JPS6245118Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is applicable to cases where a pump suction pipe or pump casing (in this specification, simply referred to as a suction pipe) is installed in a waterway, water tank, river bank, etc. (in this specification, simply referred to as a water tank). , relates to a vortex generation prevention device for preventing the generation of vortices, particularly air suction vortices.

It is known that when such a pump is installed in an aquarium to suck up water from the aquarium, various forms of vortices are generated in the aquarium, and these vortices cause various problems in the operation of the pump. . Figures 1A and 1B show how such vortices are generated. In FIGS. 1A and 1B, the vertical suction pipe 2 has a suction port 2a, and the water tank 1 has a bottom surface 1a, side surfaces 1b, 1b, and end surface 1c, and the free surface of the water in the water tank 1 is indicated by 1d. ing.

In such pump equipment, there are three underwater vortices: ``0'' connecting the suction port 2a and the bottom surface 1a, ``1'' connecting the suction port 2a and the side surface 1b, and an air suction vortex ``2'' connecting the suction port 2a and the free surface 1d. A vortex is created.

The underwater vortex ``1'' induces a strong downward flow in the hollow vortex generated near the free surface 1d near the suction pipe, and due to the downward flow, the hollow vortex reaches the suction port 2a, and the air suction vortex ``2'' Among the vortices ``0'', ``1'' and ``2'', the air suction vortex ``2'' has an adverse effect on the pump's original function and performance, and causes vibration and noise, so it must be prevented as much as possible.

Figure 2A shows the state of the flow velocity distribution of the approaching velocity of the water flow in the pump suction tank and the generation form of vortices ``2'' when the suction pipe is installed perpendicular to the water surface as shown in Figure 1A. That is, in the aquarium, the flow velocity V is slow near the free surface 1d, fast near the intermediate depth, and slower near the bottom 1a than the flow velocity near the free surface 1d. It can be seen that this occurs on the downstream side of the suction pipe 2, that is, between the suction pipe 2 and the end surface 1c.

FIG. 2B shows a case where the suction port 2b is provided on the end face 1c of the water tank. Also in the case of FIG. 2B, a strong downward force is applied to the corner vortex generated near the end face 1c, reaching the suction port 2b, and an air suction vortex "2" is generated.

The vortex generation prevention devices for water tanks shown in FIGS. 2A and 2B are well known, and are disclosed, for example, in Japanese Patent Publication No. 55-8672, where the generation process of the air generation vortex "2" has also been theoretically elucidated.

However, if the wall surface is sloped, such as on a river bank, the conventional vortex generation prevention device cannot be applied. This is because the various equipment is located far away from the water tank, the suction pipe extends at an angle, and the water tank itself does not have walls such as concrete. This is because there is no holding means and the vortex generation process is different from that shown in FIGS. 2A and 2B.

FIG. 2C shows a case where the suction pipe 2 is installed at an angle. It is provided. Even in this case, an air suction vortex "2" is still generated at the suction port 2a from the free surface 1d.

For example, Japanese Utility Model Publication No. 51-6723 discloses a technique for preventing the generation of vortices by providing walls on the upstream and downstream sides of a suction pipe that extends perpendicularly to a water tank whose top is closed. However, when using an inclined suction pipe installed in a river or the like, it is not possible to construct a closed waterway as in the prior art, and the flow pattern is different because it is an open waterway. For this reason, air suction vortices cannot be prevented simply by providing a wall.

Furthermore, Japanese Utility Model Publication No. 51-26324 discloses a technique in which a small protrusion 13 is provided on the side surface of a vertical suction pipe to forcibly separate the liquid flowing around the pipe, thereby preventing the generation of vortices. . However, if a slanted suction pipe is used, such a technique cannot be used since there is no flow around the suction pipe.

Furthermore, although JP-A-57-32100 discloses a diagonal suction pipe, it does not disclose a technique for preventing the generation of vortices in relation to water channels.

In any case, the mechanism of vortex generation is different in the case of a vertical suction pipe and in the case of an inclined suction pipe, so the vortex generation prevention technology for a vertical suction pipe can be used as the vortex generation prevention technology for an inclined suction pipe. cannot be applied.

In order to better understand the present invention, the mode of vortex generation when the suction pipe is installed obliquely will be explained with reference to FIGS. 3A and 3B.

Figures 3A and 3B show how air suction vortices ``2'' occur in a diagonal pump water tank when no vortex prevention device is provided. The air suction vortex ``2'' occurs in area B near the suction port 2a (slightly upstream in Figure 3A), and its suction port 2a extends close to the bottom surface 1a of the tank. The distribution state of the flow velocity V of the approaching velocity is shown by the solid line A (Figure 3 B).
Since the solid line A is located slightly above the bottom surface 1a, the flow velocity slightly above the bottom surface 1a is fastest, and the flow velocity near the free surface 1d is slow. Also, a relatively strong downward flow is generated from the free surface 1d toward the suction port 2a. Therefore, a stagnation region is created downstream of the downward flow where no fluid flow occurs. Therefore, a depression vortex is generated near the boundary between the stagnation region and the flowing part, and when the downward flow from the free surface 1d toward the suction port 2a merges, the depression vortex grows and becomes an air suction vortex "2." Ivy.

Furthermore, as a result of various experiments, it was found that the area indicated by the solid line B in Fig. 3A, that is, the area above the suction port 2a, is the area where air suction vortices ``2'' occur.In other words, the suction pipe 2 is inclined with respect to the horizontal plane. If it is installed in such a way, an air suction vortex "2" will be generated in this region B.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vortex generation prevention device that effectively weakens the downward flow in a device in which an inclined suction pipe is installed, thereby preventing the generation of air suction vortices.

