JP2021099087A - Draft tube of water turbine - Google Patents

Abstract

To obtain a draft tube of a water turbine that can restrain a swirl flow in a flow passage central part in the draft tube and leave a swirl flow in a flow passage outer peripheral part in the draft tube.SOLUTION: A draft tube 1 of a water turbine comprises a peripheral wall part 2 forming a first flow passage 1a through which water flows, and a swirl stop plate 3 installed in a flow passage central part of the first flow passage 1a in a cross section orthogonal to an axial direction of the first flow passage 1a. The swirl stop plate 3 extends toward the peripheral wall part 2 from the flow passage central part of the first flow passage 1a. A gap 4 is provided between a tip 3a of the swirl stop plate 3 and the peripheral wall part 2.SELECTED DRAWING: Figure 3

Description

The present invention relates to a draft tube of a water turbine that generates electricity.

Conventionally, there is known a turbine that generates electricity by rotating a runner according to an effective head of water between the inlet and the outlet of the turbine. In such a water turbine, a flow path is formed in the order of a scroll casing, a guide vane, a runner, and a draft tube from upstream to downstream in the water flow direction. The draft tube is an expansion channel located at the most downstream of the turbine. The flow of water flowing out from the runner into the draft tube recovers pressure by expanding the cross-sectional area of the flow path in the draft tube. As such a draft tube, for example, the one described in Patent Document 1 is known.

Since the draft tube is installed on the downstream side of the runner, the water to which the swirling energy is added by the downstream edge of the runner recovers the pressure by expanding the cross-sectional area of the flow path in the draft tube and flows. Loss factors in the draft tube include expansion loss in the expansion flow path and rotation loss due to the swirling component of the outflow flow from the runner. By giving swirling energy to water, water adheres to the inner wall surface of the draft tube due to the centrifugal effect, and the peeling flow on the inner wall surface of the draft tube can be suppressed, but this swirling energy is conversely the center of the flow path of the draft tube. It causes backflow in the part.

The swirling flow generated in the draft tube can be grouped into two swirling flows generated in the central portion of the flow path and the outer peripheral portion of the flow path. The swirling flow generated in the central part of the flow path causes a swirling loss. On the other hand, the swirling flow generated on the outer peripheral portion of the flow path plays a role of suppressing the peeling flow on the inner wall surface of the draft tube and reducing the expansion loss.

The draft tube described in Patent Document 1 includes a swivel stop plate extending from the central portion of the flow path of the draft tube toward the inner wall surface. In the draft tube described in Patent Document 1, the turning energy is reduced by colliding the turning flow with the turning stop plate.

Japanese Unexamined Patent Publication No. 2015-711948

However, in the draft tube described in Patent Document 1, since the tip of the swivel stop plate is in contact with the inner wall surface of the draft tube, the swivel flow swirling around the outer peripheral portion of the flow path of the draft tube also collides with the swivel stop plate. Therefore, the swirling energy of the swirling flow at the outer periphery of the flow path of the draft tube is reduced. As a result, there is a problem that the peeling flow on the inner wall surface of the draft tube is promoted and the expansion loss in the draft tube is increased.

The present invention has been made in view of the above, and is a draft tube of a water turbine capable of suppressing a swirling flow in the central portion of the flow path in the draft tube and leaving a swirling flow in the outer peripheral portion of the flow path in the draft tube. The purpose is to obtain.

In order to achieve the above object, the draft tube of the water turbine according to the present invention is installed at the peripheral wall portion forming the flow path through which water flows and at the center of the flow path in a cross section orthogonal to the axial direction of the flow path. It is provided with a swivel stop plate. The swivel stop plate extends from the center of the flow path toward the peripheral wall. A gap is provided between the tip of the swivel stop plate and the peripheral wall portion.

The draft tube of the water turbine according to the present invention has the effect of suppressing the swirling flow in the central portion of the flow path in the draft tube and leaving the swirling flow in the outer peripheral portion of the flow path in the draft tube.

