JP3993371B2 - Runner blade of mixed flow hydraulic machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a runner blade of a mixed flow hydraulic machine such as a mixed flow turbine or mixed flow pump turbine.
[0002]
[Prior art]
First, the general structure of a mixed flow hydraulic machine such as a mixed flow turbine or mixed flow pump turbine will be described with reference to FIG.
The mixed-flow hydraulic machine 1 has a main shaft (only the axis 2 of the main shaft is shown), and a runner boss 4 is directly connected to a lower end portion of the main shaft. A plurality of runners are arranged in a row in the circumferential direction on the runner boss 4. A blade 6 is arranged. The runner blade 6 includes a blade shaft 8 that is rotatably inserted into the runner boss 4, and a blade 10 provided on the blade shaft 8. Discharge rings 12 that are spherically processed so as to surround the runner blades 6 with a predetermined gap 11 are disposed on the lower outer peripheral side of these runner blades 6. An upper suction pipe 16 is provided below the discharge ring 12 via a throat portion 14. A plurality of variable opening guide vanes 18 are arranged on the outer periphery in the horizontal direction of the runner boss 4 and the runner blades 6. Further, the blade 10 of the runner blade 6 includes a boss side 20, a tip side 22, an inlet end (front edge) 24, and an outlet end (rear edge) 26.
[0003]
When the mixed-flow hydraulic machine 1 having such a structure is used as a turbine, water falling from a hydraulic iron pipe (not shown) is guided to a spiral casing (not shown), and a stay vane (not shown) and a guide vane 18 are provided. To the runner blade 6 and rotate the runner blade 6. Moreover, when using as a pump, water is pushed up from the upper suction pipe 16 side by rotating a main shaft reversely with the case of a water turbine.
[0004]
On the other hand, Japanese Patent Application Laid-Open No. 8-165579 discloses an example of a guide blade of a mixed flow hydraulic machine as a related art. In the conventional example of this publication, the tip side of the exit end (rear edge) of the runner blade is moved upstream, thereby moving the blade away from the throat portion, thereby reducing the throat cavitation without reducing the efficiency. It is what I did.
[0005]
[Problems to be solved by the invention]
In the mixed flow hydraulic machine described above, chip cavitation is generated in the gap (tip gap) 11 between the blade 10 and the discharge ring 12 due to the pressure difference between the pressure surface on the tip side of the blade 10 and the negative pressure surface. . If this tip cavitation occurs excessively under normal operating conditions, the tip side of the blade 10 is damaged by corrosion, and this damage needs to be repaired, which requires extra time and cost. For this reason, suppression of chip cavitation is desired.
In addition, due to the influence of critical cavitation characteristics (cavitation coefficient at which efficiency begins to decline), it was necessary to embed the draft tube deeper underground when constructing the plant, which increased the construction cost.
Furthermore, in a mixed flow hydraulic machine, local static pressure drop tends to occur on the suction surface of the runner blade tip side on the tip side, and therefore flow separation occurs on the suction surface on the tip side of the tip end, resulting from this. Cavitation may occur. This phenomenon occurs remarkably under relatively high flow rate conditions with high efficiency.
Accordingly, there is a demand for suppression of such chip cavitation and improvement of critical cavitation characteristics.
[0006]
Therefore, the present invention has been made to satisfy the conventional demands, and the runner blade of a mixed flow hydraulic machine capable of improving efficiency and suppressing chip cavitation and improving critical cavitation characteristics is provided. It is intended to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a runner blade of a mixed flow hydraulic machine having a blade shaft rotatably inserted into a runner boss and a blade provided on the blade shaft. The side profile warp is set from 50 degrees to 60 degrees, the tip side profile warpage is set from 30 degrees to 35 degrees, and the blades have an inlet end at 5 with respect to the axis of the main shaft of the mixed-flow hydraulic machine. It is characterized in that it is set to be inclined degrees.
