JP2024030232A - fluid machinery - Google Patents

Abstract

An object of the present invention is to provide a fluid machine that can suppress disk friction loss.
A fluid machine according to an embodiment is a fluid machine in which a runner is rotatably housed between an upper cover and a lower cover that face each other, and a backbone formed between the upper cover and the runner. A pressure chamber, a side pressure chamber formed between the lower cover and the runner, and a wing provided in at least one of the back pressure chamber and the side pressure chamber, and the upstream end of the water flow flowing into the wing. and a flow straightening device whose blade surface is inclined in the rotational direction of the runner toward the downstream end.
[Selection diagram] Figure 1

Description

Embodiments of the present invention relate to fluid machines.

A runner of a Francis turbine, which is an example of a centrifugal fluid machine, is configured such that a plurality of blades are sandwiched between a shroud and a hub, and is rotated by the flow of working fluid flowing into the runner.

The upper part of the runner is covered by the upper cover, and a part of the high-pressure working fluid flowing to the runner flows into the back pressure chamber, which is an annular space surrounded by the runner hub and the upper cover. It flows in the inner radial direction with respect to the rotational axis of the runner along the runner, and flows in the outer radial direction along the hub side. The working fluid is led to the suction pipe and then to the lower reservoir together with the working fluid that has passed through the runner. Since the runner rotates at high speed, friction at the contact surface between the working fluid and the hub causes an energy loss called disk friction loss.

JP2019-85960A

In such a fluid machine, the disk friction loss tends to increase as the peripheral speed of the runner increases relative to the peripheral speed of the working fluid in the back pressure chamber around the axis of rotation of the runner. This disk friction loss is one of the causes of reducing the efficiency of fluid machinery.

The problem to be solved by the present invention is to provide a fluid machine that can suppress disk friction loss.

In order to solve the above problems, a fluid machine according to an embodiment is a fluid machine in which a runner is rotatably housed between an upper cover and a lower cover that face each other, and a runner is rotatably housed between the upper cover and the runner. A back pressure chamber is formed, a side pressure chamber is formed between the lower cover and the runner, and a blade is provided in at least one of the back pressure chamber and the side pressure chamber. A flow straightening device is provided, the blade surface of which is inclined in the rotational direction of the runner from the upstream end toward the downstream end.

FIG. 1 is a meridional cross-sectional view of the Francis turbine according to the first embodiment. FIG. 2 is an enlarged view of area A of the Francis turbine according to the first embodiment. (a) is a sectional view of the rectifier according to the first embodiment as seen from the upper wall side of the upper cover, and (b) is a sectional view of the rectifier according to a modification of the first embodiment as seen from the upper wall side of the upper cover. Cross-sectional view. (a) is a diagram showing the speed of water in the rotation direction in the back pressure chamber of a general Francis turbine, and (b) is a diagram showing the speed of water in the rotation direction in the back pressure chamber of the Francis turbine according to the first embodiment. . FIG. 3 is a partially enlarged view of a Francis turbine according to a modification of the first embodiment. A cross-sectional view of a rectifier during operation of a water turbine according to a modification of the first embodiment, viewed from the upper wall side of the upper cover, and (b) is a sectional view of the rectifier during operation of a pump according to a modification of the first embodiment, shown on the upper cover. A sectional view seen from the upper wall side. FIG. 3 is a partially enlarged view of a Francis turbine according to a modification of the first embodiment. FIG. 3 is a partially enlarged view of a Francis turbine according to a modification of the first embodiment. FIG. 6 is a partially enlarged view of a Francis turbine according to a second embodiment. FIG. 7 is a schematic diagram of a flow rectifier according to a second embodiment viewed from the main shaft side of the runner toward the outside in the radial direction of the runner.

Embodiments for carrying out the invention will be described below.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 to 8. FIG. 1 is a meridional cross-sectional view of a Francis turbine according to this embodiment. Here, a Francis turbine will be explained as an example of a centrifugal fluid machine. The Francis turbine 1 includes a casing 10 and a stay vane 20.
, a guide vane 30 , a runner 40 , an upper cover 50 , and a lower cover 60 .

The casing 10 is provided in a spiral shape on the outer circumferential side of a runner 40, which will be described later, and allows water, which is a working fluid that has flowed from an upper reservoir through an iron pipe (not shown), to stay vanes 20 and guide vanes 30 (both described later). It is supplied to the runner 40 via the runner 40. Note that the casing 10 is normally formed so that its cross-sectional diameter gradually decreases from the start of winding to the end of winding.

