CN111706454B - Passive blade anti-cavitation structure for axial-flow Kaplan turbine - Google Patents

Passive blade anti-cavitation structure for axial-flow Kaplan turbine Download PDF

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Publication number
CN111706454B
CN111706454B CN202010496027.XA CN202010496027A CN111706454B CN 111706454 B CN111706454 B CN 111706454B CN 202010496027 A CN202010496027 A CN 202010496027A CN 111706454 B CN111706454 B CN 111706454B
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blade
turbulence
rotating
blades
runner
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CN111706454A (en
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马建峰
童哲铭
刘思靓
周叶
童水光
李昀哲
刘胜柱
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Zhejiang Fuchunjiang Hydropower Equipment Co ltd
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Zhejiang Fuchunjiang Hydropower Equipment Co ltd
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Priority to CN202110291897.8A priority Critical patent/CN113062826B/en
Priority to CN202010496027.XA priority patent/CN111706454B/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B3/00—Machines or engines of reaction type; Parts or details peculiar thereto
    • F03B3/12—Blades; Blade-carrying rotors
    • F03B3/121—Blades, their form or construction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B11/00—Parts or details not provided for in, or of interest apart from, the preceding groups, e.g. wear-protection couplings, between turbine and generator
    • F03B11/04—Parts or details not provided for in, or of interest apart from, the preceding groups, e.g. wear-protection couplings, between turbine and generator for diminishing cavitation or vibration, e.g. balancing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/20—Hydro energy

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Hydraulic Turbines (AREA)

Abstract

The invention discloses a passive blade anti-cavitation structure for a shaft through-flow Kaplan turbine, which comprises a rotating wheel arranged in a rotating wheel chamber, wherein a rotating gap is formed between the edge of the outer end of a blade of the rotating wheel and the inner wall of the rotating wheel chamber, the back of the runner blade is provided with a plurality of turbulence resisting blades near the outer end edge, the turbulence resisting blades are rotationally connected to the blade through a rotating shaft eccentrically arranged at the edge of the turbulence resisting blades, the rotating shaft is provided with a coil spring, the coil spring resists the turbulence blades to form a torque consistent with the rotating direction of the runner, the turbulence resisting blades are provided with a standby position and a working position, when the turbulence resisting blades are in the standby position, the front and the rear adjacent turbulence resisting blades are separated, when the rotating wheel rotates, the turbulence resisting blades rotate to the working position, in the rotating direction of the runner, the rear part of the front turbulence resisting blade is overlapped with the outer side of the rear turbulence resisting blade. The invention can not only reduce the cavitation and cavitation phenomena of the blade tip of the runner, but also not influence the working efficiency of the water turbine.

Description

Passive blade anti-cavitation structure for axial-flow Kaplan turbine
Technical Field
The invention relates to the technical field of hydraulic generators, in particular to a passive blade anti-cavitation structure for a shaft through-flow Kaplan turbine.
Background
With the enhancement of the awareness of energy conservation and environmental protection of people, the hydroelectric power generation as a green energy source is being vigorously developed, and the through-flow turbine plays an important role in the development of low-head large-flow hydraulic resources in China and is widely applied to water resource development projects in the middle east region with relatively rich water resources and relatively developed economy. A certain rotating clearance is formed between the blade tip of a runner blade of the axial through-flow turbine and a runner chamber. Under the action of the pressure difference between the front surface and the back surface of the blade, high-speed water flow is formed when the water flow passes through the fine rotating gap. When high-speed water flow passes through the rotating gap, the air space is expanded sharply, and accordingly, the local pressure is reduced sharply, so that strong vortex is formed and bubbles are generated, and further cavitation is formed on the back of the blade tip of the blade. After the water turbine runs for a long time, the back of the blade tip of the blade can be uneven due to cavitation erosion on the surface caused by long-time cavitation, so that the output and the efficiency of the runner are reduced, and the economic benefit of a power station is influenced.
Disclosure of Invention
The invention aims to solve the problem that the blade tips of a rotating wheel of the conventional axial-flow turbine are easy to cavitate and cavitate, and provides a passive blade anti-cavitation structure for the axial-flow Kaplan turbine, which can remarkably reduce the cavitation and cavitation phenomena of the blade tips of the rotating wheel and simultaneously can not influence the working efficiency of the turbine.
