An airborne prediction method for ball bearing outer ring spalling faults in aero-engines

Abstract

The present application relates to an airborne prediction method for ball bearing outer ring spalling fault in an aero-engine. Starting from the search for the characteristic frequency of the ball bearing fault, the resonant frequency band of the vibration signal is adaptively extracted, envelope analysis and autocorrelation noise reduction are performed, and the characteristic frequency of the ball bearing outer ring spalling fault is extracted from the envelope signal of signals in different frequency bands. This method can highlight the periodic impact characteristics of the ball bearing outer ring spalling fault to the greatest extent and filter out noise and other clutter interference. At the same time, considering the influence of the change in the contact angle of the ball bearing, the contact angle range is selected to ensure the correctness and effectiveness of the extraction of the characteristic frequency of the ball bearing fault. By performing envelope analysis and autocorrelation noise reduction processing on different frequency bands, the normalized frequency characteristic quantity of the ball bearing outer ring spalling fault is directly extracted from the envelope spectrum, which can effectively avoid missed reports and false alarms caused by changes in the characteristic frequency of the ball bearing outer ring spalling fault, thereby improving the accuracy of the prediction of the ball bearing outer ring spalling fault.

Description

Technical Field

[0001] The present application belongs to the technical field of airborne prediction of ball bearing outer ring spalling faults in aircraft engines, and specifically relates to an airborne prediction method for ball bearing outer ring spalling faults in aircraft engines. Background Art

[0002] Aircraft engine main bearing failures are frequent, endangering the safe operation of aircraft engines. Statistics of a large number of main bearing failure analysis results show that the main failure mode of aircraft engine main bearing outer ring spalling failure is.

[0003] Currently, the prediction of ball bearing outer ring spalling fault in aero-engine mainly adopts vibration signal processing methods such as sparse decomposition, singular value decomposition or spectrum analysis.

[0004] Vibration signal processing methods such as sparse decomposition and singular value decomposition involve complex matrix operations during the calculation process, have low computational efficiency, and easily exceed the onboard system memory.

[0005] The spectrum analysis method directly searches for the characteristic frequency of the ball bearing outer ring peeling fault from the spectrum. Due to the interference of the complex internal structure and transmission path of the aircraft engine, the ball bearing outer ring peeling fault characteristics will be severely attenuated when transmitted to the casing. The ball bearing outer ring peeling fault information in the vibration signal is extremely weak, and the signal-to-noise ratio is extremely low, making it difficult to extract the ball bearing outer ring peeling fault characteristic frequency from it. In addition, the ball bearing is an angular contact ball bearing, and the contact angle has a certain range of variation, and there is a certain slippage phenomenon, which causes the ball bearing outer ring peeling fault characteristic frequency to have a certain range of variation. Without knowing the range of variation of the ball bearing outer ring peeling fault characteristic frequency, directly searching for the ball bearing outer ring peeling fault characteristic frequency from the spectrum will lead to large errors, resulting in missed reports and false alarms.

[0006] This application is proposed in view of the above-mentioned technical defects.

[0007] It should be noted that the disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention, and it does not necessarily belong to the prior art of the present application. In the absence of clear evidence that the above content has been disclosed on the filing date of the present application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the Invention

[0008] The purpose of this application is to provide an onboard prediction method for ball bearing outer ring spalling failure in an aircraft engine to overcome or alleviate at least one of the known technical defects.

[0009] The technical solution of this application is:

[0010] An onboard prediction method for ball bearing outer ring spalling fault in an aero-engine, comprising:

[0011] The vibration signal is decomposed into five layers using the db8 wavelet basis to obtain five detail sub-signals and one approximate sub-signal.

