A method for optimizing the structure of low-pressure exhaust cylinder of steam turbine based on the parameters of last-stage blades

Abstract

A method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades, relates to the structure of a low-pressure exhaust cylinder of a steam turbine, and aims at the problem in the prior art that the pressure at the outlet of the last-stage moving blades is higher than the back pressure of the condenser, resulting in a reduction in the work done in the last stage, which reduces the efficiency of the unit. This application performs dimensionless processing on the structural parameters of the low-pressure exhaust cylinder based on the size parameters of the average diameter D and blade height L of the last-stage blades, and provides a dimensionless structural parameter design range of the low-pressure exhaust cylinder with good aerodynamic performance through research summary and numerical calculation, and the preliminary structural parameters of the low-pressure exhaust cylinder can be determined according to the constraints. This application can find the structural parameters of the low-pressure exhaust cylinder with the best aerodynamic performance under the existing constraints, thereby significantly improving the efficiency of the unit, reducing the heat consumption of the unit or increasing the output power of the unit. This application solves the problem that the pressure at the outlet of the last-stage moving blades is higher than the back pressure of the condenser, resulting in a reduction in the work done in the last stage, which reduces the efficiency of the unit.

Description

Technical Field

[0001] The invention relates to a steam turbine low-pressure exhaust cylinder structure, in particular to a steam turbine low-pressure exhaust cylinder structure optimization method based on last-stage blade parameters. Background Art

[0002] The main task of the low-pressure exhaust cylinder of the steam turbine is to organize and guide the axial exhaust (with a certain radial deviation angle) of the last-stage blades of the flow-through part to the condenser.

[0003] If the low-pressure exhaust cylinder is designed properly, the residual velocity loss of the last stage can be partially recovered, so that the work capacity of the last-stage blades can be improved, thereby improving the efficiency of the entire unit; if the low-pressure exhaust cylinder is designed poorly, when the last-stage exhaust steam reaches the condenser inlet through a long and tortuous path, not only will the residual velocity kinetic energy be completely lost, but also a part of the pressure energy of the last-stage exhaust steam will be lost, which makes the pressure at the outlet of the last-stage moving blades higher than the condenser back pressure, resulting in reduced work done by the last stage and reduced unit efficiency.

[0004] In the past few decades, the academic community has conducted in-depth research on the optimization methods of turbine blade design, and the blade efficiency has reached an extremely high level, but there is little research on the exhaust cylinder, which is considered to be one of the components with the most potential for improving unit efficiency in the current flow structure.

[0005] The internal flow of the low-pressure exhaust cylinder is extremely complex. It is extremely difficult to theoretically estimate its performance and design a high-performance exhaust cylinder. In the past, the design of the low-pressure exhaust cylinder of a steam turbine mainly carried out blowing tests and numerical calculations on the individual low-pressure exhaust cylinders, and improved the local dimensions of the low-pressure exhaust cylinders to improve their aerodynamic performance. Summary of the invention

[0006] The purpose of the present invention is to propose a method for optimizing the low-pressure exhaust cylinder structure of a steam turbine based on the parameters of the last-stage blades in order to solve the problem in the prior art that the pressure at the outlet of the last-stage moving blades is higher than the back pressure of the condenser, resulting in reduced work done in the last stage and reduced efficiency of the unit.

[0007] The technical solution adopted by the present invention to solve the above technical problems is:

[0008] A method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on last-stage blade parameters comprises the following steps:

[0009] Step 1: Establish a geometric model of a low-pressure exhaust cylinder of a steam turbine, and obtain parameters characterizing the geometric dimensions of the exhaust cylinder according to the established geometric model of the low-pressure exhaust cylinder of the steam turbine;

[0010] Step 2: Determine the average diameter D and height L of the last-stage blade according to the flow design, and then perform dimensionless processing on the parameters characterizing the geometric dimensions of the exhaust cylinder based on the average diameter D and height L of the last-stage blade to obtain a parameterized low-pressure exhaust cylinder model;

[0011] Step 3: Calculate the parameterized low-pressure exhaust cylinder model using the automatic optimization platform to obtain the angle parameters and dimensionless length parameters of the low-pressure exhaust cylinder with the best performance within the parameter range;

[0012] Step 4: Model the exhaust cylinder structure based on the average diameter D and height L of the last-stage blades as well as the optimal angle parameters and dimensionless length parameters.

[0013] The beneficial effects of the present invention are:

[0014] (1) It breaks through the limitations of the individual design of the low-pressure exhaust cylinder and has wide applicability.

