Acoustic measurement device for open fan wind tunnel test

Abstract

The invention relates to the technical field of wind tunnel acoustic measurement, in particular to an acoustic measurement device for an open fan wind tunnel test. The acoustic measurement device provided by the invention comprises an acoustic measurement rod which is used for installing a microphone array so as to acquire a noise signal in a wind tunnel test of an open fan and realize acoustic measurement of noise characteristics of the open fan; the supporting structure is used for supporting the acoustic measuring rod in an open fan wind tunnel flow field; the connecting assembly is used for connecting the acoustic measuring rod and the supporting structure; wherein the supporting structure adopts an integrated bionic airfoil design, has an airfoil section, and is used for reducing aerodynamic resistance and noise caused by the supporting structure in an open fan wind tunnel flow field. Through a low-interference pneumatic structure and a multi-dimensional interference suppression design, high-fidelity measurement of open fan noise in a high-speed wind tunnel environment is jointly realized, and the accuracy and reliability of noise test data are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wind tunnel acoustic measurement, in particular to an acoustic measurement device for open fan wind tunnel test. BACKGROUND

[0002] The open fan engine is an advanced aviation power device combining the high propulsion efficiency of the turboprop engine and the high flight speed advantage of the turbofan engine, and is one of the important development directions in the current aviation power field. At present, the open fan engines researched at home and abroad mainly adopt counter-rotating fan, separate fan and separate stator blade and paddle fan combination structure forms. However, the flow field of the open fan has strong complexity, making it difficult to accurately predict its aerodynamic and acoustic characteristics by engineering estimation and numerical simulation methods. Therefore, wind tunnel test is still the most direct and highly reliable research means for current open fan aerodynamic design and aerodynamic performance evaluation.

[0003] In the wind tunnel test, since the design cruising speed of the open fan engine is high (up to 0.78Ma), the noise characteristic research must be carried out in the high-speed wind tunnel environment. However, under such high-speed conditions, the traditional acoustic measurement device faces serious challenges: the measurement rod and its support structure existing in the flow channel itself will become an interference source. These structures are easy to cause significant flow field disturbance, periodic vortex shedding in the high-speed flow field, and produce unnecessary sound reflection and scattering. These interference noises introduced by the measurement device itself will seriously pollute the target sound signal, resulting in a significant decrease in the accuracy and reliability of the noise measurement results.

[0004] Therefore, in order to solve the above problems, it is urgent to develop a new type of acoustic measurement device to meet the urgent need for high-precision acoustic measurement of open fan engines in high-speed wind tunnel environment. SUMMARY

[0005] The purpose of the present application is to provide an acoustic measurement device for open fan wind tunnel test, which solves the problem of the decrease in the accuracy and reliability of open fan noise measurement data caused by the multi-source interference superposition of the traditional acoustic measurement device due to its own structure in the high-speed wind tunnel test of the open fan.

[0006] In order to achieve the above purpose, the present application provides an acoustic measurement device for open fan wind tunnel test, comprising an acoustic measurement rod, a support structure and a connecting assembly:

[0007] The acoustic measurement rod is used to install a microphone array to collect noise signals in the open fan wind tunnel test, and realize acoustic measurement of the noise characteristics of the open fan.

[0008] The support structure is connected with the acoustic measurement rod, and is used to support and place the acoustic measurement rod in the open fan wind tunnel flow field.

[0009] The connecting assembly is used to connect the acoustic measurement rod and the support structure.

[0010] The support structure adopts an integrated bionic airfoil design and has an airfoil cross section, which is used to reduce the aerodynamic resistance and noise caused by the support structure itself in the open fan wind tunnel flow field.

[0011] In some embodiments, the acoustic measurement rod is provided with a plurality of microphone mounting grooves.

[0012] The microphone mounting groove is a groove structure, which is used to replaceably mount microphone arrays of different models and different distribution forms.

[0013] In some embodiments, the distribution form of the microphone array includes any one of a linear array, a ring array or a three-dimensional array.

[0014] In some embodiments, the connecting assembly includes a flange connection structure.

[0015] The flange connection structure is used to realize the fixed connection of the acoustic measurement rod and the support structure, and the flange connection structure is equal in width to the acoustic measurement rod to avoid flow interference.

[0016] In some embodiments, the connecting assembly further includes a damping bushing.

[0017] The damping bushing is a ring sleeve structure, which is arranged between the flange connection structure and the acoustic measurement rod and is used to isolate vibration.

