A method for detecting oscillatory combustion in an afterburner of an aeroengine

Abstract

The application belongs to the field of turbofan afterburner, and particularly relates to a turbofan afterburner oscillation combustion detection method. The method comprises the following steps: acquiring afterburner pulsation pressure calibration data under multiple calibration frequencies, and fitting a first amplitude-frequency curve; collecting multiple afterburner pulsation pressure test data, obtaining multiple second amplitude-frequency curves, and calculating the amplitude-frequency average values of the multiple second amplitude-frequency curves; calculating the average value v of the average amplitude P2 in a predetermined frequency interval, and calculating the ratio of the average amplitude P2 to the average value v at all frequencies, to generate a third amplitude-frequency curve; acquiring the frequency interval Δf and the ratio coefficient k of the peak values of the amplitude signals P1 and P3; changing the frequency corresponding to the amplitude signal P1 from the original f to f+Δf, and re-fitting P1; determining the signal P4 according to the amplitude signal P1 and the amplitude signal P3; extracting the maximum characteristic frequency amplitude p' and the absolute value y of the amplitude signal P4, to complete the detection and alarm of oscillation combustion, and the detection is accurate and reliable.

Description

Technical Field

[0001] This application belongs to the field of afterburners in aero-engines, and specifically relates to a method for detecting oscillating combustion in afterburners of aero-engines. Background Technology

[0002] With the development of aero-engine technology, a series of afterburners have been developed to achieve greater thrust and higher thrust-to-weight ratios. As the thrust and thrust-to-weight ratio of advanced engines increase, combustion instability becomes increasingly prominent. The combustion instability frequency in afterburners is often related to the engine's operating conditions. Its frequency range can reach 50Hz to 3000Hz. When oscillating combustion occurs in the engine, it poses a significant threat to engine testing and flight safety. If its frequency couples with the natural frequency of structural components, it can cause damage to engine structural components in a very short time, seriously threatening engine testing and flight safety.

[0003] Due to the harsh testing environment of afterburners, pulsating pressure testing remains the only engineering-approved testing method for afterburners. However, because of the high ambient temperature in afterburners, pulsating pressure testing can only be performed by extending the pressure tap. Increasing the tap length significantly affects the accuracy of the test frequency response and amplitude, generally limiting the frequency response to below 500Hz. Another testing method involves adding a waveguide for oscillating combustion testing. While this method can improve the frequency response and accuracy, it has drawbacks: firstly, the semi-infinite tube structure is bulky and cannot be used under flight test conditions; secondly, the semi-infinite tube significantly affects the phase of the pulsating pressure data, hindering modal analysis of oscillating combustion. Furthermore, current detection methods all use single eigenvalue and single threshold triggering, making it difficult to reliably guarantee accuracy and stability.

[0004] Therefore, it is desirable to have a technical solution to overcome or at least mitigate one of the aforementioned defects of the prior art. Summary of the Invention

[0005] The purpose of this application is to provide a method for detecting oscillating combustion in the afterburner of an aero-engine, in order to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is:

[0007] A method for detecting oscillating combustion in the afterburner of an aero-engine includes:

[0008] Step 1: Obtain afterburner pulsating pressure calibration data at multiple calibration frequencies, and fit a first amplitude-frequency curve based on the afterburner pulsating pressure calibration data. The amplitude signal in the first amplitude-frequency curve is P1.

[0009] Step 2: Collect multiple afterburner pulsating pressure test data, and obtain multiple sets of second amplitude-frequency curves by performing fast Fourier transform on the afterburner pulsating pressure test data. Calculate the average amplitude-frequency value of the multiple sets of second amplitude-frequency curves to obtain the average amplitude P2 of the amplitude-frequency curve of the afterburner pulsating pressure test data.

[0010] Step 3: Calculate the average value v of the average amplitude P2 in the predetermined frequency range, and calculate the ratio of the average amplitude P2 to the average value v in all frequencies to generate a third amplitude-frequency curve, wherein the amplitude signal in the third amplitude-frequency curve is P3;

[0011] Step 4: Obtain the frequency interval Δf between the peak values ​​of amplitude signal P1 and amplitude signal P3, and the ratio coefficient k between the peak values ​​of amplitude signal P1 and amplitude signal P3;

[0012] Step 5: Change the frequency corresponding to the amplitude signal P1 from the original f to f+Δf, and refit the first amplitude-frequency curve;

[0013] Step 6: Determine amplitude signal P4 based on the amplitude values ​​of amplitude signals P1 and P3 at the same frequency.

