Guide vane design method based on U-shaped flow channel and improved guide vane wheel structure

Abstract

The invention discloses a guide vane design method based on a U-shaped flow channel and an improved guide vane wheel structure. The method specifically comprises the following steps that based on the structural characteristics of the U-shaped flow channel, a guide vane is subjected to multi-section structural design, and a guide vane preliminary structure is obtained; establishing an energy loss model, and calculating the energy loss of the fluid in the flowing process in the U-shaped flow channel, including friction loss generated by viscous friction between the fluid and the inner wall surface of the U-shaped flow channel, and flow separation loss and turbulence loss caused by curvature change of the U-shaped flow channel; guide vane geometric parameters forming the structural characteristics of the U-shaped flow channel are extracted, a mapping relation between the guide vane geometric parameters and fluid flowing performance is established, and an explicit relation between the guide vane geometric parameters and energy loss is established based on key guide vane geometric parameters influencing fluid flowing; constructing a guide vane design target equation associated with the geometric parameters of the guide vane based on the display relationship between the geometric parameters of the guide vane and the energy loss; and performing iterative calculation based on the guide vane geometric parameter design equation to obtain a guide vane structure design target value.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid machinery, and more specifically, to a guide vane design method based on a U-shaped flow channel and an improved guide vane impeller structure. Background Art

[0002] In the design of the guide vane structure of a pump, the rectangular flow channel structure of a traditional radial guide vane is prone to generating local vortices at the corners, increasing local energy losses. At the same time, the guide vanes of traditional multi-stage pumps mostly rely on empirical formulas or CFD simulations, and there are the following problems:

[0003] I. Limitations of empirical formulas: It is impossible to globally optimize the interaction between multiple parameters and difficult to meet the constraints of complex flow channels;

[0004] II. High cost of simulation calculation: CFD simulation is time-consuming and difficult to iterate quickly;

[0005] III. Low efficiency of the guide vane structure: Flow separation and turbulent losses are significant, affecting the pump efficiency;

[0006] In view of this, the present invention proposes a guide vane design method based on a U-shaped flow channel and an improved guide vane impeller structure. The use of the U-shaped flow channel design avoids the vortex energy loss of traditional radial guide vanes. At the same time, by establishing an explicit model of the energy loss of the U-shaped flow channel, the global optimization of the geometric parameters of the guide vane is realized, and the pump efficiency is improved. Summary of the Invention

[0007] In order to solve the above technical problems, the purpose of the present invention is to provide a guide vane design method based on a U-shaped flow channel and an improved guide vane impeller structure. The U-shaped flow channel design is adopted to reduce the vortex energy loss of the rectangular flow channel structure of traditional radial guide vanes. At the same time, through the GA genetic algorithm combined with the energy loss model, the efficient optimization of the geometric parameters of the guide vane is realized, which is applicable to the guide vane design of high-pressure and high-lift pumps.

[0008] In order to achieve the above purpose, on the one hand, the present invention provides a guide vane design method based on a U-shaped flow channel, which specifically includes the following steps:

[0009] Step S1: Based on the structural characteristics of the U-shaped flow channel, a multi-segment structure design is adopted for the guide vane to obtain a preliminary guide vane structure;

[0010] Step S2: Establish an energy loss model to calculate the energy loss of the fluid during the flow in the U-shaped flow channel, including the friction loss generated by the viscous friction between the fluid and the inner wall surface of the U-shaped flow channel, the flow separation loss and the turbulent loss caused by the curvature change of the U-shaped flow channel;

[0011] Step S3: Extract the guide vane geometric parameters that constitute the U-shaped flow channel structure characteristics, establish the mapping relationship between the guide vane geometric parameters and the fluid flow performance, and based on the key guide vane geometric parameters that affect the fluid flow, establish the explicit relationship between the guide vane geometric parameters and the energy loss;

[0012] Step S4: Based on the explicit relationship between the guide vane geometric parameters and the energy loss, construct the guide vane design objective equation related to the guide vane geometric parameters;

[0013] Step S5: According to the guide vane design objective equation, use the GA genetic algorithm to perform iterative calculations on the guide vane geometric parameters, calculate the optimal value until the convergence condition is met to obtain the design target value of the guide vane geometric parameters.

