A method for optimizing design of a flat tube water outlet flow channel

Abstract

The application discloses a straight pipe water outlet flow channel optimization design method and relates to the technical field of hydraulic engineering, which comprises the following steps: S1, obtaining basic fluid parameters and outlet size parameters, setting constraint conditions and calculating derivative parameters; S2, calculating each energy loss component according to the current diffusion section length L, and establishing a total energy loss model; S3, checking whether each current solution satisfies the constraint conditions, calculating a penalty function value and calculating a corrected target function F; and S4, searching for the optimal diffusion section length based on the target function by using a genetic algorithm. The application establishes a complete energy loss calculation model, sets the diffusion section length as an optimization variable, sets constraint conditions and makes the energy loss minimum, so that the straight pipe water outlet flow channel can be quickly and reliably designed, and the application is suitable for the design of water outlet flow channels with various outlet diameters.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to an optimized design method for straight pipe outlet flow channels. Background Technology

[0002] Pumping station projects play a vital role in agricultural irrigation, urban drainage, and industrial water treatment. The outlet channel, as a key component of the pumping unit, directly impacts the pumping station's operational efficiency and energy consumption.

[0003] Compared to siphon and bidirectional water outlet channels, straight pipe outlet channels have significant advantages such as simple structure, stable flow rate, low energy consumption, and small footprint. Its working principle is as follows: water flows from the pump outlet, turns through a bend in the pipe section, enters the diffuser section, and gradually increases in cross-section to reduce velocity and convert kinetic energy into pressure energy, ultimately flowing smoothly into the outlet pool or downstream pipeline.

[0004] However, current designs for straight pipe outlet channels suffer from the following prominent problems: the designs are overly simplified and lack detailed consideration. Traditional design methods rely primarily on empirical formulas and engineering analogies, failing to fully account for the combined effects of bend losses, diffusion losses, friction losses, and shape transition losses, resulting in high flow resistance and low efficiency. Furthermore, existing design methods often involve manual calculations or simple Excel spreadsheets, hindering automatic optimization and multi-scheme comparison, leading to low design efficiency. Therefore, there is an urgent need for optimized design methods for straight pipe outlet channels to quickly design channels with low flow resistance and low efficiency. Summary of the Invention

[0005] In view of the aforementioned existing problems, the present invention is proposed.

[0006] Therefore, this invention provides an optimized design method for straight pipe outlet channels to solve the problem that existing technologies mainly rely on empirical formulas and engineering analogies, without fully considering the combined effects of bend losses, diffusion losses, friction losses, and shape transition losses, resulting in high flow resistance and low energy efficiency in the designed straight pipe outlet channels.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] This invention provides an optimized design method for a straight pipe outlet flow channel. The straight pipe outlet flow channel includes a bend section, one end of which has an inlet, the other end of which is fixed to one end of a transition section, the other end of which is fixed to one end of a diffuser section, and the other end of the diffuser section has an outlet. The method includes the following steps:

[0009] S1. Obtain basic fluid parameters and outlet size parameters, set constraints, and calculate derived parameters;

[0010] S2. Based on the diffusion section length L, calculate the various energy loss components and establish the total energy loss model P. total ;

[0011] S3. Calculate the penalty function value P. penalty and the corrected objective function F, F=P total +P penalty ;

[0012] S4. Based on the objective function, use a genetic algorithm to find the optimal diffusion segment length to minimize the objective function value;

[0013] S5. Extract the optimal diffuser length L*, calculate the hyperelliptical transition parameters n(t), a(t), b(t), and use MATLAB software to automatically generate the three-dimensional mesh points of the bend and diffuser sections according to the set number of bend segments, diffuser segments, and circumferential segments. Use periodic sampling and explicit copying of the first column to eliminate model gaps and ensure geometric closure. Export the STL format file to complete the design of the straight pipe outlet flow channel.

[0014] As a preferred embodiment of the straight pipe outlet flow channel optimization design method of the present invention, the basic fluid parameters include inlet flow rate Q, inlet diameter D1, fluid density ρ, and kinematic viscosity ν, and the outlet size parameters include outlet rectangular length W. out and the width H of the export rectangle out Setting constraint parameters includes the diffusion section length range [L] min , L max Maximum diffusion angle θ max Maximum outlet velocity V max Derived parameters include import area A1, export area A2, and area ratio A. R Inlet flow velocity V1, outlet flow velocity V2, , The diffusion angle is in the width direction. The diffusion angle is in the vertical direction, specifically, on the vertical plane containing any horizontal axis of the outlet flow channel. The angle between the straight line intersecting any of the vertical planes and the inner wall of the diffuser section and the corresponding horizontal axis is defined as follows: the width direction is the horizontal direction that passes through any horizontal axis and is perpendicular to any corresponding horizontal axis; the width direction is perpendicular to the height direction.