A plurality of stay vanes 20 are arranged at predetermined intervals on the inner circumferential side of the casing 10 and in the circumferential direction (hereinafter referred to as the circumferential direction) with respect to the rotational axis C of the main shaft 42 described later. A channel through which water flows is formed between adjacent stay vanes 20.

A plurality of guide vanes 30 are arranged on the inner peripheral side of the stay vane 20 at predetermined intervals in the circumferential direction. Each of the guide vanes 30 is rotatable, and by controlling the degree of opening thereof, the area of the flow path formed between adjacent guide vanes 30 can be changed. Therefore, by controlling the opening degree of the guide vane 30, the amount of water flowing inside the water turbine can be adjusted.

The runner 40 includes a hub 44 connected to a main shaft 42, a shroud 46 provided to face the hub 44, and a plurality of runner blades 4 provided between the hub 44 and the shroud 46.
8. The runner 40 is provided on the inner peripheral side of the guide vane 30 so as to rotate about the rotation axis C, and is connected to a generator (not shown) via a main shaft 42. In the following description, the generator side of the rotational axis C will be referred to as the upper direction of the C-axis, and the side of the suction pipe (not shown) provided downstream of the runner 40 will be referred to as the lower direction of the C-axis.

The main shaft 42 is provided rotatably about the rotation axis C together with the runner 40 . Main shaft 42
A generator is connected to the runner 40, and the rotational energy of the runner 40 is transmitted to the generator via the main shaft 42 to generate electricity.

The runner blades 48 are arranged at predetermined intervals in the circumferential direction, and a flow path through which water flows is formed between adjacent runner blades 48.

Note that the generator connected to the runner 40 via the main shaft 42 also has a function as an electric motor,
The runner 40 may be configured to be rotated by being supplied with electric power. In this case, water from the lower pond (both not shown) can be sucked up and discharged into the upper pond through the suction pipe, making it possible to perform water pumping operation as a pump-turbine.

The upper cover 50 is provided above the hub 44 (in the C-axis upward direction) as a stationary member. hub 4
4 and the upper cover 50, a back pressure chamber 70, which is an annular gap, is formed. Back pressure chamber 7
A part of the water that has flowed through the flow path of the guide vane 30 during operation of the water turbine flows into the water turbine 0 as a leakage flow. Most of the water that has flowed into the back pressure chamber 70 flows out into the suction pipe together with the water that flowed out from the runner 40 through the balance hole made in the hub 44 of the runner 40 and the piping installed in the upper cover 50, and some It leaks along the main axis 42 to the top of the top cover.

The lower cover 60 is provided below the shroud 46 of the runner 40 (in the C-axis downward direction) as a stationary member. An annular gap called a lateral pressure chamber 72 is formed between the shroud 46 and the lower cover 60. A portion of the water that has flowed through the flow path of the guide vane 30 during operation of the water turbine flows into the side pressure chamber 72 as a leakage flow. The water flowing into the side pressure chamber 72 flows out into the suction pipe together with the water flowing out from the runner 40.

The upper cover 50 and the lower cover 60 are provided facing each other, and the runner 40 is accommodated therebetween.

Next, the upper cover 50 according to this embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is an enlarged view of area A surrounded by dotted lines in FIG. FIG. 3 is a cross-sectional view of the rectifying device 56 viewed from the upper wall surface 54 side in the C-axis downward direction.

The upper cover 50 has a side wall surface 52 that is a wall surface facing inward in the radial direction so as to face the main shaft 42 , and a side wall surface 52 that is connected to the side wall surface 52 and is located below the C-axis so as to face the hub 44 . An upper wall surface 54, which is a wall surface formed to face the direction, and a rectifier 5 provided on the upper wall surface 54.
6. In addition, in the following description, the radial direction refers to the radial direction when the rotation axis C is the center.

As shown in FIG. 3(a), the flow straightening device 56 is a wing that protrudes from the upper wall surface 54,
A plurality of them are provided on the upper wall surface 54 at predetermined intervals in the circumferential direction. The rectifying device 56 includes an upstream end 56a, which is an end into which the water flow flows, and a downstream end 56b, which is an end where the water flow flows out. It is inclined toward the rotation direction R10 of the runner 40. In FIG. 3, the radially outer side is the upstream side, and the radially inner side is the downstream side, so the flow straightening device 56 moves from the radially outer side to the radially inner side about the rotation axis C. The blade surface is inclined in the rotation direction R10. That is, the flow straightening device 56 is arranged such that the pressure surface is concave along the rotational direction R10, and the downstream end 56b is located further downstream in the rotational direction R10 than the upstream end 56a.

