Method, system, medium and device for acoustic identification of synchronous vibration of aero-engine fan blade

Abstract

A method, system, medium and device for identifying synchronous vibration of an aero-engine fan blade, in which the layout of a microphone array is determined through parameters of a fan model; the multi-channel sound pressure time domain signals of the fan are synchronously collected through the microphone array; the multi-channel sound pressure time domain signals are sequentially arranged to construct a time domain signal matrix; the sound pressure time domain signals are subjected to frequency spectrum analysis through a fast Fourier transform algorithm to obtain the frequency spectrum diagram of each channel of the sound pressure time domain signals; whether the amplitude of the blade passing frequency of the fan increases by more than a first predetermined value and whether wideband noise components with a frequency band distribution greater than a predetermined range appear are monitored through the frequency spectrum diagram; if not, it indicates that the fan is in a normal working state; when synchronous vibration of the fan blade occurs, the sound mode of the blade passing frequency and its multiple frequencies reflects the vibration of the blade; and the vibration nodal diameter and frequency of the fan disk are output based on the frequency coupling relationship through the sound mode of the blade passing frequency.

Description

Technical Field

[0001] This invention relates to the field of fan noise testing technology, and in particular to a method, system, medium, and equipment for acoustic identification of synchronous vibration of aero-engine fan blades. Background Technology

[0002] A fan is a typical multiphysics highly coupled system, with its internal blades subjected to the combined effects of structural elastic forces, rotational inertial forces, and unsteady flow excitations. When a fan operates under abnormal conditions, its critical thin-walled structure undergoes abnormal vibrations under the interaction of high centrifugal loads, alternating vibrational loads, and aerodynamic excitation loads. On the one hand, certain unsteady flow excitations can cause the blade vibration amplitude to increase exponentially, forcing high-cycle fatigue failure, crack formation, and even fatigue fracture of the blades. On the other hand, abnormal fan vibrations can alter the internal flow field structure, threatening the aerodynamic stability of the compression system. Furthermore, abnormal vibrations of the critical thin-walled structure can create new aerodynamic noise sources, and under specific low Mach number conditions, sound waves may act on the structure, affecting the vibration state.

[0003] Currently, strain gauges are typically installed on rotating blades to monitor the vibration state of fan blades, which is costly and the invasive measurement method can interfere with the fan flow field. Acoustic sensors, on the other hand, have advantages such as high sensitivity and short transmission paths, and are non-invasive, thus not interfering with the fan flow field. By performing modal decomposition on the acoustic array signal, key information such as the blade's vibration frequency and pitch diameter can be fully reflected. The acoustic feature-driven fan blade vibration monitoring method improves the diagnostic accuracy of typical abnormal conditions and provides a new approach for monitoring the condition of aero-engine fans.

[0004] Large-amplitude synchronous vibration of fan blades not only increases fan noise but can also lead to severe fatigue failure and even blade breakage, seriously threatening the safe and stable operation of high-performance aero-engine fans. Therefore, accurate identification and analysis of its fault characteristics are crucial for the maintenance and repair of aero-engines. Traditional fault detection methods mainly rely on visual inspection, non-destructive testing techniques, and vibration analysis; however, these methods often have limitations when dealing with synchronous vibration faults in fan blades.

[0005] The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a method, system, medium, and device for acoustic identification of synchronous vibration of aero-engine fan blades. It measures acoustic signals and uses signal processing to convert the acoustic field signals from the time domain to the frequency domain to the wavenumber domain, thereby obtaining a more effective acoustic pattern for detecting synchronous vibration of fan blades and identifying acoustic signal fault characteristics in synchronous vibration of fan blades.

[0007] An acoustic identification method for synchronous vibration of aero-engine fan blades includes:

[0008] In the first step, the microphone array layout is determined by the parameters of the fan model;

[0009] In the second step, the number of microphones and the installation angle of the microphone Construct a microphone array; synchronously acquire the multi-channel sound pressure time-domain signals of the fan using the microphone array; construct a time-domain signal matrix by arranging the multi-channel sound pressure time-domain signals in sequence;

[0010] In the third step, the Fast Fourier Transform algorithm is used to perform spectral analysis on the sound pressure time domain signal to obtain the spectrum of the sound pressure time domain signal of each channel. By monitoring the spectrum, it is found that the increase in the frequency amplitude of the fan blades exceeds the first predetermined value and there are broadband noise components with a frequency band distribution greater than the predetermined range. If none of these exist, it means that the fan is in normal working condition.

[0011] In the aforementioned method for acoustic identification of synchronous vibration of aero-engine fan blades, if the increase in the frequency amplitude of the fan blade exceeds a first predetermined value and a broadband noise component with a frequency band distribution greater than a predetermined range appears, then proceed to the fourth step.

