EP2582983B1 - Dual-flow centrifugal pump - Google Patents

Description

The invention relates to a, preferably single-stage, double-flow centrifugal pump, in particular a cooling water pump for a marine diesel engine or a Balastwasserförderpumpe on a ship, according to the preamble of claim 1. Further, the invention relates to a use according to claim 9.

In known double-flow centrifugal pumps designed as annular gaps sealing gaps extend in the axial direction and are formed between the impeller and the pump housing. During operation of the known centrifugal pumps, especially when the centrifugal pumps are not operated at their optimum operating point, a resulting radial force component acting on the cantilevered shaft occurs, so that the shaft is deflected in the radial direction with the impeller fixed to it in a rotationally fixed manner. In order to prevent the impeller from contacting the pump housing during this deflection movement, the sealing gaps formed as axial gaps must be dimensioned correspondingly broad. However, this in turn leads to a loss of power of the pump, as constantly conveyed medium flows from the radial overpressure region in the axial direction through the sealing gaps in the negative pressure region (suction). As a result, the efficiency of the known centrifugal pumps deteriorates considerably. The aforementioned centrifugal pumps are suitable, if the shaft is mounted on one side, only for applications in which comparatively low volume flows have to be conveyed. In double-flow centrifugal pumps for large volume applications, such as cooling water pumps for a marine diesel engine or Balastwasserförderpumpen on a ship, the impeller bearing shaft is usually mounted on both axial sides of the impeller to minimize the radial deflection movement during operation. In a only one-sided storage of the shaft for these applications, a shaft with a correspondingly large diameter and / or complex storage would have to be used.

From the FR-A-723344 is a double-flow centrifugal pump for conveying small volume flows known. The centrifugal pump has sealing gaps between the impeller and a position-variable, ie non-stationary pump component. The known centrifugal pump is not suitable for use on ships.

The GB 242230 A also shows a centrifugal pump, wherein the Dichtspaltmaß between the impeller and a non-stationary component is adjustable.

Based on the aforementioned prior art, the present invention seeks to provide a double-flow centrifugal pump, for large volume flows of at least 500m ³ / h, especially for use on ships, with a high efficiency without complex design measures is possible. In this case, the impeller bearing shaft of the centrifugal pump should be stored exclusively on one side and have the smallest possible diameter. A striking of the impeller on the pump housing should be safely avoided.

This object is achieved by a double-flow centrifugal pump with the features of claim 1.

Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention. In order to avoid repetition, features disclosed according to the device should be regarded as disclosed according to the method and be able to be claimed. Likewise, according to the method disclosed features should be considered as device disclosed and claimed claimable.

The invention is based on the idea that the sealing gaps between the impeller and at least one pump part, with which the suction side of the centrifugal pump is sealed against the pressure side, extending in the radial direction with respect to their longitudinal extent, ie as an axial gap train. In other words, the impeller according to the invention by means of the sealing gaps in the axial direction spaced from the at least one, preferably exclusively a pump component, ie, a stationary pump housing and / or a stationary built-in part. The at least approximately in the axial direction extending width of the sealing gap, at least at one point, preferably over its longitudinal extent less than the distance between the impeller and all other radially spaced from the impeller components of the pump. In other words, the gap width of the sealing gap is smaller than the radial distance of the impeller to all components of the pumps located radially outside the impeller. The sealing gaps are characterized by the fact that their axial extent is (substantially) less than their radial extent. The gap width of the axial gap (sealing gap) measured in the axial direction is preferably greater than the gap width measured in the radial direction of a radial gap arranged between the impeller and the pump component bounding the axial gap.

