A test-bed monitoring method for improving the safety of a whole turbofan engine test

Abstract

The application belongs to the field of engine overall test, and is a kind of test bench monitoring method for improving the safety of overall test of a turbofan engine. An engine overall monitoring system is arranged to associate each sampling measurement point of the engine overall. During the overall test, the sampling measurement point data is received under normal conditions. When different determination conditions are triggered, abnormal monitoring is performed. When abnormal data is found, the test can be immediately stopped in real time to ensure safety. Through engine performance parameters, overall vibration fundamental frequency and special frequency, overall pulsation special frequency, key parameters of the oil system and detailed analysis of oil samples, the working state of the engine can be comprehensively and multi-dimensionally analyzed. When an abnormality occurs, it can be quickly and accurately captured, thereby effectively improving the safety of the overall test of the double-rotor turbofan engine fulcrum bearing, and providing technical support for a large number of overall tests under heavy load during the engine development stage.

Description

Technical Field

[0001] This application belongs to the field of engine whole machine testing, and specifically relates to a bench monitoring method for improving the safety of turbofan engine whole machine testing. Background Technology

[0002] Main bearings and accessory bearings in aero-engines support rotating components such as rotors and drive shafts, playing a crucial role in supporting and transmitting loads, and are an important part of the aero-engine drivetrain. The pivot bearings in a twin-rotor turbofan engine are particularly important components supporting the high- and low-pressure rotor structures. If pivot bearings fail through spalling, wear, or fracture, it can lead to engine shutdown in flight, single-engine landing, or other accident symptoms, with significant consequences. In the case of a single-engine aircraft, the consequences would be even more severe. Furthermore, the causes of pivot bearing failure involve many factors, including the bearing's external operating environment, bearing design, manufacturing quality, and raw materials, making the mechanisms complex.

[0003] Currently, both in-service and under-development high-performance military aero engines have evolved into dual-rotor afterburning turbofan engines. Besides placing higher demands on functionality and performance, these engines also require stricter requirements regarding structural integrity and safety to ensure their reliability and airworthiness in field operations meet user needs. Based on these requirements, turbofan engines necessitate extensive system testing during the development phase to guarantee the quality of delivered engines. Therefore, improving the safety of system testing for the pivot bearings of dual-rotor turbofan engines is particularly important during system testing. Existing system testing rig monitoring requirements based solely on bearing measurements are no longer sufficient to meet the needs of ongoing projects.

[0004] Existing engine test bench monitoring requirements for bearing support points are relatively simple, typically characterized by monitoring a few routine parameters such as total engine vibration, lubricating oil spectrum, and bearing cavity lubricating oil temperature and pressure. While this can ensure engine test safety to a certain extent, a comprehensive and systematic design guideline and methodology for monitoring engine bearing support points on test benches, considering multiple dimensions including engine performance parameters, engine vibration, engine pulsation, and lubricating oil system parameters, has not yet been established. These design deficiencies mean that existing technical solutions can no longer adequately meet usage requirements, impacting engine test safety.

[0005] Therefore, improving the safety of the overall test of the pivot bearing of a twin-rotor turbofan engine is a problem that needs to be solved. Summary of the Invention

[0006] The purpose of this application is to provide a bench monitoring method to improve the safety of turbofan engine whole-machine testing, in order to solve the problem that the existing whole-machine test support bearing bench monitoring requirements are relatively simple and the safety performance is difficult to meet current requirements.

[0007] The technical solution of this application is: a bench monitoring method for improving the safety of turbofan engine overall testing, including:

[0008] Set up an engine monitoring system to associate each sampling point of the engine, conduct engine tests, and control the engine to perform test tasks according to the specified settings.

[0009] The engine performance parameters, whole machine vibration parameters, whole machine pulsation parameters and lubricating oil system parameters are collected in parallel, and high and low pressure speed monitoring, whole machine vibration monitoring and lubricating oil system monitoring are performed respectively; high and low pressure speed abnormality criteria and first judgment condition, whole machine vibration abnormality criteria and second judgment condition, and lubricating oil system abnormality criteria and third judgment condition are set respectively.