[0012] Perform envelope demodulation on each sub-signal;

[0013] Perform normalized autocorrelation noise reduction on each sub-signal;

[0014] Perform spectrum analysis on each sub-signal to obtain the wavelet envelope spectrum, which reflects the frequency characteristics of the health status of the ball bearing outer ring;

[0015] Taking the range of ball bearing contact angle variation, the characteristic frequency variation range of ball bearing outer ring spalling fault [f o1 ,f o2 ], in this frequency range, search for the maximum value of the spectrum line from each wavelet envelope spectrum:

[0016] A l =max[W l (f o1 +i△f)], i∈[0,m], l=1, 2, 3, 4, 5, 6;

[0017] m=δf / △f;

[0018] δf=f o2 -f o1 ;

[0019] in,

[0020] A l is the lth wavelet envelope spectrum in [f o1 ,f o2 ]The maximum value of the spectrum line within the frequency range;

[0021] W l (f o1 +i△f) is the lth wavelet envelope spectrum, in f o1 +i△f frequency spectrum line value, △f is the frequency interval in the wavelet envelope spectrum;

[0022] δf is the tolerance range of the characteristic frequency of ball bearing outer ring spalling fault;

[0023] Compute the average of the individual wavelet envelope spectra:

[0024]

[0025] in,

[0026] is the average value of the lth wavelet envelope spectrum;

[0027] W l (f j ) is the value of the jth spectral line of the lth wavelet envelope spectrum;

[0028] N e is the number of spectral lines of the wavelet envelope spectrum;

[0029] The envelope spectrum of each wavelet is [f o1 ,f o2 ]The maximum value of the spectrum line within the frequency range is dimensionless:

[0030]

[0031] in,

[0032] F ol is the lth wavelet envelope spectrum in [f o1 ,f o2 ] dimensionless value of the maximum value of the spectral line within the frequency range;

[0033] Select each wavelet envelope spectrum in [f o1 ,f o2 The maximum value of the dimensionless spectrum within the frequency range is used as the characteristic value of the ball bearing outer ring fault F o :

[0034]

[0035] The fault characteristic value F of the ball bearing outer ring o Converted into fault frequency characteristic quantity F dB , output in dB:

[0036] F dB =20log(F o );

[0037] Comparison of ball bearing outer ring fault frequency characteristic F dB , fault frequency characteristic threshold Th,

[0038] Determine whether the ball bearing outer ring peeling failure occurs;

[0039] If F V3 >Th, it is judged that the ball bearing outer ring is peeling fault;

[0040] If F V3 ≤Th, the outer ring of the ball bearing is judged to be normal.

[0041] According to at least one embodiment of the present application, in the above-mentioned airborne prediction method for ball bearing outer ring spalling fault in an aircraft engine, the range of variation of the ball bearing contact angle is specifically:

[0042] Taking more than 95% of the operating conditions of the aircraft engine, the contact angle of the ball bearing varies from 20° to 45°.

[0043] According to at least one embodiment of the present application, in the above-mentioned airborne prediction method for ball bearing outer race spalling fault in an aircraft engine, the ball bearing outer race fault frequency characteristic value threshold Th is set to 15. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of an airborne prediction method for ball bearing outer ring spalling fault in an aero-engine provided by an embodiment of the present application;

[0045] Figure 2 This is an airborne prediction method for ball bearing outer ring peeling fault in an aircraft engine provided by an embodiment of the present application. Ball bearing outer ring peeling fault diagnosis is performed on aircraft engines with ball bearing outer ring peeling fault and normal aircraft engines, and a schematic diagram of the comparison of diagnosis results is provided. DETAILED DESCRIPTION

[0046] To make the technical solution and its advantages of the present application clearer, the technical solution of the present application will be described in further detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of the present application and are only used to explain the present application, not to limit the present application. It should be noted that, for ease of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0047] In addition, unless otherwise defined, the technical or scientific terms used in the description of this application should have the ordinary meanings understood by those of ordinary skill in the art to which this application belongs. The words "upper," "lower," "left," "right," "center," "vertical," "horizontal," "inner," and "outer" used in the description of this application are only used to indicate relative directions or positional relationships, and do not imply that the device or component must have a specific orientation, be constructed, or operate in a specific orientation. When the absolute position of the described object changes, its relative positional relationship may also change accordingly. Therefore, they should not be understood as limitations on this application. The words "first," "second," "third," and similar terms used in the description of this application are used only for descriptive purposes to distinguish different components and should not be understood to indicate or imply relative importance. The words "one," "an," or "the" used in the description of this application should not be understood as absolute limitations on quantity, but should be understood as meaning the presence of at least one. The words "include" or "comprises" used in the description of this application mean that the element or object listed before the word includes the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0048] The following is combined with Figures 1 to 2 This application is described in further detail.

