JP2002235652A - Francis turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Francis turbine capable of restraining deterioration of turbine efficiency caused by a stream of water flowing from a sealing communication passage to a draft tube. SOLUTION: The sealing communication passage 15 for communicating an upper stream side 13 with a lower stream side 14 of a runner 3 is formed on an outer peripherary of a shroud ring 5 provided on an outer peripheral part 3a of the runner 3 integrally rotating with a main shaft 2 of the Francis turbine 1, and a lower cover 7 is disposed so as to seal an upper stream side end part 15a. The draft tube 4 is disposed on the lower stream side of the runner 3. A lower stream side end part 15b, which is a tube 4 side part of the communication passage 15, is tilted to a forward direction with respect to a flowing direction of a main stream flowing through an inlet part 4a of the tube 4, and a seal ring 6 is provided on a lower stream side end part 7a of the cover 7 in order to seal between the ring 5 and the cover 7 at the upper stream side. The water intruding into the communication passage 15 is made to join at the inlet part 4a of the tube 4 from the forward direction, which is oblique with respect to the main stream, so as to avoid disturbing the main stream.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Francis turbine installed inside a dam or weir and used for hydroelectric power generation.

[0002]

2. Description of the Related Art In a Francis turbine, a plurality of runner vanes of a runner (impeller) connected to a main shaft are rotated by receiving a water flow.

[0003] Water for rotating the runner is taken into a hydraulic line from a water storage tank such as a dam through an intake port or the like. In the water introduced into the hydraulic line, energy corresponding to the potential energy held in the water storage tank is taken out by the runner, and low-pressure water that has lost energy is released from the draft tube. You.

[0004] Around the runner, a spiral casing (spiral chamber) for flowing a water flow guided by a hydraulic line from the outer peripheral side toward the runner in a substantially constant direction along the circumferential direction is provided. The runner is arranged to surround the runner from outside. In this casing, a runner is rotatably arranged at the center thereof. Around the runner, a plurality of guide vanes (guide vanes) for guiding the flow while controlling the flow rate of the water flow toward the runner vane is arranged so that the water flow flowing in the casing hits each runner vane efficiently. I have. A speed ring having a plurality of stay vanes is arranged around these guide vanes to regulate (rectify) the flow of the water flow and for structural strength. Further, a draft tube (draft tube) for discharging the water flow after rotating the runner to the outside of the water turbine, for example, to a water discharge channel, is provided downstream of the runner.

[0005] A shroud ring is provided on the outer periphery of the runner, and a gap is provided in the outer periphery of the ring to communicate the upstream side of the runner and the upstream end of the draft tube. This gap is covered by a lower cover provided to support the casing from below so that water does not leak out of the water turbine from here. That is, the gap is formed as a seal communication passage that communicates the casing and the draft tube. Thereby, a part of the water flow in the casing flows directly into the draft tube from the upstream side of the runner through the communication passage for sealing without passing through the inside of the runner.

When the flow rate of the water flow passing through the seal communication passage increases, the flow rate of the water flow for rotating the runner decreases, and the power generation efficiency of the water turbine is impaired. In order to suppress this loss, the communication passage for sealing is narrowed at the entrance thereof so as to approach between the upstream side of the runner of the lower cover and the upper part of the shroud ring. At the same time, the space between the downstream end of the shroud ring and the upstream end of the draft tube is narrowed by a seal ring provided on the lower cover at the outlet of the communication passage for sealing.

According to the above-described configuration, most of the water flow flowing into the casing from the hydraulic line is adjusted to a predetermined flow state by the speed ring and the guide vane, and then flowed toward the runner. The runner rotates as the runner vanes receive the water flow. When the runner rotates, the main shaft connected to the runner rotates. The main shaft is connected to a generator, and the generator generates power when the main shaft rotates. After rotating the runner, the water flow is discharged through a draft tube to a drain.

[0008]

The water that has flowed into the sealing communication passage from the upstream side of the runner flows out into the draft tube from the upstream end of the draft tube. The outlet side end of the communication passage for sealing can be easily formed.
Generally, it is formed substantially at right angles to the inlet side wall surface of the draft tube, and communicates with the inlet of the draft tube. Therefore, the flow of water flowing out of the sealing communication passage into the draft tube joins the flow of the water flow (main flow) flowing into the draft tube through the runner from a direction substantially perpendicular to the flow. Thereby, the mainstream flow is easily disturbed. Disturbing the main flow causes energy loss and impairs the efficiency of the turbine.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a Francis turbine capable of suppressing a decrease in runner efficiency due to a water flow flowing out of a seal communication passage into a draft tube.

[0010]

In order to solve the above-mentioned problems, a Francis turbine according to the present invention is provided with a main shaft, a runner that receives water flow and rotates integrally with the main shaft, and is provided downstream of the runner. A draft tube for releasing the water flow, a shroud ring provided on the outer periphery of the runner, and a sealing communication passage communicating the upstream and downstream sides of the runner with the outer periphery of the shroud ring. And, the draft tube side portion of the seal communication passage is inclined in the forward direction with respect to the flow direction of the water flow passing through the inlet of the draft tube, and at the upstream side thereof. And a lower cover having a seal ring for sealing between the shroud ring and the shroud ring.

In order to solve the above-mentioned problems, a Francis turbine according to the present invention includes a main shaft, a runner that receives the water flow and rotates integrally with the main shaft, and is provided downstream of the runner to reduce the water flow. A draft tube to be discharged, a shroud ring provided on an outer peripheral portion of the runner, and a seal communication passage communicating the upstream and downstream sides of the runner to the outer periphery of the shroud ring, between the shroud ring and the shroud ring. An outer seal ring that is formed and provided, and seals between the shroud ring at one end thereof, so as to be adjacent to a downstream end surface of the shroud ring downstream of a seal portion formed by the outer seal ring. An inner seal ring disposed inside the outer seal ring, and a flow direction of water flowing through an inlet of the draft tube. It is characterized in that it comprises a lower cover having a leak passage formed between both the sealing ring has a passage outlet inclined direction.