The centrifugal pump according to the invention is designed for large-volume, in particular marine applications. Preferably, the centrifugal pump for conveying a volume flow from a value range between about 500m ³ / h and about 4000m ³ / h, preferably between about 800m ³ / h and about 1500m ³ / h (for example, smaller cooling water pumps) or between about 1500m ³ / h and about 2300m ³ / h (for example, in medium-sized cooling water pumps) or between 2300m ³ / h and 3500m ³ / h (for example, larger cooling water pump) designed preferably at a maximum head from a range between about 20m and about 50m, preferably from about 30m. For marine applications in particular, it is particularly preferred for reasons of space that the double-flow centrifugal pump is realized in a vertical design, that is to say in such a way that the shaft runs perpendicular to a stationary surface of the centrifugal pump.

As already indicated, it is provided according to the invention with regard to the most cost-effective variant of the centrifugal pump that the the impeller bearing shaft is supported only on one side, preferably on an upper side.

Preferably, the gap width of the sealing gaps is at least 20%, preferably at least 12%, more preferably 6% of the radial distance of the impeller 7 to the axial gap defining pump component, i. the pump housing and / or to the, preferably a housing portion forming, insert part.

Of course, it is possible to provide on both axial sides of the radial outlet region of the impeller, a plurality of sealing gaps each formed as an axial gap. However, it is preferred to provide only one sealing gap designed as an axial gap, with the gaps each having the smallest gap width being understood as the sealing gaps.

Very particular preference is given to an embodiment variant in which the, preferably exclusively, two sealing gaps are arranged in a region radially inwardly of circumferentially closed radial gaps, via which the impeller is spaced from the at least one, preferably only one, pump component. It is particularly preferred if the axial gaps, starting from the radial gaps in the radial direction extend inwards. Particularly preferred is therefore an embodiment variant in which the axial gaps, at least in a radially inner region, have a smaller distance from the shaft than the radial gaps. Advantageously, the sealing gaps are located within an imaginary circular cylinder whose lateral surface receives the radial gaps in itself. Due to such a variant, the sealing effect is improved.

It is particularly useful if the impeller has a circular cylindrical envelope contour, wherein it is even more preferred if the sealing gaps (axial gaps) between each end face of a cylindrical envelope contour having impeller and the at least one, preferably exclusively one, pump component are formed.

Alternatively, an envelope contour can also be provided in which the impeller extends with its outlet region farther outward in the radial direction. However, as will be explained later, it is also preferred in such a geometry if the axial sealing gap is arranged in a region which has a smaller radius than a possible radial gap, which is arranged between the pump jet and the impeller.

Due to the inventive design of the sealing gaps as axial gaps, it is possible to measure the gap width of the sealing gaps much lower than in the prior art, without the risk that the impeller strikes at a radial deflection of the sealing gap limiting pump component. It is thus possible to achieve a high efficiency of the centrifugal pump by the inventive design of the sealing gaps, since the amount of liquid flowing from the pressure region in the suction region (negative pressure region) is minimized by the small gap width of the sealing gaps. In the radial direction, the distance between the impeller and the pump component and / or other components of the pump can be dimensioned so that there is no risk of collision even with the largest possible occurring during operation deflection of the impeller. It is thus possible to realize only one-sided storage of the impeller shaft even before large-volume applications, in particular for marine applications, since larger radial deflections of the impeller can be accepted than before. In addition, the dimensioning of the shaft as such can be minimized.

Structurally particularly simple and thus preferred is an embodiment in which the sealing gaps - within the tolerances - exactly in relation to their longitudinal extent in the radial direction. However, it is also a slightly curved or slightly oblique configuration of the sealing gaps by a corresponding formation of at least one of the sealing gaps bounding component (impeller and / or pump component, in particular pump housing) possible, in particular such that the gap geometry of the curved deflection movement of the impeller, especially in unilateral shaft bearing follows, so that the gap width, regardless of the degree of deflection of the impeller in operation, at least independently remains constant. Particularly preferably, the radius of curvature at least approximately corresponds to the distance of the impeller to the bearing of the impeller bearing shaft.

In a development of the invention, it is advantageously provided that the gap width of the sealing gaps designed as axial gaps is selected from a value range between 200 μm and 2000 μm, very particularly preferably between 200 μm and 400 μm.