[0049] An onboard prediction method for ball bearing outer ring spalling fault in aircraft engines, such as Figure 1 As shown, the following steps are included:

[0050] The vibration signal is decomposed into five layers using the db8 wavelet basis to obtain five detail sub-signals and one approximate sub-signal.

[0051] Perform envelope demodulation on each sub-signal;

[0052] Perform normalized autocorrelation noise reduction on each sub-signal;

[0053] Perform spectrum analysis on each sub-signal to obtain the wavelet envelope spectrum, which reflects the frequency characteristics of the health status of the ball bearing outer ring;

[0054] Taking the range of contact angle of ball bearings in 95% of the working conditions of aircraft engines, which is 20°~45°, the characteristic frequency calculation formula is used to calculate the characteristic frequency variation range of ball bearing outer ring spalling fault [f o1 ,f o2 ], in this frequency range, search for the maximum value of the spectrum line from each wavelet envelope spectrum:

[0055] A l =max[W l (f o1+i△f)], i∈[0,m], l=1, 2, 3, 4, 5, 6;

[0056] m=δf / △f;

[0057] δf=f o2 -f o1 ;

[0058] in,

[0059] A l is the lth wavelet envelope spectrum in [f o1 ,f o2 ]The maximum value of the spectrum line within the frequency range;

[0060] W l (f o1 +i△f) is the lth wavelet envelope spectrum, in f o1 +i△f frequency spectrum line value, △f is the frequency interval in the wavelet envelope spectrum;

[0061] δf is the tolerance range of the characteristic frequency of ball bearing outer ring spalling fault;

[0062] Take 10Hz~f o1 +f o2 The number of spectral lines of the wavelet envelope spectrum within the frequency range is N e , calculate the average value of each wavelet envelope spectrum:

[0063]

[0064] in,

[0065] is the average value of the lth wavelet envelope spectrum;

[0066] W l (f j ) is the value of the jth spectral line of the lth wavelet envelope spectrum;

[0067] The envelope spectrum of each wavelet is [f o1 ,f o2 ]The maximum value of the spectrum line within the frequency range is dimensionless:

[0068]

[0069] in,

[0070] F ol is the lth wavelet envelope spectrum in [f o1 ,f o2 ] dimensionless value of the maximum value of the spectral line within the frequency range;

[0071] Select each wavelet envelope spectrum in [fo1 ,f o2 The maximum value of the dimensionless spectrum within the frequency range is used as the characteristic value of the ball bearing outer ring fault F o :

[0072]

[0073] The fault characteristic value F of the ball bearing outer ring o Converted into fault frequency characteristic quantity F dB , output in dB:

[0074] F dB =20log(F o );

[0075] Comparison of ball bearing outer ring fault frequency characteristic F dB , fault frequency characteristic value threshold Th, to determine whether a ball bearing outer ring peeling fault occurs.

[0076] If F V3 >Th, it is judged that the ball bearing outer ring is peeling fault;

[0077] If F V3 ≤Th, the outer ring of the ball bearing is judged to be normal.

[0078] Th can be 15.

[0079] The warning duration for ball bearing outer ring peeling failure is the interval between the moment the ball bearing outer ring peeling failure is determined to occur and the time when the ball bearing fails.

[0080] In a specific embodiment, the above-mentioned onboard prediction method for ball bearing outer ring spalling fault in an aircraft engine is used to diagnose the ball bearing outer ring spalling fault on an aircraft engine with a ball bearing outer ring spalling fault and a normal aircraft engine. The diagnosis results are as follows: Figure 2 As shown in the figure, it can be seen that the characteristic fusion feature quantity F of the ball bearing outer ring peeling fault aerospace engine V3 Most of them are significantly greater than 15, with obvious fault evolution trend. The feature fusion feature quantity F of normal engine V3 All of them were significantly less than 15, with high diagnostic accuracy.

