Centrifugal pump

Abstract

A centrifugal pump includes at least one pump stage, with a rotatable impeller (5) with a suction port (6) which is sealed with respect to a stationary pump part (1) by way of a sealing arrangement. The sealing arrangement includes a sealing ring (9) between the impeller (5) and the stationary pump part (1). The sealing arrangement is configured such that at least on delivery operation of the pump, the sealing arrangement has sealing sections which are distanced to the counter sealing surface and sealing sections which bear on the counter sealing surface, in an alternatingly successive manner considered in the peripheral direction of the sealing ring (9).

Claims

1. A centrifugal pump with at least one pump stage comprising: a rotatable impeller; a stationary pump part; a suction port; a sealing arrangement, the suction port being sealed with respect to the stationary pump part by way of the sealing arrangement, wherein the sealing arrangement comprises a sealing ring between the impeller and the stationary pump part, wherein the sealing ring comprises sealing sections interacting with a counter sealing surface and the sealing arrangement is configured such that at least on delivery operation of the pump, the sealing sections are distanced to the counter sealing surface and the sealing sections bear on the counter sealing surface, in an alternatingly successive manner considered in a peripheral direction of the sealing ring, wherein the sealing ring at least in sections is elastically configured and a contact surface of the sealing ring or of sealing ring sections on the counter surface is controlled by hydraulic forces at a delivery side of the impeller, the sealing ring having sections of different stiffness, which are distributed over a sealing ring periphery, wherein the sealing ring on a sealing ring outer periphery comprises recesses which reduce a sealing ring cross section, the sealing sections of the sealing ring being located at a spaced location from the counter sealing surface when the impeller is at a standstill.

2. A centrifugal pump according to claim 1, wherein the sealing ring on a sealing ring inner periphery comprises recesses which reduce the sealing ring cross section.

3. A centrifugal pump according to claim 2, wherein the recesses extend parallel to an axis direction of the sealing ring or obliquely thereto.

4. A centrifugal pump according to claim 2, wherein the recesses have a wedge configuration in the peripheral direction.

5. A centrifugal pump according to claim 2, wherein the recesses are open towards the delivery side of the impeller as well as towards a suction side of the impeller.

6. A centrifugal pump according to claim 5, wherein: the recesses have a wedge configuration in the peripheral direction; and the wedge configuration of the recesses on the outer periphery and the wedge configuration of the recesses on the inner periphery are directed oppositely to one another.

7. A centrifugal pump according to claim 1, wherein the sealing ring is arranged on the stationary pump part, and is arranged adjacent to the suction port, for sealing with respect to an outer surface of the impeller.

8. A centrifugal pump according to claim 1, wherein the sealing ring is arranged on the impeller, at the suction-side end of the impeller, and the counter sealing surface is formed by a ring section of the stationary pump part which overlaps the sealing ring.

9. A centrifugal pump according to claim 1, wherein the sealing ring is arranged on the impeller, at the suction-side end of the impeller, and the counter sealing surface is formed by an annular surface of the stationary pump part.

10. A centrifugal pump according to claim 1, wherein the sealing ring defines an extent of the suction port of the impeller.

11. A centrifugal pump according to claim 1, wherein the sealing ring is configured such that on operation, a hydrodynamic or hydrostatic fluid film forms between the surfaces of the sealing arrangement which are moved relative to one another.

12. A centrifugal pump according to claim 1, wherein the recesses extend parallel to an axis direction of the sealing ring or obliquely thereto.

13. A centrifugal pump according to claim 1, wherein the recesses have a wedge configuration in the peripheral direction.

14. A centrifugal pump according to claim 13, wherein the recesses are open towards the delivery side of the impeller as well as towards the suction side of the impeller.

15. A centrifugal pump according to claim 14, wherein: the sealing ring on a sealing ring inner periphery comprises recesses which reduce the sealing ring cross section, the recesses having a wedge configuration in the peripheral direction; and the wedge configuration of the recesses on the outer periphery and the wedge configuration of the recesses on the inner periphery are directed oppositely to one another.

16. A centrifugal pump according to claim 1, wherein each recess is defined by at least an edge portion of the sealing ring and a base portion of the sealing ring, the sealing ring having a first thickness at the base portion and the sealing ring having a second thickness at the base portion, the first thickness being less than the second thickness.

