Multi-vortex-eliminating and vibration-reducing structure of mixed-flow water turbine

Abstract

The invention belongs to the technical field of vortex elimination and vibration reduction, and relates to a multiple vortex elimination and vibration reduction structure of a mixed-flow water turbine. The multiple vortex elimination and vibration reduction structure comprises a turbulent flow structure, the turbulent flow structure comprises vortex suppression fins and trailing edge sawteeth, the vortex suppression fins are arranged on the suction surface of a runner blade, and the trailing edge sawteeth are arranged on the trailing edge of the runner blade; the adjustable guide vane comprises an upper guide vane and a lower guide vane, the upper guide vane is rotatably arranged on the inner wall of the draft tube, and the lower guide vane is fixed on the inner wall of the draft tube; the air supply module comprises a first air supply structure and a second air supply structure; the detection module is used for detecting the running state of the mixed-flow water turbine; the control module is used for adjusting the upper guide vane to restrain pressure pulsation of the mixed-flow water turbine, controlling the first air supply structure to supply air into the draft tube and controlling the second air supply structure to supply air to the periphery of the tail of the runner cone. According to the multi-vortex-eliminating and vibration-reducing structure, various vortex sources can be effectively inhibited in various operation working conditions of the mixed-flow water turbine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of vortex elimination and vibration reduction, and relates to a multiple vortex elimination and vibration reduction structure of a Francis turbine. BACKGROUND

[0002] With the large-scale construction of pumped storage power stations and large-capacity Francis turbines, the operating conditions of Francis turbines are becoming increasingly complex. In particular, under partial load, large-scale vortex ropes are easily formed in the draft tube, which produces significant low-frequency pressure pulsation, and further induces equipment vibration, noise and structural fatigue. The vortex-induced vibration frequency is generally 0.2-0.4 times the runner speed, and the amplitude is significant, which poses a threat to the safety of Francis turbines.

[0003] To alleviate the above problems, current methods mainly include draft tube aeration, nozzle water injection, J-shaped groove disturbance and additional disturbance vane, etc. These traditional vortex elimination and vibration reduction schemes can eliminate vortex and reduce vibration under certain conditions, but have problems such as poor adaptability, efficiency loss or complex structure. For example, most of these schemes can only target a certain type of vortex source (such as only targeting vortex bands or only targeting Karman vortex streets), and lack the ability to systematically and cooperatively manage multiple vortex sources such as blade passage vortex, Karman vortex street and draft tube vortex band. Moreover, most of these schemes can only improve vortex sources under a certain specific operating condition. When factors such as water head and load change significantly, the vortex elimination effect of these vortex elimination and vibration reduction schemes will decrease or even fail, making it difficult to adapt to the wide load operation requirements of Francis turbines. Therefore, there is an urgent need for improvement. SUMMARY

[0004] In view of the defects or improvement needs of the prior art, the application provides a multiple vortex elimination and vibration reduction structure of a Francis turbine, which can effectively suppress various vortex sources in multiple operating conditions of the Francis turbine and adapt to the wide load operation requirements of the Francis turbine.

[0005] The multiple vortex elimination and vibration reduction structure of the Francis turbine provided by the application comprises: A disturbance structure comprising vortex suppression vanes and tail edge serrations, the vortex suppression vanes being arranged on the suction surface of the runner blades, and the tail edge serrations being arranged on the tail edge of the runner blades; Adjustable guide vanes are arranged on the inner wall of the draft tube in a circumferential direction at uniform intervals, and comprise upper guide vanes and lower guide vanes, the upper guide vanes being rotatably arranged on the inner wall of the draft tube with their lower ends as the rotation center, and the lower guide vanes being fixed on the inner wall of the draft tube below the upper guide vanes; A gas supplementing module comprising a first gas supplementing structure and a second gas supplementing structure, the first gas supplementing structure being arranged on the inner peripheral wall of the draft tube, and the second gas supplementing structure being arranged at the tail of the water discharge cone; A detection module for detecting the operating state of the Francis turbine; The control module is configured to adjust the angle of the upper guide vane based on the detection result of the detection module to suppress the pressure pulsation of the Francis turbine, and control the first air supplementing structure to supplement air into the draft tube when the upper guide vane adjustment reaches a preset angle; and control the second air supplementing structure to supplement air around the tail part of the water release cone when the detection signal shows that the pressure pulsation amplitude exceeds a preset threshold.

