Improvement method for complex flow in draft tube of pump turbine

Abstract

The invention relates to the technical field of hydroelectric power generation energy storage, and discloses a method for improving complex flow in a draft tube of a pump turbine, which comprises the following steps: S1, referring to pump turbine unit data, arranging a flow guide partition plate at a draft tube diffusion section, and positioning the flow guide partition plate at the middle position of the diffusion section, comparing internal flow characteristics of the unit with or without the flow guide partition plates under different working conditions; s2, according to different working conditions, the positions and the angles of the flow guide partition plates are sequentially adjusted, unit flow characteristic analysis is conducted, and internal relations between unit working condition points and the positions and the angles of the flow guide partition plates are correspondingly established; and S3, according to the recording result of the internal relation, the optimal position and angle of the flow guide partition plate are determined, so that the design position capable of balancing efficiency and stability under different working conditions is achieved. The purpose of eliminating or weakening the complex vortex is achieved by adjusting the position and angle of the draft tube flow guide partition plate. The method is economical and effective, the structure is simple, implementation is convenient, parts are easy to machine and manufacture, and the working process is environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of hydroelectric power generation and energy storage, and in particular to a method for improving the complex flow inside a tailwater pipe of a pump turbine. Background Art

[0002] As a mature and reliable energy storage method, pumped storage power stations have the functions of peak load regulation, frequency regulation, phase regulation, emergency backup, and stable power system, and are an important part of hydropower development. The pump-turbine uses the same runner to realize forward rotation pumping as the pump working condition and reverse rotation power generation as the turbine working condition. It is a widely used power equipment in pumped storage power stations. Compared with conventional pump units or turbine units, pump-turbine working conditions are frequently changed and will face more complex internal flow characteristics.

[0003] Under power generation conditions, the tailwater pipe has the function of energy recovery and is the last flow component that allows the water to flow out stably. Under pumping conditions, the tailwater pipe is the first flow component that ensures that the water flows smoothly into the unit. Therefore, the internal flow characteristics of the tailwater pipe are crucial to the safety and stability of the unit. When the pump-turbine deviates from the optimal operating conditions, the flow of water in the tailwater pipe becomes extremely complex. After the high-speed vortex flows through the tailwater pipe, vortices and turbulence will be generated. The pressure at the center of the vortex is very low, and cavitation may occur. The water flow entrains cavitation bubbles to form a tailwater pipe vortex belt under the action of centrifugal force, and eccentricity occurs under the influence of periodic non-balanced factors, which increases the complexity and instability of the internal flow of the unit. The tailwater pipe vortex belt sometimes hits the side wall of the tailwater pipe, which causes cracks, misalignment, and empty shells in the tailwater pipe wall in severe cases. In addition, the pressure pulsation caused by the eccentric vortex of the tailwater under partial load conditions. This pressure pulsation can be decomposed into two parts: synchronous and asynchronous. The asynchronous part is caused by the movement of the vortex belt, which will cause strong noise. When the frequency of the synchronous part is close to the natural frequency of the system, it will cause unit resonance and damage to structural components. Summary of the invention

[0004] For the vibration problem caused by the complex internal flow of the tailwater pipe, the rotating flow intensity at the runner outlet can be reduced by arranging flow stabilizers, damping doors, guide plates, etc. in the tailwater pipe cone section, and air or water can be added at the runner discharge cone to weaken the cavitation vortex belt intensity in the tailwater pipe. The purpose of the present invention is to provide a method for improving the complex flow inside the tailwater pipe of a pump turbine, by arranging an adjustable guide baffle in the diffuser section of the tailwater pipe, adjusting the position and angle of the guide baffle, improving the complex flow inside the tailwater pipe, further eliminating or weakening the vortex, and at the same time ensuring that the tailwater pipe as the inlet component of the unit under pumping conditions allows the water flow to enter the runner smoothly, improving the flow performance of the water flow, and reducing the energy loss of the system.

