A method for determining the bending deformation deflection angle of a shaft at a cylindrical roller intermediate bearing

Abstract

The present application belongs to the field of engine design technology, and specifically relates to a method for determining the bending deformation deflection angle of the shaft at the intermediate cylindrical roller bearing. The method includes step S1, based on the constructed aircraft engine model, selecting the maximum overload coefficient in the pitch direction and the yaw direction, and the highest speed state of the high and low pressure rotors as calculation nodes, and determining the first deflection angle of the shaft at the intermediate bearing; step S2, based on the constructed engine high and low pressure rotor model, selecting the maximum thermal load and the highest speed state of the high and low pressure rotors as calculation nodes, and determining the second deflection angle of the shaft at the intermediate bearing caused by the change in the taper of the drum shaft of the high and low pressure rotors; step S3, determining the third deflection angle of the shaft caused by the different axiality of the fulcrum; step S4, accumulating and determining the bending deformation deflection angle of the shaft at the intermediate cylindrical roller bearing. The present application fully introduces engineering use environments such as thermal load, centrifugal load, maneuvering load, dual rotor system, and fulcrum coaxiality, and the calculation results are more accurate.

Description

Technical Field

[0001] The present application belongs to the technical field of engine design, and specifically relates to a method for determining the bending deformation deflection angle of a shaft at a cylindrical roller intermediate bearing. Background Art

[0002] The mechanical design manual points out that the shaft will bend and torsionally deform under load. If the deformation exceeds the allowable limit, it will affect the normal operation of the parts on the shaft. Therefore, when designing important shafts, it is necessary to check the deformation of the shaft, that is, to check the stiffness of the shaft. The stiffness of the shaft is divided into bending stiffness and torsion stiffness. Bending stiffness is measured by deflection and deflection angle.

[0003] In general mechanical manufacturing, the allowable value of the bending deformation of the shaft is based on the deflection angle at the bearing. The bending deformation deflection angle can be calculated using simplified algorithms such as the energy method, equivalent diameter method, and graphical method of material mechanics. However, for cylindrical roller intermediate bearings widely used in aircraft engines, due to the complexity of structure, load, assembly, and use, the existing bending deformation deflection angle calculation method cannot obtain accurate results and cannot meet the requirements of shaft stiffness verification and bearing anti-deflection ability design.

[0004] The use of simplified algorithms such as the energy method, equivalent diameter method, and graphical method in material mechanics to calculate the bending deformation deflection angle has the following disadvantages:

[0005] 1. Only the basic property factors such as shaft elastic modulus, section inertia moment, shaft length, and diameter are considered, and the bending deformation caused by temperature difference, centrifugal load, maneuvering load, etc. in the working state of the aircraft engine rotor is ignored;

[0006] 2. Only the bending deformation under the action of bending moment and unit force can be calculated, while most aircraft engine rotors are drum-shaft structures. The existing calculation method cannot calculate the deformation deflection angle at the bearing caused by the taper deformation of the drum shaft;

[0007] 3. Only the bending deformation of the shaft system can be calculated. The intermediate bearing used in the aircraft engine is supported on the stator load-bearing system through the high- and low-pressure dual-rotor system. The existing calculation method cannot calculate the dual-rotor system and the deflection angle at the bearing caused by the different axial degrees of the fulcrum;

[0008] 4. The existing calculation method can only simply check the bending stiffness of the shaft. For the calculation of the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing under the complex structure and load conditions of the aircraft engine, the accuracy cannot meet the engineering design requirements such as the shaft stiffness design and the bearing anti-deflection ability design. Summary of the invention

[0009] In order to solve the above problems, the present application provides a method for determining the bending deformation deflection angle of the shaft at a cylindrical roller intermediate bearing, superimposing the influence of complex structure and load limit conditions on the bending deformation of the shaft, and finally obtaining an accurate bending deformation deflection angle of the shaft for use in shaft stiffness verification and bearing anti-deflection capacity design.