In order to solve the above-mentioned problems, a Francis turbine according to the present invention includes a main shaft, a runner that receives a water flow and rotates integrally with the main shaft, and is provided downstream of the runner to reduce the water flow. A draft tube to be discharged, a shroud ring provided on an outer peripheral portion of the runner, and a flow direction of a water flow passing from a downstream end of the shroud ring to an inlet of the draft tube are provided in substantially the same direction. A flow guide and a seal communication passage communicating between the upstream and downstream sides of the runner are formed between the shroud ring and an outer periphery of the shroud ring, and the seal communication passage is provided with the seal communication passage. A part of the draft tube side portion is sealed together with the shroud ring, and the draft tube It is characterized by comprising a lower cover having a seal ring for guiding the flow on the outlet side of the sealing communication path, together with the flow guide, in a direction substantially the same as the flow direction of the water flow passing through the inlet portion. Is what you do.

In order to solve the above-mentioned problems, a Francis turbine according to the present invention comprises a main shaft, a runner which receives the water flow and rotates integrally with the main shaft, and is provided on a downstream side of the runner to reduce the water flow. A draft tube to be discharged, a shroud ring provided on an outer peripheral portion of the runner, and a seal communication passage communicating the upstream and downstream sides of the runner to the outer periphery of the shroud ring, between the shroud ring and the shroud ring. A lower cover formed and provided is provided over the runner vane of the runner and the shroud ring, one end of which is opened to the communication passage for sealing, and the outlet of the other end is provided with respect to a water flow passing through the runner. And a blowing passage opened to the runner vane so as to blow water in a forward direction.

In practicing the present invention, the blow-out port is provided on a negative pressure blade surface on the opposite side to the pressure blade surface of the runner vane on which the water flow passing through the runner acts, where the operating pressure of the water flow is low. It is good to have composition.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a Francis turbine 1 according to a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, a Francis turbine 1 of this embodiment is a vertical single-wheel single-flow type, and has a main shaft 2 and a main shaft 2.
A lower cover having a runner 3 rotating integrally with the shaft, a draft tube 4 for discharging a water flow, a shroud ring 5 provided on an outer peripheral portion 3 a of the runner 3, and a seal ring 6 for sealing between the shroud ring 5. 7 is provided.

As shown in FIG. 1, the main shaft 2 is rotatably disposed inside an upper cover 8 formed in a substantially cylindrical shape. The main shaft 2 extending in the vertical direction is supported by a main bearing (not shown) so as to be rotatable and hardly displaced. The upper end of the main shaft 2 is connected to a generator (not shown). The main shaft 2 is rotated by the rotation of a runner 3 to be described later receiving the water flow, and the generator is operated to generate electric power.

The runner 3 connected to the lower end of the spindle 2
As shown in FIG. 1, a plurality of runner vanes 9 are provided, and these runner vanes 9 rotate by receiving a water flow. On the upstream side of the runner 3, a casing (not shown) for sending a water flow toward the runner 3 is attached so as to surround the runner 3 from outside. The casing is formed in a spiral shape, and can guide a water flow conveyed at a predetermined water pressure by a hydraulic line (not shown) so as to hit the runner vane 9 in a fixed rotation direction along the circumferential direction of the runner 3. it can. The water flow passes between a plurality of guide vanes 12 to be described later and flows into the entire circumference of the runner 3 substantially uniformly during one round of the spiral casing.

A speed ring 10 for rectifying the water flow in the casing is attached to the inner peripheral side of the casing. The speed ring 10 also serves to reinforce the casing. A plurality of stay vanes 11 are attached to the speed ring 10 at a predetermined radius along the circumferential direction thereof for rectifying and strengthening the flow of water flowing into the casing from the hydraulic line.

Between the speed ring 10 and the runner 3, a predetermined radius is provided along the outer peripheral direction of the runner 3,
A plurality of guide vanes 12 are rotatably mounted to guide the water flow flowing from the inside of the casing toward the runner 3 while controlling the flow rate and the like. Each guide vane 12 is rotated around an axis of the guide vane 12 by a guide vane driving device (not shown). Each guide vane 12 guides the flow of water flowing from the inside of the casing toward the runner 3 while adjusting the amount of the water flowing into each runner vane 9, and controls their postures so as to obtain a predetermined flow rate output.

Downstream of the runner 3, a draft tube 4 is provided for discharging a water flow (main flow) after rotating the runner 3 indicated by a white arrow X in FIG. ing. The draft tube 4 is set to such a size that the water flow can pass through the inlet 4a and flow smoothly toward an outlet (not shown) as a downstream end.

The draft tube 4 is formed such that its flow path cross-sectional area gradually increases from the inlet 4a as the upstream end to the outlet. For example, as shown by a two-dot chain line in FIG. 1, the draft tube 4 has an angle that is expanded (inclined) outward from the diameter of the opening of the inlet portion 4 a on the basis of the diameter of the opening.
By optimizing the angle φ (also referred to as an enlargement angle), it is possible to set the main flow to flow smoothly. As a result, the flow velocity of the main flow at the outlet can be reduced, and the loss of velocity energy corresponding to the outflow velocity can be reduced. Further, by optimizing the expansion angle φ of the draft tube 4, of the water flow flowing through the draft tube 4, the water flow flowing near the inner wall surface 4 b of the draft tube 4 is prevented from separating from the vicinity of the inner wall surface 4 b. it can. Therefore, by setting the expansion angle φ of the draft tube 4 to an appropriate value, the main flow can be prevented from being disturbed or obstructed, and can be set so that the flow can flow smoothly without interruption. . Furthermore, by increasing the expansion angle φ of the draft tube 4 within an appropriate range, the overall length of the draft tube 4 can be shortened without substantially impeding the flowability of the water flowing therethrough. Thereby, the whole Francis turbine 1 can be made compact.