[0005] The present invention provides the following technical solutions:

[0006] A method for improving the complex flow inside the draft tube of a pump turbine comprises the following steps:

[0007] S1: Referring to the data of the pump-turbine unit, a guide baffle is set in the diffuser section of the tailwater pipe. The guide baffle is located in the middle of the diffuser section. The internal flow characteristics of the unit with and without the guide baffle under different working conditions are compared to clarify the effect of the guide baffle on improving the vortex;

[0008] S2: According to different operating conditions, the position and angle of the guide baffle are adjusted in sequence, and the flow characteristics of the unit are analyzed respectively, and the internal connection between the unit operating point and the position and angle of the guide baffle is established accordingly;

[0009] S3: Based on the recorded results of the internal connection, determine the optimal guide baffle position and angle to achieve a design position that can balance efficiency and stability under different working conditions.

[0010] According to some embodiments, the guide baffle has two ends with variable radius sharp corners, and the middle is a structure with two parallel ends running through the diffusion section from top to bottom; the width of the guide baffle is 1% of the flow channel width of the diffusion section.

[0011] According to some embodiments, step S2 comprises the following steps:

[0012] S21: Firstly, the vortex structure, velocity distribution and pressure pulsation characteristics of the draft tube with and without the guide baffle are compared when the guide baffle is located at the center of the diffuser, and the effect of the guide baffle on the pump turbine is clarified;

[0013] S22: The guide baffle is translated based on the center line of the draft tube, and the guide baffle is adjusted and fixed according to the set translation amount. Under each translation amount, the flow characteristics of the unit are analyzed, and the inherent relationship between the vortex characteristics and the pressure pulsation characteristics of the draft tube and the translation amount of the guide baffle is established, and the suppression, destruction and reduction of the vortex are recorded;

[0014] S23: Adjust the angle of the guide baffle and fix the guide baffle according to the set angle. At each adjustment angle, analyze the flow characteristics of the unit, establish the intrinsic connection between the vortex characteristics and pressure pulsation characteristics of the tailwater pipe and the angle of the guide baffle, and record the suppression, destruction and reduction of the vortex.

[0015] According to some embodiments, the different operating conditions include non-design load conditions when the pump turbine is operating.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a method for improving the complex flow inside the tailwater pipe of a pump-turbine. Without the need for external power input, an adjustable guide baffle is arranged in the diffusion section of the tailwater pipe. By adjusting the angle and position of the guide baffle, the complex flow inside the tailwater pipe is improved, and the vortex is further eliminated or weakened. At the same time, the tailwater pipe is guaranteed to function as an inlet component of the unit under pumping conditions to enable water to smoothly enter the runner, thereby improving the flow performance of the water flow and reducing system energy loss.

[0018] The purpose of eliminating or weakening complex vortices is achieved by adjusting the position and angle of the tailwater pipe guide baffle. This method is economical and effective, has a simple structure, is easy to implement, has easy processing and manufacturing of components, and a green and environmentally friendly working process. It is suitable for various types of tailwater pipe structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A side view of a tailwater pipe provided in an embodiment of the present invention.

[0020] Figure 2 A top view of a tailwater pipe for adjusting the angle of a guide baffle provided in an embodiment of the present invention.

[0021] Figure 3 A top view of a tailwater pipe for adjusting the position of a guide baffle provided in an embodiment of the present invention.

[0022] Figure 4 A schematic diagram of a diffuser section provided in an embodiment of the present invention.

[0023] Figure 5 The cross-sectional position of the tailwater pipe provided in an embodiment of the present invention.

[0024] Figure 6 This is a streamline diagram of the first section without a guide baffle provided in an embodiment of the present invention.

[0025] Figure 7 A streamline diagram of the first cross section when the guide baffle is located in the middle, provided in an embodiment of the present invention.

[0026] Figure 8 This is a streamline diagram of the second section without a guide baffle provided in an embodiment of the present invention.

[0027] Fig. 9 A streamline diagram of the second cross section when the guide baffle is located in the middle, provided in an embodiment of the present invention.

[0028] Fig.10 A schematic diagram of the translation of the guide baffle provided in an embodiment of the present invention.

[0029] Fig.11 A schematic diagram of the simultaneous translation and rotation of the guide baffle provided in an embodiment of the present invention.

[0030] Fig.12 A streamline diagram of the first cross section when the guide baffle is set to translate according to an embodiment of the present invention.

[0031] Fig.13 A streamline diagram of the first cross section when the guide baffle is provided with simultaneous translation and rotation provided in an embodiment of the present invention.