[0018] In some embodiments, the cross section of the support structure is a NACA series airfoil, a RAF series airfoil or a DVL series airfoil.

[0019] In some embodiments, the cross section of the support structure is a NACA0020 airfoil; the NACA0020 airfoil is a symmetrical airfoil, the maximum thickness is located at the center of the chord length, and the maximum thickness is 20% of the chord length.

[0020] In some embodiments, the surface of the acoustic measurement rod is provided with an acoustic absorption layer, which is used to suppress sound wave reflection.

[0021] In some embodiments, the acoustic absorption layer is a microporous structure metal material, which is used to reduce the reflection of the acoustic measurement rod on the target sound signal to reduce measurement error.

[0022] The surface of the microporous structure metal material is a micropore array formed by laser drilling, electrochemical etching or powder metallurgy sintering process, and the pore size of the micropore array is uniform, regularly distributed and perpendicular to the surface of the material.

[0023] In some embodiments, the microporous structure metal material has a pore size of no more than 0.5 mm and a cavity depth of no more than 20 mm.

[0024] The application provides an acoustic measurement device for open fan wind tunnel test, which realizes high-fidelity measurement of open fan noise in a high-speed wind tunnel environment through low-interference aerodynamic structure and multi-dimensional interference suppression design, and greatly improves the accuracy and reliability of noise test data. BRIEF DESCRIPTION OF DRAWINGS

[0025] The above and other features, properties, and advantages of the present application will become more apparent by referring to the following description in conjunction with the accompanying drawings, in which like reference numerals refer to like structures throughout the drawings, and in which:

[0026] Figure 1 A side view of the acoustic measurement device for open fan wind tunnel test according to an embodiment of the application is disclosed;

[0027] Figure 2 A schematic view of a support structure according to an embodiment of the application is disclosed;

[0028] Figure 3 A connection schematic view of a flange connection structure and an acoustic measurement rod when the wind tunnel wall is fixed according to an embodiment of the application is disclosed;

[0029] Figure 4 A connection schematic view of a flange connection structure and an acoustic measurement rod when the test device is fixed according to an embodiment of the application is disclosed;

[0030] Figure 5 A structural schematic view of an acoustic measurement rod according to an embodiment of the application is disclosed.

[0031] The meanings of the reference numerals in the drawings are as follows:

[0032] 1 acoustic measurement rod;

[0033] 2 flange connection structure;

[0034] 3 support structure;

[0035] 4 damping bushing;

[0036] 5 microphone mounting slot;

[0037] 6 microporous structure metal material. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0039] In the current open fan engine wind tunnel acoustic test, due to the high speed of the wind tunnel flow, the traditional acoustic measuring rod and its support structure are easy to cause flow field disturbance, periodic vortex shedding and unnecessary sound reflection and scattering in the high speed flow field, and these interference factors will significantly affect the accuracy and reliability of acoustic measurement. In order to accurately obtain the real noise characteristics of the open fan under high speed conditions, the present application proposes a new type of acoustic measuring device, which is based on the core idea of "low interference aerodynamic structure" and "multi-dimensional interference suppression design", has excellent aerodynamic shape and acoustic design, and can realize the coordinated suppression of interference from multiple dimensions such as flow field interference, structure vibration, sound reflection and measurement layout, so as to ensure the high fidelity of noise test data.

[0040] Figure 1 Disclosed is a side view of an acoustic measuring device for open fan wind tunnel test according to an embodiment of the present application, as shown in Figure 1 The acoustic measuring device for open fan wind tunnel test proposed by the present application comprises an acoustic measuring rod 1, a support structure 3 and a connecting assembly:

[0041] The acoustic measuring rod 1 is used to install a microphone array to collect noise signals in the open fan wind tunnel test, and realize acoustic measurement of the noise characteristics of the open fan;

[0042] The support structure 3 is connected with the acoustic measuring rod 1, and is used to support and place the acoustic measuring rod 1 in the open fan wind tunnel flow field;

[0043] The connecting assembly is used to connect the acoustic measuring rod 1 and the support structure 3;

[0044] The support structure 3 adopts an integrated bionic airfoil design and has an airfoil section, which is used to reduce the aerodynamic resistance and noise caused by the support structure itself in the open fan wind tunnel flow field.

[0045] The acoustic measuring device for open fan wind tunnel test proposed by the present application realizes the suppression of vortex generation and reduction of aerodynamic noise from the source through the integrated bionic airfoil design and airfoil section optimization of the support structure, thereby significantly weakening the interference of the acoustic measuring device itself on the open fan wind tunnel flow field and acoustic measurement.

