JPH08312518A - Runner of reversible pump-turbine - Google Patents

Abstract

PURPOSE: To extensively improve cavitation performance by forming a bulged part at least on one of a vane back surface and a vane front surface near a hydraulic turbine impeller vane outlet end of a runner vane and connecting the front and the rear of this bulged part by a smooth curved surface. CONSTITUTION: A bulged part 10 is formed on a vane back surface 4a near a hydraulic turbine impeller vane outlet end 8 of a runner vane 4, and an area of an angle θs is connected by a smooth curve. In other words, vane thickness B1 near the hydraulic turbine impeller vane outlet end 8 is formed thicker than vane thickness Bo of a central part of the runner vane 4, and a vane tip extending angle α of the runner vane 4 is set large. In this way, as the vane thickness B1 near the hydraulic turbine impeller vane outlet end 8 is locally set larger than the vane thickness Bo of the vane central part, it is possible to set the head end extending angle α of the vane and to extensively restrain generation of cavitation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump turbine runner, and more particularly to a runner blade shape having improved performance against cavitation.

[0002]

2. Description of the Related Art A runner of a pump turbine can perform power generation and pumping operation by changing its rotating direction.

FIG. 8 shows the outline of the structure of a pump turbine. During the power generation operation, the water that has flown into the casing 1 flows into the runner 2, which is rotationally driven and discharged from the suction pipe 3. On the contrary, in the pumping operation mode, the runner 2 is rotationally driven by a generator motor (not shown) in the opposite direction to that in the power generating operation, and the water guided into the runner chamber through the suction pipe 3 is given energy by the runner 2 and the casing 1 Water is pumped to the upper pond (not shown) via the water. The runner 2 of this type of pump turbine has a plurality of runner blades 4 which are evenly arranged in the circumferential direction. These runner blades 4 include a runner crown 6 and a runner band 7 connected to the lower end of a main shaft 5. Is fixed between.

FIG. 9 shows a view of the runner 2 as seen from the outlet side of the water turbine. The tip of the runner blade on the outlet side in the flow direction of the turbine (hereinafter referred to as the outlet end of the turbine blade) 8 extends radially substantially in the radial direction. are doing. The blade cross-sectional shape of the water turbine blade outlet end 8 is mainly determined by the pumping operation conditions. Figure 10 (a)
8B shows a velocity triangle of the flow at the exit end of the turbine blade in the AA cross section of FIG. 8 during the pumping operation, and the absolute velocity C of the flow is decomposed into the runner peripheral velocity U and the relative velocity W. FIG. 10 (a) shows a state during high head operation with a small flow rate. In this state, the runner peripheral speed U with respect to the blade angle β ₀
The relative inflow angle β formed by the relative velocity W and the relative velocity W becomes smaller. As a result, the pressure is greatly reduced on the blade back surface 4a, and when this pressure becomes equal to or lower than the vapor pressure, cavitation (generally, cavitation generated at this position is referred to as K2) occurs. If this cavitation occurs for a long time, erosion will occur near the cavitation generation part.

On the other hand, FIG. 10 (b) shows a state during low head operation with a large flow rate. In this state,
The relative inflow angle β of water becomes larger than the blade angle β ₀ , the pressure greatly decreases on the blade surface 4b, and cavitation (generally, the cavitation generated at this position is K ₁ ) will occur. In order to suppress the occurrence of cavitation to some extent, as shown in FIG. 11, it is known to make the blade shape at the outlet end of the water turbine blade a streamline shown by the solid line. When the blade tip divergence angle α is increased and the streamlined surface is smooth in this way, the pressure drop near the tip is smaller than that of the shape shown by the broken line, and cavitation is less likely to occur.

[0006]

As described above, the pump turbine performs the generator turbine operation and the pumping pump operation using the same runner, so that the flow direction of water passing through the runner is reversible depending on the operation mode. Therefore, considering the performance of both, the conventional runner blades have almost the same thickness along the flow direction except the tips of the turbine turbine inlet and outlet, and each tip has a blade thickness toward the tip. Is monotonically thin. In addition, since the blade of the pump turbine runner has a relatively small blade thickness, it is impossible to increase the blade tip spreading angle α, and thus there is a problem that the cavitation performance cannot be significantly improved.