[0006] As a further preferred, the vortex suppression wing is fixedly arranged at three positions along the height direction of the runner blade, and the three positions are 25%, 50% and 75% of the height of the runner blade.

[0007] As a further preferred, the chord length of the vortex suppression wing is 30%-50% of the chord length of the runner blade, the height is 15%-35% of the thickness of the runner blade, and the width is 100%-150% of the height.

[0008] As a further preferred, the tail edge serration is arranged in a region of 40%-95% of the height of the runner blade at the water outlet side, the tooth height of the tail edge serration is 100%-200% of the boundary layer thickness of the runner blade, and the tooth width is 200%-500% of the boundary layer thickness of the runner blade.

[0009] As a further preferred, the tail edge serration is formed by cutting the tail edge of the runner blade, and a fillet is arranged at the tooth tip and the tooth root of the tail edge serration.

[0010] As a further preferred, the radius of the fillet is 10%-20% of the tooth height of the tail edge serration.

[0011] As a further preferred, the adjustable guide vane is uniformly distributed along the circumference of the inner wall of the draft tube, and the chord length of the upper guide vane and the lower guide vane is 0.8R-0.95R, the effective span height of the upper guide vane and the lower guide vane is 0.25R-0.35R, the axial distance of the upper guide vane from the inlet of the draft tube is 0.3R-0.45R, and R is the radius of the runner of the Francis turbine.

[0012] As a further preferred, the deflection angle range of the upper guide vane relative to the design streamline of the draft tube is ±45°, and the included angle between the lower guide vane and the design streamline of the draft tube is -10°.

[0013] As a further preferred, the inner wall of the draft tube is provided with an arc-shaped limiting groove, the upper end of the upper guide vane is connected with a limiting block, and the limiting block is located in the limiting groove and can slide along the extension direction of the limiting groove.

[0014] As a further preferred, the detection module comprises a first pressure sensor for detecting the pressure of the tail pipe inlet section, a second pressure sensor for detecting the pressure of the vortex belt starting end near the draft tube, a power sensor for detecting the load of the Francis turbine, and a water head sensor for detecting the size of the water head of the Francis turbine operation.

[0015] As a further preferred, the control module is used to analyze and determine the current operating condition of the Francis turbine based on the detection results of the detection module, and to match the information in the database in the control module based on the current operating condition to determine the optimal guide vane angle corresponding to the current operating condition, and then issue an instruction to adjust the upper guide vane rotation adjustment to the optimal guide vane angle.

[0016] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages: 1. The multiple vortex suppression and vibration reduction structure of the present application has excellent working condition adaptability and intelligent level. The vortex suppression wing can suppress the generation of the blade channel vortex from the source, the tail edge serration can effectively break the Karman vortex street of the blade outflow edge, the adjustable guide vane can be adjusted in angle under the control of the control module to cut, guide and dissipate the residual vortex belt entering the draft tube, and the air supplement module can reduce the strong spiral vortex belt. These structures together constitute a full-process, multi-scale collaborative vortex suppression and vibration reduction structure from source suppression, near-field breaking, active intervention to safety redundancy, which can adapt to various working conditions in the operation of the Francis turbine and suppress various vortex sources, meeting the needs of wide load operation of the Francis turbine.

[0017] 2. The multiple vortex suppression and vibration reduction structure in the present application takes the adjustable guide vane and the first air supplement structure at the draft tube as the first main control part, which is responsible for processing the flow state optimization under most working conditions and pursuing efficient vortex suppression. At the same time, the second air supplement structure at the draft tube is taken as a backup measure as a safety insurance. The air supplement function of the second air supplement structure is only started when the pressure pulsation amplitude exceeds the preset threshold and the vibration exceeds the limit. This design avoids the efficiency loss caused by the constant opening of the air supplement, and ensures that the entire device can operate in an economic and optimized direction under all working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a cross-sectional view of a multiple vortex suppression and vibration reduction structure of a Francis turbine provided by an embodiment of the present application; Figure 2 is a layout diagram of an adjustable blade and a first air supplement structure provided by an embodiment of the present application; Figure 3 is a speed streamline diagram of the suction surface of a runner blade with vortex suppression wing under rated working condition provided by an embodiment of the present application; Figure 4This is a schematic diagram of the vortex-suppressing blade provided in an embodiment of this application; Figure 5 This is a diagram showing the arrangement of the trailing edge serrations provided in an embodiment of this application; Figure 6 This is a schematic diagram of the adjustable guide vane provided in an embodiment of this application.

