GB2035474A

GB2035474A - Seals

Info

Publication number: GB2035474A
Application number: GB7938911A
Authority: GB
Original assignee: Sulzer AG; Gebrueder Sulzer AG
Current assignee: Sulzer AG
Priority date: 1978-11-09
Filing date: 1979-11-09
Publication date: 1980-06-18
Also published as: JPS5566625A; SE7909227L; FR2441060A1; AT358336B; ATA817778A; CH633351A5; DE2849665A1

Abstract

The invention provides a seal arrangement for the exit end of an annular combustion chamber for a gas turbine engine, which combustion chamber is attached to the engine at a point adjacent the burners thereon, the arrangement comprising tubular casings (16, 17) attached to the exit end of the combustion chamber and resilient diaphragms (18, 19) mounted on the engine and arranged to bear on and seal against the free end of said tubular casing, thereby to accommodate relative displacements due to thermal expansion. <IMAGE>

Description

SPECIFICATION Seat arrangement for a gas turbine annular combustion chamber This invention relates to a seal for an annular combustion chamber of a gas turbine.

If an annular gas turbine combustion chamber is fixed adjacent its burners in relation to other parts of the machine, its downstream or exit end undergoes considerable relative displacements, because of the considerable material temperature differences of the adjoining components with respect to the same, both on starting and stopping, and during steady operation of the turbine. It is also necessary to prevent the cooling air-which flows outside the combustion chamber and which is at positive pressure with respect to the combustion gases-from uncontrollably flowing into the combustion gas flow duct between the combustion chamber exit and the turbine inlet.

It is therefore an object of the invention to provide a seal between (a) the combustion chamber exit and the combustion gas flow path and (b) the outer chamber filled with cooling air and surrounding the combustion chamber, and such seals must be able to follow the considerable relative displacements of the machine components which expand at different speeds and by different amounts.

Accordingly the present invention provides a seal arrangement for the exit end of an annular combustion chamber for a gas turbine engine, which combustion chamber is attached to the engine at a point adjacent the burners thereon, the arrangement comprising a tubular casing attached to the exit end of the combustion chamber and a resilient diaphragm mounted on the engine and arranged to bear on and seal against the free end of said tubular casing.

The diaphragm which, for example, is formed of a high-allow sheet steel, because of the required mechanical strength, is elastically deformable at right angles to its surface to such an extent that on the one hand it can follow the expansion and contraction of the casing of the combustion chamber and of the casing tube or tubes connected thereto and, on the other hand, bear permanently as a sealing element on the end face of the casing tube. It may be mounted to be freely movable or be clamped.

Advantageously, cooling air flows all around the diaphragm in operation of the turbine to give uniform temperature distribution both peripherally and readially.

In order to promote a fuller understanding of the above and other aspects of the invention, an embodiment will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a partial section of a detail of a gas turbine showing the position of the annular combustion chamber in relation to the surrounding parts of the machine, Figure 2 is an enlarged-scale view of a detail of Fig. 1 confined to the zone containing annular diaphragms embodying the invention, and Figures 3 and 4 show the position of the outer diaphragm (Fig.3) and the inner diaphragm (Fig. 4) with the machine cold and in a displaced position due to thermal expansion, respectively.

As illustrated diagrammatically in Fig. 1, an annular combustion chamber 3 is provided inside an outer stator housing 1 of a gas turbine engine, only the middle zone of the axial length of which is shown. The combustion chamber is radially centred so as to be movable under heat and is axially fixed, at a point adjacent the burners 4, with respect to the inner stator housing over a number of points around the periphery, as shown at 34.

This inner stator housing is connected to a hollow inner housing 5, for example, by means of struts (not shown) which are situated farther upstream. Housing 5 together with a central housing 1 3 described hereinafter forms a unit, which is in turn fixed in the outer stator housing 1. On the outside the combustion chamber 3 is enclosed by an antiradiation sleeve 2, which also serves to guide the current of cooling air along the outer casing of the annular combustion chamber 3.

The current of cooling air flows through openings in an outer casing 32 of the combustion structure into the combustion chamber 3 to provide inter alia air for combustion. The sleeve 2 bears slidably on the downstream end portion 30 of the outer casing 32 of the combustion chamber annulus. The inner casing 33 of the combustion chamber 3 is similarly surrounded by an inner anti-radiation sleeve 6 which correspondingly bears slidably on an end portion 31. The sleeve 6 also guides the stream of cooling air or air for combustion.

The inner housing 5 closes off the annular space 8 containing the combustion chamber 3, with respect to the rotor (not shown). The annular chamber 8 between the outer housing 1 and the inner housing 5 has the cooling air or air for combustion flowing through it on operation, as already stated, and this air is at positive pressure in comparison with the combustion gases inside the combustion chamber 3 and in the adjoining flow duct 10.

