High efficiency double suction impeller

Abstract

A double suction impeller is disclosed. In at least one embodiment, the impeller is configured for centrifugal pumps and hydraulic power recovery turbines. The impeller's flow-path arrangement comprises inter-blade channels, intersecting each other at the impeller's outer diameter and defining a variable cross section shape, so that the equivalent number of blades is at least doubled with respect to a conventional configuration obtained by the coupling of two single suction impellers and an improved control over the velocity of the flow within the inter-blade channels is achieved.

Claims

1. A double suction impeller, comprising: a plurality of blades attached to a hub and to a left side shroud and to a right side shroud, the left side shroud and the right side shroud each having a center aperture, and an outer edge of the left side shroud and the outer edge of the right side shroud define an impeller exit; each pair of adjacent blades of the plurality of blades defines a plurality of inter-blade channels configured to connect a plurality of input apertures located within the center apertures of the left side shroud and the right side shroud to a plurality of output apertures located on the impeller exit, wherein each of the plurality of inter-blade channels has a variable cross section shape, the variable cross section shape being quadrilateral at an inlet of each inter-blade channel of the plurality of inter-blade channels, then becoming at least a five sided polygon, and then becoming quadrilateral again before the impeller exit.

2. The double suction impeller of claim 1, wherein the plurality of inter-blade channels comprises left side inter-blade channels having their respective input apertures located within the center aperture of the left side shroud, and right side inter-blade channels having their respective input apertures located within the center aperture of the right side shroud.

3. The double suction impeller of claim 2, wherein the left side inter-blade channels and the right side inter-blade channels intersect a median plane of the impeller exit in a configuration where the plurality of output apertures of the left side inter-blade channels are in alternating alignment with the plurality of output apertures of the right side inter-blade channels on the impeller exit.

4. The double suction impeller of claim 1, wherein the double suction impeller is made of a single piece.

5. The double suction impeller of claim 1, wherein the double suction impeller is made of two pieces.

6. The double suction impeller of claim 1, wherein the hub defines a tubular center bore configured to receive an impeller drive shaft.

7. The double suction impeller of claim 6, wherein the center apertures of the left side shroud and the right side shroud are adjacent to the tubular center bore.

8. The double suction impeller of claim 7, wherein the center apertures of the left side shroud and the right side shroud comprise an aperture edge and an aperture rim.

9. The double suction impeller of claim 1, further comprising a housing having axial inlets and a circumferential volute or diffuser outlet passage.

10. The double suction impeller of claim 1, wherein the plurality of blades are integrally attached to the hub.

11. A centrifugal pump comprising the double suction impeller of claim 1.

12. A hydraulic power recovery turbine comprising the double suction impeller of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features, aspects, and advantages of embodiments of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

(2) FIG. 1 illustrates a meridional section of a state of the art double suction impeller;

(3) FIG. 2 illustrates a view of the inter-blade channel of the state of the art double suction impeller;

(4) FIG. 3 illustrates a detail of the outer diameter arrangement of the state of the art double suction impeller;

(5) FIG. 4 illustrates a detail of the section of an embodiment of a new double suction impeller according to the present disclosure;

(6) FIG. 5 illustrates a view of the inter-blade channel of another embodiment of the new double suction impeller according to the present disclosure;

(7) FIG. 6 illustrates a detail of the outer diameter arrangement of another embodiment of the new double suction impeller according to the present disclosure;

(8) FIG. 7 illustrates a first front view of another embodiment of the new double suction impeller according to the present disclosure;

(9) FIG. 8 illustrates a meridional cross section of an embodiment of the new double suction impeller according to the present disclosure;

(10) FIG. 9 illustrates a side view of an embodiment of the new double suction impeller according to the present disclosure;

(11) FIG. 10 illustrates a graph plotting the efficiency and the head coefficient vs the flow coefficient of the new double suction impeller according to the present disclosure compared to state-of-the-art impellers; and

(12) FIG. 11 illustrates a view of the inter-blade channel of another embodiment of the new double suction impeller according to the present disclosure.

DETAILED DESCRIPTION

(13) With reference to the attached drawings and according to an exemplary embodiment, embodiments of the present invention relate to new a double suction impeller, in particular for centrifugal pumps, wherein the flow-path arrangement is characterized by inter-blade channels intersecting each other at the impeller outer diameter.

(14) In one embodiment, the new double suction impeller comprises channels between the blades starting from both inlets and intersecting at the outer diameter of the impeller in such a way that the equivalent blade number is doubled with respect to a conventional configuration obtained by simply adjoining to a central rib two single suction impellers, as illustrated in FIGS. 1, 2 and 3.

(15) In greater detail, and with reference to FIGS. 4, 5, 6, 7, 8, 9 and 11, the new double suction impeller includes a shrouded impeller 10. The shrouded impeller 10 may further include a hub 11 associated with a tubular center bore 12. The tubular center bore 12 may be adapted to receive the impeller drive shaft which is drivingly connected thereto, generally by a key and a keyway.