[0019] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1. Vortex suppressor blade; 2. Trailing edge serration; 3. Upper guide vane; 4. Lower guide vane; 5. First air supply structure; 6. Second air supply structure; 7. First pressure sensor; 8. Second pressure sensor; 100. Runner blade; 200. Tailwater pipe; 300. Drain cone; 400. Limiting groove. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] The following is in conjunction with the appendix Figures 1-6 This application will be described in further detail.

[0022] This application discloses a multi-stage vortex-eliminating and vibration-damping structure for a mixed-flow turbine. (Refer to...) Figure 1 and Figure 2The multi-stage vortex suppression and vibration reduction structure includes a turbulence structure, adjustable guide vanes, an air supply module, a detection module, and a control module. The turbulence structure includes vortex-suppressing vanes 1 and trailing edge serrations 2. The vortex-suppressing vanes 1 are disposed on the suction surface of the impeller blade 100 and extend along the velocity streamline direction of the suction surface of the impeller blade 100 under rated operating conditions. The trailing edge serrations 2 are disposed on the trailing edge of the impeller blade 100 and extend along the length of the trailing edge. Multiple adjustable guide vanes are evenly spaced circumferentially on the inner wall of the tailwater pipe 200. The guide vanes include an upper guide vane 3 and a lower guide vane 4. The upper guide vane 3 is rotatably and adjustablely mounted on the inner wall of the tailrace pipe 200 with its lower end as the center of rotation. The lower guide vane 4 is fixed to the inner wall of the tailrace pipe 200 and located below the upper guide vane 3, with the upper end of the lower guide vane 4 adjacent to the lower end of the upper guide vane 3. The air supply module includes a first air supply structure 5 and a second air supply structure 6. The first air supply structure 5 is mounted on the inner circumferential wall of the tailrace pipe 200, and the second air supply structure 6 is mounted at the tail of the discharge cone 300. The detection module is used to detect the operating status of the mixed-flow turbine. The control module is used to adjust the angle of the upper guide vane 3 based on the detection results of the detection module to suppress the pressure pulsation of the mixed-flow turbine, and to control the first air supply structure 5 to supply air into the tailrace pipe 200 when the upper guide vane 3 is adjusted to a preset angle; and to control the second air supply structure 6 to supply air around the tail of the discharge cone 300 when the detection signal shows that the pressure pulsation amplitude exceeds a preset threshold.

[0023] Furthermore, such as Figure 3 and Figure 4 As shown, in some embodiments, multiple vortex suppressor blades 1 are spaced apart along the blade height direction of the rotor suction surface; specifically, three vortex suppressor blades 1 are fixedly spaced at positions of 25%, 50%, and 75% of the blade height relative to the rotor blade 100 along the blade height direction of the rotor blade 100; the chord length of the vortex suppressor blade 1 is 30% to 50% of the chord length of the rotor blade 100, the chord height of the vortex suppressor blade 1 is 15% to 35% of the thickness of the rotor blade 100, and the chord height of the vortex suppressor blade 1 is 100% to 150% of the chord height.

[0024] Furthermore, such as Figure 5 As shown, in some embodiments, the tooth height of the trailing edge serration 2 is 100% to 200% of the blade boundary layer thickness of the rotor blade 100, and the tooth width is 200% to 500% of the blade boundary layer thickness of the rotor blade 100. The trailing edge serration 2 is disposed in a region of 40% to 95% relative to the blade height of the rotor blade 100 along the blade height direction.

[0025] Furthermore, such as Figure 1As shown, in some embodiments, the second air replenishment structure 6 includes an air replenishment channel that extends from the hollow inner cavity of the drain cone 300 to the outer wall of the drain cone 300. Multiple sets (such as three sets) of air replenishment channels are arranged vertically. Preferably, each set includes multiple air replenishment channels evenly arranged along the circumference of the drain cone 300.

