JPS5848796A - Centrifugal impeller - Google Patents

Abstract

PURPOSE:To prevent generation of cavitation by a method wherein a communicating hole is provided in the shroud of the impeller and a part of flowing water increased in the pressure thereof by the impeller is introduced into the inlet of the impeller through said communicating hole to increase the static pressure of the inlet port of the impeller. CONSTITUTION:A communicating hole 13 is provided in a front shroud 1a and a gap 8 between a fixed wall 6 and the front shroud 1a is communicated directly with the inlet port of the impeller. Therefore, the static pressure of the inlet port of the impeller may be increased by introducing a part of the flowing water, increased in its pressure by the impeller, from the gap 8 into the inlet port of the impeller even when the suction pressure of the pump is reduced. According to this method, the cavitation will never be generated, and therefore, corrosion due to the cavitation may be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an impeller for a centrifugal pump, and particularly to a centrifugal impeller suitable for preventing cavitation.

A conventional centrifugal impeller will be explained using a centrifugal pump shown in FIGS. 1 and 2. The centrifugal impeller 1 consists of a front shroud of 1 m, blades 1b, and a rear shroud IC. A diffuser 3 is provided on the outlet side of the impeller 1 fixed to the rotating shaft 2, and A flow path 5 leading to the next stage impeller (not shown) is formed. Front shroud 1g of impeller 1, rear shroud 1. A fixed wall 6.7 is provided adjacent to the wall surface of c. A gap 8.9 and a narrow gap 10.11 are formed between the front shroud 1a and the fixed wall 6, and between the rear shroud 1c and the fixed wall 7.

With the above configuration, a portion of the flowing water discharged from the impeller 1 flows through the gap 8. It leaks through the narrow gap 10 to the suction side of the impeller 1. On the other hand, a part of the flowing water from the suction side of the next-stage impeller passes through the narrow gap 11t, flows into the gap 9, and leaks to the outlet side of the impeller 1. Therefore, when the suction pressure of the pump is low, cavitation 12 occurs near the leading edge of the blade 1b. If the pump is operated for a long period of time with cavitation occurring, the cavitation causes erosion on the blade surface near where the cavitation collapses, making it impossible to maintain the original pump performance.

An object of the present invention is to provide a centrifugal impeller that can prevent cavitation from occurring and prevent erosion due to cavitation with an extremely simple structure.

Cavitation is known to occur when the static pressure near the impeller inlet drops to around the saturated steam pressure, which is detrimental to the temperature of the flowing water. Therefore, by increasing the static pressure near the impeller inlet, cavitation can be prevented from occurring. In the present invention, a communication hole is provided in the impeller shroud, and a part of the flowing water pressurized by the impeller is guided to the impeller through the communication hole to increase the static pressure at the impeller inlet and prevent the occurrence of cavitation. That is.

Embodiment t of the present invention - FIGS. 3 to 7 will be described below. The same parts as in FIGS. 1 and 2 are designated by the same reference numerals and their explanations are omitted.a FIGS. 3 and 4 show a first embodiment of the present invention, in which a first communication hole is provided in the front shroud 11. , the gap 8 and the impeller inlet are directly connected. For this reason,
Even if the suction pressure of the engine becomes low, the pressure is increased by the impeller and a part of the water is guided from Seki 8 to the impeller inlet to increase the static pressure at the impeller inlet, so cavitation does not occur and cavitation Erosion does not occur either, so the original pump performance is maintained.

FIG. 5 shows a second embodiment of the present invention, in which the front shroud l
A is provided in the communication hole 14 facing the blade 1b, and the narrow gap 10
and the impeller inlet section are electrically connected.

By configuring it in this way, it is possible to obtain the same effect as explained in the @l embodiment, as well as
The flow of water from the communication hole 14 is less likely to be disturbed.

FIG. 111r6 shows a third embodiment of the present invention, in which a communication hole 15 is provided in the back shroud lc, and the gap 9 and the impeller inlet are electrically connected. FIG. 7 shows a fourth embodiment of the present invention, in which a communication hole 16 is provided in the back shroud IC,
The flow path 5 and the impeller inlet are electrically connected. With this configuration, substantially the same effects as those described in the first embodiment can be obtained. - According to the present invention, even if the suction pressure of the pump becomes low, the static pressure at the impeller inlet can be increased, so cavitation does not occur and erosion due to cavities can be prevented.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of a centrifugal pump equipped with a conventional centrifugal impeller, Figure @2 is a front view of the impeller showing cavitation that occurs in the centrifugal impeller shown in Figure @1, and #! Figure 3 shows a centrifugal impeller according to the @l embodiment of the present invention? 4 is a front view of the impeller in FIG. 3, wi5, 6, and 7.
These are side sectional views of centrifugal pumps equipped with centrifugal impellers according to the second, third and fourth embodiments of the present invention, respectively. 1a...Front shutter, lb...Blade, IC...
・Back shroud, 8.9... Gap, 10.11...
- Slit portion, 13.14, 15.16... communicating hole. ¥J 1 figure ¥Jz figure ¥J5 figure ¥-J t figure'E℃ 1 5 /2

Claims (1)

[Claims] A centrifugal impeller in which a blade and a shroud constitute an impeller, characterized in that a communication hole is provided in the shroud for guiding a part of the flowing water pressurized by the impeller to the inlet of the impeller. Centrifugal impeller.