Method for optimizing installation scheme of direct-current spray pipe of large impulse turbine

Abstract

The invention discloses a method for optimizing an installation scheme of a direct current nozzle of a large impulse turbine, and relates to the technical field of hydraulic engineering, the method comprises the following steps: carrying out geometric modeling on a target nozzle, and carrying out grid division on the model according to a preset grid quality standard to generate a target nozzle grid; and performing flow velocity analysis on the nozzle grid by using operation simulation to obtain flow velocity distribution. Performing streamline transition calculation according to the flow velocity distribution, and monitoring the transition flow velocity to obtain the target flow velocity. And performing periodic flow velocity optimization on the nozzle grid based on a flow velocity monitoring result, and finally determining an optimized nozzle mounting scheme. The technical problem that the flow velocity is unstable due to sudden flow velocity change in the running process of an existing large impulse turbine direct-current spray pipe is solved, the technical target of improving the flow velocity stability is achieved by optimizing the configuration of the spray pipe, and the technical effect of improving the running reliability and efficiency of the turbine is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of water conservancy engineering, and in particular to a method for optimizing the installation scheme of a direct-flow nozzle of a large impulse turbine. Background Art

[0002] As the core equipment in the hydropower generation system, large-scale impulse turbines are widely used in various hydropower stations. Their operating performance directly affects the power generation efficiency and the overall stability of the system. As an important component of the turbine, the DC nozzle is responsible for accurately guiding the water flow to the impeller to achieve efficient conversion of water energy into mechanical energy. However, in the actual operation process, the flow velocity distribution of the DC nozzle is often affected by the fluctuation of water flow and the change of working conditions, resulting in frequent flow velocity mutations, which in turn cause flow velocity instability. This flow velocity instability not only affects the operating efficiency of the turbine, but also may cause mechanical vibration and excessive wear of the equipment, increasing maintenance costs. In addition, the traditional nozzle installation method mainly relies on empirical settings, lacks systematic fluid dynamics analysis and real-time monitoring methods, and is difficult to effectively deal with complex flow phenomena such as flow separation. Therefore, it is urgent to develop more scientific and accurate nozzle installation and flow velocity control methods to solve the technical problems caused by unstable flow velocity, improve the overall performance and operating reliability of the turbine, and meet the needs of modern hydropower generation for efficient and stable operation.

[0003] In the current related technologies, there is a technical problem of flow velocity instability caused by sudden changes in flow velocity during the operation of the DC nozzle of a large impulse turbine. Summary of the invention

[0004] The present application solves the technical problem of flow velocity instability caused by sudden changes in flow velocity during operation of the existing large impulse turbine direct current nozzle by providing a method for optimizing the installation scheme of the large impulse turbine direct current nozzle.

[0005] The present application provides a method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine, comprising:

[0006] The target nozzle is geometrically modeled, and the target nozzle model is meshed based on a preset mesh quality to obtain a target nozzle mesh; a flow velocity analysis is performed based on a target flow velocity mesh obtained through a running simulation of the target nozzle mesh to obtain a target flow velocity distribution; streamline transition of the target nozzle mesh is performed according to the target nozzle flow velocity distribution, and the transition flow velocity is monitored to obtain a target flow velocity; based on the target flow velocity, the target nozzle mesh is monitored for a preset period of flow velocity optimization to obtain a target installation solution.

[0007] The present application proposes a method for optimizing the installation scheme of a DC nozzle of a large impulse turbine. First, the target nozzle is geometrically modeled, and the model is meshed according to a preset mesh quality standard to generate a target nozzle mesh. The nozzle mesh is subjected to flow velocity analysis using a running simulation to obtain a flow velocity distribution. Streamline transition calculations are performed based on the flow velocity distribution, and the transition flow velocity is monitored to obtain the target flow velocity. The nozzle mesh is periodically optimized for flow velocity based on the flow velocity monitoring results, and the optimized nozzle installation scheme is finally determined, achieving the technical goal of improving flow velocity stability by optimizing the configuration of the nozzle, and achieving the technical effect of improving the operational reliability and efficiency of the turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the accompanying drawings of the embodiment of the present invention will be briefly introduced below. A flow chart is used in the present application to illustrate the operations performed by the system according to the embodiment of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps can be processed in reverse order or simultaneously as needed. At the same time, other operations can also be added to these processes, or one or more operations can be removed from these processes.

[0009] Figure 1 A schematic diagram of a flow chart of a method for optimizing a large-scale impulse turbine DC nozzle installation scheme provided in an embodiment of the present application;

[0010] Figure 2 A schematic diagram of a target flow grid process for obtaining a large impulse turbine DC nozzle installation scheme optimization method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0011] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below.

