A blade chamfering and endwall design method applicable to deep peak shaving

Abstract

The present invention discloses a blade chamfering and end wall design method applicable to deep peak shaving, belonging to the technical field of steam turbines. This method sets chamfering structures with different radii at the leading edge, middle and trailing edge positions, and simultaneously adjusts the thickness and inclination angle of the end wall. Considering the overall strength, vibration modes and flutter conditions of the blade and the end wall, the blade chamfering and end wall design under the deep peak shaving operation condition of the turbine is carried out and checked, realizing the reasonable distribution of stresses between the blade and the end wall in the deep peak shaving state, reducing the blade flutter by changing the blade vibration form, and enhancing the safety and stability of the blade and the end wall under the deep peak shaving working condition.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbines, and particularly relates to a blade chamfering and end wall design method suitable for deep peak shaving. Background Art

[0002] The energy supply of new energy (wind energy, solar energy, etc.) is greatly affected by the surrounding actual environment and climate, and it has large fluctuations at different times. In order to maintain the stability of the power grid, thermal power needs to participate in deep peak shaving work, and the power generation power of thermal power is adjusted to adapt to the peak and valley values of new energy power. However, the participation of thermal power in deep peak shaving work causes a large deviation between the operating conditions of the steam turbine and the design conditions, and it needs to be started and stopped frequently, resulting in strong and frequent fluctuations in aerodynamic load and component thermal load, and a series of safety problems such as components being more prone to failure. In the traditional design of the chamfer and end wall structure of the turbine blade, it is mainly carried out under the design conditions, and its operating characteristics and safety under the deep peak shaving state are not yet clear. Summary of the Invention

[0003] In order to overcome the deficiencies of the above traditional design method of the chamfer and end wall structure of the turbine blade under deep peak shaving conditions, the purpose of the present invention is to provide a blade chamfering and end wall design method suitable for deep peak shaving, which sets chamfer structures with different radii at the leading edge, middle part and trailing edge, and at the same time adjusts the thickness and inclination angle of the end wall, and considers the overall strength, vibration mode and flutter of the blade and the end wall, and carries out the design of the blade chamfering and end wall under the operating conditions of the turbine deep peak shaving, so as to enhance the safety and stability of the blade and the end wall under the deep peak shaving conditions.

[0004] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A blade chamfering and end wall design method suitable for deep peak shaving, comprising the following steps:

[0006] Step 1: Input the blade profile, end wall shape, and model parameters of the blade root and disk shape, and use the commercial software UG to generate the three-dimensional geometric models of the blade assembly and the disk respectively, and assemble them according to their actual operating conditions;

[0007] Step 2: Determine the chamfer radius, where the chamfer radius refers to the radius of the transition circle geometry existing during the machining process between the blade and the end wall;

[0008] Step 3: Determine the thickness d and inclination angle α of the end wall platform;

[0009] Step 4: Generate the finite element mesh of the solid domain of the blade assembly; import the geometric models of the blade and the disk generated in Step 1 into the commercial software ANSYS Mechanical to generate the finite element analysis mesh of the solid domain;

[0010] Step 5: Strength check and vibration mode analysis of the blade and end wall; Input the physical property parameters of the blade and the disk respectively, input the initial temperature of the blade and the end wall, and use the finite element mesh of the solid domain of the blade and the disk generated in Step 4. Using the commercial software ANSYS Mechanical, under the deep peak shaving condition of 20%-30% of the design flow load, at the static state, rated speed, 95% rated speed, and 105% rated speed, conduct stress analysis and vibration mode analysis of the blade respectively, obtain the stress distribution, maximum stress value and its position of the blade assembly, and obtain the 1st - 8th order vibration modes and vibration frequencies of the blade;

[0011] Step 6: Generate the grid of the cascade fluid domain;

[0012] Step 7: Blade flutter analysis; Import the grid of the cascade fluid domain generated in Step 6 into the commercial software ANSYS CFX in cfx5 format, and at the same time import the 1st and 2nd order vibration modes of the blade obtained in Step 5 into the software ANSYS CFX in csv format; Set the dynamic grid boundary conditions on the blade surface of the middle flow passage according to the imported vibration modes and vibration frequencies of the blade; Use the method of solving the three-dimensional Reynolds-averaged N - S equations to conduct unsteady numerical calculations on the cascade flow under the deep peak shaving condition of 20%-30% of the design flow load, and select the time step as 1 / 25 - 1 / 30 of the blade vibration period; Subsequently, conduct flutter analysis of the blade in the middle flow passage, integrate the work done by the fluid exciting force on the blade within one vibration period, and obtain the work value of the cascade airflow on the blade within one period;

[0013] Step 8: Check the strength and flutter situation of the blade and the end wall.

