Method and system for evaluating fitting state of shrouded blade of turbomachinery

Abstract

The invention discloses a method and system for evaluating the fitting state of a shrouded blade of a turbomachine, and the method comprises the steps: firstly carrying out the stress analysis of the shrouded blade of the turbomachine through finite element software; extracting or calculating a contact surface resultant force F of contact surfaces of adjacent shrouded blades of the turbomachinery at a fixed rotating speed from a result file of the finite element software; the dimensionless fitting state discrimination coefficient K of the shrouded blade of the turbomachine is calculated, K = K0 * F / (myx * hw * w2), K0 is the safety coefficient, myx is the blade crown structure normalization mass of the shrouded blade of the turbomachine, and the unit is kilogram; hw is the radial height of the mass center of the blade crown structure, and the unit is meter; w is the rotating speed, and the unit is radian / second; and finally, determining the sizes of K and f to determine the fitting state. When the method is adopted to judge the fitting state of the shrouded blade, the deviation between the blade calculation frequency and the test frequency can be ensured to be within 5%, and the evaluation method is high in universality and high in accuracy.

Description

Technical Field

[0001] The present invention relates to the field of impeller machinery, and in particular to a method and system for evaluating the fitting state of shrouded blades of an impeller machinery. Background Art

[0002] Shrouded blades are one of the current mainstream design concepts for turbomachinery blades, and are mostly used in industrial steam turbines, gas turbines, etc. The shroud structures of adjacent blades come into contact and fit together under the centrifugal force of the blades, achieving the effect of reducing vibration and improving overall rigidity and frequency. The frequency calculation and experimental test of a single blade by the current general finite element software are very close, but for shrouded blades, the calculated frequency may deviate greatly from the experimental test frequency, and some blades may even exceed 10%. This is because the shrouded blades are in an intermediate state of contact but not complete fit during actual operation. This intermediate state is the main reason for the deviation between the blade frequency value in actual operation and the finite element software calculation. If the frequency modulation capability of the blade is not enough to cover the deviation value, the blade will have serious resonance safety risks. Summary of the invention

[0003] In order to avoid the shrouded blades from being in such an uncontrollable intermediate state from the design source, the present invention proposes a method and system for evaluating the fitting state of the shrouded blades of an impeller machinery, which are used to determine whether the shrouded blades have reached a completely fitting state. The calculated frequency and the frequency deviation of the experimental test of the shrouded blades that are judged to have reached the fitting state by the present invention can be guaranteed to be within 5%, thereby avoiding possible blade resonance safety issues in the design stage.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for evaluating the fitting state of shrouded blades of an impeller machine, the method comprising the following steps:

[0006] S1: The finite element software is used to perform stress analysis on the shrouded blades of the impeller machinery, wherein the shroud contact surface of the shrouded blades of the impeller machinery adopts a surface-to-surface contact pair setting, and the friction coefficient of the contact surface is f;

[0007] S2: Extract or calculate the contact surface resultant force F of the contact surface of adjacent impeller machinery shrouded blades at a fixed speed from the result file of the finite element software;

[0008] S3: Calculate the dimensionless fitting state discrimination coefficient K of the impeller machinery shrouded blade, K = K0*F / (m yx *h w *w 2 ), where K0 is the safety factor, ranging from 0.8 to 1.2; m yx h is the normalized mass of the shroud structure of the impeller machinery shrouded blade, in kilograms;w is the radial height of the centroid of the blade crown structure, in meters; w is the rotation speed, in radians per second;

[0009] S4: Compare the fitting state discrimination coefficient K with the friction coefficient f. If K≥f, it is considered that the impeller machine shrouded blades have reached a complete fitting state; if K<f, it is considered that the impeller machine shrouded blades have not reached a complete fitting state.

[0010] Furthermore, the normalized mass m of the shroud of the impeller machine shrouded blade is yx The calculation formula is as follows:

[0011] m yx =m 叶冠 / m 叶型 *1kg

[0012] Among them, m 叶冠 is the mass of the canopy structure, m 叶型 It is the mass of the blade body structure without the crown.