[0012] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present application. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0013] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments, but it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict, and the terms "first\second" involved are merely to distinguish similar objects and do not represent a specific ordering of objects. The terms "including" and "having" and any variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or modules that are not clearly listed or inherent to these processes, methods, products, or devices. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of this application. The terms used herein are for the purpose of describing the embodiments of the present application only.

[0014] The present application embodiment provides a method for optimizing the installation scheme of a DC nozzle of a large impulse turbine, such as Figure 1 As shown, the method includes:

[0015] Step S100, geometric modeling of the target nozzle is performed, and the target nozzle model is meshed based on the preset mesh quality to obtain the target nozzle mesh. Specifically, according to the actual structure and size parameters of the target nozzle, a three-dimensional geometric model is created using professional three-dimensional modeling software such as CATIA to ensure that the model accurately and completely presents the details of the nozzle's inlet profile, outlet shape, main body length, bending degree, and internal cavity characteristics. The flow velocity range, flow properties, and other information of the fluid in the nozzle are extracted to preset the flow type to determine the preset mesh quality. For laminar flow, a relatively sparse mesh with a refined wall surface can be set, while a finer mesh with good orthogonal smoothness is required for turbulent flow. Then, tools such as ANSYS_Meshing are used to generate hexahedral units for regular parts such as the inlet section, and unstructured meshing is used to generate tetrahedral units for complex areas such as the curved transition section, and local refinement is performed on key areas such as the throat and near the wall surface to finally obtain the target nozzle mesh.

[0016] In a possible implementation, geometric modeling is performed on the target nozzle, and the target nozzle model is meshed based on a preset mesh quality to obtain a target nozzle mesh. Step S100 further includes step S110, extracting the fluid velocity and fluid flow properties, and presetting the flow type. Specifically, key information related to the fluid in the target nozzle is extracted, among which the fluid velocity and fluid flow properties are particularly important. Fluid velocity information is obtained by various means, such as referring to experimental data of similar nozzle systems in the past, theoretical calculation estimates, or using preliminary fluid simulation software to perform simple flow field estimates, and determining the possible velocity range of the fluid at different positions of the nozzle. For example, if the velocity at the inlet is high, the velocity in the gradually expanding or contracting section inside the nozzle will change accordingly. At the same time, the flow properties of the fluid are analyzed to determine whether it is laminar or turbulent. Laminar flow has the characteristics of parallel flow and non-interference between the layers of the fluid, which usually occurs when the flow velocity is low, the pipe diameter is small, and the fluid viscosity is large; while turbulent flow is full of irregular vortex motion and strong mixing phenomena inside the fluid, which often occurs when the flow velocity is high, the pipe diameter is large, or the fluid viscosity is small. Based on the information of flow velocity and flow properties, the flow type is accurately preset. For example, if the flow velocity is low and it is more likely to be laminar flow after analysis, it is preset as laminar flow type; if the flow velocity is high and there are obvious signs of turbulent characteristics, it is preset as turbulent flow type.

[0017] Step S120, configure the grid quality based on the flow type to obtain the preset grid quality. Specifically, after determining the flow type, the preset grid quality is obtained based on the grid quality configuration. For the case where the flow is preset to laminar flow, since the laminar flow is relatively stable, the grid can be relatively sparse, but in order to accurately simulate the flow characteristics of the boundary layer, special treatment must be performed near the nozzle wall. Using boundary layer grid technology, multiple layers of gradually refined grids are generated near the wall, which can accurately capture the velocity gradient changes of the fluid at the wall. In areas far away from the wall, the grid unit size can be appropriately increased to improve the calculation efficiency while ensuring the calculation accuracy. For example, in the axial direction of the nozzle, the length of the grid unit in the area far away from the wall is set to several times the length of the grid unit near the wall. For the case where the flow is preset to turbulent, due to the complexity and randomness of the turbulent flow, a finer grid is required to capture its vortex structure and drastic changes in velocity. Reduce the grid unit size, improve the orthogonality and smoothness of the grid, and ensure that the grid can accurately reflect the various characteristics of turbulence. For example, in the core area of ​​turbulence, the size of the grid unit should be small enough to capture the details of the vortex, and the angle between adjacent grid units should be as close to a right angle as possible to ensure the accuracy and stability of the calculation. By configuring the grid quality for different flow types, the preset grid quality suitable for the target nozzle fluid analysis is finally determined, providing an important quality standard basis for subsequent grid division work.