[0014] A further improvement of the present invention lies in that in Step 2, different radii are respectively adopted for the leading edge, the middle part and the trailing edge.

[0015] A further improvement of the present invention lies in that the chamfer radius of the leading edge is 5 - 8 mm; the chamfer radii of the pressure side and the suction side corner areas in the middle part of the blade are 3 - 8 mm; the chamfer radius of the trailing edge is 3 - 5 mm.

[0016] A further improvement of the present invention lies in that in Step 3, the thickness of the end wall platform is 2% - 3% of the blade height.

[0017] A further improvement of the present invention lies in that in Step 3, the end wall platform inclination angle refers to the angle between the line connecting the leading edge and the trailing edge edges of the end wall at the same circumferential position and the axis.

[0018] A further improvement of the present invention lies in that the end wall platform inclination angle is -5° - 5°, so as to further accelerate the fluid near the end wall in the cascade.

[0019] A further improvement of the present invention lies in that in step 6, three rotation periods are selected to generate a hexahedral structured grid of the cascade fluid domain bounded by the blade, the end wall and the periodic surface.

[0020] A further improvement of the present invention lies in that in step 8, the blade safety judgment conditions are as follows:

[0021] The maximum centrifugal stress between the blade and the end wall is less than 90% of the material endurance strength;

[0022] The work done by the airflow on the blade within one vibration period is less than 0;

[0023] The vibration frequency is not within the range of ±5% of f = k × n.

[0024] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0025] The blade chamfering and end wall design method applicable to deep peak shaving provided by the present invention realizes a reasonable distribution of the stresses between the blade and the end wall under the deep peak shaving state by setting chamfer structures with different radii at the leading edge, the middle part and the trailing edge positions, and simultaneously adjusting the thickness and the inclination angle of the end wall, considering the overall strength, the vibration mode and the flutter of the blade and the end wall, reduces the blade flutter by changing the blade vibration form, and enhances the safety and stability of the blade and the end wall under the deep peak shaving working conditions. Description of the Drawings

[0026] Figure 1 It is a design method diagram of the blade chamfering and the end wall;

[0027] Figure 2 It is a schematic diagram of the geometric model of the blade and the end wall;

[0028] Figure 3 It is a schematic diagram of the geometric model of the end wall platform.

[0029] Description of the Reference Numerals:

[0030] 1 - blade, 2 - end wall, 3 - blade root, 4 - leading edge chamfer, 5 - middle chamfer, 6 - trailing edge chamfer. Detailed Embodiments

[0031] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. Hereinafter, the present invention will be described in detail with reference to the drawings and in combination with the embodiments.

[0032] The detailed process of this embodiment includes the following steps:

[0033] Step 1: According to the research object for which calculation and analysis are required, model parameters such as blade profile, endwall shape, and blade root and disk shapes, which characterize the basic geometric shapes of the blade and its fittings, are obtained from the determined research object and manually input into the commercial software UG. Three-dimensional geometric models of the blade fittings and the disk are respectively generated, and they are assembled according to the contact type in their actual operation.

[0034] In this embodiment, the contact type of the blade root is surface contact, the shape of the blade root is a mushroom-shaped blade root, and the basic geometric parameters of the blade are shown in Table 1.

[0035] Table 1 Geometric parameters

[0036] Name Value Chord length (C) 41.3 mm <![CDATA[Axial chord length (C ax )]]> 32.6 mm Blade height (S) 145 mm Cascade pitch (P) 97.3 mm Total number of blades in one revolution 124 blades

[0037] Step 2: Determine the chamfer radius. The chamfer radius refers to the radius of the transitional circular geometry existing during the machining process between the blade and the endwall. Preferably, different radii are used for the leading edge, middle, and trailing edge respectively. Among them, the chamfer radius of the leading edge is 5 - 8 mm; the chamfer radius of the pressure side and suction side corner regions in the middle of the blade is 3 - 8 mm; the chamfer radius of the trailing edge is 3 - 5 mm.

[0038] In this embodiment, the chamfer radii of the leading edge, middle, and trailing edge are first determined as the medians of the optional ranges, and are selected as 6.5 mm, 5.5 mm, and 4.0 mm respectively.

