A water pump turbine air supply structure

Abstract

The invention discloses a pump turbine air supply structure, comprising a main shaft connected to a generator at the upper end and provided with a through hole at the center, a mixed flow area located at the lower end of the main shaft, a runner with blades located in the mixed flow area, and a volute located at the periphery of the mixed flow area, a water outlet is provided on the inner side of the volute, a guide vane capable of guiding the direction of water flow is provided in the water outlet, the lower part of the mixed flow area is connected to a tailwater pipe, and a drainage pipe is further provided, one end of the drainage pipe is connected to a fluid source, and the other end is communicated with the through hole at the upper end of the main shaft, the lower end of the main shaft is communicated with the mixed flow area, when negative pressure and vortex appear in the water flow in the mixed flow area, the fluid in the drainage pipe can enter the mixed flow area through the through hole of the main shaft to balance the negative pressure and disperse the vortex. The invention can effectively eliminate the problems of negative pressure and cavitation during the operation of the turbine, ensure the stable operation of the turbine, and can be adjusted according to different operating conditions of the turbine to improve the power generation efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of fluid machinery and energy engineering equipment, and in particular to an air supply structure for a 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 a water pump turbine air supply structure, which can effectively eliminate the negative pressure, cavitation and other problems of the water pump turbine during operation, ensure the smooth operation of the water pump turbine, and at the same time can be adjusted according to different operating conditions of the water pump turbine to improve the power generation efficiency.

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

[0007] A water pump turbine air replenishment structure includes a main shaft connected to a generator at the upper end and provided with a through hole in the center, a mixed flow area located at the lower end of the main shaft, a runner with blades located in the mixed flow area, and a volute located at the periphery of the mixed flow area. A water 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 lower part of the mixed flow area is connected to a tailwater pipe, and also includes a drainage pipe, one end of the drainage pipe is connected to a fluid source, and the other end is connected to the through hole at the upper end of the main shaft. The lower end of the main shaft is connected to the mixed flow area. When negative pressure and vortex appear in the water flow in the mixed flow area, the fluid in the drainage pipe can enter the mixed flow area through the through hole of the main shaft to balance the negative pressure and disperse the vortex.

[0008] The present invention sets a through hole in the main shaft, so that the main shaft is tubular, which can greatly reduce the weight of the main shaft and reduce the manufacturing cost of the main shaft, and it is convenient to introduce external gas, water flow and other fluids into the mixed flow area at the bottom of the main shaft, so as to balance the negative pressure in the mixed flow area and disperse 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] In particular, compared with additional fluid pipelines, the through hole in the rotating shaft can effectively avoid entanglement and interference when the main shaft rotates, greatly facilitating structural layout and assembly. Of course, we need to set a corresponding sealing structure at the connection between the drainage tube and the through hole at the upper end of the main shaft.

[0010] Specifically, we can set a sealing cover to block the through hole at the upper end of the main shaft, set a sealing through hole in the center of the sealing cover, and vertically set a rotatable connecting tube in the sealing through hole. The upper end of the connecting tube is connected to the drainage tube, and an annular groove is provided on the circumferential surface of the connecting tube in the sealing through hole. An O-ring is provided in the annular groove, so as to achieve sealing between the connecting tube and the sealing cover without hindering the rotation of the main shaft.

[0011] It can be understood that for the pump-turbine, when operating in the power generation mode, the high-pressure water flow in the volute impacts the water-facing surface of the blade, that is, the upstream side of the blade is the water-facing surface; when operating in the pumping mode, the impeller extracts the low-pressure water in the reservoir and transports it to the upstream reservoir, and at this time the upstream side of the blade is still the high-pressure water-facing surface, that is, no matter which mode the pump-turbine works in, the water-facing surface and the back-water surface of the blade remain unchanged, therefore, the above structure and technical solution are applicable in both modes.

[0012] Preferably, one end of the drainage pipe is connected to the volute, and when negative pressure and vortex appear in the water flow in the mixed flow area, the high-pressure water flow in the volute enters the mixed flow area through the drainage pipe and the through hole of the main shaft to balance the negative pressure and disperse the vortex.

[0013] We know that no matter the turbine is working in power generation mode or pumping mode, there is high-pressure water flow in the volute. In this scheme, the drainage pipe introduces the high-pressure water flow in the volute, which will form a large pressure difference relative to the local negative pressure area in the mixed flow area. The present invention utilizes the siphon principle of water and can deliver water into the through hole of the main shaft without the need for a conveying power such as a water pump, thereby simplifying the structural layout and reducing energy consumption. 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 with water".

