JP7178260B2 - Pump with vortex suppressor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump used for pumping water in a suction water tank, and more particularly to a pump equipped with a vortex suppression device for suppressing the generation of air-suction vortexes.

In the case of pump equipment that drains rivers and sewage, lowering the water level of the suction tank of the pump equipment is required due to uneven subsidence over time such as the inflow channel of the area subject to flood control on the upstream side. In addition, as a countermeasure against sudden rainfall such as the recent torrential downpour, there is a demand for an improvement in the pumping capacity of the pump.

However, at the suction port of the pump, as the water level drops (the water surface approaches the suction port), vortices can occur on the free surface of the water in the suction sump. When the vortex is drawn into the pump, it becomes an air intake vortex, and air enters the inside of the pump. In particular, a continuous vortex that continuously extends from the water surface to the suction port of the pump is a harmful air intake vortex that causes abnormal vibration of the pump. Such harmful air entrainment vortices can cause pump failure. Therefore, in order to prevent air from being sucked in, the bottom level of the suction water tank should be lowered, the position of the suction port of the pump should be lowered, or the suction water level should be limited, and the pump should not be operated below that water level. has traditionally been done.

However, the method of lowering the bottom level of the suction water tank increases civil engineering and construction costs. In addition, when the existing pump equipment is to be repaired, the construction period is long, and it is practically impossible to perform repair work including civil engineering work while the pump equipment is in operation. Furthermore, when the suction port approaches the bottom surface of the suction water tank, an underwater vortex is likely to occur from the bottom surface and side walls of the suction water tank.

As other vortex prevention measures, various attempts have been made, such as connecting a horizontally-opening suction pipe to the suction port of a pump (see Patent Document 1).

JP-A-2000-97199

In Patent Document 1, since the suction port is covered with a cylinder, the suction loss of the pump increases. In other words, there is a problem that it causes piping loss or efficiency deterioration, and deteriorates the drainage performance of the pump.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and provides a pump that can effectively prevent the generation of harmful air-suction vortices in the suction water tank without impairing the suction performance of the pump. intended to

In order to achieve the above object, one aspect of the present invention provides a pump for pumping up water in a suction water tank, comprising a main shaft extending in a vertical direction, an impeller fixed to the main shaft, and the impeller inside. and a plurality of vertical rods and a plurality of vertical ribs arranged outside the pump casing, wherein the plurality of vertical rods and the plurality of vertical ribs are located at the same height and the suction The plurality of vertical rods are arranged downstream of the main shaft with respect to the direction of water flow in the water tank, and the plurality of vertical rods are arranged with a gap between them and the outer peripheral surface of the pump casing. The vertical ribs are fixed to the outer peripheral surface of the pump casing, and the plurality of vertical bars and the plurality of vertical ribs are positioned inside an opening formed in the pump installation floor when viewed from the axial direction of the main shaft. wherein said plurality of vertical bars are arranged adjacent to said plurality of vertical ribs respectively , said vertical bars and said vertical ribs are spaced apart from each other, said vertical bars are positioned adjacent to said vertical ribs The pump is arranged radially outward of the pump casing .

A preferred aspect of the present invention is characterized in that the plurality of vertical bars and the plurality of vertical ribs are arranged symmetrically with respect to a straight line passing through the axis of the main shaft and parallel to the water flow direction.
A preferred aspect of the present invention is characterized in that the vertical bar is arranged on an extension line of a line connecting the axis of the main shaft and the vertical rib, or on the downstream side of the extension line.
In a preferred embodiment of the present invention, the pump casing includes a suction bell mouth having a suction port that opens downward, and the upper end of the vertical rod is located at the suction port, where d is the diameter of the discharge side of the pump casing. It is characterized by being located within a range of 0.8 d or more from the lower end of the bellmouth and not more than the operation start water level.
A preferred aspect of the present invention is characterized in that the lower end of the vertical bar is positioned below the upper end of the impeller.

One aspect of the present invention is a pump for pumping water in a suction water tank, comprising: a main shaft extending in a vertical direction; an impeller fixed to the main shaft; a pump casing housing the impeller inside; and a semi-cylindrical body disposed outside of the pump casing, the semi-cylindrical body being disposed downstream of the main shaft with respect to the flow direction of water in the suction water tank, and the semi-cylindrical body The semi-cylindrical body is fixed to the pump casing with a gap between it and the outer peripheral surface, and the semi-cylindrical body is positioned inside an opening formed in the pump installation floor when viewed from the axial direction of the main shaft. and wherein said semi-cylindrical body has an inner peripheral surface extending parallel to said main axis.

A preferred aspect of the present invention is characterized in that the pump casing includes a suction bell mouth having a downwardly opening suction port, and the semi-cylindrical body is fixed to the suction bell mouth.
A preferred aspect of the present invention is characterized in that an angle formed by two lines connecting the axis of the main shaft and both side edges of the semi-cylindrical body is 120° to 180°.
A preferred aspect of the present invention further includes an arc member fixed to the pump casing with a gap between it and the outer peripheral surface of the pump casing, and the arc member extends in the circumferential direction of the outer peripheral surface of the pump casing. and the arc member is arranged above the semi-cylindrical body.
A preferred aspect of the present invention is characterized in that an angle formed by two lines connecting the axis of the main shaft and both side edges of the arc member is 120° to 180°.
In a preferred aspect of the present invention, the arc member comprises a first arc member and a second arc member spaced apart from each other, and the first arc member and the second arc member are aligned with the axis of the main shaft. It is characterized by being arranged symmetrically with respect to a straight line parallel to the flow direction of the water passing through the center.
A preferred aspect of the present invention is characterized by further comprising the plurality of vertical bars and the plurality of vertical ribs.

