Rotary water replenishing nozzle and method for inhibiting power fluctuation induced by cavitation of water turbine

Abstract

The invention discloses a rotating direction water supplementing nozzle and method for restraining power fluctuation induced by cavitation of a water turbine, the water supplementing nozzle comprises a flow guide disc arranged in a draft tube, the flow guide disc is communicated with a water supplementing tube of a main shaft of the water turbine, and a plurality of flow guide blades are arranged in the flow guide disc. The multiple flow guide blades are all rotationally connected with the lower surface of the flow guide disc, and angle adjusting knobs connected with the flow guide blades are further arranged on the upper surface of the flow guide disc in a penetrating mode so that the flow guide blades can conduct directional and reverse rotational flow on the hedging vorticity. A draft tube does not need to be transformed, the adaptability is high, the draft tube can be independently installed after the whole water turbine is installed, the design period is short, the transformation cost is low, the blade angle and the directional rotational flow formed by the guide blades can be directly controlled through the angle adjusting knob, the vortex strip core can be accurately covered no matter under the large-flow non-design working condition or under the small-flow non-design working condition, and the vortex strip core can be effectively protected. The inhibition effect is obvious.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic control technology for turbine power fluctuations, and particularly relates to a directional water supply nozzle and method for suppressing power fluctuations induced by turbine cavitation. Background Technology

[0002] The turbine is the core power equipment of a hydropower station. It converts the potential and kinetic energy of the water flow into rotational mechanical energy through the runner, driving the generator to generate electricity. Among them, the reaction turbine is equipped with a tailrace pipe. Its core function is to recover the residual energy of the water flow at the runner outlet, reduce the flow velocity and increase the pressure, and at the same time discharge the water flow smoothly downstream. That is, the flow characteristics of the tailrace pipe directly determine the operating efficiency and stability of the turbine. In actual operation, due to fluctuations in operating conditions (especially non-design conditions such as small flow and large flow), cavitation vortex flow is easily formed in the tailrace pipe: under small flow conditions, a positive eccentric vortex belt appears downstream of the runner in the same direction as the runner; under large flow conditions, a columnar vortex belt is formed in the opposite direction to the runner. These vortex belts are prone to evolve into cavitation vortex belts, causing violent power fluctuations and threatening the safe operation of the hydropower station. The applicant found that the current technical solutions used to solve this problem all have some shortcomings. For example, there are inventive ideas to broaden the stable operating range by improving the design of the impeller, but their design cycle is long and the cost is high, and they cannot fully cover all non-design conditions. There are also technical solutions that use axial or radial direct water / air injection, but they only alleviate cavitation by increasing the flow rate and do not intervene in the rotation characteristics of the vortex belt. The water injection flow and the original vortex flow are difficult to counteract, and the suppression effect is limited. There are also solutions that set up a fixed flow stabilizing structure in the tailrace pipe to destroy the vortex belt, but the adaptability to different conditions is poor (increases hydraulic loss at high flow rates), and some devices have complex structures and are easily damaged by water flow impact. The applicant also found two major defects in the traditional water replenishment technology: First, under the action of traditional nozzles, the water replenishment flow diffuses irregularly and has a low velocity, making it difficult to act on the cavitation core area and easily causing the channel to be blocked by impurities; Second, the circumferential velocity characteristics of the tailpipe vortex are not considered, the water replenishment direction and the vortex direction lack coordination, and the vortex cannot be offset by reverse vortex. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies by providing a vortex-induced water supply nozzle and method for suppressing power fluctuations caused by cavitation in water turbines. This method requires no modification to the tailrace pipe, has high adaptability, and can be installed separately after the overall installation of the water turbine. It has a short design cycle and low modification cost. The blade angle can be directly controlled by the angle adjustment knob. The directional vortex formed by the guide blades can accurately cover the vortex core under both high-flow-rate and low-flow-rate non-design conditions, resulting in a significant suppression effect.

[0004] The objective of this invention is achieved through the following technical solution: A vortex-induced power fluctuation suppressor for water turbines includes a guide disc disposed inside a tailrace pipe. The guide disc is connected to the water supply pipe of the turbine main shaft. Multiple guide vanes are disposed inside the guide disc, and each guide vane is rotatably connected to the lower surface of the guide disc. An angle adjustment knob connected to the guide vanes is also disposed through the upper surface of the guide disc to allow the guide vanes to directional reverse vortex flow to counteract the vortex.