[0081] The airborne prediction method for ball bearing outer ring spalling fault in an aero-engine disclosed in the above embodiment starts from the search for the characteristic frequency of the ball bearing fault, adaptively extracts the resonant frequency band of the vibration signal, performs envelope analysis and autocorrelation noise reduction, and extracts the characteristic frequency of the ball bearing outer ring spalling fault from the envelope signal of signals in different frequency bands. This can maximize the periodic impact characteristics of the ball bearing outer ring spalling fault and filter out noise and other interference. At the same time, considering the influence of the change in the contact angle of the ball bearing, the contact angle range is selected to ensure the correctness and effectiveness of the extraction of the characteristic frequency of the ball bearing fault. By performing envelope analysis and autocorrelation noise reduction processing on different frequency bands, the normalized frequency characteristic quantity of the ball bearing outer ring spalling fault is directly extracted from the envelope spectrum. This can effectively avoid missed reports and false alarms caused by changes in the characteristic frequency of the ball bearing outer ring spalling fault. In this way, the accuracy of ball bearing outer ring spalling fault prediction can be improved. The overall computational complexity is small and the computation speed is fast, which can well meet the needs of airborne early warning of ball bearing outer ring spalling fault in aero-engines.

[0082] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to in detail.

[0083] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or replacements to the relevant technical features, and the technical solutions after these changes or replacements will fall within the scope of protection of the present application.

Claims

1. An onboard prediction method for ball bearing outer ring spalling fault in an aero-engine, characterized by: include: The vibration signal is decomposed into five layers using the db8 wavelet basis to obtain five detail sub-signals and one approximate sub-signal. Perform envelope demodulation on each sub-signal; Perform normalized autocorrelation noise reduction on each sub-signal; Perform spectrum analysis on each sub-signal to obtain the wavelet envelope spectrum, which reflects the frequency characteristics of the health status of the ball bearing outer ring; Taking the range of ball bearing contact angle variation, the characteristic frequency variation range of ball bearing outer ring spalling fault [f o1 ,f o2 ], in this frequency range, search for the maximum value of the spectrum line from each wavelet envelope spectrum: A l =max[W l (f o1 +i△f)],i∈[0,m],l=1,2,3,4,5,6; m=δf / △f; δf=f o2 -f o1 ; in, A l is the lth wavelet envelope spectrum in [f o1 ,f o2 ]The maximum value of the spectrum line within the frequency range; W l (f o1 +i△f) is the lth wavelet envelope spectrum, in f o1 +i△f frequency spectrum line value, △f is the frequency interval in the wavelet envelope spectrum; δf is the tolerance range of the characteristic frequency of ball bearing outer ring spalling fault; Compute the average of the individual wavelet envelope spectra: in, is the average value of the lth wavelet envelope spectrum; W l (f j ) is the value of the jth spectral line of the lth wavelet envelope spectrum; N e is the number of spectral lines of the wavelet envelope spectrum; The envelope spectrum of each wavelet is [f o1 ,f o2 ]The maximum value of the spectrum line within the frequency range is dimensionless: in, F ol is the lth wavelet envelope spectrum in [f o1 ,f o2 ] dimensionless value of the maximum value of the spectral line within the frequency range; Select each wavelet envelope spectrum in [f o1 ,f o2 The maximum value of the dimensionless spectrum within the frequency range is used as the characteristic value of the ball bearing outer ring fault F o : The fault characteristic value F of the ball bearing outer ring o Converted into fault frequency characteristic quantity F dB , output in dB: F dB =20log(F o ); Comparison of ball bearing outer ring fault frequency characteristic F dB , fault frequency characteristic value threshold Th, to determine whether a ball bearing outer ring peeling fault occurs; If F V3 >Th, it is judged that the ball bearing outer ring is peeling fault; If F V3 ≤Th, the outer ring of the ball bearing is judged to be normal.

2. The onboard prediction method for ball bearing outer ring spalling fault in an aircraft engine according to claim 1, characterized in that: The range of variation of the ball bearing contact angle is specifically: Taking more than 95% of the operating conditions of the aircraft engine, the contact angle of the ball bearing varies from 20° to 45°.

3. The onboard prediction method for ball bearing outer ring spalling fault in an aircraft engine according to claim 1, characterized in that: The threshold value Th of the frequency characteristic value of the ball bearing outer ring fault is set to 15.

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