[0032] Fig.14 A streamline diagram of the second cross section when the guide baffle is set to translate according to an embodiment of the present invention.

[0033] Fig.15 A streamline diagram of the second cross section when the guide baffle is provided with simultaneous translation and rotation provided in an embodiment of the present invention.

[0034] Fig.16 A flow chart of a method for improving complex flow inside a draft tube of a pump-turbine provided in an embodiment of the present invention.

[0035] In the figure:

[0036] 1. Straight cone section; 2. Elbow section; 3. Diffuser section; 4. Extension section; 5. Guide baffle; 6. First section; 7. Second section. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with the embodiments and drawings, but it should be understood that the embodiments and drawings are only used to exemplify the present invention and do not constitute any limitation on the protection scope of the present invention. All reasonable changes and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0038] like Figure 1 The tailwater pipe of the pump turbine includes a straight cone section 1, an elbow section 2, a diffuser section 3 and an extension section 4; water flows into the tailwater pipe through the straight cone section 1, flows through the elbow section 2, the diffuser section 3, and finally flows out from the extension section 4. Figure 4 .a is a top view of the diffusion section 3, as shown Figure 4 .b is a side view of the diffusion section 3.

[0039] The design idea of ​​the present invention is to target the obvious vortex structure inside the tailwater pipe under non-design conditions. The vortex belt in the tailwater pipe will be eccentric under the action of periodic non-equilibrium factors, and will make a spiral motion around the center of the tailwater pipe and rotate inward. After the vortex belt collides with the wall of the cone tube, a reflected wave is formed and propagates upstream. The flow field will be redistributed and a new vortex structure will be induced, while the tailwater pipe flow channel will be blocked, resulting in flow separation inside the tailwater pipe, especially the elbow section 2 and the diffuser section 3 are full of vortex motion, which will increase hydraulic losses, reduce efficiency, and generate vibration and noise, affecting the safe and stable operation of the power station.

[0040] like Fig.16 The present invention provides a method for improving the complex flow inside the draft tube of a pump turbine, the method comprising the following steps:

[0041] S1: Referring to the unit data, the guide baffle 5 is located in the middle of the diffuser section 3, and the internal flow characteristics of the unit with and without the guide baffle under different working conditions are compared.

[0042] In the above step S1, the guide baffle 5 is located in the middle of the diffuser section 3, and the shapes of the two ends of the guide baffle 5 are variable radius sharp angles to reduce the impact of water flow. The middle is a structural form in which the two ends are parallel and penetrate the diffuser section from top to bottom. The height of the guide baffle 5 matches the height of the tailwater diffuser section 3 and part of the elbow section 2. In order not to affect the flow of the tailwater flow channel, the width of the guide baffle 5 is small and is set to 1% of the flow channel width of the diffuser section 3.

[0043] S2: According to different working conditions, the position and angle of the guide baffle 5 are adjusted in sequence, and the flow characteristics of the unit are analyzed respectively to establish the internal connection between the unit operating point and the position and angle of the guide baffle;

[0044] The principle of step S2 is: firstly, the internal flow analysis of the pump-turbine tailwater pipe without the guide baffle is carried out to clarify the effect of the guide baffle 5 on the internal flow of the tailwater pipe. It is found that under non-design conditions, the generation of vortex flow in the straight cone section 1 of the tailwater pipe leads to uneven distribution of flow. The guide baffle 5 can redistribute the flow and hinder the propagation of the downstream of the tailwater pipe under the vortex structure. According to the uneven analysis of flow, the position of the guide baffle 5 is adjusted by translation left and right along the position of the center line of the tailwater pipe, and the flow characteristics of the tailwater pipe under different positions are analyzed to expand the vortex flow channel, reduce the vortex area, improve the hindering effect of the vortex area on the water flow, and make the flow inside the unit smooth.

[0045] According to the analysis of the vortex structure, the angle of the guide baffle 5 is further adjusted to change the angle of attack of the water flow and reduce the angle of attack of the vortex water flow, so that the flow in the tailwater pipe is smoother.

[0046] Different working conditions include non-design working conditions when the pump turbine is running, such as 75% load, 50% load, and 20% load. At the same time, it is also necessary to ensure smooth water flow at the tailwater pipe inlet under pumping conditions.