[0005] In one embodiment, the guide vane has a streamlined hydrofoil structure, the thickness of the guide vane gradually decreases from its root to its tip, and the chord length of the guide vane is equal to the radius of the guide disk. times; This implementation method ensures uniform swirling flow while avoiding excessive resistance. The chord length design of the guide vanes ensures swirling flow intensity while also taking into account the smoothness of the water flow.

[0006] In one embodiment, multiple guide vanes are evenly distributed along the circumference of the guide disk.

[0007] In one embodiment, the diameter of the guide disk is equal to the diameter of the tailrace pipe inlet. times; Through this embodiment, the diameter range design of the guide coil can ensure that it covers the core area of ​​the vortex zone while reducing hydraulic loss.

[0008] In one embodiment, the angle adjustment range of the guide vanes is: .

[0009] In one embodiment, the system further includes an inlet pipe, the top of which is connected to the turbine main shaft water supply pipe, and the bottom of which is connected to the guide disc. The guide disc has a water flow channel at its center that matches the inner diameter of the inlet pipe.

[0010] In one embodiment, a fixing component is also included, the fixing component comprising a threaded connector that mates with the external thread of the inlet connection pipe to detachably install the water supply nozzle onto the outlet water pipe of the water turbine, and a sealing gasket is provided between the threaded connector and the mounting surface of the outlet water pipe.

[0011] The present invention also provides a method for suppressing power fluctuations induced by cavitation in water turbines, based on the aforementioned vortex water supply nozzle, comprising: Real-time acquisition of turbine flow rate and power fluctuation signals in the tailrace tube is used to determine whether the turbine's real-time operating conditions are stable. When the real-time operating condition of the turbine is determined to be unstable or slightly unstable, a swivel water supply nozzle is installed and the angle of the guide vanes is adjusted according to the real-time operating condition of the turbine. If the real-time operating condition of the turbine is determined to be stable, no water replenishment will be performed. In one implementation, determining whether the real-time operating condition of the turbine is stable includes: When the power fluctuation amplitude in the tailrace pipe is greater than 0.01 times the output power, the real-time operating condition of the turbine is judged to be slightly unstable. When the real-time flow rate of the water turbine deviates from its design flow rate If the above conditions are met, the real-time operating condition of the turbine is determined to be an unstable condition. When the real-time flow rate of the turbine does not deviate from its design flow rate by more than ±30%, and the power fluctuation amplitude in the tailrace is not greater than 0.01 times the output power, the real-time operating condition of the turbine is judged to be a stable operating condition. In one embodiment, adjusting the angle of the guide vanes according to the real-time operating conditions of the turbine includes: When the real-time operating condition of the turbine is determined to be slightly unstable, the guide vane angle is adjusted to -10° to 10°. When the real-time operating condition of the water turbine is determined to be unstable; If the real-time flow rate of the water turbine is lower than its design flow rate When the above is the case, the angle of the guide vanes should be adjusted to -15° to -30°; If the real-time flow rate of the turbine is more than 30% higher than its design flow rate, the angle of the guide vanes should be adjusted to 15° to 30°.

[0012] The beneficial effects of this invention are as follows: (1) No tailrace pipe modification is required, and it has high adaptability. It can be installed separately after the turbine is installed. The design cycle is short and the modification cost is low. The adjustable vortex structure makes the makeup water flow form a circumferential velocity opposite to the vortex direction. The guide vanes can be continuously adjusted between -30° and 30° to adapt to non-design conditions such as small flow and large flow. It can also be dynamically adjusted according to the intensity of cavitation vortex to meet the vortex suppression requirements under different conditions, accurately counteract vortex volume, effectively suppress cavitation vortex, alleviate power fluctuations, and expand the safe operating range of the turbine.

[0013] (2) By counteracting the vortex by directional reverse swirl, the cavitation suppression efficiency is increased by more than 40% compared with the traditional direct injection water supply, and the power fluctuation amplitude of the unit can be reduced to less than 1%. It can be disassembled under the design conditions, and the hydraulic loss is reduced by more than 30% compared with the fixed flow stabilization device.

[0014] (3) The water supply source is the same as the main shaft water supply system, and no additional device is required. It is applicable to existing and newly built reaction turbines. Attached Figure Description

[0015] The invention will now be described in more detail with reference to embodiments and the accompanying drawings. Figure 1 A schematic diagram of the water supply nozzle structure of the present invention is shown; Figure 2 A schematic diagram of the installation position of the present invention is shown; Figure 3 A schematic diagram of the water supply nozzle of the present invention is shown; In the accompanying drawings, the same parts use the same reference numerals. The drawings are not to scale.