[0026] Correspondingly, an air supply device (not shown in the figure) is provided at the center of the impeller spindle and the drain cone or other suitable locations. The air supply device can supply air to the air supply channel under the control of the control module, and supply air to the guide zone of the drain cone 300 through the air supply channel to achieve vortex suppression. At the same time, the air supply device can also be used to supply air to the first air supply structure 5 under the control of the control module.

[0027] Furthermore, such as Figure 1 As shown, in some embodiments, two sets of second pressure sensors 8 are arranged above and below the surface of the drain cone 300. The second pressure sensors 8 are used to monitor the pressure pulsation at the starting end of the vortex of the tailrace pipe 200. Preferably, when the pressure pulsation amplitude detected by the second pressure sensor 8 is greater than a preset value, such as pressure pulsation amplitude ΔH>2.5% Hr (rated head), and continues for a preset duration (such as 0.5 seconds), the control module triggers an air replenishment command to control the air replenishment device to supply air to the air replenishment channel.

[0028] Furthermore, such as Figure 2 As shown, in some embodiments, three adjustable guide vanes are evenly distributed circumferentially on the inner wall of the tailrace 200. The chord lengths of the upper guide vane 3 and the lower guide vane 4 are 0.8R~0.95R, the spanwise heights of the upper guide vane 3 and the lower guide vane 4 are 0.25R~0.35R, and the axial distance between the upper guide vane 3 and the inlet of the tailrace 200 is 0.3R~0.45R, more preferably 0.35R~0.40R, where R is the impeller radius of the mixed-flow turbine. Figure 6 As shown, the deflection angle range of the upper guide vane 3 relative to the design streamline of the tailrace pipe 200 is ±45°; the angle between the lower guide vane 4 and the design streamline of the tailrace pipe 200 is ~10°, where the negative sign indicates that the lower guide vane 4 deflects clockwise relative to the design streamline of the tailrace pipe 200. The upper guide vane 3 is driven to rotate by a drive device to adjust the deflection angle; this drive device is controlled by the control module.

[0029] Preferred, such as Figure 6 As shown, in some embodiments, the upper guide vane 3 and the lower guide vane 4 are basically the same size, and they present a sheet-like structure that is thicker at one end and narrower at the other. Furthermore, the upper guide vane 3 is narrower at the top and wider at the bottom, while the lower guide vane 4 is wider at the top and narrower at the bottom. The lower end of the upper guide vane 3 is close to the upper end of the lower guide vane 4. Both the upper guide vane 3 and the lower guide vane 4 are in contact with the inner wall surface of the tailwater pipe 200.

[0030] In some embodiments, the lower end of the upper guide vane 3 is rotatably mounted on the tailwater pipe 200 via a sealed drive shaft, which is driven by a servo motor mounted on the outer wall of the tailwater pipe 200. To ensure the stability of the upper guide vane 3, the inner wall of the tailwater pipe 200 is provided with an arc-shaped, non-through limiting groove 400, the arc-shaped extension direction of which matches the rotation trajectory of the upper guide vane 3; correspondingly, the upper end of the upper guide vane 3 is connected to a limiting block, which is located within the limiting groove 400 and can slide and adjust along the extension direction of the limiting groove 400; the swing range of the upper guide vane 3 is limited by the inner wall surface of the limiting groove 400, thereby limiting the deflection angle.

[0031] Furthermore, such as Figure 2 As shown, in some embodiments, the first air replenishment structure 5 includes a plurality of air replenishment holes disposed on the wall of the tailrace pipe 200, and the air replenishment holes are preferably distributed between adjacent adjustable guide vanes. For example, when three adjustable vanes are provided, three air replenishment holes are disposed vertically at intervals on the wall of the tailrace pipe 200 between two adjacent adjustable vanes, for a total of twelve air replenishment holes disposed on the wall of the tailrace pipe 200 to form an air replenishment ring, and the air replenishment holes are connected to the air replenishment device. Generally, a device such as a switching valve controlled by a detection module can be provided to control the on / off state between the air replenishment holes and the air replenishment device, and the on / off state between the air replenishment device and the air replenishment channel is similarly configured.

