GB2415017A

GB2415017A - Heat shield for attachment to a casing of a gas turbine engine

Info

Publication number: GB2415017A
Application number: GB0412699A
Authority: GB
Inventors: Gerald Roderick Macgregor
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2004-06-08
Filing date: 2004-06-08
Publication date: 2005-12-14
Also published as: GB0412699D0

Abstract

A casing arrangement for a gas turbine engine (10 figure 1) comprises a casing 36, a heat shield 38 and attaching means 40. The attaching means 40 may comprise bolts, which can be undone to allow the heat shield 38 to be removed from the casing 36. The bolts 40 may also be used to attach further components, such as stator blades 34, to the casing 36. The heat shield 38 may include a pair of parallel flanges 42 which are joined together by connecting members (44 figure 4) through which the bolts 40 may pass. The connecting members (44 figure 4) may be arranged to define gaps (46 figure 4) through which fluid may flow. The casing arrangement may be used to extend around rotary components in a high pressure compressor (14 figure 1) of a gas turbine engine (10 figure 1).

Description

Casing Arrangement The present invention relates to casing arrangements.

More particularly, but not exclusively, casing arrangements suitable for use around rotary components in a gas turbine engine.

The casing of rotary components, for instance compressors, in gas turbine engines often incorporate heat shields. In current casing arrangements the heat shield is an integral part of the casing member. There are several problems with manufacturing such casing members. The component is complex to manufacture and thus costly. Also the manufacture of complex components requires a lot of machining and often results in material being wasted.

According to one aspect of the invention there is a casing arrangement comprising a casing and a heat shield which is removably attached to the casing.

The casing arrangement may be suitable for extending round a rotary component of an engine such as a gas turbine engine. The rotary component may be a compressor e.g. a high pressure compressor.

The heat shield may comprise a flange, preferably a plurality of flanges. In the preferred embodiment the heat shield comprises two flanges. The flanges may be arranged parallel to each other.

Preferably the casing arrangement comprises a connecting member connecting the flanges together. The casing arrangement may comprise a plurality of connecting members each connecting the flanges together. The connecting members may be spaced from each other so as to define gaps therebetween which allow fluid to flow through.

In the case of a high pressure compressor, this fluid may be air flowing out of the compressor.

The casing may have an annular cross section. The casing may comprise a plurality of casing sections.

The heat shield may be removably attached to the casing so that the flanges extend outward from the casing, preferably, radially outward from the casing.

The, or each, flange of the heat shield may extend substantially wholly around the casing or they may extend only part way round. Alternatively the, or each, flange may comprise a plurality of flange sections which can be arranged around the casing.

The casing arrangement may further comprise attaching means for removably attaching the heat shield to the casing. The attaching means may be in the form of a plurality of bolts, for example, stop bolts. Where the heat shield has connecting members between flanges, the attaching means may attach the heat shield to the casing at the connecting members. The attaching means may attach further components to the inside of the casing. Where the casing arrangement is used in a gas turbine engine the attaching means may also be used to attach stator vanes to the casing of the compressor.

According to another aspect of this invention, there is provided a rotary assembly comprising a rotary component of an angle, and a casing arrangement as described above extending around the rotary component. The rotary component may comprise at least a part of a compressor.

The compressor may comprise a high pressure compressor.

The rotary assembly may comprise stator members mounted on the casing arrangement. The stator members may extend radially outwardly from the casing arrangement.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a sectional side view of the upper half of a gas turbine engine; Figure 2 shows a circumferential sectional view of a high pressure compressor in a gas turbine engine; Figure 3 shows a circumferential sectional view of a casing arrangement of a high pressure compressor; Figure 4 shows a perspective view of part of a heat shield for use with the casing arrangement shown in Fig 3; and Figure 5 shows a perspective view of part of a casing for use with the heat shield shown in Fig 4.

