EP4675111A1

EP4675111A1 - Centrifugal device and rotating electric machine comprising the centrifugal device

Info

Publication number: EP4675111A1
Application number: EP24185706.9A
Authority: EP
Inventors: Matti Halme; Juha Jokinen; Markus Asikainen
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2024-07-01
Filing date: 2024-07-01
Publication date: 2026-01-07

Abstract

A centrifugal device comprising a frame (2) having a first frame wall (21) and an impeller (4) having at least one main vane (401) and a first wall (41) extending in a direction perpendicular to a rotation axis of the impeller (4), wherein in an axial direction, the first wall (41) is located between the at least one main vane (401) and the first frame wall (21). The centrifugal device comprises a seal (6) between the first frame wall (21) and the first wall (41) of the impeller such that the seal (6), the first frame wall (21) and the first wall (41) of the impeller define an intermediate chamber (124) between the first frame wall (21) and the first wall (41) of the impeller, and the seal (6) is adapted to at least impede an outlet fluid flow generated by the impeller (4) from entering the intermediate chamber (124).

Description

FIELD OF THE INVENTION

The present invention relates to a centrifugal device and a rotating electric machine comprising the centrifugal device.

BACKGROUND OF THE INVENTION

A centrifugal device is a mechanical device through which a fluid flow is adapted to take place such that a pressure of fluid and a direction of the fluid changes. Examples of centrifugal devices include centrifugal fans and centrifugal pumps.
During operation of a centrifugal device, an axial force is inherently exerted on an impeller of the centrifugal device as the direction of the flow is changed from axial to radial. Herein, an effect of inherent axial forces exerted on the impeller and caused by operation of the centrifugal device is referred to as mechanical pull.
One of the disadvantages associated with the mechanical pull is that the mechanical pull attempts to move the impeller of the centrifugal device in an axial direction relative to a frame of the centrifugal device. This is a potential problem especially in a centrifugal device in which the impeller is supported to the frame by a bearing system that is not designed to support an axial load.
It should be noted that in a rotating electric machine comprising a centrifugal device whose impeller is stationary relative to a rotor of the rotating electric machine, there are multiple magnetic and mechanical factors causing axial pull. However, removing or at least substantially reducing one of the factors for axial pull is useful since it makes diagnosis and mitigation of the problem easier.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a centrifugal device so as to alleviate disadvantages relating to axial pull. The objects of the invention are achieved by a centrifugal device which is characterized by what is stated in the independent claim. The preferred embodiments of the invention are disclosed in the dependent claims.
The invention is based on the idea of providing a centrifugal device with a seal adapted to at least impede an outlet fluid flow generated by an impeller of the centrifugal device from entering an intermediate chamber located in an axial direction on an inlet side of the impeller, between a first frame wall and a first wall of the impeller.
An advantage of the centrifugal device of the invention is that a factor of the axial pull caused by the outlet fluid flow entering the intermediate chamber is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which

