EP2863062B1 - Canned motor pump - Google Patents

Description

The invention relates to a centrifugal pump with a housing with a stator area receiving a stator and a rotor chamber receiving a rotor part and through which a delivery medium can flow. The rotor part is rotatably mounted in the rotor chamber about a longitudinal axis and has an impeller section with blade parts for the medium to be conveyed. An annular gap is formed between a rear section of the rotor part encircling the stator and an outer side wall of the housing.

Centrifugal pumps with wet-running external rotor rotors are known. In these pumps, the pumped medium, in particular water, enters the rotor chamber via a suction pipe and is carried outwards on a spiral path. The increasing radial velocity of the conveying medium leads to an outwardly increasing pressure which conveys the conveying medium into an outlet pipe. The rotor part of the motor, which sits on a shaft, runs in the fluid, which can simultaneously lubricate the bearings and cool the motor. The separation from the current-carrying stator of the motor is carried out by a partition such as a can or a can.

Due to the design of these pumps, there is a delivery area in the rotor chamber through which the blade parts of the rotor part pass, so that the delivery medium is accelerated radially outwards, and an annular area surrounding the stator, in which a rotor section of the rotor part is exposed to the magnetic forces of the stator windings is driven and rotates in it, the conveying medium reaching both areas of the rotor chamber.

Conventional pumps with wet-running external rotor are among others in the publications DE 100 09 900 A1 , US 2005/0249609 A1 and JP 2010-7539 A described. The rotor parts of these pumps, which are rotatably mounted about a longitudinal axis, each have a rotor section which runs in an intermediate space between the containment shell and the housing wall and which forms the rear section of the rotor part, and an impeller section with blade parts which forms the front section of the rotor part. The blade parts protrude into a conveying area of the rotor chamber, in which the fluid is accelerated radially outwards. However, the efficiency of these pumps is unsatisfactory.

Pumps with wet-running internal rotor rotors are more efficient. However, the torque of these pumps is regularly lower. Pumps with an internal rotor rotor also require a larger installation space.

From the US 2007/0177993 A1 a centrifugal pump according to the preamble of claim 1 is known.

In view of the problems described, it is the object of the present invention to provide a centrifugal pump with a satisfactory overall efficiency, which at the same time takes up little space.

This object is achieved by a development of the known centrifugal pumps, which is essentially characterized in that the gap has a widening section in which the radial dimension of the gap gradually increases in the axial direction and which at its front end becomes one of blade parts of the The rotor section of the rotor chamber can be passed through. The widening section extends in the axial direction over a length that is greater than 10%, preferably greater than 20%, in particular greater than 30% of the total length of the gap in the axial direction.

In other words, the radial gap which is formed between the rotor part and a side wall of the housing does not consistently have a constant gap width in the axial direction, but becomes wider in the direction of the conveying region of the rotor chamber in a widening section. This broadening takes place gradually, ie not in a single step or the like. In particular, the gap in the Widening section in a linear manner wider. The length of the widening section in the axial direction is long compared to the total length of the gap and is more than 10% of the total length, in particular 30% or more, but preferably less than 50%. In other words, the widening takes place over a distance that is extended in the axial direction. The entire gap extends in the longitudinal direction from the front end of the widening section to the rear end of the rotor part. At the rear end of the widening section, there is preferably a gap section with a constant gap width in the axial direction, which rotates in an annular manner around the rear section of the rotor part. This constant gap width is preferably more than 0.1 mm and less than 1.5 mm, in particular more than 0.3 mm and less than 1 mm, since a gap of this width has only a slight influence on the losses.

The invention is based on the knowledge that a narrow gap between a rotating inner wall and a stationary outer side wall leads to the formation of numerous small roller movements of the conveying medium in the gap, the so-called Taylor Couette instabilities. These tightly packed rollers have high turbulent losses and overall lead to a reduced efficiency of the centrifugal pump. However, if the gap width is initially large and only gradually decreases in the direction of the rear section of the gap, a single controllable roller movement or a single vortex is formed in the widening portion, which has significantly less internal losses, which leads to the formation of numerous small vortexes in this gap area is avoided. Overall, the hydraulic losses in the gap are reduced and the overall efficiency is increased. The loss optimization results in a lower need for drive power with the same hydraulic power.

Alternatively or additionally, the rear end of the gap, which faces away from the conveying area, forms the widening section.

