Vertical pump

Abstract

To provide a vertical shaft pump capable of inhibiting occurrence of air suction vortexes.SOLUTION: A vertical shaft pump includes vortex breakers 20 which are respectively disposed facing a suction casing 4 on left and right sides at the downstream side of the suction casing 4 which houses an impeller. The vortex breaker 20 has: a first vortex suppression plate 21; and a second vortex suppression plate 22 disposed at the downstream side of the first vortex suppression plate 21 in a main stream direction 17. The second vortex suppression plate 22 has a through hole 25 serving as a through part at a lower part.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a vertical pump, and more particularly to a vertical pump equipped with a vortex prevention device that suppresses the occurrence of air-suction vortices. [Background technology]

[0002] When using a vertical pump (hereinafter simply referred to as "pump") installed in a suction sump with a free surface, fluctuations in the water level in the suction sump or changes in specifications such as an increase in discharge volume when the pump is replaced can change the flow field within the suction sump, resulting in an air-sucking vortex that reaches from the water surface to the vicinity of the bellmouth, which is the suction port of the suction casing that houses the impeller.

[0003] This air-sucking vortex often occurs when the flow of fluid near the water surface in the suction sump passes through the suction casing, separating downstream from the suction casing and creating a swirling flow (hereafter referred to as "swirl flow"). If such a vortex is sucked into the pump, it can cause problems such as excessive vibration and reduced performance, and can also cause damage to the pump.

[0004] In order to prevent the occurrence of air suction vortices, a pump has been disclosed in which prevention plates 34 (vortex suppression plates) are arranged on the left and right downstream sides of the pump suction pipe 30 (suction casing) (see paragraph 0006 and Figure 11 of Patent Document 1).

[0005] The pump described in Patent Document 1 suppresses the generation of swirling flow downstream of the pump suction pipe 30 by allowing flow from the upstream side of the pump suction pipe 30 to pass between the pump suction pipe 30 and the prevention plate 34 and flow out from the downstream side. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-041200 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the pump described in Patent Document 1, if the flow velocity in the suction sump becomes high or if drift occurs upstream of the suction sump, the flow from the upstream side of the pump suction pipe 30 (suction casing) may separate at the outer middle part of the prevention plate 34 (vortex suppression plate), creating a swirling flow that can cause an air-intake vortex. In other words, installing a vortex suppression plate itself may cause an air-intake vortex to be generated.

[0008] Therefore, an object of the present invention is to provide a vertical pump that can better suppress the occurrence of air-sucking vortices that occur when the flow velocity in the suction tank increases. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the vertical pump according to the present invention comprises a suction casing that houses an impeller therein, and a vortex prevention device that suppresses the generation of air-suction vortices. The vortex prevention devices are disposed opposite the suction casing on the left and right sides of the downstream side of the suction casing in the mainstream direction of fluid in a suction tank in which the suction casing is installed. The vortex prevention device comprises a first vortex suppression plate and a second vortex suppression plate disposed downstream of the first vortex suppression plate in the mainstream direction. The second vortex suppression plate has a through portion at its lower portion that includes at least one of a through hole and a notch. The first vortex suppression plate is disposed farther from the central axis of the suction casing than the second vortex suppression plate. are. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a vertical pump that can further suppress the occurrence of air-suction vortices. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic vertical cross-sectional view of a vertical pump according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is an enlarged side view showing the periphery of the vortex prevention device according to the present embodiment. [Figure 3]FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is an enlarged perspective view showing the periphery of the vortex prevention device according to the present embodiment. [Figure 5] FIG. 2 is a front view of the periphery of the vortex prevention device according to the present embodiment, viewed from the upstream side. [Figure 6] FIG. 2 is a rear view of the vortex prevention device and its periphery according to the present embodiment, viewed from the downstream side. [Figure 7] FIG. 2 is a side view of the periphery of the vortex prevention device according to the present embodiment, viewed from the right side. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] FIG. 1 is a plan view schematically showing the flow around a vortex prevention device composed of one vortex suppression plate. [Figure 10] FIG. 2 is a plan view schematically showing the flow around the vortex suppression device of the present embodiment, which is divided into a first vortex suppression plate and a second vortex suppression plate. [Figure 11] 10 is a perspective view seen from the outside of the second vortex suppression plate, schematically showing the flow around the through-holes in the second vortex suppression plate. FIG. [Figure 12] 10 is a perspective view seen from the inside of the second vortex suppression plate, schematically showing the flow around the through-holes in the second vortex suppression plate. FIG. [Figure 13] FIG. 10 is a rear view of the periphery of the vortex prevention device according to the modified example, viewed from the downstream side. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the drawings shown below, common or similar components are denoted by the same reference numerals, and redundant explanations will be omitted where appropriate. Furthermore, the size and shape of components may be exaggerated or distorted for ease of explanation.

