JP2017031923A - Runner and hydraulic machine - Google Patents

Abstract

The present invention provides a runner that can effectively suppress the generation of cavitation and / or separation vortices and sufficiently expand the operating range of a hydraulic machine. A runner 4 according to an embodiment includes a blade body 14 and an inlet-side blade forming member 15 provided inside the blade body 14 and exposing a part of the blade body 14 to the outside of the blade body 14. A runner blade 13 is provided. A part of the inlet-side blade forming member 15 exposed to the outside of the blade body 14 forms an inlet-side flowing water surface 15n continuous with the negative pressure surface 14n of the blade body 14. The inlet-side blade forming member 15 is formed so as to change the shape of the inlet-side water surface 15n according to a change in pressure around it. [Selection] Figure 1

Description

  Embodiments described herein relate generally to a runner and a hydraulic machine.

  A Francis turbine is known as an example of a hydraulic machine. In a general Francis turbine, a runner is fixed to the lower end of the turbine main shaft, and a plurality of guide vanes and stay vanes are arranged side by side on a circumference in a parallel flow path formed on the outer peripheral side of the runner. . A casing is disposed on the outer peripheral side of the stay vane. In this configuration, water guided from the hydraulic iron pipe flows through the casing over the entire circumference of the plurality of stay vanes. The water flowing out from the stay vane is guided to the runner through the guide vane and rotationally drives the runner. As a result, the turbine main shaft rotates and the generator connected to the water turbine main shaft is driven. On the other hand, the water which rotated the runner is discharged into the lower pond through the suction pipe. Further, by changing the opening of the guide vane during the water turbine operation, the amount of water flowing into the runner can be adjusted, and the amount of power generation can be changed.

  Since the runner blades in the runner of the Francis turbine are fixed blades, when the relative angle β1 of the flow flowing from the guide vane to the runner matches the inlet angle βb of the runner blades, the collision loss is small and the most efficient. However, since the Francis turbine is operated in various operating conditions that deviate from such a most efficient design point, it is not always operated in an optimal operating condition.

  FIG. 7 shows the flow in the operation on the high head side deviating from the design point, and FIG. 8 shows the flow in the operation on the low head side deviating from the design point. 7 and 8, Cu1 represents the peripheral speed of the runner, Cv1 represents the absolute velocity of the flow, and Cw1 represents the relative velocity of the flow. The relative angle β1 is determined from the peripheral speed Cu1 and the relative speed Cw1. Rd indicates the rotation direction of the runner.

  For example, as shown in FIG. 7, at the operating point on the high head side, the relative angle β1 of the flow flowing into the runner blades 40 of the runner becomes larger than the inlet angle βb of the runner blades 40, resulting in a mismatch of the flow angles. As a result, cavitation ca tends to occur on the inlet side of the suction surface 40n of the runner blade 40. Such cavitation can cause erosion of the water surface of the runner blade, which is problematic from the viewpoint of equipment reliability.

  Further, as shown in FIG. 8, at the operating point on the low head side, the relative angle β1 of the flow flowing into the runner blades 40 of the runner becomes smaller than the inlet angle βb of the runner blades 40, resulting in a mismatch of the flow angles. As a result, the separation vortex wh tends to be generated from the pressure surface 40p side of the runner blade 40. Such a separation vortex is accompanied by a plosive sound, unlike cavitation that can occur in operation on the high head side. Even if this separation vortex occurs, it does not lead to harmful erosion unless it extends downstream and adheres to, for example, the flow surface of another runner blade. Therefore, the separation vortex is not a big problem compared with cavitation. However, when the separation vortex adheres to the surface of the water flow or is accompanied by noise, it is desirable to design the runner appropriately so that the generation limit does not fall within the normal operating range as much as possible.

