JP2011137407A - Water turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water turbine which reduces its hydraulic pressure pulsation, vibration and noises while reducing its thrust. <P>SOLUTION: The water turbine includes a runner 10 having a plurality of runner vanes 12 in the peripheral direction. Balance holes 21 are formed in the runner 10. The balance holes 21 have openings 23a formed at the rear edges of the runner vanes. The openings 23a are communicated with the back face 11b of a crown 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water wheel.

For example, there is a Francis type turbine as a turbine. The Francis-type water turbine includes a main shaft, a runner provided at the tip of the main shaft, a casing provided on the outer peripheral side of the runner, for feeding water, and a draft tube (a suction pipe) for guiding the water discharged from the runner. ing.
The Francis-type water turbine includes an upper cover (front cover) that forms a back pressure chamber together with the runner, and a lower cover (rear cover) that forms a side pressure chamber together with the runner. A draft tube is connected to the lower cover.
The runner has a substantially disc-shaped crown fixed to the main shaft, and a plurality of runner vanes provided on the front surface of the crown on the draft tube side.

Here, when the runner is rotated, an imbalance occurs between the pressure in the back pressure chamber and the pressure in the side pressure chamber, and a thrust force acts on the runner. As the thrust force increases, the thrust bearings that receive this increase in size, and various techniques have been proposed to reduce the thrust force.
For example, a technology is disclosed in which a back pressure chamber and a draft tube are connected via a balance pipe, and an adjustment valve is provided on the balance pipe (see, for example, Patent Document 1). According to this, since the high pressure water on the back pressure chamber side flows into the low pressure side draft tube via the balance pipe, the pressure difference between the runner back pressure and the runner outlet pressure can be adjusted by the regulating valve. become.

  By the way, as means for reducing the thrust force, in addition to the above-mentioned Patent Document 1, there is a case where a balance hole is formed near the root of the cone at the exit of the runner. The balance hole is formed so that the back surface of the crown communicates with the front surface of the crown, that is, the surface on the draft tube side. The opening formed in the front surface of the crown by the balance hole is arranged on the radially inner side of the crown, that is, on the low pressure side on the front surface of the crown. By forming the balance hole, it becomes possible to reduce the thrust force without providing a balance pipe or an adjustment valve.

Japanese Patent Publication No. 61-9515

However, when forming the balance hole, the water on the crown back side flows out from the balance hole to the front surface, which may adversely affect the flow of the mainstream portion of the water turbine. That is, there is a problem that the water flowing out from the balance hole disturbs the flow of the main flow part, and as a result, the efficiency of the water turbine decreases and the vibration and noise during driving of the water turbine increase.
In the case of a partial load (for example, about 50% output), the runner outlet flow strongly swirls in the same direction as the runner rotation due to the low flow rate of water, and water pressure pulsation, vibration, and noise are generated in the draft tube. There is a problem of doing it.
Further, if the flow rate flowing out from the balance hole is increased in order to reduce the thrust force, there is a problem that the efficiency of the entire water turbine is reduced by the amount of leakage.

  Accordingly, the present invention has been made in view of the above-described circumstances, and provides a water turbine that can reduce the thrust force, improve the efficiency of the water turbine, and reduce hydraulic pulsation, vibration, and noise. To do.

  In order to solve the above problems, a water turbine according to the present invention includes a runner having a plurality of runner vanes provided in a circumferential direction, and forms a balance hole in the runner, and the balance hole is formed on a rear edge side of the runner vane. An opening is formed, and the opening is communicated with the back side of the runner.

By comprising in this way, the water on the runner back side can be made to flow out from the trailing edge side of the runner vane. For this reason, since irrigation water flows out from the opening along the wall surface of the runner vane, the disturbance of the mainstream portion can be reduced while reducing the thrust force, and vibration and noise during driving of the water turbine can be suppressed.
Further, since the flow rate passing between the runner vanes increases, it is possible to reduce water pressure pulsation, vibration, and noise in the draft tube in the case of partial load.
Furthermore, by causing the water to flow out from the opening of the runner vane, it is possible to prevent separation of the flow in the vicinity of the opening. For this reason, it becomes possible to improve the blade element efficiency of a water turbine.

