Gas turbine engine blade disc vibration characteristic evaluation method and design method

Abstract

The invention belongs to the field of gas turbine engines, and particularly relates to a gas turbine engine blade disc vibration characteristic evaluation method and a design method. According to the method for evaluating the vibration characteristics of the bladed disc of the gas turbine engine, the mode of the bladed disc is obtained through calculation according to the obtained pitch diameter number; obtaining the minimum resonance frequency and the maximum resonance frequency in the working rotation speed range according to the engine rotation speed, the exciting force order and the blade disc mode; according to the minimum resonant frequency and the maximum resonant frequency, obtaining a minimum modal order and a maximum modal order in the working rotating speed range of the bladed disc, and calculating effective modal masses of all modals in the range; obtaining a mass fraction according to the minimum modal order, the maximum modal order and the effective modal mass; and evaluating the vibration characteristics of the leaf disc according to the mass fraction. According to the method, the blade disk modality which easily generates resonance and brings harmful consequences in the designed rotating speed range can be identified, a certain basis is provided for vibration design of the blade disk, and high-cycle fatigue failure caused by resonance of the blade disk can be effectively avoided.

Description

Technical Field

[0001] The present invention belongs to the field of gas turbine engines, and in particular relates to a method for evaluating and designing vibration characteristics of a gas turbine engine blade disk. Background Art

[0002] A blisk is a rotor structure widely used in gas turbine engines and other turbomachinery. It is usually composed of blades and a disk. The blades and disk can be machined as a whole, or they can be processed separately and connected into a whole through special structures (such as tenons).

[0003] During operation, the blades and disk of a blisk are subject to coupled vibrations due to airflow excitation. This can cause the blades and disk to vibrate in a variety of modes, each associated with a specific vibration frequency. When the excitation frequency generated by the stator blades or support plates upstream and downstream of the blisk coincides with this vibration frequency, the blisk may resonate, and in severe cases, cause high-cycle fatigue failure of the blades. To avoid high-cycle fatigue failure caused by resonance, vibration design is required for the blisk.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a method for evaluating and designing the vibration characteristics of a gas turbine engine blade disk. The evaluation method of the present invention can identify blade disk modes that are prone to resonance and bring harmful consequences within the design speed range, provide a certain basis for the vibration design of the blade disk, and effectively avoid high-cycle fatigue failure caused by blade disk resonance.

[0006] The present invention includes the following technical solutions:

[0007] A first aspect of the present invention provides a method for evaluating vibration characteristics of a gas turbine engine blade disk, comprising the following steps:

[0008] The number of pitch diameters is obtained based on the number of blades and the order of the exciting force of the blade disk;

[0009] Obtain the blade mode according to the number of pitch diameters;

[0010] The minimum resonance frequency and the maximum resonance frequency within the operating speed range are obtained according to the engine speed, the order of the exciting force and the blade disk mode;

[0011] Obtaining the minimum modal order and the maximum modal order within the operating speed range of the blade disk according to the minimum resonant frequency and the maximum resonant frequency, and calculating the effective modal mass of all modes within the range;

[0012] Obtaining a mass score according to the minimum modal order, the maximum modal order, and the effective modal mass;

[0013] Evaluate the vibration characteristics of the blisk according to the mass fraction.

[0014] Furthermore, the mass fraction is Z i ; where i represents the modal order of the blisk;

[0015] Evaluating the vibration characteristics of the blisk according to the mass fraction includes the following steps:

[0016] When the mass fraction Z i ≤ X1, the blisk meets the vibration characteristics;

[0017] When the mass fraction X1 < Z i < X2, the blisk does not meet the vibration characteristics;

[0018] When the mass fraction Z i ≥ X2, the blisk does not meet the vibration characteristics.

[0019] Furthermore, the mass fraction

[0020] where M ei represents the effective modal mass, t1 represents the minimum modal order, and t2 represents the maximum modal order.

[0021] Furthermore, the

[0022] where {φ i} represents the normalized eigenvector obtained from the vibration mode of the blisk modal order i, {φ i} T represents the transpose matrix of {φ i}, [M] represents the mass matrix, and γ i represents the modal participation factor.

[0023] Furthermore, the

[0024] where {D} is the direction vector obtained from the direction of the excitation force application.

[0025] Furthermore, the number of nodal diameters d = |n1×κ - n2×B|;

[0026] where κ represents the excitation force order and B represents the number of blades of the blisk.

[0027] Furthermore, κ is equal to the number of stator blades or the number of struts.