  The generation limit of cavitation and separation vortex as described above can be shown on the turbine performance diagram as an initial line, and may be used as a guideline for limiting operation. FIG. 10 shows an example of a turbine performance diagram of a general Francis turbine. In this diagram, the horizontal axis indicates a drop and the vertical axis indicates a flow rate. An alternate long and short dash line L11 indicates an initial line of cavitation on the inlet side of the suction surface of the runner blade, and an alternate long and short dashed line L12 indicates an initial line of separation vortex on the inlet side of the pressure surface of the runner blade. A plurality of broken lines indicate isoefficiency lines. In the diagram shown in FIG. 10, a range indicated by two primary lines L11 and L12 is included in a part of the operating range indicated by hatching in the figure, and cavitation and separation vortex occur at such an operating point. Driving may be restricted due to fears.

  Francis turbines, especially when they are high specific speed type turbine models with a low head and large flow rate, when driving under conditions where dam water level changes are large in order to improve operational efficiency, In the case where it is required to enlarge the operating range of the equipment, it is required to suppress the occurrence of cavitation and separation vortex.

  For example, as one of the countermeasures, as shown by the broken line in FIG. 9, the inlet side of the suction surface of the runner blade 40 swells more than the normal shape (shape indicated by the solid line in the figure) (reference numeral 40a). Can be formed. With respect to such a bulging portion, a technique for reducing hydraulic loss and suppressing peeling has been conventionally proposed by limiting the numerical value to define the shape.

JP 2006-291865 A Japanese Patent No. 40944495

  However, as a measure to suppress the occurrence of cavitation and separation vortices, even if a bulging part is formed on the inlet side of the suction surface of the runner blade as described above, the flow changes rapidly from the most protruding part to the downstream side. Therefore, cavitation often occurs, and it is difficult to completely suppress cavitation. In particular, in a high specific speed type runner, since the blade length from the inlet to the outlet of the runner blade is short, the load is high at the inlet, and cavitation is more difficult to suppress than in the low specific speed type runner. Further, when defining the shape of the bulging portion, it is necessary to search for the optimum shape by trial and error while taking into consideration the influence of the bending of the band surface shape of the runner, which takes time and effort.

  In addition, when the bulging part is formed on the inlet side of the suction surface of the runner blade, cavitation that can occur in the operation on the high head side can be suppressed, but both the cavitation on the high head side and the separation vortex on the low head side are prevented. It is difficult to suppress.

  The present invention has been made in view of such circumstances, and a runner and a hydraulic machine that can effectively suppress the generation of cavitation and / or separation vortex and can sufficiently expand the operating range of the hydraulic machine. The purpose is to provide.

The runner according to the embodiment is a runner of a hydraulic machine, and is provided in a blade main body and an inlet side of the blade main body, and an inlet-side blade forming member that exposes a part thereof to the outside of the blade main body, A runner blade having The part of the inlet-side blade forming member exposed to the outside of the blade body forms an inlet-side flowing water surface that is continuous with the negative pressure surface or the pressure surface of the blade body. The inlet-side blade forming member is formed so as to change the shape of the inlet-side water surface in accordance with a change in pressure around the inlet-side blade forming member.
Moreover, the hydraulic machine by embodiment is provided with the said runner.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a cavitation and / or peeling vortex can be suppressed effectively, and the operating range of a hydraulic machine can fully be expanded.

It is a schematic diagram of a Francis turbine concerning a 1st embodiment. It is sectional drawing which follows the radial direction of the runner blade | wing in the runner of the Francis turbine which concerns on 1st Embodiment. It is sectional drawing which follows the radial direction of the runner blade | wing in the runner of the Francis turbine which concerns on 2nd Embodiment. It is sectional drawing which follows the radial direction of the runner blade | wing in the runner of the Francis turbine which concerns on 3rd Embodiment. It is sectional drawing in alignment with the radial direction of the runner blade | wing in the runner of the Francis turbine which concerns on 4th Embodiment. It is a water turbine performance diagram for demonstrating the effect of each embodiment. It is a figure explaining the relationship between the relative angle of the flow in the driving | running | working of the high head side of a common Francis turbine, and the inlet angle of a runner blade, Comprising: It is the figure which showed the mode of generation | occurrence | production of cavitation. It is a figure explaining the relationship between the relative angle of the flow in the driving | running | working of the low head side of a common Francis turbine, and the inlet angle of a runner blade, Comprising: It is the figure which showed the mode of generation | occurrence | production of peeling vortex. It is a figure which shows the runner blade | wing formed in the shape which swelled the inlet side of the suction surface. It is the figure which showed an example of the turbine performance diagram of a general Francis turbine.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of each embodiment, the same reference numerals are used for components and common items that are common to the general Francis turbine described with reference to FIGS.

