An adaptive control anti-cavitation pump turbine

Abstract

The invention discloses an adaptively controlled anti-cavitation pump turbine, comprising a main shaft, a runner, a volute with a water outlet, a tailwater pipe connected to a water reservoir through a pipeline, the runner comprising an upper crown, a lower ring, and blades, a drainage hole is provided at the lower end of the main shaft, the drainage hole is connected to an external water source through a pipeline, a plurality of radial fluid holes are provided in the upper crown, a water outlet hole connected to the outer end of the fluid hole is provided near the back water surface of the blade, the inner end of the fluid hole penetrates the drainage hole of the main shaft, when the runner drives the main shaft to rotate, the main shaft drainage hole introduces water flow from an external water source, passes through the fluid hole, enters the water outlet hole at the back water surface of the blade, and then disperses the vortex and balances the negative pressure. The invention can carry out targeted "defoaming" according to the position of the real negative pressure area, so as to effectively eliminate cavitation problems such as negative pressure and cavitation of the pump turbine during operation, ensure the smooth operation of the turbine, and can be adjusted according to the operating conditions of the turbine to reduce the anti-cavitation cost.

Description

Technical Field

[0001] The invention relates to the technical field of fluid machinery and energy engineering equipment, and in particular to an adaptively controlled anti-cavitation water pump turbine. Background Art

[0002] As people's awareness of energy conservation and environmental protection increases, wind power generation, solar power generation, and hydropower generation, as clean energy sources, are being vigorously developed. At present, hydropower generation is still the main clean energy source. The basic principle of hydropower generation is to use the potential energy of water stored in the reservoir to drive the turbine to rotate, and the turbine in turn drives the generator to rotate to generate electricity. Due to the uneven electricity consumption in different periods of the day, in order to make full use of electricity, people have invented pumped storage power stations. During the peak period of electricity consumption during the day, the high-pressure water flow from the reservoir and upstream is used to drive the turbine to drive the generator to generate electricity, and the low-pressure water flow after power generation enters a large reservoir; at night, when electricity consumption is low, the generator is powered on and reversed to become a large motor. At this time, the motor drives the turbine to rotate, and the turbine at this time becomes a water pump, thereby extracting the water stored in the reservoir and transporting the stored water to the upstream reservoir for power generation during the day.

[0003] We know that for a vertical mixed flow turbine, it usually includes a vertical shaft, a ring-shaped runner is provided at the lower end of the shaft, and a ring-shaped volute is provided on the periphery of the runner. The volute is connected to the upstream water flow, thereby forming a high-pressure mixed flow area inside the ring-shaped volute, that is, the runner is located in the mixed flow area, and the lower part of the runner is connected to the low-pressure tailwater pipe, and the tailwater pipe is connected to the reservoir. When the upstream is waterproof and the water flow in the volute impacts the blades of the runner, thereby driving the runner to rotate, it can drive the shaft to rotate, and then drive the generator to generate electricity. After doing work on the blades, the water flow with a slow flow rate and a reduced pressure flows into the reservoir through the tailwater pipe. In other words, the mixed flow area is a high-pressure area with a certain water pressure, while the tailwater pipe area is a normal pressure area. When the high-pressure water flow drives the turbine shaft to rotate at high speed through the blades, a temporary vacancy is formed on the back of the runner blades due to the "original water flow being removed", and the water flow next to it cannot fill the temporary vacancy in time. Therefore, local negative pressure or low pressure will appear to form a negative pressure area, and accordingly, its water flow will form vortices and cavitation. In particular, when the local pressure in the liquid is reduced, the vapor or gas originally dissolved in the liquid or on the liquid-solid interface will precipitate to form cavities (cavitations). When the cavitations are continuously "generated", "grown", "broken", and "generated again", the so-called "cavitation" is formed. At this time, after the metal material is subjected to the impact of cavitation, the surface will be deformed and the material will be eroded, which is called cavitation. In the cavitation process, the cavitation bubbles are rapidly generated, expanded and collapsed, forming shock waves or high-speed microjets in the liquid. After the metal material is impacted, the surface crystal structure is distorted, chemical instability occurs, and the adjacent grains have different potentials, thereby accelerating the electrochemical corrosion process. The mechanical properties of the material in the eroded area deteriorate significantly, resulting in a sharp increase in the amount of cavitation. This causes the vibration of the unit to increase, and after long-term operation, it will cause cavitation on the surface of the blades, endangering the safe and stable operation of the unit. Since the above-mentioned cavitation process is a common phenomenon in the technical field of fluid machinery and energy engineering equipment, it belongs to "existing technical problems", so in this application document, its principles are not described in detail. In order to effectively solve the above-mentioned cavitation problem, when designing a turbine, a corresponding anti-cavitation structure is usually set up. Specifically, by setting a corresponding air supply pipeline, external air can be input into the negative pressure area such as the mixed flow area for air supply, so as to eliminate the negative pressure of the water flow in the negative pressure area and the formation of vortices.

