Finite element calculation method of blade with hoop-wrapped belt structure

Abstract

The application relates to a finite element calculation method of a blade with a hoop surrounding band structure, and relates to a finite element calculation method. The application is used to solve the problem that the safety check of the blade with the hoop surrounding band structure cannot be carried out by the finite element method in the prior art. The application can carry out the safety check of the hoop surrounding band structure, carries out three-dimensional simulation, analysis calculation by using finite element calculation software, checks the safety of the hoop surrounding band structure by using the finite element calculation method, can especially investigate the strength and vibration characteristics of the hoop surrounding band structure and the stress level at the connecting strip of the surrounding band, can directly obtain the blade frequency value, is very important for the safety design and check of the hoop surrounding band blade, and ensures that the steam turbine blade can be safely and reliably operated. The application belongs to the technical field of steam turbine blades.

Description

TECHNICAL FIELD

[0001] The present application relates to a finite element calculation method, in particular to a finite element calculation method of a blade with a cuff shroud structure, and belongs to the technical field of steam turbine blades. BACKGROUND

[0002] Many medium and long blades (blade height 200-300mm) of steam turbine plants are not suitable for being designed into pre-twisted blades, nor are they suitable for being designed into frequency-modulated blades. In order to ensure the vibration safety of the blades, a shroud connecting strip is added, so that the shrouds at the top of each blade are connected to form a cuff shroud structure. Designing the blades into cuff shroud blades is a good measure. In order to ensure safe operation, it is very important to perform finite element calculation on this structure in the design work.

[0003] In view of the above technical problems, how to provide a finite element calculation method has become a problem to be solved by the technical personnel in the field. SUMMARY

[0004] The present application provides a finite element calculation method of a blade with a cuff shroud structure.

[0005] The technical scheme of the present application is as follows: a finite element calculation method of a blade with a cuff shroud structure, which is specifically performed according to the following steps:

[0006] Step one, establishing an entity model for calculation

[0007] Step one, entity modeling

[0008] In the modeling software, the models of the rotor, one blade, the first shroud connecting strip and the second shroud connecting strip are established;

[0009] The shroud is integrally arranged at the top of the blade, and the outer circumferential surface of the shroud is provided with a dovetail groove;

[0010] The cross sections of the first shroud connecting strip and the second shroud connecting strip are both right trapezoids, and the first shroud connecting strip and the second shroud connecting strip are both assembled in the dovetail groove;

[0011] The butt joints of the first shroud connecting strip and the second shroud connecting strip are both arranged in the dovetail groove, and the two butt joints are staggered in the circumferential direction;

[0012] Step two, the model established in step one is cyclically and symmetrically arranged, and the model after the cyclic and symmetric arrangement includes one pitch of the rotor, the first shroud connecting strip and the second shroud connecting strip;

[0013] Step three, the model in step two is saved as an entity model in stp format;

[0014] Step two, import the entity model in step one three into ANSA software to draw a mesh, and get a mesh model in inp format;

[0015] Step three, import the mesh model in step two into finite element calculation software to set parameters;

[0016] Step three one, give the mesh model material properties;

[0017] Step three two, define boundary conditions for the mesh model, the boundary conditions at least include:

[0018] Define the contact friction coefficient between the rotor and the blade;

[0019] Define the contact friction coefficient between the first shroud connecting strip and the shroud;

[0020] Define the contact friction coefficient between the second shroud connecting strip and the shroud;

[0021] Define the contact friction coefficient between the first shroud connecting strip and the second shroud connecting strip;

[0022] Define the contact pair between the rotor and the blade;

[0023] Define the contact pair and the contact gap between the first shroud connecting strip and the shroud, and give the contact pair contact control and tolerance;

[0024] Define the contact pair and the contact gap between the second shroud connecting strip and the shroud, and give the contact pair contact control and tolerance;

[0025] Define the contact pair between the first shroud connecting strip and the second shroud connecting strip;

[0026] Define the radial constraint of the rotor rotation center;

[0027] Define the axial constraint and the circumferential constraint of the rotor end face;

[0028] Define the cyclic symmetry surface, and exert the cyclic symmetry constraint on the cyclic symmetry surface;

[0029] Step three, define the running condition for the mesh model, the running condition at least includes:

[0030] The steam force exerted on the airfoil surface of the blade;

[0031] The working temperature and the centrifugal force of the entire mesh model;

[0032] Define the stress analysis step, the temperature analysis step and the vibration frequency analysis step of the entire mesh model;

[0033] Step four, calculate with finite element calculation software.

