EP1031703A2

EP1031703A2 - Operating arrangements for stator vanes

Info

Publication number: EP1031703A2
Application number: EP00300999A
Authority: EP
Inventors: Alan Leslie Selby
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1999-02-23
Filing date: 2000-02-09
Publication date: 2000-08-30
Also published as: EP1031703A3; GB9904032D0

Abstract

An operating arrangement for adjustable stator vanes (14) in a gas turbine engine comprises a control member (30) defining a plurality of apertures (32, 132) and a plurality of operating levers (24). Each operating lever (24) has a first end region (28) to be secured to the stator vane (14) and a second end region (36). A pin (34, 134) extends from the second end region (36) to be received in an associated aperture (32, 132) in the control member. Each pin (34, 134) and the respective aperture (32, 132) are movable longitudinally relative to each other. A laterally extending projection (41, 141) is provided on the pin (34) or on the wall (50) of the aperture (32, 132). The arrangement is such that relative pivotal and longitudinal movement of the longitudinal axes of the pin (34) and of the aperture or recess (32, 132) is permitted on movement of the control member (30) to move the operating levers (24). In one embodiment, the projection (41) is provided on the pin (34) and, in another embodiment, the projection (141) is provided on the wall of the aperture (132).

Description

This invention relates to operating arrangements for stator vanes. More particularly, the invention relates to operating arrangements for stator vanes in gas turbine engines. The invention also relates to operating levers for stator vanes and to control members for controlling such operating levers.

Gas turbine engines generally comprise an arrangement of compressors, fans and turbines. These may be provided with adjustable stator vanes alternating with rotating blades. The orientation of the stator vanes can be adjusted by pivotally rotating each of them about its longitudinal axis to vary the flow of air through the engine. The movement of the variable stator vanes is controlled by a number of levers, each attached by a pin to a unison ring extending around the stator. As the unison ring rotates, it moves the levers to adjust the vanes in unison. On rotation of the ring, the apertures in which the pins are received remain aligned with the radiis of the ring. The pins, however, are fixed and do not maintain their alignment with the radiis of the ring on such rotation. This causes flexing in the lever, which can lead to failure of the pins or levers.

It is an object of the invention to obviate or mitigate this disadvantage of the prior art.

According to one aspect of the invention there is provided an operating arrangement for an adjustable stator vane in a gas turbine engine, said arrangement comprising a control member defining an aperture, and an operating lever having a first end region to be secured to the stator vane, and a second end region having a pin extending therefrom to be received in said aperture in the control member, wherein the pin is movable longitudinally relative to the aperture, and a laterally extending projection is provided on one of the pin and the aperture to engage the other of the pin and the wall of the aperture, such that relative pivotal and longitudinal movement of the longitudinal axes of the pin and of the aperture is permitted on movement of the control member to move the operating lever.

In the preferred embodiment, the projection is provided on the pin. In an another embodiment, the projection is provided on the wall of the aperture or recess.

According to another aspect of the invention, there is provided an operating lever for use in an operating arrangement for an adjustable stator vane in a gas turbine engine, said lever comprising a first end region to be secured to the stator vane and a second end region having a pin extending therefrom to be received in an aperture defined in a control member, the pin and the aperture being movable longitudinally relative to each other, and a laterally extending projection being provided on the pin to engage the wall of the aperture, such that relative pivotal and longitudinal movement of the longitudinal axes of the pin and of the aperture is permitted on movement of the control member to move the operating lever.

The projection may extend at least partially around and, preferably, substantially wholly around, the pin.

Preferably, the pin comprises a first portion comprising a shank of the pin, said first portion extending from the second end region of the operating lever, and said pin further including a second portion extending substantially co-axially from the first portion, said projection extending laterally from the second portion. Both said first and second, portions are preferably conveniently of substantially circular cross-section.

The projection may extend longitudinally of the pin, and may extend throughout the length of the second portion. Desirably, the projection tapers such that the cross-section of the second portion increases to a maximum, and then decreases from said maximum. The taper may be arcuate. Desirably, the projection is substantially barrel shaped.

According to a further aspect of the invention, there is provided a control member for use in an operating arrangement for a stator vane in a gas turbine engine, said control member defining an aperture adapted to receive a pin of an operating lever secured to the stator vane, the pin and the aperture being movable longitudinally relative to each other, wherein a laterally extending projection is provided on the wall of the aperture to engage the pin such that relative pivotal movement of the longitudinal axes of the pin and the aperture is permitted on movement of the control member to move the operating lever.

The projection may extend substantially wholly around the aperture, and may extend longitudinally of the recess. Preferably, the projection tapers such that the cross-section of the aperture decreases to a minimum, and then increases from said minimum. The taper may be arcuate.

It will be appreciated by those skilled in the art that an insert may be fitted into the aperture in the control member to receive the pin. The insert may be a low friction bush. In view of this, the expression

wall of the aperture should be interpreted to cover both the wall of such an insert and the wall of the aperture itself.