In order to achieve the purpose, the invention adopts the following technical scheme:
a passive blade anti-cavitation structure for a shaft through-flow Kaplan turbine comprises a rotating wheel rotatably arranged in a rotating wheel chamber, a rotating gap is arranged between the outer end edge of each blade of the rotating wheel and the inner wall of the rotating wheel chamber, a plurality of anti-turbulence blades extending along the axial direction of the rotating wheel are arranged on the back surface of each blade of the rotating wheel close to the outer end edge, the anti-turbulence blades are rotatably connected to the blades through a vertical rotating shaft eccentrically arranged on the edges of the anti-turbulence blades, the anti-turbulence blades are uniformly arranged along the outer end edges of the blades, a coil spring is arranged on the rotating shaft, the coil spring resists the turbulence blades to form torque consistent with the rotating direction of the rotating wheel, so that the anti-turbulence blades have a standby position and a working position, when the anti-turbulence blades are in the standby position, the front and the back adjacent anti-turbulence blades are separated, the rear part of the turbulence resisting blade positioned at the front in the rotation direction of the runner is overlapped with the outer side of the front part of the turbulence resisting blade at the rear.
When the generator set starts to operate, water flow enters the rotating wheel chamber and impacts the blades of the rotating wheel so as to drive the rotating wheel to rotate to generate electricity. It will be appreciated that the water pressure at the front of the vane is now very high, while the water pressure at the back of the vane is much lower than the pressure at the front, so that there is a very high pressure differential between the front and back of the vane. In the existing axial flow turbine, when water flows downwards through a rotating gap between the outer end edge of each blade and the inner wall of the rotating wheel chamber, the water pressure is further increased because the cross section of the water flow is rapidly reduced, and water flow with high flow speed and high pressure is formed in the rotating gap; when water flow passes through the rotating gap, the space of the water flow is expanded instantly, the water pressure on the back surface of the blade is reduced instantly, the water flow rotates towards one side of the back surface of the blade to form an extremely strong vortex, and meanwhile, once the water pressure of the vortex is reduced to be lower than the vaporization pressure of the water flow, part of the water flow is vaporized to form bubbles (or called cavitation bubbles). When the cavitation bubbles in the vortex burst and collapse, the back of the blade is repeatedly impacted by huge water pressure, thereby causing fatigue damage of the material and even surface degradation to form cavitation erosion.
The invention creatively arranges a plurality of rotatable turbulence resisting blades on the back of the runner blade near the outer end edge through a vertical rotating shaft, and the rotating shaft is provided with a coil spring which resists the turbulence blades and forms a torque consistent with the rotating direction of the runner. For example, when the rotation direction of the runner is counterclockwise, the coil spring generates a counterclockwise torque against the turbulence resisting blades to rotate the turbulence resisting blades counterclockwise, so that adjacent turbulence resisting blades in the rotation direction of the runner are separated from each other into louver-like structures. When the rotating wheel rotates, the anti-turbulence blades are subjected to the resistance of water flow flowing from the front surface to the back surface of the blades, and the rotating shaft is eccentrically arranged at the edges of the anti-turbulence blades, so that the anti-turbulence blades subjected to the resistance of the water flow automatically rotate, the direction of the anti-turbulence blades at the moment is basically consistent with the rotating direction of the rotating wheel, and the anti-turbulence blades at the front are lapped at the outer sides of the anti-turbulence blades at the back. Like this, from the high-speed high-pressure water current of running clearance downward flow can receive the sheltering from and the guide of anti turbulent blade, avoid rivers in the twinkling of an eye pressure release behind the running clearance on the one hand, on the other hand, the vortex that anti turbulent blade guide rivers formed is kept away from the blade back to greatly reduce the cavitation effect to the blade back, ensure the work efficiency of hydraulic turbine.
It will be appreciated that there will be gaps between the successive anti-turbulence vanes, so that when the water flows through the turning gap, part of the water flows through the gaps into the region of the rear face of the end of the vane under the action of the pressure difference, and this part of the water flow does not form a vortex and will have a pressure between the high pressure at the front face and the low pressure at the rear face, which contributes to a significant reduction in the generation of cavitation bubbles and to a reduction in the cavitation effect on the rear face of the vane.