[0034] Compared with the prior art, the present application has the following effects:

[0035] 1、The present application can perform safety checking of the hoop shroud structure, adopt finite element calculation software to perform three-dimensional simulation, analysis and calculation, check the safety of the hoop shroud structure by the finite element calculation method, especially can investigate the strength and vibration characteristics of the hoop shroud structure, the stress level at the shroud connecting strip, and can intuitively obtain the blade frequency value, which is very important for the safety design and checking of the hoop shroud blade, and ensures that the steam turbine blade can be safely and reliably operated. BRIEF DESCRIPTION OF DRAWINGS

[0036] Fig. 1 is the axonometric view of the rotor 1 and the blade 2 of the present application;

[0037] Fig. 2 is the schematic view of the first shroud connecting strip 201 and the second shroud connecting strip 202 assembled in the shroud of the present application;

[0038] Fig. 3 is the axonometric view of the first shroud connecting strip 201 and the second shroud connecting strip 202 of the present application.

[0039] In the figure: 1, rotor; 2, blade; 201, first shroud connecting strip; 202, second shroud connecting strip. DETAILED DESCRIPTION

[0040] In order to make the invention purpose, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application.

[0041] Specific embodiment one: in combination with Figs. 1-3 The finite element calculation method of the blade adopting the hoop shroud structure in the present embodiment is specifically performed according to the following steps.

[0042] Step one, establish the entity model for calculation

[0043] Step one, entity modeling

[0044] The model of the rotor 1, one blade 2, the first shroud connecting strip 201 and the second shroud connecting strip 202 is established in the modeling software.

[0045] The shroud is integrally arranged at the blade tip of the blade 2, and the outer circumferential surface of the shroud is provided with a dovetail groove.

[0046] The cross sections of the first shroud connecting strip 201 and the second shroud connecting strip 202 are both right trapezoids, and the first shroud connecting strip 201 and the second shroud connecting strip 202 are both assembled in the dovetail groove.

[0047] The butt joints of the first shroud connecting strip 201 and the butt joints of the second shroud connecting strip 202 are arranged in the dovetail groove, and the two butt joints are staggered in the circumferential direction.

[0048] Step two, the model built in step one is cyclically symmetrically arranged, and the model after the cyclically symmetric arrangement includes one pitch of the rotor 1, the first shroud connecting strip 201 and the second shroud connecting strip 202.

[0049] Further, the mechanism of the cyclically symmetric arrangement is as follows:

[0050] If an object includes material constants and is exactly the same as before rotation when the object rotates by an angle a around its rotation axis, the structure of the object is called a cyclically symmetric structure.

[0051] In practice, the rotor 1 is provided with N identical blades 2, and the geometric shape, material properties and boundary conditions of the blades 2 are the same, so that the blade-rotor system is an N-order cyclically symmetric structure, and the rotation axis of the rotor 1 is the cyclically symmetric axis. According to the characteristics of the structure, as long as one cyclically symmetric structure is analyzed and calculated, the solution of the entire blade-rotor system can be obtained, thereby greatly simplifying the analysis and solution of the entire blade-rotor system.

[0052] Step three, the grid model in step two is imported into a finite element calculation software for parameter setting.

[0053] Step two, the solid model in step three is imported into ANSA software to draw a grid, and an inp format grid model is obtained.

[0054] Step three, the grid model in step two is imported into a finite element calculation software for parameter setting.

[0055] Step three one, material properties are given to the grid model.

[0056] Step three two, boundary conditions are defined for the grid model, and the boundary conditions at least include:

[0057] The contact friction coefficient between the rotor 1 and the blade 2 is defined.

[0058] The contact friction coefficient between the first shroud connecting strip 201 and the shroud is defined.