(First embodiment)
FIG. 1 shows a Francis turbine 100 as a hydraulic machine according to a first embodiment of the present invention. The Francis turbine 100 includes a spiral casing 1 into which water flows from an upper pond (not shown) through an iron pipe, a plurality of stay vanes 2, a plurality of guide vanes 3, and a runner 4. A parallel flow path including an upper cover and a lower cover (not shown) is formed between the casing 1 and the runner 4 disposed on the inner peripheral side thereof. In the parallel flow path, a plurality of stay vanes 2 and A plurality of guide vanes 3 are arranged. The runner 4 is provided to be rotatable about the rotation axis C <b> 1 with respect to the casing 1.

  The plurality of stay vanes 2 are for guiding water flowing out from the casing 1 to the guide vanes 3, and on the inner peripheral side of the casing 1, a predetermined interval in the circumferential direction with respect to the rotation axis C <b> 1 (hereinafter referred to as the circumferential direction). It is arranged with a gap. The plurality of guide vanes 3 are for guiding the inflowing water to the runner 4, and are arranged at a predetermined interval in the circumferential direction on the inner peripheral side of the stay vane 2. Each of the guide vanes 3 is rotatable, and the amount of water flowing into the runner 4 can be adjusted by changing the opening degree.

  The runner 4 includes a crown 11, a band 12, and a plurality of runner blades 13 provided between the crown 11 and the band 12. The plurality of runner blades 13 are arranged at predetermined intervals in the circumferential direction.

  A generator 7 is connected to the runner 4 through a turbine main shaft 6, and the generator 7 generates power by being rotated by the runner 4. A suction pipe 5 is provided on the downstream side of the runner 4. The water flowing out of the runner 4 is discharged into the lower pond through the suction pipe 5.

  As shown in FIG. 2, the runner blade 13 in the present embodiment is provided inside the blade body 14 and the inlet side of the blade body 14 (that is, the water inflow side during water turbine operation). And an inlet-side blade forming member 15 exposed to the outside of the main body 14. In the present embodiment, a part of the inlet-side blade forming member 15 exposed to the outside of the blade body 14 forms an inlet-side flowing water surface 15 n continuous with the negative pressure surface 14 n of the blade body 14. That is, the negative pressure surface of the runner blade 13 is composed of the negative pressure surface 14n of the blade body 14 and the inlet-side flow surface 15n.

  On the other hand, the other part different from the inlet-side flow surface 15n of the inlet-side blade forming member 15 is covered with the inner surface of the accommodating portion 14C for accommodating the inlet-side blade forming member 15 formed in the blade body 14. It is in the state. In the present embodiment, the accommodating portion 14 </ b> C is formed in a long shape extending in the longitudinal direction in the flowing direction of the blade body 14 in a sectional view along the radial direction of the runner 4, and is open to the suction surface side. The inlet-side blade forming member 15 is fixed in the accommodating portion 14C by press-fitting or the like, and is prevented from falling off from the blade body 14.

  In the present embodiment, the inlet-side blade forming member 15 is made of a hollow elastic body and has a longitudinal direction in the flowing direction of the blade body 14 in a sectional view along the radial direction of the runner 4 so as to be aligned with the accommodating portion 14C. It is formed in a substantially rectangular shape that extends and has an internal space 16. The internal space 16 is sealed and its pressure is set to a first predetermined value.

  The first predetermined value described above is, for example, the operation of the Francis turbine 100 at the most efficient design point (design head and design flow rate) where the relative angle of the flow flowing into the runner 4 matches the inlet angle of the runner blade 13. In this case, the pressure is equivalent to the pressure of the water flowing on the suction surface 14n side. In the present embodiment, in order to set the pressure of the internal space 16 to such a first predetermined value, fluid (air, high-pressure water, etc.) whose pressure is adjusted is enclosed in the internal space 16 in advance. The runner 4 may be provided with a control mechanism for adjusting the pressure in the internal space 16 to an arbitrary value.