[0015] As a preferred embodiment of the straight pipe outlet flow channel optimization design method described in this invention, the formula for calculating the inlet area is as follows: The formula for calculating the export area is: The formula for calculating the area ratio is: The formula for calculating the inlet velocity is V1 = Q / A1; the formula for calculating the outlet velocity is... .

[0016] As a preferred embodiment of the straight pipe outlet flow channel optimization design method described in this invention, the various energy loss components include the local power loss in the bend pipe. diffusion loss power Power loss due to friction in pipe bends Shape transition power loss , .

[0017] As a preferred embodiment of the straight pipe outlet flow channel optimization design method described in this invention, the calculation formulas for each energy loss component are as follows:

[0018] ;

[0019] ;

[0020] ;

[0021] ;

[0022] in, Let f be the diffusion loss coefficient, and D be the friction factor. avg = (D1+D 2eq ) / 2, D 2eq = sqrt(4*A² / π), D avg For the equivalent average diameter, D 2eq For the equivalent diameter at the outlet, K s This is the shape transition loss coefficient.

[0023] As a preferred embodiment of the straight pipe outlet flow channel optimization design method of the present invention, in step S4, the specific steps for finding the optimal diffuser section length are as follows:

[0024] S401. Set the initial iteration count i=1;

[0025] S402, in the search space [L] min , L max Within the population, popSize individuals are randomly generated to form the initial population;

[0026] S403. Calculate the objective function value P for each individual. total As the fitness value, the corresponding value for each individual is calculated. and Take the maximum value as the constraint criterion and apply the constraint conditions: Individuals that meet the constraints retain their original fitness values, while individuals that do not meet the constraints are corrected using a penalty function.

[0027] S404. Use roulette wheel selection to select superior individuals for the next generation based on their fitness values.

[0028] S405. Perform single-point crossover on the selected individuals with crossover probability pc to generate new individuals;

[0029] S406. Perform Gaussian mutation on individuals with mutation probability pm to generate the next generation population;

[0030] S407. Determine whether the change in the optimal fitness value is less than the set change threshold tol or whether the number of iterations has reached the set number threshold n. The change in the optimal fitness value is the absolute difference between the global minimum objective function values ​​in two adjacent generations of the population. If the above conditions are met, stop and output the optimal individual corresponding to the minimum objective function value. Otherwise, assign the value of i plus 1 to the new i and return to step S403.

[0031] As a preferred embodiment of the straight pipe outlet flow channel optimization design method of the present invention, wherein: the penalty function P penalty The calculation formula is as follows: ;

[0032] in, This is the upper limit of the export flow rate. To allow the maximum diffusion angle.

[0033] As a preferred embodiment of the straight pipe outlet flow channel optimization design method of the present invention, in step S5, a hyperelliptic function is used to describe the cross-sectional shape of the transition section, and the hyperelliptic function is:

[0034] ;

[0035] in, Let be the shape index, and a and b be the semi-major and semi-minor axes, respectively. The transition parameter t∈[0,1] is defined as the normalized position along the flow channel, where t=0 corresponds to the inlet (circular) and t=1 corresponds to the outlet (rectangular). The variation of each parameter with t is as follows:

[0036] ;

[0037] ;

[0038] ;

[0039] ;

[0040] in, For smooth transition function, Let t be the transition cross-sectional area at the position corresponding to the axial parameter t of the diffuser section. The aspect ratio is a function, varying from 1 to A. R .

[0041] As a preferred embodiment of the straight pipe outlet flow channel optimization design method of the present invention, wherein: the formula for calculating the diffusion loss coefficient is, θ max = max(θ W ,θ H ), θ max For the maximum diffusion angle, , .

