JPS59180002A - Centrifugal type fluid machine - Google Patents

Abstract

PURPOSE:To increase the dynamic pressure bearing effect that will be generate in a space so as to lower the shaft vibrations and to prevent the shaft self-vibrations, by making the shape of the inner circumferential surface of a casing nonround, the inner circumferetial surface being opposed to the outer circumferential surfaces of main plates or side plates of an impeller with a space therebetween. CONSTITUTION:The centrifugal impeller 1 consists of side plates 1a, blades 1b and main plates 1c and is fixed to a rotating shaft 2. On the outlet side of the impeller 1 are arranged guide blades 3 and are formed with paths 5 via flashing blades 4 to be led to the subsequent impeller. Fixed casings 6, 7 are arranged adjacent the wall surfaces of the side plates 1a and the main plates 1c. The inner circumferential surfaces of the casings 6, 7 are nonround and formed with circumferentially arranged steps. Consequently, the dynamic pressure bearing effect that will be generated in gaps 8, 9 between the casings 6, 7 and the side plates 1a and the main plates 1c as a result of the rotation of the impeller 1 can be increased thereby lowering the shaft vibrations and preventing the shaft self- vibrations.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a centrifugal fluid machine that operates at high speed, is concerned with shaft vibration, and requires high reliability.

[Background of the invention]

A conventional centrifugal fluid machine will be explained using a centrifugal pump shown in FIGS. 1(a) and 1(b). The centrifugal impeller 1 has a side plate la,
The blade tb, main plate IC, etc. are fixed to the rotating shaft 2. A guide vane 3 is provided on the outlet side of the impeller 1, and a flow path 5 is formed that goes to the next stage impeller (not shown) via a water return vane 4.

A fixed casing 6.7 is provided close to the side plate 1g of the impeller 1 and the wall surface of the main plate IC. Gaps 8 and 9 are formed between the outer peripheral surface of the side plate 1a and the inner peripheral surface of the fixed casing 6, and between the outer peripheral surface of the main plate IC and the inner peripheral surface of the fixed casing 7. In addition, the side plate 11a, the fixed casing 6, the main plate IC
Gaps 10 and 11 and narrow gaps 12 and 13 are formed between the fixed casing 7 and the fixed casing 7.

With the above configuration, a part of the flowing water discharged from the impeller 1 passes through the slit 8, the gap 101 and the slit 12, and passes through the impeller 1.
leaks to the suction side. On the other hand, part of the flowing water from the suction side of the next-stage impeller flows into the gap 11 through the slit 13 and leaks from the slit 9 to the outlet side of the impeller 1.

By the way, the slit 8.9 is an annular gap as shown in Fig. 1(b), and when the impeller rotates at a high speed, this slit 8.9 has a ring-shaped gap similar to an oil-lubricated hydrodynamic bearing. A bearing effect occurs. In this case, if the shape of the inner circumferential surface of the casing is a perfect circle, the dynamic pressure bearing effect is small, so the load capacity against eccentricity in the radial direction of the impeller is small, and the vibration isolation effect against shaft self-excited vibration is also small. .

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and provide a centrifugal fluid machine with small shaft vibrations and no shaft self-excited vibrations. - [Summary of the Invention] In order to achieve the above object, the present invention makes the shape of the inner circumferential surface of the casing non-perfect circular, thereby thickening the dynamic pressure bearing action and suppressing the self-excited motion of the comb shaft. It is something.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 2 to 4. Components that are the same as those in FIG. 1 are given the same reference numerals, and their explanation will be omitted. FIG. 2 shows a first embodiment of the present invention, in which the shape of the inner peripheral surface of the casing 6.7 is stepped in the circumferential direction. Therefore, the dynamic pressure bearing effect generated in the narrow gaps 8 and 9 due to the rotation of the impeller is greatly increased, the load capacity against eccentricity in the radial direction of the impeller is increased, and shaft vibration is reduced. Furthermore, since the vibration damping effect against shaft self-excited vibration is increased, stable pump operation can be continued without producing shaft self-excited vibration.

FIG. 3 shows a second embodiment of the invention, in which the casing 6.7
The shape of the inner peripheral surface is multi-arc shaped (three arcs in the figure) in the circumferential direction. Further, FIG. 4 shows a third embodiment of the present invention,
The shape of the inner circumferential surface of the casing 6.7 is made into a multi-circular arc shape with slight differences in the circumferential direction (in the figure, three circular arcs with different angles). With this configuration, it is possible to obtain the same effects as those described in the first embodiment.

〔Effect of the invention〕

According to the present invention as described above, the shape of the inner circumferential surface of the casing that faces the outer circumferential surface of the main plate spanning the side plates of the impeller through the gap is made non-circular, so that the dynamic pressure bearing action that occurs in the gap is suppressed. This has the effect of reducing shaft vibration and preventing shaft self-excited vibration.

[Brief explanation of the drawing]

Figure 1(a) is a vertical cross-sectional view of a conventional centrifugal fluid machine.
FIG. 2(b) is a sectional view taken along arrows A or B in FIG. 1(a), FIG. ) is a sectional view taken along arrow A or B in FIG. 2(a), and FIGS.
FIG. 3 is a cross-sectional view of an embodiment and a third embodiment. 1a... Side plate, IC... Main plate, 6.7... Casing, 8.9... Slit. Kaya 2 Prisoner (oL) Tosa (To 2

Claims (1)

[Scope of Claims] 1. A centrifugal fluid machine characterized in that the inner peripheral surface of the casing, which faces the outer peripheral surface of the side plate or main plate of the impeller with a gap in between, has a non-perfect circular shape. 2. The centrifugal fluid machine according to claim 1, wherein the inner circumferential surface of the casing has a step-like shape so that it is not a perfect circle. & The centrifugal fluid machine according to claim 1, wherein the shape of the inner peripheral surface of the casing is made into a multi-arc shape so that the shape is not a perfect circle. 4. The centrifugal fluid machine according to claim 1, wherein the shape of the inner circumferential surface of the casing is made into a polygonal arc shape so that it is not a perfect circle.