[0028] Furthermore, obtaining the minimum resonance frequency and the maximum resonance frequency within the operating speed range according to the engine speed and the excitation force order includes the following steps:

[0029] Based on the calculation errors of the exciting force and blade disk mode at different speeds, the minimum resonance frequency is calculated at 80% speed and the maximum resonance frequency is calculated at 105% speed;

[0030] The minimum resonant frequency The maximum resonance frequency

[0031] Where N is the maximum operating speed of the engine, in r / min; k is the order of the exciting force.

[0032] A second invention of the present invention provides a method for designing a gas turbine engine blade disk, the method further comprising the following steps:

[0033] Evaluating the vibration characteristics of a gas turbine engine blade disk using the above-mentioned method for evaluating the vibration characteristics of the blade disk;

[0034] When the mass fraction is greater than the first preset value x1 and less than the second preset value x2, the blade disk surface is strengthened;

[0035] When the mass fraction is greater than or equal to the second preset value x2, the blade disk is optimized:

[0036] Optimize the blade disk structure, or optimize the number of stator blades or support plates;

[0037] The optimized blade disk structure is evaluated for blade disk vibration characteristics according to a gas turbine engine blade disk vibration characteristic evaluation method according to any one of claims 1 to 8 until the mass score is less than a first preset value x2.

[0038] Furthermore, optimizing the blade disk structure includes modifying the blade structure.

[0039] By adopting the above technical solution, the present invention has the following advantages:

[0040] 1. The evaluation method of the present invention can identify blade disk modes that are prone to resonance and bring harmful consequences within the design speed range, providing a certain basis for the vibration design of the blade disk and effectively avoiding high-cycle fatigue failure caused by blade disk resonance.

[0041] 2. The present invention uses mass fractions to quantitatively analyze the difficulty of high-order blade disk modes to resonate under the action of exciting forces, identify first-order or multi-order blade disk modes with extremely high resonance risks, and by changing the number of excitation sources or optimizing the blade disk structure, the identified dangerous modes are kept away from the operating speed range of the blade disk, thereby avoiding fatigue damage caused by resonance during the operation of the blade disk.

[0042] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 Flowchart of a method for evaluating vibration characteristics of a gas turbine engine blade disk according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The following description provides many different embodiments or examples for implementing different features of the present invention. The components and arrangements described in the following specific examples are only used to simplify the present invention and are only used as examples, not to limit the present invention.

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0047] Existing gas turbine engine blade disk vibration design specifications only provide design assessment criteria for low-order vibration modes (generally vibration modes below the fourth order). The main purpose of low-order vibration mode design is to ensure that the vibration frequency of the low-order vibration modes has sufficient resonant frequency margin relative to the excitation frequency. However, in actual design and testing, many blade high-cycle fatigue failures caused by high-order vibration modes have occurred. Because the frequency distribution of high-order vibration modes is denser than that of low-order vibration modes, it is impossible to ensure that each vibration mode has sufficient resonant frequency margin within the engine operating speed range. Therefore, the vibration design method for low-order vibration modes is not suitable for dealing with high-order vibration problems.

[0048] A first aspect of this embodiment provides a method for evaluating vibration characteristics of a gas turbine engine blade disk, comprising the following steps:

[0049] The number of pitch diameters is obtained based on the number of blades and the order of the exciting force of the blade disk;

[0050] The blisk mode is obtained by calculating according to the number of nodal diameters;

[0051] The minimum mode frequency and the maximum mode frequency are obtained based on the mode frequency and the mode shape of the blisk mode;

[0052] The minimum resonance frequency and the maximum resonance frequency within the operating speed range are obtained based on the engine speed, the excitation force order, and the blisk mode;

[0053] The minimum mode order and the maximum mode order within the blisk operating speed range are obtained based on the minimum resonance frequency and the maximum resonance frequency, and the effective modal mass of all modes within this range is calculated;

[0054] The vibration characteristics of the blisk are evaluated based on the mass fraction.

[0055] The method of the present invention is applicable to the vibration design of high-order blisks, can identify the blisk modes that are prone to resonance and cause harmful consequences within the design speed range, provides a certain basis for the vibration design of blisks, and can effectively avoid the high-cycle fatigue failure caused by blisk resonance.

[0056] In some embodiments, the mass fraction is Z i ; where i represents the blisk mode order;

[0057] Evaluating the vibration characteristics of the blisk based on the mass fraction includes the following steps:

[0058] When the mass fraction Z i ≤X1, it indicates that the probability of this blisk mode occurring under the excitation in the excitation force application direction is small, and the blisk meets the vibration characteristics;

[0059] When the mass fraction X1 < Z i <X2, it indicates that the possibility of this blisk mode resonating under the excitation in the excitation force application direction significantly increases, and the blisk does not meet the vibration characteristics, and the surface of the blisk needs to be strengthened;

[0060] When the mass fraction Z i ≥X2, it indicates that the possibility of this order mode resonating under the excitation in the excitation force application direction is extremely high, and the blisk does not meet the vibration characteristics, and the structure of the blisk needs to be optimized.