[0010] Real-time judgment is performed. When the first judgment condition is met and a sudden change in the relative physical speed of high pressure or low pressure occurs, the high and low pressure speed anomaly criterion is invoked to determine whether the engine performance exceeds the limit. If it exceeds the limit, the engine state is reduced to idle in real time and the engine is verified to be abnormal. If it is abnormal, the test is stopped immediately. When the second judgment condition is met and a change in fundamental frequency vibration or a sudden increase in amplitude occurs, the whole machine vibration anomaly criterion is invoked to determine whether the whole machine vibration exceeds the limit. If it exceeds the limit, the engine state is reduced to idle in real time and the engine is verified to be abnormal. If it is abnormal, the test is stopped immediately. When the third judgment condition is met, the lubricating oil system anomaly criterion is invoked to determine whether the lubricating oil supply and return oil temperature difference exceeds the limit. If it exceeds the limit, an anomaly is marked.

[0011] Determine whether the test task has been completed. If so, stop the machine and send the collected engine performance parameters, whole machine vibration parameters, whole machine pulsation parameters, and lubricating oil system parameters to the test monitoring system. Perform whole machine performance parameter analysis, vibration spectrum analysis, pulsation spectrum analysis, and abrasive and lubricating oil supply and return temperature difference analysis respectively, and determine whether any item is abnormal. If so, locate and mark the abnormality.

[0012] Preferably, the first determination condition includes a constant throttle lever angle, a stable engine speed for a first set time, and the high-pressure relative physical speed and the low-pressure relative physical speed being at the same operating node; the second determination condition includes monitoring of abnormal vibration of the entire machine and monitoring of abnormal pulsation of the entire machine. Abnormal vibration monitoring is performed when the entire engine is in a stable state for a second set time, and abnormal pulsation monitoring is performed after the engine stops; the third determination condition includes monitoring of abnormal temperature difference between the supply and return oil and monitoring of abnormal abrasive particles in the lubricating oil. Abnormal temperature difference monitoring is performed when the high-pressure speed reaches a stable speed for a third set time, and abnormal abrasive particle monitoring is performed when the engine stops.

[0013] Preferably, the method for judging the abnormality of the lubricating oil supply and return temperature difference is as follows: set a limit value for the lubricating oil supply and return temperature difference for the pivot bearing, collect the pivot bearing supply temperature value and the pivot bearing return temperature value respectively, and determine whether the difference between the pivot bearing supply temperature value and the pivot bearing return temperature value exceeds the limit value for the lubricating oil supply and return temperature difference. If so, reduce the engine state to idle. After the engine test stops, sample the lubricating oil tank, accessory housing and fly attachment housing, and collect the total characteristic abrasive concentration and fatigue abrasive concentration respectively. Determine whether the total characteristic abrasive concentration and fatigue abrasive concentration are abnormal. If abnormal, perform maintenance.

[0014] Preferably, the method for judging the abnormal abrasive particle monitoring of the lubricating oil is as follows: different abrasive particle warning values ​​and abrasive particle abnormal values ​​are set for the lubricating oil tank, accessory housing, and flight attachment housing respectively. After collecting the total characteristic abrasive particle concentration and fatigue abrasive particle concentration, it is first judged whether the total characteristic abrasive particle concentration and fatigue abrasive particle concentration exceed the abrasive particle warning value limit. If so, an alarm mark is made on the corresponding location. The abrasive particle abnormal value limit is judged again for the parts that exceed the alarm mark. If it is judged that the abrasive particle abnormality limit is exceeded, the corresponding location is marked as abnormal.

[0015] Preferably, the method for judging whether the engine performance parameters are abnormal is as follows: real-time acquisition of the sampling parameters of the whole engine and judgment of the current state of the engine. When the throttle lever angle remains unchanged and the engine is in a stable speed state, the throttle lever angle parameters, high pressure relative physical speed parameters and low pressure relative physical speed parameters are collected at continuous time nodes according to time, and high pressure relative physical speed curves and low pressure relative physical speed curves are generated respectively. It is then judged whether there is a sudden change. If so, the abnormality is judged based on the value of the sudden change.

[0016] Set a first limit value. Under stable engine speed, determine whether the sudden change in the high-pressure relative physical speed or the low-pressure relative physical speed exceeds the limit value. If so, reduce the engine speed to idle and check whether there is any abnormality in the engine. If there is an abnormality, stop the test immediately.

