GB2393941A

GB2393941A - Vectorable variable area nozzle

Info

Publication number: GB2393941A
Application number: GB9001822A
Authority: GB
Inventors: Nicholas James Joyce
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1990-01-26
Filing date: 1990-01-26
Publication date: 2004-04-14
Anticipated expiration: 2010-01-26
Also published as: GB2393941B; US6910328B1; GB9001822D0

Abstract

A vectorable variable area nozzle is formed by a pair of parallel sidewalls 15, a pair of opposed clamshell elements 16 arranged between the sidewalls and each able to rotate about an axis 22 perpendicular to the sidewalls and a pair of flaps 17 each pivotally linked to the downstream end of one of the clamshell elements. The elements 16 form a convergent section of the nozzle, and the flaps 17a divergent section. In use the thrust produced by the nozzle can be vectored by rotating the two clamshell elements about their respective axes and/or by rotating the flaps 17 about their axes 23 relative to the elements.

Description

- 1 - 239394 1

VECTORABLE VARIABLE AREA NOZZLE

This invention relates to a vectorable variable area nozzle for use on a jet engine, and particularly to a nozzle able to vector in a single plane.

A known nozzle of this type is shown in cross section on figures 1 and 2. This nozzle comprises a jet pipe connected to the downstream end of a gas turbine engine (not shown). A first cylindrical section 2 having an axis 3 is linked to the end of the jet pipe 1 an a second larger cylindrical section 4 coaxial with the first is placed with its inner surface in sliding contact with the outer surface of the first cylindrical section 2. A duct 5 is linked to the downstream end of the second cylindrical section 4. A convergent variable area section 6 is then linked to the downstream end of the duct 5 and a divergent variable area section 7 is linked to the downstream end of the convergent section 6. To vector the thrust of the nozzle the second cylindrical section 4 is pivoted about the axis 3, sliding over the first cylindrical section 1 and altering the facing of the convergent and divergent sections 6 and 7 which are secured to it.

The convergent section 6 is formed by a plurality of linked segments, each of the segments forming a circumferential sector of the convergent section 6 and 5. In order to vary the throat area of the nozzle the segments are pivoted relative to the duct 5 so that their downstream ends define a smaller or larger area.

The nozzle is kept gas tight during this movement by the segments remaining in sliding contact with one another.

- 2 - The divergent section 7 is also formed by a plurality of linked segments. Each of the segments forms a circumferential section of the divergent section 7 and is pivotally linked to the end of the convergent section 6. To vary the exit area of the nozzle the segments are pivoted relative to the convergent section 6 so that their downstream ends define a smaller or larger area.

Again the nozzle is kept gas tight by the segments remaining in sliding contact with one another.

In figure 1 the nozzle is shown with minimum throat and exit areas while in figure 2 the nozzle is shown with maximum throat and exit areas. Such a system has a number of disadvantages, a complex and heavy actuating system is needed because separate actuators are required to vector the nozzle and to alter it's throat and exit areas, the vectoring actuator especially must be very powerful because it must move the other actuators. The large number of moving parts requires complex sealing arrangements, which add weight and cost.

This invention is intended to provide a vectorable variable area nozzle at least partially overcoming these problems. This invention provides a vectorable variable area nozzle for a gas turbine engine, the nozzle comprising, a pair of fixed parallel sidewalls, a pair of opposed elements extending between the sidewalls defining a convergent section of the nozzle between them and each able to rotate relative to the sidewalls about an axis perpendicular to the sidewalls in order to vector the thrust produced by the nozzle, and a pair of opposed flaps extending between the sidewalls downstream of the convergent section defining a divergent portion of the nozzle between them and each able to rotate relative to

- 3 - a respective one of the elements about a separate axis.

A nozzle embodying the invention is shown by way of example only in the accompanying diagrammatic figures in which; Figure 3 shows a nozzle employing the invention in cross section in a first configuration, Figures 4, 5 and 6 show the same nozzle in cross section in three further configurations, Figure 7 shows a rear view of the same nozzle in the configuration of figure 1, and, Figure 8 shows a detail of the nozzle of figure 3, identical parts having the same reference numerals throughout. Referring to figures 3 to 6 a cross section along the axis of a variable area nozzle 10 is shown. Exhaust gasses from a gas turbine engine including an afterburner (not shown) travel along a duct 11 in the direction of the arrow 12. The duct ll is formed by a pair of parallel walls 14 and a pair of parallel sidewalls 15 and is rectangular and symmetrica; about an axis 13.

