JPH0540317Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a vertical shaft multi-stage pump with a gas suction countermeasure structure. This article relates to a gas suction countermeasure structure for a multistage pump.

``Conventional technology'' In general, hot water from source wells for hot springs is usually
The water is pumped from an underground source at a temperature of 40℃ to 80℃, but some sources emit gas, and the amount of gas mixed in and the size of the bubbles vary. It is well known that the size of the air bubbles involved is also influenced by water pressure and temperature.

In recent years, submersible motor pumps have come to be used to pump hot water from source wells, and when pumping hot water from source wells using submersible motor pumps, as shown in Figure 2, a centrifugal vertical shaft is installed in the source well 1. Multistage pump 2
Insert it to an appropriate diving depth T below the automatic stop water level. In normal operation, the water level in the well is operated at an operating water level that is lower than the natural water level, but if it drops further below the operating water level and reaches the automatic stop water level, the sensor 3 detects this drop and The operation of the multistage pump 2 is stopped.

On the other hand, some hot spring sources emit gas, and when the gas is sucked into the submersible motor pump along with the hot water, cavitation occurs inside the hot spring, reducing the hot water pumping performance. becomes incapable. Therefore,
The applicant has submitted Utility Model Application No. 60-28294 and Utility Model Application No. 62-
A submersible motor pump such as No. 197788 has already been proposed. The submersible motor pump of Utility Model No. 60-28294 is
From the suction side, the first and second stage centrifugal impellers are open-type impellers with back blades, and the gas sucked together with hot water from the suction port by the open-type impellers is When hot water is divided into small pieces and pumped using closed impellers with good hot water pumping efficiency in the third and upper stages, cavitation phenomenon does not occur in the pump section due to the closed impellers. . on the other hand,
The submersible motor pump of Utility Model No. 60-197788 was the first
The second stage and second stage use an open type impeller with a back blade, similar to the submersible motor pump of Utility Model No. 60-28294, and the third stage and above have a balancing hole and a back liner ring. A closed type impeller is used, and a back blade is provided on the closed type impeller. The gas that has been finely divided by the open impellers in the first and second stages gathers in the space around the shaft on the back side of the closed impellers in the third and upper stages, forming a gas pool. This prevents cavitation from occurring, which is caused by the high pressure inside the pump due to the pumping of hot water by the closed impeller and the breakup of air bubbles by the back blade attached to the closed impeller. , which prevents bubbles from growing.

``Problems to be solved by the invention'' However, in any of the above submersible motor pumps, the gas inhaled with hot water gathers inside the bubbles, grows large, and stays in the center of the pump, causing cavitation phenomenon. This prevents a drop in hot water pumping efficiency or the inability to pump hot water, but when drawing hot water into the interior from the suction port of the submersible motor pump, it is actively prevented from mixing in gas just before the suction port. No measures were taken to prevent this.

Therefore, in view of the above circumstances, the present invention more effectively prevents gas inhalation, which is the fundamental cause of the cavitation phenomenon caused by the deterioration of hot water pumping performance and the inability to pump hot water, before it enters the pump. The purpose of the present invention is to provide a structure for preventing gas suction of a vertical shaft multi-stage pump.

"Means and effects for solving the problem" In order to achieve the above-mentioned object, the present invention provides a vertical shaft multi-stage pump in which a plurality of centrifugal impellers are mounted in multiple stages on a vertical shaft directly connected to a motor. a long outer cylinder with an open bottom and a closed bottom;
and a suction port attached near the bottom of the inside of the outer cylinder, so that hot water flowing into the inside of the outer cylinder through a gap between the inner diameter of the well and the outer diameter of the outer cylinder is pumped up from the bottom of the inside of the outer cylinder. To provide a gas suction countermeasure structure for a vertical shaft multistage pump characterized by the following features.

According to the present invention, after air bubbles are released in the low water pressure area, hot water is called back to the deep part of the well.
Since this is pumped out using a pump, cavitation that occurs at the pump impeller can be prevented and efficient pumping can be achieved.

"Embodiment" Hereinafter, an embodiment of the gas suction countermeasure structure of the vertical shaft multistage pump according to the present invention will be described based on the drawings. In FIG. 1, reference numeral 11 denotes a vertical shaft multistage pump comprising a motor 12 and a pump action section 13 in which a plurality of impellers are mounted in multiple stages on a vertical shaft that is rotationally driven by the motor 12. The vertical shaft multistage pump 11 is
A pump suction port 14 is provided at the lowest part of the pump action section 13, that is, at a position between the motor 12 and the pump action section 13. A hot water pipe 15 is connected to the top of the pumping section 13, and after the hot water in the source well 16 is pumped up by the vertical shaft multistage pump 11, the hot water is pumped to a predetermined location such as a hot water storage tank on the ground surface. It is now equipped with hot water. The pump action portion 13 above the pump suction port 14 including the pump suction port 14 is surrounded by a bottomed cylindrical outer cylinder 17 having an open upper end.
The bottom of the outer cylinder 17 has a fitting part, and the fitting part is fitted and fixed to the vertical shaft multistage pump 11 below the pump suction port 14. The upper end of the outer cylinder 17 is supported on the hot water pipe 15 by a support member 18 in a state in which an opening is maintained. The length of the outer cylinder 17 is
The length is selected depending on various conditions such as the amount of gas gushing out from the source well 16, but the optimum length is selected so that gas will not be introduced into the outer cylinder 17 from the upper end opening 17a of the outer cylinder 17 together with the hot water. It goes without saying that the upper end of the outer cylinder 17 is located below the operating water level and below the automatic stop position. The diameter of the outer cylinder 17 is set so as to maintain a distance between the outer surface of the outer cylinder 17 and the inner surface of the source well 16, which is sufficient to allow at least a predetermined amount of hot water to flow. Furthermore, the outer cylinder 17 has an inner diameter that can maintain a distance between the inner surface of the outer cylinder 17 and the outer surface of the pump action part 13, which is sufficient to allow at least a predetermined amount of hot water to flow for pumping hot water. .