Figure 1 shows an exploded view of a centrifugal device according to an embodiment of the invention;
Figure 2 shows a cross section of a portion of the centrifugal device of Figure 1 in an operational state thereof;
Figure 3 shows a detail of a cross section of a centrifugal device according to another embodiment of the invention;
Figure 4 shows a simplified section of a centrifugal device according to yet another embodiment of the invention; and
Figure 5 shows a portion of an exploded view of a centrifugal device according to still another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a centrifugal device comprising a frame 2, an impeller 4, a seal 6, a shaft 8, a bearing system and a flow guide 15.
The frame 2 has a primary frame part 201, a first frame wall 21 and a second frame wall omitted from Figure 1. The first frame wall 21 and the second frame wall are stationary relative to the primary frame part 201. The first frame wall 21 and the second frame wall are spaced apart in an axial direction, and each of them extends in a direction perpendicular to the axial direction.
The impeller 4 is adapted to rotate around a rotation axis relative to the frame 2. The rotation axis is parallel with the axial direction. The impeller 4 has a first wall 41, a second wall 42 and a plurality of main vanes 401 adapted for generating a fluid flow of the centrifugal device. An inlet side of the impeller 4 is on the side of the impeller 4 facing the first frame wall 21. An inlet flow is adapted to enter the impeller 4 in a direction parallel to the axial direction.
The impeller 4 is stationary relative to the shaft 8. The shaft 8 is supported to the frame 2 by the bearing system comprising a first bearing unit 91 adjacent to the first frame wall 21, and a second bearing unit adjacent to the second frame wall. The second bearing unit is omitted from Figure 1.
The bearing system is not designed to support an axial load. In an embodiment, the bearing system comprises at least one slide bearing.
The first wall 41 and the second wall 42 of the impeller 4 are spaced apart in the axial direction. Each of the first wall 41 and the second wall 42 extends in a direction perpendicular to the axial direction. The plurality of main vanes 401 is located between the first wall 41 and the second wall 42 in the axial direction. The first wall 41 is facing the first frame wall 21 such that the first wall 41 is located between the plurality of main vanes 401 and the first frame wall 21 in the axial direction.
Figure 2 shows a cross section of a portion of the centrifugal device of Figure 1 in an operational state of the centrifugal device. Figure 2 is a side view such that the rotation axis extends on the image plane.
The seal 6 is located between the first frame wall 21 and the first wall 41 of the impeller such that the seal 6, the first frame wall 21 and the first wall 41 of the impeller define an intermediate chamber 124 between the first frame wall 21 and the first wall 41 of the impeller. The seal 6 is adapted to at least impede an outlet fluid flow generated by the impeller 4 from entering the intermediate chamber 124. During operation of the centrifugal device, a pressure in the intermediate chamber 124 is lower than on the outlet side of the impeller 4.
The seal 6 comprises a tubular section 62 and an outer section 64. The tubular section 62 has a tubular form. The tubular section 62 extends in the axial direction between the first frame wall 21 and the first wall 41 of the impeller. A centre line of the tubular section 62 coincides with the rotation axis. In an embodiment, a dimension of the tubular section in the axial direction is greater than or equal to 5 mm.
The outer section 64 extends outwards from the tubular section 62 in a direction perpendicular to the axial direction. The outer section 64 comprises a planar section having a form of a hollow circle. An inner edge of the planar section is attached to the tubular section 62. The outer section 64 is in contact with the first frame wall 21.
In an embodiment comprising a thick tubular section, an outer section of the seal is omitted.
In radial direction, a thickness of the tubular section 62 is approximately one per cent of the radius of the impeller. In an alternative embodiment, the thickness of the tubular section is less than or equal to ten per cent of the radius of the impeller.
An outer diameter of the tubular section 62 is equal to an outer diameter of the first wall 41 of the impeller 4. An inner diameter of the tubular section 62 is approximately 99 % of the outer diameter of the first wall 41 of the impeller 4. In an alternative embodiment, the inner diameter of the tubular section is smaller than or equal to the outer diameter of the first wall of the impeller, thereby blocking a direct axial path from an outlet side of the impeller to the intermediate chamber.
The seal 6 is stationary relative to the first frame wall 21. The seal 6 is a one-piece component separate from the frame 2. In an embodiment, the seal is made of plastic material. In another embodiment, the seal comprises metal. In a further embodiment, the seal is an integral part of the first frame wall, and is made of the same material as the first frame wall. In an embodiment, the first frame wall is a cast metal component.
In an alternative embodiment, the seal is stationary relative to the impeller. In such an alternative embodiment, the seal can be a separate component fastened to the impeller or an integral part of the impeller. In a further alternative embodiment, the seal comprises a first section stationary relative to the first frame wall, and a second section stationary relative to the impeller.
