CENTRIFUGAL PUMP WITH OPPOSED IMPELLERS

Abstract

 The centrifugal pump with opposed impellers comprises a pump body (10), which has an internal cavity having a longitudinal axis and defining a first chamber (11) and a second chamber (12) adjacent to each other, separated by a partition wall (13). The pump body (10) forms a suction inlet (14) in communication with said first chamber (11) and a delivery outlet (15) in communication with said second chamber (12). A first impeller (21) and a second impeller (22) are arranged, in opposite positions, respectively inside said first chamber (11) and said second chamber (12) of the internal cavity, said impellers (21, 22) being equipped with respective axial hubs (23, 24) adapted to be associated with a driving shaft (20) coaxial to said longitudinal axis. The centrifugal pump comprises a plurality of conduits (30) adapted to convey the liquid coming out of said first impeller (21) to the axial inlet of said second impeller (22).

Description

Technical field

[0001] The present invention relates to a centrifugal pump with opposed impellers.

Prior art

[0002] The use of centrifugal pumps for domestic, agricultural or industrial purposes, in particular for pumping water, is currently known. Such centrifugal pumps comprise one or more impeller assemblies adapted to be rotated by a suitable motor member, generally of the electric type.

[0003] More specifically, known centrifugal pumps comprise a body having an internal cavity in communication with a liquid suction inlet, for example arranged at the front, and a delivery inlet, for example arranged on an upper side. The impeller assembly is housed in the internal cavity of the pump and is capable of being rotated by a suitable motor member, generally of the electric type.

[0004] A known type of centrifugal pumps involves the use of a pair of oppositely arranged centrifugal impellers, that is having the entrance of the second impeller opposite to the entrance of the first impeller. The two impellers are housed within separate chambers defined in the inner cavity of the pump. Basically, the liquid coming out of the first impeller is conveyed, by means of a special conduit, to the axial inlet of the second impeller.

[0005] The main advantage of this solution is that the axial thrust of the impellers on the driving shaft is balanced and does not weigh on the bearing. This allows smaller size and longer life of the pump.

[0006] Such an opposed impeller centrifugal pump is illustrated for example in patent document EP 0 726 397.

[0007] A problem complained of in the use of centrifugal pumps of the aforementioned type is the need to efficiently convey the liquid coming out of the first impeller to the axial inlet of the second impeller. Lack of efficiency of this conveying, in fact, causes a deterioration in the performance of the pump, compared to the traditional solution with two or more tandem impellers. In particular, the efficiency of the pump may be compromised.

Disclosure

[0008] The aim of the present invention is to solve the aforementioned problem by devising a centrifugal pump with opposed impellers capable of providing high levels of performance.

[0009] As part of this aim, it is a further object of the present invention to provide a centrifugal pump with opposed impellers that ensures high efficiency.

[0010] A further object of the invention is to provide a centrifugal pump with opposed impellers of simple construction and functional design, having reliable operation, versatile use, as well as relatively low cost.

[0011] The aforementioned objects are achieved, according to the present invention, by the centrifugal pump with opposed impellers according to claim 1.

[0012] The centrifugal pump with opposed impellers comprises a pump body, which has an internal cavity having a longitudinal axis and defining at least a first chamber and a second chamber adjacent to each other, separated by a partition wall (13).

[0013] Preferably, the pump body is formed by a first half-shell and a second half-shell, coupled in operation to form a casing containing the aforementioned internal cavity.

[0014] Preferably, the first chamber is defined inside the first half-shell, while the second chamber is defined inside the second half-shell.

[0015] Preferably, the first half-shell and the second half-shell are disposed in mutually opposite positions along the longitudinal axis.

[0016] The pump body forms a suction inlet in communication with said first chamber and a delivery outlet in communication with said second chamber.

[0017] Preferably, the first half-shell forms a first surface.

[0018] Preferably, the suction inlet opens onto the first surface of the first half-shell.

[0019] Preferably, the second half-shell forms a peripheral edge.

[0020] Preferably, the delivery outlet opens on the peripheral edge of the second half-shell.

[0021] The centrifugal pump with opposed impellers comprises at least a first impeller and a second impeller disposed, in opposite positions, respectively inside said first chamber and said second chamber of said internal cavity of the pump body.

[0022] Said impellers are equipped with respective axial hubs adapted to be associated with a driving shaft coaxial to said longitudinal axis.

[0023] Preferably, said longitudinal axis of the internal cavity of the pump is arranged in a horizontal position in the configuration of operation.

