Engine surge determination method

Abstract

This application provides a method for judging engine surge, belonging to the field of aero-engine technology. The method includes: collecting pressure data at the compressor outlet, using N collected pressure data as an analysis window; fitting the N collected pressure data using a linear fitting method to obtain a fitted straight line; dividing the analysis window into a threshold calculation area, a surge judgment area, and an isolation area set between the threshold calculation area and the surge judgment area; calculating the compressor outlet pressure fitting value in the threshold calculation area based on the fitted straight line, and combining the compressor outlet pressure acquisition value of each acquisition cycle to obtain the difference between the outlet pressure fitting value and the outlet pressure acquisition value; obtaining the compressor outlet pressure variance based on the difference between the outlet pressure fitting value and the outlet pressure acquisition value; obtaining the surge threshold based on the variance; judging that the engine has surged when the compressor outlet pressure variance in the surge judgment area is greater than the surge threshold and meets the cycle requirement.

Description

Technical Field

[0001] This application belongs to the field of aero-engines, and specifically relates to a method for judging engine surge. Background Technology

[0002] Engine surge is an abnormal operating condition of an engine, usually caused by a deviation of the compressor's operating condition from the design point. This results in a larger angle of attack of the airflow on the compressor, airflow separation, loss of compressor boosting function, and airflow oscillation along the compressor axis. Engine parameters also fluctuate significantly, and in severe cases, it can lead to engine shutdown in mid-air or even damage the engine.

[0003] Due to its severe consequences, measures to address engine surge must be considered from the initial engine design stage. Because the mechanism of surge is complex, it is currently difficult to prevent surge in engineering. The focus is more on how to quickly remove the engine from surge when it occurs to avoid serious consequences. Therefore, the most important thing is to determine when engine surge will occur.

[0004] The fluctuation range of the high-pressure compressor outlet pressure in an aero-engine can reflect whether the compressor is operating stably. Therefore, existing technologies generally use the high-pressure compressor outlet pressure to determine whether the engine is experiencing surge. However, this method has the following drawbacks:

[0005] 1) Using the high-pressure compressor outlet pressure to judge engine surge can cause fluctuations in the high-pressure compressor outlet pressure during transient changes such as engine acceleration, deceleration or power extraction. Such fluctuations are normal and can easily lead to misdiagnosis of surge.

[0006] 2) After surge occurs, the pressure data during surge will be included in the surge threshold calculation, which will cause the threshold calculation to be inaccurate and affect the judgment of engine surge. Summary of the Invention

[0007] The purpose of this application is to provide a method for judging engine surge, so as to solve or mitigate at least one of the problems in the prior art.

[0008] The technical solution of this application is: a method for judging engine surge, including:

[0009] Collect pressure data at the compressor outlet, and use the collected N pressure data points as an analysis window. The sampling time in the analysis window is the x-axis, and the compressor outlet pressure is the y-axis.

[0010] The N collected pressure data points were fitted using a linear fitting method to obtain a fitted straight line;

[0011] The analysis window is divided into a threshold calculation area, a surge judgment area, and an isolation area located between the threshold calculation area and the surge judgment area.

[0012] The compressor outlet pressure fitting value within the threshold calculation area is calculated based on the fitted straight line, and the difference between the outlet pressure fitting value and the outlet pressure acquisition value is obtained by combining the compressor outlet pressure acquisition value of each acquisition cycle. The compressor outlet pressure variance is obtained based on the difference between the outlet pressure fitting value and the outlet pressure acquisition value, and the surge threshold is obtained based on the variance.

[0013] When the compressor outlet pressure variance within the surge judgment zone is greater than the surge threshold and meets the period requirement, the engine is judged to have surged.

[0014] In at least one embodiment of this application, the fitted straight line is y = kx + b, wherein the slope k and intercept b of the fitted straight line satisfy:

[0015]

[0016] In the formula, y i For the analysis window and the i-th pressure acquisition cycle x i The corresponding fitted value of the compressor outlet pressure, where N is the number of compressor outlet pressure data.

[0017] In at least one embodiment of this application, the length of the analysis window and the isolation zone is determined according to the engineering scenario.

[0018] In at least one embodiment of this application, the time interval of the isolation zone is greater than the actual time required to determine surge.

[0019] In at least one embodiment of this application, the difference between the fitted outlet pressure value and the acquired outlet pressure value is: Δy i =y i '-y i =y i '-(kx i +b), where y i 'The compressor outlet pressure collected for each acquisition cycle, y i This is the fitted value for the compressor outlet pressure.

