JP2560651Y2 - Vertical pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vertical shaft pump applied to, for example, rainwater drainage.

[Conventional technology]

2. Description of the Related Art Conventionally, a vertical shaft pump used for rainwater drainage or the like sometimes operates in preparation for increasing water even when the water surface on the suction side, that is, when the water absorption level is lower than a specified water absorption level. In such a case, an air suction vortex is likely to be generated on the water surface on the suction side, and the impact of the vortex makes it impossible to operate the vertical shaft pump. Therefore, various eddy current prevention measures have been taken.
FIG. 4 is a sectional view of a conventional vertical pump. In the figure, this vertical shaft pump operates at 100% speed when the water absorption level is equal to or higher than the water absorption level A, which is the limit water absorption level at which the water can be safely sucked. In order to operate at a water level A or lower, the rotation speed is reduced to limit the discharge flow rate, and a vortex preventing wall 14 is provided.

FIG. 5 is a front view of another conventional vertical pump. In the figure, the vertical shaft type pump has a suction port 3 longer than usual, an impeller 5 mounted above a water level A corresponding to a limited water suction level, and a drain pipe 11 directly below the impeller 5.
Is mounted, and the upper portion is connected to the air / water switching device 12. When the water absorption level is equal to or higher than the water level A, steady operation is performed at 100% speed. However, when the water absorption level is equal to or lower than the water level A, the air suction vortex is likely to be generated. The air is sent directly below the car 5 to separate the water and water. The operation is performed with the discharge flow rate being zero while stirring the water and water at the speed of 100%.

[Problems to be solved by the invention]

As described above, in the conventional vertical pump, when the water absorption level is equal to or lower than the water level A corresponding to the limited water absorption level, it is necessary to perform deceleration or air / water separation or to provide the vortex prevention wall 14, but for that purpose, In addition to requiring a control system for deceleration, a drain pipe 11, a steam-water switching device 12, and the like, the mounting position of the impeller 5 is increased, and the water level at which pumping is started is increased by that amount. The effective suction water depth becomes shallow. Even if the vortex preventing wall 14 is installed, the limit water depth h at which air is not sucked from the water surface on the suction side is about 1.2 times as large as the diameter of the three suction ports. It is necessary to limit the discharge flow rate by controlling the rotation speed of the nozzle and the opening degree of the discharge valve.

[Means for solving the problem]

The vertical shaft pump according to the present invention is intended to solve the above-described problems, and has a small hole drilled near the impeller inlet of the suction port, and a base end opening at the suction port to operate the pump at a specified flow rate. The air suction pipe is characterized in that it has an air suction pipe whose tip is open from the water surface on the suction side to a water level where no air suction vortex is generated and whose opening area is 0.5 to 3% of the area of the throat portion.

[Action]

That is, in the vertical shaft pump according to the present invention, the base end opens to the suction port, and the front end opens to the water level where the air suction vortex does not occur from the water surface on the suction side during the pump operation at the specified flow rate, and the opening area is the throat part. An air suction pipe that is opened with an optimal size of 0.5 to 3% of the area is installed, and when the liquid level on the suction side is lower than a predetermined level, an appropriate amount of air is sucked into the suction port from the air suction pipe, By reducing the discharge flow rate of the pump without particularly increasing the radial thrust of the main shaft, no air suction vortex is generated from the liquid surface on the suction side. Also, a small hole is drilled near the impeller inlet of the suction port, and when the liquid level on the suction side is lower than the impeller inlet, a large amount of air is sucked into the suction port from the small hole together with the air suction pipe, Since the inside of the suction port quickly becomes a state of complete gas-liquid separation, extremely stable in-air operation is performed.

〔Example〕

FIG. 1 is a structural explanatory view of a vertical shaft type pump according to an embodiment of the present invention, and FIG. 2 is an explanatory view of its operation. In the figure,
The vertical shaft type pump according to this embodiment is used for draining rainwater, and has a size corresponding to 0.5 to 3.0% of the area of the throat portion 15 near the inlet of the impeller 5 of the suction port 3 as shown in FIG. Three small holes 10 are provided. Further, the base end 7 is opened at substantially the same level as the small hole 10 in the suction port 3 and the throat portion 15 is opened.
Air suction pipe 8 having a size equivalent to 0.5 to 3.0% of the area of
Is installed. The distal end 9 of the air suction pipe 8 opens to a water level A where no air suction vortex is generated from the water surface on the suction side when the pump is operated at a specified discharge flow rate, and rises once from the water surface. It has an inverted U shape.
The number of the small holes 10 and the number of the air suction pipes 8 may be one or plural. 1 is a main shaft, and 2 is a guide blade.

As shown in FIG. 2 (a), when the water surface on the suction side, that is, the water absorption level is smaller than the small hole 10, the inside of the suction port 3 is in a completely separated state of water and water, and the pump sucks both air and water. Not
Perform stable aerial driving. Next, as shown in FIG. 3B, when the water absorption level rises and reaches the lower end of the impeller 5, the impeller 5
Although the pumping action starts water from the suction port 3, the throat portion 15 of the flow rate at the time of pumping upsilon, the loss counts in the pressure alpha, acceleration only when α × υ ² / 2g and g pressure of gravity is lowered As a result, air that is lower than the atmospheric pressure and matches the pressure difference ΔP from the atmospheric pressure is sucked from the air suction pipe 8. The air sucked from the air suction pipe 8 closes the flow path between the blades of the impeller 5 and reduces the discharge flow rate of the pump. Throat part 15
Is lower as the water absorption level is lower.
In the case of the lower end, since only about 20% of the prescribed discharge flow rate is pumped due to the water absorption, no air vortex is generated from the water surface on the suction side, and stable operation with small vibration is performed. Further, as shown in FIG. 3 (c), when the water absorption level rises, the pressure of the throat portion 15 rises, the amount of air sucked from the air suction pipe 8 decreases, and the amount of water absorbed from the suction port 3 increases. The specified discharge flow of the pump is approached.