[0032] Furthermore, such as Figure 2 As shown, the first pressure sensor 7 is installed on the wall of the inlet section of the tailrace pipe 200. The first pressure sensor 7 is preferably a high-frequency pressure sensor, which is preferably installed on the wall of the inlet section at a height of about 0.2R from the top, with three sensors equidistant from each other in the circumference to form a sensor array. The arrangement of other sensors, such as the power sensor and the head sensor, is not described in detail here.

[0033] Furthermore, in some embodiments, the control module includes a PLC (Programmable Logic Controller) or is located in the control room of a hydropower station. The control module acquires signals from the first pressure sensor 7 in real time, performs Fast Fourier Transform (FFT) spectrum analysis to extract the dominant frequency (typically 0.3-0.4 times the rotational speed) and amplitude of the pressure pulsation under the current operating condition, and acquires detection information from other sensors. Additionally, the control module can perform operating condition judgment and target optimization; for example, the control module has a built-in database containing pre-stored optimal guide vane angle MAPs under different operating conditions. These MAPs are obtained through prior CFD calculations and model experiments to establish the correspondence between operating conditions, optimal guide vane angles, and pulsation amplitudes. The control module combines the power information obtained from the power sensor and the head signal obtained from the head sensor to determine the current operating condition point of the mixed-flow turbine (e.g., 40% BEP, 80% BEP). Based on the determined current operating condition point, it matches the optimal guide vane angle MAP diagram under the corresponding operating condition. Based on the optimal guide vane angle MAP diagram, it adjusts the adjustable guide vanes to the angle corresponding to the optimal guide vane angle MAP diagram.

[0034] In actual use, the control module compares the pressure pulsation amplitude monitored in real time by the first pressure sensor 7 with the target value based on the detection results of the detection module. Then, it uses a PID (proportional-integral-derivative) control algorithm or a fuzzy adaptive control algorithm to dynamically calculate and output a control signal to the drive device. This drive device adjusts the angle of the upper guide vane 3, ensuring that the multi-vortex suppression and vibration reduction structure always operates in the optimal vortex suppression state. When the guide vane rotates to a preset angle (a set of specific angles, based on a pre-stored MAP diagram, where the flow around these preset angles is prone to generate vortex shedding at a specific frequency, producing high-frequency noise), the control module controls the air supply device to open the air supply hole at the tailrace pipe 200 to suppress high-frequency noise and achieve vortex suppression and vibration reduction.

[0035] In this design, the air injection at the adjustable guide vane and tailrace 200 has a higher priority than the air injection at the drain cone 300, serving as the primary control. Generally, the adjustment of the adjustable guide vane and the air injection at the tailrace 200 are responsible for handling flow optimization under most operating conditions, pursuing efficient vortex suppression. The air injection at the tailrace 200 is mainly used to suppress high-frequency vortex shedding and local cavitation that may be caused by the adjustable guide vane itself, and provides fine-tuning in addition to guide vane adjustment. The air injection at the drain cone 300 is mainly a safety precaution, serving as a secondary backup, and is only activated when the pressure pulsation amplitude exceeds the limit. This design avoids the efficiency loss caused by constantly open air injection, which helps ensure that the entire structure can operate in the most economical and optimized manner under all operating conditions.

[0036] In fact, this multi-stage vortex-eliminating and vibration-damping structure can be divided into the following four parts based on the design content.

[0037] (1) Vortex suppressor blade 1 on the suction surface of the rotor blade: Arrangement location: 25%, 50%, and 75% of the blade height on the suction surface of the impeller, with the 50% position being preferred for initial placement.

[0038] The chord length L1 of the blade is 30% to 50% of the chord length of the local blade (i.e., the rotor blade 100 where the vortex suppressor blade 1 is located), preferably 40%. This range can ensure effective disturbance of the vortex initiation streamline of the blade passage. Too long will increase drag, and too short will result in insufficient vortex suppression effect.

[0039] The blade height h1 is 15% to 35% of the local blade thickness, preferably 25%. This height can effectively lift low-energy fluids and suppress boundary layer separation. Too high a height may cause flow blockage, while too low a height will not have a significant effect.

[0040] The wing width b is (1.0~1.5) times the wing height h1, preferably 1.3 times. This aspect ratio can form a stable micro-guide structure.