Preferably, a spherical rotating cavity is arranged in the rotating wheel blade close to the outer end, a round connecting through hole and a rectangular mounting hole are formed in the back of the rotating wheel blade, the connecting through hole penetrates through the front face of the blade, a group of opposite sides in the width of the mounting hole are tangent to the rotating cavity, the center of the rotating cavity is located on the central line of the mounting hole, a round rotating ring is arranged in the rotating cavity, the circumferential surface of the rotating ring is a spherical surface matched with the rotating cavity, the upper end of the rotating shaft penetrates through the connecting through hole and then is connected with the inner hole of the rotating ring in a threaded mode, the lower end of the rotating shaft is connected with the upper edge of the turbulence resisting blade, the thickness of the rotating ring is not larger than the width of the mounting hole, the coil spring is arranged in the connecting through hole in the front face of the blade, the upper end of the rotating shaft extending out of the rotating ring is clamped in the coil spring, and the outer end of the coil spring is clamped in the connecting through hole.
Because the circumferential surface of the rotating ring is a spherical surface matched with the rotating cavity, the rotating shaft connected to the rotating ring can swing 360 degrees by taking the spherical center of the rotating cavity as the center, all the turbulence resisting blades can rotate to the same direction and are mutually overlapped when the blades rotate, and the inconsistent rotating angles of the turbulence resisting blades caused by manufacturing and installation errors are avoided.
Because a group of opposite sides on the width of the mounting hole are tangent to the rotating cavity, and the thickness of the rotating ring is not more than the width of the mounting hole, when the assembly is needed, the axis of the rotating ring can be firstly approximately vertical to the axial direction of the connecting through hole, the thickness of the rotating ring is conveniently placed in the mounting hole until the circumferential surface of the rotating ring is attached to the rotating cavity, at the moment, the rotating ring is rotated for 90 degrees, the axis of the rotating ring is approximately coincident with the axial direction of the connecting through hole, and the rotating shaft can be conveniently connected into the inner hole of the rotating ring in a threaded manner until the upper end of the rotating shaft extends out of the rotating ring. In particular, the upper end of the rotating shaft extending out of the rotating ring is clamped in the coil spring, and the outer end of the coil spring is clamped in the connecting through hole. Thus, on the one hand, the coil spring elastically positions the rotary shaft in the circumferential direction to ensure reliable overlapping between adjacent turbulence resisting vanes, and on the other hand, the coil spring elastically supports the upper end of the rotary shaft to elastically position the rotary shaft in the vertical state.
It is known that when the height of a head, the amount of water, the load, and the like are changed when a water turbine generates electricity, the angle of blades of the water turbine, which is a Kaplan type water turbine, is changed so as to match the output power of the water turbine to the load and to maintain the rotational speed of the water turbine stable. When the load is reduced, the blades rotate so as to reduce the pressure bearing surface of the front face; the energy of the water flow acting on the blades is correspondingly reduced; when the load is increased, the blades rotate so as to enlarge the pressure bearing surface of the front face; the energy exerted by the water flow on the blades becomes correspondingly greater. It can be understood that, when the blade itself has a slight rotation, because the rotation shaft is elastically positioned at the end of the blade, when the blade rotates and the turbulence resisting blade is subjected to the resistance of water flow, the rotation shaft can automatically swing by an angle, so that the rotation shaft is always elastically positioned in a vertical state.
Preferably, the upper end surface of the rotating shaft and the inner side wall of the connecting through hole in the front of the blade are respectively provided with a radial clamping groove extending downwards along the axial direction, the inner end of the coil spring is bent towards the center to form an inner clamping end clamped in the radial clamping groove of the rotating shaft, and the outer end of the coil spring is bent outwards and radially to form an outer clamping end clamped in the radial clamping groove of the connecting through hole.
Because the upper end face of the rotating shaft and the inner side wall of the connecting through hole in the front face of the blade are respectively provided with the radial clamping groove which extends downwards along the axial direction, when the upper end of the rotating shaft extends out of the rotating ring, a coil spring can be placed into the upper end of the connecting through hole, the inner clamping end at the inner end of the coil spring is clamped in the radial clamping groove of the rotating shaft, the outer clamping end at the outer end of the coil spring is clamped in the radial clamping groove of the connecting through hole, elastic positioning can be conveniently formed between the rotating shaft and the connecting through hole, and therefore processing and assembling are convenient.
