CN117627837A - Air supplementing, corrosion reducing and vibration reducing device for tail part of runner blade of low-specific-speed water turbine - Google Patents

Abstract

The invention discloses an air supplementing, corrosion reducing and vibration reducing device for the tail part of a runner blade of a low-specific-speed water turbine, and the power generation field, comprising a mounting chamber, an air extractor blade, a central through hole, an air supplementing hole and a water vapor supplementing piece for supplementing water vapor into the mounting chamber, wherein the air extractor blade is arranged in the mounting chamber, the central through hole penetrates through the air extractor blade and a main shaft, the air supplementing hole is arranged on a top cover of the runner, and a first end of the air supplementing hole is positioned in the mounting chamber; through setting up the central through-hole on the main shaft, install centrifugal air pump in the installation room, centrifugal air pump is inhaled air and vapor of central through-hole and is produced high pressure catch water mixed fluid under the drive of hydraulic turbine runner, through arranging the top cap air make-up hole at the runner, the catch water mixed fluid is mended in the easy cavitation district upper reaches of blade afterbody play water limit region, form vapour liquid mixed fluid in the play water limit region of blade, improved the carrying capacity of air, increased the efficiency of tonifying qi, and then produce the effect of tonifying qi and reducing corrosion vibration.

Description

Air supplementing, corrosion reducing and vibration reducing device for tail part of runner blade of low-specific-speed water turbine

Technical Field

The invention relates to the field of power generation, in particular to a device for supplementing air, reducing corrosion and reducing vibration at the tail of a runner blade of a low-specific-speed water turbine.

Background

Hydropower is being developed greatly as clean energy, wherein efficiency, cavitation erosion and stability are three main indexes of hydraulic performance of a water turbine, and an air supplementing mode has direct influence on eliminating vibration in a flow field of the water turbine, improving stable operation, improving cavitation erosion performance of a runner blade and improving hydraulic efficiency.

Firstly, the air supplementing can lighten the hydraulic vibration of the rotating wheel of the water turbine, and reduce cavitation erosion damage. The principle of air supplementing, vibration reduction and corrosion reduction is that air supplementing can form bubbles in water, and the air supplementing is a compressible air-liquid mixed fluid medium, can absorb vibration and reduce amplitude. In addition, the air of the medium can disperse the vortex belt and fill the whole space at the lower part of the rotating wheel and the upper part of the draft tube with bubbles, so that the air supplementing has remarkable buffer effect on destroying cavitation erosion of the cavity and absorbing cavitation impact energy. When the collapse of the hollow bubbles in the flow field generates strong shock waves to reach the wall surface, the wall can be damaged within a few microseconds. The energy of the shock wave can be dissipated by the large quantity of reflection action of the air-doped bubbles, so that the effects of supplementing air, reducing vibration (reducing vibration) and reducing corrosion (reducing cavitation damage) are achieved. Vibration reduction (vibration reduction) can effectively reduce the amplitude of the water turbine under the working condition deviating from rated load; erosion reduction (reducing cavitation damage) prevents cavitation pits in the blade, thereby preventing perforation damage.

The air supplementing, vibration reducing and corrosion reducing are not only related to the size of the air doping amount and the diameter of the air bubble, but also closely related to the air doping position. It is generally considered by the hydropower industry that the larger the aeration quantity is, the more remarkable the vibration and corrosion reduction effect is. In addition, researchers have found that the size of the bubbles also affects the erosion reduction effect. Later, it was further found that the most important factor affecting the effectiveness of the cavitation reduction of the make-up air was the number of bubbles per unit volume in the vicinity of the through-flow wall of the turbine, especially the number of small diameter bubbles. This means that a significant effect of supplementing air and reducing corrosion can be achieved without a large amount of gas as long as a proper amount of air is supplemented at a proper position upstream of the cavitation-prone region of the turbine runner blade and a small bubble group with a certain concentration in a unit volume is formed in the cavitation-prone region of the blade. The basic principle of implementing air supplementing vibration reduction (vibration reduction) corrosion reduction in engineering is to supplement air at a proper position as close as possible to the upstream of a blade cavitation zone and form a small bubble group on the side wall.