[0004] However, the existing turbine air supply structure and air supply principle have the following technical defects: First, when the external air or compressed air is input into the mixed flow area and other negative pressure areas for air supply, it is a fixed rhythm of "passive air supply", that is, it is impossible to scientifically and reasonably adjust the air supply amount according to the actual needs of the different operating conditions of the turbine. The consequence is that it either causes insufficient air supply, which makes the turbine a safety hazard; or causes excessive air supply, which not only causes waste, is not conducive to improving efficiency and reducing costs, but also increases bubbles. Secondly, because the high-speed operation of the runner will cause the position of the back water surface to change continuously, even if people install corresponding pressure sensors inside the turbine unit, they cannot truly detect the pressure of the negative pressure area and then determine the appropriate air supply amount. In other words, in the entire mixed flow area, the real negative pressure cavitation area is only a few positions, and it is difficult for the existing technology to "air supply and defoam" for the real negative pressure cavitation area. In particular, water flow is an almost incompressible fluid, while gas is a compressible fluid. Therefore, using compressible gas to compensate for the negative pressure area and cavitation formed by the incompressible water flow cannot be equivalent to the water flow performance under the pressure balance state. In other words, the above-mentioned gas replenishment method can only reduce the effects of negative pressure, cavitation, etc., but cannot fundamentally eliminate the problems caused by negative pressure and cavitation. In fact, gas replenishment itself will also cause additional bubbles. Summary of the invention

[0005] The purpose of the present invention is to provide an adaptively regulated anti-cavitation water pump turbine, which can perform targeted "defoaming" according to the actual position of the negative pressure area, so as to effectively eliminate cavitation problems such as negative pressure and cavitation during the operation of the water pump turbine, ensure the smooth operation of the turbine, and at the same time can be adjusted according to different operating conditions of the turbine to improve the power generation efficiency and reduce the operating cost of anti-cavitation.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] An adaptively controlled anti-cavitation water pump turbine comprises a main shaft connected to a generator at the upper end, a mixed flow area located at the lower end of the main shaft, a runner located in the mixed flow area, and a volute located outside the mixed flow area. The lower part of the mixed flow area is connected to a tailwater pipe, and the tailwater pipe is connected to a reservoir through a pipeline. An outlet is arranged on the inner side of the volute, and a guide vane for guiding the direction of water flow is arranged in the water outlet. The runner comprises an upper crown connected to the main shaft, a lower ring, and a plurality of blades connected between the upper crown and the lower ring and uniformly distributed in the circumferential direction. The lower end of the main shaft is provided with a guide vane extending axially upward and communicating with the mixed flow area on the water-facing side of the blade. Flow hole, a plurality of radial fluid holes are arranged in the upper crown, the side of the blade located in the front side of the rotation direction is the water-facing side, and the side located in the rear side of the rotation direction is the water-receiving side, a vertical water supply pipe is arranged near the water-receiving side, the water supply pipe is provided with a water outlet hole, the upper end of the water supply pipe is sealed and connected in the upper crown, the outer end of the fluid hole is connected with the corresponding upper end of the water supply pipe, and the inner end of the fluid hole passes through the drainage hole of the main shaft. When the impeller rotates at high speed, negative pressure and vortex are generated on the water-receiving side of the blade, and the drainage hole of the main shaft introduces high-pressure water flow in the mixed flow area, and then enters the water-receiving side of the blade through the fluid hole and the water supply pipe and is sprayed out to disperse the vortex and balance the negative pressure.

[0008] We know that for a water pump turbine, the volute and impeller at the lower part of the main shaft form a mixed flow area with both high pressure and local negative pressure, wherein the mixed flow area on the water-facing side of the impeller is a high-pressure mixed flow area, and the mixed flow area on the water-receiving side of the impeller is a local negative pressure mixed flow area. The present invention provides a drainage hole at the lower end of the main shaft that is connected to the mixed flow area on the water-facing side of the blade, so as to facilitate the introduction of water flow in the high-pressure mixed flow area into the mixed flow area with local negative pressure, thereby balancing the negative pressure in the mixed flow area and dispersing the vortex in the mixed flow area, so that the water flow in the mixed flow area becomes "as smooth as possible" to avoid cavitation on the surface of the impeller.