[0012] In the fourth step, the acoustic mode spectrum at the blade passage frequency is obtained by the single-frequency acoustic mode decomposition method. By monitoring whether the synchronous vibration characteristics of the fan blades appear in the spectrum, it is determined whether the fan blades are vibrating synchronously. When the fan blades vibrate synchronously, the change in the amplitude of the static interference mode in the acoustic mode spectrum at the blade passage frequency exceeds the second predetermined value.

[0013] In the fifth step, the spectrum of the sound pressure time-domain signal is obtained through continuous broadband acoustic mode decomposition. The horizontal axis of the spectrum represents the frequency analysis range, the vertical axis represents the acoustic mode monitoring range, and the color intensity represents the amplitude. The darker the color, the larger the amplitude. By monitoring whether the synchronous vibration characteristics of the fan blades appear in the spectrum, when the fan blades vibrate synchronously, the amplitude of the broadband noise mode in the spectrum increases beyond the third predetermined value, and the change in the amplitude of the static interference mode at the blade passing frequency exceeds the second predetermined value and propagates to the surrounding frequencies, forming a bright cross band phenomenon with the sound source at the blade passing frequency.

[0014] In the sixth step, when the fan blades vibrate synchronously, the acoustic modes of the blades through frequency and its harmonics reflect the vibration of the blades. At this time, the vibration frequency of the blade disk is coupled with the blade through frequency. Based on the frequency coupling relationship, the vibration pitch diameter and frequency of the fan blade disk are output through the acoustic mode of the blade through frequency.

[0015] In the aforementioned method for acoustic identification of synchronous vibration of aero-engine fan blades, the second step includes the following steps:

[0016] S201. The sound pressure signal of the fan is measured using a ring acoustic array. The measured sound pressure time-domain signal is: The length of the time-domain signal sequence measured by a single microphone is [length missing]. subscript These are microphones positioned at corresponding installation angles;

[0017] S202. Based on the sound pressure time-domain signals measured by the microphones at different installation angles, construct a time-domain signal matrix. , of which elements express The first measurement obtained by the microphone at the corresponding installation angle position Signal,

[0018] When using a uniform acoustic array layout, the time-domain signal matrix The size is When using a non-uniform acoustic array layout with few measurement points, the time-domain signal matrix... The size is .

[0019] In the aforementioned method for acoustic identification of synchronous vibration of aero-engine fan blades, the third step (S3) includes:

[0020] S301, Regarding the time-domain signal matrix The frequency domain matrix is ​​obtained by performing a Fourier transform on each column. , of which elements express The signal measured by the microphone at the corresponding installation angle position is Amplitude at frequency, The length is According to the Nyquist sampling theorem, ,

[0021] In a uniform acoustic array layout, the frequency domain matrix The size is In a non-uniform acoustic array layout, the frequency domain matrix The size is ,

[0022] S302, According to the frequency domain matrix Plot the spectrum of signals measured by sensors at different installation angles, and the frequency of the fan blades passing through them. The amplitude increases beyond the first predetermined value and broadband noise components with a frequency band distribution greater than the predetermined range appear.

[0023] In the aforementioned method for acoustic identification of synchronous vibration of aero-engine fan blades, the fourth step (S4) includes:

[0024] S401, When using a uniform acoustic array layout, the subscript... The microphone at the corresponding installation angle position at the predetermined frequency Frequency domain signal at It can be viewed as a linear superposition of different circumferential acoustic modes, i.e. Construct the transformation matrix The format is as follows:

[0025] ,

[0026] When using a non-uniform acoustic array layout with few measurement points, an observation matrix is ​​constructed based on randomly selected sensor installation angles. Observation matrix Size is ,

[0027] ,

[0028] S402. When using a uniform acoustic array layout, the frequency domain matrix... Perform a spatial Fourier transform to obtain the wavenumber domain matrix. , ,in Frequency domain matrix The transpose of the matrix, ,in Represents the transformation matrix The false rebellion,

[0029] When using a non-uniform acoustic array layout with few measurement points, the compressed sensing model is: sparse dictionary Composed of orthogonal Fourier transform bases, For the sensing matrix, sparsely reconstruct the wavenumber domain matrix based on the compressed sensing model. ;

[0030] S403. Based on the obtained wavenumber domain matrix Plot the acoustic modal spectrum; when the fan blades vibrate synchronously, the excitation frequency of the sound source is coupled with the vibration frequency of the blades, and the change in the amplitude of the static interference mode in the acoustic modal spectrum of the blade passing frequency exceeds the second predetermined value.