Low specific speed francis turbines are often used in high head hydroelectric power stations, with most widespread use in pumped storage power stations.

The runner of the low specific speed mixed flow water turbine is characterized in that: the shape of the runner of the mixed-flow turbine is different due to the difference of water heads and flow rates of different power stations. The higher the water head, the lower the specific rotation speed, the lower the height of the runner blade, the longer the length is, the more the water flow tends to flow along the radial direction in the runner, the blade runner is in a long and narrow characteristic, namely the relative distance from the inlet side to the outlet side of the blade is longer, as shown in (1) of fig. 1; as the working head decreases, the rotor blades shorten and increase in height, and the blade flow channels are characterized by height and width, as shown in fig. 1 (5).

The thickness distribution characteristic of the turbine blade. The thickness of the inlet edge area of the turbine runner blade is large, the thickness of the head part of the blade of the large turbine is generally 50-150 mm, the thickness of the blade at the tail part is thinner, and the thickness of the tail part of the blade is generally 4-8 mm.

Aiming at the cavitation area at the tail part of the water outlet edge of the runner blade of the low-specific-speed water turbine, the air supplementing mode of the existing water turbine has obvious defects.

At present, the common air supplementing modes of the water turbine comprise four modes of main shaft center hole air supplementing, draft tube taper tube cross air supplementing, draft tube short tube air supplementing, top cover air supplementing and blade air supplementing. However, aiming at the cavitation area at the tail part of the runner blade of the low-specific-speed water turbine, the air supplementing structure and the air supplementing principle of the water turbine have technical defects: firstly, for the natural air supply technology of air supply in the central hole of the main shaft and the cross air supply of the draft tube taper pipe, vacuum generated from the water outlet edge of the runner of the water turbine to the taper pipe area of the downstream draft tube is used for forming negative pressure in the water turbine running at low load, and air sucked into the central hole of the main shaft fills the vacuum in the negative pressure area such as the outlet area of the runner blade to achieve the purpose of air supply, corrosion reduction and vibration reduction. And the air supplementing position of the air supplementing mode is unsuitable for the easily cavitation area of the water outlet side of the blade. The negative pressure cavitation area of the runner blade is mostly positioned in the water outlet edge area of the tail part of the blade, and the air supplementing position of the traditional main shaft center hole air supplementing technology and the air supplementing of the draft tube taper pipe cross frame is arranged at the downstream of the water outlet edge of the tail part of the blade, so that the accurate air supplementing, corrosion reducing and vibration reducing of the negative pressure cavitation area of the upstream runner blade are difficult to realize; and secondly, in the full-load working condition, the cavitation of the water outlet edge area of the runner blade cannot be supplemented by adopting a main shaft central hole air supplementing mode and a draft tube taper tube cross air supplementing mode, so that the obvious effects of air supplementing, corrosion reducing and vibration reducing cannot be achieved. Because the air supplementing of the central hole of the main shaft can naturally supplement external air through negative pressure under a low-load working condition, when the water turbine runs under a full-load working condition, the vacuum degree of the central hole of the main shaft is very small, and at the moment, the air supplementing of the central hole of the main shaft by the negative pressure of the vacuum of the draft tube cannot be completely realized to reduce cavitation erosion of the downstream of the water outlet edge of the runner blade. However, in practice, in the full-load working condition, the cavitation state of the water outlet edge area at the tail of the runner blade is serious, and no effective and economical accurate air supplementing mode for the area exists at present. Although the large air compressor is installed in the power station and a large amount of air is injected through the draft tube taper pipe cross and the main shaft center hole to eliminate the severe vibration and cavitation generated by the water turbine in a forced air supplementing mode, the forced air supplementing mode can achieve the purposes of supplementing air, reducing corrosion and reducing vibration of the water turbine under the low-load working condition, but the two obvious defects still exist, namely, if the large air compressor is installed in the power station, compressed air is injected into the main shaft center hole or the top cover, the investment of additional air compressor electromechanical equipment is increased, the large air compressor is not suitable for long-time working, the reliability of the equipment is reduced, and the air supplementing mode cannot permanently meet the power generation requirement; in addition, the low specific speed turbine runner with long and narrow blade path can not achieve the purpose of effectively supplementing air, reducing corrosion and reducing vibration in the cavitation area of the tail water outlet edge area of the runner no matter the main shaft center hole is used for supplementing air or the draft tube taper tube cross frame is used for supplementing air, because the air supplementing position is positioned at the downstream of the blade water outlet edge cavitation area.

