JPH0579000U - Vortex prevention device for pump water absorption tank - Google Patents

Abstract

(57) [Abstract] [Purpose] Vibration caused by the suction of the vortex by the pump P sucking the vortex by preventing the flow separation and backflow phenomenon from occurring in the region C on the step surface 2 of the pump water absorption tank 6 Avoid obstacles such as noise and noise. [Structure] A flow separation / backflow phenomenon suppressing member 8 is provided on a step surface 2 formed between a pump installation area 1 and an upstream area 4 in a pump water absorption tank 6.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a vortex prevention device for a pump water absorption tank.

[0002]

[Prior Art]

 As shown in FIGS. 7 and 8, a step surface 2 that descends with an inclination angle θ toward the pump installation area 1 is provided on the upstream side of the pump installation area 1 in which the pump P is installed. When the pump P is operated in the conventional pump water absorption tank 6 in which the bottom portion 3 of 1 is deeper than the bottom portion 5 of the upstream area 4 of the step surface 2, in the upstream area 4, the depth from the water surface WL to the bottom portion 5 of FIG. The flow state shown by the arrow group B in FIG. 8 is substantially uniform over the entire region D in the depth direction. That is, in the vicinity of the side walls 7 and 7, there is a flow state in which the boundary layers b and b in which the flow velocity suddenly changes and becomes small occur in the entire region D in the depth direction. In FIG. 7, when a substantially uniform flow (a group of arrows B, but a boundary layer develops near the bottom 5) across the entire region D in the depth direction reaches a region C on the step surface 2. Due to the suction action of the pump P and the drop of the step surface 2, the flow velocity of the flow portion indicated by B1 in the central portion in the depth direction of the substantially uniform flow arrow group B is increased in the upper region B2 and the lower region B. It becomes larger than the flow velocity of 3. Thus, even if the flow velocity of the flow portion B1 is higher than that of the other regions B2 and B3, it does not have a great influence on the flow of the upper region B2. However, it acts to block the flow of the lower region B3. Further, due to the rapid expansion of the flow path, the flow in the lower region B3 in the region C on the step surface 2 is decelerated. Moreover, even near both side walls 7 and 7 of the step surface 2, the flow velocity near the side walls 7 and 7 suddenly decreases due to the boundary layers b and b which are generated in the entire region in the depth direction. Therefore, due to the deceleration of the main flow, the flow of the boundary layers b, b in the lower region B separates from the side walls 7, 7 and flows backward, that is, the flow separation / backflow phenomenon shown by the arrow Z in FIG. And a vortex shown by an arrow Z in FIG. 7 is generated.

On the other hand, the vortex Z generated in the region C on the step surface 2 is sucked into the pump P, and causes an obstacle such as vibration or noise in the pump P. On the other hand, in order to reduce the civil engineering cost of constructing the pump water absorption tank 6, if the length L of the pump water absorption tank 6 is shortened and the step surface 2 is brought closer to the pump P, the inclination angle θ of the step surface 2 becomes large. As a result, the generation of the vortex Z due to the flow of the boundary layers b and the portion corresponding to b in the lower region B is promoted, and the above-mentioned obstacle is increased.

[0004]

[Problems to be solved by the device]

 The problem to be solved is that vortices are generated in the boundary layer in the lower area on the step surface of the pump water absorption tank, and the vortices are sucked into the pump and cause problems such as vibration and noise in the pump. is there.

[0005]

[Means for Solving the Problems]

 According to the present invention, a step surface is provided on the upstream side of the pump installation area so that the bottom of the pump installation area is deeper than the bottom of the upstream area of the step surface. A separation / backflow phenomenon suppression member is provided to prevent the flow separation / backflow phenomenon from occurring in the region above the step surface of the pump water absorption tank, prevent vortex generation, and allow the pump to suck in the vortex. Achieved the purpose of avoiding obstacles such as vibration and noise caused by.

[0006]

[Action]

 According to the present invention, the separation / backflow phenomenon of the flow generated in the lower region on the step surface, particularly in the boundary layer equivalent portion, can be suppressed by the separation / backflow phenomenon suppressing member, so that the generation of the vortex is prevented. To be prevented.

[0007]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a pump water absorption tank to which the present invention is applied, and FIG. 2 is a vertical side view. In addition, the same or corresponding portions as those of the conventional pump water absorption tank will be described with the same reference numerals. In these drawings, the pump water absorption tank 6 is provided with a step surface 2 that descends at an inclination angle θ toward the pump installation area 1 on the upstream side of the pump installation area 1 where the pump P is installed. The bottom 3 of the installation area 1 is deeper than the bottom 5 of the upstream area 4 of the step surface 2. The step surface 2 is provided with separation / backflow phenomenon suppressing members 8 made of a pair of vertically rising plate materials corresponding to boundary layers b, which will be described later.