The nozzle 10 is at the downstream end of the duct 11 and is formed by a pair of opposed clamshell elements 16 and a pair of opposed flaps 17.

The clamshell elements 16 and flaps 17 extend across the full width of the duct 11 between the two sidewalls 15.

Each of the clamshell elements 16 has an inner surface

- 4 - 18 curved to form a section of a cylinder and a flat outer surface 19. Each of the flaps 17 has a flat inner surface 20.

The opposed inner surfaces 18 of the clamshell elements 16 and the upstream ends of the flaps 17 define a convergent section of the nozzle 10, while the opposed inner faces 20 of the flaps 17 define a divergent section of the nozzle 10. The throat area of the nozzle 10 is controlled by the separation of the upstream ends of the two flaps 17 and the exit area of the nozzle 10 is controlled by the separation of the downstream ends of the two flaps 17.

Each of the clamshell elements 16 has a support member 21 at each end adjacent to the sidewalls 15. Each support member 21 is secured at one end to a clamshell element 16 and is pivotally linked at its other end to a sidewall 15 for rotation about an axis 22. All of the support members 21 are arranged to rotate about the same axis 22 which is perpendicular to the sidewalls 15.

The axis of the cylindrical surfaces 18 of the clamshells 16 are coaxial with the axis 22.

Each of the flaps 17 is pivotally linked to a respective one of the clamshell elements 16 for rotation about an axis 23 perpendicular to the sidewalls 15.

Each of the axes 23 are situated at a position adjacent the mean centre of pressure on their respective flaps 17, that is approximately halfway along their respective flaps 17, in order to reduce the couple acting on the flaps 17 about their respective axis 23 due to the pressure of the gas in the duct 11 acting on the inner faces 20 of the flaps 17.

- 5 - Linear actuators 24 are each attached to a clamshell element 16 at a point 25 and to a flap 17 at a point 26, By altering the lengths of the actuators 24 the flaps 17 can be rotated about their respective axes 23 relative to the clamshell elements 16. The linear actuators 24 are contained within recesses 33 inside the clamshell elements 16. As a consequence of the positioning of the axes 23 to reduce the pressure generated couple on the flaps 17 the linear actuators 24 can be made relatively lightweight because the load they have to apply is much less than if the axes 23 were at one end of the flaps 17 and so generating a larger pressure couple.

In order to prevent the gasses travelling along the duct 11 escaping as the flap 17 moves relative to the clamshell element 16 a sealplate 28 is pivotally attached to the leading edge of each flap 17. Each sealplate 28 forms a sliding contact seal with the bottom of a recess 29 in the inner surface 18 of a clamshell element 16. The sealplate 28 is held in contact with the clamshell element 16 by the gas pressure within the duct 11.

Linear actuators 27 are each attached to a clamshell element 16 at a point 34 and to a sidewall 14 at a point 35. By altering the lengths of the linear actuators 27 the clamshell elements 16 can be rotated about the axis 22 relative to the duct 11. The linear actuators 27 are contained within recesses 36 inside the walls 14.

In order to prevent the gasses travelling along the duct 11 escaping as the clamshell elements 16 move relative to the walls 14 a sliding seal is formed between the curved inner surface 18 of each of the clamshell elements 16 and a curved outwardly facing surface 29 of

- 6 - a respective wall 14. The curved surfaces 18 and 29 are all cylindrical arcs having the axis 22 as their axis of curvature, as a result they remain in contact and form a seal as the clamshell elements 16 rotate about the axis 22. In operation it is possible to vary the throat and exit areas, divergence angle and direction of thrust of the nozzle 10 by altering the lengths of the linear actuators 27 and rotating the clamshells 16 about the axis 22. It is also possible to vary the throat and exit areas, divergence angle and direction of thrust of the nozzle 10 by altering the lengths of the linear actuators 24 and rotating the flaps 17 about their respective axes 23.

The direction of thrust of the nozzle 10 can be altered independently of the throat and exit areas and divergence angle of the nozzle 10 by rotating the clamshells 16 in the same direction and through the same angle about the axis 22.