In order to solve the cavitation erosion and vibration crack problems of the tail water outlet edge of the runner blade of the low-specific-speed mixed-flow turbine, although a top cover air supplementing technology in a bladeless area at the upstream of the runner can be adopted, namely, forced air supplementing is implemented on openings in the bladeless area of the top cover between the runner and the movable guide vane of the turbine, cavitation and vibration caused by the blade flow-shedding vortex in the inlet area of the runner blade can be obviously relieved, the runner of the low-specific-speed mixed-flow turbine is relatively long and narrow, and the area where cavitation and crack easily occur in the runner blade is generally distributed in the water outlet edge area, so that compressed air injected by the top cover is far away from the area of the water outlet edge of the blade needing air supplementing, and bubbles are uniformly scattered in the blade channel due to turbulence, and the obvious effect of air supplementing and corrosion reduction cannot be effectively generated in the tail area of the blade where cavitation occurs.

The main shaft central hole and the draft tube are subjected to air supplementing by vacuum, so that air supplementing and air supplementing under any working conditions cannot be controlled; from the position of tonifying qi, because the above-mentioned main shaft centre bore and draft tube tonifying qi mode tonifying qi's position all is in runner blade play water limit regional low reaches, can't effectively solve cavitation erosion and the vibration problem of blade play water limit regional that leads to because of operating mode changes. The top cover air supplementing technology at the upstream of the runner is long and narrow aiming at the runner of the mixed-flow water turbine with low specific speed, the air supplementing holes are far away from the water outlet edge area of the blade, and the air supplementing effect is weakened because the supplemented air cannot accurately reach the cavitation erosion area at the tail part of the blade. In addition, there is an air supplementing technology in which an air duct is buried in the blade in the inlet region of the rotating wheel, and the cavitation of the rotating wheel blade is relieved by injecting compressed air from the top cover. Although the technology can obviously reduce cavitation in the water inlet edge area of the blade, the technology is also limited to be implemented in the inlet edge area of the runner blade of the water turbine, because the blade head of the large-sized water turbine is generally 50-150 mm thick, and a gas supplementing pipe can be buried. The thickness of the water outlet edge area at the tail part of the blade is thin, so that the application of air supplement of the buried pipe is limited in terms of structure and strength, and the problem of blade cracks caused by cavitation erosion and vibration of the tail part of the runner blade cannot be effectively solved.

In a word, the air supplementing method can only reduce the effects of cavitation, vibration and the like of the runner blade of the mixed-flow water turbine with low specific speed to a limited extent, but cannot fundamentally solve the problem caused by the elimination of cavitation, cavitation and vibration of the runner blade running under the full-load working condition. In particular to the problem of cavitation erosion and vibration-induced blade crack in the water outlet edge area of the runner blade of the mixed flow turbine with low specific rotation speed.

Disclosure of Invention

The invention aims to solve the problems and designs a device for supplementing air, reducing corrosion and reducing vibration for the tail of a runner blade of a low-specific-speed water turbine.

The invention realizes the above purpose through the following technical scheme:

a make-up air is subtracted and is eroded vibration damper for low specific speed hydraulic turbine runner blade afterbody includes:

a mounting chamber; the installation chamber is positioned between the rotating wheel of the water turbine and the main shaft of the water turbine;

a centrifugal air extractor; the first blade of the centrifugal air extractor is arranged in the installation chamber and is fixedly connected with the rotating wheel;

a central through hole; the central through hole penetrates through the first blade and the main shaft;

a plurality of air supply holes; the air-filling hole is arranged on the top cover of the rotating wheel, and the first end of the air-filling hole is positioned in the mounting chamber;

a water vapor replenishing member; the steam supplementing piece is used for supplementing steam into the installation chamber, and steam and air form steam-water mixed fluid in the installation chamber.