Referring to figure 1, a gas turbine engine is generally indicated at 10 and comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high pressure compressor 14, a combustor 15, a turbine arrangement comprising a high pressure turbine 16, an intermediate pressure turbine 17 and a low pressure turbine 18, and an exhaust nozzle 19.

The gas turbine engine 10 operates in a conventional manner so that air entering the intake 11 is accelerated by the fan 12 which produces two air flows: a first air flow into the intermediate pressure compressor 13 and a second air flow which provides propulsive thrust. The intermediate pressure compressor 13 compresses the air flow 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 combustor 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 and 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high intermediate and low pressure turbines 16, 17 and 18 respectively drive the high and intermediate pressure compressors, 14 and 13 and the fan 12 by suitable interconnecting shafts.

Referring to figure 2, the high pressure compressor 14 is a multi-stage unit wherein each stage comprises a row of rotating blades 32 followed by a row of stator vanes 34. A casing arrangement 35 extends around the high pressure compressor 14.

The rotating blades 32 and stator vanes 34 alternately accelerate and decelerate the air until the required pressure is obtained. During operation the rotating blades 32 are turned at high speed by the high pressure turbine 16. The rotating blades 32 continually induce air into the high pressure compressor 14. As the air passes through the rotating blades 32 it is accelerated, resulting in an increase of the kinetic energy of the air. After passing through the rotating blades 32 the accelerated air is swept onto the subsequent row of stator vanes 34. The stator vanes 34 decelerate the air, translating the increase in kinetic energy, imparted by the rotating blades 32, into an increase in pressure. This process of acceleration and deceleration occurs in each stage of the high pressure compressor 14. Each stage results in a small increase of pressure. A large pressure increase can be built up over a series of successive stages.

As the air passes through the high pressure compressor 14 it is deflected by the rotating blades 32. This results in an increase of the velocity component normal to the direction of axial flow through the high pressure compressor 14. The stator vanes 34 are shaped and positioned so that they correct the deflection of the incident air and present it at the correct angle for the next stage of rotating blades 32.

The casing arrangement 35 is assembled around the rotating blades 32 of the high pressure compressor 14. The casing arrangement 35 may comprise a plurality of cylindrical portions which can be attached together axially of each other. In one embodiment, there may be one portion for each stage of the compressor. In another embodiment the casing arrangement 35 may be in two or more longitudinally split casings which can be attached together around the other components.

In the embodiment shown, the stator vanes 34 are attached to the casing arrangement 35 to prevent unwanted movement during operation of the high pressure compressor 14.

Referring to figure 3, there is shown an embodiment of the present invention wherein the casing arrangement 35 comprises an annular casing 36 and an annular heat shield 38 which are removably attached to each other by attaching means in the form of bolts 40, such as stop bolts.

The bolts 40 are used to removably attach the heat shield 38 to the casing 36 may also be used to attach the stator vanes 34 to the casing 36. A benefit of using the bolts 40 is that they do not significantly increase the weight or reduce the strength of the casing arrangement.

Figure 4 shows a perspective view of a part of the heat shield 38. In this embodiment the heat shield 38 comprises two parallel flanges 42, which extend in an annular manner around the casing 36. When attached to the casing 36 the flanges extend radially outwardly therefrom.

The heat shield 38 also comprises a plurality of connecting members 44 which are provided to connect the flanges 42 to each other, and arranged at intervals around the inner circumference of the flanges 42. The connecting members 44 define apertures 46 which are suitable for use with the attaching means 40.

The flanges 42 act so as to control the flow of air bled from the high pressure compressor 14, for use elsewhere in the engine, as would be understood by persons skilled in the art. As a result of passing through several stages of compression this bled air will have increased in temperature. The flanges 42 prevent a transfer of heat from this air to the region outside the heat shield 38, thus preventing any undesirable heating of components around the outside of the compressor casing 36.

In this particular embodiment there are a plurality of connecting members 44, which are arranged so as to define gaps 46 through which air from the high pressure compressor 14 can flow.

In this embodiment the connecting members 44 define apertures 48 which are suitable for use with the bolts 40.