[0013] Furthermore, when the contact surface resultant force F of the shrouded blades of the impeller machinery in S2 at a fixed speed cannot be directly extracted from the result file of the finite element software, the following method is used for calculation:

[0014] Open the result file post-processing interface of the finite element software and enter the contact pressure stress result display. Set the lower limit of the pressure stress cloud map to 1Mpa, and the colored area in the result cloud map is the effective contact area; count the total number of units in the effective contact area n, where the unit area of ​​the i-th unit is s i The mean contact pressure stress of the nodes in this unit is m i ; The contact angle α is the angle between the contact surface and the circumferential direction of the blade; then the contact surface force F = (s0*m0+s1*m1+……+s n *m n )*sinα.

[0015] Furthermore, the friction coefficient f has a value range of 0.1 to 0.3.

[0016] Furthermore, the mesh of the blade shroud contact surface of the impeller machinery shrouded blade is a hexahedral structured mesh.

[0017] A system for evaluating the fit of shrouded blades of a turbomachinery, the system comprising:

[0018] The finite element analysis pre-processing module of the shrouded blade is used to call the finite element software to automatically complete the stress analysis of the shrouded blade of the impeller machinery; wherein, the shroud contact surface of the shrouded blade of the impeller machinery adopts the surface-to-surface contact pair setting, and the friction coefficient of the contact surface is f;

[0019] Finite element analysis post-processing module for shrouded blades: used to extract or calculate the contact surface resultant force F of the contact surface of adjacent impeller machinery shrouded blades at a fixed speed from the result file of the finite element software;

[0020] The fitting state judgment module of the shrouded blade is used to calculate the dimensionless fitting state judgment coefficient K of the shrouded blade of the impeller machinery, and compare the fitting state judgment coefficient K with the friction coefficient f. If K≥f, it is considered that the shrouded blade of the impeller machinery has reached a complete fitting state; if K<f, it is considered that the shrouded blade of the impeller machinery has not reached a complete fitting state; wherein, K=K0*F / (m yx *h w *w 2 ), where K0 is the safety factor, ranging from 0.8 to 1.2; m yx h is the normalized mass of the shrouded blade of the impeller machinery, in kilograms; w is the radial height of the center of mass of the blade crown structure, in meters; w is the rotation speed, in radians per second.

[0021] The beneficial effects of the present invention are as follows:

[0022] The method and system for evaluating the fitting state of shrouded blades of an impeller machine of the present invention integrate parameters such as rotational speed and blade size. The method of the present invention is used to judge the fitting state of shrouded blades, and its calculation efficiency and frequency deviation of experimental tests can be guaranteed to be within 5%, which can avoid possible blade resonance safety issues in the blade design stage; at the same time, the evaluation method of the present invention has strong versatility and high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flowchart of a method for evaluating the fitting status of shrouded blades of an impeller machine according to an embodiment of the present invention.

[0024] Figure 2 It is a schematic diagram of a device for evaluating the fitting state of shrouded blades of an impeller machine according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] like Figure 1 As shown, the method for evaluating the fitting state of shrouded blades of an impeller machine according to an embodiment of the present invention comprises the following steps:

[0027] S1: Use finite element software to perform stress analysis on shrouded blades of turbomachinery.

[0028] First, the pre-processing settings before finite element analysis of the impeller machinery shrouded blades are performed, including importing the blade geometry model and dividing the mesh (or directly importing the mesh model), defining the unit type, defining the material parameters, defining the load and boundary conditions, defining the analysis settings, etc. The overall mesh needs to be verified for mesh independence to obtain a reasonable mesh division density; preferably, the mesh in the shroud contact area should be guaranteed to be a hexahedral structured mesh. In addition, because the blades are periodic, cyclic symmetric boundaries are defined to simplify the calculation. The shroud contact surface adopts a face-to-face contact pair setting, and the friction coefficient of the contact surface is f. The value of the friction coefficient f is related to the material, the smoothness of the contact surface, etc. The friction coefficient f of the impeller machinery blade is generally in the range of 0.1 to 0.3.