[0015] In the past, the design of low-pressure exhaust cylinders of steam turbines mainly focused on the exhaust cylinders themselves. Wind blowing tests or numerical calculations were carried out under certain structures. Based on the calculation or test results, local adjustments were made to the exhaust cylinder structure. This process was repeated to obtain the final design structure.

[0016] This application non-dimensionalizes the structural parameters of the low-pressure exhaust cylinder based on the dimensional parameters of the average diameter D and blade height L of the last-stage blades, and through research summary and numerical calculation, gives the dimensionless structural parameter design range of the low-pressure exhaust cylinder with good aerodynamic performance. The preliminary structural parameters of the low-pressure exhaust cylinder can be determined according to the restrictive conditions.

[0017] The present application is not limited by the individual exhaust cylinders and is applicable to the structural design of low-pressure cylinders of steam turbines with various power levels and various exhaust parameters. Once the parameters of the last-stage blades are determined, the structural design of the low-pressure exhaust cylinder can be completed, which has wide applicability.

[0018] (2) Introduce the low-pressure exhaust cylinder structure optimization method to shorten the low-pressure exhaust cylinder design cycle.

[0019] This application is used to build a parametric optimization platform for the low-pressure exhaust cylinder. The static pressure recovery coefficient is used as the evaluation standard to automatically optimize the preliminary structural parameters of the low-pressure exhaust cylinder. The dimensionless structural parameters of the low-pressure exhaust cylinder corresponding to the optimal aerodynamic performance can be obtained, which effectively avoids the blindness and randomness of "calculation (or test)-structural adjustment-recalculation (or test)", and greatly shortens the design cycle of the low-pressure exhaust cylinder.

[0020] (III) Effectively improve unit efficiency and reduce unit heat consumption.

[0021] This application can find the structural parameters of the low-pressure exhaust cylinder with the best aerodynamic performance under the existing constraints, thereby significantly improving the unit efficiency, reducing the unit heat consumption or increasing the unit output power. This application solves the problem that the pressure at the outlet of the last stage moving blade is higher than the condenser back pressure, resulting in a reduction in the work done at the last stage and a reduction in the unit efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The geometric parameters of the low-pressure exhaust cylinder block are shown in Figure 2. Figure 1 ;

[0023] Figure 2 The geometric parameters of the low-pressure exhaust cylinder block are shown in Figure 2. Figure 2 ;

[0024] Figure 3 This is a schematic diagram of the geometric parameters of the guide ring of the low-pressure exhaust cylinder;

[0025] Figure 4 This is a schematic diagram of the position of the last stage blades in the low pressure exhaust cylinder;

[0026] Figure 5 Schematic diagram of the functional modules of the steam turbine low-pressure exhaust cylinder parameter optimization platform. DETAILED DESCRIPTION

[0027] It should be particularly noted that, in the absence of conflict, the various embodiments disclosed in this application can be combined with each other.

[0028] Specific implementation method 1: refer to Figure 1 Specifically describing this embodiment, a method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades described in this embodiment comprises the following steps:

[0029] Step 1: Establish a geometric model of a low-pressure exhaust cylinder of a steam turbine, and obtain parameters characterizing the geometric dimensions of the exhaust cylinder according to the established geometric model of the low-pressure exhaust cylinder of the steam turbine;

[0030] Step 2: Determine the average diameter D and height L of the last-stage blade according to the flow design, and then perform dimensionless processing on the parameters characterizing the geometric dimensions of the exhaust cylinder based on the average diameter D and height L of the last-stage blade to obtain a parameterized low-pressure exhaust cylinder model;

[0031] Step 3: Calculate the parameterized low-pressure exhaust cylinder model using the automatic optimization platform to obtain the angle parameters and dimensionless length parameters of the low-pressure exhaust cylinder with the best performance within the parameter range;

[0032] Step 4: Model the exhaust cylinder structure based on the average diameter D and height L of the last-stage blades as well as the optimal angle parameters and dimensionless length parameters.

[0033] Specific implementation method 2: This implementation method is a further description of specific implementation method 1. The difference between this implementation method and specific implementation method 1 is that the parameters characterizing the geometric dimensions of the exhaust cylinder include geometric parameters characterizing the cylinder body and geometric parameters characterizing the guide ring.

