Vibration reduction runner cone of mixed-flow water turbine

Abstract

The invention discloses a vibration reduction runner cone of a mixed-flow water turbine, belongs to the technical field of hydroelectric power generation equipment, is applied to the mixed-flow water turbine provided with a large-shaft center hole air supply device, is connected with a rotating wheel to replace a conventional runner cone, and is of a structure with an attached wing, the outer conical surface is provided with a wing, and parameters of the wing are determined through hydrodynamic force and vibration analysis and calculation. An air supplementing hole can be formed in the conical surface, and an outer ring can be arranged on the outer edge of the fin; the vane is combined with a large shaft center hole air supply device to work, the vane is used as a runner aileron to form main-aileron matching with the main blade, and the quantity of the vane independent of the runner can be set as required. Secondary backflow at a runner outlet of the mixed-flow water turbine is directly improved, the amplitude and frequency of vortex pressure pulsation of the draft tube are effectively adjusted, frequency coupling is avoided, the vibration strength is greatly reduced, the efficiency and output of the mixed-flow water turbine are basically not affected, the safety and reliability of a hydropower station unit and a dam are remarkably improved, the maintenance cost is reduced, and the service life of the hydropower station unit is prolonged. The method is suitable for large and giant mixed-flow water-turbine generator sets, and the engineering application value is extremely high.

Description

Technical Field

[0001] This invention relates to the field of hydropower equipment technology, specifically to a vibration damping and drainage cone for mixed-flow turbines, which is suitable for vibration reduction and noise reduction of large and giant mixed-flow turbine generator sets and can effectively improve the unit vibration problem caused by pressure pulsation in the tailrace vortex. Background Technology

[0002] Pressure pulsation caused by vortex in the tailrace is a typical hydraulic vibration characteristic of mixed-flow turbines, and the hazards it causes are particularly prominent in large and giant hydroelectric power stations. A serious safety accident occurred at the Sayan Hydroelectric Power Station in the Soviet Union due to this characteristic. Large and giant hydroelectric power stations in China, such as Yantan, Dachaoshan, Three Gorges, and Ertan, have also experienced varying degrees of turbine vibration and runner cracking problems. These issues not only pose hidden dangers to the safe and stable operation of the power stations but also increase operating costs significantly due to extensive maintenance.

[0003] The industry has clearly identified hydraulic factors as the core cause of turbine vibration. Among them, pressure pulsation caused by tailrace vortex is the most typical, while blade passage vortices and Karman vortices may be direct causes. These are often accompanied by secondary backflow at the runner outlet. This problem manifests differently in the turbine's ultra-low load, high partial load, and ultra-high load operating areas, and the harm is aggravated when frequency coupling occurs.

[0004] Current vibration reduction measures mainly include developing high-performance impellers and tailrace pipe air supply. However, utilizing existing structural conditions to develop vibration-damping drainage cones through innovative design to optimize the flow state of the hydraulic system has become a technical problem that urgently needs to be solved and has extremely high engineering value. Summary of the Invention

[0005] This invention aims to develop a novel vibration-damping spillway cone for mixed-flow turbines through structural innovation combined with fluid dynamics analysis (CFD). This cone effectively controls the amplitude and frequency of pressure pulsations in the tailrace vortex, reduces the safety hazards of vibration to hydropower station equipment and dams, avoids major safety accidents, and improves the reliability of safe operation of the units.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A vibration damping discharge cone for a mixed-flow turbine is applied to a mixed-flow turbine (1). The mixed-flow turbine (1) is equipped with a shaft center hole air supply device (3). The vibration damping discharge cone (2) is used to replace the conventional discharge cone at the center position of the runner outlet of the mixed-flow turbine (1) and is connected to the runner. The vibration damping discharge cone (2) is a structure with attached wings. Its outer cone surface is attached with winglets. The shape and number of winglets are determined by CFD and vibration analysis calculations. The cone angle of the vibration damping discharge cone (2) can vary from the cone angle determined by the original model design test. Air supply holes can be uniformly opened on the cone surface. The air supply holes cooperate with the shaft center hole air supply device (3) to improve the effectiveness and uniformity of air supply.

