JPH05306697A - Leakage loss reduction system of chip clearance in pump - Google Patents

Abstract

PURPOSE:To improve pump performance by restraining flow of liquid flowing around a negative pressure surface side from a pressure surface side of a blade through a chip clearance formed between the inside surface of a casing of a pump and a chip of an impeller. CONSTITUTION:It is devised so as to take a part of liquid passing in a casing 2 in a passage 11 from a liquid intake port 10 formed on an impeller boss 51 by rotation of a main shaft 1 and an impeller 5, give large pressure on the liquid in the passage 11 by way of applying centrifugal force generated by the rotation of the impeller 5 and discharge the liquid from a plural number of liquid discharge ports 12, 12... formed on a chip 5a of the impeller 5 to a chip clearance 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leakage loss reduction structure for effectively reducing leakage loss of a tip clearance generated during operation of an axial flow pump or an oblique flow pump using an open type impeller. ..

[0002]

2. Description of the Related Art A main shaft 1 shown in FIGS. 7 to 9 has a sealed liquid bearing 3 provided in a casing 2 and a submersible bearing 4 in the casing 2.
In the axial flow pump which is rotatably supported by the main shaft 1 and the impeller 5 is fixed to the main shaft 1 so as to be rotatable at the same time, the main shaft 1 and the impeller 5 are rotated in the arrow R direction to move the liquid in the axial direction of the main shaft 1 (arrow X ) To the tip (blade tip) of the impeller 5 of FIGS. 7 and 8 due to the pressure difference of the liquid generated between the pressure surface 50A on the ventral side and the suction surface 50B on the back side of the airfoil 50 of FIG. ) A phenomenon in which it passes through the tip gap 6 between the inner surface 2A of the casing 2 and the casing 2 and goes around from the pressure surface 50A side to the negative pressure surface 50B side, that is, the phenomenon that leakage loss occurs in the tip gap 6, This is one of the causes of poor performance. However, in the current situation, no measures have been taken to effectively reduce the leakage loss of the tip gap 6 in the axial flow pump or the mixed flow pump.

[0003]

The problem to be solved is that due to the pressure difference between the pressure surface and the suction surface of the impeller, the liquid causes a gap between the tip of the impeller and the inner surface of the casing. This is because leak loss occurs in the tip clearance that wraps around from the pressure surface side to the suction surface side, which deteriorates pump performance.

[0004]

According to the present invention, a liquid intake port is formed in a region of the impeller fixed to a main shaft on the side of the main shaft, and the liquid intake port is formed in the tip of the impeller between the chip and the inner surface of the casing. Is formed in the gap between the chips, and the liquid discharge port and the liquid intake port are communicated with each other by a passage formed inside the impeller. By discharging the liquid to the gap and always interposing the discharge flow in the tip gap, the flow of the liquid that passes through the tip gap from the pressure surface side of the impeller to the negative pressure surface side is suppressed, and the pump performance is improved. Achieved the purpose of.

[0005]

According to the present invention, a part of the liquid passing through the casing due to the rotation of the main shaft and the impeller is continuously taken into the impeller through the liquid intake opening which opens toward the liquid flow. The centrifugal force generated by the rotation of the impeller is applied with a larger pressure to move radially outward in the passage, and is discharged into the tip gap from the liquid discharge port formed in the tip of the impeller and flows down from here. To do. Depending on the leak characteristic of the tip gap peculiar to the pump, the discharge water amount and the discharge amount should be considered in consideration of the opening area of the liquid intake port, the cross-sectional area of the passage, the opening area of the liquid discharge port and the formation distribution state of the liquid discharge port. By setting the distribution state, the discharge flow discharged from the liquid discharge port is always interposed in the tip gap, and the flow of the liquid passing through the tip gap from the pressure surface side of the impeller to the suction side is suppressed. be able to.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a longitudinal sectional view of a main part, FIG. 2 is a sectional view taken along the line AA of FIG. 1, FIG. 3 is an enlarged front view of one blade, and FIG. 4 is a plan view of FIG. It should be noted that the same or corresponding portions as those of the conventional example will be described by attaching the same reference numerals. In these drawings, the impeller 5 is composed of an impeller boss 51 and four blades 52, 52 ... And a male screw portion 52A of each blade 52, 52.
Is integrally attached to the impeller boss 51 by penetrating the peripheral wall of the impeller boss 51 and being fastened by the lock nut 7, and the impeller boss 51 can be simultaneously rotated with the main shaft 1 via the impeller key 8. And is prevented from moving in the axial direction by the impeller lock collar 9.