[0016] Figure label: 1-Inlet water connection pipe, 2-Guide vane, 3-Cover plate, 4-Angle adjustment knob, 5-Guide disc, 6-Tail water pipe, 7-Main shaft water supply pipe, 8-Rotator, 100-Water supply nozzle. Detailed Implementation

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] This invention provides a swirl-type water supply nozzle for suppressing power fluctuations induced by cavitation in water turbines, such as... Figure 1 As shown, it includes a guide disc 5 installed in the tailrace pipe 6. The guide disc 5 is connected to the turbine main shaft water supply pipe 7. Multiple guide blades 2 are installed in the guide disc 5. The multiple guide blades 2 are rotatably connected to the lower surface of the guide disc 5. An angle adjustment knob 4 connected to the guide blades 2 is also installed through the upper surface of the guide disc 5 to allow the guide blades 2 to directional reverse swirling flow to counteract the vortex. Specifically, such as Figure 1 and Figure 2 As shown, it also includes an inlet connection pipe 1. The top of the inlet connection pipe 1 is connected to the water supply pipe 7 of the turbine main shaft, and the bottom of the inlet connection pipe 1 is connected to the guide disc 5. A water flow channel matching the inner diameter of the inlet connection pipe 1 is opened in the center of the guide disc 5. It should be noted that the inlet connecting pipe 1 is a hollow tubular structure with external threads on its lower outer circumference to connect with the guide disc 5. The guide disc 5 is coaxially fixed to the lower end of the inlet connecting pipe 1, and a water flow hole matching the inner diameter of the inlet connecting pipe 1 is opened in the center. The water flow hole is connected to the internal channel of the inlet connecting pipe 1, which means that there is no need to modify the tailrace pipe 6. It can be installed separately after the turbine is installed. It has high adaptability, short design cycle and low modification cost. The adjustable vortex structure makes the makeup water flow form a circumferential velocity opposite to the vortex belt rotation direction. It can also be dynamically adjusted according to the intensity of the cavitation vortex belt to meet the vortex belt suppression requirements under different operating conditions, accurately counteract vortex volume, effectively suppress cavitation vortex belt, alleviate power fluctuations and expand the safe operating range of the turbine. Furthermore, it also includes a fixing component, which includes a threaded connector that mates with the external thread of the water inlet connection pipe 1, so as to detachably install the water supply nozzle 100 onto the water outlet pipe of the water turbine. A sealing gasket is also provided between the threaded connector and the mounting surface of the water outlet pipe. In one embodiment, such as Figure 1 As shown, the guide vane 2 has a streamlined hydrofoil structure. The thickness of the guide vane 2 gradually decreases from its root to its tip. The chord length of the guide vane 2 is equal to the radius of the guide disk 5. times; It should be noted that in this embodiment, the chord length of the guide vane 2 is designed according to the radius of the guide disk 5 to ensure uniform swirling flow while avoiding excessive increase in resistance. The chord length design of the guide vane 2 ensures the swirling flow intensity while taking into account the smoothness of the water flow. Furthermore, such as Figure 1 As shown, multiple guide vanes 2 are evenly distributed around the circumference of the guide disk 5; In one embodiment, such as Figure 2 As shown, the diameter of the guide disc 5 is equal to the inlet diameter of the tailrace pipe 6. times; It should be noted that in this embodiment, the diameter of the guide disc 5 is designed according to the inlet diameter of the tailrace pipe 6 to ensure that it covers the core area of ​​the vortex zone while reducing hydraulic loss. In one embodiment, such as Figure 3 As shown, in this embodiment, the guide vane 2 is continuously adjustable between -30° and 30° to adapt to non-design conditions such as small flow rate and large flow rate; It should be noted that, as Figure 3 As shown, when the extension direction of the guide vane 2 is parallel to the radial direction of the guide disk 5, it is considered 0°. The guide vane 2 extends along the direction shown in the figure. Figure 3 Rotation in the indicated direction is a positive angle, and vice versa for a negative angle; Specifically, when the turbine operates under non-design conditions, the water flow from the runner 8 outlet enters the straight conical section of the draft tube. Due to uneven velocity distribution, a swirling flow with circumferential velocity is formed. Under low flow conditions (Q < 0.7Q0), the swirling flow forms a positive eccentric vortex band in the same direction as the runner, and cavitation easily occurs at the center of the vortex band. Under high flow conditions (Q > 1.3Q0), the swirling flow forms a reverse columnar cavitation vortex band in the opposite direction to the runner, causing pressure pulsation on the draft tube wall and power fluctuations in the unit. In this embodiment, the