A method for improving the strength of a water turbine blade in a water conservancy project

Abstract

The application provides a method for improving the strength of a water turbine blade in a hydraulic engineering, and relates to the technical field of water turbine blades, and comprises the following steps: S1, recording the shape and cross-sectional shape of the blade; S2, establishing a wind wave flow tank model and a hydrodynamic performance test; S3, changing the interaction between the pressure surface and the suction surface at the blade tip through tip optimization; S4, analyzing the influence of the tip optimization on the hydrodynamic performance of the water turbine; and S5, establishing a fluid-structure coupling control equation of the flexible blade in the fluid. Through the design, the hydrodynamic performance of the blade can be effectively improved, local corrosion can be reduced, and the risk of blade fracture can be further reduced. The stress can be effectively dispersed, the local stress concentration can be reduced, the risk of fatigue damage of the blade caused by stress concentration can be reduced, the vibration intensity of the blade in the working process can be reduced by avoiding the resonance frequency and optimizing the weld arc transition radius, and the stability of the blade in operation can be ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water turbine blade technology, and particularly relates to a method for improving the strength of a water turbine blade in water conservancy projects. BACKGROUND

[0002] Water turbine blades are key components of water turbines in hydroelectric power generation systems. They are a series of precisely designed blades installed on the runner of the water turbine. When water flows through, the blades convert the kinetic energy of the water into mechanical energy, pushing the runner to rotate and driving the generator to generate electricity.

[0003] However, in actual water conservancy projects, due to the complexity and variability of water flow conditions, traditional water turbine blades are prone to local corrosion such as pitting, erosion corrosion and corrosion fatigue under the interaction of water flow, sediment scouring and complex electrochemical environment underwater. This corrosion can cause the material properties of the blades to degrade, and the water flow will increase the design stress of the blades, causing stress concentration and even perforation, leading to the rupture of the water turbine blades. SUMMARY

[0004] The purpose of the present application is to solve the problems existing in the prior art and provide a method for improving the strength of a water turbine blade in water conservancy projects.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solution: a method for improving the strength of a water turbine blade in water conservancy projects, comprising the following steps:

[0006] S1, record the shape and cross-sectional shape of the blade;

[0007] S2, establish a wind wave flow tank model and hydrodynamic performance test;

[0008] S3, change the interaction between the pressure surface and the suction surface at the blade tip through blade tip optimization;

[0009] S4, analyze the influence of blade tip optimization on the hydrodynamic performance of the water turbine;

[0010] S5, establish the fluid-structure coupling control equation of the flexible blade in the fluid;

[0011] S6, solve the blade deformation and establish the instantaneous physical model;

[0012] S7, test the strength and stiffness of the blade.

[0013] As a preferred embodiment, in step S2, the specific steps are: by selecting different geology, terrain and obstacles to realize the construction of autonomous scene, and exploring the interaction between waves and terrain;

[0014] In the step S2, the specific steps are: selecting appropriate experimental instruments and installing them to the corresponding positions of the water tank, such as wave pole and pitot tube, and performing correct installation and calibration.

[0015] As a preferred embodiment, in the step S2, the specific steps are: determining the calibration coefficient, calibrating the relationship between the load and the reading, including the calibration of the torque speed measuring instrument and the current and voltage signals.

[0016] In the step S2, the specific steps are: creating a new test project in the data acquisition and analysis processing system software, performing balancing, zeroing and recording.

[0017] In the step S2, the specific steps are: starting the circulating water tank and setting the water flow speed to the experimental flow speed.

[0018] In the step S2, the specific steps are: measuring the torque, speed, force values of the front and rear strain gauges, and the output of current and voltage of the water turbine main shaft under each working condition.

[0019] In the step S2, the specific steps are: closing the circulating water tank, removing the impeller, and then opening the circulating water tank to the experimental speed and reading the stress value of the strain gauge.

[0020] As a preferred embodiment, in the step S3, the specific steps are: using the blade element momentum theory to obtain the distribution of blade twist angle and chord, and establishing a parameterized model of the original rotor based on this.

[0021] In the step S3, the specific steps are: applying the winglet technology to the blade design of the tidal current energy water turbine.