[0031] In the aforementioned method for acoustic identification of synchronous vibration of aero-engine fan blades, the fifth step (S5) includes:

[0032] S501, the wavenumber domain matrix Extending to the full frequency domain, wavenumber domain matrix Size expansion to , of which elements Indicates frequency First The amplitude of the step sound mode,

[0033] ,

[0034] S502, According to the wavenumber domain matrix A spectrum diagram is plotted, and the amplitude increase of the broadband noise mode in the spectrum diagram exceeds the third predetermined value. The change of the amplitude of the static interference mode at the blade passage frequency exceeds the second predetermined value and propagates to the surrounding frequencies. This combination with the sound source at the blade passage frequency forms a cross-shaped bright band phenomenon, which is defined as the acoustic signature of synchronous vibration of the fan blade. Based on this, it is determined whether the fan blade is vibrating synchronously.

[0035] In the aforementioned acoustic identification method for synchronous vibration of aero-engine fan blades, in the sixth step (S6), when the fan blades vibrate synchronously, the vibration pitch diameter and frequency of the fan blade disk are output.

[0036] S601. When the fan blades vibrate synchronously, the vibration frequency of the blade disk is coupled with that of the blades through frequency coupling. The acoustic mode order is equal to the number of blade pitch diameters. At this time, the excitation frequency of the sound source is... With blade vibration frequency satisfaction,

[0037] In the formula, Indicates the rotor frequency.

[0038] S602. Calculate and output the blade vibration frequency and vibration pitch diameter based on the excitation frequency and modal order of the sound source in the spectral diagram.

[0039] A fan blade synchronous vibration identification system implementing the method includes:

[0040] The sound field measurement module includes a sound array measurement submodule and a data acquisition submodule, which are used to measure the sound field information propagated in the pipe to the sound array installation location when the fan is working;

[0041] The spectrum analysis module is used to transform the time-domain sound field signal at the location of the acoustic array to the frequency domain to detect whether there are abnormal changes in the frequency of the blades passing through and abnormal frequency components.

[0042] The acoustic mode decomposition module is used to perform single-tone acoustic mode decomposition and continuous broadband acoustic mode decomposition, transforming the sound field information from the frequency domain to the wavenumber domain, and detecting whether the synchronous vibration characteristics of the fan blades appear in the acoustic mode spectrum and wavenumber spectrum.

[0043] The synchronous vibration calculation module is used to determine whether the fan blades are vibrating synchronously and outputs the vibration pitch diameter and frequency of the fan blade disk.

[0044] A computer storage medium including computer instructions that, when run on a computer, cause the computer to perform the method.

[0045] An electronic device, the electronic device comprising:

[0046] Memory, processor, and computer programs stored in memory and executable on the processor, wherein,

[0047] The processor implements the method when executing the program.

[0048] Compared with existing technologies, this invention has the following advantages: The invention utilizes acoustic information to identify the synchronous vibration of fan blades, which is more sensitive and adaptable than traditional methods that use vibration signals and interstage pressure signals. It obtains the synchronous vibration characteristics of the fan blades in the frequency domain through Fast Fourier Transform, resulting in clear features and a simple process. It also obtains the synchronous vibration characteristics of the fan blades in the wavenumber domain through Spatial Fourier Transform, offering high sensitivity and adaptability to different speeds. Even with limited testing resources, a non-uniform layout scheme can be used to extract the acoustic signature features of synchronous vibration of aero-engine fan blades. Abnormal components in the spectrum, modal spectrum, and wave spectrum of the acoustic signal are defined as the acoustic signature features of synchronous vibration of the fan blades. Attached Figure Description

[0049] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0050] In the attached diagram:

[0051] Figure 1 This is the flowchart of this disclosure;

[0052] Figure 2This is a schematic diagram of a detection device for a fan blade synchronous vibration identification method based on acoustic signature features, provided in one embodiment of this disclosure.

[0053] Figures 3(a) to 3(b) Figure 3(a) shows the spectrum of the fan in normal operation and the blades in synchronous vibration, according to an embodiment of this disclosure. Figure 3(b) shows the spectrum of the fan in normal operation and the fan blades in synchronous vibration.

[0054] Figures 4(a) to 4(b) This is an embodiment of the present disclosure, showing the acoustic modal spectrum of a fan blade at the passing frequency during normal operation and the synchronous vibration state of the blade; wherein, Figure 4(a) is the acoustic modal spectrum of the blade at the passing frequency during normal operation of the fan, and Figure 4(b) is the acoustic modal spectrum of the blade at the passing frequency during synchronous vibration of the fan blade;

[0055] Figures 5(a) to 5(b) Figure 5(a) shows the spectrum of synchronous blade vibration under normal fan operation and under subsonic fan operation, provided in one embodiment of this disclosure. Figure 5(b) shows the spectrum of synchronous blade vibration when no synchronous blade vibration occurs, and Figure 5(a) shows the spectrum of synchronous blade vibration when the fan is under subsonic operation.

