EP0961033B1 - Radial compressor - Google Patents

Description

Technical field

The invention relates to a method for operating a radial compressor, according to the preamble of claim 1 and a corresponding radial compressor, according to the preamble of claim 6.

State of the art

To seal rotating systems, non-contact is used in turbomachinery Seals, especially labyrinth seals, are widely used. In fluid flow Separation gap between rotating and standing parts occurs as a result of forming flow boundary layers on a high friction. Thereby there is a heating of the fluid in the separation gap and thus also a heating the components surrounding the separation gap. The high material temperatures have a reduction in the lifespan of the corresponding components Episode.

Exhaust gas turbochargers have an axial thrust of the exhaust gas turbine, depending on their design which counteracts or rectifies that of the radial compressor like this one. In the latter case, the resulting pressure in the separation gap must be between the rotating rear wall of the compressor wheel and the neighboring one, stationary compressor housing can be dismantled. That is why there are such gaps tolerated very closely. In addition, they usually have a non-contact Poetry. There is a particularly high level of friction in such narrow separation gaps to be recorded. In addition, the redirection and swirling of the working fluid flowing through the separation gap at the throttle points of the seal to a constantly new mixing of the working fluid with a high momentum and heat exchange. Must be downstream of the throttle the working fluid on the rotating component is again accelerated in the circumferential direction be, whereby the friction and thus the heat development in this area continues to rise.

EP 0 518 027 B1 describes a cooling device for radial compressors on the Rear wall of the compressor wheel, between this and the compressor housing, sealing elements arranged in the separating gap are known. It will be a cold one Gas with a higher than that prevailing at the outlet of the compressor wheel Pressure is passed through the seal. This gas bounces the rear wall of the compressor wheel and at the same time acts as sealing air a flow of hot compressor air from the outlet through the labyrinth gap of the compressor wheel. This can reduce the service life of such, with a sealing geometry provided compressor wheel can be increased significantly. It proves to be disadvantageous It is with this solution that the specially trained seal entire construction and assembly of the compressor complicated and expensive. Because the clear width of the separation gap is also in the tenths of a millimeter range there is always a latent risk of rubbing against the rotating compressor wheel on the compressor housing.

In contrast, there is an axial thrust counteracting the radial compressor the exhaust gas turbine requires no pressure reduction in the separation gap, so that clear width is in the millimeter range and the need for sealing the separation gap in the area of the rear wall of the compressor wheel is eliminated. A radial compressor without such sealing elements is known from DE 195 48 852. It has a simple structure and is therefore inexpensive to manufacture. A risk of grazing of the rotating compressor wheel on the compressor housing does not exist. Yet also ensures the result of flow shear layers on the rear wall of the Frictional heat generated for the compressor wheel to heat the compressor wheel and thus for a reduction in its lifespan. A reduction solution the heat development in radial compressors without sealing elements in the The area of the rear wall of the compressor wheel is not known.

Presentation of the invention

The invention tries to avoid all these disadvantages. It is based on the task a method for operating a simply constructed, in the field of Rear wall of the compressor wheel without sealing elements in the separating gap of the compressor wheel as well as creating a compressor housing equipped with a radial compressor, which increases the service life of the radial compressor. In addition, a device be provided to carry out the method.

According to the invention, this is achieved in that in a method according to the preamble of claim 1, downstream of the leakage flow of the working medium a cooling medium is introduced into the separation gap and the cooling medium after heat exchange is finally discharged again. With one device According to the preamble of claim 5, at least in the compressor housing a penetrating in the area of the rear wall of the compressor wheel feed channel opening into the separating gap and aligned with the rear wall for a gaseous cooling medium and at least one discharge channel for the Cooling medium arranged.

Because of this method and the corresponding design of the radial compressor can the rear wall of the compressor wheel by means of the gaseous Cooling medium effectively cooled and thus increases the service life of the radial compressor become. Because the cooling of the hot leakage flow of the Sufficient working medium through the cooling medium, the penetration of the Leakage flow in the separation gap cannot be prevented. So that's enough the addition of relatively small amounts of the cooling medium, making it easy Feeder can be used.