[0013] FIG. 1 is a schematic vertical cross-sectional view of a vertical pump 100 according to an embodiment of the present invention. As shown in FIG. 1, a vertical pump 100 is installed in, for example, a water channel 1 (suction tank) of a drainage pumping station.

[0014] The vertical shaft pump 100 comprises a rotating shaft 2 extending in the vertical direction, an impeller 3 attached to the lower end of the rotating shaft 2, and a suction casing 4 that houses the impeller 3. The suction casing 4 is installed at a predetermined distance from the base 12 of the waterway 1, the left and right side wall surfaces 15 of the waterway 1, and the downstream wall surface 16 of the waterway 1.

[0015] The suction casing 4 includes a casing liner 41, a bell mouth (suction port) 42, and a bowl portion 43. The casing liner 41 is disposed on the shroud side of the impeller 3. The bell mouth 42 is disposed below the casing liner 41. The bowl portion 43 is disposed above the casing liner 41. In this vertical pump 100, a mixed flow pump is used, which discharges fluid from the impeller 3 in a direction oblique to the rotating shaft 2.

[0016] The vertical pump 100 also includes a lifting pipe 5, a discharge bend 6, and a prime mover 7. The lifting pipe 5 is connected to the upper side of the suction casing 4, and the rotating shaft 2 is inserted through it, causing the fluid to flow vertically upward. The discharge bend 6 is connected to the upper side of the lifting pipe 5, and changes the flow of the fluid sent from the lifting pipe 5 to a horizontal direction. The prime mover 7 is connected to the upper end of the rotating shaft 2 that protrudes above the discharge bend 6, and is a motor or the like that rotates the rotating shaft 2.

[0017] A drain pipe 8 is connected to the end of the discharge bend 6 opposite the lift pipe 5. The vertical pump 100 is inserted into the mounting hole 10 from the suction end side, and is installed in the waterway 1 so that a flange 9 provided on the discharge bend 6 is supported on the pump installation floor 11.

[0018] When the impeller 3 is rotated via the rotating shaft 2 by the drive of the prime mover 7, the water flowing in from the bell mouth 42 is pressurized and discharged through the suction casing 4, the lift pipe 5, the discharge bend 6 and the drain pipe 8 into the discharge channel (not shown).

[0019] The vertical pump 100 of this embodiment is provided with a vortex prevention device 20 that suppresses the generation of air-sucking vortices that reach the vicinity of the bell mouth from the water surface.

[0020] FIG. 2 is an enlarged side view showing the periphery of the vortex prevention device 20 according to this embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is an enlarged perspective view showing the periphery of the vortex prevention device 20 according to this embodiment. FIG. 5 is a front view of the periphery of the vortex prevention device 20 according to this embodiment, seen from the upstream side. FIG. 6 is a rear view of the periphery of the vortex prevention device 20 according to this embodiment, seen from the downstream side, i.e., a view from A in FIG. 2. FIG. 7 is a side view of the periphery of the vortex prevention device 20 according to this embodiment, seen from the right side. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 3. Note that the internal configurations of the suction casing 4 and the riser pipe 5 are omitted in FIGS. 3 and 8.

[0021] 2 to 4, the vortex prevention devices 20 are disposed facing the suction casing 4 on the left and right sides (see FIG. 3) of the downstream side of the suction casing 4 in the main flow direction 17 of the fluid in the waterway 1 in which the suction casing 4 is installed. The vortex prevention devices 20 are disposed radially outward of the suction casing 4 at a distance from the suction casing 4.