In a preferred embodiment, the control member is in the form of a unison ring having a plurality of apertures. The unison ring may extend at least partially, and preferably substantially wholly around the engine. In this embodiment, the arrangement includes a plurality of operating levers, each adapted to be secured to a respective stator vane and the pin of each lever is received in a respective one of the recesses or apertures in the unison ring.

Preferably the stator vane has an axis and the pin extends in a direction substantially parallel to the axis of the stator vane so that the longitudinal axis of the pin is substantially parallel to the axis of the stator vane. The stator vane preferably adjustably pivoting about said axis of the stator vane.

The invention also provides an axial flow compressor incorporating an operating arrangement as described above and a gas turbine engine incorporating such a compressor.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings in which:-

Fig. 1 is a sectional view of part of a gas turbine engine showing a plurality of operating arrangements connected to a plurality of variable stator vanes.

Fig. 2 is in an exploded perspective view showing one operating lever and an associated stator vane;

Fig. 3 is a perspective view of an operating lever;

Fig. 4 is a schematic side view of the pin forming part of the operating lever shown in Fig. 3;

Fig. 5A to C are a sequence of diagrammatic representations showing the relative positions of the pin and the recess or aperture in the associated control member, and

Fig. 6 is a cross sectional view of an alternative embodiment.

Referring to Fig. 1, there is shown a sectional view of an axial flow compressor 10 of a gas turbine engine which comprises a plurality of stator vane assemblies 12, wherein each assembly 12 comprises a plurality of stator vanes 14 arranged in an annular fashion about the axis of the compressor 10. Alternating with the stator vane assemblies 12 are a plurality of rotor assemblies 16.

Each stator vane 14 comprises a spindle 18 extending radially of the compressor 10. Each spindle 18 is rotatably mounted in a respective bearing 20 formed on the casing 22 of the compressor 10, and each stator vane 14 can pivot about its respective spindle 18 about a central axis C of the vane 14.

The pivotal movement of each stator vane 14 is controlled by an operating lever 24 which is fastened to the spindle by appropriate fastening means 26 at a first end region 28 of the operating lever 24. A pin 34 extends from the opposite second end region 36 of the operating lever 24 (see Figs. 2 and 3). The pin 34 extends from the operating lever 24 in a direction substantially parallel to the axis C of the stator vane 14 and spindle 18.

An annular control member in the form of a unison ring 30 extends circumferentially around the casing 22 of the compressor 10. Referring to Fig. 2, the unison ring 30 and the mounting thereon of one of the levers 24 is shown. In this figure, only half of the unison ring 30 is shown for clarity. Each unison ring 30 is of substantially square cross section, and defines a plurality of substantially equi-spaced apertures 32 extending therethrough.

Each pin 34 has a first cylindrical shank portion 38 secured to and extending from the second end region 36 of the lever 24. A second portion 40 extends from the first portion 38 and is provided with a laterally extending projection 41. The projection 41 is of circular cross section and has an arcuate longitudinal profile. The circular cross-section of the pin 34 is tapered, increasing at a region 42 to a maximum at a central region of the second portion 40 and then decreasing from the maximum at a second region 44. In the embodiment shown, the projection 41 is substantially barrel shaped. The projection 41 extends laterally beyond the cylindrical portion 38 at shoulder 43. It will be appreciated that the second portion 40 may be formed integrally with the cylindrical portion 38, for example by casting. Although, the projection 41 has been shown such that it is widest at the central region 46, it will be appreciated that the position of the widest region of the projection 41 will be dependent on various factors including the overall geometry of the arrangement and will vary for different situations.

Referring to Fig. 2, it can be seen that the pin 34 of each operating lever 24 is received in a respective one of the apertures 32 in the unison ring 30. In operation, the unison ring 30 is rotated about its central axis to move each of the operating levers 24 rotationally therewith. The rotational movement of each operating lever causes consequential pivotal movement of its respective stator vane 14.

Referring to Figs. 5A to 5C there is shown three positions of one pin 38 in relation to the aperture 32 of the unison ring 30 in which it is received. The aperture 32 is defined by a cylindrical wall 50. In Fig. 5A there is shown the central or null position of the unison ring 30 and operating lever 24, whereas Figs. 5B and 5C show respectively the extreme positions either side of the central or null position.

In Figs. 5A to 5C the longitudinal central axis of the aperture 32 is shown by the solid line designated A, and the longitudinal central axis of the pin 34 is shown by the dashed line designated B. In Fig. 5A, the axes A and B are coincident and, therefore, only one of the axes, i.e. A is designated. In this position, both diametrically

opposite regions

50A, 50B of the wall 50 of the aperture 32 engage the centre region 46 of the projection 41.

If the unison ring is rotated to the left as shown in the drawing, the aperture will take up the position shown in Fig. 5B. In this position, the axis A of the aperture remains radially oriented with respect to the centre of the unison ring 30. However, the longitudinal axis B of the pin 34 remains parallel to the axis of the pin 34 in the central position as shown in Fig. 5A. The two axes A and B are thus angled to each other. This is represented by the angle α in Fig. 5B. In addition, there will also be a slight longitudinal movement of the pin 34 and the aperture 32 relative to each other.

