Sealing of variable guide vanes

Abstract

The guiding device of a turbine has guide vanes which are rotatably mounted in the turbine housing. A sealing sleeve is arranged between the turbine housing and the guide vane stem. The additional axial compression spring ensures that the sealing sleeve is continuously pressed onto the guide vane mating contour, and that the axial gap and also the leakage flow are prevented as a result.

Description

TECHNICAL FIELD

The disclosure relates to the field of turbomachines. It refers to the guiding device of a turbomachine, for example of the turbine of an exhaust gas turbocharger, with rotatably mounted, variable guide vanes, and also to an exhaust gas turbocharger with a turbine with such a guiding device.

BACKGROUND INFORMATION

Exhaust gas turbines, for example of turbochargers, are used in conjunction with an internal combustion engine. The exhaust gas from the internal combustion engine in this case is used as a propulsive means for driving the turbine wheel. The turbine wheel is connected by means of a shaft to the compressor wheel, by which the inlet air, which is for feeding to the internal combustion engine, is compressed. In order to meet the variable operating conditions of modern engines, variable turbine geometries (VTG) can be used in exhaust gas turbines instead of fixed flow cascades (nozzle ring). In this case, the angle of incidence of turbine guide vanes can be adapted to the respective operating point by means of an adjusting mechanism.

A VTG device as a rule comprises a plurality of guide vanes which are mounted in a bearing housing, and an adjusting mechanism for rotating the guide vanes. VTG devices are described for example in EP 0 226 444 or DE 43 09 636.

The guide vanes of an exhaust gas turbine, which during operation are very intensely heated, must be installed in the bearing bushes with adequate radial clearance so that in the hot operating state they do not seize in the bearing bushes. Due to the radial clearance between the bearing bushes s and the guide vane stem, a small amount of hot gases always escapes from the region around the guide vane into the environment. With increasing bearing clearance, this leakage flow through the bearing bush increases. This effect leads to a loss of turbine efficiency, and also to an increased noise development, as a rule in the form of a whistling which becomes more and more intense.

SUMMARY

An adjusting device for a guiding device of a turbomachine is disclosed to the effect that despite the operation-related clearance between the moving parts of the guiding device, no leakage flow, or only a slight leakage flow, escapes through the bearings of the guide vanes.

According to the disclosure, this can be realized by a sealing sleeve (also referred to as a sealing diaphragm or sealing element) being arranged between the housing, in which the guide vanes are rotatably mounted, and the respective guide vanes.

The sealing sleeve in this case is optionally axially guided through the cylindrical outside or inside diameter of the guide bush which is used for support of the guide vane stem. A radial residual gap, which possibly remains between the sealing sleeve and the guide bush, is tolerated to a minimum clearance so that only a small residual mass flow escapes through the fit.

According to the disclosure, an additional axial compression spring can ensure that the sealing sleeve is continuously pressed onto the guide vane mating contour, and that the axial gap and also the leakage flow are prevented as a result.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is subsequently explained in more detail with reference to the figures. In this connection, in the drawing:

FIG. 1 shows a section through a part of an exhaust gas turbocharger, on the turbine side, with a guiding device with variable guide vanes.

FIG. 2 shows a section through a part of the guiding device according to FIG. 1, with an unsealed guide vane, and

FIG. 3 shows a section through the arrangement according to FIG. 2, with a guide vane which is sealed according to the disclosure.

DETAILED DESCRIPTION

The sealing of variable guide vanes, according to the disclosure, can be used on all turbomachines with guiding devices, for example exhaust gas turbochargers, power turbines, gas turbines or compressors, with variable guide vanes.

FIG. 1 shows the turbine side of an exhaust gas turbocharger with a turbine wheel 10 which is arranged in a turbine housing. The turbine wheel comprises a hub 11 and rotor blades 12 which are fastened upon it or manufactured integrally with the hub. The turbine housing comprises a gas inlet housing 21, a bearing housing 22, and also a partition 23 in the back of the hub of the turbine wheel. The partition serves for the thermal shielding of the bearing housing from the hot turbine wheel. It can alternatively also be formed by parts of the bearing housing or the gas inlet housing.