Preferably, the outer end edge of the back surface of the runner blade is provided with a downward extending surrounding edge.
It will be appreciated that there will be some clearance between the upper edge of the anti-turbulence blade and the back of the blade. The edge of the back of the runner blade is provided with the downward extending surrounding edge, so that water flow passing through the rotating gap can not directly enter the back of the blade through the gap between the upper edge of the turbulence-resistant blade and the back of the blade, and cavitation bubbles are prevented from being formed on the back of the blade. Particularly, a step is formed between the surrounding edge and the turbulence resisting blades which are overlapped into a row, so that water flow passing through the rotating gap can be gradually released and decompressed, and the cavitation caused by sudden pressure change due to instant release and decompression is effectively avoided.
Preferably, a plurality of upper guide holes and a plurality of lower guide holes are formed in the inner wall of the runner chamber, the upper guide holes and the lower guide holes are uniformly distributed along the circumferential direction of the runner chamber, a circular pressure relief cavity is formed in the inner wall of the runner chamber, an input port of each upper guide hole in the inner wall of the runner chamber corresponds to the outer end of each blade, an output port of the other end of each upper guide hole is connected with the upper portion of the pressure relief cavity, an output port of each lower guide hole in the inner wall of the runner chamber is lower than the lower end of each anti-turbulent flow blade, and an input port of the other end of each lower guide hole is connected with the lower portion of the pressure relief cavity.
The invention arranges a ring-shaped pressure relief cavity in the inner wall of the runner chamber, and arranges a plurality of upper flow guide holes and lower flow guide holes which are communicated with the pressure relief cavity on the inner wall of the runner chamber. Therefore, high-speed high-pressure water flow entering the rotating gap can enter the pressure release cavity through the upper flow guide hole to be released and released, and then flows downwards through the lower flow guide hole, so that the flow speed and pressure of the water flow in the rotating gap are greatly reduced, and the cavitation erosion to the back of the blade is further reduced.
Preferably, the output port of the upper diversion hole is higher than the input port, and the input port of the lower diversion hole is higher than the output port.
Because the output port of the upper diversion hole is higher than the input port, and the input port of the lower diversion hole is higher than the output port, the upper diversion hole is inclined upwards from the input port to the output port, and the lower diversion hole is inclined downwards. Because the water flow entering the runner chamber has the characteristic of large flow, when the water flow passes through the gaps between the adjacent blades and flows downwards, the flow speed and the pressure of the water flow are basically kept unchanged, and therefore a large pressure difference cannot be formed between the water flow and the pressure relief cavity in the runner chamber. Like this, indoor rivers of runner are when passing through the space between the adjacent blade, and rivers can not get into the pressure release intracavity through the last water conservancy diversion hole of tilt up to reduce the turbulent flow of the indoor rivers of runner, be favorable to the abundant doing work of the energy of flood peak and promote the efficiency of hydraulic turbine. The high-speed high-pressure water flow entering the rotating gap has larger pressure difference with the pressure relief cavity, so that partial water flow can enter the pressure relief cavity through the upper flow guide hole to be released and decompressed, and is smoothly discharged outwards through the downward inclined lower flow guide hole.
Therefore, the invention has the following beneficial effects: the cavitation and cavitation phenomena of the blade tips of the runner can be obviously reduced, and meanwhile, the working efficiency of the water turbine cannot be influenced.
Drawings
FIG. 1 is a schematic diagram of an embodiment of the present invention.
FIG. 2 is a partial schematic view of the blade back near the outer edge.
Fig. 3 is a schematic view of a coupling structure of a rotating shaft and a vane.
FIG. 4 is another schematic view of the vane and rotor chamber configuration at the turning clearance.
In the figure: 1. the impeller comprises a runner chamber 11, a rotating gap 12, a pressure relief cavity 13, an upper guide hole 14, a lower guide hole 2, a runner 21, blades 211, a rotating cavity 212, a connecting through hole 213, a mounting hole 214, a surrounding edge 215, a guide hole 3, turbulence resisting blades 4, a rotating shaft 41, a radial clamping groove 5, a coil spring 51, an inner clamping end 52, an outer clamping end 6 and a rotating ring.
Detailed Description
The invention is further described with reference to the following detailed description and accompanying drawings.