[0056] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0057] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0058] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0059] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0060] like Figures 1 to 5(b) As shown, the acoustic identification method for synchronous vibration of aero-engine fan blades includes the following steps:

[0061] In the first step (S1), the microphone array layout is determined by the parameters of the fan model, wherein the number of fan rotor blades is used as a reference. With the number of stator blades Calculate the static-to-static interference mode order of fan single-tone noise Based on the order of the static interference mode The maximum modal order determines the acoustic modal monitoring range and the number of microphones. and the circumferential mounting angle of the microphone ;

[0062] In the second step (S2), the number of microphones and the installation angle of the microphone Construct a microphone array; synchronously acquire the multi-channel sound pressure time-domain signals of the fan using the microphone array; construct a time-domain signal matrix by arranging the multi-channel sound pressure time-domain signals in sequence;

[0063] In the third step (S3), the fast Fourier transform algorithm is used to perform spectrum analysis on the sound pressure time domain signal to obtain the spectrum of the sound pressure time domain signal of each channel. By monitoring the spectrum, it is found that the increase in the frequency amplitude of the fan blades exceeds the first predetermined value and there are broadband noise components with a frequency band distribution greater than the predetermined range. If none of these exist, it means that the fan is in normal working condition. If they exist, proceed to the fourth step (S4).

[0064] In the fourth step (S4), the acoustic mode spectrum at the blade passage frequency is obtained by the single-frequency acoustic mode decomposition method. By monitoring whether the synchronous vibration characteristics of the fan blade appear in the spectrum, it is determined whether the fan blade is synchronously vibrating. When the fan blade is synchronously vibrating, the change in the amplitude of its static interference mode exceeds the second predetermined value in the acoustic mode spectrum at the blade passage frequency.

[0065] In the fifth step (S5), the spectrum of the sound pressure time domain signal is obtained by continuous broadband acoustic mode decomposition. The horizontal axis of the spectrum represents the frequency analysis range, the vertical axis represents the acoustic mode monitoring range, and the color depth represents the amplitude. The darker the color, the larger the amplitude. By monitoring whether the synchronous vibration characteristics of the fan blades appear in the spectrum, when the fan blades vibrate synchronously, the amplitude of the broadband noise mode in the spectrum increases beyond the third predetermined value, and the change in the amplitude of the static interference mode at the blade passing frequency exceeds the second predetermined value and propagates to the surrounding frequencies, forming a bright cross band phenomenon with the sound source at the blade passing frequency.

[0066] In the sixth step (S6), when the fan blades vibrate synchronously, the acoustic modes of the blades through frequency and its harmonics reflect the vibration of the blades. At this time, the vibration frequency of the blade disk is coupled with the blade through frequency. Based on the frequency coupling relationship, the vibration pitch diameter and frequency of the fan blade disk are output through the acoustic mode of the blade through frequency.

[0067] In a preferred embodiment of the acoustic identification method for synchronous vibration of aero-engine fan blades, in the first step (S1), the order of the fan's rotation-to-stationary interference modes is determined. for, ,in, This indicates the order of pressure pulsations caused by unsteady aerodynamic forces resulting from the interference of the fan's rotation and stationary motion. Represents an integer, determining the number of microphones in the microphone array. And in the microphone installation angle,

[0068] When using a uniform acoustic array layout, calculate the number of sensors required for modal detection based on the Nyquist sampling theorem. Its order with the static interference mode The relationship is: When using a non-uniform acoustic array layout with few measurement points, in a virtually uniform layout... Randomly selected from the positions Install sensors at various locations. ;

[0069] When using a uniform acoustic array layout scheme, A circular acoustic array is composed of several sensors, with a spacing between the sensors being [missing information]. The microphone is installed at an angle of 100°. ,in , , And so on; when using a non-uniform acoustic array layout with few measurement points, the microphone installation angle... Random selection .

[0070] In a preferred embodiment of the method for acoustic identification of synchronous vibration of aero-engine fan blades, the second step (S2) includes the following steps:

[0071] S201. The sound pressure signal of the fan is measured using a ring acoustic array. The measured sound pressure time-domain signal is: The length of the time-domain signal sequence measured by a single microphone is [length missing]. subscript These are microphones positioned at corresponding installation angles;

[0072] S202. Based on the sound pressure time-domain signals measured by the microphones at different installation angles, construct a time-domain signal matrix. , of which elements express The first measurement obtained by the microphone at the corresponding installation angle position Signal,

[0073] When using a uniform acoustic array layout, the time-domain signal matrix The size is When using a non-uniform acoustic array layout with few measurement points, the time-domain signal matrix... The size is .