The end portions 30 and 31 at the exit end of the combustion chamber 3 narrow so that the combustion gases can enter the flow duct 10. The entrance to the latter is formed by the first guide blade ring 11 of the turbine (not shown in detail), this ring bearing a centring ring 1 2. The latter is centred on the ring 11 so as to be movable under the action of heat--e.g. by radial struts (not shown), ring 11 in turn being supported on the central housing 1 3. A casing 14, which is shown only in outline, for the moving blade duct follows in the downstream direction and in the ideal position is in line with, but is not con nected to, the centring ring 12. The casing 14 also serves as a carrier for the guide blades of the other turbine stages.The casing 14 is fixed in the outer housing 1 so as to be movable under the action of heat, as shown diagrammatically at 1 5.

To prevent cooling air from flowing uncontrollably into the flow duct 10, the annular chamber 8 filled with cooling air must be sealed off from the flow path 10 of the combustion gases. Since, in addition, the material temperatures of the annular combustion chamber 3 and the other adjacent parts, e.g. particularly the guide blade ring 11 with the centring ring 12, differ considerably during the different stages of operation of the machine, the seal must be so constructed that it can yield to relative axial and radial displacements of the said parts.

Tubular casings 1 6 and 1 7 are therefore fitted to the respective end portions 30 and 31 and are provided with thickened free ends which bear against respective annular diaphragms 18 and 19. The diaphragms 18 and 1 9 are held on the one hand by the inner periphery and on the other hand the outer periphery in mounts 20 and 21, which are in turn fixed, e.g. screwed, to the centring ring 12 and the central housing 13.

Bores 22 and 23 (Fig. 2) are distributed around the periphery of the mounts 20 and 21 and enable a controlled quantity of cooling air to flow from the annular chamber 8 into the flow duct 10. Anti-radiation or guide shields 24 and 25 are clamped between the mounts 20 and 21 and the ring 12 and the central housing 1 3 so as to guide the cooling air so that the two diaphragms 1 8 and 1 9 are completely swept by it. The flow paths for the cooling air are indicated by small arrows in Fig. 2.

The effect of this cooling air supply is that the diaphragms 18 and 19, which may be made from a CrNi steel of adequate hot strength, have a uniform temperature both peripherally and radially, so that the minimum thermal stresses occur in them and hence a minimum of thermal deformation. The plates 24 and 25 at the same time act as radiation protection for the diaphragms 1 8 and 1 9 and as baffle and guide plates for the cooling air.

The diaphragms 1 8 and 1 9 are either unilaterally clamped in the mounts 20 and 21 (Fig. 2) or else just movably inserted into slots 26 and 27 (Figs. 3 and 4). In the latter case they are mounted in the slots which have constricted cross-sections 28 and 29 so that they can perform tipping movements about the narrowest pair of cross-sections 28, 29 which act as pivots. Movable mounts in which the diaphragms 1 8 and 1 9 rest by their weight on the top and bottom parts of the slost 26 and 27 respectively are shown in Fig.

3 in respect of the outer diaphragm 1 8 and Fig. 4 in respect of the inner diaphragm 1 9.

The chain-dotted lines in these Figures also show the position and shape of the diaphragms 1 8 and 1 9 when the annular combustion chamber 3 is lengthened by thermal expansion in relation to its surroundings.

Claims

1. A seal arrangement for the exit of an annular combustion chamber for a gas turbine engine, which combustion chamber is attached to the engine at a point adjacent the burners thereon, the arrangement comprising a tubular casing attached to the exit end of the combustion chamber and a resilient diaphragm mounted on the engine and arranged to bear on and seal against the free end of said tubular casing.

2. A seal arrangement as claimed in Claim 1 including two such tubular casings respectively attached to inner and outer parts of the exit end of the combustion chamber, each with a respective associated such resilient diaphragm.

3. A seal arrangement as claimed in Claim 1 or 2, in which means is provided to direct cooling air over the inner surface of the or each said diaphragm.

4. A seal arrangement as claimed in Claim 1, 2 or 3, in which the or each diaphragm is annular and fixedly mounted by its inner or outer periphery.

5. A seal arrangement as claimed in Claim 1, 2 or 3, in which the or each diaphragm is annular and is mounted in a slot by its inner or outer periphery.

6. A seal arrangement as claimed in Claim 5, in which the cross-section of each such slot is constricted so that the diaphragm may pivot about the narrowest portion of the slot.

7. A seal arrangement substantially as herein described with reference to the accompanying drawings.