[0010] The method for determining the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing provided in the present application mainly includes:

[0011] Step S1, based on the constructed aircraft engine model, the maximum overload coefficients in the pitch direction and the yaw direction, and the highest speed states of the high-pressure and low-pressure rotors are selected as calculation nodes, and the first deflection angle of the shaft at the intermediate bearing is determined with the main mounting node as the origin;

[0012] Step S2: Based on the constructed engine high and low pressure rotor models, the maximum heat load and the highest speed state of the high and low pressure rotors are selected as calculation nodes to determine the second deflection angle of the shaft at the intermediate bearing caused by the taper change of the drum shaft of the high and low pressure rotors;

[0013] Step S3, determining a third deflection angle of the shaft caused by the different axial degrees of the fulcrum;

[0014] Step S4, determining the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing by accumulating the first deflection angle, the second deflection angle and the third deflection angle.

[0015] Preferably, in step S1, when constructing the aircraft engine model, the low-pressure rotor, the high-pressure rotor and the casing are simulated using beam elements, and the bearings, supports and mounting nodes are simulated using spring elements.

[0016] Preferably, in step S2, for the high-pressure rotor or the low-pressure rotor, the taper deformation of the shaft at the bearing is determined according to the distance and deformation difference between two end points of the shaft and the bearing.

[0017] Preferably, for the intermediate bearing of the dual-rotor system, the deflection angles of the high-pressure and low-pressure rotors at the bearings are determined respectively, and then the deflection angles are superimposed according to the deflection directions to form the second deflection angle.

[0018] Preferably, in step S3, the misalignment of the fulcrums includes the deflection of the shaft caused by the fitting clearance between the centering surfaces of the stator connecting parts, the end face runout of the stator connecting parts and the radial runout of the centering surfaces of the stator connecting parts, and the extreme value method is used to accumulate the coaxiality deviations of each stator connecting part to form the misalignment between the fulcrums.

[0019] Preferably, step S3 further includes determining the third deflection angle according to a ratio of the different axialities of the two fulcrums to the span of the two fulcrums.

[0020] Preferably, step S3 further includes converting the deflection angles of the high-pressure and low-pressure rotors at the bearings of the intermediate bearing of the dual-rotor system according to the span between the intermediate bearing and the adjacent bearings.

[0021] Preferably, the method for determining the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing also includes: step S5, comparing the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing with the allowable value of shaft deformation to determine whether the shaft can meet the actual application requirements of the aircraft engine.

[0022] The key points of this application are:

[0023] 1. Structural and load factors that should be considered when calculating the deflection angle of the shaft at the cylindrical roller intermediate bearing.

[0024] 2. Methods for calculating the limit value of deflection angle under various conditions, and evaluation methods for aircraft engine rotor stiffness design.

[0025] 3. The calculated deflection angle is used as the design input for the cylindrical roller intermediate bearing.

[0026] This application aims at the design characteristics of the rotor shaft and the intermediate bearing of the aircraft engine, and the structure and load considered in the calculation are more comprehensive. It fully introduces the engineering use environment such as thermal load, centrifugal load, maneuvering load, dual rotor system, and fulcrum coaxiality, and the calculation result is more accurate; this application uses the limit value calculation result to be compared with the allowable value of the shaft deformation, which can be used as an evaluation condition for the stiffness of the shaft, forming a stiffness evaluation method to meet the actual application needs of aircraft engines; the deflection angle of the shaft at the intermediate bearing calculated by this method makes it possible to introduce the anti-deflection capability design concept into the design requirements of the cylindrical roller bearing of the aircraft engine for the first time, solving the problem of fatigue life design requirements of the intermediate bearing under the action of deflection load. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of a preferred embodiment of a method for determining the bending deformation deflection angle of a shaft at a cylindrical roller intermediate bearing of the present invention.

[0028] Figure 2 This is a schematic diagram of the deflection angles of the inner and outer rings of a bearing according to a preferred embodiment of the present application.

[0029] Figure 3 For this application Figure 2 Schematic diagram of the positions of the matching endpoints of the shaft and the bearing in the illustrated embodiment.

[0030] Figure 4 For this application Figure 2 A schematic diagram of deflection angle calculation in the illustrated embodiment.

[0031] Figure 5 This is a schematic diagram of a fulcrum different axiality model of a preferred embodiment of the present application.

[0032] Figure 6 For this application Figure 5 Schematic diagram of the effect of end face error accumulation on the concentricity of the casing in the illustrated embodiment. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the implementation of this application will be described in more detail in combination with the drawings in the implementation of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and cannot be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in combination with the drawings.