The connecting members are located to correspond to the positions of corresponding web portions extending across the attaching means 40 on the casing 36.

Figure 5 shows a perspective view of part of the casing 36 which can be removably attached to the heat shield 38. The casing 36 comprises a main portion 49 and an annular flange member 50 extending radially outwardly from the main portion 49. The annular flange member 50 define a plurality of equal spaced aperture 51 for receiving bolts to secure the casing arrangement 35 to adjacent components of the engine. The main portion 49 defines a plurality of bleed aperture 52 through which compressed air in the compressor can pass. The bleed apertures 52 are separated from each other by web portion 54. Some of the web portions 54 define bolt blades 56 to receive the same bolts 40 that extend through the apertures 48 in the heat shield 38. Thus, the heat shield 38 is secured to the casing 30 by a plurality of bolts 40 which extend through the apertures 48 and the bolt holes 56.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims 1. A casing arrangement comprising a casing, a heat shield and

attaching means for removably attaching the head shield to the casing.
2. A casing arrangement as claimed in claim 1 wherein the attaching means comprise bolts.
3. A casing arrangement as claimed in claim 1 or 2 wherein the attaching means used to removably attach the heat shield component to the casing can be used to attach at least one further component to the casing.
4. A casing arrangement as claimed in any preceding claim wherein the casing member has an annular cross section.
5. A casing arrangement as claimed in any preceding claim wherein the casing comprises a plurality of casing sections which can be arranged together to define an annular casing member.
6. A casing arrangement as claimed in any preceding claim wherein the heat shield comprises at least one flange.
7. A casing arrangement as claimed in any preceding claim wherein the heat shield comprises a plurality of flanges.
8. A casing arrangement as claimed in claim 7 wherein the flanges are arranged parallel to each other.
9. A casing arrangement as claimed in claim 8 wherein the heat shield comprises a pair of spaced substantially parallel flanges.
10. A casing arrangement as claimed in claims 7, 8 or 9 wherein the casing arrangement comprises a connecting member connecting the flanges together.
11. A casing arrangement as claimed in any of claims 7 to wherein the casing arrangement comprises a plurality of connecting members connecting the flanges together.
12. A casing arrangement as claimed in claim 11 wherein the connecting members are arranged so as to define gaps between adjacent connecting members, to allow fluid to flow therethrough.
13. A casing arrangement as claimed in any of claims 10 to 12 wherein the connecting members used to connect the flanges of the heat shield each other also form part of the attaching means used to removably attach the heat shield to the casing.
14. A casing arrangement as claimed in any of claims 6 to 13 wherein the heat shield is removably attached to the casing so that the, or each, flange extends radially outwardly from the casing.
15. A casing arrangement as claimed in any of claims 6 to 14 wherein the, or each, flange of the heat shield extend substantially wholly around the casing.
16. A casing arrangement as claimed in any of claims 6 to wherein the, or each, flange of the heat shield extend only part way round the casing.
17. A casing arrangement as claimed in any of claims 6 to 16 wherein the, or each, flange of the heat shield comprises a plurality of sections which can be arranged around the casing.
18. A rotary assembly comprising a rotary component of an angle, and a casing arrangement as claimed in any preceding claim extending around the rotary component.
19. A rotary assembly according to claim 18 wherein the rotary component comprises at least a part of a compressor.
20. A rotary assembly according to claim 14 wherein the compressor comprises a high pressure compressor.
21. A rotary assembly according to claim 18, 19, or 20 comprising stator members mounted on the casing arrangement.
22. A rotary assembly according to claim 21 wherein the stator members extend radially outwardly from the casing arrangement.
23. A gas turbine engine incorporating a rotary assembly as claimed in any of claims 18 to 22.
24. A casing arrangement substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings.
25. A rotary assembly substantially as hereinbefore described with reference to and/or ash shown in Fig. 2 of the accompanying drawings.
26. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as the preceding claims.