It is particularly expedient if the minimum, i. the smallest radial distance of the impeller to which the axial gap formed as a sealing column limiting pump component of the centrifugal pump (with stationary impeller) is selected from a range of values between 2mm to 10mm. In other words, the distance between the impeller and the aforementioned pump component is preferably greater than the distances of the specified range of values. Most preferably, the aforementioned minimum radial distance is not only the minimum radial distance of the impeller to the at least one, preferably only a sealing column defining pump component, but the minimum radial distance of the impeller to all components of the pump to a collision at radial To prevent deflection safely.

An embodiment of the double-flow centrifugal pump in which the sealing gaps are arranged between the end faces of the impeller pointing in the axial direction and the at least one pump component is particularly preferred. In other words, it is preferred if the sealing gaps have the greatest possible axial distance from each other. This can for example be realized in that the impeller has an at least approximately circular cylindrical envelope contour. Especially preferred encloses an imaginary, the radial gaps receiving circular cylindrical surface, the axial gaps radially outward.

As explained at the outset, an axial gap (sealing gap) extending in the radial direction is understood to mean not only an embodiment in which the sealing gaps extend exactly in the radial direction with respect to their longitudinal extent, ie they are, for example, annular disk-shaped. An embodiment is also conceivable in which the sealing gaps have a small pitch angle or are slightly curved, i. have a large radius of curvature, which preferably, at least approximately, in particular in one-sided bearing shaft, corresponds to the distance of the respective sealing gap of the shaft bearing. The respective sealing gap is then designed such that the gap width during operation of the centrifugal pump, ie not with a possible radial deflection of the impeller, or only slightly as possible, since the gap geometry follows the deflection movement. The curvature or bevel of the sealing gaps can be realized by a corresponding geometric shape of the impeller and / or the at least one, preferably only one, the sealing gaps on the opposite axial side of the impeller pump component. Most preferably, the angle (inclination angle) of the respective sealing gap to an imaginary, arranged orthogonal to the longitudinal extent of the shaft radial plane is selected from a range of values between 0.01 ° and 2.0 °. Preferably, a possible radius of curvature is selected from a value range between 200 mm and 1000 mm, preferably 300 mm and 700 mm.

The radius of curvature of the respective sealing gap, more precisely at least one surface delimiting the sealing gap (the impeller and / or the pump component) preferably corresponds, at least approximately, to the distance of the respective sealing gap (in particular at a radially innermost region of the sealing gap) to the shaft bearing, in particular on one side stored (pump shaft). Accordingly, the angle of inclination of the gap explained in the description refers to the inclination of at least one of them Sealing gap limiting surface (of the impeller and / or the pump component) relative to the aforementioned radial plane.

It is particularly preferred if the centrifugal pump is a single-stage centrifugal pump, that is to say exclusively an impeller.

It is particularly expedient if the pump housing is a so-called spiral housing, which predetermines the flow path on the suction side to the two axial sides of the impeller and preferably spirally combines two outlet channels on the pressure side.

The invention also leads to the use of a trained according to the concept of the invention double-flow centrifugal pump as a cooling water pump for a marine diesel engine or ballast water pump on a ship.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings.

Fig. 1:

eine geschnittene Darstellung eines Ausführungsbeispieles einer nach dem Konzept der Erfindung ausgebildeten doppelflutigen Kreiselpumpe,

Fig. 2:

eine Prinzipzeichnung zur Darstellung der Spaltverhältnisse,

Fig. 3 bis Fig. 7:

unterschiedliche Ausgestaltungsmöglichkeiten der Dichtspalte.

These show in:

Fig. 1:

a sectional view of an embodiment of a trained according to the concept of the invention double-flow centrifugal pump,

Fig. 2:

a principle drawing to show the gap conditions,

3 to 7:

different design options of the sealing column.

In the figures, like elements and elements having the same function are denoted by the same reference numerals.

