A high-performance transition section structure and flow design method for a gas turbine compressor

Abstract

The present invention aims to provide a high-performance transition section structure for a gas turbine compressor and a flow design method thereof. The structure comprises an outer wall, an inner wall, and a support plate. The inner wall is located on the inner side of the outer wall. The support plate is inserted and installed in the middle of the outer and inner walls along a circular hole extending through the outer and inner walls. The front end of the outer and inner walls forms the low-pressure compressor outlet side, where the low-pressure compressor outlet stator ring is installed. The rear end of the outer and inner walls forms the high-pressure compressor inlet side, where the high-pressure compressor inlet stator ring is installed. A gas seal sleeve is provided below the high-pressure compressor inlet stator ring and is mounted to the inner wall via screws arranged along the circumferential direction. The gas seal sleeve is equipped with a honeycomb seal to seal the flow into the high-pressure compressor. The transition section structure proposed in the present invention can be applied to various types of three-spool simple cycle gas turbines. The flow design method thereof is not limited to gas turbine compressors but is also applicable to various industrial compressors and aircraft engine compressors with flow transition structures.

Description

Technical Field

[0001] The present invention relates to a gas turbine and a design method thereof, in particular to a compressor transition section and a design method thereof. Background Art

[0002] The compressor is one of the three core components of a gas turbine, and its performance directly determines the achievement of the overall technical specifications of the gas turbine. As gas turbine power increases and efficiency improves, performance indicators continue to reach new heights, placing higher demands on the performance of compressor components. This requires continuous improvement in compressor design and research into breakthrough compressor design technologies to meet the strong demand for high-performance compressors in gas turbine development.

[0003] The three-spool simple cycle layout is a common gas turbine configuration. The transition section structure between the low-pressure and high-pressure compressors plays a crucial role in flow matching between the two compressors. The degree of pressure loss within the transition section and the uniformity of the outlet flow field are directly related to the inlet flow conditions of the downstream high-pressure compressor, which in turn has a significant impact on the performance of the high-pressure compressor. The casing and support plate structures commonly used in the transition section of current gas turbines are relatively simple. While these structures ensure structural safety and reliability and facilitate fabrication, they also result in significant flow losses within the transition section, hindering performance improvements of the compressor and, ultimately, the gas turbine. To address this issue, many research institutions and researchers have proposed various flow design methods. However, due to shortcomings in loss reduction, applicability, structural feasibility, time and resource costs, most methods have ultimately been implemented in engineering applications. With the rapid development of gas turbine performance indicators, the performance levels of various components are also continuously improving. Designing a compressor transition section flow layout that is suitable for the operating characteristics of gas turbines in different fields and has low loss performance has become a key technical link in the gas turbine R&D system. Summary of the Invention

[0004] The object of the present invention is to provide a high-performance transition section structure of a gas turbine compressor and a flow design method thereof, which can solve the problems of gas turbine matching imbalance and performance degradation caused by flow loss in the compressor transition section.

[0005] The object of the present invention is achieved like this:

[0006] The present invention provides a high-performance transition section structure for a gas turbine compressor, which is characterized by comprising an outer wall, an inner wall, and a support plate, wherein the inner wall is located on the inner side of the outer wall, and the support plate is inserted into and installed in the middle of the outer wall and the inner wall along a circular hole penetrating the outer wall and the inner wall. The front end of the outer wall and the inner wall is the low-pressure compressor outlet side, on which the low-pressure compressor outlet stator ring is installed, and the rear end of the outer wall and the inner wall is the high-pressure compressor inlet side, on which the high-pressure compressor inlet stator ring is installed. An air seal sleeve is provided below the high-pressure compressor inlet stator ring and is installed on the inner wall by screws arranged in the circumferential direction. The air seal sleeve is equipped with a honeycomb seal for sealing the flow gas flowing into the high-pressure compressor.

[0007] The high-performance transition section structure of a gas turbine compressor of the present invention may further include:

[0008] 1. The low-pressure compressor outlet stator ring is installed with the inner wall by tight-fitting bolts and nuts, and is positioned with the outer wall in the axial and radial directions by screws.

[0009] 2. The high-pressure compressor inlet stator ring is installed with the outer wall through radial screws.