[0029] S2: After the finite element calculation is completed, the contact surface resultant force F (unit: N) of the blade crown contact surface at a fixed speed is extracted or calculated from the finite element software result file.

[0030] In detail, commercial finite element software can generally directly extract the contact surface force F. If it does not support extraction, the following method can be used for calculation: open the result file post-processing interface and enter the contact pressure stress result display, set its cloud map display lower limit to 1Mpa, and the colored area in the result cloud map is the effective contact area. Count the total number of cells in the effective contact area n, where the cell area of ​​the i-th cell is s i The mean contact pressure stress of the nodes in this unit is m i ; The contact angle α is the angle between the contact surface and the circumferential direction of the blade; then the contact surface force F = (s0*m0+s1*m1+……+s n *m n )*sinα.

[0031] S3: Calculate the dimensionless fitting state discrimination coefficient K of the impeller machinery shrouded blade, K = K0*F / (m yx *h w *w 2 ), where K0 is the safety factor; m yx h is the normalized mass of the shroud structure of the impeller machinery shrouded blade, in kilograms; w is the radial height of the center of mass of the blade crown structure, in meters; w is the rotation speed, in radians per second.

[0032] The value of the K0 safety factor is related to the blade hub ratio, and preferably, its value range is 0.8 to 1.2. The normalized mass of the blade crown structure is defined as follows: yx =m 叶冠 / m 叶型 *1kg, m 叶冠 is the mass of the canopy structure, m 叶型 It is the mass of the blade body structure without the crown.

[0033] S4: Compare the fitting state discrimination coefficient K with the friction coefficient f. If K≥f, it is considered that the impeller machine shrouded blades have reached a complete fitting state; if K<f, it is considered that the impeller machine shrouded blades have not reached a complete fitting state.

[0034] Among them, for the same blade, the calculation result of the contact surface force F is proportional to the value of the friction coefficient f, so the value of the friction coefficient f does not affect the determination of the blade fitting state.

[0035] like Figure 2 As shown, the device for evaluating the fitting state of shrouded blades of an impeller machine according to an embodiment of the present invention comprises:

[0036] The finite element analysis pre-processing module of the shrouded blade is used to call the finite element software to automatically complete the stress analysis of the shrouded blade of the impeller machinery; wherein, the shroud contact surface of the shrouded blade of the impeller machinery adopts the surface-to-surface contact pair setting, and the friction coefficient of the contact surface is f;

[0037] Finite element analysis post-processing module for shrouded blades: used to extract or calculate the contact surface resultant force F of the contact surface of adjacent impeller machinery shrouded blades at a fixed speed from the result file of the finite element software;

[0038] The fitting state judgment module of the shrouded blade is used to calculate the dimensionless fitting state judgment coefficient K of the shrouded blade of the impeller machinery, and compare the fitting state judgment coefficient K with the friction coefficient f. If K≥f, it is considered that the shrouded damping structure has reached a complete fitting state; if K<f, it is considered that the shrouded damping structure has not reached a complete fitting state; where K=K0*F / (m yx *h w *w 2 ), where K0 is the safety factor, ranging from 0.8 to 1.2; m yx h is the normalized mass of the shrouded blade of the impeller machinery, in kilograms; w is the radial height of the center of mass of the blade crown structure, in meters; w is the rotation speed, in radians per second.

[0039] The following is an example of applying the method and device of the present invention to a shrouded blade of an industrial steam turbine to evaluate the fitting state, so as to further illustrate the method and device of the present invention.

