JP2000120573A - Vertical shaft pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce vibration or noise generated when the water level is lowered to reach the air-intake position of a suction pipe and a vertical shaft pump begins to suck air. SOLUTION: The vertical shaft pump is provided with a suction pipe 8 one end 8a of which opens into a pump well 9 in a higher position than an impeller 2 and the other end 8b of which opens in a bell-mouth 3 in a lower position than the impeller 2, and is adapted to control the water-supply and stopping by the suction of air from the suction pipe 8. In this case, a porous orifice 12 is provided in the suction pipe 8 so that it is located above one end 8a of the suction pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stand-by type vertical shaft pump which can be started even when a pump well has a low water level.

[0002]

2. Description of the Related Art In recent years, with the rapid progress of urbanization and land use in a river basin, almost no rainfall is absorbed by the ground. For this reason, when the amount of rainfall is large, a large amount of rainwater flows into the pumping station in a short time after starting to descend. In order to cope with such a rapid inflow of rainwater, a so-called advance standby type vertical shaft pump which can be started even in a state where the water level of the pump well is low and can stand by at full speed has been conventionally used. In addition, such a vertical shaft pump is used not only for a pump station but also for agricultural land drainage and other drainage.

FIG. 4 is an overall configuration diagram of a conventional prior standby type vertical shaft pump. As shown in FIG. 4, the vertical pump 1 includes an impeller 2, a bell mouth 3, a main shaft 4, a casing 5, a suspension pipe 6, a discharge elbow 7, an intake pipe 8, and the like, and a diesel engine (not shown). Thus, the impeller 2 is rotated via the main shaft 4. The rotation of the impeller 2 sucks rainwater or the like accumulated in the pump well 9 from the open end (lower end) of the bell mouth 3 and drains it through the discharge elbow 7 or the like.

The intake pipe 8 has one end 8a opening into the pump well 9 at a position slightly higher than the impeller 2, and the other end 8b opening inside the bell mouth 3 at a position below the impeller 2.

The above-described vertical pump 1 is operated as described below. That is, as shown in FIG. 5, the vertical shaft pump 1 is kept in a state where the water level of the pump well 9 is lower than that of the impeller 2.
Is started, the aerial operation state is established, the vertical pump 1 does not suck in water, and the impeller 2 is in an idling state while the discharge amount remains zero.

Next, as shown in FIG. 6, when the water level reaches the lower end of the blade of the impeller 2, drainage is started. At the water level below a certain level (LWL) after the start of drainage, air flows into the pump from one end 8a of the suction pipe 8 whose end is released to the atmosphere due to the differential pressure between the atmosphere and the pump suction pressure. The operation becomes a gas-water mixing operation. In this operating state,
Due to the mixing of a large amount of air, the flow state of water near the impeller 2 in the casing 5 is disturbed and the pump performance is reduced, so that the discharge amount is reduced.

As shown in FIG. 7, when the water level in the pump well 9 further rises and one end 8a of the intake pipe 8 is submerged and closed, air does not flow into the pump and normal drainage operation is performed. .

Further, the discharge amount of the vertical shaft pump 1 becomes larger than the flow amount of water into the pump well 9, and as a result, the water level decreases, as shown in FIG. At the one end 8a, the intake pipe 8 starts sucking air again. However, immediately before the start of suction, the lower end of the intake pipe 8
The part b becomes a negative pressure, and therefore, inside the intake pipe 8,
A water column 10 is formed so as to be located above one end 8a.

When the intake pipe 8 starts sucking air again, as shown in FIG. 9, a mushroom-like bubble 11a is formed in a water column 10 in the intake pipe 8 at one end 8a of the intake pipe 8.
Is formed, and the formed bubble 11 a rises in the water column 10 in the intake pipe 8.

The bubble 11a grows in the vertical direction as it rises in the water column 10, further rises as a bullet-like bubble 11b, and is destroyed when it grows to a certain length. When the bubbles 11a and 11b rise, the bubbles 11a and 11b
The water below is drawn up and rises.

When the bubble 11b is broken, the water at the top falls and the water rises from the bottom at the place where the bubble 11b in the water column 10 is broken, and the bubble 11b is broken. The water column 10 is formed again so as to fill the place. In addition, the water rises below the water column.
A cavity is formed in 0, and a new air column is formed.

As a result, the bubbles 11a and 11b are intermittently formed and disappeared repeatedly. As a result, the water level of the water column 10 fluctuates up and down, and sometimes water flows to the pump side.

[0013]

As described above, when a slag flow in which air bubbles 11a, 11b and water are present alternately occurs inside the intake pipe 8, the intake air in the intake pipe 8 as shown in FIG. With the change in the amount, the operating point of the vertical shaft pump 1 moves along the operating line as shown in FIG. 10, and the head also fluctuates as shown by the arrow A, resulting in an unstable operation state. Therefore, as shown in FIG. 11, there is a problem that a large fluctuation occurs in the discharge pressure of the vertical shaft pump 1, and as a result, large vibration and noise are generated in the vertical shaft pump 1.