[0024] Preferably, the second half-shell forms, in a central portion, a protrusion extending in the direction of the longitudinal axis.

[0025] Preferably, the protrusion houses support means of the driving shaft.

[0026] Preferably, the protrusion radial extension is less than the radial extension of the second half-shell.

[0027] Preferably, the second half-shell forms a second surface, opposed to the first surface of the first half-shell along the longitudinal axis.

[0028] Preferably, the first surface and the second surface, respectively of the first half-shell and the second half-shell, are external surfaces of the pump body.

[0029] Preferably, the second surface comprises an inclined surface portion.

[0030] Preferably, the inclined surface portion extends substantially between the peripheral edge and the protrusion of the second half-shell.

[0031] According to the present invention, the centrifugal pump with opposed impellers comprises a plurality of conduits adapted to convey the liquid leaving said first impeller to the axial inlet of said second impeller.

[0032] According to an embodiment of the invention, the centrifugal pump having opposing impellers comprises a pair of said conduits adapted to convey the liquid leaving said first impeller to the axial inlet of said second impeller, arranged in positions radially opposite to said longitudinal axis.

[0033] The adoption of a plurality of conduits makes it possible to balance the pre-rotation at the entry of said second impeller, i.e. the presence of a tangential component of the inlet flow rate to the impeller member, obtaining an inlet operation of the second impeller substantially similar to that of the first impeller.

[0034] Preferably, said conduits adapted to convey the liquid outgoing from said first impeller to the axial inlet of said second conduit respectively comprise a first channel which develops at a peripheral portion of the pump body, delimiting said first chamber of the internal cavity of said pump body, and a second channel which extends, on a longitudinal plane to the same longitudinal axis, in a rear portion of the pump body, delimiting said second chamber of the internal cavity of said pump body.

[0035] Preferably, said first channel develops on a plane transverse to said longitudinal axis.

[0036] Preferably, said first channel has a diverging shape and terminates at a through hole in communication with said second channel.

[0037] Preferably, said second channel develops on a longitudinal plane to said longitudinal axis.

[0038] Preferably, said second channel terminates at the axial inlet of said second impeller.

[0039] Preferably, the second channel is made on the second surface of the second half-shell.

[0040] Preferably, the second channel protrudes externally with respect to the same second surface.

[0041] Preferably, the second channel extends in the radial direction from the peripheral edge towards the center.

[0042] Preferably, the second channel extends over the inclined surface portion of the second surface.

[0043] The arrangement of the second channel advantageously allows the reduction in size and weight of the pump compared to the prior art, thus creating a particularly compact pump.

[0044] Preferably, the end portions of said second channels of said pair of conduits are aligned diametrically so as to balance the pre-rotation at the input to said second impeller.

[0045] Preferably, the centrifugal pump with opposed impellers comprises an outlet channel in communication with said delivery outlet that develops on a plane transverse to the longitudinal axis, at the periphery of said second impeller.

[0046] Preferably, said outlet channel has a divergent shape.

[0047] Preferably, the centrifugal pump with opposed impellers comprises, at the central inlet area of said second impeller, a plurality of straightening fins, adapted to facilitate the transition from a flow perpendicular to said longitudinal axis of the pump, at the end section of said second channel, to a flow parallel to the same longitudinal axis, at the axial inlet of said second impeller.

[0048] These straightening fins prevent a circular pre-rotation motion that would decrease the performance of the second impeller and slow down the flow, thus decreasing the speed and the relative pressure drops.

Description of drawings

[0049] The details of the invention will be apparent from the detailed description of a preferred embodiment of the centrifugal pump with opposed impellers according to the invention, illustrated by way of an example in the accompanying drawings, wherein:

Figure 1 is a side view of the centrifugal pump with opposed impellers;

Figure 2 is an axial sectional view of the centrifugal pump with opposed impellers;

Figure 3 is a cross-sectional view of the centrifugal pump with opposed impellers on the suction side;

Figures 4 and 5 are respective cross-sectional views of the centrifugal pump with opposed impellers on the delivery side;

Figures 6 and 7 are a graph of the head and efficiency of the pump as a function of flow rate, respectively.

Description of embodiments of the invention

[0050] With particular reference to these figures, the centrifugal pump with opposed impellers according to the invention is indicated as a whole with the reference character 1. The centrifugal pump 1 comprises a pump body 10 which forms an internal cavity in which the operative parts of the pump are housed. In particular, the internal cavity defines a first chamber 11 and a second chamber 12 adjacent to each other, separated by a partition wall 13.