The invention has the beneficial effects that: aiming at cavitation of a water outlet edge area at the tail part of a runner blade of a large-sized mixed-flow water turbine with low specific speed under a full-load working condition, a centrifugal air extractor is designed through a central through hole on a main shaft and is connected with the main shaft in an area where the runner is connected, the centrifugal air extractor sucks air in the central through hole of the main shaft and water vapor fed in by a water turbine runner and generates high-pressure steam-water mixed fluid, the steam-water mixed fluid is fed in a proper position at the upper stream of an easy cavitation area of the water outlet edge area at the tail part of the runner through a top cover air-supplementing hole arranged on the runner, and a gas-liquid mixed fluid is formed in the water outlet edge area of the blade, so that the effects of supplementing air, reducing corrosion and reducing vibration are generated. Moreover, the invention is characterized in that the steam-water mixed fluid, namely the steam with the gas content of more than 90 percent is supplemented. The high-pressure steam-water mixed fluid can improve the air carrying rate, generate uniform small bubbles in the flow field, and enhance the technical effects of supplementing air, reducing corrosion and reducing vibration.

Drawings

FIG. 1 is a schematic diagram of the device for supplementing air, reducing erosion and damping of the tail of a runner blade of a low specific speed water turbine;

FIG. 2 is a schematic structural view of the device for supplementing air, reducing erosion and damping of the tail of the runner blade of the low specific speed water turbine;

FIG. 3 is a schematic diagram of the device for supplementing air, reducing erosion and damping at full load for the tail of the runner blade of the low specific speed turbine;

FIG. 4 is a schematic diagram of the device for supplementing air, reducing erosion and damping at the tail of the runner blade of the low-specific-speed water turbine under a partial load condition;

FIG. 5 is a schematic cross-sectional view of A-A in the device for supplementing air, reducing erosion and damping of the tail of the runner blade of the low-specific-speed water turbine;

FIG. 6 is a schematic diagram showing a sectional structure of B-B in the air supplementing, corrosion reducing and vibration reducing device for the tail part of the runner blade of the low-specific-speed water turbine;

FIG. 7 is a schematic view of a region of a runner blade of a low specific speed turbine;

FIG. 8 is a schematic structural view of a ball float check valve;

FIG. 9 is a schematic structural view of a floating ball;

wherein corresponding reference numerals are as follows:

the device comprises a 1-rotating wheel, 2-blades, a 3-top cover, 4-air supplementing holes, 5-first blades, 6-main shafts, 7-vacuum breaking valves, 8-center through holes, 9-floating ball check valves, 901-mounting sleeves, 902-floating balls, 903-communicating channels, 904-steam-water mixture channels, 905-steel balls, 906-rubber, 10-mounting chambers, 11-cavitation areas, 12-blade water outlet edge areas, 13-tail pipes, 14-vacuum areas, 15-blade water inlet edge areas and 16-vacuum vortexes.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the present invention, it should be understood that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. are based on the directions or positional relationships shown in the drawings, or the directions or positional relationships conventionally put in place when the inventive product is used, or the directions or positional relationships conventionally understood by those skilled in the art are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific direction, be configured and operated in a specific direction, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.

In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, terms such as "disposed," "connected," and the like are to be construed broadly, and for example, "connected" may be either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

The following describes specific embodiments of the present invention in detail with reference to the drawings.

As shown in fig. 2, 3, 4, 5, 6 and 7, the air supplementing, corrosion reducing and vibration reducing device for the tail of the runner blade of the low-specific-speed water turbine comprises:

a mounting chamber 10; the installation chamber 10 is positioned between the runner 1 of the water turbine and the main shaft 6 of the water turbine;

a centrifugal air extractor; the first blade 5 of the centrifugal air extractor is arranged in the installation chamber 10, and the first blade 5 is fixedly connected with the rotating wheel 1;

a central through hole 8; the central through hole 8 penetrates through the first blade 5 and the main shaft 6;

a plurality of air supply holes 4; the air-filling hole 4 is arranged on the top cover 3 of the rotating wheel 1, and the first end of the air-filling hole 4 is positioned in the installation chamber 10;

a water vapor replenishing member; the steam supplementing member is used for supplementing steam into the installation chamber 10, and the steam and air form a steam-water mixed fluid in the installation chamber 10.

