GB2339244A

GB2339244A - A variable camber vane and casing having matching part-spherical surfaces

Info

Publication number: GB2339244A
Application number: GB9813254A
Authority: GB
Inventors: Kevin John Weaver
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1998-06-19
Filing date: 1998-06-19
Publication date: 2000-01-19
Anticipated expiration: 2018-06-19
Also published as: DE69916367T2; GB9813254D0; EP0965727B1; DE69916367D1; US6179559B1; EP0965727A2; GB2339244B; EP0965727A3

Description

A VARIABLE C.-VNIBER VANE The invention relates to a variable camber vane

for a aas turbine enaine.

0 0 More particularly the invention concerns the movable section of a variable camber intake guide vane which forms part of a vane ring in the intake of a gas turbine propulsion engine ahead of the first compressor rotor stage.

In order to maintain operating stability of the compressor of a gas turbine propulsion IP engiric over a wide rance of mass flow rates and operating speeds it is considered advisable to employ a movable vane. Such vanes have two major aerodynamic effects: one, to turn the airstream throucr an angle to meet the blades of a succeeding gh rotary stage; two, to reduce the effective inlet area of the stacre. Because the D I I dimensions of the inlet tract are relatively large at the front of an engine such vanes 0 C.

are correspondingly big and the aerodynamically generated forces acting on a movable blade when it is turned to the incoming airstream are also larce. It is usual for the vanes to be pivoted on an axis in the midchord region in order that the forces may be balanced about the axis. This reduces the actuation forces required to turn and hold the vane, and consequently the stresses and strains to which the vane is subject as compared to an edge pivoted vane.

I However, in some circumstances it may be necessary to employ an edge pivoted vane in which case the problems resulting from high and unbalanced forces acting on the 0 ID vane have to be tackled. The present invention has for one objective to provide a solution to these problems.

According to one aspect of the invention there is provided a variable camber vane for a gas turbine encrine comprising a fixed leading section and a movable trailina section compnsina a vane section pivotally mounted about an axis through its upstream edge adjacent the downstream edge of the fixed leading section wherein a radially outer edge of the movable section and the surface of a surroundina casing are matching part-sphenical surfaces in a region includinCT at least the sweep of the movable vane section.

A preferred embodiment of the invention will now be described xvith reference to the accompanying drawings, in which:

I - Figure I shows a part cut-away view of an engine inlet annulus incorporating, a ring of variable camber vanes, Fic,ure 2 shows a section of the casinc, includina three of the variable camber 0 al vanes, Figure 3 shows a section of the movable sections of two variable camber vanes,and Fiaure 4 shows a close-up view of the radially outer edge of the movable 0 section of a vane of Figures 1-3 illustrating the circular bearing member, and the curved outer, flanged edge.

0 Referring to the drawings, Figure I shows an engine inlet annulus generally indicated 0 0 at 2 incorporating a ring of ten variable camber vanes 4 spaced apart equidistantly around the intake annulus of the engine. Also visible is a first compressor rotary stage 1 0 generally indicated at 6. Surrounding the intake annulus is an engine casing structure 8 partly cut-away to reveal some more details of the vanes 4. The vanes 4 extend in a generally radial direction between the outer engine casing 8 and an inner concentric structure -enerally indicated at 10 within which there may be provided a front engine bearing, (not shown) supporting the front end of an engine shaft carrying the rotary stage 6. The front of the circular bearing housing structure 10 is enclosed by a n conventional tapering nose bullet 12. Generally, in order to support the front shaft C bearincy, the vanes 4 incorporate a fixed, and load bearing section. This fixed upstream vane section has a part airfoil shape as can be seen more clearly in Figure 2.

1 C) The fixed portion of each of the vanes is indicated by reference 14 and in all the drawings like parts carry like references.

In Figure 2 the fixed vane sections 14 are partly sectioned in order to show the airfoil shape more clearly. It will be apparent that the thickness of the vanes gradually increases in a downstream direction up to the upstream edge of the movable sections 16 of each of the vanes. The movable sections 16 conform to the overall airfoil shape required of the vanes.

