US20220170477A1

US20220170477A1 - Pump impeller and radial pump comprising the impeller

Info

Publication number: US20220170477A1
Application number: US17/456,095
Authority: US
Inventors: Constantin Richlich
Original assignee: Nidec GPM GmbH
Current assignee: Nidec GPM GmbH
Priority date: 2020-11-27
Filing date: 2021-11-22
Publication date: 2022-06-02
Also published as: DE102020131524B3; CN114278608A

Abstract

The invention relates to a pump impeller for a radial pump with a carrier plate comprising an intake side and a rear side situated opposite the intake side, a blading being provided on the intake side for conveying a medium to be pumped, characterized in that, on the rear side of the carrier plate, at least one flow profile is situated which is configured and formed to reduce at least a difference between a pressure-induced balance of forces on the carrier plate and on a cover plate in the case of a rotation of the pump impeller in a rotational direction (DR).

Description

CLAIM FOR PRIORITY

This application claims the benefit of priority of German Application No. 10 2020 131 524.4, filed 27 Nov. 2020, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

Embodiments of the invention relate to a pump impeller and to a radial pump comprising the impeller.

BACKGROUND

Impellers for radial pumps from the prior art comprise a carrier plate, which comprises towards an intake side a blading provided for conveying a fluid to be pumped. Optionally, a pump impeller of this type is covered with a cover plate on the intake side. During operation of an impeller of this type, a pressure difference occurs between the intake side, i.e., on the side of the blading as seen from the carrier plate, and a rear side, since fluid to be pumped is conveyed radially outwards by the rotation of the impeller, in such a way that a suction area occurs radially inwards. An axial force thus occurs at the impeller as a result of the difference between the pressure-induced balance of forces on the carrier plate and on the cover plate. The axial force has to be absorbed or braced by suitably formed axial bearing systems. Axial bearings of this type therefore have to be dimensioned, formed and constituted in such a way that they can reliably receive the axial forces over the service life of the radial pump.