[0009] That is to say, the present invention cleverly utilizes the water pressure difference existing in the mixed flow area itself, "sucks" the high-pressure water flow into the negative pressure area, and quickly fills the gap formed by "the original water flow being removed" in the mixed flow area without the need to input external airflow or water flow, thereby improving the anti-cavitation effect and enhancing the anti-cavitation efficiency. When the high-pressure water flow enters the local negative pressure area in the mixed flow area, it can well balance the negative pressure in the mixed flow area and disperse the vortex in the mixed flow area, thereby truly achieving "water replenishment" and reducing the consumption of external water sources and the operating cost of the turbine.

[0010] In addition, the present invention sets a vertical water supply pipe near the back water surface of the blade, and sets a radial fluid hole in the upper crown. In this way, when the main shaft rotates at a high speed, the radial fluid hole will form a negative pressure under the action of centrifugal force and "suck" the water flow introduced into the high-pressure mixed flow area in the drainage hole, and then enter the back water surface of the blade through the water supply pipe to balance the negative pressure and disperse the vortex.

[0011] Since the position of the water supply pipe and the upper crown is relatively fixed, it is not only convenient to install, but also no matter which position the impeller rotates to, the water supply pipe can always be located in the negative pressure area on the back water surface of the blade to perform targeted water supply balance, which is beneficial to reduce the consumption of balancing water, and improve the balancing effect of water flow, and there is no need for additional pressure sensors to detect the water pressure.

[0012] It can be understood that the present invention only shifts the water flow in the mixed flow area to achieve the effect of pressure balance, and when the impeller speed is high and the negative pressure is serious, the water replenishment amount is large; correspondingly, when the impeller speed is low and the negative pressure is not serious, the water replenishment amount is small. It will not have any adverse effect on the normal operation of the pump turbine, and can truly realize "adaptive control and anti-cavitation".

[0013] Preferably, the lower end of the drainage hole is closed, and a plurality of guide holes penetrating the drainage hole are provided on the circumferential surface of the lower end of the main shaft. The guide holes are arranged close to the water-facing surface of the blades, and the guide holes are inclined from the inside to the outside toward the front side of the blade rotation direction.

[0014] Since the lower end of the drainage hole is closed, when the main shaft rotates at a high speed, the fluid hole forming a negative pressure can easily "suck in" the high-pressure water flow in the mixed flow area introduced into the drainage hole.

[0015] We know that when the pump turbine is working, there will be high-pressure water flow in the volute. In other words, the area inside the volute is actually a "water area", and the lower end of the main shaft and the runner are located in this "water area". Since the guide hole at the lower end of the main shaft is inclined from the inside to the outside toward the front side of the blade rotation direction, when the main shaft rotates, the water flow in the "water area" will enter the drainage hole inside the main shaft through the guide hole, and form a "water-facing pressure increase" effect, which is conducive to increasing the pressure of the water flow entering the drainage hole.

[0016] Preferably, a guide vane is provided on the outer circumferential surface of the main shaft corresponding to the guide hole, one side of the guide vane is connected to the rear side of the guide hole in the direction of blade rotation, and the guide vane is inclined from inside to outside toward the front side in the direction of blade rotation.

[0017] When the wheel rotates at high speed, the guide vane will "scrape" the water flow into the guide hole and increase the pressure of the water flow entering the guide hole. In other words, the guide vane can play a similar role as the water-facing surface, and it only increases the pressure of the water flow entering the guide hole to balance the negative pressure, thus avoiding unnecessary power consumption of the main shaft.

[0018] Preferably, a booster blade is provided at the lower part of the drainage hole of the main shaft, and the drainage hole is located below the booster blade. A silicone sheet for sealing the drainage hole is provided on the inner wall of the drainage hole corresponding to the position of the drainage hole, and one side of the silicone sheet is bonded to the inner wall of the drainage hole. The fluid hole connected to the drainage hole is located above the booster blade. When the main shaft rotates at high speed, the external water flow squeezes the silicone sheet and enters the drainage hole through the guide hole, and the booster blade pressurizes the water flow above the drainage hole and enters the fluid hole.

[0019] When the main shaft rotates at high speed, the booster blades in the main shaft drainage hole will rotate synchronously at high speed, and then the water flow in the drainage hole will be boosted and accelerated upward. In other words, the booster blades at this time cleverly utilize the energy of the main shaft rotation and play a role similar to a booster pump, which is conducive to simplifying the structure and facilitating assembly. In particular, the negative pressure effect formed by the rotation of the booster blades can be used to suck water from the outside and enter the drainage hole through the diversion hole.

