WO2003019013A1

WO2003019013A1 - Centrifugal pump

Info

Publication number: WO2003019013A1
Application number: PCT/SE2002/001503
Authority: WO
Inventors: Erik Ehlin
Original assignee: Aerodyn Ab
Priority date: 2001-08-27
Filing date: 2002-08-23
Publication date: 2003-03-06
Also published as: SE0102839L; SE523740C2; SE0102839D0

Abstract

A pump device of centrifugal type comprising a pump housing (1) with an axial inlet opening (10) and a tangential outlet opening (11) and also an impeller (2) arranged rotatable about an axis of rotation (27), the impeller comprising blades (33, 45) for transporting a fluid from the inlet opening to the outlet opening, and also a drive means (3) connected to the impeller for driving the impeller. In accordance with the invention the impeller comprises a plurality of adjacent pairs of blades (51) defining between them channels (14) with adjustable flow openings (52) for the fluid, each comprising a main blade (33) arranged on a main blade wheel (28) rotatable about the axis of rotation, and also a regulating blade (45) arranged on a regulating-blade wheel (29) and rotatable together with the main blade wheel and pivotable in relation to the main blade wheel, the pump device comprising a control device (13) connected to the regulating-blade wheel which, by turning of the regulating-blade wheel in relation to the main blade wheel, is arranged to regulate the flow openings.

Description

CENTRIFUGAL PUMP.

The present invention relates to a pump device of centrifugal type comprising - a pump housing comprising a helical structural element with an axial inlet opening and a tangential outlet opening,

- an impeller arranged rotatable about an axis of rotation in the pump housing, the impeller comprising blades for transporting a fluid from the inlet opening to the outlet opening, and

- a drive means connected to the impeller for driving the impeller.

The term "pump device of centrifugal type" refers here to a centrifugal pump or fan for pumping a fluid, i.e. a liquid or gas or a mixture thereof.

When pumping a clean or polluted fluid with the aid of a pump or fan of the type described above it is desirable to be able to regulate the flow through the pump device. A known method of regulating the flow comprises throttle-control of the flow to or from the pump. However, this gives the usually undesired effect of the pressure being altered when the flow is altered. Another known method of regulating the flow is speed control of the motor driving the pump device, which may be achieved by controlling the frequency of the motor. However, speed control requires the use of a more or less technically complicated and expensive motor. Furthermore, regulating the flow by means of speed control also results in both pressure and flow being altered simultaneously.

The object of the present invention is to overcome these problems and enable flow control while maintaining substantially constant pressure. The pump device in accordance with the invention is characterized in

- that the impeller comprises a plurality of adjacent pairs of blades defining between them channels with adjustable flow openings for the fluid, each comprising a main blade arranged on a main blade wheel rotatable about the axis of rotation, and also a regulating blade arranged on a regulating-blade wheel rotatable about the axis of rotation and rotatable together with the main blade wheel and pivotable in relation to the main blade wheel, and

- that the pump device comprises a control device connected to the regulating-blade wheel which, by turning of the regulating-blade wheel in relation to the main blade wheel, is arranged to regulate the flow openings .

Since the regulating blades are pivotable in relation to the main blades, therefore, the flow through the pump can easily be regulated while pumping is in progress, without speed control, and opening or reduction of said flow opening is possible without the impeller dimensions being changed. Since the adjustable flow opening is arranged in the pump housing the flow control takes place under substantially constant pressure.

If the fluid is a liquid, for instance, and if pollution is expected to occur in the liquid during a limited period of time, the flow opening can be temporarily maximized to prevent clogging of the pump device. Alternatively, before the pump is started, the regulating blades can be turned so that the desired initial flow opening is obtained. It may be desirable, for instance, to close or minimize the flow opening before the pump is started, in order to obtain as little starting torque as possible. The regulating blades are pivotable in relation to the main blades, both during operation or when no fluid is flowing through the pump device .

The invention will be described in more detail in the following with reference to the drawings in which

Figure 1 shows an axial section through a centrifugal pump with a hydraulic control device,

Figure 2 shows a horizontal view of a main blade wheel,

Figure 3 shows a horizontal view of a regulating-blade wheel ,

Figure 4 shows an impeller with main blade wheel and regulating-blade wheel in open position,

Figure 5 shows an impeller with main blade wheel and regulating-blade wheel in throttled position,

Figures 6-7 show partial views of a supply system to a hydraulic control device,

Figure 8 shows an axial section through a centrifugal pump with an electric control device in the form of a stepping motor, and

Figure 9 shows an alternative embodiment of an impeller.

