JPH0754754A - High efficient operating method for hydraulic machine and the hydraulic machine - Google Patents

Abstract

PURPOSE:To prevent a decrease in water turbine efficiency by balancing the respective flow amount of a flow path, and improving draft tube efficiency, in a water turbine provided with a center pier for dividing the flow path in a tube into two equal parts in a draft tube enlarged part. CONSTITUTION:A point end part 10 of a center pier 9, provided by dividing a flow path into two equal parts in a draft tube enlarged part 8 which is partly a draft tube 5 for guiding water flowing out from a runner 4 to the outside, is made turnable with a shaft 11 vertical to upper/bottom wall surfaces of the enlarged part serving as the center, to control the point end part 10 in accordance with an operating condition of a water turbine, and an opening of each flow path inlet is adjusted, so as to balance a flow amount of each flow path regardless of the operating condition of the water turbine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water turbine, a pump turbine, or the like, which is provided with a center pier as a strength member in a flow path of a suction pipe thereof, and a method for highly efficient operation of the hydraulic machine.

[0002]

2. Description of the Related Art FIG. 4 (a) is a vertical sectional view of a general Francis turbine, and FIG. 4 (b) is a plan view of its main part. In these drawings, 1 is a Francis turbine casing, 2 is a stay vane, 3 is a guide vane, and 4 is a runner.
The water flowing out from the runner 4 is guided to the suction pipe 5. Since the suction pipe 5 has a role of efficiently converting velocity energy of water flowing out from the runner 4 into pressure energy, the suction pipe 5 has a shape that gradually increases the flow passage cross-sectional area. The suction pipe 5 is formed by connecting an upper suction pipe 6, a suction pipe elbow portion 7, and a suction pipe enlarged portion 8 in this order from the side closer to the runner 4. In addition to the elbow-type suction pipe shown in FIG. 4, the suction pipe 5 includes a cone-type suction pipe or the like in which water flowing out from the runner outlet is directly flowed in parallel to the water wheel shaft.

A suction pipe of a hydraulic machine plays an important role in efficiently collecting velocity energy of water overflowing from an impeller. Therefore, the cross-sectional area of the flow path in the suction pipe is designed to gradually increase so that the velocity of the flowing water is gradually decreased and the energy can be efficiently exchanged. Therefore, when there is a factor that hinders the exchange of energy in the suction pipe, the suction pipe efficiency is reduced and the turbine efficiency is significantly reduced.

In general, the loss in the suction pipe is eddy loss due to the size of the swirling flow of water flowing out from the runner vane, the expansion loss due to the expansion of the cross-sectional area of the suction pipe flow passage, and the size of the area in contact with the running water. There is friction loss due to Further, in the case of the elbow type suction pipe, there is a bending loss due to the 90 ° direction change of the flow. Further, there is a collision loss and the like due to the water flow colliding with the tip of the center pier provided as a structurally strong member of the suction pipe. The magnitudes of the losses listed above are all proportional to the square of the velocity of the flowing water flowing in the suction pipe.

[0005]

In the suction pipe 5 having the above structure, since the suction pipe expanded portion 8 belongs to the production range on civil engineering and is made of concrete, the suction pipe enlarged portion 8 is attached to the elbow portion 7 formed by the welded structure. There is a point that the strength is inferior to that. Therefore, a pillar-shaped center pier 9 as a reinforcing member is provided in the flow passage of the suction pipe flow passage enlarged portion 8 from the inlet to the outlet so as to divide the suction pipe flow passage cross section into two equal parts. In the case of a large hydraulic machine, the size of the suction pipe becomes large, so the number of center piers may be two. It may also be omitted in small hydraulic machines.