Example 1: as shown in fig. 1, a passive blade cavitation prevention structure for a shaft through-flow Kaplan turbine includes a runner 2 rotatably disposed in a runner chamber 1 with a rotating gap 11 between an outer end edge of a blade 21 of the runner and an inner wall of the runner chamber. When the generator set starts to operate, water flow enters the rotating wheel chamber to impact the front face of the rotating wheel blade so as to drive the rotating wheel to rotate to generate electricity. It will be appreciated that the water pressure at the front of the vane is now very high, while the water pressure at the back of the vane is much lower than the pressure at the front, so that there is a very high pressure differential between the front and back of the vane. In the existing axial through-flow turbine, when water flows downwards through a rotating gap between the outer end edge of each blade and the inner wall of the rotating wheel chamber, the water pressure can be further increased because the cross section of the water flow is rapidly reduced, and water flow with high flow speed and high pressure can be formed in the rotating gap; when water flow passes through the rotating gap, the space of the water flow is expanded instantly, the water pressure on the back of the blade is reduced instantly, the water flow rotates towards one side of the back of the blade to form a strong vortex due to the fact that the outer side of the water flow is blocked by the inner wall of the rotating wheel chamber, and meanwhile, once the water pressure of the vortex is reduced to be lower than the vaporization pressure of the water flow, part of the water flow is vaporized to form bubbles (or called cavitation bubbles). When the cavitation in the vortex bursts and collapses, the back of the blade is repeatedly impacted by huge water pressure, thereby causing fatigue damage of materials and even surface ablation to form cavitation erosion, and further reducing the working efficiency of the water turbine.
In order to reduce the cavitation as much as possible, as shown in fig. 1 and 2, a plurality of anti-turbulence blades 3 extending along the axial direction of the runner are arranged on the back surface of the runner blade near the outer end edge, and the anti-turbulence blades are uniformly arranged along the outer end edge of the blade. In addition, the upper edge of the anti-turbulent vane is rotatably connected to the back of the vane by a vertical rotating shaft 4, and a coil spring is sleeved on the rotating shaft, and the coil spring forms a torque which is consistent with the rotating direction of the rotating wheel to the rotating shaft and the anti-turbulent vane. For example, when the rotation direction of the runner is counterclockwise, the coil spring generates a counterclockwise torque against the turbulence resisting blades, so that the turbulence resisting blades can be rotated counterclockwise from the operating position to the standby position. Of course, it is necessary to provide an axial limit structure for limiting the rotation angle of the anti-turbulence blades so that the anti-turbulence blades can stay at the standby position or the working position.
When the water turbine stops, the coil spring drives the turbulence resisting blades to rotate anticlockwise to be in a standby position, and adjacent turbulence resisting blades are separated from each other to form a radial gap. When the runner rotates, the anti-turbulence blades receive the resistance of water flow, so that the resistance moment of a client coil spring rotates clockwise to a working position, at the moment, the rear parts of the anti-turbulence blades positioned in front in the rotating direction of the runner are lapped on the outer sides of the front parts of the anti-turbulence blades behind, and a row of elastic anti-turbulence blades are formed on the back surfaces of the outer ends of the blades close to the edges. From the high-speed high-pressure rivers of running down of running clearance can receive the sheltering from and the guide of anti turbulent blade behind the blade outer end, avoid rivers in the twinkling of an eye pressure release behind the running clearance on the one hand, on the other hand, the vortex that anti turbulent blade guide rivers formed keeps away from the blade back as far as possible to greatly reduce the cavitation effect to the blade back, ensure the work efficiency of hydraulic turbine. Particularly, a certain gap exists between the front and rear anti-turbulence blades which are mutually overlapped, so that when water flows through the rotating gap, under the action of the water flow pressure difference on two sides of the anti-turbulence blades, part of the water flows enter the area on the back of the end part of each blade through the gap, and the pressure of the part of the water flows is remarkably reduced and is between the high pressure on the front surface of each blade and the low pressure on the back surface of each blade, thereby being beneficial to reducing the generation of cavitation bubbles and reducing the cavitation erosion effect on the back surface of each blade.
It should be noted that, when the turbulence resisting blade is damaged, the replacement and maintenance can be conveniently carried out, thereby greatly reducing the practical maintenance cost of the water turbine. In addition, the passive mode means that the anti-cavitation structure of the invention does not need to provide extra power and can be automatically realized according to the working condition. That is, it does not require additional energy consumption.