[0051] In particular, the pump body 10 is formed by a first half-shell 110 and a second half-shell 120, which are coupled in operation to form a casing containing the aforementioned internal cavity.

[0052] The first chamber 11 is defined within the first half-shell 110, while the second chamber 12 is defined within the second half-shell 120.

[0053] The pump body 10 has a longitudinal axis A arranged in a horizontal position in the configuration of use. As specified below, the longitudinal axis A is the drive axis of the rotating parts of the pump. However, it is possible to provide that the centrifugal pump in question is made so as to assume a different configuration of use, for example vertical.

[0054] In particular, the first half-shell 110 and the second half-shell 120 are arranged in mutually opposed positions along the longitudinal axis A.

[0055] The pump body 10 forms a suction inlet 14 open on a front surface of said pump body 10, in communication with said first chamber 11, and a delivery outlet 15 open on an upper surface of the same pump body 10, in communication with said second chamber 12.

[0056] In particular, the suction inlet 14 is arranged coaxially to the longitudinal axis A of the pump body 10; the delivery outlet 15 is arranged in the radial direction with respect to the longitudinal axis A of the pump body 10.

[0057] In particular, the first half-shell 110 forms a first surface 111, on which the suction inlet 14 opens.

[0058] The second half-shell 120 forms a peripheral edge 123, on which the delivery outlet 15 opens.

[0059] Inside the inner cavity of the pump body 10, a first impeller 21 and a second impeller 22 are housed in opposite positions, i.e. respectively faced backwards. In particular, the first impeller 21 and the second impeller 22 are arranged in opposing positions respectively within said first chamber 11 and said second chamber 12 of the inner cavity.

[0060] The impellers 21, 22, having a shape known per se, are provided with a respective axial hub 23, 24 which is associated axially with a driving shaft 20 coaxial thereto. The driving shaft 20 is adapted to be rotated by a motor member, for example of an electrical type, not shown in the figures.

[0061] The second half-shell 120 shapes, in a central portion, a protrusion 125, which extends in the direction of the longitudinal axis A, and which houses support means 126 of the driving shaft 20.

[0062] The protrusion 125 has a lower extension in the radial direction than the extension in the radial direction of the second half-shell 120.

[0063] The second half-shell 120 forms a second surface 121, opposed to the first surface 111 of the first half-shell 110 along the longitudinal axis A.

[0064] Preferably, the first surface 111 and the second surface 121, respectively of the first half-shell 110 and of the second half-shell 120, are external surfaces of the pump body 10.

[0065] Preferably, the second surface 122 comprises a portion of an inclined surface 128 which extends substantially between the peripheral edge 123 and the protrusion 125 of the second half-shell 120.

[0066] According to the present invention, the centrifugal pump comprises a plurality of conduits 30 adapted to convey the liquid coming out of the first impeller 21 to the axial inlet of the second impeller 22.

[0067] In the illustrated embodiment, the centrifugal pump comprises a pair of conduits 30 adapted to convey the liquid coming out of the first impeller 21 to the axial inlet of the second impeller 22, arranged in radially opposite positions with respect to said longitudinal axis.

[0068] More specifically, the conduits 30 respectively comprise a first channel 31 having diverging shape which extends, on a plane transversal to the longitudinal axis of the pump, at an annular peripheral portion 16 of the pump body 10, delimiting the first chamber 11 of the internal cavity of the pump body 10. The first channel 31 is in communication, from the internal side, with the output of the first impeller 21 (see Fig. 3).

[0069] The first channel 31 ends at a passage hole 32 made in the same peripheral portion 16 having annular shape of the pump body 10 and in communication with a second channel 33 which develops, on a longitudinal plane, in a rear portion 17 of the pump body 10, delimiting the second chamber 12 of the internal cavity of the pump body 10. The second channel 33 ends at the axial inlet of the second impeller 22 (see fig. 2). In practice, the passage hole 32 is the element of continuity between the first channel 31 and the second channel 33 of the conduit 30.

[0070] In particular, the second channel 33 is made on the second surface 121 and protrudes externally with respect to the same second surface 121 (see fig. 1 and fig. 4). The second channel 33 extends in a radial direction starting from the peripheral edge 123 towards the center.

[0071] Preferably, the second channel 33 extends on the inclined surface portion 128 of the second surface 122.

[0072] The liquid that passes through the second impeller 22 is conveyed by an outlet channel 34 to the delivery outlet 15. The outlet channel 34 has a divergent shape that develops on the rear portion 17 of the pump body 10, on a plane transversal to the longitudinal axis of the pump, at the periphery of the second impeller 22 (see Fig. 5).

