Method for analyzing modal frequencies of a gas turbine tie rod rotor taking into account temperature influences

Abstract

The application discloses a method for analyzing modal frequency of a gas turbine tie rod rotor considering temperature influence, which is used for calculating dynamic characteristics of the gas turbine tie rod rotor. The method calculates and analyzes influences of temperature and rotation speed changes on tie rod pretightening force during a starting process of the gas turbine tie rod rotor; the changes of the tie rod pretightening force are introduced into a tie rod rotor contact stiffness calculation model, a calculation model of tie rod rotor contact interface bending stiffness during the starting process is established, and dynamic change data of the bending stiffness are obtained; through comprehensively considering influences of the temperature on the elastic modulus and influences of the pretightening force changes on the bending stiffness, the modal frequency of the rotor is calculated by using a transfer matrix method. The application can effectively consider influences of the temperature on the dynamic characteristics of the gas turbine tie rod rotor during the starting process, can more accurately calculate the modal frequency of the gas turbine tie rod rotor, and provides a basis for gas turbine tie rod rotor design.

Description

Technical Field

[0001] This invention belongs to the field of gas turbine technology, and specifically relates to a method for analyzing the modal frequency of a gas turbine tie rod rotor considering the influence of temperature. Background Technology

[0002] Heavy-duty gas turbine tie-rod rotors are a typical type of composite rotor. They consist of a central tie rod or multiple circumferential tie rods passing through each stage of the rotor discs. Preload is applied to the tie rods to press the discs together, thus integrating the rotor into a single unit. Due to their lightweight, ease of assembly, and excellent cooling performance, this type of rotor is widely used in gas turbines and aero-engines. Gas turbine rotors operate in high-temperature, high-pressure environments, and the complex temperature fields and discontinuous contact interfaces significantly influence the dynamic characteristics of tie-rod rotors. Therefore, determining a method for calculating the modal frequencies of tie-rod rotors that considers temperature effects is crucial for accurately analyzing the dynamic characteristics of gas turbine tie-rod rotors. Summary of the Invention

[0003] The purpose of this invention is to establish a modal frequency analysis method for gas turbine tie rod rotors that considers the influence of temperature. This method establishes a bending stiffness model of the contact interface of the tie rod rotor during startup, analyzes the influence of preload changes on bending stiffness, and combines this with the effect of temperature on the elastic modulus to more accurately calculate the modal frequencies of the gas turbine tie rod rotor.

[0004] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0005] A method for modal frequency analysis of a gas turbine tie rod rotor considering the effects of temperature includes the following steps:

[0006] 1) Based on the changes in temperature and speed during the start-up of the gas turbine tie rod rotor, the start-up process is divided into a speed-up stage and a stable operation stage, and the change data of tie rod preload in the two stages are obtained;

[0007] 2) Based on the stiffness model theory of the contact interface of the tie rod rotor, and based on the dual analysis-regular surface contact stiffness model, the functional relationship between the bending stiffness of the contact interface and the preload is calculated.

[0008] 3) Substitute the preload change data from step 1) into the functional relationship between bending stiffness and preload from step 2) to obtain the dynamic change data of the bending stiffness of the tie rod rotor during the start-up process;

[0009] 4) Taking into account the influence of temperature on the modulus of elasticity and the influence of preload variation on bending stiffness, both are corrected using the modulus of elasticity, and the transfer matrix method is used to calculate the rotor's modal frequency.

[0010] A further improvement of this invention is that it incorporates the changes in temperature and preload during startup into the rotor dynamics calculation model, which allows for a more accurate calculation of the modal frequencies of the gas turbine tie rod rotor.

[0011] A further improvement of the present invention is that, in step 1), the finite element method is used to calculate the change law of the preload of the tie rod during the start-up process, and the start-up process is divided into two stages: acceleration and stable operation.

[0012] A further improvement of the present invention is that, in step 2), a bending stiffness model of the contact interface of the tie rod rotor is established based on the dual-fractal-regular surface contact stiffness model.