By the pressure of the leakage flow of the working medium when it is supplied in the separation gap compared to the pressure of the main flow of the working medium is reduced, the cooling medium can be advantageous both with a higher than also with a lower pressure than the pressure of the main flow of the working medium be introduced into the separation gap. This is upstream of the back wall a sealing element of the compressor wheel is arranged in the separating gap. The exhaustion of the used cooling medium takes place through the compressor housing, either outwards or into the main flow of the working medium of the radial compressor, why the discharge channel for the cooling medium either into the ambient air or opens into the flow channel of the radial compressor. Surrender this way there are numerous possible variations for cooling the compressor wheel, which optimally adapts the radial compressor to that in use allow prevailing conditions.

The supply channel of the cooling medium is approximately parallel or approximately diagonal to the shaft of the compressor wheel or approximately tangential to the rear wall of the compressor wheel arranged in the separating gap. With a parallel for the alignment of the shaft, the cooling medium is supplied Impact cooling implemented. This can be particularly vulnerable areas of the rear wall of the compressor wheel can be cooled directly and effectively. In contrast, a radial Feeding the cooling medium realizes film cooling, with the help of which larger areas of the rear wall of the compressor wheel can also be cooled. The diagonal feed of the cooling medium combines the advantages of the previous ones described solutions with lower cooling effectiveness. To this To compensate for the disadvantage, at least one of the feed channels takes up into the separation gap protruding and aligned to the rear wall of the compressor wheel Tubes on. Each of the tubes opens particularly advantageously in the region of the radially outer wall part of the rear wall of the compressor wheel into the separation gap. Because the greatest temperature load can be recorded in this area thus an effective use of the cooling medium can be achieved.

It is also advantageous if a plurality of feed channels are arranged in the compressor housing are opposite the rear wall of the compressor wheel to the separation gap open annular space or at least a partial annular space formed in the compressor housing is and the feed channels with the annular space or at least two of each Feed channels are connected to a partial annulus. This allows a more even The supply of the cooling medium is reached over the circumference of the compressor wheel regardless of the number, design and arrangement of the feed channels.

Brief description of the drawing

In the drawing, several embodiments of the invention are based on the Radial compressor of an exhaust gas turbocharger shown.

Fig. 1

einen Teillängsschnitt durch den Radialverdichter, mit der erfindungsgemässen Zuführ- und Abführeinrichtung;

Fig. 2

eine Darstellung gemäss Fig. 1, jedoch in einem zweiten Ausführungsbeispiel;

Fig. 3

eine Darstellung gemäss Fig. 1, jedoch in einem dritten Ausführungsbeispiel;

Fig. 4

eine Darstellung gemäss Fig. 1, jedoch in einem nächsten Ausführungsbeispiel

Fig. 5

einen vergrösserten Ausschnitt der Figur 4, welcher insbesondere den ersten Spaltbereich des Trennspaltes in einem weiteren Ausführungsbeispiel darstellt.

Show it:

Fig. 1

a partial longitudinal section through the radial compressor, with the feed and discharge device according to the invention;

Fig. 2

a representation of Figure 1, but in a second embodiment.

Fig. 3

a representation of Figure 1, but in a third embodiment.

Fig. 4

a representation of FIG. 1, but in a next embodiment

Fig. 5

an enlarged section of Figure 4, which in particular shows the first gap area of the separation gap in a further embodiment.

Only the elements essential for understanding the invention are shown. The bearing section and the turbine side of the are not shown, for example Exhaust gas turbocharger. The direction of flow of the work equipment is indicated by arrows.

