A design method for a twisted, swept structured stationary blade for a steam turbine

Abstract

A method for designing a stator blade with a twisted, bent and swept structure for a steam turbine, which relates to the technical field of steam turbine blades. The present invention is to solve the problem of flow loss of long blades in the last few low-pressure stages of existing steam turbines. The method comprises: determining the design basis and stacking rule of the blades: the design basis of the blades is a straight blade without a twisted, swept structure, and the stacking rule is stacking along the center of the steam outlet circle; based on the basic straight blades and the stacking rule, the blades are bent, swept and twisted to obtain a stator blade with a twisted, swept structure; the initial stacking line is determined, and the geometric entity of the stator blade is obtained in combination with the blade profile of a typical section; the obtained geometric entity is imported into a three-dimensional simulation calculation and optimization platform for the blades, and further blade aerodynamic calculation and blade strength calculation are performed; the optimal stacking line is obtained based on the calculation results, and finally each typical section is stacked along the optimal stacking line to obtain a twisted, swept blade. The present invention is used for the design of stator blades for steam turbines.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine blades, and in particular to a design method for a stationary blade with a twisted, bent and swept structure for a steam turbine. Background Art

[0002] As one of the three main equipment in thermal power plants, the aerodynamic performance of steam turbines is directly related to the cost and efficiency of power generation, and has a significant impact on the national economy. However, in the design process of low-pressure long blades of steam turbines, due to the long radial length of the blades, large expansion angle, high steam humidity and other problems, there are problems such as supersonic working fluid, large secondary flow loss at the end, drastic radial flow changes, and poor flow matching of moving and static blades during the working process of the blades, which seriously affect the aerodynamic efficiency of the low-pressure last-stage blades. Considering the safety issues such as the strength and vibration of the moving blades, the blade design usually first designs the moving blades, and then designs the static blades. In this way, in order to solve the aerodynamic loss problem of long blades, it is necessary to design static blades that match the moving blades well based on the blade aerodynamic design theory, on the one hand, to control the aerodynamic loss of the static blades themselves, and on the other hand, to match the flow of the moving blades and reduce the aerodynamic loss of the moving blades. In view of the above-mentioned blade design problems, the present invention proposes a design method for static blades with a twisted swept structure, which can be used to guide steam turbine blade designers to clarify the design direction and design criteria of static blades. Summary of the invention

[0003] The present invention aims to solve the problem of flow loss of long blades in the last few low-pressure stages of existing steam turbines, and further proposes a design method for a stationary blade with a twisted, swept structure for a steam turbine.

[0004] The technical solution adopted by the present invention to solve the above technical problems is:

[0005] A method for designing a twisted, swept structure stationary blade for a steam turbine comprises the following steps:

[0006] Step 1: Determine the blade design basis and stacking rule: The blade design basis is a straight blade with no bending, twisting and sweeping structure. The stacking rule is stacking along the center of the steam outlet circle. The structural parameters of the basic straight blade include the total height of the blade as L, the top axial width of the blade working part as V, and the root diameter of the blade as The exhaust area of ​​the working part of the blade is A;

[0007] Step 2: Based on the basic straight blade and the stacking rule, the blade is bent, swept and twisted to obtain a bent-twisted-swept static blade;

[0008] Step 3: Determine the initial stacking line and obtain the geometric entity of the stationary blade by combining the typical cross-section blade profile;

[0009] Step 4: Import the obtained geometric entities into the blade 3D simulation calculation and optimization platform to further perform blade aerodynamic calculation and blade strength calculation;

[0010] Step 5: The optimal stacking line is obtained based on the calculation results. Finally, each typical section is stacked along the optimal stacking line to obtain a bent, twisted and swept blade.

[0011] Furthermore, in the step 2, the blade bending includes determining the parameters of the bending direction, bending height and bending angle, wherein the bending direction adopts positive bending, the bending area is located at the root of the blade, the bending height is 10% to 15% of the total height L of the blade, and the bending angle is the angle with the vertical direction, which is controlled between 10° and 45°.