[0040] Step 1: Use the finite element software ABAQUS to perform stress analysis on a certain industrial steam turbine blade with a shroud. The pre-processing settings include importing the mesh model (file suffix inp), defining the element type (C3D8I), defining the material parameters (elastic modulus 2.1*e 5 Mpa, density 7.8*e -9 t / mm 3, Poisson's ratio 0.28), define loads and boundary conditions (centrifugal load with a rotation speed of 3300 rpm; set periodic cyclic symmetry according to the number of blades = 78; set all contact surfaces to surface contact and set the friction coefficient f = 0.15;), define calculation steps (steady-state stress calculation), and define analysis settings. After the settings are completed, drive the finite element software ABAQUS to solve.

[0041] Among them, the overall mesh needs to be verified for mesh independence first to obtain a reasonable mesh division density; the mesh in the contact surface area of ​​the blade crown structure should be guaranteed to be a hexahedral structured mesh. Since the blades are periodic, the cyclic symmetric boundary is defined to simplify the calculation, and the number of blades = 78; all contact surfaces are set to face-to-face contact pairs and the friction coefficient f = 0.15. The load is a single centrifugal force load, that is, the speed w = 3300 rpm = 345rad / s.

[0042] Step 2: After the finite element analysis is completed, the contact surface resultant force F of the blade shroud contact surface at a fixed speed is extracted in the post-processing interface of the finite element software ABAQUS. In this example, the blade shroud contact surface resultant force F value is 4148.

[0043] Among them, the resultant force F of the blade crown contact surface can be directly extracted in ABAQUS software, and its value is the CFT located in the Contact result.

[0044] Step 3: Calculate the discriminant coefficient K of the crowned blade circle state, K = K0*F / (m yx *h w *w 2 ), where K0 is the comprehensive safety factor, m yx is the normalized mass of the canopy structure (unit: kg), h w is the radial height of the mass center of the canopy structure (unit: meter), and w is the rotation speed (unit: radian / second). yx = 0.15 kg, radial height h of the blade crown structure w =1.24 m, w = 3300 rpm = 345 rad / s, so the calculated K of the blade in this example is 0.18.

[0045] The value of K0 safety factor is related to the blade-hub ratio. In this example, the blade value is 1. Normalized mass of the crown structure m yx =m 叶冠 / m 叶型 *1kg=1.25 / 8.1*1kg=0.15kg.

[0046] Step 4: In this embodiment, K = 0.18, f = 0.15, so K>f, so the impeller blades with shrouds in this embodiment reach a fitted state. Through experimental verification, the deviation between the calculated frequency value and the actual operation value of the blades in this embodiment at a fixed speed (w = 3300 rpm) is 1.5%.

[0047] In addition, in this embodiment, a system for evaluating the fitting state of shrouded blades of an impeller machine includes:

[0048] The finite element analysis pre-processing module for crowned blades written in Python and run through the ABAQUS script interface is used to automatically complete the above step 1. Specifically, it automatically completes the import of blade mesh model (file suffix inp), definition of element type (C3D8I), definition of material parameters (elastic modulus 2.1*e 5 Mpa, density 7.8*e -9 t / mm 3 , Poisson's ratio 0.28), define loads and boundary conditions (centrifugal load at a speed of 3300 rpm; set periodic cyclic symmetry according to the number of blades; all contact surfaces are set to surface contact and the friction coefficient f=0.15;), define the calculation step (steady-state stress calculation), define the analysis settings, and submit the calculation.

[0049] The post-processing module of the finite element analysis of the shrouded blade written in Python and run through the ABAQUS script interface is used to automatically complete step 2. Specifically, it automatically opens the result file (file suffix is ​​odb) and reads the result value of the shroud contact surface force (CFT).

[0050] The crown blade fitting state determination module written in Python and run through the ABAQUS script interface is used to automatically complete the above step 3. Specifically, the GUI prompts the user to input the parameters m required for loop determination. yx 、h w , the discriminant coefficient of the circle state of the crowned blade K=K0*F / (m yx *h w *w 2 ) is built into the module, automatically completes the calculation and outputs the loop status determination results through the GUI.

