Aeroengine Circumferential Acoustic Mode Measurement Method Based on Lp-Norm Regularization

Abstract

An aero-engine circumferential acoustic mode measurement method based on Lp-norm regularization is disclosed. In the method, the highest order m of the circumferential dominant acoustic mode of the fan tonal noise is calculated through the number B of fan rotor blades and the number V of stator blades of the aero-engine. max , based on the highest order m max , determine the number of microphones required under Nyquist sampling arranged circumferentially on the aero-engine fan casing. Randomly select the circumferential installation positions and angles of a predetermined number of installations at the pipeline inlet to install microphones to form a microphone array to collect sound pressure signals. Perform a fast Fourier transform on the sound pressure signals measured by the microphone array, and take the complex amplitude of the sound pressure signal at the blade passing frequency as the observation vector; based on the installation positions and angles and the highest order m max , construct an orthogonal Fourier sensing matrix, establish an Lp-norm non-convex regularized compressive sensing model under non-uniform few measurement points, and use the generalized threshold shrinkage algorithm to obtain the circumferential acoustic mode amplitude of the aero-engine fan tonal noise.

Description

Technical Field

[0001] The present invention relates to the technical field of aero - engine noise testing, and particularly to a method for measuring the circumferential acoustic mode of an aero - engine based on Lp - norm regularization. Background Technique

[0002] With the wide application of high - bypass - ratio turbofan aero - engines, fan noise has gradually become the dominant part of aero - engine noise, attracting wide social attention. Fan noise is divided into tonal noise at each blade - passing frequency and broadband noise distributed in the entire frequency domain according to its formation method. Among them, the intensity of tonal noise is significantly greater than that of other noise components and is the main component of aero - engine fan noise. To conduct refined noise reduction design for aero - engine fans, it is necessary to deeply understand the generation and propagation modes of tonal noise acoustic modes, and the identification and decomposition of the acoustic mode structure of the duct play an important guiding role in this regard.

[0003] Using an annular microphone array to decompose the circumferential acoustic mode of aero - engine fan noise is the most commonly used method in the field of aero - engine fan noise acoustic mode decomposition. The classic uniformly - arranged microphone array has disadvantages such as high test cost and poor anti - failure ability, making it difficult to be applied to the measurement of the acoustic mode of a real aero - engine duct.

[0004] The above information disclosed in the background - technique section is only used to enhance the understanding of the background of the present invention, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for measuring the circumferential acoustic mode of an aero - engine based on Lp - norm regularization. By reconstructing the circumferential acoustic mode of fan noise through the generalized threshold shrinkage algorithm, the order identification and amplitude reconstruction of the circumferential dominant acoustic mode are realized, solving the problems of high test cost and poor anti - failure ability of the traditional uniformly - arranged microphone array. The identification of the dominant acoustic mode of aero - engine fan noise can be completed with far fewer microphone arrays than the classical method.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A method for measuring the circumferential acoustic mode of an aero - engine based on Lp - norm regularization of the present invention includes:

[0008] In the first step, calculate the highest order m of the circumferential dominant acoustic mode of fan tonal noise through the number B of rotor blades and the number V of stator blades of the aero - engine fan, max , based on the highest order m max determine the number of microphones required for Nyquist sampling arranged circumferentially on the aero - engine fan casing,

[0009] In the second step, a predetermined number of circumferential installation positions and angles are randomly selected at the pipeline inlet to install microphones to form a microphone array for collecting sound pressure signals. The predetermined number of installations is a predetermined ratio of the number of microphones required under Nyquist sampling. The fast Fourier transform is performed on the sound pressure signals measured by the microphone array, and the complex amplitude of the sound pressure signal at the blade passing frequency is taken as the observation vector;

[0010] In the third step, based on the installation positions and angles and the highest order m max Construct an orthogonal Fourier sensing matrix and establish an Lp-norm non-convex regularized compressive sensing model under non-uniform few measurement points.

[0011] In the fourth step, based on the Lp-norm non-convex regularized compressive sensing model, the generalized threshold shrinkage algorithm is used to obtain the circumferential sound mode amplitude of the aeroengine fan tonal noise.

