WO 2014/153616 PCT/AU2014/000337 SLURRY PUMP IMPELLER Technical Field 10001] This disclosure relates generally to impellers for centrifugal slurry pumps. Slurries are usually a mixture of liquid and particulate solids, and are commonly found in the minerals processing, sand and gravel and/or dredging industry. Background Art 10002] Centrifugal slurry pumps generally include a pump casing 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 casing 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 casing to the drive shaft. There is also a discharge outlet typically located at a periphery of the pump casing. The pump casing may be in the form of a liner which is encased within an outer pump housing. 100031 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. The impeller may be of the closed type where two shrouds are provided with the pumping vanes being disposed therebetween. The impeller may however be of the "open" face type which comprises one shroud only. [00041 In some applications conventional pumping vanes are laid over such that a section through the vane forms an acute angle to the shroud on a pressure surface of the vane and provides for a smooth transition from inlet to discharge along the vane length.
WO 2014/153616 PCT/AU2014/000337 -2 [0005] Two examples of impellers having warped vanes are illustrated in US 2010/0284812 and US 6,082,000. US 2010/0284812 discloses a centrifugal water pump having an impeller which has aerofoil shaped vanes with a thick base (portion in contact with back shroud) tapering to a thin tip (portion closest to the fluid inlet). Although the vanes are twisted along their length, they would not be suitable for use in slurry pumps. In US 6,082,000, the vanes of D2 are typical of the mixed flow type, that is the vanes are of a double curvature type. The patent is concerned with a novel method to produce such a vane. [00061 For slurry pumps handling heterogeneous slurries (with settling particles of typical size 0.5mm) it is common for there to be solids concentration gradients throughout the flows in the inlet pipe and within the impeller and pump casing. The concentration gradients are caused by the various forces acting on the particle including: gravity, fluid drag and centrifugal forces. As the slurry enters the impeller it has to turn through a 90 degree angle of flow so as to be directed out of the pump, and with both inertial forces and Coriolis forces (exerted by the vane), the slurry particles are at their highest concentration at the root of the vane on the back shroud of the impeller, that is, in the region where a side edge of the vane contacts the shroud. [0007] A consequence of this flow of concentrated particles along the root of the vane is high and uneven wear due to grooving of the impeller at that point, which can prematurely render the impeller ineffective. Summary of the Disclosure [00081 In a first aspect, embodiments are disclosed of a pump impeller which includes: - a back shroud having an inner main face with an outer peripheral edge and a central axis, the impeller in use being rotatable about the central axis in a direction of rotation, WO 2014/153616 PCT/AU2014/000337 -3 - a plurality of pumping vanes extending from the inner main face of the back shroud, the pumping vanes being disposed in spaced apart relation, and each pumping vane including: -opposed first and second side faces, - a leading edge in the region of the central axis and - a trailing edge in the region of the outer peripheral edge of the back shroud, and - with a passageway between adjacent pumping vanes, wherein the first side face at the leading edge is in a plane which is at an acute angle with respect to a plane of the inner main face of the back shroud, and the first side face at the trailing edge is in a plane which is at an obtuse angle with respect to the plane of the inner main face of the back shroud. 10009] The configuration of the vane is such that in use the Coriolis force generated by the vane disperses particles across that vane at its trailing edge thereby reducing wear near the region where the vane abuts against the face of the back shroud. [00101 In certain embodiments, the first side face at the trailing edge is in a plane which is at an obtuse angle in a range of greater than about 900 to about 135". [0011] In certain embodiments, the impeller further includes a front shroud having an inner main face the pumping vanes extending between the inner main faces of the front and back shrouds, although in some embodiments the impeller may not have a front shroud at all (in "open" face type impellers). 