A parameterized design method for turbine blade shroud clearance of a marine gas turbine

Abstract

This invention provides a parametric design method for the crown clearance of marine gas turbine turbine pre-twisting blades, aiming to improve the fatigue damage resistance of marine gas turbine turbine blades and extend their service life. The parametric design method for the crown clearance of marine gas turbine turbine pre-twisting blades involves adjusting the interference and clearance parameters between the blade crowns, analyzing and evaluating the compressive stress and clearance calculation results corresponding to different parameters, and obtaining the optimal blade crown clearance value that meets the strength and vibration design requirements. The crown clearance value will serve as the basis for the design of the turbine pre-twisting blade crown structure. This invention can accurately simulate the interaction relationship between the blade crowns under operating conditions, optimize the design of the crown clearance value, and adjust the overall blade structural damping. It has significant engineering application value for improving the fatigue resistance and extending the service life of gas turbine pre-twisting blades.

Description

Technical Field

[0001] This invention belongs to the technical field of pre-twisted blade structure design for gas turbines, specifically relating to a parametric design method for the crown clearance of pre-twisted blades for marine gas turbines. Background Technology

[0002] A gas turbine is a rotating mechanical kinetic energy device that converts the thermal energy of high-temperature, high-pressure combustion gases into mechanical energy. The turbine's moving blade disk coupling structure is a key component for the gas turbine's thermal energy output. The turbine moving blade structure is the most demanding critical component of a gas turbine. It operates under a coupled stress field of multiple loads, including thermal stress, centrifugal force, and vibration stress, resulting in complex stress conditions and high stress values. Compared to other critical components of a gas turbine, the turbine blades have a relatively short lifespan, ultimately determining the overall service life of the gas turbine.

[0003] To meet the long service life requirements of marine gas turbines, turbine blades need high static strength reserves and fatigue resistance. Past turbine blade maintenance data shows that the probability of vibration fatigue damage is far greater than the probability of damage due to insufficient static strength. Improving the fatigue resistance of turbine blades will significantly extend their service life. Enhancing the resonance resistance of turbine blades is key to preventing fatigue damage. To improve the vibration resistance of turbine blades, crown pre-twist designs are commonly used.

[0004] The pre-torsional vibration reduction design of turbine blade crowns is achieved by setting damping between the blade crowns. The damping magnitude is controlled by the clearance value between the crowns. A suitable clearance value design can improve the overall stiffness of the turbine blades, thereby improving the vibration resistance of the entire turbine rotor.

[0005] The technical challenge in designing the clearance of pre-twisted blades lies in accurately determining the clearance value. If the clearance value is too large, it will cause excessive static stress in the blade crown and blade root, leading to cracks in the blade crown; if the clearance value is too small, the damping setting between the blade crowns will be too small, resulting in low blade stiffness, reduced vibration reduction capacity, and blade resonance.

[0006] The traditional design process for the pre-twisted blade clearance of gas turbine turbines involves: designing based on empirical values ​​from existing gas turbines, setting an initial clearance value for the pre-twisted blade crown, and then adjusting the design clearance value of the pre-twisted blade using vibration test results from whole-machine testing and blade disassembly inspection results. This method requires multiple sets of test data and disassembly inspection results, resulting in high design costs and long design time. Summary of the Invention

[0007] The purpose of this invention is to provide a parameterized design method for the crown clearance of pre-twisted blades of marine gas turbines, which improves the fatigue damage resistance of marine gas turbine moving blades.