In this embodiment, a configuration in which the rectifier 56 is directly fixed to the upper wall surface 54 will be described as an example, but for example, a plurality of rectifiers 56 may be fixed to an annular foundation (not shown) and integrated. A configuration may also be adopted in which a foundation to which the rectifying device 56 is fixed is provided on the upper wall surface 54. Also,
In this embodiment, the case where the flow straightening device 56 is concave along the rotation direction R10 is illustrated, but for example, the flow straightening device 56 may have the shape of a reaction blade that is convex in the opposite direction to the rotation direction R10, or the upstream side It may have a streamlined shape that tapers toward the end 56a and the downstream end 56b.
In addition, as another modification of this embodiment, for example, as shown in FIG. 3(b), a rectifier 56
However, it may be provided so as to be in contact with the upper wall surface 54 and the side wall surface 52, and there may be no gap between the side wall surface 52 and the rectifying device 56.

Next, the operation of this embodiment will be explained using FIG. 2, FIG. 3(a), and FIG. 4.

During operation of the water turbine, water from the upper pond passes through the casing 10, the stay vane 20, and the guide vane 30 in order and is supplied to the runner 40. When the runner 40 receives work from this water and is driven to rotate, its rotational energy is used to rotate the water turbine. The power is transmitted to the generator via the shaft 50 to generate electricity. The water after working in the runner 40 flows through the suction pipe and is discharged to the lower pond.

At this time, most of the water that has passed through the guide vane 30 (hereinafter referred to as the mainstream) flows to the runner 40.
The water flows radially inward toward the runner 40 to rotate the water, but a portion of the water that does not flow as the main stream flows into the back pressure chamber 70. As shown by the arrow in FIG. 2 (the arrow drawn between the hub 44 and the side wall 52, pointing upward in the C-axis direction), the water flowing into the back pressure chamber flows along the side wall 52. After flowing toward the upper wall surface 54, it flows radially inward along the upper wall surface 54. Since the rectifier 56 is provided on the upper wall surface 54, the water flowing into the rectifier 56 is guided in the direction from the upstream end 56a of the rectifier 56 to the downstream end 56b as shown in FIG. 3(a). , water flows from the outside in the radial direction to the inside in a direction inclined to the rotation direction R10. In other words, the water flowing through the back pressure chamber 70 is given a velocity component in the rotation direction R10 by the rectifier 56, while the water flows through the upper wall surface 5.
4 in the radial direction.

The water flowing inward in the radial direction is branched along the main axis 42 into water flowing upward on the C-axis and water flowing downward on the C-axis. Of this water, the water flowing upward along the C-axis is drained to the outside by a drain pump (not shown) at the upper part of the upper cover 50. On the other hand, the water flowing in the C-axis downward direction flows radially outward along the hub 44 and flows out to the downstream side of the runner 40 via a balance hole (not shown) formed in the hub 44.

In a typical Francis turbine, the runner 40 rotates at high speed when the turbine is operating. Therefore, as shown by the arrow in FIG. 4(a), the velocity component of the water flowing in the back pressure chamber 70 in the rotational direction R10 becomes larger on the hub 44 side of the rotating runner 40, and cover 50
The velocity component in the rotation direction R10 becomes smaller as it approaches (the upper wall surface 54 side).

On the other hand, in the present embodiment described above, the rectifier 56 is provided on the upper wall surface 54, and the water flowing in the back pressure chamber 70 is given a velocity component in the rotation direction R10 by the rectifier 56. As a result, as shown by the arrow in FIG. 4(b), in addition to the overall speed component in the rotational direction R10 at the intermediate point between the hub 44 and the upper wall surface 54 increasing, the speed component near the hub 44 also increases. The amount of change becomes gradual. As a result, the difference in circumferential speed in the rotation direction R10 between the water flowing in the back pressure chamber 70 and the runner 40 is reduced, so that disc friction loss in the back pressure chamber 70 can be suppressed, and the Efficiency can be improved.