[0020] Preferably, the main shaft includes a main body section and a connecting section with a narrowed lower end, so that a step is formed between the main body section and the connecting section, a receiving hole is provided at the center of the upper crown of the runner, the upper crown of the runner is connected to the step, the connecting section coaxially extends into the receiving hole and forms a tubular valve cavity, a balancing hole penetrating the lower end of the upper crown is provided at the lower end of the tubular valve cavity, a valve sleeve movable up and down is provided in the tubular valve cavity, a spring for pressing the valve sleeve is provided at the lower part of the tubular valve cavity, and the connecting section is provided with a radially penetrating main shaft drainage hole at the position corresponding to the fluid hole The valve sleeve is provided with a radial conducting hole at a position corresponding to the diverter hole in the circumferential direction, and the valve sleeve includes a conducting position and a cut-off position. When the water pressure difference between the mixed flow area and the tailwater pipe is greater than or equal to δP, the valve sleeve is in the cut-off position, and the diverter hole and the corresponding fluid hole are misaligned and in a cut-off state; when the water pressure difference between the mixed flow area and the tailwater pipe is less than δP, the valve sleeve moves up and is in the conducting position, and the diverter hole and the corresponding fluid hole are butted and in a conducting state.

[0021] The main shaft of the present invention includes a main body section and a connecting section with a narrowed lower end, thereby forming a step between the main body section and the connecting section, which not only facilitates the installation of the upper crown of the runner on the main shaft and the axial positioning, but also forms a tubular valve cavity between the upper crown and the connecting section. We can set a valve sleeve and a spring in the tubular valve cavity to form a reversing valve.

[0022] We know that for turbines with different head heights or operating in different working conditions, the water pressure in the mixed flow area and the return pipe will be different. Usually, the water pressure in the mixed flow area is mainly determined by the head height, and its water pressure will be much higher than one atmosphere. The higher the head height, the higher the water pressure in the mixed flow area. The tailwater pipe is connected to the downstream, and its water pressure is basically maintained at about one atmosphere. The lower side of the valve sleeve senses the low water pressure in the tailwater pipe through the balancing hole, while the upper part of the valve sleeve senses the high water pressure in the mixed flow area.

[0023] When the water pressure difference between the mixed flow area and the tailwater pipe is greater than or equal to the set pressure difference δP, it means that the negative pressure state in the mixed flow area of ​​the pump-turbine is not too serious. Accordingly, the negative pressure area of ​​the pump-turbine is mainly located in the tailwater pipe. At this time, the water pressure in the mixed flow area above the valve sleeve causes the valve sleeve to overcome the elastic force of the spring and move down to the cut-off position. Accordingly, the conducting hole on the valve sleeve is misaligned with the fluid hole and the diversion hole. Therefore, the water flow in the diversion hole of the main shaft cannot enter the mixed flow area, and can only directly enter the tailwater pipe through the through hole of the connecting section for water replenishment balance, which not only achieves the effect of water replenishment, but also minimizes the cost of water replenishment.

[0024] When the water pressure difference between the mixed flow area and the tailwater pipe is less than the set pressure difference δP, it means that the negative pressure state in the mixed flow area of ​​the pump-turbine is relatively serious. Therefore, the mixed flow area of ​​the pump-turbine becomes an important negative pressure area and needs to be replenished with water. At this time, the elastic force of the spring is greater than the downward pressure on the valve sleeve formed by the water pressure difference on both sides of the valve sleeve, so that the valve sleeve moves up to the cut-off position. Correspondingly, the conducting hole on the valve sleeve is connected with the fluid hole and the diverter hole. Therefore, part of the water flow in the through hole enters the mixed flow area, and the other part directly enters the tailwater pipe through the through hole of the connecting section, and then the two areas are replenished with water for balance.

[0025] It should be noted that we can set a number of radial grooves extending to the tubular valve cavity at the step, or we can set a transition hole on the upper crown near the step, the upper end of the transition hole is connected to the radial groove, and the lower end of the transition hole is connected to the corresponding fluid hole, so that the upper part of the valve sleeve in the tubular valve cavity can sense the high water pressure in the mixed flow area.

[0026] Therefore, the present invention has the following beneficial effects: targeted "defoaming" can be performed according to the actual position of the negative pressure area to effectively eliminate cavitation problems such as negative pressure and cavitation during the operation of the pump-turbine, ensuring the smooth operation of the pump-turbine, and at the same time, adaptively adjust according to different operating conditions of the pump-turbine to improve the power generation efficiency and reduce the operating cost of anti-cavitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention.

[0028] Figure 2 It is a local structural diagram of the connection between the main shaft and the runner.

[0029] Figure 3 It is another partial structural schematic diagram of the connection between the main shaft and the runner.