[0010] 3. When installing the support plate, it is positioned with the outer wall through the cylindrical pin, and the gas seal is achieved by tightening the sealing ring and the sealing ring below it with a nut. The top of the support plate is sealed by compacting the copper gasket through the end cover flange and fastened by bolts arranged along the circumferential direction.

[0011] 4. The outer wall includes the outer casing and the outer wall plate. The outer casing and the outer wall plate are welded together along the entire circumference by gas shielded arc welding on the inlet side of the high-pressure compressor. The flow channel lines of the outer wall plate and the flow-through part of the inner wall are both fourth-order Bezier curves.

[0012] 5. The flow passage of the support plate adopts an airfoil structure, and its profile is a customized blade shape based on a polynomial curve. The inside of the support plate is hollow. Lubricating oil supply and return pipelines, speed sensors, and turning tool channels are arranged inside the support plate at different positions along the circumferential direction. This is achieved by setting corresponding structural interfaces on the top of the end cover flange.

[0013] The present invention provides a flow design method for a high-performance transition section structure of a gas turbine compressor, which is characterized by:

[0014] (1) Design of flow end wall profile: Based on the structural dimensional constraints of the compressor transition section flow passage of the gas turbine, a parametric design of the transition section flow passage profile is performed, and the end wall flow passage profile is optimized using global optimization technology;

[0015] (2) Selection of the number of support plates: The number of support plates inside the transition section is selected based on the vibration analysis results of the low-pressure compressor and high-pressure compressor blades;

[0016] (3) Support plate profile design: Based on the structural dimensional constraints of the gas turbine on the compressor transition section support plate, the transition section support plate profile is parametrically designed;

[0017] (4) Three-dimensional CFD calculation and analysis: including full three-dimensional CFD numerical simulation analysis of the transition section design point and variable operating conditions. Through three-dimensional CFD calculation, the performance and internal flow field conditions of the transition section at the design point and variable operating conditions are obtained to determine whether the design requirements are met. If the design requirements are met, the current transition section flow design scheme is the final design scheme; if not, the corresponding parameter values ​​in the end wall flow channel profile design or the support plate profile design are adjusted according to the specific analysis results of the internal flow field of the transition section. Through repeated iterations of the above links, the compressor transition section flow design scheme that finally meets the performance index requirements is obtained.

[0018] The flow-through design method for a high-performance transition section structure of a gas turbine compressor of the present invention may further include:

[0019] 1. The structural dimension constraints of the gas turbine on the compressor transition section flow passage in step (1) refer to the inner and outer diameter dimensions of the outlet of the low-pressure compressor, the inner and outer diameter dimensions of the inlet of the high-pressure compressor, and the axial length dimension of the transition section.

[0020] 2. Parametric design of the flow channel profile of the end wall of the transition section in step (1), using high-order Bezier curves to describe the inner and outer wall flow channels of the transition section.

[0021] 3. The global optimization technology in step (1) takes the total pressure recovery coefficient of the transition section under all working conditions as the objective function, and performs global optimization design of the inner and outer wall flow channel profiles of the transition section based on the combined optimization strategy of DOE experimental design and gradient optimization algorithm.

[0022] 4. Take the total pressure recovery coefficient of the transition section under all working conditions as the objective function and use the following function OF:

[0023]

[0024] The variables in the above formula are defined as follows:

[0025] i = 1 to 3, corresponding to different incoming air Mach numbers, determined according to the commonly used intake air flow range of the transition section components. When i = 1, it is the Mach number at the design intake air flow rate; when i = 2, it is the Mach number at the commonly used minimum intake air flow rate; when i = 3, it is the average of the above two incoming air Mach numbers;

[0026] σ i is the total pressure recovery coefficient of the transition section under different incoming flow Mach numbers, in, is the total pressure at the inlet of the transition section, is the total pressure at the transition section outlet;

[0027] c i The weight factor affecting the different incoming flow Mach number conditions is determined by the common degree of incoming flow Mach number of the transition section components.

[0028] 5. The principle for selecting the number of support plates in step (2) is to select the number of support plates that can avoid causing blade resonance based on the Campbell diagram of the low-pressure compressor outlet stage blades and the high-pressure compressor inlet stage blades, with the principle of optimizing the safe and stable operation margin within the entire operating range of the blades.