[0034] Specific implementation method three: This implementation method is a further description of specific implementation method two. The difference between this implementation method and specific implementation method two is that the geometric parameters characterizing the cylinder body include: the axial length L of the cylinder body C 、Cylinder body width W C 、Cylinder block upper half height H u 、Height of lower half of cylinder block H d , cylinder block rear wall inclination angle δ, cylinder block wall thickness T C 、Cylinder body guide cone inlet angle α in 、Cylinder body guide cone turning radius R N and cylinder block guide cone outlet angle α out .

[0035] Specific implementation method 4: This implementation method is a further explanation of specific implementation method 3. The difference between this implementation method and specific implementation method 3 is that the geometric parameters characterizing the guide ring include: the guide ring starting expansion angle β, the guide ring turning radius R K 、Axial length of guide ring L K and guide ring wall thickness T K .

[0036] Specific implementation mode 5: This implementation mode is a further description of specific implementation mode 4. The difference between this implementation mode and specific implementation mode 4 is that the specific steps of step 2 are:

[0037] According to the flow design, the average diameter D and the height L of the last-stage blades are determined. Then, the average diameter D and the height L of the last-stage blades are used as characteristic variables, and the length variables in the parameters characterizing the geometric dimensions of the exhaust cylinder are dimensionlessly processed to obtain the dimensionless parameters of the low-pressure exhaust cylinder. Then, a parameterized low-pressure exhaust cylinder model is obtained based on the dimensionless parameters of the low-pressure exhaust cylinder and the angle parameters in the parameters characterizing the geometric dimensions of the exhaust cylinder.

[0038] Specific implementation method 6: This implementation method is a further explanation of specific implementation method 5. The difference between this implementation method and specific implementation method 5 is that the dimensionless parameters of the low-pressure exhaust cylinder include: cylinder body axial length factor P1 = L C / L, cylinder width factor P2 = W C / D, cylinder block upper half height factor P3 = H u / D, cylinder block lower half height factor P4 = H d / D, cylinder wall thickness factor P5 = T C / L, cylinder body guide cone turning radius factor P6 = R N / D, guide ring turning radius factor P7 = R K / D, guide ring axial length factor P8 = L K / L and cylinder wall thickness factor P9 = T K / L.

[0039] Specific implementation method 7: This implementation method is a further explanation of specific implementation method 6. The difference between this implementation method and specific implementation method 6 is that the angle parameters include: cylinder body rear wall inclination angle δ, cylinder body guide cone inlet angle α in 、Cylinder body guide cone outlet angle α out and the guide ring initial expansion angle β.

[0040] Specific implementation eight: This implementation is a further explanation of specific implementation seven. The difference between this implementation and specific implementation seven is that the automatic optimization platform includes a three-dimensional modeling module, a meshing module, a low-pressure exhaust cylinder CFD numerical calculation module and an optimization module;

[0041] The three-dimensional modeling module is used to convert the average diameter D of the last-stage blade, the height L of the last-stage blade, the angle parameter, and the dimensionless length parameter into a three-dimensional structural model of the low-pressure exhaust cylinder, and obtain the fluid calculation domain through Boolean operation;

[0042] The grid division module is used to divide the fluid calculation domain into unstructured grids;

[0043] The low-pressure exhaust cylinder CFD numerical calculation module is used to perform numerical calculations according to the fluid calculation domain after dividing the unstructured grid and under specified boundary conditions to obtain the aerodynamic performance evaluation parameters of the low-pressure exhaust cylinder under a given three-dimensional structure;

[0044] The optimization module is used to optimize the structural parameters of the low-pressure exhaust cylinder according to the aerodynamic performance evaluation parameters of the low-pressure exhaust cylinder under a given three-dimensional structure.

[0045] Optimize the platform such as Figure 5 shown.

[0046] Specific implementation method 9: This implementation method is a further explanation of specific implementation method 8. The difference between this implementation method and specific implementation method 8 is that the optimization module adopts a combined optimization strategy of orthogonal experiment and response surface approximation model. The optimization module specifically performs the following steps:

[0047] 1. Within the given parameter range, the orthogonal test method is used to scan the design space and obtain the design parameter sample library;

[0048] Second: Use the CFD module to calculate the design parameter sample library to obtain the performance evaluation parameters under each sample parameter;

[0049] 3. Use the response surface method to establish a mathematical approximate model between sample parameters and performance evaluation parameters, and obtain the sample parameters corresponding to the optimal performance evaluation parameters;

[0050] 4: Given the optimal sample parameters, use the CFD module to verify the aerodynamic performance.