Perspective view which shows the whole structure of the draft tube of the water turbine which concerns on Example 1 of this invention. FIG. 5 is a perspective view in which a part of the draft tube according to the first embodiment is broken, and shows a peripheral wall portion and a swivel stop plate. Sectional view of the draft tube along lines III-III shown in FIG. A graph showing the relationship between the radial position of the draft tube and the turning speed according to the comparative example. A graph showing the relationship between the radial position of the draft tube according to the first embodiment of the present invention and the turning speed. It is a figure which shows the draft tube of the water turbine which concerns on Example 2 of this invention, and corresponds to the cross-sectional view of line III-III shown in FIG. It is a figure which shows the draft tube of the water turbine which concerns on Example 3 of this invention, and corresponds to the cross-sectional view of line III-III shown in FIG. FIG. 5 is a perspective view in which a part of the draft tube according to the fourth embodiment of the present invention is broken, and shows a peripheral wall portion and a swivel stop plate. FIG. 5 is a perspective view in which a part of the draft tube according to the fifth embodiment of the present invention is broken, showing a peripheral wall portion and a swivel stop plate. Cross-sectional view of the draft tube along the XX line shown in FIG. FIG. 5 is a perspective view in which a part of the draft tube according to the sixth embodiment of the present invention is broken, and shows a peripheral wall portion and a swivel stop plate. FIG. 5 is a perspective view in which a part of the draft tube according to the seventh embodiment of the present invention is broken, and shows a peripheral wall portion and a swivel stop plate.

Hereinafter, examples of the draft tube of the water turbine according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

FIG. 1 is a perspective view showing the overall structure of the draft tube 1 of the water turbine according to the first embodiment of the present invention. The linear arrow X in FIG. 1 indicates the flow of water. The spiral arrow Y in FIG. 1 indicates the swirling flow of water. Hereinafter, the upstream side and the downstream side mean the upstream side and the downstream side along the water flow direction. The draft tube 1 is installed on the downstream side of a runner (not shown) that rotates by the potential energy of water. Therefore, the water with the swirling flow Y remaining after the power is taken out by the runner flows from the runner into the draft tube 1 in the direction of the arrow X. The draft tube 1 has a first flow path 1a located on the upstream side and a second flow path 1b located on the downstream side. The first flow path 1a is formed in a cylindrical shape extending in the vertical direction. The second flow path 1b extends downward from the first flow path 1a and then further extends in the horizontal direction.

FIG. 2 is a perspective view in which a part of the draft tube 1 according to the first embodiment is broken, and is a view showing a peripheral wall portion 2 and a swivel stop plate 3. Hereinafter, the axial direction, the radial direction, and the circumferential direction mean the axial direction, the radial direction, and the circumferential direction of the first flow path 1a. In this embodiment, the axial direction and the vertical direction of the first flow path 1a coincide with each other. The draft tube 1 is installed at the peripheral wall portion 2 forming the first flow path 1a through which water flows, and at the center of the flow path of the first flow path 1a in a cross section orthogonal to the axial direction of the first flow path 1a. A swivel stop plate 3 is provided.

The peripheral wall portion 2 is a cylindrical wall portion. The peripheral wall portion 2 has an inner wall surface 2a facing the inside of the first flow path 1a.

FIG. 3 is a cross-sectional view of the draft tube 1 along the line III-III shown in FIG. The swivel stop plate 3 extends from the central portion of the flow path of the first flow path 1a toward the peripheral wall portion 2. The number of the swivel stop plates 3 is not particularly limited, but is four in this embodiment. The four swivel stop plates 3 extend radially from one center point. The four swivel stop plates 3 are installed at intervals of 90 degrees in the circumferential direction of the first flow path 1a. The swivel stop plate 3 extends radially outward from the center C of the first flow path 1a. A gap 4 is provided between the tip 3a of the swivel stop plate 3 and the peripheral wall portion 2. The swivel stop plate 3 is held in the first flow path 1a via a fixing member (not shown). The swivel stop plate 3 is arranged so that its in-plane direction faces the axial direction and the radial direction. In other words, the swivel stop plate 3 is arranged so that the plate surface having the largest area of the swivel stop plates 3 collides with the swivel flow. The number of the swivel stop plates 3 may be one or a plurality. Further, although the center point of the swivel stop plate 3 and the center C of the first flow path 1a coincide with each other in this embodiment, they may deviate in the radial direction.