In Fig. 1 is a sectional view of a double-flow centrifugal pump 1 shown in a vertical design. In the illustrated embodiment is a cooling water pump for a marine diesel engine, which is designed to promote a flow rate of 2300m3 / h at a maximum head of 30m.

The centrifugal pump 1 comprises a pump housing 2 designed as a spiral housing with a suction-side inlet 3 and a pressure-side outlet 4. In the pump housing 2 projects from above in a vertical downward direction a shaft 5 mounted on one side, which is mounted by means of a bearing 6 designed as a ball bearing , The end of the shaft 5 carries a doppelflutiges impeller 7 with a substantially circular cylindrical envelope contour. The impeller 7 is rotatably mounted on the shaft 5. In a region axially between the bearing 6 and the impeller 7 is a shaft seal 8. As is apparent from Fig. 1 results, the shaft 5 passes through in a region above the shaft seal 8 fixed to the pump housing 2 by screwing cover. 9

The impeller 7 separates a negative pressure region 10 (suction side) from an overpressure region 11 (pressure side).

The shaft 5 is rotatable by means of a motor, not shown, in particular an electric motor in a conventional manner, said rotating with the shaft 5 impeller 7 from both axial sides of the negative pressure region 10 fluid, here sucking cooling water and in the radial direction outwardly into the overpressure region 11 promotes, wherein the pressure area 11 is divided into two spirally arranged flow channels 12, 13 which are separated by a partition 14 from each other. In the region of the outlet 4, the two flow channels 12, 13 or the fluid streams are brought together again.

In operation of the centrifugal pump 1, especially when the centrifugal pump 1 is not operating at an optimum operating point, there is a radial force load on the shaft 5 in the area of the impeller 7, which tends to deflect the shaft 5 with impeller 7 in the radial direction. In order to prevent the impeller 7 from colliding with the pump housing 2 (pump component) in the radial direction, two axially spaced radial gaps 15, 16 extending in the axial direction are dimensioned so wide that even a maximum conceivable deflection of the shaft 5 during operation is not can lead to a collision of the impeller 7 with the pump housing 2. Due to their comparatively large gap width (measured at the narrowest point), the radial gaps 15, 16 are not designed as sealing gaps by the approximately 5 mm in the exemplary embodiment shown or do not fulfill a sufficient sealing function. The radial gaps are in the form of circular cylinder jacket surfaces. If the radial gaps 15, 16 were the only sealing gaps, the centrifugal pump 1 would have a very poor efficiency due to the comparatively large gap width, since liquid, here cooling water constantly in large quantity through the radial gaps 15, 16 from the overpressure region 11 in the Vacuum range 10 flow and thus would be funded directly in a circle.

To achieve the desired sealing effect with avoided risk of collision between impeller 7 and pump housing 2 (pump component), the pump housing 2 (pump component) engages the impeller 7 at both axial sides, ie up and down in the radial direction inwards, such that between each end face 17, 18th of the impeller 7 and the pump housing 2 (pump component) formed as an axial gap, extending in terms of its longitudinal extent in the radial direction sealing gap 19, 20 is formed is. It is essential that these sealing gaps 19, 20, measured at their narrowest point, have a smaller gap width than the radial gaps 15, 16.

The sealing gaps 19, 20 are located radially inside the radial gaps 15, 16, wherein the radial gaps 15, 16 pass into the sealing gaps 19, 20 and the sealing gaps 19, 20 directly adjoin the radial gaps 15, 15.
In the embodiment shown, the gap width of the sealing gaps 19, 20 corresponds to approximately 400 μm.

The sealing gaps 19, 20 are, as explained on the one hand in the axial direction bounded by the impeller 7, in the embodiment shown by one end face 17, 18 of the impeller 7 and opposite of a parallel here to the respective end face 17, 18 aligned wall surface 21, 22nd of the pump housing 2.

If there is a deflection of the impeller 7 during operation in the radial direction, the end faces 17, 18 are displaced substantially parallel to the wall surfaces 21, 22 of the pump housing 2, so that a collision can not occur here. The radial gaps 15, 16 are, as explained, so broadly dimensioned that a collision with the impeller 7, even at a maximum permissible deflection exits.