[0042] The beneficial effects of this invention are as follows: by establishing a complete energy loss calculation model in a straight pipe channel, the energy loss characteristics of the water flow channel can be accurately predicted, the length of the diffuser section can be automatically optimized, and the optimal solution for the length of the diffuser section can be obtained quickly; it is adaptable to the design of various outlet diameters, breaking through the limitation of traditional design methods that are only applicable to limited standard specifications, and providing a flexible and universal design basis for pump devices with unconventional outlet diameters. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a top view of the straight pipe outlet channel.

[0045] Figure 2 for Figure 1 View from point AA.

[0046] Figure 3 A schematic diagram of a three-dimensional model of a straight pipe outlet flow channel designed using the method of Example 1 based on the specific implementation parameters of Example 2.

[0047] Figure 4 This is the convergence curve of the genetic algorithm in Example 2.

[0048] Figure 5 The figure shows the performance analysis results after using the specific water outlet channel designed in Example 2, including curves showing the changes in efficiency and diffusion angle with the length of the diffusion section, pressure recovery analysis, changes in flow velocity and area along the diffusion section, and a pie chart of energy loss decomposition.

[0049] Figure 6 This is an analysis diagram of the high-efficiency zone after using the specific water outlet channel designed according to the present invention in Example 2.

[0050] Figure 7 The optimization result report output in Example 2 Figure 1 .

[0051] Figure 8 The optimization result report output in Example 2 Figure 2 .

[0052] In the diagram, 100 is the straight pipe outlet channel, 101 is the diffuser section, 102 is the transition section, and 103 is the bend section. Detailed Implementation

[0053] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0054] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0055] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0056] Example 1: Refer to Figure 1 and Figure 2 This embodiment of the invention provides an optimized design method for a straight pipe outlet channel. The straight pipe outlet channel includes a bend section with a circular cross-section. One end of the bend section has an inlet, and the other end of the bend section is fixed to one end of a transition section. The other end of the transition section is fixed to one end of a diffuser section, and the other end of the diffuser section has an outlet. The method includes the following steps.

[0057] S1. Obtain basic fluid parameters and outlet size parameters, set constraints, and calculate derived parameters; the basic fluid parameters include inlet flow rate Q, inlet diameter D1, fluid density ρ, and kinematic viscosity ν, and the outlet size parameters include outlet rectangular length W. out and the width H of the export rectangle out Setting constraint parameters includes the diffusion section length range [L] min , L max Maximum allowable diffusion angle Maximum outlet velocity V max Derived parameters include import area A1, export area A2, and area ratio A. RInlet flow velocity V1, outlet flow velocity V2, , The diffusion angle is in the width direction. The diffusion angle is in the vertical direction, specifically, on the vertical plane containing any horizontal axis of the outlet flow channel. The angle between the straight line intersecting any of the vertical planes and the inner wall of the diffuser section and the corresponding horizontal axis; the width direction is the horizontal direction passing through and perpendicular to any horizontal axis, and the width direction is perpendicular to the height direction; wherein... D1 is the inner diameter of the bend section, and the formula for calculating the outlet area is... The formula for calculating the area ratio is: The formula for calculating the inlet velocity is V1 = Q / A1; the formula for calculating the outlet velocity is... , , The constraints are as follows: , , , .

[0058] S2. Establish a total energy loss model P with the diffusion section length L as the independent variable. tota , ;

[0059] ;

[0060] ;

[0061] ;

[0062] ;

[0063] ;

[0064] in, To reduce local power loss in bends, For diffusion loss power, For the power loss due to friction in the bend section, For the power loss due to friction in the diffusion section, Power loss due to shape transition , ( The formula is derived from Idelchik IE's academic monograph / engineering reference manual—Handbook of Hydraulic Resistance [M]. 3rd ed. New York: Begell House, 1996: Chapter 5 "Local Resistances", Section 5-4 "Bends and Elbows". This is the local loss coefficient for the bend; ( The calculation formula is a targeted modification based on the classical Borda-Carnot theory and Idelchik's engineering reference manual, *Handbook of Hydraulic Resistance* [M]. This aims to address the problems of discontinuity in traditional piecewise empirical formulas during optimization iterations and their difficulty in efficient integration with genetic algorithms. The improved formula adopts a continuous analytical form of exponential decay and linear superposition, using the maximum diffusion angle... With the area ratio as the sole independent variable, the effect is implicitly included in the constant term, resulting in a clear physical meaning and concise form. This avoids the discontinuity of the objective function caused by piecewise functions. This improvement makes the diffusion loss coefficient smooth and differentiable in the optimization space, significantly improving the convergence stability and computational efficiency of the genetic algorithm. Implementation examples demonstrate that its loss prediction accuracy meets engineering requirements, and its simplified parameter input and strong practicality, while reserving a smooth expansion space for incorporating the area ratio into the optimization variable in the future, showcasing good engineering applicability and scalability. θ is the diffusion loss coefficient; max = max(θ W , θ H ), θ max Maximum diffusion angle;