The vertical rods and vertical ribs are provided on the downstream side of the main shaft, and can suppress the generation of air-suction vortices without causing suction loss and reducing the pumping capacity of the pump. In addition, since the pump itself has vertical rods and vertical ribs, there is no need to fasten it to the suction water tank, and no reinforcement work for the suction water tank is required. Furthermore, by combining the vertical rods and vertical ribs, it is possible to suppress the generation of air-suction vortices over a wide range of water levels and flow velocities in the suction water tank.

Similarly, the semi-cylindrical body and arc member are provided on the downstream side of the main shaft and cause almost no suction loss, so it is possible to suppress the occurrence of air suction vortices without reducing the pumping capacity of the pump. In addition, since the semi-cylindrical body and the circular arc member are installed in the pump casing, they do not need to be fastened to the suction water tank, and reinforcement work for the suction water tank is unnecessary.

1 is a schematic diagram of one embodiment of a pump with a vortex suppressor; FIG. It is a figure which shows the Karman vortex which generate|occur|produces on the downstream side of a pumping pipe. FIG. 4 is a diagram showing examples of dimensions associated with a pump bore; It is the figure which looked at the pump and suction water tank which are shown in FIG. 3 from the top. FIG. 4 is a side view showing vertical bars and vertical ribs as a first air-entrained vortex suppressor and a semi-cylindrical body as a second air-entrained vortex suppressor; FIG. 6 is a cross-sectional view taken along line AA of FIG. 5; It is a schematic diagram which shows the other fixing method of a vertical bar. FIG. 8 is a cross-sectional view taken along line BB of FIG. 7; FIG. 11 is a schematic diagram showing still another fixing method of the vertical bar; FIG. 10 is a cross-sectional view taken along line CC of FIG. 9; FIG. 4 shows water flow diverted by a pump casing or a lift pipe; It is a figure which shows the flow which goes to a suction port from a Karman vortex. FIGS. 13A and 13B are schematic diagrams showing modifications of the cross-sectional shape of the semi-cylindrical body. FIG. 11 is a side view of another embodiment of a pump; FIG. 15 is a cross-sectional view taken along line DD of FIG. 14; FIG. 11 is a top view of yet another embodiment of a pump; 2 is a bottom view of the plurality of underwater vortex suppression plates shown in FIG. 1; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. Although the embodiments described below relate to vertical shaft pumps, the present invention is not limited to these embodiments and can also be used with horizontal shaft pumps. Furthermore, the present invention can also be used for column pipe type submersible pumps. FIG. 1 is a schematic diagram illustrating one embodiment of a pump with a vortex suppressor. As shown in FIG. 1 , the pump 20 includes a vertically extending main shaft 32 , an impeller 31 fixed to the main shaft 32 , a pump casing 27 housing the impeller 31 inside, and an upper end of the pump casing 27 connected to the upper end of the pump casing 27 . and a curved discharge pipe 30 connected to the upper end of the pumping pipe 28 . The pump casing 27 is suspended inside the suction water tank 1 by a pumping pipe 28 . Pump casing 27 comprises suction bell mouth 22 , impeller casing 21 and discharge bowl 24 . The upper end of the discharge bowl 24 is connected to the lower end of the lift pipe 28 . The suction bell mouth 22 has a suction port 22a that opens downward. The upper end of suction bell mouth 22 is connected to the lower end of impeller casing 21 . Impeller 31 is housed within impeller casing 21 and discharge bowl 24 .

The pumping pipe 28 extends downward through an opening 5 formed in the pump installation floor 2 forming the upper wall of the suction water tank 1 . The pump 20 further includes a hanging pipe 33 , and the hanging pipe 33 is fixed to the upper end of the pumping pipe 28 . The hanging pipe 33 is fixed to a pump base 35 installed on the pump installation floor 2 . The pumping pipe 28 is fixed to the pump installation floor 2 via a suspension pipe 33 and a pump base 35 . The main shaft 32 extends vertically through the curved discharge pipe 30 , the pumping pipe 28 , and the pump casing 27 , and its lower end is located within the pump casing 27 .

Main shaft 32 is rotatably supported by outer bearing 45 and underwater bearing 41 . The outer bearing 45 is fixed to the upper portion of the discharge curved pipe 30 and supports the upper portion of the main shaft 32 . A water bearing 41 is housed within the discharge bowl 24 and supports the lower portion of the main shaft 32 . Disposed within discharge bowl 24 is inner bowl 25 , which is connected to discharge bowl 24 by a plurality of guide vanes 37 . The underwater bearing 41 is fixed to the inner peripheral surface of the inner bowl 25 via a support member 41a.