[0022] In the step S3, the specific steps are: applying the winglet technology to the blade design of the tidal current energy water turbine.

[0023] In the step S3, the specific steps are: performing hydrodynamic performance research on the blade improvement scheme, including comparative analysis of blade surface pressure data, velocity flow field data and energy capture coefficient Cp data.

[0024] As a preferred embodiment, in the step S4, the specific steps are: establishing a water turbine water tank model test system and a hydrodynamic performance test platform, and performing a large number of experiments such as variable pitch angle, variable blade number and variable flow speed on different types of blades to obtain the speed, power, torque and other parameters of the water turbine under different working conditions.

[0025] In the step S4, the specific steps are: studying the influence of blades of different shapes and different thicknesses on the performance of the unit, especially the performance under reverse working conditions.

[0026] As a preferred implementation, in the step S5, the specific steps are: establishing a three-dimensional finite element analysis model of the whole runner blade and the single blade of the Francis turbine;

[0027] In the step S5, the specific steps are: using the fluid-structure coupling function in the finite element software to perform modal analysis on the whole runner blade and the single blade, obtaining the self-vibration characteristics of the runner blade and the single blade in air and static fluid, and performing comparative analysis.

[0028] As a preferred implementation, in the step S6, the specific steps are: on the pre-set fluid-structure coupling interface, the aerodynamic load / temperature field is transmitted to the structure field, and the geometric deformation / solid temperature is transmitted to the flow field, and the converged coupled multi-physical field results are obtained through iterative solution;

[0029] In the step S6, the specific steps are: the flow field and the structure field are iteratively solved in time domain according to the pre-set total time length and time step, and the final converged bidirectional fluid-structure coupling solution results varying with time domain are obtained;

[0030] In the step S6, the specific steps are: on the pre-set fluid-structure coupling interface, the aerodynamic load and the geometric deformation are iteratively solved to obtain the converged coupled multi-physical field results;

[0031] In the step S6, the specific steps are: according to the blade deformation results, an instantaneous physical model is established to simulate the dynamic behavior of the blade in the fluid, including the waving, oscillation and torsional deformation of the blade.

[0032] As a preferred implementation, in the step S7, the specific steps are: finding out the resonance points that will appear on the blade, and designing the geometric parameters of the blade to avoid these resonance points;

[0033] In the step S7, the specific steps are: according to the stress distribution of the blade, appropriately increasing the thickness of the blade, especially in the high stress area, to improve the carrying capacity of the blade and reduce stress concentration;

[0034] In the step S7, the specific steps are: optimizing the weld arc transition radius at the connection between the blade and the upper crown and the lower ring to reduce stress concentration and improve stress distribution;

[0035] In the step S7, the specific steps are: comprehensively measuring the vibration characteristics of the blade of the newly installed unit, including the identification of frequency dispersion rate and resonance safety rate, to ensure the optimal shape of the blade in operation.

[0036] Compared with the prior art, the advantages and positive effects of the present application are

[0037] By establishing a wind wave flow tank model and hydrodynamic performance test, the working state of the water turbine in the actual water flow environment is simulated, the wave pole, pitot tube and other equipment are used to monitor the water surface height change and fluid velocity distribution in the experiment, and the torque, speed and stress data of the main shaft of the water turbine are measured under different working conditions, so as to optimize the design of the water turbine blade; This design can simulate the interaction between water flow and blade in the real environment by selecting different bottom materials, terrain and obstacles, monitor the torque, speed and stress value of the water turbine, accurately understand the influence of water flow, sediment, corrosion and other factors on the blade, and optimize the blade design on this basis, reduce the stress concentration and corrosion risk.

[0038] By using wing and winglet technology at the tip, the hydrodynamic performance can be significantly improved. These technologies improve airflow distribution and reduce vortex resistance, improve blade efficiency, accurately calculate the twist angle and chord length of the blade based on blade element momentum theory, ensure reasonable design and stable performance, and comprehensively evaluate the operation performance of the improved blade through hydrodynamic performance test and experiment; In this way, by applying wing and winglet technology, and conducting hydrodynamic performance test and fluid-structure coupling analysis, the hydrodynamic performance of the blade can be effectively improved, local corrosion can be reduced, the design stress of the blade can be reduced, and the risk of blade fracture can be reduced.