According to the above-described flow channel including the hydraulic pressure line, the casing, the speed ring 10, the draft tube 4, etc., the water flow in the turbulent state is caused by the casing shown in FIG. During one round of the inside, the air flows between the respective stay vanes 11 and between the guide vanes 12, and is rectified to a predetermined state, and from the upstream (inlet) side 13 of the outer periphery of the runner 3 to the entire circumference of the runner 3. Flow in the same way. In this state, most of the water flow flows while pushing each runner vane 9 in a certain direction so as to rotate the runner 3 at a certain speed. The water flow that rotates the runner 3 flows along the surface of each runner vane 9, and flows out as a main flow to the downstream (outlet) side 14 below the runner 3 as shown by a white arrow X in FIG. 1. This mainstream is
The gas flows into the draft tube 4 through the inlet 4a, and is transported to the outlet while maintaining a smooth flow state by the draft tube 4. The outlet of the draft tube 4 communicates with the water discharge channel, and the water flow is discharged to the water discharge channel through the outlet.

As shown in FIG. 1, the shroud ring 5 is provided on the outer peripheral portion 3a of the runner 3 so as to surround the entire circumference. Also, the shroud ring 5
The shape on the inner peripheral side forms a flow channel of the runner, and water flows smoothly in the runner 3 at the head, flow rate, and rotation speed in which the water turbine 1 is used, and the energy of the pressure and speed of the water is reduced. Each runner vane 9 is formed in a shape that can be efficiently received. By using the runners 3 including the shroud rings 5, the runners 3 can be efficiently rotated by the energy of the water flow pushing the respective runner vanes 9.

Further, each runner vane 9 itself is formed in such a shape that it can receive the water flow almost evenly and convert its energy to the rotational kinetic energy of the runner 3 efficiently. Each runner vane 9 is formed in such a shape that the water flow after rotating the runner 3 can flow smoothly to the downstream side 14 of the runner 3.

The outer shape of the shroud ring 5 seals a gap provided between the rotating runner 3, a fixed lower cover 6 described later, and the draft tube 4. Is formed in a shape suitable for forming the seal communication passage 15.

As shown in FIG. 1, the lower cover 7 includes a speed ring 10, a rotating runner 3, a draft tube 4 fixed below the runner 3, and the like.
It is formed in a shape that covers the entire circumference from the outside. The lower cover 7 is formed in a shape that can support the speed ring 10, the draft tube 4, and the like from the outside, and has sufficient support strength for that. The inner shape of the lower cover 7 forms a gap between the shroud ring 5 and the lower cover 7 such that the runner 3 can rotate smoothly, and water flows from the runner upstream side 13 into this gap. Is formed so as to restrict the vicinity of the runner upstream side 13 of the gap so as to suppress the above. A gap is also provided between the inlet 4a of the draft tube 4 and the runner 3 so that the runner 3 can rotate smoothly. Inside the draft tube side end (downstream end) 7 a of the lower cover 7, the draft tube side end (downstream) of the shroud ring 5, which is a part of the gap, is controlled so as to suppress leakage flow from upstream. A seal ring 6 for narrowing the vicinity of the outer periphery of the (side end portion) 5a is provided over the entire periphery of the draft tube 4.

Thus, this Francis turbine 1
A gap communicating between the upstream side 13 and the downstream side 14 of the runner 3 is provided between the inside of the lower cover 7 and the seal ring 6 of the lower cover 7 and the outside of the shroud ring 5. It is provided over the entire circumference of the runner 3.

On the upstream side 13 of the runner, a part of the water flow flows into the gap without hitting each runner vane 9 as shown by a solid line arrow in FIG. The water that has flowed into the gap is guided by this gap, flows out to the runner downstream side 14, merges with the main flow, flows through the draft tube 4, and is discharged. Thus, the gap is located between the runner upstream side 1
3 and a communication passage 15 for a seal communicating the runner downstream side 14
It is formed as.

A communication passage entrance 15 communicating with a runner upstream 13 as an upstream end of the sealing communication passage 15.
As described above, a is narrowed by the upstream end 5b of the shroud ring 5 and the upstream end 7b of the lower cover 7 in order to prevent water from flowing into the communication passage 15 for sealing. (Sealed). With it,
As described above, a part of the communication passage outlet portion 15b as a downstream end portion as a draft tube side portion communicating with the runner downstream side 14 of the seal communication passage 15 also prevents leakage flow from the upstream. In order to suppress this, the downstream end 5a of the shroud ring 5 and the seal ring 6 are squeezed (sealed).

The communication passage outlet 1 of the seal communication passage 15
As shown in FIGS. 1 and 2, the draft tube 4b has a downstream portion from the sealed portion.
Is formed to be inclined in the forward direction with respect to the flow direction of the main flow indicated by a white arrow X passing through the inlet portion 4a.

More specifically, the downstream end 5a of the shroud ring 5 is arranged such that the communication passage outlet 15b of the seal communication passage 15 has a forward direction with respect to the flow direction of the water flow passing through the inlet 4a of the draft tube 4. The downstream end surface 5c is formed to be inclined by an angle θ with respect to the inner wall surface 5d of the downstream end portion 5a of the shroud ring 5 so as to be inclined. The magnitude of the angle θ is set to an arbitrary value from 0 ° to less than 90 °, but is preferably as small as possible, and is preferably set to a practically possible acute angle, for example, 45 ° or less. As described above, by tilting the communication passage outlet 15b of the sealing communication passage 15 in the forward direction to reduce the magnitude of the angle θ, the water flowing out of the sealing communication passage 15 into the draft tube 4 is reduced. As shown by a solid line arrow in FIG. 2, it can be made to flow into the draft tube 4 so as to smoothly merge with the main flow indicated by the outline arrow X in FIG. 2 along the direction of the flow. Therefore, the communication passage for sealing 1
The water flowing out from inside the draft tube 4 into the draft tube 4 disturbs or obstructs the flow of the main flow passing therethrough at the inlet 4a of the draft tube 4 in combination with the fact that the flow rate is considerably smaller than the flow rate of the main flow. Is suppressed.

