EP2993357A2 - Radial compressor stage - Google Patents

Abstract

A centrifugal compressor stage comprising a rotor (10) rotating with respect to a stator (12) and having a plurality of stator vanes (20) positioned downstream of the impeller (10) and having a plurality of stator vanes (20), and between Impeller (10) and the stator (12) has a Radseitenraum (28) is formed. Flow inlet edges (22) of the stator vanes (20) lie on a first circular contour, namely such that the flow inlet edges (22) of all stator Leitschaufein (20) to the flow inlet edges (22) of the respective adjacent vanes (20) have an identical distance. Flow outlet edges (23) of the stator vanes (20) lie on a second circular contour, namely such that at at least one first circumferential position the flow outlet edge (23) of the respective stator side vane (20) to the flow outlet edge (23) of at least one adjacent vanes (20) has a different distance than at second circumferential positions. (Fig. 1)

Description

The invention relates to a radial compressor stage for a radial compressor according to the Oberbergriff of claim 1, 4 and 5 respectively.

From the DE 195 02 808 C2 is the basic structure of a centrifugal compressor with at least one radial compressor stage known. Thus, it is disclosed in this prior art that the or each radial compressor stage of a radial compressor comprises an impeller rotating with respect to a stator, the impeller comprising a hub and a plurality of rotor-side impeller blades. Each impeller vane of the impeller has a flow entrance edge and a flow exit edge, wherein a suction side, a pressure side, and an outer surface facing the stator extend between the flow entrance edge and the flow exit edge of each impeller vane, the outer surface of the respective impeller vane adjacent to the stator and sealing against the stator vane Stator is used. Such an impeller of a centrifugal compressor, in which the outer surfaces of the impeller blades indirectly adjacent to the stator, has no shroud and is also referred to as an open impeller. The impeller blades are positioned in an impeller flow passage delimited by the hub of the impeller and the stator.

Furthermore, it is from the DE 195 02 808 C2 It is known that the centrifugal compressor stage includes a diffuser positioned downstream of the impeller having a plurality of stator vanes. Each of the vanes of the diffuser has a flow inlet edge and a flow outlet edge, wherein a suction side and a pressure side extend between the flow inlet edge and the flow outlet edge of each guide vanes. The vanes are positioned in a diffuser flow channel defined by the stator.

From the DE 195 02 802 C2 can be seen that between the impeller and the stator of the radial compressor stage shown there is formed a so-called Radseitenraum, namely between a rear side of the impeller and the stator. This wheel side space is connected to an intermediate flow passage extending between the impeller flow passage and the diffuser flow passage.

Another radial compressor stage with such a Radseitenraum is from the DE 10 2007 019 264 A1 known.

From the EP 2 014 925 A1 is a radial compressor stage with a diffuser known, in which the angular distance of flow inlet edges of two adjacently arranged guide elements is different from the angular distance of flow inlet edges of two other adjacently arranged guide elements.

During operation of a radial compressor, the centrifugal compressor stages are exposed to mechanical stimuli and vibrations which can cause damage to the radial compressor stage, in particular to the rotor blades of the impeller of the radial compressor stage. Such mechanical excitations can be based on synchronous excitation mechanisms as well as on asynchronous excitation mechanisms.

In particular, three-dimensional and transient flow phenomena are generated by the interaction of rotating and stationary components. Under certain conditions, pressure fluctuations occur, which have a direction of rotation or of a direction opposite to that in the direction of rotation. The number and the circulation speed of these pressure fluctuations is arbitrary.

This phenomenon is the basis for asynchronous excitation of open impellers in centrifugal compressors. So far, no methods are known with the aid of which such asynchronous suggestions can be specifically counteracted to avoid a critical vibration excitation in particular of the impeller blades of the impeller.

There is therefore a need for a radial compressor stage for a radial compressor, in which in particular the impeller blades of the impeller are exposed to a low vibration excitation, in particular by such asynchronous excitations.