[0046] The present application realizes high-fidelity noise measurement under high-speed flow field through the synergistic optimization of "low-interference aerodynamic structure" and "multi-dimensional interference suppression design", which is further illustrated by the following embodiments.

[0047] Figure 2 Disclosed is a schematic view of a support structure according to an embodiment of the present application, as shown in Figure 2To minimize the vortex shedding and aerodynamic noise of the support device itself, the support structure 3 adopts an integrated bionic airfoil design with an airfoil cross section to reduce the aerodynamic resistance and noise caused by the support structure itself in the wind tunnel flow field. This support structure is a key embodiment of low interference aerodynamic structure design, which reduces the aerodynamic noise introduced by the device itself from the source.

[0048] The integrated bionic airfoil design takes the wings of birds or insects in nature as the bionic prototype, and optimizes the aerodynamic performance by simulating the streamline characteristics of the biological airfoil when moving in the fluid. The core is that the support structure is integrally formed without splicing gaps, the shape is continuous and smooth, and it conforms to the laws of fluid dynamics, which can reduce the separation phenomenon of airflow and structure surface in high-speed flow field, and inhibit vortex generation from the source.

[0049] In a preferred embodiment, the airfoil cross section can be a NACA0020 airfoil, or other NACA series airfoils well known to those skilled in the art. In addition, the airfoil cross section can also adopt other airfoils that meet the low resistance and low noise aerodynamic requirements, such as but not limited to RAF series, DVL series and other low resistance airfoils commonly used in existing technologies. This low resistance aerodynamic shape can significantly reduce the aerodynamic resistance and flow interference caused by the support structure in high-speed flow field.

[0050] Among them, the NACA series airfoil is a standardized aerodynamic airfoil system in the prior art, with clear geometric parameter definition and detailed aerodynamic performance data, which is a classic reference scheme for low resistance and stable airfoil design in the field of aerospace. RAF series airfoil is another aerodynamic airfoil system in the prior art, which also has standardized geometric definition and aerodynamic data verified by actual measurement, and exhibits excellent low resistance and vortex shedding resistance performance in subsonic and transonic speed range; DVL series airfoil is another classic general airfoil in the prior art, which can effectively reduce aerodynamic noise and flow separation phenomenon in high-speed flow field through precise optimization of airfoil leading edge curvature and trailing edge contraction ratio, and adapt to the severe aerodynamic requirements of wind tunnel test. These verified classic airfoil systems can provide reliable aerodynamic shape basis for the low interference support structure of the present application.

[0051] The airfoil cross section refers to the cross section of the support structure along the direction perpendicular to the airflow, which has a typical aviation airfoil profile. Taking the preferred NACA0020 airfoil as an example, the cross section is a symmetrical airfoil with a smooth leading edge and a sharp trailing edge. The leading edge is blunt to disperse the impact force of the airflow, and the trailing edge is sharp to reduce the drag of the wake. The maximum thickness is located at the center of the chord length, and the maximum thickness is 20% of the chord length. This symmetrical airfoil can effectively reduce the resistance and minimize the flow interference in high-speed flow field, and is suitable for application scenarios that require low noise and high aerodynamic efficiency.

[0052] Figure 3Fig. 1 shows a schematic diagram of the connection between the flange connection structure and the acoustic measurement rod when the wind tunnel wall is fixed according to an embodiment of the present application. Figure 3 As shown in Fig. 1, when the measuring device is fixed to the inner wall of the wind tunnel, the connection assembly comprises a flange connection structure 2.

[0053] The flange connection structure 2 is used to achieve the fixed connection between the acoustic measurement rod 1 and the support structure 3.

[0054] The flange connection structure is a common mechanical connector, usually composed of a pair of disc-shaped structures (flanges) with bolt holes and fastening bolts, used to achieve the fixation, sealing and force transmission between two components.

[0055] In particular, the flange connection structure 2 is kept the same width as the acoustic measurement rod 1, thereby avoiding the generation of additional protruding structures and effectively preventing additional flow interference caused by the connection structure. This equal-width design is a refinement of the low-interference aerodynamic structure on the connection assembly, ensuring the continuity of the aerodynamic shape.

[0056] In this embodiment, the flange connection structure 2 is aerodynamically optimized, with a smooth transition and strict equal-width of the outer contour to the acoustic measurement rod, forming a streamlined whole without steps or protrusions, which fundamentally eliminates the flow separation and vortex shedding that may be caused by structural discontinuity.