[0007] Furthermore, the outer edge of the blade of the vibration damping and drainage cone (2) can be set with an outer ring of a specific shape according to the needs of CFD and vibration analysis calculations.

[0008] Furthermore, the blades of the vibration damping and drainage cone (2) serve as the ailerons of the runner of the mixed-flow turbine (1), forming a main and aileron cooperating structure with the runner blades, and the flow pattern is optimized by drawing on the design concept of long and short blades arranged in double rows.

[0009] Furthermore, the vibration damping and drainage cone (2) is independent of the runner of the mixed-flow turbine (1), and the number of its blades can be set as needed, without being limited by the number of runner blades, so as to adjust and improve the pressure pulsation frequency of the tailrace vortex of the mixed-flow turbine (1) and avoid frequency coupling.

[0010] Furthermore, the airfoil shape, length and placement angle of the damping and drainage cone (2) are determined by CFD and vibration analysis calculations to change the amplitude of the pressure pulsation of the tailrace tube of the mixed-flow turbine (1) and reduce the vibration intensity.

[0011] A vibration reduction system for a mixed-flow turbine includes a mixed-flow turbine (1), a vibration-damping drain cone (2) as described in any one of claims 1-5, and an air supply device (3) for the central hole of the main shaft. The vibration-damping drain cone (2) and the air supply device (3) for the central hole of the main shaft work together. The installation position of the vibration-damping drain cone (2) highly overlaps with the secondary return flow area at the runner outlet of the mixed-flow turbine (1).

[0012] Furthermore, the vibration reduction system affects and changes the amplitude and frequency of the secondary backflow at the runner outlet and the pressure pulsation of the tailrace tube vortex of the mixed-flow turbine (1) through the vibration reduction discharge cone (2), thereby improving the vibration problem of the mixed-flow turbine (1).

[0013] This invention employs a vibration-damping and drainage cone with attached wings, working in conjunction with an air supply device for the central hole of the main shaft, to achieve multi-dimensional improvement in the hydraulic vibration problem of mixed-flow turbines. Specific beneficial effects include: 1. It directly affects and changes the secondary backflow phenomenon at the runner outlet of the mixed-flow turbine. The installation position of the vibration damping and drainage cone highly overlaps with the secondary backflow area of ​​the runner, which can directly optimize the flow pattern in this area. 2. By using CFD and vibration analysis calculations, the airfoil, length, and placement angle of the damping and drainage cone blades can be reasonably selected to effectively influence and change the amplitude of pressure pulsation in the tailrace vortex, thereby reducing the vibration intensity. 3. Set the number of vibration damping and drainage cone blades as needed to affect and change the frequency of pressure pulsation in the tailrace vortex, so as to avoid coupling with the natural frequency of the main structural components of the mixed-flow turbine and eliminate the serious vibration hazards caused by frequency coupling. 4. By comprehensively improving the vibration problem of mixed-flow turbines through flow optimization, amplitude reduction, and frequency regulation, and combining with specific engineering applications, the safety and reliability of hydropower station units and dams can be greatly improved, unit maintenance costs can be reduced, and the long-term stable operation of the power station can be guaranteed. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of the overall structure of the vibration damping and drainage cone for the mixed-flow turbine of the present invention; Figure 2 This is a side view of the overall structure of the vibration damping and drainage cone for the mixed-flow turbine of the present invention; Figure 3 This diagram illustrates the secondary backflow phenomenon at the runner outlet of a mixed-flow turbine. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0016] The vibration reduction system for a mixed-flow turbine proposed in this invention comprises three functional parts: a mixed-flow turbine (1), a vibration-damping drain cone (2), and an air supply device for the central hole of the main shaft (3). The core component is the vibration-damping drain cone (2) with attached wings, which works in conjunction with the air supply device for the central hole of the main shaft (3) to achieve the vibration reduction effect. The specific technical features are as follows: The mixed-flow turbine (1) is a normally designed mixed-flow turbine, which inherently includes a water discharge cone mounting position and a main shaft center hole air supply device (3) mounting position, providing a basis for the adaptation of the vibration damping water discharge cone (2); the vibration damping water discharge cone (2) is used to replace the conventional water discharge cone at the center position of the runner outlet of the mixed-flow turbine (1), and is connected to the runner, and its cone angle can vary from the cone angle determined by the original model design test; the vibration damping water discharge cone (2) is a structure with attached wings, and the number of attached wings on the outer cone surface varies. The shape and number of the blades are determined by CFD and vibration analysis calculations; the outer edge of the blades can be set with a specific shape of outer ring according to the analysis calculation needs; the damping and drainage cone (2) allows uniform opening of air injection holes on the cone surface to improve the effectiveness and uniformity of air injection of the shaft center hole air injection device (3); the shaft center hole air injection device (3) is a standard tailrace pipe pressure pulsation improvement component of modern large mixed flow turbine (1), which works in conjunction with the damping and drainage cone (2) to form a synergistic vibration reduction effect.

