Method for calculating service load spectrum life of low-pressure turbine shaft of aero-engine

Abstract

The invention belongs to the technical field of aero-engines, and particularly relates to an aero-engine low-pressure turbine shaft service load spectrum life calculation method which comprises the steps that key state points for calculating the life of a low-pressure turbine shaft are selected; searching an aerodynamic load in an aerodynamic load spectrum of the low-pressure turbine shaft based on the key state points, and searching a maneuvering load in a maneuvering load spectrum of the low-pressure turbine shaft based on the key state points; calculating low-pressure turbine shaft stress based on the aerodynamic load and the maneuvering load; the service life of the low-pressure turbine shaft is calculated based on the stress, aerodynamic load calculation models and maneuvering load calculation models are respectively established through theoretical derivation, numerical simulation, regression analysis and other methods based on test parameters in engine flight parameter data, the use load spectrum of the low-pressure turbine shaft of the engine is rapidly and accurately obtained, a large amount of calculation iteration is avoided, and the service life of the low-pressure turbine shaft is calculated. The engine does not need to be modified and tested, the design period is shortened, and the development cost is saved.

Description

Technical Field

[0001] The present application belongs to the technical field of aero-engines, and in particular relates to a method for calculating the load spectrum life of a low-pressure turbine shaft of an aero-engine. Background Art

[0002] The low-pressure turbine shaft of an aircraft engine is an important load-bearing and force-transmitting component. During use, the load on the low-pressure turbine shaft is very complex. It bears both aerodynamic loads caused by changes in the internal aerodynamic parameters of the engine, including aerodynamic torque and axial force; it also bears maneuvering loads caused by the flight of the aircraft, including inertial force, inertial moment and gyroscopic moment.

[0003] Load is the main factor affecting the life of components and is also the basis for component life analysis and testing. Although current aircraft engines are equipped with flight parameter recorders that record a large number of parameters related to the engine's operating status, it is still impossible to achieve real-time measurement of the operating load of the low-pressure turbine shaft. Although current aircraft engines are equipped with flight parameter recorders that can record a large number of parameters related to the engine's operating status, due to limitations such as safety of use and testing technology, it is still impossible to achieve real-time measurement and recording of the aerodynamic torque, axial force, and inertial load caused by maneuvering flight of the low-pressure turbine shaft, and it is impossible to provide a load spectrum for the life design and testing of the low-pressure turbine shaft. Summary of the invention

[0004] In order to solve the above problems, the present application provides a method for calculating the service life of a low-pressure turbine shaft of an aircraft engine using a load spectrum, comprising:

[0005] Select the key state points for calculating the life of the low-pressure turbine shaft;

[0006] Find the aerodynamic load in the aerodynamic load spectrum of the low-pressure turbine shaft based on the key state points, and find the maneuvering load in the maneuvering load spectrum of the low-pressure turbine shaft based on the key state points;

[0007] Calculate the low-pressure turbine shaft stress based on aerodynamic loads and maneuvering loads;

[0008] The life of the low-pressure turbine shaft is calculated based on the stresses.

[0009] The calculation method of the low-pressure turbine shaft aerodynamic load spectrum includes:

[0010] Select the calculation state points for aerodynamic load simulation calculation;

[0011] Calculate the aerodynamic torque and axial force of the low-pressure turbine shaft based on the overall performance parameters, component aerodynamic parameters, air system parameters, and lubricating oil system parameters at the calculated state point;

[0012] A multivariate regression model was established with the engine inlet total pressure, inlet total temperature and low-pressure turbine speed as regression parameters and the aerodynamic torque and aerodynamic axial force at the calculated state point as the results; the fitting coefficients of the multivariate regression model were obtained by fitting using the least squares method;

[0013] The inlet total pressure, inlet total temperature, and low-pressure rotor speed recorded in the engine flight parameters are substituted into the multivariate regression model to obtain the aerodynamic torque spectrum and aerodynamic axial force spectrum of the low-pressure turbine shaft.

[0014] Preferably, the multivariate regression model is in the following form:

[0015]

[0016] F i is the aerodynamic load at a certain state point, including aerodynamic torque and aerodynamic axial force; P i 、T i 、N i are the inlet total pressure, total temperature and rotor speed at a certain state point, and c0, c1, c2 and c3 are the fitting coefficients.