[0007] The range of pump head change from the maximum pump head to the minimum pump head in pumped-storage power plants (the change width of the head as viewed from the turbine operation) is limited by the performance against cavitation. Therefore, the runner of the conventional pump turbine cannot increase the change range of the head or the head. Therefore, the operating time in the power generation operation or the pumping operation is shortened, and the operation efficiency is deteriorated. In addition, there is a problem that the amount of water that cannot be used effectively in the dam increases and resources cannot be used effectively. Therefore, an object of the present invention is to provide a pump turbine runner capable of improving the cavitation performance generated in the runner of the pump turbine during the pumping operation and expanding the operable head and the variation range of the head.

[0008]

To achieve this object, the present invention relates to a pump turbine in which a plurality of runner blades are fixedly held at equal intervals in the circumferential direction between a runner crown and a runner band. In the runner, a bulging portion is formed on the blade back surface and / or the blade surface near the water turbine blade outlet end of the runner blade, and the front and rear of the bulging portion are connected by a smooth curved surface.

In this structure, the bulging portion starts to bulge in the blade cross section in the flow direction of the water turbine (hereinafter,
(The blade thickness increase start point) and the turbine blade outlet end are defined as θ _s , and the circumferential pitch angle between the blade outlet ends of a pair of adjacent runner blades is defined as θ _0. ,
It is desirable that θ _s be in the relation of θ _s ≦ 1.2 θ _o .

When the blade thickness at the blade thickness increase start point of the runner blade is B ₀ , a virtual circle drawn with a radius of B _0/2 around the outlet end of the water turbine blade and the blade front surface and blade back surface. When a tangent line that passes through the intersection point formed by intersecting with and that is in contact with the blade shape curve on the front surface and the back surface of the blade is drawn and the angle formed by both tangent lines is α, α is 35 ° ≦ α ≦ 60
It is desirable to have a relationship of °. Further, it is desirable that the maximum blade thickness at the water turbine blade outlet end of the runner blade is set to gradually increase from the center between the runner bands to the runner band.

[0011]

In the pump turbine runner according to the present invention, since the blade thickness near the tip of the runner blade becomes thicker, the runner blade tip spreading angle can be made large and the streamlined shape can be made smooth. Therefore, the performance against cavitation during the pumping operation can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a runner for a pump turbine according to the present invention will be described below with reference to FIG. FIG. 1 shows a vertical cross-sectional shape of a pair of adjacent runner blades, which is cut along the line AA in FIG. In FIG. 1, the bulging portion 10 is provided on the blade back surface 4a near the water turbine blade outlet end 8 of the runner blade 4.
Are formed, and the range of the angle θ _s is connected by a smooth curve. In other words, the blade thickness B _{1 in} the vicinity of the water turbine blade outlet end is formed thicker than the blade thickness B _{0 in} the central portion of the runner blade 4, and the tip spread angle α of the runner blade is set to be large. .

As described above, according to the present invention, the blade thickness B _{1 in the} vicinity of the water turbine blade outlet end 8 is locally set to be larger than the blade thickness B _{0 in the} blade central portion, so that the blade tip spreading angle α
Can be set to a value larger than that of the conventional one, and the occurrence of cavitation can be significantly suppressed.

Next, the effect of the embodiment of the present invention described above will be described with reference to FIG. The horizontal axis of the graph shown in Fig. 2 is the pumped water quantity Q with respect to the pumped water quantity Q _{0 at the} design point.
And the vertical axis represents the cavitation coefficient (called the initial cavitation coefficient) σ _i when cavitation starts to occur. The solid line shows the embodiment of the present invention, and the broken line shows the case of the conventional example, which means that cavitation occurs in the area below the curve. Further, K1 indicates cavitation generated on the blade front surface side, and K2 indicates cavitation generated on the blade back surface side. As can be seen from this graph, for example, when comparing the pumping amount range ΔQ _{i in} which cavitation does not occur with a cavitation coefficient of 0.14, according to the embodiment of the present invention, the operating range in which cavitation does not occur is approximately doubled as compared with the conventional example. Can be expanded to.

