GB2425155A - A mounting arrangement - Google Patents

Abstract

A mounting arrangement 30 for abradable liners used with respect to stator vanes with gas turbine engines. The arrangement 30 comprises a single strut 39 secured through a mounting end 34 to a mounting recess 33 of a vane platform 32. The strut 39 is part of a shroud ring 35 which incorporates a metal abradable liner 37 in order to create a seal between stages within the gas turbine engine. A mounting end 34 incorporates divergent limbs 40, 41 which act through their respective entrant axes X-X, Y-Y to facilitate axial and radial location of the single strut 39 and therefore the shroud ring 35 with liner 37.

Description

A Mounting Arrangement The present invention relates to mounting

arrangements and more particularly to such arrangements used with regard to gas turbine engines for locating shroud rings at compressor stages of such engines.

Referring to Fig. 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 produce 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 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.

It will be understood that the tips of blade stages in the compressor and turbine stages as well as the stator vanes between those blade rows may be shrouded. The shroud rings are secured appropriately in order to control and regulate fluid flow through the various stages for best engine operation. Figs. 2 and 3 illustrate two previous approaches to securing stator vanes in a gas turbine engine. In Fig. 2, shrouded vanes 20 are secured in reciprocal slots 21 of a casing 22. Thus, as can be seen, the vanes have a box section type arrangement 23.

The ends of this box section 23 engage reciprocal parts of the recess 21 in order to provide axial as well as radial location for the stator vanes 20 as mounted within the casing 22 and upon an engine core. At the bottom end of the shroud rings there is support for an area which carries a felt metal abradable liner. The junction of the liner is to allow radial clearances to be set so that light rubs can occur without damage - this tight clearance gives minimum leakage. The vanes are often assembled in segments in the front stages and may be shrouded at their inner ends to minimise the vibrational effects of load variations. Generally, it is necessary to lock the vanes in such a manner that they will not rotate about the casing.

Retaining the felt metal abradable liner upon a box section at the inner end of the vane to provide axial as well as radial location and support for the liner creates significant problems.

In accordance with the present invention there is provided a mounting arrangement for a gas turbine engine, the arrangement comprising a strut with a mounting end and a mounting recess for the mounting end, the mounting end comprising divergent limbs for reciprocal location in the mounting recess for axial and radial location by virtue of the entrant axis of each limb in its respective part of the mounting recess.

Generally, the strut is secured to a platform upon which a liner is presented within a gas turbine engine.

Typically, the mounting end has a T-shaped cross section. Generally, the divergent limbs are perpendicular to each other.

Generally, the mounting end is slid into position within the mounting recess.

Generally, the mounting arrangement is secured upon the end of a stator vane.

Also, in accordance with the present invention there is provided a gas turbine engine incorporating a mounting arrangement as described above.

An embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings in which: Fig. 3 provides a part cross-section of a mounting arrangement in accordance with the present invention associated with a stator vane; and Fig. 4 provides an exploded view of the mounting arrangement depicted in Fig. 3.

In order to reduce weight as well as complications with respect to assembly and parts count in accordance with the present invention, a single strut is utilised in order to support a sealing liner. Referring to Fig. 3 showing a cross-section of a mounting arrangement 30 in accordance with the present invention, it can be seen a stator vane 31 incorporates a platform 32 with a mounting recess 33. This mounting recess as depicted in Fig. 3 can be at the front of the platform 33 or alternatively at other axial locations across the width of the platform 32.

The mounting recess 33 is associated with a mounting end 34 of a shroud ring 35. This shroud ring 35 incorporates a lateral portion 36 in order to present a felt metal abradable liner 37 towards rib flanges 38 in order to create a seal either side of the stator vane 31.

As can be seen in Fig. 3, the mounting end 34 extends into a strut 39 in order to provide both axial location, that is to say in the direction of arrowhead A, as well as radial location, that is to say in the direction of arrowhead B, relative to the stator vane 31. This strut 39 is the single means of support for the liner 37.

It will be appreciated in the above circumstances, provision of a single strut 39 generally provides a weight saving in comparison with prior mounting arrangements as well as considerably reduces machining difficulties with respect to both the shroud ring 35 and the platform 32.

It will be understood the principle difficulty with providing a single strut is that of ensuring adequate axial location as well as radial location for the lateral portion 36 and in particular the liner 37 in order to ensure appropriate sealing is achieved. Previously, shroud rings were held in position with legs at either end of the shroud providing axial and radial location as well as support for a liner. With the present invention the mounting end 34 of the strut 39 is shaped in order to have divergent limbs whereby both axial and radial location is achieved and retained. Clearly, the divergence of these limbs as well as their size and configuration will be dependent particularly upon expected operational requirements. Nevertheless, a T-shaped head for the mounting end 34 provides the desired benefits of both axial and radial location with a single strut whilst also offering a reduction in weight and assembly complication in comparison with a bolted arrangement.

Fig. 4 provides an exploded cross-section of the mounting end 34 in the mounting recess 33 as depicted in Fig. 3. Thus, the mounting end 34 incorporates limbs 40, 41 which diverge to enter reciprocal parts of the mounting recess 33. It will be noted that the limbs 40, 41 respectively diverge at right angles to each other in the embodiment depicted in Fig. 4, but other configurations may be used dependent upon operational requirements.