17. A centrifugal pump with at least one pump stage comprising: a rotatable impeller; a stationary pump part; a suction port; a sealing arrangement, the suction port being sealed with respect to the stationary pump part via the sealing arrangement, the sealing arrangement comprising a sealing ring between the impeller and the stationary pump part, the sealing ring comprising sealing sections interacting with a counter sealing surface and the sealing arrangement being configured such that at least on delivery operation of the pump, the sealing sections are distanced to the counter sealing surface and the sealing sections bear on the counter sealing surface, in an alternatingly successive manner considered in a peripheral direction of the sealing ring, the sealing ring at least in sections being elastically configured and a contact surface of the sealing ring or of sealing ring sections on the counter surface being controlled by hydraulic forces at a delivery side of the impeller, the sealing ring having sections of different stiffness, which are distributed over a sealing ring periphery, the sealing ring comprising a sealing ring outer peripheral surface facing in a direction away from the counter sealing surface, the sealing ring outer peripheral surface defining recesses which reduce a cross section of the sealing ring, each of the sealing sections of the sealing ring being located at a spaced location from the counter sealing surface when the impeller is at a standstill.

18. A centrifugal pump according to claim 17, wherein the sealing ring outer peripheral surface is located a spaced location from the counter sealing surface.

19. A centrifugal pump according to claim 18, wherein the sealing ring outer peripheral surface comprises a plurality of base portions and a plurality of edge portions, each of the recesses being defined by at least one of the edge portions and one of the base portions, the sealing ring having a first thickness at each of the base portions and the sealing ring having a second thickness at each of the edge portions, the second thickness being greater than the first thickness.

20. A centrifugal pump according to claim 18, wherein the sealing ring comprises a sealing ring inner peripheral surface facing in a direction of the counter sealing surface, the sealing ring inner peripheral surface comprising inner recesses which reduce the sealing ring cross section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a greatly simplified and showing a centrifugal pump with a sealing arrangement according to the invention;

(3) FIG. 2 is a perspective sectional view of a first embodiment variant of the sealing arrangement with a stationary sealing ring;

(4) FIG. 3 is a schematic longitudinally sectional representation showing a sealing arrangement in a standstill state of the impeller;

(5) FIG. 4 is a schematic longitudinally sectional representation showing a sealing arrangement according to claim 3 in an operation state of the pump;

(6) FIG. 5 is a schematic longitudinally sectional representation showing a further sealing arrangement in a standstill state of the impeller;

(7) FIG. 6 is a schematic longitudinally sectional representation showing a first embodiment of a sealing arrangement with a rotating sealing ring in a standstill state of the impeller;

(8) FIG. 7 is a schematic longitudinally sectional representation showing an alternative arrangement with a rotating sealing ring in a standstill state of the impeller;

(9) FIG. 8 is a perspective representation of a sealing ring according to the invention; and

(10) FIG. 9 is a perspective representation of an alternative embodiment of the sealing ring.

DESCRIPTION OF PREFERRED EMBODIMENTS

(11) Referring to the drawings, the centrifugal pump which is represented in a greatly simplified manner in FIG. 1, comprises a stationary pump casing 1 which comprises a suction connection 2 as well as a delivery connection 3, in which a shaft 4 is rotatably mounted, said shaft driving an impeller 5 which is seated therein and whose axial suction port 6 is conductively connected to the suction connection 2 and whose downstream side 7 is arranged in a radial manner and conductively connected to the delivery connection 3.

(12) The pump casing 1 here represents any stationary pump component, for example with a multi-stage pump represents the stationary part of a pump stage, which is to say that the principle representation represented by way of FIG. 1 can be applied to one or several arbitrary impellers with the respective stationary pump parts.

(13) A leakage channel 8 which can be shut off by a sealing ring 9 in the pump, is formed between the downstream side 7 thus the delivery side of the pump, and the suction port 6, thus the suction side of the pump. Examples concerning the design of the sealing arrangement between the suction port 6 of the centrifugal pump, thus the suction side and the leakage channel 8 connected to the delivery side are represented in detail in FIGS. 2 to 7, but these only schematically show a part of this leakage channel 8, of the impeller 5, of the pump casing 1 as well as of the sealing ring 9.

