JPH0587292U - Centrifugal pump - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a centrifugal pump that does not generate harmful bubbles even when performing a suction operation with a large head in an extremely small flow rate range, and can reduce manufacturing costs and operation costs. [Structure] An impeller 5 in a centrifugal pump is in a range from a circumferential center 15 of a flow path 11 to a front side 16 of a blade 10 which is the closest to the impeller ring 12, and from an outer peripheral portion 16 of the impeller ring 12 to an inner peripheral portion 18 of the blade 10. And a through hole 19 formed in the rear shroud 9 facing each other. A part of the discharged high pressure water is guided to the vicinity of the inner circumference of the blade through the through hole, and the negative pressure is relieved to prevent bubbles from being generated.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a centrifugal pump that is mainly operated for suction, such as in a small water supply device.

[0002]

[Prior Art]

 When the centrifugal pump sucks up in a very small flow rate range close to the deadline operation, water separation occurs because the angle between the water flow direction and the blade front side is large near the inlet of the blade where negative pressure occurs, and air in water is released. The air bubbles generated as a result stay. Such a phenomenon is more likely to occur as the suction head is larger and the discharge flow rate is smaller, and if the suction head is prolonged, the amount of accumulated bubbles increases and the discharge head decreases, and eventually pumping becomes impossible.

Conventionally, as a solution to such a problem, a part of pumped water is recirculated from the discharge side to the suction side by a jet method or a relief valve method, and the flow rate through the impeller is increased even if the demand flow rate is low. I was trying to do it.

[0004]

[Problems to be solved by the device]

 In the conventional solution as described above, not only the jet pump or the relief valve but also the bypass flow passage and the like are required, so that the device structure is complicated and the number of parts is large, and the manufacturing cost is inevitably high. Further, since extra water is sucked up in order to prevent the generation of bubbles, there is a drawback that the operating cost also increases.

The present invention has been made in order to solve the above-mentioned problems, and has a large suction head, prevents bubbles from being generated even in an extremely small flow rate range, and can reduce manufacturing costs and operating costs. The purpose is to provide a centrifugal pump.

[0006]

[Means for Solving the Problems]

 According to the present invention, the impeller in the centrifugal pump is located in the range from the center of the flow passage in the circumferential direction to the nearest blade surface side, and in the range from the outer peripheral part of the impeller ring to the inner peripheral part of the blade in the rear shroud. It is characterized by having an opened through hole.

[0007]

[Action]

 In the above configuration, during pump operation, part of the high-pressure water discharged from the impeller is guided from the rear of the rear shroud to the vicinity of the inner circumference of the blade through the through hole, and the negative pressure is relieved, thereby generating bubbles. Or retention is prevented.

[0008]

【Example】

 The present invention will be described below with reference to an embodiment shown in FIGS. In FIG. 1, an impeller 5 supported by a main shaft 4 of an electric motor 3 is rotatably housed inside a casing 1 and a casing cover 2 of a centrifugal pump, and a slight gap 6 is formed on both sides in the axial direction. , 7 are formed.

As shown in FIG. 2, the impeller 5 includes a pair of front shrouds 8 and rear shrouds 9 facing each other in the front-rear direction, and a plurality of spirally-shaped spiral shrouds disposed therebetween in an alternating manner in the circumferential direction. It has vanes 10 (only three are shown in the figure) and channels 11. Further, an impeller ring 12 is provided on the front side of the front shroud 8 so as to project in the axial direction. The inflow port 13 of the impeller 5 is opened in the impeller ring 12, and the outflow port 14 is arranged in the outer peripheral portion.

The rear shroud 9 has a range from the center 15 of the flow passage 11 in the circumferential direction to the front side 16 of the nearest blade 10, and the outer peripheral portion 17 of the impeller ring 12 to the inner peripheral portion 18 of the blade 10. Up to a desired number (two in the figure) of through-holes 19 communicating between the flow path 11 and the gap 7 are formed at positions opposite to each other (shown by hatching the common part of the two ranges). ing. Next, the operation of the above embodiment will be described.

When the impeller 5 is rotationally driven through the electric motor 3, the water sucked from the inflow port 13 is pressurized by the centrifugal force and discharged from the outflow port 14, and most of it is supplied to the outside, but part of it is supplied. It is guided to the gaps 6 and 7. At this time, the water pressure between the adjacent blades 10, 10 becomes higher as it approaches the outlet 14, so that part of the high-pressure water that has once flowed out of the outlet 14 penetrates through the outer gap 7 of the rear shroud 9. It flows out through the hole 19 to the vicinity of the inner peripheral portion 18 of the blade 10.

Assuming that the through hole 19 is provided near the outer peripheral portion of the blade 10, the pressure in the flow passage increases as the blade approaches the outer peripheral portion, so that air is less released and inevitably sufficient bubble blocking is achieved. No effect. Further, since the circumferential component of the water flow in the flow passage 11 is directed from the front side to the back side of the blade 10, if the through hole 19 is provided near the back side of the blade, the jetted pressure water is not diffused in the front side direction, Since the pressure does not rise near the front side, bubbles are generated due to the release of air.

On the other hand, in the above embodiment, the high-pressure water is jetted out in the vicinity of the blade inner peripheral portion 18 where the pressure is lowest, so that the pressure in the low-pressure portion is extremely effectively increased. Therefore, even if the suction operation with a high head is performed in the minimum flow rate region close to the dead-time operation, the generation or growth of bubbles is effectively prevented, and the accumulated bubbles do not cause the pump to be unable to pump. In addition, for that purpose, since it is only necessary to open the through hole 19, the structure is simple, no additional parts are required, and the size can be reduced, so that the manufacturing cost can be reduced. In addition, since the amount of water recirculated from the high pressure side to the low pressure side is small, the increase in operating cost is also small.

It should be noted that the present invention is not limited to the above embodiment, but is effective when applied to the first stage in a multistage centrifugal pump, for example. In addition, various modifications and applications are possible within the scope of the present invention.

[0015]

[Effect of the device]

 As described above, according to the present invention, it is possible to provide a centrifugal pump that has a large suction head, prevents bubbles from being generated even in an extremely small flow rate range, and can reduce manufacturing costs and operating costs.

[Brief description of drawings]

FIG. 1 is a cutaway side view showing an embodiment of the present invention.

FIG. 2 shows an impeller in the embodiment, (A) is a cross-sectional view taken along the line AA of (B), and (B) is a cross section of (A).
Sectional drawing which follows the B line.

[Explanation of symbols]

5 ... impeller, 8 ... front shroud, 9 ... rear shroud,
10 ... Blade, 11 ... Flow path, 12 ... Impeller ring, 15
... center, 16 ... front side, 17 ... outer peripheral portion, 18 ... inner peripheral portion, 1
9 ... Through hole.

Claims (1)

[Scope of utility model registration request] 1. A front shroud having an impeller ring projecting in the axial direction, a rear shroud facing the shroud, and a plurality of spiral blades and a stream interposed between the shrouds and arranged alternately in the circumferential direction. In a centrifugal pump provided with an impeller having a passage, in the range from the circumferential center of the flow path to the nearest blade surface side, and facing the range from the outer peripheral portion of the impeller ring to the inner peripheral portion of the blade, A centrifugal pump comprising a through hole formed in a rear shroud.