The second end of the air supplementing hole 4 is positioned in the water outlet edge area of the blade 2.

The water vapor supplementing piece comprises a water vapor source and a flow regulating piece, and the flow regulating piece is used for regulating the flow of water vapor of the water vapor source entering the central through hole 8.

The water vapor source is water vapor in the draft tube 13, the center through hole 8 penetrates through the rotating wheel 1 and is communicated with the draft tube 13, the flow regulating piece is used for regulating the flow of the water vapor in the draft tube 13 entering the center through hole 8, and the regulating action end of the flow regulating piece is positioned below the installation chamber 10.

The flow regulating member comprises a float check valve 9, and the float check valve 9 is arranged at one end of the central through hole 8, which is close to the draft tube 13.

The floating ball check valve 9 comprises a mounting sleeve 901 and a floating ball 902, wherein the mounting sleeve 901 is mounted at one end, close to a draft tube 13, of a central through hole, a communication channel 903 is arranged at the center of the mounting sleeve 901, the sizes of the two ends of the communication channel 903 are smaller than those of the middle of the communication channel 903, the floating ball 902 is located in the middle of the communication channel 903, the sizes of the floating ball 902 are larger than those of the two ends of the communication channel 903, a plurality of steam-water mixture channels 904 are formed in one end, close to the draft tube, of the mounting sleeve 901, and the steam-water mixture channels 904 are communicated with the middle of the communication channel 903.

The floating ball 902 comprises a hollow steel ball 905 and rubber 906, wherein air is arranged in the hollow part of the steel ball 905, and the rubber 906 is wrapped on the outer surface of the steel ball 905.

When the float check valve 9 operates under a low-load working condition, the float check valve 9 is opened, and water vapor enters the installation chamber through the float check valve 9; the ball check valve 9 closes when the ball check valve 9 is operating at full load.

The vacuum area of the water outlet edge of the blades 2 of the rotating wheel 1 is a gas-liquid mixed fluid medium formed by mixing air and a large amount of water drops, and the density of the fluid medium changes along with the change of working conditions. When the low-load working condition is running, the fluid medium is driven by the rotation of the rotating wheel 1 to form a vortex belt in the draft tube 13; and the vacuum area becomes smaller or even disappears during full load operation. The average density of the steam-water mixture in the vacuum region varies with operating conditions due to the variation of the volume fractions of air and water.

In order to improve the content (gas content) of air sucked by the centrifugal air extractor, the invention is characterized in that the invention is different from other air supplementing, corrosion reducing and vibration reducing:

according to the characteristics of gas-liquid mixed fluid in vacuum areas generated by different operation conditions of the rotating wheel 1, a certain proportion of gas-water mixture (the gas content is more than 90%) in the vacuum areas is extracted through a centrifugal air extractor, the average density of the floating ball 902 in the floating ball check valve 9 is designed to regulate the flow of the sucked gas-water mixture in the vacuum areas, and the effects of increasing the air carrying capacity and generating small bubbles in a flow field are achieved. The principle is as follows: the water droplets in the supplemented steam-water mixture can be dissolved under the pressure of the centrifugal air pump to absorb and store part of air, so that the air carrying capacity of the centrifugal air pump is increased, and the effect of small bubbles can be generated in a flow field.