[0059] The contact friction coefficient between the second shroud connecting strip 202 and the shroud is defined.

[0060] The contact friction coefficient between the first shroud connecting strip 201 and the second shroud connecting strip 202 is defined.

[0061] Define the contact pair between the rotor 1 and the blade 2, so set up, through the contact pair to simulate the dynamic contact between the rotor 1 and the blade 2.

[0062] Define the contact pair and the contact gap between the first shroud connecting strip 201 and the shroud, since the cross section of the first shroud connecting strip 201 is a right trapezoid, the lower base and the inclined surface of the first shroud connecting strip 201 are both provided with the contact pair with the shroud, and the contact pair is endowed with the contact control and the tolerance.

[0063] Contact gap: refers to the initial separation distance between two surfaces, if the contact gap between the two surfaces is 0, it is considered that the two surfaces have been in contact, and the force can be transmitted between the surfaces in contact and the size is not limited

[0064] Contact control: that is, the management and control of the interaction between the contact surfaces, including the selection of the contact algorithm, the definition of the contact pair, the specification of the contact attribute, and the adjustment of the contact behavior, which can finely manage the contact behavior and improve the accuracy and stability of the finite element calculation.

[0065] Tolerance: since the parts will inevitably deviate during actual manufacturing or assembly, an error limit should generally be set for the deviation between the contact surfaces of two or more parts when defining the contact, and the error limit here refers to the tolerance.

[0066] Define the contact pair and the contact gap between the second shroud connecting strip 202 and the shroud, since the cross section of the second shroud connecting strip 202 is a right trapezoid, the lower base and the inclined surface of the second shroud connecting strip 202 are both provided with the contact pair with the shroud, and the contact pair is endowed with the contact control and the tolerance.

[0067] Define the contact pair between the first shroud connecting strip 201 and the second shroud connecting strip 202, and further, since the cross sections of the first shroud connecting strip 201 and the second shroud connecting strip 202 are right trapezoids, the side vertical surfaces of the first shroud connecting strip 201 and the second shroud connecting strip 202 are provided with the contact pair;

[0068] Further, the butt joint of the first shroud connecting strip 201 is provided with the contact pair;

[0069] Further, the butt joint of the second shroud connecting strip 202 is provided with the contact pair.

[0070] Define the radial constraint of the rotation center of the rotor 1;

[0071] Define the axial constraint and the circumferential constraint of the end surface of the rotor 1;

[0072] Define the cyclic symmetry plane, and ensure that the cyclic symmetry plane does not appear over-constrained, and apply the cyclic symmetry constraint on the cyclic symmetry plane.

[0073] Step three, defining the operating condition of the grid model, the operating condition at least includes:

[0074] Steam force applied on the blade profile surface of the blade 2;

[0075] Working temperature and centrifugal force applied on the entire grid model;

[0076] Defining stress analysis step, temperature analysis step and vibration frequency analysis step of the entire grid model, further, the analysis step step refers to dividing the entire loading and solving process into several sub-stages, each sub-stage is called an analysis step.

[0077] Step four, calculating by using finite element calculation software.

[0078] Specific implementation method two: combined with Figs. 1-3 It is explained that in the step one of the embodiment, UG-NX software is selected for modeling.

[0079] Further, in the step two, the first shroud connecting strip 201 and the second shroud connecting strip 202 are both hexahedral grids, and the hexahedral grids are all set to be aligned, so that the grid nodes are aligned. It can ensure that the arrangement of the grid remains consistent, thereby improving the quality of the grid and the accuracy of the calculation.

[0080] The rotor 1 adopts pentahedral grid or hexahedral grid, preferably, the pentahedral grid is selected at the circumferential center of the rotor 1, and the hexahedral grid is adopted at the remaining parts of the rotor 1.

[0081] The blade root and the blade profile transition area of the blade 2 adopt tetrahedral or pentahedral grid, and the remaining parts of the blade 2 adopt hexahedral grid.

[0082] Further, in the step three, ABAQUS software is selected for parameter setting.

[0083] Further, in the step three, the material properties at least include density, elastic modulus, specific heat capacity and linear expansion coefficient.

