GB2422176A

GB2422176A - Retaining components/blades on a rotor

Info

Publication number: GB2422176A
Application number: GB0500983A
Authority: GB
Inventors: Ian Adrian Hood
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2005-01-18
Filing date: 2005-01-18
Publication date: 2006-07-19
Also published as: GB0500983D0

Abstract

Upstanding components (such as compressor blades 4) are carried on the periphery of a rotary component (such as a compressor disc 2) by means of interlocking features (which may be formed on blade roots 10 and disc slots 14 within which the roots are received). The upstanding members 4 are held in place by a resilient member 20 engaged with the rotary component 2 and all of the upstanding components 4. The resilient member 20 may comprise a split ring which is engaged with a groove 26 defined by overhang portions 22, 24 of the members 4 and the component 2.

Description

I. * I. a a * * * I * * I a I * * * III * S * *5S -1- 2422176

ADE RETENTION

The Invention relates to a rotating assembly.

In particular it Concerns blade retention in a rotary stage of a gas turbine engine.

It is commonplace to mount blades on the periphery of a rotary disc by means of interlocking root and slot formations. Each blade has a root at its base that is designed to interlock with a complementary formation in the rim of the disc. Engagement is achieved by sliding the blade root into the disc slot in an axial direction. The formations are urged into engagement by centrifugal/centrIpt forces when the assembly is rotated at engine speed but otherwise the assembly is not a "force fit". Thus provision is made to avoid the blades moving out of position by Preventing further axial movement. A known arrangement for retaining the blades involves a number of small items, such as clips or the like, fitted into each individual blade slot. Such items, however, can be difficult to handle and time consuming to fit. Also difficulties in fitting them can lead to part damage and later failure. In another known arrangement a number of blades, up to half of the blades in one annulus, are locked in place by large ring segments, which, in turn, are themselves, held in position by several smaller items.

Again these are time consuming to fit and a possibility of consequential damage remains. The present Invention is intended to overcome these drawbacks and dispensing with a proliferation of parts by providing a single component to retain the whole assembly.

According to the present invention there is provided a rotating assembly comprising a rotary component a plurality of upstanding components carried on the periphery of the rotary component by means of interlocking formations, and a resilient member engaged with the rotary component and all of the upstanding components to hold them in place.

Preferably the interlocking formations slide in an axial direction with respect to the rotary component and the resilient member restricts further movement.

S

: . . ,** I * * IS S S * * .:. *s ** In a preferred embodiment the rotating assembly comprises a rotary stage of a gas turbine engine wherein the rotary component comprises a disc and the upstanding components are blades. The resilient member is engaged with a groove formed as an undercut in overhanging formations on the rotary component and the upstanding components and the resilient member expands outwardly into the groove.

The Invention will now be described in greater detail with reference to the preferred embodiment illustrated in the accompanying drawings in which: Figure 1 shows a detail and part cut-away view of a compressor stage of a gas turbine engine; and Figure 2 shows an overall view of the resilient ring used in the assembly of Figure 1.

Referring first to Figure 1 there is shown part of a rotating assembly in the form of a rotary compressor stage for a gas turbine engine. The illustrated portion of the rotary component comprises a portion of a rotary disc 2 together with one Upstanding component 4 in the form of a rotary compressor blade. In total the assembly includes a multiplicity of such blades Spaced apart equidistantly around the Periphery of the disc 2.

Each blade is formed with an airfoil portion 6 upstanding from a platform 8, and a root portion io that depends below the platform. At each blade location around the rim 12 of disc 2 there is formed a slot 14, therefore there are as many slots as there are blades which divide the peripheral surface of the disc rim 12 into a multiplicity of lands 16, of which three are visible in the drawing.