Next, the effect of the draft tube 1 of the water turbine according to the first embodiment will be described. FIG. 4 is a graph showing the relationship between the radial position of the draft tube 1 and the turning speed according to the comparative example. FIG. 5 is a graph showing the relationship between the radial position of the draft tube 1 and the turning speed according to the first embodiment of the present invention. The horizontal axis of FIGS. 4 and 5 indicates the radial position of the draft tube 1 in the first flow path 1a. 0 (zero) on the horizontal axis of FIGS. 4 and 5 indicates the center position in the first flow path 1a, and the farther away from 0 (zero) along the horizontal axis, the more outward in the radial direction in the first flow path 1a. Means to be located. 4 and 5 show a distribution in which the swirling speed of water becomes zero at the position of the peripheral wall portion 2 in the first flow path 1a of the draft tube 1 indicated by the black dot.

First, the draft tube 1 of the water turbine according to the comparative example will be described. The swivel stop plate 3 is not installed on the draft tube 1 of the water turbine according to the comparative example. As shown in the shaded area of the graph of FIG. 4, a swirling flow 6a is generated in the central portion of the flow path of the first flow path 1a. Further, a swirling flow 6b is generated on the outer peripheral portion of the flow path of the first flow path 1a. The swirling flow 6a generated in the central portion of the flow path of the first flow path 1a causes a backflow, but the swirling flow 6b generated in the outer peripheral portion of the flow path of the first flow path 1a is the peripheral wall portion 2. It plays a role of suppressing the peeling flow on the inner wall surface 2a.

On the other hand, a swivel stop plate 3 is installed in the draft tube 1 of the water turbine according to the first embodiment. The swivel stop plate 3 is installed at the center of the flow path of the first flow path 1a. When the swirl stop plate 3 is installed at the center of the flow path of the first flow path 1a in this way, the first flow path 1a shown in FIG. 5 is compared with the swirl speed of the swirl flow 6a in the comparative example shown in FIG. The swirling speed of the swirling flow 5a at the center of the flow path can be slowed down. On the other hand, the swirling flow 5b in the outer peripheral portion of the flow path of the first flow path 1a can maintain substantially the same swirling speed as the swirling flow 6b of the comparative example shown in FIG.

In this embodiment, the swivel stop plate 3 extends from the center of the flow path of the first flow path 1a toward the peripheral wall portion 2, so that the water swirls in the center of the flow path of the first flow path 1a. Collides with the swivel stop plate 3. Therefore, the swirling energy is reduced, and the speed of the swirling flow in the central portion of the flow path of the first flow path 1a can be reduced. On the other hand, since the gap 4 is provided between the tip 3a of the swivel stop plate 3 and the peripheral wall portion 2, the water swirling in the outer peripheral portion of the flow path of the first flow path 1a passes through the gap 4. Since it does not collide with the swirl stop plate 3, the speed of the swirl flow in the outer peripheral portion of the flow path of the first flow path 1a can be maintained. That is, it is possible to leave the swirling flow in the outer peripheral portion of the flow path of the first flow path 1a while suppressing the swirling flow in the central portion of the flow path of the first flow path 1a. As a result, it is possible to reduce the swirling loss due to the swirling flow in the central portion of the flow path of the first flow path 1a, and suppress the peeling flow on the inner wall surface 2a of the peripheral wall portion 2 to expand the first flow path 1a. The loss can be reduced.

Next, the draft tube 1A of the water turbine according to the second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a diagram showing a draft tube 1A of a water turbine according to a second embodiment of the present invention, and is a diagram corresponding to a cross-sectional view taken along the line III-III shown in FIG. In the second embodiment, the same reference numerals are given to the parts that overlap with the first embodiment, and the description thereof will be omitted.

In this embodiment, one swivel stop plate 3 is installed at the center of the flow path of the first flow path 1a. The swivel stop plate 3 extends radially outward from the center of the first flow path 1a. A gap 4 is provided between the tip 3a of the swivel stop plate 3 and the peripheral wall portion 2. Also in this example, the same effect as in Example 1 described above can be obtained.

Next, the draft tube 1B of the water turbine according to the third embodiment of the present invention will be described with reference to FIG. 7. FIG. 7 is a diagram showing a draft tube 1B of a water turbine according to a third embodiment of the present invention, and is a diagram corresponding to a cross-sectional view taken along the line III-III shown in FIG. In the third embodiment, the same reference numerals are given to the parts that overlap with the first embodiment, and the description thereof will be omitted.