[0039] By using the physical model of fluid-structure coupling, the dynamic response of the water turbine blade in a complex fluid environment is simulated, and the aerodynamic load, temperature field and geometric deformation of the blade are transmitted to the structure field, and the interaction between the fluid and the structure is iteratively solved, which can track the deformation and stress state of the blade in different working conditions in real time. This multi-physical field coupling simulation reflects the dynamic behavior of the blade in actual operation, such as waving, oscillation, torsional deformation, etc. Finally, by accurately simulating these dynamic behaviors, the converged fluid-structure coupling results can be obtained; By fine-tuning the geometry and thickness of the blade, the stress can be effectively dispersed, the local stress concentration can be reduced, and the risk of fatigue failure of the blade caused by stress concentration can be reduced, and by avoiding resonance frequency and optimizing the weld round transition radius, the vibration intensity of the blade during operation is reduced, and the stability of the blade during operation is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A flowchart of a method for improving the strength of a water turbine blade in a water conservancy project is provided.

[0041] Figure 2 A flowchart of a method for improving the strength of a water turbine blade in a water conservancy project is provided.

[0042] Figure 3A hydrodynamic performance test flowchart of a strength improvement method of a water turbine blade in a water conservancy project provided by the application is shown in the figure;

[0043] Figure 4 A blade tip optimization flowchart of a strength improvement method of a water turbine blade in a water conservancy project provided by the application is shown in the figure;

[0044] Figure 5 An analysis blade tip optimization flowchart of a strength improvement method of a water turbine blade in a water conservancy project provided by the application is shown in the figure;

[0045] Figure 6 A flowchart of a fluid-solid coupling control equation of a strength improvement method of a water turbine blade in a water conservancy project provided by the application is shown in the figure;

[0046] Figure 7 A flowchart of establishing a transient physical model of a strength improvement method of a water turbine blade in a water conservancy project provided by the application is shown in the figure;

[0047] Figure 8 A flowchart of blade strength and rigidity testing of a strength improvement method of a water turbine blade in a water conservancy project provided by the application is shown in the figure. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the application will be apparently and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0049] As shown in the figure, Figure 1 - Figure 3 The embodiment provides a technical solution: a strength improvement method of a water turbine blade in a water conservancy project, which comprises the following steps:

[0050] S1, record the shape and cross-sectional shape of the blade;

[0051] S2, establish a wind wave flow tank model and hydrodynamic performance test;

[0052] In step S2, the specific steps are: the self-scene construction is realized by selecting different geology, terrain and obstacles to explore the interaction between waves and terrain; in step S2, the specific steps are: selecting appropriate experimental instruments to be installed at the corresponding positions of the water tank, such as wave measuring rods and pitot tubes, and performing correct installation and calibration;

[0053] The predetermined terrain features are shaped using highly malleable materials, and the terrain structure is precisely sculpted after the substrate is laid at the bottom of the water tank. At the same time, obstacles such as breakwaters or shipwrecks are placed in appropriate locations according to experimental requirements and fixed to prevent movement. Then, wave measuring rods and Pitot tubes are installed in key locations to monitor changes in water level and fluid velocity distribution, and are carefully calibrated. Finally, the system is debugged and pre-run, the working status of each component is observed, and the data acquisition settings are adjusted to ensure that the required information can be recorded efficiently.