According to the present invention, in the vortex generation prevention device when a pump suction pipe or a pump casing which is provided diagonally with respect to the water surface is installed in a water tank, the rear wall of the water tank is inclined, and the pump The suction pipe or pump casing is provided along the rear wall, and a vertical plate is provided along the longitudinal direction of the suction pipe or pump casing on the central axis of the upper part of the suction port connected to the suction pipe or pump casing. There is.

Therefore, the suction flow to the suction port flows toward the suction port from above the upstream side of the suction port and from both left and right sides, but at this time, a swirling flow around the vertical axis occurs at the top of the suction port, This swirling flow causes the hollow vortex to grow into an air suction vortex. However, since a vertical plate is provided along the longitudinal direction of the suction pipe on the central axis of the upper part of the suction port, the swirling flow that is about to occur near the suction port is prevented by the vertical plate. As a result, a swirling flow is not generated, so even if a depression vortex is generated due to a downward flow, it does not grow into an air suction vortex. Therefore, generation of air suction vortices can be prevented.

Embodiments of the present invention will be described below with reference to FIGS. 4A, 4B, and 5 and FIG. 5.

As shown in FIGS. 4A and 4B, a suction pipe 2 is inserted into a water tank 1 having a rear wall 3 inclined at an angle θ with respect to the horizontal plane, and the suction pipe 2 is installed along the rear wall 3. ing. The suction port 2a of the suction pipe 2 extends to near the bottom surface 1a of the aquarium 1, and its opening edge widens in a trumpet shape. In the present invention, a plate 4 perpendicular to the horizontal plane is installed on the center line of the upper part of the suction port 2a. That is, the plate 4 is located at the center of the width D of the suction port 2a and is provided along the longitudinal direction of the suction pipe 2.

During operation, when water is sucked in from the suction port 2a by the pump body (not shown), the state of the water flow in the water tank 1 will be such that a swirling flow will occur above the suction port 2a, as shown by the dotted line arrow in FIG. 4C. shall be. However, in the present invention, the suction port 2 is
The swirling flow near a is blocked and cut off.
The swirling flow shown by this dotted line is a factor that causes the hollow vortex to grow into the air suction vortex ``2'', and by suppressing this, the generation of the air suction vortex ``2'' can be prevented. .

According to experiments, the length in the longitudinal direction of the plate 4 is L, and the suction port 2a is connected to the downstream mounting part of the plate 4, that is, in the illustrated embodiment, from the part of the flange 5 where the suction port 2a is attached to the suction pipe 2. If the length to the upper tip 2b is l, and the angle between the upper edge of the suction port 2a and the horizontal plane is α, then the dimensions of the plate 4 are L≧lcos
It was found that it is most effective to set α, N≧lsinα, and α≒θ<90 degrees.

FIG. 5 is a graph showing the effects of the present invention. In Fig. 5, the horizontal axis represents the flow velocity v in the suction pipe, and the vertical axis represents the critical submergence depth Sc of the suction pipe (distance from the free surface 1d to the upper tip of the suction port 2a when air suction vortices ``2'' begin to occur). ).Curve X is the case where the plate 4 is not provided, and curve Y is the case where the plate 4 is provided.The curve X, which is not provided with the plate 4, shows the critical sinking of the suction pipe as the flow velocity v increases. Although the depth Sc increases significantly, according to the present invention, as can be seen from the curve Y, the suction pipe critical submersion depth Sc is significantly reduced.Also, according to experiments, even with the plate 4 provided, the pump performance It has been confirmed that there are no adverse effects on

In addition, in the above-mentioned embodiment, the shape of the plate 4 can be changed freely. Also, the suction port 2a
When the width of the plate 4 is wide, a plurality of plates 4 may be erected in parallel above the suction port 2a.

As explained above, according to this invention, since a vertical plate is installed above the suction port along the longitudinal direction of the suction pipe, it cuts off the swirling flow near the suction port and transforms the hollow vortex into an air suction vortex. Factors that cause it to grow can be removed. Therefore, the generation of air suction vortices can be prevented with a simple structure.

[Brief explanation of the drawing]

Figure 1 A and B are side sectional views and plan views showing the forms of various vortices generated in the pump suction tank, and Figure 2 A, B, and C are representative flow velocity distribution states and vortices in the pump suction tank, respectively. A side sectional view showing the generation state, Figures 3A and 3B are a plan view and side sectional view showing the form of air suction vortex generation in the oblique shaft pump water tank,
Figures 4A and 4B are a side sectional view and a plan view showing the vortex generation prevention device according to the present invention, Figure 4C is a plan view showing the water flow state when the same device is used, and Figure 5 is the suction pipe critical potential. It is a chart showing the relationship between the immersion depth Sc and the flow velocity v in the suction pipe. 1...Aquarium, 1a...Bottom, 1b...Side wall, 1
c... End face, 1d... Free surface, 2... Suction pipe,
2a...Suction port, 3...Rear wall, 4...Plate body.

Claims (1)

[Scope of utility model registration request] In a vortex generation prevention device when a pump suction pipe or pump casing is installed in a water tank, the rear wall of the water tank is inclined, and the pump suction pipe or pump casing is installed at an angle to the water surface. is provided along the rear wall, and is characterized in that a vertical plate is provided along the longitudinal direction of the suction pipe or pump casing on the central axis of the upper part of the suction port connected to the suction pipe or pump casing. Vortex generation prevention device.