GB2603792A

GB2603792A - Air guide tube connection

Info

Publication number: GB2603792A
Application number: GB2102060.7A
Authority: GB
Inventors: A Evans Peter
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2021-02-15
Filing date: 2021-02-15
Publication date: 2022-08-17
Also published as: GB202102060D0

Abstract

A compressor for a gas turbine engine has a plurality of compressor disks, an air tube 103 located between two compressor disks 101, 102 and configured to receive air from a first air bleed, a carrier 104 connected to the two compressor disks and configured to support the air tube, and an air guide 105 configured to separate air from the air tube and air from a second air bleed. The air guide is connected to the compressor by the carrier. The carrier may be supported by cobs 106, 107 of the compressor disks. The air guide may have an axially or radially extending face which makes contact with the carrier. The air tube may have first and second flanges at which it is connected to the carrier and air guide. The compressor may form part of a gas turbine engine and the air bleeds may be supplied to a turbine and/or bearing of the engine.

Description

AIR GUIDE TUBE CONNECTION

Field of the disclosure

The present invention relates to a compressor for a gas turbine engine, and particularly a carrier for connecting an air guide tube to the compressor disk.

Background

A compressor in a gas turbine engine typically has several bleeds, where gas from the compressor gas flow path is removed and directed to other parts of the engine, such as a turbine or a bearing, to act as cooling air.

This is typically done by use of an air tube, which may be known as a vortex reducer tube.

These are typically elongate tubes with their longitudinal axis in the radial direction of the compressor. Thus, air is channelled from the compressor gas flow path, through the air tube radially inwards, and is then directed axially towards the parts which are to be cooled.

Conventionally, the air tube may be secured in the space between two compressor disks being held in place by an attachment on the cob (radially inner) part of the disk. These are machined directly onto the compressor disk cob, which adds weight and cost to the disk, and generates high stresses on the disk.

When multiple bleeds are used in an engine, an air guide tube may be used to separate the various air bleeds. An air guide tube may be secured to the shaft of the compressor, and be arranged to rotate with the shaft.

An improved configuration of compressor disk, air tube, carrier and air guide may be desirable.

Summary

In a first aspect the present disclosure provides a compressor for a gas turbine engine comprising a plurality of compressor disks; an air tube located between two compressor disks and configured to receive air from a first air bleed; a carrier connected to the two compressor disks and configured to support the air tube; and an air guide configured to separate air from the air tube and air from a second air bleed; wherein the air guide is connected to the compressor by the carrier.

The compressor disks may include respective cobs and the carrier may be connected to the compressor disks at the cobs of the compressor disks.

The carrier may be connected between respective faces of the cobs of the compressor disks which face each other at respective locations on the cobs which are adjacent a radially outward end of the cob in the radial direction of the compressor.

The carrier may be connected between respective faces of the cobs of the compressor disks which face each other at respective locations on the cobs which are adjacent a radially inward end of the cob in the radial direction of the compressor.

The carrier may be connected to respective protrusions on the respective compressor disks.

The air guide may comprise an air guide tube connection portion including a contact face configured to contact the carrier, wherein the contact face extends in the axial direction of the compressor.

The air guide may comprise an air guide tube connection portion including a contact face configured to contact the carrier, wherein the contact face extends in the radial direction of the compressor.

The carrier may comprise a first holding portion between a first of the two compressor disks and the air tube and a second holding portion between a second of the two compressor disks and the air tube.

The air tube may comprise a first flange configured to contact the carrier.

The first holding portion may be held between the first of the two compressor disks and the first flange of the air tube and the second holding portion may be held between the second of the two compressor disks and the first flange of the air tube.

The air tube may include a second flange positioned radially inward of the first flange in the radial direction of the compressor, and positioned such that a portion of the second flange of the air tube is adjacent a portion of the air guide tube.

In a second aspect the present disclosure provides a gas turbine engine comprising a compressor of the first aspect.

In the gas turbine engine, the first air bleed may be configured to supply cooling air to a first component, and the second air bleed may be configured to supply cooling air to a second component.

In the gas turbine engine, the first component may be a turbine and the second component may be a bearing.

The skilled person would appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive, any feature described here may be applied to any aspect and/or combined with any other feature described herein.

Brief description of the drawings

Embodiments will be more clearly understood from the following description, given by way of non-limitative example only, with reference to the following drawings in which: Figure 1 shows schematically a longitudinal cross-section through a ducted fan gas turbine engine; Figure 2 shows an isometric view of a typical single stage cooled turbine; Figure 3 shows a compressor according to the present disclosure; and Figure 4 shows a second arrangement of compressor according to the present disclosure.