[0054] In step S2, the specific steps are as follows: determine the calibration coefficients and calibrate the relationship between load and readings, including the calibration of the torque and speed measuring instrument and the current and voltage signals; in step S2, the specific steps are as follows: create a new test project, perform balancing, zeroing, and recording in the data acquisition and analysis processing system software; in step S2, the specific steps are as follows: turn on the circulating water tank and set the water flow speed to the experimental flow rate; in step S2, the specific steps are as follows: measure the torque, speed, force values ​​of the front and rear strain gauges, and current and voltage outputs of the turbine main shaft under various working conditions; in step S2, the specific steps are as follows: close the circulating water tank and remove the impeller; then turn the circulating water tank back to the experimental speed and read the stress values ​​of the strain gauges;

[0055] A new test project was created in the data acquisition and analysis system software, and balancing and zeroing operations were performed to prepare for subsequent tests. Then, the circulating water tank was turned on and set to the water flow speed required for the experiment to simulate the actual operating environment of the water turbine. Under various operating conditions, the torque, speed, force values ​​of the front and rear strain gauges, and current and voltage outputs of the water turbine main shaft were measured in detail. After completing one round of testing, the circulating water tank was turned off and the impeller was removed. The impeller was then reinstalled or adjusted for the next round of testing. Finally, the circulating water tank was turned on again to the experimental speed, and the stress values ​​of the strain gauges were read as control group data.

[0056] like Figure 1 and Figure 4 S3. By optimizing the blade tip, the interaction between the pressure surface and the suction surface at the blade tip is changed;

[0057] In step S3, the specific steps are as follows: The distribution of the blade twist angle and chord is obtained using blade element momentum theory, and a parameterized model of the original rotor is established based on this. In step S3, the specific steps are as follows: The winglet technology is applied to the design of tidal power turbine blades. In step S3, the specific steps are as follows: The winglet technology is applied to the design of tidal power turbine blades. In step S3, the specific steps are as follows: Hydrodynamic performance studies are conducted on the improved blade design, including comparative analysis of blade surface pressure data, velocity flow field data, and energy capture coefficient Cp data.

[0058] The precise calculation of the twist angle and chord length distribution of the blade using the blade element momentum theory can predict the performance of the blade under different operating conditions. By this method, a parameterized model can be established to describe the characteristics of the original rotor, providing basic data for subsequent design improvement. Next, the winglet technology is introduced into the design of the tidal current turbine blade. Winglet is a device used to reduce the vortex-induced drag. It optimizes the flow characteristics by changing the air separation point near the blade tip. The application of this technology can effectively improve the efficiency of the blade. In addition, the winglet technology is applied to the design of the tidal current turbine blade. Winglet is a small structure located at the tip of the blade, which can further improve the aerodynamic characteristics around the blade, thereby improving the energy efficiency ratio of the whole system. Finally, the improved blade is comprehensively studied for its hydrodynamic performance, and data such as the pressure distribution on the blade surface, the velocity field information of the surrounding fluid, and the variation trend of the overall energy capture coefficient Cp are collected.

[0059] As Figure 1 With Figure 5 , S4, analyze the influence of tip optimization on the hydrodynamic performance of the turbine;

[0060] In step S4, the specific steps are: establishing a water turbine water tank model test system and a hydrodynamic performance test platform, and conducting a large number of tests on different types of blades with variable pitch angle, variable blade number, and variable flow rate to obtain the parameters such as speed, power, and torque of the turbine under different operating conditions. In step S4, the specific steps are: studying the influence of blades with different shapes and thicknesses on the performance of the unit, especially under reverse operating conditions.

[0061] A water turbine water tank model test system and a hydrodynamic performance test platform are established, which can simulate different flow conditions and test various types of blades. The tail of blades with multiple shapes and thicknesses is studied and compared in detail, especially under reverse operating conditions, to detect the flow characteristics and energy loss mechanism of the blade tail under reverse operating conditions and record the data.

[0062] As Figure 1 With Figure 6 , S5, establish the fluid-structure coupling control equation of flexible blades in fluid;

[0063] In step S5, the specific steps are: establishing a three-dimensional finite element analysis model of the overall runner blade and single blade of the mixed-flow turbine; In step S5, the specific steps are: using the fluid-structure coupling function in the finite element software to perform modal analysis on the overall runner blade and single blade, obtaining the natural vibration characteristics of the runner blade and single blade in air and stationary fluid, and performing comparative analysis.