[0022] The vortex suppression device 20 has a first vortex suppression plate 21 and a second vortex suppression plate 22. The second vortex suppression plate 22 is disposed downstream of the first vortex suppression plate 21 in the main flow direction 17. The first vortex suppression plate 21 is disposed farther away from the central axis CL of the suction casing 4 than the second vortex suppression plate 22. The first vortex suppression plate 21 and the second vortex suppression plate 22 are plates with the same length in the up-down direction.

[0023] As shown in Figure 4, the first vortex suppression plate 21 is attached to the suction casing 4 or the riser pipe 5 via support plates 31, 31 whose base ends are fixed to the inner surface of the first vortex suppression plate 21. The second vortex suppression plate 22 is attached to the suction casing 4 or the riser pipe 5 via support plates 32, 32 whose base ends are fixed to the inner surface of the second vortex suppression plate 22. Here, the tips of the upper support plates 31, 32 are fixed by welding or the like to a flange 51 provided at the lower end of the riser pipe 5. In addition, the tips of the lower support plates 31, 32 are fixed by welding or the like to a flange 44 provided at the lower end of the bowl portion 43.

[0024] The locations where the tips of the support plates 31, 32 are fixed may be anywhere on the suction casing 4 or the lifting pipe 5, and can be changed as appropriate. The width and thickness of the first vortex suppression plate 21 and the second vortex suppression plate 22 can be changed as appropriate, and the vertical length is determined taking into account the highest and lowest water levels of the water to be suctioned when the vertical pump 100 is in use.

[0025] As shown in FIGS. 5 to 8 , the second vortex suppression plate 22 has through-holes 25 in its lower portion as through-holes through which a flow passes from the inside to the outside. The through-holes 25 are, for example, long in the direction along the central axis CL of the suction casing 4, i.e., are axially elongated. Here, three through-holes 25 are provided in each of the left and right second vortex suppression plates 22, but the number of through-holes 25 is not particularly limited. The through-holes 25 are provided only in the lower portion of the second vortex suppression plate 22, and are not provided in the first vortex suppression plate 21. Specifically, the through-holes 25 are provided only in a region extending from the lower end of the second vortex suppression plate 22 to within one-third, preferably within one-quarter, of the vertical length of the second vortex suppression plate 22. Here, the through-holes 25 are provided below the lower support plate 32. The function of the through-holes 25 will be described later.

[0026] Furthermore, the second vortex suppression plate 22 has a convex structure 27 that protrudes inward below the through hole 25. The convex structure 27 has a right-angled triangular cross section when cut along a plane (vertical plane) including the central axis CL of the suction casing 4 (see FIGS. 2 to 4), and extends circumferentially inside the second vortex suppression plate 22. The convex structure 27 has an inclined surface 28 that slopes downward toward the inside. The convex structure 27 is formed, for example, separately from the second vortex suppression plate 22 and fixed to the second vortex suppression plate 22 by a fastening means such as welding, but the present invention is not limited to this and the convex structure 27 may be formed integrally with the second vortex suppression plate 22. The function of the convex structure 27 will be described later.

[0027] As shown in FIG. 3, the first vortex suppression plate 21 is an arc-shaped plate having a first radius R1 (see FIG. 3) centered on the central axis CL. The second vortex suppression plate 22 is an arc-shaped plate having a second radius R2 (see FIG. 3) centered on the central axis CL. Here, the first vortex suppression plate 21 and the second vortex suppression plate 22 are formed of plates of the same thickness. The first radius R1 is indicated as the inner radius, and the second radius R2 is indicated as the outer radius. The first radius R1 is set to be larger than the second radius R2.

[0028] The downstream end 23 of the first vortex suppression plate 21 in the main flow direction 17 and the upstream end 24 of the second vortex suppression plate 22 in the main flow direction 17 overlap in the circumferential direction about the central axis CL. In other words, when viewed from a position on the central axis CL, there is no gap in the circumferential direction between the first vortex suppression plate 21 and the second vortex suppression plate 22.

[0029] Next, the operation of the vertical pump 100 configured as above will be described. As shown in Figure 1, when the water level to be suctioned in the waterway 1 exceeds the lower end of the bell mouth 42 (see water level L1 in Figure 1) and the bell mouth 42 is fully submerged, when the vertical pump 100 is started, the rotation of the impeller 3 causes water to be sucked in through the bell mouth 42, pressurized, and sent through the suction casing 4, the lift pipe 5, the discharge bend 6, and to the drain pipe 8.