angle of the guide vanes 2 is adjusted according to the real-time flow rate of the turbine, such as: When the turbine's real-time operating condition is slightly unstable (the power fluctuation amplitude in the tailrace pipe 6 is greater than 0.01 times the output power while the turbine's real-time flow rate does not deviate from its design flow rate by more than ±30%), adjust the angle of the guide vane 2 to -10° to 10°. When the real-time operating condition of the water turbine is unstable; If the real-time flow rate of the water turbine is lower than its design flow rate When the above conditions are met, adjust the angle of guide vane 2 to -15° to -30°. If the real-time flow rate of the turbine is more than 30% higher than its design flow rate, the angle of the guide vanes 2 should be adjusted to 15° to 30°. That is, it can dynamically control the direction and intensity of the effluent vortex according to the type of vortex. When the vortex is low flow rate, it can be adjusted to a negative angle (reverse vortex) and when the vortex is high flow rate, it can be adjusted to a positive angle (reverse vortex) to achieve precise vortex cancellation and significantly weaken the intensity of the vortex. Specifically, such as Figure 3 As shown, the height of the guide disc 5, i.e., the distance between its upper and lower cover plates 3, is d, and the diameter of the water inlet connection pipe 1 is... The diameter of the guide disk 5 is That is, different tailrace pipe 6 specifications can be adapted by simply adjusting the above 3 key dimensions, without modifying the main structure of tailrace pipe 6. It can be installed separately after the turbine is installed, with a short design cycle and low modification cost. In one embodiment, the guide vane 2 is made of high-strength wear-resistant stainless steel and the surface is treated with anti-corrosion. The adjustment mechanism of the guide vane 2 adopts gear transmission and drives the vane to rotate synchronously through an external knob. The adjustment accuracy can reach 1°. In one embodiment, the inner wall of the water flow channel of the water inlet connection pipe 1 is polished, with a surface roughness Ra≤0.8μm. This reduces the frictional resistance of the water flow and increases the water replenishment flow rate (up to 5-8m / s), while also reducing the deposition and blockage of impurities. In one embodiment, the edge of the guide disk 5 is designed with rounded corners, and the rounded corner radius is 5-8mm. The present invention also provides a method for suppressing power fluctuations induced by cavitation in water turbines, based on the aforementioned vortex water supply nozzle 100, comprising: Real-time acquisition of turbine flow rate and power fluctuation signals within draft tube 6 is used to determine whether the turbine's real-time operating conditions are stable, including: When the power fluctuation amplitude in the tailrace pipe 6 is greater than 0.01 times the output power, the real-time operating condition of the turbine is judged to be slightly unstable. When the real-time flow rate of the turbine deviates from its design flow rate by more than ±30%, the real-time operating condition of the turbine is judged to be an unstable operating condition. When the real-time flow rate of the turbine does not deviate from its design flow rate by more than ±30%, and the power fluctuation amplitude in the tailrace pipe 6 is not greater than 0.01 times the output power, the real-time operating condition of the turbine is judged to be a stable operating condition. Specifically, when the real-time operating condition of the turbine is determined to be unstable or slightly unstable, the directional water supply nozzle 100 is installed and the angle of the guide vanes 2 is adjusted according to the real-time operating condition of the turbine, including: When the real-time operating condition of the turbine is determined to be slightly unstable, the guide vane angle 2 is adjusted to -10° to 10°. When the real-time operating condition of the water turbine is determined to be unstable; If the real-time flow rate of the turbine is more than 30% lower than its design flow rate, the angle of the guide vanes 2 should be adjusted to -15° to -30°. If the real-time flow rate of the turbine is more than 30% higher than its design flow rate, the angle of the guide vanes 2 should be adjusted to 15° to 30°. If the real-time operating condition of the turbine is determined to be stable, no water replenishment will be performed. It should be noted that the water replenishment method provided by this invention dynamically controls the direction and intensity of the water flow according to the type of vortex. When the vortex is low flow, it is adjusted to a negative angle (reverse vortex) and when the vortex is high flow, it is adjusted to a positive angle (reverse vortex). This achieves precise vortex cancellation and significantly weakens the intensity of the vortex. In other words, by using directional reverse vortex to counteract the vortex, compared with traditional direct water replenishment, the cavitation suppression efficiency is improved by more than 40%, and the power fluctuation amplitude of the unit can be reduced to below 1%.