The water flowing into the draft tube 4 from the seal communication passage 15 smoothly merges with the main flow, so that a part of the main flow flowing in contact with the inner wall surface 4b of the draft tube 4 is reduced. The formation of turbulence by peeling from the vicinity of 4b and the development of the boundary layer are suppressed. Thus, the risk that water flowing out of the seal communication passage 15 into the draft tube 4 disturbs or hinders the main flow can be suppressed. Therefore, a decrease in the energy absorption efficiency of the runner 3 due to the disturbance of the main flow can be suppressed.

The downstream end 6a of the seal ring 6 is connected to the draft tube 4 at the downstream end 5a of the shroud ring 5 and at the inlet 4a of the draft tube 4. It is formed so as to be located on a surface connecting the edge of the opening. As a result, the water that has flowed into the communication passage 15 for sealing is
Due to the pressure difference between 5a and the communication passage outlet 15b, it is discharged into the draft tube 4.

According to the seal communication passage 15 having the above-described configuration and shape, the seal communication passage 15 is provided from the runner upstream side 13 without hitting each runner vane 9.
Since the amount of water flowing into the inside can be reduced, it is possible to suppress a decrease in the amount of water flowing to rotate the runner 3. Also,
Since the flow of the main flow is not disturbed by the water discharged from the sealing communication passage 15 into the draft tube 4, the decrease in the efficiency of the runner 3 due to the disturbance of the main flow can be suppressed. At the same time, since the separation of the flow at the inlet of the draft tube 4 is unlikely to occur, the enlargement angle φ can be increased, so that the draft tube 4 can be made compact, and furthermore, the Francis turbine 1 including the draft tube 4 can be made compact. Can be promoted.

In the Francis turbine 1 according to the present embodiment having the above-described configuration, most of the water flow flowing into the casing from the hydraulic line flows toward each runner vane 9 so as to rotate the runner 3. Runner 3
Rotates at a constant speed as each runner vane 9 receives a water flow. When the runner 3 rotates, the runner 3
The main shaft 2 connected to is rotated. The main shaft 2 is connected to a generator, and when the main shaft 2 rotates, the generator operates to generate electric power. The water flow that has rotated the runner 3 flows into the draft tube 4 as the main flow. In addition, a part of the water flow that has flowed into the casing flows into the seal communication passage 15 and is directly discharged into the draft tube 4 without rotating the runner 3, and the water flow flows from the forward direction of the main flow. Join. These combined streams are
The water is smoothly discharged to the water discharge passage through the draft tube 4.

According to the Francis turbine 1 of the present embodiment having the seal communication passage 15 described above, the energy conversion efficiency loss for converting the energy of the water flow into the rotational motion of the runner 3 is lost, and the Francis turbine 1 The loss of power generation efficiency including the generator connected to the power supply can be reduced.
That is, the efficiency of hydroelectric power generation can be improved.

Next, a Francis turbine 21 according to a second embodiment of the present invention will be described with reference to FIG.

The Francis turbine 21 of the second embodiment
Is different from the shroud ring 5, the seal ring 6, and the lower cover 7 of the first embodiment in the structure of the shroud ring 22, the seal ring 23, and the lower cover 24 provided therein. Configuration,
The action and effect are similar. Therefore, the different portions will be described, and the same components as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

The Francis turbine 21 according to the present embodiment has a seal ring 23 provided on a lower cover 24 provided therein.
Are composed of two seal members, an outer seal ring 25 and an inner seal ring 26 arranged inside the outer seal ring 25.

The shroud ring 22 included in the runner 3 of this embodiment has a downstream end surface 22a formed as a flat surface. The inner seal ring 26 is formed as a flat surface so that its upstream end surface 26a can face the downstream end surface 22a of the shroud ring 22 in parallel. The inner seal ring 26 is disposed so as to be adjacent to the downstream end face 22a of the shroud ring 22 with a slight gap that does not hinder the rotation of the runner 3 and be continuous.

The inner seal ring 26 is formed in a substantially cylindrical shape extending a predetermined length from the upstream side to the downstream side. The thickness of the inner seal ring 26 is formed to be thinner than the thickness of the lower end 22 b of the shroud ring 22. Also, this inner seal ring 2
6, the inner wall surface 26c is tapered so that the cross-sectional area of the flow path gradually increases from the upstream side to the downstream side. More specifically, in the Francis turbine 21 of the present embodiment, the draft tube 4 has a lower end 25 of an outer seal ring 25 whose inlet end 4c is described later.
b. The draft tube 4 has a downstream end face 22a of the shroud ring 22 so that the cross-sectional area of the flow passage gradually increases from the inlet 4a toward the outlet as shown by a two-dot chain line in FIG. With reference to the diameter of the inner edge as a reference, the inner edge is formed to be inclined by an enlargement angle φ from here. The inner wall surface 26c of the inner seal ring 26 is a downstream end surface 22a of the shroud ring 22.
Is formed in a tapered shape so as to be located on a surface connecting the inner edge of the opening of the draft tube 4 with the edge of the opening of the inlet portion 4a.

The inner seal ring 26 has a leak passage 27 formed by the inner seal ring 26 and an outer seal ring 25 described later.
Of the passage outlet 27a of the draft tube 4
So as to tilt forward with respect to the flow direction of the water flow passing through
The downstream end face 26d is formed to be inclined at an acute angle δ with respect to the inner wall face 26c. This angle δ is preferably smaller as in the case of the above-mentioned angle θ, and is preferably set to 45 ° or less within a practical range.

