JPH07158550A - Draft tube of hydraulic machine - Google Patents

Abstract

PURPOSE:To improve the draft tube efficiency by reducing an energy loss by a draft tube, in the operating condition along a wide scope from a high head to a low head. CONSTITUTION:At the front end face 9a of a pier 9, an inlet opening 10 is formed. The position of the inlet opening 10 is positioned between the center of the pier front end face 9a in the height direction, and the bottom surface 8c of the expansion part 8 of a draft tube. At the both side surface 9a and 9b in the downstream of the pier 9, longitudinal slit form of outlet openings 11 and 12 are formed at the left side and the right side symmetric positions relative to the pier 9 respectively. The positions in the height direction of the pier, of the outlet openings 11 and 12 are set to be between the center of the pier in the height direction, and the upper surface 8b of the expansion part 8 of the draft tube. The inlet opening 10, and the outlet openings 11 and 12 are connected through communicating holes 13 formed to the pier 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suction pipe of a hydraulic machine such as a water turbine or a pump turbine, and more particularly to a suction pipe of a hydraulic machine having a pier as a strength member in a flow path of an expanded portion of the suction pipe.

[0002]

2. Description of the Related Art The suction pipe of a hydraulic machine has a shape such that the flow passage area in the suction pipe gradually increases, and the velocity of the flowing water flowing out from the runner is gradually reduced to efficiently collect the kinetic energy of the flowing water. There is. 14 and 15 show a general Francis turbine, in which pressure water from the casing 1 drives the runner 4 to rotate through the stay vanes 2 and the guide vanes 3. The running water flowing out from the runner 4 is guided by the suction pipe 5 and is discharged to a water discharge channel (not shown). The suction pipe 5 is composed of an upper suction pipe 6, a suction pipe elbow portion 7 and a suction pipe enlarged portion 8.

The upper suction pipe 6 and the suction pipe elbow portion 7 are
It has a welded structure and sufficient strength. However, since the suction pipe expanded portion 8 has a concrete structure and is inferior in strength, a pillar-shaped pier 9 is installed as a strength member. The pier 9 extends from the inlet to the outlet of the suction pipe expansion part 8 so as to divide the flow path of the suction pipe expansion part 8 into right and left. In the case of a large hydraulic machine, a plurality of piers 9 may be installed in parallel with each other.

16 to 18 show the movement of running water flowing out from the runner. The runner blade has a swirling velocity component of substantially zero as shown in FIG. 16 in an operating state near the design head. Is designed to be. Therefore, the main stream of the flowing water flowing out from the runner flows in the suction pipe 5 along the suction pipe axial direction OO. However, in the operation of low head and high head apart from the design head, the swirling flow remains in the water flowing out from the runner blade. Therefore,
In the case of the operating point on the low head side, as shown in FIG. 17, the main flow of the running water is biased toward one side wall 8a of the suction pipe expanding portion 8, and conversely, in the case of the operating point on the high head side. As shown in FIG. 18, the main flow is biased toward the other side wall 8b of the suction pipe expansion portion 8.

FIG. 19 is a graph showing the experimental results obtained by measuring the flow velocity distribution at the positions A and B symmetrical with respect to the pier 9 of FIG. 15 at the cross section W shown in FIG. The distance h from the bottom of the expanded portion of the suction pipe is taken, and the vertical axis shows the flow velocity (V / V ₀ ) in the direction of the suction pipe. The distance h on the horizontal axis is the distance from the bottom surface of the expanded portion of the suction pipe to the measurement points A and B measured in the vertical direction as shown in FIG. 14, and the flow velocity (V / V ₀ ) is The flow velocity V in the direction of the suction pipe at the measurement points A and B is divided by the average flow velocity V ₀ in the cross-sectional area of the suction pipe including the measurement point to make it dimensionless.

