JPH02196200A - jet pump - Google Patents

Abstract

PURPOSE:To make a decompression pipe on the side of feedwater unnecessary and pumping possible without need to increase the quantity of feedwater by providing a perforated plate in the diffuser part or the pipe following the diffuser part of a jet pump. CONSTITUTION:Although the feedwater of high feedwater pressure becomes a jet 10 and flows from a nozzle 3 to a diffuser 6 through a throat 5, whereat a part flows to a pipe 9 because of a perforated plate 12, the remainder flows backward in the diffuser 6 to the throat 5 like an arrow 11. And, the space between the jet 10 and the throat 5 is filled with water by the reversed flow, air 15 in an injection tube 4 is discharged, water in a drainage part 7 is raised through a suction pipe 8, and the water level 16 in the suction pipe 8 is raised. And, when the water level 16 is raised up to the position of the nozzle 3, water is quickly lifted as the jet and the water on the side of pumping contact together. Although pumping by a jet pump designed for high feedwater pressure having an area ratio in a matter of 0.2 for nozzle area/throat area with this pumping is impossible, pumping become possible by providing the perforated plate 12.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is a jet pump that pumps liquid by injecting liquid from a nozzle, particularly a jet pump of high water supply pressure and low head type, which pumps up liquid at startup. Concerning the hydraulic configuration of the jet pump to facilitate.

[Conventional technology]

Jet pumps are used as drainage pumps in hydroelectric power plants, etc., and are used to inject liquid, such as water, from a nozzle and pump the liquid, such as water, using the negative pressure generated at this time.
Conventionally, a structure shown in FIG. 4 is known. No.! In the figure, l is a jet pump, which is connected to a water supply pipe 2 that supplies pressurized water, has a nozzle 3 that injects pressurized water, a truncated conical injection tube 4 that houses this nozzle 3, and is connected to this injection tube 4. It consists of a throat 5 located in front of the nozzle 3 and a diffuser 6 following this throat 5, and a suction pipe 8 inserted into a drainage part 7 is attached to the other end of the injection cylinder 4. . Note that 9 is a pipe connected to the diffuser to supply pumped water to the outside.

With such a structure, the jet pump 1 has its suction pipe 8
is inserted into the drainage section 7 from which water is to be pumped. When pressurized water is supplied to the nozzle 3 through the water supply pipe 2 in this state, a high-speed jet is injected from the nozzle 3 to the injection cylinder 4. This high-speed jet creates a negative pressure and sucks up water from the drainage section 7 through the suction pipe 8. This sucked up water flows into the diffuser 6 through the throat 5, recovers its pressure by the diffuser 6, flows into the piping 9, and the water in the drainage section 7 is discharged to the outside.

By the way, when manufacturing a jet pump, when specifications for high water supply pressure and low head are given, a pressure reducing pipe is installed on the water supply side to lower the water supply pressure, and the nozzle area of nozzle 3 is increased to increase the water supply amount. Is going.

[Problem to be solved by the invention]

The characteristics of jet pumps are that even if they have the same head and displacement, the jet speed is high when the water supply pressure is high.
When the water supply pressure is low, the jet speed is low, so the nozzle area must be increased and water must be pumped at a large amount of water. Therefore, by increasing the water supply pressure, the water supply amount can be reduced. On the other hand, the throat section, which serves as the mixing chamber for high-speed jet water and pumped water, must have a cross-sectional area that prevents the speed of the mixed water from becoming too high in order to prevent cavity silane. / In high water supply pressure, low head type jet pumps with a large ratio of water supply amount, the throat area/nozzle area ratio becomes large.

By the way, if the jet pump is installed at a location where the nozzle section is higher than the water level of the drainage section from which water is pumped, the nozzle section will be placed in the air when the jet pump is stopped. Therefore, when a high water supply pressure, low head jet pump with a small nozzle area compared to the throat area blows out the jet again, the jet will not come into contact with the throat wall and will fly out into the diffuser section, resulting in negative pressure inside the injection cylinder where the nozzle is located. It becomes impossible to pump water. To avoid this situation, in the past, when the water supply pressure was high, a pressure reducing pipe was installed on the water supply side to lower the water supply pressure, prevent the ratio of displacement volume/water supply volume from becoming too large, and adjust the throat area/nozzle area ratio. I was going. However, this method has the disadvantage that a pressure reducing pipe must be provided which consumes the input energy of the water on the water supply side, and the amount of water supplied must also be increased.

An object of the present invention is to provide a jet pump that can pump water without requiring a pressure reducing pipe on the water supply side or increasing the amount of water supplied even if the specifications of the jet pump are high water supply pressure and low head. .