(16) The shrouded impeller 10 can be made either of one single piece—or assembly—or it can be made of a plurality of assemblies, e.g. comprising one left shroud, one right shroud and a central core.

(17) In one embodiment, the new impeller is made of one single assembly, and the hub 11 further includes a plurality of blades 13 integrally attached to the hub 11 and to a pair of integral shrouds, a left side shroud 14 and a right side shroud 15. Each one of the integral shrouds 14, 15 is provided with a center aperture 16, 31 that constitutes the impeller eye. The impeller eye is adjacent to said tubular center bore 12 and comprises an aperture edge 17 with an aperture edge radius and an aperture rim 18 with an aperture rim radius.

(18) The left side shroud 14 defines the left side aperture and the right side shroud 15 defines the right side aperture of the double suction impeller according to the present invention.

(19) The outer edge of said left side shroud 14 and the outer edge of said right side shroud 15 define the impeller exit, said impeller exit having a width 19 and a median plane 20.

(20) In greater detail, each pair of adjacent blades 13 of said plurality of blades 13 define a plurality of inter-blade channels, referred to in FIGS. 5 and 11. Said inter-blade channels are adapted to connect a plurality of input apertures, located within the center apertures of both said left side shroud 14 and said right side shroud 15, to a plurality of output apertures located on said impeller exit.

(21) With reference, in particular, to FIGS. 4 and 6, said inter-blade channels comprise left side inter-blade channels 21, having their respective input apertures 22 located within the center aperture of said left side shroud 14, and right side inter-blade channels 24, having their respective input apertures 25 located within the center aperture of said right side shroud 15.

(22) Advantageously, said left side inter-blade channels 21 and said right side inter-blade channels 24 are such as intersecting the median plane 20 of said impeller exit in a way to dispose the output apertures 23 of said left side inter-blade channels 21 to be aligned and alternated with the output apertures 26 of said right side inter-blade channels 24, on said impeller exit.

(23) In operation, when rotated, fluid will be drawn axially into the impeller as indicated by the arrows 27, 28, impelled by the plurality of blades 13 passing between the hub 11 and said left and right shrouds 14, 15 and finally expelled radially through said exit as indicated by the arrows 29. The impeller runs in the direction of arrow 30 in a suitable housing having axial inlets and a circumferential volute or diffuser outlet passage.

(24) In the double suction impeller according to the present invention, the effect connected to the crossing by said inter-blade channels of the median axis of the impeller exit is such that the equivalent blades number is doubled with respect to a conventional configuration obtained by the coupling of two single suction impellers.

(25) With reference to FIG. 2, the section 33 corresponds to the inlet of a channel of an impeller of the state of the art, and area 32 corresponds to the outlet of a channel of an impeller of the state of the art.

(26) With reference to FIGS. 5 and 11, the section labeled 35 corresponds to the inlet of a channel of the new impeller, and the area labeled 34 corresponds to the outlet of a channel of the new impeller.

(27) It is apparent that, when comparing inter-blade channels of a double suction impeller of the prior art with the inter-blade channels of the new double suction impeller, the outlet area 34 of the inter-blade channels of the new double suction impeller has a rectangular shape with an aspect ratio much closer to 1 with respect to that of a state of the art impeller.

(28) The cross section area of the inter-blade channel is designed to have control over the velocity of the flow inside the inter-blade channel. Moreover, the shape of the inter-blade channel is such as to avoid intersections between opposing channels and at the same time to maintain a target cross section area.

(29) The shape of the new inter-blade channel is adapted to ensure a suitable distribution of the velocity inside the channel and to avoid channels intersection. Furthermore, the shape of the new inter-blade channel is such as the area of the cross section of the channel changes gradually, allowing for a precise control of the fluid velocity inside. This feature leads to higher performance and higher overall efficiency compared to solutions where the area of the internal section of the channel changes abruptly in order to avoid mutual intersection between channels or solutions where the area of the internal section of the channel is kept constant. In a preferred embodiment the cross section area of the channel is such as it allows the velocity of the fluid inside the channel being described by a function continuous in its first and second derivative. As a non-limiting example, such functions can be those represented by Bezier curves.

(30) According to another embodiment, shown in FIG. 11, the inter-blade channels of the double suction impeller have a variable cross section shape. The channel starts at the inlet having an essentially quadrilateral cross-section. Then, moving along the flow toward the outlet, the channel cross-section becomes a five sided polygon until a small length before the impeller outlet where the channel cross-section changes back to being substantially quadrilateral. The additional fifth side defines the channel cross section between the suction side and the hub surfaces of the channel. The length of the additional fifth side of the channel cross section starts from zero, increases until it reaches its maximum length and then decreases back to zero.

(31) Finally, benefits introduced by the new double suction impeller include, inter alia, reduction of the slip and reduction of hydraulic losses. These reductions may translate to an efficiency increase of about 3% to 4% and, ultimately, to a lower operating expenditure and lower capital expenditure.

(32) The above description of exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

(33) Throughout the specification, the terms “one embodiment” or “an embodiment” indicate that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. The above detailed description does not limit the scope of the claimed invention. Instead, the scope of the invention is defined by the appended claims.