[0017] Preferably, the method for monitoring abnormal vibration of the entire machine is as follows: setting vibration limit values ​​and amplitude limit values, collecting the fundamental frequency vibration parameters of the engine in real time during the test, and making the following judgments:

[0018] 1) Determine whether a sudden increase in the fundamental frequency vibration amplitude occurs at the same time point by calculating the difference. If so, determine whether the sudden increase in the fundamental frequency vibration amplitude exceeds the vibration limit value.

[0019] 2) Determine if the fundamental frequency vibration amplitude exceeds the amplitude limit;

[0020] If one of the conditions is met, the engine speed is reduced to idle.

[0021] The method for monitoring the overall engine pulsation anomaly is as follows: receive the pulsation data of the engine during the test, perform three-dimensional spectrum analysis on the pulsation data, set a second limit value, determine whether there are pulsation measurement points in the pulsation data that exceed the second limit value, if so, reduce the engine state to slow down, and confirm whether there is an abnormality in the engine. If there is an abnormality, stop the test immediately.

[0022] Preferably, during the monitoring of abnormal vibration of the entire machine, the characteristic frequency amplitude is simultaneously judged to exceed the limit. The specific method is as follows: set the characteristic frequency amplitude limit value, collect the fundamental frequency vibration parameters of the engine in real time during the test, establish a typical vibration spectrum diagram of the entire machine, obtain the low-voltage fundamental frequency vibration amplitude and the high-voltage fundamental frequency vibration amplitude and calculate the mean value, obtain the mean value of the low-voltage fundamental frequency vibration amplitude and the mean value of the high-voltage fundamental frequency vibration amplitude respectively, and judge whether the difference between the mean value of the low-voltage fundamental frequency vibration amplitude and the low-voltage fundamental frequency vibration amplitude at different time points exceeds a certain value, and whether the difference between the mean value of the high-voltage fundamental frequency vibration amplitude and the high-voltage fundamental frequency vibration amplitude at different time points exceeds a certain value. If either exceeds the limit, it is judged that a characteristic frequency has appeared; judge whether the appeared characteristic frequency exceeds the characteristic frequency amplitude limit value. If it exceeds the limit, reduce the engine state to slow down, confirm whether the vibration exceeds the limit, and if it still exceeds the limit, stop the test immediately.

[0023] This application presents a bench monitoring method for improving the safety of turbofan engine whole-machine testing. By setting up a whole-machine monitoring system, it correlates various sampling and measurement points of the engine. During the whole-machine test, it receives data from these sampling and measurement points under normal conditions. When different judgment conditions are triggered, it monitors for anomalies. Upon detecting abnormal data, it can immediately reduce the engine speed to idle and verify whether the engine is abnormal. If an anomaly is detected, the test is immediately stopped to ensure safety performance. Through detailed analysis of engine performance parameters, the fundamental and special frequencies of whole-machine vibration, the special frequencies of whole-machine pulsation, key parameters of the lubricating oil system, and oil samples, it can comprehensively and multidimensionally analyze the engine's operating status. It can quickly and accurately detect any anomalies, thereby effectively improving the safety of whole-machine testing of the pivot bearings of a dual-rotor turbofan engine and providing technical support for conducting extensive, high-load whole-machine testing and verification during the engine development phase. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a schematic diagram of the overall process of this application;

[0026] Figure 2 This is a schematic diagram illustrating a typical sudden change in high-voltage rotational speed in this application;

[0027] Figure 3 This is a typical frequency spectrum diagram of the vibration of the whole machine in this application. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] A bench monitoring method for improving the safety of turbofan engine testing, such as... Figure 1 As shown, it includes the following steps:

[0030] Step S100: Set up the engine whole machine monitoring system, associate each sampling measurement point of the engine whole machine, conduct engine whole machine test, and control the engine whole machine to execute the test task according to the specified set process.

[0031] Step S200: Engine performance parameters, overall vibration parameters, overall pulsation parameters, and lubricating oil system parameters are collected in parallel, and high and low pressure speed monitoring, overall vibration monitoring, and lubricating oil system monitoring are performed respectively. Abnormal judgment criteria and first judgment conditions for high and low pressure speed, abnormal judgment criteria and second judgment conditions for overall vibration, and abnormal judgment criteria and third judgment conditions for lubricating oil system are set respectively.