The movable vane sections 16 are mounted for typical movement about a radial axis 18 which passes through a spindle formation 20 integral with the upstream edge of the vane sections. The angular movement required of the movable vane sections 16 is up to a maximum deflection of approximately 70'. Clearly over such a large range of movement the arc swept by the radially outer edges 22 of the vanes has potential for interference with the annular shape of the inner surface 24 of the engine casing 8. In order to accommodate this ranue of vane movement and to avoid Gaps between the vane radially outer edge 22 and the casing surface 24 these both conform to a part spherical surface configuration. Therefore a constant and minimal gap between the edge 22 and surface 24 may be maintained over the whole range of vane movement.

The movable vane sections 16, it will be apparent, are pivoted at their upstream edge so that, in use, at relative large angles of deflection considerable forces are Generated Z> 0 ZI on the pressure side of the vanes due to airstream movement. It follows therefore that to move and maintain an angular setting of the vanes considerable actuation forces are required and these result in considerable stresses within the airfoil sections of the vane.

A vane actuating mechanism (not shown) is provided on the radially outer side of 0 annular engine casing 8. Basically this comprises a circum ferenti ally movable unison I ring to which the spindles 20 of each of the vanes is connected by means of an actuator lever (also not shown). As shown more clearly in Figure 4 the radially outer end of the vanes is formed with a spindle extension 26 which projects through a circular aperture 28 in the engine casing 8. The actuating levers are engaged N7,-ith the spindle extensions 26. The radially inner ends of the spindles 20 are also fon-ned with a spindle projection 30 which is en- aged with a bearing or bush 32, indicated in t 1.) In Figure 1. Where the spindle 20 passes through the engine casing 8 an increased diameter bearing member 34 is provided concentric with the spindle and pivot axis 18. Preferably, as shown in Figure 4 the member 34 has a chanifered surface 36 which I engages, or has minimum clearance from, a similarly chanifered surface of a bush housed in the casing wall 8. Bearing loads are taken by a bearing concentric with the I axis IS and the aperture 32 in the casing 8 on an annular bearing surface 3 8 on the I I member 34. The plane of annular surface 38 is orthogonal to axis 18.

it will be appreciated that actuation loads applied to the movable vane section 16 throuah spindle 26 will necessarily be of considerable magnitude bearing in mind the chord length of the vane section 16 since these vanes are located in the engine intake, and therefore the vanes are of large dimension. These large forces have potential to create great stresses within the vane section which must be contained if they are not to result in the propagation of stress cracks.

I The present invention provides a solution to these problems by providing, the movable I vane section 16 with a flange 40 at its radially outer edge. As shown in Figure 4 flange 40 follows the part circular shape of the vane edge and tapers from a maximum width at the vane section spindle 20 towards the trailing edge 21 of the vane. In the particular embodiment the diameter of member 34 is greater than the maximum width of flange 40 and the edges of the member and the flange are blended one into the other and the flange 40 tapers in a downstream direction to the width of the vane section 16 at the trailing edge 2 1, Z:' For reasons of aerodynamic and mechanical efficiency the flange 40 and member 34 1 on the gas path side of the vane are blended smoothly from thier maximum dimension into the airfoil surface of the movable vane section. This blending is achieved by means of a curved surface generally indicated at 42 in Figure 4. This curved surface 42 tapers into the vane width in a radially inward direction and runs out towards the t'I'n,> 1= 11.1 ral 1 edae of the movable vane section 16. In this manner abrupt changes in the shape of the airfoil surface which could lead to discontinuities and stress concentrations are avoided. The flange 40 stiffens the vane in particular its torsional stifffiess and raises the basic resonant frequency above the engine range thereby a'ding excitation. The flange taper and gradual blending of the undersurface of the vol C) C- 1-1) I'D flanue into the vane airfoil surface help to avoid stress raisincy or stress concentratinc, features by gradually tapening-in ie distributing forces acting on the vane and spindle. Similarly, the charrifered surface 36 of member 34 tapers-in stresses and avoids stress raisers such as sharp comers in region subject to high forces.

As shown more clearly in Figures 2 and 3 the outer edges of the cur-ved underside of I I member 34 and flange 40 blend into the part sphenical surface 24 of the engine casing 8. Also the movable vane section 16 is mounted in the casin- such that the charrifered surface 34 lies within the mounting aperture 28 in the casing surface 24 further I I avoiding discontinuities. The upstream of vane section 16 which comprises a spindle is formed along its len-th with a constant radius section which is matched to a 1 0 correspondingly curved section trailing edge at the downstream edge of the fixed vane sections 14.