Proceeding from this, the present invention has the object to provide a radial compressor stage for a centrifugal compressor, which meets the above requirements and therefore a low vibration excitation is exposed in particular by such asynchronous excitations.

This object is achieved according to a first aspect of the invention by a radial compressor stage according to claim 1. Thereafter, the flow inlet edges of the stator vanes of the diffuser lie on a first circular contour, namely such that the flow inlet edges of all the stator vanes have an identical distance to the flow inlet edges of the respective adjacent vanes. The flow outlet edges of the stator-side guide vanes of the diffuser lie on a second circular contour, namely such that at at least one first circumferential position the flow exit edge of the respective stator side vane has a different distance from the flow exit edge of at least one adjacent vane than at second circumferential positions.

According to a second aspect of the invention, this object is achieved by a radial compressor stage according to claim 4. After this, at least one stator-side guide vane of the diffuser has a curvature deviating from the other stator-side guide vanes.

According to a third aspect of the invention, this object is achieved by a radial compressor stage according to claim 5. Hereinafter, at least a first circumferential position, a diffuser flow channel section formed between adjacent stator-side guide vanes of the diffuser has a flow cross-section deviating from the diffuser flow channel sections formed at second circumferential positions.

With any of the above aspects of the invention, asynchronous excitations of open wheels in radial compressors can be easily and reliably counteracted, whereby the vibration excitation can be reduced in particular for the impeller blades of the impeller of the radial compressor stage.

In this case, the above aspects of the invention can be used either alone or preferably in combination of several such inventive aspects of a radial compressor stage.

The above aspects of the invention all relate to structural design of the diffuser.

Fig. 1:

einen Meridionalschnitt durch eine erfindungsgemäße Radialverdichterstufe nach einem ersten Aspekt der Erfindung;

Fig. 2:

einen Axialschnitt durch die Radialverdichterstufe der Fig. 1;

Fig. 3:

einen Axialschnitt durch eine Radialverdichterstufe nach einem zweiten Aspekt der Erfindung; und

Fig. 4:

einen Meridionalschnitt durch eine erfindungsgemäße Radialverdichterstufe nach einem dritten Aspekt der Erfindung.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

Fig. 1:

a meridional section through a radial compressor stage according to the invention according to a first aspect of the invention;

Fig. 2:

an axial section through the radial compressor stage of Fig. 1 ;

3:

an axial section through a radial compressor stage according to a second aspect of the invention; and

4:

a meridional section through a radial compressor stage according to the invention according to a third aspect of the invention.

The present invention relates to a centrifugal compressor with at least one radial compressor stage.

Fig. 1 shows a detail of a radial compressor stage according to the invention in meridional section according to a first aspect of the invention, wherein Fig. 2 an axial section through the radial compressor stage of Fig. 1 shows.

The radial compressor stage of Fig. 1 has an impeller 10 with a plurality of rotor-side impeller blades 11. The impeller 10 rotates with respect to a stator 12. The stator 12 may be a housing or a stator ring or the like. The impeller blades 11 are positioned in an impeller flow channel 13 which is delimited by a rotor-side hub contour 14 and a stator contour 15. Each impeller blade 11 has a flow inlet edge 16 and a flow outlet edge 17. Between the flow inlet edge 16 and the flow outlet edge 17 of each impeller blade 11 extends a pressure side, a suction side and radially outside of the impeller blade 11 a stator 12 facing outer surface 18 of the respective impeller blade 11. The outer surface 18 of the impeller blade 11 adjacent to the stator 12 and is used to seal against the stator 12. Such an impeller 10, in which the outer surfaces 18 of the impeller blades 11 adjacent to the stator 12 indirectly, has no shroud and is also referred to as an open impeller.