Nevertheless, it will be appreciated that the respective entrant axes for the limbs 40, 41 essentially provide resilient presentation of the single strut 39 upon which the liner 37 (Fig. 3) is presented in use. In short, axial location is ensured by the limb 40 entering its respective part of the recess 33 along the entrant axis Y- Y such that movement in the direction of arrowhead A is inhibited. Similarly, radial movement in the direction of arrowhead B is inhibited by entry of the limb 41 in its reciprocal part of the recess 33 along the entrant axis X- X. The respective limbs 40, 41 are thereby constrained within their respective channels of the mounting recess 33.

It will be understood that the platforms 32 from which the stator vanes 31 extend will generally be formed in a circle with several individual or multiple stator vane segments associated in order to provide a complete ring of such stator vanes 31 within a compressor between compressor stages as described and known.

It will be understood that the depth of the respective portions of the recess 33 in order to accommodate the limbs 40, 41 will be chosen such that there is adequate engagement between those limbs 40, 41 and the recess 33. This overlap or channel depth is depicted respectively as 42, 43 in Fig. 4. It will also be understood that generally the limbs 40, 41 will substantially fill the respective portions of the mounting recess 33 within which they enter. Generally, the pressure differential across the mounting arrangement will be such that a front side F is at a lower pressure than a rear side R such that the strut 39 is also supported across a greater width 45 against that pressure on the front side F in comparison with upstream, width 42. This approach further enhances stability and axial location of the strut 39 and therefore the liner 37 (Fig. 3) Generally, the limb 41 which resists radial displacement and therefore provides radial location, will be of a narrower cross-section than the limb 40 which provides for axial location in view of the greater stability of the strut 39 in that direction due to the mass of the platform 33 and vane 31.

For assembly, the mounting end 34 will be circumferentially slid from an open end of the mounting recess 33 until it achieves location. As indicated previously, the limbs 40, 41 will generally be a close fit within their respective parts of the mounting recess 33 in order to reduce any leakage path and also ensure accurate/robust and radial location for the arrangement in use. everthe1ess, it will be appreciated that in order to facilitate the circumferential slide motion a certain clearance between the end 34 and the recess 33 is beneficial. In such circumstances, the recess 33 may be coated with an appropriate material which will facilitate such circumferential slide motion into position and may also provide a sealing matrix subsequent to assembly.

In terms of assembly, generally the shroud ring 35 for a compressor stage will be manufactured in two or more segments. Thus, stator vanes either individually or as group components will be slid into position through their respective mounting recesses in the platform 32. As indicated, these recesses generally take the form of channels or grooves to accept the divergent limbs of the mounting end of the respective shroud ring 35 segments.

In such circumstances the mounting end 34 locates in the recess 33 on the underside of the platform 32 in order to provide support and location for the ring 35 in use. By use of a T-shaped mounting end it will be understood that adequate axial and radial support is provided for location without the use of re-entrant features such that machining of both the stator vane including platform 32 as well as the mounting end of the shroud ring 35 is far easier. it will be understood that assembly and build time will be greatly reduced as it will no longer be necessary to provide bolts for securing location of each shroud ring segment and this will also reduce the number of component parts in those assemblies additionally simplifying machining processes as well as possibly weight for the combined assembly.

Although described with regard to compressor stages of a gas turbine engine it will be appreciated that vanes utilised with regard to turbine stages of a gas turbine engine may also be mounted using similar arrangements to that described above.

It will be noted that the mounting recess 33 generally incorporates chamfers between the respective parts of that recess 33 to accommodate the limbs 40, 41.

These chamfered corners act to facilitate circumferential slide motion for location of the shroud ring through the mounting ends 34 in the mounting recess 33 of the platform 32.

As can be seen, particularly in Fig. 4, the limbs 40, 41 will generally have square ends in order to maximise overlap and therefore locational Positioning of the limbs 40, 41 into the recess 33. However, where possible and in view of the circumferential slide motion, it will be appreciated that one or more of the divergent limbs may have a waisted or dove-tail cross-section in order to further facilitate capture of that respective limb 40, 41 in its reciprocal part of the recess 33 for greater axial or radial location. However, such an approach may create fatigue stress failure through vibrational cycling.

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 (9)

1. A mounting arrangement for a gas turbine engine, the arrangement comprising a strut with a mounting end and a mounting recess for the mounting end, the mounting end comprising divergent limbs for reciprocal location in the mounting recess for axial and radial location by virtue of the entrant axis of each limb in its respective part of the mounting recess.

2. An arrangement as claimed in claim 1 wherein the strut is secured to a platform upon which a liner is presented within a gas turbine engine.

3. An arrangement as claimed in claim 1 or claim 2 wherein the mounting end has a T-shaped cross section.

4. An arrangement as claimed in claims 1, 2 or 3 wherein the divergent limbs are perpendicular to each other.

5. An arrangement as claimed in any preceding claim wherein the mounting end is slid into position within the mounting recess.

6. An arrangement as claimed in any preceding claim wherein the mounting arrangement is secured upon the end of a stator vane.

7. A mounting arrangement for a gas turbine engine substantially as hereinbefore described in reference to figures 3 and 4.

8. A turbine engine incorporating a mounting arrangement as claimed in any preceding claim.

9. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.