[0018] Step S200, based on the target velocity grid obtained by the simulation of the operation of the target nozzle grid, a velocity analysis is performed to obtain a target velocity distribution. Specifically, the target nozzle grid model is imported using computational fluid dynamics software such as ANSYS_Fluent, and the inlet velocity, pressure, temperature, outlet pressure or flow rate, and boundary conditions such as wall roughness and no slip are set according to the actual working conditions of the nozzle, and the Navier-Stokes equation is solved to obtain the target velocity grid. The mutation threshold is determined according to the nozzle design requirements and the actual working conditions, and the target velocity grid data is scanned to identify the target mutation grid whose velocity change exceeds the threshold, which is often located at the nozzle structure change and may affect the performance. The streamline, velocity vector and pressure change of the target mutation grid are analyzed to verify the flow separation, and the target pressure grid is identified based on the pressure gradient threshold. The target pressure grid is subjected to pressure gradient trend analysis in combination with the target adjacent grid, and the target mutation grid and the target pressure grid that meet the flow separation or pressure gradient anomaly are added to the target velocity distribution to provide a basis for optimizing the nozzle.

[0019] In one possible implementation, Figure 2 As shown, based on the target flow velocity grid obtained by the operation simulation of the target nozzle grid, the target flow velocity distribution is obtained, and step S200 further includes step S210, extracting the target inlet, target outlet and target wall in the target nozzle grid. Specifically, for the target nozzle grid, the target inlet, target outlet and target wall are accurately extracted. The target inlet is the starting point for the fluid to enter the nozzle, and its shape and size have a key influence on the flow rate, flow velocity and flow pattern of the fluid flowing into the nozzle. For example, if the inlet is circular, its diameter will directly determine the initial fluid flux entering the nozzle; if it is a rectangular inlet, the ratio of length to width will affect the velocity distribution of the fluid at the inlet. The target outlet is the part where the fluid flows out of the nozzle. The shape and area of ​​the outlet determine the velocity and pressure changes of the fluid when it flows out. For example, a contraction-shaped outlet will accelerate the fluid, while an expansion-shaped outlet may decelerate the fluid and reduce the pressure. The target wall is the boundary of the internal cavity of the nozzle. Its surface properties such as roughness and temperature will affect the viscous resistance and heat transfer process of the fluid, thereby affecting the flow state of the fluid in the entire nozzle.

[0020] Step S220, configure the inlet boundary condition for the target inlet, configure the outlet boundary condition for the target outlet, and configure the wall condition for the target wall, and complete the boundary condition configuration. Specifically, after successfully extracting the target inlet, target outlet and target wall, the boundary condition configuration is performed. For the target inlet, the inlet boundary condition is configured according to the fluid inflow in the actual working scene of the nozzle. If the nozzle is connected to a pipeline system with a stable pressure source, then the corresponding pressure value is set at the inlet; if the flow rate flowing into the nozzle is known, the flow value can be used as the inlet boundary condition; it can also be configured according to the actual measured or estimated inlet flow rate, while considering the physical parameters such as the temperature and density of the fluid to ensure that the inlet boundary condition can accurately reflect the inflow characteristics of the actual fluid. For the target outlet, the outlet boundary condition is configured according to the external environment of the nozzle outlet or the requirements of the subsequent connection equipment. For example, if the nozzle outlet leads to the atmosphere, it can be set to the ambient pressure; if it is connected to another cavity with lower pressure, the corresponding pressure difference condition is set; or the outlet boundary condition is determined according to the expected outlet flow rate or flow rate. For the target wall, the wall condition is configured according to the actual physical properties of the wall. If the wall is relatively smooth, set a lower roughness value; if the wall has a certain amount of heat dissipation or heating, set the corresponding wall temperature or heat flux conditions; usually set the wall to a no-slip condition, that is, the velocity of the fluid at the wall is zero, to simulate the interaction between the actual fluid and the wall. By accurately configuring the boundary conditions of the target inlet, target outlet and target wall, the boundary condition setting of the entire target nozzle grid is completed.

[0021] Step S230, based on the boundary conditions, the target nozzle grid is simulated and the target flow rate grid is obtained. Specifically, after the boundary conditions are configured, the target nozzle grid is simulated using professional computational fluid dynamics (CFD) software based on the boundary conditions. The target nozzle grid model with the configured boundary conditions is imported into CFD software platforms such as ANSYS_Fluent and CFX. The software will calculate the flow rate information at each grid node in the nozzle by numerically solving the control equations of fluid flow, such as the Navier-Stokes equations, according to the set boundary conditions and the geometry of the nozzle grid. During the simulation process, the software will use appropriate numerical calculation methods, such as the finite volume method, the finite difference method, etc., to discretize the control equations, and iteratively solve them to gradually approach the real flow field solution. After a certain calculation time and number of iterations, the flow rate distribution of the fluid at each position in the entire nozzle is obtained, and the flow rate information is presented in the form of grid node data, thereby obtaining the target flow rate grid. The target velocity grid can intuitively reflect the velocity field characteristics of the fluid in the nozzle under the set boundary conditions, and provide a basic data source for further analysis of the fluid flow characteristics in the nozzle, such as the uniformity of velocity distribution and whether there is flow separation, so as to evaluate and optimize the performance of the nozzle.