[0020] In at least one embodiment of this application, the compressor outlet pressure variance Var is:

[0021] In at least one embodiment of this application, the period requirement is that the compressor outlet pressure variance within the surge judgment zone is greater than the surge threshold for at least a number of consecutive periods.

[0022] In at least one embodiment of this application, it further includes:

[0023] When engine surge is detected, the compressor outlet pressure data in the threshold calculation area and isolation area are stopped from being updated until the engine returns to normal operation. Then, the pressure data in the threshold calculation area and isolation area in the analysis window are resumed to be updated. After all the pressure data in the threshold calculation area and isolation area have been updated, the surge threshold is recalculated.

[0024] While the pressure data is not fully updated, surge diagnosis is performed using the previous valid surge threshold.

[0025] The engine surge judgment method of this application adopts the parameter fitting method, which can eliminate the influence of changes in the normal state of the engine on the surge threshold calculation, avoid false triggering of surge alarm when the normal working state of the engine changes, and reduce the false alarm rate of surge judgment. Attached Figure Description

[0026] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0027] Figure 1 This is a schematic diagram of the engine surge judgment method of this application.

[0028] Figure 2 This is a schematic diagram of the analysis window division in this application. Detailed Implementation

[0029] 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.

[0030] To address the problems mentioned in the background art, this application proposes an engine surge judgment method. The method of this application eliminates the influence of normal engine pressure changes on the surge threshold calculation by fitting the compressor outlet data, and improves the accuracy and reliability of surge judgment by setting a data isolation zone to isolate surge data and prevent the pressure during surge from entering the surge threshold calculation.

[0031] like Figure 1 As shown, the engine surge judgment method of this application specifically includes the following steps:

[0032] S10, Data Acquisition

[0033] This embodiment of the application uses a high-pressure compressor as an example. A pressure sensor continuously collects outlet pressure data from the high-pressure compressor, and the N most recently collected pressure data points are used as an analysis window. The number or length N of pressure data points in the analysis window is selected based on the specific engineering requirements.

[0034] S20, Parameter Fitting

[0035] The collected N pressure data points are processed to remove pressure fluctuations caused by normal engine operation.

[0036] In this application, a linear fitting method is used to perform linear fitting on the collected N high-pressure compressor outlet pressure data. During the fitting, the sampling time is used as the x-axis and the high-pressure compressor outlet pressure is used as the y-axis, and the data is fitted to a straight line y = kx + b. The slope k and intercept b in the linear equation are determined by the following formula:

[0037]

[0038] Where k and b are the slope and intercept of the fitted line, respectively, and y i For the analysis window and the i-th pressure acquisition cycle x i The corresponding fitted value of the high-pressure compressor outlet pressure, where N is the number of high-pressure compressor outlet pressure data.

[0039] Since the acquisition frequency of the high-pressure compressor outlet pressure data is fixed, the size of the selected analysis window is also fixed. Therefore, the value and number of x are also fixed.

[0040] S30, parameter isolation

[0041] like Figure 2 As shown, in order to avoid surge data entering the threshold calculation and affecting the surge judgment when surge occurs, this application divides the analysis window into a threshold calculation area, a surge judgment area, and an isolation area set between the surge judgment area and the threshold calculation area. Thus, when surge occurs, the data in the isolation area is contaminated, but it will not affect the calculation of the surge threshold in the analysis window. Therefore, the surge threshold is accurate.

[0042] The length of the isolation zone is selected based on the specific engineering design. The selection principle is that the time interval of the isolation zone must be greater than the actual time required to detect surge.

[0043] When surge occurs, stop updating the isolation zone and analysis window. When the engine returns to normal operation, resume updating the data in the isolation zone and analysis window.

[0044] S40, Surge threshold calculation

[0045] S41. Based on the obtained fitted line y=kx+b, calculate the fitted value of the high-pressure compressor outlet pressure. That is, substitute the sampling time x of the outlet pressure into the fitted line formula y=kx+b to calculate the corresponding fitted value of the high-pressure compressor outlet pressure.

[0046] S42, calculate the high-pressure compressor outlet pressure y collected in each acquisition cycle within the threshold calculation area. i The fitted value y of the high-pressure compressor outlet pressure is obtained by fitting a straight line according to the corresponding acquisition period. i The difference Δy i This eliminates the influence of engine acceleration / deceleration and power extraction on high-pressure compressor pressure fluctuations, i.e.: Δy i =y i '-y i =y i '-(kx i +b).