[0017] This invention breaks through the technical barrier of adding blades in the flow channel of a water turbine. The blades of the vibration damping and drainage cone (2) are used as the ailerons of the runner of the mixed-flow water turbine (1). By drawing on the design concept and engineering effect of long and short blades arranged in double rows, the blades of the vibration damping and drainage cone (2) and the runner blades of the mixed-flow water turbine (1) form a main and aileron cooperation, which optimizes the flow state. At the same time, the vibration damping and drainage cone (2) is set independently of the runner of the mixed-flow water turbine (1), and the number of its blades can be set as needed, without being limited by the runner, which makes it easy to adjust and improve the vibration frequency and avoid the risk of frequency coupling.

[0018] Through CFD and vibration analysis calculations, the structural design of the present invention can basically not affect the efficiency and output of the mixed-flow turbine (1), and the slight impact of individual operating conditions can be regarded as an acceptable range for engineering.

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific engineering examples.

[0020] When the vibration damping and drainage cone (2) of the present invention is applied to a large mixed-flow turbine (1) unit, the first step is to determine the cone angle, air inlet density and position of the vibration damping and drainage cone (2) by combining the runner parameters and actual operating conditions of the mixed-flow turbine (1) with the relevant data of secondary backflow and axial velocity distribution at the runner outlet of the mixed-flow turbine shown in Figure 3 through CFD and vibration analysis calculations. At the same time, the shape, number, airfoil, length and placement angle of the outer cone surface vanes of the vibration damping and drainage cone (2) are accurately calculated. If the flow optimization design is required, an outer ring with a matching shape can be set on the outer edge of the vanes of the vibration damping and drainage cone (2).

[0021] The designed vibration damping and drainage cone (2) replaces the conventional drainage cone at the center of the runner outlet of the mixed-flow turbine (1). The overall structure shown in Figures 1 and 2 is used to complete a reliable fixed connection with the runner of the mixed-flow turbine (1), ensuring that the installation position of the vibration damping and drainage cone (2) highly overlaps with the secondary return flow area at the runner outlet of the mixed-flow turbine (1) shown in Figure 3. The air inlet hole on the cone surface of the vibration damping and drainage cone (2) is seamlessly connected with the air inlet device (3) of the main shaft center hole of the mixed-flow turbine (1), ensuring the uniformity and effectiveness of the air inlet device (3) of the main shaft center hole.

[0022] During the operation of the unit, the air supply device (3) of the main shaft center hole supplies air to the flow channel of the mixed-flow turbine (1) through the air supply hole of the vibration damping and drainage cone (2). The vanes of the vibration damping and drainage cone (2) and the runner blades of the mixed-flow turbine (1) form a main and auxiliary wing cooperation structure, which directly disturbs and guides the secondary backflow at the runner outlet of the mixed-flow turbine (1) shown in Figure 3, and improves the flow state in this area. At the same time, the vanes of the vibration damping and drainage cone (2) accurately guide the water flow according to the flow velocity distribution on the axial surface of the runner outlet in Figure 3, change the amplitude and frequency of the pressure pulsation of the tailrace vortex of the mixed-flow turbine (1), effectively avoid the frequency coupling problem, and thus achieve the vibration reduction and noise reduction effect of the mixed-flow turbine (1).