Detailed description

Aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

With reference to Figure 1, a ducted fan gas turbine engine generally indicated at 10 has a principal and rotational axis X-X. The engine comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high-pressure compressor 14, combustion equipment 15, a high-pressure turbine 16, and intermediate pressure turbine 17, a low-pressure turbine 18 and a core engine exhaust nozzle 19. A nacelle 21 generally surrounds the engine 10 and defines the air intake 11, a bypass duct 22 and a bypass exhaust nozzle 23.

The gas turbine engine 10 works in a conventional manner so that air entering the air intake 11 is accelerated by the fan 12 to produce two air flows: a first air flow A into the intermediate pressure compressor 13 and a second air flow B which passes through the bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 13 compresses the air flow A directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.

The compressed air exhausted from the high-pressure compressor 14 is directed into the combustion equipment 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 16, 17, 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low-pressure turbines respectively drive the high and intermediate pressure compressors 14, 13 and the fan 12 by suitable interconnecting shafts.

Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines.

Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

The performance of gas turbine engines, whether measured in terms of efficiency or specific output, is improved by increasing the turbine gas temperature. It is therefore desirable to operate the turbines at the highest possible temperatures. For any engine cycle compression ratio or bypass ratio, increasing the turbine entry gas temperature produces more specific thrust (e.g. engine thrust per unit of air mass flow). However as turbine entry temperatures increase, the life of an un-cooled turbine falls, necessitating the development of better materials and the introduction of internal air cooling.

In modern engines, the high-pressure turbine gas temperatures are hotter than the melting point of the material of the blades and vanes, necessitating internal air cooling of these airfoil components. During its passage through the engine, the mean temperature of the gas stream decreases as power is extracted. Therefore, the need to cool the static and rotary parts of the engine structure decreases as the gas moves from the high-pressure stage(s), through the intermediate-pressure and low-pressure stages, and towards the exit nozzle.

Figure 2 shows an isometric view of a typical single stage cooled turbine in which there is a nozzle guide vane 30 in flow series with a turbine rotor 31. The nozzle guide vane includes an aerofoil 31 which extends radially between inner 33 and outer 34 platforms. The turbine rotor 31 includes a blade mounted to the peripheral edge of a rotating disk. The blade includes an aerofoil 35 which extends radially outwards from an inner platform 36. The radially outer end of the blade includes a shroud which sits within a seal segment 37. The seal segment is a stator component and attached to the engine casing. The arrows in Figure 2 indicate cooling flows.

Internal convection and external films are the prime methods of cooling the gas path components -aerofoils, platforms, shrouds and shroud segments etc. High-pressure turbine nozzle guide vanes (NGVs) consume the greatest amount of cooling air on high temperature engines. High-pressure blades typically use about half of the NGV flow. The intermediate-pressure and low-pressure stages downstream of the HP turbine use progressively less cooling air.

The high-pressure turbine aerofoils are cooled by using high pressure air from the compressor that has by-passed the combustor and is therefore relatively cool compared to the gas temperature. Typical cooling air temperatures are between 800 and 1000 K, while gas temperatures can be in excess of 2100 K. This removal of air is known as an air bleed.

The cooling air from the compressor that is used to cool the hot turbine components is not used fully to extract work from the turbine. Therefore, as extracting coolant flow has an adverse effect on the engine operating efficiency, it is important to use the cooling air effectively.

Ever increasing gas temperature levels combined with a drive towards flatter combustion radial profiles, in the interests of reduced combustor emissions, have resulted in an increase in local gas temperature experienced by the extremities of the blades and vanes, and the working gas annulus endwalls.

Unless otherwise stated, geometric references to axial, radial, circumferential, fore and aft, and longitudinal will be in relation to the principal axis of the engine (X-X, Figurel), with upstream and downstream, in relation to the main gas path flow direction. Chord relates to the separation between the leading edge and trailing edge of an aerofoil, and span is used in relation to the radial extent of the aerofoil. The stagger angle is the angle between the aerofoil chord line and principal axis of the engine.

In an arrangement, two air bleeds may be provided. For example, one bleed may be provided to cool a bearing which supports a shaft, and another may be provided to cool the turbine disks. However, it will be appreciated that the two air bleeds may cool other parts of the gas turbine engine, or that there may be a different number of air bleeds.