(14) The sealing ring 9a which is represented by way of FIG. 2 and which is arranged in the same manner as the sealing ring 9 represented by way of FIG. 1 is fastened with its narrow face side, in FIG. 2 its lower side, to the stationary part 1 of the pump. It has a slim ring-cylindrical shape, wherein the inner side of the sealing ring 9a is envisaged to come to bear on the outer periphery which is essentially cylindrical there, in the region of the suction port 6 of the impeller 5. In the non-loaded condition, the sealing ring 9a is arranged at a small distance to the outer side of the suction port 6 of the impeller 5. The sealing ring 9a comprises recesses 10 distributed over its outer periphery, which here are provided parallel to one another and parallel to the longitudinal axis of the sealing ring 9a, at regular angular intervals on the outer periphery. The stiffness of the sealing ring 9a is weakened by these recesses 10 having a part-circular cross section, to such an extent that the sealing ring 9a has the smallest material thickness at the base of a recess 10 and the largest material thickness at the edge of the recess 10. The sealing ring 9a is constructed of elastic material and with regard to the material and size is adapted such that the gap which is formed between the inner side of the sealing ring 9a and the outer side of the suction port 6 of the impeller 5 is closed on operation of the pump. This means that when the impeller 5 is driven by the shaft 4, and a pressure difference between the suction port 6 and the downstream side 7 is produced by way of this, the hydraulic and flow forces which then set in control the sealing ring 9a to bear upon the impeller 5, in the outer region of the suction port 6. Thereby, a Venturi effect firstly arises in the region of the sealing ring 9a at the outer side due to the swirling of the fluid exiting from the impeller 5 at the downstream side 7, and this Venturi effect then, in combination with building-up differential pressure between the downstream side 7 and the suction port 6 leads to the sealing ring 9a being pressed from the outside to the inside. However, the contact of the sealing ring 9a on the outer side of the suction port 6 is not effected over the whole periphery, but only in sections on account of the different stiffness of the sealing ring 9a in the peripheral direction, caused by the different material thickness. The inner side of the sealing ring 9a thus does not peripherally bear on the counter sealing surface 11 over the whole surface, but a contacting sealing ring section, in the peripheral direction is followed by one which is distanced and then by a contacting one, etc., in an alternating manner, over the whole periphery of the ring 9a. Delivery fluid gets into the region between the sealing ring 9a and the counter sealing surface 11 via the leakage channel 8, in the non-contacting sections of the sealing ring 9a, and this fluid is distributed over the sealing surface on account of the alternating contacting and non-contacting sections and the rotation of the impeller, so that a viscous friction always prevails in the region between the sealing ring 9a and the counter sealing surface 11.

(15) As to how the sealing ring 9 which is fastened on the casing side, comes to bear from its static position (FIG. 3), in which the impeller 5 is at a standstill, onto the counter sealing surface 11 of the impeller 5, on rotation of the impeller 5 firstly due to the Venturi effect building up at the outer side and then due to the differential pressure between the delivery side and the suction side, is schematically represented by way of FIGS. 3 and 4.

(16) The structure with recesses 10 on the outer periphery of the sealing ring 9a and which is described by way of the impeller 9a in FIG. 2 can be applied, in order to create alternatingly contacting and non-contacting sections between the sealing surface 12 and the counter sealing surface 11, in order to built up a load-bearing fluid film between the sealing surface 12 of the sealing ring 9 and the counter sealing surface 11 on the impeller 5. Additionally or in an assisting manner, recesses which assist or create this effect can be present in the sealing surface 12 or in the counter sealing surface 11, in the surface. The sealing rings which are yet to be described in more detail further below by way of FIGS. 8 and 9 illustrate as to how such a design could look.

(17) The bearing (contacting) of the sealing ring 9 onto the suction port 6, as is represented in FIG. 4, is effected exclusively by hydraulic forces, so that the sealing ring 9 returns into its initial position which is represented in FIG. 3 and in which a gap between the sealing surface 12 and the counter sealing surface 11 is formed in the leakage channel 8, given a standstill of the impeller 5. This elastic movement of the sealing ring 9, with the bearing contact and the return movement cleans the sealing gap and ensures that no deposits can form, in particular on the sealing surface 12.

(18) A sealing ring 9b which comprises a profile which is L-shaped in cross section is represented by way of FIG. 5, wherein an upright limb 13 corresponds to the sealing ring 9 described by way of FIGS. 3 and 4, whereas a lying limb 14 is provided for fastening the sealing ring 9b to the stationary part 1 of the pump, thus for example on the pump casing 1. The fastening of the sealing ring 9b can be effected materially and/or non-positively, by way of the ring 9b being pressed into the corresponding recess of the pump casing 1.