It has proven advantageous from a hydrodynamic point of view that the radial dimension of the widening section at its front end is more than twice as large, preferably more than three times as large, in particular four times as large, or more than the radial dimension of the widening section at its rear end . A large entrance width of the gap starting from the conveying area of the rotor chamber supports the formation of a single roller movement of the conveying medium, as a result of which the vortex losses which arise are reduced. On the other hand, the radial dimension of the widening section at its front end is preferably less than 20 times, preferably less than 10 times as large as the radial dimension of the widening section at its rear end. Too large an inlet width supports an undesired flow of the medium into the gap.

With regard to an optimal flow behavior of the conveying medium in the gap, it has proven to be expedient for the widening section to extend in the axial direction over a length which is more than three times as large, preferably more than five times as large, in particular more than eight times as large like the radial dimension of the gap at the rear end of the widening section (ie the end facing away from the conveying area).

As already indicated, the ring section of the gap which adjoins the rear end of the widening section can be substantially in the shape of a circular cylinder jacket. Such a gap shape does not prevent the rotor from rotating around the stator and leads to a flow behavior of the conveying medium in the gap which is advantageous from a hydrodynamic point of view.

In view of an inexpensive and simple manufacture of the rotor part, it is expedient for the rotor part to have a transition section which preferably tapers conically in the direction of the conveying region and which is widened by the widening section of the gap. By installing a rotor part with a tapering transition section into an intermediate space between the housing wall and the containment shell, a widening section is created in a simple manner, in which the gap width widens in the direction of the conveying area. A rotor part shaped in this way can therefore be installed in conventional pump housings, whereby a centrifugal pump according to the invention is obtained. This can save costs. The conically tapering transition section of the rotor part can be delimited by an outer surface facing the housing wall, which forms the part of a lateral surface of a flat circular cone.

The half opening angle of the cone is preferably larger than 10 °, preferably larger than 20 °, in particular larger than 30 °, and preferably smaller than 60 °, in particular smaller than 40 °. In other words, in an axial section plane, the cutting angle between the outer surface of the transition section facing the housing wall and the longitudinal axis is greater than 10 °, preferably greater than 20 °, in particular greater than 30 °, and preferably less than 60 °, in particular less than 40 ° . Such an opening angle of the widening section leads to particularly low eddy losses in the entrance area of the gap.

The thickness of the transition section in the radial direction can essentially correspond to the thickness of a tubular section of the rotor part in the form of a cylindrical cylinder, which adjoins the rear end of the transition section. A rotor part shaped in this way allows simple dimensional monitoring in the manufacturing process of the components, in particular if the transition section is conical and the adjoining pipe section is cylindrical.

In a particularly preferred embodiment, the centrifugal pump according to the invention has a partition projecting into the interior of the housing, in particular in the form of a can or can which separates the stator region from the rotor chamber, the rear section of the rotor part being in a space between the housing wall and a circumferential one Wall of the containment shell is added.

The circumferential wall of the containment shell can have an essentially cylindrical jacket-shaped part and an essentially conical jacket-shaped part, each of which faces an inside of the rotor part. The containment shell is preferably shaped in such a way that it encloses the contours of the stator as closely as possible, while the rotor with its inner and outer contours can in turn follow the contour of the can. Such a configuration of the containment shell and rotor leads to particularly low losses due to undesired flows in the gaps on both sides of the rotor part and thus to an overall higher efficiency of the pump.

In this context, it has proven to be expedient for the cone-shaped part of the containment shell wall, the inner boundary surface of the rotor part facing this part and the outer boundary surface of the rotor part facing the widening section of the gap to run essentially parallel to one another, while they preferably have an angle of more than Include 10 °, in particular more than 30 °, but preferably less than 50 ° with the longitudinal axis. A rotor part with a transition section shaped in this way between the section surrounding the stator and the impeller section with blade parts is particularly stable and rotates particularly smoothly.

According to a further aspect of the invention, the gap has the widening section or a further widening section at its rear end facing away from the conveying region. The gap contour and the gap dimensions of the (further) widening section can correspond to the contours and dimensions of the widening section described above, and reference is made to the above statements in order to avoid repetition.

In the further widening section, a single controllable roller movement of the conveying medium can form, which leads to significantly fewer losses as a continuously narrow gap in which numerous small roller movements (Taylor-Couette instabilities) form when the rotor rotates, which lead to high internal losses. This increases the efficiency of the centrifugal pump.

Fig. 1:

eine erfindungsgemäße Kreiselpumpe in einer schematischen Querschnittsansicht, und

Fig. 2:

die Turbulenzen des Fördermediums im Spalt einer herkömmlichen Kreiselpumpe (rechts) und die Turbulenzen des Fördermediums im Spalt einer erfindungsgemäßen Kreiselpumpe mit Verbreiterungsabschnitt (links).