[0030] In the figure: 1, main shaft 11, drainage hole 12, guide hole 14, main section 15, connecting section 151, diversion hole 16, step 2, runner 21, blade 22, upper crown 221, fluid hole 222, accommodating hole 23, lower ring 24, water supply pipe 241, water outlet hole 25, tubular valve cavity 251, balance hole 26, valve sleeve 261, conducting hole 27, spring 3, volute 31, water outlet 4, guide vane 5, tailwater pipe 6, booster blade. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0032] like Figure 1 , Figure 2 As shown, an adaptively controlled anti-cavitation pump turbine includes a vertical main shaft 1, the upper end of the main shaft is connected to a generator (not shown in the figure), the lower end of the main shaft is connected to a runner 2 with blades 21, a volute 3 is provided on the periphery of the runner, a water outlet 31 is provided on the inner side of the volute, a guide vane 4 for guiding the direction of the water flow is provided in the water outlet, a tailwater pipe 5 for guiding the water flow after the runner works is provided below the runner, and the tailwater pipe is connected to a reservoir (not shown in the figure) through a pipeline. The runner includes an upper crown 22 connected to the main shaft, a lower ring 23, and a plurality of blades vertically connected between the upper crown and the lower ring and evenly distributed in the circumferential direction. The area where the runner is located is a high-pressure mixed flow area, and the water flow in the tailwater pipe at the lower part of the runner is a low-pressure area. The side of the blade located in the front side of the rotation direction is the water-facing surface, and the side located in the rear side of the rotation direction is the water-receiving surface.

[0033] During the peak electricity consumption period in the daytime, the water flow from the upstream reservoir enters the volute and impacts the water-facing surface of the impeller, causing the impeller to rotate at high speed, which drives the main shaft to rotate, and then drives the generator to generate electricity. The low-pressure water flow that has done work on the impeller flows through the tailwater pipe to the downstream reservoir for water storage. At this time, the pump turbine operates in the power generation mode.

[0034] During the period of low electricity consumption at night, the generator is powered and drives the shaft to rotate. At this time, the generator becomes an electric motor, and the shaft drives the impeller to rotate, thereby pumping water from the downstream reservoir. The pumped water is transported to the upstream reservoir through the volute and the pipes connected to the volute, in preparation for subsequent water release and power generation. At this time, the pump turbine operates in pumping mode.

[0035] Since the basic structure of the above-mentioned water turbine belongs to the prior art, it will not be described in detail in this embodiment. Of course, the water pump turbine in this embodiment preferably refers to a vertical Francis turbine.

[0036] As described in the background art, when the impeller rotates at high speed, the water pressure on the water-facing side of the blades will increase, while the water pressure on the water-repellent side will decrease, thereby forming a negative pressure area and corresponding vortices and cavitations.

[0037] To this end, we can set a drainage hole 11 extending axially upward at the lower end of the main shaft, the lower end of the drainage hole is connected to the mixed flow area on the water-facing side of the blade, a number of radial fluid holes 221 are provided in the upper crown, and a number of vertical water supply pipes 24 are provided near the back water surface of the upper crown. The lower end of the water supply pipe is opened to form a water outlet 241. The upper end of the water supply pipe is sealed and connected in the upper crown. The outer end of the fluid hole is connected to the upper end of the corresponding water supply pipe, and the inner end of the fluid hole passes through the drainage hole of the main shaft. When the impeller and the main shaft rotate at high speed, negative pressure and vortex are generated on the back water surface of the blade. The main shaft drainage hole introduces high-pressure water flow from the mixed flow area on the water-facing side of the blade, and then enters the negative pressure area on the back water surface of the blade through the fluid hole and the water supply pipe, and is sprayed out through the water outlet to disperse the vortex and balance the negative pressure.

[0038] The drainage holes facilitate the introduction of water flow in the mixed flow area into the negative pressure area of ​​the mixed flow area, thereby balancing the negative pressure in the mixed flow area and dispersing the vortex in the mixed flow area, making the water flow in the mixed flow area become "as smooth as possible" to avoid cavitation on the surface of the impeller.

[0039] That is to say, the present invention cleverly utilizes the water pressure difference existing in the mixed flow area itself, "sucks" the high-pressure water flow into the negative pressure area, and quickly fills the gap formed by "the original water flow being removed" in the mixed flow area without the need to input external airflow or water flow, thereby improving the anti-cavitation effect and enhancing the anti-cavitation efficiency. When the high-pressure water flow enters the local negative pressure area in the mixed flow area, it can well balance the negative pressure in the mixed flow area and disperse the vortex in the mixed flow area, thereby truly achieving "water replenishment" and reducing the consumption of external water sources and the operating cost of the turbine.

[0040] In order to prevent the water supply pipe from "stirring" the water flow when the impeller rotates at high speed, the water supply pipe can be basically set inside the upper crown. In other words, the exposed part of the water supply pipe should be as short as possible.