  Such an inlet side blade | wing formation member 15 is formed so that the shape of the inlet side water surface 15n may be changed according to the pressure change of the circumference | surroundings. Specifically, the inlet-side blade forming member 15 has a shape of the inlet-side flowing water surface 15n on the side in contact with the mainstream water depending on the relationship (difference) between the surrounding pressure condition and the pressure condition of the internal space 16, for example, as shown in FIG. It is possible to change to the state shown by the broken line. It should be noted that the inlet-side flow surface 15n and the suction surface 14n of the blade body 14 of the present embodiment are smooth as shown by the solid line in FIG. 2 when the Francis turbine 100 is operated with a design drop and a design flow rate. It is comprised so that a streamline may be made continuously.

  The operation of the present embodiment will be described.

  In the Francis turbine 1 according to the present embodiment, water guided from the upper pond is guided to the casing 1 through an iron pipe. The water is made uniform in the circumferential direction by the casing 1 and flows into the runner 4 through the stay vane 2 and the guide vane 3 arranged on the inner circumferential side of the casing 1. The runner 4 is rotated by the pressure energy of the passing water, and drives a generator 7 connected via a turbine main shaft 6. As a result, the generator 7 generates power. Water flowing out of the runner 4 is discharged to the lower pond through the suction pipe 5.

  When the Francis turbine 100 is operated with the design head and the design flow rate, the pressure of the internal space 16 of the inlet blade formation member 15 and the pressure of the water flowing on the negative pressure surface 14n side are balanced, so that FIG. As indicated by the solid line, the inlet-side flow surface 15n and the suction surface 14n of the blade body 14 are smoothly and continuously streamed.

  On the other hand, when the operating point is on the high head side, as shown in FIG. 2, the relative angle β1 of the flow flowing into the runner vane 13 becomes larger than the inlet angle βb of the runner vane 13, and the flow angles do not match. As a result, the pressure on the inlet side of the negative pressure surface 14n, that is, the pressure around the inlet-side flowing water surface 15n in the runner blade 13 decreases. At this time, the pressure in the internal space 16 of the inlet-side blade forming member 15 is higher than the pressure around the inlet-side water surface 15n, so that the inlet-side water surface 15n has a mainstream water as shown by a broken line in FIG. Project to the side. At the time of protrusion, the shape of the inlet-side water surface 15n is deformed so as to follow the surrounding flow.

  As a result, according to the present embodiment, the inlet angle βb of the runner blade 13 approaches the relative angle β1 as indicated by the arrow A1 in the figure, thereby suppressing the occurrence of cavitation due to the mismatch of the flow angles. Further, the shape of the inlet-side flow surface 15n is deformed so as to follow the flow around it, so that sudden pressure changes before and after the inlet-side flow surface 15n are alleviated. The occurrence of cavitation on the downstream side of 15n is suppressed.

  Therefore, according to this Embodiment, generation | occurrence | production of cavitation can be suppressed effectively and the operation range of Francis turbine 100 which is a hydraulic machine can fully be expanded. FIG. 6 shows a water turbine performance diagram for explaining the operation and effect of the present embodiment. In FIG. 6, an alternate long and short dash line L11 indicates an initial line of cavitation when the inlet-side blade forming member 15 is not provided, and an alternate long and short dash line L12 indicates an initial line of a separation vortex. Specifically, according to the present embodiment, the initial line L11 in FIG. 6 can be separated to the high head side like the solid initial line L1 in the drawing. As a result, the operating range can be expanded over a wider range as indicated by the arrow α in the figure.