[0014]

[0015] Step 7: Extract the maximum characteristic frequency amplitude p′ of the amplitude signal P4, and calculate the maximum characteristic frequency amplitude p′ and the average steady-state pressure value. The absolute value of the ratio:

[0016]

[0017] Step 8: Based on the amplitude p′ and absolute value y of the maximum characteristic frequency, determine whether to activate the boost oscillation combustion alarm.

[0018] In at least one embodiment of this application, in step one, the calibration frequency includes:

[0019] 5Hz, 50Hz, 100Hz, 200Hz, 300Hz, 400Hz, 500Hz, 600Hz, 700Hz, 800Hz, 900Hz, 1000Hz, 1200Hz, 1400Hz, 1600Hz, 1800Hz, 2000Hz.

[0020] In at least one embodiment of this application, in step one, a first amplitude-frequency curve P1 is fitted by second-order interpolation.

[0021] In at least one embodiment of this application, in step two, data from five afterburner pulsating pressure tests are collected.

[0022] In at least one embodiment of this application, in step three, the predetermined frequency range is 5Hz to 200Hz.

[0023] In at least one embodiment of this application, in step eight,

[0024] When p′≥14kPa and y≥4.0%, an enhanced oscillating combustion alarm is triggered.

[0025] In alarm mode, the afterburning oscillation combustion alarm is turned off when p′≤10kPa and y≤2.5%.

[0026] The invention has at least the following beneficial technical effects:

[0027] The method for detecting oscillating combustion in the afterburner of an aero-engine in this application employs dynamic calibration technology to correct the pulsating pressure test data of the afterburner, which can greatly improve the frequency response and accuracy of the oscillating combustion pulsating pressure test. After correction, the pulsating pressure test data of the afterburner can be improved to 2000Hz. Based on this, a method for extracting the characteristic value of the pulsating pressure of the afterburner is proposed. Using dual characteristic values ​​and dual thresholds, the detection and alarm of oscillating combustion are completed, which has higher detection accuracy and reliability. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the amplitude dynamic calibration result curve at room temperature according to one embodiment of this application;

[0029] Figure 2 This is a schematic diagram comparing the room temperature calibration results with real-world test data of one embodiment of this application. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0031] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this application.

[0032] The following is in conjunction with the appendix Figures 1 to 2 This application will be described in further detail.

[0033] This application provides a method for detecting oscillating combustion in the afterburner of an aero-engine, including the following steps:

[0034] Step 1: Obtain afterburner pulsating pressure calibration data at multiple calibration frequencies, and fit the first amplitude-frequency curve based on the afterburner pulsating pressure calibration data. The amplitude signal in the first amplitude-frequency curve is P1.

[0035] Step 2: Collect multiple afterburner pulsating pressure test data, obtain multiple sets of second amplitude-frequency curves by performing fast Fourier transform on the afterburner pulsating pressure test data, calculate the average amplitude-frequency value of the multiple sets of second amplitude-frequency curves, and obtain the average amplitude P2 of the amplitude-frequency curve of the afterburner pulsating pressure test data.

[0036] Step 3: Calculate the average value v of the average amplitude P2 in the predetermined frequency range, and calculate the ratio of the average amplitude P2 to the average value v in all frequencies to generate the third amplitude-frequency curve. The amplitude signal in the third amplitude-frequency curve is P3.

[0037] Step 4: Obtain the frequency interval Δf between the peak values ​​of amplitude signal P1 and amplitude signal P3, and the ratio coefficient k between the peak values ​​of amplitude signal P1 and amplitude signal P3;

[0038] Step 5: Change the frequency corresponding to the amplitude signal P1 from the original f to f+Δf, and refit the first amplitude-frequency curve to obtain the amplitude signal P1 in the refitted first amplitude-frequency curve;

[0039] Step 6: Determine amplitude signal P4 based on the amplitude values ​​of amplitude signals P1 and P3 at the same frequency.