[0022] In a possible implementation, based on the target flow velocity grid obtained by the operation simulation of the target nozzle grid, the flow velocity analysis is performed to obtain the target flow velocity distribution, and step S200 further includes step S240, based on the mutation threshold, the flow velocity of the target flow velocity grid is identified, and the target mutation grid is extracted. Specifically, it is necessary to determine the mutation threshold. The setting of the mutation threshold is not arbitrary, and depends on the in-depth analysis of the normal flow velocity variation range of the fluid in the target nozzle and the accurate grasp of the flow velocity stability requirements. The threshold can be determined by theoretical analysis, previous experimental data statistics of similar nozzle systems, or preliminary numerical simulation tests. For example, if it is found in a large amount of experimental data that the fluctuation amplitude of the fluid flow velocity in the target nozzle under normal operating conditions is usually between ±2m / s, then in order to more keenly capture the abnormal changes in flow velocity that may affect the nozzle performance, the mutation threshold can be set to 3m / s. After determining the mutation threshold, the target flow velocity grid is carefully identified. Since the target velocity grid contains the velocity information of each position in the nozzle, the grid node is used as the basic unit to check the difference between the velocity value at each node and the velocity value of the adjacent node one by one. When the difference between the velocity of a node and the velocity of its adjacent node exceeds the mutation threshold, the grid area where the node is located is marked as a possible mutation area. Through this point-by-point scanning and comparison method, all eligible grid areas are extracted, and these areas together constitute the target mutation grid. The target mutation grid is often concentrated in the parts where the internal structure of the nozzle changes significantly, such as the throat of the nozzle, where the cross-sectional area decreases sharply, the fluid velocity will increase rapidly, and the velocity mutation is easy to occur; there is also the curved section of the nozzle, where the velocity distribution of the fluid changes due to the centrifugal force when turning, and mutations may also occur.

[0023] Step S250, if the target mutation grid is subjected to flow separation verification and identification to obtain a separation result, the target mutation grid is added to the target flow velocity distribution. Specifically, after the target mutation grid is extracted, flow separation verification and identification is performed on it. It is necessary to comprehensively use a variety of fluid mechanics analysis methods and tools. Starting from the streamline morphology of the flow field, observe whether the streamline has abnormal phenomena such as backflow, vortex or sudden interruption of the streamline in the target mutation grid area. For example, in normal fluid flow, the streamline should be smooth, continuous and gradually change along the mainstream direction. If the streamline is found to begin to bend and form a closed vortex ring in the target mutation grid area, it is an important sign of flow separation. At the same time, analyze the velocity vector distribution. In the area where flow separation occurs, the direction and size of the velocity vector will change sharply, and an obvious velocity component will appear perpendicular to the mainstream direction. In addition, pressure distribution is also one of the key factors in judging flow separation. Near the flow separation point, the pressure will be locally reduced, forming a low-pressure area, causing the fluid to flow from the high-pressure area to the low-pressure area, thereby destroying the original mainstream morphology. By comprehensively analyzing the streamlines, velocity vectors, and pressure distribution characteristics of the target mutation grid area, if it is determined that there is flow separation in the area, that is, a separation result is obtained, then the target mutation grid is added to the target velocity distribution. The purpose is to more accurately depict the overall picture of the velocity distribution in the nozzle, especially in areas with abnormal flow conditions, so that the nozzle structure or operating parameters can be optimized and adjusted in a targeted manner in the future, the stability and uniformity of the fluid velocity in the nozzle can be improved, and the working efficiency and performance of the entire nozzle system can be improved.

[0024] In a possible implementation, if the target mutation grid is subjected to flow separation verification and identification to obtain a separation result, the target mutation grid is added to the target velocity distribution, and step S250 further includes step S251, in which the target mutation grid is subjected to pressure identification based on the pressure gradient threshold to obtain the target pressure grid. Specifically, the pressure gradient threshold is determined. The determination of the threshold requires a comprehensive analysis of multiple factors such as the design specifications, working conditions, and fluid characteristics of the target nozzle. For example, for a high-pressure nozzle system, the internal pressure gradient has a large range of variation, and the pressure gradient threshold may be set higher accordingly; while for a low-pressure, precision nozzle system, the pressure gradient threshold needs to be set more precisely. A suitable pressure gradient threshold is determined through theoretical calculations, experimental data references, or preliminary simulation analysis. Pressure identification is performed on the target mutation grid. Since the target mutation grid is an area with flow anomalies previously screened out based on velocity mutations, in these areas, the pressure difference between each grid node and its adjacent nodes is calculated by computational fluid dynamics software or related algorithms. The pressure difference is compared with the set pressure gradient threshold. When the pressure difference exceeds the pressure gradient threshold, the grid area where the grid node is located is determined as a pressure anomaly area. The pressure anomaly areas together constitute the target pressure grid. The target pressure grid is usually located in the part of the nozzle where the flow velocity changes drastically and the structure is complex, such as the transition area between the throat and the bend of the nozzle. Due to the rapid change of the geometric shape, the change of fluid pressure is also more complex, which is easy to produce a pressure gradient that does not conform to the normal flow law.