In the above configuration, when the pump P is operated, in the upstream region 4, the entire region D in the depth direction from the water surface WL to the bottom portion 5 in FIG. And the flow state shown by the arrow group B is reached. That is, in the vicinity of the side walls 7 and 7, the boundary layers b and b in which the flow velocity suddenly changes and becomes small are in a flow state in which they are generated in the entire region D in the depth direction. In FIG. 2, when a substantially uniform flow (arrow group B) across the entire area D in the depth direction reaches the area C on the step surface 2, it is affected by the suction action of the pump P and the drop of the step surface 2. In particular, the flow velocity of the flow portion indicated by B1 is higher than the flow velocity of the upper region B2 and the lower region B3 in the central portion in the depth direction of the substantially uniform flow arrow group B. As a result, the flow in the lower region B3 is decelerated in the region C on the step surface 2 for the same reason as in the conventional example. Moreover, even near the side walls 7 and 7 of the step surface 2, the flow velocity near the side walls 7 and 7 suddenly decreases due to the boundary layers b and b which are generated in the entire region in the depth direction. Therefore, due to the deceleration of the main flow, the flow of the boundary layers b 1 and b 2 in the lower region B is separated from the side walls 7 and 7 and tries to generate a “flow separation / backflow phenomenon” in which the flow flows backward. However, since the occurrence of this phenomenon is suppressed by the separation / backflow phenomenon suppressing member 8, it is possible to reliably prevent the generation of vortices. Therefore, the pump P will not be disturbed by vibration or noise due to the suction of the vortex. Of course, even if the length L of the pump water absorption tank 6 is shortened, the step surface 2 is brought closer to the pump P, and the inclination angle θ of the step surface 2 is increased, no vortex is generated. The cost can be reduced. Further, if the distance a2 on the downstream side is set to a1> a2 with respect to the distance a1 on the upstream side between the separation / backflow phenomenon suppressing members 8 and 8 and the side walls 7,7, the direction opposite to the vortex Z (see FIG. 8) is obtained. Since a vortex is given, Z can be effectively prevented from occurring even if the length of the separation / backflow phenomenon suppressing members 8 is short.

In the above-described embodiment, the separation / backflow phenomenon suppressing members 8 made of a pair of plate materials that rise vertically corresponding to the boundary layers b, which will be described later, are provided on the step surface 2. However, as shown in FIG. 3 and FIG. 4, FIG. 5 and FIG. 6, even if the separation / backflow phenomenon suppressing members 8 made of inclined plate materials are provided in the vicinity of the step surface 2 so as to face each other. Good. Further, the inclination angle β of the separation / backflow phenomenon suppressing members 8 1, 8 made of these inclined plate materials may be set to be substantially the same as or slightly larger than the inclination angle θ of the step surface 2.

[0010]

[Effect of the device]

 As described above, according to the present invention, the separation / backflow phenomenon of the flow generated in the lower region on the step surface, particularly in the boundary layer corresponding portion can be suppressed by the separation / backflow phenomenon suppressing member, Is surely prevented, and the vortex is not sucked into the pump.

[Brief description of drawings]

FIG. 1 is a plan view of a pump water absorption tank to which the present invention is applied.

FIG. 2 is a vertical sectional side view.

FIG. 3 is a plan view showing a modified example of a separation / backflow phenomenon suppressing member.

FIG. 4 is a sectional view taken along the line AA of FIG.

FIG. 5 is a plan view showing another modified example of the separation / backflow phenomenon suppressing member.

6 is a sectional view taken along the line EE of FIG.

FIG. 7 is a vertical sectional side view showing a conventional pump water absorption tank.

FIG. 8 is a plan view of FIG.

[Explanation of symbols]

 1 Pump installation area 2 Step surface 3 Bottom of pump installation area 4 Upstream area of step surface 5 Bottom of upstream area of step surface 6 Pump suction tank 8 Separation / backflow phenomenon suppression member P pump

Claims (1)

[Scope of utility model registration request] 1. A pump water absorption tank in which a step surface is provided on the upstream side of the pump installation area, and the bottom of the pump installation area is deeper than the bottom of the upstream area of the step surface. A vortex preventive device for a pump water absorption tank, which is provided with a separation / backflow phenomenon suppressing member.