The main shaft 32 protrudes upward from the discharge curved pipe 30 and is connected to a prime mover (for example, a motor) not shown. The motor is configured to rotate the main shaft 32 and the impeller 31 . A plurality of guide vanes 37 are arranged above the impeller 31 (discharge side). A water flow path is formed between the inner peripheral surface of the discharge bowl 24 and the outer peripheral surface of the inner bowl 25 . When the impeller 31 rotates, the water in the suction water tank 1 is sucked from the suction port 22a of the suction bell mouth 22. - 特許庁As the impeller 31 rotates, the water is transferred through the discharge bowl 24, the pumping pipe 28, and the discharge curved pipe 30 to a discharge pipe (not shown).

The pump 20 comprises a plurality of vertical rods 61 and a plurality of vertical ribs 62 as a first air entrainment vortex suppression device for suppressing the generation of air entrainment vortexes, and a semi-cylindrical body 71 as a second air entrainment vortex suppression device. I have more. In FIG. 1 only one longitudinal bar 61 and one longitudinal rib 62 are shown. The vertical rod 61 , vertical rib 62 and semi-cylindrical body 71 are arranged outside the pump casing 27 . The vertical rod 61 , the vertical rib 62 and the semi-cylindrical body 71 are located inside the opening 5 when viewed from the axial direction of the main shaft 32 . Therefore, the entire pump 20 can be pulled up through the opening 5 when performing maintenance or repair of the pump 20 . Vertical rod 61 , vertical rib 62 , and semi-cylindrical body 71 are arranged downstream of main shaft 32 with respect to the direction of water flow in suction water tank 1 .

As the pumping capacity of the pump 20 is improved, the water flow velocity of the suction water tank 1 increases, and as a result, an underwater vortex is likely to occur from the bottom surface of the suction water tank 1 . Therefore, the pump 20 is provided with a plurality of underwater vortex suppression plates 49 as underwater vortex suppression devices for suppressing the underwater vortex generated between the suction bell mouth 22 and the bottom surface of the suction water tank 1 under the suction bell mouth 22. ing. The underwater vortex suppression plate 49 is a flat member.

As shown in FIG. 2, the air entrainment vortices are produced by the development of Karman vortices 7 which occur when the water flow forming the free surface is diverted by the lift pipe 28 or discharge bowl 24 . Karman vortices 7 are thus generated downstream of the lift pipe 28 or the discharge bowl 24 . Further, the Karman vortices 7 are swept downstream by the flow of water. Therefore, the vertical rod 61 , vertical rib 62 and semi-cylindrical body 71 are arranged downstream of the main shaft 32 .

FIG. 3 is a diagram showing an example of each dimension associated with the pump diameter, and FIG. 4 is a top view of the pump 20 and the suction water tank 1 shown in FIG. As shown in FIG. 3, assuming that the diameter of the pump (the diameter of the discharge side of the pump casing 27 in this embodiment) is d, the distance from the lower end of the suction bell mouth 22 (that is, the lower end of the pump casing 27) to the bottom of the suction water tank 1 is is generally 0.5d or more, and as an example is within the range of 0.75d to 1.0d. The distance from the center of the pump 20 (the axis O of the main shaft 32) to the rear wall of the suction water tank 1 is 1.5d or less. The diameter of the opening 5 is approximately determined by the pump diameter d, but in one embodiment is in the range 1.6d to 2.1d. As shown in FIG. 4, the water channel width of the suction water tank 1 is about 3.0 d. When designed with these dimensions, the minimum water level LWL of the suction water tank 1 at which the pump 20 can operate can be lowered by about 0.5d to 0.9d compared to the conventional pump.

FIG. 5 is a side view showing the vertical rod 61 and vertical rib 62 as the first air-entrained vortex suppressor and the semi-cylindrical body 71 as the second air-entrained vortex suppressor, and FIG. 1 is a cross-sectional view taken along line AA of FIG. In FIG. 5, illustration of the plurality of underwater vortex suppression plates 49 is omitted. As shown in FIGS. 5 and 6 , the pump 20 has a plurality of vertical bars 61 and a plurality of vertical ribs 62 . In this embodiment, two vertical bars 61 and two vertical ribs 62 are provided, but the number of vertical bars 61 and vertical ribs 62 is not limited to this embodiment.

Each vertical bar 61 extends generally along main axis 32 . Similarly, each longitudinal rib 62 extends generally along main axis 32 . The two vertical bars 61 and the two vertical ribs 62 are entirely positioned inside the opening 5 when viewed from the axial direction of the main shaft 32 . The vertical rods 61 and vertical ribs 62 extend vertically as a whole, and some of them may be curved. In this embodiment, part of the vertical rod 61 is curved along the outer peripheral surface of the pump casing 27, but the shape of the vertical rod 61 is not limited to this embodiment. In one embodiment, vertical bar 61 may have a linear shape extending parallel to main axis 32 .