[0025] Step S252, according to the target pressure grid combined with the target adjacent grid, the pressure gradient trend analysis is performed to obtain the target pressure trend. Specifically, after obtaining the target pressure grid, the pressure gradient trend analysis is performed in combination with the target adjacent grid. The target adjacent grid refers to the grid area that is spatially adjacent to the target pressure grid. During the analysis, the target pressure grid is taken as the core, and the pressure change direction and amplitude of the surrounding grids are observed. For example, from the nozzle inlet to the outlet direction, if under normal flow conditions, the pressure should be gradually reduced, but in the target pressure grid and its adjacent grid area, if it is found that the pressure first decreases and then increases, or the rate of pressure reduction is abnormally slow or fast, it indicates that the pressure gradient trend is abnormal. By fitting, differentiating and other mathematical processing of the pressure data of multiple adjacent grids, a pressure gradient change curve is drawn to determine the target pressure trend. The trend can intuitively reflect the change direction of the pressure in the target pressure grid area, which is an important basis for judging whether the fluid flow in the area is stable and whether it meets the expectations of the nozzle design.

[0026] Step S253, if it is determined that the target pressure trend does not meet the gradient drop threshold, the target pressure grid is added to the target flow velocity distribution. Specifically, it is determined whether the target pressure trend meets the gradient drop threshold. The gradient drop threshold is also set according to the ideal working state of the nozzle and the principle of fluid mechanics. If the pressure trend presents a smooth, gradually decreasing feature toward the nozzle outlet and the amplitude of change is within a preset range, then it is considered that the gradient drop threshold is met, indicating that the pressure change in the area conforms to the normal flow law; on the contrary, if the pressure trend fluctuates, stagnates or even changes in the reverse direction, and exceeds the range allowed by the gradient drop threshold, it is determined that the gradient drop threshold is not met. Add the target pressure grid to the target flow velocity distribution. Because the pressure anomaly in the area will affect the flow velocity distribution of the fluid, resulting in unstable flow velocity or the occurrence of local vortices and other undesirable phenomena. After adding it to the target flow velocity distribution, it can more comprehensively and accurately reflect the actual flow state of the fluid in the nozzle, and provide a more detailed basis for the subsequent optimization of the nozzle structure and adjustment of the working parameters, so as to improve the fluid flow characteristics in the nozzle and improve the working efficiency and performance of the nozzle.

[0027] Step S300, perform streamline transition of the target nozzle grid according to the target nozzle velocity distribution, monitor the transition velocity to obtain the target velocity. Specifically, according to the target nozzle velocity distribution, use numerical calculation methods such as finite difference or finite volume to solve the relevant equations, determine the streamline direction and curvature when transitioning from the area with drastic velocity changes and the area with stable velocity changes, and calculate the preliminary shape and size parameters of the progressive channel. Collect the transition section configuration length, diameter and velocity samples of the preset time period, use regression and other machine learning algorithms to train and build a transition section configuration model, input the mutation threshold into the model to calculate the appropriate transition section configuration length and diameter, and optimize the progressive channel to obtain the transition channel. After the transition channel is constructed, the target velocity feedback monitoring is performed based on its length and diameter parameters to obtain the iterative velocity, and the parameter combination is adjusted by assignment iteration, and the optimized velocity is determined as the target velocity to improve the efficiency and performance of the nozzle system.

[0028] In a possible implementation, the streamline transition of the target nozzle grid is performed according to the target nozzle velocity distribution, and the transition velocity is monitored to obtain the target flow velocity. Step S300 further includes step S310, in which the streamline progressive transition section is calculated for the target nozzle grid according to the target velocity distribution to obtain a progressive channel. Specifically, the streamline progressive transition section of the target nozzle grid is calculated according to the target velocity distribution. The target velocity distribution presents the velocity size and change trend of the fluid in the nozzle at different positions, which is an important basis for calculating the streamline progressive transition section. The velocity distribution data is deeply analyzed to identify areas where the velocity changes significantly, such as the throat of the nozzle, where the velocity usually increases rapidly; and areas where the velocity is relatively stable, such as the outlet section of the nozzle. For the junction of regions with different velocity characteristics, the relevant principles of computational fluid dynamics and numerical calculation methods, such as the finite volume method, are used to determine how the streamlines gradually transition between different velocity regions. By solving the fluid motion equation and iterative calculation, taking into account the viscosity, inertia and nozzle geometry of the fluid, the curvature path of the streamline from the high velocity area to the low velocity area, the density change of the streamline, and the acceleration or deceleration law of the fluid during the transition process are gradually determined. Based on this, the shape and size of the channel that can achieve this progressive transition of the streamline are calculated, that is, the progressive channel is obtained. The design of the progressive channel is to enable the fluid to transition smoothly when flowing through different velocity areas, reduce the energy loss, vortex formation and flow separation caused by sudden changes in velocity, and thus improve the overall efficiency and stability of the fluid flow in the nozzle.