According to Fig. 1 downstream of the impeller 10, a stator-side diffuser 19 is positioned. The diffuser 19 includes a plurality of stator vanes 20. The stator vanes 20 of the diffuser 19 are positioned in a diffuser flow channel 21 defined by the stator 12, wherein each of the stator vanes 20 of the diffuser 19 includes a flow entrance edge 22 and a flow exit edge 23. Between the flow inlet edge 22 and the flow outlet edge 23 of the respective stator side vane 20 extends a suction side 24 and a pressure side 25 of the respective vane.

Between the flow channel 13, in which the rotor-side impeller blades 11 of the impeller 10 are positioned, and the diffuser flow channel 21, in which the stator vanes 20 of the diffuser 19 are positioned, an intermediate flow channel 26 extends, via which medium compressed in the radial compressor stage, starting from the impeller 10 in the direction of the diffuser 19 can flow. According to Fig. 1 is formed between a rear side 27 of the impeller 10 and the stator 12, a Radseitenraum 28, said Radseitenraum 28 according to Fig. 1 is coupled to the intermediate flow passage 26 via a gap 34.

The above with reference to Fig. 1 and 2 described details of a radial compressor stage are state of the art.

The invention now relates to such details of a centrifugal compressor stage, with the help of which the risk of transient flow phenomena, which can lead to an asynchronous excitation of the open wheels, can be reduced.

According to a first aspect of the invention, with reference to Fig. 1 and 2 will be described, are all flow inlet edges 22 of all the stator vanes 20 of the diffuser 19 on a first circular contour 29th

In this case, the flow inlet edges 22 of the stator vanes 20 of the diffuser 19 are located on the first circular contour 29 such that the flow inlet edges 22 of all the stator vanes 20 have an identical spacing from the flow inlet edges 22 of the adjacent vanes 20. The flow inlet edges 22 of the guide vanes 20 of the diffuser 19 positioned next to one another in the circumferential direction of the diffuser flow channel 21 are thus distributed identically in the circumferential direction, so that accordingly all flow inlet edges 22 lying on the first circular contour 29 have identical circumferential spacings to adjacent flow inlet edges 22.

According to the first aspect of the invention, provision is further made for the flow outlet edges 23 of the stator-side guide vanes 20 of the diffuser 19 to lie on a second circular contour 30.

In this case, the flow outlet edges 23 of the stator vanes 20 of the diffuser 19 are located on the second circular contour 30, that at least a first circumferential position of the diffuser flow channel 21, the flow outlet edge 23 of the respective stator side vane 20 positioned there to the flow outlet edge of at least one adjacent vane 20 at a different distance than at second circumferential positions of the diffuser flow channel 21.

Accordingly, in the area of the flow outlet edges 23, no uniform distribution of the flow outlet edges 23 is provided in the circumferential direction of the diffuser flow channel 21; rather, the uniform distribution of the flow outlet edges 23, which are all located on the second circular contour 30, is preferably canceled at the first circumferential positions, thus avoiding the risk of unsteady flow phenomena , which can lead to an asynchronous excitation of the open wheels, to reduce.

According to the first aspect of the invention, it is possible in a first extreme that only at a single circumferential position of the diffuser flow channel 21, the corresponding flow outlet edge 23 has a different distance to the respective adjacent flow outlet edges 23, however, that at the other circumferential positions the flow outlet edges 23 with respect to their circumferential positions are equally distributed.

Likewise, according to the first aspect of the invention, in a second extreme case, it is possible for the flow outlet edges 23 to have respective different spacings at all circumferential positions of the diffuser flow channel 21 relative to the respectively adjacent flow outlet edges 23.

At the second circumferential positions of the diffuser flow channel 21, the respective stator-side vanes 20 of the diffuser 19 preferably all have identical second stagger angles.

The stator vanes 20 positioned at the or each first circumferential position, on the other hand, preferably have a first staggering angle deviating from the second staggering angle, in particular ± 10 °, preferably ± 7 °, more preferably ± 5 °, most preferably ± 3 ° ,

According to the first aspect of the present invention is therefore proposed to reduce the risk of unsteady flow phenomena that can lead to an asynchronous excitation of the open wheels, the flow outlet edges 23 selected stator side vanes 20 of the diffuser 19 in the circumferential direction, preferably with suspension or Interruption of the otherwise uniformly distributed in the circumferential direction of the diffuser flow channel 21 flow outlet edges 23rd

In an extreme case, the flow outlet edges 23 of all stator-side guide vanes 20 of the diffuser 19 may have different distances to the respectively adjacent flow outlet edges 23.