In order to ensure that the turbulence resisting vanes are automatically rotated from the standby position to the operating position when the rotor is rotated, the turbulence resisting vanes are substantially rectangular, and the rotating shaft is eccentrically disposed at the upper edges in the width direction of the turbulence resisting vanes, and specifically, the rotating shaft is disposed near the front portions of the turbulence resisting vanes so that the area of the turbulence resisting vanes located behind the rotating shaft is larger than the area of the turbulence resisting vanes located in front of the rotating shaft. When the runner rotates, the resistance of the water flow on the rear part of the turbulence resisting blades is larger than that on the front part of the turbulence resisting blades, so that a rotating torque is formed. Preferably, the ratio of the width of the turbulence resisting blades at the front of the rotating shaft to the width of the turbulence resisting blades at the rear of the rotating shaft may be controlled to be between 0.6 and 0.8.
To facilitate the connection between the rotating shaft and the vane, as a preferred scheme, as shown in fig. 3, a spherical rotating cavity 211 is provided inside the rotating wheel vane near the outer end for each rotating shaft, a circular connecting through hole 212 and a rectangular mounting hole 213 are provided on the back of the rotating wheel vane, and the center lines of the connecting through hole and the mounting hole are coaxial and pass through the spherical center of the rotating cavity. The center line of the rectangular mounting hole is a line that passes through the intersection of two diagonal lines in the cross section and is perpendicular to the cross section.
In addition, the connecting through hole extends upwards, penetrates through the rotating cavity firstly and then penetrates through the front face of the blade, and the mounting hole extends upwards to a group of opposite sides in the width and is tangent to the rotating cavity. That is, the length of the mounting hole is matched with the diameter of the rotating cavity, and the depth of the mounting hole reaches the sphere center of the rotating cavity. In addition, a circular rotating ring 6 is arranged in the rotating cavity, and the circumferential surface of the rotating ring is a spherical surface matched with the rotating cavity, so that the rotating ring is in a spherical frustum shape. The coil spring 5 sets up in the positive connection via hole of blade, and the outer end joint of coil spring is in connecting the via hole, and the lower extreme and the anti turbulent flow blade top edge of axis of rotation are connected, and the hole threaded connection with the swivel becket after connecting the via hole is passed to the upper end of axis of rotation, and the upper end joint that the swivel becket was stretched out to the axis of rotation is in the coil spring, and the thickness of swivel becket is not more than the width of mounting hole.
Because the circumferential surface of the rotating ring is a spherical surface matched with the rotating cavity, the rotating shaft connected to the rotating ring can swing 360 degrees by taking the spherical center of the rotating cavity as the center, so that all the turbulence resisting blades can rotate to the same direction and are mutually overlapped when the blades rotate, and the inconsistent rotating angles of the turbulence resisting blades caused by manufacturing and mounting errors are avoided.
When the assembly is needed, the axis of the rotating ring is approximately vertical to the axial direction of the connecting through hole, the thickness of the rotating ring is conveniently placed in the mounting hole until the circumferential surface of the rotating ring is attached to the rotating cavity, at the moment, the rotating ring is rotated by 90 degrees, the axis of the rotating ring is approximately overlapped with the axial direction of the connecting through hole, and then the rotating shaft can be conveniently connected into the inner hole of the rotating ring in a threaded mode until the upper end of the rotating shaft extends out of the rotating ring. Because the upper end joint that the axis of rotation stretches out the rotating ring is in the coil spring, the outer end joint of coil spring is in connecting the downthehole. Thus, on the one hand, the coil spring elastically positions the rotary shaft in the circumferential direction to ensure reliable overlapping between the adjacent turbulence resisting vanes, and on the other hand, the coil spring elastically supports the upper end of the rotary shaft to elastically position the rotary shaft in the vertical state, and the turbulence resisting vanes elastically swing 360 degrees around the center of the rotary ring.