A distance in the axial direction between the tubular section 62 and the first wall 41 of the impeller is less than or equal to 2 mm. In an alternative embodiment, the distance in the axial direction between the tubular section and the first wall of the impeller is less than or equal to 5 mm. In a further alternative embodiment, the tubular section of the seal is in contact with the first wall of the impeller thereby at least theoretically completely preventing a fluid flow into the intermediate chamber between an outer edge of the first wall of the impeller and the tubular section of the seal. However, a physical contact between a seal and a counterpart component is not a desirable feature in all embodiments since the physical contact increases mechanical losses of the centrifugal device, and causes wear-and-tear in the seal and/or the counterpart component.
Figure 3 shows a detail of a cross section of a centrifugal device in which a seal 6' extending from a first frame wall is provided with two grooves 106' on a sealing surface facing a first wall 41' of the impeller 4'. The grooves 106' are circular grooves.
In an alternative embodiment, at least one seal is provided with at least one groove on at least one sealing surface of the at least one seal. An axial dimension of the at least one groove is greater than or equal to 3% of an axial distance between the first frame wall and the first wall of the impeller. In a further alternative embodiment, an axial dimension of the at least one groove is greater than or equal to 10% of difference between an outer diameter of the tubular section and an inner diameter of the tubular section. In a still further alternative embodiment, an axial dimension of the at least one groove is greater than or equal to 0.5mm. An axial dimension of the at least one groove can be considered as a depth of the at least one groove. The at least one groove improves performance of the seal.
In an embodiment, the centrifugal device comprises a pressure balancing system adapted for balancing pressure between the intermediate chamber and the inlet side of the impeller.
Figure 4 shows a simplified section of a centrifugal device in which the pressure balancing system comprises a through hole 104" provided in the impeller 4", the through hole 104" forming a fluid passage between the inlet side of the impeller 4" and the intermediate chamber 124". The through hole 104" is provided in the first wall 41' of the impeller 4', at a distance from an outer edge of the first wall 41' of the impeller 4'. In radial direction, a distance between the through hole 104" and the rotation axis of the impeller 4' is shorter than a distance between the through hole 104" and an outer edge of the first wall 41' of the impeller 4'.
In an alternative embodiment, the pressure balancing system comprises at least one through hole provided in the impeller, the at least one through hole forming a fluid passage between the inlet side of the impeller and the intermediate chamber. A surface area of the at least one through hole is less than or equal to 5% of a surface area of a circle having the same diameter as the impeller.
Figure 5 shows a portion of an exploded view of a centrifugal device in which the pressure balancing system comprises a plurality of auxiliary vanes 304‴ provided on the impeller 4‴, the plurality of auxiliary vanes 304‴ being adapted for generating a pressure gradient inside the intermediate chamber during operation of the centrifugal device, wherein the pressure gradient is directed outwards. The plurality of auxiliary vanes 304‴ protrudes from the first wall 41‴ of the impeller 4‴ on an opposite side of the first wall 41‴ compared to the main vanes. In an alternative embodiment, the pressure balancing system comprises at least one auxiliary vane provided on the impeller.
It is possible to combine embodiments shown in Figures 1, 3, 4 and 5. In the embodiment shown in Figures 1 and 2, the centrifugal device is a centrifugal fan adapted to cool active parts of a rotating electric machine. The active parts of the rotating electric machine comprise active parts of a rotor and active parts of a stator. The active parts are components adapted to interact magnetically during operation of the rotating electric machine. In the axial direction, the active parts are located between the first frame wall 21 and the second frame wall. Further, in the axial direction, the impeller 4 is located between the first frame wall 21 and the active parts.
The flow guide 15 is adapted for guiding the fluid flow generated by the impeller 4. The flow guide 15 is adapted to reduce back flow, i.e. to decrease flow from radially outer section of the plurality of main vanes 401 towards radially inner section of the plurality of main vanes 401. The flow guide 15 is located adjacent to the impeller 4 such that in the axial direction, the plurality of main vanes 401 is located between the seal 6 and the flow guide 15. In an embodiment, an axial distance between the flow guide and the second wall of the impeller is less than or equal to 500% of a thickness of the second wall of the impeller in the axial direction.
The fluid flow is adapted to enter the rotating electric machine through the first wall 41 in the axial direction, pass through the primary frame part 201 and exit the rotating electric machine through the second wall in the axial direction. In an alternative embodiment, a portion of the fluid flow is adapted to exit the primary frame part in a radial direction perpendicular to the axial direction.
The centrifugal fan shown in Figures 1 and 2 is adapted for moving air. In an alternative embodiment, the centrifugal device is a centrifugal pump adapted for moving fluid.
It will be obvious to a person skilled in the art that the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