The root portion 10 of a blade has a substantially constant profile in the axial direction, that in the direction of rotation of the disc 2. The cross-section of a slot 14 has a complementary profile to receive the root 10 in an axial direction. The shapes of the root 10 and slot 14 prevent any significant movement in a radial direction. Under centrifugal loading forces the external surface of a blade root lOis urged into engagement with the internal surface of its receiving slot 14. However, the blades 4 are 1 I I I * * I I * * I I * * * * *:. .* *.* not held in place in the axial direction by their roots and friction loads generated by a spinning assembly do not alone guarantee blade retention. In a stationary assembly of course, these centrifugally generated loads are not present. Therefore it has always been necessary to provide some means of blade retention to Positively locate the blades in their slots at all times. In accordance with the present invention a resilient member in the form of ring 20 shown in Figure 2 is provided for this purpose.

The lands 16 between slots 14 in the disc rim 12 have a portion 22 that overhangs one side of the rim 12, the side towards the left in the plane of Figure l.Similarly the blade platforms 6 have a portion 24 that overhangs the adjacent edge of root 10. Together these overhanging portions 22, 24 form a radially inward facing groove 26, Although formed of a multiplicity of individual groove portions on the rim lands and blade root/platforms in a complete rotary assembly they form a continuous groove the dimensions if which are adapted to receive the ring 20.

Ring 20 comprises a resilient member, in particular it consists of a split ring composed of resilient material capable of withstanding the operating temperatures inside a gas turbine engine, at least within the compressor. The design of the ring, that is its diameter and thickness and the corresponding dimensions of the groove 26 are chosen such that the ring when fitted it is received within the groove. To allow the ring to be fitted into position it is constructed as a split ring with a ring gap at 28. Thus its diameter may be made smaller so that it can be fitted through the inner diameter of the circle formed by all the overhanging portions 22, 24. The diameter of ring 20 is determined by the large diameter of the disc rim 10 and the groove 26.Given the Size of these dimensions it is arranged that the ends of the split ring, rather than simply closing the gap, overlap when it is compressed.

The ring IS designed to spring back when released. However, it is preferred that it shall not spring back to its original, uncompressed state. The diameter of the uncompressed ring 20 is made larger than the diameter of the groove 26 so that in position it retains a residual tension. This residual force urging the ring to further outward expansion tends to lock the ring in position inside the groove 26 Preventing forward and rearward axial S. I at.

I. * S S I * * I I * * * I.. * I * * * II * movement of the blades relative to the disc. This springbac characteristic also enables the ring to be self-locating in the groove. It is envisaged that the ring may be compressed and fitted by hand. The chosen material of the ring is Sufficiently resilient so the ring springs back when released and to ensure that it always operates within its elastic limit within the engine temperature operating range.

The in-plane thickness, or radial depth, of the ring is chosen to provide an abutment across one end of the roots slots 14. Similarly the depth of the overhangs 22, 24 on the rim lands and the blade platforms is sufficient to hold the ring in place in the groove 26.

The thickness of the ring 20 in the axial direction and the width of the groove 26 are also selected to secure the ring 20 in place without excessive movement in either axial direction 1* S * If,

Claims

S I * * I I * * 5* I I * * * * *:. 1.1 **

IMS

A rotating assembly comprising a rotary component a Plurality of upstanding components carried on the periphery of the rotary component by means of interlocking formations, and a resilient member engaged with the rotary component and all of the Upstanding components to hold them in place.

2 A rotating assembly as claimed in claim I comprising a rotary stage of a gas turbine engine wherein the rotary component comprises a disc and the upstanding components are blades, and the interlocking formations engage in an axial direction.

3 A rotating assembly as claimed in claim 1 or claim 2 comprising a rotary compressor stage.

4 A rotating assembly as Claimed in any Preceding claim wherein the resilient member is engaged with a groove formed in the rotary component and the Upstanding components A rotating assembly as claimed in claim 4 wherein the groove IS formed as an undercut in overhanging formations on the rotary component and the upstanding components and the resilient member expands outwardly into the groove.

6 A rotating assembly as claimed in claim 5 wherein the resilient member comprises a split ring of resilient material.

7 A rotating assembly substantially as hereinbefore described with reference to the accompanying drawings.