A method for judging low-pressure rotor seizure in low-bypass-ratio aircraft engines

Abstract

This application belongs to the field of aero-engine design and is a method for determining low-pressure rotor seizure in a low-bypass ratio aero-engine. By first performing an engine start test, the speed NH of the high-pressure rotor corresponding to the low-pressure rotor's stable speed is determined, and the relative conversion speed nHR_D of the seizure is further determined. 判 Then control the engine to work according to the set high-pressure rotor speed increase rate, and obtain the corresponding actual conversion speed nHR_D of the shaft under different high-pressure rotor speed increase rates. 实 By setting criteria for complete and incomplete rotor sticking and validating them during an engine start test, successful validation indicates the criteria are valid, and both criteria are written into the CNC system. By combining speed control and speed rise rate control during the engine start process to form a combined criterion, it is possible to effectively identify low-pressure rotor seizure during the test run and prevent engine casing burnout caused by seizure.

Description

Technical Field

[0001] The present application belongs to the field of aero-engine design, and in particular relates to a method for determining whether a low-pressure rotor of a small bypass ratio aero-engine is seizing the shaft. Background Art

[0002] Low-pressure rotor seizure in low-bypass aircraft engines (hereinafter referred to as "engines") occurs when the low-pressure rotor rubs against the casing during restart after a run-in. Low-pressure rotor seizure is difficult to detect, and currently only can be determined by rocking the engine. However, rocking the engine before every run, especially for adjustment and endurance runs, is labor-intensive and impractical for engineering applications.

[0003] When the low-pressure rotor is stuck after the engine is ignited, the low-pressure rotor does not rotate, the fan's circulation capacity decreases, and the outlet flow rate is difficult to meet the compressor inlet flow rate requirement. The high-pressure compressor needs to inhale air from the outer duct, and the fan does not pressurize the outer duct inlet air. The high-pressure compressor inlet pressure and the outer duct air are basically equal to atmospheric pressure, which is lower than the turbine rear gas pressure. Under the action of flow difference and pressure difference, the high-temperature inner duct gas flows back from the turbine rear casing outlet to the front of the outer duct. Since the temperature of the turbine rear gas is as high as about 700°C during the startup process, it far exceeds the allowable operating temperature of the outer duct, which causes the outer duct casing to burn.

[0004] Currently, the low-pressure rotor is usually judged to be stuck by manually shaking it. This method is labor-intensive and inefficient, and cannot meet the current engine test needs.

[0005] Therefore, how to automatically and accurately judge the low-pressure rotor shaft seizure is a problem that needs to be solved. Summary of the Invention

[0006] The purpose of this application is to provide a method for determining whether a low-pressure rotor is seizing a small bypass ratio aircraft engine, so as to solve the problem in the prior art that the manual shaking method for determining whether a low-pressure rotor is seizing a shaft is labor-intensive and inefficient.

[0007] The technical solution of the present application is: a method for determining whether a low-pressure rotor of a low-bypass ratio aircraft engine is stuck, comprising:

[0008] Perform an engine starting test to determine the speed of the high-pressure rotor when the low-pressure rotor reaches a stable speed. NH , and further determine the relative conversion speed nHR_D of the shaft 判 ;

[0009] Get the set high-pressure rotor speed increase rate. During the engine startup process, control the engine to work according to the set high-pressure rotor speed increase rate, and get the corresponding actual conversion speed nHR_D of the shaft under different high-pressure rotor speed increase rates. 实 ;

[0010] ① When nHR_D 实 ≥nHR_D 判 ② When the low-pressure rotor has a speed increase, but the low-pressure rotor speed increase rate is lower than the specified speed increase rate, and T 6. The exhaust temperature continues to rise and reaches the allowable temperature Tw of the outer casing. When any of the above criteria occurs, it is determined that the low-pressure rotor is stuck.

[0011] Perform the engine starting test again. When the engine is controlled to meet any of the above criteria, execute the shutdown procedure and perform a shaking inspection on the low-pressure rotor. If it is determined after the inspection that the low-pressure rotor is stuck, the criterion is determined to be valid. When it is determined that both criteria are valid, write the two criteria into the CNC system. When any of the criteria is triggered in the CNC system, an alarm signal is given and the shutdown procedure is executed.

[0012] Preferably, the relative conversion speed of the shaft is nHR_D 判 :

[0013] nHR_D 判 =ε*NH / NHs*(288.15K / T t2 ) 0.5

[0014] Where ε is the low-pressure speed correction coefficient, NHs is the high-pressure rotor design speed, T t2 is the engine inlet temperature, K is the Kelvin unit.

[0015] The present invention provides a method for judging the low-pressure rotor seizure of a small bypass ratio aircraft engine. The method first conducts an engine start test to determine the speed of the high-pressure rotor when the low-pressure rotor has a stable speed. NH , and further determine the relative conversion speed nHR_D of the shaft 判 Then control the engine to work according to the set high-pressure rotor speed increase rate, and obtain the corresponding actual conversion speed nHR_D of the shaft under different high-pressure rotor speed increase rates. 实By setting criteria for complete and incomplete rotor sticking and validating them during an engine start test, successful validation indicates the criteria are valid, and both criteria are written into the CNC system. By combining speed control and speed rise rate control during the engine start process to form a combined criterion, it is possible to effectively identify low-pressure rotor seizure during the test run and prevent engine casing burnout caused by seizure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions provided by this application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application.

