Technical Field

[0001] This disclosure relates generally to impellers for pumps and more particularly but not exclusively to centrifugal slurry pumps for handling slurries which are usually a mixture of liquid and particulate solids, and are commonly encountered in the minerals processing, sand and gravel and/or dredging industry.

Background Art

[0002] Centrifugal slurry pumps generally include a pump housing having a pumping chamber therein which may be of a volute configuration with an impeller mounted for rotation within the pumping chamber. A drive shaft is operatively connected to the pump impeller for causing rotation thereof, the drive shaft entering the pump housing from one side. The pump further includes a pump inlet which is typically coaxial with respect to the drive shaft and located on the opposite side of the pump housing to the drive shaft. There is also a discharge outlet typically located at a periphery of the pump housing.

[0003] The impeller typically includes a hub to which the drive shaft is operatively connected and at least one shroud. Pumping vanes are provided on one side of the shroud with discharge passageways between adjacent pumping vanes. In one form of impeller two shrouds are provided with the pumping vanes being disposed therebetween. The pump impeller is adapted to be run at different speeds to generate the required pressure head.

[0004] Conventional slurry pumps tend to generate turbulence because of the configuration of the impeller. Conventional impellers when viewed in cross section have a generally square or rectangular shape because of shrouds and the position of the pumping blades relative to those shrouds. The configuration tends to give rise to the development of a vortex having a "horseshoe" shape which tends to develop in the passage between adjacent pumping vanes and is responsible for wear on the blade and shrouds.

[0005] EP 146027 and US 2003/0215343 disclose pumps which include an electric motor having a rotor to which an impeller is attached. In essence the impeller in each of these documents is conventional. The spherical, or part-spherical, rotor serves to house the magnet forming part of the electric motor. US 3,476,488 discloses a spherical pump housing, but again the impeller is essentially conventional in structure.

[0006] DE 344907 discloses a pump which is used in situations where reverse flows are required, such as in recirculating heating pumps and pumps in filter systems. The pump has a pump casing 10 with a chamber therein for receiving a spherical impeller 11 rotatable by drive shaft 12. The spherical impeller 11 comprises two hemispherical sections each being associated with a respective flow channel 14, and each channel 14 being capable of functioning as a fluid intake channel or a discharge channel depending on the direction of rotation of the impeller. A series of tubes are disposed within the impeller extending from one side of the spherical impeller to the other side. The pumping chamber has recessed sections 31 which facilitate flow of fluid from one flow channel to the other intake/discharge channel and therefore the flow direction is at right angles to the impeller rotation axis and the tubes have 90° bends therein.

Summary of the Disclosure

[0007] In a first aspect, embodiments are disclosed of an impeller for a pump the impeller comprising a main body which in use is rotatable about a central axis, the main body including a front side and a rear side, the front side having a generally spherical cap like or dome shaped surface with an apex region in the vicinity of the central axis and a peripheral outer region in the vicinity of the rear side, a plurality of channels extending through the main body each having an inlet opening and an outlet opening, the inlet openings being in the vicinity of the apex region and the outlet openings being in the vicinity of the peripheral outer region.

[0008] In certain embodiments, the channels are curved in a direction between the inlet opening and outlet opening. In certain embodiments at least a part of the channel surface provides for a pumping surface. In certain embodiments the distance of each channel with respect to the central axis progressively increases in the radial direction when moving from the inlet opening to the outlet opening.

[0009] In certain embodiments, the inlet openings are spaced around the central axis. In certain embodiments the outlet openings are spaced around the peripheral outer region.

[0010] In certain embodiments, the inlet openings are generally oval or elliptically shaped and have a long or major axis, the long or major axis being inclined to the central axis.

[0011] In certain embodiments, the outlet openings are generally oval or elliptically shaped and have a long or major axis the long or major axis generally following the periphery of the peripheral outer region.

[0012] In certain embodiments, the inlet openings have a curved leading edge portion.

[0013] In certain embodiments, the main body includes a central mount to which a pump drive shaft can be operatively fitted.

[0014] In certain embodiments, the rear side comprises a recessed face. In certain embodiments auxiliary pump out vanes are provided on the recessed face. In certain embodiments a cover overlies the recess face.