[0014] In particular, for a hydroelectric power station, the thing that is least lacking is water. The present invention ingeniously introduces the high-pressure water flow in the volute into the mixed flow area, which can not only greatly reduce the consumption of additional resources and the operating cost of the turbine, but also allow the water flow to quickly fill the gap in the mixed flow area after the "original water flow is removed", thereby improving the air replenishment effect and increasing the air replenishment efficiency.

[0015] Preferably, a plurality of booster impellers arranged at intervals along the axial direction are provided in the main shaft through hole, and the booster impeller comprises a rotating shaft and booster blades arranged on the rotating shaft, and the rotating shafts of the booster blades are coaxially connected. When the rotating wheel drives the main shaft to rotate at a high speed, the booster impeller rotates at a high speed relative to the fluid in the through hole, thereby pressurizing the fluid in the through hole.

[0016] It is understandable that when the rotating wheel drives the main shaft to rotate at high speed, the booster impeller in the main shaft through hole will rotate synchronously at high speed, thereby boosting the fluid flowing through the through hole. In other words, the present invention cleverly utilizes the energy of the main shaft rotation to boost the fluid, thereby saving external booster pumps and other equipment, thereby greatly simplifying the structure and facilitating assembly.

[0017] Preferably, the impeller comprises an upper crown, a lower ring, and a plurality of blades connected between the upper crown and the lower ring, the blades being evenly distributed in the circumferential direction, a plurality of radial fluid holes being provided in the upper crown, the side of the blade located in front of the rotation direction being the water-facing side, the side located in the rear of the rotation direction being the water-receiving side, a vertical water supply pipe being provided near the water-receiving side, the water supply pipe being provided with a water outlet, the upper end of the water supply pipe being sealed and connected in the upper crown and being communicated with the fluid holes, when the impeller drives the main shaft to rotate at a high speed, negative pressure and vortex are generated on the water-receiving side of the blade, the water flow in the main shaft through-hole enters the water-receiving side of the blade through the water supply pipe to balance the negative pressure and disperse the vortex.

[0018] As we know, the existing turbine runner usually includes an upper crown, a lower ring, and a plurality of blades connected between the upper crown and the lower ring. 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, the high-pressure water flow in the main shaft can enter the back water surface of the blade through the water supply pipe to balance the negative pressure and disperse the vortex.

[0019] In particular, the water supply pipe is arranged on the back surface of the blade, and the upper end of the water supply pipe is sealed and connected in the upper crown. In other words, the position of the water supply pipe and the upper crown is relatively fixed, which is not only convenient for installation, but also no matter which position the runner rotates to, the water supply pipe can always be located in the negative pressure area on the back surface of the blade to carry out targeted water supply balance, which is beneficial to reduce the consumption of balancing water and improve the balancing effect of water flow. And no additional pressure sensor is required to detect the water pressure.

[0020] It is understandable that, since the negative pressure area is supplemented with water flow, even if the actual water replenishment exceeds the required water replenishment, it will be discharged downstream through the tailwater pipe below, and will not have any adverse effect on the normal operation of the turbine.

[0021] Preferably, the main shaft includes a main body section and a connecting section with a narrowed lower end, so as to form a step 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 at the step, the connecting section coaxially extends into the receiving hole and forms a tubular valve cavity, a valve sleeve which can move 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, a diverter hole which radially penetrates the main shaft through hole is provided in the connecting section at a position corresponding to the fluid hole, and a radial conducting hole is provided at a position corresponding to the diverter hole in the circumferential direction, the valve sleeve includes a conducting position and a shut-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 shut-off position, and the diverter hole and the corresponding fluid hole are shut off; 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 conducting.

[0022] 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.

[0023] 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. 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 turbine is not too serious. Accordingly, the negative pressure area of ​​the turbine is mainly located in the tailwater pipe. At this time, the water pressure in the mixed flow area on the upper part of 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 conduction hole on the valve sleeve is misaligned with the fluid hole and the diversion hole. Therefore, the water flow in the through hole 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, that is, to achieve the effect of water replenishment and minimize the cost of water replenishment. 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.

[0024] It should be noted that we can set a number of radial grooves extending into the tubular valve cavity at the step. Of course, we can also set a transition hole at 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.

[0025] Therefore, the present invention has the following beneficial effects: it can effectively eliminate negative pressure, cavitation and other problems during the operation of the 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the present invention.