[0008] A parametric design method for the crown clearance of pre-twist blades in marine gas turbines includes the following steps: S1. Establish the geometric model of the turbine pre-twisted blade disk, select the blade disk coupling structure as the strength calculation model, and determine the allowable compressive stress range of the pre-twisted blade crown extrusion surface and the minimum clearance value of the gap surface based on design experience. S2, mesh the computational model; set the material parameters for computation, apply temperature and centrifugal load; apply displacement and contact boundary constraints to the computational model; apply contact interference and clearance parameter values ​​at the blade contact area; S3, complete the static strength calculation of the blade-disc coupling structure, and extract the compressive stress value of the pre-twisted blade crown pressure surface and the gap value of the gap surface from the calculation results; S4 assesses the compressive stress on the crown pressure surface and the clearance on the clearance surface of the designed blade; when the compressive stress and clearance values ​​of the designed blade crown pass the assessment in S4, the pre-twisted blade design is completed.

[0009] Furthermore, in S1, the blade-disk coupling structure is selected as the strength calculation model, wherein the calculation model is selected as a cyclic symmetric model of a blade.

[0010] Furthermore, in S1, the allowable compressive stress range of the pre-twisted blade crown pressure surface and the minimum clearance value of the clearance surface are determined based on design experience. The allowable values ​​are empirical values ​​derived from a comprehensive analysis of pre-twisted blade crown clearance design data, gas turbine operation data, and gas turbine whole-machine test and disassembly data of similar models of gas turbines. When the pre-twisted blade crown compressive stress and minimum clearance value obtained from static strength calculation are within the allowable value range, the blade crown clearance value can ensure the vibration stiffness of the turbine pre-twisted blades and the impeller, avoid resonance, and improve the vibration resistance of the turbine structure.

[0011] Furthermore, the material parameters used for calculation in S2 include: density, elastic modulus and Poisson's ratio under different temperature conditions, stress-strain curves at different temperatures fitted using material test data, coefficient of linear expansion at different temperatures, and thermal conductivity at different temperatures.

[0012] Furthermore, in S2, temperature load and centrifugal load are applied to the calculation model. The centrifugal load is applied in the form of rotational speed, and the rotational speed for long-term operation is selected. The temperature load is the result of flow field calculation and is applied to the nodes of the calculation model in the form of node temperature.

[0013] Furthermore, S2 applies displacement and contact boundary constraints to the calculation model, applies cyclic symmetric displacement constraints to the cyclic symmetric boundary of the calculation model, applies axial and circumferential displacement constraints to the journal of the wheel end, and applies contact displacement constraints to the assembly contact area of ​​the wheel blades.

[0014] Furthermore, in S2, the blade crown pre-twist contact boundary setting involves designing initial interference data on the blade crown compression contact surface and designing initial clearance values ​​on the clearance surface. The blade crown clearance calculation parameters are adjusted by adjusting the interference and clearance parameter values.

[0015] Furthermore, S4 assesses the compressive stress values ​​at the blade crown contact surface and the clearance values ​​at the gap surface; the assessment conditions are as follows: in: The maximum compressive stress on the blade crown extrusion surface, The average compressive stress on the blade crown extrusion surface, and For the allowable maximum compressive stress and minimum compressive stress, The yield strength of the blade material. Minimum gap between leaf crown surfaces To determine the minimum allowable clearance in the design.

[0016] Furthermore, if the design blade crown compressive stress and clearance value fail the test in S4, the interference parameters of the pre-twisted crown part and the clearance parameters of the clearance surface in the calculation model are adjusted, and the static strength calculation is performed again; the calculation results are tested again until the test is passed and the design work is completed.

[0017] The advantages of this invention are as follows: This invention utilizes a parametric numerical simulation method for blade-crown clearance design, resulting in low design cost, short cycle time, and more accurate design results. The parametric numerical simulation method obtains the optimal blade-crown clearance value by adjusting the interference and clearance parameters between the blades and crowns, and analyzing and evaluating the compressive stress and clearance calculation results. Attached Figure Description

[0018] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of the static strength calculation model of the present invention; Figure 3 This is a graph showing the stress-strain curves of the elastoplastic material at different temperatures in the strength calculation of this invention; Figure 4 A diagram showing the static strength applied temperature load of the present invention; Figure 5 This is a schematic diagram of the leaf crown compression and gap portion of the present invention; Figure 6 The static strength calculation results of this invention are shown in the turbine rotor stress diagram. Figure 7 The turbine blade displacement diagram is the result of static strength calculation according to the present invention. Figure 8 The static strength calculation results of this invention are shown in the turbine blade crown compressive stress diagram. Figure 9 The image shows the turbine blade crown clearance cloud diagram, representing the static strength calculation results of this invention. Detailed Implementation

[0019] The present invention will now be further described with reference to the accompanying drawings.

