JP2000303549A - Suction passage for pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a suction passage for a pump for preventing the generation of harmful vortex by realizing ideal passage shape even in the unstandard shape of a suction tank, particularly in suction tank shape with the suction passage miniaturized in its plane shape and relatively large in height dimension. SOLUTION: This suction passage for a pump is provided with a pedestal- shaped structure on the wall surface of a suction tank opposed to a suction port, between the wall surface and a structure equivalent to a suction cone 8, in addition to this structure. The generation of vortex caused by flow separation from the suction cone 8 can be prevented even if the height dimension of the passage is large compared to the size of plane shape such as the maximum diameter of the suction cone 8 and the width of the suction passage. The height dimension of the passage can therefore be made relatively large for the purpose of preventing the generation of vortex in the suction passage 9 unstandard for word execution reasons and ensuring cross-sectional area of the passage 9 while reducing site area, and the construction cost of a pumping plant is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suction channel of a pump, and more particularly to a suction channel of a pump suitable for guiding water from a water source to a pump body.

[0002]

2. Description of the Related Art Pumps play an important role in various industrial and public fields. Among them, water pumps for water supply and drainage account for a particularly large proportion. Examples include water supply pump systems that take in and supply cooling water from power sources and various plants from water sources such as the sea and rivers, and drainage pump systems that discharge rainwater collected through sewage during rainfall to rivers and the like. .

[0003] In these pump systems, a small and high flow rate is required to reduce land acquisition costs and construction costs. Since the suction channel for guiding the flow from the water source to the pump body is a large-scale civil engineering structure, there is a strong demand for a small size and high flow rate. If the suction channel is made smaller and the flow velocity is increased, a strong vortex is easily generated in the flow.

[0004] Since such eddies cause vibration and noise, it is necessary to prevent them. For this reason, for example, [Model Test Method for Suction Water Tank of Pump, JSM
ES 004-1984, p. 25]
A plate-shaped vortex prevention structure is installed on the bottom surface or side surface, or on the upper surface or near the liquid surface of the water absorption tank, which is a component of the suction channel.

FIGS. 6, 7 and 8 show examples of the structure of a suction channel of a conventional pump. FIG. 6 is a view taken along the line AA of FIG. 7 showing a planar shape, and FIG.
FIG.

[0006] As shown in the figure, the suction flow path includes a water conduit 1 for guiding water to the pump (the upstream side is not shown), a water absorption tank 2 for adjusting the inflow condition to the pump, a water absorption pipe 3 and It is composed of a pump (not shown). This conventional example does not have a free liquid level in the water absorption tank 2 and is of a type called a closed type. A bell mouth 5 for smoothly sucking water is provided in the suction port 4 of the water suction pipe 3.
As shown in FIG. 8, the bell mouth 5 may be provided to protrude into the water absorption tank 2. A pier 6 serving as a strength member and a rectifying structure may be provided in the water conduit 1, and a rectifying plate 7 may be provided on the rear wall of the water absorbing tank 2.

Here, the wall surface of the suction flow path facing the suction port 4, that is, the structure 8 installed on the bottom surface in the conventional example is a conventional typical vortex prevention structure in a closed type water absorption tank. This structure (hereinafter, referred to as a suction cone) has a substantially truncated conical shape as shown in the figure, and the inclination of the side surface of the suction cone 8 with respect to the suction channel bottom surface is indicated by the bottom. It is the smallest at the contact portion, and increases monotonically as it approaches the suction port, forming a so-called Mt. Fuji shape. As described below, such a shape
This is necessary because the cross-sectional area of the flow path between the bell mouth and the suction cone is gradually reduced.