[0040]

[0041] Step 7: Extract the maximum characteristic frequency amplitude p′ of the amplitude signal P4, and calculate the maximum characteristic frequency amplitude p′ and the average steady-state pressure value. The absolute value of the ratio:

[0042]

[0043] Step 8: Based on the amplitude p′ and absolute value y of the maximum characteristic frequency, determine whether to activate the boost oscillation combustion alarm.

[0044] The method for detecting oscillating combustion in the afterburner of an aero-engine disclosed in this application firstly involves acquiring afterburner pulsating pressure calibration data in step one. Calibration at multiple frequencies is performed under ambient temperature (20°C) using an afterburner pulsating pressure test probe consistent with the engine test structure and a sinusoidal pressure signal calibrator, and the calibration results are recorded. The afterburner pulsating pressure calibration data includes the amplitude corresponding to each calibration frequency, and corrections for the frequency and corresponding amplitude of the measured afterburner pulsating pressure data are added. The acquired calibration data is then fitted using a second-order interpolation method to form a... Figure 1 The first amplitude-frequency curve shown is represented by amplitude signal P1. In a preferred embodiment of this application, the calibration frequency selected during data calibration is: 5Hz, 50Hz, 100Hz, 200Hz, 300Hz, 400Hz, 500Hz, 600Hz, 700Hz, 800Hz, 900Hz, 1000Hz, 1200Hz, 1400Hz, 1600Hz, 1800Hz, or 2000Hz.

[0045] The method for detecting oscillating combustion in the afterburner of an aero-engine disclosed in this application, secondly, in step two, preferably, collects five afterburner pulsating pressure test data under real-world conditions, and obtains the amplitude-frequency curves of the five sets of test data by performing a Fast Fourier Transform (FFT). The average value of the afterburner pulsating pressure test amplitude at the corresponding frequency of the five sets of amplitude-frequency curves is taken to obtain the average amplitude of the amplitude-frequency curve of the test data, and its amplitude signal is P2, with units of 100 kPa.

[0046] In the method for detecting oscillating combustion in the afterburner of an aero-engine disclosed in this application, step three preferably involves calculating the average value v based on the average amplitude P2 at frequencies ranging from 5Hz to 200Hz, and then calculating the ratio of all amplitude signals within the average amplitude P2 to the average value v to obtain a third amplitude-frequency curve, thus yielding the amplitude signal P3. In this embodiment, the comparison between the first and third amplitude-frequency curves is as follows: Figure 2 As shown.

[0047] In the method for detecting oscillating combustion in the afterburner of an aero-engine disclosed in this application, step four involves obtaining the frequency interval Δf between the peak values ​​of amplitude signal P1 and amplitude signal P3, as well as the ratio coefficient k between the peak values ​​of amplitude signal P1 and amplitude signal P3.

[0048] In the method for detecting oscillating combustion in the afterburner of an aero-engine in this application, step five involves changing the frequency corresponding to the amplitude signal P1 from the original f to f+Δf, and then refitting to obtain P1.

[0049] In the method for detecting oscillating combustion in the afterburner of an aero-engine in this application, step six involves determining the amplitude signal P4 based on the amplitude of the refitted amplitude signal P1 and the amplitude corresponding to the same frequency of the amplitude signal P3.

[0050]

[0051] The method for detecting oscillating combustion in the afterburner of an aero-engine disclosed in this application extracts the characteristic values ​​of pulsating pressure in the afterburner based on a comparison of room temperature calibration results with real environmental test data and correction results. This is achieved by using the maximum characteristic frequency amplitude p′ of the amplitude signal P4 and the relationship between the maximum characteristic frequency amplitude p′ and the average steady-state pressure value. The absolute value of the ratio, y, is used, along with corresponding dual thresholds, to detect and alarm for afterburning oscillation combustion. In this embodiment, an afterburning oscillation combustion alarm is triggered when p′≥14kPa and y≥4.0%, and no alarm is triggered in other states. In the alarm state, the afterburning oscillation combustion alarm is deactivated when p′≤10kPa and y≤2.5%. That is, when the conditions p′≥14kPa and y≥4.0% are met, an afterburning oscillation combustion alarm is triggered. In the alarm state, if the conditions p′≥14kPa and y≥4.0% are no longer met, but the conditions p′≤10kPa and y≤2.5% are met, the afterburning oscillation combustion alarm continues until the conditions p′≤10kPa and y≤2.5% are no longer met, at which point the alarm is deactivated.