Further, the inner seal ring 26 is provided at a predetermined distance from the inner wall surface 25a of the outer seal ring 25, and is provided concentrically with the outer seal ring 25. The inner seal ring 26 is used for the outer seal ring 2.
5 are connected to and supported by several connecting members (not shown) on the inner wall surface 25a.

The outer seal ring 25 is formed in a substantially cylindrical shape by extending a predetermined length from the upstream side to the downstream side so that the outer seal ring 25 can concentrically face the inner seal ring 26 described above. I have. The outer seal ring 25 has an upstream end portion 25 a and a shroud ring 22.
And a downstream end portion 22b of the seal communication passage 15 to form a seal communication passage downstream seal portion 28 for sealing a part of the draft tube side portion of the seal communication passage 15. The downstream end 25b of the outer seal ring 25 is
The connection portion with the draft tube 4 is tapered so that it is located on a surface connecting the inner edge of the downstream end surface 22a of the shroud ring 22 and the edge of the opening of the inlet portion 4a of the draft tube 4. I have.

In the outer seal ring 25 and the inner seal ring 26 having the above-described structures, the seal communication passages 15 are formed by the two seal rings 25 and 26.
A leakage passage 27 communicating with the downstream end is formed.
The width of the leak passage 27 is determined by the width of the downstream seal portion 28 of the seal communication passage 15 and the downstream end surface 22 a of the shroud ring 22 and the upstream end surface 26 of the inner seal ring 26.
The width is set to be larger than the width of the gap at the portion facing the portion a. Further, as shown by a solid arrow in FIG. 3, the angle of the flow of the water discharged from the passage outlet 27 a of the leakage passage 27 is in the forward direction with respect to the flow direction of the water flow passing through the inlet 4 a of the draft tube 4. It is formed so as to be inclined in the direction.

The lower cover 24 includes an outer seal ring 25
So that it can be supported over its entire length from its outer periphery,
It is formed to extend from the upstream side to the downstream side by a predetermined length.

The Francis turbine 21 of the second embodiment
Is the same as the Francis turbine 1 of the first embodiment except for the points described above, and it is needless to say that the problem of the present invention can be solved.
2, the seal ring 23, the lower cover 24, and the leakage passage 27 formed by the outer seal ring 25 and the inner seal ring 26, etc., are excellent in the following points.

In the Francis turbine 21 of this embodiment, the inlet 4 a of the draft tube 4 is
And is installed below the runner 3 so as to be separated from the downstream side 14 of the runner 3 by substantially the entire length of the runner 3. Therefore, the main flow that has passed through the runner 3 is decelerated in accordance with the length of the inner seal ring 26 as shown by a white arrow X in FIG. 3, and can flow into the draft tube 4 in this decelerated state. Thereby, the flow of the main flow due to the leakage flow is disturbed, and the risk of lowering the efficiency of the water turbine 21 can be further reduced.

The width of the leak passage 27 is determined by the width of the downstream seal portion 28 of the seal communication passage 15 and the portion of the downstream end surface 22a of the shroud ring 22 facing the upstream end surface 26a of the inner seal ring 26. It is formed larger than the width of the gap. Therefore, most of the leakage flow rate of the water leaked from the upstream side 13 of the runner 3 and flowing into the seal communication passage 15 passes through the downstream seal portion 28,
It can flow into the leak passage 27, pass through the passage outlet 27 a and the inlet 4 a of the draft tube 4, and can flow more smoothly into the inside of the draft tube 4. As a result, as shown by the dashed arrow in FIG. 3, the inner seal is removed from the very small gap between the opposing portions of the downstream end face 22 a of the shroud ring 22 and the upstream end face 26 a of the inner seal ring 26 immediately below the runner 3. The amount of water flowing into the ring 26 can be greatly reduced, and the amount of water passing through the gap merging at right angles to the mainstream flow can be suppressed.

As described above, in the Francis turbine 21 of the present embodiment, the inner seal ring 26 can reduce the speed of the main flow passing therethrough without causing disturbance due to leakage. That is, the communication passage 15 for sealing is used.
By passing most of the water flowing into the inside of the leak passage 27, at a position further away from immediately below the runner 3 to the downstream side, the main flow smoothly merges with the decelerated main flow from the forward direction along the flow. be able to. Therefore, at the entrance 4a of the draft tube 4, the leakage passage 27
Of the main flow caused by the blowing of the seal water flowing out of the passage outlet 27a of the first tube, or separation of the flow flowing along the inner wall surface 4b of the draft tube 4 in the main flow flowing in the draft tube 4 Can be further reduced. Therefore, this Francis turbine 21
In the above, the loss of the mainstream can be further reduced, and the efficiency of the water turbine can be improved.

Next, a Francis turbine 31 according to a third embodiment of the present invention will be described with reference to FIG.

The Francis turbine 31 of the third embodiment
Is different from the above-described structure of the shroud ring 5 and the seal ring 6 of the first embodiment in the structure of the shroud ring 32 and the seal ring 33, and the other configurations, operations, and effects are the same. is there.
Therefore, the different portions will be described, and the same components as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

FIG. 4 shows a Francis turbine 31 according to this embodiment.
As shown in FIG.
2, a part of the downstream end 32a is formed to be thinner than the other part, and is provided to extend in substantially the same direction as the flow direction of the water flow passing through the inlet 4a of the draft tube 4. I have. The extended portion passes through the sealing communication path 15 formed by the shroud ring 32 and a seal ring 33 described later, and flows into the draft tube 4 through the sealing communication path. A flow guide 34 for guiding the flow at the outlet side of the draft tube 15 in substantially the same direction as the flow direction of the water flow passing through the inlet portion 4a of the draft tube 4.
It is formed as.