As a prior art, a blade of a Kaplan turbine can be rotated by itself to adjust an angle. When the water turbine generates power, if the height of a water head, the water quantity, the load and the like are changed, the angle of the blade of the water turbine serving as a Kaplan type water turbine is changed, so that the output power of the water turbine is matched with the load, and the rotating speed of the water turbine is kept stable. When the load is reduced, the blades rotate so that the pressure bearing surface of the front face becomes smaller, and the torque of the water flow acting on the blades becomes correspondingly smaller; when the load is increased, the blades rotate so as to enlarge the pressure bearing surface of the front face; the torque of the water flow acting on the blades becomes correspondingly greater. It will be appreciated that because the shaft is resiliently located at the end of the blade, the shaft automatically swings through an angle when the anti-turbulence blade is subjected to the resistance of the water flow as the blade itself rotates, thereby allowing the shaft to be resiliently located in a generally vertical position at all times.
In order to facilitate installation of the coil spring, a radial clamping groove 41 extending downwards along the axial direction can be arranged on the upper end face of the rotating shaft, a radial clamping groove extending downwards along the axial direction is arranged on the inner side wall of a connecting through hole in the front face of the blade, the upper end of the rotating shaft is located in the coil spring, the inner end of the coil spring is bent towards the center to form an inner clamping end 51 clamped in the radial clamping groove of the rotating shaft, the outer end of the coil spring is bent outwards and radially to form an outer clamping end 52 clamped in the radial clamping groove of the connecting through hole, when the upper end of the rotating shaft extends out of the rotating ring, the coil spring can be placed into the upper end of the connecting through hole, the inner clamping end of the coil spring is clamped in the radial clamping groove of the rotating shaft, the outer clamping end of the coil spring is clamped in the radial clamping groove of the connecting through hole, elastic positioning can be conveniently formed between the rotating shaft and the connecting through hole, and processing and assembling are convenient.
Preferably, the coil spring can be made by winding a flat spring steel strip, and the elasticity of the coil spring can be conveniently controlled by reasonably controlling the thickness and the width of the spring steel strip, so that the elastic positioning of the turbulence resisting blade is ensured.
Because the turbulence resisting blade is rotatably connected to the back surface of the blade through the rotating shaft, a certain gap exists between the upper edge of the turbulence resisting blade and the back surface of the blade. Further, a downwardly extending skirt 214 may be provided at the outer end edge of the back of the blade to form a step between the skirt and the anti-turbulence blades that are overlapped in a row. That is, the rotational gap at this time is stepped. Like this, on the one hand, the surrounding edge can prevent effectively that the rivers through running clearance directly get into the blade back through the clearance between anti turbulent blade upper edge and the blade back, and on the other hand, rivers can release and the pressure release step by step after the running clearance of step-like to avoid effectively because of the cavitation phenomenon that the pressure sudden change that instantaneous release, pressure release formed caused.
Further, as shown in fig. 4, a circular pressure relief cavity 12 may be disposed inside the inner wall of the runner chamber, and the pressure relief cavity is disposed coaxially with the runner chamber. The inner wall of the runner chamber is provided with a plurality of upper diversion holes 13 and a plurality of lower diversion holes 14, each upper diversion hole and each lower diversion hole are uniformly distributed along the circumferential direction of the runner chamber, the input ports of the upper diversion holes arranged on the inner wall of the runner chamber correspond to the outer ends of the blades in height, the output port of the other end of the upper diversion hole is connected with the upper part of the pressure relief cavity, the output ports of the lower diversion holes arranged on the inner wall of the runner chamber are lower than the lower ends of the turbulence resisting blades, and the input ports of the other end of the lower diversion holes are connected with the lower part of the pressure relief cavity.
Therefore, high-speed high-pressure water flow entering the rotating gap can partially enter the pressure release cavity through the upper flow guide hole to be released and released, and then flows downwards through the lower flow guide hole, so that the flow speed and pressure of the water flow in the rotating gap are greatly reduced, and the cavitation erosion to the back of the blade is further reduced.
It should be noted that, a stepped annular groove may be formed on the inner wall of the runner chamber, and then a plurality of arc-shaped plugging blocks are disposed at the step of the opening of the annular groove, so as to form a substantially sealed annular pressure relief cavity, and the upper flow guide hole and the lower flow guide holes are disposed on the plugging blocks, thereby facilitating the manufacturing and assembly.
Finally, the output port of the upper diversion hole is higher than the input port, so that the upper diversion hole is inclined upwards from the input port to the output port; and the input port of the lower diversion hole is higher than the output port, so that the lower diversion hole is inclined downwards from the input port to the output port.