[0020] like Figures 1-9 As shown, a parametric design method for the crown clearance of a pre-twist blade in a marine gas turbine includes the following steps: S1. Establish the geometric model of the turbine pre-twisted blade disk, select the blade disk coupling structure as the strength calculation model, and determine the allowable compressive stress range of the pre-twisted blade crown extrusion surface and the minimum clearance value of the gap surface based on design experience. The blade-disk coupling structure is selected as the strength calculation model, and the calculation model is a cyclic symmetric model of one blade. Based on design experience, the allowable compressive stress range of the pre-twisted blade crown pressure surface and the minimum clearance value of the clearance surface are determined. The allowable values ​​are empirical values ​​derived from a comprehensive analysis of pre-twisted blade crown clearance design data, gas turbine operation data, and gas turbine whole-machine test and disassembly data of similar models. When the pre-twisted blade crown compressive stress and minimum clearance value obtained from static strength calculation are within the allowable range, the blade crown clearance value can ensure the vibration stiffness of the turbine pre-twisted blades and the impeller, avoid resonance, and improve the vibration resistance of the turbine structure. S2, mesh the computational model; set the material parameters for computation, apply temperature and centrifugal load; apply displacement and contact boundary constraints to the computational model; apply contact interference and clearance parameter values ​​at the blade contact area; The material parameters used in the calculation include: density, elastic modulus and Poisson's ratio under different temperature conditions, stress-strain curves at different temperatures fitted using material test data, coefficient of linear expansion at different temperatures, and thermal conductivity at different temperatures. Temperature load and centrifugal load are applied to the computational model. The centrifugal load is applied in the form of rotational speed, and the rotational speed for long-term operation is selected. The temperature load is the result of the flow field calculation and is applied to the nodes of the computational model in the form of nodal temperature. Displacement and contact boundary constraints are applied to the computational model; cyclic symmetric displacement constraints are applied to the cyclic symmetric boundary of the computational model; axial and circumferential displacement constraints are applied to the journal of the wheel end; and contact displacement constraints are applied to the contact area of ​​the wheel blade assembly. The blade crown pre-twist contact boundary setting involves designing initial interference data on the blade crown extrusion contact surface and designing initial clearance values ​​on the clearance surface. The blade crown clearance calculation parameters are adjusted by adjusting the interference and clearance parameter values. S3, complete the static strength calculation of the blade-disc coupling structure, and extract the compressive stress value of the pre-twisted blade crown pressure surface and the gap value of the gap surface from the calculation results; S4 assesses the compressive stress on the crown pressure surface and the clearance on the gap surface of the designed blade. When the compressive stress and clearance values ​​of the designed blade crown pass the S4 assessment, the pre-twisted blade design is complete. If the compressive stress and clearance values ​​of the designed blade crown fail the assessment, the interference parameters and clearance parameters of the pre-twisted blade crown part in the calculation model need to be adjusted, and the static strength calculation needs to be performed again. The calculation results are assessed again until they pass the assessment, and the design work is completed.

[0021] The compressive stress values ​​at the blade crown contact surface and the clearance values ​​at the gap surface were evaluated; the evaluation conditions were as follows: in: The maximum compressive stress on the blade crown extrusion surface, The average compressive stress on the blade crown extrusion surface, and For the allowable maximum compressive stress and minimum compressive stress, The yield strength of the blade material. Minimum gap between leaf crown surfaces To determine the minimum allowable clearance in the design.

