A variable-stage axial flow fan fine aerodynamic acoustic experiment device and experiment method

Abstract

The application discloses a variable-stage axial flow fan fine aerodynamic acoustic experiment device and experiment method, and belongs to the field of aero-engine aerodynamic acoustics, and comprises: a two-stage fan test piece for simulating a fan component sound source flow field in an aero-engine and located outside a full soundproof room; an air inlet system for generating an air inlet condition of the tested fan test piece and located in the full soundproof room; an air outlet system for changing a flow area of gas at an outlet of the tested fan test piece; a control system for adjusting a working condition of the tested fan; a driving system for providing power for the two-stage fan test piece; and a test system for synchronously measuring aerodynamic performance and sound field characteristics. The application can simultaneously satisfy aerodynamic performance measurement and inlet / outlet air noise measurement of a single-stage fan component of a current aero-engine and a multi-stage fan component of a next-generation variable cycle engine, and has better adaptability.

Description

Technical Field

[0001] This invention relates to the field of aeroacoustics of aircraft engines. More specifically, this invention relates to a sophisticated aeroacoustic experimental apparatus and method for variable-stage axial flow fans. Background Technology

[0002] To address the inability of traditional noise control methods for aircraft and aero-engines to meet future airworthiness standards, integrated aerodynamic and acoustic design technology for aero-engines has become a research hotspot over the past decade. Its aim is to couple the low-noise design of various aero-engine components into the aerodynamic design system, thereby significantly reducing noise levels while maintaining or even improving the aerodynamic performance of the aero-engine. As one of the three core components of an aero-engine and currently a major noise source, the fan urgently requires the development of high-precision integrated aerodynamic and acoustic design methods in the design system, as well as the construction of sophisticated aerodynamic and acoustic experimental facilities and methods during the method verification and experimental research phases.

[0003] However, due to the characteristics of the operation of the rotating fan components of aero engines, fan component testing requires high-power motor drive and complex intake and exhaust pipe systems. This does not place high demands on the design of aerodynamic performance testing equipment, but it will seriously disrupt the actual situation of fan component noise generation and propagation. Consequently, this experimental layout cannot accurately simulate the intake / exhaust noise propagation characteristics of the fan components, and therefore cannot carry out refined integrated aerodynamic-acoustic experimental measurements of the fan.

[0004] Furthermore, as the next generation of major aero-engine power plants, adaptive variable cycle engines generally adopt a front / rear (multi-stage) fan design, which will bring a series of new fan noise problems, such as diversified noise sources, significantly increased sound source intensity, and complex interstage effects of sound propagation. These problems cannot be captured in past experiments on single-stage fan components, such as the "A Refined Acoustic Experimental Device and Experimental Method for Axial Turbines" application number CN202010998256.1. However, the working characteristics of aero-engine turbines and fans are completely different, and there are obvious differences in the structural layout of experimental devices. Aero-engine turbines are mostly multi-stage designs, while the experimental devices involved in the existing technology are only single-stage, which cannot realize the measurement of variable number of stages and the study of blade exhaust sound wave interference effects, resulting in low functionality and applicability. In addition, the experimental devices involved in the existing technology cannot perform refined measurements of the sound source flow field, cannot effectively correlate the relationship between the near field of the sound source and sound propagation and radiation, and cannot effectively separate the sound pressure signal from the interstage microphone signal. They can only measure the turbine exhaust pipe noise and far-field noise. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these objectives and other advantages of the present invention, a refined aeroacoustic experimental apparatus for a variable-stage axial fan is provided, comprising: A two-stage fan test piece used to simulate the sound source flow field of fan components in aero engines, located outside a fully anechoic chamber; An intake system used to generate the intake conditions of the tested fan specimen and located in a fully anechoic chamber; An exhaust system used to change the gas flow area at the outlet of the tested fan specimen; A control system used to adjust the operating conditions of the tested fan; A drive system that provides power to a two-stage fan test specimen; A test system for synchronously measuring aerodynamic performance and acoustic field characteristics; The testing system includes: an aerodynamic performance data acquisition module and an acoustic signal data acquisition module; The aerodynamic performance data acquisition module includes: a pressure acquisition unit for measuring static pressure, total pressure, pulsating static pressure, blade surface pulsating pressure, and inter-blade wall pulsating pressure; a temperature measurement unit for measuring total temperature and monitoring bearing temperature; and a dynamic testing subsystem for realizing aerodynamic data acquisition and processing. The acoustic signal acquisition module includes: a microphone unit for measuring the acoustic field information inside the inlet / exhaust pipe, inlet far field, and between blade stages of the test piece; and a static test subsystem for acquiring and processing acoustic signals.