[0051] This application performs parametric modeling of the low-pressure exhaust cylinder according to the last-stage blade parameters determined by the flow design, and optimizes key structural parameters to improve the aerodynamic performance of the low-pressure exhaust cylinder and the efficiency of the unit. It is applied in the ultra-supercritical 660MW reconstruction unit and 1000MW nuclear power unit of Harbin Steam Turbine Plant Co., Ltd. (hereinafter referred to as Harbin Steam Company), and has good application prospects and economic value.

[0052] This application aims to solve the problem of improving the aerodynamic performance of the low-pressure exhaust cylinder of a steam turbine. This application provides a method for optimizing the structure of the low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades, that is, this application can provide the geometric structure dimensions of the low-pressure exhaust cylinder corresponding to the optimal aerodynamic performance through an automatic optimization platform according to the parameters of the last-stage blades of the steam turbine, thereby effectively improving the efficiency of the unit.

[0053] This application has been applied to the low-pressure exhaust cylinder optimization design engineering practice of Harbin Steam Turbine Company's ultra-supercritical 660MW modified steam turbine unit and 1000MW Hualong One nuclear power half-speed steam turbine unit. Compared with the original design scheme, the design heat consumption of the ultra-supercritical 660MW modified steam turbine unit decreased by 1.1‰, and the design power of the 1000MW Hualong One nuclear power half-speed steam turbine unit increased by 1.5‰.

[0054] This application specifically:

[0055] W1. Establish the geometric model of the turbine low-pressure exhaust cylinder.

[0056] From a structural perspective, the low-pressure exhaust cylinder has two main structural components, namely the guide ring and the cylinder body. The guide ring and the guide cone on the cylinder body form a diffuser, which is used to recover the residual kinetic energy and convert it into the pressure energy of the exhaust steam; the diffuser outlet in the cylinder body to the cylinder body outlet forms a volute, which realizes a 90° turn of the airflow.

[0057] There are 9 geometric parameters that characterize the cylinder block, as shown in the attached Figure 1 As shown, they are:

[0058] (1) Cylinder block axial length L C ;

[0059] (2) Cylinder block width W C ;

[0060] (3) Height of the upper part of the cylinder block Hu ;

[0061] (4) Height of lower half of cylinder block H d ;

[0062] (5) Cylinder rear wall inclination angle δ;

[0063] (6) Cylinder wall thickness T C ;

[0064] (7) Cylinder body guide cone inlet angle α in ;

[0065] (8) Cylinder body guide cone turning radius R N ;

[0066] (9) Cylinder body guide cone outlet angle α out ;

[0067] There are four geometric parameters that characterize the guide ring, as shown in the attached figure. Figure 2 As shown, they are:

[0068] (10) Initial expansion angle of the guide ring β;

[0069] (11) Turning radius of guide ring R K ;

[0070] (12) Axial length of guide ring L K ;

[0071] (13) Guide ring wall thickness T K ;

[0072] There are two other parameters used to determine the radial position of the guide ring and cylinder block guide cone, as shown in the attached figure. Figure 3 As shown, they are:

[0073] (14) Average diameter D of the last blade;

[0074] (15) Final blade height L;

[0075] The present invention establishes a geometric model of a low-pressure exhaust cylinder of a steam turbine through the 15-parameter method, including 11 length variables and 4 angle variables.

[0076] W2. Based on the mid-diameter D and blade height L of the last-stage blade, the parameters characterizing the geometric dimensions of the exhaust cylinder are dimensionlessly processed to obtain a parameterized low-pressure exhaust cylinder model.

[0077] The median diameter D and blade height L are selected as characteristic variables, and the remaining length variables expressing the low-pressure exhaust cylinder are dimensionlessly processed to obtain the following dimensionless parameters of the low-pressure exhaust cylinder:

[0078] (1) Cylinder block axial length factor P1 = LC / L;

[0079] (2) Cylinder width factor P2 = W C / D;

[0080] (3) Cylinder upper half height factor P3 = H u / D;

[0081] (4) Cylinder lower half height factor P4 = H a / D;

[0082] (5) Cylinder wall thickness factor P5 = T C / L;

[0083] (6) Cylinder guide cone turning radius factor P6 = R N / D;

[0084] (7) Guide ring turning radius factor P7 = R K / D;

[0085] (8) The axial length factor of the guide ring P8 = L K / L;

[0086] (9) Cylinder wall thickness factor P9 = T K / L;

[0087] After the turbine flow design determines the mid-diameter D and blade height L of the last-stage blade, the parameterized low-pressure exhaust cylinder model can be obtained by giving the above-mentioned 9 dimensionless length parameters and 4 angle parameters.