The suction cone 8 has three main functions. If the velocity distribution flowing into the headrace channel 1 is unbalanced, a strong vortex having a turning axis in the direction from the bottom surface of the water absorption tank 2 to the suction port 4 is generated. Therefore, the first function of the suction cone 8 is to prevent a vortex immediately below the suction port by eliminating such a vortex region from the wall surface facing the suction port toward the suction port. The second function of the suction cone is, for example, in the case of this conventional example, a headrace,
The purpose is to change the flow in the substantially horizontal direction in the water absorption tank smoothly in the vertical direction toward the water absorption pipe, and to flow into the water absorption pipe so as not to disturb the flow and generate a new vortex. The third function is to gradually reduce the cross-sectional area of the flow path formed between the suction cone and the bell mouth, thereby smoothly increasing the flow toward the suction port and allowing the flow to flow in the circumferential direction as uniformly as possible. Also have.

[0009]

The preferred shape of the flow path 9 formed by the bell mouth 5 and the suction cone 8 that satisfies the function of the suction cone is, for example, based on the diameter of the water suction pipe 3. It is empirically defined by the radius of curvature of the flow path 9 and the change in the cross-sectional area, and cannot be largely changed.

On the other hand, the water absorption tank is usually a civil engineering structure made of concrete, and has a primary construction for forming a rough shape prior to the installation of the pump equipment, a bell mouth 5, a rectifying plate 7, a suction cone 8 and the like at the time of installation of the pump equipment. And the secondary construction that forms the internal structure. At the stage of the primary construction, detailed specifications are not clear, or there are cases where the shape of the water absorption tank and the suitable shape of the flow passage 9 do not match well due to the limitation of the acquisition site. Alternatively, in the case of a specification change or replacement of an existing pump station, a suitable shape of the flow path 9 is changed with a change in the pump diameter, and the shape of the water absorption tank and the shape of the preferable flow path 9 are similarly matched. May disappear.

In such a case, it is not realistic from the viewpoint of cost to re-create the water absorption tank. Therefore, it is necessary to realize a suction passage free of vortex by designing an internal structure centering on the suction cone. However, a technique for realizing this has not been established, and when trying to forcibly connect the shape of the water absorption tank and the shape of the flow path, the flow is disturbed and a harmful vortex may be generated in some cases.

Further, with the recent improvement of the pavement rate, the need for constructing a pumping station for drainage in urban areas has been increasing in order to prevent urban flooding that rapidly increases immediately after rainfall. When a strong vortex is generated in the suction flow path, it causes noise, which is particularly problematic in such a location. In addition, land acquisition is difficult in urban areas due to high land prices, and there is a strong demand for reducing the site area of pumping stations. For this reason, the height tends to be larger than the conventional width of the suction flow channel in order to secure the cross-sectional area of the suction flow channel in addition to the small size and high flow velocity described above.

With the above situation as a background, how the vortex becomes a problem will be specifically described below.

FIGS. 9 and 10 show examples of vortices generated when the height of the suction channel is relatively large with respect to the width of the suction channel and the diameter of the suction cone as compared with the conventional standard shape.

In this case, the shape of the flow path formed by the bell mouth 5 and the suction cone 8 has the greatest influence on the generation of the vortex. The parameters that characterize this channel shape are the channel height H to the lower end of the bellmouth and the maximum diameter D of the suction cone. When the bell mouth is projected as shown in FIG. 8, the height to the lower end is defined as H at that time. Since the suction cone needs to form a flow path with a gradually decreasing cross-sectional area together with the bell mouth, the height of the suction cone must be increased as H becomes relatively large. Therefore, as the H / D increases, the shape of the suction cone 8 becomes longer as shown in FIG.

[0016] In such a state, the shape of the suction cone is felt close to a columnar shape for the fluid flowing from the headrace. This tendency is particularly remarkable in the upper part of the water absorption tank, and the flow in the upper part separates on the downstream side of the suction cone as shown by an arrow 11 in the figure, and generates a swirling flow similar to the Karman vortex generated by the cylindrical alternating current. Such a swirling flow develops toward the suction port, causes the strong vortex 11, and may cause problems such as vibration and noise. In the case of such a flow, the function of smoothly changing the flow in the substantially horizontal direction in the water absorption tank, which is one of the important roles of the suction cone 8, toward the water suction pipe in the vertical direction has been lost. It is clear that there are adverse effects such as a decrease in efficiency.

