Mixed-flow water turbine applied to medium-high water head

Abstract

The mixed-flow water turbine comprises a water guide mechanism and a rotating wheel, the rotating wheel and a main shaft of the water turbine are fixed through a bolt, and the rotating wheel is located in a space rotating wheel chamber formed in the water guide mechanism. A cross central air supply device is arranged on the lower side of the rotating wheel and is fixed on the tail water taper pipe; the cross center air supply device comprises an air supply cross, an air supply taper pipe is fixed to the center of the air supply cross, and air supply holes are formed in the upper side and the lower side of the air supply taper pipe. An air supplementing ring pipe is arranged outside the tail water taper pipe, the air supplementing cross is composed of four air supplementing pipes, the outer side ends of the air supplementing pipes penetrate through the tail water taper pipe to be communicated with the air supplementing ring pipe, and the interior of the air supplementing ring pipe is communicated with the external atmosphere through open holes.

Description

Technical Field

[0001] The utility model relates to the technical field of mechanical engines, in particular to a mixed flow turbine applied to medium and high water heads. Background Art

[0002] Francis turbine is also called Francis turbine, which is a type of reaction turbine. It was invented by American engineer Francis in 1849. It is also called Francis turbine or spoke-axial turbine. Water flows into the runner radially from all sides and then flows out of the runner approximately axially. The runner consists of an upper crown, a lower ring and blades. The development trend in recent years is high head, large capacity, high specific speed and high efficiency.

[0003] The three units of Mupo Power Station have experienced through cracks and falling pieces on the runners many times since they were put into operation in 2014. The cracks are located at the blades at the outlet of the lower ring of the runner, and the length is 100-150mm. The runners need to be inspected before and after the flood season every year, and on-site repairs are carried out after cracks are found. The runner blades are worn by sediment at the outlet of the water, and the thickness becomes thinner, with the thinnest thickness being only 1mm. After multiple on-site repairs, the blade strength is already in a critical state, and there is a phenomenon of falling pieces. There are great safety hazards in the units.

[0004] At present, turbines are mainly supplied with air through short pipes. This structural method will result in uneven distribution of air supply in the tailwater cone. Some areas may have too much air supply, while other areas may have insufficient air supply, thus affecting the overall air supply effect. The protruding structure of the short pipe may cause significant interference to the water flow in the tailwater cone, increase hydraulic losses, and reduce the efficiency of the turbine. For different turbine operating conditions and tailwater cone structures, the adaptability of short-tube air supply may be limited, and it is difficult to automatically adjust the air supply effect according to changes. Utility Model Content

[0005] The purpose of the utility model is to overcome the deficiencies of the prior art and provide a mixed flow turbine for medium and high water heads, thereby solving the above-mentioned defects.

[0006] The purpose of this utility model is achieved through the following technical solutions:

[0007] A Francis turbine for medium and high water heads, comprising:

[0008] A water-guiding mechanism and a runner, wherein the runner is fixed to the main shaft of the turbine by bolts, and the runner is located in a space runner chamber formed inside the water-guiding mechanism; a cross-centered air-supply device is provided on the lower side of the runner, and the cross-centered air-supply device is fixed on the tailwater cone; the cross-centered air-supply device comprises an air-supply cross, and an air-supply cone is fixed at the center position of the air-supply cross, and air-supply holes are provided on the upper and lower sides of the air-supply cone.

[0009] In one or more embodiments of the present utility model, an air supplement ring pipe is provided outside the draft tube cone. The air supplement cross is composed of four air supplement pipes. The outer ends of the air supplement pipes penetrate through the draft tube cone and are communicated with the air supplement ring pipe. The inside of the air supplement ring pipe is communicated with the outside atmosphere through openings.

[0010] In one or more embodiments of the present utility model, one section of the air supplement pipe is located inside the draft tube cone and is inclined, and the other section is located outside the draft tube cone and is horizontal. The inner end of the air supplement pipe is fixedly communicated with the air supplement cone tube.

[0011] In one or more embodiments of the present utility model, the water guide mechanism includes a volute and a stay ring. Fixed guide vanes are arranged on the stay ring and movable guide vanes are arranged inside. A top cover is fixed to the stay ring by bolts. Sliding bearings are respectively fixed to the top cover and the bottom ring. The movable guide vanes are installed between the sliding bearings, and the movable guide vanes are driven by a driving assembly.

[0012] In one or more embodiments of the present utility model, the movable guide vanes are driven by a control ring, and the control ring is driven by a servomotor.