[0088] The steam turbine low-pressure cylinder structural design proposed by the present invention is applicable to various power levels and various exhaust parameters. Once the parameter size of the last-stage blade is determined, the preliminary structural design of the low-pressure exhaust cylinder can be completed, and it has wide applicability.

[0089] Taking the ultra-supercritical 660MW steam turbine unit of Harbin Steam Turbine Company as an example, the middle diameter of the last stage blade D = 2768mm, the blade height L = 1040mm, and the following dimensionless factors are given:

[0090] (1) Cylinder block axial length factor P1 = 2.1;

[0091] (2) Cylinder width factor P2 = 2.4;

[0092] (3) Cylinder block upper half height factor P3 = 1.10;

[0093] (4) Cylinder block lower half height factor P4 = 1.13;

[0094] (5) Cylinder wall thickness factor P5 = 0.030;

[0095] (6) Cylinder guide cone turning radius factor P6 = 0.61;

[0096] (7) Guide ring turning radius factor P7 = 0.16;

[0097] (8) The guide ring axial length factor P8 = 0.83;

[0098] (9) Cylinder wall thickness factor P9 = 0.015;

[0099] (10) Cylinder rear wall inclination angle δ = 10.0°;

[0100] (11) Cylinder body guide cone inlet angle α in =10.0°;

[0101] (12) Cylinder guide cone outlet angle α out =58.7°;

[0102] (13) The initial expansion angle of the guide ring β = 25.2°;

[0103] The parameterized low-pressure exhaust cylinder model can be obtained.

[0104] W3. Using the automatic optimization platform for low-pressure exhaust cylinder parameters, determine the angle parameters and dimensionless length parameters corresponding to the optimal aerodynamic performance of the low-pressure exhaust cylinder within a given parameter range.

[0105] The low-pressure exhaust cylinder optimization platform developed by various companies can be used for calculation. The present invention adopts the turbine low-pressure exhaust cylinder parameter optimization platform independently developed by Harbin Steam Turbine Co., Ltd. The functional module of the platform is shown as follows: Figure 4 shown.

[0106] The optimization platform includes a low-pressure exhaust cylinder three-dimensional modeling module, a meshing module, a low-pressure exhaust cylinder CFD numerical calculation module, and an optimization module for optimizing the low-pressure exhaust cylinder structural parameters based on the low-pressure exhaust cylinder aerodynamic performance evaluation parameters.

[0107] The median diameter D, blade height L of the last stage blade, the above-mentioned 9 dimensionless length parameters and 4 angle parameters, a total of 15 parameters are used as the input structural parameters of the low-pressure exhaust cylinder, and the static pressure recovery coefficient is used as the aerodynamic performance evaluation parameter of the low-pressure exhaust cylinder.

[0108] The optimization module adopts a combined optimization strategy of orthogonal experiment and response surface approximation model. The optimization process is as follows:

[0109] (1) Within a given parameter range, the orthogonal test method is used to scan the design space and obtain a design parameter sample library;

[0110] (2) Use the CFD module to calculate the sample library and obtain the performance evaluation parameters under each sample parameter;

[0111] (3) Using the response surface method, a mathematical approximation model is established between the input sample data and the performance evaluation parameters to find the input sample parameters that best correspond to the performance evaluation parameters.

[0112] (4) Given the optimal input sample parameters, the aerodynamic performance is verified using the CFD module.

[0113] This step utilizes the low-pressure exhaust cylinder automatic optimization platform to automatically find the angle parameters and dimensionless length parameters corresponding to the optimal aerodynamic performance of the low-pressure exhaust cylinder within a given parameter range.

[0114] W4. Use 3D modeling tools to complete the final structural design of the low-pressure exhaust cylinder;

[0115] According to the middle diameter D and blade height L of the last-stage blade, as well as the angle parameters and dimensionless length parameters corresponding to the optimal aerodynamic performance obtained by the previous optimization calculation, the exhaust cylinder structure modeling can be completed using a three-dimensional modeling tool. According to the strength calculation results, appropriate ribs and struts are added to complete the final structural design of the turbine low-pressure exhaust cylinder.

[0116] It should be noted that the specific implementation is only an explanation and description of the technical solution of the present invention, and cannot be used to limit the scope of protection of the rights. Any partial changes made according to the claims and description of the present invention should still fall within the scope of protection of the present invention.