[0007] Preferably, the two-stage fan test piece includes: two sets of rotor assemblies and two sets of stator assemblies, and the rotor blades in the two sets of rotor assemblies adopt a disc-separated structure, and the stator blades in the two sets of stator assemblies are all mounted on the casing, and the stator blades are a detachable structure with segmented rings. A sealing structure consisting of grating teeth and a coating is provided between the rotor assembly and the stator assembly to ensure sufficient axial clearance between the rotor and stator.

[0008] Preferably, the microphone unit includes: It is set in a fully anechoic chamber, and a 1 / 4 arc-shaped far-field microphone array is set with the air inlet axis as the center; Rotary microphone array I and rotary microphone array II are set in the rotating measurement area of ​​the intake section and the exhaust section, and are evenly distributed along the circumference. Rotary microphone array I is placed in a fully anechoic chamber, and a muffler is installed between rotary microphone array II and the drive system. An interstage microphone array is set between different blade rows of a two-stage fan test specimen; The circumferential rotation speed of both the rotary microphone array I and the rotary microphone array II is controlled by a drive system.

[0009] Preferably, the pressure acquisition unit includes: 7 total pressure test probes and 4 static pressure test probes evenly distributed at the air inlet and air outlet ends; The temperature acquisition unit includes: a hot wire probe installed at the air inlet to measure the total temperature, and thermocouples installed at each bearing.

[0010] A refined aeroacoustic experimental method includes: Step 1: Install, debug, and calibrate the pneumatic and acoustic measurement equipment; Step 2: Start the drive system, and after the control system adjusts the working condition of the fan test piece to a stable state, collect the sound pressure signal I on the pipe wall through the rotating microphone array, and simultaneously collect the aerodynamic signal I, far-field sound pressure signal I, and interstage sound pressure signal I. Step 3: Control the rotary microphone array to rotate clockwise by a predetermined angle through the drive system, and collect the sound pressure signal II on the pipe wall again, and simultaneously collect the pneumatic signal II, the far-field sound pressure signal II, and the interstage sound pressure signal II. Step 4: Repeat step 3 to complete the acquisition of sound pressure signals from the pipe wall within a 360° circumferential range, as well as the corresponding aerodynamic signals, far-field sound pressure signals, and interstage sound pressure signals. Step four: Process the aerodynamic signals at the inlet / outlet to obtain the fan aerodynamic efficiency; process the aerodynamic signals between the blade rows to obtain the total pressure loss and flow field information; Step four: Process the far-field sound pressure signal II, the pipe wall sound pressure signal, and the interstage sound pressure signal respectively to obtain the total sound power of the far-field noise, the pipe modal sound field, and the near-field information of the fan test specimen sound source.