As a modification of this embodiment, for example, as shown in FIG. 6, the rectifier 56 may be provided with a spindle 58 as a rotating shaft, and the rectifier 56 may be configured to be rotatable around the spindle 58. At this time, a control signal may be output from the control device to a drive device (both not shown), and the rectifier 56 may be rotated by the drive device. The rotational direction of the runner 40 is opposite when the water turbine is operating and when the pump is operating, so when the water turbine is operating, the rotation direction of the runner 40 is lower than the upstream end 56a than the downstream end 56a. On the downstream side of R10, during pumping operation,
As shown in FIG. 6(b), each of the flow straightening devices 56 can be rotated such that the downstream end 56b is inclined more downstream in the rotation direction R20 than the upstream end 56a. By providing the configuration of this modified example, not only the same effects as the first embodiment can be obtained, but also the back pressure chamber 70
By changing the angle of the rectifying device 56 according to the flow of water within, disk friction loss can be reduced more effectively. As a result, the efficiency of the Francis turbine 1 can be further improved.

Further, as another modification of the present embodiment, for example, as shown in FIG. It is also possible to have a configuration in which Generally, when the runner 40 is rotating at a constant speed, the rotation speed of the surface of the hub 44 that faces the upper wall surface 54 increases in proportion to the radius. Along with this, the disc friction loss increases as the outer diameter side of the hub 44 increases, so it is possible to effectively reduce the disc friction loss by increasing the velocity component of the water flowing on the outer diameter side in the rotation direction R10. can. Therefore, by installing the rectifier 56 in a region of 0.9Rc or more, it is possible to reduce disk friction loss and improve the efficiency of the Francis turbine 1 compared to the present embodiment.

As another modification of this embodiment, as shown in FIG. 8, the upper wall surface 54 is formed into an inclined wall surface 54a that is inclined toward the C-axis upward toward the outside in the radial direction.
6 may be provided. That is, the rectifier 5 is arranged such that the distance between the upstream end 56a and the hub 44 in the C-axis direction is larger than the distance between the downstream end 56b and the hub 44 in the C-axis direction.
6, and the water flowing into the straightening device 56 may be configured to flow out toward the hub 44 while being given a velocity component in the rotational direction R10. Generally, the disc friction loss increases as the difference in circumferential speed in the rotational direction R10 between the hub 44 and the water flowing around the hub 44 increases. Therefore, water imparted with a velocity component in the rotational direction R10 flows out toward the hub 44, so that
The difference in circumferential speed between the hub 44 and the water flowing near the hub 44 is smaller than in the present embodiment, and disc friction loss can be further reduced. As a result, the efficiency of the Francis turbine 1 can be further improved.

Note that the above-described rectifier 56 may be provided in the side pressure chamber 72 formed between the shroud 46 and the lower cover 60, and the same effects as in this embodiment can be obtained in the back pressure chamber 72 as well. That is, the rotation direction R1 of water flowing through the side pressure chamber 72 by the rectifier provided in the side pressure chamber 72 is
By increasing the velocity component toward 0, the difference in circumferential velocity between this water and the shroud 46 becomes smaller, and disc friction loss can be reduced. As a result, the efficiency of the Francis turbine 1 can be improved.

It is assumed that each of the above-described modifications of the present embodiment applies similarly to the second embodiment and subsequent embodiments.

(Second embodiment)
A second embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a partially enlarged view of the Francis turbine 1 according to the present embodiment, and FIG. 10 is a view of the rectifier 156 viewed from the main shaft 42 side toward the outside in the radial direction. Note that the same parts as in the first embodiment are denoted by the same reference numerals.
Detailed explanation will be omitted. The main difference between this embodiment and the first embodiment is that the rectifier 156 is provided on the side wall surface 52 of the upper cover 50.

The rectifying device 156 is provided on the side wall surface 52 facing the main shaft 42, as shown in FIG. As shown in FIG. 10, the flow straightening devices 156 are blades that protrude from the side wall surface 52, and are provided in plural on the side wall surface 52 at predetermined intervals in the circumferential direction. The rectifying device 156 has an upstream end 156a, which is an end into which the water flow flows, and a downstream end 156b, which is the end where the water flow flows out.
from the upstream end 156a toward the downstream end 156b, the blade surface is connected to the runner 4.
0 in the rotation direction R10. That is, the flow straightening device 156 is arranged such that the pressure surface is concave along the rotational direction R10, and the downstream end 56b is located further downstream in the rotational direction R10 than the upstream end 56a. In FIG. 10, the end in the C-axis downward direction is the upstream end 156a, and the C-axis upward direction is the downstream end 156b.
In other words, the blade surface of the flow straightening device 156 is inclined in the rotation direction R10 from below the C-axis toward the top.