10012] In certain embodiments the inner main face of the back shroud is at right angles to the central axis, although in other embodiments there can be some alignment of these at other than right angles. [00131 In certain embodiments, the angle of the first side face progressively changes when moving from the leading edge to the trailing edge of the vane. This may be in a continuous form of curvature when moving from the leading edge to the trailing edge, or in multiple straight sectors at different acute or obtuse angles to form the shape of the WO 2014/153616 PCT/AU2014/000337 -4 pumping vane. [0014] In certain embodiments, the first side face is a leading face with respect to the direction of rotation, so that fluid being pumped is impacted against it. [0015] In certain embodiments each pumping vane includes a leading edge section terminating at the leading edge the leading edge section tapering inwardly towards the leading edge, and a trailing edge section terminating at the trailing edge the trailing edge section tapering inwardly towards the trailing edge, each pumping vane including a main section between the leading and trailing edge sections which has a width or thickness which is generally constant from one side edge thereof to an opposed side edge and along its length from the leading edge section to the trailing edge section. [0016] In certain embodiments the first side face is a pumping or pressure side face. [00171 In certain embodiments, the first side face is configured such that the surface thereof, at any line between the leading and trailing edges which is at 90 from one side edge to the other, is flat or linear in the direction of that line. [0018] In certain embodiments the pumping vanes are curved in a lengthwise direction between the leading and trailing edges although in some other embodiments the impeller pumping vanes can be straight along their distal length. [0019] In certain embodiments, the vanes are backwardly curved with respect to the direction of rotation of the impeller, although for some applications the direction of curvature may be forwardly curved with respect to the direction of rotation of the impeller, depending on the nature of fluid. [0020] In another aspect, embodiments are disclosed of a pump impeller which includes: WO 2014/153616 PCT/AU2014/000337 -5 - a back shroud having an inner main face with an outer peripheral edge and a central axis, the impeller in use being rotatable about the central axis in a direction of rotation, - a plurality of pumping vanes extending from the inner main face of the back shroud, the pumping vanes being disposed in spaced apart relation, and each pumping vane including: - opposed first and second side faces, - opposed side edges one of which is located at the back shroud, - a leading edge in the region of the central axis and - a trailing edge in the region of the outer peripheral edge of the back shroud, and - with a passageway between adjacent pumping vanes, wherein a line extending from one side edge to the other side edge of the pumping vane at the leading edge is at an acute angle with respect to a plane of the inner main face of the back shroud, and a line extending from one side edge to the other side edge of the pumping vane at the trailing edge is at an obtuse angle with respect to the plane of the inner main face of the back shroud. [00211 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. Brief Description of the Drawings [00221 Notwithstanding any other forms which may fall within the scope of the method and apparatus as set forth in the Summary, specific embodiments of the method and apparatus will now be described, by way of example, and with reference to the accompanying drawings in which: [00231 Figure 1 illustrates an exemplary, schematic, partial cross-sectional side elevation of a pump incorporating an impeller and an impeller and liner combination, in WO 2014/153616 PCT/AU2014/000337 -6 accordance with one embodiment; 100241 Figure 2 illustrates an exemplary, schematic view of part of an impeller and a pumping vane in accordance with one embodiment; [00251 Figures 3 to 5 illustrate exemplary sectional views of an impeller shroud and an impeller pumping vane taken along the lines 1, 2 and 3 in Figure 2; and 10026] Figures 6 and 7 are pictorial views of a portion of an impeller illustrating features of the pumping vanes according to one embodiment. [0027] Figure 8 is a top, perspective view of an impeller illustrating features of the pumping vanes according to one embodiment. [0028] Figure 9 is a bottom, perspective view of an impeller illustrating features of the pumping vanes according to one embodiment. 