[0010]
[Action]
In the present invention configured as described above, the warpage of the boss side profile of the blade is set from 50 degrees to 60 degrees, and the warpage of the tip side profile is set from 30 degrees to 35 degrees. The pressure difference between the pressure surface side and the suction surface side can be reduced, and the occurrence of chip cavitation can be effectively suppressed . Further, the blade has an inlet end that is opposite to the axis of the main shaft of the mixed flow hydraulic machine. Therefore, the secondary flow in the flow path of the runner blade can be reduced , and the efficiency is improved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a perspective view showing a first embodiment of a runner blade of a mixed-flow hydraulic machine according to the present invention, FIG. 2 (a) shows a conventional example, and FIG. 2 (b) shows the first embodiment. . FIG. 3 is a partial perspective view showing the blade of the first embodiment. FIG. 4 is a diagram showing a boss side profile and a tip side profile of a runner blade in the first embodiment. FIGS. 5A and 5B are a plan view and a cross-sectional view for explaining warpage of the runner blade profile. FIG. 6 is a diagram showing the pressure distribution on the blade surface on the boss side and tip side of the runner blade in the first embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
[0014]
First, as shown in FIG. 1, the gap 11 exists between the tip side 22 of the blade 10 and the spherically processed discharge ring 12 as described above. For this reason, the outlet end 28 on the tip side 22 of the blade 10 moves away from the spherical portion of the discharge ring 12 as the flow rate increases, and the gap 11 becomes larger. As a result, the pressure difference existing between the pressure surface side and the suction surface side of the blade 10 increases, and this large pressure difference generates a jet (jet flow), thereby generating the above-described chip cavitation. The first embodiment suppresses the occurrence of this chip cavitation and has the following configuration.
[0015]
As shown in FIGS. 2 and 4, in the first embodiment, when the mixed-flow hydraulic machine 1 is used as a water turbine, it rotates in the direction of the rotation direction A and from the boss side 20 of the blade 10 to the tip side. The work distribution over 22 is adjusted so that the occurrence of chip cavitation can be suppressed.
Conventionally, as shown in FIGS. 2, 4, and 6, the work distribution tends to be small on the boss side 20 of the blade 10 and large on the tip side 22, and therefore, on the pressure side of the blade surface on the tip side 22. The pressure difference 34 (see FIG. 6) between 30 and the suction surface side 32 was large. In contrast, as shown in FIGS. 2, 4 and 6, in the first embodiment, the boss side 20 profile (airfoil type) warpage of the blade 10 is made larger than in the prior art to increase the load on the blade 10. In addition to the increase, the warpage of the profile on the tip side 22 is reduced to reduce the load on the blades, and the pressure difference 34 between the pressure side 30 and the suction side 32 on the tip side 22 is reduced.
[0016]
Next, the warping of the profile on the boss side 20 and the tip side 22 of the blade 10 will be specifically described with reference to FIG. The warp of the profile of the blade 10 is represented by the maximum value of the blade angle β (also referred to as blade angle). The blade angle β is an arbitrary position from the inlet end 24 to the outlet end 26 of the arbitrary cross section XX from the boss side 20 to the tip side 22 of the blade 10 in the rotation direction A (tangential direction) when used as a water wheel. Is defined as the angle β. Usually, the maximum value of the blade angle β exists at a position 20% to 30% of the blade length from the inlet end 24. In the first embodiment, based on this definition, the profile warpage (maximum value of the blade angle β) on the boss side 20 of the blade 10 is preferably in the range of 50 degrees to 60 degrees, and is 55 degrees. There is optimal. In addition, the profile warpage (maximum value of the blade angle β) on the tip side 22 of the blade 10 is preferably in the range of 30 to 35 degrees, and most preferably 33 degrees.
[0017]
According to the first embodiment, as shown in FIG. 6, as compared with the conventional example, the warpage of the profile (airfoil type) on the boss side 20 of the blade 10 is increased to increase the load of the blade 10 and the tip. The side 22 profile warpage is reduced to reduce the load on the blade, and the pressure difference between the pressure side 30 and the suction side 32 of the tip side 22 blade surface is reduced. Can be suppressed.
[0018]
Further, in the first embodiment, as shown in FIG. 3, the inlet end (front edge) 24 of the blade 10 is set to be inclined from 0 degree to 5 degrees with respect to the axis 2 of the main shaft of the mixed flow hydraulic machine 1. (Indicated by an angle α in FIG. 3). In the conventional example, the angle α is 10 to 15 degrees.