Vertical bar 61 has a generally circular cross-sectional shape and extends axially of main shaft 32 . Each vertical bar 61 is arranged with a gap between it and the outer peripheral surface of the pump casing 27 . In this embodiment, each vertical rod 61 is connected to the outer peripheral surface of the pump casing 27 by a plurality of brackets 65 . That is, each vertical rod 61 is fixed to the pump casing 27 with a gap between the vertical rod 61 and the outer peripheral surface of the pump casing 27 .

In one embodiment, vertical rod 61 may be fixed to lift pipe 28 or suspension pipe 33 . FIG. 7 is a schematic diagram showing another fixing method of the vertical bar 61, and FIG. 8 is a cross-sectional view taken along line BB of FIG. As shown in FIGS. 7 and 8, the plurality of brackets 65 of this embodiment have an L-shape. A plurality of brackets 65 are attached to the flange 33 a of the suspension pipe 33 and the flange 28 a of the lift pipe 28 . Each of the two vertical bars 61 is fixed by a plurality of fasteners 67 to a bracket 65 attached to the flange 33a and to a bracket 65 attached to the flange 28a. Examples of the fixture 67 include U-bolts, U-bands, and the like. Although four brackets 65 and four fixtures 67 are provided in this embodiment, the number of brackets 65 and fixtures 67 is not limited to this embodiment.

FIG. 9 is a schematic diagram showing still another fixing method of the vertical bar 61, and FIG. 10 is a sectional view taken along line CC of FIG. As shown in FIGS. 9 and 10, the bracket 65 of this embodiment has a flat plate shape and includes an annular portion 68 and a plurality of vertical rod holding portions 69 . A plurality of vertical rod holding portions 69 are connected to the outer peripheral surface of the annular portion 68 and formed integrally with the annular portion 68 . Each of the vertical rod holding portions 69 has a through hole 69a. The bracket 65 is sandwiched and fixed between the flange 33 a of the hanging pipe 33 and the flange 28 b of the water lifting pipe 28 . Each vertical rod 61 is inserted into each through hole 69a and fixed to a vertical rod holding portion 69. As shown in FIG. In this embodiment, the bracket 65 has two vertical rod holders 69 and two through holes 69a, but the number of vertical rod holders 69 and through holes 69a is determined based on the number of vertical rods 61. Since it is determined, it is not limited to this embodiment.

According to the example of each dimension shown in FIG. 3, the upper end of the vertical bar 61 is positioned within the range of 0.8d to 1.75d from the lower end of the suction bell mouth 22. As shown in FIG. The lower end of the vertical rod 61 is located below the upper end of the impeller 31 (see FIG. 1).

As described above, the Karman vortices 7 (see FIG. 2) may occur on the free surface of the suction water tank 1 as the water level of the suction water tank 1 decreases. In order to suppress the generation of the Karman vortex 7, the upper end of the vertical bar 61 must be positioned above the water level of the suction water tank 1 when the Karman vortex 7 is generated. When the water channel width of the suction water tank 1 is about 3.0d and the distance from the center of the pump 20 (the axis O of the main shaft 32) to the rear wall of the suction water tank 1 is 1.5d or less, the minimum water level of the conventional pump is generally a water level above 2.5d. At a water level higher than the minimum water level of this conventional pump, the Karman vortex 7 is generally not generated, but depending on the shape of the suction water tank 1, the Karman vortex 7 may be generated. According to the example of each dimension shown in FIG. 3, since the pump 20 of this embodiment operates even at a water level lower than the minimum water level of the conventional pump, the upper end of the vertical rod 61 is positioned below the minimum water level of the conventional pump. Become. This is to suppress the occurrence of the Karman vortex 7 when the water level of the suction water tank 1 drops after the pump 20 starts operating. According to FIG. 3, since the distance from the lower end of the suction bell mouth 22 to the bottom of the suction water tank 1 is within the range of 0.75d to 1.0d, the upper end of the vertical bar 61 is located at the lower end of the suction bell mouth 22 to 0.8 d or more and less than or equal to the operation start water level. In one embodiment, the upper end of vertical bar 61 is located 0.8d to 1.75d from the lower end of suction bell mouth 22 .

In the embodiment described with reference to FIGS. 1 to 6, the longitudinal rib 62 has a curved shape along the outer peripheral surface of the pump casing 27 and extends in the axial direction of the main shaft 32 . The vertical rib 62 is fixed to the outer peripheral surface of the pump casing 27 and protrudes radially outward of the pump casing 27 from the outer peripheral surface of the pump casing 27 . In one embodiment, the upper portion of longitudinal rib 62 may be fixed to the outer peripheral surface of lift pipe 28 . Furthermore, in one embodiment, the longitudinal ribs 62 may be integrally formed with the pump casing 27 and/or the lift pipe 28 .

The two vertical bars 61 are arranged adjacent to the two vertical ribs 62 respectively. Each vertical rod 61 is located farther from the axis O of the main shaft 32 than the adjacent vertical rib 62 is. That is, the distance between the axis O of the main shaft 32 and the vertical rod 61 is longer than the distance between the axis O of the main shaft 32 and the vertical rib 62 . Similar to the vertical rod 61, the upper end of the vertical rib 62 must be positioned above the water level of the suction water tank 1 when the Karman vortices 7 are generated. In the embodiment shown in FIG. 5, the longitudinal ribs 62 are shorter than the longitudinal bars 61, but in one embodiment the longitudinal ribs 62 may be as long as the longitudinal bars 61 or longer than the longitudinal bars 61. .

