A finite element calculation method for thermal stress of steam turbine blades

Abstract

A finite element calculation method for thermal stress of a steam turbine blade relates to steam turbine blade processing technology, in order to solve the problem that the existing finite element calculation of applying a fixed working temperature to the entire model cannot accurately express the influence of the temperature field on the blade strength, thus resulting in poor safety of the blade verification. The present invention constructs a 3D solid model of the steam turbine blade by geometric modeling of the steam turbine blade; meshes the constructed 3D solid model of the steam turbine blade to draw a mesh model; then imports the drawn mesh model into the finite element calculation software ABAQUS to perform finite element settings and calculate the temperature field of the mesh model; finally, the calculated temperature field is applied to the blade under steady-state operation to calculate the thermal stress of the steam turbine blade. The beneficial effect is that the safety of the blade verification is higher.

Description

Technical Field

[0001] The invention relates to a steam turbine blade processing technology. Background Art

[0002] When checking the blade strength during the design phase, the temperature processing is generally limited to applying a fixed operating temperature to the entire model for finite element calculation. Although the influence of the linear expansion coefficient can be roughly taken into account in the calculation, the operating temperature of the turbine blade is high and the temperature at different positions is different, which often produces considerable thermal stress and has a strong impact on the strength of the blade. That is, applying a fixed operating temperature to the entire model for finite element calculation cannot accurately express the impact of the temperature field on the blade strength, resulting in poor safety in checking the blade. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that the existing finite element calculation of applying a fixed operating temperature to the entire model cannot accurately express the influence of the temperature field on the blade strength, thereby resulting in poor safety of blade verification. A finite element calculation method for thermal stress of turbine blades is proposed.

[0004] A finite element calculation method for thermal stress of a steam turbine blade according to the present invention comprises the following steps:

[0005] Step 1: geometrically model the turbine blades and construct a 3D solid model of the turbine blades;

[0006] Step 2: mesh the 3D solid model of the steam turbine blade constructed in step 1 to draw a mesh model;

[0007] Step 3: Import the mesh model drawn in step 2 into the finite element calculation software ABAQUS to perform finite element settings and calculate the temperature field of the mesh model;

[0008] Step 4: Apply the temperature field calculated in step 3 to the blades under steady-state operation to calculate the thermal stress of the turbine blades.

[0009] The beneficial effects of the present invention are: accurately calculating the temperature field of the steam turbine blade and the thermal stress caused by the temperature field, thereby completing the thermal stress safety check of the steam turbine blade, and the safety of the checked blade is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A flowchart of a finite element calculation method for thermal stress of a steam turbine blade according to a specific implementation mode 1;

[0011] Figure 2 It is a schematic diagram of the structure of the blade in the second specific implementation mode. DETAILED DESCRIPTION

[0012] Specific implementation method 1: Combination Figure 1 This embodiment describes a finite element calculation method for thermal stress of a steam turbine blade, and the calculation method comprises the following steps:

[0013] Step 1: geometrically model the turbine blades and construct a 3D solid model of the turbine blades;

[0014] Step 2: mesh the 3D solid model of the steam turbine blade constructed in step 1 to draw a mesh model;

[0015] Step 3: Import the mesh model drawn in step 2 into the finite element calculation software ABAQUS to perform finite element settings and calculate the temperature field of the mesh model;

[0016] Step 4: Apply the temperature field calculated in step 3 to the blades under steady-state operation to calculate the thermal stress of the turbine blades.

[0017] In this embodiment, in step one, geometric modeling is performed using UG; and the turbine blade in step one is a CO2 unit blade; one of the blades in the entire circle is modeled; in step two, the mesh model is drawn using mesh software ANSA, and a hexahedral mesh is used, and the drawn mesh model is inp format.

[0018] Specific implementation method 2: Combination Figure 2 This embodiment is described. This embodiment further limits the finite element calculation method for thermal stress of a steam turbine blade described in the specific embodiment 1. In this embodiment, when geometrically modeling the steam turbine blade in step 1, a single blade is taken for geometric modeling, and the blade includes a blade profile 1, a wheel disc 2, and a connecting shaft 3;

[0019] The connecting shaft 3 is used to connect the outer circumference of the turbine rotor;

[0020] The wheel disc 2 is mounted on the connecting shaft 3;

[0021] The blade profile 1 is fixed on the wheel disc 2 .