Next, with reference to FIGS. 1 and 3, the range in which the wall thickness of the runner blade 4 is increased and the mode of variation of the cavitation coefficient will be considered. In FIG. 1, the angle θ _s from the blade tip 8 to the circumferential direction at the position where the thickness of the runner blade starts to increase from the blade thickness B ₀ near the center (hereinafter referred to as the blade thickness increase start point S), and the blade The relationship with the inter-pitch angle θ ₀ is preferably selected so that θ _s satisfies the following range. θ _s ≦ 1.2 θ ₀

As shown in FIG. 1, when θ _s is set small, the curved surface of the blade back surface 4a is convex on the blade tip side and concave on the turbine upstream side. The pressure decreases near the changing position, and cavitation (hereinafter referred to as K3) easily occurs. However, conversely, when θ _s is increased, the flow passage width a between the blades is narrowed, the flow velocity of the water flow between the blades is increased, the pressure near the blade tips of the blade surface 4b is decreased, and the cavitation (K ₁ ) is reduced. It tends to occur.

FIG. 3 is a graph showing the position of the starting point of the blade thickness increase and the mode of change of the initial cavitation coefficient. The horizontal axis is the dimension of the blade thickness increasing start point made dimensionless by the blade pitch angle θ _0. θ _s is represented, and the vertical axis represents a change ΔσiK1 of the K1 initial cavitation coefficient with reference to the K1 initial cavitation coefficient at θ _s = θ ₀ under a constant pumping amount on the low pump head side of a large flow rate. As can be seen from this graph, the change Δσ _i K1 in the K1 initial cavitation coefficient rapidly increases when θ _s > 1.2θ ₀ . According to this embodiment, it is possible to significantly suppress the deterioration of the K1 initial cavitation performance.

Next, another embodiment of the present invention will be described with reference to FIG. An example is shown in which the bulged portions 10 and 10 are formed at symmetrical positions on both the blade back surface 4a and the blade surface 4b near the water turbine blade outlet end 8 of the runner blade 4. In FIG. 4, a circle having a radius of 1/2 times the blade thickness B ₀ at the blade thickness increasing point S at the blade tip 8 is drawn to draw the blade back surface 4 of the runner blade.
Let Xa and Xb be the intersections of a and the surface 4b with the vane curves. Then, a tangent line tangent to each blade curve is drawn from the points Xa and Xb, and an angle formed by both tangent lines is defined as a blade tip spread angle α.

In this embodiment, the blade tip spread angle α
Is selected to satisfy the following range.

35 ≦ α ≦ 60 °

The larger the value of α, the better the performance of K1 and K2 against cavitation.
Becomes larger, the curvature of the convex shape on the blade back surface 4a side becomes larger, the pressure drop in the vicinity of the change from the convex portion to the concave portion becomes larger, and K3 cavitation easily occurs.

FIG. 5 is a graph showing the relationship between the blade tip spread angle α and the cavitation-free width. The horizontal axis represents the blade tip spread angle α, and the vertical axis, as shown in FIG.
A zero-dimensionalized cavitation-free pumping range ΔQ _i is represented, where K _{1 to} K ₂ are between K ₁ and K ₂ primary cavitation curves, and K _{1 to} K ₃ are K ₁ and K ₃ primary cavitation curves. Represents the range of pumping volume where cavitation does not occur.

As can be seen from this graph, α = 35 °
The range where cavitation does not occur greatly expands from the vicinity, but the K ₃ cavitation performance deteriorates from around α = 60 °, and the pumped-up range where cavitation does not occur does not expand significantly. As described above, according to the present invention, it is possible to provide the blade tip spread angle α that contributes to the expansion of the operable range.

Next, description will be made with reference to FIG. 6 showing the maximum blade thickness change in the vicinity of the runner turbine blade outlet end 8. The horizontal axis is
Water turbine blade outlet end 8 between the runner crown and the runner band
Represents the distance l from the dimensionless runner crown along the distance l ₀ along the vertical axis, and the vertical axis represents the maximum blade thickness B _1B on the runner band.
Represents the maximum blade thickness B ₁ made dimensionless. In this embodiment,
The maximum blade thickness is almost the same from the runner crown to the center of the outlet end, but the maximum blade thickness gradually increases from the center to the runner band. This action will be described with reference to FIG. Generally, the pressure drop near the blade inlet is represented by the following equation.