As described above, in the conventional suction channel shape, when the ratio H / D between the height H to the lower end of the bell mouth and the maximum suction cone diameter D exceeds a certain limit value, a harmful vortex is generated.

As described above, in recent years, the suction passage of the pump has become smaller and has a higher flow velocity, and the width of the passage has been particularly narrowed in order to reduce the site area. In the suction channel where the
It is becoming increasingly important to prevent the generation of strong vortices that cause vibration noise.

The present invention has been made in view of the above points,
The objectives are the shape of the non-standard water absorption tank,
In particular, the suction channel of the pump, which prevents the generation of harmful vortices by reducing the planar shape of the suction channel and realizing a suitable channel shape even in the shape of a suction tank having a relatively large suction channel height, is realized. To provide.

[0020]

A feature of the present invention that achieves the above object is that a water absorption tank facing a suction port is provided on a wall surface thereof.
In addition to the structure protruding toward the suction port corresponding to the suction cone in the above-mentioned conventional example, the suction passage of the pump includes a pedestal-shaped structure between the wall surface and the structure.

According to such a configuration, when the height of the water absorption tank is higher than the standard design, or when the width of the suction channel and the diameter of the suction port are small and the height of the suction channel is relatively large, In addition, by adjusting the height of the pedestal-shaped structure, a suitable flow path shape can be maintained. That is, as shown in the following examples, the substantial height H to the lower end of the bell mouth is reduced by the pedestal-like structure, and H / D, which is the dominant shape parameter of vortex generation, is changed to harmful vortex generation. It can be below the limit.

It is naturally also possible to integrally manufacture the suction cone and the pedestal-like structure, and this can be regarded as one eddy prevention structure. As described above, the suction cone, which is the conventional vortex prevention structure, has a so-called Mt. Fuji shape in which the inclination of the side surface monotonically increases toward the suction port,
The features of the present invention as an integral eddy prevention structure can be shown.

Further, another feature of the present invention from this viewpoint is that the cross-sectional shape by a plane that is substantially axially symmetric about an axis perpendicular to the bottom surface of the water absorption tank and includes an axis perpendicular to the bottom surface is as follows: The suction passage of the pump has a vortex prevention structure in which the inclination of the side surface of the structure with respect to the bottom surface has a minimum value on the way from the bottom surface to the suction port.

Conventionally, the reason why such a shape was not used was that it was considered that the flow separated from the upper end of the pedestal-like structure and a vortex was generated. However, it is known that in a flow in which the cross-sectional area of the flow channel decreases in the direction of the flow and accelerates, separation of the flow is unlikely to occur,
Actually, even if a pedestal-like structure like the present invention is installed,
This does not create any vortices.

Therefore, by adopting the above-described configuration, it is possible to provide a suction flow path in which generation of harmful vortices is prevented even in the case of a water absorption tank having a shape that is not standard in view of conventional standards.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

(Embodiment 1) FIG. 1 shows an embodiment of the present invention in a suction channel of a type having a bell mouth projecting into a water absorption tank. It has already been mentioned that the suction cone 8 has the role of forming a channel whose cross-sectional area decreases gradually towards the suction port. For this purpose, the top of the suction cone 8 must reach near the lower end of the bell mouth. For this reason, in the conventional vortex prevention structure, when the height of the suction channel becomes relatively large, the shape of the suction cone becomes vertically long,
The flow from the upstream separates, and a vortex similar to the Karman vortex behind the cylinder is generated.