In FIG. 6, the two vertical bars 61 are positioned downstream of the main shaft 32 with respect to the direction of water flow in the suction water tank 1, and are positioned with respect to a straight line RL parallel to the direction of water flow passing through the axis O of the main shaft 32. arranged symmetrically. Similarly, the two longitudinal ribs 62 are positioned downstream of the main shaft 32 with respect to the water flow direction, and are arranged symmetrically with respect to a straight line RL parallel to the water flow direction passing through the axis O of the main shaft 32. . In this embodiment, the two vertical bars 61 and the two vertical ribs 62 are arranged downstream of the water flow separation point on the outer peripheral surface of the pump casing 27 .

When the water level in the suction water tank 1 is high, the flow rate of water in the suction water tank 1 is low, and when the water level in the suction water tank 1 is low, the flow rate of water in the suction water tank 1 is high. The position where the Karman vortex 7 is generated changes depending on the water level of the suction water tank 1 and the flow velocity of water in the suction water tank 1 during pumping. The Karman vortex 7 is likely to occur near the outer peripheral surface of the pump casing 27 or the water discharge pipe 28 when the flow velocity of the water in the suction water tank 1 is low.

FIG. 11 is a diagram showing the flow of water split by the pump casing 27 or the pumping pipe 28. As shown in FIG. As shown by the arrows in FIG. 11 , the water near the outer peripheral surface of the pump casing 27 or the water pipe 28 diverted by the pump casing 27 or the water pipe 28 collides with the longitudinal ribs 62 and is disturbed. As a result, the vertical ribs 62 can suppress the occurrence of the Karman vortices 7 near the outer peripheral surface of the pump casing 27 or the pumping pipe 28 .

The vertical ribs 62 can effectively suppress the generation of air suction vortices when the water level in the suction water tank 1 is high (when the flow velocity of water in the suction water tank 1 is low). As an example, the vertical rib 62 has a height (radial length of the pump casing 27) of approximately 0.1 d and a width (circumferential length of the pump casing 27) of approximately 0.1 d. Occasionally, the occurrence of the Karman vortices 7 can be effectively suppressed.

The water that has collided with the longitudinal ribs 62 and has its flow disturbed flows outside the pump casing 27 and may generate the Karman vortices 7 at a position away from the pump casing 27 . It is also known that the Karman vortices 7 are likely to occur at a position distant from the pump casing 27 when the water level in the suction water tank 1 is relatively low (when the flow velocity of water in the suction water tank 1 is high). Therefore, in order to suppress the occurrence of such Karman vortices 7, the vertical rods 61 are arranged radially outside the vertical ribs 62 in the present embodiment. As indicated by arrows in FIG. 11 , some of the water collided with the vertical ribs 62 and flowed outside the pump casing 27 and part of the water diverted by the pump casing 27 or the water discharge pipe 28 collides with the vertical rods 61 . However, since it flows between the vertical rod 61 and the vertical rib 62 or around the vertical rod 61, the flow is disturbed. As a result, the vertical bar 61 can suppress the occurrence of the Karman vortices 7 at a position distant from the pump casing 27 .

When the water level of the suction water tank 1 further drops from the water level range of the suction water tank 1 in which the vertical ribs 62 can suppress the generation of the air suction vortex (that is, when the flow velocity of the water in the suction water tank 1 is high) In some cases, the generation of air entrainment vortices can be effectively suppressed. The Karman vortices 7 generated by the water that collides with the vertical ribs 62 and flowed outside the pump casing 27 are generated downstream of the vertical ribs 62 . Therefore, the vertical rod 61 is arranged downstream (see FIG. 6) of the extension of the line connecting the axis O of the main shaft 32 and the vertical rib 62 . In one embodiment, the vertical bar 61 may be arranged on the extension line.

Is the angle θ0 formed by the two lines connecting the axis O of the main shaft 32 and the two vertical ribs 62 greater than the angle θ1 formed by the two lines connecting the axis O of the main shaft 32 and the two vertical bars 61? , or equal (θ0≧θ1). In this embodiment, as shown in FIG. 6, the angle θ0 is greater than the angle θ1. When the values of θ0 and θ1 are approximately 30° to 120°, the combination of the vertical ribs 62 and the vertical bars 61 can effectively suppress the generation of the Karman vortices 7 .

In one embodiment, the cross-sectional shape of the vertical bar 61 may be rectangular, L-shaped, or other polygonal. Although the vertical ribs 62 in each of the embodiments described above have a rectangular cross-sectional shape, the cross-sectional shape of the vertical ribs 62 is not limited to this shape. In one embodiment, the cross-sectional shape of longitudinal ribs 62 may be triangular or circular.

The combination of the plurality of vertical rods 61 and the plurality of vertical ribs 62 that constitute the first air entrainment vortex suppression device in each of the above-described embodiments suppresses the generation of the Karman vortices 7 over a wide range of water levels and flow velocities in the suction water tank 1. It is possible to suppress the generation of air entrainment vortices.