Thus, by setting the angle α to 0 degrees to 5 degrees, it is possible to reduce the secondary flow in the flow path of the runner blades 6 as compared with the conventional case, and as a result, the efficiency can be improved. .
[0019]
Next, a second embodiment of the present invention will be described with reference to FIGS. 7 is a perspective view showing a runner blade of the second embodiment, FIG. 8 is a plan view showing the runner blade of the second embodiment, a cross-sectional view showing a cross section of the runner blade of FIG. 9 on the tip side, and FIG. It is a diagram which shows the pressure distribution of the blade surface of the tip part of the runner blade | wing of embodiment.
As shown in FIGS. 7 and 8, in the runner blade 6 of the second embodiment, the position of the axis 7 of the runner blade 6 is from the inlet end (front edge) 24 on the tip side from 30% of the blade length. It is located at 40%, and on the boss side, it is set to be located from 35% to 45% of the blade length from the inlet end (front edge) 24. Further, the tip end of the blade 10 on the tip side is set up, that is, the angle of the tip end of the blade 10 on the tip side is set to be 5 to 8 degrees larger than the flow angle.
[0020]
On the other hand, as shown in FIG. 7, the conventional runner blade has a shape in which the tip side of the blade is downstream, that is, retreated, so that the local static pressure on the suction surface side of the inlet end on the tip side of the blade. The decrease 36 (see FIG. 10) is likely to occur, so that the flow is separated at that portion, and cavitation is generated due to the separation. This cavitation was conspicuous under conditions of relatively high flow rate with high efficiency.
[0021]
However, in the above-described second embodiment of the present invention, the shape of the inlet end 24 on the tip side 22 of the blade 10 that is advanced or advanced from the upstream side, more specifically, the axis 7 of the runner blade 10. Is set to be 30% to 40% of the blade length from the inlet end (leading edge) 24 on the tip side 22, and the angle of the inlet end on the tip side 22 of the blade 10 is set to the flow angle. Therefore, it is possible to prevent the occurrence of the local static pressure drop 36 on the suction surface side 32 of the inlet end 24 on the tip side 22 of the blade 10 described above. Further, in the second embodiment, the inlet end 24 on the tip side 22 of the blade 10 is set higher than in the conventional example, that is, the angle of the inlet end on the tip side 22 of the blade 10 is 5 degrees to 8 degrees from the flow angle B. Therefore, when the flow flows from the pressure surface side 30, the flow smoothly flows into the blade 10, and even when the flow flows from the suction surface side 32, the pressure surface side 30. Then, since the pressure is originally high, the flow is hardly separated.
Thus, according to the second embodiment, flow separation on the suction surface side 32 of the inlet end 24 on the tip side 22 of the blade 10 is suppressed, and generation of cavitation due to flow separation is suppressed. Can do.
[0022]
Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a front view showing a third embodiment of the present invention, and FIG. 12 is a diagram showing the pressure distribution on the blade surface on the tip side of the blade according to the third embodiment.
First, as shown in FIG. 11, there is a gap (seal clearance) 42 between the run boss 4 and the stationary part 40, and the position where this gap 42 exists is called a seal diameter 44. As the seal diameter 44 increases, the downward thrust force applied to the main shaft of the mixed flow hydraulic machine (used as a turbine) 1 increases, and the load on the thrust bearing (not shown) increases. For this reason, it is necessary to reduce the seal diameter 44 in order to reduce the cost. Therefore, since the runner blade 6 is a movable blade whose opening degree can be changed for each operation condition, the boss of the blade 10 is not exposed to the seal diameter 44 at the maximum opening 46 considered in plant operation. The dimensions of the side 20 profile need to be determined. Further, the blade 10 is partially cut off so that the inlet end or the outlet end of the profile on the boss side 20 of the blade 10 does not protrude from the spherical processed portion 50 provided on the boss side 20 of the runner boss 4. Since it is not necessary, it is advantageous in terms of performance.