[0029] Step S320, parameter configuration is performed on the progressive channel based on the transition section configuration model to obtain the transition channel. Specifically, after the progressive channel is obtained, the parameters are configured based on the transition section configuration model to obtain the transition channel. The construction of the transition section configuration model requires the collection of a large amount of relevant data in advance, including transition section configuration length samples, transition section configuration diameter samples and transition section flow rate samples within a preset time period. The sample data can come from the data accumulated from previous experimental tests on similar nozzles, or valid data obtained through multiple numerical simulation verifications. Using the rich data samples, the transition section configuration model is constructed by machine learning or data fitting methods. For example, a regression analysis algorithm is used to model the relationship between the transition section configuration length, diameter and flow rate, and determine the optimal length and diameter combination law of the transition section under different flow rate conditions. After the transition section configuration model is constructed, a specific mutation threshold is input into the model. The mutation threshold is determined when the target flow rate distribution is analyzed before, and is a key indicator for measuring whether the flow rate change is abnormal. According to the mutation threshold, the transition section configuration model calculates the transition section configuration length and transition section configuration diameter parameters suitable for the current progressive channel based on its internal algorithm and data relationship. Then, the progressive channel is precisely configured based on the calculated parameters, and its length, diameter, and internal geometric details are adjusted to obtain a transition channel. The transition channel is more optimized in structure and size, and can better adapt to the flow velocity changes of the fluid in the nozzle, further improving the stability and efficiency of the fluid flow.

[0030] Step S330, monitoring the transition flow rate of the transition channel to obtain the target flow rate. Specifically, after the transition channel is constructed, its transition flow rate is monitored to obtain the target flow rate. In the monitoring process, the structural parameters of the transition channel are fully utilized, that is, feedback monitoring of the target flow rate is performed based on the transition section configuration length and transition section configuration diameter. Since the length and diameter of the transition channel directly affect the flow velocity and distribution of the fluid therein, by changing these parameters and monitoring the change of the flow velocity in real time, the flow velocity response law under different parameter combinations can be explored. For example, gradually increase the length of the transition channel and observe how the flow velocity gradually decreases; or reduce the diameter of the transition channel and analyze the increase in the flow velocity. In this process, a series of iterative flow velocity data are obtained. According to the iterative flow velocity data, the transition channel is assigned iteratively, that is, the length and diameter parameters of the transition channel are continuously adjusted, and then the change of the flow velocity is monitored again. Through multiple such iterative operations, the optimal flow velocity state is gradually approached. Finally, the optimized flow velocity obtained in this iterative optimization process is determined as the target flow velocity. This target flow rate is obtained after comprehensive consideration of multiple factors such as flow velocity distribution in the nozzle, streamline transition, and optimization of transition channel parameters. It can maximize the stability and uniformity of the fluid flow velocity in the nozzle, reduce energy loss and equipment wear caused by flow velocity fluctuations, and thus significantly improve the working performance and operating efficiency of the entire nozzle system.

[0031] In a possible implementation, the progressive channel is parameterized based on the transition section configuration model to obtain the transition channel, and step S320 further includes step S321, performing supervised training according to the transition section configuration length samples, transition section configuration diameter samples and transition section flow rate samples in a preset time period to obtain the transition section configuration model. Specifically, the transition section configuration length samples, transition section configuration diameter samples and transition section flow rate samples in the preset time period are collected. The source of the sample data is crucial, and it is obtained by experimentally testing a large number of nozzles of the same type or under similar working conditions. During the experiment, the configuration length, diameter and corresponding flow rate data of the transition section of different nozzles are accurately measured during operation. For example, for a series of nozzles of different specifications but similar uses, tests are carried out under different working conditions such as pressure and flow, and the actual length and diameter of each nozzle transition section, as well as the flow rate value measured under the parameters, are recorded. At the same time, strictly verified numerical simulation data can also be used as supplementary samples. After the rich and diverse sample data are sorted out, supervised learning algorithms are used for training. For example, by using algorithms such as linear regression and neural networks, with the transition section configuration length and diameter as input features and the transition section flow rate as the output label, the model can accurately learn the intrinsic relationship between the transition section configuration length, diameter and flow rate by continuously adjusting the model parameters, thereby obtaining a transition section configuration model. The model can predict the corresponding flow rate based on the given transition section length and diameter information, or conversely, calculate the appropriate transition section length and diameter based on the expected flow rate.