[0012] In the described method for measuring the circumferential sound mode of an aeroengine based on Lp-norm regularization, in the first step, the modal order of the circumferential dominant sound mode of the fan tonal noise is m = kB ± ζV, where k represents the order of the pressure pulsation caused by the unsteady aerodynamic force caused by the fan rotor-stator interference, and ζ represents a non-negative integer; the measurable number is determined to be in the modal range {-m max ,..., -1, 0, 1,... m max}, the number of measurable modes M = 2m max + 1, and the number of microphones required K is K = 2m max .

[0013] In the described method for measuring the circumferential sound mode of an aeroengine based on Lp-norm regularization, in the second step, the number of microphones randomly installed on the casing wall in the circumferential direction is N, where N is a predetermined ratio of the number of microphones required, and the installation angles Θ = [θ1, θ2,... θ N T ; the fast Fourier transform is performed on the sound pressure signals measured by N non-uniformly distributed microphones: y f = FFT(y t ), where y t represents the time-domain sound pressure signal of the fan noise measured by the non-uniform microphone array, FFT(·) represents the discrete Fourier transform, and y f = [y1(ω), y2(ω),... y N (ω)] T represents the frequency-domain signals of N non-uniformly distributed microphones; based on the frequency-domain signals of the N non-uniformly distributed microphones, the complex amplitude at the fan rotor blade passing frequency f BPF = B × f Ω is selected to construct the observation vector y = [y1(f BPF ​),y2(f BPF ),...y N (f BPF )] T ,f Ω is the rotational frequency of the rotor shaft.

[0014] In the described method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization, in the third step, construct an orthogonal Fourier sensing matrix where θ k is the installation angle of the k-th sensor, and m j is the modal order of the j-th circumferential mode wave; based on the orthogonal Fourier sensing matrix W N×M and the observation vector y, establish an Lp-norm non-convex regularized compressive sensing model under non-uniform few measurement points:

[0015]

[0016] where λ represents the regularization parameter, p is the sparsity coefficient, is the estimated circumferential acoustic mode amplitude.

[0017] In the described method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization, in the fourth step, solve the Lp-norm non-convex regularized compressive sensing model through the generalized threshold shrinkage algorithm, where,

[0018] Step S401: Input the orthogonal Fourier sensing matrix W and the observation vector y; set the maximum number of iterations, the initial iteration value x (0) =(x i ) T =0, the iteration step size ε = ||W|| -2 , the regularization parameter λ = 0.2×||W|| 2 , and the sparsity coefficient p = 0.6;

[0019] Step S402: Set the threshold T = (2λε(1 - p)) 1 / (2-p) +λεp(2λε(1 - p)) (p-1) / (2-p) ;

[0020] Step S403: Iterate z = x - εW T (Wx - y);

[0021] Step S404: Traverse the elements of the vector z = (z i ) T , if then execute Step S405 and skip Step S406, otherwise execute Step S406;

[0022] Step S405: Continuously iterate 3 times x i = sgn(zi )(|z i |-λεp(x i ) p-1 );

[0023] Step S406. Let x i = 0;

[0024] Step S407. Check whether the maximum number of iterations L is reached. If so, output the circumferential acoustic mode amplitude x of the aeroengine fan tonal noise; otherwise, return to Step S403.

[0025] In the described method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization, the predetermined ratio is 50%.

[0026] In the above technical solution, based on the sparse characteristic of the fan noise duct acoustic mode in the wavenumber domain, the present invention establishes a compressive sensing model based on non-convex regularization of the Lp-norm; solves the model through the generalized threshold shrinkage algorithm to realize the identification of the circumferential dominant acoustic mode of the tonal noise. Compared with the traditional method of decomposing the circumferential acoustic mode of the fan noise using an all-microphone array, the method provided by the present invention can realize the accurate identification of the order of the circumferential dominant acoustic mode of the duct noise and the accurate reconstruction of the amplitude with fewer measurement points; compared with the classical L1-norm regularized compressive sensing method, it improves the identification accuracy of the modal amplitude, reduces the number of microphones, and lowers the test cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a schematic flowchart of an embodiment of the method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization;

[0029] Figure 2 It is a schematic diagram of the multi-stage aeroengine fan structure of an embodiment of the method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization;

[0030] Figure 3 It is a comparison diagram of the results of solving the modal amplitude by the method of the present invention and the classical L1-norm method in an embodiment of the method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be combined with the attached drawings in the embodiments of the present invention Figures 1 to 3, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] It should be noted that like reference numerals and letters denote like items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0035] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0036] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0038] In a method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization,