[0023]
From this point of view, in the third embodiment, the warpage of the boss side profile of the blade 10 (same meaning as in the first embodiment) is made larger than that of the first embodiment, that is, the warp of the boss side profile of the blade 10. Is set to 60 degrees to 70 degrees (the optimum value is 65 degrees), so that the blade length (code length) of the profile on the boss side is shortened.
On the other hand, on the tip side 22, since there is no limit other than the need to pay attention to the water pressure pulsation in the flowing water portion between the guide vane 18 and the runner blade 6, the tip-side profile warpage of the blade 10 is almost eliminated. The design is flat, that is, the warp of the profile on the tip side 22 of the blade is set to 20 to 30 degrees (the optimum value is 25 degrees). As a result, the tip side 22 of the blade 10 can have a shape in which the blade length (code length) of the tip side profile is increased.
[0024]
Thus, according to the third embodiment, the blade length of the boss side profile can be shortened, the seal diameter 44 can be reduced, and the thrust can also be reduced. In addition, since the blade length is lengthened by eliminating the warpage of the tip side profile, the load is reduced, and the pressure difference 34 between the pressure surface side 30 and the suction surface side 32 of the blade surface is made smaller than in the first embodiment. Therefore, chip cavitation can be more effectively suppressed accordingly. Furthermore, since the minimum pressure 52 in the vicinity of the outlet on the suction side 32 on the tip side 22 can be made relatively large, the critical cavitation characteristics can also be improved.
[0025]
【The invention's effect】
As described above, according to the runner blade of the mixed-flow hydraulic machine of the present invention, it is possible to improve efficiency, suppress chip cavitation, improve critical cavitation characteristics, and the like.
[Brief description of the drawings]
FIG. 1 is a front view showing a general structure of a mixed flow hydraulic machine such as a mixed flow turbine or a mixed flow pump turbine.
FIG. 2 is a perspective view showing a first embodiment of a runner blade of a mixed-flow hydraulic machine according to the present invention, FIG. 2 (a) shows a conventional example, and FIG. 2 (b) shows the first embodiment. Yes.
FIG. 3 is a partial perspective view showing a blade of the first embodiment.
FIG. 4 is a diagram showing a boss side profile and a tip side profile of a runner blade in the first embodiment.
FIGS. 5A and 5B are a plan view and a cross-sectional view for explaining warpage of a runner blade profile. FIGS.
FIG. 6 is a diagram showing a pressure distribution on a blade surface on a boss side and a tip side of a runner blade in the first embodiment.
FIG. 7 is a perspective view showing a runner blade according to a second embodiment of the present invention.
FIG. 8 is a plan view showing a runner blade according to a second embodiment.
FIG. 9 is a cross-sectional view showing a cross section of the runner blade on the tip side.
FIG. 10 is a diagram showing the pressure distribution on the blade surface of the tip portion of the runner blade according to the second embodiment.
FIG. 11 is a front view showing a third embodiment of the present invention.
FIG. 12 is a diagram showing the pressure distribution on the blade surface on the tip side of the blade according to the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Diagonal-flow hydraulic machine 2 Main shaft axis 4 Runner boss 6 Runner blade 7 Nanna blade axis 8 Blade shaft 10 Blade 12 Discharge ring 14 Throat section 16 Upper suction pipe 18 Guide vane 20 Boss side 22 Tip side 24 Inlet end (front edge)
26 Exit end (rear edge)
28 Outlet end 30 on the chip side Pressure surface 32 Negative pressure surface 34 Pressure difference 36 Local pressure drop 40 Stationary portion 42 Gap 44 Seal diameter 46 Maximum opening 48 Minimum opening 50 Spherical surface processing portion 52 Minimum pressure

Claims (1)

In a runner blade of a mixed flow hydraulic machine having a blade shaft rotatably inserted into a runner boss and a blade provided on the blade shaft,
The blade has a boss-side profile warpage set from 50 degrees to 60 degrees, a tip-side profile warpage set from 30 degrees to 35 degrees, and the blade has an inlet end at the main shaft of the mixed-flow hydraulic machine. A runner blade of a mixed-flow hydraulic machine, which is set to be inclined at 5 degrees with respect to the axis of

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