[0052] The method for detecting oscillating combustion in the afterburner of an aero-engine in this application employs dynamic calibration technology to correct the pulsating pressure test data of the afterburner, which can greatly improve the frequency response and accuracy of the oscillating combustion pulsating pressure test. After correction, the pulsating pressure test data of the afterburner can be improved to 2000Hz. Based on this, a method for extracting the characteristic value of the pulsating pressure of the afterburner is proposed. Using dual characteristic values ​​and dual thresholds, the detection and alarm of oscillating combustion are completed, which has higher detection accuracy and reliability.

[0053] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method of detecting oscillating combustion in an afterburner of an aircraft engine, the method comprising: include: Step 1: Obtain afterburner pulsating pressure calibration data at multiple calibration frequencies. Under normal temperature conditions, use an afterburner pulsating pressure test probe consistent with the engine test structure and a sinusoidal pressure signal calibrator to complete calibration at multiple frequencies, record the calibration results, and fit a first amplitude-frequency curve based on the afterburner pulsating pressure calibration data. The amplitude signal in the first amplitude-frequency curve is P1. Step 2: Collect afterburner pulsating pressure test data under multiple real-world conditions. Obtain multiple sets of second amplitude-frequency curves by performing fast Fourier transform on the afterburner pulsating pressure test data. Calculate the average amplitude-frequency value of the multiple sets of second amplitude-frequency curves to obtain the average amplitude P2 of the amplitude-frequency curve of the afterburner pulsating pressure test data. Step 3: Calculate the average value v of the average amplitude P2 in the predetermined frequency range, and calculate the ratio of the average amplitude P2 to the average value v in all frequencies to generate a third amplitude-frequency curve, wherein the amplitude signal in the third amplitude-frequency curve is P3; Step 4: Obtain the frequency interval ∆f between the peak values ​​of amplitude signal P1 and amplitude signal P3, and the ratio coefficient k between the peak values ​​of amplitude signal P1 and amplitude signal P3; Step 5: Change the frequency corresponding to the amplitude signal P1 from the original f to f+∆f, and refit the first amplitude-frequency curve to obtain the amplitude signal P1 in the refitted first amplitude-frequency curve; Step 6: Based on the amplitude values ​​corresponding to the same frequency of the refitted amplitude signal P1 and amplitude signal P3, determine the amplitude signal P4: ； Step 7: Extract the maximum characteristic frequency amplitude of amplitude signal P4. Calculate the amplitude of the maximum characteristic frequency. With average steady-state pressure value The absolute value of the ratio: ； Step 8: Based on the amplitude of the maximum characteristic frequency with absolute value Determine whether to activate the booster oscillation combustion alarm; when ≥ First threshold and When the value is greater than or equal to the second threshold, an enhanced oscillation combustion alarm will be triggered.

2. The method for detecting oscillating combustion in the afterburner of an aero-engine according to claim 1, characterized in that, In step one, the calibration frequency includes: 5Hz, 50 Hz, 100 Hz, 200 Hz, 300 Hz, 400 Hz, 500 Hz, 600 Hz, 700 Hz, 800 Hz, 900 Hz, 1000 Hz, 1200 Hz, 1400 Hz, 1600 Hz, 1800 Hz, 2000 Hz.

3. The method for detecting oscillating combustion in the afterburner of an aero-engine according to claim 2, characterized in that, In step one, the first amplitude-frequency curve P1 is fitted using second-order interpolation.

4. The method for detecting oscillating combustion in the afterburner of an aero-engine according to claim 3, characterized in that, In step two, data from five afterburner pulsating pressure tests were collected.

5. The method for detecting oscillating combustion in the afterburner of an aero-engine according to claim 4, characterized in that, In step three, the predetermined frequency range is 5Hz to 200Hz.

6. The method for detecting oscillating combustion in the afterburner of an aero-engine according to claim 5, characterized in that, In step eight, when ≥14kPa and When the concentration is ≥4.0%, an enhanced oscillating combustion alarm will be triggered; In alarm state, when ≤10kPa and The afterburner oscillation combustion alarm will be turned off when the concentration is ≤2.5%.

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