[0032] Step S322, input the mutation threshold into the transition section configuration model for parameter configuration, perform progressive channel configuration based on the obtained transition section configuration length and transition section configuration diameter, and obtain the transition channel. Specifically, after obtaining the transition section configuration model, input the mutation threshold into the model for parameter configuration. The mutation threshold is a key indicator previously determined in the process of analyzing the target nozzle flow rate, reflecting the sensitivity of the flow rate change in the nozzle and the requirement for flow rate stability. After the mutation threshold is input into the transition section configuration model, the model calculates the appropriate transition section configuration length and transition section configuration diameter based on the relationship and algorithm learned inside it. For example, if the mutation threshold is set to a lower value, reflecting the higher requirement for flow rate stability, the model will calculate a longer transition section configuration length and a smaller transition section configuration diameter, which can make the fluid have a smoother flow rate change during the transition process; conversely, if the mutation threshold is higher, the length and diameter of the transition section will be adjusted accordingly. Perform progressive channel configuration based on the obtained transition section configuration length and transition section configuration diameter. According to the calculated length and diameter parameters, the geometric shape of the transition channel is constructed to determine the internal surface curvature, the expansion or contraction ratio of the channel and other details. For example, if the transition section is configured with a longer length, then when constructing a progressive channel, the flow velocity of the channel will gradually change over a longer distance; if the transition section is configured with a smaller diameter, the cross-section of the channel will also be reduced accordingly to achieve precise control of the fluid flow rate. In this way, a transition channel is finally obtained, which can effectively guide the fluid to smoothly transition from one flow rate area to another, reduce energy loss and flow instability caused by sudden changes in flow rate, and improve the fluid transmission efficiency and stability of the entire nozzle system.

[0033] In a possible implementation, the mutation threshold is input into the transition section configuration model for parameter configuration, and a progressive channel configuration is performed based on the obtained transition section configuration length and transition section configuration diameter to obtain the transition channel. Step S322 further includes step S3221, feedback monitoring of the target flow rate is performed based on the transition section configuration length and transition section configuration diameter to obtain an iterative flow rate. Specifically, feedback monitoring of the target flow rate is performed based on the determined transition section configuration length and transition section configuration diameter. Since the transition section configuration length and diameter have a fundamental impact on the flow rate of the fluid in the transition channel, under a specific transition section configuration length and diameter, multiple flow rate monitoring points are set in the transition channel, and high-precision flow rate measuring instruments, such as laser Doppler velocimeters (LDVs) or hot wire anemometers, are used to collect flow rate data of the fluid at different positions in real time. The monitoring points are distributed in key parts of the transition channel, such as the entrance, the middle section, and near the exit, so as to fully grasp the changes in the flow rate of the fluid in the transition channel. The large amount of velocity data collected is sorted and analyzed to obtain the velocity distribution under the current transition section configuration length and diameter, and then determine the overall iterative velocity. The iterative velocity reflects the actual flow characteristics of the fluid under this set of transition section parameters and provides a basis for subsequent parameter adjustments.

[0034] Step S3222, assigning iteration to the transition channel according to the iterative flow rate, and taking the obtained optimized flow rate as the target flow rate. Specifically, after obtaining the iterative flow rate, assigning iteration to the transition channel according to the data. Specifically, according to the difference between the iterative flow rate and the expected target flow rate, the two key parameters of the transition section configuration length and the transition section configuration diameter are adjusted. If the iterative flow rate is higher than the expected target flow rate, it may be necessary to appropriately increase the transition section configuration length so that the fluid has a longer path in the channel to slow down, or reduce the transition section configuration diameter to increase the flow resistance of the fluid and thus reduce the flow rate; conversely, if the iterative flow rate is lower than the expected target flow rate, the transition section configuration length can be shortened or the transition section configuration diameter can be increased. After adjusting the parameters, the flow rate in the transition channel is monitored again using the flow rate monitoring device to obtain a new iterative flow rate. Repeat this process, continuously adjust the transition section configuration length and diameter, and monitor the flow rate changes to form an iterative cycle. As the number of iterations increases, the parameters of the transition channel are gradually optimized, and the iterative flow rate is getting closer and closer to the expected optimal flow rate state. When the iterative flow rate meets the preset convergence conditions, such as the change in flow rate is less than a certain set value or reaches a predetermined number of iterations, the optimized flow rate obtained at this time is used as the target flow rate. The target flow rate is obtained after multiple iterations of optimization, which can ensure that the fluid in the transition channel flows at the most stable and most satisfactory flow rate state, thereby improving the working efficiency and performance of the entire nozzle system and reducing energy loss, vibration and adverse effects on the nozzle structure caused by unstable flow rate.