SUMMARY/OVERVIEW

An aspect of embodiments according to the invention is to specify a pump impeller by means of which pressure-induced axial forces acting towards the suction mouth of the impeller can be reduced without significantly detracting from an internal efficiency of the pump impeller or of the radial pump comprising the pump impeller.
A pump impeller of this type should additionally be producible in a simple manner, without any particular additional complexity over the production of a prior art pump impeller.
Another aspect of embodiments according to the invention is to specify a radial pump which generates, as regards the pump impeller, lower axial forces which have to be braced/absorbed in the interior of the radial pump.
A further aspect of embodiments according to the invention is to specify a radial pump which can be produced cost-efficiently overall and ends up less complex as regards the axial bearing system of a drive shaft/of the pump impeller.
The above aspect as regards the pump impeller is achieved by a pump impeller having the features according to embodiments of the invention. Advantageous embodiments are specified in the dependent claims.
As regards the radial pump, the aspects are achieved by a radial pump having the features according to embodiments of the invention.
In the context of the following description, the influence on the balance of forces at the impeller from the flow profiles is sometimes referred to for simplicity as a “negative pressure” in the area of the carrier plate rear side.
According to embodiments of the invention, the pump impeller for a radial pump with a carrier plate comprises an intake side and a rear side situated opposite the intake side, a blading being provided on the intake side for conveying a medium to be pumped, wherein, on the rear side of the carrier plate, at least one flow profile is situated which is configured and formed to reduce at least a difference between a pressure-induced balance of forces on the carrier plate and on a cover plate in the case of a rotation of the pump impeller in a rotational direction DR.
In a pump impeller according to embodiments of the invention, it is particularly advantageous that a rear-side contouring of the carrier plate of the impeller reduces an axial force at the impeller, due to a difference in the pressure-induced balance of forces on the carrier plate and on the cover plate, during the operation of the impeller wheel, i.e., in dynamic use within a pump fluid. This takes place by way of a dynamic flow around the at least one flow profile. As a result of the rotational movement of the impeller, the fluid to be pumped which surrounds the flow profiles, the profiles and the cut-off edges flows over the flow profile(s), resulting in separation of the flow behind the cut-off edges. The rise in the flow profiles is orientated counter to the rotational direction DR of the impeller, meaning that nearby fluid to be pumped migrates along the flow profile, for example towards the cut-off edge, as the impeller rotates. The separation of the flow at the cut-off edge brings about a fall in pressure after the flow profile, which reduces the total static pressure distribution in a sealing gap between the pump impeller and a pump housing. This changes the pressure-dependent balance of forces on the pump impeller, and the resulting axial thrust (the axial resultant force of the static pressure balance over the impeller geometry) orientated towards the suction area (the suction mouth) is reduced. Flowing over the flow profile also does not cause a significant dynamic pressure, such as occurs, by contrast, in a blade with a rectangular profile for example, and this additionally influences the pressure level. In this case, an influence on the pressure level means a reduction in the static pressure distribution in the rear side space of the wheel, in other words the pressure distribution on the carrier plate rear side. This results in a lower resultant axial force towards the suction mouth.
Thus, embodiments of the invention take the approach of specifying a pump impeller and a radial pump comprising the pump impeller wherein it is possible to provide a reduction in the static pressure distribution on the rear side of the carrier plate and thus to achieve an influence on the balance of the forces acting on the pump impeller. In particular, the static pressure distribution at the rear side of the carrier is changed, or reduced in total over all of the forces, in such a way that the balance of forces is influenced.
Embodiments of the invention thus manage to reduce the resultant axial thrust at the impeller in a targeted manner. This results in relief for the bearing system in the axial direction, potentially leading to a saving on costs and to constructional simplification in the selection and design of the axial bearing. The flow profile, in other words for example the ramp profile structures, may be made use of both in mechanical and in electrical pumps. Because no undercutting contours are applied on the rear side of the carrier plate, production by injection moulding can be implemented in a simple manner, without a slide, in an appropriate injection-moulding tool.
The relatively low dynamic pressure, generated for example over the flat flow profiles, also only leads to an extremely small loss of efficiency in the pump impeller or in a fluid pump comprising the pump impeller.
In a preferred embodiment of the invention, the at least one flow profile, as seen in a circumferential direction UR, is a ramp contour, in particular a short ramp contour, i.e., a ramp ridge, or a long ramp contour, i.e., a circular surface segment ramp.