[0013] A further improvement of this invention is that, in step 2), the bending stiffness K of the contact interface is a function of the contact pressure P, as follows:

[0014]

[0015] Where k n The value represents the contact stiffness per unit area, obtained through surface topography measurement; y represents the ordinate of the contact surface; and A represents the contact area.

[0016] A further improvement of the present invention is that, in step 3), the change of preload during the start-up process is considered, and a bending stiffness model of the contact interface between the tie rod and the rotor is established during the start-up process.

[0017] A further improvement of the present invention is that, in step 4), the influence of temperature on elastic modulus and the influence of preload change on bending stiffness are comprehensively considered, and both are corrected using elastic modulus. The modal frequency of the tie rod rotor is calculated using the transfer matrix method.

[0018] A further improvement of the present invention is that, in step 4), during the start-up process of the gas turbine tie rod rotor, the temperature change affects the elastic modulus of the material, and the relationship is expressed by a quadratic function: E = E0(aT2 + bT + c), where a, b, and c are constants related to the material; E0 is the elastic modulus of the material at 20℃; and T is the temperature.

[0019] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0020] This invention corrects the effects of temperature on elastic modulus and preload variation on bending stiffness by using elastic modulus, effectively considering the impact of temperature and preload variation on the dynamic characteristics of gas turbine tie rod rotors during startup. This allows for more accurate calculation of the modal frequencies of gas turbine tie rod rotors, providing a basis for gas turbine tie rod rotor design. Attached Figure Description

[0021] Figure 1This is a schematic diagram of a typical structure of a gas turbine tie rod rotor; the rotor contact interface and tie rod structure are shown in the figure.

[0022] Figure 2 This is the start-up curve of the gas turbine tie rod rotor; the figure shows the acceleration phase and the stable operation phase.

[0023] Figure 3 This is a schematic diagram showing the change in preload of a gas turbine tie rod rotor over time.

[0024] Figure 4 This is a schematic diagram showing the change in bending stiffness of the contact interface of the gas turbine tie rod rotor over time during the start-up phase; (a) and (b) in the figure show the acceleration phase and the stable operation phase, respectively.

[0025] Figure 5 This is a schematic diagram showing the variation of the first-order modal frequency of the bending vibration of the gas turbine tie rod rotor; (a) and (b) in the figure show the acceleration stage and the stable operation stage, respectively.

[0026] Figure 6 This is a flowchart of the method for analyzing the modal frequency of a gas turbine tie rod rotor that takes into account the temperature effect, according to the present invention. Detailed Implementation

[0027] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a schematic diagram of a typical structure of a gas turbine center-coupled rotor. The rotor's various stages of discs have planar contact interfaces, and the various stages of discs are connected by tie rods.

[0029] See Figures 2 to 6 The present invention provides a method for modal frequency analysis of a gas turbine tie rod rotor considering the effects of temperature, comprising the following steps:

[0030] 1) Determination of the change in preload during the start-up process of the gas turbine tie rod rotor.

[0031] To obtain the change data of the preload of the tie rod rotor, the starting process was divided into two stages: acceleration and stable operation, based on the starting curve data provided by the manufacturer. Considering the changes in temperature and speed, the finite element method was used to obtain the change data of the tie rod preload. Figure 2The start-up curve of the gas turbine tie rod rotor is given, which includes the acceleration phase and the stable operation phase. Figure 3 The data on the variation of the preload of the gas turbine tie rod rotor are presented. The preload changes continuously over time, and the variation law of the preload considering the effect of temperature is different from that considering only the speed.

[0032] 2) Determination of the bending stiffness of the contact interface during the start-up process of the gas turbine rotor.

[0033] Because the tie rod rotor has numerous contact interfaces, it is necessary to determine the impact of discontinuous contact on the bending stiffness of the contact interfaces. A fractal-regular surface contact stiffness model is used to calculate the contact stiffness of the tie rod rotor contact interfaces, and a bending stiffness calculation model is obtained. The bending stiffness K of the contact interface is a function of the contact pressure P:

[0034]

[0035] Where k n The value represents the contact stiffness per unit area, obtained through surface topography measurement; y represents the ordinate of the contact surface; and A represents the contact area.