As can be seen from FIG. 19, in the operating state corresponding to the design head, the flow velocity (V / V ₀ ) from the bottom wall surface to the top wall surface of the suction pipe is almost constant at both measurement points A and B, and the measurement points are divided by the piers. The flow rates of the left and right flow paths of the suction pipe are almost equal. However, in the operating state corresponding to the low head, the flow velocity at the measuring point B is larger than that at the measuring point A. Conversely, in the operating state corresponding to the high head, the flow velocity at the measuring point A is opposite to that at the measuring point B. Is bigger.

Further, in the operating state corresponding to the design head, the flow velocity is almost constant irrespective of the distance h, but in the operating state corresponding to the low head and the high head, the flow velocity greatly decreases as the distance h increases, that is, The flow velocity near the top of the suction pipe is significantly lower than that near the bottom of the suction pipe.

FIG. 20 schematically shows the result of analysis of the flow state in the suction pipe in the operation with a high head, in which the high energy fluid spreads on the bottom side of the suction pipe expanding portion 8 and the low energy fluid spreads on the suction pipe. Backflow regions C and D are respectively generated on the upper surface side of the portion 8 and near the upper surface of the suction pipe expansion portion 8. The reverse flow area C of the right flow passage is located near the side wall of the suction pipe expansion portion 8, and the reverse flow area D of the left flow passage is located near the side surface of the pier 9. In the operation with a low head, the reverse flow area of the right flow passage is located near the side surface of the pier 9, and the reverse flow area of the left flow passage is located near the side wall of the suction pipe expansion portion 8, contrary to the case of the high head.

Further, FIG. 21 schematically shows the flow in the expansion portion 8 of the suction pipe by using velocity vectors. The flow velocity is high on the bottom side of the suction pipe and relatively small on the top side.
A backflow occurs near the downstream outlet of the expanded suction pipe. Such a flow velocity non-uniformity phenomenon in which the flow velocity at the bottom of the expanded suction pipe 8 is high and the flow velocity at the upper surface is slow, has a problem that the pressure recovery rate is reduced and the efficiency of the suction pipe is reduced. Further, as a result of the flow velocity non-uniformity phenomenon, the backflow that occurs near the downstream outlet of the expansion portion of the suction pipe causes a large energy loss and significantly reduces the turbine efficiency.

Therefore, various suction pipes in which such a phenomenon of non-uniform flow velocity is reduced have been proposed. JP-A-2-140
Japanese Patent No. 466 discloses a suction pipe in which a plurality of swirl suppression fins are installed on the inner wall of the upper suction pipe to suppress swirling flow and make the flow distribution uniform. In addition, special fair 3-
In the suction pipe disclosed in Japanese Patent No. 35511, straightening vanes are installed in the flow path of the widening part of the suction pipe along the axial direction of the suction pipe, and the running water flowing into the widening part of the suction pipe is divided into two parts by the tip part of the straightening vane. And then join again at the end of the straightening vane. This suppresses the generation of swirling flow.

[0011]

However, the suction pipe disclosed in the above-mentioned Japanese Patent Laid-Open No. 2-140466 has a structure in which a plurality of swirl suppression fins are installed on the inner wall of the upper suction pipe to suppress the flow. Therefore, there are problems that energy is lost due to these swirl suppressing fins themselves, and swirl flow cannot be sufficiently suppressed in the expansion portion of the suction pipe. In addition, the above-mentioned Japanese Patent Publication 3-35
In the suction pipe disclosed in Japanese Patent No. 511 gazette, when a pier is installed in the suction pipe, the straightening vanes are installed in the left and right flow passages divided by the pier, respectively. There is a problem of generating energy loss.

Therefore, an object of the present invention is to provide a suction pipe of a hydraulic machine capable of reducing the energy loss in the suction pipe and enhancing the efficiency of the suction pipe in a wide range of operating conditions from a high head to a low head. Especially.

[0013]

In order to achieve this object, the invention described in claim 1 is a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel. In the suction pipe, a communication hole that communicates with an inlet opening formed on the tip end surface of the pier and a pair of outlet openings formed on both side surfaces on the downstream side of the pier is bored in the pier, and the inlet opening is formed. Is located relatively below the tip surface and the outlet opening is located relatively above the side surface.