[0047] Therefore, under the operating condition of the pump turbine, S2 specifically includes the following steps:

[0048] S21: Considering the vortex formation mechanism and the feasibility of adjustment, translation adjustment is preferred: it can directly change the complex flow caused by uneven flow distribution, improve the degree of obstruction of the vortex structure to the water flow, and thus affect the formation and propagation of the vortex. First, when the guide baffle is located at the center of the diffuser, the vortex structure, velocity distribution, pressure pulsation and other characteristics of the tailwater pipe with and without the guide baffle are compared to clarify the role of the guide baffle on the pump turbine.

[0049] S22: The guide baffle is translated based on the center line of the draft tube, and the guide baffle is adjusted and fixed according to the set translation amount. Under each translation amount, the flow characteristics of the unit are analyzed, and the inherent relationship between the vortex characteristics and the pressure pulsation characteristics of the draft tube and the translation amount of the guide baffle is established, and the suppression, destruction and reduction of the vortex are recorded;

[0050] S23: After the analysis of the translation adjustment results is completed, further consider angle adjustment. At this time, by adjusting the angle of the guide baffle, the flow direction and speed of the water flow can be changed to reduce the angle of the water flow, so as to further optimize the vortex control effect. The guide baffle is adjusted and fixed according to the set angle. At each adjustment angle, the unit flow characteristics are analyzed to establish the intrinsic connection between the tailwater pipe vortex characteristics and pressure pulsation characteristics and the guide baffle angle, and the suppression, destruction and reduction of the vortex are recorded;

[0051] S3: Based on the recorded results, determine the optimal baffle position and angle to achieve a design position that balances efficiency and stability under different working conditions, and incorporate it into the design document for reference during actual manufacturing and installation to ensure that the final product can meet the expected performance requirements.

[0052] The above method effectively improves the complex flow inside the tailwater pipe, while ensuring that the tailwater pipe, as the inlet component of the unit, can smoothly enter the runner under pumping conditions, thereby improving the fluidity and stability of the water flow in the unit.

[0053] The present invention will be further described below in conjunction with the accompanying drawings.

[0054] Example 1

[0055] The turbine operating conditions (i.e. power generation conditions) can be 75%, 50% and 20%. The following takes the power generation condition of 50% load as an example. Under 50% load, the working process of the pump turbine tailwater pipe is as follows:

[0056] like Figure 1As shown, the water flows into the tailwater pipe through the straight cone section 1, flows through the elbow section 2, the diffuser section 3, and finally flows out of the extension section 4. Above the water inlet of the straight cone section 1, the runner cone rotates to make the water flow have a rotating circulation. When the rotating component increases to a certain extent, a tailwater pipe vortex belt will be formed and move downstream, and make a spiral motion around the center of the tailwater pipe and rotate inward. After the vortex belt collides with the wall of the cone tube, a reflected wave is formed and propagates upstream. The flow field will be redistributed and induce a new vortex structure, while blocking the tailwater pipe flow channel, causing flow separation inside the tailwater pipe, especially the elbow section and the diffuser section are full of vortex motion, affecting the safety and stability of the unit.

[0057] Taking the pump turbine runner of a certain energy storage power station as an example, the internal flow of the tailwater pipe is improved as follows:

[0058] First, a guide baffle 5 is set in the middle of the tailwater pipe diffusion section 3, and numerical calculations are performed to compare the internal flow characteristics of the unit with and without the guide baffle under 50% load in power generation conditions. The results show that the guide baffle will have a certain hindering effect on the generation of vortices, and some vortex bands in the straight cone section of the tailwater pipe will be partially dispersed when moving downstream, preventing the pressure disturbance from propagating to the upstream of the tailwater pipe, but the improvement effect of the internal flow can be further improved.

[0059] The numerical calculation process is as follows:

[0060] 1. Establish the tailwater pipe model: First, use UG software to establish the geometric model of the tailwater pipe system. Ensure that the model accurately reflects the actual engineering situation, including the size, shape and layout of the adjacent components of the tailwater pipe. Secondly, install the guide baffle inside the tailwater pipe diffuser, usually from a small part at the end of the elbow section to the entire diffuser. Ensure that the position of the baffle can effectively prevent the formation and propagation of vortices.