A centrifugal device comprising:
a frame (2) having a first frame wall (21); and

an impeller (4) adapted to rotate around a rotation axis relative to the frame (2), wherein the impeller (4) has at least one main vane (401) and a first wall (41) extending in a direction perpendicular to the rotation axis and facing the first frame wall (21) such that in an axial direction, the first wall (41) is located between the at least one main vane (401) and the first frame wall (21),

characterized in that the centrifugal device comprises a seal (6) between the first frame wall (21) and the first wall (41) of the impeller such that the seal (6), the first frame wall (21) and the first wall (41) of the impeller define an intermediate chamber (124) between the first frame wall (21) and the first wall (41) of the impeller, and the seal (6) is adapted to at least impede an outlet fluid flow generated by the impeller (4) from entering the intermediate chamber (124).
The centrifugal device according to claim 1, wherein the seal (6) comprises a tubular section (62) extending in the axial direction between the first frame wall (21) and the first wall (41) of the impeller, wherein a centre line of the tubular section (62) coincides with the rotation axis.
The centrifugal device according to claim 2, wherein the seal (6) comprises an outer section (64) extending outwards from the tubular section (62).
The centrifugal device according to claim 3, wherein the outer section (64) is in contact with the first frame wall (21).
The centrifugal device according to any one of claims 2 to 4, wherein an inner diameter of the tubular section (62) is smaller than or equal to an outer diameter of the first wall (41) of the impeller (4).
The centrifugal device according to any one of claims 2 to 5, wherein the seal (6) is stationary relative to the first frame wall (21).
The centrifugal device according to any one of claims 2 to 6, wherein a distance in the axial direction between the tubular section (62) and the first wall (41) of the impeller is less than or equal to 5 mm.
The centrifugal device according to any one of the preceding claims, wherein the centrifugal device comprises a pressure balancing system adapted for balancing pressure between the intermediate chamber (124) and an inlet side of the impeller (4).
The centrifugal device according to claim 8, wherein the pressure balancing system comprises at least one through hole (104") provided in the impeller (4"), the at least one through hole (104") forming a fluid passage between the inlet side of the impeller (4") and the intermediate chamber (124").
The centrifugal device according to claim 9, wherein a surface area of the at least one through hole (104") is less than or equal to 5% of a surface area of a circle having the same diameter as the impeller (4").
The centrifugal device according to any one of the preceding claims, wherein the at least one seal (6') is provided with at least one groove (106') on at least one sealing surface of the at least one seal (6').
The centrifugal device according to claim 11 and referring to claim 2, wherein an axial dimension of the at least one groove (106') is greater than or equal to 10% of difference between an outer diameter of the tubular section and an inner diameter of the tubular section.
The centrifugal device as claimed in any one of the preceding claims, wherein the impeller (4) is supported to the frame (2) by a bearing system that is not designed to support an axial load.
The centrifugal device as claimed in any one of the preceding claims, wherein the centrifugal device is a centrifugal fan.
A rotating electric machine comprising the centrifugal device as claimed in claim 14, wherein the impeller (4) is stationary relative to a rotor of the rotating electric machine.