[0074] In a preferred embodiment of the acoustic identification method for synchronous vibration of aero-engine fan blades, the third step (S3) includes:

[0075] S301, Regarding the time-domain signal matrix The frequency domain matrix is ​​obtained by performing a Fourier transform on each column. , of which elements express The signal measured by the microphone at the corresponding installation angle position is Amplitude at frequency, The length is According to the Nyquist sampling theorem, ,

[0076] In a uniform acoustic array layout, the frequency domain matrix The size is In a non-uniform acoustic array layout, the frequency domain matrix The size is ,

[0077] S302, According to the frequency domain matrix Plot the spectrum of signals measured by sensors at different installation angles, and the frequency of the fan blades passing through them. The amplitude increases beyond the first predetermined value and broadband noise components with a frequency band distribution greater than the predetermined range appear.

[0078] In a preferred embodiment of the acoustic identification method for synchronous vibration of aero-engine fan blades, the fourth step (S4) includes:

[0079] S401, When using a uniform acoustic array layout, the subscript... The microphone at the corresponding installation angle position at the predetermined frequency Frequency domain signal at It can be viewed as a linear superposition of different circumferential acoustic modes, i.e. Construct the transformation matrix The format is as follows:

[0080] ,

[0081] When using a non-uniform acoustic array layout with few measurement points, an observation matrix is ​​constructed based on randomly selected sensor installation angles. Observation matrix Size is ,

[0082] ,

[0083] S402. When using a uniform acoustic array layout, the frequency domain matrix... Perform a spatial Fourier transform to obtain the wavenumber domain matrix. , ,in Frequency domain matrix The transpose of the matrix, ,in Represents the transformation matrix The false rebellion,

[0084] When using a non-uniform acoustic array layout with few measurement points, the compressed sensing model is: sparse dictionary Composed of orthogonal Fourier transform bases, For the sensing matrix, sparsely reconstruct the wavenumber domain matrix based on the compressed sensing model. ;

[0085] S403. Based on the obtained wavenumber domain matrix Plot the acoustic modal spectrum; when the fan blades vibrate synchronously, the excitation frequency of the sound source is coupled with the vibration frequency of the blades, and the change in the amplitude of the static interference mode in the acoustic modal spectrum of the blade passing frequency exceeds the second predetermined value.

[0086] In a preferred embodiment of the acoustic identification method for synchronous vibration of aero-engine fan blades, the fifth step (S5) includes:

[0087] S501, the wavenumber domain matrix Extending to the full frequency domain, wavenumber domain matrix Size expansion to , of which elements Indicates frequency First The amplitude of the step sound mode,

[0088] ,

[0089] S502, According to the wavenumber domain matrix A spectrum diagram is plotted, and the amplitude increase of the broadband noise mode in the spectrum diagram exceeds the third predetermined value. The change of the amplitude of the static interference mode at the blade passage frequency exceeds the second predetermined value and propagates to the surrounding frequencies. This combination with the sound source at the blade passage frequency forms a cross-shaped bright band phenomenon, which is defined as the acoustic signature of synchronous vibration of the fan blade. Based on this, it is determined whether the fan blade is vibrating synchronously.

[0090] In a preferred embodiment of the acoustic identification method for synchronous vibration of aero-engine fan blades, in the sixth step (S6), when the fan blades vibrate synchronously, the vibration pitch diameter and frequency of the fan blade disk are output.

[0091] S601. When the fan blades vibrate synchronously, the vibration frequency of the blade disk is coupled with that of the blades through frequency coupling. The acoustic mode order is equal to the number of blade pitch diameters. At this time, the excitation frequency of the sound source is... With blade vibration frequency satisfaction,

[0092] In the formula, Indicates the rotor frequency.

[0093] S602. Calculate and output the blade vibration frequency and vibration pitch diameter based on the excitation frequency and modal order of the sound source in the spectral diagram.

[0094] A fan blade synchronous vibration identification system implementing the method includes:

[0095] The sound field measurement module includes a sound array measurement submodule and a data acquisition submodule, which are used to measure the sound field information propagated in the pipe to the sound array installation location when the fan is working;

[0096] The spectrum analysis module is used to transform the time-domain sound field signal at the location of the acoustic array to the frequency domain to detect whether there are abnormal changes in the frequency of the blades passing through and abnormal frequency components.

[0097] The acoustic mode decomposition module is used to perform single-tone acoustic mode decomposition and continuous broadband acoustic mode decomposition, transforming the sound field information from the frequency domain to the wavenumber domain, and detecting whether the synchronous vibration characteristics of the fan blades appear in the acoustic mode spectrum and wavenumber spectrum.