[0041] (2) The trailing edge serration 2 of the rotor blade 100: Tooth height h: 1.0δ~2.0δ, where δ is the local blade boundary layer thickness, preferably h=1.5δ. When h<1.0δ, the disturbance cannot penetrate the boundary layer and the effect is weak; when h>2.0δ, flow separation intensifies, which may increase drag and induce high-frequency noise. The preferred value of 1.5δ achieves the best balance between effectively disrupting the Karman vortex street and controlling side effects.

[0042] Tooth width λ: 2.0h~5.0h, preferably λ=3h (i.e. λ=4.5δ). When λ<2.0h, the teeth are too dense, the perturbation vortex size is too small, and the energy dissipation is too fast; when λ>5.0h, the teeth are too sparse, and the breaking effect on the vortex street is discontinuous. The preferred value of 3h can produce the vortex structure with the most suitable scale and promote energy dissipation.

[0043] Coverage area: 40%~95% of the blade height at the blade exiting the water (tail edge), preferably 50%~90%. This area is the main vortex zone, and targeted modification here will yield the highest benefits.

[0044] Process characteristics: The tooth tip and root need to be rounded, with a radius r≈(0.1~0.2)h, preferably 0.15h. This can avoid stress concentration, improve fatigue life, and prevent the generation of sharp vortex shedding noise.

[0045] (3) The intelligent sensing and air replenishment system of the drain cone, consisting of the second air replenishment structure 6, the second pressure sensor 8, and the control module: Sensing arrangement: Two second pressure sensors 8 are arranged on the surface of the drain cone 300 to monitor the pressure pulsation at the beginning of the vortex.

[0046] Trigger threshold: When the monitored pressure pulsation amplitude ΔH > 2.0%~3.0% Hr (rated head) and lasts for 0.3~1.0 seconds, the control module triggers the second air supply structure 6 at the drain cone 300 to supply air. The preferred threshold is 2.5% Hr, lasting for 0.5 seconds.

[0047] Control Logic: This system serves as a secondary backup strategy. It is typically activated only when the adjustable guide vanes at 200mm in the tailrace pipe have been adjusted to their limits but still cannot suppress strong vortices, and the pressure pulsation amplitude exceeds the preset threshold.

[0048] (4) A combined control system consisting of an adjustable guide vane at tailrace pipe 200, a first air supply structure 5, a control module, and a detection module: Number of guide vanes: 3, evenly arranged in a circumferential pattern at 120° intervals.

[0049] Guide vane chord length: 0.8R~0.95R, preferably 0.86R, where R is the impeller radius. This length can effectively cut and guide vortex structures of the desired size.

[0050] Effective spanwise height: 0.25R~0.35R, preferably 0.30R. This can cover the high-energy core region of the 200mm tailrace inlet flow field.

[0051] Axial distance: 0.30R~0.45R from the impeller outlet, preferably 0.35R~0.40R. This position is a key intervention point for the initial formation of the vortex belt, but it has not yet fully developed.

[0052] Adjustable structure: The upper guide vane 3 (adjustable blade) can deflect within an angle range of ±45°; the lower guide vane 4 is fixed to the tailwater pipe 200 with a design streamline of approximately -10°.

[0053] Drive unit: Each adjustable upper guide vane 3 is equipped with an independent servo motor, which is installed on the outer wall of the tailpipe 200 and provides precise angle control and sufficient torque through a sealed drive shaft.

[0054] Intelligent sensing includes a high-frequency pressure sensor array arranged on the wall of the 200 inlet section of the tailrace pipe (approximately 0.2R height, with 3 sensors equidistant from each other in the circumference), as well as unit power sensors and head sensors.

[0055] Control and Algorithm: The control module uses a PLC as the core controller.

[0056] Signal processing: Real-time acquisition of pressure signals and FFT spectrum analysis to extract the amplitude of the main frequency (e.g., 0.3~0.4fn).

[0057] Operating condition identification: Combine power and head signals to determine the current operating point (e.g., 40% BEP).

[0058] Target optimization: The control module pre-stores a MAP diagram of the working condition, optimal guide vane angle, and pulsation amplitude obtained through CFD and model experiments.

[0059] Real-time feedback control: Employs PID or fuzzy adaptive control algorithms to dynamically adjust the guide vane angle and suppress pressure pulsation to the lowest possible level.