Claims

A variable camber vane for a gas turbine engine comprising a fix,-d leading sec+ion and a movable trallinc, senion comorisina a vane secticn pivotally mounted about an axis through its upstreain edge adjacent the downstream I - edae of the fixed leadina section v,herel n a radially outer edge of the movable section and the surface of a surroundinc, casina are matchincy part- spherical 4_1 surfaces in a re-ion including at least the sweep of the movable vane section.
2 A variable camber vane as claimed in claim I wherein the radially outer edge I of the movable vane section is curved to match the part-spherical surface of the adjacent casing region.
3 A variable camber vane as claimed in claim I or claim 2 wherein the flanged outer edge is tapered towards the vane trailing edge. 4 A variable camber vane as claimed in any one of the preceding claims wherein the flanged outer edge is blended in a radial direction into the airfoil surface of the vane at least on the pressure side thereof. 5 A variable camber vane as claimed in any preceding claim wherein the upstream edge of the middle section of the vane comprises a spindle formed integrally with the airfoil section of the vane concentric with the pivot axis. 6 A variable camber vane as claimed in claim 5 wherein the spindle projects in a radially outward direction and is adapted to be engaged by a vane actuation mechanism.

Ok 7 A variable camber vane as claimed in claim 6 wherein a circular bearing member for mounting the vane in an engine casing is formed integrally with the spindle and the flanged outer edge of the vane, the bearing member being concentric with the axis of the spindle and having a diameter greater than the width of the flange. 8 A variable camber vane as claimed in claim 7 wherein the bearing member is formed with a chanifered radially outer surface. 9 A variable camber vane as claimed in claim 7 or claim 8 wherein the radially inner surface of the bearing member is blended with the spindle and the airfoil surface of the vane. 10 A variable camber vane substantially as hereiribefore described with reference to the accompanying drawings.

3 A variable camber vane as claimed in claim I or claim 2 wherein the radially outer curved, edoe of the vane is flanged.

4 A variable camber vane as claimed in claim 3 wherein the flanged outer ed-1 of the vane is broadest towards the vane pivot axis.

A variable camber vane as claimed in claim 3 or claim 4 wherein the flanged outer edcre is tapered towards the vane trailing edge.

C ID ID 6 A variable camber vane as claimed in any one of claims 3 to 5 wherein the flanged outer edge is blended in a radial direction into the airfoil surface of tile I I vane at least on the pressure side thereof 7 A,,-ariable camber vane as clainled in any preceding claim wherein the I upstream edge of the middle section of the vane comprises a spindle forrneJ 0 integrally with the airfoil section of the vane concentric with the pivot axis.

8 A variable camber vane as claimed in claim 7 wherein the spindle projects in a radially outward direction and is adapted to be engaged by a vane actuation mechanism. 9 A variable camber vane as claimed in claim 8 wherein a circular bearing member for mounting the vane in an engine casing is formed integrally with the spindle and the flanged outer edge of the vane, the bearing member being concentric with the axis of the spindle and having a diameter greater than the width of the flange.

I A variable camber vane as claimed in claim 9 wherein the bearing member is formed with a charnfered radially outer surface.

I I A variable camber vane as claimed in claim 9 or claim 10 Nvherein the radially inner surface of the bearing member is blended with the spindle and the airfoil surface of the vane.

12 A variable camber vane substantially as hereiribefore described with reference to the accompanying drawings.

Amendments to the claims have been riled as follows CLAIMS 1 A variable camber vane for a gas turbine engine comprising a fixed leading section and a movable trailing section comprising a vane section pivotally mounted about an axis through its upstream edge adjacent the downstream edge of the fixed leading section wherein a radially outer edge of the movable section and the surface of a surrounding casing are matching part-spherical surfaces in a region including at least the sweep of the movable vane section and the radially outer edge of the movable vane section is flanged and curved to match the part-spherical surface of the adjacent casing region. 2 A variable camber vane as claimed in claim 1 wherein the flanged outer edge of the vane is broadest towards the vane pivot axis.