[0032] Preferably, the first determination condition includes a constant throttle lever angle, a stable engine speed for a first set time, and both the high-pressure relative physical speed and the low-pressure relative physical speed being at the same operating point. That is, when the operating conditions such as intake conditions, variable geometry, anti-icing, bleed air, and loading are the same.

[0033] The second determination condition includes monitoring of abnormal vibration of the whole machine and monitoring of abnormal pulsation of the whole machine. When the whole engine is in a stable state for a second set time, monitoring of abnormal vibration of the whole machine is performed. When the engine is stopped, monitoring of abnormal pulsation of the whole machine is performed. The third determination condition includes monitoring of abnormal temperature difference between oil supply and return and monitoring of abnormal abrasive particles in oil. When the high pressure speed reaches a stable speed and continues for a third set time, monitoring of abnormal temperature difference between oil supply and return is performed. When the engine is stopped, monitoring of abnormal abrasive particles in oil is performed.

[0034] Similarly, under normal conditions, the engine monitoring system only needs to receive data. Only when certain conditions are met does it determine whether an anomaly or exceeding limits is necessary. This process of identifying operating conditions effectively improves monitoring efficiency. The first to third time settings can be configured as needed, and can be the same or different.

[0035] Step S300: Real-time judgment is performed. When the first judgment condition is met and a sudden change in the relative physical speed of high pressure or low pressure occurs, the high and low pressure speed anomaly criterion is called to determine whether the engine performance exceeds the limit. If it exceeds the limit, the engine state is reduced to idle in real time and the engine is verified to be abnormal. If it is abnormal, the test is stopped immediately. When the second judgment condition is met and a change in fundamental frequency vibration or a sudden increase in amplitude occurs, the whole machine vibration anomaly criterion is called to determine whether the whole machine vibration exceeds the limit. If it exceeds the limit, the engine state is reduced to idle in real time and the engine is verified to be abnormal. If it is abnormal, the test is stopped immediately. When the third judgment condition is met, the lubricating oil system anomaly criterion is called to determine whether the lubricating oil supply and return oil temperature difference exceeds the limit. If it exceeds the limit, an anomaly is marked.

[0036] Preferably, the method for judging abnormal temperature difference monitoring of lubricating oil supply and return is as follows: set a limit value for the temperature difference between the lubricating oil supply and return for the pivot bearing: a*n2 2 -b*n2+c, where a / b / c are constants, collect the oil supply temperature and return temperature of the pivot bearing respectively, and determine whether the difference between the oil supply temperature and return temperature of the pivot bearing exceeds the limit value of the lubricating oil supply and return temperature difference. If so, reduce the engine speed to idle. After the engine test stops, sample the lubricating oil tank, accessory housing, and fly-attachment housing, and collect the total characteristic abrasive concentration and fatigue abrasive concentration respectively. Determine whether the total characteristic abrasive concentration and fatigue abrasive concentration are abnormal. If abnormal, perform maintenance.

[0037] Preferably, the method for judging abnormal abrasive particle monitoring of lubricating oil is as follows: different abrasive particle warning values ​​and abrasive particle abnormal values ​​are set for the lubricating oil tank, accessory housing, and flight attachment housing respectively. After collecting the total characteristic abrasive particle concentration and fatigue abrasive particle concentration, it is first judged whether the total characteristic abrasive particle concentration and fatigue abrasive particle concentration exceed the abrasive particle warning value limit. If so, an alarm mark is made on the corresponding location. The abrasive particle abnormal value limit is judged again for the parts that exceed the alarm mark. If it is judged that the abrasive particle abnormality limit is exceeded, the corresponding location is marked as abnormal.

[0038] The abrasive warning values ​​and abrasive abnormal values ​​meet the requirements of Table 1.

[0039] Table 1. Monitoring Indicators for Lubricating Oil Abrasives

[0040]

[0041] Preferably, the method for judging whether the engine performance parameters are abnormal is as follows: real-time acquisition of the sampling parameters of the whole engine and judgment of the current state of the engine. When the throttle lever angle remains unchanged and the engine is in a stable speed state, the throttle lever angle parameters, high pressure relative physical speed parameters and low pressure relative physical speed parameters are collected at continuous time nodes according to time, and high pressure relative physical speed curves and low pressure relative physical speed curves are generated respectively. It is then judged whether there is a sudden change. If so, the abnormality is judged based on the value of the sudden change.