Way of carrying out the invention

The exhaust gas turbocharger shown only partially in FIG. 1 consists of a radial compressor 1 and an exhaust gas turbine, not shown, which in a Bearing housing 2 supported shaft 3 are interconnected. The radial compressor 1 has a machine axis 4 lying in the shaft 3. He is with equipped with a compressor housing 5 in which a compressor wheel 6 rotates with the shaft 3 is connected. The compressor wheel 6 has one with a variety of Blades 7 occupied hub 8. Between the hub 8 and the compressor housing 5, a flow channel 9 is formed. Downstream of the blades 7 connects to the flow channel 9 a radially arranged, bladed diffuser 10 on, which in turn opens into a spiral 11 of the radial compressor 1. The Compressor housing 5 mainly consists of an air inlet housing 12, one Air outlet housing 13, a diffuser plate 14 and an intermediate wall 15 to the bearing housing 2.

The hub 8 has a rear wall 16 on the turbine side and a fastening sleeve 17 for the shaft 3, the latter and the fastening sleeve 17 together are connected. The fastening sleeve 17 is of the intermediate wall 15 of the Compressor housing 5 added. Of course, another suitable one Compressor wheel-shaft connection can be selected. The use is also the same of a non-bladed diffuser possible.

Between the rotating compressor wheel 6 and the fixed partition 15 of the compressor housing 5 is an existing from different gap areas Separation gap 18 is formed. A first gap area 19 runs parallel to the machine axis 4 and is with both the outlet of the compressor wheel 6 and one predominantly radial in the area of the rear wall 16 of the compressor wheel 6 extending, second gap region 20 connected. The second gap area 20 goes into a formed between the fastening sleeve 17 and the intermediate wall 15 and also third, parallel to the machine axis 4 Gap area 21 over. The latter in turn communicates with one that is not shown Discharge. The rear wall 16 of the compressor wheel 6 has a radially inner one Wall part 22 and a radially outer wall part 23.

The second gap area 20 of the separation gap 18 opens parallel to the shaft 3 of the compressor wheel 6 a plurality of the intermediate wall 15 of the compressor housing 5 penetrating supply channels 24 for a gaseous cooling medium 25. The mouths lie in the region of the radially outer wall part 23 of the rear wall 16 of the compressor wheel 6, while also the intermediate wall 15 of the compressor housing 5 penetrating discharge channel 26 for the cooling medium 25 in the area of the radially inner wall part 22 is arranged.

When the exhaust gas turbocharger is operating, the compressor wheel 6 sucks as the working medium 27 ambient air, which acts as a main flow 28 via the flow channel 9 and the diffuser 10 arrives in the spiral 11, further compressed there and finally for charging a not shown, connected to the exhaust gas turbocharger Internal combustion engine is used. On their way from the flow channel 9 to the diffuser 10 acts on the main flow heated in the radial compressor 1 28 of the working medium 27 as the leakage flow 29 also the first gap area 19 and thus the separation gap 18. At the same time, however, via the feed channels 24 the gaseous cooling medium 25 with a higher pressure than that Pressure of the main flow 28 of the working medium 27 in the second gap area 20 of the separation gap 18 introduced. For example, air from not shown outlet of the charge air cooler of the internal combustion engine used become. Of course, the use of other cooling media is also one external supply of these cooling media possible.

The cooling medium 25 hits the rear wall 16 of the compressor wheel 6 and causes it an impact cooling in its particularly stressed, radially outer wall part 23. The cooling medium 25 is then distributed in the separation gap 18 and diluted the hot leakage flow 29. Most of the cooling medium 25 and Leakage flow 29 is then via the discharge channel 26 from the Separation gap 18 passed. Depending on the prevailing pressure conditions, too a certain part of the cooling medium 25 and the leakage flow 29 over the first gap area 19 introduced into the flow channel 9 of the radial compressor 1.

