JPS60135672A - Turning flow path for multistage multistage hydraulic machine - Google Patents

Abstract

PURPOSE:To prevent separation of water flow and generation of secondary flow in the turning flow path of the multistage hydraulic machine by a method wherein a turning blade is provided in the U-turn flow path of the turning flow path while the blade having smaller declining angle is provided in the radial flow path thereof. CONSTITUTION:A plurality of first turning blades 21 are provided in the radial flow path 15 of the turning flow path 10 connecting the runner chambers 8, 9 of high pressure and low pressure stages with intervals circumferentially. The same number of second turning blades 22 are provided in the U-turn flow path 16. The first turning blades 21 are provided with the angle of 90 deg. substantially with respect to the upper and lower flow path wall surfaces of the side face 21a of the blade while the second turning blades 22 are provided from the inside stream line 18 to the outside stream line 17 with angles changing smoothly along respective stream lines.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a return flow path of a multi-stage hydraulic machine, and in particular, a method that prevents separation of flowing water and generation of secondary flow in the flow path, and improves strength and rigidity. Concerning the structure of a high return flow path.

[Technical background and problems of the invention]

Generally, in a multi-stage hydraulic machine, the outlet of the runner chamber of the previous stage and the inlet of the runner chamber of the next stage are connected by a return flow path, and this return flow path is composed of a radial flow path and a U-turn b'6 path. , a return vane is provided in each flow path.

When the turbine is in operation, the water flow discharged from the runners on the high-pressure stage is guided to the low-pressure stage while giving rotational motion, while when the pump is in operation, the water flow discharged from the runners on the low-pressure stage is guided to the low-pressure stage runner. It is responsible for guiding the high-speed water flow to the high-pressure side stage while efficiently restoring pressure. In addition, the return vane is continuously provided in the return flow path from the vicinity of the outlet of the high-pressure side step runner to the vicinity of the low-pressure side step guide vane. While it acts as a guide vane to efficiently guide the flowing water flow, it also takes charge of the structural strength of the return flow path, so when designing it, it is important to simultaneously satisfy the fluid design requirements and the structural design requirements. It is necessary to take this into account. Particularly in curved channels such as return channels, secondary flow and separation are likely to occur due to centrifugal force caused by the bending of the channel. It is necessary to determine the blade shape so that the blade angle changes smoothly along the streamline.

The structure and problems of the conventional return flow path will now be described with reference to FIGS. 1 to 5.

FIG. 1 shows the structure of a two-stage pump-turbine, in which a high-pressure stage runner 2 and a low-pressure stage runner 3 are fixed to the main shaft 1 of the water turbine at a distance in the axial direction. The high-pressure stage runner 2 is surrounded by an upper cover 4 and a lower cover 5, while the low-pressure stage runner 3 is surrounded by an upper cover 6 and a lower cover 7, forming a high-pressure stage runner chamber 8 and a low-pressure stage launch chamber 9. . Further, the high-pressure stage runner chamber 8 and the low-pressure stage runner chamber 9 are connected through a return passage 10. Further, a spiral casing 11 is tightly placed outside the high pressure stage runner chamber 8, and the spiral chamber 12 and the high pressure stage runner chamber 8 are in communication with each other, and the inlet of the thin chamber 120 is connected to the water pressure via a large mouth valve. connected to iron pipes. Furthermore, a movable guide vane 13 is provided on the outside of the high-pressure stage runner 2, and the opening degree of the water port can be changed.
Also outside the low-pressure stage runner 3, movable guide vanes 14 whose water openings can be changed are arranged in a circular blade row.

2 and 3 show details of the configuration of the return flow path 10, which includes a radial flow path 5 and a U-turn flow path 16.
It is composed of. In this example, the width of the channel is indicated by B, and the radius of curvature inside the U-turn channel 16 is indicated by R.

By the way, when the radius of curvature R of the channel is small relative to the channel width B, when water passes through the U-turn channel 16, the passing distance along the outer streamline 17 of the U-turn channel]6 is is significantly longer than the passage distance l along the inner streamline 18. Therefore, in the radial flow path 15 and the U-turn flow path 16, a plurality of return blades 19 are arranged at intervals in the circumferential direction so that the blade angle changes smoothly along the respective streamlines. has been done. However, as seen in the plan view of FIG. 3, the conventional return blade 19 is
The blade winding angle θ along the outer streamline 17 of the turn channel 16!
is significantly larger than the blade winding angle θ along the inner streamline 18 of the U-turn flow path 16. If we look at this in terms of the blade cross-sectional shape, we can see that it is a U-turn (cross section A-A near the end point of AU516).
The cross section 19A is vertical, whereas the cross section BB near the starting point of the U-turn flow path 16 has a shape 19B in which the blades are extremely sagging relative to the upper and lower walls of the flow path. Further, since the radial flow path 150 and the blades 19 are continuous, the shape is also significantly bent with respect to the vertical plane. Therefore, the rigidity of the radial flow path 15 is low, and when a force that compresses or pulls the return flow path 1o vertically acts, or when high water pressure acts within the return flow path 10, the return flow path 10 is easily closed. There was a problem that it deformed. In order to solve this problem, conventionally the blade 19 was unavoidable.
By increasing the wall thickness of the blade 19 or by rapidly changing the angle of the blade 19 along the streamline of the U-turn flow path 16, the winding angle of the blade can be forcefully adjusted between the outer streamline and the inner streamline of the U-turn flow path. Methods such as combining them have been used.

However, with this solution, water is likely to separate from the blades and secondary flow may occur, resulting in problems such as increased hydraulic power loss and generation of vibrations due to separation.