[0041] In addition, the present invention sets a vertical water supply pipe near the back water surface of the blade, and sets a radial fluid hole in the upper crown. In this way, when the main shaft rotates at a high speed, the radial fluid hole will form a negative pressure under the action of centrifugal force and "suck" the water flow introduced into the high-pressure mixed flow area in the drainage hole, and then enter the back water surface of the blade through the water supply pipe to balance the negative pressure and disperse the vortex.

[0042] Since the position of the water supply pipe and the upper crown is relatively fixed, it is not only convenient to install, but also no matter which position the impeller rotates to, the water supply pipe can always be located in the negative pressure area on the back water surface of the blade to perform targeted water supply balance, which is beneficial to reduce the consumption of balancing water, and improve the balancing effect of water flow, and there is no need for additional pressure sensors to detect the water pressure.

[0043] It can be understood that the present invention only shifts the water flow in the mixed flow area to achieve the effect of pressure balance, and when the impeller speed is high and the negative pressure is serious, the water replenishment amount is large; correspondingly, when the impeller speed is low and the negative pressure is not serious, the water replenishment amount is small. It will not have any adverse effect on the normal operation of the pump turbine, and can truly realize "adaptive control and anti-cavitation".

[0044] As a first preferred solution, Figure 2 As shown, we can close the lower end of the drainage hole to facilitate "storing water flow" in the drainage hole. In addition, a plurality of diversion holes 12 penetrating the drainage hole are arranged on the circumferential surface of the lower end of the main shaft. The diversion holes are arranged near the water-facing surface of the blades, and the diversion holes are inclined from the inside to the outside toward the front side of the blade rotation direction.

[0045] Since the lower end of the drainage hole is closed, when the main shaft rotates at a high speed, the fluid hole forming a negative pressure can easily "suck in" the high-pressure water flow in the mixed flow area introduced into the drainage hole.

[0046] We know that when the pump turbine is working, there will be high-pressure water flow in the volute. In other words, the volute and runner at the bottom of the main shaft are actually located in the mixed flow area with water. When the main shaft rotates at high speed, the water flow in the fluid hole of the upper crown is radially "thrown out" under the action of centrifugal force, so that the fluid hole and the drainage hole connected to it form a negative pressure (the drainage hole closed at the lower end will enhance the negative pressure effect). At this time, the water flow outside the main shaft can be "sucked" into the drainage hole through the diversion hole, and transported to the negative pressure area on the back of the blade through the fluid hole.

[0047] Since the guide hole is inclined from the inside to the outside toward the front side of the blade rotation direction, when the main shaft rotates, the water flow will enter the drainage hole inside the main shaft through the guide hole, and form a "water-facing pressure increase" effect, which is beneficial to increase the pressure of the water flow entering the drainage hole.

[0048] Furthermore, we can set a guide vane on the circumferential surface of the lower end of the main shaft corresponding to the guide hole, one side of the guide vane is welded to the main shaft where the guide hole is located on the rear side of the blade rotation direction, and the guide vane is inclined from the inside to the outside toward the front side of the blade rotation direction.

[0049] When the wheel rotates at high speed, the guide vane will "scrape" the water flow into the guide hole and increase the pressure of the water flow entering the guide hole. In other words, the guide vane can play a similar role as the water-facing surface, and it only increases the pressure of the water flow entering the guide hole to balance the negative pressure, thereby avoiding unnecessary power consumption of the main shaft.

[0050] Furthermore, we can also set a booster blade 6 including a central axis at the lower part of the drainage hole of the main shaft, the drainage hole is located below the booster blade, and the inner wall of the drainage hole is provided with a silicone sheet for sealing the drainage hole corresponding to the position of the drainage hole, one side of the silicone sheet is bonded to the inner wall of the drainage hole, and the inner wall of the drainage hole is provided with a silicone sheet for sealing the drainage hole corresponding to the position of the drainage hole.

[0051] When the main shaft rotates at high speed, the booster blades in the main shaft drainage hole will rotate synchronously at high speed, and then the water flow in the drainage hole will be pressurized and accelerated upward. In other words, the booster blades cleverly utilize the energy of the main shaft rotation and play a role similar to a booster pump, which is conducive to simplifying the structure and facilitating assembly. In particular, the negative pressure effect formed by the rotation of the booster blades can be used to suck water from the outside and enter the drainage hole through the diversion hole.

[0052] When the turbine runs at a low speed or stops running, negative pressure and cavitation will not form on the back surface of the blade. At this time, the external water flow cannot squeeze the silicone sheet, and the water flow in the drainage hole acts on the silicone sheet, so that the silicone sheet reliably blocks the diversion hole. At this time, the water flow in the diversion hole cannot flow out through the diversion hole. In other words, the silicone sheet at this time plays the role of a simple check valve, which is conducive to simplifying the structure and facilitating assembly.