[0011] The present invention has at least the following beneficial effects: This invention enables precise synchronous measurement of the aerodynamic and acoustic characteristics of a fan. Secondly, through inventions and innovations in three aspects—"a variable-stage axial-flow fan test piece simulating the intake / exhaust noise radiation conditions of a real aero-engine fan," "a precise synchronous testing method for fan aerodynamic performance, sound source flow field, intake / exhaust pipe propagation, blade exhaust sound wave interference effect, and far-field radiation," and "a method for sound pressure separation of interstage microphone signals"—this invention achieves precise experimental synchronous measurement of the aerodynamic and acoustic characteristics of aero-engine axial-flow (single / double-stage) fans. The measurement content covers the sound source generation-propagation-radiation characteristics of the fan test piece in the near-field, pipe modal sound field, and free far-field, as well as the correlations between them (it should be noted that sound source generation here refers to the sound source flow field and interstage measurement, propagation refers to pipe measurement, and radiation refers to far-field measurement; correlations can be obtained through analysis and comparison of measurement data from different locations). This provides hardware conditions and experimental foundation for subsequent integrated aerodynamic and acoustic design of fans.

[0012] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0013] Figure 1 This is the overall technical solution of the variable-stage fan experimental device of the present invention; Figure 2 This is a schematic diagram comparing the aerodynamic characteristics of a two-stage fan using a standard blade profile and a biomimetic blade profile in an embodiment of the present invention. Figure 3 This is a schematic diagram comparing the total sound power spectrum of a two-stage fan using a reference still blade and a bionic still blade in an embodiment of the present invention. Figure 4 This is a schematic diagram of the energy distribution and far-field directivity distribution of a reference stator blade two-stage fan in the R1_1BPF mode, as shown in this embodiment of the invention. Figure 5 This is a schematic diagram of the energy distribution and far-field directivity distribution of the biomimetic bladeless two-stage fan in the R1_1BPF mode, as shown in this embodiment of the invention. Figure 6 This is a schematic diagram of the circumferential acoustic modal structure distribution of a two-stage fan measured between the R1_1BPF stages under the reference stator blades, in an embodiment of the present invention. Figure 7 This is a schematic diagram of the circumferential acoustic modal structure distribution of a two-stage fan measured under the reference stator blades using the R1_1BPF pipe array, as shown in this embodiment of the invention. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0015] A refined aeroacoustic experimental device for a variable-stage axial flow fan mainly includes: an intake / exhaust system, a control system, a drive system, a two-stage fan test piece, and a testing system.