[0065] f = 64 / Re, Re ≤ 2300; The Reynolds number is... , L is the kinematic viscosity. b =π*R b / 2,L b D is the length of the bend section. avg = (D1+ D 2eq ) / 2, D avg D is the equivalent average diameter; 2eq = sqrt(4*A² / π), D 2eq For the equivalent diameter at the outlet; K s This is the shape transition loss coefficient. The fluid density is given.

[0066] S3. Calculate the penalty function value P. penalty and the corrected objective function F, F=P total +P penalty , The coefficient 1000 has the dimension of kg / s and is used to control the penalty intensity for exceeding the outlet flow rate limit; the coefficient 2000 has the dimension of W / °. 2 ², used to control the penalty intensity for exceeding the diffusion angle limit.

[0067] S4. Based on the objective function, use a genetic algorithm to find the optimal diffusion segment length to minimize the objective function value. Specifically, this includes:

[0068] S401. Set the initial iteration count i=1;

[0069] S402, in the search space [L] min , L max Within the population, popSize individuals are randomly generated to form the initial population;

[0070] S403. Calculate the objective function value P for each individual. total As the fitness value, the corresponding value for each individual is calculated. and Take the maximum value as the constraint criterion and apply the constraint condition: L min ≤L≤L max , , ≤ Individuals that meet the above constraints retain their original fitness values, while individuals that do not meet the constraints are penalized using the penalty function P. penalty Make corrections. This is the upper limit of the export flow rate;

[0071] S404. Use roulette wheel selection to select superior individuals for the next generation based on their fitness values.

[0072] S405. Perform single-point crossover on the selected individuals with crossover probability pc to generate new individuals;

[0073] S406. Perform Gaussian mutation on individuals with mutation probability pm to generate the next generation population;

[0074] S407. Determine whether the change in the optimal fitness value is less than the set change threshold tol or whether the number of iterations has reached the set number threshold n. The change in the optimal fitness value is the absolute difference between the global minimum objective function values ​​in two adjacent generations of the population. If the above conditions are met, stop and output the optimal individual corresponding to the minimum objective function value. Otherwise, assign the value of i plus 1 to the new i and return to step S403.

[0075] S5. Extract the optimal diffuser length L*, calculate the hyperelliptical transition parameters n(t), a(t), b(t), and use MATLAB software to automatically generate the three-dimensional mesh points of the bend and diffuser sections according to the set number of bend segments, diffuser segments, and circumferential segments (the number of mesh segments in the circumferential direction for all sections of the bend, transition, and diffuser sections). Use periodic sampling and explicit copying of the first column to eliminate model gaps and ensure geometric closure. Export the STL format file to complete the design of the straight pipe outlet flow channel.

[0076] The hyperelliptic function is:

[0077] ;

[0078] in, Let be the shape index, and a and b be the semi-major and semi-minor axes, respectively. The transition parameter t∈[0,1] is defined as the normalized position along the flow channel, where t=0 corresponds to the inlet (circular) and t=1 corresponds to the outlet (rectangular). The variation of each parameter with t is as follows:

[0079] ;

[0080] ;

[0081] ;

[0082] ;

[0083] in, For smooth transition function, Let t be the transition cross-sectional area at the position corresponding to the axial parameter t of the diffuser section. The aspect ratio is a function, varying from 1 to A. R .

[0084] This invention establishes a complete energy loss calculation model for straight pipe flow channels, which can accurately predict the energy loss characteristics of water flow channels, automatically optimize the length of the diffuser section, and quickly obtain the optimal solution for the length of the diffuser section; it adopts bidirectional diffuser angle constraints (width direction and height direction) to more accurately control the risk of flow separation; it is adaptable to the design of various outlet diameters, breaking through the limitation of traditional design methods that are only applicable to limited standard specifications, and provides a flexible and universal design basis for pump devices with unconventional outlet diameters, realizing an integrated design process from optimization calculation to three-dimensional modeling, thus improving design efficiency.