The invention designs the floating ball 902 in the floating ball check valve 9, and designs the flow of the steam-water mixture which is blown up to the centrifugal air extractor through the central through hole 8 by designing the average density value of the floating ball 902. When the density of the floating ball 902 is higher than that of the steam-water mixture in the vacuum area during the low-load working condition, the floating ball 902 falls down, and water vapor flows up to the suction inlet of the centrifugal air extractor through the floating ball check valve 9; when the running is under the full-load working condition, the vacuum area of the water outlet edge of the blade 2 of the rotating wheel 1 is reduced and even disappears (the gas content is less than 5 percent in the process), and the floating ball 902 floats upwards to close the central through hole 8 because the density of the floating ball is less than that of the gas-water mixture, so that the gas-water mixture with the too small gas content is prevented from entering the centrifugal air extractor.

The air supplementing, corrosion reducing and vibration reducing device also comprises a vacuum breaking valve 7, wherein the vacuum breaking valve 7 is arranged at one end of the central through hole 8, which is far away from the installation chamber 10.

The distance between the first end of the air-compensating hole 4 and the central axis of the central through hole 8 is a first distance, the distance between the second end of the air-compensating hole 4 and the central axis of the central through hole 8 is a second distance, and the first distance is not smaller than the second distance.

The diameter of the first end of the air-compensating hole 4 is larger than the diameter of the second end of the air-compensating hole 4.

The working principle of the air supplementing, corrosion reducing and vibration reducing device for the tail part of the runner blade of the low-specific-speed water turbine is as follows:

the turbine runner 1 starts to rotate under the impact of the water flow. When the water turbine runs under the low-load working condition, vacuum appears in the water outlet edge area of the blades 2 of the rotating wheel 1, the floating ball check valve 9 at the lower end of the main shaft 6 and the vacuum breaking valve 7 at the upper end are opened, and external air enters through the central through hole 8 of the main shaft 6. A part of air and a small amount of water vapor overflowed by the floating ball check valve 9 are sucked, mixed and compressed by the first blade 5 of the centrifugal air extractor to the air supplementing holes 4 positioned on the top cover 3 of the rotating wheel 1, and injected into the water outlet edge area of the blade 2 of the rotating wheel 1; a further portion of the air is fed into the downstream region of the outlet side of the blades 2 of the rotor 1 via the ball check valve 9. When the water turbine operates under the full-load working condition, the vacuum of the water outlet edge area of the blades 2 of the rotating wheel 1 is weakened, the average density of the steam-water mixture of the draft tube 13 is larger than that of the floating ball check valve 9 at the lower end of the main shaft 6, the floating ball 902 of the floating ball check valve 9 floats upwards, and the steam-liquid mixed fluid with the over-high average density is prevented from flowing upwards to the centrifugal air extractor through the central through hole 8. At this time, the centrifugal pump mainly uses air from the main shaft as a main air supplementing medium.

Because of the suction of the centrifugal air extractor, the vacuum breaking valve 7 at the upper end is opened, the outside air and the air-liquid mixed fluid are mixed and compressed by the centrifugal air extractor, and the air is fed into the water outlet edge area of the blades 2 of the rotating wheel 1 through the air feeding holes 4 of the top cover 3 of the rotating wheel 1.

Aiming at cavitation of the water outlet edge region of the blades 2 of the large-sized mixed-flow turbine runner 1 with low specific speed under the full-load working condition, a centrifugal air extractor is designed through a central through hole 8 on a main shaft 6 and a region installation chamber 10 connected with the main shaft 6 at the runner 1, the centrifugal air extractor sucks air of the central through hole 8 and water vapor of a draft tube 13 under the driving of the turbine runner 1 and generates high-pressure water-vapor mixed fluid, the size of the water vapor flow is regulated by regulating the weight of a floating ball check valve 9, the water-vapor mixed fluid is supplemented into a proper position at the upstream of a cavitation-prone region of the water outlet edge region of the blades 2 through an air supplementing hole 4 arranged on a top cover 3 of the runner 1, and the air-liquid mixed fluid is formed in the water outlet edge region of the blades 2, so that the effects of air supplementing, corrosion reducing and vibration are further generated. The size of the aperture is related to the diameter of the air-supplementing air bubble, and the diameter of the air bubble injected into the water flow is adjusted by controlling the aperture to form an air bubble group which is favorable for reducing cavitation, so that the effects of reducing vibration and cavitation and preventing cracks and cavitation in the water outlet edge area of the blade 2 are achieved. In addition, when the high-pressure air flow formed by the centrifugal air pump is mixed with the water vapor from the draft tube 13, the air bubbles are uniformly dispersed into the water vapor drops to form small air bubbles, and the water vapor of the draft tube 13 is doped to carry more small air bubbles, so that the air supplementing efficiency of the centrifugal air pump is improved. The degree to which the bubbles are suspended in the water vapor depends on the flow rate of the gas stream, the proportion of water vapor and the flow conditions.