In this orientation, the first region 50A of the wall 50 (i.e. the right hand side of the drawings as shown in Fig. 5B) engages the corresponding section of the first region 42 of the pin 34, and the diametrically opposite second region 50B of the wall 50 (i.e. the left hand side) engages the diametrically opposite section of the second region 44, as shown.

Similarly, when the unison ring is rotated from the null position to the right to the position shown in Fig. 5C, the central axis A of the aperture 32 extends radially of the unison ring 30, whereas the central axis B of the pin 34 remains parallel to the central axis B shown in Fig. 5A, the two axes A and B being angled to each other by an angle β as shown in Fig. 5C. In this orientation, the first region 50A of the wall 50 engages the second region 44 of the pin 34 and the second region 50B engages the first region 42 of the pin 34. In addition, the movement of the aperture 32 to the position shown in Fig. 5C will cause a slight longitudinal movement of the pin 34 relative to the aperture 32. Thus, as can be seen, the effect is of relative rotational or rolling movement of the wall 50 of the aperture 32 with respect to the projection 41 of the pin 34. Thus, twisting of the pin 34 and of the lever 24, which causes failure in prior art operating arrangements is eliminated or reduced.

Referring to Fig. 6 there is shown an alternative arrangement comprising a pin 134 which is cylindrical in configuration and omits the projection 41 of the pin 34 described above. The arrangement also comprises an aperture 132 in the unison ring 30, in which the side wall of the aperture 132 is provided with an inwardly directed lateral projection 141 which is of an arcuate or barrelled configuration. The projection 141 on the wall 150 engages the cylindrical pin 134. This arrangement operates in a similar manner to that shown in the previous drawings.

Various modifications can be made without departing from the scope of the invention. For example, while primarily designed for use with low pressure compressors or fans the invention could be applied to high pressure compressors or to turbine sections of the engine. The linkage between the unison ring and the pin could differ and the unison ring could be replaced by an alternative form of control member operable to adjust the stator vanes in unison.

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

An operating arrangement for an adjustable stator vane (14) in a gas turbine engine, said arrangement comprising a control member (30) defining an aperture (32,132), and an operating lever (24) having a first end region (28) to be secured to the stator vane (14), and a second end region (36) having a pin (34,134) extending therefrom to be received in said aperture (32,132) in the control member (30), characterised in that the pin (34,134) is movable longitudinally relative to the aperture (32,132), and a laterally extending projection (41,141) is provided on one of the pin (34,134) and the aperture (32,132) to engage the other of the pin (34,134) and the wall (50) of the aperture (32,132), such that relative pivotal and longitudinal movement of the longitudinal axes (A,B) of the pin (34,134) and of the aperture (32,132) is permitted on movement of the control member (30) to move the operating lever (24).
An operating arrangement according to claim 1 wherein the projection (41) is provided on the pin (34).
An operating arrangement according to claim 2 wherein the projection (41) extends substantially wholly around the pin (34).
An operating arrangement according to claim 2 or 3 wherein the pin (34) comprises a first portion (38) constituting a shank, said first portion (38) extending from the second end region (36) of the operating lever (24), and said pin (34) further including a second portion (40) extending substantially co-axially from the first portion (38), longitudinally of the pin (34), the projection (41) extending laterally from the second portion (40).
An operating arrangement according to claim 4 wherein the projection (41) extends substantially the length of the second portion (40) of the pin (34).
An operating arrangement according to claim 4 or 5 wherein the projection (41) tapers such that the cross-section of the second portion (40) increases to a maximum and then decreases from said maximum.
An operating arrangement according to claim 6 wherein the taper is arcuate.
An operating arrangement according to any of claims 4 to 7 wherein both the first portion (38) and the projection (41) are of substantially circular cross-section.
An operating arrangement according to any of claims 3 to 8 wherein the projection (41) is substantially barrel shaped.
An operating arrangement according to claim 1 wherein the projection (141) is provided on the wall (150) of the aperture (132).
An operating arrangement according to claim 10 wherein the projection (141) extends substantially wholly around the aperture (132), and extends longitudinally thereof.
An operating arrangement according to claim 11 wherein the projection (141) tapers such that the cross-section of the aperture (132) decreases to a minimum and then increases from said minimum.
An operating arrangement according to claim 12 wherein the taper is arcuate.
An operating arrangement according to any preceding claim wherein the stator vane (14) has an axis (C) and the pin (34,134) extends in a direction substantially parallel to the axis (C) of the stator vane (14) so that the longitudinal axis (B) of the pin (34,134) is substantially parallel to the axis (C) of the stator vane (C).
An operating arrangement according to claim 14 wherein the stator vane (14) adjustably pivots about said axis of said stator vane (14).
An axial flow compressor incorporating an operating arrangement according to any of claims 1 to 15.
A gas turbine engine incorporating an axial flow compressor according to claim 16.