[0027] Figure 2 It is a structural diagram of a booster impeller.

[0028] Figure 3 It is a schematic diagram of the connection structure between the impeller and the water supply pipe when the valve sleeve is in the cut-off position.

[0029] In the figure: 1, main shaft 11, through hole 12, sealing cover 13, connecting pipe 14, main body section 15, connecting section 151, diverter hole 16, step 2, runner 21, blade 22, upper crown 221, fluid hole 222, accommodating hole 223, balance hole 23, lower ring 24, water supply pipe 241, water outlet hole 25, tubular valve cavity 26, valve sleeve 261, guide hole 27, spring 3, volute 31, water outlet 4, guide vane 5, tailwater pipe 6, drainage pipe 7, booster impeller 71, booster blade 72, rotating shaft. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, a pump turbine air supply structure comprises a vertical main shaft 1, a through hole 11 is arranged in the center of the main shaft, so that the main shaft is tubular, the upper end of the main shaft is connected to the generator (not shown in the figure), and the lower end of the main shaft is connected to the runner 2 with blades 21, a volute 3 is arranged on the periphery of the runner, a water outlet 31 is arranged on the inner side of the volute, and a guide vane 4 for guiding the direction of water flow is arranged in the water outlet, a tailwater pipe 5 for guiding the water flow after the runner does work is arranged below the runner, and the tailwater pipe is connected to a reservoir (not shown in the figure) through a pipeline, 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 at the front side of the rotation direction and the side with higher water pressure is the water-facing surface, and the side located at the rear side of the rotation direction and the side with lower water pressure is the water-repelling surface.

[0032] 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.

[0033] 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.

[0034] Since the basic structure and working principle of the pump turbine belong to the prior art, no detailed description is given in this embodiment. Of course, the turbine in this embodiment preferably refers to a vertical Francis turbine.

[0035] 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.

[0036] To this end, the present invention further includes a drainage pipe 6, one end of which is connected to a fluid source such as gas or water (not shown in the figure), and the other end is connected to the through hole at the upper end of the main shaft. Since the lower end of the through hole of the main shaft is connected to the mixed flow area, when negative pressure, cavitation, and vortex appear in the mixed flow area and the water flow in the tailwater pipe, the fluid in the drainage pipe can enter the mixed flow area through the through hole of the main shaft to balance the negative pressure and disperse the vortex.

[0037] Of course, the fluid source in this embodiment can be compressed air provided by an air pump, upstream water flow, or even external air or water source. In addition, we can set a corresponding control device at the fluid source to reasonably replenish air or water according to the operating conditions of the turbine.

[0038] Since the main shaft is tubular due to the through hole, the weight of the main shaft can be greatly reduced, the manufacturing cost of the main shaft can be reduced, and at the same time, it is convenient to introduce external gas, water flow and other fluids into the mixed flow area at the bottom of the main shaft and the tailwater pipe to balance the negative pressure in the mixed flow area and the tailwater pipe, and disperse the vortex in the mixed flow area and the tailwater pipe, so that the water flow in the mixed flow area and the tailwater pipe becomes "as smooth as possible" to avoid cavitation on the surface of the runner and the tailwater pipe.

[0039] It is understandable that the through hole in the rotating shaft can not only transport the fluid, but also effectively avoid entanglement and interference caused by the rotation of the main shaft, greatly facilitating the structural arrangement and assembly. Of course, we need to set a corresponding sealing structure at the connection between the drainage tube and the through hole at the upper end of the main shaft.

[0040] Specifically, we can set a sealing cover 12 for sealing the through hole at the upper end of the main shaft, set a sealing through hole in the center of the sealing cover, and vertically set a rotatable connecting tube 13 in the sealing through hole. The upper end of the connecting tube is connected to the drainage tube, and an annular groove is provided on the circumferential surface of the connecting tube in the sealing through hole. An O-ring is provided in the annular groove, which can achieve sealing between the connecting tube and the sealing cover without hindering the rotation of the main shaft.

[0041] As a preferred solution, the end of the drainage pipe away from the main shaft can be connected to the volute. In this way, when negative pressure and vortex appear in the mixed flow area or the water flow in the tailwater pipe, the high-pressure water flow in the volute passes through the drainage pipe and the through hole of the main shaft into the mixed flow area and the tailwater pipe to balance the negative pressure and disperse the vortex, thereby truly achieving "water replenishment".