[0061] In some embodiments,

[0062] The mass fraction

[0063] where M ei represents the effective modal mass, t1 represents the minimum mode order, and t2 represents the maximum mode order.

[0064] In some embodiments, the

[0065] Among them, {φ i} represents the normalized eigenvector obtained by the vibration mode of the blade mode order i, {φ i} T represents {φ i}, [M] represents the mass matrix, γ i represents the modal participation factor.

[0066] In some embodiments, the

[0067] Wherein, {D} is the direction vector obtained by applying the exciting force.

[0068] In some embodiments, the number of node diameters d = |n1×κ-n2×B|;

[0069] Where κ represents the order of the exciting force, and B represents the number of blades in the blisk.

[0070] In some embodiments, the κ is equal to the number of stator blades or the number of support plates.

[0071] In some embodiments, obtaining the minimum resonance frequency and the maximum resonance frequency within the operating speed range according to the engine speed and the exciting force order comprises the following steps:

[0072] Based on the calculation errors of the exciting force and blade disk mode at different speeds, the minimum resonance frequency is calculated at 80% speed and the maximum resonance frequency is calculated at 105% speed;

[0073] The minimum resonant frequency The maximum resonance frequency

[0074] Where N is the maximum operating speed of the engine, in r / min; k is the order of the exciting force.

[0075] Currently, there are two commonly used blade disk design methods:

[0076] Method 1: During the blade disk design process, modal analysis is performed on the blade disk to identify potential excitation sources, assess the resonant frequency margin of the corresponding modes, and optimize the structure to ensure that the frequency margin is no less than the minimum value required by the design specification. This ensures that the excitation frequency does not overlap with the blade disk's natural frequency during operation, thus avoiding resonance. However, since the frequency distribution of high-order vibration modes is more dense than that of low-order vibration modes, it cannot be guaranteed that each vibration mode has sufficient resonant frequency margin within the engine's operating speed range. Therefore, this method is only suitable for vibration design of low-order modes.

[0077] Method 2 involves performing dynamic stress measurement tests on the blades while they are operating, and evaluating the high-cycle fatigue life of the blades based on the measured vibration stresses and material fatigue strength. If the high-cycle fatigue life of the blades does not meet the design requirements, the blade structure must be optimized based on test data and design experience, and further testing and measurement must be performed until the high-cycle fatigue life of the blades meets the design requirements. This method can ultimately achieve the design requirements, but the continuous iterative design and testing process reduces the development efficiency of the impeller machinery and requires a significant amount of human and material resources.

[0078] A second aspect of this embodiment provides a method for designing a gas turbine engine blade disk, the method further comprising the following steps:

[0079] Evaluating the vibration characteristics of a gas turbine engine blade disk using the above-mentioned method for evaluating the vibration characteristics of the blade disk;

[0080] When the mass fraction is greater than the first preset value x1 and less than the second preset value x2, the blade disk surface is strengthened;

[0081] When the mass fraction is greater than or equal to the second preset value x2, the blade disk is optimized:

[0082] Optimize the blade disc structure,

[0083] Or optimize the number of stator blades or support plates;

[0084] The optimized blade disk structure is evaluated for blade disk vibration characteristics using the above-mentioned gas turbine engine blade disk vibration characteristic evaluation method until the mass score is less than the first preset value x2.

[0085] In some embodiments, optimizing the blade disk structure includes modifying the blade structure to adjust the natural frequency and mode shape of the blade disk.

[0086] According to the method provided in this embodiment, illustratively:

[0087] The blade disk has 10 blades, the excitation source is the adjacent stator blade, and the excitation order is 17. According to step 1, the number of node diameters where the blade disk works is d = |1x17-2x10| = 3.

[0088] The maximum modal order of the blade disk within 105% of the speed is 3 pitch diameters and 20th order mode; according to step three, the finite element method is used to calculate the frequency, vibration mode and effective modal mass of each order mode, and the frequency and effective modal weight are normalized (wherein the frequency ratio is defined as the ratio of the modal frequency to the rotor fundamental frequency, and the effective modal mass is normalized by the sum of the effective modal masses of the first 20 modes). The results are shown in Table 1. The orders within the range of 80% to 105% of the maximum design speed are 13 to 20.