  In the present embodiment, by providing the inlet blade forming member 15 on the suction surface side, it is possible to suppress cavitation that can occur in the operation on the high head side, but the shape of the blade body 14 can be reduced in the operation on the low head side. The inlet side blade forming member 15 may be combined with such a blade body 14 by forming in a shape that can suppress the separation vortex that may occur. In this case, it becomes possible to suppress the occurrence of cavitation that can occur on the high head side and separation vortices that can occur on the low head side, and the operating range can be expanded in a wider range.

(Second Embodiment)
Next, a second embodiment will be described. The same components as those of the first embodiment in the present embodiment are denoted by the same reference numerals and description thereof is omitted. A part of the description of the same operations and effects as those of the first embodiment is also omitted.

  As shown in FIG. 3, in the present embodiment, the communication path 18 that communicates the internal space 16 from the portion of the pressure surface 14p of the blade body 14 that faces the inlet-side blade forming member 15 in the blade thickness direction, It is formed across the blade body 14 and the inlet side blade forming member 15. In other words, the pressure surface 14p of the blade body 14 extends from the portion facing the inlet-side blade forming member 15 in the blade thickness direction to the internal space 16, and the flow of water between the pressure surface 14p and the internal space 16 is increased. An allowable communication path 18 is formed across the blade body 14 and the inlet-side blade forming member 15.

  The communication path 18 includes a first hole portion 18A extending from the pressure surface 14p to the accommodating portion 14C, and a second hole portion 18B formed on the surface facing the pressure surface 14p side of the inlet-side blade forming member 15. Has been. The first hole 18A and the second hole 18B are connected to each other.

  Therefore, the internal space 16 is not sealed and is open to the pressure surface 14p side. Thereby, when the Francis turbine 100 is operated, the water on the pressure surface 14 p side of the blade body 14 flows into the internal space 16. Further, the inlet-side flow surface 15n and the negative pressure surface 14n of the blade body 14 of the present embodiment are in a state in which water on the pressure surface 14p side flows into the internal space 16 when the Francis turbine 100 is operated at the design drop and the design flow rate. As shown by the solid line in FIG. 3, it is configured to smoothly and continuously form a streamline.

  The operation of the present embodiment will be described.

  In the present embodiment, when the operating point is on the high head side, the relative angle β1 of the flow flowing into the runner blade 13 becomes larger than the inlet angle βb of the runner blade 13 as shown in FIG. Due to the angle mismatch, the pressure on the inlet side of the suction surface 14n, that is, the pressure around the inlet-side water flow surface 15n in the runner blade 13 decreases. At this time, since the pressure of the water flowing into the internal space 16 of the inlet-side blade forming member 15 becomes higher than the pressure around the inlet-side water surface 15n, the inlet-side water surface 15n is indicated by a broken line in FIG. As shown, project to the mainstream water side. At the time of protrusion, the shape of the inlet-side water surface 15n is deformed so as to follow the surrounding flow, as in the first embodiment.

  Thereby, according to this Embodiment, even if it is a driving | running | working by the side of a high head, generation | occurrence | production of the cavitation by the mismatch of a flow angle is suppressed because the inlet angle (beta) b of the runner blade 13 approaches relative angle (beta) 1. Further, the shape of the inlet-side flow surface 15n is deformed so as to follow the flow around it, so that sudden pressure changes before and after the inlet-side flow surface 15n are alleviated. The occurrence of cavitation on the downstream side of 15n is suppressed.

  On the other hand, when the operating point is on the low head side, as shown in FIG. 8, the relative angle β1 of the flow flowing into the runner blade 13 becomes smaller than the inlet angle βb of the runner blade 13, and the flow angle Due to the mismatch, the flow is separated at the inlet side of the pressure surface 14p in the runner blade 13, and the pressure around the inlet side of the pressure surface 14p is rapidly reduced. At this time, the pressure of the water flowing into the internal space 16 of the inlet-side blade forming member 15 also decreases, and the pressure around the inlet-side flow surface 15n becomes higher than the water pressure of the internal space 16, so that the inlet The side water surface 15n is recessed toward the pressure surface 14p.

  Thereby, according to the present embodiment, even when the operation is on the low head side, the separation angle vortex is prevented from being generated due to the mismatch of the flow angles because the inlet angle βb of the runner blade 13 approaches the relative angle β1. .