[0016] The intake system is used to generate the intake conditions for the tested fan. Specifically, the intake system includes an intake rectifier section with a flared end and an external support for the intake rectifier section. The total length of the intake rectifier section is approximately 500mm (the length can be adjusted according to actual needs). The intake rectifier section includes a straight pipe section and a flared end cap, which are connected by a flange. The surface machining accuracy of the flared end should be above level seven, and the surface roughness should be below [specific value missing]. To ensure a uniform velocity field at the inlet; The exhaust system is used to adjust the outlet back pressure by changing the flow area of ​​the gas exiting the test piece, thereby changing the working state of the test piece. Specifically, the exhaust system includes: a rear adapter housing, a rear adapter inner ring, a throttle valve assembly, and an exhaust inner ring. In practical applications, the radial dimensions of the rear adapter housing and the rear adapter inner ring are appropriately enlarged, and the drive system components such as the drive motor and torque meter are supported on the exhaust inner ring by a support ring. The throttle valve assembly consists of a moving ring and a pressure ring with exhaust holes. The adjustment mechanism is driven by an electric cylinder, causing the moving ring and the pressure ring to rotate relative to each other, and the exhaust hole area gradually changes, thereby achieving the throttle function. A thrust ball bearing is installed between the moving ring and the pressure ring to reduce the friction between the relative rotation and ensure the stable operation of the adjustment mechanism. The control system is used for independent, remote, and precise adjustment and control of fan speed, flow rate, and other operating conditions. Specifically, the control system includes a motor speed control subsystem and an air valve subsystem. The motor speed control subsystem is connected to the PLC controller and host computer through a switch. The host computer sends relevant operation commands, and the PLC controller controls the opening / closing of the electric valve. The two subsystems operate independently, thereby realizing remote and precise control of fan speed, flow rate, and other operating conditions. The drive system includes: a variable frequency drive motor, a speed-increasing gearbox, a torque meter, etc. All components are connected by couplings. The entire shaft system is quite long. The components are installed and adjusted in sequence with the drive motor as the reference to meet the concentricity requirements of the high-speed fan test shaft system. The two-stage fan test specimen is used to simulate the sound source flow field working state of aero-engine fan components, and together with the intake and exhaust system, it simulates the duct sound propagation characteristics of the fan components. Specifically, the two-stage fan test specimen mainly includes two sets of rotor assemblies and two sets of stator assemblies. In the rotor assemblies, the rotor blades are all of a separate disk structure, and the disk and blades are connected by dovetail tenons, with axial restraint rings at the front and rear. The stator blades in the stator assemblies are all mounted on the casing, and are a detachable structure of segmented whole ring (through the detachable design of the rotor and stator assemblies, the blades can be added or removed as needed to complete variable-stage operation). They are connected to the casing through tenons on the outer edge plate, and the casing and inner ring are connected by stop centering and bolts. The rotor and stator are sealed with grates and coating. The sealing structure allows for a small cavity design to reduce the impact of cavity effect on aerodynamics, while ensuring sufficient axial clearance between the rotor and stator. This structural design improves the maintainability and strength requirements of the fan test piece. Most importantly, it facilitates the disassembly and replacement of rotor and stator blades, enabling flexible variation of the number of fan stages and providing hardware support for conducting experimental research on the optimization design of single / double-stage fans. The testing system is used for synchronous and precise measurement of fan aerodynamic performance, intake and exhaust noise duct acoustic field characteristics, and inter-stage sound source flow field characteristics. Specifically, the testing system includes an aerodynamic performance data acquisition module and an acoustic signal data acquisition module. The aerodynamic performance data acquisition module consists of a speed sensor, a pressure scanning valve, a temperature measuring instrument, a dynamic testing subsystem, and data acquisition and processing software. It can be used to measure aerodynamic parameters such as static pressure, total pressure, total temperature, pulsating static pressure, airflow angle, blade surface pulsating pressure, and inter-blade wall pulsating pressure. The acoustic signal acquisition system consists of a microphone and acoustic signal acquisition and processing software. It can be used to measure acoustic field information in the intake / exhaust ducts of the test specimen, the far field of the intake, and the inter-stage sound field. Furthermore, the test specimen has 500mm of space in both the intake and exhaust sections. Currently, both the intake and exhaust ports have 4 total temperature and total pressure probe measurement holes and 4 static pressure probe measurement holes, which can flexibly install total temperature and total pressure probes (in practical applications, the probes are used in conjunction with the pressure scanning valve, i.e., one end of the probe extends into the measurement position, and the other end is connected to the pressure scanning valve to output the measurement signal to the outside through the pressure scanning valve), dynamic pressure sensors and other testing instruments; the two-stage fan test specimen is installed in the fully anechoic chamber. The rotary microphone array (18 equally spaced axial measurement holes arranged every 90° along the circumference) and the far-field noise array (a 1 / 4 circle with the axis of the inlet section as the center, the number of microphones can be flexibly adjusted) in the intake section are both placed in the fully anechoic chamber. A silencer is installed between the rotary microphone array (16 equally spaced axial measurement holes arranged every 90° along the circumference) in the exhaust section and the drive motor to eliminate the drive motor and other interference noise sources entering through the exhaust port. The circumferential rotation speed of the microphone array is controlled by the drive motor; The axial clearance between different blade rows is 18 mm. Sixteen (the number can be adjusted according to testing requirements) measuring holes are evenly arranged circumferentially before the first-stage rotor inlet, after the second-stage stator outlet, and between different blade rows. These holes allow for the installation of either aerodynamic or acoustic measuring instruments, depending on the specific needs. This structural layout enables simultaneous and precise measurement of the aerodynamic and acoustic characteristics of single / dual-stage fans, providing an experimental foundation for research on integrated aerodynamic and acoustic design technology for single / dual-stage fans.