Ramp contours have proven expedient in generating the negative pressure; in particular, ramp-ridge-like short ramp contours or a long ramp contour, i.e. ramps with circular surface segment ramp surfaces, are conceivable. In the case of a short ramp contour, in which an uninclined subsurface of the rear side face of the carrier plate is present between two ramp ridges which are adjacent in the circumferential direction UR, the effect according to embodiments of the invention is already pronounced, but occurs in a locally concentrated manner in the area of the ramp rear surfaces, which are relatively short in the circumferential direction UR, of the ramp ridges.
If the flow profiles are formed as a long ramp contour, a single inclined ramp rear surface is provided between two cut-off edges of adjacent ramps, and is a circular surface segment. In other words, in the case of a long ramp contour, the surface between two cut-off edges is fully inclined with respect to a plane of the rear side of the carrier disc, whereas a short ramp, by contrast, has an inclined ramp rear surface and an uninclined subsurface of the rear side of the carrier plate between two cut-off edges.
In the case of a long ramp structure, the negative pressure distribution is present over a larger area on the rear side of the pump impeller, and the total negative pressure is greater in magnitude.
In a further preferred embodiment of the invention, n ramp contours are distributed over a circumference U of the pump impeller, n preferably being ≥2, particularly preferably n≥4, more preferably n≥6.
With an increasing number of ramp contours on the rear side of the pump impeller, it has been possible to establish, as a basic principle, a decreasing pressure difference and also a more uniform pressure distribution over the rear side of the pump impeller. So as to meet acoustic demands to a particular degree, it has proven expedient to select an integer multiple of the number of blades of the pump impeller for the number of ramp contours on the rear side of the pump impeller.
In a further embodiment of the pump impeller according to the invention, the at least one ramp contour is formed raised up from a base surface of the rear side counter to the rotational direction DR.
Alternatively, it may be provided that the at least one ramp contour (cut-off edge) is flush with respect to the base surface of the rear side and that intervals between two ramp contours (cut-off edges) are formed recessed with respect to the base surface.
Aside from the above-described raised ramp contours and/or the sunk cut-off edges with a ramp contour flush with the annular edge, it is naturally also possible to form the ramp contours only partially sunk, in such a way that a cut-off edge raised with respect to a base surface is present and at least one sub-area between two adjacent ramp contours is sunk with respect to the base surface.
In a further embodiment of the pump impeller according to the invention, the at least one ramp contour is formed raised with respect to the base surface of the rear side, and at least part of the intervals between two ramp contours is formed recessed with respect to the base surface.
In a further embodiment of the pump impeller, the ramp contour has a cut-off edge which extends in particular radially.
In the case of a radially progressing extension of the cut-off edge, in particular progressing radially in a straight line in the manner of spokes, it has been possible to observe a particularly high negative pressure development.
In a further embodiment of the pump impeller according to the invention, a maximum height h of the ramp contour is smaller than a wall thickness t of the carrier disc.
According to embodiments of the invention, it has been recognised that even a relatively small ramp height h, which may be smaller than the wall thickness of the carrier disc, is sufficient to achieve a good compromise between the achievable negative pressure and the loss of efficiency to be accepted.
In a further embodiment of the present invention, a radial extension of the cut-off edge extends from a hub area of the pump impeller to a radially outward circumferential annular edge of the base surface.
The radial extension of the cut-off edges is advantageously not taken as far as the outermost circumferential edge of the carrier plate of the pump impeller, so as not to generate any additional flow cut-offs or eddies there with flows occurring at the end of the opposite pump blading, potentially leading to an undesirable reduction in efficiency. Therefore, an annular ring is left on the rear side of the carrier plate of the pump impeller, and leaves a distance from the circumferential edge of the carrier plate.
In a further preferred embodiment, a ramp rear surface of the at least one ramp contour is a plane.
A ramp rear surface in the form of a plane constitutes a particularly simple three-dimensional shape and can in particular be implemented in a simple manner in a production tool.
In a further particular embodiment, the ramp rear surface, as seen in the circumferential direction UR, is formed curved, and the curvature is formed constant along the circumferential direction UR or increasing towards the cut-off edge.
As a result of the curved formation of the ramp rear surface, localisation of the negative pressure foci can be influenced for each ramp in a targeted manner.
In a further preferred embodiment of the invention, the cut-off edge descends perpendicular to the base surface.
In another embodiment, the cut-off edge descends perpendicular to the ramp rear surface or, in the case of a curved formation of the ramp rear surface, descends perpendicular to a tangent plane to the ramp rear surface in the area of the cut-off edge.
A descent of the cut-off edge perpendicular to the base surface, i.e., either to the plane of the carrier plate rear side or to the plane/tangent plane of the ramp rear surface, in particular without undercutting, ensures a configuration free of undercuts, facilitating implementation in the tool.
In a second aspect of the invention, a radial pump comprises a pump impeller in accordance with one of the aforementioned embodiments.
For the radial pump according to the invention, the aforementioned advantages can be anticipated if a pump impeller according to the invention is used.