[0042] Set a first limit value. Under stable engine speed, determine whether the sudden change in the high-pressure relative physical speed or the low-pressure relative physical speed exceeds the limit value. If so, reduce the engine speed to idle and check whether there is any abnormality in the engine. If there is an abnormality, stop the test immediately.

[0043] Combination Figure 2 , n2 is the abrupt change in the relative physical speed of high pressure. The abrupt changes in the relative physical speeds of high and low pressure, n1 and n2, should not exceed the limit value (%).

[0044] If the speeds of n1 and n2 suddenly exceed the limit, reduce the engine speed to idle and check for any abnormalities in the engine; if an abnormality is found, stop the test immediately.

[0045] Preferably, the method for monitoring abnormal vibration of the entire machine is as follows: setting vibration limit values ​​and amplitude limit values, collecting the fundamental frequency vibration parameters of the engine in real time during the test, and making the following judgments:

[0046] 1) Determine whether a sudden increase in the fundamental frequency vibration amplitude occurs at the same time point by calculating the difference. If so, determine whether the sudden increase in the fundamental frequency vibration amplitude exceeds the vibration limit value.

[0047] 2) Determine if the fundamental frequency vibration amplitude exceeds the amplitude limit;

[0048] If one of the conditions is met, reduce the engine speed to idle and check for any abnormalities in the engine. If any abnormalities are found, stop the test immediately.

[0049] The method for monitoring the overall engine pulsation anomaly is as follows: receive the pulsation data of the engine during the test, perform three-dimensional spectrum analysis on the pulsation data, set a second limit value, determine whether there are pulsation measurement points in the pulsation data that exceed the second limit value, if so, reduce the engine state to slow down, and confirm whether there is an abnormality in the engine. If there is an abnormality, stop the test immediately.

[0050] Preferably, during the monitoring of abnormal vibration of the entire machine, the judgment of excessive characteristic frequency amplitude is performed simultaneously. The specific method is as follows: setting a characteristic frequency amplitude limit value, collecting the fundamental frequency vibration parameters of the engine in real time during the test, establishing a typical vibration spectrum diagram of the entire machine, and combining it with... Figure 3 Where f1 is the low-voltage fundamental frequency vibration amplitude and f2 is the high-voltage fundamental frequency vibration amplitude, the low-voltage fundamental frequency vibration amplitude and the high-voltage fundamental frequency vibration amplitude are obtained and their average values ​​are calculated. The average values ​​of the low-voltage fundamental frequency vibration amplitude and the high-voltage fundamental frequency vibration amplitude are obtained respectively. It is determined whether the difference between the average value of the low-voltage fundamental frequency vibration amplitude and the low-voltage fundamental frequency vibration amplitude at different time points exceeds a certain value, and whether the difference between the average value of the high-voltage fundamental frequency vibration amplitude and the high-voltage fundamental frequency vibration amplitude at different time points exceeds a certain value. If either exceeds the limit, a characteristic frequency is identified. It is then determined whether the identified characteristic frequency exceeds the characteristic frequency amplitude limit. If it does, the engine speed is reduced to idle to confirm whether the vibration exceeds the limit. If it still exceeds the limit, the test is stopped immediately.

[0051] The specific parameter monitoring values ​​involved in the above-mentioned engine test bench monitoring requirements need to be adjusted according to the engine test verification and changes in the engine's technical condition to ensure the safety of the engine test.

[0052] Step S400: Determine if the test task is complete. If so, stop the machine and send the collected engine performance parameters, overall vibration parameters, overall pulsation parameters, and lubricating oil system parameters to the test monitoring system. Perform overall performance parameter analysis, vibration spectrum analysis, pulsation spectrum analysis, and abrasive particle and lubricating oil supply and return temperature difference analysis, and determine if any item is abnormal. If so, locate and mark the abnormality. If an abnormality is found, the problem is repaired, and the overall machine test is repeated until the abnormality is eliminated.