[0023] In the experimental application of a giant hydropower station, the vibration reduction spillway cone (2) designed above, combined with the structural layout of Figure 1 and Figure 2 and the flow velocity and backflow region analysis of Figure 3, reduced the pressure pulsation amplitude of the tailrace vortex of the mixed-flow turbine (1) by more than 60%, and the vibration frequency successfully avoided the natural frequency of the main structural components of the mixed-flow turbine (1). The vibration value of the unit operation was reduced to the national standard allowable range, and the efficiency and output of the mixed-flow turbine (1) did not show significant attenuation. The efficiency of some low-load conditions decreased slightly (the decrease was <1%), which is within the acceptable range of the project.

[0024] The scope of protection of this invention is not limited to the specific embodiments described above. For those skilled in the art, any fine-tuning of the cone angle, blade parameters, air inlet layout, etc. of the damping and drainage cone (2) in relation to the matching structure of the mixed-flow turbine (1), the damping and drainage cone (2), and the air inlet device (3) of the main shaft center hole, without departing from the technical principle of this invention, shall fall within the scope of protection of this invention.

Claims

1. A vibration damping and drainage cone for a mixed-flow turbine, applied to a mixed-flow turbine (1), characterized in that: The mixed-flow turbine (1) is equipped with a shaft center hole air supply device (3). The vibration damping discharge cone (2) is used to replace the conventional discharge cone at the center position of the runner outlet of the mixed-flow turbine (1) and is connected to the runner. The vibration damping discharge cone (2) is a structure with attached wings. Its outer cone surface is attached with winglets. The shape and number of winglets are determined by hydrodynamic analysis and vibration analysis. The cone angle of the vibration damping discharge cone (2) can vary from the cone angle determined by the original model design test. Air supply holes can be evenly opened on the cone surface. The air supply holes cooperate with the shaft center hole air supply device (3) to improve the effectiveness and uniformity of air supply.

2. The vibration damping and drainage cone for a mixed-flow turbine according to claim 1, characterized in that, The outer edge of the blade of the vibration damping and drainage cone (2) can be set with a specific shape of outer ring according to the needs of hydrodynamic analysis and vibration analysis calculation.

3. The vibration damping and drainage cone for a mixed-flow turbine according to claim 1, characterized in that, The blades of the vibration damping and drainage cone (2) serve as the ailerons of the runner of the mixed-flow turbine (1), forming a main and aileron cooperation structure with the runner blades. The flow pattern is optimized by drawing on the design concept of long and short blades arranged in double rows.

4. The vibration damping and drainage cone for a mixed-flow turbine according to claim 1, characterized in that, The vibration damping and drainage cone (2) is independent of the runner of the mixed-flow turbine (1). The number of its blades can be set as needed and is not limited by the number of runner blades, so as to adjust and improve the pressure pulsation frequency of the tailrace vortex of the mixed-flow turbine (1) and avoid frequency coupling.

5. The vibration damping and drainage cone for a mixed-flow turbine according to claim 1, characterized in that, The airfoil, length and placement angle of the damping and drainage cone (2) are determined by hydrodynamic analysis and vibration analysis to change the amplitude of the pressure pulsation of the tailrace tube of the mixed-flow turbine (1) and reduce the vibration intensity.

6. A vibration reduction system for a mixed-flow turbine, characterized in that, The device includes a mixed-flow turbine (1), a damping and draining cone (2) as described in any one of claims 1-5, and a shaft center hole air supply device (3). The damping and draining cone (2) and the shaft center hole air supply device (3) work together. The installation position of the damping and draining cone (2) highly overlaps with the secondary return flow area at the runner outlet of the mixed-flow turbine (1).

7. The vibration reduction system for a mixed-flow turbine according to claim 6, characterized in that, The vibration reduction system affects and changes the amplitude and frequency of the secondary backflow at the runner outlet and the pressure pulsation of the tailrace tube vortex of the mixed-flow turbine (1) through the vibration reduction and drainage cone (2), thereby improving the vibration problem of the mixed-flow turbine (1).

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