BRIEF DESCRIPTION OF THE FIGURES

In the following, embodiments of the invention are described in greater detail by way of example with reference to the drawings, in which:

FIG. 1 is a perspective view of a rear side of a pump impeller according to embodiments of the invention;

FIG. 2 is a perspective drawing of a cut-out representation of a rear-side flow profile in the formation of a ramp;

FIG. 3 schematically shows a comparison of a negative pressure distribution on the rear side of a pump impeller without rear-side contouring (left), with seven short ramp contours (centre), and with six long ramp contours (right);

FIG. 4 schematically shows part of a radial pump according to embodiments of the invention comprising the impeller, in a longitudinal section.

DETAILED DESCRIPTION

FIG. 1 is a perspective view towards a rear side 2 of an embodiment of the pump impeller 1 according to embodiments of the invention. Opposite the rear side is an intake side 3 of the pump impeller 1. The rear side 2 is formed by a carrier plate 4. On the intake side 3 of the carrier plate 4 is a blading 5. To the intake side, the blading 5 is followed by a cover plate 6. Flow ducts 7 are formed between the carrier plate 4 and the cover plate 6, and are respectively delimited in a circumferential direction UR by blades of the blading 5. In an axial direction AR, the flow ducts 7 are delimited by the carrier plate 4 and the cover plate 6. An intake opening (not shown) for fluid to be pumped is aligned with the axial direction AR, which in FIG. 1 is coincident with the axis of rotation of the pump impeller 1 on the intake side 3 of the pump impeller 1.
In FIG. 1, a schematically shown hub area 8 is positioned centrally on the middle of the rear side 2 of the carrier plate 4. The rear side 2 has an annular edge 9 outward in a radial direction R. Between the hub area 8 and the annular edge 9 in the radial direction R, a plurality of flow profiles 10 are situated on the rear side 2 of the pump impeller 1. In the embodiment of FIG. 1, the flow profiles 10 are formed as ramp contours 11.
In a plan view, a ramp contour 11 has a circle-segment-shaped ramp rear surface 12. The ramp rear surface 12 is situated inclined at an angle α (cf. FIG. 2) to a base surface 13 forming the rear side 2, and has a cut-off edge 14 as seen counter to a rotational direction DR. The cut-off edge 14 is orientated approximately parallel to the axial direction AR, and forms a step 15 of height h (cf. FIG. 2). The step 15 is raised with respect to the base surface 13 by the magnitude of the height h. Following a cut-off edge 14 counter to the rotational direction DR, the ramp rear surface 12 of the following ramp contour 11 joins on seamlessly. In the axial direction AR, in this joining area, the ramp rear surface 12 is approximately flush with the base surface 13 and rises at the angle α.
In the embodiment of FIG. 1, in total six ramp contours 11, each of the same area size (in a plan view), are situated distributed over the circumference U of the rear side 2. In total, six cut-off edges 14 thus occur. The cut-off edges 14 are arranged proceeding from the hub area 8 radially in a spoke shape, and have an angle β of 60° between them in each case. Naturally, in a modification to FIG. 1, the number of cut-off edges 14 and/or associated ramp contours 11 may be lower or higher than six. A number n=6 has proven particularly expedient.
In the context of modifications to embodiments of the invention, it is also possible to configure the individual ramp contours 11 differently sized in the circumferential direction UR. Thus, for example, a ramp contour 11 having a larger angle β, for example having the angle β=80°, may be followed by a ramp contour 11 having a smaller angle (for example β=40°), and differently sized ramp contours 11 of this type may follow one another alternately.
In the selection of the segment size (angle β) of the ramps, it is important to have as uniform a distribution as possible over the circumference U, in such a way that no imbalances occur.
So as to keep the efficiency reduction due to increased flow resistance at the rear side 2 of the pump impeller 1 within the tightest possible limits, it is advisable to select a height h of the step 15 less than or equal to a thickness t of the carrier plate 4. In the embodiment, by comparison with the thickness t, the height h is about half of the thickness t.
FIG. 2 shows a ramp contour 11 cut away in an enlarged cut-out. The ramp contour 11 of FIG. 2 is a ramp contour 11 such as was described in connection with FIG. 1. The ramp rear surface 12 is circle-segment-shaped in a plan view, and rises from the level of the base surface 13 linearly at the angle α. The ramp rear surface 12 of this embodiment is thus an inclined plane with respect to the base surface 13.
Equally, it is of course possible to form the ramp rear surface 12 not as a plane but rather as a curved ramp rear surface 12, which rises, for example in a uniformly curved manner, by the height h from the level of the base surface 13 to the cut-off edge 14. In addition, it is possible for the curvature along the circumferential direction UR as far as the cut-off edge 14 not to be uniform, but rather for a lower curvature initially to be present and for the curvature to increase towards the cut-off edge 14.
FIG. 3 shows in total three rear sides 2 of pump impellers 1. On the far left of FIG. 3, a pump impeller 1 from the prior art without flow profiles 10 on the rear side 2 is shown. In the embodiment of FIG. 3 (centre), the pump impeller 1 has in total seven ramp ridges 20 uniformly distributed in the circumferential direction UR as flow profiles. The ramp ridges 20 likewise have cut-off edges 14. By contrast with the above-described ramp contours 11 (long ramp contours) of the embodiments of FIGS. 1 and 2, ramp ridges 20 differ from the above-described ramp contours 11 (long ramp contours) in that a cut-off edge 14 of a ramp ridge 20 is initially followed in the rotational direction DR by a circle segment surface, which is positioned on the vertical level in the axial direction AR of the base surface 13 and is not inclined with respect to the base surface 13.
In a plan view, the ramp ridge 20 is formed rectangular with a width b, within which the ramp rear surface 12 rises from the level of the base surface 13 by the height h. Ramp ridges 20 of this type constitute spoke-shaped local elevations. In particular in the area of the ramp ridges 20, i.e., in particular in the region downstream from the cut-off edges 14 counter to the rotational direction DR, a negative pressure occurs locally when the pump impeller 1 is driven in the rotational direction DR. This is indicated in FIG. 3 (centre) by the darker shading in the area of the radial centre of the ramp ridges 20.
The embodiment of FIG. 3 (right) corresponds to the above-described embodiment of FIG. 1, 2, and has in total six ramp contours 11, which as described above are circle-segment-shaped in a plan view and rise from a cut-off edge 14, leading in the rotational direction DR, of the ramp contour 11 to the cut-off edge 14, trailing in the rotational direction DR, of the ramp rear surface 12.
FIG. 3 (right) illustrates that, with this type of rear-side contouring of a pump impeller 1 according to embodiments of the invention, a negative pressure that is overall greater and also higher in magnitude can be achieved by comparison with the embodiment in FIG. 3 (centre) and by comparison with the embodiment in FIG. 3 (left) (prior art). The increased negative pressure formation (in FIG. 3, right) is marked with darker hatching in the vicinity U of the cut-off edges 14.
In tests, the highest negative pressure values, and thus the highest axial force relief of the corresponding axial bearings of the pump, were brought about with the contouring of FIGS. 1 and 2.
The pump impeller 1 sits on a drive shaft 101, which can be motor-driven in the rotational direction DR. The radial pump 100 has a pump housing 102, which forms a pump chamber 103. The pump impeller 1 sits in the pump chamber 103. The carrier plate 4 forms, with a rear wall 104 of the pump housing 102, a gap 105 in which fluid to be pumped is present. The flow profiles 10 are situated on the rear side 2 of the carrier plate 4. In FIG. 4, the flow ducts 7 are delimited axially to the left by the cover plate 6. In FIG. 4, the fluid to be pumped flows from left to right, flows through the flow ducts 7, and arrives outside through an outlet duct 106. The flow direction of the fluid to be pumped is indicated by arrows 107.