In this embodiment, eight swivel stopper plates 3 are installed at the center of the flow path of the first flow path 1a. The eight swivel stop plates 3 extend radially from one center point. The eight swivel stopper plates 3 are installed at intervals of 45 degrees in the circumferential direction of the first flow path 1a. The swivel stop plate 3 extends radially outward from the center of the first flow path 1a. A gap 4 is provided between the tip 3a of the swivel stop plate 3 and the peripheral wall portion 2. Also in this example, the same effect as in Example 1 described above can be obtained. By increasing the number of the swivel stop plates 3, the swirl flow in the central portion of the flow path of the first flow path 1a can be effectively suppressed, but the collision loss and the wall friction loss in the swivel stop plate 3 are increased. It will increase. The number of swivel stop plates 3 installed can effectively suppress the swirl flow in the center of the flow path of the first flow path 1a while minimizing the collision loss and the wall friction loss generated by the swivel stop plate 3 itself. It may be set appropriately.

Next, the draft tube 1C of the water turbine according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a perspective view in which a part of the draft tube 1C according to the fourth embodiment of the present invention is broken, and shows the peripheral wall portion 2 and the swivel stop plate 3. In the fourth embodiment, the same reference numerals are given to the parts that overlap with the first embodiment, and the description thereof will be omitted.

In this embodiment, four swivel stop plates 3 are installed at the center of the flow path of the first flow path 1a. The four swivel stop plates 3 extend radially from one center point. The four swivel stop plates 3 are installed at intervals of 90 degrees in the circumferential direction of the first flow path 1a. The swivel stop plate 3 extends radially outward from the center of the first flow path 1a. A gap 4 is provided between the tip 3a of the swivel stop plate 3 and the peripheral wall portion 2. The tip 3a of the swivel stop plate 3 is provided with a support column 7 extending in one direction in the circumferential direction. The support column 7 extends perpendicular to the extending direction of the swivel stop plate 3. Since two columns 7 are provided at the tip 3a of each swivel stop plate 3, a total of eight columns 7 are arranged in the first flow path 1a. The support column 7 extends toward the peripheral wall portion 2. The tip of the support column 7 is attached to the inner wall surface 2a of the peripheral wall portion 2. The support column 7 connects the swivel stop plate 3 and the peripheral wall portion 2 and plays a role of supporting the swivel stop plate 3 with respect to the peripheral wall portion 2. The number of columns 7 may be appropriately determined so that the strength of the swivel stop plate 3 can be sufficiently maintained with respect to the strength of the swirling flow of water flowing into the first flow path 1a. Also in this example, the same effect as in Example 1 described above can be obtained. Further, since the swivel stop plate 3 can be supported by the support column 7 with respect to the peripheral wall portion 2, the strength of the swivel stop plate 3 against the swirl flow can be increased.

Next, the draft tube 1D of the water turbine according to the fifth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a perspective view in which a part of the draft tube 1D according to the fifth embodiment of the present invention is broken, and shows the peripheral wall portion 2 and the swivel stop plate 3. FIG. 10 is a cross-sectional view of the draft tube 1D along the XX line shown in FIG. In the fifth embodiment, the same reference numerals are given to the parts that overlap with the first embodiment, and the description thereof will be omitted.

As shown in FIG. 10, the swivel stop plate 3 extends from the flow path center portion of the first flow path 1a toward the peripheral wall portion 2. The number of the swivel stop plates 3 is not particularly limited, but is four in this embodiment. The four swivel stop plates 3 extend radially from one center point. The four swivel stop plates 3 are installed at intervals of 90 degrees in the circumferential direction of the first flow path 1a. The swivel stop plate 3 extends radially outward from the center C of the first flow path 1a. The tip 3a of the swivel stop plate 3 reaches the peripheral wall portion 2. The tip 3a of the swivel stop plate 3 is in contact with the inner wall surface 2a of the peripheral wall portion 2. As shown in FIG. 9, a through hole 3b penetrating in the circumferential direction is formed in a portion of the swivel stop plate 3 closer to the peripheral wall portion 2, that is, a portion on the outer side in the radial direction. In other words, the through hole 3b is located radially outside the center along the radial direction of the swivel stop plate 3. The number of through holes 3b may be singular or plural, but in this embodiment, one through hole 3b is formed for each of the swivel stop plates 3. The shape of the through hole 3b when viewed from the through direction is not particularly limited, but in this embodiment, it is a rectangle longer in the axial direction than in the radial direction. The shape of the through hole 3b when viewed from the through direction may be circular or the like.