[0053] The analysis of overall machine performance parameters, vibration spectrum analysis, pulsation spectrum analysis, and abrasive and lubricating oil supply and return temperature difference analysis are carried out according to existing analysis methods. By finding specific abnormal parameters, the corresponding location can be located and the cause of the problem can be analyzed.

[0054] This application establishes an engine whole-machine monitoring system, which associates various sampling and measurement points of the engine. During the whole-machine test, the system receives data from the sampling and measurement points under normal conditions. When different judgment conditions are triggered, anomalies are monitored. If abnormal data is detected, the engine state can be reduced to idle speed in real time to verify whether the engine is abnormal. If an anomaly is detected, the test is stopped immediately to ensure safety performance. By performing detailed analysis of engine performance parameters, engine vibration fundamental frequency and special frequencies, engine pulsation special frequencies, key parameters of the lubricating oil system, and oil samples, the system can comprehensively and multidimensionally analyze the engine's operating status. It can quickly and accurately detect any recognized anomalies, thereby effectively improving the safety of the whole-machine test of the pivot bearing of the dual-rotor turbofan engine and providing technical support for conducting large-scale, high-load whole-machine test verification during the engine development stage.

[0055] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0056] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0057] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for monitoring a test stand to improve the safety of a turbofan engine overall test, characterized in that, include: Set up an engine monitoring system to associate each sampling point of the engine, conduct engine tests, and control the engine to perform test tasks according to the specified settings. The engine performance parameters, whole machine vibration parameters, whole machine pulsation parameters and lubricating oil system parameters are collected in parallel, and high and low pressure speed monitoring, whole machine vibration monitoring and lubricating oil system monitoring are performed respectively; high and low pressure speed abnormality criteria and first judgment condition, whole machine vibration abnormality criteria and second judgment condition, and lubricating oil system abnormality criteria and third judgment condition are set respectively. Real-time judgment is performed. When the first judgment condition is met and a sudden change in the relative physical speed of high pressure or low pressure occurs, the high and low pressure speed anomaly criterion is invoked to determine whether the engine performance exceeds the limit. If it exceeds the limit, the engine state is reduced to idle in real time and the engine is verified to be abnormal. If it is abnormal, the test is stopped immediately. When the second judgment condition is met and a change in fundamental frequency vibration or a sudden increase in amplitude occurs, the whole machine vibration anomaly criterion is invoked to determine whether the whole machine vibration exceeds the limit. If it exceeds the limit, the engine state is reduced to idle in real time and the engine is verified to be abnormal. If it is abnormal, the test is stopped immediately. When the third judgment condition is met, the lubricating oil system anomaly criterion is invoked to determine whether the lubricating oil supply and return oil temperature difference exceeds the limit. If it exceeds the limit, an anomaly is marked. Determine whether the test task has been completed. If so, stop the machine and send the collected engine performance parameters, whole machine vibration parameters, whole machine pulsation parameters and lubricating oil system parameters to the test monitoring system. Perform whole machine performance parameter analysis, vibration spectrum analysis, pulsation spectrum analysis and abrasive and lubricating oil supply and return temperature difference analysis respectively, and determine whether any item is abnormal. If so, locate and mark the abnormality. The first determination condition includes a constant throttle lever angle, a stable engine speed for a first set time, and the high-pressure relative physical speed and the low-pressure relative physical speed being at the same operating node. The second determination condition includes monitoring of abnormal vibration and abnormal pulsation of the entire engine. When the entire engine is in a stable state for a second set time, abnormal vibration monitoring is performed. When the engine is stopped, abnormal pulsation monitoring is performed. The third determination condition includes monitoring of abnormal temperature difference between oil supply and return and abnormal abrasive wear of oil. When the high-pressure speed reaches a stable speed for a third set time, abnormal temperature difference monitoring between oil supply and return is performed. When the engine is stopped, abnormal abrasive wear of oil is performed.