[0039] Step 3: Determine the endwall platform thickness d and the inclination angle α. Preferably, the endwall platform thickness is 2% - 3% of the blade height. The endwall platform inclination angle refers to the angle between the line connecting the leading edge and trailing edge edges of the endwall at the same circumferential position and the axis. Preferably, the endwall platform inclination angle is 0° - 5°, so as to further accelerate the fluid near the endwall in the cascade. Optionally, the endwall platform inclination angle is -5° - 0°.

[0040] In this embodiment, the endwall platform thickness is determined to be 3% of the blade height, which is 4.35 mm; the endwall platform inclination angle is determined to be 1°.

[0041] Step 4: Generate the finite element mesh of the solid domain of the blade fittings. The geometric models of the blade and the disk generated by UG in Step 1 are respectively imported into the commercial software ANSYS Mechanical. For the basic geometric parameters of the blade and blade root of the input blade fittings, as well as the blade chamfer and blade root parameters, a finite element analysis mesh of the solid domain is generated.

[0042] In this embodiment, the total number of mesh nodes in the generated solid domain is 89302.

[0043] Step 5: Strength check and vibration mode analysis of the blade and end wall. Input the physical property parameters of the blade and the disk respectively, input the initial temperature of the blade and the end wall, and use the finite element mesh of the solid domain of the blade and the disk generated in Step 4. Using the commercial software ANSYS Mechanical, under the deep peak shaving condition of 20%-30% of the design flow load, under the stationary state, rated speed, 95% rated speed, and 105% rated speed, carry out the stress analysis and vibration mode analysis of the blade respectively, obtain the stress distribution, the maximum stress value and its position of the blade assembly, and obtain the 1st - 8th order vibration modes and vibration frequencies of the blade.

[0044] In this embodiment, the rotational speed boundary condition for finite element calculation is set to 3000 rpm, the contact type boundary condition is set according to the same conditions as in Step 1, the material of the blade and the end wall is 1Cr13, the initial temperature of the blade is 620 K, and the initial pressure of the blade is 7.16 MPa. The maximum stress of the blade and the end wall is calculated to be 362 MPa, and the vibration frequencies of the blade are shown in Table 2.

[0045] Table 2 Blade dynamic frequencies

[0046] Order Frequency (Hz) 1 990 2 1276 3 1591 4 3536 5 3707 6 3826

[0047] Step 6: Generate the grid of the cascade fluid domain. Import the geometric models of the blade, end wall, and blade root generated in Step 1 into the commercial software ICEM CFD, select 3 rotation periods, and generate the hexahedral structured grid of the cascade fluid domain with the blade, end wall, and periodic surface as boundaries.

[0048] In this embodiment, the total number of grid nodes is 5.82 million.

[0049] Step 7: Blade flutter analysis. Import the grid of the cascade fluid domain generated in Step 6 into the commercial software ANSYS CFX in cfx5 format, and at the same time import the 1st and 2nd order vibration modes of the blade obtained in Step 5 into the software ANSYS CFX in csv format; set the dynamic grid boundary conditions on the blade surface of the middle flow passage according to the imported vibration modes and vibration frequencies of the blade; use the method of solving the three - dimensional Reynolds - averaged N - S equations to carry out the unsteady numerical calculation of the cascade flow under the deep peak shaving condition of 20%-30% of the design flow load. Preferably, the time step is selected as 1 / 25 - 1 / 30 of the blade vibration period; then carry out the flutter analysis of the blade in the middle flow passage, integrate the work done by the fluid exciting force on the blade within one vibration period, and obtain the work value of the cascade air flow on the blade within one period.

[0050] In this embodiment, the turbulence model for computational fluid dynamics numerical calculation is the standard k-ε model. The inlet pressure and temperature are 620 K and 7.16 MPa respectively, and the time step is 1 / 25 of the vibration period. The work done by the airflow on the blade within one vibration period is calculated to be -0.28 J.

[0051] Step 8: Check the strength of the blade and end wall and the flutter situation.

[0052] Repeat steps 2 - 8 until the following requirements are met:

[0053] 1) The maximum centrifugal stress of the blade and end wall is less than 90% of the material's endurance strength;

[0054] 2) The work done by the airflow on the blade within one vibration period is less than 0;

[0055] 3) The vibration frequency is not within ±5% of the following values: f = k × n.

[0056] In the formula, f is the blade's dynamic frequency; k is the harmonic order of the exciting force, and n is the rotational speed.