[0022] Specific implementation method three: This implementation method further limits the finite element calculation method for thermal stress of a steam turbine blade described in specific implementation method two. In this implementation method, in step three, the specific process of importing the mesh model drawn in step two into the finite element calculation software ABAQUS for finite element setting includes:

[0023] Step 31: Establish a finite element mesh calculation model in the finite element calculation software ABAQUS;

[0024] Step 32: defining the heat conduction data of the steam turbine blades in the finite element mesh calculation model established in step 31;

[0025] Step 33: Add a temperature field calculation request in the finite element mesh calculation model;

[0026] Step 34: Set the heat transfer grid cell format;

[0027] Step 35: define the three-dimensional blade surface set, node set, heat transfer coefficient of contact between the wheel 2 and the connecting shaft 3 and boundary temperature constraints of the finite element mesh calculation model required for pre-processing on the finite element mesh calculation model;

[0028] Step 36. Use the defined turbine blade thermal conductivity data, temperature field calculation request, set heat transfer grid unit format, three-dimensional blade surface set, node set, heat transfer coefficient of contact between disk 2 and connecting shaft 3, and finite element grid calculation model boundary temperature constraints to derive and submit finite element calculation to obtain the temperature field.

[0029] Specific implementation method four: This implementation method further limits the finite element calculation method of thermal stress of a turbine blade described in specific implementation method three. In this implementation method, the thermal conductivity data of the turbine blade described in step three two includes the thermal conductivity of the blade profile 1, the thermal conductivity of the wheel disc 2 and the thermal conductivity of the connecting shaft 3.

[0030] Specific implementation method five: This implementation method further defines the finite element calculation method for thermal stress of a steam turbine blade described in specific implementation method three. In this implementation method, the three-dimensional blade surface set described in steps three and five is: the contact surface between the wheel disc 2 and the connecting shaft 3;

[0031] The node set described in step 35 is: nodes for temperature constraints on both sides of the end surface of the disk 2, nodes for temperature constraints on both sides of the end surface of the connecting shaft 3, nodes for temperature constraints on the surface of the disk 2, and nodes for temperature constraints on the surface of the blade 1;

[0032] The boundary temperature constraints of the finite element mesh calculation model described in step three and five are: temperature constraints on the end surfaces on both sides of the impeller 2, temperature constraints on the end surfaces on both sides of the connecting shaft 3, surface temperature constraints on the impeller 2 and surface temperature constraints on the blade profile 1.

[0033] Specific implementation method 6: This implementation method further limits the finite element calculation method for thermal stress of a steam turbine blade described in specific implementation method 3. In this implementation method, the specific steps for calculating the thermal stress of the steam turbine blade in step 4 are as follows:

[0034] Step 41: define material data of the steam turbine blade in the finite element mesh calculation model; the material data of the steam turbine blade includes: density of blade profile 1 at different temperatures, density of disk 2 at different temperatures, density of connecting shaft 3 at different temperatures, linear expansion coefficient of blade profile 1 at different temperatures, linear expansion coefficient of disk 2 at different temperatures, linear expansion coefficient of connecting shaft 3 at different temperatures, elastic modulus of blade profile 1 at different temperatures, elastic modulus of disk 2 at different temperatures, and elastic modulus of connecting shaft 3 at different temperatures;

[0035] Step 42: Add a request for thermal stress calculation in the finite element mesh calculation model;

[0036] Step 43: Set the C3D8R grid unit format;

[0037] Step 44: define the unit set required for pre-processing, the centrifugal force strength between the wheel disc 2 and the connecting shaft 3, the friction coefficient of contact between the wheel disc 2 and the connecting shaft 3, and the displacement constraint of the finite element mesh calculation model on the finite element mesh calculation model;

[0038] Step 4 and 5: Utilize the defined material data of the steam turbine blade, the request for thermal stress calculation, the set C3D8R mesh unit format and unit set, the centrifugal force strength between the impeller 2 and the connecting shaft 3, the friction coefficient of the contact between the impeller 2 and the connecting shaft 3, and the displacement constraint of the finite element mesh calculation model to obtain the thermal stress by finite element calculation.

[0039] Specific embodiment seven: This embodiment further limits the finite element calculation method for thermal stress of a turbine blade described in specific embodiment six. In this embodiment, the material data of the turbine blade described in step 4-1 include: the density of blade profile 1 at different temperatures, the density of disk 2 at different temperatures, the density of connecting shaft 3 at different temperatures, the linear expansion coefficient of blade profile 1 at different temperatures, the linear expansion coefficient of disk 2 at different temperatures, the linear expansion coefficient of connecting shaft 3 at different temperatures, the elastic modulus of blade profile 1 at different temperatures, the elastic modulus of disk 2 at different temperatures and the elastic modulus of connecting shaft 3 at different temperatures.

[0040] Specific implementation eight: This implementation further defines the finite element calculation method for thermal stress of a steam turbine blade described in specific implementation six. In this implementation, the unit set described in step four-four is: all model units used to load centrifugal force;

[0041] The displacement constraints of the finite element mesh calculation model described in step 4 are: radial constraints on the center of the connecting shaft 3, axial and circumferential constraints on the end face of one side of the wheel disc 2, and axial and circumferential constraints on one side of the connecting shaft 3.