[0039] In the first step S1, the highest order m of the circumferential dominant acoustic mode of the fan tonal noise is calculated through the number B of fan rotor blades and the number V of stator blades of the aeroengine max , based on the highest order m max to determine the number of microphones required under Nyquist sampling arranged circumferentially along the fan casing of the aeroengine,

[0040] In the second step S2, at the inlet of the duct, a predetermined number of circumferential installation positions and angles are randomly selected to install microphones to form a microphone array for collecting sound pressure signals. The predetermined installation number is a predetermined proportion of the number of microphones required under Nyquist sampling. The fast Fourier transform is performed on the sound pressure signals measured by the microphone array, and the complex amplitude of the sound pressure signal at the blade passing frequency is taken as the observation vector;

[0041] In the third step S3, based on the installation positions and angles and the highest order m max an orthogonal Fourier sensing matrix is constructed to establish an Lp-norm non-convex regularized compressive sensing model under non-uniform few measurement points,

[0042] In the fourth step S4, based on the Lp-norm non-convex regularized compressive sensing model, the generalized threshold shrinkage algorithm is used to obtain the circumferential acoustic mode amplitude of the aeroengine fan tonal noise.

[0043] Aiming at the problems of the classical acoustic mode decomposition method, based on the sparse prior of the circumferential acoustic mode of the tonal noise in the wavenumber domain, an Lp-norm non-convex regularized compressive sensing model is constructed to establish a circumferential acoustic mode method under few measurement points and non-uniform microphone layouts. Based on the generalized threshold shrinkage algorithm, the circumferential acoustic mode amplitude of the aeroengine fan tonal noise is solved, realizing the order identification and accurate reconstruction of the amplitude of the dominant acoustic mode of the aeroengine fan noise by a few microphones.

[0044] In the preferred implementation of the described method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization, in the first step S1, the modal order of the circumferential dominant acoustic mode of the fan tonal noise is m = kB ± ζV, where k represents the order of the pressure pulsation caused by the unsteady aerodynamic force resulting from the fan rotor-stator interference, and ζ represents a non-negative integer; determine the measurable number as the modal range is {-m max ,..., -1, 0, 1,...m max}, the number of measurable modes M = 2m max + 1, and the required number of microphones K is K = 2m max .

[0045] In the preferred implementation of the described method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization, in the second step S2, randomly install N microphones on the casing wall in the circumferential direction, where N is a predetermined proportion of the required number of microphones, and the installation angles Θ = [θ1, θ2,...θ N T ; perform a fast Fourier transform on the sound pressure signals measured by the N non-uniformly distributed microphones: y f = FFT(y t ), where y t represents the time-domain sound pressure signal of the fan noise measured by the non-uniform microphone array, FFT(·) represents the discrete Fourier transform, and y f = [y1(ω), y2(ω),...y N (ω)] T represents the frequency-domain signals of the N non-uniformly distributed microphones; based on the frequency-domain signals of the N non-uniformly distributed microphones, select the complex amplitude at the fan rotor blade passing frequency f BPF = B × f Ω to construct the observation vector y = [y1(f BPF ), y2(f BPF ),...y N (f BPF )] T , and f Ω is the rotational frequency of the rotor shaft.

[0046] In the preferred implementation of the described method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization, in the third step S3, construct the orthogonal Fourier sensing matrix where θ k is the installation angle of the kth sensor, and m j is the modal order of the jth circumferential modal wave; based on the orthogonal Fourier sensing matrix W N×M and the observation vector y, establish the Lp-norm non-convex regularized compressive sensing model under non-uniform few measurement points: ​

[0047]

[0048] Among them, λ represents the regularization parameter, and p is the sparsity coefficient. is the estimated circumferential acoustic mode amplitude.

[0049] In the preferred embodiment of the method for measuring the circumferential acoustic mode of an aero-engine based on Lp-norm regularization, in the fourth step S4, the Lp-norm non-convex regularized compressive sensing model is solved by the generalized thresholding shrinkage algorithm, where

[0050] Step S401: Input the orthogonal Fourier sensing matrix W and the observation vector y; set the maximum number of iterations, and the initial iteration value x (0) =(x i ) T =0, the iteration step size ε = ||W|| -2 , the regularization parameter λ = 0.2×||W|| 2 , and the sparsity coefficient p = 0.6;

[0051] Step S402: Set the threshold T = (2λε(1 - p)) 1 / (2-p) +λεp(2λε(1 - p)) (p-1) / (2-p) ;

[0052] Step S403: Iterate z = x - εW T (Wx - y);

[0053] Step S404: Traverse the elements of the vector z = (z i ) T . If then execute step S405 and skip step S406, otherwise execute step S406;

[0054] Step S405: Continuously iterate 3 times x i = sgn(z i )(|z i |-λεp(x i ) p-1 );

[0055] Step S406: Let x i = 0;

[0056] Step S407: Check whether the maximum number of iterations L is reached. If it is reached, output the circumferential acoustic mode amplitude x of the aero-engine fan tonal noise, otherwise return to step S403.