In this structure, the inlet opening is located between the center of the pier in the height direction and the bottom of the suction pipe, and the outlet opening is from the center of the pier in the height direction. It is desirable that the distance between the tip end surface and the outlet opening in the flowing direction is about 1 to 3 times the length in the height direction of the tip end surface, which is located between the upper surface of the suction pipe.

According to a third aspect of the present invention, in a suction pipe of a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel, both side surfaces of the pier are connected to the pier. A through hole is formed, and the through hole is located between the center part in the height direction of the pier and the upper surface of the suction pipe, and is located near the backflow generation region on the downstream side of the suction pipe. It is characterized by.

According to the invention described in claim 4, in a suction pipe of a hydraulic machine having a pier as a strength member inside the suction pipe for guiding the water discharged from the runner to the discharge channel, the suction pipe is provided at or near the tip surface of the pier. A communicating pipe having an inlet opening and having an outlet opening on a side surface on the downstream side of the suction pipe, wherein the inlet opening is located relatively below, and the outlet opening is located above the inlet opening. It is a feature.

According to a fifth aspect of the present invention, in a suction pipe of a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel, the suction pipe is located near the tip surface of the pier and the suction pipe. A guide vane is disposed at a position near the bottom surface of the pipe and extends between a side surface of the pier and a side wall of the suction pipe, and the guide vane guides the flow near the bottom surface of the suction pipe to the suction pipe. It is characterized by guiding to the upper surface.

According to a sixth aspect of the present invention, in a suction pipe of a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel, the tip end surface of the pier has the tip end. So that the bottom side of the surface is located upstream and the top side of the tip surface is located relatively downstream.
It is characterized by being inclined. In this configuration, it is preferable that the tip end surface of the pier be concavely curved.

[0019]

In the suction pipe of the hydraulic machine according to the first aspect of the present invention, the high-pressure water near the bottom of the suction pipe flows into the communication hole from the inlet opening of the tip surface and is jetted from the outlet opening to the low pressure portion of the backflow generation region. The generation of the backflow can be suppressed by jetting the high-pressure water to the low-pressure portion in the backflow generation region. Since the outlet openings of the communication holes are formed on both side surfaces of the pier, it is possible to suppress backflow from occurring in the left and right flow channels divided by the pier.

In the suction pipe of the hydraulic machine according to the third aspect of the present invention, the pressures in the flow passages near both side surfaces on the downstream side of the pier are substantially equal to each other in the case of operation at the design head. However, in the case of operation at a high head, the flow path on one side surface on the downstream side of the pier becomes low pressure, and in the case of operation at a low head,
The flow path on the other side has a low pressure, and backflow occurs in these low-pressure side flow paths. However, when a pressure difference occurs on both side surfaces of the pier, the pressure water on the high pressure side is jetted to the low pressure side through the through hole. This can suppress the occurrence of backflow on the low pressure side.

In the suction pipe of the hydraulic machine according to the fourth aspect, the high-pressure water in the vicinity of the bottom face of the suction pipe flows into the communication pipe from the inlet opening and is jetted from the outlet opening to the low pressure portion in the backflow generation region.
The jetting of the high-pressure water to the low-pressure portion can suppress the backflow.

In the suction pipe of the hydraulic machine according to the fifth aspect, the running water flowing near the bottom surface of the suction pipe is turned upward by the guide vanes and flows toward the upper surface of the suction pipe. This homogenizes the flow in the suction tube over its entire cross section. In the suction pipe of the hydraulic machine according to the sixth aspect, the flowing water flowing near the bottom surface of the suction pipe is turned upward by the inclined tip surface of the pier and flows toward the upper surface of the suction pipe. This homogenizes the flow in the suction tube over its entire cross section.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a suction pipe of a hydraulic machine according to the present invention will be described below with reference to FIGS. 1 to 13 in which the same parts as those in FIGS. 1 and 2, the pressurized water from the casing 1 drives the runner 4 to rotate through the stay vanes 2 and the guide vanes 3. The running water flowing out from the runner 4 is guided by the suction pipe 5 and is discharged to a water discharge channel (not shown). The suction pipe 5 includes an upper suction pipe 6 and a suction pipe elbow portion 7
And a suction pipe expansion section 8. A strut-shaped pier 9 is installed as a strength member in the suction pipe expansion portion 8. The pier 9 extends from the inlet to the outlet of the suction pipe expansion part 8 so as to divide the flow path of the suction pipe expansion part 8 into right and left. The above structure is the same as that of the general Francis turbine shown in FIG.