[0017] Preferably, the fitting coefficients are obtained by fitting using the least squares method.

[0018] Preferably, the total inlet pressure at each moment during the flight is calculated by the flight altitude and the flight Mach number, and the calculation formula is as follows:

[0019]

[0020] Where: H is the flight altitude, in km;

[0021] P s is the static pressure, in Pa;

[0022] P1 is the total inlet pressure, in Pa;

[0023] Ma is the flight Mach number;

[0024] k is the specific heat ratio of the atmosphere.

[0025] Preferably, the method for calculating the low-pressure turbine shaft maneuvering load spectrum includes: establishing a structural beam model for the engine rotor and its supporting system;

[0026] Calculate the reaction force of the low pressure axis at each support point in the structural beam model;

[0027] According to the force balance, the maneuvering load under the unit maneuvering condition and the maneuvering load coefficient time series in the flight parameter data are matrix operated to obtain the maneuvering load spectrum including the maneuvering bending moment and shear force at the key section of the low-pressure shaft.

[0028] Preferably, the structural beam model principles include: the engine rotor support system is simplified to a simply supported beam; the ball bearings in the rotor support system are simplified to fixed hinge supports, and the roller bearings are simplified to movable hinge supports; the mass of the rotor components acts at the center of mass of the components in the form of concentrated force; and the distance of the rotor fulcrum is taken as the symmetric center of the bearing center.

[0029] Preferably, the method for calculating the reaction force at the fulcrum includes:

[0030] The inertial force, inertial moment and gyroscopic moment generated at the center of mass of each rotor component when the aircraft performs maneuvering flight;

[0031] According to the equilibrium equations of forces and moments, the fulcrum reaction forces of the low-pressure turbine shaft under unit maneuvering conditions are calculated respectively.

[0032] The present invention proposes a method for calculating the load spectrum of a low-pressure turbine shaft of an aero-engine. Based on the test parameters in the engine flight parameter data, aerodynamic load and maneuvering load calculation models are established respectively through theoretical deduction, numerical simulation and regression analysis, so as to quickly and accurately obtain the load spectrum of the low-pressure turbine shaft of the engine, avoid a large number of calculation iterations, eliminate the need for engine modification testing, shorten the design cycle, and save development costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a calculation process of the aerodynamic load spectrum of the low-pressure turbine shaft in a preferred embodiment of the present application.

[0034] Figure 2 This is a low-pressure turbine shaft maneuvering load spectrum calculation process in a preferred embodiment of the present application.

[0035] Figure 3 It is a low-pressure turbine shaft maneuvering load calculation model of a preferred embodiment of the present application;

[0036] Figure 4 This is a force analysis diagram of the low-pressure turbine shaft maneuvering load fulcrum in a preferred embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be further described in detail in detail and in detail in conjunction with the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments in the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0038] A method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum, such as Figure 1-Figure 4 As shown, including:

[0039] Select a key state point for calculating the life of a low-pressure turbine shaft; search for an aerodynamic load in an aerodynamic load spectrum of the low-pressure turbine shaft based on the key state point, and search for a maneuvering load in a maneuvering load spectrum of the low-pressure turbine shaft based on the key state point; calculate the stress of the low-pressure turbine shaft based on the aerodynamic load and the maneuvering load; calculate the life of the low-pressure turbine shaft based on the stress, wherein:

[0040] 1. Aerodynamic load spectrum calculation

[0041] 1) Select the calculation state point

[0042] Determine the state points used for aerodynamic load simulation calculation. The number of state points can generally be 6 to 10. In order to ensure that the limit load boundary can be covered, the calculated state points must include the main corner points in the flight envelope.

[0043] 2) Calculate aerodynamic torque and axial force

[0044] The overall performance parameters, component aerodynamic parameters, air system parameters, and lubricating oil system parameters are calculated and analyzed for the calculated state points. With the above parameters as input, the aerodynamic torque and axial force of the low-pressure turbine shaft are further calculated, as shown in Table 1.

[0045] Table 1 Calculation results of aerodynamic loads on low-pressure turbine shaft

[0046]

[0047] 3) Perform regression analysis

[0048] Based on the data in Table 1, a regression analysis is performed on the aerodynamic torque and aerodynamic axial force at the calculation state point, and the regression parameters are the engine inlet total pressure, inlet total temperature and low-pressure turbine speed.