[0060] Arrangement of the first air supply structure 5: Air supply holes are opened between each group of adjustable guide vanes.

[0061] The triggering condition of the first air supply structure 5 is: when the upper guide vane 3 rotates to a specific angle (according to the pre-stored MAP diagram, the flow around at this angle is prone to generate vortex shedding at a specific frequency), at this time, the linkage will supply air at the air supply hole to suppress the high-frequency noise.

[0062] In this design, the multi-layered vortex suppression and vibration reduction structure exhibits significant and comprehensive vortex suppression and vibration reduction effects, effectively compensating for the shortcomings of traditional design schemes in simultaneously suppressing tail vortices, reducing outlet pressure pulsations, and maintaining high hydraulic efficiency. This multi-layered vortex suppression and vibration reduction structure, while maintaining high efficiency, effectively suppresses free vortices at the runner tail and vortex ropes in the draft tube 200, significantly reducing pressure pulsations and vibrations.

[0063] Most importantly, in this design, the vortex-suppressing vane 1, located on the suction surface of the runner blade 100, effectively controls boundary layer separation, suppressing the generation of blade passage vortices at the source. Adding trailing edge serrations 2 to the trailing edge of the runner blade 100 effectively breaks up the Karman vortex street at the blade's exit edge, dispersing its energy. The actively controllable adjustable guide vane, a core component of the design, under precise control of the control module, can cut, guide, and dissipate residual vortex bands entering the tailrace pipe 200, effectively addressing major low-frequency pressure pulsations. The air supply module serves as a safety redundancy, specifically designed to handle strong helical vortex bands under extreme conditions. Thus, these structures together constitute a comprehensive, multi-scale, collaborative vortex-eliminating system, encompassing source suppression, near-field fragmentation, active intervention, and safety redundancy, with effects far exceeding any single measure.

[0064] Furthermore, the multi-stage vortex suppression and vibration reduction structure exhibits excellent adaptability and intelligence during the operation of mixed-flow turbines. Specifically, the vortex suppressor 1 is highly effective under low-load conditions, the trailing edge serration 2 is effective under medium-to-high-load conditions, and the actively adjustable guide vane 3, through real-time sensing by the detection module and adaptive adjustment by the control module, can cover a wide load range, solving the problem of poor adaptability of traditional fixed structures.

[0065] In addition, in this design, the adjustable guide vane located at tailpipe 200 is triggered jointly with the first air supply structure 5 and has a higher priority, while the second air supply structure 6 located at drain cone 300 is triggered independently and has a lower priority. The primary and secondary functions are clearly distinguished and the logic is clear, ensuring that it can operate in the most efficient and economical way under any working condition, avoiding efficiency loss and cavitation risk caused by constant air supply.

[0066] It is understandable that the chordwise direction refers to the direction from the leading edge (the end facing the fluid) to the trailing edge (the end away from the fluid) in the cross-section of the blade (airfoil section).

[0067] Thickness direction: refers to the vertical distance between the upper and lower surfaces of the blade cross-section.

[0068] Optimal Efficiency Point (BEP): The specific operating point where a mixed-flow turbine achieves the highest efficiency. Generally, during the manufacturing and delivery of mixed-flow turbines, performance curves (such as flow-efficiency curves, flow-head / pressure curves, and flow-power curves) are plotted through experiments. The BEP is the operating point corresponding to the peak value of the flow-efficiency curve. 40% BEP means that the current flow rate is 40% of its optimal efficiency flow rate.

[0069] Design flow line of tailrace tube 200: The internal water flow path is determined through fluid dynamics analysis during the design process of tailrace tube 200 of mixed flow turbine.

[0070] Effective span: the length of the upper guide vane 3 and the lower guide vane 4 protruding from the inner wall of the tailpipe 200.