[0022] This implementation method focuses on turbine pre-twisted blades and completes the parametric design of the blade crown clearance; the specific process is achieved through the following steps: S1. A geometric model of the turbine pre-torsion blade disk was created using the 3D modeling software UG. A coupled cyclic symmetric structure containing one blade was selected as the strength calculation model. (See...) Figure 1 Based on design experience, the allowable compressive stress range of the pre-twisted blade crown extrusion surface and the minimum clearance value of the gap surface are determined, see [reference needed]. Figure 5 .

[0023] S2, Step 2: Perform static strength calculations on the blade-disk coupling structure using the finite element software ANSYS. First, mesh the model; set the material parameters for the blade-disk calculation, including: density, elastic modulus and Poisson's ratio under different temperature conditions, and stress-strain curves at different temperatures fitted using elasto-plastic material test data (see [link]). Figure 3 The coefficient of linear expansion at different temperatures and the coefficient of thermal conductivity at different temperatures.

[0024] Loads are applied to the computational model, including temperature loads and centrifugal loads. The temperature load is extracted from the aerodynamic calculation results, see [link to relevant documentation]. Figure 4 The centrifugal load speed is 7200 rpm.

[0025] Cyclic symmetric displacement constraints are applied to the cyclic symmetric boundary of the model, and axial and circumferential displacement constraints are applied to the journal of the wheel end; contact displacement constraints are applied to the assembly contact area of ​​the wheel blades.

[0026] Apply an interference displacement of 0.5 to the leaf crown compression surface; apply a gap value of -0.05 to the leaf crown gap.

[0027] S3, complete the static strength calculation of the turbine rotor blade coupling structure, see turbine rotor stress cloud diagram. Figure 6 Turbine blade displacement contour map, see Figure 7 Extract the compressive stress values ​​of the crown compression surface and the clearance values ​​of the pre-twisted blade from the calculation results, see... Figure 8 and Figure 9 .

[0028] S4, evaluate the compressive stress values ​​on the blade crown extrusion surface and the clearance values ​​on the clearance surface. Evaluation conditions: in: The maximum compressive stress on the blade crown extrusion surface, The average compressive stress on the blade crown extrusion surface, and Allowable maximum compressive stress and minimum compressive stress Yield strength of blade material Minimum gap between leaf crown surfaces The design allows for a minimum clearance.

[0029] Static strength calculation results show that the maximum compressive stress on the blade crown extrusion surface is The yield strength of the blade material at 212 MPa and 800℃. It is 810 MPa. Less than It meets the design requirements.

[0030] Average compressive stress on the crown extrusion surface The average compressive stress is 25 MPa, and the maximum allowable compressive stress is within the allowable range. =40MPa and minimum compressive stress =20MPa, which meets the design requirements.

[0031] Minimum gap value of leaf crown interfacial The gap is 0.0069mm, which is less than the minimum allowable clearance in the design. =0.02mm, which does not meet the design requirements. In order to increase the minimum gap between the leaf crowns, it is necessary to increase the leaf crown gap parameter value in the calculation model and recalculate the static strength.

[0032] After adjusting the parameters, the compressive stress on the blade extrusion surface and the minimum clearance value on the blade clearance surface obtained from the static strength calculation need to be re-evaluated. The design is completed only after the evaluation is passed.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A parametric design method for the crown clearance of pre-twisted blades in marine gas turbines, characterized in that, Includes the following steps: S1. Establish the geometric model of the turbine pre-twisted blade disk, select the blade disk coupling structure as the strength calculation model, and determine the allowable compressive stress range of the pre-twisted blade crown extrusion surface and the minimum clearance value of the gap surface based on design experience. S2, mesh the computational model; set the material parameters for the calculation, apply the temperature and centrifugal load; Displacement and contact boundary constraints are applied to the computational model; contact interference and clearance parameter values ​​are applied at the blade crown contact area; S3, complete the static strength calculation of the blade-disc coupling structure, and extract the compressive stress value of the pre-twisted blade crown pressure surface and the gap value of the gap surface from the calculation results; S4, assesses the compressive stress on the pressure surface of the blade crown and the clearance on the gap surface; The design of the pre-twisted blade is complete when the blade crown compressive stress and clearance value pass the S4 test.