A longitudinally elongated slit-shaped inlet opening 10 is formed in the tip surface 9a of the pier 9. This entrance opening 10
Is located between the center of the pier tip surface 9a in the height direction and the bottom surface 8c of the suction pipe expansion portion 8. In other words, the position of the inlet opening 10 is selected between the midpoint of the height H ₀ of the pier tip surface 9a in the height direction and the bottom surface 8c of the suction pipe. Vertically elongated slit-shaped outlet openings 11 and 12 are formed symmetrically with respect to the pier 9 on both side surfaces 9b and 9c on the downstream side of the pier 9, respectively. These outlet openings 1
Nos. 1 and 12 are set such that the position of the pier 9 in the height direction is between the center of the pier in the height direction and the upper surface 8d of the suction pipe expansion portion 8. Inlet opening 10 and Outlet opening 1
1 and 12 are connected to each other by a communication hole 13 bored in the pier 9. The communication hole 13 extends from the inlet opening 10 to the inside of the pier 9 and bifurcates on the way to form the outlet opening 1
It has reached 1 and 12.

Next, the operation of this embodiment will be described. The high-pressure water near the bottom surface 8c of the suction pipe flows into the communication hole 13 from the inlet opening 10 of the pier tip surface 9a, passes through this communication hole 13, and exits from the outlet openings 11 and 12 in the backflow generation area near the pier side surfaces 9b and 9c. Eject into the low pressure part. The water pressure of the pier tip surface 9a is several times higher than the surrounding pressure because the pier tip surface 9a dams the flowing water flowing therein. Therefore, by the high-pressure water jetted from the outlet openings 11 and 12, the low-pressure portion in the backflow generation region near the pier side surfaces 9b and 9c can be sufficiently pressurized and the backflow can be suppressed. It should be noted that the backflow generation area near the pier side surfaces 9b and 9c (see FIG.
The region D) of 0 is larger than the backflow generation region (region C in FIG. 20) in the vicinity of the side surface of the expansion pipe 8 and therefore suppression of the backflow in the vicinity of the side face of the pier greatly contributes to improvement in the efficiency of the extraction pipe.

As for the position of the outlet openings 11 and 12 in the direction of the suction pipe flow path, the length in the height direction of the pier tip surface 9a is set to H ₀ as described above, and as shown in FIG. When the distance to the outlet openings 11 and 12 is L ₀ , it is selected so as to satisfy the following formula. L ₀ = (1 to 3) × H _{0 The} reason why the positions of the outlet openings 11 and 12 in the suction pipe flow path direction are selected as described above is that the distance L ₀ from the tip surface 9 a is generally.
This is because backflow occurs after the point. This will be described in detail below. The backflow phenomenon that occurs on the downstream side of the suction pipe is closely related to the direction of the swirling flow at the inlet of the suction pipe. Further, the size of the swirling flow increases as the operating point moves away from the designed operating state, and the swirling angle also increases accordingly. The operating head range of a typical real turbine is about 0.7 to 1.3 of the design state, and the starting point of backflow generation in the suction pipe when the turbine is operated within this range is the runner performance or Although it is affected by various factors such as the shape of the suction pipe, it is a point about 1 to 3 times downstream of the height H ₀ of the pier tip surface 9a with the pier tip surface 9a as the starting point.