  Therefore, in this Embodiment, generation | occurrence | production of a cavitation and peeling vortex can be suppressed effectively and the operation range of the Francis turbine 100 which is a hydraulic machine can fully be expanded. Specifically, according to the present embodiment, the initial line L11 in FIG. 6 can be separated to the high head side like the solid initial line L1 in the drawing. In addition, the initial line L12 can be separated to the low head side like the solid initial line L2 in the figure. As a result, the operating range can be expanded over a wider range as indicated by arrows α and β in the figure.

  In addition, in the present embodiment, the pressure surface 14p of the blade body 14 and the internal space 16 communicate with each other, so that the pressure on the inlet-side flow surface 15n can be appropriately adjusted without adjusting the pressure in the internal space 16 depending on the operating state. The shape changes. Therefore, it is not necessary to install a work for adjusting the pressure in the internal space 16 and a mechanism for adjusting the pressure, and thus an advantage relating to the manufacturing cost can be obtained.

(Third embodiment)
Next, a third embodiment will be described. Components similar to those of the first and second embodiments in the present embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 4, also in the present embodiment, the runner blade 13 is provided inside the blade body 14 and the inlet side of the blade body 14, and an inlet side that exposes a part of the runner blade 13 to the outside of the blade body 14. A part of the inlet-side blade forming member 15 exposed to the outside of the blade body 14 forms an inlet-side flowing water surface 15p that is continuous with the pressure surface 14p of the blade body 14. Yes. That is, the pressure surface of the runner blade 13 is composed of the pressure surface 14p of the blade body 14 and the inlet-side flowing water surface 15p.

  The inlet-side blade forming member 15 in the present embodiment is made of a hollow elastic body, and is aligned with the accommodating portion 14C formed in the blade main body 14 in a sectional view along the radial direction of the runner 4 in the blade main body 14. It is formed in a substantially rectangular shape whose longitudinal direction extends in the flowing water direction and has an internal space 16. The internal space 16 is sealed and its pressure is set to a second predetermined value. In addition, 14 C of accommodating parts in this Embodiment are open | released to the pressure surface side.

  As an example, the second predetermined value is that the Francis turbine 100 is operated at the most efficient design point (design head and design flow rate) at which the relative angle of the flow flowing into the runner 4 matches the inlet angle of the runner blade 13. It is a value equivalent to the pressure value of the water flowing on the pressure surface 14p side. In the present embodiment, in order to set the pressure in the internal space 16 to such a second predetermined value, a fluid (air or high pressure) in which the pressure is adjusted in the internal space 16 as in the first embodiment. Water, etc.) is enclosed in advance.

  In the inlet-side blade forming member 15 in the present embodiment, the shape of the inlet-side flowing water surface 15p on the side in contact with the mainstream water is, for example, shown in FIG. 4 depending on the relationship (difference) between the surrounding pressure conditions and the pressure conditions in the internal space 16. It is possible to change to the state shown by the broken line. It should be noted that the inlet-side flow surface 15p and the pressure surface 14p of the blade body 14 of the present embodiment are smooth as shown by the solid line in FIG. 4 when the Francis turbine 100 is operated with a design drop and a design flow rate. It is comprised so that a streamline may be made continuously.

  The operation of the present embodiment will be described.

  In the present embodiment, when the Francis turbine 100 is operated with the design head and the design flow rate, the pressure of the internal space 16 of the inlet blade formation member 15 and the pressure of the water flowing on the pressure surface 14p side are the same. By balancing, as shown by the solid line in FIG. 4, the inlet-side water surface 15p and the pressure surface 14p of the blade body 14 are smoothly and continuously streamlined.

  On the other hand, when the operating point is on the low head side, as shown in FIG. 4, the relative angle β1 of the flow flowing into the runner blade 13 is smaller than the inlet angle βb (not shown) of the runner blade 13, Due to the mismatch of the flow angles, the flow is separated at the inlet side of the pressure surface 14p in the runner blade 13, and the pressure around the inlet side of the pressure surface 14p, that is, the inlet-side flowing water surface 15p rapidly decreases. At this time, the pressure in the internal space 16 of the inlet-side blade forming member 15 is higher than the pressure around the inlet-side water surface 15p, so that the inlet-side water surface 15p has the mainstream water as shown by the broken line in FIG. Project to the side. At the time of protrusion, the shape of the inlet-side water surface 15p is deformed so as to follow the surrounding flow.