[0085] Establish performance evaluation metrics:

[0086] 1. Calculate diffusion efficiency (diffusion efficiency reflects the effectiveness of kinetic energy recovery and is defined as the ratio of actual pressure recovery to ideal pressure recovery). , For imported dynamic pressure, For the outlet dynamic pressure, P loss This represents the total pressure loss; the closer η is to 1, the smaller the energy loss.

[0087] 2. Calculate the pressure recovery coefficient (It characterizes the pressure recovery capability of the flow channel). .

[0088] In the project ≥70% is considered good. ≥80% is considered excellent. Pressure recovery coefficient. Used to evaluate static pressure recovery capability The larger the value, the more complete the conversion of kinetic energy. ≥0.6 is considered reasonable. ≥0.7 is considered excellent. In practical applications, a combination of two indicators is used for judgment: if and If all are within the excellent range, then the design scheme meets the requirements; if Low A high value may indicate insufficient diffusion section length; if Too high If both values ​​are too low, the outlet velocity may be too high; if both are too low, the diffuser length or outlet size needs to be re-optimized. This evaluation system can quickly determine the quality of the design and provide direction for optimization.

[0089] Example 2: Referring to the figure, this is the second embodiment of the present invention. The difference between this embodiment and Example 1 is that this embodiment provides a specific case to verify the effectiveness of using this application for the design of a straight pipe outlet flow channel.

[0090] This embodiment simulates a design scenario for the outlet channel of a medium-sized pumping station. A medium-sized farmland irrigation pumping station needs to replace its old outlet channel. The original channel used an empirical estimation method to determine the length of the diffuser section. After many years of operation, it was found that the outlet water flow was turbulent, the channel was severely eroded, and the pumping station's diffusion efficiency was approximately 64.8%. (The original design used a traditional empirical estimation method, and the empirical design parameters referenced actual engineering data from a small pumping station in China. However, its hydraulic performance was not refined and optimized. Therefore, the model of this invention was used as a comparison benchmark. Its parameters are representative in the design of outlet channels for small and medium-sized pumping stations: the inlet diameter of 0.3m is the standard outlet diameter of the pump device; the outlet rectangular size of 0.4m × 0.3m is a common simplification in engineering practice, directly using the pump outlet size with a slight enlargement; the bend radius of curvature of 0.3m is empirically taken as "equal to the inlet diameter," a common value under space-constrained conditions; the diffuser section length of 1.0m is roughly estimated as "3~5 times the pipe diameter," taking 3.3 times the pipe diameter; the inlet flow rate is 0.5...) The flow rate (m³ / s) is determined by the rated operating conditions of the pump unit. The bend loss uses the Miller empirical formula, the diffusion loss uses the Sovran-Komp diffusion loss model, the friction loss uses the Darcy-Weisbach formula, and the shape transition loss uses an empirical coefficient of 0.08. The calculation process is transparent: inlet velocity 7.0736 m / s, outlet velocity 4.1667 m / s, ideal pressure recovery 16340 Pa, total pressure loss 5749 Pa, actual pressure recovery 10591 Pa, resulting in a diffusion efficiency of 64.8% and a pressure recovery coefficient of 0.423. Pump station technicians hope to redesign the outlet flow channel to improve operating efficiency and reduce channel maintenance costs. This optimization design system is used to find the optimal diffusion section length based on the actual operating parameters of the pump station, minimizing energy loss while meeting engineering constraints.

[0091] The various parameters used in this embodiment are as follows:

[0092] Basic fluid parameters: inlet flow rate Q = 0.5 m³ / s, inlet diameter D1 = 0.3 m, fluid density ρ = 1000 kg / m³, kinematic viscosity ν = 1.0 × 10⁻ 6 m² / s, radius of curvature of the bend R b =0.5 m.

[0093] Export dimension parameters: Export rectangle length W out =0.5 m, exit rectangle width H out =0.4 m.

[0094] Diffusion section length range [L] min , L max = [1.0, 5.0] m, maximum diffusion angle θ max =12°, maximum outlet velocity V max =3.0 m / s.

[0095] Genetic algorithm parameters: Population size popSize=50, maximum number of iterations maxGen=100, convergence tolerance tol=10 -6 .