[0019] In the description of this invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "rear", "inner", "outer", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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 invention.

[0020] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A vortex-driven water supply nozzle for suppressing power fluctuations induced by cavitation in a water turbine, characterized in that, It includes a guide disc installed inside the tailrace pipe, the guide disc being connected to the turbine main shaft water supply pipe, and multiple guide vanes installed inside the guide disc, all of which are rotatably connected to the lower surface of the guide disc. An angle adjustment knob connected to the guide vanes is also provided through the upper surface of the guide disc, so as to allow the guide vanes to directional reverse swirling flow to counteract the vortex.

2. The vortex-type water supply nozzle for suppressing power fluctuations induced by cavitation in a water turbine according to claim 1, characterized in that, The guide vanes have a streamlined hydrofoil structure, and the thickness of the guide vanes gradually decreases from their root to their tip. The chord length of the guide vanes is equal to the radius of the guide disk. times.

3. The vortex-type water supply nozzle for suppressing power fluctuations induced by cavitation in a water turbine according to claim 1, characterized in that, The multiple guide vanes are evenly distributed along the circumference of the guide disk.

4. The swirl-type water supply nozzle for suppressing power fluctuations induced by cavitation in a water turbine according to claim 1, characterized in that, The diameter of the guide disc is the same as the diameter of the tailrace pipe inlet. times.

5. A vortex-type water supply nozzle for suppressing power fluctuations induced by cavitation in a water turbine according to claim 1, characterized in that, The angle adjustment range of the guide vanes is: .

6. A vortex-type water supply nozzle for suppressing power fluctuations induced by cavitation in a water turbine according to claim 1, characterized in that, It also includes a water inlet connection pipe, the top of which is connected to the water supply pipe of the turbine main shaft, and the bottom of which is connected to the guide disc. The center of the guide disc has a water flow channel that matches the inner diameter of the water inlet connection pipe.

7. A vortex-type water supply nozzle for suppressing power fluctuations induced by cavitation in a water turbine according to claim 1, characterized in that, It also includes a fixing component, which includes a threaded connector that mates with the external thread of the water inlet connection pipe to detachably install the water supply nozzle onto the water outlet pipe of the water turbine. A sealing gasket is also provided between the threaded connector and the mounting surface of the water outlet pipe.

8. A method for suppressing power fluctuations induced by cavitation in a water turbine, based on the vortex water supply nozzle according to any one of claims 1 to 7, characterized in that, include: Real-time acquisition of turbine flow rate and power fluctuation signals in the tailrace tube is used to determine whether the turbine's real-time operating conditions are stable. When the real-time operating condition of the turbine is determined to be unstable or slightly unstable, a swivel water supply nozzle is installed and the angle of the guide vanes is adjusted according to the real-time operating condition of the turbine. If the turbine's real-time operating condition is determined to be stable, no water replenishment will be performed.

9. The method for suppressing power fluctuations induced by cavitation in a water turbine according to claim 8, characterized in that, Determining whether the real-time operating conditions of a water turbine are stable includes: When the power fluctuation amplitude in the tailrace pipe is greater than 0.01 times the output power, the real-time operating condition of the turbine is judged to be slightly unstable. When the real-time flow rate of the water turbine deviates from its design flow rate If the above conditions are met, the real-time operating condition of the turbine is determined to be an unstable condition. When the real-time flow rate of the turbine does not deviate from its design flow rate by more than ±30%, and the power fluctuation amplitude in the tailrace is not greater than 0.01 times the output power, the real-time operating condition of the turbine is judged to be a stable operating condition.

10. A method for suppressing power fluctuations induced by cavitation in a water turbine according to claim 9, characterized in that, Adjusting the angle of the guide vanes according to the real-time operating conditions of the turbine includes: When the real-time operating condition of the turbine is determined to be slightly unstable, the guide vane angle is adjusted to -10° to 10°. When the real-time operating condition of the water turbine is determined to be unstable; If the real-time flow rate of the water turbine is lower than its design flow rate When the above is the case, the angle of the guide vanes should be adjusted to -15° to -30°; If the real-time flow rate of the turbine is more than 30% higher than its design flow rate, the angle of the guide vanes should be adjusted to 15° to 30°.

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