[0061] 2. Meshing: Discretize the tailwater model into finite volume meshes. This step is to accurately calculate the flow field during the numerical solution process. Special attention should be paid to the meshing around the baffle to ensure fine mesh resolution.

[0062] 3. Set boundary conditions: In the simulation, you need to set the inlet and outlet boundary conditions of the flow field, as well as the boundary conditions of the baffle surface. The inlet boundary conditions can be set according to the actual water flow conditions, and the boundary conditions of the baffle surface are set as no-slip wall.

[0063] 4. Select turbulence model: Considering numerical stability and convergence, select turbulence model.

[0064] 5. Solve the flow field equations: Based on the selected numerical method, the computational fluid dynamics (CFD) software is used to numerically solve the flow of water in the tailwater pipe. Through iterative calculations, the internal flow characteristics such as the velocity field and pressure field of the flow field are solved.

[0065] 6. Evaluate the baffle setting scheme: Analyze the numerical simulation results and evaluate the impact of different baffle setting schemes on vortex formation and propagation.

[0066] 7. Optimization design: According to the evaluation results, adjust the size, shape and position of the partitions and re-run the numerical simulation. Through repeated iterations of optimization design, the optimal partition setting scheme is found to improve the flow state inside the unit.

[0067] Secondly, if Figure 2 , adjust the position of the guide baffle. When the guide baffle is located in the middle of the tailwater pipe, due to the generation of the tailwater pipe vortex, the flow distribution of the flow channel on both sides of the guide baffle is not uniform, which will lead to complex internal flow in the elbow section and the diffuser section. Based on this, the position of the guide baffle is adjusted, and the l value is selected as 0.3m, 1m, -0.3m and -1m respectively. Observe the deviation degree of the vortex motion trajectory with the change of the guide baffle position, change the vortex motion trajectory, and achieve the purpose of improving the internal flow of the tailwater pipe.

[0068] Secondly, if Figure 3 , analyze the internal flow characteristics of the tailwater pipe under different guide baffle angles. At the same time, it should be noted that if the angle is too large, it will hinder the flow of the tailwater pipe. At the same time, the flow stability of the tailwater pipe inlet under pumping conditions cannot be guaranteed. Therefore, the adjustment of the guide baffle angle in this embodiment is relatively small, taking 1°, 2°, 3°, 4° and 5° respectively, and the reverse direction is -1°, -2°, -3°, -4° and -5°. Analyze the flow characteristics of the unit under these 10 conditions of the guide baffle, establish the intrinsic connection between the vortex characteristics and pressure pulsation characteristics of the tailwater pipe and the guide baffle angle, suppress, destroy and reduce the vortex, and improve the flow state of the unit.

[0069] Finally, the flow channels in the tailwater pipe divided by the guide baffles converge in the extension section 4. Through the improvement of the flow in the diffusion section by the guide baffles, the rotation of the low-speed spiral motion vortex gradually tends to be stable, the flow impact at the tailwater pipe outlet is reduced, the mutual collision between the water flows is reduced, the loss is reduced, the pressure pulsation is reduced, the energy recovery rate is improved, and the operating efficiency of the unit is increased.

[0070] Under pumping conditions, the tailwater pipe serves as the inlet of the pump-turbine. The internal flow characteristics of the unit are analyzed when the pump is running according to the position and angle of the guide baffle under the above optimal condition, including pressure, velocity and other characteristics of each part, to ensure the fluidity and stability of the water flow of the pump-turbine under pumping conditions with the guide baffle added.

[0071] After adjusting the position and angle of the guide baffle of the tailwater pipe, the internal flow state of the power generation condition (i.e., turbine condition) is improved. However, in practice, the energy storage unit will also operate in the pumping condition (i.e., water pump condition). At this time, the tailwater pipe serves as the inlet, and the addition of the guide baffle 5 does not affect the smooth flow of water in the pumping condition.

[0072] This embodiment is the calculation result under 50% load of power generation condition, in which when the guide baffle 5 is in the middle position of the tailwater pipe, such as Figure 5 The flow conditions of the first section 6 and the second section 7 are compared in two cases where there is no guide baffle 5 and the guide baffle 5 is located at the middle center position, wherein the first section 6 is located above the guide baffle 5 and the second section 7 is located below the guide baffle 5.