[0017] The experimental device of this invention can simulate the noise radiation characteristics of real fan components of aero engines. Through structural designs such as "rotor blades with separate disk structure" and "detachable structure of stator casing segmented (whole ring)," the number of fan stages can be flexibly changed, meeting the dual experimental requirements of current single-stage fans of aero engines and multi-stage fans of next-generation variable cycle engines. At the same time, the structural designs such as "far-field array and intake rotation measurement section located in a fully anechoic chamber" and "silencer installed between exhaust rotation measurement section and drive system" make this experimental device the first fan experimental device in China that can simultaneously and precisely simulate and measure intake and exhaust noise.

[0018] A refined aerodynamic-acoustic experimental method for a variable-stage axial fan includes the following steps: Step 1: Debug, calibrate, and install the pneumatic measurement equipment. Based on actual measurement requirements, arrange pneumatic measurement equipment circumferentially at the inlet and outlet, such as total temperature and pressure probes, boundary layer hot wire probes, and five-hole probes; place total pressure probes, five-hole probes, or hot wire probes, along with their corresponding displacement mechanisms, before the first-stage rotor, before the first-stage rotor inlet, after the second-stage stator outlet, and between different blade rows; the measurement equipment needs to be calibrated and standardized before testing; all probes are connected to the test system at their rear ends. Step two: Debugging, calibrating, and installing the acoustic measurement equipment. Based on actual measurement requirements, a 1 / 4-circle array of far-field measuring microphones, centered on the air inlet axis, is set up in the anechoic chamber. The array is parallel to the ground, with the microphone probes facing the air inlet axis. A fixed microphone array between the intake / exhaust rotary microphone array and the blade array is inserted into the pipe through small holes in the pipe wall, with the microphone probe plane flush with the inner wall of the pipe. All microphones are connected to the test system at their rear ends. Step 3: Start the drive system until the test specimen is in stable operation. Start the drive motor and adjust the control system to bring the fan test specimen to the required operating state (mainly speed and flow rate); Step four: Rotate the array and acquire the microphone sound pressure signals. A stepper-controlled drive motor rotates the microphone array to a preset circumferential position and acquires the sound pressure signals from the sensor array. This step is repeated continuously to obtain the sound pressure signals from the microphone array within a 360° circumferential range. It should be noted that this experimental setup has four rows of axial microphone arrays arranged circumferentially; only a 90° rotation is needed to acquire sound pressure signals within a 360° range. During rotation, the aerodynamic measurement equipment, the far-field microphone array, and the fixed microphone array between the blade rows can remain in measurement mode to check and improve data repeatability. Step 5: Process the aerodynamic measurement data of the inlet / exhaust port to obtain the fan aerodynamic efficiency; process the aerodynamic measurement data between the blade rows to obtain flow field information such as total pressure loss, tail stage velocity deficit distribution, and wake pulsation velocity distribution. Step 6: Perform Fourier transform on the sound pressure data of the far-field microphone array to obtain the sound pressure spectrum information and the directivity of noise at different frequencies at each measurement point. Sum the sound pressure information at each measurement point to obtain the total directivity of the far-field noise. Sum the sound pressure information at all measurement points to obtain the total sound power of the far-field noise. Step 7: Perform Fourier transform on the sound pressure data of the rotating microphone array to zero out the phase difference of the sound pressure signal caused by the blade position error at the measurement time. Then, perform circumferential mode decomposition through spatial discrete Fourier transform. Finally, solve the circumferential mode information by least squares fitting method or perform radial mode decomposition by a linear overdetermined system of equations consisting of multiple radial mode cross-correlation functions. Step 8: Perform Fourier transform on the sound pressure signal of the microphone array between different blade rows. Since it is a fixed array, phase correction is not required. First, through spatial discrete Fourier transform and time discrete Fourier transform, according to the slope relationship between spatial wavenumber and frequency, separate the sound pressure pulsation signal (spatial wavenumber / slope is greater than the speed of sound) from the microphone signal (when the sound source is measured in the near field, the microphone signal is the sum of turbulent pulsation and sound pressure pulsation). Then, through spatial inverse Fourier transform, pass the sound pressure frequency domain signal through the measuring hole. Finally, perform circumferential mode decomposition according to the pipe mode decomposition theory.