The invention is explained in more detail below with reference to an embodiment shown in a drawing. In the drawing shows

Fig. 1:

a centrifugal pump according to the invention in a schematic cross-sectional view, and

Fig. 2:

the turbulence of the delivery medium in the gap of a conventional centrifugal pump (right) and the turbulence of the delivery medium in the gap of a centrifugal pump according to the invention with a widening section (left).

Fig. 1 shows a centrifugal pump 10 according to the invention in a cross-sectional view. A pumped medium, in particular water, is fed to the pump through an inlet pipe 52 and pumped in the direction of an outlet pipe 54. A radial acceleration of the water is generated by a rotor part 3 which is equipped with blade parts 32 and which is rotatably mounted about a longitudinal axis A.

The pump 10 has a housing 4, which forms a rotor chamber 31 through which the pumped medium flows and a stator region 22 which receives the stator 2. The rotor chamber 31 and the stator area 22 are separated from one another by a can 1 projecting into the housing interior. The containment shell 1 forms in the interior of the housing a peripheral can wall 1.1, 1.2, which is shaped such that an annular space is formed between the can wall and a side wall 42 of the housing 4.

The rotor part 3 has a front section facing the inlet pipe 52 with the blade parts 32 which protrude into a conveying area 33 of the rotor chamber 31. Furthermore, the rotor part 3 has a rear section which surrounds the containment shell 1 in an annular manner and is received in the space between the containment shell wall 1.1, 1.2 and the housing wall 42. The rear section of the rotor part has a substantially cylindrical jacket section 3.1 and a conically tapering transition section 3.2, which connects the pipe section 3.1 to the front rotor section. The rear portion of the rotor part 3 is driven due to the magnetic field generated by windings 6 of the stator 2, so that the front section of the rotor part 3, which is connected in a rotationally fixed manner, is also set in rotation. The moving blade parts 32 accelerate the pumped medium radially outwards.

A gap 7 is formed between the rear section of the rotor part 3 and the side wall 42 of the housing 4. The gap 7 comprises a widening section 5, in which the radial dimension of the gap gradually increases in the axial direction A in the direction of the conveying area 33 and which at its front end merges into the conveying area 33 of the rotor chamber 31.

The widening section 5 extends in the axial direction over a length L that is greater than 10% of the total length G of the gap 7 in the axial direction. In the embodiment shown, the length L of the widening section 5 is approximately 35% of the total length G of the gap 7. In this way, a widening section which is expanded in comparison with the total length of the rotor in the axial direction results in the formation of a controllable roller movement of the conveying medium in the transition region leads between the conveying area 33 and the gap 7, whereby hydraulic gap losses can be avoided.

Furthermore, the widening section 5 extends in the axial direction A over a length L which is more than eight times as large as the radial dimension X of the gap at the rear end of the widening section 5, at which the gap width is small. In addition, the radial dimension of the widening section 5 at its front end is more than four times as large as at its rear end. The gap in the widening section thus widens considerably.

The pipe section 3.1 of the rotor part 3 and the transition section 3.2 of the rotor part 3 have approximately the same thickness in the radial direction. The transition section 3.2 runs in the cross-sectional view of FIG Fig. 1 at an angle a / 2 to the longitudinal axis A, while the cylindrical jacket-shaped pipe section 3.1 runs approximately parallel to the longitudinal axis A. The angle α / 2 is more than 20 ° and less than 40 °, in particular about 30 ° and corresponds to the opening angle of the widening section of the gap 7. In other words, the transition section 3.2 tapers conically in the direction of the conveying area 33. In the widening section 5 of the gap 7, the gap width is thereby widened in a linear manner in the direction of the conveying region 33.

The containment shell 1 also has a cylindrical shell-shaped part 1.1, which will run around the pipe section 3.1 of the rotor part 3, and a conically tapering part 1.2, which will run around the transition section 3.2 of the rotor part 3. The conical section 1.2 of the containment shell 1 is adjoined by an essentially flat ceiling of the containment shell 1, which extends approximately in the radial direction. The containment shell 1 closely follows the contours of the stator that it surrounds. The inner boundary surface of the transition section 3.2 facing the containment shell 1 and the outer boundary surface of the transition section 3.2 facing the widening section 5 run essentially parallel to one another and parallel to the conical part 1.2 of the containment shell.

In Fig. 2 the turbulence of the pumped medium in the gap of a conventional centrifugal pump is shown on the right. The gap has a uniform gap width over its entire axial dimension. Numerous small roller movements 60, so-called Taylor Couette instabilities, form, which lead to high hydraulic losses in the gap. In Fig. 2 the turbulences of the pumped medium in the gap of a centrifugal pump according to the invention are shown on the left. The gap has a widening section 5 which widens in a wedge shape upwards. In the widening section, a single controllable roller movement 62 is formed during pump operation, which leads to significantly lower losses overall. This increases the efficiency of the pump.