[0012] Furthermore, in the step 2, the blade sweeping includes determining parameters of the sweeping direction, the sweeping height and the sweeping angle, wherein the sweeping direction is axial, and the sweeping is from the steam inlet edge to the steam outlet edge. The sweeping area is at the top of the blade. The shapes of two adjacent cross sections during the sweeping process are exactly the same, and only the axial position changes. The sweeping height is less than or equal to 10% of the height of the working part of the blade. The sweeping angle is the angle with the vertical direction, which is controlled between 20° and 40°.

[0013] Furthermore, in the step 2, the blade twisting includes determining the parameters of the twisting section and the twisting angle. The twisting section is the section where relative twisting occurs. Except for the top swept part, the remaining sections are twisted. According to the height of the blade, a typical section is taken every 10% of the blade height for relative twisting. The twisting angle is the installation angle of the typical section of the blade that changes by twisting in the vertical direction. The twisting angle is determined according to the change of the inlet airflow angle along the blade height direction to match the airflow flow direction.

[0014] Furthermore, in the step three, the stacking line is a spatial curve connecting the centers of steam outlet circles of each typical cross-section along the blade height direction, which contains structural information of three aspects of bending, twisting and sweeping of the typical cross-section. The structural parameters involved include bending direction, bending height, bending angle, and sweeping direction, sweeping height, sweeping angle, as well as torsional cross-section and torsion angle, a total of 8 parameters. Basic recommended values ​​are given for the above 8 bending, twisting and sweeping parameters, respectively. An initial stacking line is given according to the basic recommended values, and the static blade geometric entity is obtained from the initial stacking line and the typical cross-section blade profile.

[0015] Furthermore, in the step 4, the blade three-dimensional simulation calculation and optimization platform includes a grid division module, a boundary setting module, an aerodynamic calculation module, a strength calculation module and an optimization calculation module.

[0016] Further, the meshing module uses structured hexahedral meshes to divide the imported blade geometric entities into computational meshes;

[0017] The boundary setting module is used to set the working fluid type, set the turbulence model, set the pressure and temperature values ​​of the inlet and outlet of the calculation fluid domain, and set the calculation convergence criterion;

[0018] The aerodynamic calculation module performs aerodynamic simulation calculation in the fluid domain, and the aerodynamic calculation is completed when the calculation reaches the convergence criterion set in the boundary setting module;

[0019] The strength calculation module calculates the blade strength and determines whether the blade strength is qualified according to the strength assessment standard;

[0020] The optimization calculation module uses the above-mentioned 8 bending, twisting and sweep parameters as optimization variables, the above-mentioned aerodynamic efficiency as optimization target, and the above-mentioned strength assessment result as constraint condition to perform iterative calculation until the optimal solution of the 8 bending, twisting and sweep parameters with the highest aerodynamic efficiency under the premise of qualified strength is obtained.

[0021] Furthermore, the stacking line obtained under the optimal solution is the optimal stacking line.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The design method of the twisted, swept structured stator blades in the present invention is based on one-dimensional / quasi-three-dimensional / full three-dimensional aerodynamic and thermal analysis calculations, and combined with the static pressure of engineering applications, a full three-dimensional design method of twisted, swept and combined forming stator blades is proposed. The blades are stacked and formed along the center of the steam outlet circle of each section. The present invention can guide blade designers to optimize the design of the stator blades in the low-pressure long blade stage of the steam turbine, reduce the aerodynamic loss of the stator blades, increase the flow matching between the dynamic and static blades, and thus improve the aerodynamic efficiency.

[0024] 2. The use range of the control parameters mentioned in the present invention is based on a large amount of aerodynamic calculations, optimization analysis and engineering experience. The unique twist, bend and sweep combined structure formed can effectively organize the flow of the working fluid during the working process, reduce secondary flow losses, enhance dynamic and static flow matching, and thus improve the inlet air flow field of the moving blades, reduce vibration problems caused by airflow pressure pulsation, and reduce aerodynamic noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of pressure monitoring and early warning in the present invention. DETAILED DESCRIPTION

[0026] Specific implementation method 1: Combination Figure 1 This embodiment describes a method for designing a twisted, swept structured stationary blade for a steam turbine, comprising the following steps:

[0027] Step 1: Determine the blade design basis and stacking rule: The blade design basis is a straight blade with no bending, twisting and sweeping structure. The stacking rule is stacking along the center of the steam outlet circle. The structural parameters of the basic straight blade include the total height of the blade as L, the top axial width of the blade working part as V, and the root diameter of the blade as The exhaust area of ​​the working part of the blade is A;