[0014] Further, in the technical solution of the present invention, in the step S1, the preliminary structure of the guide vane specifically includes a guide vane fixing plate and multiple groups of guide vanes fixedly spaced on the guide vane fixing plate. Each group of the guide vanes includes a positive guide vane section, a semi-circular space guide vane section, and a negative guide vane section connected in sequence;

[0015] The positive guide vane section is fixedly connected to one end face of the guide vane fixing plate along the direction from the center of the guide vane fixing plate to the edge. The negative guide vane section is fixedly connected to the other end face of the guide vane fixing plate along the direction from the edge of the guide vane fixing plate to the center. The semi-circular space guide vane section is fixedly connected to the edge of the guide vane fixing plate. The two ends of the semi-circular space guide vane section are respectively located at the edges of the two end faces of the guide vane fixing plate, and the two ends of the semi-circular space guide vane section are respectively connected to the positive guide vane section and the negative guide vane section at one end located at the edge of the guide vane fixing plate. The cross-sections at the connection points of the semi-circular space guide vane section with the positive guide vane section and the negative guide vane section are the same and are connected into an integrated structure. The fluid channels are formed between the positive guide vane sections, the negative guide vane sections, and the semi-circular space guide vane sections of adjacent guide vanes. The fluid channels between the positive guide vane section, the negative guide vane section, and the semi-circular space guide vane section together form a U-shaped flow channel.

[0016] Further, in the technical solution of the present invention, in the step S2, establish an energy loss model to calculate the energy loss during the fluid flow in the U-shaped flow channel. The energy loss is composed of three parts: friction loss, flow separation loss, and turbulence loss, which reflects the main dissipation mechanism of the fluid in the U-shaped flow channel. Calculate the energy loss of the fluid in the U-shaped flow channel by adding them up, specifically expressed as:

[0017] , where, is expressed as the energy loss, is expressed as the friction loss, is expressed as the flow separation loss, is expressed as the turbulence loss.

[0018] Further, in the technical solution of the present invention, in the step S3, the extraction of the guide vane geometric parameters constituting the U-shaped channel structure features specifically includes:

[0019] Positive guide vane section: Positive guide vane inlet angle , positive guide vane outlet angle , positive guide vane curvature radius ;

[0020] [[ID=!2]]Semicircular space guide vane section: Semicircular space guide vane curvature radius , central angle ;

[0021] Negative guide vane section: Negative guide vane inlet angle , negative guide vane outlet angle , negative guide vane curvature radius ;

[0022] Among them, the central angle of the semicircular space guide vane section is 180°, and the mapping relationship between the guide vane geometric parameters and the fluid flow performance is specifically expressed as: .

[0023] Further, in the technical solution of the present invention, in the step S4, the construction of the guide vane design objective equation associated with the guide vane geometric parameters specifically includes:

[0024] Taking the minimum energy loss of the fluid in the U-shaped channel as the objective function, the guide vane design objective equation associated with the guide vane geometric parameters is established: . [[ID=!3]]

[0025] Further, in the technical solution of the present invention, in the step S5, the convergence condition is expressed as that in the iterative calculation of 10 consecutive generations, the optimal value does not change.

[0026] Further, in the technical solution of the present invention, the friction loss is related to the channel surface roughness, hydraulic diameter and flow velocity, and the friction loss is specifically expressed as:

[0027] [[ID=5!]] represents the friction coefficient, represents the channel length, represents the hydraulic diameter, represents the fluid density, represents the fluid flow velocity, respectively represent the positive guide vane section, the semicircular space guide vane section and the negative guide vane section.

[0028] Further, in the technical solution of the present invention, the flow separation loss​ Based on the curvature change of the U-shaped flow channel, the flow separation loss Specifically expressed as:

[0029] , where is expressed as the separation loss coefficient, is expressed as the maximum fluid velocity.