[0098] The synchronous vibration calculation module is used to determine whether the fan blades are vibrating synchronously and outputs the vibration pitch diameter and frequency of the fan blade disk.

[0099] A computer storage medium including computer instructions that, when run on a computer, cause the computer to perform the method.

[0100] An electronic device, the electronic device comprising:

[0101] Memory, processor, and computer programs stored in memory and executable on the processor, wherein,

[0102] The processor implements the method when executing the program.

[0103] In one embodiment, the first predetermined value is 1.5 times the sound pressure amplitude under normal operating conditions, and the predetermined range is 1.5 times the maximum sound pressure amplitude within the frequency band under normal operating conditions.

[0104] The second predetermined value is 1.5 times the modal amplitude under normal operating conditions, and the third predetermined value is 1.5 times the maximum modal amplitude within the frequency band under normal operating conditions.

[0105] In one embodiment, the fan is an aircraft engine fan.

[0106] In one embodiment, the sound field information is measured by a microphone array to obtain a time-domain signal matrix. , of which elements express The first angular position measured by the microphone Signal.

[0107] In one embodiment, Figure 1 This is a flowchart of the synchronous vibration identification method for aero-engine fan blades based on acoustic signature features, which is the result of this invention. The method calculates the order of the transition-to-stationary interference mode in the single-tone noise of the aero-engine using a fan model. Based on the maximum order of the mode of interest, it determines the acoustic mode monitoring range, the number of microphones, the axial mounting position, and the circumferential mounting angle. A fast Fourier transform is then performed on the acoustic array signal to obtain the frequency domain signal matrix. The system outputs a spectrum diagram to observe whether abnormal broadband noise components, blade passage frequencies, and their harmonic amplitudes increase significantly. Based on the constructed transformation matrix, it obtains the acoustic mode spectrum of the blade passage frequency using single-frequency acoustic mode decomposition, observing whether the amplitude of the static-to-static interference mode increases significantly. It then obtains the spectrum diagram of the array signal through continuous broadband acoustic mode decomposition, observing whether the amplitude of the broadband noise mode increases significantly, and whether the static-to-static interference mode at the blade passage frequency is significantly enhanced and propagates to surrounding frequencies, combining with the blade passage frequency sound source to form a distinct bright cross band. If the fan blades vibrate synchronously, the system outputs the blade disk vibration pitch diameter and frequency. The specific steps are as follows:

[0108] Assuming the number of rotor blades of an aircraft engine fan With the number of stator blades According to the formula for calculating the modal order of fan single-tone noise... , usually take The order of the pressure pulsation caused by the unsteady aerodynamic forces resulting from the fan's rotation and stationary interference is 1. In this case, we take... Representing the first-order acoustic mode, the calculation yields... ,Pick Representing the second-order acoustic mode, the calculation yields... According to the Nyquist sampling theorem: The required number of sensors Therefore, the number of sensors is selected as follows: ;

[0109] Several sensors are arranged in a uniform circular acoustic array, with a sampling frequency set to 20000 Hz and a spacing between the sensors of [missing information]. The microphone is installed at an angle of 100°. ,in , , And so on;

[0110] The sound pressure signal of an aircraft engine fan was measured using a circular acoustic array, with each channel measured as follows: The constructed time-domain signal matrix consists of 10 data points. The size is The time-domain signal matrix measured for the circular acoustic array Perform a Fourier transform on each column to transform the signal from the time domain to the frequency domain, obtaining the frequency domain matrix. Frequency domain matrix The size is According to the Nyquist sampling theorem, ;

[0111] Based on the obtained frequency domain matrix Plot the spectrum of signals measured by the sensor at different angles, with the installation position as the baseline. Taking the microphone signal as an example, Figure 3(a) shows the main component of the spectrum when the fan blades do not vibrate synchronously, which is the frequency of the blades. Furthermore, its amplitude is 195 Pa. Figure 3(b) shows the frequency of the fan blades when they vibrate synchronously. The amplitude increased to 281 Pa, and broadband noise components with a large frequency band distribution appeared;

[0112] Elements in the frequency domain matrix Indicates subscript A microphone at a corresponding angular position at a specific frequency The acoustic signal at that location can be considered as a linear superposition of different circumferential acoustic modes, i.e. Therefore, the constructed transformation matrix Size is .