[0013] In one or more embodiments of the present utility model, the runner is connected to the main shaft of the water turbine by bolts. A main shaft seal is installed at the upper end of the top cover. A water guide oil sump is also installed at the upper end of the top cover, and a split water guide bearing is installed in the oil sump.

[0014] In one or more embodiments of the present utility model, the runner includes a crown and a lower ring. Seventeen runner blades are welded and fixed between the crown and the lower ring. The outside of the runner abuts against the top cover and the bottom ring. Channels are formed between adjacent runner blades. One end of the channel corresponds to the fixed guide vane, and the other end of the channel is communicated with the draft tube cone. A drain cone is formed at the central position of the runner blade.

[0015] In one or more embodiments of the present utility model, the runner is made of ZG04Cr13Ni5Mo.

[0016] The beneficial effects of the present utility model:

[0017] A Francis turbine applied to medium and high water heads proposed by the present utility model replaces the original short-pipe air admission with cross-center air admission. The cross-center air admission can evenly disperse gas into the draft tube in multiple directions, making the air admission more comprehensive and balanced. In contrast, the short-pipe air admission has uneven air admission distribution, resulting in insufficient or excessive air admission in some areas. The structure of the cross-center air admission is relatively more conformable to the shape of the draft tube and causes relatively less interference to the water flow. Due to its prominent pipe structure, the short-pipe air admission will, to a certain extent, hinder the smooth flow of water and increase hydraulic losses. The cross-center air admission has stronger adaptability to different turbine operating conditions and draft tube structures. It can automatically adjust the air admission effect according to the changes in water flow, while the adaptability of the short-pipe air admission may be relatively weak. For example, when the turbine load changes frequently, the cross-center air admission can respond faster and provide an appropriate air admission volume. By optimizing the number and shape of the runner blades and replacing the manufacturing materials, this turbine makes the impeller more durable and has a longer service life. Brief Description of the Drawings

[0018] Figure 1 is a cross-sectional view of the present utility model.

[0019] Figure 2 is a top view of the air admission cross. Detailed Description of the Embodiments

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. The components of the embodiments of the present utility model described and illustrated herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present utility model provided in the drawings is not intended to limit the scope of the present utility model claimed, but merely represents selected embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0021] Example 1. In this example, as Figures 1 to 2As shown in the figure, a Francis turbine applied to medium and high water heads includes a wicket gate mechanism and a runner 17. The runner 17 is fixed to the main shaft of the turbine by bolts. The runner 17 is located in the space runner chamber formed inside the wicket gate mechanism. A cross-shaped central air admission device is arranged below the runner 17, and the cross-shaped central air admission device is fixed to the draft tube cone 3. The cross-shaped central air admission device includes an air admission cross, and an air admission cone tube 4 is fixed at the central position of the air admission cross. Air admission holes are formed on both the upper and lower sides of the air admission cone tube 4.

[0022] In this embodiment, by replacing the original short tube air admission with cross-shaped central air admission, the cross-shaped central air admission can evenly disperse the gas into the draft tube cone 3 in multiple directions, making the air admission more comprehensive and balanced. However, the short tube air admission has an uneven air admission distribution, resulting in insufficient or excessive air admission in some areas. The structure of the cross-shaped central air admission is relatively more conforming to the shape of the draft tube cone, and has relatively less interference with the water flow. Due to its prominent pipe structure, the short tube air admission will, to a certain extent, hinder the smooth flow of the water flow and increase the hydraulic loss. The cross-shaped central air admission has stronger adaptability to different operating conditions of the turbine and the structure of the draft tube cone. It can automatically adjust the air admission effect according to the change of the water flow, while the adaptability of the short tube air admission may be relatively weak. For example, when the load of the turbine changes frequently, the cross-shaped central air admission can respond faster and provide an appropriate air admission volume.

[0023] In one or more embodiments of the present utility model, an air admission ring pipe 18 is arranged outside the draft tube cone 3. The air admission cross is composed of four air admission pipes 6. The outer ends of the air admission pipes 6 penetrate through the draft tube cone 3 and are communicated with the air admission ring pipe 18. The inside of the air admission ring pipe 18 is communicated with the outside atmosphere through openings.

[0024] In this embodiment, through the arrangement of the air admission ring pipe 18, the air intake of the four air admission pipes 6 can be balanced. The inside of the air admission ring pipe 18 is communicated with the outside atmosphere, and the air is automatically admitted through the air pressure principle.