[0015] In a second aspect there is provided a pump intake device for use with an impeller as described in the first aspect, the pump intake device comprising an outer section comprising a conduit having an inner surface and an inner section having an inner profiled surface which is substantially similar in profile to part of the impeller surface.

[0016] In certain embodiments, the inner surface of the outer section diverges or curves outwardly. In certain embodiments the inner surface of the outer section and the inner profiled surface of the inner section provide a continuous curving surface between regions adjacent opposed ends of the device.

[0017] In accordance with a third aspect there is provided a pump comprising a pump casing which includes a main casing part and front side casing part comprising a pump intake device as described in the second aspect, and an impeller as described in the first aspect mounted within the pump casing.

[0018] Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of inventions disclosed.

Description of the Figures

[0019] The accompanying drawings facilitate an understanding of the embodiments.

[0020] Figure 1 is an isometric view of a pump impeller according to one embodiment of the present disclosure;

[0021] Figure 2 is an first side elevation of the pump impeller shown in Figure 1 ;

[0022] Figure 3 is a second side elevation of the pump impeller shown in Figures 1 and 2;

[0023] Figure 4 is a front elevation of the pump impeller shown in Figures 1 to 3;

[0024] Figure 5 and 6 are sectional views of the pump impeller shown in Figures 1 to 4;

[0025] Figure 7 is a sectional view of a pump impeller according to a further embodiment;

[0026] Figure 8 is a sectional view of a pump impeller according to a further embodiment; and

[0027] Figure 9 is a schematic view partially in section of a pump assembly according to one embodiment.

Detailed Description

[0028] Referring to Figure 9 of the drawings there is illustrated a pump assembly 50 which includes a pump 51 having a pump casing 60 which is mounted to a pump casing support or pedestal 55. The pump casing 60 comprises a main casing part (or volute) 61, a front side casing part 62 and a rear side casing part 63 which, when assembled together provide for a pumping chamber 68 located therein. The front side casing part 62 is in the form of a pump intake device 70 through which the fluid to be pumped enters the pumping chamber 68. The rear side casing part 62 provides for a seal chamber housing 90. A pump impeller 10 is disposed within the pumping chamber 68 and is operatively connected to a drive shaft 53 for rotation about a central axis X-X.

[0029] As shown in the Figures, the impeller 10 comprises a main body 12 with a front side 14 and a rear side 16. The front side 14 has a generally dome-shaped, or spherical cap-like, outer surface 18 (that is, the region of a sphere disposed to one side of a given plane) having an apex region 20 in the vicinity of the central axis X-X and a peripheral outer region 22 adjacent the rear side 16. The outer surface may for example be generally hemispherical in shape but is not limited to that shape. In use, the apex region 20 is the forward-most part of the main body 12 and faces the pump inlet when in an assembled position. As shown schematically in one form shown in dotted outline in Figure 8, the impeller 10 is positioned within a pump housing or casing 50 having an inlet 51 and an outlet 52, the apex region 20 of the main body facing the inlet 51.

[0030] The impeller 10 further includes a plurality of channels which extend through the main body 12 of the impeller 10. In the embodiment shown, there are four separate channels, 25, 26, 27, 28 although in other embodiments two, three, five or six channels are also possible. Each channel has an inlet opening and an outlet opening; channel 25 has an inlet opening 31 and an outlet opening 35; channel 26 has an inlet opening 32 and an outlet opening 36; channel 27 has an inlet opening 33 and an outlet opening 37; and channel 28 has an inlet opening 34 and an outlet opening 38. As is best seen in Figures 1 and 4, the inlet openings 31, 32, 33 and 34 are in the vicinity of the apex region 20 and are spaced around the central axis X-X. The inlet openings are generally oval in shape each having a major axis Y-Y. As shown the major axes Y-Y are inclined to the central axis X-X and are arranged offset to one another as well as one behind the other, around the central axis X-X. Each inlet opening has a curved (or blended) leading edge 39 to facilitate fluid entry. The distance of each channel away from the central axis X-X progressively increases in a general radial direction when moving from the inlet openings 31, 32, 33, 34 to the respective outlet openings 35, 36, 37, 38, for example as can be seen in dotted outline in Figure 2 in relation to one exemplary channel 27. With reference to Figure 1 , the continuation of channel 27 can be seen beyond a bend therein.