The invention has the advantages compared with the traditional scheme:

(1) Through the centrifugal air extractor blade 2 arranged between the main shaft 6 and the rotating wheel 1, air of the central through hole 8 and water vapor of the draft tube 13 with a certain proportion are sucked and compressed to form steam-water mixed fluid, the steam-water mixed fluid is injected into the crown air-supplementing hole 4 on the rotating wheel 1, and through the direction and the position of the air-supplementing hole 4, the precise air-supplementing vibration reduction and corrosion reduction of the water outlet edge area of the blade 2 of the low-specific-speed mixed-flow rotating wheel 1 are implemented.

(2) By designing the float check valve 9, a certain proportion of water vapor in the draft tube 13 is sucked by the centrifugal air extractor (for example, 5% of the sucked air flow), the suction of the water vapor enhances the air carrying capacity and is beneficial to forming small bubbles under the action of the air compressor, and the small bubbles are injected into the installation chamber 10. The floating ball check valve 9 is composed of a thin steel plate, a high polymer material and air, and the main design idea is to change the average density of the floating ball 902 by adjusting the weight of the floating ball 902 so that the density of the floating ball 902 is equal to the density of a certain proportion in the steam-water mixture. When the water content of the steam-water mixture exceeds the design requirement, the density of the steam-water mixture is higher than that of the floating ball 902, and the floating ball 902 floats upwards under the action of the floating force, so that the water flow sealing the draft tube 13 upwards rushes to the central through hole 8; when the water content of the steam-water mixed fluid is lower than the design requirement, the density of the steam-water mixed fluid is lower than that of the floating ball 902, the floating ball 902 falls down, and the steam of the draft tube 13 is sucked into the centrifugal air extractor and is mixed with the air of the central through hole 8 to form high-pressure steam-water mixed fluid, and the high-pressure steam-water mixed fluid is injected into the blade path through the air supplementing holes 4.

(3) The air in the central through hole 8 and the steam in the draft tube 13 with a certain proportion are sucked and compressed to form steam-water mixed fluid, which is more energy-saving than the traditional mode of simply injecting compressed air. The reason is that: the liquid drop in the first water vapor can dissolve more air under high pressure because of the increased surface area of the water, and can carry more air quantity; the second water vapor has a higher density than air and can form a higher pressure under the action of the centrifugal pump to inject bubbles contained in the liquid drops into the water turbine. Droplets of water vapor have a carrying effect on the supplied air and assist in the formation of small bubbles.

(4) According to the invention, the external steam-water mixed fluid can be accurately fed into the water outlet edge region of the blade 2 through the centrifugal air extractor under the full-load working condition of the turbine runner 1, and the air-feeding holes 4 are close to the cavitation position of the water outlet edge region of the blade 2, so that the obvious effects of air-feeding and corrosion-reducing of the blade 2 of the runner 1 in the water outlet edge region of the blade 2 operated under the full-load working condition are obtained. The added air changes the local fluid property of the blade 2 water outlet edge blade path area, so that the rigidity of the fluid is reduced, the hydraulic vibration of the vortex of the blade path is relieved, a remarkable vibration reduction effect can be generated, and the hydraulic pulsation stress causing the blade 2 water outlet edge crack is reduced.

(5) The invention simplifies the traditional forced air supplementing device, does not need to add an additional air compressor and device system, saves investment and saves the reliability of unit operation.

(6) Because the position of the air supplementing hole 4 is close to the cavitation zone of the water outlet edge area of the water turbine blade 2, a large amount of air supplementing quantity is not needed.