[0034] Aiming at the calculation of the bending deformation deflection angle of the rotor shaft of an aircraft engine at the cylindrical roller intermediate bearing, this application provides a limit value calculation method, which superimposes the influence of complex structure and load limit conditions on the bending deformation of the shaft, and finally obtains an accurate bending deformation deflection angle of the shaft for the stiffness verification of the shaft and the design of the anti-deflection capacity of the bearing. The specific method is as follows Figure 1 As shown, it mainly includes:

[0035] Step S1, based on the constructed aircraft engine model, the maximum overload coefficients in the pitch direction and the yaw direction, and the highest speed states of the high-pressure and low-pressure rotors are selected as calculation nodes, and the first deflection angle of the shaft at the intermediate bearing is determined with the main mounting node as the origin;

[0036] Step S2: Based on the constructed engine high and low pressure rotor models, the maximum heat load and the highest speed state of the high and low pressure rotors are selected as calculation nodes to determine the second deflection angle of the shaft at the intermediate bearing caused by the taper change of the drum shaft of the high and low pressure rotors;

[0037] Step S3, determining a third deflection angle of the shaft caused by the different axial degrees of the fulcrum;

[0038] Step S4, determining the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing by accumulating the first deflection angle, the second deflection angle and the third deflection angle.

[0039] Step S1 mainly involves the calculation of the flexural deformation of the shaft under the action of gravity and maneuvering overload. Since the structure of the aircraft engine is very complex, a simplified model is established, and the low-pressure rotor, high-pressure rotor and casing are simulated with beam elements, and the bearings, supports and mounting nodes are simulated with spring elements; the maximum overload coefficients in the pitch and yaw directions, and the highest speed state points of the high and low-pressure rotors are selected; the main mounting node is taken as the origin, and the finite element analysis software MSC.Nastran is used to calculate the deflection and deflection angle at the intermediate bearing.

[0040] In this embodiment, the mounting node refers to a connecting piece between the engine and the aircraft, which is used to transmit various external loads of the engine to the aircraft.

[0041] Step S2 involves the calculation of the drum shaft taper deformation under thermal load and centrifugal load. The radial thermal deformation of the shaft at the local position of the bearing under the axial temperature difference is different, which causes the drum shaft taper to change. The centrifugal force generated by the high-speed rotation of the disk and blades at one end of the shaft also causes the drum shaft taper to change. The drum shaft taper causes the inner and outer rings of the bearing to deflect, just like the rotor deflection. Figure 2 The calculation of drum shaft taper deformation first uses the general finite element analysis software ANSYS to establish a rotor model; select the maximum state point, generally the state point of maximum heat load and maximum speed, to calculate the radial deformation of the shaft; select the end point position of the shaft and bearing, such as Figure 3 As shown, select point A and point B for calculation, refer to Figure 4 , calculate the deformation x1 and deformation x2 of the two endpoints respectively, and determine the inclination angle according to the distance L between the two endpoints, that is, calculate the deflection angle according to the ratio of the deformation difference to the original position length.

[0042] In some optional implementations, for the intermediate bearing of the dual-rotor system, the deflection angles of the high-pressure and low-pressure rotors at the bearings are determined respectively, and then the deflection angles are superimposed according to the deflection directions to form the second deflection angle.

[0043] Step S3 is used to calculate the shaft bending deformation caused by different axiality of the fulcrums: During the actual assembly and use of aircraft engines, there are different degrees of different axiality between the fulcrums of the support shaft, which in turn affects the deflection angle of the shaft at the intermediate bearing position. The calculation is based on the positioning bearing of the support shaft, and considers the factors that affect the different axiality of the cold fulcrums of the engine, mainly including the fitting clearance between the centering surfaces of the stator connector, the end face runout (non-parallelism) of the stator connector, and the radial runout of the centering surface of the stator connector. The extreme value method is used to accumulate the coaxiality deviation of each stator connector to form the different axiality between the fulcrums. The calculation model is as follows: Figure 5 and Figure 6 As shown, the deflection angle is calculated according to the ratio of different axis degrees to the support span.