[0030] Furthermore, in the technical solution of the present invention, the turbulent loss is caused by the velocity gradient and the secondary flow. The turbulent loss is specifically expressed as:

[0031] , where is expressed as the turbulent loss coefficient, is expressed as the change in the positive guide vane angle, is expressed as the change in the reverse guide vane angle, is expressed as the average fluid velocity.

[0032] On the other hand, the present invention also provides an improved guide impeller structure, and the improved guide impeller structure is designed by using a guide vane design method based on the U-shaped flow channel described above.

[0033] Beneficial effects: In summary, the present invention provides a guide vane design method and an improved guide impeller structure based on the U-shaped flow channel. The present invention adopts the U-shaped flow channel design to reduce the vortex energy loss of the traditional radial guide vane rectangular flow channel structure. At the same time, in the technical solution of the present invention, by establishing an explicit model of the energy loss of the U-shaped flow channel, based on the friction loss generated by the viscous friction between the fluid and the inner wall surface of the U-shaped flow channel, the flow separation loss caused by the curvature change of the U-shaped flow channel, and the turbulent loss, the design target values of the guide vane geometric parameters are calculated through the genetic algorithm, realizing the multi-parameter global optimization of the guide vane geometric parameters, improving the pump efficiency, and being applicable to the guide vane design of high-pressure and high-lift pumps.

[0034] Other features and advantages of the present invention will be described in the subsequent specification. Brief Description of the Drawings

[0035] In order to more clearly illustrate the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 It is a flowchart of a guide vane design method based on the U-shaped flow channel according to an embodiment of the present invention;

[0037] Figure 2Schematic diagram of the preliminary structure of a guide vane based on a U-shaped flow channel according to an embodiment of the present invention, where (a) is the schematic diagram of the front guide vane side structure of the preliminary guide vane structure, and (b) is the schematic diagram of the reverse guide vane side structure of the preliminary guide vane structure;

[0038] In the figure: A, guide vane fixing plate; A01, front guide vane section; A02, semi-circular space guide vane section; A03, reverse guide vane section; A04, U-shaped flow channel. Specific implementation manners

[0039] In order to make the objectives, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0040] The core of the embodiment of the present invention is to provide a guide vane design method and an improved guide vane impeller structure based on a U-shaped flow channel. The U-shaped flow channel design is adopted to reduce the vortex energy loss of the traditional radial guide vane rectangular flow channel structure. At the same time, through the GA genetic algorithm combined with the energy loss model, the efficient optimization of the guide vane geometric parameters is realized, which is applicable to the guide vane design of high-pressure and high-lift pumps.

[0041] On the one hand, the embodiment of the present invention proposes a guide vane design method based on a U-shaped flow channel. Figure 1 Schematic flow chart of a guide vane design method based on a U-shaped flow channel according to an embodiment of the present invention. As Figure 1 shown, in this embodiment, the guide vane design method specifically includes the following steps:

[0042] Step S1: Based on the structural characteristics of the U-shaped flow channel, a multi-section structure design is adopted for the guide vane to obtain a preliminary guide vane structure;

[0043] Step S2: Establish an energy loss model to calculate the energy loss of the fluid during the flow in the U-shaped flow channel, including the friction loss generated by the viscous friction between the fluid and the inner wall surface of the U-shaped flow channel, the flow separation loss and the turbulence loss caused by the curvature change of the U-shaped flow channel;

[0044] Step S3: Extract the guide vane geometric parameters that constitute the structural characteristics of the U-shaped flow channel, establish the mapping relationship between the guide vane geometric parameters and the fluid flow performance, and based on the key guide vane geometric parameters affecting the fluid flow, establish the explicit relationship between the guide vane geometric parameters and the energy loss;

[0045] Step S4: Based on the explicit relationship between the guide vane geometric parameters and the energy loss, construct a guide vane design objective equation related to the guide vane geometric parameters;

[0046] Step S5: According to the guide vane design target equation, use the GA genetic algorithm to iteratively calculate the geometric parameters of the guide vane, calculate the optimal value until the convergence condition is met, and obtain the design target value of the guide vane geometric parameters.