[0073] The centrifugal pump is also equipped, at the central inlet area of the second impeller 22, with a pair of straightening fins 35.

[0074] The straightening fins 35 have the function of helping the transition from a flow which takes place on a plane perpendicular to the longitudinal axis of the pump, at the terminal section of the second channel 33, to a flow parallel to the axis, at the axial inlet of the second impeller 22.

[0075] The operation of the centrifugal pump with opposed impellers is easily understood from the above description.

[0076] In operation, the total flow rate of the liquid entering the suction inlet 14 passes through the first impeller 21 and is divided between the first channels 31, arranged in radially opposite positions with respect to the longitudinal axis, of the pair of conduits 30 which convey the liquid coming out of the first impeller 21 at the axial inlet of the second impeller 22.

[0077] The flow thus distributed is introduced into the second channels 33, equally arranged in radially opposite positions with respect to the longitudinal axis, of the pair of conduits 30 and conveyed by said second channels 33 to the axial inlet of the second impeller 22.

[0078] It should be noted that the terminal portions of the second channels 33 are substantially aligned diametrically and thus balance the pre-rotation at the inlet of the second impeller 22, i.e. the presence of a tangential component of the speed of the inlet flow of the second impeller (see Fig. 4).

[0079] The flow rate of the liquid entering the second impeller 22 passes through the same second impeller 22 and is conveyed, through the outlet channel 34, to the delivery outlet 15.

[0080] The centrifugal pump with opposed impellers according to the present invention achieves the purpose of providing a high level of performance, in particular ensuring a high efficiency.

[0081] This result is achieved thanks to the inventive idea of providing a plurality of conduits adapted to convey the liquid coming out of the first impeller to the axial inlet of the second impeller, in order to increase the efficiency of the pump.

[0082] According to the illustrated embodiment, the centrifugal pump in question has a pair of said conduits adapted to convey the liquid coming out of the first impeller to the axial inlet of the second impeller, arranged in radially opposite positions with respect to the longitudinal axis of the pump. However, it is possible to provide for a greater number of such conveyance conduits, depending on the needs and the size of the pump.

[0083] A prerogative of the present invention is given by the fact that the presence of said pair of conduits suitable for conveying the liquid to the axial inlet of the second impeller, arranged in radially opposite positions with respect to the longitudinal axis of the pump, allows balancing the pre-rotation at the inlet of said second impeller, that is the tangential component of the speed of the inlet flow of said second impeller. In fact, during the design phase of the impeller, an inlet angle of the flow between the blades is predetermined. If the flow enters with an inlet angle different from the expected one, altered by the pre-rotation, a decrease in performance occurs.

[0084] In the traditional solution, providing a single conduit adapted to convey the liquid to the axial inlet of the second impeller, an asymmetry is created that forms vortices or preferential paths of pre-rotation that do not allow a uniform and regular flow at the inlet of the impeller to be created. The implementation of a plurality of conduits allows these asymmetries to be balanced and cancelled, obtaining an intake operation of the second impeller substantially similar to that of the first impeller.

[0085] Another advantage of the centrifugal pump in question is provided by the straightening fins that facilitate the transition from a flow perpendicular to the longitudinal axis of the pump, at the end section of the second channel, to a flow parallel to the same longitudinal axis, at the axial inlet of the second impeller.

[0086] These straightening fins prevent a circular pre-rotation motion that would decrease the performance of the second impeller and slow down the flow, thus decreasing the speed and the relative pressure drops.

[0087] In practice, it has been verified that the centrifugal pump with opposed impellers according to the present invention has a head and efficiency trend that maintain high values for significantly higher flow rates compared to the traditional opposed impeller pumps, as shown in the graphs of Figures 6 and 7 where the variation of the head H and the percentage efficiency of the pump in question, respectively, as a function of the flow rate Q, is indicated with continuous lines, compared to that of a traditional opposed impeller pump of the same characteristics, represented by dashed lines.

[0088] It should be noted that the head and efficiency of the centrifugal pump with opposed impellers according to the present invention maintains a satisfactory value even at significantly high flow values, higher than those achievable in conventional centrifugal pumps having opposed impellers.

[0089] The centrifugal pump with opposing impellers described by way of example is susceptible to numerous changes and modifications depending on the different needs.

[0090] In particular, it is possible to provide that the pump has a plurality of opposed impellers arranged stacked.