[0031] The channels 25, 26, 27, 28 are in the form of a tube or tube-like formation or passageway, having a generally oval-shaped cross section which progressively increases in cross-sectional area when moving in a direction from the inlet openings 31, 32, 33, 34 to the respective outlet openings 35, 36, 37, 38. The configuration and path of one exemplary channel 25 through the impeller body 12 is illustrated by phantom lines in Figures 1 and 4. The configuration and path of a further exemplary channel 27 is illustrated by phantom lines in Figure 2. The configuration and path of a further exemplary channel 26 is illustrated by phantom lines in Figure 3. Only one channel has been illustrated in each of the Figures 1, 2, 3 and 4 for reasons of clarity.

[0032] As shown in Figures 1 and 4, the channel 25 follows a curved path from the inlet opening 31 to the outlet opening 35. Each of the other channels 26, 27, 28 is of similar configuration. The progressive increase in cross sectional area of the channels 25, 26, 27, 28 is analogous to the shaping of the channels formed between pumping vanes and shrouds of conventional impellers. The distinction between the shape of the channels formed in a conventional impeller and the channels 25, 26, 27, 28 of the impeller which is the subject of this disclosure, resides in their oval cross section, which is believed to reduce the formation of vortices as a fluid moves through the channels 25, 26, 27, 28, as compared to the situation in conventional impellers, as will now be described.

[0033] In conventional impellers, strong flow vortices can be generated in the region of the leading edge of the pumping vanes and also at the junction of the pumping vane sides and the impeller shroud side faces. In the conventional apparatus, there is an abrupt change in direction, or sharp corner, between the face of the pumping vanes and the face of the shrouds. Such sharp corners can cause the generation of vortices as pumped fluid flows across these edges, which in turn results in increased wear in those regions of the impeller. The curved cross-sectional shape of the channels 25, 26, 27, 28 in the impeller which is the subject of this disclosure does not result in the same extent of formation of such fluid vortices.

[0034] The outlet openings 35, 36, 37 and 38 are also generally oval shaped having a major axis Z-Z. The major axes Z-Z are arranged so as to follow around the peripheral outer region one behind the other and offset to one another.

[0035] The rear side 16 of the main body 12 has a recess or void 40 therein which as shown in Figures 7 and 8, and over which a back cover 45 can be received. As shown, the back cover 45 is generally frusto-conical in shape having a curved side. Auxiliary expeller vanes 47 may be provide on the back cover as shown in Figure 8.

[0036] A drive shaft mount 42 is provided in the main body at the central axis X-X for fitting the drive shaft 53 thereto (Figure 8).

[0037] As shown in Figure 9, the front side casing part 62 is in the form of a pump intake device 70 which comprises an outer (forward) section 72 generally shaped in the form of a conduit 73, and an inner section 74 which is operatively connected to the main casing part 61. In the form illustrated, the pump intake device 70 is of a one piece construction. The inner section 74 has an inner profiled surface 77 which follows closely in shape a part of the surface 18 of the impeller 10, so that in the assembled position there is a small gap therebetween. As shown in Figure 9, the outer section 72 has an inner surface 78 which diverges or curves outwardly from the central axis X-X and smoothly joins the profiled surface 77 which in turn curves inwardly. The overall inner surface of the intake device provides for a smooth, continuously-curving surface which terminates at an end section 75. As shown in the Figure, the pump intake device 70 is generally bell- shape with convex inner surface portion in the outer section, and a concave inner surface portion in the inner section.