Other configurations of the widening section 33 are also conceivable. In particular, the conical portions of the containment shell and the rotor part can be replaced by any geometrical contours which are suitable for closely following the contours of the stator, so that a widening section arises between the rotor part and the housing wall. You can also deviate from the parallel contours. Otherwise, the centrifugal pump according to the invention is not necessarily limited to a radial pump, but can also be a diagonal pump. Furthermore, the gap can have a further widening section at its end facing away from the conveying area.

Reference list

1

Containment shell

1.1

cylindrical shell-shaped part of the can wall

1.2

cone-shaped part of the containment wall

2nd

stator

3rd

Rotor part

3.1

Pipe section of the rotor part

3.2

Transitional section of the rotor part

4th

casing

5

Widening section of the gap

7

gap

8th

Ring section of the gap

10th

Centrifugal pump

22

Stator area

31

Rotor chamber

32

Bucket parts

33

Funding area

42

Side wall

50

Inlet pipe

52

Outlet pipe

60

Roller movements

62

Roll movement in the widening section

A

Longitudinal axis

L

Length of the widening section of the gap

G

Total length of the gap

X, Y

radial dimensions of the gap

Claims (11)

1. Centrifugal pump (10) in the form of a radial pump or a diagonal pump, having a housing (4) having a stator region (22) receiving a stator (2) and a rotor chamber (31) which receives a rotor part (3) which is mounted so as to be rotatable about a longitudinal axis (A), and through which chamber a delivery medium can flow, wherein an annular gap (7) is formed between a rear portion of the rotor part that runs around the stator and an outer side wall (42) of the housing (4), characterized in that the gap has a widening portion (5) in which the radial dimension (X) of the gap (7) gradually increases in the axial direction (A) and which extends in the axial direction (A) over a length (L) which is greater than 10%, preferably greater than 20%, in particular greater than 30%, of the total length (G) of the gap (7) in the axial direction (A), wherein the widening portion opens at its front end towards a delivery region of the rotor chamber (31) through which blade parts (32) of the rotor part (3) can run.
2. Centrifugal pump according to Claim 1, characterized in that the radial dimension (Y) of the widening portion (5) at its front end is more than two times, preferably more than three times, in particular four or more times the radial dimension (X) of the widening portion at its rear end.
3. Centrifugal pump according to Claim 1 or 2, characterized in that the length (L) of the widening portion is more than three times, preferably more than five times, in particular more than eight times, the radial dimension (X) of the gap at the rear end of the widening portion.
4. Centrifugal pump according to one of the preceding claims, characterized in that an annular portion (8) of the gap (7) that adjoins the rear end of the widening portion (5) is substantially in the form of a circular cylinder shell.
5. Centrifugal pump according to one of the preceding claims, characterized in that the rotor part (3) has a transition portion (3.2) which tapers, preferably conically, in the direction of the delivery region and which is enclosed by the widening portion (5) of the gap.
6. Centrifugal pump according to Claim 5, characterized in that the half opening angle (α/2) of the cone is greater than 10°, preferably greater than 20°, in particular greater than 30° and less than 60°, in particular less than 40°.
7. Centrifugal pump according to Claim 5 or 6, characterized in that the thickness of the transition portion (3.2) in the radial direction corresponds substantially to the thickness of a tubular portion (3.1) which is in the form of a circular cylinder shell and which adjoins the rear end of the transition portion (3.2).
8. Centrifugal pump according to one of the preceding claims, characterized by a split cage (1) which projects into the interior of the housing (4) and which separates the stator region (22) from the rotor chamber (31), wherein the rear portion of the rotor is received in an intermediate space between the housing wall (42) and a peripheral wall of the split cage (1).
9. Centrifugal pump according to Claim 8, characterized in that the peripheral wall of the split cage (1) has a substantially cylinder shell-shaped part (1.1) and a substantially conical shell-shaped part (1.2) which each face an inner side of the rotor part.
10. Centrifugal pump according to Claim 8 or 9, characterized in that the conical shell-shaped part (1.2) of the split cage wall, the inner boundary surface of the rotor part (3) that faces this part, and the outer boundary surface of the rotor part (3) that faces the widening portion (5) of the gap extend substantially parallel to one another.
11. Centrifugal pump according to one of the preceding claims, characterized in that the gap has a further widening portion at its rear end facing away from the delivery chamber.

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