[0029] 6. The structural dimension constraints of the gas turbine on the compressor transition section support plate in step (3) refer to the dimension restrictions on the axial length and thickness range of the transition section support plate, as the internal space of the gas turbine transition section support plate needs to be arranged with the lubricating oil supply and return pipelines, speed sensor, and turning tool channel.

[0030] 7. The parametric design of the transition section support plate profile in step (3) adopts a customized blade profile design method based on the high-order polynomial curve airfoil thickness distribution. By adaptively adjusting the airfoil thickness according to the support plate requirements, a customized blade profile thickness distribution is formed as the cross-sectional profile of the transition section support plate. During the design process, the parameters such as the axial chord length, maximum thickness and its relative position, and the leading and trailing edge radius of the blade profile are adjusted to achieve parametric customized design of the support plate profile.

[0031] 8. In step (4), the parameter values ​​in the end wall flow channel profile design or the support plate profile design are adjusted, including the value range of the coordinates of the Bezier curve control points of the transition section end wall flow channel, the convergence accuracy and relative step size of the gradient optimization algorithm, and the value range of the axial chord length, maximum thickness and relative position of the transition section support plate and the leading and trailing edge radius.

[0032] The advantages of the present invention are:

[0033] (1) The present invention starts from the specific performance requirements of the gas turbine for the compressor transition section, and designs the end wall flow channel profile and support plate profile of the transition section based on the customized design concept, thereby realizing the fine regulation of the internal flow of the gas turbine compressor transition section, effectively reducing the flow loss, and improving the performance of the compressor components and the gas turbine as a whole.

[0034] (2) Aiming at the actual needs of flow design of transition section of high-performance compressor of gas turbine and its engineering application, the present invention realizes the process of flow design by adopting parameterization means with appropriate order and better mathematical properties and global optimization technology with fewer iterations, which effectively shortens the design cycle while achieving fine control of design elements.

[0035] (3) While ensuring high performance of the compressor transition section, the present invention adopts a simple and reliable transition section structure, which facilitates production, processing, and assembly, achieving a balance between aerodynamic performance, structural reliability, and manufacturing processability. Furthermore, the speed sensor and other internal components of the support plate can be disassembled and assembled on-site through the end cover flange, improving maintainability. This transition section structure has been successfully applied in various high-power marine gas turbines, industrial drive, and power generation gas turbines, with significant engineering application results.

[0036] (4) The present invention can be applied to various types of three-rotor simple cycle gas turbines; its flow design method is not limited to gas turbine compressors, but is also applicable to various industrial compressors and aircraft engine compressors with flow transition structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural schematic diagram of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of the outer wall before the support plate, the low-pressure compressor outlet stator ring, and the high-pressure compressor inlet stator ring are installed;

[0039] Figure 3 This is a schematic diagram of the structure of the inner wall before the support plate, low-pressure compressor outlet stator ring, and high-pressure compressor inlet stator ring are installed;

[0040] Figure 4 Schematic diagram of the support plate structure;

[0041] Figure 5 It is the A-direction view of the support plate;

[0042] Figure 6 It is the BB cross-sectional view of the support plate;

[0043] Figure 7 Flowchart of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be described in more detail below with reference to the accompanying drawings:

[0045] Combine Figure 1-7The present invention provides a high-performance transition section structure of a gas turbine compressor, comprising an outer wall 1, an inner wall 2, a support plate 3, a low-pressure compressor outlet static blade ring 4, a high-pressure compressor inlet static blade ring 5, and a gas seal sleeve 6; the outer wall 1 structure comprises an outer casing 18 and an outer wall plate 19, which are welded together along the entire circumference by gas shielded arc welding on the high-pressure compressor inlet side; the support plate 3 is inserted and installed along the circular hole passing through the outer wall 1 and the inner wall 2, and is positioned by a cylindrical pin 9 during installation, and a gas seal is achieved by pressing a sealing ring 10 and a sealing ring 11 below it with a nut 8 to prevent leakage of high-temperature and high-pressure gas in the flow; the top of the support plate 3 is sealed by compacting a copper gasket 13 through an end cover flange 7, and is fastened with 8 bolts 12 arranged along the circumferential direction; the low-pressure compressor outlet static blade ring 4 is installed with the inner wall 2 by tight-fitting bolts 14 and nuts 15, and is fixed to the outer wall 3 at Figure 1 The X and Y surfaces are positioned with several screws; the high pressure compressor inlet stator ring 5 and the outer wall 1 are positioned at Figure 1 The Z surface shown is mounted together with several radial screws; the gas seal sleeve 6 is located below the high-pressure compressor inlet stator ring 5 and is mounted on the inner wall 2 by screws 17 arranged along the circumferential direction.