[0038] It is believed that the impeller 10 can offer reduced fluid turbulence and vortices generated when in use, when compared to a conventional pumping impeller, which in turn will lead to a relative reduction in wear of the impeller while at the same time producing similar levels of head pressure and efficiency to that of a conventional impeller. The reduction in the amount of vortices in the pumping channels has already been described. In addition, the skin friction over the spherical or dome shaped front side surface will be minimised, thus reducing wear which normally occurs as a result of small particles which become entrained in the boundary layer of the slurry on the surface of the front side of a moving impeller. It is believed that the "horseshoe" shaped vortex developed in use over the pumping vanes of conventional impellers will be much weaker. [0039] During use, when the fluid approaches the spherical or domed shaped surface, the interaction is the smoothest possible due to sphere/fluid motion characteristics. This reduces impact and friction at the time the fluid enters into the impeller's channels 25, 26, 27, 28. Each channel opening 31, 32, 33, 34 has an entry edge with an optimized rounded shape with a curved (or blended) leading edge to facilitate fluid entry, which allows the fluid to enter the channel 25, 26, 27, 28 with minimum fluid separation. In conventional centrifugal impellers, this fluid separation is what gives origin to the undesired "horseshoe" vortex.

[0040] While points of high turbulence on the entry surface exist, they are not in the proximity of any other wet surface. For this reason they do not cause the erosion that typically occurs between impeller's inlet eye and throatbush. Any points of turbulence are most likely to be associated with the edges of the impeller channels, and since these face forward and into the inlet fluid flowstream only, erosive wear of adjacent physical components is minimised.

[0041] The impeller does not have a back shroud, for this reason the void space in the body is covered by a lid or back cover, which can be plain or contain the back vanes as illustrated in Figure 8 which are needed to hydraulically seal the gap between the impeller and the pump liner.

[0042] As mentioned earlier, the outlets of the impeller channels 25, 26, 27, 28 also have an oval shape, and their edges have an optimized rounded shape to induce a smooth transition impeller/volute. The purpose is also to reduce the turbulence generated by the interaction between this impeller outlet surface and the fluid which is just leaving the impeller's channel.

Computational Simulation Data

[0043] The shape of impeller which is the subject of this disclosure, is quite different to the conventional design of a centrifugal pump impeller which involves two shrouds with pumping vanes disposed therebetween.

[0044] The level of erosion intensity of a fluid passing into a centrifugal pump impeller of conventional design was simulated using Computational Fluid Dynamics (CFD). It was observed that the maximum value of erosion intensity measured was 7000 units, especially at the area where the fluid enters the impeller and is turned into the pumping vane channels (that is, at the eye of impeller).

[0045] The level of erosion intensity of a fluid passing into the impeller which is the subject of this disclosure was also simulated using Computational Fluid Dynamics (CFD). Here, it was observed that the maximum value of erosion intensity measured was 3600 units at the rims of the impeller inlets to the channels where the fluid enters the impeller.

[0046] This computational data indicated that the erosion level for the impeller, which is the subject of this disclosure, is 49% lower than the conventional impeller design for similar flow pumping conditions (including head pressure and flow rate).

[0047] It was further observed that when the rims of inlets to the channels of the impeller which is the subject of the disclosure, are made even more blended with the front face of the impeller, it is possible to reduce the erosion intensity to around 1700 units, in the area of the rims, which is even lower than the 3600 units of erosion intensity in the first design simulated.

[0048] Based on such computational data, it is believed that the impeller which is the subject of this disclosure offers longer wear life than the conventional impeller design.

[0049] In the foregoing description of preferred embodiments, specific terminology has been resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "front" and "rear", "inner" and "outer", "above", "below", "upper" and "lower" and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

[0050] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

[0051] In this specification, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of. A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear.

[0052] In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive.

[0053] Furthermore, invention(s) have been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment. Table of Parts

Pump impeller 10

Main body 12

Front side 14

Rear side 16

Dome shaped surface 18

Apex region 20

Peripheral outer region 22

Central axis X-X

Channels 25 26 27 28

Inlet openings 31 32 33 34

Outlet openings 35 36 37 38

Leading edge 39

Oval shape

Major axis Y-Y

Major axis Z-Z

Recess/void 40

Drive shaft mount 42

Back cover 45

Auxiliary vanes 47

Pump assembly 50

Pump 51

Pump casing 60

Drive shaft 53

Pedestal 55

Main casing part 61

Front side casing part 62

Rear side casing part 63

Pumping chamber 68

Pump intake device 70 Discharge outlet 69

Seal chamber housing 90

Outer section 72

Conduit 73

Inner section 74

Inner profiled surface 77

Inner surface 78

End section 75