Also in this example, the same effect as in Example 1 described above can be obtained. When the tip 3a of the swivel stop plate 3 reaches the peripheral wall portion 2, the swirling flow is suppressed at both the central portion of the flow path and the outer peripheral portion of the flow path of the first flow path 1a, and the inner wall surface 2a of the peripheral wall portion 2 Peeling flow occurs in. Therefore, in this embodiment, by forming a through hole 3b that penetrates in the circumferential direction in the portion of the swivel stop plate 3 that is closer to the peripheral wall portion 2, water with a swirl flow passes through the through hole 3b. , The swirling flow in the outer peripheral portion of the flow path of the first flow path 1a is less likely to be attenuated. As a result, the peeling flow on the inner wall surface 2a of the peripheral wall portion 2 can be suppressed, so that the expansion loss in the first flow path 1a can be reduced. The shape and number of the through holes 3b may be appropriately determined in consideration of the manufacturing cost, the purpose of making it difficult to attenuate the swirling flow in the outer peripheral portion of the flow path, and the like.

Next, the draft tube 1E of the water turbine according to the sixth embodiment of the present invention will be described with reference to FIG. FIG. 11 is a perspective view in which a part of the draft tube 1E according to the sixth embodiment of the present invention is broken, and shows the peripheral wall portion 2 and the swivel stop plate 3. In the sixth embodiment, the same reference numerals are given to the parts that overlap with the first embodiment, and the description thereof will be omitted.

The swivel stop plate 3 extends from the central portion of the flow path of the first flow path 1a toward the peripheral wall portion 2. The number of the swivel stop plates 3 is not particularly limited, but is four in this embodiment. The four swivel stop plates 3 extend radially from one center point. The four swivel stop plates 3 are installed at intervals of 90 degrees in the circumferential direction of the first flow path 1a. The swivel stop plate 3 extends radially outward from the center of the first flow path 1a. The tip 3a of the swivel stop plate 3 reaches the peripheral wall portion 2. The tip 3a of the swivel stop plate 3 is in contact with the inner wall surface 2a of the peripheral wall portion 2. A through hole 3b penetrating in the circumferential direction is formed in a portion of the swivel stop plate 3 that is closer to the peripheral wall portion 2, that is, a portion on the outer side in the radial direction. In other words, the through hole 3b is located radially outside the center along the radial direction of the swivel stop plate 3. The number of through holes 3b may be singular or plural, but in this embodiment, three through holes 3b are formed in each of the swivel stop plates 3. The three through holes 3b are arranged at intervals in the axial direction. The shape of the through hole 3b when viewed from the through direction is not particularly limited, but in this embodiment, it is a rectangle longer in the radial direction than in the axial direction. The shape of the through hole 3b when viewed from the through direction may be circular or the like.

Also in this example, the same effect as in Example 1 described above can be obtained. When the tip 3a of the swivel stop plate 3 reaches the peripheral wall portion 2, the swirling flow is suppressed at both the central portion of the flow path and the outer peripheral portion of the flow path of the first flow path 1a, and the inner wall surface 2a of the peripheral wall portion 2 Peeling flow occurs in. Therefore, in this embodiment, by forming a through hole 3b that penetrates in the circumferential direction in the portion of the swivel stop plate 3 that is closer to the peripheral wall portion 2, water with a swirl flow passes through the through hole 3b. , The swirling flow in the outer peripheral portion of the flow path of the first flow path 1a is less likely to be attenuated. As a result, the peeling flow on the inner wall surface 2a of the peripheral wall portion 2 can be suppressed, so that the expansion loss in the first flow path 1a can be reduced. The shape and number of the through holes 3b may be appropriately determined in consideration of the manufacturing cost, the purpose of making it difficult to attenuate the swirling flow in the outer peripheral portion of the flow path, and the like.