[0046] The flow path profiles of the outer wall plate 19 and the inner wall 2 flow passage portion are both fourth-order Bezier curves ( Figure 2-3 ); The flow passage portion of the support plate 3 adopts an airfoil structure, and its profile adopts a customized blade profile based on a fourth-order polynomial curve ( Figure 5 、 6 ), with a hollow structure inside ( Figure 4-6 ), support plates for different purposes are installed along the circumferential direction, and lubricating oil supply and return pipelines, speed sensors, turning tool channels, etc. are arranged inside. The above functions are realized by setting corresponding structural interfaces on the top of the end cover flange 7; a honeycomb seal is installed on the gas seal sleeve 6 to seal the flow gas into the high-pressure compressor.

[0047] Combine Figure 7 The specific implementation of the flow design method for a high-performance transition section structure of a gas turbine compressor of the present invention is achieved by the following steps:

[0048] Step 1: Design the flow endwall profile. Based on the structural dimensional constraints imposed by the gas turbine on the compressor transition section flow passage, high-order Bezier curves are used to describe the inner and outer wall flow passages of the transition section. A parametric design of the transition section endwall profile is performed, and global optimization techniques are used to optimize the endwall profile.

[0049] The constraints are as follows: the inner and outer diameter dimensions of the low-pressure compressor outlet, the inner and outer diameter dimensions of the high-pressure compressor inlet, and the axial length dimension of the transition section.

[0050] The mathematical definition of the n-th order Bezier curve is as follows:

[0051]

[0052] Where p i is the position vector of the control point of the Bezier curve, that is, the coordinates of each control point (xi, yi), i = 0, 1, 2, ..., n; B i,n (t) is the Bernstein basis function:

[0053] Step 2: Select the number of support plates. Based on the vibration analysis results of the low-pressure compressor and high-pressure compressor blades, select the number of support plates inside the transition section. The selection method and principles are as follows:

[0054] Based on the Campbell diagrams of the low-pressure compressor outlet stage blades and the high-pressure compressor inlet stage blades, the number of struts that can effectively avoid blade resonance is selected based on the principle of optimizing the safe and stable operation margin within the entire operating range of the blades.

[0055] Step 3: Design of the support plate profile. Based on the structural dimensional constraints of the gas turbine on the compressor transition section support plate, a parametric design of the transition section support plate profile is performed.

[0056] The constraints are as follows: Since the internal space of the transition section support plate of the gas turbine needs to be arranged with lubricating oil supply and return pipelines, speed sensors, turning tool channels, etc., there are dimensional restrictions on the axial length and thickness range of the transition section support plate.

[0057] The parametric design method for the strut profile is as follows: a customized blade profile design method based on the high-order polynomial curve airfoil thickness distribution is adopted. By adaptively adjusting the airfoil thickness according to the strut requirements, a customized blade profile thickness distribution is formed. This serves as the cross-sectional profile of the transition section strut. During the design process, parameters such as the axial chord length, maximum thickness and its relative position, and leading and trailing edge radius of the blade profile can be adjusted, thereby achieving parametric customized design of the strut profile.

[0058] Step 4: Three-dimensional CFD calculation and analysis. This includes full three-dimensional CFD numerical simulation and analysis of the transition section design point and variable operating conditions. Through three-dimensional CFD calculation, the performance and internal flow field conditions of the transition section at the design point and variable operating conditions are obtained to determine whether the design requirements are met. If the design requirements are met, the current transition section flow design scheme can be considered as the final design scheme; if the design requirements are not met, the corresponding parameter values ​​in the end wall flow channel profile design or the support plate profile design are adjusted according to the specific analysis results of the internal flow field of the transition section, including the value range of the Bezier curve control point coordinates of the transition section end wall flow channel, the convergence accuracy and relative step size of the gradient optimization algorithm, and the value range of the axial chord length of the transition section support plate, the maximum thickness and its relative position, and the leading and trailing edge radius.