[0025] In one or more embodiments of the present utility model, one section of the air admission pipe 6 is located inside the draft tube cone 3 and is inclined, and the other section is located outside the draft tube cone 3 and is horizontal. The inner end of the air admission pipe 6 is fixedly communicated with the air admission cone tube 4.

[0026] In this embodiment, by arranging the air supply pipe 6 obliquely, the air supply airflow can enter the draft tube or related parts at a specific angle, thereby more effectively improving the water flow pattern and pressure distribution, and reducing vortex and cavitation phenomena. The internal space layout of the hydropower station may be relatively complex. Welding the air supply pipe obliquely can better adapt to the positions of surrounding equipment and structures, avoiding interference with other components. The inclined welding angle helps reduce the resistance suffered by the air supply airflow when entering, enabling the gas to enter more smoothly and reducing energy loss.

[0027] In one or more embodiments of the present utility model, the water guide mechanism includes a spiral case 1 and a stay ring 7. Fixed guide vanes 10 are arranged on the stay ring 7, and movable guide vanes 11 are on the inner side. The top cover 8 is fixed to the stay ring 7 by bolts; sliding bearings are respectively fixed on the top cover 8 and the bottom ring 12, and the movable guide vanes 11 are installed between the sliding bearings. The movable guide vanes 11 are driven by a driving assembly.

[0028] In this embodiment, several of the fixed guide vanes 10 are arranged in a circular array, and one side thereof is a convex arc surface. The whole of the fixed guide vanes 10 is arranged at a certain angle with the central axis to form a circulation flow; the movable guide vanes 11 adopt an integrally formed structure, which includes an upper rotating shaft, a blade body and a lower rotating shaft. The blade body is fixed between the upper rotating shaft and the lower rotating shaft. The upper rotating shaft vertically penetrates the top cover 8 and is fixed in the sliding bearing. The length of the upper rotating shaft is much greater than the length of the lower rotating shaft. The upper side end of the upper rotating shaft is connected to the driving assembly. The two ends of the blade body in the length direction are respectively in a circular arc shape and a sharp corner structure. The connections between the blade body and the upper rotating shaft and the lower rotating shaft have convex blocks, and the cross sections at the two convex blocks form a mountain pass shape. The bottom ring 12 is fixed to the base by bolts, and several round holes are opened on the bottom ring. The lower rotating shafts on the fixed guide vanes are installed in another sliding bearing; a stepped surface is formed on the base, and the bottom ring 12 is installed in the stepped surface.

[0029] In one or more embodiments of the present utility model, the movable guide vanes 11 are driven by a control ring 14, and the control ring 14 is driven by a servomotor.

[0030] In this embodiment, the control ring 14 is used to drive the driving assembly. The driving assembly includes a connecting rod, an ear handle and a crank arm. The ear handle is connected to the connecting rod by a thread, and the length of the connecting rod can be adjusted by rotating the ear handle. When individual guide vanes are not tightly closed during the operation of the unit, the closing gap can be reduced by adjusting the length of the ear handle; a limiting structure for limiting the maximum opening degree and reverse rotation possibility of the guide vanes is provided on the crank arm.

[0031] In one or more embodiments of the present utility model, the runner 17 is connected to the main shaft of the water turbine by bolts. A main shaft seal 15 is installed at the upper end of the top cover 8, and a water guide oil sump is also installed at the upper end of the top cover 8. A split water guide bearing is installed in the oil sump.

[0032] In this embodiment, the main shaft is a hollow structure with double flanges. The main shaft seal adopts a contact packing seal form. The sealing device consists of parts such as a rotating ring, a sealing seat, and a sealing ring. During installation, the position of the sealing seat is adjusted to ensure concentricity with the rotating shaft. Before operation, the compressed air in the air shroud must be discharged and kept in constant communication with the atmosphere to withdraw the air shroud. A pressure water inlet is provided on the sealing seat, and pressure water is used to lubricate the seal to prevent damage to the seal due to temperature rise during high-speed rotation of the unit. The parts of the seal are of split structure, which is convenient for installation and replacement of vulnerable parts (such as sealing plates, rotating rings, etc.); the sealing material is wear-resistant packing, which is installed in four layers.

[0033] In one or more embodiments of the present invention, the runner 17 includes a crown 171 and a band 172. Seventeen runner blades 173 are fixedly welded between the crown 171 and the band 172. The outer side of the runner 17 abuts against the top cover 8 and the bottom ring 12; a channel is formed between adjacent runner blades 173. One end of the channel corresponds to the stay vane 10, and the other end of the channel communicates with the draft cone 3; a drain cone 174 is formed at the central position of the runner blade 173.