[0047] Specifically, in this embodiment, Figure 2 is a schematic diagram of the preliminary structure of the guide vane based on a U-shaped flow channel according to an embodiment of the present invention. As Figure 2 shown, in step S1, the preliminary structure of the guide vane specifically includes a guide vane fixing plate A and multiple groups of guide vanes fixedly spaced on the guide vane fixing plate. Each group of guide vanes includes a positive guide vane section A01, a semi-circular space guide vane section A02, and a negative guide vane section A03 connected in sequence; please continue to refer to Figure 2 , where (a) is a schematic diagram of the positive guide vane side structure of the preliminary structure of the guide vane, and (b) is a schematic diagram of the negative guide vane side structure of the preliminary structure of the guide vane. The positive guide vane section A01 is fixedly connected to one end face of the guide vane fixing plate A along the direction from the center of the guide vane fixing plate A to the edge. The negative guide vane section A03 is fixedly connected to the other end face of the guide vane fixing plate A along the direction from the edge of the guide vane fixing plate A to the center. The semi-circular space guide vane section A02 is fixedly connected to the edge of the guide vane fixing plate A. The two ends of the semi-circular space guide vane section A02 are respectively located at the edges of the two end faces of the guide vane fixing plate A, and the two ends of the semi-circular space guide vane section A02 are respectively connected to one end of the positive guide vane section A01 and the negative guide vane section A03 located at the edge of the guide vane fixing plate A. The cross-sections at the connection points of the semi-circular space guide vane section A02 with the positive guide vane section A01 and the negative guide vane section A03 are the same and are connected into an integrated structure. Fluid channels are formed between the positive guide vane sections A01 of adjacent guide vanes, between the negative guide vane sections A03, and between the semi-circular space guide vane sections A02. The fluid channels between the positive guide vane section A01, the negative guide vane section A03, and the semi-circular space guide vane section A02 together form a U-shaped flow channel A04. It should be noted that the positive guide vane section A01 and the negative guide vane section A03 are preferably arc-shaped structures in this embodiment (not shown in the figure). Based on the different curvature radii of the positive guide vane section A01 and the negative guide vane section A03, the inlet angles and outlet angles of the positive guide vane section A01 and the negative guide vane section A03 are different respectively. This embodiment Figure 2 is only a simplified schematic diagram for easy understanding.

[0048] Among them, in the U-shaped flow channel A04, the fluid enters from the positive guide vane section A01, turns after passing through the semi-circular space guide vane section A02, and is led out by the negative guide vane section A03. The gaps between adjacent guide vanes form continuous channels to ensure continuous flow. Compared with the traditional rectangular flow channel, the U-shaped flow channel A04 design can avoid large-angle changes at the vertical angles of the rectangular flow channel, reduce eddy currents and separations, improve hydraulic efficiency, have small turning losses, high energy conversion efficiency, and is suitable for step-by-step pressurization of multi-stage pumps.

[0049] Specifically, in this embodiment, in step S2, an energy loss model is established to calculate the energy loss during the flow of the fluid in the U-shaped channel A04. The energy loss consists of three parts: frictional loss, flow separation loss, and turbulent loss, which reflects the main dissipation mechanism of the fluid in the U-shaped channel A04. The energy loss of the fluid in the U-shaped channel A04 is calculated by summing up, and is specifically expressed as:

[0050] , where represents the energy loss, represents the frictional loss, represents the flow separation loss, represents the turbulent loss; the frictional loss is generated by the friction between the fluid and the wall of the U-shaped channel A04, and is related to the length of the U-shaped channel A04 and the fluid flow velocity. The flow separation loss is caused by the boundary layer separation due to the sudden change in the curvature of the U-shaped channel A04. The turbulent loss is caused by the turbulent kinetic energy dissipation generated by the drastic change in the flow velocity direction of the fluid in the U-shaped channel A04.