Figure 1 shows an axial section through a pump of centrifugal type for pumping a liquid. The pump comprises a pump housing 1, an impeller 2 arranged in the pump housing 1 and a drive means 3 connected to the impeller 2. The pump housing 1 comprises first 4, second 5, third 6, fourth 7, fifth 8 and sixth 9 structural elements which are arranged in the stated order, and held by a screw joint, as shown in Figure 1. The fifth structural element 8 is helical and has an axial inlet opening 10 and a tangential outlet opening 11 for the fluid. The sixth structural element 9 surrounds the impeller 2 which is arranged to drive the fluid from the inlet opening 10 to the outlet opening 11. The drive means 3 comprises a pump motor, not shown, and a pump shaft 12. The pump shaft 12 comprises a first, upper shaft section 15 and a second, lower shaft section 16, which are axially connected by a connection device 17. The first shaft section 15 is homogenous and runs through an opening 18 in the first structural element 4 into the second structural element 5 and on into the third structural element 6 where the first shaft section 15 is connected by said connection device 17 to the upper end 19 of the second shaft section 16. The first shaft section 15 is rotatably journalled in the second structural element 5 by a ball bearing 20, for connection to the pump motor, this preferably being an electric motor. The second shaft section 16 is hollow and runs through the third structural element 6 into the fourth structural element 7 and on into the sixth structural element 9, through an opening 21 therein. The second shaft section 16 is rotatably journalled in the sixth structural element 9, at its mid-section 22 by a ball bearing 23. At the ball bearing 23 the fourth structural element 7 surrounds an oil-filled chamber 24 for cooling the ball bearing 23. In the sixth structural element 9 the second shaft section 16 is connected at its other, lower end 25 to the impeller 2 via a key joint 26. The impeller 2 is thus rotatable about an axis of rotation 27 that coincides with the axis of rotation of the pump shaft 12. The directions indicated in the following are in relation to this axis of rotation 27 unless otherwise stated.

In accordance with the invention the impeller 2 comprises a main blade wheel 28 (see Figure 2) , and a regulating-blade wheel 29 (see Figure 3) , said blade wheels 28, 29 preferably being made of metal. Figures 2 and 3 show the main and regulating-blade wheels, respectively, along the section marked II-II in Figure 1.

The main blade wheel 28 comprises a structural element 30, substantially symmetrical when rotated, shaped substantially as a truncated cone and having a central hole 31 running through it for receiving the pump shaft 12. The central axis of the hole 31 thus coincides with the axis of rotation of the main blade wheel 28. The central hole 31 has a key way 32 which constitutes a part of said key joint 26 between the impeller 2 and the pump shaft 12. The main blade wheel 28 also comprises three identical main blades 33 which protrude in axial direction from the structural element 30 so that the structural element 30 reveals an inner surface 40 free from the main blades 33 and an outer surface 41 where the main blades 33 protrude from the structural element 30. In this case the main blades 33 are double curved, i.e. they are curved in both axial and rotational direction. The main blades 33 may alternatively be single-curved, i.e. be curved only in rotational direction. Each main blade 33 has an inlet end 34 located a predetermined distance from the central hole 31, and also an outlet end 35 located at the outer edge 36 of the structural element 30. Each main blade 33 extends along a curved line between the inlet end 34 and the outlet end 35 so that each main blade 33 has a concave suction side 37 and a convex pressure side 38. On the suction side 37 each main blade 33 has at its inlet end 34 a surface portion 39 which is symmetrical when turned about the axis of rotation of the main blade wheel 28.

The regulating-blade wheel 29 comprises a structural element 42 shaped substantially as a truncated cone 63, which is substantially symmetrical when rotated, from the outer edge 44 of which protrude three spiral attachment arms 64. The cone 63 has a central hole 43 running through it and the axis of rotation of the regulating-blade wheel 29 coincides with the central axis of this hole 43. The regulating-blade wheel 29 also comprises three identical regulating blades 45 which protrude from the attachment arms 64 and in the axial direction of the regulating-blade wheel 29. Each regulating blade 45 has substantially the same shape as the main blades 33 of the main blade wheel 28, i.e. each regulating blade 45 is double curved and has an inlet end 46 and an outlet end 47 between which the regulating blade 45 extends along a curved line so that each regulating blade 45 has a concave suction side 48 and a convex pressure side 49. On the pressure side 49 each regulating blade 45 has at its inlet end 46 a surface portion 50 which is symmetrical when turned about the axis of rotation of the regulating-blade wheel 29.