A guiding device is arranged in the flow passage which leads to the rotor blades. The guiding device comprises variable guide vanes 31 for controlling the exhaust gas flow 70. The guide vanes are rotatably mounted by a guide vane stem 32 in the turbine housing. The guide vanes 31 can be rotated via an adjusting lever 41 around the axis of the guide 35 vane stem 32. The adjusting lever is driven via an adjusting ring 42 in order to position the guide vanes 31 in a defined set angle.

The guide vane stem 32 is mounted in the turbine housing with a small clearance. The turbine housing, in the region of the bearing of the guide vane stem, advantageously comprises guide bushes 50 which have a high abrasion resistance and a good slidability. The guide bushes are pressed into the turbine housing and fixed.

As is apparent from FIG. 2 and FIG. 3, the guide vane stem has a bearing 33 which is mounted inside the guide bush 50 in a sliding manner. In addition, the guide vane stem can have a further bearing, e.g, on the end opposite the guide vane. The axial support of the guide vanes as a rule is carried out via one or two axial stops or via the end of the guide vane stem on the one side and via the guide vane profile on the other side. The axial locking of the guide vane can be ensured by means of compression springs.

The guide vanes, which during operation are very intensely heated, must be installed with adequate radial clearance in the bearing bushes so that in the hot operating state they do not seize in the bearing bushes. Both in the region of the bearings 33 and also radially outside the mating contour 34 of the guide vanes, small gaps, through which leakage flows can flow out, ensue as a result.

In order to be able to avoid as far as possible leakage-related losses of turbine efficiency, and to prevent penetration of hot exhaust gases into the bearings of the turbocharger, which are to be kept as cool as possible, sealing air can be introduced into the cavities 61 in the back of the partition. This compressed air, which is significantly colder in comparison to the exhaust gases, can be externally supplied, or, as shown in FIG. 1, branched off at the compressor outlet and guided via a sealing air passage 62 to the turbine side. The sealing air is guided into the cavities 61 and distributed along the entire circumference of the turbine. The sealing air can have an at least slightly higher pressure than the exhaust gas flow 70.

In the case of conventional guiding devices according to FIG. 2, hot gas, or, if present, sealing air, can escape from the cavities 61 into the environment due to the radial clearance between the guide bush 50 and the bearing 33 of the guide vane stem. A leakage flow 63 results.

This leakage flow is prevented according to the disclsoure by a sealing sleeve 80 being slipped onto the guide bush 50 according to FIG. 3. The sealing sleeve according to the disclosure is advantageously manufactured, and can be cast, turned or milled, from a heat-resistant steel. Depending upon the axial length of the axial gap which is to be bridged by the sealing sleeve, the sealing sleeve can be formed axially longer and more tubular, or else shorter and more annular. The sealing sleeve has a cylindrical collar, a radially projecting, at least partially encompassing collar with an axial stop. The sealing sleeve 80, in the exemplary embodiment which is shown, is supported by the cylindrical outside diameter of the guide bush 50. A possible radial gap between the sealing sleeve 80 and the guide bush 50 is tolerated to a minimum clearance. This radial clearance between parts which, during operation, do not move or hardly move in relation to each other, can be kept significantly smaller than the clearance between the bearing 33 of the guide vane stem and the guide bush. Therefore, only a small residual mass flow, if any at all, escapes through the fit. The additional axial compression spring 90 ensures that the sealing sleeve is continuously pressed onto the guide vane mating contour 34 and that the axial gap and also the leakage flow are prevented as a result. The compression spring 90 is clamped between an axial stop on the turbine housing 22 and the axial stop of the cylindrical collar of the sealing sleeve 80. The compression spring 90 can additionally also undertake the axial securing of the guide vane by the guide vane profile being pressed by the compression spring against the opposite wall of the flow passage or against another axial stop on the turbine housing.