[0030] If the vertical pump 100 were not equipped with the vortex breaker 20, the flow of the fluid near the water surface in the water passage 1 could separate downstream of the suction casing 4 as it passed through the suction casing 4, causing a swirling flow. In this case, an air-sucking vortex could occur, reaching from the water surface to near the bell mouth 42 of the suction casing 4. However, in this embodiment, the flow from the upstream side in the main flow direction 17 of the suction casing 4 passes between the suction casing 4 and the vortex prevention device 20 and flows out from the downstream side. This suppresses the generation of a swirling flow downstream of the suction casing 4, thereby suppressing the occurrence of an air-intake vortex.

[0031] Next, further operations of the vortex prevention device 20 will be described with reference to FIGS. FIG. 9 is a plan view schematically showing the flow around a vortex prevention device 35 composed of a single vortex suppression plate 36. FIG. 10 is a plan view schematically showing the flow around a vortex prevention device 20 of this embodiment composed of a first vortex suppression plate 21 and a second vortex suppression plate 22. FIG. 11 is a perspective view seen from the outside of the second vortex suppression plate 22, schematically showing the flow around the through-hole 25 in the second vortex suppression plate 22. FIG. 12 is a perspective view seen from the inside of the second vortex suppression plate 22, schematically showing the flow around the through-hole 25 in the second vortex suppression plate 22.

[0032] As shown in Figure 9, when one vortex suppression plate 36 is used, the flow from the upstream side in the main flow direction 17 of the suction casing 4 is divided into a flow that passes outside the vortex suppression plate 36 and a flow that passes inside the vortex suppression plate 36. If the specifications of the vertical pump are changed when it is updated and the flow velocity in the suction sump increases, the flow that passes outside the vortex suppression plate 36 may separate at the outer middle part of the vortex suppression plate 36, generating a swirling flow 37 that can cause an air-intake vortex. Here, the outside refers to the outside in the radial direction centered on the central axis CL, and the inside refers to the inside in the radial direction centered on the central axis CL.

[0033] 10 to 12 is used, a radial gap is generated around the central axis CL between the first vortex suppression plate 21, which has a large first radius R1, and the second vortex suppression plate 22, which has a small second radius R2. As a result, part of the flow passing inside the first vortex suppression plate 21 passes through the radial gap and outside the second vortex suppression plate 22. This suppresses the generation of a swirling flow (see swirling flow 37 in FIG. 9) in the outer middle part of the vortex suppression device 20, thereby suppressing the occurrence of air-ingesting vortices.

[0034] Furthermore, since the second vortex suppression plate 22 has the through-holes 25 in its lower portion, a through-flow 38 is generated that passes through the through-holes 25 from the inside to the outside. For example, when the water level drops further from the water level L1 in FIG. 1 to the low water level LWL in FIG. 11, the flow 39 from the gap between the first vortex suppression plate 21 and the second vortex suppression plate 22 alone may not be sufficient to suppress the generation of air-ingesting vortices. In this case, the through-flow 38 that passes through the through-holes 25 can be merged with the flow 39 from the gap between the first vortex suppression plate 21 and the second vortex suppression plate 22 on the outside of the second vortex suppression plate 22. In this way, the through-holes 25 provided in the lower portion of the second vortex suppression plate 22 more effectively suppress the generation of swirling flows, thereby further strengthening the suppression of the generation of air-ingesting vortices.

[0035] Furthermore, in this embodiment, a convex structure 27 is provided on the inside below the through-hole 25. Of the flows that have passed inside the first vortex suppression plate 21 (on the central axis CL side), those that do not flow into the gap between the first vortex suppression plate 21 and the second vortex suppression plate 22 are guided by the inclined surface 28 of the convex structure 27 and directed toward the through-hole 25. As a result, a larger amount of the through-flow 38 can be made to merge with the flow 39 from the gap between the first vortex suppression plate 21 and the second vortex suppression plate 22.