100291 Figure 10 illustrates an exemplary schematic view of part of an impeller and a pumping vane in accordance with another embodiment. Detailed Description of Specific Embodiments 10030] Referring to Figure 1, there is illustrated a typical example of a pump 10 which includes a pump casing or volute 12, a back liner 14, a front liner 30 and a pump outlet 18. An internal chamber 20 is adapted to receive an impeller 40 for rotation about rotational axis X-X. [0031] The front liner 30 includes a cylindrically-shaped delivery section 32 through which slurry enters the pump chamber 20. The delivery section 32 has a passage 33 therein with a first, outermost end 34 operatively connectable to a feed pipe (not shown) WO 2014/153616 PCT/AU2014/000337 -7 and a second, innermost end 35 adjacent the chamber 20. The front liner 30 further includes a side wall section 15 which mates in use with the pump casing 12 to form and enclose the chamber 20, the side wall section 15 having an inner face 37. The second end 35 of the front liner 30 has a raised lip 38 thereat, which is arranged in a close facing relationship with the impeller 40. 100321 The impeller 40 includes a hub 41 from which a plurality of circumferentially spaced pumping vanes 42 extend. An eye portion 47 extends forwardly from the hub towards the passage 33 in the front liner. The impeller further includes a front shroud 50 and a back shroud 51, the vanes 42 being disposed therebetween. 10033] Referring now to Figure 2, this illustrates an impeller according to one embodiment. The same reference numerals as used to identify parts in Figure 1 are used to identify similar parts in the embodiment of Figure 2. The pumping vanes include a leading edge section 60 having a leading edge 43 and a trailing edge section 61 having a trailing edge 44. The leading edge section 60 is tapered inwardly towards the leading edge 43 and the trailing edge section 61 is tapered inwardly towards the trailing edge 44. The pumping vanes have a main section 63 between the leading edge section 60 and trailing edge section 61 which at any planar height above the back shroud 51 has a width or thickness 64 which is generally constant from one side edge 56 to the other side edge 57 and along its length from the leading edge section 60 to the trailing edge section 61. 10034] In Figure 2 only one exemplary pumping vane 42 is shown which extends between opposing main inner faces 53, 54 of the shrouds 50, 51. Normally such an impeller has a plurality of such pumping vanes spaced evenly around the area between the shrouds 50, 51. Typically three, four or five pumping vanes are usual in slurry pumps. In this drawing only one pumping vane has been shown for convenience to illustrate the features. As shown in Figure 2, the pumping vane 42 is generally arcuate in cross-section and includes an inner leading edge 43 and an outer trailing edge 44, opposed side edges 56, 57 and opposed first and second faces 45, 46 between the side edges 56, 57, the face 45 being a pumping or pressure side face. The vanes of this type are normally referred to as WO 2014/153616 PCT/AU2014/000337 -8 backward-curving vanes when viewed with the direction of rotation. The side edge 56, 57 are disposed against respective inner faces of the shrouds 50, 51. The inner faces 53. 54 are generally at right angles to the central rotation axis X-X. The face 45 which is a pumping or pressure side face of the pumping vane 42 is configured such that the surface thereof at any line between the leading and trailing edges 43, 44 which is at 900 from one side edge 56 to the other 57 is flat or linear in the direction of that line. 10035] Described in another way, the face 45 may be likened to a face of a rectangular flat strip with the leading edge 43 and the trailing edge 44 forming the two shorter sides of the rectangular flat strip and the side edges 56, 57 each forming the two respective longer sides of the rectangular flat strip. The rectangular flat strip is twisted about an axis that extends from the leading edge 43 to the trailing edge 44. In addition to being twisted, the rectangular flat strip is also curved between the leading edge 43 and the trailing edge 44 which provides that face 45 is backward-curved. A face (that is face 45) of the rectangular flat strip that is twisted and curved in this way, is linear or flat in the direction of a line which is drawn from one longer side (that is side edge 56) to the other longer side (that is side edge 57) at any point between the two shorter sides (that is the leading edge 43 and the trailing edge 44) of the rectangular flat strip when the line meets each of the longer sides at an angle of 900. 