[0034] In this embodiment, the runner blade 173 is a twisted sheet structure, and it adopts a forward-inclined blade shape. The drain cone 174 is formed by the enclosure of the impeller blades. The drain cone 174 can guide the water flow at the runner outlet to drain smoothly, reduce the resistance and turbulence of the water flow, and improve the outflow efficiency of the water flow.

[0035] In one or more embodiments of the present invention, the runner 17 is made of ZG04Cr13Ni5Mo.

[0036] In this embodiment, ZG04Cr13Ni5Mo is a cast stainless steel material. This material has good corrosion resistance, strength and toughness.

[0037] Technical parameters of the above technical solution:

[0038] Rotating direction when looking down at the water turbine: clockwise;

[0039] Maximum head (m): 134.61;

[0040] Rated head (m): 118.0;

[0041] Rated output (MW): 15.54;

[0042] Rated speed: 500 r / min;

[0043] Runaway speed: 973.8 r / min;

[0044] Air supply method of the water turbine: Air supply at the center of the cross in the draft tube cone;

[0045] Number of water turbine blades: 17;

[0046] Material: ZG04Cr13Ni5Mo.

[0047] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present utility model is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model. In addition, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance. In the description of the present utility model, it should also be noted that unless otherwise clearly specified and limited, terms such as "set", "connected" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

Claims

1. A Francis turbine for medium and high head, characterized in that: include: A water guide mechanism and a runner (17), wherein the runner (17) is fixed to the main shaft of the water turbine by bolts, and the runner (17) is located in a space runner chamber formed inside the water guide mechanism; a cross-shaped central air supply device is arranged at the lower side of the runner (17), and the cross-shaped central air supply device is fixed on the tailwater cone (3); the cross-shaped central air supply device comprises an air supply cross, and an air supply cone (4) is fixed at the center position of the air supply cross, and air supply holes are opened on the upper and lower sides of the air supply cone (4).

2. A Francis turbine for medium and high water heads according to claim 1, characterized in that: An air supply ring pipe (18) is arranged outside the tailwater cone pipe (3), and the air supply cross is composed of four air supply pipes (6). The outer ends of the air supply pipes (6) penetrate the tailwater cone pipe (3) and are connected to the air supply ring pipe (18), and the interior of the air supply ring pipe (18) is connected to the external atmosphere through an opening.

3. A Francis turbine for medium and high water heads according to claim 2, characterized in that: One section of the air supply pipe (6) is located inside the tailwater cone pipe (3) and is arranged obliquely, and the other section is located outside the tailwater cone pipe (3) and is arranged horizontally. The inner end of the air supply pipe (6) is fixedly connected to the air supply cone pipe (4).

4. The Francis turbine for medium and high water heads according to claim 1, characterized in that: The water guide mechanism comprises a volute (1) and a seat ring (7); a fixed guide vane (10) is arranged on the seat ring (7), and a movable guide vane (11) is arranged inside the seat ring (7); a top cover (8) is fixed to the seat ring (7) by bolts; sliding bearings are respectively fixed to the top cover (8) and the bottom ring (12); the movable guide vane (11) is installed between the sliding bearings; and the movable guide vane (11) is driven by a driving assembly.

5. A Francis turbine for medium and high water heads according to claim 4, characterized in that: The movable guide vane (11) is driven by a control ring (14), and the control ring (14) is driven by a servomotor.

6. The Francis turbine for medium and high water heads according to claim 4, characterized in that: The runner (17) is connected to the main shaft of the turbine through bolts, a main shaft seal (15) is installed on the upper end of the top cover (8), and a water guide oil basin is also installed on the upper end of the top cover (8), and a split water guide bearing is installed in the oil basin.

7. The Francis turbine for medium and high water heads according to claim 4, characterized in that: The runner (17) comprises an upper crown (171) and a lower ring (172), and seventeen runner blades (173) are welded and fixed between the upper crown (171) and the lower ring (172). The outer side of the runner (17) is in contact with the top cover (8) and the bottom ring (12); a channel is formed between adjacent runner blades (173), one end of the channel corresponds to the fixed guide vane (10), and the other end of the channel is connected to the tailwater cone pipe (3); and a water discharge cone (174) is formed at the center of the runner blades (173).

8. The Francis turbine for medium and high water heads according to claim 6, characterized in that: The rotating wheel (17) is made of ZG04Cr13Ni5Mo.

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