[0036] As described above, the vertical pump 100 according to this embodiment is equipped with vortex suppression devices 20 disposed on the left and right sides of the downstream side of the suction casing 4, which houses the impeller 3, facing the suction casing 4. The vortex suppression devices 20 each have a first vortex suppression plate 21 and a second vortex suppression plate 22 disposed downstream of the first vortex suppression plate 21 in the main flow direction 17. The second vortex suppression plate 22 has a through-hole 25 at its bottom as a penetration portion.

[0037] In this embodiment, the flow from the upstream side passes between the suction casing 4 and the vortex prevention device 20 and flows out from the downstream side, thereby suppressing the generation of swirling flow downstream of the suction casing 4. In addition, a portion of the flow passing inside the first vortex suppression plate 21 passes through the gap between the first vortex suppression plate 21 and the second vortex suppression plate 22 and passes outside the second vortex suppression plate 22, thereby suppressing the generation of swirling flow in the outer middle part of the vortex prevention device 20. Furthermore, outside the second vortex suppression plate 22, the through-flow 38 passing through the through-holes 25 can be merged with the flow 39 from the gap between the first vortex suppression plate 21 and the second vortex suppression plate 22. This more effectively suppresses the generation of swirling flows, further reinforcing the suppression of air-ingestion vortices. Therefore, according to this embodiment, it is possible to provide a vertical pump 100 that can further suppress the occurrence of air-suction vortices.

[0038] In this embodiment, the vortex suppression device 20 is divided into two parts, the first vortex suppression plate 21 and the second vortex suppression plate 22, in the main flow direction 17, but this is not limited to this and the device may be divided into three or more parts.

[0039] Furthermore, in this embodiment, the first vortex suppression plate 21 is disposed farther away from the central axis CL of the suction casing 4 than the second vortex suppression plate 22. In this configuration, part of the flow passing inside the first vortex suppression plate 21 passes through a radial gap centered on the central axis CL between the first vortex suppression plate 21 and the second vortex suppression plate 22 and easily passes outside the second vortex suppression plate 22. This further suppresses the generation of swirling flow in the outer middle portion of the vortex prevention device 20.

[0040] In this embodiment, the first vortex suppression plate 21 is an arc-shaped plate having a first radius R1 centered on the central axis CL, and the second vortex suppression plate 22 is an arc-shaped plate having a second radius R2 centered on the central axis CL. The first radius R1 is set to be larger than the second radius R2. With this configuration, the flow around the vortex suppression device 20 becomes smoother, including the flow passing inside the first vortex suppression plate 21 and outside the second vortex suppression plate 22.

[0041] Furthermore, in this embodiment, the downstream end 23 of the first vortex suppression plate 21 and the upstream end 24 of the second vortex suppression plate 22 overlap in the circumferential direction about the central axis CL. With this configuration, there is no circumferential gap between the first vortex suppression plate 21 and the second vortex suppression plate 22. This allows a portion of the flow passing inside the first vortex suppression plate 21 to pass outside the second vortex suppression plate 22 more reliably, and the generation of a swirling flow in the outer intermediate portion of the vortex prevention device 20 is further suppressed.

[0042] Furthermore, in this embodiment, the second vortex suppression plate 22 has a convex structure 27 that protrudes inward below the through-holes 25. With this configuration, of the flows that pass inside the first vortex suppression plate 21, those that do not flow into the gaps between the first vortex suppression plate 21 and the second vortex suppression plate 22 are guided by the convex structure 27 and directed toward the through-holes 25. As a result, a larger amount of the through-flow 38 can be merged with the flow 39 from the gaps between the first vortex suppression plate 21 and the second vortex suppression plate 22. This further suppresses the generation of swirling flows, further enhancing the vortex generation suppression effect.

[0043] In this embodiment, the convex structure 27 has an inclined surface 28 that slopes downward toward the inside. With this configuration, the flow that has passed inside the first vortex suppression plate 21 but has not flowed into the gap between the first vortex suppression plate 21 and the second vortex suppression plate 22 is guided by the inclined surface 28 of the convex structure 27 and directed toward the through-holes 25.

[0044] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the described configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of the embodiments with other configurations.

