GB2098275A - A centrifugal machine - Google Patents

Abstract

A single or multistage centrifugal machine such as a pump or turbine is provided with partition walls 7 in the impeller side chambers 1 to improve the efficiency of the machine by reducing friction losses. The walls 7 may be cast integrally with the corresponding machine part or they may be separate plates made of metal or plastics. <IMAGE>

Description

SPECIFICATION A centrifugal machine This invention relates to single or multi-stage centrifugal machines such as centrifugal pumps or turbines.

For a variety of reasons, e.g. simple casting technique, or some mechanical assembly systems, or inter-penetration of various flow chambers, more particularly in mass-produced centrifugal pumps, centrifugal machines in general, whether single or multi-stage centrifugal pumps or turbines, have often excessively large water-filled side chambers slowing down the vortex in the impeller side chambers and closely adjacent the rotating impellers, thus producing greater increased friction losses at the side wall of the rotating impeller and thus reducing the total efficiency of the centrifugal machine.

It is also known for side chambers of centrifugal pumps to be given other disadvantageous shapes, for example to make an impeller side chamber with a form having a long axial dimension and which is also highly asymmetrical in rotation.

An object of the invention is to avoid the effects of such disadvantageous chamber shapes.

According to the invention there is provided a single or multi-stage centrifugal machine in which at least one radial and/or axial partitioning component is provided in an impeller side chamber which has a form such that, but for said partitioning component or components, the form would detract from the efficient operation of the machine, said partitioning component or components serving to reduce the detrimental effect of the form of said impeller side chamber on the efficient operation of the machine.

Thus, the disadvantageously-shaped impeller side chambers may be bounded by radial and/or axial partition components or alternatively by a suitably disposed partition wall or by devices in the form of encircling e.g. integrally-cast webs, in combination with a partition plate where necessary. These partition or bounding devices can thus produce an impeller side chamber which is advantageous with regard to the friction loss at the side of the impeller.

In the accompanying drawings: FIGURES 1, 2 and 3 are fragmentary axialsection views of respective known centrifugal machines having unfavourably-shaped impeller side chambers, and FIGURES 4, 5 and 6 are fragmentary axialsection views of centrifugal machines embodying the invention and which correspond in design with the machines of Figures 1, 2 and 3 with the addition of respective partitioning components.

Figure 1 shows a centrifugal machine in which an impeller 2 is mounted on a vertical shaft for rotation in a housing affording, as well as a chamber disposed radially outwardly of the impeller, chambers 1, in communication with the last-noted chamber, disposed above and below the radially outer part of the impeller. The chambers 1 are excessively large in the axial direction and this leads to greatly increased friction losses as discussed above.

In the corresponding machine shown in Figure 4, the major, upper and lower parts of the upper and lower chambers 1 respectively are partitioned off from the parts 9 adjoining the sides 3 of the impeller by annular plates 7 fitted to the housing and extending in respective radial planes, relative to the impeller axis, across the respective chambers 1.

Figure 2 shows a multi-stage centrifugal machine in which an annular chamber 4, coaxial with the horizontal rotational axis of the impeller 2 is defined, to the right of the impeller 2, between the side 3 of the impeller 2, the housing, and a diffuser, the chamber 4 being extended both in the axial direction and radially from a position radially inwardly of the periphery of the impeller 2 to a position radially outwardly thereof, to one side of the diffuser. A similar chamber, 5, of somewhat lesser axial extent is defined between the impeller of the next stage, the housing and the respective diffuser.

In the corresponding machine of Figure 5, the chamber 4 is divided, at approximately the position of the periphery of the impeller 2, into a radially inner part and a radially outer part by a circumferentially extending web 8, extending, parallel with the impeller axis, from the housing towards the opposing side face of the impeller 12.

A similar circumferentially extending web 8 extending, in this case, from the respective diffuser, divides the chamber 5 into radially outer and inner parts. The webs 8 are preferably cast integrally with the respective housing or diffuser parts. Alternatively the webs 8 may be in the form of separately formed inserts or rings.

In the embodiment of Figure 5, the radially inner part of the chamber 4 is itself partitioned by an annular partitioning plate 7, extending radially with respect to the impeller axis, into a major portion remote from the impeller side 3 and a minor portion adjacent the impeller side 3. The portions of the respective chambers in Figure 5 which directly adjoin the respective impellers are again referenced 9.

Figure 3 shows a centrifugal machine in which the side 3 of an impeller 21 shown with its axis horizontal, defines, with an adjoining housing part to the right of the impeller in the figure, a circumferentially extending chamber 6 which is highly asymmetrical in rotation, and is, for example, of substantially greater radial and axial extent in its lower portion than in its upper portion.