[0036] Figure 4 Data on the variation of bending stiffness of the gas turbine tie rod rotor contact interface over time during startup are presented, including both the acceleration and steady-state operation phases. The effects of temperature and speed variations are considered, and the variation pattern is related to the trend of preload variation.

[0037] 3) Determination of the modal frequency of the gas turbine tie rod rotor considering the effect of temperature.

[0038] Since there is a functional relationship between bending stiffness and elastic modulus E: K = EI, where I is the bending section modulus, the variation of bending stiffness can be represented by the variation of elastic modulus. During the start-up process of the gas turbine tie rod rotor, temperature changes affect the elastic modulus of the material, and this relationship can be represented by a quadratic function: E = E0(aT² + bT + c), where a, b, and c are material-related constants; E0 is the elastic modulus of the material at 20℃; and T is the temperature. Therefore, the effects of temperature on elastic modulus and the effects of preload changes on bending stiffness are both corrected using the elastic modulus. Furthermore, the transfer matrix method is used to analyze the modal frequencies of the gas turbine tie rod rotor.

[0039] Figure 5 The data on the variation of the first-order modal frequency of the gas turbine tie rod rotor bending vibration during startup are presented, including both the acceleration phase and the steady-state operation phase. The modal frequency variation considering the temperature effect differs from that considering only the rotational speed; the temperature effect results in a larger amplitude of modal frequency variation.

[0040] The calculated modal frequencies were compared with the experimental results of modal frequencies at a specific temperature, as shown in Table 1, demonstrating the feasibility of the calculation method.

[0041] Table 1 Comparative Analysis of Gas Turbine Rotor Modal Frequency Results

[0042]

[0043]

[0044] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for modal frequency analysis of a gas turbine tie rod rotor considering the effect of temperature, characterized in that, Includes the following steps: 1) Based on the changes in temperature and speed during the start-up of the gas turbine tie rod rotor, the start-up process is divided into a speed-up stage and a stable operation stage, and the changes in tie rod preload in the two stages are obtained; 2) Based on the stiffness model theory of the contact interface of the tie rod rotor, a bending stiffness model of the contact interface of the tie rod rotor is established based on the double-fractal-regular surface contact stiffness model. The functional relationship between the bending stiffness of the contact interface and the preload is calculated, where the bending stiffness of the contact interface is... K It is contact pressure P The function is as follows: in k n It represents the contact stiffness per unit area and is obtained through surface topography measurement; y The vertical coordinate represents the contact surface. A Indicates the contact area; 3) Substitute the preload change data from step 1) into the functional relationship between bending stiffness and preload from step 2) to obtain the dynamic change data of the bending stiffness of the tie rod rotor during the startup process; 4) Taking into account the influence of temperature on the modulus of elasticity and the influence of preload variation on bending stiffness, both are corrected using the modulus of elasticity, and the transfer matrix method is used to calculate the rotor's modal frequency.

2. The method for modal frequency analysis of a gas turbine tie rod rotor considering temperature effects according to claim 1, characterized in that, Meanwhile, by incorporating the changes in temperature and preload during startup into the rotor dynamics calculation model, the modal frequencies of the gas turbine tie rod rotor can be calculated more accurately.

3. The method for modal frequency analysis of a gas turbine tie rod rotor considering temperature effects according to claim 1, characterized in that, In step 1), the finite element method is used to calculate the variation law of the tie rod preload during the start-up process.

4. The method for modal frequency analysis of a gas turbine tie rod rotor considering temperature effects according to claim 1, characterized in that, In step 3), considering the change in preload during startup, a bending stiffness model of the contact interface between the tie rod and the rotor is established during startup.

5. The method for modal frequency analysis of a gas turbine tie rod rotor considering temperature effects according to claim 1, characterized in that, In step 4), during the start-up process of the gas turbine tie rod rotor, temperature changes affect the elastic modulus of the material, and the relationship is expressed as a quadratic function: E = E 0( aT 2 + bT + c ),in a , b and c These are material-related constants; E 0 represents the elastic modulus of the material at 20℃; T For temperature.

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