  The water wheel according to the present invention is characterized in that the opening is formed on the suction surface side of the runner vane.

By comprising in this way, the pressure difference of the runner back side and front side of a balance hole can be ensured reliably, and the pressure of a runner back side can be reduced reliably. For this reason, it becomes possible to reduce thrust force reliably.
Furthermore, it is possible to more reliably prevent the flow separation that is likely to occur on the suction surface side of the runner vane, thereby increasing the efficiency.

  The water wheel according to the present invention is characterized in that a balance hole is formed in each runner vane.

  By configuring in this way, the flow rate passing between the runner vanes can be reliably increased. It can be surely reduced.

  In the water wheel according to the present invention, when the angle between a tangent to the opening in the camber line of the runner vane and the axis of the opening is θ, the angle θ satisfies θ ≦ 45 °. It is set so that it may satisfy | fill.

  By comprising in this way, it becomes possible to make sure the water which flows out of an opening part follows the wall surface of a runner vane. For this reason, the disturbance of the mainstream part can be reduced more reliably, and vibration and noise during driving of the water turbine can be reliably suppressed.

  The water turbine according to the present invention is characterized in that the formation position of the opening is set within a range within 10% of the chord length of the runner vane from the trailing edge of the runner vane.

  By comprising in this way, the pressure difference of the runner back side and front side of a balance hole can be ensured reliably.

According to the present invention, the water on the runner back side can be discharged from the rear edge side of the runner vane. For this reason, since irrigation water flows out from the opening along the wall surface of the runner vane, the influence on the mainstream portion can be reduced, and the vibration and noise during driving of the turbine can be suppressed while improving the turbine efficiency.
Further, since the flow rate passing between the runner vanes increases, it is possible to reduce water pressure pulsation, vibration, and noise in the draft tube in the case of partial load.
Furthermore, by causing the water to flow out from the opening of the runner vane, it is possible to prevent separation of the flow in the vicinity of the opening. For this reason, it becomes possible to improve the blade element efficiency of a water turbine.

It is a schematic block diagram of the water wheel in embodiment of this invention. It is the bottom view which looked at the runner in the embodiment of the present invention from the direction of the lower draft tube. It is the A section enlarged view of FIG. It is a cross-sectional view of the runner in the embodiment of the present invention. It is behavior explanatory drawing of the water which passes between runner vanes in embodiment of this invention. It is the graph which showed the turning improvement effect of the swirling flow in the embodiment of the present invention with respect to the past, and the mainstream separation prevention effect.

(Water wheel)
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a water turbine 1.
As shown in the figure, a water turbine 1 is a so-called Francis-type water turbine, which is a rotating shaft 2 as a main shaft, a runner 10 provided at the tip of the rotating shaft 2, and a fluid provided on the outer peripheral side of the runner 10. And a speed casing 4 for connecting the spiral casing 3 and the runner 10 to each other.

  Further, an upper cover 31 is provided above the runner 10 (upward in FIG. 1, the base end side of the rotating shaft 2), and below the runner 10 (downward in FIG. 1, the distal end side of the rotating shaft 2). A lower cover 32 is provided. Connected to the lower cover 32 is a draft tube 5 that is coaxially arranged with the rotary shaft 2 and guides the water W discharged from the runner 10. Although not shown, a generator is provided at the base end of the rotating shaft 2, and power can be generated by the rotation of the rotating shaft 2.

  The spiral casing 3 is disposed in a spiral shape and is formed in a substantially circular cross section. And this inside becomes the guide channel 3a through which the water W flows. The guide channel 3a is formed so as to gradually decrease in diameter as it goes downstream in the circumferential direction. In addition, the spiral casing 3 is provided with a water intake port (not shown) connected to the outside, and is provided with a water supply outlet 3 b that opens in an annular shape on the inner peripheral side and is connected to the speed ring 4. .