[0059] Through repeated iterations of the above steps, a compressor transition section flow design scheme that ultimately meets the performance index requirements is obtained.

[0060] Among them, for the global optimization technology, the specific implementation of the present invention is:

[0061] Taking the total pressure recovery coefficient of the transition section under all working conditions as the objective function, the inner and outer wall flow channel profiles of the transition section are globally optimized based on the combined optimization strategy of DOE (experimental design) and gradient optimization algorithm.

[0062] For the objective function, the specific implementation of the present invention is:

[0063] Define the objective function OF:

[0064]

[0065] The variables in the above formula are defined as follows:

[0066] i = 1 to 3, corresponding to different incoming air Mach numbers, determined according to the commonly used intake air flow range of the transition section components. When i = 1, it is the Mach number at the design intake air flow rate; when i = 2, it is the Mach number at the commonly used minimum intake air flow rate; when i = 3, it is the average of the above two incoming air Mach numbers;

[0067] σ i is the total pressure recovery coefficient of the transition section under different incoming flow Mach numbers, in, is the total pressure at the inlet of the transition section, is the total pressure at the transition section outlet;

[0068] c i The weight factor affecting the different incoming flow Mach number conditions is determined by the common degree of incoming flow Mach number of the transition section components, and can be adjusted according to the specific working conditions of the transition section of different units.

[0069] The high-performance transition section structure of the gas turbine compressor proposed in the present invention can be applied to various types of three-rotor simple cycle gas turbines; its flow design method is not limited to gas turbine compressors, but is also applicable to various industrial compressors and aircraft engine compressors with flow transition structures.

Claims

1. A flow design method for a high-performance transition section structure of a gas turbine compressor, characterized by: The transition section structure includes an outer wall, an inner wall, and a support plate. The inner wall is located on the inner side of the outer wall. The support plate is inserted into the middle of the outer wall and the inner wall along a circular hole that passes through the outer wall and the inner wall. The front end of the outer wall and the inner wall is the low-pressure compressor outlet side, and the low-pressure compressor outlet stator ring is installed. The rear end of the outer wall and the inner wall is the high-pressure compressor inlet side, and the high-pressure compressor inlet stator ring is installed. A gas seal sleeve is provided below the high-pressure compressor inlet stator ring. The gas seal sleeve is installed on the inner wall by screws arranged in the circumferential direction. The gas seal sleeve is equipped with a honeycomb seal for sealing the flow gas into the high-pressure compressor. The flow design method of the transition section structure includes the following steps: (1) Design of the flow end wall flow channel profile: According to the structural size constraints of the gas turbine on the compressor transition section flow channel, the parameterized design of the transition section end wall flow channel profile is performed, and the end wall flow channel profile is optimized using global optimization technology; (2) Selection of the number of support plates: Based on the vibration analysis results of the low-pressure compressor and high-pressure compressor blades, the number of support plates inside the transition section is selected; (3) Design of support plate profile: Based on the structural dimension constraints of the gas turbine on the compressor transition section support plate, a parametric design of the transition section support plate profile is performed; (4) Three-dimensional CFD calculation and analysis: including full three-dimensional CFD numerical simulation analysis of the transition section design point and variable operating conditions. Through three-dimensional CFD calculation, the performance and internal flow field conditions of the transition section at the design point and variable operating conditions are obtained to determine whether the design requirements are met. If the design requirements are met, the current transition section flow design scheme is the final design scheme; if not, the corresponding parameter values ​​in the end wall flow channel profile design or the support plate profile design are adjusted according to the specific analysis results of the internal flow field of the transition section. Through repeated iterations of the above steps, the compressor transition section flow design scheme that finally meets the performance index requirements is obtained; The structural dimension constraints of the gas turbine on the compressor transition section flow passage in step (1) refer to the inner and outer diameter dimensions of the outlet of the low-pressure compressor, the inner and outer diameter dimensions of the inlet of the high-pressure compressor, and the axial length dimension of the transition section; In step (1), the parametric design of the flow channel profile of the transition section end wall is performed, and high-order Bezier curves are used to describe the flow channels on the inner and outer walls of the transition section; The global optimization technology in step (1) takes the total pressure recovery coefficient of the transition section under all working conditions as the objective function, and performs global optimization design of the inner and outer wall flow channel profiles of the transition section based on the combined optimization strategy of DOE experimental design and gradient optimization algorithm; The total pressure recovery coefficient of the transition section under all working conditions is used as the objective function and the following function is adopted: : The variables in the above formula are defined as follows: Corresponding to different incoming Mach numbers, the common intake flow range of the transition section components is determined. is the Mach number at the design intake flow rate, is the Mach number at the commonly used minimum intake flow rate, When is the average value of the above two incoming flow Mach numbers; is the total pressure recovery coefficient of the transition section under different incoming flow Mach numbers ,in, is the total pressure at the inlet of the transition section, is the total pressure at the transition section outlet; The weight factor affecting the different incoming flow Mach number conditions is determined by the common degree of incoming flow Mach number of the transition section components.