[0057] Figure 4 Fig. 2 shows a schematic diagram of the connection between the flange connection structure and the acoustic measurement rod when the test vehicle is fixed according to an embodiment of the present application. Figure 4 As shown in Fig. 2, the connection assembly further comprises a damping bushing 4.

[0058] The damping bushing 4 is arranged between the flange connection structure 2 and the acoustic measurement rod 1, and is used to isolate vibration.

[0059] More specifically, when the test site conditions are limited and the measuring device needs to be fixed on the test vehicle base, in order to avoid the vibration generated by the test vehicle running being transmitted to the acoustic measurement rod 1 through the support structure, thereby affecting the measurement accuracy of the microphone, a damping bushing 4 is additionally arranged between the flange connection structure 2 and the acoustic measurement rod 1. The damping bushing 4 can effectively isolate and reduce the vibration interference from the test vehicle, ensuring the purity of the acoustic measurement data. The introduction of the damping bushing constitutes a suppression dimension for mechanical vibration interference in the multi-dimensional interference suppression design.

[0060] The damping bushing is an elastic element used for vibration reduction and isolation, usually in the form of a ring-shaped sleeve structure, composed of viscoelastic materials with high internal friction characteristics.

[0061] In the embodiment, the damping bushing 4 is press-fitted or bonded at the interface of the flange connection structure 2 and the acoustic measurement rod 1, the inner wall of which is tightly fitted with the outer surface of the acoustic measurement rod 1, and the outer wall is fitted with the mounting hole of the flange connection structure 2, and the inner part is usually provided with a plurality of composite damping layers (such as carbon fiber reinforced skeleton embedded in rubber matrix), forming a "sandwich" type vibration isolation layer.

[0062] The material of the damping bushing 4 is preferably a high-damping elastomer, such as nitrile rubber, silicone rubber or polyurethane composite material, which has excellent elastic recovery and energy dissipation capacity, can absorb vibration energy through its own deformation, block the transmission path of vibration from the flange structure to the measurement rod, and protect the acoustic measurement rod and the microphone array thereon from the interference of the foundation vibration.

[0063] Figure 5 The structural diagram of the acoustic measurement rod according to an embodiment of the present application is disclosed, as shown in Figure 5 As shown, the surface of the acoustic measurement rod 1 is coated with a sound absorption layer for suppressing sound wave reflection. The sound absorption layer is a core measure for sound wave reflection interference in multi-dimensional interference suppression design.

[0064] In the embodiment, the sound absorption layer is a microporous structure metal material 6, which is suitable for the harsh working conditions of high-speed wind tunnels and can avoid the problems of easy falling off and poor resistance to airflow scouring of traditional porous materials.

[0065] The microporous structure metal material is a high-efficiency broadband sound absorption material, which takes metal or alloy as the base material, forms a large number of micropores on the surface and inside the material through a specific precise uniform micropore processing process, and its basic working principle is that when the sound wave enters the micropores on the surface of the material, it causes air vibration in the pores and rubs with the pore wall, thereby converting the sound energy into heat energy and consuming it.

[0066] The porosity of the microporous structure metal material 6 is usually between 20%-80%, which has the structural strength of metal material and the sound absorption and noise reduction characteristics of porous material, and can provide a channel for sound energy dissipation while ensuring the mechanical stability of the sound absorption layer.

[0067] In the embodiment, the surface of the microporous structure metal material 6 is precisely and uniformly processed with micropores, which is used to reduce the reflection of the acoustic measurement rod to the target sound signal to reduce the measurement error.

[0068] Precise and uniform micro-hole processing is an advanced manufacturing process. Through high-precision processing technologies such as laser drilling, electrochemical etching, and powder metallurgy sintering process, a micro-hole array with consistent aperture size, regular distribution, and perpendicular to the material surface is prepared on the surface and inside of the metal material, ensuring that the geometric parameters (aperture, hole shape, and hole spacing) of each micro-hole are highly uniform, avoiding fluctuations in sound absorption effect caused by uneven pore distribution, while ensuring the flatness of the material surface and not damaging the aerodynamic shape of the measuring rod. This highly ordered micro-hole structure is the key to achieving stable and predictable sound absorption performance.

[0069] In the present embodiment, the regular distribution of the micro-hole array means that the hole spacing is uniform (e.g., the distance between adjacent hole centers is 1-2 mm), ensuring uniform and stable sound absorption effect.