[0051] Specifically, in this embodiment, in step S3, the guide vane geometric parameters that constitute the structural characteristics of the U-shaped channel A04 are extracted, specifically including:

[0052] Positive guide vane section A01: positive guide vane inlet angle , positive guide vane outlet angle , positive guide vane curvature radius ;

[0053] Semicircular space guide vane section A02: semicircular space guide vane curvature radius , central angle ;

[0054] Negative guide vane section A03: negative guide vane inlet angle , negative guide vane outlet angle , negative guide vane curvature radius ;

[0055] Among them, the central angle of the semicircular space guide vane section A02 is 180°. The mapping relationship between the guide vane geometric parameters and the fluid flow performance is specifically expressed as: . It should be noted that the guide vane geometric parameters are subject to geometric constraints based on basic theories and process constraints during the production of the guide vane.

[0056] Specifically, in this embodiment, in step S4, the guide vane design target equation related to the guide vane geometric parameters is constructed, specifically including:

[0057] Taking the energy loss of the fluid in the U-shaped channel A04 Minimize the objective function, reduce energy loss to improve efficiency, and establish a guide vane design objective equation related to the geometric parameters of the guide vane: .

[0058] Specifically, in this embodiment, in step S5, the convergence condition is expressed as that the optimal value does not change in the iterative calculation of 10 consecutive generations, that is, the optimal value at this time is the design target value of the guide vane geometric parameters.

[0059] Specifically, in this embodiment, the friction loss is related to the surface roughness of the flow channel, the hydraulic diameter, and the flow velocity. Based on the standard Darcy - Weisbach formula for flow friction loss, the friction loss is specifically expressed as:

[0060] , where represents the friction coefficient, represents the flow channel length, represents the hydraulic diameter, represents the fluid density, represents the fluid flow velocity, respectively represent the positive guide vane section A01, the semi - circular space guide vane section A02, and the reverse guide vane section A03, that is , , , represent the friction coefficient, flow channel length, hydraulic diameter, and fluid flow velocity of the positive guide vane section A01, , , , represent the friction coefficient, flow channel length, hydraulic diameter, and fluid flow velocity of the semi - circular space guide vane section A02, , , , represent the friction coefficient, flow channel length, hydraulic diameter, and fluid flow velocity of the reverse guide vane section A03.

[0061] Among them, the friction coefficient is calculated by the Colebrook formula as: ( represents the Reynolds number); the flow channel lengths of the positive guide vane section A01, the semi - circular space guide vane section A02, and the reverse guide vane section A03 are respectively calculated from the inlet angle, outlet angle, and curvature radius of each section:

[0062] Flow channel length of the positive guide vane section A01 : , (in radians);

[0063] Semicircular space guide vane section A02 flow channel length : Fixed center angle , ;

[0064] Length of flow channel of reverse guide vane section A03 : , (radians);

[0065] Among them, the hydraulic diameter Specifically expressed as: , Expressed as the flow channel cross-sectional area, Expressed as wetted perimeter; fluid flow rate According to the law of flow conservation, it is calculated as: , Expressed as fluid flow rate.

[0066] Specifically, in this embodiment, the flow separation loss Based on the curvature change of the U-shaped flow channel A04, the smaller the curvature radius, the more severe the streamline bending, the more significant the boundary layer separation, and based on the Dean flow theory, the flow separation loss Specifically expressed as:

[0067] ,in, Expressed as the separation loss coefficient, according to the shape of the flow channel cross section, the separation loss coefficient The value range is 0.05-0.2, Expressed as the maximum flow rate of the fluid.

[0068] Specifically, in this embodiment, the turbulence loss Caused by velocity gradient and secondary flow, the greater the angle change rate, the stronger the streamline curvature mutation, and the increase in turbulent pulsation energy dissipation. According to the relationship between turbulence intensity and velocity gradient, turbulence loss Specifically expressed as:

[0069] ,in, It is expressed as the turbulence loss coefficient, with a value range of 0.01-0.1. Expressed as the change in the positive guide vane angle, Expressed as the change in the guide vane angle, Expressed as the average flow velocity of the fluid;

[0070] in, , .