The reason why the inlet opening 10 and the outlet openings 11 and 12 of the communication hole 13 are defined as vertically elongated slits is as follows. That is, the larger the size of the communication hole 13 is, the more effective it is. Therefore, it is desirable to make the area of both the inlet opening and the outlet opening as large as possible. Therefore, a vertically long slit shape is selected in order to form an opening having a large area in the thin pier 9. FIG. 3 is a graph showing the results of a model experiment for verifying the effects of the above-mentioned embodiment. The horizontal axis shows the operating speed of the model turbine against the actual head of the turbine, the ratio of rotational speed (n / n ₀ ) (n ₀
Is the model turbine rotation speed corresponding to the design head), and the vertical axis represents the relative efficiency value when the efficiency value in the conventional model turbine is 1.0. The solid line is the case of this embodiment, and the broken line is the conventional case. As you can see from this graph,
According to the present embodiment, it is possible to achieve an efficiency improvement of about 0.5% under the operating conditions of high head and low head, respectively, from the rotational speed at the design point.

Next, a second embodiment of the present invention will be described.
4 and 5, the pier 9 has both side surfaces 9b, 9
A through hole 14 that penetrates c is formed. The positions of the through holes 14 are selected so as to be substantially the same as the positions of the outlet openings 11 and 12 of the first embodiment. That is, the through hole 14 is located between the center of the pier 9 in the height direction and the upper surface 8d of the suction pipe expansion part 8 and near the backflow generation region on the downstream side of the suction pipe expansion part 8. With such a configuration, in the case of high head operation, as shown in FIG. 5, the suction pipe enlarging portion 8 is provided in the right flow passage as viewed from the suction pipe outlet side.
A backflow region C is generated on the side wall 8a of the above and becomes a low pressure portion, and a backflow region D is generated on the left side surface 9b of the pier 9 in the left flow passage and becomes a low pressure portion. In this case, the flow path on the right side surface 9c of the pier 9 has a relatively high pressure as compared with the flow path on the left side surface 9b, so that the water in the high pressure portion passes through the through hole 14 and forms a low pressure as shown by the arrow. Flow into the section and suppress the occurrence of backflow in the backflow region D.

In the case of the low head operation, the flow is opposite to that in the high head operation, so that the flowing water flowing through the through hole 14 is in the direction opposite to the arrow. In this way, by forming the through hole 14, it is possible to suppress the occurrence of backflow near the side surface of the pier.

Next, a third embodiment of the present invention will be described.
6 and 7, an inlet opening 15 is formed near the bottom surface of the pier tip surface 9a, and two communicating pipes 16 and 17 are connected to the inlet opening 15. The outlet opening 18 of the communication pipe 16 is located on the side wall 8a of the suction pipe expansion portion 8,
The outlet opening 19 of the communication pipe 17 is provided on the side wall 8 of the suction pipe expansion portion 8.
Located in b. The outlet openings 18 and 19 are located near the upper surface of the suction pipe expansion portion 8. With such a configuration, the high pressure water near the bottom surface of the suction pipe expansion portion 8 flows into the communication pipes 16 and 17 from the inlet opening 15, and the outlet openings 18 and 1
It spouts from 9 to the backflow generation region near the side wall of the suction pipe expansion portion 8 to suppress the backflow generation. The inlet openings of the communication pipes 16 and 17 may be provided immediately before the pier tip surface 9a, instead of being provided in the pier tip surface 9a. In this case, the communication pipe is installed independently of the pier 9 without being connected to the pier 9.

Next, a fourth embodiment of the present invention will be described.
8 and 9, the pair of guide vanes 20 extend between the pier side surface 9b and the side wall 8b of the suction pipe expansion portion 8, and between the pier side surface 9c and the side wall 8a of the suction pipe expansion portion 8, respectively. is doing. The guide vanes 20 are arranged near the tip end surface 9a of the pier and near the bottom surface 8c of the suction pipe enlarged portion. As shown in FIG. 10, the guide vanes 20 forcibly turn upward the flow in the vicinity of the bottom surface of the suction pipe expansion portion 8 and guide it toward the upper surface of the suction pipe expansion portion 8. In this way, the deviation of the flow in the expansion portion 8 of the suction pipe is suppressed, and the flow distribution on the downstream side of the guide blade 20 is made uniform.
By installing the guide vanes 20 as described above, the efficiency of the suction pipe can be improved in the entire operation range of the water turbine.