In Fig. 2 the gap ratios are shown schematically.

Evident is the impeller 2 shown schematically, which is rotatably mounted on a rotatably mounted shaft 5.

The impeller 7 is surrounded by a pump component 23, here the pump housing 2, more precisely an insert part 24, which forms part of the pump housing 2. Alternatively, the insert can not be formed and arranged forming part of the housing, ie within the pump housing and that at a distance to a housing outside. During a rotation of the impeller 7, the liquid flows in arrow directions from the suction side (negative pressure region) 10 to the pressure side (overpressure region) 11.

Between the pump component 23, which may be formed in one or more parts and the impeller 7, more precisely between the end faces 17, 18 of a circular cylindrical envelope contour having impeller 7, here two sealing gaps 19, 20 are formed. These sealing gaps 19, 20 are axial gaps, which are formed axially between the pump component 23 and the impeller 7. The gap width s of the sealing gaps 19, 20 is 400 μm in the embodiment shown. The two flat annular disc-shaped sealing gaps 19, 20 are spaced apart in the axial direction and u.a. separated from the one or more radial outlet regions of the impeller. 7

In the embodiment shown, two radial gaps 15, 16 are provided in addition to the sealing gaps 19, 20 between the impeller 7 and the pump component 23, the gap width a is greater than the gap width s of the sealing gaps. In the illustrated embodiment, the gap width a with stationary impeller 7 is about 5mm. The sealing gaps 19, 20 are located radially inside the radial gaps 15, 16, that is, they are spaced less far from the shaft 5 than the radial gaps 15, 16. The radial gaps are circular-cylinder-jacket-shaped. The sealing gaps 19, 20 have approximately the shape of a circular disk. On the provision of the (narrow) radial gaps 15, 16 can also be dispensed with a modified design of the pump component 23. It is also conceivable on at least one of the two axial sides, preferably on both axial sides, of the impeller 7 to provide a plurality of sealing gaps 19, 20, which are preferably located in parallel planes and in which they are each provided with axial gaps. Preferably, then, on at least one axial side of the impeller 7, two axially adjacent sealing gaps are connected to one another via a radial gap with a larger gap width than the gap width of the sealing gaps. Thus, a stepped gap formation would result, with the axial gap sections representing the sealing gaps. This results in a stepped gap design.

Based on Fig. 3 to 7 conceivable alternative sealing gap geometries are shown, wherein the angles or radii of curvature are exaggerated for reasons of illustration. In reality, these are minimal gradients or large radii of curvature.

It is common in all exemplary embodiments that the sealing gaps are axial gaps which essentially extend in the radial direction with respect to their longitudinal extent and whose axial extent is (substantially) less than their radial extent.

In the embodiment according to Fig. 3 a sealing gap 19 is formed between the impeller 7 and a pump component 23. The sealing gap 19 delimiting portion of the impeller 7 extends in relation to the longitudinal extent of the shaft exactly in the radial direction, whereas the surface portion of the pump member 23 which limits the sealing gap 19 is slightly inclined with respect to a radial plane, here at an angle α of < 1 °. This results in a sealing gap inclination by this angle α with respect to an imaginary radial plane, in which in the embodiment shown, the illustrated surface portion of the impeller 7 is located.

In the embodiment according to Fig. 4 are both the sealing gap 19 delimiting surface portion of the impeller 7 and the sealing gap 19 opposite limiting surface portion of the pump member 23 inclined with respect to a radial plane, in the embodiment shown both at the same angle α from here <10 °. It is also the realization of different, but similar inclination angle feasible.

In the embodiment according to Fig. 5 the area of the impeller 7 bordering the sealing gap 19 lies in a radial plane with respect to the longitudinal extent of the shaft, whereas the surface portion of the pump component 23 delimiting the sealing gap 19 is curved, Preferably, the curvature has a radius which has the sealing gap 19 from the bearing of the shaft 5, not shown.