2. The bench monitoring method for improving the overall test safety of turbofan engines as described in claim 1, characterized in that, The method for judging the abnormality of the lubricating oil supply and return temperature difference is as follows: Set a limit value for the lubricating oil supply and return temperature difference for the pivot bearing, collect the pivot bearing supply temperature value and the pivot bearing return temperature value respectively, and judge whether the difference between the pivot bearing supply temperature value and the pivot bearing return temperature value exceeds the limit value for the lubricating oil supply and return temperature difference. If so, reduce the engine state to idle. After the engine test stops, sample the lubricating oil tank, accessory housing and flight accessory housing, and collect the total characteristic abrasive concentration and fatigue abrasive concentration respectively. Judge whether the total characteristic abrasive concentration and fatigue abrasive concentration are abnormal. If abnormal, perform maintenance.

3. The bench monitoring method for improving the overall test safety of turbofan engines as described in claim 1, characterized in that, The method for judging abnormal abrasive particle monitoring of lubricating oil is as follows: different abrasive particle warning values ​​and abrasive particle abnormal values ​​are set for the lubricating oil tank, accessory housing, and flight accessory housing respectively. After collecting the total characteristic abrasive particle concentration and fatigue abrasive particle concentration, it is first judged whether the total characteristic abrasive particle concentration and fatigue abrasive particle concentration exceed the abrasive particle warning value limit. If so, an alarm mark is made on the corresponding location. Then, the abrasive particle abnormal value limit is judged again for the parts that exceed the alarm mark. If it is judged that the abrasive particle abnormality limit is exceeded, the corresponding location is marked as abnormal.

4. The bench monitoring method for improving the overall test safety of turbofan engines as described in claim 1, characterized in that, The method for judging whether the engine performance parameters are abnormal is as follows: real-time acquisition of the sampling parameters of the whole engine and judgment of the current state of the engine. When the throttle lever angle remains unchanged and the engine is in a stable speed state, the throttle lever angle parameters, high pressure relative physical speed parameters and low pressure relative physical speed parameters are collected at continuous time nodes according to time, and the high pressure relative physical speed curve and low pressure relative physical speed curve are generated respectively. It is judged whether there is a sudden change. If there is, the abnormality is judged according to the value of the sudden change. Set a first limit value. Under stable engine speed, determine whether the sudden change in the high-pressure relative physical speed or the low-pressure relative physical speed exceeds the limit value. If so, reduce the engine speed to idle and check whether there is any abnormality in the engine. If there is an abnormality, stop the test immediately.

5. The bench monitoring method for improving the overall test safety of turbofan engines as described in claim 1, characterized in that, The method for monitoring abnormal vibration of the entire machine is as follows: setting vibration limit values ​​and amplitude limit values, collecting the fundamental frequency vibration parameters of the engine in real time during the test, and making the following judgments: 1) Determine whether a sudden increase in the fundamental frequency vibration amplitude occurs at the same time point by calculating the difference. If so, determine whether the sudden increase in the fundamental frequency vibration amplitude exceeds the vibration limit value. 2) Determine if the fundamental frequency vibration amplitude exceeds the amplitude limit; If one of the conditions is met, the engine speed is reduced to idle.

6. The bench monitoring method for improving the overall test safety of turbofan engines as described in claim 5, characterized in that, During the monitoring of abnormal vibration of the entire machine, the characteristic frequency amplitude is simultaneously judged to exceed the limit. The specific method is as follows: set the characteristic frequency amplitude limit value, collect the fundamental frequency vibration parameters of the engine in real time during the test, establish a typical vibration spectrum diagram of the entire machine, obtain the low-voltage fundamental frequency vibration amplitude and the high-voltage fundamental frequency vibration amplitude and calculate the mean value, obtain the mean value of the low-voltage fundamental frequency vibration amplitude and the mean value of the high-voltage fundamental frequency vibration amplitude respectively, and judge whether the difference between the mean value of the low-voltage fundamental frequency vibration amplitude and the low-voltage fundamental frequency vibration amplitude at different time points exceeds a certain value, and whether the difference between the mean value of the high-voltage fundamental frequency vibration amplitude and the high-voltage fundamental frequency vibration amplitude at different time points exceeds a certain value. If either exceeds the limit, it is judged that a characteristic frequency has appeared. It is judged whether the appeared characteristic frequency exceeds the characteristic frequency amplitude limit value. If it exceeds the limit, the engine state is reduced to slow speed to confirm whether the vibration exceeds the limit. If it still exceeds the limit, the test is stopped immediately.

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