noise installation device according to one aspect of the present invention is shown.

[0043] Figure 4A schematic diagram of a structure for dividing an acoustic processing region along the span direction is shown according to one aspect of the present invention.

[0044] Figure 5 A schematic diagram of a structure for dividing an acoustic processing region along the flow direction is shown according to one aspect of the present invention.

[0045] Figure 6 A schematic diagram of a structure for dividing an acoustic processing region along a spiral direction, according to one aspect of the present invention, is shown.

[0046] Figure label:

[0047] 100 - Low-noise mounting device; 110 - Main structure; 111 - Wing; 112 - Suspension; 113 - Engine; 121 - Acoustic treatment area. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0049] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," "outer," or "vertical" appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use, and does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0050] At the same time, it should be noted that the terms "first" and "second" are used only for distinguishing descriptions and should not be interpreted as indicating or implying relative importance.

[0051] In the description of this invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an integral connection, or a detachable connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components, etc. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0052] The following definitions apply to terms that may appear in the description of this invention:

[0053] Acoustic liner: A sound-absorbing structure, typically a combination of a perforated panel, a honeycomb cavity, and a back panel;

[0054] Installation effect: The impact of an aircraft engine on the aerodynamic performance of the aircraft and engine due to its location, installation method, and interaction with the surrounding airflow when the engine is installed on the aircraft body (such as the wing or fuselage).

[0055] Open rotor engine: combines the high efficiency of turbofan engine with the economy of propeller engine. Its characteristic is that the unenclosed rotor is directly exposed to the air.

[0056] Figure 2 This is a schematic diagram of the main structure 110 in the low-noise installation device 100 provided in this embodiment. Figure 3 This diagram illustrates the steps of the noise reduction structure design method for the low-noise installation device provided in this embodiment. Please refer to the attached diagram. Figure 2 and Figure 3 This embodiment provides a low-noise installation device 100, which includes a main structure 110 and a noise reduction structure disposed on the surface of the main structure 110. This embodiment also provides a design method for the noise reduction structure of the low-noise installation device (hereinafter referred to as the design method). The noise reduction structure of the low-noise installation device 100 can be set according to the design method.

[0057] In this embodiment, the main structure 110 of the low-noise mounting device 100 includes a fuselage, a sling 112, and an engine 113. The surface on which the noise reduction structure is set may include at least one of the fuselage surface, the windward surface A1 of the sling 112, and the side surface A2 of the sling 112. The fuselage surface may be the windward surface A3 of the wing 111. It is understood that in some other embodiments, the noise reduction structure may also be set on other surfaces of the fuselage (e.g., parts of the fuselage surface) as needed.

[0058] In this embodiment, the noise reduction structure design method for the low-noise installation device specifically includes the following steps:

[0059] S01: Obtain unsteady pressure pulsation data on the surface of the computational model.

[0060] In this embodiment, the calculation model is based on the low-noise installation device.

[0061] A three-dimensional model constructed from the main structure of 100 and features of 110.

[0062] Specifically, step S01 includes: simulating unsteady flow data on the computational model using computational fluid dynamics (CFD) methods, and extracting unsteady pressure pulsation data from the surface of the computational model from the calculation results, thereby designing the subsequent noise reduction structure based on the unsteady pressure pulsation data. The process of simulating unsteady flow data on the computational model using computational fluid dynamics (CFD) methods can be completed using commercial CFD software or other self-developed programs; no specific restrictions are imposed here.

[0063] When using computational fluid dynamics (CFD) methods to simulate unsteady flow data in a computational model, boundary conditions need to be set. During boundary condition setting, the operating conditions involved in the low-noise design can be obtained in advance, allowing for the definition of the boundary of the unsteady flow field computational domain based on the acquired data. The acquired operating conditions can include multiple conditions. Boundary conditions can be set comprehensively based on these multiple conditions, or different boundary conditions can be set separately for different operating conditions. When subsequently selecting the acoustic impedance matching structure, the calculation results obtained from the boundary conditions corresponding to multiple operating conditions are comprehensively considered, ensuring that the final noise reduction structure design can meet the noise reduction requirements under multiple operating conditions.