The seal ring 33 includes the shroud ring 3
2 are disposed facing the outside of the shroud ring 32 so as to form a draft tube side portion which is a downstream portion of the communication passage 15 for sealing. The shape of the seal ring 33 on the inner peripheral side is such that the upstream end 33a and the downstream end 32a of the shroud ring 32 seal a part of the sealing tube 15 on the draft tube side. The passage downstream side seal portion 35 is formed. The shape of the inner peripheral side of the outer seal ring 33 is such that the downstream end portion 33b and the outer peripheral wall surface 34a of the flow guide 34 form a seal for the blowout flow flowing out into the draft tube 4 through the communication passage 15 for sealing. The flow on the outlet side of the communication passage 15 is formed to be guided in substantially the same direction as the flow direction of the water flow passing through the inlet 4 a of the draft tube 4. The thickness of the downstream end 33 b of the outer seal ring 33 along the radial direction is such that the width of the seal communication passage 15 on the downstream side from the seal communication passage downstream seal 35 is equal to the width of the downstream seal 35. Is formed so as to be wider than the width.

The Francis turbine 31 of the third embodiment
Is the same as the Francis turbine 1 of the first embodiment except for the points described above, and it is possible to solve the problem of the present invention.
2 and the seal ring 33, and the flow guide, etc., are excellent in the following points.

In the Francis turbine 31 of this embodiment, the width of the seal communication passage 15 downstream from the downstream seal portion 35 of the seal communication passage 15 is wider than the width of the downstream seal portion 35. Is formed. Therefore, water leaking from the upstream side 13 of the runner 3 and flowing into the seal communication passage 15 can flow smoothly into the draft tube 4.

As shown by solid arrows in FIG. 4, the blow-off flow flowing from the downstream seal portion 35 of the sealing communication passage 15 to the downstream portion is changed by the flow guide 34 through the draft tube 4. Is guided in substantially the same direction as the flow direction of the water flow passing through the inlet portion 4a, and is discharged into the draft tube 4. Therefore, the blowout flow discharged from the seal communication passage 15 is the same as that in FIG.
There is almost no possibility that the main flow after rotating the runner 3 indicated by the hollow arrow X will be disturbed or obstructed. At the same time, the blowout flow hardly causes separation of the flow flowing along the inner wall surface 4b of the draft tube 4 in the main flow flowing in the draft tube 4. That is, the blowing flow can merge with the main flow very smoothly. Thus, in the Francis turbine 31, the loss of the main flow can be further reduced, and the efficiency of the turbine can be further improved.

Next, a Francis turbine 41 according to a fourth embodiment of the present invention will be described with reference to FIGS.

The Francis turbine 41 of the fourth embodiment
Is different from the first embodiment in the structure of the shroud ring 42, the runner vane 43, and the seal ring 44, which are different from the structure of the shroud ring 5, the runner vane 9, and the seal ring 6 described above. , Actions and effects are similar. Therefore, the different portions will be described, and the same components as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

The Francis turbine 41 of this embodiment is similar to that of FIG.
As shown in FIG. 2, the water (seal water) flowing into the seal communication passage 15 is supplied to the runner 3 provided therein without passing through the outlet portion 15b of the seal communication passage 15 so as to be connected to the downstream side 1 of the runner 3.
The outlet passage 45 for discharging to the shroud ring 42 and each runner vane 4 corresponds to the number of the runner vanes 43.
3 are provided through. Each of the outlet passages 45 is provided at a downstream end portion of each of the runner vanes 43 so as to form a smooth flowing channel along the inside thereof.

An inlet portion 45a as one end of the blow-out passage 45 has an opening on the outer peripheral surface of the shroud ring 43 so as to communicate with an intermediate portion between the inlet portion 15a of the seal communication passage 15 and the downstream seal portion 15c. It is provided. Each of the outlet passages 45 has a plurality of outlets 45b as outlets for discharging the sealing water flowing into the inside to the outside as the other end thereof. In the present embodiment, four outlets 45 are provided for each outlet passage 45. Have each one. In the present embodiment, each of the outlet passages 45 is configured such that most of the seal water flowing into the seal communication passage 15 from the upstream side 13 of the runner 3 flows from the seal communication passage inlet portion 15a to each of the outlet passage inlet portions 45a. Due to the pressure difference,
Each of the outlet passages 45 a is provided so as to flow into each of the outlet passages 45 through the inlet portion 45 a, and to be discharged from each outlet passage outlet 45 b toward the downstream side 14 of the runner 3.

Each of the outlets 45b blows out sealing water in a forward direction with respect to the water flow passing through the runner 3.
The inside of each runner vane 43 is provided so as to face the flow direction.

In more detail, each runner vane 43
5 and FIG. 6, when a water stream hits from the upstream side 13 of the runner 3, the runner 3 having each runner vane 43 is indicated by a hatched arrow in FIGS. 5 and 6. Rotate in the direction. At this time, as shown in FIG.
The surface on which the water flow of each runner vane 43 mainly acts, that is, the surface pressed by the water flow is referred to as a pressure blade surface 43a,
The surface of each runner vane 43 where the acting pressure (pressing force) of the water flow is low, that is, the surface substantially opposite to the pressure blade surface 43a is referred to as a negative pressure blade surface 43b. In the present embodiment, since the cross-sectional shape of each runner vane 43 taken along the line AA in FIG. 5 is formed as shown in FIG. 6, most of the pressure blade surface 43a of each runner vane 43 is It is on the rear side with respect to the rotation direction of the runner 3. In addition, each runner vane 4
Most of the negative pressure wing surfaces 43b of the runners 3 are on the front side in the rotation direction of each runner 3.

In this embodiment, the communication passage 1 for sealing is used.
5. Each runner vane 43 and each outlet passage 45
Most of the seal water flowing into the seal communication passage 15 from the upstream side 13 of the runner 3 has a pressure difference between the above-described seal communication passage entrance portion 15a and each of the blowout passage entrance portions 45a, and a description of the sealing communication passage. 15 and the pressure of each runner vane 43 on the side of the negative pressure wing surface 43b, the air passes through each of the outlet passage inlet portions 45a, and each of the outlet passages 4a.
5 and is preferably set so as to be blown toward the downstream side 14 of the runner 3 from each blowout passage outlet 45b.