[0053] It should be noted that we can set a detachable sealing cover at the lower end of the main shaft, and the central axis of the booster blade is fixed inside the sealing cover. When we install the sealing cover at the lower end of the main shaft, the booster blade can be fixed in the drainage hole of the main shaft.

[0054] As a second preferred solution, Figure 3As shown, the main shaft includes a main body section 14 at the upper part and a connecting section 15 with a reduced lower end, so that a step 16 is formed between the main body section and the connecting section. A receiving hole 222 is provided at the center of the upper crown of the runner, and the upper crown of the runner is connected at the step. The connecting section coaxially extends into the receiving hole, and a tubular valve cavity 25 is formed between the connecting section and the receiving cavity. A balancing hole 251 penetrating the lower end of the upper crown is provided at the lower end of the tubular valve cavity. In addition, a valve sleeve 26 that can move up and down is provided in the tubular valve cavity, and a spring 27 that presses the valve sleeve is provided at the lower part of the tubular valve cavity. A diverter hole 151 that radially penetrates the main shaft drainage hole is provided at the corresponding fluid hole position of the connecting section, and a radial conducting hole 261 is provided at the corresponding diverter hole position in the circumferential direction of the valve sleeve. The valve sleeve includes a conducting position and a cut-off position. When the water pressure difference between the mixed flow area and the tailwater pipe is greater than or equal to δP, the valve sleeve is in the cut-off position, and the diverter hole and the corresponding fluid hole are misaligned and in the cut-off state; when the water pressure difference between the mixed flow area and the tailwater pipe is less than δP, the valve sleeve moves up and is in the conducting position, and the diverter hole and the corresponding fluid hole are docked and in the conducting state.

[0055] Since the main shaft includes a main section and a connecting section with a narrowed lower end, a step is formed between the main section and the connecting section, which not only facilitates the installation of the upper crown of the runner on the main shaft and the axial positioning, but also forms a tubular valve cavity between the upper crown and the connecting section. We can set a valve sleeve and a spring in the tubular valve cavity to form a reversing valve.

[0056] It should be noted that we can make the spring sleeve mounted on the connecting section, or we can also set a number of positioning posts at the lower end of the valve sleeve, the positioning posts are evenly distributed in the circumferential direction, and each positioning post is sleeved with the spring. In this way, when the valve sleeve is in the cut-off position, the positioning posts are positioned against the lower end surface of the tubular valve cavity.

[0057] Of course, we can set a number of radial grooves extending to the tubular valve cavity at the step, or we can set a transition hole on the upper crown near the step, the upper end of the transition hole is connected to the radial groove, and the lower end of the transition hole is connected to the corresponding fluid hole, so that the upper part of the valve sleeve in the tubular valve cavity can sense the high water pressure in the mixed flow area.

[0058] We know that for turbines with different head heights or operating in different working conditions, the water pressure in the mixed flow area and the return pipe will be different. Usually, the water pressure in the mixed flow area is mainly determined by the head height, and its water pressure will be much higher than one atmosphere. The higher the head height, the higher the water pressure in the mixed flow area. The tailwater pipe is connected to the downstream, and its water pressure is basically maintained at around one atmosphere. The lower side of the valve sleeve senses the low water pressure in the tailwater pipe through the balancing hole, while the upper part of the valve sleeve senses the high water pressure in the mixed flow area. The water flow pressure in the mixed flow area is usually between 0.25MPa-0.30MPa, while the water flow pressure in the tailwater pipe is roughly maintained within the range of ±0.05MPa.

[0059] When the water pressure difference between the mixed flow area and the tailwater pipe is greater than or equal to the set pressure difference δP, it means that the negative pressure state in the mixed flow area of ​​the pump-turbine is not too serious. Accordingly, the negative pressure area of ​​the pump-turbine is mainly located in the tailwater pipe. At this time, the water pressure in the mixed flow area above the valve sleeve causes the valve sleeve to overcome the elastic force of the spring and move down to the cut-off position. Accordingly, the conducting hole on the valve sleeve is misaligned with the fluid hole and the diversion hole. Therefore, the water flow in the diversion hole of the main shaft cannot enter the mixed flow area, and can only directly enter the tailwater pipe through the through hole of the connecting section for water replenishment balance, which not only achieves the effect of water replenishment, but also minimizes the cost of water replenishment.