  As a result, according to the present embodiment, the entrance angle βb of the runner blade 13 approaches the relative angle β1 as indicated by the arrow A2 in the figure, so that the generation of separation vortices due to the mismatch of the flow angles is suppressed. In addition, the shape of the inlet-side flow surface 15p is deformed so as to follow the surrounding flow, so that sudden pressure changes before and after the inlet-side flow surface 15p are alleviated.

  Therefore, according to this Embodiment, generation | occurrence | production of peeling vortex can be suppressed effectively and the operation range of Francis turbine 100 which is a hydraulic machine can fully be expanded. Specifically, according to the present embodiment, the initial line L12 in FIG. 6 can be separated to the low head side as the solid initial line L2 in the figure. As a result, the operating range can be expanded over a wider range as indicated by the arrow β in the figure.

(Fourth embodiment)
Next, a fourth embodiment will be described. Components similar to those of the first to third embodiments in the present embodiment are denoted by the same reference numerals, and description thereof is omitted. In particular, part of the description of the same operations and effects as those of the third embodiment is also omitted.

  The inlet side blade forming member 15 of the present embodiment is provided at the same position as that of the third embodiment. On the other hand, as shown in FIG. 5, in the present embodiment, the communication path 18 that communicates the internal space 16 from the portion of the suction surface 14 n of the blade body 14 that faces the inlet-side blade forming member 15 in the blade thickness direction. Is formed across the blade body 14 and the inlet-side blade forming member 15.

  The communication path 18 includes a first hole portion 18A extending from the negative pressure surface 14n to the accommodating portion 14C, and a second hole portion 18B formed on the surface of the inlet side blade forming member 15 facing the negative pressure surface 14n side. Has been. The first hole 18A and the second hole 18B are connected to each other.

  Therefore, the internal space 16 is not sealed and is open to the negative pressure surface 14n side. Thereby, when the Francis turbine 100 is operated, the water on the negative pressure surface 14 n side of the blade body 14 flows into the internal space 16. In addition, the inlet-side flow surface 15p and the pressure surface 14p of the blade body 14 of the present embodiment are in a state where water on the negative pressure surface 14n side flows into the internal space 16 during operation of the Francis turbine 100 at the design drop and design flow rate. As shown by the solid line in FIG. 5, it is configured to smoothly and continuously form a streamline.

  The operation of the present embodiment will be described.

  In the present embodiment, when the operating point is on the low head side, as shown in FIG. 5, the relative angle β1 of the flow flowing into the runner blade 13 is larger than the inlet angle βb (not shown) of the runner blade 13. Due to the smaller flow angle, the flow is separated at the inlet side of the pressure surface 14p in the runner blade 13 and the pressure around the inlet side of the pressure surface 14p, that is, the inlet-side flowing water surface 15p rapidly decreases. At this time, since the pressure in the internal space 16 of the inlet-side blade forming member 15 is higher than the pressure around the inlet-side water surface 15p, the inlet-side water surface 15p has a mainstream water as shown by the broken line in FIG. Project to the side. At the time of protrusion, the shape of the inlet-side water surface 15p is deformed so as to follow the surrounding flow.

  As a result, according to the present embodiment, even in the operation on the low head side, the inlet angle βb of the runner blade 13 is the relative angle β1 as shown by the arrow A2 in the figure, as in the third embodiment. By approaching, generation of separation vortices due to inconsistent flow angles is suppressed. In addition, the shape of the inlet-side flow surface 15p is deformed so as to follow the surrounding flow, so that sudden pressure changes before and after the inlet-side flow surface 15p are alleviated.