0#, bright purpose] Therefore, the purpose of the present invention is to reduce the water flow in the return flow path to 2
To provide a return flow path for a multi-stage hydraulic machine that allows flow without peeling off from blades or generating secondary flow, and can provide a return flow path section with high quality properties.

[Summary of the invention]

In order to achieve the above object, the present invention provides return vanes that smooth the change in vane angle along each streamline in the U-turn flow passage section of the return flow passage to prevent flow separation and secondary distortion. While suppressing the generation of flow, by providing blades with small blade sag in the radial direction # and channel section, high rigidity is provided to the radial flow channel, and the U-turn flow channel section and the radial direction flow channel section are By arranging the blade surfaces of each flow path section so that they have a relative twist angle at the connection part with the flow line, and by making the blade corner layer relative to the streamline smoothly continuous with each other, the blades of each flow path section are This is designed to prevent collision loss from occurring at the connection between the radial flow path and the U-turn flow path.

[Embodiments of the invention]

Hereinafter, an embodiment of the structure of a return flow path of a multi-stage hydraulic machine according to the present invention will be described with reference to FIGS. 6 to 9, in which the same parts as in the previous example are given the same reference numerals.

In FIG. 6, a high pressure stage runner chamber 8 and a low pressure stage runner chamber 9 are shown.
are connected to each other by a return flow path io, and this return flow path 10 is composed of a radial flow path 15 and a U-turn flow path 16. And according to the invention.

A plurality of first return blades 21 are provided in the radial flow path 15 at intervals in the circumferential direction, while the same number of second return blades η are provided in the U-turn flow path 16. There is.

Among these, the first return blade 21 has a side surface 21a of the blade.
The angle α with respect to the upper and lower channel wall surfaces is 90 degrees, and as is clear from FIG. 7, the angle α extends in the radial direction. Further, the front wheel 21b and the rear edge 21c have a dimension in the thickness direction that gradually decreases and a rounded tip.

On the other hand, the second return blade n provided in the U-turn flow path 16
is designed so that the blade angle changes smoothly along each streamline from the inner streamline 18 to the outer streamline 17, and as a result, the blade winding from the starting point S to the ending point F of the U-turn flow path 16 is The blade winding angle θ along the outer streamline 17 and the blade winding angle θ1 along the inner streamline 18 have an angular difference of Δθ.

In addition, at the connection part between the radial flow path section 15 and the U-turn flow path section 16, the first return blade 21 and the second return blade 4 are different from each other, as shown in FIG. are arranged discontinuously so that the outlet end of the second return blade 21 intersects with the inlet end of the second return blade 21, or the exit angle β of the water flow at the outlet end of the first return blade 21 and the second return blade B The inlet angles γ of the water flows at the inlet ends of the inlets are made equal. On the other hand, near the outlet end of the second return blade 4, as shown in FIG. 8, the included angle δ of the side surface 22a with respect to the upper and lower wall surfaces is 90 degrees.

In addition, in the above embodiment, the number of the first return blade 21 and the second return blade n are equal, but they may be different. In that case, the number of the second return blade n may be smaller. is suitable.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, since the folding of the first return vane in the radial flow path is configured to be small, the rigidity of the entire return flow path can be increased, and the U
In the turn channel, the blade surface is formed in a hydrodynamically appropriate shape with smooth blade angle changes along each streamline, so flow separation and secondary flow do not occur.

Furthermore, at the connection part between the radial flow path and the U-turn flow path, the blade tips of the return blades of the U-turn flow path and the return blades of the radial flow path are arranged at a position where they intersect with each other. Since the exit angle of the first return vane 21 and the inlet angle of the second vane 4 are set equal and the vane angle with respect to the streamline is continuous, collision loss occurs at the connection between the radial flow path and the U-turn flow path. Hydraulic performance can be improved without the occurrence of

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view showing the structure of a two-stage pump turbine, Fig. 2 is a schematic sectional view showing a conventional return flow path, Fig. 3 is a plan view showing the return blade, and Fig. 4 is a cross-sectional view taken along the line A-A in FIG. 3, FIG. 5 is a cross-sectional view taken along the line B-B in FIG. 3, FIG. 8 is a sectional view taken along line AA in FIG. 7, and FIG. 9 is a sectional view taken along line BB in FIG. 7. 2...High pressure stage runner, 3...Low pressure stage runner, 8...
・High pressure stage runner chamber, 9...Low pressure stage runner chamber, 10...
- Return flow path, 15... Radial flow path, 16... U-turn flow path, 17... Outer streamline, 18... Inner streamline,
21...First return blade, n...Second return blade. Applicant's agent Kiyota Inomata

Claims (1)

[Claims] 1. A runner is provided in each stage from the highest pressure stage to the lowest pressure stage, and the coronal pressure side stage and low pressure side stage that are in instant contact are connected by a return flow path, and this return flow path is provided. In a return flow path of a multi-stage hydraulic machine whose flow path is composed of a radial flow path and a U-turn flow path; A plurality of first return blades are arranged at intervals in the circumferential direction, and in the U-turn flow path, the inlet end of the blade intersects the outlet end of the first return blade, and the water flow A return flow path for a multi-stage hydraulic machine, characterized in that a plurality of second return vanes are arranged at intervals in the circumferential direction so that the vane angles thereof vary smoothly along the streamlines. 2. The return of the multi-stage hydraulic machine according to claim 1, characterized in that the exit angle of the first return blade and the inlet angle of the second return blade are set to be equal. flow path. 3. The return channel of a multi-stage hydraulic machine according to claim 1, wherein the number of the first return blades and the number of the second return blades are set to be equal. 4. The return channel of a multi-stage hydraulic machine according to claim 1, wherein the number of the first return vanes and the number of the second return vanes are set to be different.