[0113] Single-frequency acoustic mode decomposition at the abnormal peak frequency yields a value of... wavenumber domain matrix And plot the acoustic modal spectrum. Figure 4(a) shows the amplitude of the static-to-stationary interference mode when the fan blades do not vibrate synchronously. Figure 4(b) shows the amplitude of the static-rotation interference mode when the fan blades vibrate synchronously. The amplitude increased to ;

[0114] For frequency domain matrix Performing continuous broadband acoustic mode decomposition yields a value of wavenumber domain matrix wavenumber domain matrix medium elements Indicates frequency First The amplitude of the graded acoustic mode. Based on the obtained wavenumber domain matrix. Spectrum diagrams were plotted. Figure 5(a) shows a lighter overall color in the spectrum when the fan blades are not vibrating synchronously, with the main sound source being the sound source at the blade passage frequency. Figure 5(b) shows a significantly darker overall color in the spectrum when the fan blades are vibrating synchronously, indicating a significant increase in the amplitude of the broadband noise mode. The static interference mode at the blade passage frequency shows a significant enhancement and propagates to surrounding frequencies, forming a distinct bright cross band phenomenon when combined with the sound source at the blade passage frequency.

[0115] It was determined that the fan blades were vibrating synchronously at this time. Based on the excitation frequency and modal order of the sound source in the spectral diagram, the vibration pitch diameter of the fan blade disk was calculated as follows: The vibration frequency is .

[0116] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for acoustic identification of synchronous vibration of aero-engine fan blades, characterized in that, Includes the following steps: In the first step (S1), the microphone array layout is determined by the parameters of the fan model; In the second step (S2), the number of microphones... and the installation angle of the microphone Construct a microphone array; synchronously acquire the multi-channel sound pressure time-domain signals of the fan using the microphone array; construct a time-domain signal matrix by arranging the multi-channel sound pressure time-domain signals in sequence; In the third step (S3), the Fast Fourier Transform algorithm is used to perform spectral analysis on the sound pressure time-domain signal to obtain the spectrum of the sound pressure time-domain signal of each channel. By monitoring the spectrum, it is found whether the increase in the frequency amplitude of the fan blades exceeds the first predetermined value and whether there are broadband noise components with a frequency band distribution greater than the predetermined range. If none of these exist, it means that the fan is in normal working condition. If there are broadband noise components with a frequency band distribution greater than the predetermined range and the increase in the frequency amplitude of the fan blades exceeds the first predetermined value, then proceed to the fourth step (S4). In the fourth step (S4), the acoustic mode spectrum at the blade passage frequency is obtained by the single-frequency acoustic mode decomposition method. By monitoring whether the synchronous vibration characteristics of the fan blade appear in the spectrum, it is determined whether the fan blade is synchronously vibrating. When the fan blade is synchronously vibrating, the change in the amplitude of its static interference mode exceeds the second predetermined value in the acoustic mode spectrum at the blade passage frequency. In the fifth step (S5), the spectrum of the sound pressure time domain signal is obtained by continuous broadband acoustic mode decomposition. The horizontal axis of the spectrum represents the frequency analysis range, the vertical axis represents the acoustic mode monitoring range, and the color depth represents the amplitude. The darker the color, the larger the amplitude. By monitoring whether the synchronous vibration characteristics of the fan blades appear in the spectrum, when the fan blades vibrate synchronously, the amplitude of the broadband noise mode in the spectrum increases beyond the third predetermined value, and the change in the amplitude of the static interference mode at the blade passing frequency exceeds the second predetermined value and propagates to the surrounding frequencies, forming a bright cross band phenomenon with the sound source at the blade passing frequency. In the sixth step (S6), when the fan blades vibrate synchronously, the acoustic modes of the blades through frequency and its harmonics reflect the vibration of the blades. At this time, the vibration frequency of the blade disk is coupled with the blade through frequency. Based on the frequency coupling relationship, the vibration pitch diameter and frequency of the fan blade disk are output through the acoustic mode of the blade through frequency.

2. The method for acoustic identification of synchronous vibration of aero-engine fan blades according to claim 1, characterized in that, The second step (S2) includes the following steps: S201. The sound pressure signal of the fan is measured using a ring acoustic array. The measured sound pressure time-domain signal is: The length of the time-domain signal sequence measured by a single microphone is [length missing]. subscript These are microphones positioned at corresponding installation angles; S202. Based on the sound pressure time-domain signals measured by the microphones at different installation angles, construct a time-domain signal matrix. , of which elements express The first measurement obtained by the microphone at the corresponding installation angle position Signal, When using a uniform acoustic array layout, the time-domain signal matrix The size is When using a non-uniform acoustic array layout with few measurement points, the time-domain signal matrix... The size is .