On the other hand, a pedestal-like structure 12 is installed as in the present embodiment, and a Mt. Fuji-shaped suction cone 8 similar to the conventional one is installed thereon, thereby providing a bell mouth and a suction cone. The height H of the channel, which characterizes the shape of the channel 9 formed by the above, can be reduced. As a result, as described above, the ratio H / D to the suction cone diameter D can be made smaller than the limit value at which vortices are generated, thereby preventing vortices from being generated. Therefore, it is possible to prevent the vortex, which is an important role of the suction cone, and to form a flow path having a gradually decreasing cross-sectional area.

It is considered that the same effect can be obtained to some extent by increasing the length of the bell mouth protruding toward the water absorption tank.
However, installation of civil engineering structures on the ceiling is very laborious and costly. Such a method cannot be applied unconditionally because the construction difficulty and cost increase as the size of the structure increases. Further, by raising the entire bottom surface or making the suction cone a Mt. Fuji type having a very wide base, H / D can be reduced. However, this requires secondary construction using a large amount of concrete, which is costly. In addition, since the cross-sectional area of the inlet of the water absorption tank is reduced by this method, it cannot be applied to the case where the height of the flow path is increased to secure the flow rate while reducing the site area.

Thus, it can be seen that the present invention has cost and construction advantages compared to many alternatives.

In this embodiment, it goes without saying that the same effect can be obtained even if the suction cone 8 and the pedestal-shaped structure 12 are manufactured integrally. In this case, the vertical cross-sectional shape of the integrated structure once rises with a large inclination from the bottom of the water absorption tank, and has a minimal part with a small inclination as it goes toward the suction port, and monotonously above it. It has the feature that the inclination increases.

(Embodiment 2) FIG. 2 shows an embodiment in which the present invention is applied to a suction channel having a bell mouth of the type shown in FIG. In this embodiment, as in the first embodiment, the height H to the lower end of the bell mouth is reduced to prevent generation of a vortex, and the other functions of the suction cone 8 are not impaired.

Further, as described in the first embodiment, the construction of the civil engineering structure on the ceiling is troublesome and costly. Therefore, the present embodiment employs a bell mouth having a projection length similar to that of the pedestal-shaped structure 12. Can be considered as an alternative to the suction flow path having

(Embodiment 3) In the above embodiment, the pedestal-shaped structure 12 is constructed as a civil engineering structure, but it is not always necessary. FIG. 3 shows such an embodiment. In the present embodiment, the pedestal-shaped structure 12 is assembled with, for example, a steel material, and the suction cone 8 is provided thereon. Since the height to the lower end of the bell mouth is reduced in the same manner as in the above-described embodiment, it is possible to prevent the generation of vortices.

According to the configuration of the present invention, the number of steps that can be performed in a factory or the like is increased in advance, and it is expected that the on-site construction period can be shortened and the cost can be reduced. Further, if the pedestal-shaped structure 12 is fixed to the bottom of the water-absorbing tank by, for example, a bolt so that it can be detached from the bottom of the water-absorbing tank, flexibility such that the height of the pedestal-shaped structure can be locally adjusted is obtained. Can be

(Embodiment 4) In Embodiments 1 and 2, the pedestal-shaped structure 12 is configured to become thinner toward the suction port, but this is not always necessary. FIG. 4 shows such an embodiment of the present invention. In the present embodiment, the pedestal-shaped structure 12 is configured to become thicker toward the suction port. The vortex prevention effect is the same as in the above embodiment.

According to the structure of this embodiment, the flow rate on the rear wall side of the water absorption tank close to the current plate 7 is reduced.
When the flow rate imbalance in the circumferential direction occurs, the pedestal-shaped structure 12 plays a role of a flow guide for guiding the fluid to the rear wall side, so that the balance of the inflow amount in the circumferential direction is improved and the generation of vortices is further prevented. There is an advantage that the effect is increased. In addition, there is also an effect that the cost is reduced by reducing the amount of concrete used.

(Embodiment 5) In the above embodiment, the pedestal-shaped structure has a substantially axially symmetric shape, but this is not always necessary. Such an embodiment of the invention is shown in FIG.