[0019] The experimental method of this invention enables integrated aerodynamic-acoustic experimental measurement of fans by performing refined and simultaneous measurements of fan aerodynamic performance, sound source flow field, inlet / exhaust pipe propagation, blade row acoustic interference effect, and far-field radiation (including a reasonable structural design at different locations such as the far-field radiation region, inlet / exhaust section, pipe acoustic propagation section, and fan test piece, and equipped with professional aerodynamic performance data acquisition modules and acoustic signal data acquisition modules that can operate simultaneously and independently). Simultaneously, by using spectrum transformation technology and the difference in spatial wavenumber / frequency slope between turbulent pulsation signals and sound pressure pulsation signals, sound pressure pulsation signals are separated from microphone array signals at locations such as before the first-stage rotor inlet, after the second-stage stator outlet, and between different blade rows. Furthermore, by utilizing pipe modal theory to decouple the acoustic modal structure, refined measurements of the near-field (flow field) of the fan component's sound source are achieved. This can be used for refined experimental research on the blade row acoustic interference effect, a study that previously could only be inferred from pipe acoustic propagation measurement results and could not be effectively correlated with the details of the sound source flow field.

[0020] Example: like Figure 1 As shown, this invention discloses a variable-stage axial flow fan aerodynamic-acoustic experimental device, comprising an intake and exhaust system consisting of a horn-shaped air inlet 1, a drive system consisting of a drive motor 2, a two-stage fan test piece 3, a test system consisting of a rotating microphone array I 4 and a rotating microphone array II 5, and a control system consisting of a throttle valve 6. The structural components and connection methods of different systems are fully implemented according to the technical solution described in this invention. The two-stage test piece can be disassembled into a single-stage fan test piece without affecting the normal operation of the experimental device. The performance indicators of the two-stage fan test piece under its design state are shown in Table 1.

[0021] Table 1: Performance Parameters of Fan Test Specimens The following uses a two-stage fan test specimen as an illustrative example to measure the basic aerodynamic and acoustic characteristics of the fan and to conduct an experimental study on the noise reduction effect of the first-stage biomimetic wave-leading blade. The experimental test steps and results are explained in detail: Step 1: Set up the pneumatic measurement equipment. (Refer to...) Figure 1 The test bench is equipped with seven total pressure points, four static pressure points, and one temperature point evenly distributed at the inlet and outlet. Thermocouples are installed at three bearing locations to monitor bearing temperature during the test. Vibration monitoring devices are installed at the front and rear of the casing, one directly above the test piece and one horizontally, to monitor the vibration of the test bench during the test and ensure the safe operation of the test piece. The measuring devices at each point are connected to the aerodynamic performance data acquisition module and are debugged and calibrated. Step two: Set up the acoustic measurement equipment. (Refer to...) Figure 1A quarter-circular far-field microphone array 9, consisting of 16 evenly distributed microphones, is set in a fully anechoic chamber 8 with an air inlet 7, centered on the air inlet axis; (Refer to...) Figure 1 The intake and exhaust rotary measurement section has two axial arrays of microphones evenly distributed along its circumference (i.e., rotary microphone array I4 and rotary microphone array II5), each array consisting of 14 microphones; refer to Figure 1 Sixteen microphones were arranged circumferentially in the interstage measurement port 10 to construct an interstage microphone array. All microphones were numbered for easy data processing later, and all microphones were connected to the acoustic signal acquisition system via cables for debugging and calibration. A silencer 11 was installed in front of the drive system. Step 3: Open the drive motor and throttle valve assembly through the drive system, remotely set the fan speed and working flow. After the working condition stabilizes, it usually only takes a few seconds. Then start collecting data. Collecting a set of data usually only takes 20 seconds. At this time, the position of the rotary microphone array is 0° by default. Step 4: Control the rotating microphone array to rotate clockwise to 4° by driving the motor, collect data again, and repeat this step continuously until the array rotates to 180°, so as to obtain the sound pressure signal of the pipe wall at different circumferential positions of a complete 360° circle. Step 5: Referring to the invention, post-process the experimental data to obtain the measurement results of the fan's aerodynamic and acoustic performance at that speed and flow rate; Step six: Repeat the above steps. By changing the fan speed and flow rate through the control system, the aerodynamic-acoustic characteristics of the fan under different operating conditions can be obtained. With enough changes in operating conditions, the aerodynamic characteristic curve of the fan and the variation law of noise with operating conditions can be completely measured.