LIST OF REFERENCE NUMERALS

1 Pump impeller
2 Rear side
3 Intake side
4 Carrier plate
5 Blading
6 Cover plate
7 Flow ducts
8 Hub area
9 Annular edge
10 Flow profile
11 Ramp contour
12 Ramp rear surface
13 Base surface
14 Cut-off edge
15 Step
20 Ramp ridge
100 Radial pump
101 Drive shaft
102 Pump housing
103 Pump chamber
104 Rear wall
105 Gap
106 Outlet duct
107 Arrows
AR Axial direction
DR Rotational direction
R Radial direction
UR Circumferential direction
U Circumference
b Width
h Height
t Wall thickness
n Number
α Angle
β Angle

Claims

What is claimed is:

1. A pump impeller for a radial pump with a carrier plate comprising:

an intake side and a rear side situated opposite the intake side, a blading being provided on the intake side for conveying a medium to be pumped,

wherein, on the rear side of the carrier plate, at least one flow profile is situated which is configured and formed to reduce at least a difference between a pressure-induced balance of forces on the carrier plate and on a cover plate in the case of a rotation of the pump impeller in a rotational direction (DR).

2. The pump impeller according to claim 1, wherein the at least one flow profile, as seen in a circumferential direction (UR), is a ramp contour, in particular a short ramp contour, i.e., a ramp ridge, or a long ramp contour, i.e., a circular surface segment ramp.

3. The pump impeller according to claim 1, wherein n ramp contours are distributed over a circumference (U) of the pump impeller, n being ≥2.

4. The pump impeller according to claim 1, wherein in an, as seen in a radial direction (R), internal area of the rear side of the carrier plate, the number (n) of the ramp contours is lower than in an area further outside, which has a higher number (n) of ramp contours, in particular an integer multiple of the number (n), in particular in that six ramp contours are provided in the inner area and twelve ramp contours are provided in the outer area (closer to the annular edge).

5. The pump impeller according to claim 1, wherein the at least one ramp contour is formed raised from a base surface of the rear side counter to the rotational direction (DR).

6. The pump impeller according to claim 1, wherein the at least one ramp contour is flush with respect to the base surface of the rear side counter to the rotational direction (DR) and intervals between two ramp contours are formed recessed with respect to the base surface.

7. The pump impeller according to claim 1, wherein the at least one ramp contour is formed raised with respect to the base surface of the rear side, and at least part of the intervals between two ramp contours is formed recessed with respect to the base surface.

8. The pump impeller according to claim 1, wherein the ramp contour has a cut-off edge which extends in particular radially.

9. The pump impeller according to claim 1, wherein a maximum height (h) of the ramp contour is smaller than a wall thickness (t) of the carrier plate.

10. The pump impeller according to claim 1, wherein a radial extension of the cut-off edge extends from a hub area of the pump impeller to a radially outward circumferential annular edge of the base surface.

11. The pump impeller according to claim 1, wherein in that a ramp rear surface of the at least one ramp contour is a plane.

12. The pump impeller according to claim 9, wherein the ramp rear surface, as seen in the circumferential direction (UR), is formed curved, and the curvature is formed constant along the circumferential direction (UR) or increasing towards the cut-off edge.

13. The pump impeller according to claim 1, wherein the cut-off edge descends perpendicular to the base surface.

14. The pump impeller according to claim 1, wherein the cut-off edge descends perpendicular to the ramp rear surface or, in the case of a curved formation of the ramp rear surface, descends perpendicular to a tangent plane to the ramp rear surface in the area of the cut-off edge.

15. A radial pump comprising a pump impeller according to claim 1.