[0071] Specifically, in the above step S5, the GA genetic algorithm is used to iteratively calculate the guide vane geometric parameters. This embodiment provides a specific application scenario: a guide vane design process based on a U-shaped flow channel;

[0072] Guide vane geometric parameters:

[0073]

[0074] The constraint conditions include:

[0075] The flow channel length of the positive guide vane section and the flow channel length of the negative guide vane section Length range constraint;

[0076] The angle range constraints of the inlet angle and outlet angle of the positive guide vane and the negative guide vane;

[0077] Curvature radius value range constraint;

[0078] GA genetic algorithm settings:

[0079]

[0080] Specific calculation steps:

[0081] Step M1: Randomly generate 50 groups of parameters based on the constraint conditions. Each group of parameters contains 7 variables:

[0082] ;

[0083] Step M2: Fitness calculation:

[0084] Calculate the energy loss of each group of parameters : ;

[0085] Calculate the fitness : , where represents the fitness, is used to avoid division by zero error;

[0086] Step M3: Random selection. Randomly select 3 groups from the 50 groups of parameters according to the selection scale, compare the fitness sizes, and retain the parameter group corresponding to the maximum fitness . Repeat the selection process until 30 groups of high-quality parameters are selected, that is, the parameter groups with higher fitness .

[0087] Step M4: Crossover calculation. Perform arithmetic crossover calculation on the 30 groups of high-quality parameters to calculate the offspring parameter groups:

[0088] Parent 1: ;

[0089] Parent 2: ;

[0090] Offspring: ;

[0091] Wherein, , ;

[0092] , ;

[0093] , , ;

[0094] Step M5: Iterative update. The 30 groups of high-quality parameters plus the 20 groups of offspring parameters form a new generation of population. The fitness calculation, random selection, and crossover calculation are carried out in the same way as above until in the iterative calculation of 10 consecutive generations, the maximum value of the fitness does not change, which means that the parameter group corresponding to the maximum value of the fitness at this time is the design target value of the guide vane geometric parameters.

[0095] On the other hand, this embodiment also provides an improved guide impeller structure, and this improved guide impeller structure is designed by using a guide vane design method based on a U-shaped flow channel described above.

[0096] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A guide vane design method based on a U-shaped flow channel, characterized in that Specifically, it includes the following steps: Step S1: Based on the structural characteristics of the U-shaped flow channel, a multi-segment structure design is adopted for the guide vane to obtain the preliminary structure of the guide vane; Step S2: Establish an energy loss model to calculate the energy loss during the flow of the fluid in the U-shaped flow channel, including frictional loss caused by viscous friction between the fluid and the inner wall surface of the U-shaped flow channel, flow separation loss and turbulent loss caused by the curvature change of the U-shaped flow channel; Step S3: Extract the guide vane geometric parameters that constitute the structural characteristics of the U-shaped flow channel, establish the mapping relationship between the guide vane geometric parameters and the fluid flow performance, and based on the key guide vane geometric parameters affecting the fluid flow, establish the explicit relationship between the guide vane geometric parameters and the energy loss; Step S4: Based on the explicit relationship between the guide vane geometric parameters and the energy loss, construct a guide vane design objective equation related to the guide vane geometric parameters; Step S5: According to the guide vane design objective equation, use the GA genetic algorithm to iteratively calculate the guide vane geometric parameters, calculate the optimal value until the convergence condition is met to obtain the design target value of the guide vane geometric parameters.