[0022] Step 8: Disassemble and replace the first-stage stator blade S1 with a biomimetic wave-leading edge stator blade. This biomimetic blade design is not the focus of this invention and will not be described in detail. Repeat the above steps to conduct experimental measurements of the aerodynamic-acoustic noise characteristics of the two-stage fan under the biomimetic stator blade leading edge, and perform data post-processing.

[0023] The measurement results of this implementation case are as follows: Figures 2-7 As shown. Figure 2 A comparison of the aerodynamic characteristics and total power stage of a two-stage fan with a reference stator and a bionic stator (where the red box represents the reference stator and the black triangle represents the bionic stator). Figure 3 This is a schematic diagram comparing the total acoustic power spectrum of a two-stage fan using standard and biomimetic rotor blades; taking the 1 BPF generated by the first-stage rotor as an example. Figures 4-5 A comparison of the far-field directivity of the lower circumferential acoustic modes of the reference stationary blade and the biomimetic stationary blade is presented. Figures 6-7Furthermore, a comparison of the circumferential acoustic modal structure distribution obtained from interstage measurements of R1_1BPF under the reference stator and from pipe array measurements is presented. As can be seen from the above figures: like Figure 2-5 As shown, the wave leading edge not only did not reduce the fan's aerodynamic performance, but also improved the fan's total pressure ratio to some extent. The flow rate change was also small under the same throttle valve opening. Simultaneously, it reduced the total acoustic power, pipe acoustic mode energy, and far-field directivity. For the 1BPF single-tone noise corresponding to R1, its dominant mode is m=-2, which is caused by the interference between R1 and S1. Therefore, as... Figures 6-7 As shown, comparing the acoustic modes measured between the interstage modes and the inlet duct array, it can be found that even though the interstage sound field is in a complex nonlinear flow field region, the interstage single-tone noise still has a significant dominant mode m=-2. Overall, the amplitude of the dominant mode is larger than that inside the duct, and the energy distribution of other modes increases significantly, which is related to near-field noise. Through the above brief analysis, it can be seen that the variable-stage axial fan aerodynamic-acoustic experimental device and method used in this embodiment can accurately simulate and capture the aerodynamic-acoustic characteristics of aero-engine fan components, and can be used to analyze the correlation between the sound source flow field structure, the duct sound field structure, and far-field radiation.

[0024] The above solution is merely an illustration of a preferred example and is not limited thereto. When implementing this invention, appropriate substitutions and / or modifications can be made according to the user's needs.