Δp = λ1 · C ² / 2g + λ2 · W ² / 2g

Here, λ1 and λ2 are coefficients, and approximately λ
The values are 1 to 1.2 and λ2 to 0.3. FIG. 7A shows a velocity triangle on the runner band side, but since the radius is large on the runner band side, the peripheral velocity U _B becomes faster, so the relative velocity W
_B also becomes faster. Therefore, the pressure drop Δp becomes relatively large on the runner band side, and cavitation easily occurs. On the contrary, FIG. 7B shows a velocity triangle on the runner crown side. Although the absolute velocity C is almost the same as that on the runner band side, the peripheral velocity Uc due to the smaller radius becomes slower and the relative velocity Wc also becomes Become slow. Therefore, the pressure drop Δp is relatively small on the runner crown side, and cavitation is relatively unlikely to occur. Therefore, according to the present embodiment, by increasing the maximum blade thickness near the blade tip on the side of the band where cavitation is likely to occur, the cavitation performance from the runner crown to the runner band can be balanced.

[0027]

As is apparent from the above description, according to the present invention, since the blade cross section near the blade tip of the runner blade of the pump turbine has a swollen and smooth streamline shape, during pumping operation, A large pressure drop on the back surface and the front surface of the blade tip can be suppressed. As a result, the cavitation performance can be improved, and the operable range between the maximum head and the minimum head can be greatly expanded.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a runner blade schematically showing an embodiment of a runner of a pump turbine according to the present invention.

FIG. 2 is a graph showing the relationship between the pumping rate and the primary cavitation coefficient in comparison with the conventional example in order to demonstrate the effect of the present invention.

FIG. 3 is a graph showing the relationship between the blade thickness increase start point position ratio and the change in initial cavitation coefficient.

FIG. 4 is a sectional view of a runner blade schematically showing another embodiment of the runner of the pump turbine according to the present invention.

FIG. 5 is a graph showing the relationship between the runner blade tip spreading angle and the cavitation-free width.

FIG. 6 is a graph showing the relationship between the distance from the crown along the outlet end of the turbine blade and the maximum thickness of the outlet end of the blade.

FIG. 7 (a) is a schematic view showing a velocity triangle on the runner band side. (B) Schematic diagram showing a velocity triangle on the runner crown side.

FIG. 8 is a sectional view schematically showing the structure of a conventional pump turbine.

FIG. 9 is a blade configuration diagram of a conventional runner as seen from the water turbine outlet side.

FIG. 10 (a) is a schematic view schematically showing a runner blade inflow state during high head operation with a speed triangle. (B) A schematic view schematically showing a runner blade inflow state during low head operation with a speed triangle.

FIG. 11A is a sectional view showing a tip shape of a conventional runner blade. (B) The schematic diagram which showed typically the state of vane surface pressure distribution.

[Explanation of symbols]

 1 casing 2 runner 3 suction pipe 4 runner blade 4a runner blade back surface 4b runner blade surface 6 runner crown 7 runner band 8 turbine blade outlet end 10 bulging portion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiko Yoshi Mori 3-22-3 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. 2-4, Machi Within the Keihin office of Toshiba Corporation

Claims (4)

[Claims] 1. A runner of a pump turbine in which a plurality of runner blades are fixedly held at equal intervals in the circumferential direction between a runner crown and a runner band, and a blade back surface near the outlet end of the turbine blade of the runner blade. A runner for a pump turbine, wherein a bulging portion is formed on at least one of the blade surfaces, and the front and rear of the bulging portion are connected with a smooth curved surface. 2. The angle in the circumferential direction between the position where the bulging portion begins to swell in the blade cross section in the turbine flow direction (hereinafter referred to as the blade thickness increase start point) and the outlet end of the turbine blade, θ _s ,
When the pitch angle in the circumferential direction between the blade outlet ends of a pair of adjacent runner blades is θ ₀ , θ _s is θ _s ≦ 1.2 θ
The runner for a pump turbine according to claim 1, wherein the runner has a relationship of ₀ . 3. When the blade thickness at the start point of increasing the blade thickness of the runner blade is B ₀ , B is centered at the outlet end of the turbine blade.
_{When a} tangent line that passes through the intersection point formed by the virtual circle drawn with the radius of 0/2 and the blade surface and the blade back surface and that is in contact with the blade shape curve of the blade front surface and the blade back surface is defined as α , Α is in the relationship of 35 ° ≦ α ≦ 60 °. The runner for a pump turbine according to claim 1, wherein 4. The maximum blade thickness at the outlet end of the water turbine blade of the runner blade is set so as to gradually increase from the center between the runner band and the runner crown toward the runner band. A runner for a pump turbine according to any one of Items 3.