[0084] Further, in the step four, ABAQUS software is selected for calculation.

[0085] The other components and connection relationships are the same as those in the specific implementation method one.

[0086] The above has disclosed the preferred embodiments of the present application, however, it is not intended to limit the present application, any person skilled in the art, without departing from the technical solution of the present application, according to the technical essence of the present application, any simple modification, equivalent change and modification of the above implementation examples, still belongs to the technical solution range of the present application.

Claims

1. A finite element calculation method of a blade using a shroud band structure, characterized by: The method is specifically performed according to the following steps: Step one, establishing an entity model for calculation Step one, entity modeling In the modeling software, the model of the rotor (1), one blade (2), the first shroud connecting strip (201) and the second shroud connecting strip (202) is established; The blade (2) is integrally provided with a shroud at the blade tip, and the outer circumferential surface of the shroud is provided with a dovetail groove; The cross sections of the first shroud connecting strip (201) and the second shroud connecting strip (202) are both right trapezoids, and the first shroud connecting strip (201) and the second shroud connecting strip (202) are both assembled in the dovetail groove; The butt joints of the first shroud connecting strip (201) and the second shroud connecting strip (202) are both arranged in the dovetail groove, and the two butt joints are staggered in the circumferential direction; Step two, the model established in step one is cyclically and symmetrically arranged, and the model after the cyclic and symmetric arrangement includes one pitch of the rotor (1), the first shroud connecting strip (201) and the second shroud connecting strip (202); Step three, the model in step two is saved as an entity model in stp format; Step four, the entity model in step three is imported into ANSA software to draw a mesh, and an inp format mesh model is obtained; Step five, the mesh model in step four is imported into a finite element calculation software to perform parameter setting; Step five one, material properties are given to the mesh model; Step five two, boundary conditions are defined for the mesh model, and the boundary conditions at least include: Defining the contact friction coefficient between the rotor (1) and the blade (2); Defining the contact friction coefficient between the first shroud connecting strip (201) and the shroud; Defining the contact friction coefficient between the second shroud connecting strip (202) and the shroud; Defining the contact friction coefficient between the first shroud connecting strip (201) and the second shroud connecting strip (202); Defining the contact pair between the rotor (1) and the blade (2); Defining the contact pair and the contact gap between the first shroud connecting strip (201) and the shroud, and giving the contact pair contact control and tolerance; Defining the contact pair and the contact gap between the second shroud connecting strip (202) and the shroud, and giving the contact pair contact control and tolerance; Defining the contact pair between the first shroud connecting strip (201) and the second shroud connecting strip (202); Defining the radial constraint of the rotation center of the rotor (1); Defining the axial constraint and the circumferential constraint of the end surface of the rotor (1); Defining a cyclic symmetry surface, and applying a cyclic symmetry constraint on the cyclic symmetry surface; Step five three, the running conditions of the mesh model are defined, and the running conditions at least include: The steam force applied to the airfoil surface of the blade (2); The working temperature and the centrifugal force of the entire mesh model; Defining the stress analysis step, the temperature analysis step and the vibration frequency analysis step of the entire mesh model; Step six, calculating by using the finite element calculation software.

2. The finite element calculation method of a blade using a band structure of a wrapping band according to claim 1, characterized in that: In step one, UG-NX software is selected for modeling.

3. The finite element calculation method of a blade using a shroud structure according to claim 2, characterized in that: In step two, the first shroud connecting strip (201) and the second shroud connecting strip (202) are both hexahedral meshes; The rotor (1) is a pentahedral mesh or a hexahedral mesh; The blade root and the blade profile transition area of the blade (2) adopt tetrahedral or pentahedral grid, and the rest of the blade (2) adopts hexahedral grid.

4. The finite element calculation method of a blade with a band structure of a banding according to claim 3, characterized in that: The step three selects ABAQUS software to set parameters.

5. The finite element calculation method of a blade using a shroud structure according to claim 4, characterized in that: The material properties in the step three at least include density, elastic modulus, specific heat capacity and linear expansion coefficient.

6. The finite element calculation method of a blade using a shroud structure according to claim 5, characterized in that: The step four selects ABAQUS software to calculate.

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