[0070] Preferably, the aperture of the micro-hole structure metal material is not more than 0.5 mm, and the cavity depth is not more than 20 mm.

[0071] Regarding the design of an aperture not more than 0.5 mm and a cavity depth not more than 20 mm, the principle is based on the theory of viscous dissipation of sound waves propagating in micro-tubes and the Helmholtz resonator. This parameter combination is mainly optimized for the medium and high frequency noise generated by open fans. The smaller aperture increases the friction area between the sound wave and the hole wall, enhancing the viscous dissipation effect. The specific cavity depth matches the wavelength of the target frequency band, together determining the frequency and bandwidth of the sound absorption peak, thereby effectively absorbing specific interfering reflected sound waves in the complex sound field of a high-speed wind tunnel.

[0072] The micro-hole structure metal material can effectively reduce the reflection of the target sound signal on the surface of the measuring rod, suppress sound wave reflection, thereby improving the signal-to-noise ratio of the data and reducing measurement errors.

[0073] Further, the acoustic measuring rod 1 is provided with a plurality of microphone mounting grooves 5:

[0074] The microphone mounting grooves 5 are groove structures for replaceably mounting different models and different distribution forms of microphone arrays.

[0075] The microphone mounting grooves 5 are standardized grooves precisely processed on the rod body of the acoustic measuring rod 1, and their shape and size are standardized designed to match the mounting bases of various commercial microphones. The modular design of the microphone mounting grooves forms the last link of the multi-dimensional interference suppression design from the measurement strategy level, indirectly improving the ability to suppress non-target noise and extract effective sound source information through flexible array reconstruction capability.

[0076] In one specific embodiment, the groove depth is 5-10 mm, the width is adapted to the package size of the main flow microphone array (such as 6 mm, 8 mm, 10 mm, etc.), the groove bottom is provided with a positioning pin hole and a threaded fixing hole, the positioning pin is used to realize accurate positioning of the microphone array, and the fastening bolt is used to realize reliable detachable fixing. The edges of the groove are all treated with round corner transition to effectively avoid airflow separation caused by the groove structure and ensure the continuity of the aerodynamic shape of the measuring rod.

[0077] The microphone array is a measuring system composed of a plurality of microphone units arranged according to a specific geometric rule (such as linear, cross-shaped, ring-shaped, spiral-shaped or planar grid-shaped). By flexibly configuring different models (such as 1 / 4 inch, 1 / 2 inch pressure field microphones) and quantities of microphone arrays in the above-mentioned standardized installation groove, an array suitable for different purposes such as sound source positioning, beam forming or sound power measurement can be quickly constructed.

[0078] More specifically, the microphone models of the microphone array adapted to the installation groove of the application include miniature condenser microphones, high-temperature-resistant piezoelectric microphones, etc., and the distribution form can be flexibly selected according to the measurement requirements, such as a linear array arranged along the axial direction of the measuring rod (used to capture the noise distribution of the airflow direction), a ring-shaped array arranged in the circumferential direction (used to collect the radiation noise of the open fan in all directions), or a three-dimensional array combining the axial and circumferential directions (used to accurately locate the noise source position).

[0079] Such a modular design makes the microphone array layout flexible and reconfigurable, can flexibly meet a variety of different noise measurement requirements, realizes the modularity and reconfigurability of "one rod body, multiple arrays", and greatly improves the universality and test efficiency of the measuring device.

[0080] The application provides an acoustic measuring device for open fan wind tunnel test, which has the following beneficial effects:

[0081] 1) By adopting a support structure with an airfoil section, the aerodynamic resistance and vortex shedding of the device in a high-speed flow field are significantly reduced, the aerodynamic noise generated by the support components is reduced from the source, and the interference with the flow field is effectively reduced;

[0082] 2) By ensuring that the flange connection structure and the acoustic measuring rod are of the same width, additional protruding structures at the connection are avoided, flow separation and acoustic scattering caused by the connection link are minimized, and the accuracy of acoustic measurement is further ensured;

[0083] 3) By combining the flange connection structure and the damping bushing, the vibration transmitted from the tester base to the acoustic measuring rod is effectively isolated, the interference of mechanical vibration with the microphone signal is avoided, and the accuracy and reliability of the noise test data are significantly improved;

[0084] 4) By coating the surface of the acoustic measuring rod with a sound-absorbing layer of a microporous structure metal material with specific parameters, the reflection interference of the sound wave on the surface of the acoustic measuring rod is effectively suppressed, the measurement error is reduced, and the signal-to-noise ratio of the acoustic signal is improved;

[0085] 5) By providing a modular microphone mounting groove on the acoustic measuring rod, different types and distribution forms of microphone arrays can be quickly and flexibly replaced according to different test requirements, so that the layout of the microphone is flexibly reconfigurable, can adapt to various noise measurement schemes, and has strong versatility.