A gas turbine engine with such an arrangement may have a plurality of concentric shafts. A shaft may link the intermediate pressure turbine and the intermediate pressure compressor, and another shaft may link the high pressure turbine and the high pressure compressor. One of the air bleeds may originate from the high pressure compressor, and the other bleed may originate from the intermediate pressure compressor.

Each of the air bleeds may be extracted from the gas flow path through the compressor by means of an air tube. This may be an elongate tube with its longitudinal axis oriented in the radial direction of the frame of reference of the engine. Such a tube may be known as a secondary air tube, vortex tube, or a vortex reducer tube. The term "secondary air" is used because it is extracted from the main gas path air which flows through the engine (which can be considered to be the "primary air').

After passing through the air tubes, both air bleeds may be channelled axially through the engine towards the turbine. It is desirable to separate the two air bleeds to prevent them mixing together. This may be done by means of an air guide, which extends axially from just upstream of the second bleed to just downstream of the high pressure turbine. The air guide may be positioned between an inner wall of the second shaft and an outer wall of the first shaft. In other words, the air guide starts at a location which is axially between the first bleed and the second bleed, thus separating the two bleeds from each other. The air guide may comprise an air guide tube which is secured to the first shaft and arranged to rotate therewith In an arrangement, and as shown in Figure 3, an air tube 103 is located between two compressor disks 101 and 102. The compressor disks are part of a known disk-type compressor, in which a plurality of compressor disks are located radially inward of the gas flow path, and the compressor blades are mounted at a radially outward portion of each compressor disk. The space between a pair of compressor disks is known as an interdisk space.

The compressor disks may each comprise a radially outward portion where the compressor blades are mounted, a radially inward portion, known as a disk cob 106, 107, and an elongate section joining the radially inward and radially outward sections. The elongate section may be known as a diaphragm. The disk cob is a part which has a larger cross-sectional area than the other parts of the disk when viewed in a radial cross-section. In other words, and as shown in Figures 3 and 4, the disk is thicker in the axial direction at the cobs than in the rest of the disk. This may reduce stresses at the radially outer portions of the disk. The disk cob may also be known as a hub.

The compressor disks may be joined to adjacent disks at, or near, the radially outward portion, with the disk at one axial end of the compressor joined to the shaft. Thus, the disk cobs are not directly joined to each other, and there is space between the disk cobs and the shaft. The air guide tube may be provided in this space.

The air tube 103 is configured to carry air from an air bleed radially inward towards the shafts. In other words, the air tube 103 channels air from the gas flow path. The air is then directed to the locations where it is used as cooling air, as set out above.

The air tube 103 may have a first flange 112 or shoulder on its outer surface which interfaces with a carrier 104. The configuration of the carrier 104 will be set out in more detail below.

The air tube 103 may also have a second flange 113 or shoulder on its outer surface which may be in contact with a portion of the air guide tube 105. This will be set out in more detail in the description of the air guide tube 105 below.

It will be understood that a plurality of air tubes may be located in a single interdisk space, the air tubes being spaced circumferentially around the interdisk space. This may allow bleed air to be extracted from multiple locations around the disk, and may prevent imbalanced forces being exerted on the disk, which may occur if gas path air is extracted from a single circumferential location.

The cobs of the compressor disks 101, 102 between which the air tube 103 is located may each comprise a protrusion 108, 109, which protrudes into the interdisk space. As shown in Figure 3, the protrusions on adjacent disks may be at the same radial position such that they are aligned with each other. This provides a location for the mounting of the carrier 104 and the air tube 103.

As shown in Figure 3, the protrusions 108 and 109, may be located at the radially inward end of the interdisk face of the disk cobs 106, 107. That is, the protrusions are on the face of the disk which faces the other disk. In other words, the interdisk face is the face which is oriented towards the interdisk space, in a plane parallel to the radial direction and normal to the axial direction.

A carrier 104 is provided to support the air tube 103 and to prevent unwanted movement of the air tube 103. The carrier 104 may be secured between the two compressor disks 101, 102 between the protrusions 108, 109 on the two disk cobs 106,107. This may retain the carrier 104 in position and prevent movement of the carrier 104 in the axial direction.

The carrier 104 may also have a first holding portion 115 and a second holding portion 118.