[0060] When the water pressure difference between the mixed flow area and the tailwater pipe is less than the set pressure difference δP, it means that the negative pressure state in the mixed flow area of ​​the turbine is relatively serious. Therefore, the mixed flow area of ​​the turbine becomes an important negative pressure area and needs to be replenished with water. At this time, the elastic force of the spring is greater than the downward pressure on the valve sleeve formed by the water pressure difference on both sides of the valve sleeve, so that the valve sleeve moves up to the cut-off position. Correspondingly, the conducting hole on the valve sleeve is connected with the fluid hole and the diversion hole. Therefore, part of the water flow in the through hole enters the mixed flow area, and the other part directly enters the tailwater pipe through the through hole of the connecting section, and then the two areas are replenished with water for balance.

Claims

1. An adaptively controlled anti-cavitation pump turbine, comprising a main shaft connected to a generator at the upper end, a mixed flow area located at the lower end of the main shaft, a runner located in the mixed flow area, and a volute located outside the mixed flow area, wherein the lower part of the mixed flow area is connected to a tailwater pipe, and the tailwater pipe is connected to a reservoir through a pipeline, an outlet is provided on the inner side of the volute, and a guide vane for guiding the direction of water flow is provided in the water outlet, the runner comprises an upper crown connected to the main shaft, a lower ring, and a plurality of blades connected between the upper crown and the lower ring and evenly distributed in the circumferential direction, wherein the runner comprises an upper crown connected to the main shaft, a lower ring, and a plurality of blades connected between the upper crown and the lower ring and evenly distributed in the circumferential direction, wherein the runner comprises an upper crown connected to the main shaft, a lower ring, and a plurality of blades connected between the upper crown and the lower ring and evenly distributed in the circumferential direction, wherein the runner comprises an upper crown connected to the main shaft, a lower ring, and a plurality of blades connected between the upper crown and the lower ring and evenly distributed in the circumferential direction, and wherein the runner comprises an upper crown connected to the main shaft, a lower ring, and a plurality of blades connected between the upper crown and the lower ring and evenly distributed in the circumferential direction, and wherein the runner comprises an upper crown connected to the main shaft, a lower ring, and a plurality of blades connected between the upper crown and the lower ring and evenly distributed in the circumferential direction, and wherein the runner comprises an upper crown connected to the main shaft, a lower ring, and a plurality of blades connected between the upper crown and the lower ring and uniform ... The lower end of the main shaft is provided with a drainage hole extending axially upward and connected to the mixed flow area on the water-facing side of the blade. A plurality of radial fluid holes are provided in the upper crown. The side of the blade located in the front side of the rotation direction is the water-facing side, and the side located in the rear side of the rotation direction is the back water side. A vertical water supply pipe is provided near the back water side, and a water outlet hole is provided on the water supply pipe. The upper end of the water supply pipe is sealed and connected in the upper crown. The outer end of the fluid hole is connected to the corresponding upper end of the water supply pipe, and the inner end of the fluid hole passes through the drainage hole of the main shaft. When the impeller rotates at high speed, negative pressure and vortex are generated on the back water side of the blade, and the high pressure in the mixed flow area is introduced into the drainage hole of the main shaft. The pressurized water flow then enters the back water surface of the blade through the fluid hole and the water supply pipe and is sprayed out to disperse the vortex and balance the negative pressure; the lower end of the drainage hole is closed, and a plurality of guide holes that penetrate the drainage hole are provided on the circumferential surface of the lower end of the main shaft. The guide holes are arranged near the water-facing surface of the blade, and the guide holes are inclined from the inside to the outside toward the front side of the rotation direction of the blade; a booster blade is provided at the lower part of the drainage hole of the main shaft, and the guide hole is located below the booster blade, and a silicone sheet for sealing the guide hole is provided on the inner wall of the drainage hole corresponding to the position of the guide hole, and one side of the silicone sheet is bonded to the inner wall of the drainage hole, and the fluid hole connected with the drainage hole is located above the booster blade.

2. The adaptive control anti-cavitation pump turbine according to claim 1 is characterized in that: A guide vane is arranged on the outer circumferential surface of the main shaft at a position corresponding to the guide hole. One side of the guide vane is connected to the rear side of the guide hole in the direction of rotation of the blade. The guide vane is inclined from inside to outside toward the front side in the direction of rotation of the blade.

3. The adaptive control anti-cavitation pump turbine according to claim 1 is characterized in that: When the impeller rotates at high speed, the external water flow squeezes the silicone sheet and enters the drainage hole through the guide hole. The booster blade boosts the water flow above the drainage hole and enters the fluid hole.

4. The adaptive control anti-cavitation pump turbine according to claim 1 is characterized in that: A detachable sealing cover is arranged at the lower end of the main shaft, the central axis of the booster blade is fixedly arranged inside the sealing cover, and the booster blade is fixedly arranged in the drainage hole of the main shaft.

Images