[0091] In the practical embodiment of the invention, the materials used, as well as the shape and the dimensions, may be modified depending on requirements.

[0092] Should the technical features mentioned in any claim be followed by reference signs, such reference signs were included strictly with the aim of enhancing the understanding of the claims and hence they shall not be deemed restrictive in any manner whatsoever on the scope of each element identified for exemplifying purposes by such reference signs.

Claims

1. A centrifugal pump with opposed impellers, comprising

a pump body (10) having an internal cavity, which has a longitudinal axis (A) and defining at least a first chamber (11) and a second chamber (12) adjacent to each other, separated by a partition wall (13);

a suction inlet (14) open on a surface of said pump body (10) in communication with said first chamber (11);

a delivery outlet (15) open on a surface of said pump body (10) in communication with said second chamber (12);

at least a first impeller (21) and a second impeller (22) arranged, in opposite positions, respectively inside said first chamber (11) and said second chamber (12) of the internal cavity, said impellers (21, 22) being equipped with respective axial hubs (23, 24) adapted to be associated with a driving shaft (20) coaxial to said longitudinal axis (A);

characterized in that it comprises

a plurality of conduits (30) capable of conveying the liquid outgoing from said first impeller (21) to the axial inlet of said second impeller (22).

2. The centrifugal pump of claim 1, wherein it comprises a pair of said conduits (30) adapted to convey the liquid outgoing from said first impeller (21) to the axial inlet of said second impeller (22), arranged in radially opposite positions with respect to said longitudinal axis (A).

3. A centrifugal pump of claim 1 or 2, wherein said conduits (30) adapted to convey the liquid outgoing from said first impeller (21) to the axial inlet of said second impeller (22) respectively comprise a first channel (31) which extends, on a plane transverse to said longitudinal axis, at a peripheral portion (16) of the pump body (10), delimiting said first chamber (11) of the internal cavity of said pump body (10), and a second channel (33) which extends, on a longitudinal plane to the same longitudinal axis, in a rear portion (17) of the pump body (10), delimiting said second chamber (12) of the internal cavity of said pump body (10).

4. The centrifugal pump of claim 3, wherein said first channel (31) has a divergent shape and ends at a passage hole (32) in communication with said second channel (33).

5. A centrifugal pump of claim 3 or 4, wherein said second channel (33) ends at the axial inlet of said second impeller (22).

6. A centrifugal pump of claims 2 and 3, wherein the end portions of said second channels (33) of said pair of conduits (30) are aligned diametrically so as to balance the pre-rotation at the inlet of said second impeller (22).

7. A centrifugal pump of any one of the preceding claims, wherein it comprises an outlet channel (34) in communication with said delivery outlet (15) which extends on a plane transversal to the longitudinal axis (A), at the periphery of said second impeller (22).

8. The centrifugal pump of claim 7, wherein said outlet channel (34) has a diverging shape.

9. A centrifugal pump of any one of the preceding claims, wherein it comprises, at the central inlet area of said second impeller (22), a plurality of straightening fins (35), for facilitating the transition from a flow perpendicular to said longitudinal axis of the pump, at the terminal portion of said second channel (33), to a flow parallel to the same longitudinal axis (A), at the axial inlet of said second impeller (22).

10. The centrifugal pump of claim 9, wherein it comprises a pair of said straightening fins (35), arranged respectively at the outlet of said terminal section of the second channel (33) of each of said conduits (30) capable of conveying the liquid outgoing from said first impeller (21) to the axial inlet of said second impeller (22).

11. A centrifugal pump of any one of the preceding claims, wherein said pump body (10) comprises a first half-shell (110) and a second half-shell (120), said first and second half-shells (110, 120) being mutually arranged in positions opposed along said longitudinal axis (A) and being coupled in operation to form an envelope containing said internal cavity, said first chamber (11) being defined inside said first half-shell (110) and said second chamber (12) being defined inside said second half-shell (120).

12. The centrifugal pump of claim 11, wherein said first half-shell (110) forms a first surface (111), and said second half-shell (120) forms a peripheral edge (123) and a second surface (121), said second surface (121) being opposed along said longitudinal axis (A) to said first surface (111) of said first half-shell (110).

13. The centrifugal pump of claim 12, wherein said second channel (33) is made on said second surface (121) and protrudes externally with respect to said second surface (121), said second channel (33) extending in a radial direction from said peripheral edge (123) towards the center.

14. The centrifugal pump of claim 13, wherein said second channel (33) extends on an inclined surface portion (128) of said second surface (122).

Drawing