[0049] The multiple regression model is as follows:

[0050]

[0051] Among them: F i is the aerodynamic load (torque, axial force) at a certain state point, P i 、T i 、N i are the inlet total pressure, total temperature and rotor speed at a certain state point, and c0, c1, c2 and c3 are the fitting coefficients.

[0052] The least square method is used for fitting analysis to obtain c0, c1, c2, c3, and the aerodynamic load calculation equation.

[0053] Table 2 Fitting parameters

[0054] Load <![CDATA[c0]]> <![CDATA[c1]]> <![CDATA[c2]]> <![CDATA[c3]]> Axial force * * * * Torque * * * *

[0055] 4) Calculation of inlet total pressure in flight parameters

[0056] Since the total inlet pressure is not measured in the engine's flight data, it is first necessary to calculate the total inlet pressure at each moment during the flight through the flight altitude and flight Mach number.

[0057] The calculation formula is as follows:

[0058]

[0059] Where: H is the flight altitude (km);

[0060] P s is the static pressure (Pa);

[0061] P1 is the total inlet pressure (Pa);

[0062] Ma is the flight Mach number;

[0063] k is the specific heat ratio of the atmosphere.

[0064] 5) Aerodynamic load spectrum of low-pressure turbine shaft

[0065] Substituting the inlet total pressure, inlet total temperature, and low-pressure rotor speed recorded in the engine flight parameters into the regression equation obtained in 3), the aerodynamic torque spectrum and aerodynamic axial force spectrum of the low-pressure turbine shaft are obtained.

[0066] 2. Calculation of maneuvering load spectrum

[0067] 1) Establish a calculation model for low-pressure turbine shaft maneuvering load

[0068] The calculation of the maneuvering load of the low-pressure shaft requires a certain simplification of the engine rotor and its supporting system. By establishing a structural beam model, the reaction force of the low-pressure shaft at each support point is calculated. Then, based on the force balance analysis, the maneuvering bending moment, shear force and other loads at the key sections of the low-pressure shaft are calculated.

[0069] The principles for modeling low-pressure axle maneuvering loads are as follows:

[0070] a) The engine rotor support system is simplified to a simply supported beam;

[0071] b) The ball bearing in the rotor support system is simplified to a fixed hinge support, and the roller bearing is simplified to a movable hinge support;

[0072] c) The mass of the rotor components acts in the form of concentrated forces at the center of mass of the components;

[0073] d) The distance between the rotor fulcrum and the symmetric center of the bearing center.

[0074] Computational models such as Figure 3 shown.

[0075] 2) Calculate the pivot reaction force under unit working conditions

[0076] The maneuvering loads acting on the rotating shaft include the inertial force, inertial moment and gyroscopic moment generated at the center of mass of each rotor component when the aircraft performs maneuvering flight.

[0077] Inertia force calculation formula:

[0078] F G =N·G

[0079] N is the overload factor of the component's center of mass, and G is the component's weight.

[0080] Gyro torque calculation formula:

[0081]

[0082] Where J is the moment of inertia of the rotor around the axis of rotation, is the rotor angular velocity, is the angular velocity of the aircraft during maneuvering flight.

[0083] According to the equilibrium equations of force and moment, N x =1, N y =1, N z =1,Ω y =1,Ω z =1 pivot reaction force, Ω y ,Ω z is the angular velocity around the X, Y, and Z axes, which are positive when they are forward, right, and downward, respectively.

[0084] N x 、N y 、N z is the overload coefficient in the X, Y, and Z axis directions, which are positive in the forward, right, and downward directions, respectively. The X axis is the centerline of engine rotation, which is positive along the heading direction, the Y axis is the vertical direction of the engine, which is positive downward, and the Y axis is positive in the direction specified by the right-hand rule from the Y axis to the X axis.

[0085] Table 3 Calculation results of the support reaction force of the low-pressure turbine shaft under unit maneuvering conditions (in Newton)

[0086]

[0087] Note: R1y, R1z, R2x, R2, R2z, R3x, R3y, R3z, R4y, R4z, R5y, and R5z are the fulcrum reactions at each fulcrum.