[0096] Calculate the import area A1, export area A2, and area ratio A. R Inlet velocity V1, outlet velocity V2, A1 = 0.070686 m², A2 = 0.2 m², area ratio A R =2.8294, V1 = 7.0736 m / s, V2 = 2.5 m / s.

[0097] Using the method for determining the optimal diffusion section length in this invention, the optimal diffusion section length L* is found to be 2.5712m. The diffusion angle θ in the width direction is then calculated. W and the diffusion angle θ in the height direction H θ W =2.23°, θ H =1.11°, maximum diffusion angle θ max =2.23°, local loss coefficient K of the bend b =0.1334, power loss P b =1668.6945W, diffusion loss coefficient K d =9.112×10 -3 Power loss P d =458.5073W, Reynolds number Re=2.12×10 6 Friction factor f = 0.011, friction loss power P in the bend section f,b =377.0004W, frictional loss power P in the diffuser section f,d =402.7255W, shape transition loss power P s =125.00W, total energy loss P total = P b + P d + P f,b + P f,d + P s =3032.04 W.

[0098] Diffusion angle θ in the width direction W The diffusion angle θ in the vertical direction is 2.23°. H The angle is 1.11°, which is much smaller than the maximum allowable diffusion angle θ. max =12° indicates that the design scheme has good flow characteristics and will not cause flow separation;

[0099] Compare V2 with the maximum permissible outlet velocity V maxDetermine whether the flow velocity constraint is met;

[0100] The outlet velocity V2 is 2.5 m / s, which is less than the maximum permissible outlet velocity V. max =3.0m / s, which meets the velocity constraint.

[0101] Generate a 3D model:

[0102] The hyperelliptical transition parameters n(t), a(t), and b(t) were calculated. Using MATLAB software, the three-dimensional mesh points of the bend and diffuser sections were automatically generated according to the set number of bend segments, diffuser segments, and circumferential segments (the number of mesh segments in the circumferential direction for all cross-sections of the bend, transition, and diffuser sections). Periodic sampling and explicit copying of the first column were used to eliminate gaps in the model and ensure geometric closure. The STL format file was exported to complete the design of the straight pipe outlet flow channel.

[0103] The three-dimensional model of the straight tube designed using the method of this invention is as follows: Figure 3 As shown.

[0104] Calculate the following performance indicators: diffusion efficiency η and pressure recovery coefficient C. p The diffusion efficiency η = 72.30% and the pressure recovery coefficient C p =0.6327.

[0105] Figure 4 The invention demonstrates how the objective function value changes with the number of iterations. It shows that a near-optimal solution was found in the first generation, and subsequent iterations fine-tuned and optimized the solution, eventually converging to the optimal value of 3032.04W.

[0106] Figure 5 The performance analysis results are presented, including curves showing the variation of efficiency and diffusion angle with diffusion section length, pressure recovery analysis, flow velocity and area variations along the diffusion section, and pie charts showing energy loss decomposition. These charts comprehensively demonstrate the hydraulic performance of the design scheme. The upper left subplot shows the relationship between diffusion efficiency η and maximum diffusion angle θmax with diffusion section length L. When the diffusion section length L≈2.57m, the diffusion efficiency reaches its maximum value of 72.3% (marked by the red dot in the figure), and the corresponding optimal design scheme achieves the best kinetic energy recovery effect. Simultaneously, the diffusion angle monotonically decreases with increasing length, and the maximum diffusion angle at the optimal solution is only 2.23°, far less than the constraint limit of 12°, indicating that the design scheme has good flow characteristics and will not produce flow separation. The upper right subplot shows the pressure recovery coefficient C in bar chart form. pThe calculation result of 0.6327 indicates that 63.27% of the inlet dynamic pressure is effectively converted into outlet pressure energy, demonstrating good kinetic energy recovery. This value is within a reasonable range, verifying the effectiveness of the optimized design. The lower left subplot shows the variation of flow velocity and cross-sectional area along the diffuser section. As the length of the diffuser section increases, the cross-sectional area of ​​the flow channel gradually expands (green curve), and the flow velocity decreases accordingly (blue curve), achieving a smooth conversion of kinetic energy into pressure energy. The flow velocity gradually decreases from approximately 7.07 m / s at the inlet to 2.5 m / s at the outlet, a velocity reduction ratio of 64.66%, meeting the engineering design requirements. The pie chart in the lower right subplot shows the decomposition of the total energy loss of 3032.04 W. The largest proportion of losses was localized losses at bends (55.0%, 1668.80 W), due to localized resistance losses caused by changes in flow direction at bends. Friction losses were the second largest (25.7%, 778.73 W), including friction along the bend and diffuser sections. Diffusion losses accounted for 15.1% (458.51 W), related to the diffuser angle. Shape transition losses were the smallest (4.1%, 126.00 W), reflecting energy dissipation during the transition from a circular to a rectangular cross-section. This distribution of losses provides a clear direction for further optimization design—the hydraulic optimization of bend sections should be a key focus.