Rotation of the clamshells 16 in opposite directions about the axis 22 will alter the throat and exit areas and the divergence angle of the nozzle 10 in the same sense, while rotation of the flaps 17 in opposite directions about their respective axes 23 will alter the exit area and divergence angle in one sense and the throat area in the opposite sense. Thus by appropriate rotations of the clamshells 16 and flaps 17 it is possible to set the throat and exit areas and divergence angles of the nozzle 10 as required.

A plate 31 is hinged to the downstream edge of each of the walls 14. Each of the plates 31 is urged into rubbing contact with the flat outer surface 19 of a

- 7 - respective on of the clamshell elements 16 by spring biasing means (not shown), in order to present a smooth surface to the airflow past the nozzle 10.

A plate 32 is hinged to the downstream edge of each of the clamshell elements 16. Each of the plates 32 is held in close proximity to the outer surface of a respective one of the flaps 17 by a link member 37 pivotally connected to the plate 32 and the flap 17, in order to present a smooth surface to the airflow past the nozzle 10. The link member 37 is not shown in figures 3 to 5 for clarity but is shown in figure 7.

In figures 3 and 4 the nozzle to is shown with the clamshell elements 16 and the flaps 17 arranged symmetrically on each side of the axis 13 of the duct 11, as a result the thrust produced by the nozzle 10 acts along the axis 13. This is achieved by altering the lengths of the two linear actuators 24 to be the same and the lengths of the two linear actuators 27 to be the same.

In figure 3 the lengths of the linear actuators 24 and 27 have been set to configure the nozzle 10 in a non-

afterburning cruising mode. This cruising mode having relatively small throat and exit areas, defined between the upstream and downstream ends respectively of the flaps 17, and a relatively small divergence angle, defined by the angle between the two inner faces 20 of the flaps 17.

In figure 4 the linear actuators 27 have been shortened rotating the clamshell sections 16 about the axis 22 and and so increasing the throat and exit areas and divergence angle of the nozzle lo. Also the linear actuators 24 have been lengthened, increasing the exit

- 8 - area and divergence angles but decreasing the throat area of the nozzle 10. As a result the nozzle 10 has been configured for a high engine thrust with afterburning mode. This afterburning mode having relatively large throat and exit areas and divergence angle. In figure 5 the nozzle 10 is shown configured in a non-afterburning mode with vectored thrust. In this vectored thrust mode the lengths of the linear actuators 24 have been left the same as in figure 3 while the linear actuators 27 have had their lengths altered in opposite senses so that the clamshell elements 16 have both been rotated anti-clockwise through the same angle X. As a result the throat and exit areas and divergence angle of the nozzle 10 are unchanged but the nozzle 10 has been rotated anti-clockwise through an angle X about the axis 22 so that it produces a thrust along and is symmetrical about, an axis 30 at an angle X to the axis 13. In figure 6 the nozzle 10 is shown configured in a non- afterburning mode with vectored thrust. In this vectored thrust mode the lengths of the linear actuators 27 have been left the same as in figure 3 while the linear actuators 24 have had their lengths altered in opposite senses so that the flaps 17 have both been rotated anti-clockwise through an angle y.

As a result the divergent section of the nozzle 10 has been rotated anticlockwise through an angle y so that it produces a thrust along an axis 38 at an angle y to the axis 13. The nozzle 10 is not however symmetrical about the axis 38 since it has a scarfed nozzle because

- 9 - the flaps 17 project different distances along the axis 38. If desired the nozzle 10 can be configured with any desired combination of throat and exit areas divergence angle and thrust direction by appropriate adjustment of the linear actuators 24 and 27.

The actuators 24 need only exert a relatively small force compared to the force exerted by the linear actuators 27 because the gas pressure loads on the flaps 17 are balanced, at least in part, about their respective axes 23.

Since actuators can generally be made faster acting if the force they must exert is lower this allows a quick response by moving the flaps 17 if thrust vectoring over a small angle is required, to maintain aircraft stability for example, with the clamshells 16 being moved if thrust vectoring over a larger angle is required, for take off for example.

Both the clamshells 16 and flaps 17 could be used simultaneously as desired, this would allow vectoring through larger angles.