2. The design method of a guide vane based on a U-shaped flow channel according to claim 1, characterized in that, In the step S1, the preliminary structure of the guide vane specifically includes a guide vane fixing plate and multiple groups of guide vanes fixedly spaced on the guide vane fixing plate. Each group of the guide vanes includes a positive guide vane section, a semi-circular space guide vane section, and a negative guide vane section connected in sequence; The positive guide vane section is fixedly connected to one end face of the guide vane fixing plate along the direction from the center of the guide vane fixing plate to the edge. The negative guide vane section is fixedly connected to the other end face of the guide vane fixing plate along the direction from the edge of the guide vane fixing plate to the center. The semi-circular space guide vane section is fixedly connected to the edge of the guide vane fixing plate. The two ends of the semi-circular space guide vane section are respectively located at the edges of the two end faces of the guide vane fixing plate, and the two ends of the semi-circular space guide vane section are respectively connected to one end of the positive guide vane section and the negative guide vane section located at the edge of the guide vane fixing plate. The cross-sections at the connection points of the semi-circular space guide vane section with the positive guide vane section and the negative guide vane section are the same and are connected into an integrated structure. Fluid channels are formed between the positive guide vane sections, the negative guide vane sections, and the semi-circular space guide vane sections of adjacent guide vanes. The fluid channels between the positive guide vane section, the negative guide vane section, and the semi-circular space guide vane section together form a U-shaped flow channel.

3. A guide vane design method based on a U-shaped flow channel according to claim 2, characterized in that, In the step S2, an energy loss model is established to calculate the energy loss during the flow of the fluid in the U-shaped flow channel. The energy loss is composed of three parts: frictional loss, flow separation loss, and turbulent loss, which reflects the main dissipation mechanism of the fluid in the U-shaped flow channel. The energy loss of the fluid in the U-shaped flow channel is calculated by summing up, and is specifically expressed as: , where is expressed as energy loss, is expressed as friction loss, is expressed as flow separation loss, is expressed as turbulence loss.

4. A guide vane design method based on a U-shaped flow channel according to claim 3, characterized in that In the step S3, the guide vane geometric parameters that constitute the structural characteristics of the U-shaped flow channel specifically include: Positive guide vane section: Inlet angle of positive guide vane , Outlet angle of positive guide vane , Curvature radius of positive guide vane ; Semicircular space guide vane section: Curvature radius of the semicircular space guide vane , central angle ; Reverse guide vane section: Inlet angle of reverse guide vane , Outlet angle of reverse guide vane , Curvature radius of reverse guide vane ; Among them, the central angle of the semi-circular space guide vane section is 180°, and the mapping relationship between the guide vane geometric parameters and the fluid flow performance is specifically expressed as: .

5. A guide vane design method based on a U-shaped flow channel according to claim 4, characterized in that In the step S4, constructing the guide vane design objective equation related to the guide vane geometric parameters specifically includes: Taking the energy loss of fluid in the U-shaped flow channel as the objective function, establish the guide vane design objective equation related to the geometric parameters of the guide vane: .​ 6. The design method of a guide vane based on a U-shaped flow channel according to claim 5, characterized in that, In the step S5, the convergence condition is expressed as that the optimal value does not change in 10 consecutive generations of iterative calculations.

7. A guide vane design method based on a U-shaped flow channel according to claim 4, characterized in that Friction loss Related to the surface roughness of the flow channel, hydraulic diameter, and flow velocity, the friction loss Specifically expressed as: , where is expressed as the friction coefficient, is expressed as the flow path length, is expressed as the hydraulic diameter, is expressed as the fluid density, is expressed as the fluid flow velocity, are respectively expressed as the positive guide vane section, the semi-circular space guide vane section, and the return guide vane section.

8. A guide vane design method based on a U-shaped flow channel according to claim 7, characterized in that Flow separation loss Based on the curvature change of the U-shaped flow channel, the flow separation loss Specifically expressed as: , where is expressed as the separation loss coefficient, is expressed as the maximum fluid velocity.

9. A guide vane design method based on a U-shaped flow channel according to claim 7, characterized in that, Turbulence loss Caused by velocity gradient and secondary flow, the turbulence loss Is specifically expressed as: , where is expressed as the turbulent loss coefficient, is expressed as the change in the angle of the stay vane, is expressed as the change in the angle of the guide vane, is expressed as the average fluid velocity.

10. An improved impeller structure, characterized in that, Designed by using a guide vane design method based on a U-shaped flow channel according to any one of claims 1-9.

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