[0035] Step S400, based on the target flow rate, the target nozzle grid is monitored to optimize the flow rate in a preset period to obtain a target installation plan. Specifically, based on the target flow rate, a high-precision sensor network is used to set monitoring points at key positions of the nozzle grid within a preset period to obtain flow rate data in real time and set a flow rate deviation range. At the same time, a parameter adjustment plan including nozzle throat diameter, expansion section angle, inlet shape, fluid pressure, temperature, etc. is formulated. Then, iterative optimization is performed according to the plan. After each parameter adjustment, the new flow rate data is compared with the target flow rate evaluation effect, and the interaction of multiple parameters is comprehensively considered. Multiple iterations are performed to approximate the optimal combination. Finally, when the nozzle flow rate is stable near the target flow rate and meets the requirements, the installation plan corresponding to the nozzle parameter combination at this time is the target installation plan. The application of this plan can improve the power generation efficiency of the turbine, reduce energy loss, etc. to achieve efficient and stable operation of the system.

[0036] The embodiment of the present application adopts geometric modeling of the target nozzle, and meshes the model according to a preset mesh quality standard to generate a target nozzle mesh. The nozzle mesh is subjected to flow velocity analysis by running simulation to obtain the flow velocity distribution. The streamline transition calculation is performed according to the flow velocity distribution, and the transition flow velocity is monitored to obtain the target flow velocity. The nozzle mesh is periodically optimized for flow velocity based on the flow velocity monitoring results, and the optimized nozzle installation plan is finally determined, thereby achieving the technical goal of improving the flow velocity stability by optimizing the configuration of the nozzle, and achieving the technical effect of improving the operational reliability and efficiency of the turbine.

[0037] The above specific implementation manner does not constitute a limitation to the protection scope of the present application. It should be understood by those skilled in the art that various modifications, combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application. In some cases, the actions or steps recorded in the present application can be performed in an order different from that in the embodiment and can still achieve the desired results. In addition, the process depicted in the accompanying drawings does not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine, characterized in that: include: Perform geometric modeling on the target nozzle, mesh the target nozzle model based on the preset mesh quality, and obtain the target nozzle mesh; Performing a flow velocity analysis on a target flow velocity grid obtained by running simulation of the target nozzle grid to obtain a target flow velocity distribution; Performing streamline transition of the target nozzle grid according to the target nozzle flow velocity distribution, and monitoring the transition flow velocity to obtain the target flow velocity; Based on the target flow rate, the target nozzle grid is monitored to optimize the flow rate of a preset period to obtain a target installation solution.

2. A method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine as claimed in claim 1, characterized in that: Get preset mesh qualities, including: Extract fluid velocity and fluid flow properties, and preset flow type; Grid quality configuration is performed based on the flow type to obtain the preset grid quality.

3. A method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine as claimed in claim 1, characterized in that: Obtain the target velocity grid, including: Extracting a target inlet, a target outlet, and a target wall in the target nozzle grid; The inlet boundary condition is configured for the target inlet, the outlet boundary condition is configured for the target outlet, and the wall condition is configured for the target wall, thereby completing the boundary condition configuration; The target nozzle grid is simulated based on boundary conditions to obtain the target flow velocity grid.

4. A method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine as claimed in claim 1, characterized in that: Obtain target flow velocity distribution, including: Performing flow velocity identification on the target flow velocity grid based on a mutation threshold, and extracting a target mutation grid; If flow separation verification and identification are performed on the target mutation grid to obtain a separation result, the target mutation grid is added to the target flow velocity distribution.

5. A method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine as claimed in claim 4, characterized in that: Obtaining the target flow velocity distribution also includes: Performing pressure identification on the target mutation grid based on a pressure gradient threshold to obtain a target pressure grid; Performing pressure gradient trend analysis based on the target pressure grid and target adjacent grids to obtain a target pressure trend; If it is determined that the target pressure trend does not satisfy the gradient drop threshold, the target pressure grid is added to the target flow rate distribution.

6. A method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine as claimed in claim 1, characterized in that: Obtain target flow rate, including: Performing a streamline progressive transition section calculation on the target nozzle grid according to the target flow velocity distribution to obtain a progressive channel; Performing parameter configuration on the progressive channel based on the transition segment configuration model to obtain a transition channel; The transition flow rate of the transition channel is monitored to obtain the target flow rate.

7. A method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine as claimed in claim 6, characterized in that: Gain access to transition channels, including: Perform supervised training based on transition section configuration length samples, transition section configuration diameter samples and transition section flow rate samples in a preset time period to obtain the transition section configuration model; The mutation threshold is input into the transition section configuration model for parameter configuration, and a progressive channel configuration is performed based on the obtained transition section configuration length and transition section configuration diameter to obtain the transition channel.

8. A method for optimizing the installation scheme of a direct-flow nozzle of a large-scale impulse turbine as claimed in claim 7, characterized in that: Gain access to transition channels, also includes: Performing feedback monitoring of the target flow rate based on the transition section configuration length and the transition section configuration diameter to obtain an iterative flow rate; The transition channel is iterated according to the iterative flow rate, and the obtained optimized flow rate is used as the target flow rate.

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