Next, a fifth embodiment of the present invention will be described.
11 and 12, the tip surface 9a of the pier is inclined like a backward wing. More specifically, the tip end surface 9a of the pier is inclined such that its bottom side is located upstream and its top side is located relatively downstream. The running water flowing in the vicinity of the bottom surface of the suction pipe expanding portion 8 is turned upward by the action of the inclined tip surface 9a of the pier 9 as a retreating blade as in the case of the fourth embodiment, and the flowing water of the suction pipe expanding portion 8 is changed. It flows toward the upper surface. This homogenizes the flow in the suction tube over its entire cross section.

FIG. 13 shows a modification of the fifth embodiment, in which the inclined tip end surface 9a of the pier 9 is curved concavely.
Such a curve further strengthens the action of the tip end surface 9a of the pier as a retracting blade.

[0034]

As is apparent from the above description, claim 1
According to the invention described in (1), a communication hole that communicates with the inlet opening formed in the tip end surface of the pier and the pair of outlet openings formed on both side surfaces on the downstream side of the pier is formed in the pier, and Since the inlet opening is located relatively below the tip surface and the outlet opening is located relatively above the side surface, the high pressure water near the bottom of the suction pipe passes through the communication hole and forms a low pressure portion in the backflow generation region. It is possible to suppress the generation of backflow and the occurrence of backflow. As a result, the loss generated in the suction pipe in a wide range of operating conditions can be reduced and the suction pipe efficiency can be improved.

According to the third aspect of the present invention, the pier is formed with a through hole that communicates both side surfaces of the pier. The through hole extends from the center of the pier in the height direction to the upper surface of the suction pipe. Since it is located in the vicinity of the backflow generation region on the downstream side of the suction pipe, when a pressure difference occurs on both side surfaces of the pier, pressure water on the high pressure side is jetted to the low pressure side through the through hole,
This can suppress the occurrence of backflow on the low pressure side.

According to the invention as set forth in claim 4, there is provided a communication pipe having an inlet opening at or near the tip surface of the pier and having an outlet opening on the side surface on the downstream side of the suction pipe, wherein the inlet opening comprises: Since the outlet opening is located relatively below and the outlet opening is located above the inlet opening, the high-pressure water near the bottom of the suction pipe is ejected to the low-pressure portion of the backflow generation region through the communication pipe to suppress the backflow generation. be able to.

According to the fifth aspect of the present invention, the guide vanes are provided at positions near the tip end face of the pier and near the bottom face of the suction pipe, and extend between the side surface of the pier and the side wall of the suction pipe. Since the guide vanes guide the flow in the vicinity of the bottom surface of the suction pipe toward the upper surface of the suction pipe, it suppresses the deviation of the flow in the suction pipe in a wide range of operating conditions.
The flow can be made uniform over the entire cross section of the suction pipe, the loss generated in the suction pipe can be reduced, and the suction pipe efficiency can be improved.

According to the sixth aspect of the present invention, the tip end surface of the pier is inclined so that the bottom side of the tip end surface is located upstream and the top side of the tip surface is located relatively downstream. Therefore, the flowing water near the bottom of the suction pipe is
It is turned upward by the inclined tip surface of the pier and flows toward the upper surface of the suction pipe. This homogenizes the flow in the suction tube over its entire cross section.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a first embodiment of a suction pipe of a hydraulic machine according to the present invention.

FIG. 2 is a plan view showing a partial cross section of the first embodiment.

FIG. 3 is a graph showing the effect of the first embodiment.

FIG. 4 is a sectional view schematically showing a second embodiment of the suction pipe of the hydraulic machine according to the present invention.

FIG. 5 is a plan view showing a second embodiment in a partial cross section.