Like this, indoor rivers of runner are when passing through the space between the adjacent blade, and rivers can not get into the pressure release intracavity through last water conservancy diversion hole to reduce the turbulent flow of the indoor rivers of runner, be favorable to the abundant work of the energy of flood peak, and promote the efficiency of hydraulic turbine. The high-speed high-pressure water flow entering the rotating gap has larger pressure difference with the pressure relief cavity, so that partial water flow can enter the pressure relief cavity through the upper flow guide hole to be released and decompressed, and is smoothly discharged outwards through the downward inclined lower flow guide hole.
Preferably, the inclination angle of the upper diversion holes relative to the horizontal plane can be controlled between 10 degrees and 30 degrees.
Example 2: a passive blade anti-cavitation structure for a shaft through-flow Kaplan turbine is disclosed, as shown in figure 4, and comprises a rotating wheel which is rotatably arranged in a rotating wheel chamber, a rotating gap is arranged between the edge of the outer end of a blade of the rotating wheel and the inner wall of the rotating wheel chamber, a plurality of drainage holes 215 are arranged at the outer end of the blade close to the edge, the drainage holes penetrate through the front and the back of the blade, and the drainage holes are uniformly distributed along the edge of the outer end of the blade. When the generator set starts to operate, water flow enters the rotating wheel chamber to impact the front face of the rotating wheel blade so as to drive the rotating wheel to rotate to generate electricity. At the moment, part of water flow on the front surface of the blade is flushed out from the back surface of the blade through the drainage holes, so that vortex which passes through the rotating gap and then rotates to reach the back surface of the blade is flushed away, and cavitation bubbles are prevented from being formed on the back surface of the blade.
It should be noted that the drainage holes and the anti-turbulent blades of example 1 can be implemented synchronously, that is, the drainage holes can be arranged at the gaps between adjacent rotating shafts on the blades, and the water flow rushing out from the drainage holes is at the inner sides of the anti-turbulent blades.

Claims (4)

1. A passive blade anti-cavitation structure for a shaft through-flow Kaplan turbine comprises a rotating wheel rotatably arranged in a rotating wheel chamber, a rotating gap is arranged between the outer end edge of each blade of the rotating wheel and the inner wall of the rotating wheel chamber, and is characterized in that a plurality of anti-turbulence blades extending along the axial direction of the rotating wheel are arranged on the back surface of each blade of the rotating wheel close to the outer end edge, the anti-turbulence blades are rotatably connected to the blades through a vertical rotating shaft eccentrically arranged on the edges of the anti-turbulence blades, the anti-turbulence blades are uniformly arranged along the outer end edges of the blades, a coil spring is arranged on the rotating shaft, the coil spring resists the turbulence blades to form a torque consistent with the rotating direction of the rotating wheel, so that the anti-turbulence blades have a standby position and a working position, when the anti-turbulence blades are in the standby position, the front and back adjacent anti-turbulence blades are separated, when the rotating wheel rotates, the anti-turbulence blades rotate to the working position, the rear part of the turbulence resisting blade positioned at the front in the rotation direction of the runner is overlapped with the outer side of the front part of the turbulence resisting blade at the rear.
2. The passive blade cavitation prevention structure for a shaft through-flow Kaplan turbine as claimed in claim 1, wherein the outer end edge of the back of the runner blade is provided with a downwardly extending skirt.
3. The passive blade cavitation prevention structure for an axial-flow Kaplan turbine as defined in claim 1, wherein a plurality of upper and lower guide holes are formed in the inner wall of the runner chamber, the upper and lower guide holes are uniformly distributed along the circumferential direction of the runner chamber, a circular pressure relief chamber is formed in the inner wall of the runner chamber, the upper guide hole is formed at an input port of the inner wall of the runner chamber corresponding to the outer end of the blade, an output port of the other end of the upper guide hole is connected to the upper portion of the pressure relief chamber, the lower guide hole is formed at an output port of the inner wall of the runner chamber lower than the lower end of the turbulence resistant blade, and an input port of the other end of the lower guide hole is connected to the lower portion of the pressure relief.
4. The passive blade cavitation prevention structure for an axial flow through Kaplan turbine as claimed in claim 3, wherein the output port of the upper guide hole is higher than the input port, and the input port of the lower guide hole is higher than the output port.
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