In a second exemplary embodiment, the supply channels 24 for the cooling medium open out 25 also parallel to the shaft 3 of the compressor wheel 6 in the radial outer wall part 23 of the rear wall 16 of the compressor wheel 6 in the separation gap 18. However, there is a between the feed channels 24 and the separation gap 18 the feed channels 24 interconnecting and open to the separation gap 18 Annulus 30 formed (Fig. 2). This can result in a relatively even application the rear wall 16 can be reached with the cooling medium 25. Naturally can alternatively to the annular space 30 also several partial annular spaces in the intermediate wall 15 of the compressor housing 5, which are each at least Connect two adjacent feed channels 24 to one another (not shown). The Discharge channel 26 is arranged in the diffuser plate 14 of the compressor housing 5, so that the cooling medium 25 almost completely via the flow channel 9 of the Radial compressor 1 is discharged. In operation, the leakage flow is 29 the cooling medium 25 is almost completely shut off. Because of the repatriation of the cooling medium 25 in the flow channel 9 also the volumetric efficiency improved.

According to a third exemplary embodiment, the feed channels 24 open diagonally to the shaft 3 of the compressor wheel 6 in the separation gap 18. In addition, the feed channels take 24 each projecting into the separation gap 18 and onto the radial one outer wall part 23 of the rear wall 16 of the compressor wheel 6 aligned Tube 31 on (Fig. 3). With the help of these tubes 31, the cooling medium 25 hits targeted to the areas of the rear wall 16 which have the greatest temperature load exhibit. The cooling medium 25 acts due to its diagonal introduction initially as impingement cooling. It can also move towards the first Apply a cooling film to the rear wall 16 of the gap area 19. The derivation of the Cooling medium 25 in turn takes place via the discharge channel 26. Of course, analog the second embodiment also a feedback of the cooling medium 25 in the flow channel 9 of the radial compressor 1 (not shown).

In a next embodiment, the feed channels 24 are the diffuser plate 14 arranged penetrating and open into the compressor wheel 6th facing area tangential to the rear wall 16 of the compressor wheel 6 in the Separation gap 18 (Fig. 4). The discharge channel 26 for the cooling medium 25 is in the Intermediate wall 15 of the compressor housing 5 is arranged. Through the tangential Introduction of the cooling medium 25 is a pure film cooling of the entire rear wall 16 of the compressor wheel 6 realized. The cooling medium 25 is discharged only through the discharge channel 26. Both the compressor thrust and the mechanical losses due to the rear wall 16 of the compressor wheel 6 The resulting friction is lower with this arrangement than with an axially parallel one Injection of the cooling medium 25. Of course, the diffuser plate 14 can its radially inner end can also be slotted. In this case, flow out the feed channels 24 into the slot of the diffuser plate 14, not shown.

In a further exemplary embodiment, the rear wall 16 of the compressor wheel is upstream 6 a sealing element 32 in the separation gap 18, i.e. in its first gap area 19, arranged (Fig. 5). With the help of these for all the previously described exemplary embodiments suitable solution it is possible to reduce the pressure of the remaining Leakage flow 29 to reduce so far that the pressure of the inflowing Cooling medium 25 advantageously even below that at the outlet of the compressor wheel 6 prevailing pressure of the working medium 27 may lie. That way even with relatively small amounts of the cooling medium 25 an effective cooling of the Compressor wheel 6 can be guaranteed.

LIST OF REFERENCE NUMBERS

1

centrifugal compressors

2

bearing housing

3

wave

4

machine axis

5

compressor housing

6

compressor

7

blade

8th

hub

9

flow channel

10

diffuser

11

spiral

12

Air intake housing

13

Air outlet housing

14

diffuser plate

15

partition

16

rear wall

17

mounting sleeve

18

separating gap

19

Gap area, first

20

Gap area, second

21

Gap area, third

22

Wall part, radially inner

23

Wall part, radially outer

24

feed

25

cooling medium

26

discharge channel

27

Working medium, ambient air

28

Main flow, from 27

29

Leakage flow, from 27

30

annulus

31

tube

32

sealing element

Claims (14)