[0064] Furthermore, before executing step S01, there is also a step of constructing a computational model. Specifically, when constructing the computational model, it is first necessary to obtain the geometric data of the main structure 110 and the geometric parameters of the connection between the engine 113 and the body. Then, the three-dimensional geometric model is meshed to obtain a full-ring computational mesh suitable for unsteady flow simulation and acoustic analysis. Mesh division includes, but is not limited to, structured mesh, unstructured mesh and hybrid mesh strategies.

[0065] S02: Based on the unsteady pressure pulsation data, obtain the maximum unsteady pressure pulsation amplitude on the surface of the calculation model, and divide multiple acoustic processing areas 121 outward from the maximum value as the center.

[0066] Based on the unsteady pressure pulsation data obtained in step S01, the location of the maximum unsteady pressure pulsation amplitude on the surface of the calculation model is obtained, and multiple acoustic processing regions 121 are divided outward from the region where this maximum value is located. Specifically, during the division, the expansion can be carried out along the flow direction, spanwise direction, or spiral direction to divide multiple acoustic processing regions 121, such as... Figure 4 A structural diagram showing the division of acoustic processing region 121 along the spanwise direction is shown, as follows: Figure 5 A structural diagram showing the division of acoustic treatment region 121 along the flow direction is shown, as follows: Figure 5A structural diagram showing the division of the acoustic processing region 121 along a spiral direction is shown. It is understood that in other embodiments, the acoustic processing region 121 can also be specifically divided according to specific needs. Furthermore, the specific number of acoustic processing regions 121 obtained can also be set according to requirements. For example, it can be divided based on unsteady pressure pulsation data, dividing the region within the range where the unsteady pressure pulsation data reaches a threshold value. This threshold can be set to a constant value, or it can be set to a certain proportion of the location where the unsteady pressure pulsation amplitude is maximum.

[0067] S03: Calculate for each acoustic processing region 121 and obtain the corresponding target frequency.

[0068] The steps for calculating the corresponding target frequency for each acoustic processing region 121 include:

[0069] S31: Calculate the acoustic power based on the surface unsteady force of the acoustic processing region 121.

[0070] Alternatively, the sound power can be calculated using the FW-H (Fowcs Williams-Hawkings) method, whose integral formula is as follows:

[0071]

[0072] in For fluid density; The time derivative of the normal velocity; The distance from the source point to the observation point; This represents the radial component of the Mach number; This is the time derivative of the load in the radial direction; This represents the radial component of the load. dS is the normal component of the load; dS is the unit integral area; S is the integral surface area.

[0073] S32: Process the sound power calculation results to obtain the noise energy distribution.

[0074] The acoustic calculation results obtained in step S31 are subjected to a Discrete Fourier Transform (DFT) to obtain the noise energy distribution of each frequency band. Specifically, the DFT formula is as follows:

[0075]

[0076] in, For the first in the frequency domain Complex values ​​of each frequency component (including amplitude and phase). is the value of the nth sampling point in the time domain; N is the number of sampling points.

[0077] S33: Select the target frequency from the noise energy distribution.

[0078] The dominant frequency of single-tone noise or the peak frequency of broadband noise in the noise energy distribution spectrum is selected as the target frequency for noise reduction design. It is understood that in other embodiments, other characteristic frequencies in the noise energy distribution spectrum may also be selected as the target frequency.

[0079] S04: Select the acoustic impedance matching structure according to the target frequency.

[0080] After selecting the target frequency for each acoustic processing area 121 in step S03, a suitable acoustic impedance structure is selected according to the target frequency. The resulting noise reduction structure can meet the precise control of noise in multiple frequency bands, thereby achieving an ideal noise reduction effect for the installation effect noise of the machine body, especially the installation effect noise of the open rotor engine 113.

[0081] Specific forms of acoustic impedance structures include, but are not limited to, the use of Helmholtz resonators, porous sound-absorbing structures, and acoustic metamaterial structures. Furthermore, the methods for realizing acoustic impedance structures include, but are not limited to, micro-perforation of the wall surface, installation of composite perforated plates, or installation of porous material wire mesh composite structures.