[0057] In the preferred embodiment of the method for measuring the circumferential acoustic mode of an aero-engine based on Lp-norm regularization, the predetermined ratio is 50%.

[0058] In one embodiment, the method for measuring the circumferential acoustic mode of an aeroengine based on Lp-norm regularization includes the following steps:

[0059] In the first step, calculate the order of the circumferential dominant acoustic mode of the aeroengine fan tonal noise through the number of blades of the aeroengine fan rotor and stator, and determine the number of microphones required for Nyquist sampling arranged circumferentially on the aeroengine fan casing based on the highest order of the circumferential dominant acoustic mode of the tonal noise, that is, twice the highest order;

[0060] In the second step, randomly select a small number of circumferential positions at the pipeline inlet to install microphones. The installation quantity is about 50% of the number of microphones required for Nyquist sampling determined in the first step. Perform a fast Fourier transform on the sound pressure signals measured by the microphone array, and take the complex amplitude of the sound pressure signal at the blade passing frequency as the observation vector;

[0061] In the third step, based on the microphone installation position angles determined in the second step and the highest measured modal order determined in the first step, construct an orthogonal Fourier sensing matrix and establish an Lp-norm non-convex regularized compressive sensing model under non-uniform few measurement points.

[0062] In the fourth step, for the model in the third step, use the generalized threshold shrinkage algorithm to solve the circumferential acoustic mode amplitude of the aeroengine fan tonal noise. In the method, in the first step, calculate the highest order m of the circumferential dominant acoustic mode of the fan tonal noise according to the number of rotor blades B and stator blades V of the aeroengine fan max ; where the modal order m = kB ± ζV, k represents the order of the pressure pulsation caused by the unsteady aerodynamic force caused by the fan rotor-stator interference, and ζ represents a non-negative integer; determine the measurable number as the modal range {-m max ,..., -1, 0, 1,... m max}, the number of measurable modes M = 2m max + 1; determine the required theoretical number of sensors for Nyquist sampling as K = 2m max .

[0063] In the method, in the second step, randomly install N microphones circumferentially on the casing wall, where N is about 50% of the theoretical number of sensors K for Nyquist sampling, and the installation angles Θ = [θ1, θ2,... θ N T ; perform a fast Fourier transform on the sound pressure signals measured by the N non-uniformly distributed microphones: y f = FFT(y t ), where y t represents the time-domain sound pressure signal of the fan noise measured by the non-uniform microphone array, FFT(·) represents the discrete Fourier transform, and y​f = [y1(ω), y2(ω),...y N (ω)] T represents the frequency-domain signals of N non-uniformly distributed microphones; based on the frequency-domain signals of the N non-uniformly distributed microphones, the passing frequency f of the fan rotor blade is selected BPF = B × fΩ, and the complex amplitudes at this frequency are used to construct the observation vector y = [y1(f BPF ), y2(f BPF ),...y N (f BPF )] T , where f Ω is the rotational frequency of the rotor shaft.

[0064] In the method, in the third step, an orthogonal Fourier sensing matrix is constructed where θ k is the installation angle of the k-th sensor, and m j is the modal order of the j-th circumferential mode wave. Based on the sensing matrix W N×M and the observation vector y, a non-convex regularized compressive sensing model with Lp norm p = 0.6 under non-uniform few measurement points is established:

[0065]

[0066] where λ represents the regularization parameter, is the magnitude of the estimated regularization parameter;

[0067] In the method, in the fourth step, solving this sparse model by the generalized thresholding shrinkage algorithm includes the following steps:

[0068] S401. Input the orthogonal Fourier sensing matrix W and the observation vector y; set the maximum number of iterations L = 10000, the initial iteration value x (0) = (x i ) T = 0, the iteration step size ε = ||W|| -2 , the regularization parameter λ = 0.2 × ||W|| 2 , and the sparse coefficient p = 0.6:

[0069] S402. Set the threshold T = (2λε(1 - p)) 1 / (2-p) + λεp(2λε(1 - p)) (p-1) / (2-p) ;

[0070] S403. Iterate z = x - εW T (Wx - y);

[0071] S404. Traverse the elements of the vector z = (z i ) T If Then execute S405 to skip S406; otherwise, execute S406;

[0072] S405: Continuously iterate x three times i = sgn(z i )(|z i |- λεp(x i )) p-1 );

[0073] S406: Let x i = 0;

[0074] S407: Check whether the maximum number of iterations L is reached. If so, output x; otherwise, return to S403.

[0075] In one embodiment, as Figure 1 shown, the method calculates the rotor-stator interaction modal order in the fan tonal noise through the fan model of an aeroengine, determines the acoustic modal monitoring range, the number of microphone sensors, the axial installation position, and the circumferential installation angle according to the maximum modal order of concern; determines the dimension of the spatial circumferential wavenumber domain basis vector from the acoustic modal monitoring range, constructs the acoustic modal transfer matrix, and establishes a compressive sensing optimization model based on the Lp norm regularization. The steps are as follows:

[0076] The schematic diagram of the aeroengine fan structure used in the experiment is as Figure 2 shown, where the number of first-stage rotor blades B of the aeroengine fan is 22, and the number of stator vanes V is 17. According to the acoustic modal order calculation formula of the fan tonal noise m = kB ± ζV, usually k = 1 represents the pressure pulsation order of 1 caused by the unsteady aerodynamic force caused by the rotor-stator interaction of the fan. At this time, ζ = -2 is taken to focus on the highest modal order m max = 12; it is determined that the measurable number is in the modal range {-12,..., -1, 0, 1,... 12}, and the number of measurable modes M = 25; it is determined that the required theoretical number of sensors under Nyquist sampling is K = 24.

[0077] Randomly select a small number of circumferential positions at the duct inlet to install microphones. The installation number N is about 50% of the required number of microphones under Nyquist sampling determined in the first step. Take N = 12, and the installation angles Θ = [33.75, 45, 112.5, 123.75, 146.25, 157.5, 168.75, 180, 202.5, 247.5, 315, 348.75] T ; conduct the acoustic test of the aeroengine fan at a rotational speed of about 7900 RPM, perform Fourier transform on the 12-channel microphone signals, and construct the observation vector y by taking the amplitude at the blade passing frequency.

[0078] Construct the compressive sensing matrix where θ k is the installation angle of the k-th sensor, and m j is the modal order of the j-th circumferential modal wave. A non-uniform few-measurement-point Lp-norm p = 0.6 non-convex regularized compressive sensing model is established:

[0079]

[0080] Solve this sparse model through the generalized threshold shrinkage algorithm, and the solution process is as Figure 1 shown. The results obtained by the Lp-norm regularization method and the classical L1-norm are as Figure 3 shown. Among them, for the mode m = 5, the modal amplitude error obtained by the proposed Lp-norm regularization method is 0.53 dB, and the modal amplitude error obtained by the classical L1-norm is 3.79 dB; for the mode m = 5, the modal amplitude error obtained by the proposed Lp-norm regularization method is 1.42 dB, and the modal amplitude error obtained by the classical L1-norm is 14.91 dB. Obviously, the proposed method and system for measuring the circumferential acoustic mode of an aero-engine based on Lp-norm regularization are significantly better than the classical L1-norm method.

[0081] Finally, it should be noted that: the described embodiments are only a part of the embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0082] Only some exemplary embodiments of the present invention have been described by way of illustration above. Undoubtedly, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for measuring the circumferential acoustic mode of an aeroengine based on Lp - norm regularization, characterized in that, It includes the following steps: In the first step (S1), the highest order m of the circumferential dominant acoustic mode of the fan tonal noise is calculated by the number B of the fan rotor blades and the number V of the stator blades of the aeroengine max , based on the highest order m max the number of microphones required for Nyquist sampling arranged circumferentially on the fan casing of the aeroengine is determined In the second step (S2), at the pipeline inlet, a predetermined number of circumferential installation positions and angles are randomly selected to install microphones to form a microphone array for collecting sound pressure signals. The predetermined number of installations is a predetermined proportion of the number of microphones required under Nyquist sampling. The fast Fourier transform is performed on the sound pressure signals measured by the microphone array, and the complex amplitude of the sound pressure signal at the blade passing frequency is taken as the observation vector; In the third step (S3), based on the installation position and angle and the highest order m max construct an orthogonal Fourier sensing matrix, and establish an Lp-norm non-convex regularized compressive sensing model under non-uniform few measurement points In the fourth step (S4), based on the Lp-norm non-convex regularized compressive sensing model, the generalized threshold shrinkage algorithm is used to obtain the circumferential acoustic mode amplitude of the aeroengine fan tonal noise.