In a further exemplary embodiment, which is not shown, the sealing sleeve can also be directly slipped onto a part of the turbine housing, for example if the guide bush of the guide vane bearing is not arranged in an accessible manner, or is completely absent. In this case, the sealing sleeve would be supported by a cylindrical outside diameter of a housing component. The sealing sleeve can alternatively also be radially guided inside the guide bush or inside a cylindrical recess of the turbine housing.

The sealing sleeve according to the disclosure, therefore, prevents discharging of air or gases through the bearing of the guide vanes in exhaust gas turbines with or without sealing air supply, or in any other turbomachine with rotatably mounted, variable guide vanes.

It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.

LIST OF DESIGNATIONS

10 Turbine wheel

11 Hub

12 Rotor blades

13 Shaft

21 Gas inlet housing

22 Bearing housing

23 Partition

31 Guide vane

32 Guide vane stem

33 Bearing

34 Mating contour

41 Adjusting lever

42 Adjusting ring, adjusting element

50 Guide bush

60 Sealing air flow

61 Cavity

62 Sealing air passage

63 Leakage

70 Hot gas flow

80 Sealing sleeve

90 Compression spring

Claims

1. A guiding device, comprising at least one guide vane with a guide vane stem which is rotatably mounted in a housing, and a sealing sleeve being arranged between the housing and the guide vane stem for bridging an axial gap.

2. The guiding device as claimed in claim 1, wherein the sealing sleeve has a radially projecting collar with an axial stop.

3. The guiding device as claimed in claim 1, wherein the sealing sleeve is pressed against a mating contour of the guide vane by means of a compression spring.

4. The guiding device as claimed in claim 3, wherein the sealing sleeve has a radially projecting collar with an axial stop.

5. The guiding device as claimed in claim 1, wherein the housing comprises a guide bush for supporting the guide vane stem, and the sealing sleeve bridges a gap between the guide bush and the guide vane stem.

6. A turbomachine with a guiding device, which comprises a guide vane with a guide vane stem which is rotatably mounted in a housing, and a sealing sleeve which is arranged between the housing and the guide vane stem for bridging an axial gap.

7. The turbomachine as claimed in claim 6, wherein the sealing sleeve has a radially projecting collar with an axial stop.

8. The turbomachine as claimed in claim 6, wherein the sealing sleeve is pressed against a mating contour of the guide vane by means of a compression spring.

9. The turbomachine as claimed in claim 8, wherein the sealing sleeve has a radially projecting collar with an axial stop.

10. The turbomachine as claimed in claim 6, wherein the housing comprises a guide bush for supporting the guide vane stem, and the sealing sleeve bridges a gap between the guide bush and the guide vane stem.

11. An exhaust gas turbocharger with a guiding device, which comprises at least one guide vane with a guide vane stem which is rotatably mounted in a housing, and a sealing sleeve which is arranged between the housing and the guide vane stem for bridging an axial gap.

12. The exhaust gas turbocharger as claimed in claim 11, wherein the sealing sleeve has a radially projecting collar with an axial stop.

13. The exhaust gas turbocharger as claimed in claim 11, wherein the sealing sleeve is pressed against a mating contour of the guide vane by means of a compression spring.

14. The exhaust gas turbocharger as claimed in claim 13, wherein the sealing sleeve has a radially projecting collar with an axial stop.

15. The exhaust gas turbocharger as claimed in claim 11, wherein the housing comprises a guide bush for supporting the guide vane stem, and the sealing sleeve bridges a gap between the guide bush and the guide vane stem.

16. The guiding device as claimed in claim 4, wherein the housing comprises a guide bush for supporting the guide vane stem, and the sealing sleeve bridges a gap between the guide bush and the guide vane stem.

17. The turbomachine as claimed in claim 9, wherein the housing comprises a guide bush for supporting the guide vane stem, and the sealing sleeve bridges a gap between the guide bush and the guide vane stem.

18. The exhaust gas turbocharger as claimed in claim 14, wherein the housing comprises a guide bush for supporting the guide vane stem, and the sealing sleeve bridges a gap between the guide bush and the guide vane stem.