  The speed ring 4 is formed in a substantially annular shape, and has a guide channel 4a inside, and a stay vane 6 for rectifying the circulated water W is provided. The plurality of stay vanes 6 are disposed so as to incline in the turning direction in accordance with the flow angle of the incoming water W.

  A plurality of guide vanes 7 are arranged along the circumferential direction between the speed ring 4 and the runner 10 on the inner peripheral side. Each guide vane 7 is configured to be rotatable between an open position and a closed position about a rotation shaft 7 a provided on the guide vane 7. Each guide vane 7 is configured to be rotatable between an open position and a closed position by a position adjustment drive unit 7b. And the flow volume of the water W which flows in into the runner 10 from the inside of the spiral casing 3 can be adjusted now.

(Runner)
FIG. 2 is a bottom view of the runner 10 as seen from the direction of the lower draft tube 5. In FIG. 2, the shroud 13 is not shown for convenience of explanation.
As shown in FIGS. 1 and 2, the runner 10 includes a substantially disc-shaped crown 11 fixed coaxially to the rotating shaft 2, a plurality of runner vanes 12 provided on the front surface 11 a of the crown 11, and a substantially annular crown. 11 and a shroud 13 connected to the runner vane 12 so as to be opposed to the runner vane 12.

  The plurality of runner vanes 12 are radially arranged at an equal pitch, and are disposed so as to be inclined in the swivel direction on the outer peripheral side in accordance with the flow angle of the water W flowing into the runner 10, and toward the inner peripheral side. It is arranged so that the inclination in the turning direction gradually increases. A space surrounded by the crown 11, two adjacent runner vanes 12, and the shroud 13 is configured as a flow path 14. That is, a plurality of flow paths 14 are provided by a plurality of runner vanes 12. And the flow path 14 is formed so that it may incline in a turning direction gradually as it goes to an inner peripheral side from the outer peripheral side by making the outer peripheral side into the inlet 14a and the inner peripheral side as the outlet 14b along the radial direction.

  In addition, the front surface 11a of the crown 11 is formed so as to be substantially along a plane orthogonal to the rotation axis 2 on the outer peripheral side, and is gradually curved along the rotation axis 2 toward the radially inner peripheral side. Yes. Correspondingly, the shroud 13 is also curved. Therefore, the flow path 14 is curved and formed so as to go from the radial direction to the axial direction from the outer peripheral side on the inlet 14a side toward the inner peripheral side on the outlet 14b side.

  The water W flowing through the flow path 14 is discharged along the axial direction from the outlet 14 b positioned on the inner peripheral side while rotating the runner 10 by applying pressure to the runner vane 12, and flows into the draft tube 5. . Further, a cone-shaped cone 8 is provided on the tip end side in the axial direction of the runner 10, and the water W discharged from the flow path 14 of the runner 10 is guided to the draft tube 5 by the cone 8.

Here, based on FIG. 3, FIG. 4, the shape of the runner vane 12 is explained in full detail.
3 is an enlarged view of a portion A in FIG. 2, and FIG. 4 is a cross-sectional view of the runner 10.
As shown in FIGS. 3 and 4, the runner vane 12 includes a front edge portion 12 a located on the inlet 14 a side of the flow path 14 formed in a substantially arc shape in an axial plan view, and a rear edge portion located on the outlet 14 b side. 12b, and the front edge portion 12a and the rear edge portion 12b are connected by a continuous curved surface, and have a positive pressure surface portion 12c and a negative pressure surface portion 12d that are curved.
The runner vane 12 has a thickness defined by the pressure surface portion 12c and the suction surface portion 12d gradually becoming thicker from the front edge portion 12a toward the center, and gradually thinner from the center toward the rear edge portion 12b. It is formed to become.