  On the other hand, when the operating point on the high head side is reached, as shown in FIG. 7, the relative angle β1 of the flow flowing into the runner blade 13 becomes larger than the inlet angle βb of the runner blade 13, and the flow angle Due to the mismatch, the pressure around the inlet side of the suction surface 14n in the runner blade 13 is reduced. At this time, the pressure of the water flowing into the internal space 16 of the inlet-side blade forming member 15 also decreases, and the pressure around the inlet-side flow surface 15p becomes higher than the water pressure of the internal space 16, so that the inlet The side flow surface 15p is recessed toward the negative pressure surface 14n.

  Thereby, according to this Embodiment, even if it is a driving | running | working by the side of a high head, generation | occurrence | production of the cavitation by the mismatch of a flow angle is suppressed because the inlet angle (beta) b of the runner blade 13 approaches relative angle (beta) 1.

  Therefore, according to this Embodiment, generation | occurrence | production of a cavitation and peeling vortex can be suppressed effectively and the operation range of the Francis turbine 100 which is a hydraulic machine can fully be expanded. Specifically, according to the present embodiment, the initial line L11 in FIG. 6 can be separated to the high head side like the solid initial line L1 in the drawing. In addition, the initial line L12 can be separated to the low head side like the solid initial line L2 in the figure. As a result, the operating range can be expanded over a wider range as indicated by arrows α and β in the figure.

  Although the embodiment of the present invention has been described above, the above embodiment is presented as an example, and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, in each of the above-described embodiments, the inlet-side blade forming member 15 has the internal space 16, but instead of this, the inlet-side blade forming member 15 has a solid shape that has substantially no internal space. In addition, the elastic body may be formed of an elastic body that expands and contracts in accordance with a change in pressure around the surrounding area. An example of such a member is a porous elastic body.

1 casing, 2 stay vanes, 3 guide vanes, 4 runners, 5 suction pipes, 6 turbine main shafts, 7 generators, 11 crowns, 12 bands, 13 runner blades, 14 blade bodies, 14C accommodating portions, 14n suction surfaces, 14p pressure surfaces , 15 inlet side blade forming member, 15n inlet side flow surface, 15p inlet side flow surface, 16 internal space, 18 communication passage, 18A first hole, 18B second hole, 100 Francis turbine (hydraulic machine).

Claims (7)

A hydraulic machine runner,
A runner blade having a blade body and an inlet-side blade forming member provided inside the blade body on the inlet side and exposing a part thereof to the outside of the blade body;
The part of the inlet-side blade forming member that is exposed to the outside of the blade body forms an inlet-side water surface that is continuous with the suction surface or pressure surface of the blade body,
The runner characterized in that the inlet-side blade forming member is formed so as to change the shape of the inlet-side water surface in accordance with a change in pressure around the inlet-side blade forming member. The inlet side blade forming member is provided such that the inlet side flowing water surface is continuous with the negative pressure surface of the blade body,
The inlet side blade forming member has an internal space,
The runner according to claim 1, wherein the internal space is sealed and the pressure is set to a first predetermined value. The inlet side blade forming member is provided such that the inlet side flowing water surface is continuous with the negative pressure surface of the blade body,
The inlet side blade forming member has an internal space,
2. The runner according to claim 1, wherein a communication passage that communicates the internal space from a pressure surface of the blade body is formed across the blade body and the inlet-side blade forming member. The inlet side blade forming member is provided such that the inlet side flowing water surface is continuous with the pressure surface of the blade body,
The inlet side blade forming member has an internal space,
2. The runner according to claim 1, wherein the internal space is sealed and the pressure is set to a second predetermined value. The inlet side blade forming member is provided such that the inlet side flowing water surface is continuous with the pressure surface of the blade body,
The inlet side blade forming member has an internal space,
2. The runner according to claim 1, wherein a communication path that communicates the internal space from the suction surface of the blade body is formed across the blade body and the inlet-side blade forming member.   The runner according to claim 1, wherein the inlet-side blade forming member is formed of a solid elastic body that expands and contracts in accordance with a change in pressure around the inlet-side blade forming member.   A hydraulic machine comprising the runner according to claim 1.

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