(7) The invention utilizes partial vapor (the gas content is more than 95%) of the draft tube, improves the air carrying capacity by the pressurization of the centrifugal air extractor, promotes the generation of small bubbles in the flow field, and strengthens the effect of supplementing air.

The technical scheme of the invention is not limited to the specific embodiment, and all technical modifications made according to the technical scheme of the invention fall within the protection scope of the invention.

Claims (10)

1. A make-up air is subtracted and is eroded vibration damper for low specific speed hydraulic turbine runner blade afterbody, its characterized in that includes:

a mounting chamber; the installation chamber is positioned between the rotating wheel of the water turbine and the main shaft of the water turbine;

a centrifugal air extractor; the first blade of the centrifugal air extractor is arranged in the installation chamber and is fixedly connected with the rotating wheel;

a central through hole; the central through hole penetrates through the first blade and the main shaft;

a plurality of air supply holes; the air-filling hole is arranged on the top cover of the rotating wheel, and the first end of the air-filling hole is positioned in the mounting chamber;

a water vapor replenishing member; the steam supplementing piece is used for supplementing steam into the installation chamber, and the steam and air from the upper end of the main shaft form steam-water mixed fluid in the installation chamber.

2. The device for compensating for the cavitation and vibration of a turbine runner blade tail of claim 1 wherein the second end of the air compensating port is located in the region of the water outlet edge of the runner crown blade tail.

3. The device for supplementing air and reducing corrosion to a turbine runner blade tail according to claim 1, wherein the steam supplementing member comprises a steam source and a flow regulator for regulating the flow of steam from the steam source into the central through hole.

4. The device for supplementing air and reducing corrosion and vibration reduction at the tail of a runner blade of a low-specific-speed water turbine according to claim 3, wherein the water vapor source is water vapor in a draft tube, the center through hole penetrates through the runner to be communicated with the draft tube, the flow regulating member is used for regulating the flow of the water vapor in the draft tube entering the center through hole, and the regulating action end of the flow regulating member is positioned below the installation chamber.

5. The apparatus of claim 4, wherein the flow regulator comprises a ball check valve mounted at an end of the central bore adjacent the draft tube.

6. The device for air supplementing, corrosion reducing and vibration absorbing of a turbine runner blade tail with low specific speed according to claim 5, wherein the floating ball check valve comprises a mounting sleeve and a floating ball, the mounting sleeve is mounted at one end of the central through hole close to the draft tube, the center of the mounting sleeve is provided with a communication channel, the size of two ends of the communication channel is smaller than that of the middle part of the communication channel, the floating ball is located in the middle part of the communication channel, the size of the floating ball is larger than that of two ends of the communication channel, one end of the mounting sleeve close to the near draft tube is provided with a plurality of steam-water mixture channels, and the steam-water mixture channels are communicated with the middle part of the communication channel.

7. The air make-up corrosion reducing vibration damper for low specific speed turbine runner blade tail according to claim 5 or 6, wherein the average density of the float ball is greater than the water vapor density in the draft tube when the turbine is operating under low load conditions, the float ball falls, the float ball check valve opens, and water vapor enters the mounting chamber through the float ball check valve to mix with air from the main shaft; when the floating ball check valve runs under the full-load working condition, the average density of the floating ball is smaller than the water vapor density in the draft tube, the floating ball floats upwards, and the floating ball check valve is closed.

8. The device for compensating for the cavitation vibration reduction of the tail of a runner blade of a low specific speed water turbine according to claim 1, further comprising a vacuum break valve mounted at an end of the central through hole remote from the mounting chamber.

9. The air-supplementing, corrosion-reducing and vibration-damping device for the tail of a runner blade of a low-specific-speed water turbine according to claim 1, wherein the distance between the first end of the air-supplementing hole and the central axis of the central through hole is a first distance, the distance between the second end of the air-supplementing hole and the central axis of the central through hole is a second distance, and the first distance is not smaller than the second distance.

10. The device of claim 1, wherein the first end of the air make-up hole has a diameter greater than the second end of the air make-up hole.