GB2488962A

GB2488962A - Variable section vane

Info

Publication number: GB2488962A
Application number: GB9305226.4A
Authority: GB
Inventors: Jason Neil Lloyd
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1993-03-13
Filing date: 1993-03-13
Publication date: 2012-09-19
Anticipated expiration: 2013-03-13
Also published as: GB9305226D0; GB2488962B

Abstract

A deflection vane for use, for example, in a cascade nozzle in the gas stream of a vectoring lift nozzle of a VTOL aircraft has a transverse section variable according to the position of the vane. The vane has flow surfaces 8 and 9 formed of flexible material which bear against an internal cam 14 of elliptical section. The cam is fixed so that as the vane is turned about its longitudinal axis to deflect the gas stream it changes shape. The arrangement is such that in a cascade array of parallel vanes the throat gap Y between adjacent vanes remains constant thereby avoiding throttling the gas stream.

Description

VARIABLE SECTION VANE

This invention relates to a variable section vane. In particular, the invention concerns a variable section vane for use in a vectorable thrust nozzle for an aircraft propulsion system.

Vectorable thrust nozzles are often employed in vertical take-off and landing (VTOL) aircraft and short take-off and landing (STOL) aircraft for the purpose of vectoring the direction of lift thrust and for flight attitude control. Such aircraft generally employ gas turbine engines as their primary propulsion means.

One such thrust vectoring system in a VTOL aircraft has an array or cascade of streamlined section vanes deployed into a generally downwardly moving gas stream.

The vanes may be turned to deflect the gas stream and thereby vector its thrust direction.

In this thrust vectoring system each vane in the array is mounted for angular displacement so that its angle of incidence with the exhaust stream is variable. It is a disadvantage of the arrangement however that an increase * in the angle of incidence of the vanes in the array is accompanied by a decrease in the throat gap between adjacent vanes. The result is a throttling effect on the gas flow and the efficiency of the arrangement is reduced accordingly.

It is an object of the present invention to provide a solution to this problem and to provide a thrust vectoring system in which each vane is angularly displaceable and in a cascade of such vanes the throat gap between adjacent vanes can be maintained substantially constant.

According to one aspect of the invention there is provided a variable section vane comprising vane surface means defining first and second fluid flow surfaces on opposite sides of the vane with spanwise extending upstream and downstream edges, non-circular cam means extending between the two surfaces in a spanwise direction and bearing against the internal faces of the flow surfaces urging them apart in order to shape the vane, and means for rotating the vane relative to the internal cam means whereby to alter the shape of the vane.

Preferably, the.first and second fluid flow surfaces are made of a flexible material such as thin spring steel, and the cam means comprises a substantially elliptical section cam extending through the vane. The vane is rotatable about an axis relative to the cam, and the cam may bear against the first and second fluid flow surfaces so that during such rotation the cross-section of the vanes is changed. The cam may be rotatable so as to assist and control the change in cross-section of the vanes.

According to another aspect of the invention there is provided a vectorable thrust nozzle comprising a cascade of variable section vanes of the type referred to above.

In one embodiment the vane cascade is carried by a frame which may be stowed within the fuselage of an aircraft and deployed as required to provide vectoring control a lift jet stream.

The invention and how it may be carried out in practice will now be described further by way of example with reference to the accompanying drawings in which; Figure 1 shows a section through a vane cascade with each of the vanes in a neutral position relative to the flow of gas in the duct, Figure 2 illustrates the throat gap between two of the vanes shown in Figure 1 at a first deflection angle, and Figure 3 shows the throat gap of the vanes of Figure 2 at a second deflection angle.

Referring to the drawings Figure 1 shows a section through a vane cascade for a vectoring nozzle which receives a gas stream from an aircraft propulsion engine. All the vanes 1 in the cascade array 2 are shown set at a neutral setting with respect to the direction 3 of a gas stream from the propulsion engine not shown. The vanes are mounted in a frame 4 which is either mounted permanently in the gas stream or is deployable into it. The vanes are spaced apart equidistantly in the frame 4 so the throat gap Y between any two adjacent vanes is the same.

Detail of the vanes is more clearly shown in Figure 2.

Each vane 1 has a leading edge 5, a trailing edge 6 and a central region, generally indicated at 7, formed by a first flow surface S and a second flow surface 9. The vanes have a generally elliptical transverse section and are of hollow construction. The flow surfaces 8,9 are formed of flexible material for example thin spring steel sheet. End plates, not visible in the illustrated section, ara provided at opposite ends of the vanes 1 and are adapted to mount the vanes in frame 4 for pivotal movement about a longitudinal axis. The vanes are supported for angular displacement about axes 11.

The range of angular displacement being 45° aft and 25° forwards through a vertical angle under the aircraft.

Angular displacement of the vanes is controlled by means of a shaft 12 which is coupled to the leading edges of the vanes. The shaft 12 is slidable between left and right positions, with reference to the plane of the drawing, by means of an actuator such as an air motor 13.

The shape or at least the maximum width of a vane is determined by a cam bar 14 which extends longitudinally through each vane. Cam bar 14 has an elliptical transverse cross-section and bears against the inner face of the vane surfaces 8,9. The vanes are constructed such that the vane surfaces are sprung inwards and bear tangentially against the cam surface.