Next, the draft tube 1F of the water turbine according to the seventh embodiment of the present invention will be described with reference to FIG. FIG. 12 is a perspective view in which a part of the draft tube 1F according to the seventh embodiment of the present invention is broken, and shows the peripheral wall portion 2 and the swivel stop plate 3. In the seventh embodiment, the same reference numerals are given to the parts that overlap with the first embodiment, and the description thereof will be omitted.

The swivel stop plate 3 extends from the central portion of the flow path of the first flow path 1a toward the peripheral wall portion 2. The number of the swivel stop plates 3 is not particularly limited, but is four in this embodiment. The four swivel stop plates 3 extend radially from one center point. The four swivel stop plates 3 are installed at intervals of 90 degrees in the circumferential direction of the first flow path 1a. The swivel stop plate 3 extends radially outward from the center of the first flow path 1a. A gap 4 is provided between the tip 3a of the swivel stop plate 3 and the peripheral wall portion 2. An intake pipe 8 is installed on the swivel stop plate 3. The intake pipe 8 plays a role of suppressing the swirling flow in the first flow path 1a. The intake pipe 8 is formed in an inverted T shape. The intake pipe 8 has a first intake pipe 8a extending in the radial direction and a second intake pipe 8b extending upward along the axial direction from the central portion in the radial direction of the first intake pipe 8a. The first intake pipe 8a and the second intake pipe 8b communicate with each other. Both the first intake pipe 8a and the second intake pipe 8b are formed in a cylindrical shape. A gap is provided between both ends of the first intake pipe 8a in the radial direction and the peripheral wall portion 2. The upper end of the swivel stop plate 3 is joined to the lower end of the outer peripheral surface of the first intake pipe 8a. The first intake pipe 8a is formed with a plurality of first through holes 8c penetrating the peripheral wall of the first intake pipe 8a. Bubbles are emitted from the inside to the outside of the first intake pipe 8a through the first through hole 8c. The second intake pipe 8b is formed with a plurality of second through holes 8d penetrating the peripheral wall of the second intake pipe 8b. Bubbles are emitted from the inside to the outside of the second intake pipe 8b through the second through hole 8d. The shapes of the first intake pipe 8a and the second through hole 8d are not particularly limited, but are circular in the present embodiment.

Also in this example, the same effect as in Example 1 described above can be obtained. Further, by joining the intake pipe 8 to the swirl stop plate 3 in the first flow path 1a, when a swirl flow is generated in the first flow path 1a, the first intake air is taken through the first through hole 8c. Bubbles are emitted from the inside of the pipe 8a to the outside, and bubbles are emitted from the inside to the outside of the second intake pipe 8b through the second through hole 8d. Since the bubbles reduce the swirling energy, the swirling flow in the central portion of the flow path of the first flow path 1a can be suppressed. It should be noted that such an intake pipe 8 can also be joined to the swivel stop plate 3 of Examples 2 to 6.

The configuration shown in the above examples shows an example of the content of the present invention, can be combined with another known technique, and is a part of the configuration without departing from the gist of the present invention. Can be omitted or changed.

1,1A, 1B, 1C, 1D, 1E, 1F Draft tube 1a 1st flow path 1b 2nd flow path 2 Peripheral wall part 2a Inner wall surface 3 Swivel stop plate 3a Tip 3b Through hole 4 Gap 5a, 5b, 6a, 6b Swirling flow 7 Strut 8 Intake pipe 8a First intake pipe 8b Second intake pipe 8c First through hole 8d Second through hole

Claims (3)

The peripheral wall that forms the flow path for water and
A swivel stop plate installed at the center of the flow path in a cross section orthogonal to the axial direction of the flow path,
With
The swivel stop plate extends from the central portion of the flow path of the flow path toward the peripheral wall portion.
A draft tube of a water turbine, characterized in that a gap is provided between the tip of the swivel stopper plate and the peripheral wall portion. The peripheral wall that forms the flow path for water and
A swivel stop plate installed at the center of the flow path in a cross section orthogonal to the axial direction of the flow path,
With
The swivel stop plate extends from the central portion of the flow path of the flow path toward the peripheral wall portion and reaches the peripheral wall portion.
A draft tube of a water turbine, characterized in that a through hole is formed in a portion of the swivel stopper plate that is closer to the peripheral wall portion. The draft tube of a water turbine according to claim 1 or 2, wherein one or a plurality of the swivel stop plates are installed in the circumferential direction of the flow path.

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