Claims

1. A finite element calculation method for thermal stress of a steam turbine blade, characterized in that: The calculation method includes the following steps: Step 1: geometrically model the turbine blades and construct a 3D solid model of the turbine blades; Step 2: mesh the 3D solid model of the steam turbine blade constructed in step 1 to draw a mesh model; Step 3: Import the mesh model drawn in step 2 into the finite element calculation software ABAQUS to perform finite element settings and calculate the temperature field of the mesh model; Step 4: Apply the temperature field calculated in step 3 to the blades in steady state operation to calculate the thermal stress of the turbine blades; When geometric modeling is performed on the turbine blade in step 1, a single blade is taken for geometric modeling, and the blade includes a blade profile (1), a wheel disc (2) and a connecting shaft (3); The connecting shaft (3) is used to connect to the outer circumference of the turbine rotor; The wheel disc (2) is mounted on a connecting shaft (3); The blade profile (1) is fixed on the wheel disc (2); In step 3, the specific process of importing the mesh model drawn in step 2 into the finite element calculation software ABAQUS for finite element setting includes: Step 31: Establish a finite element mesh calculation model in the finite element calculation software ABAQUS; Step 32: defining the heat conduction data of the steam turbine blades in the finite element mesh calculation model established in step 31; Step 33: Add a temperature field calculation request in the finite element mesh calculation model; Step 34: Set the heat transfer grid cell format; Step 35: define the three-dimensional blade surface set, node set, heat transfer coefficient of contact between the wheel (2) and the connecting shaft (3) and boundary temperature constraints of the finite element mesh calculation model required for pre-processing on the finite element mesh calculation model; Step 36: derive and submit the finite element calculation to obtain the temperature field by using the defined steam turbine blade heat conduction data, the temperature field calculation request, the set heat transfer grid unit format, the three-dimensional blade surface set, the node set, the heat transfer coefficient of the contact between the wheel (2) and the connecting shaft (3), and the boundary temperature constraint of the finite element grid calculation model; The specific steps for calculating the thermal stress of the turbine blade in step 4 are: Step 41: Define the material data of the steam turbine blade in the finite element mesh calculation model; Step 42: Add a request for thermal stress calculation in the finite element mesh calculation model; Step 43: Set the C3D8R grid unit format; Step 44: define the unit set required for pre-processing, the centrifugal force strength between the wheel disc (2) and the connecting shaft (3), the friction coefficient of contact between the wheel disc (2) and the connecting shaft (3), and the displacement constraint of the finite element mesh calculation model on the finite element mesh calculation model; Step 4 and 5: Utilize the defined material data of the steam turbine blade, the thermal stress calculation request, the set C3D8R mesh unit format and unit set, the centrifugal force strength between the impeller (2) and the connecting shaft (3), the friction coefficient of the contact between the impeller (2) and the connecting shaft (3), and the displacement constraint of the finite element mesh calculation model to obtain the thermal stress by finite element calculation.

2. The finite element calculation method for thermal stress of a steam turbine blade according to claim 1, characterized in that: The thermal conductivity data of the turbine blades described in step 3.2 include the thermal conductivity of the blade profile (1), the thermal conductivity of the wheel disc (2) and the thermal conductivity of the connecting shaft (3).

3. The finite element calculation method for thermal stress of a steam turbine blade according to claim 1, characterized in that: The three-dimensional blade surface set described in step 35 is: the contact surface between the wheel disc (2) and the connecting shaft (3); The node set described in step 35 is: nodes for temperature constraints on both sides of the disk (2), nodes for temperature constraints on both sides of the connecting shaft (3), nodes for temperature constraints on the surface of the disk (2) and nodes for temperature constraints on the surface of the blade (1); The boundary temperature constraints of the finite element mesh calculation model described in step three and five are: temperature constraints on the end surfaces on both sides of the wheel disc (2), temperature constraints on the end surfaces on both sides of the connecting shaft (3), surface temperature constraints on the wheel disc (2) and surface temperature constraints on the blade profile (1).

4. The finite element calculation method for thermal stress of a steam turbine blade according to claim 1, characterized in that: The material data of the steam turbine blade described in step 4-1 include: the density of the blade profile (1) at different temperatures, the density of the impeller (2) at different temperatures, the density of the connecting shaft (3) at different temperatures, the linear expansion coefficient of the blade profile (1) at different temperatures, the linear expansion coefficient of the impeller (2) at different temperatures, the linear expansion coefficient of the connecting shaft (3) at different temperatures, the elastic modulus of the blade profile (1) at different temperatures, the elastic modulus of the impeller (2) at different temperatures and the elastic modulus of the connecting shaft (3) at different temperatures.

5. The finite element calculation method for thermal stress of a steam turbine blade according to claim 1, characterized in that: The unit set described in step 44 is: all model units used to load centrifugal force; The displacement constraints of the finite element mesh calculation model described in step 44 are: radial constraints at the center of the connecting shaft (3), axial and circumferential constraints at the end face of one side of the wheel disc (2), and axial and circumferential constraints at one side of the connecting shaft (3).

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