[0088] 3) Maneuvering load spectrum of low-pressure turbine shaft

[0089] For a certain section of the low-pressure shaft, the dynamic bending moment and shear force at the section can be calculated based on the force balance analysis, such as Figure 4 As shown in Table 4. By performing matrix operations on the maneuvering load under the unit maneuvering condition and the maneuvering load coefficient time series in the flight parameter data, the corresponding maneuvering load spectrum (bending moment, shear force, etc.) can be obtained.

[0090] Table 4 Calculation results of maneuvering loads on low-pressure turbine shaft section F under unit maneuvering conditions (Unit: Newton)

[0091]

[0092] Note: Fx, Fy, Fz, Mx, My, and Mz are the shear force and bending moment acting on the required section.

[0093] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum, characterized in that: include: Select the key state points for calculating the life of the low-pressure turbine shaft; Find the aerodynamic load in the aerodynamic load spectrum of the low-pressure turbine shaft based on the key state points, and find the maneuvering load in the maneuvering load spectrum of the low-pressure turbine shaft based on the key state points; Calculate the low-pressure turbine shaft stress based on aerodynamic loads and maneuvering loads; The life of the low-pressure turbine shaft is calculated based on the stresses.

2. The method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum as claimed in claim 1, characterized in that: The aerodynamic load calculation method comprises: Select the calculation state points for aerodynamic load simulation calculation; Calculate the aerodynamic torque and axial force of the low-pressure turbine shaft based on the overall performance parameters, component aerodynamic parameters, air system parameters, and lubricating oil system parameters at the calculated state point; A multivariate regression model was established with the engine inlet total pressure, inlet total temperature and low-pressure turbine speed as regression parameters and the aerodynamic torque and aerodynamic axial force at the calculated state point as the results; the fitting coefficients of the multivariate regression model were obtained by fitting using the least squares method; The inlet total pressure, inlet total temperature, and low-pressure rotor speed recorded in the engine flight parameters are substituted into the multivariate regression model to obtain the aerodynamic torque spectrum and aerodynamic axial force spectrum of the low-pressure turbine shaft.

3. The method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum as claimed in claim 2, characterized in that: The multivariate regression model is as follows: F i is the aerodynamic load at a certain state point, including aerodynamic torque and aerodynamic axial force; P i 、T i 、N i are the inlet total pressure, total temperature and rotor speed at a certain state point, and c0, c1, c2 and c3 are the fitting coefficients.

4. The method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum as claimed in claim 3, characterized in that: The fitting coefficients were obtained by using the least squares method.

5. The method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum as claimed in claim 3, characterized in that: The total inlet pressure at each moment during the flight is calculated by the flight altitude and flight Mach number. The calculation formula is as follows: Where: H is the flight altitude, in km; P s is the static pressure, in Pa; P1 is the total inlet pressure, in Pa; Ma is the flight Mach number; k is the specific heat ratio of the atmosphere.

6. The method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum as claimed in claim 1, characterized in that: The maneuvering load spectrum calculation method comprises: Establish a structural beam model for the engine rotor and its support system; Calculate the reaction force of the low pressure axis at each support point in the structural beam model; According to the force balance, the maneuvering load under the unit maneuvering condition and the maneuvering load coefficient time series in the flight parameter data are matrix operated to obtain the maneuvering load spectrum including the maneuvering bending moment and shear force at the key section of the low-pressure shaft.

7. The method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum as claimed in claim 5, characterized in that: The principles of the structural beam model include: the engine rotor support system is simplified to a simply supported beam; the ball bearings in the rotor support system are simplified to fixed hinge supports, and the roller bearings are simplified to movable hinge supports; the mass of the rotor components acts at the center of mass of the components in the form of concentrated force; the distance of the rotor fulcrum is taken from the symmetric center of the bearing center.

8. The method for calculating the life of a low-pressure turbine shaft of an aircraft engine using a load spectrum as claimed in claim 7, characterized in that: The calculation methods of reaction force at the fulcrum include: The inertial force, inertial moment and gyroscopic moment generated at the center of mass of each rotor component when the aircraft performs maneuvering flight; According to the equilibrium equations of forces and moments, the fulcrum reaction forces of the low-pressure turbine shaft under unit maneuvering conditions are calculated respectively.

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