In the corresponding machine shown in Figure 6, the major portion of the chamber 6 is divided off from the part 9 immediately adjoining the side 3 of the impeller, by a flat annular plate 7, extending radially with respect to the impeller axis, fitted in the housing of the machine.

In Figure 5 the disadvantageous part of impeller side chamber 5 is hydraulically uncoupled outside bounding webs 8. In Figures 4, 5 and 6 the partition wall can either be directly cast integrally with the corresponding pump part or can be a separate partition plate 7. Plate 7 may also be produced e.g. in the form of a cheap sheet of metal or a plastics component. Since the e.g.

separately-produced partition plate 7 is not subjected to the full differential pressure of the impeller side chamber 9 and the now uncoupled chamber 1 in Figure 4 or the uncoupled chamber 4 in Figure 5 or the uncoupled chamber 6 in Figure 7 (which would involve increasing the dimensions of plate 7 and strengthening its securing means) apertures 10 can be disposed at a chosen diameter and connect chamber 9 to chamber 1 in Figure 4, chamber 4 in Figure 5 or chamber 6 in Figure 6. Apertures 10, however, should be disposed at substantially the same diameter, i.e. at substantially the same radial distance from the rotary axis of the impeller, to avoid secondary flows which would produce additional losses. Alternatively, apertures 10 can be at different diameters but some can be made small, e.g. when chambers 1, 4 or 6 have to be deaerated.

Preferably, apertures 10 are disposed at a smaller diameter, i.e. closer to the impeller axis, when plate 7 is disposed so that it has to be pressed away by the impeller, as shown in Figure 6, and are disposed at a greater diameter when plate 7 has to be pushed towards the impeller, as shown in Figure 4. When there is a neutral axial stress on the plate, apertures 10 should advantageously be placed on a corresponding intermediate diameter.

In Figure 5, bounding webs 8 are disposed at the outer diameter of the impeller, and may be disposed so that, for example, chamber 4 is divided into radially outer and inner parts by a web extending from diffuser 12, and a web extending from the housing 11 towards that web, to meet or lie close to the free edge of that web.

Alternatively, as shown, the respective web 8 may be formed only on one component, i.e. pump housing 11. Optionally the web 8 may be arranged so that there is no sealing-tightness but the vortex on the impeller side is hydraulically uncoupled from the outer chamber, which, in the absence of the webs 8 and plate 7, slows it down in a disadvantageous manner. By means of this feature, e.g. in the case of a centrifugal pump stage of the kind in question, a number of extra degrees of efficiency are attained, depending on the type of impeller and the disadvantages of the original shape of the side chambers. The result, in the case of a centrifugal pump, is a corresponding increase in the total efficiency of the pump and a consequent reduction in energy used. In the case of a flow turbine the result is a higher output of energy from the machine.

Claims (12)

1. A single or multi-stage centrifugal machine in which at least one radial and/or axial partitioning component is provided in an impeller side chamber which has a form such that, but for said partitioning component or components, the form would detract from the efficient operation of the machine, said partitioning component or components serving to reduce the detrimental effect of the form of said impeller side chamber on the efficient operation of the machine.

2. A centrifugal machine according to claim 1, in which impeller side chambers are separated by a partition wall.

3. A centrifugal machine according to claim 1, in which impeller side chambers are separated by webs extending around the axis of the machine the webs being disposed at one side on a housing of the machine or integral therewith and with a distributor.

4. A centrifugal machine according to claim 1, wherein impeller side chambers are defined by encircling webs in combination with a partition plate or wall.

5. A centrifugal machine according to claim 4, wherein apertures are formed in the partition plate or wall.

6. A centrifugal machine according to claim 5 wherein said apertures are formed at the same radial distance from the axis of the machine.

7. A centrifugal machine according to claim 5 wherein said apertures are formed at different radial distances from the axis of the machine.

8. A method of improving the efficiency of a centrifugal machine having an impeller side chamber which has a form such as to detract from the efficient operation of the machine, comprising fitting in said chamber at least one radial and/or axial partitioning component.

9. A centrifugal machine substantially as hereinbefore described with reference to, and as shown in, Figure 4 of the accompanying drawings.

10. A centrifugal machine substantially as hereinbefore described with reference to, and as shown in Figure 5 of the accompanying drawings.

11. A centrifugal machine substantially as hereinbefore described with reference to, and as shown in, Figure 6 of the accompanying drawings.

12. Any novel feature or combination of features described herein.