As Fig. 2 can be removed, a flow outlet edge 23 "(see dashed line of in Fig. 2 Right vane) in the direction of the pressure side 25 of the respective adjacent vane 20 or a flow outlet edge 23 '(see dashed line of in Fig. 2 left guide blade) are displaced in the direction of the suction side 24 of the respective adjacent guide blade 20 in the circumferential direction, in such a way that as before all flow outlet edges 23 lie on the second circular contour 30.

This corresponds to a change in the stagger angle of the stator-side vanes 20 of the diffuser 19 at selected circumferential positions. At selected second circumferential positions of the diffuser 19, the respective stator-side vanes 20 have deviating stagger angles.

Those selected vanes 20, which have a different staggering angle compared to the other stator vanes 20, are characterized in that their staggering angle deviates, in particular by ± 10 °, particularly preferably ± 5 °, from the staggering angles of the remaining vanes 20 of the diffuser 19 ,

By the above measures of the first aspect of the present invention, a slightly higher or a slightly lower load from the guide vanes 20 of the diffuser 19 can be impressed at defined circumferential positions in uneven circumferential distances. The danger of unsteady flow phenomena, which can lead to an asynchronous excitation of the open wheels, can thus be reduced.

According to a second aspect of the invention (see Fig. 3 ) is proposed to reduce the risk of unsteady flow phenomena that can lead to an asynchronous excitation of the open wheels, that both the positioned on the first circular contour 29 flow inlet edges 22 of the stator vanes 20 of the diffuser 19 as well as positioned on the second circular contour 30 flow outlet edges 23 of the stator-side guide vanes 20 of the diffuser 19 are distributed uniformly in the circumferential direction, ie each having identical circumferential distances.

According to the second aspect of the invention, however, at least one stator-side guide vane 20 of the diffuser 19 between the flow inlet edge 22 and the flow outlet edge 23 has a different curvature, namely a suction side 24 'and a pressure side 25' with respect to the other vanes 20 deviating curvature. This is in Fig. 3 shown by the dashed line for the middle vane 20.

According to the second aspect of the invention, it is possible in a first extreme case that exclusively a single stator vane 20 of the diffuser 19 has a different curvature, whereas all other stator vanes 20 of the diffuser 19 have identical curvatures.

Likewise, according to the second aspect of the invention, in a second extreme case, it is possible for all the stator-side guide vanes 20 of the diffuser 19 to have different curvatures.

It is preferred to use the first aspect of the invention and the second aspect of the invention in combination with one another to reduce the risk of transient flow phenomena that can lead to asynchronous excitation of the open wheels on the centrifugal compressor stage.

A third aspect of the present invention will be described below with reference to FIG Fig. 4 discussed.

According to the third aspect of the invention, in order to reduce the risk of unsteady flow phenomena which may lead to asynchronous excitation of the open wheels, it is proposed to change at least a first circumferential position of the diffuser flow channel 21 a diffuser flow channel section 33 formed between adjacent stator vanes 20 of the diffuser 19 in that it has a different flow cross section than the diffuser flow channel sections formed at second circumferential positions.

So can Fig. 4 It can be seen that, at a first peripheral position of the diffuser 19 between adjacent stator vanes 20, the respective diffuser flow channel section 33 has a reduced flow cross section, namely the stator side walls 31, 32 delimiting the respective diffuser flow channel section 33, reducing the flow cross section of the respective diffuser flow channel section 33 inwardly are arched into it. It should be noted that only one of these stator-side, the respective diffuser flow channel section 33 bounding side walls 31, 32 may be curved into the respective diffuser flow channel section 33 inside. It is likewise possible to widen the respective diffuser flow channel section with respect to its flow cross section at selected circumferential positions, wherein at least one of these side walls 31, 32 is curved outwards into the stator 12.