1. Method of operating a centrifugal compressor, in which

   a) a working medium (27) is induced by a compressor impeller (6) arranged in a compressor casing (5) and equipped with a number of impeller vanes (7), is compressed and is led on to a consumption unit as a main flow (28),

   b) after the compression process which takes place between the impeller vanes (7), a leakage flow (29) of the working medium (27) branches off and this leakage flow (29) flows into a separating gap (18) formed between the compressor impeller (6) and the compressor casing (5),

   c) the separating gap (18) is not sealed against the penetration of the leakage flow (29) of the working medium (27) in the region of a rear wall (16) of the compressor impeller (6),
   characterized in that

   d) a cooling medium (25) is introduced into the separating gap (18) downstream of the leakage flow (29) of the working medium (27) and this cooling medium is finally removed again after the cooling process has taken place.
2. Method according to Claim 1, characterized in that the cooling medium (25) is introduced into the separating gap (18) at a pressure which is higher than the pressure of the main flow (28) of the working medium (27).
3. Method according to Claim 2, characterized in that the cooling medium (25) is introduced into the main flow (28) of the working medium (27) after the cooling process has taken place.
4. Method according to Claim 1, characterized in that the pressure of the leakage flow (29) of the working medium (27) is reduced, when it is supplied to the separating gap (18), relative to the pressure of the main flow (28) of the working medium (27).
5. Method according to Claim 4, characterized in that the cooling medium (25) is introduced into the separating gap (18) at a pressure which is lower than the pressure of the main flow (28) of the working medium (27) .
6. Centrifugal compressor having a compressor impeller (6), which is arranged on a shaft (3) and has a rear wall (16) extending mainly radially, having a compressor casing (5) enclosing the compressor impeller (6), having a flow duct (9) formed between the compressor impeller (6) and the compressor casing (5) for a working medium (27) of the centrifugal compressor (1) and having a separating gap (18), which is connected to the flow duct (9), between the compressor impeller (6) and the compressor casing (5), the separating gap (18) being configured without sealing elements in the region of the rear wall (16) of the compressor impeller (6), characterized in that at least one supply duct (24) for a gaseous cooling medium (25), said duct penetrating the compressor casing (5), opening into the separating gap (18) in the region of the rear wall (16) of the compressor impeller (6) and directed onto the rear wall (16), and at least one removal duct (26) for the cooling medium (25) are arranged in the compressor casing (5).
7. Centrifugal compressor according to Claim 6, characterized in that the supply duct (24) opens into the separating gap (18) at least approximately parallel to the shaft (3) of the compressor impeller (6).
8. Centrifugal compressor according to Claim 6, characterized in that the supply duct (24) opens into the separating gap (18) at least approximately diagonally to the shaft (3) of the compressor impeller (6).
9. Centrifugal compressor according to Claim 7 or 8, characterized in that a plurality of supply ducts (24) are arranged in the compressor casing (5), in that an annular space (30) which is open towards the separating gap (18), or at least a partial annular space, is formed opposite to the rear wall (16) of the compressor impeller (6) in the compressor casing (5) and in that the supply ducts (24) are connected to the annular space (30) ar at least two of the supply ducts (24) are connected to each partial annular space.
10. Centrifugal compressor according to Claim 8, characterized in that at least one of the supply ducts (24) accommodates a tube (31) protruding into the separating gap (18) and directed onto the rear wall (16) of the compressor impeller (6).
11. Centrifugal compressor according to Claim 10, characterized in that the rear wall (16) of the compressor impeller (6) has a radially inner wall part (22) and a radially outer wall part (23) and each tube (31) opens into the separating gap (18) in the region of the radially outer wall part (23).
12. Centrifugal compressor according to one of Claims 6 to 11, characterized in that the removal duct (26) opens into the flow duct (9) of the centrifugal compressor (1).
13. Centrifugal compressor according to Claim 6, characterized in that the supply duct (24) opens into the separating gap (18) at least approximately tangentially to the rear wall (16) of the compressor impeller (1).
14. Centrifugal compressor according to one of Claims 6 to 13, characterized in that a sealing element (32) is arranged in the separating gap (18) upstream of the rear wall (16) of the compressor impeller (6).

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