[0064] The model is established by software, and then the fluid-structure coupling function in the finite element analysis software is used to perform modal analysis on the overall runner blade and single blade. Modal analysis is a method for studying the dynamic characteristics of a structure, which can reveal the natural frequency and mode shape of the structure, and is used to understand the vibration behavior of the blade during operation. Through this analysis, the natural vibration characteristics of the runner blade and single blade are obtained. In addition, the natural vibration characteristics of the blade in a stationary fluid are analyzed. In actual work, the blades of the water turbine operate in water flow, so it is also important to understand the dynamic response of the blade in the fluid. By comparing the natural vibration characteristics in air and stationary fluid, the influence of fluid on the vibration behavior of the blade is deeply understood, so as to optimize the design of the blade.

[0065] As Figure 1 With Figure 7 S6, solving blade deformation and establishing instantaneous physical model;

[0066] In step S6, the specific steps are: on the pre-set fluid-structure coupling interface, the aerodynamic load / temperature field is transmitted to the structure field, and the geometric deformation / solid temperature is transmitted to the flow field. Iterative solution is obtained after convergence of the coupled multi-physical field results; in step S6, the specific steps are: the flow field and the structure field are iteratively solved in time domain according to the pre-set total time and time step, and the final converged bidirectional fluid-structure coupling solution results are obtained; in step S6, the specific steps are: on the pre-set fluid-structure coupling interface, the aerodynamic load and geometric deformation are iteratively solved to obtain the converged coupled multi-physical field results; in step S6, the specific steps are: according to the blade deformation results, an instantaneous physical model is established to simulate the dynamic behavior of the blade in the fluid, including the waving, oscillation and torsional deformation of the blade;

[0067] On the pre-set fluid-structure coupling interface, the aerodynamic load and temperature field are transmitted to the structure field, and the geometric deformation and solid temperature are fed back to the flow field. Through iterative solution, the converged coupled multi-physical field results are obtained, which reflect the stress and deformation of the blade under actual working conditions. Next, the flow field and the structure field are iteratively solved in time domain according to the pre-set total time and time step. This step is the key to simulate the dynamic response of the blade in the real fluid environment. Through continuous iterative calculation, the final converged bidirectional fluid-structure coupling solution results are obtained, which are used to observe the instantaneous behavior of the blade at different time points. On the pre-set fluid-structure coupling interface, the interaction between the two is accurately simulated to obtain the coupled multi-physical field results. Finally, according to the deformation results of the blade, an instantaneous physical model is established to simulate the dynamic behavior of the blade in the fluid;

[0068] As Figure 1 With Figure 8 S7, blade strength and stiffness test;

[0069] In step S7, the specific steps are: finding out the resonance points that will appear on the blade, and designing the geometric parameters of the blade to avoid these resonance points; in step S7, the specific steps are: according to the stress distribution of the blade, appropriately increasing the thickness of the blade, especially in the high stress area, to improve the carrying capacity of the blade and reduce stress concentration; in step S7, the specific steps are: optimizing the weld arc transition radius of the connection between the blade and the upper crown and the lower ring to reduce stress concentration and improve stress distribution; in step S7, the specific steps are: comprehensively measuring the vibration characteristics of the new installed unit blade, including the frequency dispersion rate and the resonance safety rate, to ensure the optimal shape of the blade in operation.

[0070] First, according to the stress distribution of the blade, the geometric parameters of the blade are finely adjusted to ensure that the design of the blade can avoid resonance points, and then in order to improve the carrying capacity of the blade and reduce stress concentration, the thickness of the blade in the high stress area is increased, which not only enhances the structural strength of the blade, but also effectively disperses the stress and reduces the risk of fatigue failure caused by stress concentration. This targeted strengthening design enables our blade to maintain stable and reliable performance in harsh working environments. In addition, the weld arc transition radius of the connection between the blade and the upper crown and the lower ring is reduced to reduce stress concentration and improve the stress distribution of the entire blade. Finally, the blade of the newly installed unit is comprehensively measured to ensure that the blade can maintain the best shape in actual operation.

[0071] The above is only a preferred embodiment of the present application, and is not intended to limit the other forms of the present application. Any skilled person in the art can use the disclosed technical content to make changes or modifications to equivalent embodiments applied to other fields, but any simple modification, equivalent change and modification made according to the technical essence of the present application to the above embodiments shall still fall within the protection scope of the present application.