According to the third aspect, it is possible in a first extreme case that exclusively at a single circumferential position of the diffuser flow channel 21, the corresponding diffuser flow channel section 33 has a different flow cross section, whereas all other diffuser flow channel sections 33 have identical flow cross sections.

Likewise, according to the third aspect of the invention, in a second extreme case it is possible for the diffuser flow channel sections 33 to each have different flow cross sections at all circumferential positions of the diffuser flow channel 21.

The measures of the third aspect can be used in combination with the measures of the first aspect and / or the measures of the second aspect. The measures of the third aspect are preferably used in combination with the measures of the first aspect and with the measures of the second aspect on a radial compressor stage.

LIST OF REFERENCE NUMBERS

10

Wheel

11

impeller blade

12

stator

13

Impeller flow channel

14

hub contour

15

stator contour

16

Flow inlet edge

17

Flow outlet edge

18

outer surface

19

diffuser

20

vane

21

Diffuser flow channel

22

Flow inlet edge

23

Flow outlet edge

24

suction

25

pressure side

26

Between flow channel

27

back

28

wheel side

29

circular contour

30

circular contour

31

Side wall

32

Side wall

33

Diffuser flow channel section

34

gap

Claims (6)

A centrifugal compressor stage comprising a rotor (10) rotating with respect to a stator (12) and having a plurality of stator vanes (20) positioned downstream of the impeller (10) and having a plurality of stator vanes (20), and between Impeller (10) and the stator (12) a Radseitenraum (28) is formed, characterized in that
Flow inlet edges (22) of the stator vanes (20) on a first circular contour (29) lie, namely such that the flow inlet edges (22) of all the stator vanes (20) to the flow inlet edges (22) of the respective adjacent vanes (20) an identical distance exhibit;
Flow outlet edges (23) of the stator vanes (20) on a second circular contour (30) lie, namely such that at least a first circumferential position, the flow outlet edge (23) of the respective stator side vane (20) to the flow outlet edge (23) of at least one adjacent vanes (20) has a different distance than at second circumferential positions. Radial compressor stage according to claim 1, characterized in that
at the second circumferential positions, the respective stator-side vanes (20) all have identical second stagger angles; and
at the or each first circumferential position, the respective stator-side vanes (20) have a first stagger angle that deviates from the second stagger angle. Radial compressor stage according to claim 2, characterized in that , the first grading angle deviates from the second grading angle by ± 10 °, preferably by ± 7 °, particularly preferably by ± 5 °. A centrifugal compressor stage comprising a rotor (10) rotating with respect to a stator (12) and having a plurality of stator vanes (20) positioned downstream of the impeller (10) and having a plurality of stator vanes (20), and between Impeller (10) and the stator (12) a Radseitenraum (28) is formed, characterized in that at least one stator-side guide vane (20) has a different from the other stator-side vanes (20) curvature. A centrifugal compressor stage comprising a rotor (10) rotating with respect to a stator (12) and having a plurality of stator vanes (20) positioned downstream of the impeller (10) and having a plurality of stator vanes (20), and between Impeller (10) and the stator (12) a Radseitenraum (28) is formed, characterized in that at least a first circumferential position between adjacent stator vanes (20) formed Diffusorströmungskanalabschnitt (33) deviates from the diffuser flow duct sections formed at second circumferential positions flow cross-section having. A radial compressor stage according to claim 5, characterized in that opposite to the second circumferential positions at the or each first circumferential position between the adjacent stator vanes (20) at least one side wall (31, 32) delimiting the diffuser flow channel portion (33) reducing the flow area inwardly into the diffuser flow channel portion (33) into and / or under enlargement of the flow cross section outwardly into the stator (12) is curved into it.

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