[Means to solve the problem]

In order to solve the above problems, according to the present invention, there is provided a nozzle for injecting pressurized liquid, an injection cylinder in which the nozzle is installed, a throat connected to the injection cylinder and located in front of the nozzle, and a throat connected to the injection cylinder and located in front of the nozzle. In a jet pump that is equipped with a diffuser and a jet flow from a nozzle to lift liquid and discharge it from the diffuser through an injection cylinder, a perforated plate is provided in the diffuser part or the piping connected to the diffuser.

[Effect]

When pressurized liquid is injected from a nozzle, if this jet flows out into the diffuser without contacting the inner wall of the throat, the air that is very close to the jet inside the throat will be discharged together with the jet into the diffuser section. However, the air near the inner wall of the throat flows back from the diffuser part to the throat part by the amount of air discharged by the jet, and the pressure in the injection tube does not decrease. When a part of the air flows back through the diffuser section to the throat section, water fills between the jet and the inner wall of the throat section, thereby preventing the air from flowing back from the diffuser section to the throat section. As a result, the space between the jet and the inner wall of the throat is filled with water, which lowers the pressure near the inner wall surface than the center of the jet, and the shared becomes larger than the nozzle exit diameter, making it easier to contact the inner wall of the throat, further increasing the pressure in the injection tube. As the air inside the tank progresses, pumping begins.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of a jet pump according to an embodiment of the present invention. In FIG. 1, parts that are the same as those in the conventional example shown in FIG. 2 are given the same reference numerals, and their explanations will be omitted. In Fig. 1, the difference from the conventional example is that the outlet of the diffuser 6 is the first
The perforated plate 12 shown in the figure was attached. Perforated plate 12
In order to prevent the entire jet from flying out, a hole 13 smaller than the diameter of the jet IO from the nozzle 3 (nozzle diameter) is provided in the center.
Equipped with multiple holes around it! It is equipped with 4. In addition,
The optimal position for providing the perforated plate 12 in the diffuser section is at the outlet of the diffuser 6, where the flow velocity is slowest in the diffuser section when the inside of the jet pump is filled with water.

With this structure, the water supply with high water supply pressure becomes a jet lO from the nozzle 3 and flows through the throat 5 to the diffuser 6. At this time, because of the perforated plate 12, a part of the water flows into the pipe 9, but the rest flows into the diffuser 6. arrow 1 to throat 5
It flows backwards like 1. And due to this backflow, jet 1
0 and the inner wall of the throat 5 is filled with water, the air 15 in the injection tube 4 is discharged, the water in the drainage section 7 is pumped up through the suction pipe 8, and the water level 16 in the suction pipe 8 rises. do. When the water surface 16 rises to the position of the nozzle 3, the jet comes into contact with the water on the pumping side, so that water is pumped rapidly.

Due to such pumping, a jet pump designed with high water supply pressure has an area ratio of nozzle area/throat area of 0.
In some cases, it was impossible to pump up water in cases of about 2,000 yen, but by attaching the perforated plate 12, water can be pumped.

In this embodiment, the hole 13 is provided at the center of the perforated plate 12, but the same effect can be obtained even if no hole is provided at the center.

Further, the perforated plate 12 may be provided in a pipe downstream of the outlet of the diffuser 6, but in this case, pumping of water is possible although it takes a little longer to start pumping.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, by providing a perforated plate in the diffuser part of the jet pump or in the piping following the diffuser, the jet from the nozzle that supplies high-pressure water to the nozzle can be reduced. It collides with the perforated plate and flows back through the diffuser section to the throat section, filling the gap between the jet and the throat inner wall, discharging the air in the injection cylinder and pumping up the water, reducing the high water supply pressure as in the conventional method. Water can be pumped without requiring a pressure reducing pipe or increasing the amount of water supplied.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a jet pump according to an embodiment of the present invention, FIG. 2 is a plan view of the perforated plate of FIG. 1, and FIG. 3 is a sectional view of a conventional jet pump. 1: jet pump, 3: nozzle, 4: injection tube, 5 varnish throat, 6: diffuser, 12: perforated plate. 1st CI Figure Figure

Claims (1)

[Claims] 1) A nozzle that injects pressurized liquid, an injection cylinder that houses this nozzle, a throat that is connected to this injection cylinder and is located in front of the nozzle, and a diffuser that follows this throat, and the jet flow from the nozzle is What is claimed is: 1. A jet pump for pumping up liquid and discharging it from a diffuser through an injection cylinder, characterized in that a perforated plate is provided in the diffuser section or in the piping connected to the diffuser.