The first holding portion 115 may be located between, and in contact with, one of the cobs 106 and the air tube 103. The second holding portion 118 may be located between, and in contact with, the other cob 107 and the air tube 103. This retains both the carrier 104 and the air tube 103 in position. Because the carrier 104 cannot move in the axial direction (as set out above), the air tube 103 is prevented from moving in the axial direction. The part of the air tube 103 with which the first and second holding portions are in contact may be the first flange 112.

It will be appreciated that the first holding portion 115 and second holding portion 118 may be joined together or integrally formed, and may extend around part of the circumference of the air tube 103, or around all of the circumference of the air tube.

As shown in Figure 3, the protrusions 108,109 on the cobs 106,107 and the first flange 112 on the air tube 103 are either side of (in the axial direction), and in contact with, the carrier 104. This may prevent movement of the carrier 104 in the radial direction The carrier 104 and the air tube 103 may be held in position by virtue of the two compressor disks 101, 102 being rigidly connected together and the carrier being between the two compressor disks. This means that when carrier 104 is in position, it is secured between the disks 101,102 and the air tube 103, and prevents the air tube 103 from moving relative to the disks. It will also be appreciated that the carrier 104 and the air tube could be fixed together with bolts, rivets or any other suitable fixings.

The carrier 104 may comprise a carrier connection portion 116, to which the air guide tube is connected. This will be explained below in the description of the air guide tube 105. The carrier 104 may further comprise an elongate portion 114 which extends from the holding portion to the carrier connection portion. It will be appreciated that the length of the elongate portion 114 may be chosen as a function of the radial position of the protrusions 108, 109 of the cobs to which they are attached.

The carrier 104 may be made of a flexible material such that it can flex in response to differences in axial thermal expansion between the compressor disks and the air guide tube.

The air guide tube 105 is provided in a position radially inward of the compressor disks. The air guide tube 105 is configured to separate air from a first bleed from a second bleed. That is, the air guide tube separates the air which passes through the air tube 103 from air which originates from another bleed further upstream.

The air guide tube 105 may have a tubular portion 117 which is substantially concentric with the shaft, which extends to the location where the bleed air is used for cooling. The air guide tube 105 may also have an air guide tube connection portion 110 which is joined to the carrier 104 at the carrier connection portion 116. As shown in Figure 3, the face of the air guide tube connection portion 110 which is in contact with the carrier 104 may extend in the radial direction. Thus, in this configuration, the surfaces of the air guide tube connection portion 110 and the carrier connection portion 116 which are in contact with each other both extend radially and can be attached (i.e. connected) together. This attachment means that the air guide tube 105 is connected to the compressor. The attachment may be, for example, a bolt, a rivet, or any other suitable fastening. It will be appreciated that the bolt or rivet may be inserted in the axial direction in the configuration shown in Figure 3.

A portion of the air guide tube 105 may also be adjacent to or in contact with the second flange 113 of the air tube 103. As shown in Figure 3, this may be the air guide tube connection portion 110. This may provide additional support to the air tube 103, for example preventing it from moving inward radially. It will be appreciated that the other (i.e. radially outward) end of the air tube 103 may be secured by any known arrangement. It will also be appreciated that a part of the air guide tube 105 other than the air guide tube connection portion could be in contact with a part of the air tube 103, providing support in an equivalent manner.

The carrier of the present disclosure allows the load from the air tube and of the air guide tube to be spread over two adjacent disks, compared to known arrangements in which the air tube may only be secured to one disk.

Further, known arrangements require a large additional portion (which may be known as a "scallop") to be machined into the disk to support the air guide tube. With the arrangements of the present disclosure, this additional portion is not required. Rather, a small protrusion is provided on the disk cobs, which simplifies manufacture. This may also result in lower disk weight and reduced stresses on the disks.

In an alternative arrangement shown in Figure 4, the protrusions 108 and 109, may be located at the radially outward end of the interdisk face of the disk cobs 106 and 107. In this arrangement, as in the arrangement shown in Figure 3, the carrier 104 is positioned between the protrusions on the disk cobs and the first flange 112 of the air tube 103.

In the arrangement of Figure 4, the face of the air guide tube connection portion 110 which is in contact with the carrier 104 extends in the axial direction (rather than in the radial direction, as in the arrangement of Figure 3). In this configuration, the surfaces of the air guide tube connection portion 110 and the carrier connection portion 116 which are in contact with each other both extend axially and can be attached (i.e. connected) together. This arrangement means that the air guide tube 105 is connected to the compressor. The attachment may be by means of a sliding piston ring seal, as shown in Figure 4, or may be any suitable alternative fastening such as, for example, a bolt or a rivet. It will be appreciated that a bolt or rivet would be inserted in the radial direction in the configuration shown in Figure 4.