[0086] In summary, the acoustic measuring device for open fan wind tunnel test provided by the application integrates low-interference aerodynamic structure design (covering support structures and connecting components) and multi-dimensional interference suppression design (including vibration isolation, sound wave absorption and measurement reconstruction), and together realizes high-fidelity measurement of open fan noise in a high-speed wind tunnel environment.

[0087] As shown in the present application and claims, unless the context clearly indicates otherwise, the words "one", "an", "a", and / or "the" do not necessarily refer to the singular, but can also include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements.

[0088] In the description of the present application, it should be noted that the orientations or positional relationships indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0089] In the present application, unless otherwise explicitly specified and limited, "on" or "under" of a first feature to a second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "above" of the first feature to the second feature include that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. "Below", "below" and "below" of the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0090] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "linking" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0091] The above embodiments are provided for those skilled in the art to implement or use the present application. Those skilled in the art can make various modifications or changes to the above embodiments without departing from the inventive concept of the present application. Therefore, the protection scope of the present application should not be limited by the above embodiments, but should be the maximum scope of the innovative features mentioned in the claims.

Claims

1. An acoustic measurement device for open fan wind tunnel testing, characterized by, The application relates to an acoustic measurement rod, a support structure and a connecting assembly. The acoustic measurement rod is used for mounting a microphone array to collect noise signals in an open fan wind tunnel test, and realizes acoustic measurement of open fan noise characteristics. The support structure is connected with the acoustic measurement rod and is used for supporting the acoustic measurement rod in an open fan wind tunnel flow field. The connecting assembly is used for connecting the acoustic measurement rod and the support structure. The support structure adopts an integrated bionic airfoil design and has an airfoil section, so as to reduce the aerodynamic resistance and noise caused by the support structure itself in the open fan wind tunnel flow field.

2. An acoustic measurement apparatus for open fan wind tunnel testing according to claim 1, wherein, The acoustic measurement rod is provided with a plurality of microphone mounting grooves. The microphone mounting grooves are groove structures and are used for replaceably mounting microphone arrays of different types and different distribution forms.

3. The acoustic measurement apparatus for open fan wind tunnel testing of claim 1, wherein, The distribution form of the microphone array includes any one of a linear array, a ring array or a three-dimensional array.

4. The acoustic measurement apparatus for open fan wind tunnel testing of claim 1, wherein, The connecting assembly includes a flange connecting structure. The flange connecting structure is used for fixedly connecting the acoustic measurement rod and the support structure, and the flange connecting structure is equal in width to the acoustic measurement rod, so as to avoid flow interference.

5. An acoustic measurement apparatus for open fan wind tunnel testing according to claim 4, wherein, The connecting assembly further includes a damping bushing. The damping bushing is a ring sleeve structure and is arranged between the flange connecting structure and the acoustic measurement rod and is used for isolating vibration.

6. The acoustic measurement apparatus for open fan wind tunnel testing of claim 1, wherein, The support structure has a NACA series airfoil, a RAF series airfoil or a DVL series airfoil.

7. The acoustic measurement apparatus for open fan wind tunnel testing of claim 1, wherein, The support structure has a NACA0020 airfoil; the NACA0020 airfoil is a symmetrical airfoil, the maximum thickness is located at the center of the chord length, and the maximum thickness is 20% of the chord length.

8. The acoustic measurement apparatus for open fan wind tunnel testing of claim 1, wherein, The surface of the acoustic measurement rod is provided with an acoustic absorption layer and is used for inhibiting sound wave reflection.

9. An acoustic measurement apparatus for open fan wind tunnel testing according to claim 8, wherein, The acoustic absorption layer is a microporous structure metal material. The surface of the microporous structure metal material is formed with a micropore array through laser drilling, electrochemical etching or powder metallurgy sintering process; the micropore array has consistent pore size, regular distribution and is perpendicular to the material surface.

10. An acoustic measurement apparatus for open fan wind tunnel testing according to claim 9, wherein, The pore size of the microporous structure metal material is not more than 0.5 mm, and the cavity depth is not more than 20 mm.

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