[0073] like Figure 6 and Figure 7 The results shown are as follows: for the first section, the guide baffle 5 can effectively reduce the vortex motion of the tailwater elbow section 2, and at the same time improve the vortex structure on the middle flow channel of the diffuser section 3. Figure 8 and Fig. 9 As shown, for the second cross section, the tailwater pipe elbow section 2 without the guide baffle generates a large number of vortices, and the vortex motion continues to the tailwater pipe diffuser section 3. When the guide baffle 5 is added, the vortex structure of the elbow section changes, and the vortex motion of the diffuser section 3 disappears. It can be seen that the guide baffle 5 can improve the flow characteristics inside the tailwater pipe, and the improvement effect can be further improved by changing the position and angle of the guide baffle 5.

[0074] The guide baffle 5 is moved 0.3m to one side from the middle position of the tailwater pipe. Fig.10 The guide baffle 5 is translated from the middle position of the tailwater pipe to one side and rotated 2° clockwise, as shown in FIG. Fig.11 The flow conditions of the first section 6 and the second section 7 are compared in two cases where the guide baffle 5 only translates and translates and rotates at the same time, wherein the first section 6 is located above the guide baffle 5 and the second section 7 is located below the guide baffle 5.

[0075] like Fig.12 and Fig.13 Results shown: For the first section, the overall flow of the translational guide baffle 5 is uniform and smooth, but some areas, such as the diffuser 3, still have some unsmooth flow. In addition, the rotation effectively reduces the turbulence of the flow, and the flow in the diffuser is basically parallel to the contour of the tailwater pipe, reducing energy consumption. Fig.14 and Fig.15As shown, for the second cross section, after the guide baffle 5 is translated, the vortex flow in the tailwater elbow section 2 and the diffuser section 3 is improved to a certain extent, and after the guide baffle is rotated, the vortex near the outlet position of the diffuser section 3 disappears. It can be seen that the guide baffle 5 can improve the flow characteristics inside the tailwater pipe, and the improvement effect can be further improved by changing the position and angle of the guide baffle 5.

[0076] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for improving the complex flow inside the draft tube of a pump turbine, comprising the following steps: S1: Referring to the data of the pump-turbine unit, a guide baffle is set in the diffuser section of the tailwater pipe. The guide baffle is located in the middle of the diffuser section. The internal flow characteristics of the unit with and without the guide baffle under different working conditions are compared to clarify the effect of the guide baffle on improving the vortex; S2: According to different operating conditions, the position and angle of the guide baffle are adjusted in sequence, and the flow characteristics of the unit are analyzed respectively, and the internal connection between the unit operating point and the position and angle of the guide baffle is established accordingly; S3: Based on the recorded results of the internal connection, determine the optimal guide baffle position and angle to achieve a design position that can balance efficiency and stability under different working conditions.

2. The method for improving the complex flow inside the draft tube of a pump turbine according to claim 1, characterized in that: The two ends of the guide baffle are in the shape of variable radius sharp corners, and the middle is a structure with two parallel ends running through the diffusion section from top to bottom; the width of the guide baffle is 1% of the flow channel width of the diffusion section.

3. The method for improving the complex flow inside the draft tube of a pump turbine according to claim 1, characterized in that: Step S2 includes the following steps: S21: Firstly, the vortex structure, velocity distribution and pressure pulsation characteristics of the draft tube with and without the guide baffle are compared when the guide baffle is located at the center of the diffuser, and the effect of the guide baffle on the pump turbine is clarified; S22: The guide baffle is translated based on the center line of the draft tube, and the guide baffle is adjusted and fixed according to the set translation amount. Under each translation amount, the flow characteristics of the unit are analyzed, and the inherent relationship between the vortex characteristics and the pressure pulsation characteristics of the draft tube and the translation amount of the guide baffle is established, and the suppression, destruction and reduction of the vortex are recorded; S23: Adjust the angle of the guide baffle and fix the guide baffle according to the set angle. At each adjustment angle, analyze the flow characteristics of the unit, establish the intrinsic connection between the vortex characteristics and pressure pulsation characteristics of the tailwater pipe and the angle of the guide baffle, and record the suppression, destruction and reduction of the vortex.

4. The method for improving the complex flow inside the draft tube of a pump turbine according to claim 1, characterized in that: The different operating conditions include non-design load conditions when the pump turbine is running.

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