Other types of actuators such as rotary actuators, could be substituted for linear actuators 24 and 27 provided they were arranged to rotate the clamshell elements 16 and flaps to 17 about their respective axis 22 and 23.

The positioning of the actuators 24 and 27 and the methods of sealing the nozzle 10 could of course be altered if necessary. For example the actuators 27 could be placed outside the sidewalls 15 moving the clamshell via a mechanical linkage.

- 10 Although it is preferred to have the two clamshells 16 rotate about a common axis 22 it would be possible to have each clamshell 16 rotate about a separate axis.

Although it is preferred that each of the axes 23 be fixed relative to one of the clamshells 10, a linkage allowing the axis 13 to move relative to the clamshells 16 could be used.

The method of streamlining the nozzle 10 by way of plates 31 and 32 could be altered, for example both plates 31 and 32 could be kept in contact with the nozzle 10 by spring loading or a linkage, instead of the plates 31 and 32 being kept in contact by different methods.

Claims

- 11 - CLAIMS

1 A vectorable variable area nozzle for a gas turbine engine, the nozzle comprising, a pair of fixed parallel sidewalls, a pair of opposed elements extending between the sidewalls defining a convergent section of the nozzle between them and each able to rotate relative to the sidewalls about an axis perpendicular to the sidewalls in order to vector the thrust produced by the nozzle, and a pair of opposed flaps extending between the sidewalls downstream of the convergent section defining a divergent portion of the nozzle between them and each able to rotate relative to a respective one of the elements about a separate axis.

2 A nozzle as claimed in claim 1 in which the respective axis of rotation of each flap is situated between the upstream and downstream ends of the flap.

3 A nozzle as claimed in claim 1 or claim 2 in which each flap can rotate relative to a respective one of the elements about a separate axis fixed with respect to that element.

4 A nozzle as claimed in any preceding claim in which both of the opposed elements rotate about the same axis. 5 A nozzle as claimed in any preceding claim in which the thrust produced by the nozzle can also be vectored by rotating the flaps about their respective axes.

r - 12 6 A nozzle as claimed in any of claims 3 to 5 in which the inner faces of the opposed elements are cylindrical sections about their common axis of rotation. 7 A nozzle as claimed in any of claims 3 to 6 in which the flaps are attached only to their respective elements such that the elements may be rotated about their common axis of rotation to vector the thrust produced by the nozzle without altering the area of the nozzle.

8 A nozzle substantially as shown in or as described with reference to figures 3 to 8 of the accompanying drawings.

Amendmc',ts to the claims have been filed as follows 1 A vectorable variable area nozzle for a fluid flow duct, comprising a pair of fixed sidewalls, a pair of opposing elements which extend between the sidewalls to define a convergent nozzle section, and a pair of opposing flaps which extend between the sidewalls downstream of the opposing elements to define a divergent nozzle section, the elements being mounted for rotation about a common first À; axis orthogonal to the sidewalls and each of the flaps being mounted for rotation relative to an adjacent one of the elements about respective second and third axes orthogonal to the sidewalls, there being provided first and second actuator means for moving the elements independently about the first axis and third and fourth actuator means for respectively moving a first of the flaps about the second axis and a second of the flaps about the third axis, whereby the third actuator means is attached to a first of the elements and the fourth actuators means is attached to a second of the elements such that rotation of the elements in the same sense will vector the thrust produced by the nozzle without altering the throat area, exit area, or divergence angle of the nozzle, and rotation of the elements in opposite senses will alter the throat area, exit area and divergenceangle of the nozzle without vectoring the thrust produced by the nozzle. 2 A nozzle as claimed in claim 1 in which the respective axis of rotation of each flap is situated between the upstream and downstream ends of the flap.

A nozzle as claimed in claim 1 or claim 2 in which the second axis is fixed in relation to the first of the elements and the third axis is fixed in relation to the second of the elements.

4 A nozzle as claimed in claim 1 in which the inner faces of the opposed elements are cylindrical sections about the common first axis of rotation.

5 A nozzle as claimed in any preceding claim in which the flaps are rotatable about their respective axes to vector the thrust produced by the nozzle.

6 A gas turbine engine including a nozzle according to any preceding claim.

7 A nozzle substantially as shown in or as described with reference to figures 3 to 8 of the accompanying drawings.