Next, the operation of the gas suction countermeasure structure of the vertical shaft multistage pump having the above configuration will be explained. First, the vertical shaft multi-stage pump 11 having the above structure and the source well 16 are placed so that the pump suction port 14 is located at a depth of l ₁ from the operating water level.
It shall be installed inside. Further, the length of the outer cylinder 17 is such that the distance between the upper end opening 17a of the outer cylinder 17 and the pump suction port 14 is l ₂ in accordance with conditions such as the amount of gas gushing out. do. On the other hand, gas is gushing out from the bottom of the well 16 along with hot water, and the vertical multistage pump 11 is operated in this state. The gas gushing out from the bottom of the source well 16 along with the hot water rises toward the top of the source well 16 due to its own buoyancy and the hot water pumped by the vertical multistage pump. The gas bubbles that gush out with the hot water expand as they rise, and as they expand, their buoyancy increases and the rate of rise increases. In other words, certain pressures P ₁ , P _2
The relational expression P ₁ , V _{1 =} P ₂ , V ₂ ,
And from V=π/6D ³ (D is the diameter of the bubble), if the diameter of the bubble is D ₁ when the pressure is P ₁ and the diameter D ₂ of the bubble when the pressure is P ₂ , then P ₁ , D ₁ ³ = P ₂ , D ₂ ³ , and if P ₁ is atmospheric pressure (1 atm), then D ₂ = ³ √ ₁ ³ ₂ . Therefore, as mentioned above,
As the gas bubbles rise from the bottom of the source well 16, they expand and increase in diameter as the surrounding water pressure decreases, and this enlargement of the bubbles increases buoyancy and increases the rate of rise. For this reason, the upper end opening 1 of the outer cylinder 17
In the vicinity of 7a, the diameter of the bubble expands considerably and the rising speed is extremely fast, so that the separated gas is not mixed into the downward flow of hot water from the upper end opening 17a toward the pump suction port 14. Most of the water rises to the water surface of the source well 16 and is then dissipated into the atmosphere. Moreover, the upper end opening 17 of the outer cylinder 17
Since the flow of hot water from a toward the pump suction port 14 is in the opposite direction to the buoyancy of the bubbles, large diameter bubbles will not be caught up in the flow of hot water and directed downward. However, only a small amount of the remaining air bubbles, whose buoyancy is smaller than the downward flow of hot water, mix into the flow of hot water and enter the pump suction port 1.
4 into the vertical shaft multistage pump 11, and while flowing downward, it is compressed by the water pressure of _l1 due to the effect of the length _l2 of the outer cylinder 17, Furthermore, the particles become finer, so that cavitation phenomenon does not occur inside the vertical shaft multistage pump 11, and the pump performance does not deteriorate.

"Effect of the invention" According to the invention, as described above, since the suction port is arranged downward near the bottom of the bottomed outer cylinder with the upper part open, cavitation can be suppressed to the extent that almost no cavitation occurs. I can do it. In other words, according to the mechanism of action of the present invention, the hot spring water gushing out from the bottom of the well, where the water pressure is high, is guided to the top of the outer cylinder where the water pressure is low, and the fine air bubbles that had been compressed are expanded and raised. After that, the hot water after releasing bubbles is sucked into the bottom of the outer cylinder via the inner diameter of the outer cylinder, and then pumped out from the bottom again.

Therefore, with this invention, the hot water in the pump part is
By squeezing out the air bubbles it contained, the hot water becomes thicker, and this thicker hot water is lowered to the bottom of the outer cylinder where the water pressure is high, so the air bubbles are reduced and the water becomes thicker. Conditions that make it difficult for bitation to occur are created.

As described above, according to the present invention, cavitation caused by the pump can be prevented when pumping hot water from underground hot springs containing a lot of bubbles, using a device with an extremely simple structure, and it is possible to prevent cavitation caused by the pump. Since no equipment is required, it is possible to obtain a low-cost, high-quality vertical shaft multi-stage pump with a gas suction countermeasure structure.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram showing a gas countermeasure structure of a vertical shaft multistage pump according to the present invention, and FIG. 2 is an explanatory diagram showing a conventional vertical shaft multistage pump installed in a source well. 11...Vertical shaft multistage pump, 12...Motor, 1
3...Pump action part, 14...Pump suction port, 1
5... Hot water pipe, 16... Source well, 17... Outer cylinder, 17a... Upper end opening, 18... Supporting material.

Claims (1)

[Scope of Claim for Utility Model Registration] A vertical shaft multi-stage pump in which a plurality of centrifugal impellers are installed in multiple stages on a vertical shaft directly connected to a motor, which has a long outer cylinder with a closed bottom and an open top and a closed bottom. , and a suction port attached near the bottom of the inside of the outer cylinder, the hot water that once flows into the inside of the outer cylinder after passing through the gap between the inner diameter of the well and the outer diameter of the outer cylinder is pumped from the bottom of the inside of the outer cylinder. A gas suction countermeasure structure for a vertical shaft multi-stage pump that is characterized by its ability to lift air.