[0082] The low-noise installation device 100 and its noise reduction structure design method provided in the embodiments of the present invention are based on high-precision numerical simulation methods. Under target operating conditions, the unsteady flow field of the open rotor engine 113 and its prototype installation device is calculated in the entire ring to accurately obtain the unsteady pressure distribution on the surface of the prototype engine 113 installation device. After dividing the acoustic treatment area according to the unsteady pressure pulsation, the Ffowcs Williams-Hawkings (FW-H) acoustic equation is solved. Combined with the acoustic solution method under solid wall boundary conditions and discrete Fourier transform technology, the spectral characteristics of the noise in each acoustic treatment area 121 are obtained. For the dominant noise frequency band of different acoustic treatment areas 121, acoustic materials with specific frequency characteristics are laid to achieve precise control of multi-condition and multi-frequency noise of the entire installation device.

[0083] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for designing a noise reduction structure for a low-noise installation device, characterized in that, The noise reduction structure design method for the low-noise installation device includes: Obtain unsteady pressure pulsation data on the surface of the computational model; wherein, the computational model has the main structural features of a low-noise installation device; Based on the unsteady pressure pulsation data, the maximum unsteady pressure pulsation amplitude on the surface of the calculation model is obtained, and multiple acoustic processing areas are divided outward from the maximum value as the center. The target frequency is calculated for each acoustic processing region. An acoustic impedance matching structure is selected based on the target frequency to achieve the noise reduction structure design of the low-noise installation device; The steps for calculating the corresponding target frequency for each acoustic processing region include: The acoustic power is calculated based on the unsteady surface force of the acoustically processed area. The sound power calculation results are processed to obtain the noise energy distribution; Select the target frequency from the noise energy distribution; The steps for calculating acoustic power based on the unsteady surface forces in the acoustically treated area include: The sound power is calculated using the FW-H calculation method, and the integral formula of the FW-H calculation method is as follows: in, For fluid density; The time derivative of the normal velocity; The distance from the source point to the observation point; This represents the radial component of the Mach number; This is the time derivative of the load in the radial direction; This represents the radial component of the load. dS is the normal component of the load; dS is the unit integral area; S is the integral surface area.

2. The noise reduction structure design method for the low-noise installation device according to claim 1, characterized in that, The step of obtaining unsteady pressure pulsation data on the surface of the computational model includes: The computational fluid dynamics method is used to perform unsteady flow numerical simulation on the computational model, and the unsteady pressure pulsation data on the surface of the computational model are extracted from the calculation results.

3. The noise reduction structure design method for the low-noise installation device according to claim 1, characterized in that, The step of dividing the acoustic processing area outward from the maximum point includes: Centered on the maximum point, multiple acoustic processing regions are divided by extending along the flow direction, span direction, or spiral direction.

4. The noise reduction structure design method for the low-noise installation device according to claim 1, characterized in that, The selected target frequency is the dominant frequency of the single-tone noise or the peak frequency of the broadband noise in the noise energy distribution.

5. The noise reduction structure design method for the low-noise installation device according to claim 1, characterized in that, The steps for processing the sound power calculation results to obtain the noise energy distribution include: The noise energy distribution is obtained by performing a Discrete Fourier Transform on the sound power calculation results; the Discrete Fourier Transform formula is as follows: in, For the first in the frequency domain Complex values ​​of each frequency component; is the value of the nth sampling point in the time domain; N is the number of sampling points.

6. The noise reduction structure design method for the low-noise installation device according to claim 1, characterized in that, The acoustic impedance matching structure includes a Helmholtz resonant cavity, a porous sound-absorbing structure, and an acoustic metamaterial structure. And / or, The acoustic impedance matching structure is formed by: micro-perforation of the wall surface, installation of composite perforated plates, or installation of a combination structure of porous material and steel wire mesh.

7. A low-noise installation device, characterized in that, The low-noise installation device includes a main structure and a noise reduction structure. The noise reduction structure is disposed on the surface of the main structure and is obtained according to the noise reduction structure design method of the low-noise installation device according to any one of claims 1-6.

8. The low-noise installation device according to claim 7, characterized in that, The surface of the main structure on which the noise reduction structure is provided includes at least one of the body surface, the windward side of the suspension, and the side of the suspension.

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