[0017] Figure 1 This is a schematic diagram of the overall process of this application;

[0018] Figure 2 This is a schematic diagram of the engine starting process for this application;

[0019] Figure 3 This is a schematic diagram of the slip relationship during the engine starting process of this application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0021] A method for judging low-pressure rotor seizure in low-bypass-ratio aircraft engines Figure 2 Taking engine starting as an example, the engine starting process is divided into three stages: from the beginning to the end, they are the starter filling stage, the starting ignition stage, and the starting acceleration stage; and the locking usually occurs in the starting acceleration stage.

[0022] like Figure 1 As shown, the following steps are included:

[0023] Step S100, perform an engine starting test to determine the speed of the high-pressure rotor when the low-pressure rotor has a stable speed. NH , and further determine the relative conversion speed nHR_D of the shaft 判 ;

[0024] The speed of the low-pressure rotor can be set. When it reaches the specified speed and continues to run at this speed for a certain period of time, it is considered to have reached a stable speed. NH It can be directly collected through the monitoring equipment on the engine.

[0025] The relative conversion speed of the shaft is nHR_D 判 :

[0026] nHR_D判 =ε*NH / NHs*(288.15K / T t2 ) 0.5

[0027] Where ε is the low-pressure speed correction coefficient, NHs is the high-pressure rotor design speed, T t2 is the engine inlet temperature, K is the Kelvin unit.

[0028] Step S200: Determine the low-pressure rotor speed increase rate and the actual conversion speed of the shaft during the startup process.

[0029] Get the set high-pressure rotor speed increase rate. During the engine startup process, control the engine to work according to the set high-pressure rotor speed increase rate, and get the corresponding actual conversion speed nHR_D of the shaft under different high-pressure rotor speed increase rates. 实 ;

[0030] During the starting process, the high-pressure rotor operates according to the given high-pressure rotor speed increase rate N2dot.

[0031] The relationship between high pressure and low pressure slip during starting is shown in Figure 3 According to the control law of the high-pressure rotor speed increase rate N2dot during the starting process, the low-pressure rotor speed increase rate N1dot can be obtained, and then the actual conversion speed nHR_D of the shaft can be obtained. 实 .

[0032] Step S300: Determine the combined control criteria consisting of the speed control and the speed increase rate control.

[0033] ① When nHR_D 实 ≥nHR_D 判 ② When the low-pressure rotor has no speed, it means that the low-pressure rotor is completely stuck; ② When the low-pressure rotor has speed, but the speed increase rate of the low-pressure rotor is lower than the specified speed increase rate, and T 6 The exhaust temperature continues to rise and reaches the allowable temperature Tw of the outer casing, indicating that the low-pressure rotor is stuck to a certain extent; when any of the above criteria occurs, it is determined that the low-pressure rotor is seizing the shaft.

[0034] Step S400, perform the engine starting test again, and when the engine is controlled to meet any of the above criteria, execute the parking procedure and perform a shaking inspection on the low-pressure rotor. If it is determined after the inspection that the low-pressure rotor is stuck, the criterion is determined to be valid; when it is determined that both criteria are valid, the two criteria are written into the CNC system. When any of the criteria is triggered in the CNC system, an alarm signal is given and the parking procedure is executed.

[0035] For engines with different line signals, the engine shaft seizure logic criterion can be modified based on the test data obtained from different starting characteristics.

[0036] This application first conducts an engine starting test to determine the speed of the high-pressure rotor when the low-pressure rotor has a stable speed. NH , and further determine the relative conversion speed nHR_D of the shaft 判 Then control the engine to work according to the set high-pressure rotor speed increase rate, and obtain the corresponding actual conversion speed nHR_D of the shaft under different high-pressure rotor speed increase rates. 实 By setting criteria for complete and incomplete rotor sticking and validating them during an engine start test, successful validation indicates the criteria are valid, and both criteria are written into the CNC system. By combining speed control and speed rise rate control during the engine start process to form a combined criterion, it is possible to effectively identify low-pressure rotor seizure during the test run and prevent engine casing burnout caused by seizure.

[0037] After the judgment criteria are valid, manual cranking is generally not required. The data system can directly monitor whether the low-pressure rotor is stuck in the engine, with accurate judgment and high efficiency.

[0038] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for determining low-pressure rotor seizure in a low-bypass-ratio aircraft engine, characterized in that: include: Perform an engine starting test to determine the speed of the high-pressure rotor when the low-pressure rotor reaches a stable speed. NH , and further determine the relative conversion speed nHR_D of the shaft 判 ; Get the set high-pressure rotor speed increase rate. During the engine starting process, control the engine to work according to the set high-pressure rotor speed increase rate. According to the high-pressure rotor speed increase rate control law during the starting process, the low-pressure rotor speed increase rate is obtained, and then the actual conversion speed nHR_D of the shaft is obtained. 实 ; ① When nHR_D 实 ≥nHR_D 判 When , the low-pressure rotor does not rotate at a speed; ②When the low-pressure rotor speed increases, but the low-pressure rotor speed increase rate is lower than the specified speed increase rate, and T 6. The exhaust temperature continues to rise and reaches the allowable temperature Tw of the outer casing; when any of the above criteria occurs, it is determined that the low-pressure rotor is stuck; Conduct an engine start test again. When the engine reaches any of the above criteria, execute the shutdown procedure and perform a rocking inspection on the low-pressure rotor. If the low-pressure rotor is found to be stuck after the inspection, the criterion is determined to be valid. If both criteria are determined to be valid, write the two criteria into the numerical control system. When any of the above criteria is triggered in the numerical control system, an alarm signal is issued and the shutdown procedure is executed. The relative conversion speed of the shaft is nHR_D 判 : nHR_D 判 =ε*NH / NHs*(288.15K / T t2 ) 0.5 Where ε is the low-pressure speed correction coefficient, NHs is the high-pressure rotor design speed, T t2 is the engine inlet temperature, K is the Kelvin unit.

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