(19) With the embodiment variant represented by way of FIG. 6, a sealing ring 9c is provided and this has the shape of a ring disc and at its inner periphery is fixedly connected to the outer periphery of the impeller 5, in the region of the suction port 6. The sealing ring 9c hence co-rotates with the impeller 5, and its sealing surface 12 comes to bear on the counter sealing surface 11 on the pump casing, wherein here too, the differential pressure between the delivery side of the impeller and the suction side ensures a sectioned contacting of the sealing surface 12 on the counter sealing surface 11. With this embodiment too, the sealing ring 9c is of a differing stiffness due to recesses on its outer periphery, which are not represented, so that sections of the sealing surface 12 bearing on the counter sealing surface 11 form, and sections which are distanced to this, so that the previously described “plain bearing effect” also occurs with this arrangement, which is to say a load-bearing fluid film is formed between the sealing surface 12 and the counter sealing surface 11.

(20) With the embodiment variant which is represented by way of FIG. 7, the sealing ring 9d is arranged on the suction-side face side of the impeller 5 in the extension of the suction port 6. On the casing side, a ring section 15 which is arranged within the sealing ring 9d and which reaches up to the suction port 6 of the impeller 5 is provided. The counter sealing surface 11 for the sealing ring 9d is formed by the inner side of this ring section 15. The sealing ring 9d can be configured in the same manner as the sealing ring 9a described by way of FIG. 2, or as the sealing rings which are yet described further below by way of FIGS. 8 and 9.

(21) A sealing ring 9e is provided with the embodiment variant according to FIG. 8. FIG. 8 by way of example shows how such a sealing ring 9 of FIG. 3 or 4, which consists of elastic material, for example rubber, silicone or likewise, can be configured, so as to achieve the previously described effects. The sealing ring 9e in total comprises ten wedge-like recesses 16 which are distributed over its outer periphery, and the depth of these recesses increases in the clockwise direction, which is to say penetrate more deeply into the base material, in the representation according to FIG. 8. These wedge-like recesses 16 alternate with sections 17 which form part of a cylinder surface. The sealing ring 9e also comprises wedge-like recesses 18 at the inner side, which is to say on its inner periphery, and these recesses are interrupted by cylindrical sections 19 which likewise lie on a common cylinder surface. The recesses 18 at the inner side extend roughly over only a third of the periphery of the recesses 16 on the outer side and over a shallower depth. Thereby, the direction of the wedge shape of the recesses 18 is opposite to the direction of that of the recesses 16.

(22) Whereas the recesses 16 serve exclusively for the targeted weakening of the ring material, so that this at its inner side deforms in a humped fashion in a targeted manner given a build-up of a pressure from the outside, which is to say forms sections which bear on the counter sealing surface 11, and ones which are distanced to this, the recesses 18 on the inner periphery first and foremost serve for forming a load-bearing (load-supporting) lubricant film between the sealing surface 12, thus the inner side of the sealing ring 9e, and the counter sealing surface 11. These however can also have an influence upon the deformation of the sealing ring.

(23) An alternative embodiment of such a sealing ring 9f is represented by way of FIG. 9. The construction of the sealing ring 9f of an elastic material, with which wedge-like recesses 16a at the outer side alternate with cylindrical sections 17a and with which wedge-like recesses 18a at the inner side alternate with cylindrical sections 19a, differs from the previously described embodiment represented by way of FIG. 8, essentially in that the recesses 16a and 18a as well as the sections 17a and 19a are not arranged parallel to the axis of the ring 9f, but obliquely to it, and specifically on the outer side and on the inner side with the same obliqueness, so that contacting and non-contacting sections of the sealing ring 9f result given a subjection of pressure from the outside, and these sections overlap seen in the axis direction. A certain pumping effect is achieved due to the inclination of the wedge-like recesses 18a on the inner side, and this pump effect ensures that a load-supporting fluid film arises in the sealing gap between the sealing surface 12 and the counter sealing surface 11, even with high pressing forces. Moreover, the leakage losses are further reduced by such an oblique design.

(24) The embodiment examples specified above cannot even begin to represent the numerous possibilities of sealing ring designs which result from disclosure of the present invention. In the individual case, one is to determine experimentally and/or by computation, as to how a load-bearing fluid film sets in between the sealing ring and the counter sealing surface, and specifically over an as large as possible speed range of the pump, in or to keep wear and friction losses at the seal as low as possible.

(25) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.