[0025] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Other modifications can be readily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A refined aeroacoustic experimental device for a variable-stage axial flow fan, characterized in that, include: A two-stage fan test piece used to simulate the sound source flow field of fan components in aero engines, located outside a fully anechoic chamber; An intake system used to generate the intake conditions of the tested fan specimen and located in a fully anechoic chamber; An exhaust system used to change the gas flow area at the outlet of the tested fan specimen; A control system used to adjust the operating conditions of the tested fan; A drive system that provides power to a two-stage fan test specimen; A test system for synchronously measuring aerodynamic performance and acoustic field characteristics; The testing system includes: an aerodynamic performance data acquisition module and an acoustic signal data acquisition module; The aerodynamic performance data acquisition module includes: a pressure acquisition unit for measuring static pressure, total pressure, pulsating static pressure, blade surface pulsating pressure, and inter-blade wall pulsating pressure; a temperature measurement unit for measuring total temperature and monitoring bearing temperature; and a dynamic testing subsystem for realizing aerodynamic data acquisition and processing. The acoustic signal acquisition module includes: a microphone unit for measuring the acoustic field information inside the inlet / exhaust pipe, inlet far field, and between blade stages of the test piece; and a static test subsystem for acquiring and processing acoustic signals.

2. The refined aeroacoustic experimental device for a variable-stage axial flow fan as described in claim 1, characterized in that, The two-stage fan test piece includes: two sets of rotor assemblies and two sets of stator assemblies. The rotor blades in the two sets of rotor assemblies adopt a disc-separated structure. The stator blades in the two sets of stator assemblies are installed on the casing. The stator blades are a detachable structure with segmented rings. A sealing structure consisting of grating teeth and a coating is provided between the rotor assembly and the stator assembly to ensure sufficient axial clearance between the rotor and stator.

3. The refined aeroacoustic experimental device for a variable-stage axial flow fan as described in claim 1, characterized in that, The microphone unit includes: It is set in a fully anechoic chamber, and a 1 / 4 circular arc-shaped far-field microphone array is set with the air inlet axis as the center; Rotary microphone array I and rotary microphone array II are set in the rotating measurement area of ​​the intake section and the exhaust section, and are evenly distributed along the circumference. Rotary microphone array I is placed in a fully anechoic chamber, and a muffler is installed between rotary microphone array II and the drive system. An interstage microphone array is set between different blade rows of a two-stage fan test specimen; The circumferential rotation speed of both the rotary microphone array I and the rotary microphone array II is controlled by a drive system.

4. The refined aeroacoustic experimental device for a variable-stage axial flow fan as described in claim 1, characterized in that, The pressure acquisition unit includes: 7 total pressure test probes and 4 static pressure test probes evenly distributed at the air inlet and air outlet. The temperature acquisition unit includes: a hot wire probe installed at the air inlet to measure the total temperature, and thermocouples installed at each bearing.

5. A refined aeroacoustic experimental method, which employs the refined aeroacoustic experimental apparatus for a variable-stage axial flow fan as described in any one of claims 1-4, characterized in that, include: Step 1: Install, debug, and calibrate the pneumatic and acoustic measurement equipment; Step 2: Start the drive system, and after the control system adjusts the working condition of the fan test piece to a stable state, collect the sound pressure signal I on the pipe wall through the rotating microphone array, and simultaneously collect the aerodynamic signal I, far-field sound pressure signal I, and interstage sound pressure signal I. Step 3: Control the rotary microphone array to rotate clockwise by a predetermined angle through the drive system, and collect the sound pressure signal II on the pipe wall again, and simultaneously collect the pneumatic signal II, the far-field sound pressure signal II, and the interstage sound pressure signal II. Step 4: Repeat step 3 to complete the acquisition of sound pressure signals from the pipe wall within a 360° circumferential range, as well as the corresponding aerodynamic signals, far-field sound pressure signals, and interstage sound pressure signals. Step four: Process the aerodynamic signals at the inlet / outlet to obtain the fan aerodynamic efficiency; process the aerodynamic signals between the blade rows to obtain the total pressure loss and flow field information; Step four: Process the far-field sound pressure signal II, the pipe wall sound pressure signal, and the interstage sound pressure signal respectively to obtain the total sound power of the far-field noise, the pipe modal sound field, and the near-field information of the fan test specimen sound source.

Images