[0042] In particular, for a hydroelectric power station, the most abundant thing is water. The present invention ingeniously introduces the high-pressure water flow in the volute into the mixed flow area, which can not only greatly reduce the consumption of additional resources and the operating cost of the turbine, but also enable the water flow to quickly make up for the cavitation formed in the mixed flow area and the tailwater pipe after the "original water flow is removed", and the water flow in the mixed flow area and the tailwater pipe remains stable.

[0043] As mentioned above, whether the pump-turbine is working in power generation mode or pumping mode, the inside of the volute and the side of the runner blade close to the upstream (volute water flow) are both water-facing surfaces with high water pressure. Therefore, the above scheme of the present invention is applicable to cavitation prevention in both power generation mode and pumping mode. For the convenience of description, the following scheme only describes the working principle and technical effect of the pump-turbine working in power generation mode, and does not describe the working principle and technical effect of the pump-turbine working in pumping mode.

[0044] Furthermore, if Figure 1 , Figure 2 As shown, we can also set a number of booster impellers 7 arranged at intervals along the axial direction in the through hole of the main shaft, and the booster impellers include a central rotating shaft 72 and a number of booster blades 71 arranged on the rotating shaft, and the rotating shafts of each booster impeller are coaxially connected as a whole. In addition, a flange connected to the upper crown is provided at the lower end of the main shaft, and a fixed disc is provided between the flange and the upper crown, wherein the edge of the booster blade of at least one booster impeller is connected to the fixed disc, so that all the booster impellers are fixed in the through hole of the main shaft. In this way, when the rotating wheel drives the main shaft to rotate at a high speed, the booster blades rotate with the main shaft. In other words, at this time, the booster blades rotate at a high speed relative to the fluid in the through hole, thereby forming a downward boosting effect, so that the fluid in the through hole is pressurized. This scheme cleverly utilizes the energy of the rotation of the main shaft to pressurize the fluid, thereby saving external equipment such as a booster pump, thereby greatly simplifying the structure and facilitating assembly.

[0045] We know that Figure 1 , Figure 3 As shown, the runner of this type of turbine should include an upper crown 22, a lower ring 23, and a plurality of blades 21 connected between the upper crown and the lower ring. The blades are evenly distributed in the circumferential direction. Of course, the upper crown and the lower ring are fixedly connected to the main shaft, while the blades are separated from the main shaft.

[0046] Furthermore, we can set a number of radial fluid holes 221 in the upper crown, and the fluid holes are evenly distributed in the circumferential direction. A vertical water supply pipe 24 is set near the back water surface of the blade, and the lower end of the water supply pipe is opened to form a water outlet hole 241. The upper end of the water supply pipe is sealed and connected in the upper crown and is connected to the fluid hole in the upper crown. When the runner drives the main shaft to rotate at a high speed, the back water surface of the blade generates negative pressure and vortex, and the water flow in the main shaft through-hole enters the back water surface of the blade through the water supply pipe to balance the negative pressure and disperse the vortex.

[0047] Since the water supply pipe is set on the back water surface of the blade, and the upper end of the water supply pipe is sealed and connected in the upper crown. In other words, the position of the water supply pipe and the upper crown is relatively fixed, which is not only convenient for installation, but also no matter where 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 carry out targeted water supply balance, which is beneficial to reduce the consumption of balancing water and improve the balancing effect of water flow. And no additional pressure sensor is required to detect the water pressure.

[0048] It is understandable that when the water flow added to the negative pressure zone exceeds the required water replenishment, it will not have a negative impact on the operation of the turbine, and all the water flow will be discharged downstream through the tailwater pipe below.

[0049] 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.

[0050] We know that the water pressure in the tailwater pipe is basically the same as the water pressure downstream, roughly maintained within the range of ±0.05MPa, while the water pressure in the mixed flow area is between 0.25MPa-0.30MPa. In other words, the water pressure in the mixed flow area will be much higher than the water pressure in the tailwater pipe. In addition, for pump 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.

[0051] As another preferred solution, Figure 3 As 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 of the main shaft coaxially extends into the receiving hole, and a tubular valve cavity 25 is formed between the connecting section and the receiving 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 through hole is provided in the connecting section at a position corresponding to the fluid hole, and a radial guide hole 261 is provided on the circumferential surface of the valve sleeve at a position corresponding to the diverter hole. The valve sleeve includes a conducting position and a cut-off position. When the water pressure in the mixed flow area and the water pressure in the tailwater pipe are 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 cut off; when the water pressure in the mixed flow area and the water pressure in the tailwater pipe are less than δP, the valve sleeve moves up and is in the conducting position, and the diverter hole and the corresponding fluid hole are connected.