Each of the outlet passages 45 has a corresponding one of the runner vanes 4.
3 at the downstream end. Each outlet passage 45
As shown in FIG. 6, each of the outlets 45b is extended downward from each of the outlet passages 45 and toward the rear in the rotational direction, and the downstream end in the rotational direction of the negative pressure blade surface 43b of each of the runner vanes 43. It is provided with an opening. With such a structure, the seal water flowing into each of the outlet passages 45 is directed downward by the broken line arrows in FIG. The air is blown toward the downstream side through each of the outlets 45b.

When the main shaft 2 and the runner 3 rotate in the directions indicated by the hatched arrows in FIG. 5, the seal water flowing from the sealing communication passage 15 into each of the blow-out passages 45 is removed.
As shown by the middle dashed arrow, from the top of each runner vane 43 downward, and from the back side of the drawing to the front side, or from the top of each runner vane 43 as shown by the dashed line arrow in FIG. The air is blown downward from the outlets 45b from the near side to the far side of the drawing. That is, the seal water that has flowed into each of the outlet passages 45 is blown out from each of the outlets 45b in a direction substantially along the flow of the main flow indicated by a white arrow X in FIG.

Shroud ring 42, runner vane 4
3 and the direction of the flow of the seal water having the outlet portion 15b passing therethrough and flowing into the inlet portion 4a of the draft tube 4 in the sealing communication passage 15 formed of the seal ring 44 in FIG. As shown by the solid line arrow, it is formed so as to join at a substantially right angle to the main flow.

The Francis turbine 41 of the fourth embodiment
Is the same as the Francis turbine 1 of the first embodiment except for the points described above, and it is obvious that the object of the present invention can be solved.
2, since it is provided with the runner vane 43, the seal ring 44, the blow-out passage 45, and the like, it is excellent in the following points.

In the Francis turbine 41 of the present embodiment, the blower passage 45 penetrating through the shroud ring 42 and each runner vane 43 and communicating the seal communication passage 15 and the downstream side 14 of the runner 3 is connected to each runner vane 43. Provided. Each of the outlet passages 45 is set so that the amount of the sealing water flowing into the sealing communication passage 15 flows into the inside thereof and flows to the outlet portion 15b of the sealing communication passage 15. Therefore, the force of the flow of the seal water flowing out from the outlet portion 15b of the seal communication passage 15 is weak, and there is almost no possibility that the flow disturbs or hinders the flow of the main flow merging at a substantially right angle. Thereby, in the Francis turbine 41 of the present embodiment, the loss of the main flow can be reduced, and the efficiency of the turbine can be improved.

The outlets 45b of the outlet passages 45 extend downward from the outlet passages 45 toward the downstream side in the rotational direction, and are formed at the downstream end in the rotational direction of the negative pressure blade surface 43b of each runner vane 43. It was provided with an opening. Therefore, at the downstream end in the rotation direction of the negative pressure blade surface 43b of each runner vane 43, the sealing water can be blown out from each blowout port 45b with a pressure higher than the water flow flowing along the negative pressure blade surface 43b. Thereby, separation of the water flow flowing along the negative pressure blade surface 43b of each runner vane 43 on the downstream side in the rotation direction from each outlet 45b can be suppressed, and cavitation (bubbles) and erosion (development) at this portion ) Can be suppressed.

The Francis turbine according to the present invention is not limited to the first to fourth embodiments. For example, the Francis turbine according to the present invention may be used for types other than the vertical single wheel single flow type. In addition, the first and fourth
The flow guide 34 included in the shroud ring 32 of the third embodiment is provided on the shroud rings 5 and 42 of the embodiment.
May be provided. Alternatively, the flow guide 34 may be provided on the shroud ring 22 of the second embodiment. Further, the seal ring 44 of the fourth embodiment may be formed of two members, the outer seal ring 25 and the inner seal ring 26, like the seal ring 23 of the second embodiment.

[0073]

According to the Francis turbine according to the present invention,
Since the draft tube side portion of the communication passage for the seal is provided to be inclined in the forward direction with respect to the flow direction of the water flow passing through the inlet portion of the draft tube, the flow of the water flow passing through the inlet portion of the draft tube is prevented from being disturbed. In addition, water can flow out of the seal communication passage, and the possibility that the efficiency of the turbine of the Francis turbine decreases can be suppressed.

According to the Francis turbine according to the present invention, the leakage passage having the passage outlet inclined in the forward direction with respect to the flow direction of the water flow passing through the inlet of the draft tube is sealed between the leakage passage and the shroud ring. An outer seal ring,
Since it is provided between the shroud ring and the inner seal ring disposed inside the outer seal ring so as to be continuous with the downstream end face of the shroud ring, water flowing into the seal communication passage is passed through the leak passage. In addition, it is possible to cause water to flow out further downstream, while suppressing disturbance of the flow of the water flowing through the inlet of the draft tube, and it is possible to further suppress the possibility that the turbine efficiency of the Francis turbine decreases.

According to the Francis turbine according to the present invention, the seal guide is provided downstream of the seal portion between the shroud ring and the seal ring by the flow guide and the seal ring provided at the downstream end of the shroud ring. Since the flow of the water flowing in the passage at the outlet side of the sealing communication passage can be guided in substantially the same direction as the flow direction of the water flow passing through the inlet of the draft tube, the flow of water flowing through the inlet of the draft tube can be guided. Water can be caused to flow out of the seal communication passage while suppressing disturbance of the turbine, and the possibility that the turbine efficiency of the Francis turbine decreases can be further suppressed.