As shown in FIGS. 5 and 6 , a semi-cylindrical body 71 as a second air entrainment vortex suppressor is arranged below the vertical rod 61 and the vertical rib 62 . The semi-cylindrical body 71 is fixed to the pump casing 27 by a plurality of brackets 75 with a gap between the outer peripheral surface of the pump casing 27 and the semi-cylindrical body 71 . The semi-cylindrical body 71 has an inner peripheral surface 71 a extending parallel to the main shaft 32 .

The semi-cylindrical body 71 is arranged on the downstream side of the main shaft 32 with respect to the flow direction of water in the suction water tank 1 and is arranged so as to partially surround the outer peripheral surface of the pump casing 27 . As shown in FIG. 6 , the entire semi-cylindrical body 71 is located inside the opening 5 when viewed from the axial direction of the main shaft 32 .

In this embodiment, the semi-cylindrical body 71 is fixed to the suction bell mouth 22 via a plurality of brackets 75 and is arranged so as to partially surround the outer peripheral surface of the suction bell mouth 22 . The configuration of body 71 is not limited to this embodiment. For example, the semi-cylindrical body 71 may be arranged so that its lower end is positioned below the lower end of the suction bell mouth 22, and arranged so that its lower end is positioned at the same height as the lower end of the suction bell mouth 22. may be Furthermore, in one embodiment, the semi-cylindrical body 71 may be secured to the discharge bowl 24 .

When the Karman vortex 7 is generated, a strong downward flow is generated from the Karman vortex 7 toward the suction port 22a during pumping, and develops into an air intake vortex. FIG. 12 is a diagram showing the flow from the Karman vortex 7 toward the suction port 22a. In FIG. 12, illustration of the vertical rod 61, the vertical rib 62, and the plurality of underwater vortex suppression plates 49 is omitted. As shown in FIG. 12, a downward flow F1 from the Karman vortex 7 toward the suction port 22a is split by the semi-cylindrical body 71 into an inner flow F2 and an outer flow F3. The inner flow F2 is drawn between the semi-cylindrical body 71 and the suction bell mouth 22. The semi-cylindrical body 71 is arranged at a position where the inner flow F2 is stronger than the outer flow F3.

A strong downward flow F1 that can develop into an air entrainment vortex is decomposed into two flows F2 and F3 by the semi-cylindrical body 71 . Further, the inner flow F2 drawn between the semi-cylindrical body 71 and the suction bell mouth 22 is caused by the water flow F4 drawn into the gap between the semi-cylindrical body 71 and the suction bell mouth 22 from the upstream side. Disturbed. The inner flow F2, which has lost momentum in this way, collides with the lower edge portion of the suction bell mouth 22 when sucked from the suction port 22a, and is further disturbed.

In this way, the semi-cylindrical body 71 can destroy the strong downward flow in the process of developing from the Karman vortex 7 to the air entrainment vortex. As a result, the semi-cylindrical body 71 can suppress the generation of air entrainment vortices. As described above, the semi-cylindrical body 71 has an inner peripheral surface 71 a extending parallel to the main shaft 32 . Such an inner peripheral surface 71 a promotes the effect of drawing water flowing from the upstream side into the gap between the semi-cylindrical body 71 and the suction bell mouth 22 . As an example, the semi-cylindrical body 71 can effectively suppress the generation of air entrainment vortices when its height (the length in the direction parallel to the main shaft 32) is about 0.2d to 0.4d.

In this embodiment, as shown in FIG. 6, the angle θ2 formed by two lines connecting the axis O of the main shaft 32 and both side edges of the semi-cylindrical body 71 is 180°. It is not limited and may be selected within the range of 120° to 180°. As shown in FIGS. 13(a) and 13(b), the semi-cylindrical body 71 may have flanges 71b extending radially inwardly or radially outwardly from its upper and lower ends. In this case as well, the semi-cylindrical body 71 has an inner peripheral surface 71a extending parallel to the main shaft 32 .

14 is a side view showing another embodiment of the pump 20, and FIG. 15 is a cross-sectional view taken along line DD of FIG. Configurations related to this embodiment that are not specifically described are the same as those of the embodiment described with reference to FIGS. In FIG. 14, illustration of the plurality of underwater vortex suppression plates 49 is omitted. As shown in FIGS. 14 and 15, the pump 20 of this embodiment further includes arc members 76 . In this embodiment, the second air entrainment vortex suppression device is composed of a semi-cylindrical body 71 and an arc member 76 . The arc member 76 is arranged above the semi-cylindrical body 71 and below the vertical rib 62 and the vertical rod 61 . In one embodiment, the lower end of vertical bar 61 may contact arc member 76 . Further, in one embodiment, the vertical bar 61 may be fixedly connected to the arc member 76 . The arc member 76 curves along the circumferential direction of the outer peripheral surface of the pump casing 27 . In this embodiment, the arc member 76 is semi-annular. The arc member 76 is fixed to the pump casing 27 by a plurality of brackets 77 with a gap between the outer peripheral surface of the pump casing 27 and the arc member 76 .