[0028] Step 2: Based on the basic straight blade and the stacking rule, the blade is bent, swept and twisted to obtain a bent-twisted-swept static blade;

[0029] Step 3: Determine the initial stacking line and obtain the geometric entity of the stationary blade by combining the typical cross-section blade profile;

[0030] Step 4: Import the obtained geometric entities into the blade 3D simulation calculation and optimization platform to further perform blade aerodynamic calculation and blade strength calculation;

[0031] Step 5: The optimal stacking line is obtained based on the calculation results. Finally, each typical section is stacked along the optimal stacking line to obtain a bent, twisted and swept blade.

[0032] The present invention proposes a design method for the last-stage static blades of a steam turbine with a twisted swept structure, in particular the static blades of the last few low-pressure stages of the steam turbine, which can effectively control the aerodynamic losses of the static blades and the flow matching between the dynamic and static blades, improve the efficiency of the long-blade stage, and can be used to guide the steam turbine blade designers to clarify the design direction and design criteria of the static blades in the low-pressure long-blade stage.

[0033] The blades described in this embodiment are stacked and formed based on the center of each cross-sectional steam outlet circle.

[0034] The twist structure refers to a twisted blade with a variable cross-sectional area at different blade heights, that is, the working section of the blade gradually increases from the top section to the root section, and there is a relative twist between two adjacent sections. The cross-sectional twist angle affects the outlet airflow angle of the stationary blades at different blade heights, and then affects the inlet airflow angle of the moving blades. It is necessary to change the twist angle through repeated three-dimensional aerodynamic calculations to achieve dynamic and static flow matching.

[0035] The curved structure refers to the curved structure of the root area of ​​the working part of the blade. The present invention adopts a positive curved structure, that is, the bending direction is from the pressure surface to the suction surface. The bending height is H 1 , H 1 Not more than 15% of the height of the working part of the blade. The bending angle is α 1 , the angle is controlled between 10°-45°. Three-dimensional aerodynamic calculations show that there is an optimal value within the above bend height and bend angle range, which can effectively control the secondary flow loss at the blade root and improve aerodynamic efficiency.

[0036] The swept structure refers to the forward swept structure of the blade tip area of ​​the working part of the blade, that is, swept from the steam outlet edge to the steam inlet edge. The forward swept height is H 2 , H 2 Not more than 10% of the height of the working part of the blade. The forward sweep angle is α 2 , the angle is controlled between 20° and 40°. Three-dimensional aerodynamic calculations show that there is an optimal value within the above sweep height and sweep angle range, which can effectively control the secondary flow loss at the blade tip, enhance the flow matching between the moving and stationary blades, and improve aerodynamic efficiency.

[0037] The final typical cross sections are stacked along the optimal stacking line to obtain a bent-twisted blade with the highest design efficiency and qualified strength.

[0038] Specific implementation method 2: Combination Figure 1 To explain this embodiment, in step 2 of this embodiment, the blade bending includes determining the parameters of the bending direction, bending height and bending angle, wherein the bending direction adopts positive bending, the bending area is located at the root of the blade, the bending height is 10% to 15% of the total height L of the blade, and the bending angle is the angle with the vertical direction, which is controlled between 10° and 45°. The undisclosed technical features in this embodiment are the same as those in the first embodiment.

[0039] The bending direction is divided into positive bending and negative bending. The positive bending is that the pressure surface bends toward the suction surface, and the negative bending is that the suction surface bends toward the pressure surface. The present embodiment selects the positive bending.

[0040] Specific implementation method three: Combination Figure 1 To explain this embodiment, in step 2 of this embodiment, the blade sweeping includes the determination of parameters of the sweeping direction, sweeping height and sweeping angle, wherein the sweeping direction is axial, and the sweeping is from the steam inlet edge to the steam outlet edge, the sweeping area is at the top of the blade, the shapes of the two adjacent cross sections during the sweeping process are exactly the same, and only the axial position changes, the sweeping height is less than or equal to 10% of the height of the working part of the blade, and the sweeping angle is the angle with the vertical direction, which is controlled between 20° and 40°. The undisclosed technical features in this embodiment are the same as those in the second specific embodiment.