3. The method for acoustic identification of synchronous vibration of aero-engine fan blades according to claim 2, characterized in that, The third step (S3) includes, S301, Regarding the time-domain signal matrix The frequency domain matrix is ​​obtained by performing a Fourier transform on each column. , of which elements express The signal measured by the microphone at the corresponding installation angle position is Amplitude at frequency, The length is According to the Nyquist sampling theorem, , In a uniform acoustic array layout, the frequency domain matrix The size is In a non-uniform acoustic array layout, the frequency domain matrix The size is , S302, According to the frequency domain matrix Plot the spectrum of signals measured by sensors at different installation angles, and the frequency of the fan blades passing through them. The amplitude increases beyond the first predetermined value and broadband noise components with a frequency band distribution greater than the predetermined range appear.

4. The method for acoustic identification of synchronous vibration of aero-engine fan blades according to claim 3, characterized in that, The fourth step (S4) includes, S401, When using a uniform acoustic array layout, the subscript... The microphone at the corresponding installation angle position at the predetermined frequency Frequency domain signal at It can be viewed as a linear superposition of different circumferential acoustic modes, i.e. Construct the transformation matrix The format is as follows: ， When using a non-uniform acoustic array layout with few measurement points, an observation matrix is ​​constructed based on randomly selected sensor installation angles. Observation matrix Size is , ， S402. When using a uniform acoustic array layout, the frequency domain matrix... Perform a spatial Fourier transform to obtain the wavenumber domain matrix. , ,in Frequency domain matrix The transpose of the matrix, ,in Represents the transformation matrix The false rebellion, When using a non-uniform acoustic array layout with few measurement points, the compressed sensing model is: sparse dictionary Composed of orthogonal Fourier transform bases, For the sensing matrix, sparsely reconstruct the wavenumber domain matrix based on the compressed sensing model. ; S403. Based on the obtained wavenumber domain matrix Draw the acoustic modal spectrum; When the fan blades vibrate synchronously, the excitation frequency of the sound source is coupled with the vibration frequency of the blades. As a result, the amplitude of the static interference mode changes beyond the second predetermined value in the acoustic modal spectrum of the blades passing through the frequency.

5. The method for acoustic identification of synchronous vibration of aero-engine fan blades according to claim 4, characterized in that, The fifth step (S5) includes, S501, the wavenumber domain matrix Extending to the full frequency domain, wavenumber domain matrix Size expansion to , of which elements Indicates frequency First The amplitude of the step sound mode, ， S502, According to the wavenumber domain matrix A spectrum diagram is plotted, and the amplitude increase of the broadband noise mode in the spectrum diagram exceeds the third predetermined value. The change of the amplitude of the static interference mode at the blade passage frequency exceeds the second predetermined value and propagates to the surrounding frequencies. This combination with the sound source at the blade passage frequency forms a cross-shaped bright band phenomenon, which is defined as the acoustic signature of synchronous vibration of the fan blade. Based on this, it is determined whether the fan blade is vibrating synchronously.

6. The method for acoustic identification of synchronous vibration of aero-engine fan blades according to claim 1, characterized in that, In the sixth step (S6), when the fan blades vibrate synchronously, the fan blade disk vibration pitch diameter and frequency are output. S601. When the fan blades vibrate synchronously, the vibration frequency of the blade disk is coupled with that of the blades through frequency coupling. The acoustic mode order is equal to the number of blade pitch diameters. At this time, the excitation frequency of the sound source is... With blade vibration frequency satisfaction, In the formula, Indicates the rotor frequency. S602. Calculate and output the blade vibration frequency and vibration pitch diameter based on the excitation frequency and modal order of the sound source in the spectral diagram.

7. A fan blade synchronous vibration identification system implementing the method of any one of claims 1-6, characterized in that, It includes: The sound field measurement module includes a sound array measurement submodule and a data acquisition submodule, which are used to measure the sound field information propagated in the pipe to the sound array installation location when the fan is working; The spectrum analysis module is used to transform the time-domain sound field signal at the location of the acoustic array to the frequency domain to detect whether there are abnormal changes in the frequency of the blades passing through and abnormal frequency components. The acoustic mode decomposition module is used to perform single-tone acoustic mode decomposition and continuous broadband acoustic mode decomposition, transforming the sound field information from the frequency domain to the wavenumber domain, and detecting whether the synchronous vibration characteristics of the fan blades appear in the acoustic mode spectrum and wavenumber spectrum. The synchronous vibration calculation module is used to determine whether the fan blades are vibrating synchronously and outputs the vibration pitch diameter and frequency of the fan blade disk.

8. A computer storage medium, characterized in that, The storage medium includes computer instructions that, when executed on a computer, cause the computer to perform the method as described in any one of claims 1-6.

9. An electronic device, characterized in that, The electronic device includes: Memory, processor, and computer programs stored in memory and executable on the processor, wherein, When the processor executes the program, it implements the method as described in any one of claims 1-6.

Images