The regulating-blade wheel 29 is intended to be placed in the pump housing 1 beside the main blade wheel 28 so that the axes of rotation of the blade wheels 28, 29 coincide with the axis of rotation of the pump shaft 12, i.e. with the axis of rotation 27 of the impeller 2, and so that the rear side, not visible in Figure 3, of the structural element 42 pertaining to the regulating-blade wheel 29, abuts the inner surface 40 of the structural element 30 of the main blade wheel 28. Figures 4 and 5 show the main and regulating-blade wheels 28, 29 arranged in this way. Each main blade 33 and a regulating blade 45 together form a pair of blades 51 wherein the main blade 33 and the regulating blade 45 are in close connection with each other at their inlet ends 34, 46 so that only an extremely small flow, preferably no flow at all, can pass between the inlet ends 34, 46. Consequently, the inlet ends 34, 46 of the blades 33, 45 are preferably in tight but sliding contact with each other, as shown in Figures 4 and 5 so that substantially all liquid is forced to flow in a channel 14 between adjacent blade pairs 51. In accordance with the invention the regulating-blade wheel 29 in relation to the main blade wheel 28 is pivotable about the common axis of rotation 27 to assume an optional position between a first and a second position. In the first position, illustrated in Figure 4, the channel 14 reveals a maximum flow opening 52 with relatively large area. In the second position, illustrated in Figure 5, the channel 14 reveals a minimum flow opening 52 with relatively small area. In each pair of blades 51, in the open position, said symmetrical surface portions 39, 50 of the blades 33, 45 are in contact with each other, as can be seen in Figure 4. In order, starting from the first position, to achieve the second position in Figure 5, the regulating-blade wheel 29 is caused to turn in relation to the main blade wheel 28, whereupon in each pair of blades 51 the symmetrical surface portions 50 of the regulating blade 45 are caused to slide along the symmetrical surface portion 39 of the main blade 33 until the second position has been achieved after a predetermined angular change between the regulating blade and the main blade wheels 29, 28. It will be understood here that if movement from the first to the second position is to be possible while retaining tight contact between the main and regulating blades 33, 45 in each pair 51, the surface portions 39 and 50 must be symmetrical when turned about the axis of rotation 27.

It will be understood that the second position can be a completely closed position in which the regulating blade

45 in a blade pair 51 is in contact with the main blade 33 in an adjacent blade pair 51 and the channel 14 is fully closed. It will also be understood that the main and regulating blades 33, 45 shall be shaped so that in every position between first and second positions the channel 14 is correctly shaped from the flow point of view. Edges and protrusions in which pollution might catch shall, for instance, be avoided. As can be seen in Figure 1 the blades 33, 45 are shaped with their greatest blade height nearest the hub of the impeller 2 and their least blade height at the periphery of the impeller 2. Upon rotation of the impeller 2 about the axis of rotation 27 the distance between the blades 33, 45 and the sixth structural element 9 is constant, and also upon rotation of the regulating-blade wheel 29 in relation to the main blade wheel 28. In other words the outer dimensions of the impeller 2 remain unchanged even if the regulating-blade wheel 29 is turned to regulate the flow.

Figure 9 shows an alternative embodiment of an impeller 2 which comprises a regulating-blade wheel 29 and a main blade wheel 28 where each main blade 33 comprises only the inlet end 34 shown in Figure 2, which is sufficient for functioning of the flow control in accordance with the invention.

In order to turn the regulating-blade wheel 29 in relation to the main blade wheel 28, the centrifugal pump comprises a control device 13. In the embodiment shown in Figure 1 the control device 13 is hydraulically operated and is arranged inside the second, hollow shaft section 16 of the pump shaft 12. The control device 13 comprises a hydraulic piston 53 axially placed and operable in axial direction, and also a control shaft 54 axially placed and turnable about the axis of rotation 27. A worm gear 55 at the first, upper end 56 of the control shaft 54 transmits the axial movement of the hydraulic piston 53 to a turning movement in the control shaft 54. The hydraulic piston 53 is activated by hydraulic oil conducted through two hydraulic pipes 57, 58 leading to and from the hydraulic piston 53. Figures 6 and 7 show enlarged partial views of the hydraulic pipes 57, 58 illustrating how the hydraulic oil is conveyed in conventional manner between the stationary pump housing 1 and the rotatable pump shaft 12. At the other, lower end 59 of the control shaft 54, the regulating-blade wheel 29 is attached by means of a screw joint to the control shaft 54 by a bolt 60 running through the central hole 43 of the regulating-blade wheel 29.