Thus, when a cam is rotated about its longitudinal axis relative to the vane the distance between surface contact points changes according the chord of the ellipse.

The cam bar 14 may be held against rotation in the frame side members so that movement of actuator shaft 12 rotates the vanes in unison relative to the cam. In this way the vanes change shape as they are vectored between forward and aft deflections. As a vane is angularly displaced about axis 11 from its neutral position to either side towards the fully displaced positions, then the width of the vane is caused to change as can be seen in Figures 2 and 3. However, the throat gap Y between adjacent vanes remains unchanged avoiding throttling of the gas flowing over the vanes.

In order to assist the motion and reduce wear and friction the cam bar 14 may be provided with rollers 15 extending along the bar for engagement with the inner faces of the flow surfaces 8 and 9.

It will be understood that although the cascade nozzle, as illustrated in Figure 1, is shown set orthogonally with respect to the direction of gas flow 3 this need not always be so. The plane of the nozzle may be inclined relative to the gas 2 lOt7 direction, the range of vectoring angles may be biased further in one direction, for example, rearwards. Similarly the orientation of the cam bar 14 for may be set to art initial position other than that shown in the drawing.

Claims

CLAIMS1 A variable section vane comprising vane surface means defining first and second fluid flow surfaces on opposite sides of the vane with spanwise extending upstream and downstream edges, non-circular cam means extending between the two surfaces in a spanwise direction and bearing against the internal faces of the flow surfaces urging them apart in order to shape the vane, and means for rotating the vane relative to the internal cam means whereby to alter the shape of the vane.
2 A variable section vane as claimed in claim 1 wherein at least one of said first and second fluid flow surfaces is formed of flexible material.
3.A variable section vane as claimed in claim 2 wherein said flexible material is sheet metal.

4 A variable section vane as claimed in claim 3 wherein said sheet metal *is spring steel.6 A variable section vane according to claim 5 wherein said cam means comprises a cam located within each vane.7 A variable section vane as claimed in any preceding claim 6 wherein the cam is substantially elliptical in cross-section having a major axis and a minor axis orthogonal to the span of the vane.8 A variable section vane as claimed in claim 7 wherein the major axis of the vane and the cam are -7.-Sin the same plane and lie normal to each other when the vane occupies a neutral position.9 A variable section vane as claimed in claims 7 or 8 wherein the cam is fixed and the vane is rotatable.A variable section vane as claimed in claims 7 or 8 wherein the cam is rotatable and the vane is fixed.11 A variable section vane as claimed in claims 9 or wherein rotation of each said vane relative to each said cam causes the camber of the first and second fluid flow surfaces to change.12 A variable section vane according to any preceding claim wherein the gaps between adjacent vanes remain substantially constant when relative rotation takes place between each said vane and each said cam.13 A variable section vane according to any precedingclaim arranged for introduction into and out of astream of gaseous fluid.14 A variable section vane according to any preceding claim when installed in an aircraft for deflecting the flow of fluid derived from a gas turbine engine.A variable section vane substantially as hereinbefore described with reference to Figures 1, 2 and 3.16 A vectoring nozzle comprising a cascade array of variable section vanes substantially as claimed in any preceding claim.Amendments tO the claims have beCfl filed as follows 1 A variable section vane comprising vane surface means defining first and second fluid flow surfaces on opposite sides of the vane with spanwise extending upstream and downstream edges, non-circular cam means extending between the two surfaces in a spanwise * direction and bearing against the internal faces of the flow surfaces urging them apart in order to shape the vane, and means for rotating the vane relative to the internal cam means whereby to alter the shape of the vane.2 A variable section vane as claimed in claim 1 wherein at least one of said first and second fluid flow surfaces is formed of flexible. material..3 A variable section vane as claimed in claim 2 wherein said flexible material is sheet metal.4 A variable sectipn vane as claimed in claim 3 wherein * said sheet metal is spring steel.A variable section vane as claimed in any preceding claim wherein the vane is generally elliptical in transverse section.6 A variable section vane according to claim 5 wherein said cam means comprises a cam located within the vane.7 A variable section vane as claimed in any preceding claim 6 wherein the cam is substantially elliptical in cross-section having a major axis and a minor axis orthogonal to the span' of the vane.8 A variable section vane as claimed in claim 7 wherein the major axis of the vane and the cam are in the same plane and lie normal to each other when the vane occupies a neutral position.9 A variable section vane as claimed in claims 7 or B wherein the cam is fixed and the vane is rotatable.A variable section vane as claimed in claims 7 or 8 wherein the cam is rotatable and the vane is fixed.1]. A variable section vane as claimed in claims 9 or wherein rotation of each said vane relative to each said cam causes the camber of the first and second fluid flow surfaces to change.12 A variable section vane according to any preceding claim wherein the gaps between adj acent vanes remain substantially constant when relative rotation takes place between each said vane and each said cam.13 A variable section vane according to any precedingclaim arranged for introduction into and out of astream of gaseous fluid.14 A variable section vane according to any preceding claim when installed in an aircraft for deflecting the flow of fluid derived from a gas turbine engine.A variable section vane substantially as hereinbefore described with reference to Figures 1, 2 and 3.16 A vectoring nozzle comprising a cascade array of variable section vanes substantially as claimed in any preceding claim.