The circular arc member 76 is arranged on the downstream side of the main shaft 32 with respect to the water flow direction in the suction water tank 1 and is arranged so as to partially surround the outer peripheral surface of the pump casing 27 . As shown in FIG. 15 , the arc member 76 is entirely located inside the opening 5 when viewed from the axial direction of the main shaft 32 . The circular arc member 76 is arranged at a position that obstructs the course of the flow F1. Before being split by the semi-cylinder 71, the flow F1 is split into multiple streams F5 by striking the arc member 76, and the flow entering the semi-cylinder 71 is weakened. As a result, the strong downward flow that creates air entrainment vortices can be weakened. Thus, the combination of the circular arc member 76 and the semi-cylindrical body 71 can more effectively suppress the generation of the air intake vortex.

As shown in FIG. 15, in this embodiment, the angle θ3 formed by two lines connecting the axis O of the main shaft 32 and the both side edges of the circular arc member 76 is 180°, but this angle θ3 is limited to 180°. may be selected within the range of 120° to 180°. The cross-sectional shape of the circular arc member 76 may be circular, rectangular, polygonal such as L-shaped.

In one embodiment, as shown in FIG. 16, the arc member 76 may consist of a first arc member 76A and a second arc member 76B spaced apart from each other. The configuration related to this embodiment, which is not particularly described, is the same as that of the embodiment described with reference to FIGS. 14 and 15, so redundant description thereof will be omitted. The circumferential lengths of the arc members 76A and 76B of this embodiment are shorter than the circumferential length of the arc member 76 described with reference to FIGS.

The first circular arc member 76A and the second circular arc member 76B are arranged downstream of the main shaft 32 with respect to the direction of water flow and symmetrically with respect to a straight line RL' passing through the axis O of the main shaft 32 and parallel to the direction of water flow. ing. Specifically, the first arc member 76A and the second arc member 76B are arranged on straight lines L1 and L2. The straight lines L<b>1 and L<b>2 are straight lines that are at an angle of about 45° with respect to the straight line RL′ and that pass through the axis O of the main shaft 32 .

The Karman vortices 7 are often generated downstream of the straight lines L1 and L2 in the water flow direction in the suction water tank 1 . Therefore, the first circular arc member 76A and the second circular arc member 76B are arranged on the straight lines L1 and L2 in order to block the course of the downward flow F1 from the Karman vortex 7 toward the suction port 22a. The combination of the circular arc members 76A, 76B and the semi-cylindrical body 71 of this embodiment can suppress the generation of the air intake vortex with a compact configuration.

The semi-cylindrical body 71, or the combination of the semi-cylindrical body 71 and the arc member 76, is selected from the water level range of the suction water tank 1 in which the combination of the vertical rod 61 and the vertical rib 62 can suppress the generation of the air suction vortex. 1 (that is, when the flow velocity of the water in the suction water tank 1 is high), the generation of the air suction vortex can be effectively suppressed. Therefore, by combining the semi-cylindrical body 71 and the arc member 76 with the vertical rod 61 and the vertical rib 62, the generation of the Karman vortices 7 can be suppressed over a wider range of water levels and flow velocities in the suction water tank 1, thereby preventing harmful air suction. Vortex generation can be prevented.

In one embodiment, the pump 20 may comprise only a combination of vertical rods 61 and vertical ribs 62 . Further, in one embodiment, pump 20 may comprise only semi-cylinder 71 or only a combination of semi-cylinder 71 and arc member 76 .

According to each of the above-described embodiments, there is substantially nothing that impedes the flow of water toward the suction port 22a of the suction bell mouth 22, and there is almost no suction loss. The pump 20 with the vortex suppressor (longitudinal bar 61 and longitudinal rib 62) and/or the second air entrainment vortex suppressor (semi-cylindrical body 71 and/or arc member 76) can provide The generation of harmful air intake vortices can be prevented.

FIG. 17 is a bottom view of the plurality of underwater vortex suppression plates 49 shown in FIG. As shown in FIG. 17 , in this embodiment, four underwater vortex suppression plates 49 are fixed to the lower portion of the suction bell mouth 22 . Two of the four underwater vortex suppression plates 49 are arranged parallel to the direction of water flow in the suction water tank 1 and the other two are arranged perpendicular to the direction of water flow in the suction water tank 1 . However, the number of underwater vortex suppression plates 49 is not limited to this embodiment.

One end of the plurality of underwater vortex suppression plates 49 is fixed to each other on an extension line of the axis O of the main shaft 32, and the other end of each of the plurality of underwater vortex suppression plates 49 is attached to the inner peripheral surface of the suction bell mouth 22. is fixed to As shown in FIG. 1 , the underwater vortex suppression plate 49 protrudes downward from the lower end of the suction bell mouth 22 . The upper end of the underwater vortex suppression plate 49 is positioned higher than the lower end of the suction bell mouth 22 and lower than the impeller 31 .