[0052] 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.

[0053] Of course, we need to set a balancing hole 223 on the lower side of the upper crown that penetrates the tubular valve cavity upward, so that the water pressure in the tailwater pipe can act on the lower side of the valve sleeve. And a corresponding connecting hole should also be set between the tubular valve cavity on the upper side of the valve sleeve and the mixed flow area, so that the water pressure in the mixed flow area can act on the upper side of the valve sleeve.

[0054] That is to say, in this scheme, a reversing valve is formed by the tubular valve cavity formed by the upper crown and the connecting section, the valve sleeve and the spring. When the water pressure difference between the mixed flow area and the water pressure in 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 on the upper part of 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 diverter hole. Therefore, the water flow in the through hole 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 can achieve the effect of water replenishment and minimize the cost of water replenishment. When the water pressure in the mixed flow area and the water pressure in the tailwater pipe are 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, thereby moving the valve sleeve 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.

[0055] Of course, we can also set a number of radial grooves extending into the tubular valve cavity at the step, or we can also 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.

Claims

1. A pump turbine air supply structure, comprising a main shaft connected to a generator at the upper end and having a through hole in the center, a mixed flow area at the lower end of the main shaft, a runner with blades in the mixed flow area, and a volute located outside the mixed flow area, wherein a water 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, and the lower part of the mixed flow area is connected to a tailwater pipe, wherein: It also includes a drainage tube, one end of which is connected to a fluid source, and the other end is connected to a through hole at the upper end of the main shaft, and the lower end of the main shaft is connected to a mixed flow area. When negative pressure and vortex appear in the water flow in the mixed flow area, the fluid in the drainage tube can enter the mixed flow area through the through hole of the main shaft to balance the negative pressure and disperse the vortex. The main shaft is tubular, a sealing cover for blocking the through hole is arranged at the upper end of the main shaft, a sealing through hole is arranged at the center of the sealing cover, a rotatable connecting pipe is vertically arranged in the sealing through hole, the upper end of the connecting pipe is connected to the drainage pipe, an annular groove is arranged on the circumferential surface of the connecting pipe located in the sealing through hole, and an O-ring is arranged in the annular groove; The main shaft 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. A receiving hole is provided at the center of the upper crown of the runner, and the upper crown of the runner is connected to the step. The connecting section coaxially extends into the receiving hole to form a tubular valve cavity. A valve sleeve that can move up and down is provided in the tubular valve cavity, and a spring that presses the valve sleeve is provided at the lower part of the tubular valve cavity. The connecting section is provided with a diverter hole that radially penetrates the main shaft through hole at a position corresponding to the fluid hole radially arranged in the upper crown, and the valve sleeve is provided with a radial conducting hole at a position corresponding to the diverter hole in the circumferential direction.

2. The pump turbine air supply structure according to claim 1 is characterized in that: One end of the drainage pipe is connected to the volute. When negative pressure and vortex appear in the water flow in the mixed flow area, the high-pressure water flow in the volute enters the mixed flow area through the drainage pipe and the through hole of the main shaft to balance the negative pressure and disperse the vortex.

3. The pump turbine air supply structure according to claim 1 is characterized in that: A plurality of booster impellers arranged at intervals along the axial direction are provided in the main shaft through hole. The booster impeller includes a rotating shaft and booster blades arranged on the rotating shaft. The rotating shafts of the booster blades are coaxially connected. When the rotating wheel drives the main shaft to rotate at a high speed, the booster impeller rotates at a high speed relative to the fluid in the through hole, thereby pressurizing the fluid in the through hole.

4. The pump-turbine air supply structure according to claim 2 is characterized in that: The impeller includes an upper crown, a lower ring, and a plurality of blades connected between the upper crown and the lower ring. The blades are evenly distributed in the circumferential direction. 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 water-receiving side. A vertical water supply pipe is provided near the water-receiving side. The water supply pipe is provided with a water outlet. The upper end of the water supply pipe is sealed and connected in the upper crown and is connected with the fluid hole. When the impeller drives the main shaft to rotate at a high speed, negative pressure and vortex are generated on the water-receiving side of the blade. The water flow in the main shaft through-hole enters the water-receiving side of the blade through the water supply pipe to balance the negative pressure and disperse the vortex.

5. The pump-turbine air supply structure according to claim 1 is characterized in that: 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 cut off; 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 connected.

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