In an alternative embodiment of a centrifugal pump in accordance with the invention, illustrated in Figure 8, the control device 13 comprises an electric motor 61 instead of a hydraulic piston, preferably a stepping motor, which is arranged in the same way as the hydraulic piston described above, inside the lower, hollow shaft section 16 of the pump shaft 12. The shaft (not shown) of the electric motor 61 is connected to the control shaft 54, preferably via a planetary gear. The power source for the electric motor 61 may be a low voltage power source, e.g. 24 volt DV which, via a slip contact 62 comprising slip rings and brushes, supplies the motor 61 inside the rotating pump shaft 12. Control signals are preferably transmitted to the motor 61 in the same way.

Thus, in accordance with the invention the regulating-blade wheel 29 can be turned in relation to the main blade wheel 28 during operation to enable opening or reduction of said flow opening 52 while pumping is in progress. The flow through the pump can thus easily be regulated while pumping is in progress. If large particles are expected to occur in the liquid during a limited period of time, for instance, the flow opening 52 can be temporarily maximized to prevent clogging of the pump. Alternatively, before the pump is started, the regulating- blade wheel 29 can be turned in relation to the main blade wheel 28 so that the desired initial flow opening 52 is obtained. It may be desirable, for instance, to close or minimize the flow opening 52 before the pump is started, in order to obtain as little starting torque as possible. The invention has been described above in a centrifugal pump for a liquid. However, it will be understood that it is equally suitable in a centrifugal fan for a gas.

P1545PC TE1 021212

Claims

C L A I M S

1. A pump device of centrifugal type comprising

- a pump housing (1) comprising a helical structural element (8) with an axial inlet opening (10) and a tangential outlet opening (11) ,

- an impeller (2) arranged rotatable about an axis of rotation (27) in the pump housing (1) , the impeller comprising blades (33, 45) for transporting a fluid from the inlet opening (10) to the outlet opening (11) , and

- a drive means (3) connected to the impeller (2) for driving the impeller (2) , characterized in

- that the impeller (2) comprises a plurality of adjacent pairs of blades (51) defining between them channels (14) with adjustable flow openings (52) for the fluid, each comprising a main blade (33) arranged on a main blade wheel (28) rotatable about the axis of rotation (27) , and also a regulating blade (45) arranged on a regulating-blade wheel (29) rotatable about the axis of rotation (27) and rotatable together with the main blade wheel (28) and pivotable in relation to the main blade wheel (28) , and

- that the pump device comprises a control device (13) connected to the regulating-blade wheel (29) which, by turning of the regulating-blade wheel (29) in relation to the main blade wheel (28) , is arranged to regulate the flow openings (52) .

2. A pump device as claimed in claim 1, characterized in that the main and regulating blades (33, 45) in each pair of blades (51) are in sliding contact with each other.

3. A pump device as claimed in claim 2, characterized in that the main blade (33) in each pair of blades (51) has an inlet end (34) , at which the main blade (33) has a concave surface portion (39) , symmetrical when turned about the axis of rotation (27) , and also in that the regulating blade (45) in each pair of blades (51) has an inlet end (46) at which the regulating blade (45) has a convex surface portion (50) , symmetrical when turned about the axis of rotation (27) , the convex surface portion (50) being in said sliding contact with the concave surface portion (39) of the main blade (33) .

4. A pump device as claimed in any one of claims 1-3, characterized in that the control device (13) is arranged inside the pump shaft (12) .

5. A pump device as claimed in claim 4, characterized in that the control device (13) comprises a hydraulic piston (53) axially placed and operable in axial direction in the pump shaft (12) , and also a control shaft (54) axially placed in the pump shaft (12) and turnable about the axis of rotation (27) , the control shaft (54) being connected at one end (56) to a worm gear (55) for transmission of the axial movement of the hydraulic piston (53) to a turning movement in the control shaft (54) , and being connected at its other end (59) to the regulating-blade wheel (29) .

6. A pump device as claimed in claim 4, characterized in that the control device (13) comprises an electric motor (61) , preferably a stepping motor, axially placed in the pump shaft (12) , and also a control shaft (54) axially placed in the pump shaft (12) and turnable about the axis of rotation (27) , the control shaft (54) being connected at one end (56) to a planetary gear for transmission of the movement of the motor (61) to a turning movement in the control shaft (54) , and being connected at its other end (59) to the regulating-blade wheel (29) .

7. A pump device as claimed in any one of claims 1-6, characterized in that the outer dimensions of the impeller (2) remain unchanged upon turning the regulating-blade wheel (29) in relation to the main blade wheel (28) .

P1545PC TE1 021212