In FIG. 10, α is an intake rate, and is expressed as α = Qa / Q, where Qa is the amount of air sucked into the vertical pump 1 and Q is the discharge flow rate of the vertical pump 1.

In view of the above-mentioned circumstances, the present invention provides a so-called advance standby type vertical shaft pump with vibration and noise even in an operation state where the water level is lowered and air is sucked from one end of the intake pipe opening into the pump well. The purpose of this is to prevent the occurrence of.

[0016]

According to the present invention, there is provided an intake pipe having one end opened into a pump well at a position higher than an impeller and the other end opened into a bell mouth at a position below the impeller. In a vertical shaft pump in which water supply and stop are controlled by suction of air from a pipe, a porous orifice is provided in the intake pipe so as to be located above the one end of the intake pipe.

According to the present invention, even if the water level in the pump well drops and the intake pipe draws in air from one end and mushroom-like bubbles are generated, the mushroom-like bubbles pass through the porous orifice to form fine bubbles. Becomes For this reason, the bubble becomes a fine bubble flow above the porous orifice, and a large fluctuation in the water level of the water column in the intake pipe can be suppressed.

Therefore, since the fluctuation in the intake air amount becomes small and the water in the intake pipe falls and escapes in a more stable state,
Stable operation is performed, and vibration and noise of the vertical shaft pump can be reduced.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 to 3 show an embodiment of the present invention. Since the basic configuration of the vertical pump 1 is the same as that of the conventional one, the same reference numerals are given to the same parts and the description is omitted. I do.

Thus, the inside of the intake pipe 8 in the embodiment of the present invention is located slightly above the one end 8a.
A perforated orifice 12 is provided.

Next, the operation of the embodiment of the present invention will be described. As shown in FIGS.
Description is omitted.

When the water level in the pump well 9 decreases and reaches the intake position at one end 8a of the intake pipe 8, the intake pipe 8 starts sucking air. The other end 8b of 8 has a negative pressure. Therefore, a water column 10 is formed in the intake pipe 8 so as to be located upward from one end 8a.

As shown in FIG. 2, when the intake pipe 8 starts sucking air, a water column 10 in the intake pipe 8 contains:
A mushroom-shaped bubble 11a is formed at one end 8a of the intake pipe 8, and starts to rise in the water column 10.

However, since the porous orifice 12 is provided in the intake pipe 8, the mushroom-shaped bubbles 11a become fine bubbles 11c when passing through the holes 12a (about 3 to 10 mm in diameter) of the porous orifice 12. In this state, it rises in the water column 10 above the porous orifice 12.

For this reason, the fine bubbles 11c are uniformly dispersed in the water column 10 so that a large fluctuation of the water level of the water column 10 in the intake pipe 8 can be suppressed, and the fluctuation of the intake air amount becomes small. As a result, the water in the intake pipe 8 falls and comes out in a more stable state, so that a stable operation is performed along the operation line in FIG. 10 and the vibration and noise of the vertical pump 1 are reduced.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the spirit of the present invention.

[0028]

According to the vertical shaft pump of the present invention, it is possible to obtain an excellent effect that vibration and noise generated when the water level is lowered and the intake pipe sucks air can be reduced.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a vertical shaft pump according to the present invention.

FIG. 2 is an enlarged view of a portion of the vertical shaft pump of FIG. 1 where a porous orifice of an intake pipe is installed.

FIG. 3 is a view taken in the direction of arrows III-III in FIG. 2;

FIG. 4 is a vertical sectional view of a conventional vertical pump.

FIG. 5 is a vertical cross-sectional view showing a state in which a conventional vertical pump is performing an in-air operation.

FIG. 6 is a longitudinal sectional view showing a state in which the water level rises and a gas-water mixing operation is performed by a conventional vertical pump.

FIG. 7 is a vertical cross-sectional view showing a state in which the water level further rises in the conventional vertical pump and normal operation is performed.

FIG. 8 is a vertical cross-sectional view showing a state in which the water level is lowered and a gas-water mixing operation is performed by a conventional vertical shaft pump.

FIG. 9 is an enlarged vertical sectional view of the intake pipe showing a state of bubbles generated in the intake pipe when the water level is lowered and the vertical pump performs a gas-water mixing operation.

FIG. 10 is a graph showing a relationship between a discharge amount of a vertical shaft pump and a head.

FIG. 11 is a graph showing the relationship between the time when the air / water mixing operation as shown in FIG. 8 is performed and the discharge pressure of the vertical shaft pump.

FIG. 12 is a graph showing the relationship between the time when the air / water mixing operation as shown in FIG. 8 is performed and the amount of intake air in the intake pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical pump 2 Impeller 3 Bell mouth 8 Intake pipe 8a One end 8b Other end 9 Pump well 12 Perforated orifice

Claims (1)

[Claims] 1. An intake pipe having one end opened into a pump well at a position higher than an impeller and the other end opened into a bell mouth at a position below the impeller, and by suction of air from the intake pipe, A vertical shaft pump for controlling water supply and stop, wherein a perforated orifice is provided in the intake pipe so as to be located above the one end of the intake pipe.