In this embodiment, a configuration in which the rectifier 156 is directly fixed to the side wall surface 52 will be described as an example, but for example, a plurality of rectifiers 156 may be fixed to an annular foundation (not shown) and integrated. , a foundation to which the rectifier 156 is fixed may be provided on the side wall surface 52.
Further, in this embodiment, the case where the pressure surface of the flow straightening device 156 is concave along the rotation direction R10 is illustrated, but for example, the flow straightening device 156 has a shape of a reaction blade that is convex in the direction opposite to the rotation direction R10. Alternatively, it may have a streamlined shape that tapers toward the upstream end 156a and the downstream end 156b.

Next, the operation of this embodiment will be explained using FIGS. 9 and 10.

A portion of the water that does not flow as the main flow during operation of the water turbine flows into the back pressure chamber 70. As shown by the arrow in FIG. 9 (the arrow drawn between the hub 44 and the side wall surface 52, pointing upward in the C-axis direction),
The water that has flowed into the back pressure chamber is guided in the direction from the upstream end 156a to the downstream end 156b of the rectifier 156 shown in FIG. Water flows. That is, the water flowing through the back pressure chamber 70 flows upward along the C-axis along the side wall surface 52 while being given a velocity component in the rotation direction R10 by the rectifier 156. Then, the water flows along the side wall surface 52 toward the upper wall surface 54, and then flows radially inward along the upper wall surface 54.

The water flowing inward in the radial direction is branched along the main axis 42 into water flowing upward on the C-axis and water flowing downward on the C-axis. Of this water, the water flowing upward along the C-axis is drained to the outside by a drain pump (not shown) at the upper part of the upper cover 50. On the other hand, the water flowing in the C-axis downward direction flows radially outward along the hub 44 and flows out to the downstream side of the runner 40 via a balance hole (not shown) formed in the hub 44.

In the present embodiment described above, the rectifier 156 is provided on the side wall surface 52, and the back pressure chamber 7
0 is given a velocity component in the rotational direction R10 by the rectifier 156. As a result, similarly to the first embodiment, the rotation direction R at the intermediate point between the hub 44 and the upper wall surface 54
In addition to the overall speed component of No. 10 becoming larger, the amount of change in the speed component near the hub 44 becomes gentler. As a result, the rotation direction R1 of the water flowing inside the back pressure chamber 70 and the runner 40 is
Since the difference in the circumferential speed of zero is reduced, disc friction loss in the back pressure chamber 70 can be suppressed, and the efficiency of the Francis turbine 1 can be improved.

Note that the above-described rectifier 156 may be provided in the side pressure chamber 72 formed between the shroud 46 and the lower cover 60, and the same effects as in this embodiment can be obtained in the back pressure chamber 72 as well. In other words, the rotation direction R of the water flowing through the side pressure chamber 72 by the rectifier provided in the side pressure chamber 72
By increasing the velocity component to the shroud 10, the difference in circumferential velocity between this water and the shroud 46 becomes smaller, and disc friction loss can be reduced. As a result, the efficiency of the Francis turbine 1 can be improved.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

1...Francis water turbine, 10...casing, 20...stay vane, 30...guide vane, 4
0...Runner, 42...Main shaft, 44...Hub, 46...Shroud, 48...Runner blade, 50...Top cover, 52...Side wall surface, 54...Top wall surface, 54a...Slanted wall surface, 56, 156...Brighter, 56a , 156a...upstream end, 56b, 156b...downstream end, 58...spindle,
60... Lower cover, 70... Back pressure chamber, 72... Side pressure chamber.

Claims (6)

A fluid machine in which a runner is rotatably housed between an upper cover and a lower cover that face each other,
a back pressure chamber formed between the upper cover and the runner;
a lateral pressure chamber formed between the lower cover and the runner;
A blade provided in at least one of the back pressure chamber and the side pressure chamber, and a rectifier whose blade surface is inclined in the rotation direction of the runner from the upstream end to the downstream end of the water flow flowing into the blade. a device;
A fluid machine equipped with The fluid machine according to claim 1, wherein the rectifying device is provided on a wall surface of the upper cover facing the hub of the runner. The fluid machine according to claim 1, wherein the rectifying device is provided on a wall surface of the upper cover facing the main axis of the runner. Claims 1 to 3, wherein the flow straightening device further includes a spindle that allows the blade surface to rotate.
The fluid machine described in any of the above. The fluid machine according to claim 1 or 2, wherein the rectifying device is installed in a region of 0.9 Rc or more with respect to an outer diameter Rc of the runner centered on the rotation axis. 3. The fluid machine according to claim 1, wherein the flow straightening device has a blade surface that is inclined in a direction toward the hub of the runner from the upstream end toward the downstream end.

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