[0044] For the intermediate bearing of the dual-rotor system, the deflection angles of the high and low pressure rotors at the bearings are converted according to the span between the intermediate bearing and the adjacent bearings.

[0045] Finally, in step S4, the deflection angles obtained by the above limit state calculations are accumulated, that is, the bending deformation deflection angles of the shaft at the intermediate bearing position obtained by the limit value calculation method.

[0046] In some optional embodiments, the method for determining the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing also includes: step S5, comparing the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing with the allowable value of shaft deformation to determine whether the shaft can meet the actual application requirements of the aircraft engine.

[0047] This application fully introduces engineering use environments such as thermal loads, centrifugal loads, maneuvering loads, dual-rotor systems, and fulcrum coaxiality, and the calculation results are more accurate; this application uses limit value calculation results to be compared with the allowable value of shaft deformation, which can be used as an evaluation condition for the stiffness of the shaft, forming a stiffness evaluation method that meets the actual application needs of aircraft engines; the deflection angle of the shaft at the intermediate bearing calculated by this method makes it possible to introduce the anti-deflection capability design concept into the design requirements of cylindrical roller bearings of aircraft engines for the first time, solving the problem of fatigue life design requirements for intermediate bearings under deflection loads.

[0048] Although the present application has been described in detail above with general descriptions and specific implementation schemes, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope of protection claimed in the present application.

Claims

1. A method for determining the bending deformation deflection angle of a shaft at a cylindrical roller intermediate bearing, characterized in that: include: Step S1, based on the constructed aircraft engine model, the maximum overload coefficients in the pitch direction and the yaw direction, and the highest speed states of the high-pressure and low-pressure rotors are selected as calculation nodes, and the first deflection angle of the shaft at the intermediate bearing is determined with the main mounting node as the origin; Step S2: Based on the constructed engine high and low pressure rotor models, the maximum heat load and the highest speed state of the high and low pressure rotors are selected as calculation nodes to determine the second deflection angle of the shaft at the intermediate bearing caused by the taper change of the drum shaft of the high and low pressure rotors; Step S3, determining a third deflection angle of the shaft caused by the different axial degrees of the fulcrum; Step S4, determining the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing by accumulating the first deflection angle, the second deflection angle and the third deflection angle; Wherein, in step S3, the fulcrum misalignment includes the deflection of the shaft caused by the matching clearance between the centering surfaces of the stator connecting parts, the end face runout of the stator connecting parts and the radial runout of the centering surface of the stator connecting parts, and the extreme value method is used to accumulate the coaxiality deviation of each stator connecting part to form the misalignment between the fulcrums; In step S3, the method further includes determining the third deflection angle according to the ratio of the different axial degrees of the two fulcrums to the span of the two fulcrums; Step S3 further includes converting the deflection angles of the high-pressure and low-pressure rotors at the bearings for the intermediate bearing of the dual-rotor system according to the span between the intermediate bearing and the adjacent bearings.

2. The method for determining the bending deformation deflection angle of a shaft at a cylindrical roller intermediate bearing according to claim 1, characterized in that: In step S1, when constructing the aircraft engine model, the low-pressure rotor, the high-pressure rotor and the casing are simulated using beam elements, and the bearings, supports and mounting nodes are simulated using spring elements.

3. The method for determining the bending deformation deflection angle of a shaft at a cylindrical roller intermediate bearing according to claim 1, characterized in that: In step S2, for the high-pressure rotor or the low-pressure rotor, the taper deformation of the shaft at the bearing is determined according to the distance between the two end points of the shaft and the bearing and the deformation difference.

4. The method for determining the bending deformation deflection angle of a shaft at a cylindrical roller intermediate bearing according to claim 3, characterized in that: For the intermediate bearing of the dual-rotor system, the deflection angles of the high-pressure and low-pressure rotors at the bearings are determined respectively, and then the deflection angles are superimposed according to the deflection directions to form the second deflection angle.

5. The method for determining the bending deformation deflection angle of a shaft at a cylindrical roller intermediate bearing according to claim 1, characterized in that: Also includes: Step S5: Compare the bending deformation deflection angle of the shaft at the cylindrical roller intermediate bearing with the allowable value of shaft deformation to determine whether the shaft can meet the actual application requirements of the aircraft engine.

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