With such an underwater vortex suppression plate 49, an underwater vortex generated between the suction bell mouth 22 and the bottom surface of the suction water tank 1 can be suppressed. This underwater vortex is formed by the development of a swirling flow between the suction bell mouth 22 and the bottom of the suction water tank 1, and when the suction bell mouth 22 is positioned near the bottom of the suction water tank 1, easily occur. The pump 20 of the present embodiment can effectively suppress the occurrence of underwater vortices by eliminating the swirling flow that causes underwater vortices with the underwater vortex suppressing plate 49 . Therefore, the suction bell mouth 22 can be arranged at a lower position than in the conventional structure, and water can be pumped up at a low water level. Since the submersible vortex suppression plate 49 of this embodiment can be attached to the pump 20, it does not need to be fixed to the suction tank 1, which is a civil engineering frame, and a low-cost and highly reliable pump can be provided.

The first air-entrained vortex suppressing device (vertical bar 61 and vertical rib 62), the second air-entrained vortex suppressing device (semi-cylindrical body 71 and arc member 76), and the underwater vortex suppressing plate 49 of each of the above-described embodiments are , JP 2007-285253 A may be applied to a pump in which a submersible bearing is arranged below an impeller.

The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiments can be made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in its broadest scope in accordance with the technical spirit defined by the claims.

1 Suction Water Tank 2 Pump Installation Floor 5 Opening 7 Karman Vortex 20 Pump 21 Impeller Casing 22 Suction Bell Mouth 22a Suction Port 24 Discharge Bowl 25 Inner Bowl 27 Pump Casing 28 Lift Pipe 28a Flange 28b Flange 30 Discharge Curved Pipe 31 Impeller 32 Main Shaft 33 Suspension pipe 33a Flange 35 Pump base 37 Guide vane 41 Underwater bearing 41a Support member 45 Outer bearing 49 Underwater vortex suppression plate 61 Vertical rod 62 Vertical rib 65 Bracket 67 Fixture 68 Annular portion 69 Vertical rod holding portion 69a Through hole 71 Half cylinder Body 75 Bracket 76 Arc member 77 Bracket

Claims (12)

In a pump for pumping water in a suction tank,
a main axis extending in a vertical direction;
an impeller fixed to the main shaft;
a pump casing housing the impeller therein;
a plurality of vertical bars and a plurality of vertical ribs disposed outside the pump casing;
The plurality of vertical bars and the plurality of vertical ribs are positioned at the same height and arranged downstream of the main shaft with respect to the direction of water flow in the suction water tank,
The plurality of vertical bars are arranged with a gap between them and the outer peripheral surface of the pump casing,
The plurality of longitudinal ribs are fixed to the outer peripheral surface of the pump casing,
The plurality of vertical bars and the plurality of vertical ribs are positioned inside an opening formed in the pump installation floor when viewed from the axial direction of the main shaft,
The plurality of vertical bars are arranged adjacent to the plurality of vertical ribs ,
said longitudinal bars and said longitudinal ribs are spaced apart from each other;
A pump according to claim 1, wherein said vertical bar is arranged radially outward of said pump casing relative to said vertical rib . 2. The pump according to claim 1, wherein said plurality of vertical bars and said plurality of vertical ribs are arranged symmetrically with respect to a straight line passing through the axial center of said main shaft and parallel to said water flow direction. 3. The pump according to claim 1, wherein the vertical bar is arranged on an extension line of a line connecting the axial center of the main shaft and the vertical rib, or on a downstream side of the extension line. The pump casing includes a suction bell mouth having a suction port opening downward,
The upper end of the vertical rod is positioned within a range of 0.8 d or more from the lower end of the suction bell mouth and equal to or lower than the operation start water level, where d is the diameter of the discharge side of the pump casing. 4. A pump according to any one of claims 1 to 3, wherein 5. A pump according to claim 4, wherein the lower end of said vertical rod is located below the upper end of said impeller. Further comprising a semi-cylindrical body arranged outside the pump casing,
The semi-cylindrical body is arranged downstream of the main shaft with respect to the flow direction of water in the suction water tank,
The semi-cylindrical body is fixed to the pump casing with a gap between it and the outer peripheral surface of the pump casing,
The semi-cylindrical body is positioned inside an opening formed in the pump installation floor when viewed from the axial direction of the main shaft,
2. The pump of claim 1, wherein said semi-cylindrical body has an inner peripheral surface extending parallel to said main axis. The pump casing includes a suction bell mouth having a suction port opening downward,
7. The pump of claim 6, wherein said semi-cylindrical body is fixed to said suction bell mouth. 8. The pump according to claim 6, wherein an angle formed by two lines connecting the axis of said main shaft and both side edges of said semi-cylindrical body is 120° to 180°. further comprising an arc member fixed to the pump casing with a gap between it and the outer peripheral surface of the pump casing;
The arc member is curved along the circumferential direction of the outer peripheral surface of the pump casing,
9. The pump according to any one of claims 6 to 8, wherein the arc member is arranged above the semi-cylindrical body. 10. The pump according to claim 9, wherein an angle formed by two lines connecting the axis of the main shaft and both side edges of the arc member is 120° to 180°. The arc member includes a first arc member and a second arc member that are spaced apart from each other, and the first arc member and the second arc member are arranged so that the water flows through the axis of the main shaft. 10. Pump according to claim 9, characterized in that they are arranged symmetrically with respect to a straight line parallel to the direction. 12. A pump as claimed in any preceding claim, wherein all of the longitudinal bars and all of the longitudinal ribs extend along the main axis.

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