2. A gas turbine compressor high performance transition section structure flow design method according to claim 1, characterized in that: low pressure The compressor outlet stator ring is installed with the inner wall by means of tight-fitting bolts and nuts, and is positioned with the outer wall in the axial and radial directions by screws.

3. The method for designing a flow path for a high-performance transition section structure of a gas turbine compressor according to claim 1, wherein: The high-pressure compressor inlet stator ring is installed with the outer wall by radial screws.

4. The method for designing a flow path for a high-performance transition section structure of a gas turbine compressor according to claim 1, wherein: When the support plate is installed, it is positioned with the outer wall by means of cylindrical pins, and gas sealing is achieved by tightening the sealing ring and the sealing ring below it with nuts. The top of the support plate is sealed by compacting the copper gasket through the end cover flange and fastened by bolts arranged along the circumferential direction.

5. The method for designing a flow path for a high-performance transition section structure of a gas turbine compressor according to claim 1, wherein: The outer wall includes an outer casing and an outer wall plate. The outer casing and the outer wall plate are welded together along the entire circumference using gas shielded arc welding on the inlet side of the high-pressure compressor. The flow channel lines of the outer wall plate and the flow-through part of the inner wall are both fourth-order Bezier curves.

6. The method for designing a flow path for a high-performance transition section structure of a gas turbine compressor according to claim 4, wherein: The flow passage part of the support plate adopts an airfoil structure, and its profile is a customized blade shape based on a polynomial curve. The inside of the support plate is hollow, and the lubricating oil supply and return pipelines, speed sensors, and turning tool channels are arranged inside the support plate at different positions along the circumferential direction. This is achieved by setting corresponding structural interfaces on the top of the end cover flange.

7. The method for designing a flow path for a high-performance transition section structure of a gas turbine compressor according to claim 1, wherein: The principle for selecting the number of support plates in step (2) is to select the number of support plates that can avoid causing blade resonance based on the Campbell diagram of the low-pressure compressor outlet stage blades and the high-pressure compressor inlet stage blades, with the principle of optimizing the safe and stable operation margin within the entire operating range of the blades.

8. The method for designing a flow path for a high-performance transition section structure of a gas turbine compressor according to claim 1, wherein: The structural dimension constraints of the gas turbine on the compressor transition section support plate in step (3) refer to the dimension restrictions on the axial length and thickness range of the transition section support plate, as the internal space of the gas turbine transition section support plate needs to be arranged with the lubricating oil supply and return pipelines, the speed sensor, and the turning tool channel.

9. The method for designing a flow path for a high-performance transition section structure of a gas turbine compressor according to claim 1, wherein: The parametric design of the transition section support plate profile in step (3) adopts a customized blade profile design method based on the high-order polynomial curve airfoil thickness distribution. By adaptively adjusting the airfoil thickness according to the support plate requirements, a customized blade profile thickness distribution is formed as the cross-sectional profile of the transition section support plate. During the design process, the axial chord length, maximum thickness and its relative position, and leading and trailing edge radius of the blade profile are adjusted, thereby realizing the parametric customized design of the support plate profile.

10. The method for designing flow through a high-performance transition section structure of a gas turbine compressor according to claim 1, wherein: In step (4), the parameter values ​​in the end wall flow channel profile design or the support plate profile design are adjusted, including the value range of the coordinates of the Bezier curve control points of the transition section end wall flow channel, the convergence accuracy and relative step size of the gradient optimization algorithm, and the value range of the axial chord length, maximum thickness and relative position of the transition section support plate and the leading and trailing edge radius.

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