As shown in FIG. 1 to FIG. 4, each runner vane 12 formed in this way includes the rear edge portion 12 b side, a back pressure chamber 33 surrounded by the crown 11 of the runner 10 and the upper cover 31. A plurality of balance holes 21 communicating with each other are formed.
That is, the balance hole 21 has a main hole 22 having a circular cross section formed between the vicinity of the root portion of the cone 8 on the back surface 11 b of the crown 11 and the vicinity of the shroud 13 side of the runner vane 12, and the runner vane 12 from the main hole 22. And a plurality of (for example, four in this embodiment) branch holes 23 having a circular cross section formed in the vicinity of the rear edge portion 12b and reaching the suction surface portion 12d. And the branch hole 23 communicate with each other. The extending direction of the branch holes 23 is preferably provided so as to substantially coincide with the direction of the main flow flowing around the runner vanes 12.

The branch hole 23 has an angle θ between the axis C23 and a tangent C12 ′ at a location intersecting the axis C23 in the camber line C12 of the runner vane 12 θ ≦ 45 ° (1)
It is formed to satisfy. Therefore, a plurality of (for example, four in this embodiment) openings 23a formed in the suction surface portion 12d of the runner vane 12 by the branch holes 23 have a substantially elliptical shape in plan view.

Further, the branch hole 23 is formed so that the position of each opening 23 a is located in a range X within 10% of the chord length C of the runner vane 12 from the rear edge 12 b of the runner vane 12. The plurality of openings 23 a are arranged in parallel along the rear edge 12 b of the runner vane 12.
The balance hole 21 can be formed by various means such as drilling, electric discharge machining, and casting.

(Function)
Next, the operation of the runner 10 will be described with reference to FIGS.
FIG. 5 is an explanatory diagram of the behavior of the water W passing between the runner vanes 12.
As shown in FIGS. 1 and 5, when the runner 10 is rotated by the water W fed into the runner 10 via the spiral casing 3, a swirling flow is generated on the draft tube 5 side of the runner 10. A core portion K is formed at the radial center of the runner 10, that is, at the tip side of the cone 8.

  Further, when the runner 10 rotates, an imbalance occurs between the pressure in the back pressure chamber 33 and the pressure in the side pressure chamber 34 surrounded by the shroud 13 and the lower cover 32 of the runner 10, The pressure is high and the pressure on the side pressure chamber 34 side is low. That is, a pressure difference is generated between the negative pressure surface portion 12d side of the runner vane 12 corresponding to the outlet side of the balance hole 21 and the back pressure chamber 33 side corresponding to the inlet side. For this reason, the water W ′ leaked from the flow path 14 into the back pressure chamber 33 flows out from the opening 23 a onto the flow path 14 through the balance hole 21 (see FIG. 5). Thereby, the imbalance of the pressure difference between the back pressure chamber 33 and the side pressure chamber 34 is reduced, and the thrust force is reduced.

  Here, the outflow amount of the water W from the opening 23 a by the balance hole 21, that is, the leakage flow rate is within about 3% of the water W (main flow portion) fed into the runner 10 through the spiral casing 3. Is set. That is, the hole diameters of the main hole 22 and the branch hole 23 constituting the balance hole 21 are set so that the leakage flow rate is within about 3% of the main flow portion. This is the flow rate of the main flow portion of the entire turbine 1 including leakage from the gap between the outer peripheral portion of the crown 11 and the upper cover 31 and leakage from the gap between the shroud 13 and the lower cover 32. This is because it is desirable to set the leakage flow rate to 5% or less.

Further, in the branch hole 23 forming the opening 23a, an angle θ between the axis C23 and a tangent line C12 ′ at a location intersecting the axis C23 in the camber line C12 of the runner vane 12 satisfies the expression (1). Thus, the water W ′ flowing out from the opening 23 a flows along the negative pressure surface portion 12 d of the runner vane 12.
For this reason, since the water W ′ flows out along the mainstream flow, the disturbance of the mainstream can be reduced. That is, the angle θ between the axis C23 of the branch hole 23 and the tangent C12 ′ is better as it is smaller than 45 °.

  If a balance hole is formed at the root of the cone 8 as in the prior art, water W ′ having a velocity vector different from the swirling direction flows out to a portion where a strong swirling flow is generated. For this reason, this outflowed water collides with the mainstream, and the mainstream becomes unstable. This causes noise and vibration in the water turbine.