[0107] Figure 6 The results of the high-efficiency zone analysis are presented, showing the relationship between energy loss and maximum diffusion angle as a function of diffusion section length. The red dots in the figure mark the location of the optimal solution (L=2.571m, Loss=3032.04W), clearly indicating the location of the optimal point.

[0108] Output a complete design report, including input parameters, optimization results, flow parameters, energy analysis, efficiency indicators, etc. Figure 7 and Figure 8 Detailed parameters can be seen from this.

[0109] As can be seen from this embodiment, using the method of this application to design a straight pipe outlet flow channel has the following effects.

[0110] I. Significantly Improved Design Accuracy: This embodiment, based on the actual operating parameters of the pumping station (Q=0.5 m³ / s, D1=0.3m), employs the complete energy loss model established in this invention (including bend loss, diffusion loss, friction loss, and shape transition loss). Using the diffusion section length L as the optimization variable, an optimal diffusion section length L*=2.5712 m is obtained through automatic optimization within the range of L∈[1.0,5.0]m. Compared to the original empirical design (L=1.0 m), the optimized diffusion section length precisely matches the optimal balance point under this operating condition, achieving an optimal balance between diffusion loss and friction loss.

[0111] Second, the design efficiency is greatly improved: it only takes 5 iterations to converge to the global optimal solution and the function is evaluated 12,300 times. This is dozens of times more efficient than the traditional trial and error method (which requires multiple modifications and repeated calculations), and realizes the leap from experience-based design to intelligent optimization design.

[0112] III. Comprehensive Improvement of Flow Channel Performance: Optimized Diffusion Angle θ in the Width Direction W =2.23°, diffusion angle θ in the vertical direction H =1.11°, all far less than the constraint limit of 12°, effectively avoiding flow separation; the outlet velocity V2=2.5 m / s meets the engineering requirement of ≤3.0m / s, solving the channel scouring problem caused by the excessively high outlet velocity (4.17 m / s) in the original design; the diffusion efficiency η increased from 64.8% in the original design to 72.3%, an increase of 7.5 percentage points; the pressure recovery coefficient Cp increased from 0.423 to 0.633, indicating that the flow channel's ability to convert inlet kinetic energy into outlet pressure energy has been significantly enhanced.

[0113] IV. Adaptability to any outlet diameter: In this embodiment, the outlet rectangular size (0.5 m × 0.4 m) is a non-standard specification given by the downstream channel of the pumping station. The system directly uses it as a fixed input parameter for optimization, breaking through the limitation of traditional methods that are only applicable to a limited number of standard specifications, and verifying the universal applicability of this method to any outlet diameter.

[0114] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for optimizing the design of a straight pipe outlet flow channel, the straight pipe outlet flow channel comprising a bend section, one end of the bend section having an inlet, the other end of the bend section being fixed to one end of a transition section, the other end of the transition section being fixed to one end of a diffuser section, and the other end of the diffuser section having an outlet, characterized in that: Includes the following steps, S1. Obtain basic fluid parameters and outlet size parameters, set constraints, and calculate derived parameters; S2. Based on the diffusion section length L, calculate the various energy loss components and establish the total energy loss model P. total ; S3. Calculate the penalty function value P. penalty and the corrected objective function F, F=P total +P penalty ; S4. Based on the objective function, use a genetic algorithm to find the optimal diffusion segment length to minimize the objective function value; S5. Extract the optimal diffuser length L*, calculate the hyperelliptical transition parameters n(t), a(t), b(t), and use MATLAB software to automatically generate the three-dimensional mesh points of the bend and diffuser sections according to the set number of bend segments, diffuser segments, and circumferential segments. Use periodic sampling and explicit copying of the first column to eliminate model gaps and ensure geometric closure. Export the STL format file to complete the design of the straight pipe outlet flow channel.