In the embodiment according to Fig. 6 both the sealing gap 19 bounding surfaces as both the impeller 7 and the pump member 23 are slightly curved.

In the embodiment according to Fig. 7 is the sealing gap 19 limiting surface of the impeller 7 flat, but at an angle α of <10 ° inclined to the radial plane, whereas the sealing gap 19 delimiting surface of the pump member 23 is slightly curved and preferably has a radius of curvature of 500mm.

LIST OF REFERENCE NUMBERS

1

double-flow centrifugal pump

2

pump housing

3

Inlet (inlet)

4

Outlet (outlet)

5

wave

6

camp

7

impeller

8th

shaft seal

9

cover

10

Under pressure range

11

Overpressure range

12

flow channel

13

flow channel

14

septum

15

radial gap

16

radial gap

17

front

18

front

19

sealing gap

20

sealing gap

21

wall surface

22

wall surface

23

pump component

24

insert

s

Gap width, sealing gap

a

Gap width, radial gap

Claims (9)

1. Double-flow centrifugal pump, in particular a cooling water pump for a marine diesel engine or ballast water delivery pump, having a pump housing (2) and having a double-flow impeller (7) arranged in a rotationally fixed manner on a rotationally driven shaft (5), wherein using said impeller a fluid can be suctioned from two axial sides from a negative pressure region (10) and can be delivered in the radial direction into a positive pressure region (11), wherein the negative pressure region (10) is sealed off with respect to the positive pressure region (11) by means of at least two sealing gaps (19, 20) spaced apart axially from each other, wherein the sealing gaps (19, 20) are formed as axial gaps extending in the circumferential direction and in the radial direction, the gap width (s) of which is less than the radial distance (a) from the impeller (7) to all components mounted with a radial distance to the impeller (7), characterised in that the centrifugal pump is designed to deliver a volume flow in a range between 500m3/h and 4000m3/h and is produced in a vertical construction type, and in that the shaft (5) is only mounted on one side, and in that the sealing gaps (19,20) are formed axially between the impeller (7) and the stationary pump housing (2) and/or a stationary insert (24).
2. Centrifugal pump according to claim 1, characterised in that the gap width (s) of the sealing gap (19, 20) has a value in the range between 200µm and 2000µm.
3. Centrifugal pump according to one of claims 1 or 2, characterised in that the minimum radial distance (a) of the impeller (7) to the pump component (23) of the centrifugal pump when the impeller (7) is stationary is selected from the range between 2mm and 10mm.
4. Centrifugal pump according to one of claims 1 or 3, characterised in that the sealing gaps (19, 20) are located between the front side (17, 18) of the impeller (7) and the pump housing (2) or the mounting part (24).
5. Centrifugal pump according to any of the preceding claims, characterised in that the sealing gaps (19, 20) are formed running exactly in the radial direction, or making an angle in the range between approximately 0° and 1° with a radial plane, preferably between 0.5° and 5°, and/or that the sealing gap (19, 20) has a radius of curvature in the range between 200mm and 1000mm, preferably between 300mm and 700mm.
6. Centrifugal pump according to any of the preceding claims, characterised in that the centrifugal pump is designed to deliver a volume flow in the range between approximately 800m3/h and approximately 1500m3/h, or between approximately 1500m3/h and approximately 2300m3/h, or between 2300m3/h and 3500m3/h, preferably with a maximum head in the range between 20m and 50m, preferably approximately 30m.
7. Method according to one of the preceding claims, characterised in that the, preferably only, two sealing gaps (19, 20) have a lower radial distance to the shaft (5) than between the impeller (7) and the radial gap (15, 16) formed as a pump component.
8. Method according to one of the preceding claims, characterised in that the impeller (7) has a circular cylindrical shell contour.
9. Use of a centrifugal pump according to any of the preceding claims as a cooling water pump for a marine diesel engine or as a ballast delivery pump.

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