When the water absorption level rises above the tip 9 of the air suction pipe 8, that is, the water level A, as shown in FIG. For normal operation. At this time, there is a flow which is sucked into the impeller 5 through the air suction pipe 8 and the small hole 10, but since the flow rate is extremely small as compared with the flow rate flowing through the suction port 3, no unrectification occurs and the pump performance is not improved. Has no effect.

Next, as shown in FIG. 3E, when the water absorption level decreases and becomes equal to or less than the tip 9 of the air suction pipe 8, air is sucked from the air suction pipe 8 and the discharge flow rate of the present pump decreases.
Even when the water level is equal to or lower than A, no air suction vortex is generated from the water surface on the suction side. Further, as shown in FIG. 3 (f), when the water absorption level decreases and becomes smaller than the small hole 10, the air suction pipe 8 and the small hole are reduced.
Air enters from 10, air-water separation is performed at the lower end of the impeller 5, and the impeller 5 rotates in the air. in this case,
If the small hole 10 is not provided only with the air suction pipe 8, as shown in FIG. 3G, the water resistance is reduced due to the pipe resistance of the air suction pipe 8 and the blockage of the base end 7 due to the flow in the suction port 3. The hunting phenomenon in which the separation is not completely performed and the pumping and the air / water separation are performed alternately may occur and the transient operation may continue.However, the provision of the small holes 10 allows the water / water separation when the water surface is smaller than the small holes 10. Is performed completely, and stable aerial driving is performed.

These phenomena could be confirmed by performing a continuous operation test while making a transient state by moving the water surface on the suction side of the actual vertical shaft pump up and down. That is,
When the water surface on the suction side was moved up and down in a transient state, the thrust in the radial direction of the main shaft 1 fluctuated due to the opening area of the air suction pipe 8. FIG. 3A shows that the thrust in the radial direction is minimized when the opening area of the air suction pipe 8 is set to 0.5% of the area of the throat portion 15. When the opening area is smaller than 0.5%, the effect of the suction is reduced. And the radial thrust increases. Also, if the opening area is larger than 0.5%, the radial thrust gradually increases,
If it exceeds 3%, the thrust in the radial direction increases sharply due to the shock caused by the intake from the air suction pipe 8. Therefore, the opening area of the air suction pipe 8 is smaller than the area of the throat portion 15.
When it corresponds to 0.5-3%, an appropriate amount of air is sucked in,
It has been found that the radial thrust is reduced. Also,
The small hole 10 can reliably perform steam-water separation at the water level where pumping is unnecessary, and if there is no small hole 10, an unnecessary pumping operation will be performed if the water level drops below the small hole 10. (B) shows that the pump efficiency gradually decreases as the opening area of the small hole 10 for performing the water / water separation is gradually increased from about 0.5% of the area of the throat portion 15. This is because during normal operation of the pump, a flow is generated toward the impeller 5 through the small hole 10, but the impeller 5 is set so that the flow always flows in the direction of the main shaft 1 and the angle of the inlet is determined. It is thought that the flow in the radial direction through 10 adversely affects the pump efficiency, and the opening area of the small hole 10 was limited to 3%.

As described above, the vertical shaft pump is always in a stable and normal state without the impeller 5 agitating the air and generating the air suction vortex from the water surface on the suction side regardless of how the water suction level is lowered. Driving is possible. Further, since the tip 9 of the air suction pipe 8 once rises from the water surface to form an inverted U shape, it is difficult to swallow foreign matter from the tip 9, especially foreign matter floating on the water surface or foreign matter falling in the air, In addition, the possibility of the air suction pipe 8 being clogged by the foreign matter is very low, for example, the foreign matter once sucked up is likely to flow backward and be discharged simultaneously with the drainage. Therefore, it is suitable for the case where it is necessary to operate without lowering the rotation speed even at a water level lower than the impeller 5 such as for rainwater drainage. No special operation or device such as control is required, and even in such severe usage, the same life and reliability as conventional pumps of the same type can be obtained.

[Effect of the invention]

The vertical shaft pump according to the present invention is configured as described above. Even when the liquid surface on the suction side is lower than a predetermined level, no air suction vortex is generated from the liquid surface, and the liquid surface on the suction side has a blade. When it is lower than the car entrance, stable aerial operation is performed, so there is no need for control or equipment such as eddy current prevention, deceleration, gas-liquid separation, restriction of discharge flow, etc. be able to.

[Brief description of the drawings]

1 (a) is a sectional view of a vertical shaft type pump according to an embodiment of the present invention, FIG. 1 (b) is a sectional view taken along the line bb in FIG. 1 (a), and FIGS. FIG. 4 is a sectional view of a conventional vertical shaft pump, and FIG. 5 is a front view of another conventional vertical shaft pump. 1 ... spindle, 2 ... guide blade, 3 ... suction port, 5 ... impeller, 7 ... base end, 8 ... air suction pipe, 9 ... tip,
10 ... Small hole, 15 ... Throat part.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-78791 (JP, A) JP-A 62-28097 (JP, U) JP-A 63-121793 (JP, U) JP-A 63-280 150097 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] 1. A small hole drilled near an impeller inlet of a suction port, and a tip end at a water level where an air suction vortex does not occur from a water surface on a suction side from a water surface on a suction side during operation of a pump at a specified flow rate with a base end opening at the suction port. Is open and the opening area is
A vertical shaft type pump comprising a 0.5 to 3% air suction pipe.