FIG. 6 is a sectional view schematically showing a third embodiment of the suction pipe of the hydraulic machine according to the present invention.

FIG. 7 is a side view showing a partial cross section of a third embodiment.

FIG. 8 is a sectional view schematically showing a fourth embodiment of the suction pipe of the hydraulic machine according to the present invention.

FIG. 9 is a plan view showing a partial cross section of a fourth embodiment.

FIG. 10 is a cross-sectional view schematically showing the velocity distribution of flowing water in the expanded portion of the suction pipe according to the fourth embodiment using velocity vectors.

FIG. 11 is a sectional view schematically showing a fifth embodiment of the suction pipe of the hydraulic machine according to the present invention.

FIG. 12 is a plan view showing a partial cross section of a fifth embodiment.

FIG. 13 is a sectional view showing a modification of the fifth embodiment.

FIG. 14 is a sectional view schematically showing the structure of a conventional Francis turbine.

FIG. 15 is a plan view showing the Francis turbine of FIG. 14 in a partial cross section.

FIG. 16 is a plan view showing the flow of running water from the runner during the design head operation.

FIG. 17 is a plan view showing the flow of running water from the runner during low head operation.

FIG. 18 is a plan view showing the flow of running water from the runner during high head operation.

FIG. 19 is a graph showing the relationship between the distance from the bottom surface of the expanded portion of the suction pipe and the flow velocity for the design head operation, the low head operation and the high head operation.

FIG. 20 is a schematic diagram showing a generation region of backflow during high head operation.

FIG. 21 is a cross-sectional view that schematically shows the velocity distribution of flowing water in the enlarged portion of the conventional suction pipe using velocity vectors.

[Explanation of symbols]

 4 Runner 5 Suction pipe 8 Suction pipe expanded part 9 Pier 9a Pier tip surface 9b Pier side face 9c Pier side face 10 Inlet opening 11 Outlet opening 12 Outlet opening 13 Communication hole

Claims (7)

[Claims] 1. In a suction pipe of a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel, an inlet opening formed in a tip end surface of the pier and a downstream side of the pier. A communication hole that communicates with a pair of outlet openings formed on both side surfaces of the pier is formed in the pier,
A suction pipe for a hydraulic machine, wherein the inlet opening is located relatively below the tip end surface, and the outlet opening is located relatively above the side surface. 2. The inlet opening is located between the center of the pier in the height direction and the bottom surface of the suction pipe, and the outlet opening is from the center of the pier in the height direction to the upper surface of the suction pipe. The distance between the tip surface and the outlet opening in the direction of flowing water is approximately 1 to 3 times the length of the tip surface in the height direction. Suction pipe for hydraulic machinery. 3. A suction pipe of a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel, wherein the pier has a through hole communicating with both side surfaces thereof. The through-hole is located between the center in the height direction of the pier and the upper surface of the suction pipe, and is located in the vicinity of the backflow generation region on the downstream side of the suction pipe. tube. 4. A suction pipe of a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel, the suction pipe having an inlet opening at or near a tip end surface of the pier. A suction pipe of a hydraulic machine, comprising: a communication pipe having an outlet opening on a downstream side surface thereof, the inlet opening being located relatively below, and the outlet opening being located above the inlet opening. . 5. A suction pipe of a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel, the suction pipe being arranged at a position near a tip end face of the pier and near a bottom face of the suction pipe. A guide vane extending between a side surface of the pier and a side wall of the suction pipe, the guide vane guiding the flow near the bottom surface of the suction pipe toward the upper surface of the suction pipe. The suction pipe of the characteristic hydraulic machine. 6. A suction pipe of a hydraulic machine having a pier as a strength member inside a suction pipe for guiding water discharged from a runner to a discharge channel, wherein a tip end surface of the pier is located at an upstream side of a bottom side of the tip end surface. In addition, the suction pipe of the hydraulic machine is characterized in that it is inclined such that the upper side of the tip end face is positioned relatively downstream. 7. A suction pipe for a hydraulic machine according to claim 6, wherein the tip end surface of the pier is curved concavely.