2. The parametric design method for the crown clearance of a marine gas turbine turbine pre-twist blade according to claim 1, characterized in that, In S1, the blade-disk coupling structure is selected as the strength calculation model, wherein the calculation model is selected as a cyclic symmetric model of a blade.

3. The parametric design method for the crown clearance of a marine gas turbine turbine pre-twist blade according to claim 1, characterized in that, In S1, the allowable compressive stress range of the pre-twisted blade crown pressure surface and the minimum clearance value of the clearance surface are determined based on design experience. The allowable values ​​are empirical values ​​derived from the comprehensive analysis of pre-twisted blade crown clearance design data, gas turbine operation data, and gas turbine whole-machine test and disassembly data of similar models of gas turbines. When the pre-twisted blade crown compressive stress and minimum clearance value obtained from static strength calculation are within the allowable value range, the blade crown clearance value can ensure the vibration stiffness of the turbine pre-twisted blades and the impeller, avoid resonance, and improve the vibration resistance of the turbine structure.

4. The parametric design method for the crown clearance of a marine gas turbine turbine pre-twist blade according to claim 1, characterized in that, The material parameters used in the calculation in S2 include: density, elastic modulus and Poisson's ratio under different temperature conditions, stress-strain curves at different temperatures fitted using material test data, coefficient of linear expansion at different temperatures, and thermal conductivity at different temperatures.

5. The parametric design method for the crown clearance of a marine gas turbine turbine pre-twist blade according to claim 1, characterized in that, In S2, temperature load and centrifugal load are applied to the calculation model. The centrifugal load is applied in the form of rotational speed, and the rotational speed for long-term operation is selected. The temperature load is the result of flow field calculation and is applied to the nodes of the calculation model in the form of node temperature.

6. The parametric design method for the crown clearance of a marine gas turbine turbine pre-twist blade according to claim 1, characterized in that, S2 applies displacement and contact boundary constraints to the calculation model, applies cyclic symmetric displacement constraints to the cyclic symmetric boundary of the calculation model, applies axial and circumferential displacement constraints to the journal of the wheel end, and applies contact displacement constraints to the assembly contact area of ​​the wheel blades.

7. The parametric design method for the crown clearance of a marine gas turbine turbine pre-twist blade according to claim 1, characterized in that, In S2, the blade crown pre-twist contact boundary setting involves designing initial interference data on the crown extrusion contact surface and initial clearance value on the clearance surface. The adjustment of the crown clearance calculation parameters is completed by adjusting the interference and clearance parameter values.

8. The parametric design method for the crown clearance of a marine gas turbine turbine pre-twist blade according to claim 1, characterized in that, S4 assesses the compressive stress values ​​at the blade crown contact surface and the clearance values ​​at the gap surfaces; the assessment conditions are as follows: in: The maximum compressive stress on the blade crown extrusion surface, The average compressive stress on the blade crown extrusion surface, and For the allowable maximum compressive stress and minimum compressive stress, The yield strength of the blade material. Minimum gap between leaf crown surfaces To determine the minimum allowable clearance in the design.

9. The parametric design method for the crown clearance of a marine gas turbine turbine pre-twist blade according to claim 1, characterized in that, If the design blade crown compressive stress and clearance value fail the test in S4, the interference parameters of the pre-twisted crown part and the clearance parameters of the clearance surface in the calculation model are adjusted, and the static strength calculation is performed again; the calculation results are tested again until the test is passed and the design work is completed.

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