[0057] In this embodiment, the maximum stress of the blade and end wall is 362 MPa, which is less than 90% of the material's endurance strength; the work done by the blade within one vibration period is -0.28 J, and this value is less than 0; the vibration frequency has a large safety margin from k × n. Therefore, the design meets the requirements.

[0058] Although the present invention has been described in detail above with general descriptions and specific embodiments, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A blade chamfering and endwall design method applicable to deep peak shaving, characterized in that, it includes the following steps: Step 1: Input the blade profile, endwall shape, and the shape model parameters of the blade root and disk. Use the commercial software UG to generate the three-dimensional geometric models of the blade assembly and the disk respectively, and assemble them according to their actual operating conditions; Step 2: Determine the chamfer radius, where the chamfer radius refers to the radius of the transition circle geometry existing during the machining process between the blade and the endwall; Step 3: Determine the endwall platform thickness d and the inclination angle α; Step 4: Generate the finite element mesh of the solid domain of the blade assembly; Import the blade and disk geometric models generated in Step 1 into the commercial software ANSYS Mechanical to generate the finite element analysis mesh of the solid domain; Step 5: Strength check and vibration mode analysis of the blade and the endwall; Input the physical property parameters of the blade and the disk respectively, input the initial temperature of the blade and the endwall. Adopt the finite element mesh of the solid domain of the blade and the disk generated in Step 4, use the commercial software ANSYS Mechanical, under the deep peak shaving condition of 20%-30% of the design flow rate load, at the stationary state, rated speed, 95% rated speed, and 105% rated speed, conduct the stress analysis and vibration mode analysis of the blade respectively, obtain the stress distribution, the maximum stress value and its position of the blade assembly, and obtain the 1-8th order vibration modes and vibration frequencies of the blade; Step 6: Generate the grid of the cascade fluid domain; Step 7: Blade flutter analysis; Import the grid of the cascade fluid domain generated in Step 6 into the commercial software ANSYS CFX in cfx5 format, and at the same time import the 1st and 2nd order vibration modes of the blade obtained in Step 5 into the software ANSYS CFX in csv format; Set the dynamic grid boundary conditions on the blade surface of the intermediate flow passage according to the imported vibration modes and vibration frequencies of the blade; Adopt the method of solving the three-dimensional Reynolds-averaged N-S equations, under the deep peak shaving condition of 20%-30% of the design flow rate load, conduct the unsteady numerical calculation of the cascade flow, and select the time step as 1 / 25 - 1 / 30 of the blade vibration period; Subsequently, conduct the flutter analysis of the blade in the intermediate flow passage, integrate the work done by the fluid exciting force on the blade within one vibration period, and obtain the work value of the cascade air flow on the blade within one period; Step 8: Check the strength and flutter conditions of the blade and the endwall.

2. A blade chamfering and endwall design method applicable to deep peak shaving according to claim 1, characterized in that, in the said Step 2, different radii are adopted for the leading edge, middle part, and trailing edge respectively.

3. A blade chamfering and endwall design method applicable to deep peak shaving according to claim 2, characterized in that, the leading edge chamfer radius is 5 - 8 mm; the chamfer radius of the pressure side and suction side corner areas in the middle part of the blade is 3 - 8 mm; the chamfer radius of the trailing edge is 3 - 5 mm.

4. A blade chamfering and endwall design method applicable to deep peak shaving according to claim 1, characterized in that, in the said Step 3, the endwall platform thickness is 2% - 3% of the blade height.

5. A method for blade chamfering and endwall design applicable to deep peak shaving, according to claim 1, characterized in that, in step 3, the endwall platform inclination angle refers to the angle between the line connecting the leading edge and trailing edge edges of the endwall at the same circumferential position and the axis.

6. A method for blade chamfering and endwall design applicable to deep peak shaving, according to claim 5, characterized in that, the endwall platform inclination angle is -5° - 5°, so as to further accelerate the fluid near the endwall in the cascade.

7. A method for blade chamfering and endwall design applicable to deep peak shaving, according to claim 1, characterized in that, in step 6, select 3 rotation periods to generate a hexahedral structured grid of the cascade fluid domain bounded by the blades, endwalls and periodic surfaces.

8. A method for blade chamfering and endwall design applicable to deep peak shaving, according to claim 1, characterized in that, in step 8, the blade safety judgment conditions are: the maximum centrifugal stress of the blade and the endwall is less than 90% of the material's endurance strength; the work done by the airflow on the blade within one vibration period is less than 0; the vibration frequency is not within the range of ±5% of f = k × n.

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