Claims

1. A method for improving the strength of turbine blades in hydraulic engineering, characterized in that, Includes the following steps: S1. Record the shape and cross-sectional shape of the blade; S2. Establish a wind-wave flow tank model and conduct hydrodynamic performance testing; S3. By optimizing the blade tip, the interaction between the pressure surface and the suction surface at the blade tip is changed; S4. Analyze the impact of blade tip optimization on the hydrodynamic performance of the turbine; S5. Establish the fluid-structure interaction control equations for flexible blades in fluid; S6. Solve for blade deformation and establish an instantaneous physical model; S7. Blade strength and stiffness test; In step S2, the specific steps are as follows: by selecting different geology, terrain and obstacles, an autonomous scene is built to explore the interaction between waves and terrain; Select appropriate experimental instruments and install them in the corresponding positions in the water tank. Use the wave measuring rod and Pitot tube, and perform correct installation and calibration. Determine the calibration coefficients and calibrate the relationship between load and readings, including the calibration of torque, speed measurement, and current and voltage signals; Create a new test project in the data acquisition and analysis system software, perform balancing, zeroing, and recording; Turn on the circulating water tank and set the water flow rate to the experimental flow rate; The torque, speed, stress values ​​of the front and rear strain gauges, and current and voltage outputs of the turbine main shaft were measured under various operating conditions. Close the circulating water tank and remove the impeller; then open the circulating water tank to the experimental speed and read the stress value of the strain gauge. In step S3, the specific steps are as follows: the distribution of blade twist angle and chord is obtained by using blade element momentum theory, and a parameterized model of the original rotor is established based on this. Applying wing-blade technology to the design of tidal current turbine blades; Applying winglet technology to the design of tidal power turbine blades; Hydrodynamic performance studies were conducted on the improved blade design, including comparative analysis of blade surface pressure data, velocity flow field data, and energy capture coefficient Cp data. In step S4, the specific steps are as follows: establish a turbine tank model test system and a hydrodynamic performance test platform, and conduct tests on different types of blades with varying pitch angle, varying number of blades, and varying flow velocity to obtain the turbine's speed, power, and torque parameters under different operating conditions; The study investigates the impact of blade tails of different shapes and thicknesses on unit performance; In step S7, the specific steps are: to find the resonance points that may appear on the blade and to design the geometric parameters of the blade to avoid these resonance points. Based on the stress distribution of the blade, the blade thickness is appropriately increased to improve the load-bearing capacity of the blade and reduce stress concentration in high-stress areas. Optimize the arc transition radius of the weld at the connection between the blade and the upper crown and lower ring to reduce stress concentration and improve stress distribution; A comprehensive measurement of the blade vibration characteristics of the newly installed unit was conducted, including the assessment of frequency dispersion and resonance safety rate, to ensure the optimal blade shape during operation.

2. The method for improving the strength of turbine blades in hydraulic engineering according to claim 1, characterized in that: In step S5, the specific steps are: to establish a three-dimensional finite element analysis model of the overall runner blades and individual blades of the mixed-flow turbine; Modal analysis of the entire runner blade and individual blades was performed using the fluid-structure interaction function in finite element software. The natural vibration characteristics of the runner blade and individual blades in air and static fluid were obtained and compared.

3. The method for improving the strength of turbine blades in hydraulic engineering according to claim 1, characterized in that: In step S6, the specific steps are as follows: at the pre-set fluid-structure interaction interface, the aerodynamic load and temperature field are transferred to the structural field, and the geometric deformation and solid temperature are transferred to the flow field. The converged coupled multiphysics field results are obtained by iterative solution. The flow field and structural field are solved iteratively in the time domain according to the preset total duration and time step to obtain the final converged bidirectional fluid-structure interaction solution result that changes in the time domain. At a pre-defined fluid-structure interaction interface, aerodynamic loads and geometric deformations are iteratively solved to obtain converged coupled multiphysics results. Based on the blade deformation results, an instantaneous physical model is established to simulate the dynamic behavior of the blade in the fluid, including blade flapping, oscillation and torsional deformation.

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