  And since the opening part 23a is formed in the negative pressure surface part 12d of the runner vane 12, peeling of the main flow part which is easy to occur on the negative pressure side of the runner vane 12 is formed by forming the flow of the water W 'on the negative pressure surface part 12d. It is suppressed.

  Here, the absolute flow velocity v1 of the water W near the outlet 14b of the flow path 14 is determined based on the peripheral speed u1 of the runner 10 at the outlet 14b and the relative flow velocity w1 of the water W with respect to the runner vane 12 (see FIG. 5). ). That is, during the partial load operation, the relative flow rate w1 of the service water W with respect to the runner vane 12 decreases (see w1 ′ in FIG. 5), and the velocity vector of the absolute flow velocity v1 of the service water W greatly fluctuates in the rotation direction of the runner 10. (See v1 ′ in FIG. 5). In other words, the turning speed component of the water W increases.

  However, when the water W ′ flows out from the opening 23a, the flow rate of the water W flowing through the flow path 14 slightly increases, and as a result, the relative flow velocity w1 of the water W with respect to the runner vanes 12 can be increased. As the relative flow velocity w1 increases, the velocity vector of the absolute flow velocity v1 slightly faces the velocity vector side of the relative flow velocity w1. For this reason, an increase in the mainstream turning speed component during partial load operation can be suppressed.

(effect)
Therefore, according to the above-described embodiment, the opening 23 a of the balance hole 21 is formed in the runner 10 by forming the plurality of balance holes 21 that communicate with the rear edge portion 12 b side of the runner vane 12 and the back pressure chamber 33. The water W ′ flowing out from the water does not affect the mainstream, and vibration and noise during driving of the water turbine 1 can be suppressed.

Moreover, since the flow volume of the water W which passes the flow path 14 between each runner vane 12 increases, runner exit turning is suppressed and vortex loss reduces. For this reason, water pressure pulsation, vibration and noise in the draft tube 5 can be reduced. In particular, in the case of a partial load, water pressure pulsation, vibration, and noise in the draft tube 5 can be reliably reduced by the amount that the flow rate can be increased.
Furthermore, since the opening 23a is formed in the negative pressure surface portion 12d of the runner vane 12, the flow of the water W ′ is formed in the negative pressure surface portion 12d, and the separation of the main flow portion on the negative pressure surface portion 12d side of the runner vane 12 is suppressed. can do. For this reason, the blade element efficiency of the water turbine 1 can be increased.

FIG. 6 is a graph showing the mainstream swirl improvement effect and the mainstream part separation suppression effect when the vertical axis is the efficiency change amount and the horizontal axis is the leakage flow rate by the balance hole 21.
As shown in the figure, it can be confirmed that the gradient of the efficiency reduction amount due to the disturbance of the main flow when the leakage flow rate is increased (S1) as compared with the conventional case (J1 in FIG. 6).
Further, it can be confirmed that the gradient of the efficiency reduction amount due to the separation when the leakage flow rate increases is gentle (H1) as compared with the conventional case.

An opening 23a is formed in the suction surface portion 12d of the runner vane 12, and the position of the opening 23a is located in a range X within 10% of the chord length C of the runner vane 12 from the rear edge portion 12b of the runner vane 12. (See FIG. 4).
For this reason, the pressure difference between the opening 23 a and the back pressure chamber 33 can be ensured reliably, and the water W ′ can be reliably discharged from the opening 23 a through the balance hole 21. Therefore, it is possible to reliably reduce the thrust force.

  Here, as shown in FIG. 4, the runner vanes 12 are formed so as to gradually become thinner from the center toward the rear edge 12b, so that the balance hole 21 (branch hole 23) is directed toward the rear edge 12b. It becomes difficult to form. However, if the position of the opening 23a is in the range X within 10% of the chord length C, the pressure difference between the opening 23a and the back pressure chamber 33 can be ensured, so that the shape of the runner vane 12 can be secured. Thus, the balance hole 21 can be easily formed by changing the position of the opening 23a.