2. The method for optimizing the design of a straight pipe outlet flow channel as described in claim 1, characterized in that: The basic fluid parameters include inlet flow rate Q, inlet diameter D1, fluid density ρ, and kinematic viscosity ν. The outlet size parameters include the length W of the outlet rectangle. out and the width H of the export rectangle out Setting constraint parameters includes the diffusion section length range [L] min , L max Maximum diffusion angle θ max Maximum outlet velocity V max Derived parameters include import area A1, export area A2, and area ratio A. R Inlet flow velocity V1, outlet flow velocity V2, , The diffusion angle is in the width direction. The diffusion angle is in the vertical direction, specifically, on the vertical plane containing any horizontal axis of the outlet flow channel. The angle between the straight line intersecting any of the vertical planes and the inner wall of the diffuser section and the corresponding horizontal axis is defined as follows: the width direction is the horizontal direction that passes through any horizontal axis and is perpendicular to any corresponding horizontal axis; the width direction is perpendicular to the height direction.

3. The method for optimizing the design of a straight pipe outlet flow channel as described in claim 2, characterized in that: The formula for calculating the import area is as follows: The formula for calculating the export area is: The formula for calculating the area ratio is: The formula for calculating the inlet velocity is V1 = Q / A1; the formula for calculating the outlet velocity is... .

4. The method for optimizing the design of a straight pipe outlet flow channel as described in claim 3, characterized in that: All energy loss components include the local power loss in the bend. diffusion loss power Power loss due to friction in pipe bends Shape transition power loss , .

5. The method for optimizing the design of a straight pipe outlet flow channel as described in claim 4, characterized in that: The formulas for calculating each energy loss component are as follows: ； ； ； ； in, Let f be the diffusion loss coefficient, and D be the friction factor. avg = (D1+D 2eq ) / 2, D 2eq = sqrt(4*A² / π), D avg For the equivalent average diameter, D 2eq For the equivalent diameter at the outlet, K s This is the shape transition loss coefficient.

6. The method for optimizing the design of a straight pipe outlet flow channel as described in claim 5, characterized in that: In step S4, the specific steps for finding the optimal diffusion segment length are as follows: S401. Set the initial iteration count i=1; S402, in the search space [L] min , L max Within the population, popSize individuals are randomly generated to form the initial population; S403. Calculate the objective function value P for each individual. total As the fitness value, the corresponding value for each individual is calculated. and Take the maximum value as the constraint criterion and apply the constraint conditions: Individuals that meet the constraints retain their original fitness values, while individuals that do not meet the constraints are corrected using a penalty function. S404. Use roulette wheel selection to select superior individuals for the next generation based on their fitness values. S405. Perform single-point crossover on the selected individuals with crossover probability pc to generate new individuals; S406. Perform Gaussian mutation on individuals with mutation probability pm to generate the next generation population; S407. Determine whether the change in the optimal fitness value is less than the set change threshold tol or whether the number of iterations has reached the set number threshold n. The change in the optimal fitness value is the absolute difference between the global minimum objective function values ​​in two adjacent generations of the population. If the above conditions are met, stop and output the optimal individual corresponding to the minimum objective function value. Otherwise, assign the value of i plus 1 to the new i and return to step S403.

7. The method for optimizing the design of a straight pipe outlet flow channel as described in claim 1, characterized in that: The penalty function P penalty The calculation formula is as follows: ; in, This is the upper limit of the export flow rate. To allow the maximum diffusion angle.

8. The method for optimizing the design of a straight pipe outlet flow channel as described in claim 1, characterized in that: In step S5, a hyperelliptic function is used to describe the cross-sectional shape of the transition segment. The hyperelliptic function is: ； in, Let be the shape index, and a and b be the semi-major and semi-minor axes, respectively. The transition parameter t∈[0,1] is defined as the normalized position along the flow channel, where t=0 corresponds to the inlet (circular) and t=1 corresponds to the outlet (rectangular). The variation of each parameter with t is as follows: ； ； ； ； in, For smooth transition function, Let t be the transition cross-sectional area at the position corresponding to the axial parameter t of the diffuser section. The aspect ratio is a function, varying from 1 to A. R .

9. The method for optimizing the design of a straight pipe outlet flow channel as described in claim 6, characterized in that: The formula for calculating the diffusion loss coefficient is as follows: θ max = max(θ W , θ H ), θ max For the maximum diffusion angle, , .

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