[0051] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A method for evaluating the fitting state of shrouded blades of an impeller machine, characterized in that: The method comprises the following steps: S1: The finite element software is used to perform stress analysis on the shrouded blades of the impeller machinery, wherein the shroud contact surface of the shrouded blades of the impeller machinery adopts a surface-to-surface contact pair setting, and the friction coefficient of the contact surface is f; S2: Extract or calculate the contact surface resultant force F of the contact surface of adjacent impeller machinery shrouded blades at a fixed speed from the result file of the finite element software; S3: Calculate the dimensionless fitting state discrimination coefficient K of the impeller machinery shrouded blade, K = K0*F / (m yx *h w *w 2 ), where K0 is the safety factor, ranging from 0.8 to 1.2; m yx h is the normalized mass of the shroud structure of the impeller machinery shrouded blade, in kilograms; w is the radial height of the centroid of the blade crown structure, in meters; w is the rotation speed, in radians per second; S4: Compare the fitting state discrimination coefficient K with the friction coefficient f. If K≥f, it is considered that the impeller machine shrouded blades have reached a complete fitting state; if K<f, it is considered that the impeller machine shrouded blades have not reached a complete fitting state.

2. The method for evaluating the fitting state of shrouded blades of an impeller machine according to claim 1, characterized in that: The normalized mass m of the shroud blade of the impeller machine yx The calculation formula is as follows: m yx =m 叶冠 / m 叶型 *1kg Among them, m 叶冠 is the mass of the canopy structure, m 叶型 It is the mass of the blade body structure without the crown.

3. The method for evaluating the fitting state of shrouded blades of an impeller machine according to claim 1, characterized in that: When the contact surface resultant force F of the impeller machinery shrouded blades at a fixed speed in S2 cannot be directly extracted from the result file of the finite element software, the following method is used for calculation: Open the result file post-processing interface of the finite element software and enter the contact pressure stress result display. Set the lower limit of the pressure stress cloud map to 1Mpa, and the colored area in the result cloud map is the effective contact area; count the total number of units in the effective contact area n, where the unit area of ​​the i-th unit is s i The mean contact pressure stress of the nodes in this unit is m i ; The contact angle α is the angle between the contact surface and the circumferential direction of the blade; then the contact surface force F = (s0*m0+s1*m1+……+s n *m n )*sinα.

4. The method for evaluating the fitting state of shrouded blades of an impeller machine according to claim 1, characterized in that: The friction coefficient f has a value range of 0.1 to 0.

3.

5. The method for evaluating the fitting state of shrouded blades of a turbomachinery according to claim 1, characterized in that: The mesh of the shroud contact surface of the impeller machinery shroud blade is a hexahedral structured mesh.

6. A system for evaluating the fit of shrouded blades of an impeller machine, characterized in that: The system includes: The finite element analysis pre-processing module of the shrouded blade is used to call the finite element software to automatically complete the stress analysis of the shrouded blade of the impeller machinery; wherein, the shroud contact surface of the shrouded blade of the impeller machinery adopts the surface-to-surface contact pair setting, and the friction coefficient of the contact surface is f; Finite element analysis post-processing module for shrouded blades: used to extract or calculate the contact surface resultant force F of the contact surface of adjacent impeller machinery shrouded blades at a fixed speed from the result file of the finite element software; The fitting state judgment module of the shrouded blade is used to calculate the dimensionless fitting state judgment coefficient K of the shrouded blade of the impeller machinery, and compare the fitting state judgment coefficient K with the friction coefficient f. If K≥f, it is considered that the shrouded blade of the impeller machinery has reached a complete fitting state; if K<f, it is considered that the shrouded blade of the impeller machinery has not reached a complete fitting state; wherein, K=K0*F / (m yx *h w *w 2 ), where K0 is the safety factor, ranging from 0.8 to 1.2; m yx h is the normalized mass of the shrouded blade of the impeller machinery, in kilograms; w is the radial height of the center of mass of the blade crown structure, in meters; w is the rotation speed, in radians per second.

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