JPS6340959B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a differential user of a centrifugal rotating machine such as a differential pump, a pump water turbine, or a compressor.

As shown in FIGS. 1A and 1B, the differential user d of a conventional conventional differential user type pump is configured in an axially symmetrical shape, so that the static radial thrust is small regardless of the operating flow rate of the pump. Recent experiments have shown that in low flow regimes, significant low-cycle dynamic radial thrust due to rotating stall is disadvantageous, as shown in FIG.

As pumps have become faster in recent years, this fluid force (dynamic radial thrust) is becoming an important factor in pump design from the standpoint of preventing vibrations in the pump shaft system. In the past, it has been reported that due to insufficient consideration of this important fluid force, excessive vibrations were generated and, in some cases, pump breakage accidents were caused.

The present invention has been proposed for the purpose of eliminating the drawbacks of the conventional differential users described above and providing a differential user such as a pump that is capable of reducing the generation of dynamic radial thrust as much as possible in a low flow area of the pump. The flow path in the differential user section of a centrifugal rotating machine is divided into two, and the cross-sectional area expansion ratio in the flow direction of the flow path on the crown side of the impeller is determined from the cross-sectional area expansion ratio in the flow direction of the flow path on the shroud side. It is also characterized in that it is set large.

Hereinafter, according to the embodiment shown in FIGS. 3 and 4,
The present invention will be explained in detail, and the illustrated example shows an example in which the present invention is applied to a differential user of a differential user type pump. In Fig. 3, 1 is the impeller of the pump, 1a is its shroud, 1b is the crown, 2 is the main shaft, 3 and 4 are the pump casings, 5 is the return vane, 6 is the return passage, and 7 is the first diffuser. The blades include a second diffuser blade 8 and a partition plate 9, and these members are arranged in the relationship shown. and the first differential user blade 7,
As shown in FIGS. 4 and 5, the second diff user vane 8 has the same inlet vane angle and the same outlet flow passage cross-sectional area; The area expansion rate x is greater than the radial expansion rate y of the first differential user blade 7.
As shown in FIG. 5, it is set large. Therefore, its exit radius is becoming smaller.

An embodiment of the differential user of the present invention is configured as described above, and during normal rated flow operation, both the first differential user blade 7 channel and the second differential user blade 8 channel have an equal differential user. However, when operating in a low flow area, that is, when the pump discharge amount decreases, the second diff user, which has a large flow passage cross-sectional area expansion rate, first A rotating stall occurs on the side of the diffuser blade 8, the uniformity of pressure in the circumferential direction is disrupted, and a dynamic radial thrust is generated as shown by curve a in FIG. 6. Then, as the pump discharge rate further decreases, a complete stall occurs on the second differential user blade 8 side, uniformity in the circumferential direction is achieved by the healthy first differential user 7 side, and the dynamic radial thrust is As shown by curve b in FIG. 6, it decreases significantly.

Then, when the pump discharge rate decreases further, the first
Rotational stall also occurs on the differential user blade 7 side, the uniformity in the circumferential direction is disrupted, and the dynamic radial thrust increases again as shown by curve c in FIG. 6.

Note that if the expansion rate of the flow passage cross-sectional area along the radial direction of the second diffuser blade 8 is set to a larger value, separation of the fluid in the second diffuser blade 8 portion is likely to occur, so that the curve in FIG. b
moves to the high flow discharge side of the pump, so the dynamic diffuser thrust will be reduced by even a small decrease in pump flow rate. Therefore, by appropriately adjusting the flow passage cross-sectional area expansion rate along the radial direction of the second diffuser blade 8, the pump operating range P can be adjusted.
It becomes possible to minimize the dynamic radial thrust in (Fig. 6).

As shown in FIG. 7, it is known that an outlet backflow 10 occurs on the crown 1b side of the impeller outlet when the pump is operated at a low flow rate. The outlet is under conditions where it is susceptible to being blocked by the outlet backflow. For this reason, it can be seen that it is effective to install the diffuser blade whose flow passage cross-sectional area has a larger expansion ratio in the radial direction on the crown 1 side of the impeller 1 as in this example.

Since the differential user of a centrifugal rotary machine such as a pump according to the present invention has the above-mentioned configuration and operation, according to the present invention, when operating in a low flow rate region, the differential user of a centrifugal rotary machine such as a pump can perform low-cycle dynamic radial thrust. Since it is possible to minimize the occurrence of vibration, it is possible to prevent the occurrence of excessive vibration in the shaft system, which has the practical effect of realizing a differential user such as a pump that is free from the risk of equipment damage. .

[Brief explanation of the drawing]

1A and 1B are schematic explanatory diagrams of a conventional diffuser type pump. FIG. 1A is a vertical sectional view of the main part, FIG. 1B is a view taken along the - line in FIG. 1A, and FIG. is a graph of an actual measurement example of the dynamic radial thrust, the third
4 and 4 are schematic explanatory diagrams of an embodiment of the present invention, in which FIG. 3 is a vertical cross-sectional view of the main part, FIG. 4 is a view taken along the - line in FIG. 3, and FIG. FIG. 6 is a graph showing the expansion ratio of the cross-sectional area of the diff user flow path along the radial direction of the two diff user vanes of the invention. FIG. 6 is a graph showing the relationship between the dynamic radial thrust of the invention and the pump flow rate. FIG. FIG. 3 is an explanatory diagram of the operating state of the differential user section during low flow rate operation of the present invention. DESCRIPTION OF SYMBOLS 1... Impeller, 1a... Shroud, 1b... Crown, 2... Main shaft, 3, 4... Casing, 5... Return vane, 6... Return passage, 7... First differential user blade, 8... Second differential user blade, 9...Partition plate.

Claims (1)

[Claims] 1 The flow path of the diff user part of the centrifugal rotating machine is
A centrifugal rotary machine characterized in that the cross-sectional area expansion ratio in the flow direction of the flow path on the crown side of the impeller is set larger than the cross-sectional area expansion ratio in the flow direction of the flow path on the shroud side. Deaf user.