As set out above, and as shown in Figure 3, the protrusions 108,109, may be located at or adjacent the radially inward end of the interdisk face of the disk cobs 106, 107. Alternatively, as set out above and as shown in Figure 4, the protrusions may be located at or adjacent the radially outward end of the axial face of the disk cobs. However, it will be appreciated that the protrusions may also be located at any other location on the disk cob between the two extremes shown in Figures 3 and 4. It will also be appreciated that the protrusions on the two discs do not have to be at the same radial position, and could be located at different radial positions on the axial faces of the disk cobs. This may be dictated by the stresses on the disks. That is, the location may be chosen to minimise stresses on the disks in a particular part of the disks. Further, the protrusions need not be located on the cobs, and may be located on a portion of the disk which is radially outward of the cobs (such as the diaphragm).

In Figure 3, the air guide tube connection portion 110 extends in the radial direction. However, it will be appreciated that in this arrangement, the air guide tube connection portion 110 could extend in the axial direction (as in the arrangement of Figure 4). Likewise, in the arrangement of Figure 4, the air guide tube connection portion 110 could extend in the radial direction (as in the arrangement of Figure 3).

It will be noted that the locations of the two bleeds in the arrangements set out above are the intermediate pressure compressor and the high pressure compressor. However, it will be appreciated that the two bleeds could be from any suitable location in the gas flow path, or that more than two bleeds could be used.

It will be understood that the invention is not limited to the embodiments above described and that various modifications and improvements can be made without departing from the concepts described herein.

Claims

CLAIMS1. A compressor for a gas turbine engine (10), the compressor comprising: a plurality of compressor disks; an air tube (103) located between two compressor disks (101,102) and configured to receive air from a first air bleed; a carrier (104) connected to the two compressor disks and configured to support the air tube; and an air guide (105) configured to separate air from the air tube and air from a second air bleed; wherein the air guide is connected to the compressor by the carrier.
2. The compressor of claim 1, wherein the compressor disks include respective cobs (106,107) and the carrier is connected to the compressor disks (101,102) at the cobs (106,107) of the compressor disks.
3. The compressor of claim 2, wherein the carrier (104) is connected between respective faces of the cobs of the compressor disks which face each other at respective locations on the cobs which are adjacent a radially outward end of the cob in the radial direction of the compressor.
4. The compressor of claim 2, wherein the carrier (104) is connected between respective faces of the cobs of the compressor disks which face each other at respective locations on the cobs which are adjacent a radially inward end of the cob in the radial direction of the compressor.
5. The compressor of any preceding claim, wherein the carrier is connected to respective protrusions (108,109) on the respective compressor disks (101, 102).
6. The compressor of any preceding claim, wherein the air guide (105) comprises an air guide tube connection portion (110) including a contact face configured to contact the carrier (104), wherein the contact face extends in the axial direction of the compressor.
7. The compressor of claim 6, wherein the air guide (105) comprises an air guide tube connection portion (110) including a contact face configured to contact the carrier (104), wherein the contact face extends in the radial direction of the compressor.
8. The compressor of any preceding claim, wherein the carrier (104) comprises a first holding portion (115) between a first of the two compressor disks (101) and the air tube (103) and a second holding portion (118) between a second of the two compressor disks (102) and the air tube (103).
9. The compressor of any preceding claim, wherein the air tube (103) comprises a first flange (112) configured to contact the carrier (104).
10. The compressor of claim 9 when dependent on claim 8, wherein the first holding portion (115) is held between the first of the two compressor disks (101) and the first flange (112) of the air tube (103) and the second holding portion (118) is held between the second of the two compressor disks (102) and the first flange (112) of the air tube (103).
11. The compressor of any one of claims 8, 9 and 10, wherein the air tube (103) includes a second flange (113) positioned radially inward of the first flange (112) in the radial direction of the compressor, and positioned such that a portion of the second flange of the air tube is in adjacent a portion of the air guide tube (105).
12. A gas turbine engine (10) comprising the compressor according to any preceding claim.
13. The gas turbine engine of claim 12, wherein the first air bleed is configured to supply cooling air to a first component, and the second air bleed is configured to supply cooling air to a second component.
14. The gas turbine engine of claim 13, wherein the first component is a turbine.
15. The gas turbine engine of claim 13 or 14, wherein the second component is a 25 bearing.