Claims

1. A method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades, characterized in that The following steps are involved: Step 1: Establish a geometric model of a low-pressure exhaust cylinder of a steam turbine, and obtain parameters characterizing the geometric dimensions of the exhaust cylinder according to the established geometric model of the low-pressure exhaust cylinder of the steam turbine; Step 2: Determine the average diameter D and height L of the last-stage blade according to the flow design, and then perform dimensionless processing on the parameters characterizing the geometric dimensions of the exhaust cylinder based on the average diameter D and height L of the last-stage blade to obtain a parameterized low-pressure exhaust cylinder model; Step 3: Calculate the parameterized low-pressure exhaust cylinder model using the automatic optimization platform to obtain the angle parameters and dimensionless length parameters of the low-pressure exhaust cylinder with the best performance within the parameter range; Step 4: Model the exhaust cylinder structure based on the average diameter D and height L of the last-stage blades as well as the optimal angle parameters and dimensionless length parameters.

2. A method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades according to claim 1, characterized in that The parameters characterizing the geometrical dimensions of the exhaust cylinder include geometrical parameters characterizing the cylinder block and geometrical parameters characterizing the guide ring.

3. A method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades according to claim 2, characterized in that The geometric parameters characterizing the cylinder block include: the axial length L of the cylinder block C 、Cylinder body width W C 、Cylinder block upper half height H u 、Height of lower half of cylinder block H d , cylinder block rear wall inclination angle δ, cylinder block wall thickness T C 、Cylinder body guide cone inlet angle α in 、Cylinder body guide cone turning radius R N and cylinder block guide cone outlet angle α out .

4. A method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades according to claim 2, characterized in that The geometric parameters characterizing the guide ring include: the guide ring initial expansion angle β, the guide ring turning radius R K 、Axial length of guide ring L K and guide ring wall thickness T K .

5. The method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades according to claim 2, characterized in that The specific steps of step 2 are: According to the flow design, the average diameter D and the height L of the last-stage blades are determined. Then, the average diameter D and the height L of the last-stage blades are used as characteristic variables, and the length variables in the parameters characterizing the geometric dimensions of the exhaust cylinder are dimensionlessly processed to obtain the dimensionless parameters of the low-pressure exhaust cylinder. Then, a parameterized low-pressure exhaust cylinder model is obtained based on the dimensionless parameters of the low-pressure exhaust cylinder and the angle parameters in the parameters characterizing the geometric dimensions of the exhaust cylinder.

6. A method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades according to claim 5, characterized in that The dimensionless parameters of the low-pressure exhaust cylinder include: cylinder body axial length factor P1 = L C / L, cylinder width factor P2 = W C / D, cylinder block upper half height factor P3 = H u / D, cylinder block lower half height factor P4 = H d / D, cylinder wall thickness factor P5 = T C / L, cylinder body guide cone turning radius factor P6 = R N / D, guide ring turning radius factor P7 = R K / D, guide ring axial length factor P8 = L K / L and cylinder wall thickness factor P9 = T K / L.

7. The method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades according to claim 1, characterized in that The angle parameters include: cylinder rear wall inclination angle δ, cylinder guide cone inlet angle α in 、Cylinder body guide cone outlet angle α out and the guide ring initial expansion angle β.

8. A method for optimizing the structure of a low-pressure exhaust cylinder of a steam turbine based on the parameters of the last-stage blades according to claim 7, characterized in that The automatic optimization platform includes a three-dimensional modeling module, a meshing module, a low-pressure exhaust cylinder CFD numerical calculation module and an optimization module; The three-dimensional modeling module is used to convert the average diameter D of the last-stage blade, the height L of the last-stage blade, the angle parameter, and the dimensionless length parameter into a three-dimensional structural model of the low-pressure exhaust cylinder, and obtain the fluid calculation domain through Boolean operation; The grid division module is used to divide the fluid calculation domain into unstructured grids; The low-pressure exhaust cylinder CFD numerical calculation module is used to perform numerical calculations according to the fluid calculation domain after dividing the unstructured grid and under specified boundary conditions to obtain the aerodynamic performance evaluation parameters of the low-pressure exhaust cylinder under a given three-dimensional structure; The optimization module is used to optimize the structural parameters of the low-pressure exhaust cylinder according to the aerodynamic performance evaluation parameters of the low-pressure exhaust cylinder under a given three-dimensional structure.

Images