According to the Francis turbine according to the present invention, one end is communicated with the seal communication passage communicating the upstream side and the downstream side of the runner, and the outlet at the other end is connected to the water flow passing through the runner. The outlet passage opened to the runner vane so as to blow water in the forward direction is provided over the runner vane and the shroud ring of the runner. The water can be discharged from the passage, and the efficiency of the runner can be improved by using the high energy of the water flow blown out from the outlet passage, further reducing the possibility that the efficiency of the runner of the Francis turbine decreases. Can be suppressed.

In the Francis turbine according to the present invention, the outlet is provided on the negative pressure blade surface on the opposite side of the pressure blade surface of the runner vane on which the water flow passing through the runner mainly acts, where the water flow has a low operating pressure. For example, the separation of the water flow and the development of cavitation (bubbles) on the downstream side in the rotation direction from the outlet of the negative pressure blade surface can be suppressed, so that the efficiency and reliability of the runner can be improved. The possibility that the water turbine efficiency of the water turbine is lowered can be suppressed extremely well.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a Francis turbine according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a draft tube side portion of a seal communication passage of the Francis turbine of FIG. 1;

FIG. 3 is a sectional view showing a main part of a Francis turbine according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a main part of a Francis turbine according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing a main part of a Francis turbine according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of the runner vane taken along line AA in FIG. 5;

[Explanation of symbols]

1, 21, 31, 41 ... Francis turbine 2 ... main shaft 3 ... runner 3a ... runner outer periphery 4 ... draft tube 4a ... draft tube inlet 5, 22, 32, 42 ... shroud ring 5a ... shroud ring draft tube side end (Downstream end) 5b ... Shroud ring upstream end 6,23,33,44 ... Seal ring 7,24 ... Lower cover 7a ... Lower cover draft tube side end (downstream end) 7b ... Lower cover upstream Side end 8 Top cover 9, 43 Runner vane 13 Runner upstream (entrance) side 14 Runner downstream (exit) side 15 Communication passage for seal 15a Entrance for communication passage for seal (upstream end of communication passage for seal) 15b ... outlet of sealing communication passage (downstream end of communication passage for sealing) 15c, 28, 35 ... downstream sealing portion of communication passage for sealing 21 ... franc Water turbine 22a ... Shroud ring downstream end surface 25 ... Outer seal ring 26 ... Inner seal ring 27 ... Leak passage 27a ... Leak passage outlet 34 ... Flow guide 43a ... Runner vane pressure blade surface 43b ... Runner van negative pressure blade surface 45 ... Blow-out passage 45b … Blow-out port X… Water flow through the entrance of the draft tube Y… Water flow through the runner

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuhide Fukuda 2-1-1, Shinhama, Arai-machi, Takasago-shi, Hyogo F-term in Takasago Works, Mitsubishi Heavy Industries, Ltd. (Reference) 3H072 AA07 AA27 BB20 BB27 BB31 CC42 CC69 CC74

Claims (5)

[Claims] 1. A main shaft, a runner receiving water flow and rotating integrally with the main shaft, a draft tube provided downstream of the runner to discharge the water flow, and a shroud provided on an outer peripheral portion of the runner. A seal communication passage formed between the shroud ring and the outer periphery of the shroud ring, the seal communication passage communicating the upstream side and the downstream side of the runner with each other; A lower cover having a seal ring for inclining a tube side portion in a forward direction with respect to a flow direction of a water flow passing through an inlet of the draft tube, and having a seal ring for sealing the shroud ring at an upstream side thereof. A Francis turbine characterized by that. 2. A main shaft, a runner receiving the water flow and rotating integrally with the main shaft, a draft tube provided downstream of the runner to discharge the water flow, and a shroud provided on an outer peripheral portion of the runner. A ring and a seal communication passage communicating between the upstream side and the downstream side of the runner are formed between the shroud ring and an outer periphery of the shroud ring. Outer seal ring to seal between,
It passes through an inner seal ring disposed inside the outer seal ring so as to be continuous with a downstream end face of the shroud ring downstream of a seal portion formed by the outer seal ring and an inlet of the draft tube. A Francis turbine comprising: a lower cover having a passage outlet inclined in a forward direction with respect to a flow direction of a water flow and having a leakage passage formed between the seal rings. 3. A main shaft, a runner receiving the water flow and rotating integrally with the main shaft, a draft tube provided downstream of the runner to discharge the water flow, and a shroud provided on an outer peripheral portion of the runner. A ring, a flow guide provided from a downstream end of the shroud ring in a direction substantially the same as a flow direction of a water flow passing through an inlet of the draft tube, and an outer periphery of the shroud ring on an outer side of the runner. And a sealing communication passage communicating between the shroud ring and the downstream side, and a part of the draft communication tube side portion of the sealing communication passage is sealed together with the shroud ring. On the downstream side of the seal portion, the flow direction is substantially the same as the flow direction of the water flow passing through the inlet portion of the draft tube. Id together, Francis turbine, characterized in that it comprises a lower cover having a seal ring for guiding the flow at the outlet side of the seal communication passage. 4. A main shaft, a runner that receives the water flow and rotates integrally with the main shaft, a draft tube provided downstream of the runner to discharge the water flow, and a shroud provided on an outer peripheral portion of the runner. A ring, a lower cover provided on the outer periphery of the shroud ring and forming a seal communication passage communicating between an upstream side and a downstream side of the runner between the shroud ring, and a runner vane included in the runner; A blow-out opening provided at the runner vane so as to be provided over the shroud ring, one end of which is opened to the communication passage for sealing, and the blow-out opening of the other end blows water in a forward direction with respect to a water flow passing through the runner. A Francis turbine comprising a passage. 5. The discharge port is provided on a negative pressure blade surface having a low operating pressure of the water flow, opposite to a pressure blade surface of the runner vane on which the water flow passing through the runner mainly acts. The Francis turbine according to claim 4.