2. The method for measuring the circumferential acoustic mode of an aeroengine based on Lp - norm regularization according to claim 1, characterized in that, In the first step (S1), the modal order of the circumferential dominant acoustic mode of the fan tonal noise is m = kB ± ζV, where k represents the order of pressure pulsation caused by the unsteady aerodynamic force caused by the fan rotor-stator interaction, and ζ represents a non-negative integer; the measurable number is determined to be in the modal range {-m max ,..., -1, 0, 1,... m max}, the number of measurable modes M = 2m max + 1, and the number of microphones K required is K = 2m max .

3. The method for measuring the circumferential acoustic mode of an aeroengine based on Lp - norm regularization according to claim 2, characterized in that, In the second step (S2), N microphones are randomly installed on the casing wall surface in the circumferential direction, where N is a predetermined ratio of the number of microphones required under the Nyquist sampling, and the installation angle Θ = [θ1, θ2,... θ N T ; perform a fast Fourier transform on the sound pressure signals measured by the N non-uniformly distributed microphones: y f = FFT(y t ), where y t represents the time-domain sound pressure signal of the fan noise measured by the non-uniformly distributed microphone array, FFT(·) represents the discrete Fourier transform, and y f = [y1(ω), y2(ω),... y N (ω)] T represents the frequency-domain signals of the N non-uniformly distributed microphones; based on the frequency-domain signals of the N non-uniformly distributed microphones, select the complex amplitude at the fan rotor blade passing frequency f BPF = B × f Ω to construct the observation vector y = [y1(f BPF ), y2(f BPF ),... y N (f BPF )] T , and f Ω is the rotational frequency of the rotor shaft.​ 4. The method for measuring the circumferential acoustic mode of an aeroengine based on Lp - norm regularization according to claim 3, characterized in that, In the third step (S3), an orthogonal Fourier sensing matrix is constructed where θ k is the installation angle of the k-th sensor, and m j is the modal order of the j-th circumferential mode wave; based on the orthogonal Fourier sensing matrix W N×M and the observation vector y, an Lp-norm non-convex regularized compressive sensing model under non-uniform few measurement points is established: where λ represents the regularization parameter, and p is the sparsity coefficient. is the estimated circumferential acoustic mode amplitude, W is the orthogonal Fourier sensing matrix, and x is the circumferential acoustic mode amplitude of the tonal noise of the aeroengine fan.

5. The method for measuring the circumferential acoustic mode of an aeroengine based on Lp - norm regularization according to claim 4, characterized in that, In the fourth step (S4), the Lp-norm non-convex regularized compressive sensing model is solved by the generalized threshold shrinkage algorithm, where Step S401: Input the orthogonal Fourier sensing matrix W and the observation vector y; set the maximum number of iterations, and the initial iteration value x (0) =(x i ) T =0, the iteration step size ε = ||W|| -2 , the regularization parameter λ = 0.2×||W|| 2 , the sparse coefficient p = 0.6; Step S402, set the threshold T = (2λε(1 - p)) 1 / (2-p) + λεp(2λε(1 - p)) (p-1) / (2-p) ; Step S403, iterate z = x - εW T (W·x - y); Step S404, traverse the elements of the vector z = (z i ) T . If , then execute step S405 to skip step S406; otherwise, execute step S406; Step S405: Continuously iterate x 3 times i = sgn(z i )(|z i | - λεp(x i )) p-1 ); Step S406. Let x i = 0; Step S407: Check whether the maximum number of iterations L is reached. If so, output the circumferential acoustic mode amplitude x of the aeroengine fan tonal noise; otherwise, return to step S403.

6. The method for measuring the circumferential acoustic mode of an aeroengine based on Lp - norm regularization according to claim 3, characterized in that, The predetermined proportion is 50%.

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