[0045] For example, in the above-described embodiment, the second vortex suppression plate 22 has only the through-holes 25 in the lower portion thereof as a through-portion through which the flow passes, but this is not limited thereto. FIG. 13 is a rear view of the periphery of a vortex prevention device 20 according to a modified example, viewed from the downstream side. In the modified example shown in FIG. 13, the second vortex suppression plate 22 has a through-portion including both the through-holes 25 and the notches 26 in the lower portion thereof. This modified example can also achieve the same effects as the above-described embodiment. Furthermore, the second vortex suppression plate 22 may have only the notches 26 in the lower portion thereof as a through-portion. That is, it is sufficient that the second vortex suppression plate 22 has a through-portion including at least one of the through-holes and the notches in the lower portion thereof.

[0046] Furthermore, although the shape of the through hole 25 is an oval that is elongated in the axial direction in the above embodiment, it is not limited to this and may be, for example, a circle, an ellipse, a rectangle, a horizontally elongated slit shape, etc. Although the shape of the notch 26 is a semi-oval that is elongated in the axial direction in the above embodiment, it is not limited to this and may be, for example, a semi-circle, a semi-ellipse, a rectangle, a horizontally elongated slit shape, etc. In addition, although the cross-sectional shape of the convex structure 27 is a right triangle in the above embodiment, it is not limited to this and may be, for example, an isosceles triangle, a trapezoid, a semicircle, a semi-ellipse, etc. In addition, although the inclined surface 28 is a flat surface in the above embodiment, it may be a curved surface. In addition, although the first vortex suppression plate 21 and the second vortex suppression plate 22 are arc-shaped plates in the above-described embodiment, they are not limited to this and may be plates with any curved surface such as an ellipsoid, or flat plates. In the above embodiment, the vertical shaft pump of the present invention has been described as being applied to a mixed flow pump in which the flow discharged from the impeller 3 is within a conical surface whose axis is the rotary shaft 2, but the present invention is not limited to this. The vertical shaft pump of the present invention can also be applied to, for example, an axial flow pump in which the flow discharged from the impeller 3 is within a cylindrical surface concentric with the rotary shaft 2. [Explanation of symbols]

[0047] 1 Waterway (suction tank) 3 impeller 4. Suction casing 17 Mainstream direction 20 Vortex prevention device 21 First vortex suppressor plate 22 Second vortex suppressor plate 23 End 24 End 25 Through hole (through part) 26 Notch (through part) 27 Convex structure 28 Slope 100 Vertical pump R1 First radius R2 Second radius CL center axis

Claims

1. a suction casing that houses the impeller therein; and vortex prevention devices disposed opposite the suction casing on the left and right sides of the downstream side of the suction casing in the main flow direction of the fluid in the suction tank in which the suction casing is installed, for suppressing the generation of air-sucking vortices; the vortex prevention device includes a first vortex suppression plate and a second vortex suppression plate disposed downstream of the first vortex suppression plate in the main flow direction, the second vortex suppression plate has a through-hole or a notch at a lower portion thereof, and the first vortex suppression plate is disposed farther away from the central axis of the suction casing than the second vortex suppression plate.

2. the first vortex suppression plate is an arc-shaped plate having a first radius centered on the central axis, and the second vortex suppression plate is an arc-shaped plate having a second radius centered on the central axis, 2. The vertical pump according to claim 1, wherein the first radius is greater than the second radius.

3. 2. The vertical pump according to claim 1, wherein a downstream end of the first vortex suppression plate in the mainstream direction and an upstream end of the second vortex suppression plate in the mainstream direction overlap with each other in a circumferential direction about the central axis.

4. A suction casing that houses an impeller therein; and vortex prevention devices disposed opposite the suction casing on the left and right sides of the downstream side of the suction casing in the main flow direction of the fluid in the suction tank in which the suction casing is installed, for suppressing the generation of air-sucking vortices; the vortex prevention device includes a first vortex suppression plate and a second vortex suppression plate disposed downstream of the first vortex suppression plate in the main flow direction, the second vortex suppression plate has a through-portion at a lower portion thereof, the through-portion including at least one of a through-hole and a notch; the second vortex suppression plate has a convex structure that continuously protrudes inward in a circumferential direction below the through-portion and guides flow into the through-portion.

5. 5. The vertical shaft pump according to claim 4, wherein the convex structure has an inclined surface that slopes downward toward the inside.

Images