Hereinafter, FIG. 5 (a), FIG. 5 (b), and FIG.
The behavior of water flowing out of the runner 4 will be described with reference to (c). The runner blade is designed such that the swirling velocity component of the water flowing out from the runner 4 becomes substantially zero in the operation near the design head. Therefore, as shown in FIG. 5A, the water flowing out from the runner has a main flow in the axial direction of the suction pipe in the suction pipe. However, FIG.
As shown in (b) and (c) of FIG. 5, in the operating state in the free fall region apart from the design free drop, the flow in the swirling direction remains in the water flowing out from the runner, and the flow is maintained even in the suction pipe. The main flow is from the center of the suction pipe to the outer wall. FIG. 6 shows the flux distribution at the symmetrical positions A and B of the flow path with the center of the center pier 9 as a boundary at the downstream point “W cross section” position from the tip of the center pier 9 of the expanded suction pipe 8 shown in FIG. The result of having measured by the model test is shown. In this figure, the horizontal axis is the vertical distance L from the bottom surface of the suction pipe to the upper wall surface at the W cross-section position, and the vertical axis is the flow velocity distribution chart showing the flow velocity in the pipe axis direction. However, the flow velocity in the pipe axis direction on the vertical axis is shown by making the flow velocity measurement value in the pipe axis direction dimensionless (V / Vo) by the average flow velocity Vo obtained from the cross-sectional area of the cross section. In an operating state corresponding to the design head, there is a tendency that the flow velocity slightly changes from the wall surface to the upper wall face, but the measurement results of measurement points A and B are dimensionless by the average flow velocity Vo, that is, V / Vo = 1. It is 0.0, and it can be seen that a substantially uniform flow rate is flowing in the left and right cross sections of the suction pipe.

On the other hand, the flow velocity at the measurement point A is about twice the average flow velocity during the operation corresponding to the high head, and the average flow velocity at the measurement point B has dropped to about half of the measurement point A. I understand. Further, it can be seen that the above tendency is reversed at the time of low head equivalent operation. This is because, as is clear from the velocity triangle at the runner outlet, the swirling flow in the reverse direction with respect to the rotation direction of the runner in the operation on the high head side and the swirling flow in the rotation direction of the runner in the operation on the low head side remain. Is. That is, the main flow is water that easily flows to the right flow passage having the measurement point A in the high head operation and to the left flow passage having the measurement point B in the low head operation. Furthermore, the Kaplan turbine has the advantage that the runner vane opening changes according to the operating state, and it can always operate in a state near the non-turning region near the maximum efficiency point, but in the Francis turbine the runner vane is not movable. For partial load operation,
A swirl flow is generated in any of the overload operations, and the above phenomenon occurs.

As described above, flows having different flow distributions are generated in the left and right flow passages with the suction pipe center pier as a boundary depending on the operating state, and the flow passages are assumed at the time of design. The above losses occur and cause the reduction of turbine efficiency.

Further, since the swirling flow remains in the flow in the suction pipe, the flow has a large deflection angle with respect to the mounting angle of the center pier at the tip of the suction pipe center pier, and a large collision loss occurs at the tip of the center pier. This is a major cause of reduced efficiency.

The present invention has been made based on the above circumstances, and an axial flow turbine capable of making the flow rates of two flow passages having a center pier as a boundary uniform and preventing a reduction in turbine efficiency due to the non-uniform flow rate. To provide a highly efficient driving method.

[0011]

According to the method for highly efficient operation of a water turbine of the present invention, a tip end of a center pier, which is provided in an enlarged portion of a suction pipe of a hydraulic machine, is divided into two equal parts, and In the plane including the above, and is rotatable about an axis perpendicular to the top wall and bottom wall of the expansion pipe, and the set angle of the tip of the center pier is controlled according to the operating state of the hydraulic machine. It is characterized in that the flow rate of each of the two halves is balanced regardless of the operating state.

[0012]

According to the above-described highly efficient operation method of the water turbine of the present invention, when the operation is performed in the vicinity of the design point where the flow rates of the respective flow paths of the suction pipe whose center pier line end is bisected by the center pier are balanced, The inlets of the two flow passages are set to be substantially equally opened, and at the time of high head operation and low head operation, the inlets of the two flow paths on the side where the flow rate is increased are narrowed. Therefore, the efficiency of the suction pipe is enhanced regardless of the operating state, and the reduction of the turbine efficiency is prevented.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. 1 (a), in which the same parts as those in FIGS. 4 (a) and 4 (b) are denoted by the same reference numerals, FIG.
(B) is a plan view of the main part thereof, FIG. 2 is a diagram showing the effect of the operating method of the present invention, and FIG. 3 is a diagram showing a state of improvement in water turbine efficiency by the operating method of the present invention. In these figures, the tip portion 10 of the center pier 9 is in a plane including the center line of the center pier 9, and is rotatable about an axis 11 perpendicular to the top wall and the bottom wall of the suction pipe. Note that FIG.
In (a) and FIG. 1 (b), the other parts have the same configuration as the parts corresponding to the same reference numerals in FIG. In addition, in FIG. 1B, 10a, 10b, 1
Reference numeral 0c indicates the position of the tip portion 10 operated according to the operating state of the water turbine.