[0089] Table 1 Modal frequencies and effective modal masses

[0090]

[0091]

[0092] The effective modal mass fractions Z of the 13th to 20th modes at three pitch diameters are calculated and shown in Table 2. According to the evaluation criteria, the blade disk has a high probability of resonating in the 18th, 19th, and 20th modes, especially the 19th mode, which has the risk of generating harmful resonance.

[0093] Dynamic stress measurement tests were conducted on the blade disk, and the test results verified the reliability of the calculation. The blade disk generated large vibration stress at the frequencies corresponding to the 18th to 20th order modes, and the magnitude of the vibration stress exceeded the fatigue strength of the material, posing a risk of high-cycle fatigue failure.

[0094] Table 2 Effective modal quality fraction

[0095]

[0096]

[0097] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the vibration characteristics of a gas turbine engine blade disk, characterized in that: The steps include: The number of pitch diameters is obtained based on the number of blades and the order of the exciting force of the blade disk; Obtain the blade mode according to the number of pitch diameters; The minimum resonance frequency and the maximum resonance frequency within the operating speed range are obtained according to the engine speed, the order of the exciting force and the blade disk mode; Obtaining the minimum modal order and the maximum modal order within the operating speed range of the blade disk according to the minimum resonant frequency and the maximum resonant frequency, and calculating the effective modal mass of all modes within the range; Obtaining a mass score according to the minimum modal order, the maximum modal order, and the effective modal mass; A vibration characteristic of the blisk is evaluated based on the mass fraction.

2. A gas turbine engine blade disk vibration characteristic evaluation method according to claim 1, characterized in that: The mass fraction is Z i ; Where i represents the blade mode order; Evaluating the vibration characteristics of the blade according to the mass fraction includes the following steps: When the mass fraction Z i When ≤X1, the blade disk meets the vibration characteristics; When the mass fraction X1 < Z i < X2, the blisk does not meet the vibration characteristics; When the mass fraction Z i When ≥X2, the blade disk does not meet the vibration characteristics.

3. A gas turbine engine blade disk vibration characteristic evaluation method according to claim 2, characterized in that: The quality fraction Among them, M ei represents the effective modal mass, t1 represents the minimum modal order, and t2 represents the maximum modal order.

4. A gas turbine engine blade disk vibration characteristic evaluation method according to claim 3, characterized in that: described Among them, {φ i } represents the normalized eigenvector obtained by the vibration mode of the blade mode order i, {φ i } T represents {φ i }, [M] represents the mass matrix, γ i represents the modal participation factor.

5. A gas turbine engine blade disk vibration characteristic evaluation method according to claim 4, characterized in that: described Wherein, {D} is the direction vector obtained by applying the exciting force.

6. A gas turbine engine blade disk vibration characteristic evaluation method according to any one of claims 1 to 5, characterized in that: The number of pitch diameters d = |n1×κ-n2×B|; Where κ represents the order of the exciting force, and B represents the number of blades in the blisk.

7. A gas turbine engine blade disk vibration characteristic evaluation method according to claim 6, characterized in that: The κ is equal to the number of stator blades or the number of support plates.

8. A gas turbine engine blade disk vibration characteristic evaluation method according to claim 6, characterized in that: The step of obtaining the minimum resonance frequency and the maximum resonance frequency within the operating speed range according to the engine speed and the exciting force order comprises the following steps: Based on the calculation errors of the exciting force and blade disk mode at different speeds, the minimum resonance frequency is calculated at 80% speed and the maximum resonance frequency is calculated at 105% speed; The minimum resonant frequency The maximum resonance frequency Where N is the maximum operating speed of the engine, in r / min; k is the order of the exciting force.

9. A method for designing a gas turbine engine blade disk, characterized in that: The design method further comprises the following steps: Evaluating the vibration characteristics of a blade disk of a gas turbine engine by using a method for evaluating the vibration characteristics of a blade disk of a gas turbine engine according to any one of claims 1 to 8; When the mass fraction is greater than the first preset value x1 and less than the second preset value x2, the blade disk surface is strengthened; When the mass fraction is greater than or equal to the second preset value x2, the blade disk is optimized: Optimize the blade disk structure, or optimize the number of stator blades or support plates; The optimized blade disk structure is evaluated for blade disk vibration characteristics according to a gas turbine engine blade disk vibration characteristic evaluation method according to any one of claims 1 to 8 until the mass score is less than a first preset value x2.

10. The method for designing a gas turbine engine blade disk according to claim 9, characterized in that: Optimizing the blade disk structure includes modifying the blade structure.

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