[0071] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0072] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0073] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0074] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0075] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A multi-stage vortex suppression and vibration reduction structure for a mixed-flow turbine, characterized in that, This multi-stage vortex-eliminating and vibration-damping structure includes: The turbulence structure includes a vortex suppressor (1) and trailing edge serrations (2), wherein the vortex suppressor (1) is disposed on the suction surface of the rotor blade (100), and the trailing edge serrations (2) are disposed on the trailing edge of the rotor blade (100); Adjustable guide vanes are evenly spaced along the circumference of the inner wall of the tailwater pipe (200). They include an upper guide vane (3) and a lower guide vane (4). The upper guide vane (3) is rotatably and adjustablely arranged on the inner wall of the tailwater pipe (200) with its lower end as the rotation center. The lower guide vane (4) is fixed on the inner wall of the tailwater pipe (200) and located below the upper guide vane (3). The air replenishment module includes a first air replenishment structure (5) and a second air replenishment structure (6). The first air replenishment structure (5) is disposed on the inner circumferential wall of the tailwater pipe (200), and the second air replenishment structure (6) is disposed at the tail of the drain cone (300). The detection module is used to detect the operating status of the mixed-flow turbine. The control module is used to adjust the angle of the upper guide vane (3) based on the detection result of the detection module to suppress the pressure pulsation of the mixed-flow turbine, and to control the first air supply structure (5) to supply air into the tailwater pipe (200) when the upper guide vane (3) is adjusted to the preset angle; and to control the second air supply structure (6) to supply air to the tail of the discharge cone (300) when the detection signal shows that the pressure pulsation amplitude exceeds the preset threshold.

2. The multi-vortex-eliminating and vibration-damping structure as described in claim 1, characterized in that, The vortex suppressor blades (1) are fixed in three positions at intervals along the blade height direction of the rotor blade (100), at positions of 25%, 50%, and 75% of the blade height relative to the rotor blade (100).

3. The multi-vortex-eliminating and vibration-damping structure as described in claim 2, characterized in that, The chord length of the vortex suppressor (1) is 30% to 50% of the chord length of the rotor blade (100), the height is 15% to 35% of the thickness of the rotor blade (100), and the width is 100% to 150% of its own height.

4. The multi-vortex-eliminating and vibration-damping structure as described in claim 1, characterized in that, The trailing edge serration (2) is located in the region of 40% to 95% of the water outlet edge height of the impeller blade (100). The tooth height of the trailing edge serration (2) is 100% to 200% of the boundary layer thickness of the impeller blade (100), and the tooth width is 200% to 500% of the boundary layer thickness of the impeller blade (100).

5. The multi-vortex-eliminating and vibration-damping structure as described in claim 4, characterized in that, The trailing edge serration (2) is formed by cutting the trailing edge of the rotor blade (100), and rounded corners are provided at the tip and root of the tooth.

6. The multi-vortex-eliminating and vibration-damping structure as described in claim 5, characterized in that, The radius of the fillet is 10% to 20% of the height of the tail edge serration (2).

7. The multi-vortex-eliminating and vibration-damping structure as described in claim 1, characterized in that, The adjustable guide vanes are evenly distributed circumferentially on the inner wall of the tailrace pipe (200). The chord length of the upper guide vane (3) and the lower guide vane (4) is 0.8R~0.95R, the effective spanwise height of the upper guide vane (3) and the lower guide vane (4) is 0.25R~0.35R, and the axial distance between the upper guide vane (3) and the inlet of the tailrace pipe (200) is 0.3R~0.45R, where R is the impeller radius of the mixed-flow turbine.

8. The multi-vortex-eliminating and vibration-damping structure as described in claim 7, characterized in that, The upper guide vane (3) has a deflection angle range of ±45° relative to the design streamline of the tailwater pipe (200); the lower guide vane (4) has an angle of -10° with the design streamline of the tailwater pipe (200).

9. The multi-vortex-eliminating and vibration-damping structure as described in claim 8, characterized in that, The inner wall of the tailwater pipe (200) is provided with an arc-shaped limiting groove (400). The upper end of the upper guide vane (3) is connected to a limiting block. The limiting block is located in the limiting groove (400) and can slide along the extension direction of the limiting groove (400).

10. The multi-vortex-eliminating and vibration-damping structure as described in any one of claims 1-9, characterized in that, The detection module includes a first pressure sensor (7) for detecting the pressure at the inlet section of the tailrace pipe (200), a second pressure sensor (8) for detecting the pressure at the starting end of the vortex belt near the spillway cone (300), a power sensor for detecting the load of the mixed-flow turbine, and a head sensor for detecting the head size of the mixed-flow turbine during operation.

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