In the Francis turbine of the above construction, the tip portion 10 of the center pier 9 is set to the position indicated by 10a in the figure for operation in a state close to the design point, and the tip portion 10 for operation on the high head side in the figure. Set to the position indicated by 10b,
In the operation on the low head side, the tip portion 10 is set to the position indicated by 10c in the figure. That is, since the influence of the swirling flow is almost negligible in the operation close to the design point, the tip portion 10 of the center pier 9 is set at the position 10a where the center line of the center pier 9 coincides with the center line of the center pier 9, and The flow rate of each flow path divided into two by 9 is made substantially uniform as shown in FIG. In the operation on the high head side,
As indicated by a dotted arrow in b, there is a swirling flow in the reverse direction with respect to the rotation direction of the runner 4, and the flow rate in the flow path at the measurement point A becomes large.
0b is set at a position where the inlet of the flow path having the measurement point A is narrowed. Further, in the operation on the low head side, there is a swirling flow in the rotation direction of the runner 4 as shown by the solid line arrow in FIG. 1B, and the flow rate of the flow path having the measurement point B becomes large, so the tip of the center pier 9 The portion 10 is set at a position where the inlet of the flow path having the measurement point B is narrowed as shown in FIG. 10c.

By the above, the flow rate of each flow path of the suction pipe expansion portion 8 which is bisected by the center pier 9 can be made uniform, and the reduction of the turbine efficiency due to the non-uniform flow rate. Can be prevented. The present invention is not limited to the above embodiment. For example, it can be applied not only to the water turbine but also to the operation of the pump 01 and the like.

[0016]

As is apparent from the above, according to the operating method of the hydraulic machine of the present invention, the set position of the tip end of the center pier is changed according to the operating state of the hydraulic machine, and the suction halved by the center pier is changed. Since the flow rate of each flow path of the pipe can be made uniform, the suction pipe efficiency can be increased, and the efficiency reduction of the hydraulic machine due to the non-uniformity of the flow rate can be prevented. Further, since the position of the tip portion of the center pier is controlled as described above, it is possible to suppress the instability of the flow of the two flow passages having the center pier as a boundary, and reduce the occurrence of vibration, water pressure pulsation and the like. Therefore, the reliability of the water turbine or the like can be improved.

[Brief description of drawings]

FIG. 1A is a sectional view of an embodiment of the present invention, and FIG. 1B is a plan view of a main part thereof.

FIG. 2 is a diagram showing the effects of the driving method of the present invention.

FIG. 3 is a diagram showing a state where the turbine efficiency is improved by the driving method of the present invention.

FIG. 4A is a vertical cross-sectional view of a general Francis turbine,
(B) The principal part top view.

FIG. 5 (a) is a schematic plan view showing the flow of water in the suction pipe in the operating state at the design point of the conventional water turbine, and FIG. 5 (b) is the flow of water in the suction pipe in the same low head operating state. FIG. 3C is a schematic plan view showing the flow of water in the suction pipe in the high head operation state.

FIG. 6 is a diagram showing a flow velocity distribution in a suction pipe of a conventional water turbine.

[Explanation of symbols]

 1 ... Casing 2 ... Stay vane 3 ... Guide vane 4 ... Runner 5 ... Suction pipe 6 ... Upper suction pipe 7 ... Suction pipe elbow 8 ... Suction pipe expansion 9 ... Center pier 10 ... Center pier tip 11 ... Shaft

Claims (2)

[Claims] 1. A flow passage is provided in an enlarged portion of a suction pipe of a hydraulic machine.
The tip end of the center pier, which is equally divided, is rotatable about an axis in the plane including the center pier center line and perpendicular to the top wall and the bottom wall of the suction pipe expansion portion,
The setting angle of the tip portion of the center pier is controlled according to the operating state of the hydraulic machine, so that the above 2 can be performed regardless of the operating state.
A method of operating a hydraulic machine, characterized in that the flow rate of each of the equally divided flow paths is balanced. 2. The flow passage is provided in the enlarged portion of the suction pipe of the hydraulic machine.
The tip end of the center pier, which is equally divided, is rotatable about an axis in the plane including the center pier center line and perpendicular to the top wall and the bottom wall of the suction pipe expansion portion,
A hydraulic machine characterized in that the set angle of the tip of the center pier is controlled according to the operating state of the hydraulic machine.