On the other hand, on the upstream side (left side in FIG. 1) of the impeller boss 51 in the liquid flow direction, a plurality of liquid intake ports 10 opening toward the liquid flow are circumferentially arranged at equal intervals (for example, four liquid intake ports 10). ) Are formed, and these liquid intake ports 10 are formed through a passage 11 formed in the impeller boss 51 and blades 52, 52, ... That is, the plurality of liquid ejection openings 12, 12 ... Opened in the chip gap 6 communicate with each other. That is, the passage 11 is formed in the impeller boss 51 in parallel to the axis of the main shaft 1, and the upstream passage 11A is branched from the upstream passage 11A in the radial direction in each of the blades 52, 52. The plurality of downstream passages 11B, 11B ...
... and these downstream passages 11B, 11B ...
Are communicated with a plurality of liquid discharge ports 12, 12 ... Formed on the warp line C of the tip 5a of each blade 52, 52.

With such a structure, a part of the liquid that passes through the casing 2 in the axial direction by the rotation of the main shaft 1 and the impeller 5 has a plurality of liquid intake ports that open toward the flow of the liquid. 10 to the upstream passage 11A in the passage 11
It is continuously taken in. The liquid continuously taken into the upstream passage 11A branches into the plurality of downstream passages 11B, 11B ... From the upstream passage 11A, and flows in here, where the impeller 5 rotates, that is, each blade 52, 52. A large pressure is applied to the centrifugal action caused by the rotation of ..., the radial passages 11B, 11B move radially outwardly, and are formed on the warp line C of the chip 5a with a predetermined interval. From the plurality of liquid discharge ports 12, 12 ...
Is discharged to the downstream side. Therefore,
Corresponding to the leak characteristics of the tip gap 6 peculiar to this axial flow pump, the opening area of the liquid intake port 10, the cross-sectional area of the upstream side passage 11A and the downstream side passages 11B, 11B ... And the liquid discharge ports 12, 12 ... ... Opening area and liquid ejection ports 12, 12 ...
By setting the discharge water amount and the discharge distribution state in consideration of the formation distribution state of ..., The discharge flow discharged from the liquid discharge ports 12, 12 ...
Each blade 52, 52 through the tip gap 6 ... Pressure surface 5 of the blade
It is possible to suppress the flow of the liquid that goes around from the 0A side to the negative pressure surface 50B side (see FIG. 9), reduce the leakage loss of the tip gap 6, and improve the pump performance.

FIG. 5 shows the downstream passage 11 in the passage 11.
The modification of B is shown. As shown in this figure, each wing 5
2, 52 ... Are hollowed to form the downstream passage 11B, and the downstream passage 11B is formed into a plurality of liquid discharge ports 1 in the same manner as described above.
2, 12 ... may be connected to each other. Further, as shown in FIG. 6, the liquid discharge ports 12, 12 ... Communicating with the hollow downstream passage 11B may be formed at a position displaced slightly inward of the tip 5a.

In the embodiment described above, a plurality of liquid intake ports 10 that open toward the liquid flow are formed upstream of the impeller boss 51 in the liquid flow direction. The formation position of 10 is not limited to the above-mentioned embodiment, but may be formed on the upstream side in the liquid flow direction at the root of each blade 52, 52 ... Or in the vicinity thereof. Needless to say, the present invention is applicable not only to the axial flow pump described in the above embodiment but also to a mixed flow pump.

[0011]

As described above, according to the present invention, a part of the liquid passing through the casing is continuously taken into the passage inside the impeller by the rotation of the main shaft and the impeller, and the impeller is rotated. A large pressure is applied to the centrifugal action that is generated and is discharged from the liquid discharge port formed in the tip of the impeller into the tip gap, and this discharge flow is always interposed in the tip gap, so the impeller pressure passes through the tip gap. The flow of the liquid that wraps around from the surface side to the negative pressure surface side can be suppressed, leakage loss in the tip gap can be reduced, and pump performance can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a main part of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a bottom view of FIG.

FIG. 4 is a plan view of FIG.

FIG. 5 is a cross-sectional view showing a modified example of the downstream passage.

FIG. 6 is a cross-sectional view showing an example of displacement of the opening position of the liquid ejection port.

FIG. 7 is a cross-sectional view showing an example of an axial flow pump.

FIG. 8 is a sectional view taken along the line EE in FIG.

FIG. 9 is an explanatory diagram of a wing shape.

[Explanation of symbols]

 1 Spindle 2 Casing 2A Inner surface of casing 5 Impeller 5a Impeller tip 6 Chip clearance 10 Liquid intake 11 Passage 11A Upstream side passage 11B Downstream side passage 12 Liquid discharge port 51 Impeller boss 52 Impeller blade

Claims (1)

[Claims] 1. A liquid intake port is formed in a region on the spindle side of an impeller fixed to a spindle, and a liquid is opened in a tip gap formed between the tip of the impeller and an inner surface of the casing. A structure for reducing leakage loss of a tip gap in a pump, wherein a discharge port is formed and the liquid discharge port and the liquid intake port are communicated with each other by a passage formed inside an impeller.