[0041] The sweeping direction is axial, and is divided into two types: sweeping from the steam inlet side to the steam outlet side and sweeping from the steam outlet side to the steam inlet side. This embodiment adopts the sweeping from the steam inlet side to the steam outlet side, which can control the aerodynamic loss of the blade.

[0042] Specific implementation method four: Combination Figure 1To explain this embodiment, in step 2 of this embodiment, the blade twisting includes the determination of parameters of the twisting section and the twisting angle. The twisting section is the section where relative twisting occurs. Except for the top swept part, the remaining sections are twisted. According to the height of the blade, a typical section is taken every 10% of the blade height for relative twisting. The twisting angle is the installation angle of the typical section of the blade that changes along the vertical direction due to twisting. The twisting angle is determined according to the change of the inlet airflow angle along the blade height direction to match the airflow flow direction. The undisclosed technical features in this embodiment are the same as those in the specific embodiment 3.

[0043] Specific implementation method five: Combination Figure 1 To explain this embodiment, in step three of this embodiment, the stacking line is a spatial curve connecting the centers of steam outlet circles of each typical section along the blade height direction, and contains the structural information of the three aspects of the typical section bend, twist and sweep. The structural parameters involved include the bending direction, bending height, bending angle, and sweeping direction, sweeping height, sweeping angle, as well as twisting section and twisting angle, a total of 8 parameters. Basic recommended values ​​are given for the above 8 bending, twisting and sweeping parameters, and an initial stacking line is given according to the basic recommended values. The geometric entity of the stationary blade is obtained from the initial stacking line and the typical section blade profile. The undisclosed technical features in this embodiment are the same as those in the specific embodiment four.

[0044] Specific implementation method six: Combination Figure 1 To illustrate this embodiment, in step 4 of this embodiment, the blade three-dimensional simulation calculation and optimization platform includes a grid division module, a boundary setting module, an aerodynamic calculation module, a strength calculation module and an optimization calculation module. The undisclosed technical features in this embodiment are the same as those in the specific embodiment 5.

[0045] Specific implementation method seven: Combination Figure 1 To illustrate this embodiment, the meshing module described in this embodiment uses a structured hexahedral mesh to divide the imported blade geometric entity into a computational mesh;

[0046] The boundary setting module is used to set the working fluid type, set the turbulence model, set the pressure and temperature values ​​of the inlet and outlet of the calculation fluid domain, and set the calculation convergence criterion;

[0047] The aerodynamic calculation module performs aerodynamic simulation calculation in the fluid domain, and the aerodynamic calculation is completed when the calculation reaches the convergence criterion set in the boundary setting module;

[0048] The strength calculation module calculates the blade strength and determines whether the blade strength is qualified according to the strength assessment standard;

[0049] The optimization calculation module uses the above-mentioned 8 bending, twisting and sweep parameters as optimization variables, the above-mentioned aerodynamic efficiency as optimization target, and the above-mentioned strength assessment result as constraint condition to perform iterative calculation until the optimal solution of the 8 bending, twisting and sweep parameters with the highest aerodynamic efficiency under the premise of qualified strength is obtained.

[0050] The undisclosed technical features in this embodiment are the same as those in the sixth embodiment.

[0051] Specific implementation method eight: Combination Figure 1 This embodiment is described, and the stacking line obtained under the optimal solution described in this embodiment is the optimal stacking line. The undisclosed technical features in this embodiment are the same as those in the seventh embodiment.

[0052] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and features described herein may be combined in a manner different from that described in the original claims. It is also understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A method for designing a twisted, swept structure stator blade for a steam turbine, characterized in that: The method comprises the following steps: Step 1: Determine the blade design basis and stacking rule: The blade design basis is a straight blade with no bending, twisting and sweeping structure. The stacking rule is stacking along the center of the steam outlet circle. The structural parameters of the basic straight blade include the total height of the blade as L, the top axial width of the blade working part as V, and the root diameter of the blade as The exhaust area of ​​the working part of the blade is A; Step 2: Based on the basic straight blade and the stacking rule, the blade is bent, swept and twisted to obtain a bent-twisted-swept static blade; Step 3: Determine the initial stacking line and obtain the geometric entity of the stationary blade by combining the typical cross-section blade profile; Step 4: Import the obtained geometric entities into the blade 3D simulation calculation and optimization platform to further perform blade aerodynamic calculation and blade strength calculation; Step 5: The optimal stacking line is obtained based on the calculation results. Finally, each typical section is stacked along the optimal stacking line to obtain a bent, twisted and swept blade.