In the present embodiment, the pedestal-shaped structure 12 extends to the rear wall of the water absorption tank and is not axisymmetric, but the height H to the lower end of the bell mouth becomes smaller as in the above embodiment, Prevention effect can be expected.

As can be seen from the planar shape of the suction flow path in FIG. 6, the water absorption tank is usually configured such that the flow path area becomes smaller toward the rear wall. This is to make the circumferential distribution of the flow rate of the inflow into the suction port uniform. However, depending on the design, it may not always be sufficiently uniform. According to the configuration as in the present embodiment, even after the plane shape is determined,
The pedestal-shaped structure 12 has an advantage that the flow path area on the rear wall side can be narrowed down and the circumferential inflow flow rate distribution can be adjusted.

As can be seen from Embodiments 4 and 5, in the present invention, the shape of the pedestal-like structure 12 is changed in accordance with the situation to improve the circumferential distribution of the flow rate of the inflow into the suction port. In addition, there is an effect that vortices can be hardly generated.

[0042]

According to the suction channel of the pump of the present invention,
Even when the flow path height is larger than the planar shape such as the maximum diameter of the suction cone and the width of the suction flow path, generation of vortices due to separation of the flow from the suction cone can be prevented. This prevents the formation of vortices in the suction channel that is not standard due to construction reasons, and the channel height is relatively large in order to secure the cross-sectional area of the channel while reducing the site area. The construction cost of the pumping station can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a suction channel according to an embodiment of the present invention.

FIG. 2 is a sectional view of a suction channel according to another embodiment of the present invention.

FIG. 3 is a sectional view of a suction channel according to another embodiment of the present invention.

FIG. 4 is a sectional view of a suction channel according to another embodiment of the present invention.

FIG. 5 is a sectional view of a suction channel according to another embodiment of the present invention.

FIG. 6 is a plan view of a conventional suction channel.

FIG. 7 is a cross-sectional view of the suction channel of FIG. 6;

FIG. 8 is a cross-sectional view of another conventional suction channel.

FIG. 9 is a plan view of another conventional suction channel.

FIG. 10 is a sectional view of the suction channel of FIG. 9;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Headrace channel, 2 ... Water absorption tank, 3 ... Water absorption pipe, 4 ... Suction port,
5 bellmouth, 6 pier, 7 rectifying plate, 8 suction cone, 9 channel formed by bellmouth and suction cone, 10 separation of flow from suction cone, 11
... vortex, 12 ... pedestal-like structure.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Ichiro Harada 603, Kandamachi, Tsuchiura-shi, Ibaraki F-term in Tsuchiura Plant, Hitachi Ltd. (Reference) 2D063 DC04 3H071 AA02 BB03 CC23 CC31 CC33 DD31 DD72 DD89

Claims (4)

[Claims] 1. A suction channel having a suction port leading to a pump body, comprising a structure on a wall surface of the suction channel facing the suction port, wherein the structure is installed on the wall surface. And a structure disposed on the pedestal-shaped structure and protruding toward the suction port. 2. The structure protruding toward the suction port has a shape in which an area of a cross section parallel to a wall face of the suction channel facing the suction port gradually decreases toward the suction port. The suction passage of the pump according to claim 1, wherein: 3. The suction passage of a pump according to claim 1, wherein the pedestal-shaped structure is substantially axially symmetric about an axis perpendicular to a wall surface facing the suction port. 4. A suction flow path having a suction port communicating with a pump body, wherein the suction flow path has a structure on a wall surface facing the suction port, and the structure faces the suction port. The cross-sectional shape of the structure is substantially axially symmetric about an axis perpendicular to the wall surface and is a plane including the axis perpendicular to the wall surface. A suction flow path of the pump, wherein the suction flow path has a minimum value on the way from the wall surface of the suction flow path facing the suction opening to the suction opening.