[0047] S43, Based on the difference between the above-mentioned outlet pressure collected value and the outlet pressure fitted value, the variance Var of the high-pressure compressor outlet pressure within the threshold calculation area is calculated. The calculation formula is as follows:

[0048]

[0049] S44. Based on the obtained variance of the high-pressure compressor outlet pressure and the changes in characteristic parameters during engine surge, the surge threshold θ is calculated.

[0050] For example, some surge thresholds in the prior art are set as a percentage of the outlet pressure—for example, 10%—and exceeding this percentage is judged as surge. The surge threshold θ of this application can be the product of the above variance and the percentage.

[0051] S50, surge detection

[0052] When the variance of the high-pressure compressor outlet pressure calculated in the surge judgment area is greater than the surge threshold θ in the threshold calculation area calculated in step S44, a surge alarm command is issued.

[0053] To avoid false surge detection, an alarm should only be triggered after surge has been detected for at least several consecutive cycles. For example, an alarm can be triggered after surge has been detected for two consecutive cycles.

[0054] When an alarm signal is output, the update of the outlet pressure data in the threshold calculation area and the isolation area is stopped until the engine returns to normal operation. Updates to the data in the threshold calculation area and the isolation area within the analysis window resume only after all pressure data in both areas has been completely updated. During the period before the pressure data is fully updated, the previous valid surge threshold is used for diagnosis. After all data has been updated once, the surge threshold is recalculated following the steps described above.

[0055] S60, administer asthma relief

[0056] After surge is detected, engine surge relief measures are implemented, which may be based on specific engineering designs, including but not limited to reducing engine fuel supply, engine bleed air, and reducing the angle of the adjustable guide vanes of the high-pressure compressor. The specific methods for implementing surge relief will not be described in detail in this application.

[0057] The engine surge detection method of this application employs parameter fitting, which can eliminate the influence of changes in the engine's normal operating state on the surge threshold calculation, avoiding false surge alarms when the engine's normal operating state changes, and reducing the false alarm rate of surge detection. This application also effectively prevents high-pressure compressor outlet pressure data during surge from entering the surge threshold calculation by setting up a data isolation zone, thus improving the accuracy and reliability of surge detection.

[0058] 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 for judging engine surge, characterized in that, include: Collect pressure data at the compressor outlet, and use the collected N pressure data points as an analysis window. The sampling time in the analysis window is the x-axis, and the compressor outlet pressure is the y-axis. The N collected pressure data points were fitted using a linear fitting method to obtain a fitted straight line; The analysis window is divided into a threshold calculation area, a surge judgment area, and an isolation area located between the threshold calculation area and the surge judgment area. The compressor outlet pressure fitting value within the threshold calculation area is calculated based on the fitted straight line, and the difference between the outlet pressure fitting value and the outlet pressure acquisition value is obtained by combining the compressor outlet pressure acquisition value of each acquisition cycle. The compressor outlet pressure variance is obtained based on the difference between the outlet pressure fitting value and the outlet pressure acquisition value, and the surge threshold is obtained based on the variance. When the compressor outlet pressure variance in the surge judgment zone is greater than the surge threshold and meets the periodic requirements, the engine is judged to have surged. At the same time, when the engine is judged to have surged, the update of compressor outlet pressure data in the threshold calculation zone and isolation zone is stopped until the engine returns to normal operation. Then the update of pressure data in the threshold calculation zone and isolation zone in the analysis window is resumed. After all the pressure data in the threshold calculation zone and isolation zone has been updated, the surge threshold is recalculated. During the period when the pressure data has not been updated, the previous valid surge threshold is used for surge diagnosis.

2. The engine surge detection method as described in claim 1, characterized in that, The fitted line is y = kx + b, where the slope k and intercept b of the fitted line satisfy: ； ； In the formula, y i For the analysis window and the i-th pressure acquisition cycle x i The corresponding fitted value of the compressor outlet pressure, where N is the number of compressor outlet pressure data.

3. The engine surge judgment method as described in claim 2, characterized in that, The length of the analysis window and the isolation zone are determined according to the engineering scenario.

4. The engine surge judgment method as described in claim 3, characterized in that, The time interval of the isolation zone is greater than the actual time required to determine surge.

5. The engine surge judgment method as described in claim 4, characterized in that, The difference between the fitted value of the outlet pressure and the collected value of the outlet pressure is: In the formula, The compressor outlet pressure is collected for each data acquisition cycle. This is the fitted value for the compressor outlet pressure.

6. The engine surge judgment method as described in claim 5, characterized in that, The compressor outlet pressure variance Var is: .

7. The engine surge judgment method as described in claim 6, characterized in that, The period requirement is that the compressor outlet pressure variance within the surge judgment zone is greater than the surge threshold for at least a number of consecutive periods.

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