100361 In certain embodiments, the first face 45 is flat or linear when viewed at any cross-section along its length from the leading edge 43 to the trailing edge 44, each cross section being taken at rights angles to the side edges 56, 57 of the vane. Examples of such cross-sections are illustrated in Figures 3 to 5 showing cross-sections taken along the lines 1, 2, and 3 in Figure 2. As is apparent from viewing these Figures, the first face 45 is flat or linear at these cross sections. Described in another way, it means that the first face 45 is not bowed or convex at any of the cross-sectional views in question. In the embodiment described, the second face 46 is also flat or linear when viewed at any cross section. [00371 As illustrated, the angle of inclination Y of the side face 45 with respect to the main inner face 53 of the back shroud 51 progressively changes along the length of the WO 2014/153616 PCT/AU2014/000337 -9 vane 42 when moving from its leading edge 43 to its trailing edge 44. This change in angle is clearly shown in Figures 3 to 5. The angle of inclination Y is also referred to as the leading angle of the vane with respect to the direction of rotation of the impeller in use. As shown in Figure 3 the angle of inclination Y is an acute angle at the leading edge 43. Preferably the angle is in a range from about 450 to less than 90', more preferably the angle is in a range from about 70' to about 80', and more preferably is about 75'. The angle progressively changes and, at the position shown in Figure 4, it is at right angles (perpendicular). In the position shown in Figure 5 at the trailing edge 44 of the vane, the angle of inclination is obtuse. Preferably the angle at the trailing edge is in a range from greater than 90' up to about 135', more preferably the angle is in a range from about 1000 to about 130', and more preferably is about 1100. 100381 In operation, the Coriolis force (Arrow B in Figure 2), which is generated as a result of the in use rotation of the impeller in the direction of arrow A in Figure 2, causes the particulates C in a slurry or fluid which is being conveyed by the pump impeller of the present embodiment, to disperse over the face of the vane as the particulates travel along the vane from the leading edge to the trailing edge. The vane shape arrangement can assist to break up solid particle concentration gradients within the impeller where the slurry particles are at their highest concentration at the root of the vane on the back shroud of the impeller, that is, in the region where a side edge of the vane contacts the shroud. This can result in a reduction of the wear due to grooving of the impeller at that point. 10039] Figures 6, 7, 8 and 9 illustrate an impeller according to one embodiment. The same reference numerals as used to identify parts in Figures 1, 2, 3, 4 and 5 are used to identify similar parts in the embodiment of Figures 6, 7, 8 and 9. Figures 6 and 7 depict portions of an impeller 40 from different sides looking into the discharge passageways between the vanes 42, and Figures 8 and 9 each show an impeller 40 in its entirety. As can be seen, the angle of inclination of the side face 45 with respect to the main inner face 53 of the back shroud 51 progressively changes along the length of the vanes 42 when moving from the leading edge (now shown) to its trailing edge 44.
WO 2014/153616 PCT/AU2014/000337 -10 [00401 Figure 10 illustrates a modified form of the arrangement shown in Figure 2. The same reference numerals as used to identify parts in Figure 2 are used to identify similar parts in the modified form of Figure 10. The change in the angle of inclination Y along the length of the vane 42 as shown in Figure 10 is greater than the change in the angle of inclination Y along the length of the vane 42 as shown in Figure 2. 10041] 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. 100421 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. [00431 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. [0044J 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. [0045] Furthermore, invention(s) have been described in connection with what are WO 2014/153616 PCT/AU2014/000337 - 11 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.
WO 2014/153616 PCT/AU2014/000337 - 12 Table of Parts Pump 10 Pump casing (volute) 12 Back liner 14 Front liner 30 Pump outlet 18 Internal chamber 20 Central or rotational axis X-X Delivery section 32 Passage 33 Outer end 34 Inner end 35 Sidewall section 15 Inner face 37 Lip 38 Impeller 40 Hub 41 Pumping vanes 42 Eye portion 47 Leading edge section 60 Leading edge 43 Impeller inlet 48 Trailing edge section 61 Trailing edge 44 Main section 63 Width or thickness 64 Outlet 49 Front shroud 50 Back shroud 51 First face 45 WO 2014/153616 PCT/AU2014/000337 - 13 Second face 46 Side edge 56 Side edge 57