2. A method for designing a twisted, swept structured stationary blade for a steam turbine according to claim 1, characterized in that: In the step 2, the blade bending includes determining the parameters of the bending direction, bending height and bending angle, wherein the bending direction adopts positive bending, the bending area is located at the root of the blade, the bending height is 10% to 15% of the total height L of the blade, and the bending angle is the angle with the vertical direction, which is controlled between 10° and 45°.

3. The method for designing a twisted, swept structure stator blade for a steam turbine according to claim 2, characterized in that: In the step 2, the blade sweeping includes determining the parameters of the sweeping direction, the sweeping height and the sweeping angle, wherein the sweeping direction is axial, and the sweeping is from the steam inlet edge to the steam outlet edge. The sweeping area is at the top of the blade. The shapes of two adjacent cross sections during the sweeping process are exactly the same, and only the axial position changes. The sweeping height is less than or equal to 10% of the height of the working part of the blade. The sweeping angle is the angle with the vertical direction, which is controlled between 20° and 40°.

4. The method for designing a twisted, swept structure stator blade for a steam turbine according to claim 3, characterized in that: In the step 2, the blade twisting includes determining the parameters of the twisting section and the twisting angle. The twisting section is the section where relative twisting occurs. Except for the top swept part, the other sections are twisted. According to the height of the blade, a typical section is taken every 10% of the blade height for relative twisting. The twisting angle is the installation angle of the typical section of the blade that changes by twisting in the vertical direction. The twisting angle is determined according to the change of the inlet airflow angle along the blade height direction to match the airflow flow direction.

5. A method for designing a twisted, swept structured stationary blade for a steam turbine according to claim 4, characterized in that: In the step three, the stacking line is a spatial curve connecting the centers of steam outlet circles of each typical cross-section along the blade height direction, which contains structural information of three aspects of bending, twisting and sweeping of the typical cross-section. The structural parameters involved include bending direction, bending height, bending angle, sweeping direction, sweeping height, sweeping angle, twisting cross-section and twisting angle, totaling 8 parameters. Basic recommended values ​​are given for the above 8 bending, twisting and sweeping parameters respectively, and an initial stacking line is given according to the basic recommended values. The geometric entity of the stationary blade is obtained from the initial stacking line and the blade profile of the typical cross-section.

6. A method for designing a twisted, swept structure stator blade for a steam turbine according to claim 5, characterized in that: In the step 4, the blade three-dimensional simulation calculation and optimization platform includes a grid division module, a boundary setting module, an aerodynamic calculation module, a strength calculation module and an optimization calculation module.

7. A method for designing a twisted, swept structure stator blade for a steam turbine according to claim 6, characterized in that: The meshing module divides the imported blade geometric entity into computational meshes using a structured hexahedral mesh; The boundary setting module is used to set the working fluid type, set the turbulence model, set the pressure and temperature values ​​of the inlet and outlet of the calculation fluid domain, and set the calculation convergence criterion; The aerodynamic calculation module performs aerodynamic simulation calculation in the fluid domain, and the aerodynamic calculation is completed when the calculation reaches the convergence criterion set in the boundary setting module; The strength calculation module calculates the blade strength and determines whether the blade strength is qualified according to the strength assessment standard; The optimization calculation module uses the above-mentioned 8 bending, twisting and sweep parameters as optimization variables, the above-mentioned aerodynamic efficiency as optimization target, and the above-mentioned strength assessment result as constraint condition to perform iterative calculation until the optimal solution of the 8 bending, twisting and sweep parameters with the highest aerodynamic efficiency under the premise of qualified strength is obtained.

8. The method for designing a twisted, swept structured stationary blade for a steam turbine according to claim 7, characterized in that: The stacking line obtained under the optimal solution is the optimal stacking line.

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