  Furthermore, since the plurality of balance holes 21 are formed in each runner vane 12, the flow rate of the water W passing through the flow path 14 between the runner vanes 12 can be reliably increased. For this reason, especially in the case of a partial load, water pressure pulsation, vibration, and noise in the draft tube 5 can be reliably reduced.

  The branch hole 23 forming the opening 23a of the balance hole 21 is formed so that the angle θ between the axis C23 and the tangent C12 ′ of the camber line C12 satisfies the formula (1). . For this reason, since the water W ′ flowing out from the opening 23a flows along the negative pressure surface portion 12d of the runner vane 12, disturbance of the main flow portion can be reliably reduced, and vibration and noise during driving of the water turbine 1 are reliably suppressed. can do.

The present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention.
For example, in the above-described embodiment, the opening 23a is formed in the suction surface portion 12d of the runner vane 12, and the position of the opening 23a is within 10% of the chord length C of the runner vane 12 from the rear edge portion 12b of the runner vane 12. The case where it is formed so as to be located in the range X of has been described. However, the shape of the balance hole 21 is not limited to this, and it is sufficient that the pressure difference between the opening 23a and the back pressure chamber 33 can be secured and the water W ′ can flow out from the opening 23a.

  That is, the formation position of the opening 23a may be set near the rear edge 12b of the runner vane 12 and on the positive pressure surface 12c side. Furthermore, the formation position of the opening 23a may be set on the front edge 12a side from the range X within 10% of the chord length C of the runner vane 12 from the rear edge 12b. In this case, it is desirable to form the opening 23 a on the rear edge 12 b side at least from the center of the runner vane 12. Thereby, a pressure difference between the opening 23a and the back pressure chamber 33 can be secured.

In the above-described embodiment, the case where the balance hole 21 is formed in each runner vane 12 has been described. However, the present invention is not limited to this, and the balance holes 21 may be formed at equal intervals in the circumferential direction. For example, among the runner vanes 12 adjacent in the circumferential direction, the balance hole 21 may be formed in any one of the runner vanes 12 of every other, every second, or every third.
Furthermore, in the above-described embodiment, the case where four openings 23a are formed in one runner vane 12 has been described. However, the present invention is not limited to this, and it is sufficient that at least one opening 23a is formed.

In the above-described embodiment, the case where the main hole 22 of the balance hole 21 is formed between the vicinity of the root portion of the cone 8 on the back surface 11 b of the crown 11 and the vicinity of the shroud 13 side of the runner vane 12 has been described. However, the present invention is not limited to this, and the main hole 22 may be formed so as to communicate the pressure (back pressure) on the back side of the runner 10 and the branch hole 23.
Moreover, in the above-mentioned embodiment, the case where the cross section of the main hole 22 or the branch hole 23 was formed in circular shape was demonstrated. However, the present invention is not limited to this, and an ellipse, a long hole, a polygon, or the like may be formed, and one or more slits may be formed along the rear edge portion 12b.

1 water wheel 10 runner 11 crown 11b rear surface 12 runner vane 12b rear edge (rear edge)
12d Negative pressure surface (negative pressure surface)
21 balance hole 22 main hole 23 branch hole 23a opening 33 back pressure chamber C chord length C12 camber line C12 ′ tangent C23 axis X range θ angle

Claims (5)

A runner having a plurality of runner vanes provided in the circumferential direction;
Forming a balance hole in the runner,
This balance hole
An opening is formed in the rear edge side of the runner vane, and the opening is in communication with the back side of the runner.   The water wheel according to claim 1, wherein the opening is formed on the suction surface side of the runner vane.   The water wheel according to claim 1 or 2, wherein a balance hole is formed in each runner vane. When the angle between the tangent corresponding to the opening in the camber line of the runner vane and the axis of the opening is θ,
The angle θ is
θ ≦ 45 °
The water turbine according to any one of claims 1 to 3, wherein the water wheel is set so as to satisfy.   The formation position of the said opening part is set in the range within 10% of the chord length of this runner vane from the rear-end edge of the said runner vane, The Claim 1 characterized by the above-mentioned. Water wheel.

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