GB2042434A - Gas turbine engine gas deflection apparatus - Google Patents

Abstract

A gas turbine engine which has thrust vectoring nozzle outlet doors (16, 18) is provided with a door actuating mechanism comprising levers (32, 40) which are both pivotable about 'fixed' points (33, 42) and movable bodily along a screwed shaft (22), to achieve the desired range of door movement. Pivot points (33, 42) are on nuts (28, 30) on sections (24, 26) of shaft (22) having different thread pitches. A motor (46) can drive shaft (22) to move the nuts axially. A pilot's control lever 44 is connected to the lever (40) for direct actuation of the doors (16-18). Applicable to puffer jets. <IMAGE>

Description

SPECIFICATION A gas turbine engine including gas deflection apparatus This invention relates to gas deflection apparatus, of the kind utilised on the exhaust nozzles of gas turbine jet propulsion engines.

It is known to constrict or totally divert a gas flow from a gas turbine jet propulsion engine, to achieve certain functions, e.g. nozzle area variation, thrust vectoring and attitude control of an aircraft powered by the gas turbine jet propulsion engine.

The method normally employed is to move pivotable doors, or cowls across the exhaust gas flow, to a position relative to the exhaust gas flow, and which will achieve the desired object.

Hydraulic rams or individually operable screw jacks comprise the present form of actuating means for achieving the appropriate movements of the doors or cowls, but those systems require complicated, heavy and expensive conduits to convey power to them.

The present invention seeks to provide gas deflection apparatus for a gas turbine jet propulsion engine, including actuation means which is simpler in construction and operation, than known actuation means.

According to the present invention there is provided a gas turbine engine, the exhaust duct of which terminates in at least one gas outlet, which duct includes a pair of doors pivotally connected thereto for movement between a position wherein said doors lie adjacent the wall of said duct and a position wherein at least one of the doors obstructs the or one of said gas outlets, door moving means comprising a shaft supported by the gas turbine engine, a first lever carried by said shaft and movable and pivotable relative thereto, said first lever being connected via its ends to said doors, a second lever carried by said shaft and movable and pivotable relative thereto, one end of said second lever being connected to one end of said first lever and the other end of said second lever being connected to lever pivoting means and means for bodily moving said first and second levers relative to the shaft, said pivoting and movement bodily of the lever being such as to achieve the desired positioning of the doors relative to the exhaust duct gas outlet.

The invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic part view of a gas turbine jet propulsion engine have opposed exhaust nozzles and apparatus in accordance with an embodiment of the invention, Figure 2 is a diagrammatic part view of a gas turbine jet propulsion engine having a single exhaust nozzle and apparatus in accordance with an embodiment of the invention.

In Fig. 1 a gas turbine jet propulsion engine (not shown) has a jet pipe 10 which terminates in an opposed pair of nozzles, 12, 1 4.

A pair of scoop shaped doors 16, 1 8 are mounted within the closed, bulbous portion 20 of jet pipe 10, the mounting consisting of an axle 1 9 about which both doors can pivot independently or together, as explained later in this specification. As can be seen, door 1 8 nests partly within door 1 6 and both lie closely adjacent the inner wall of the bulbous portion 20.

A shaft 22 is rotatably supported from jet pipe 1 0. The left hand end of shaft 22 as viewed in Fig. 1 has a screw thread 24 formed thereon. The right hand end of shaft 22 has a further screw thread 26 formed thereon. The pitch of screw thread 24 is greater than that of screw thread 26, for reasons which are explained later in this specification.

A sleeve 28 engages with screw thread 24 and a further sleeve 30 engages with screw thread 26. Sleeve 28 carries a lever 32, supporting lever 32 at point 33, intermediate its ends, for pivoting movement relative to the sleeve 28 and therefore, relative to shaft 22.

The upper end of lever 32 is connected via a link 34, to door 1 6 at position 1 7 and the lower end of lever 32 is connected via a further link 36, to door 18 at position 1 5.

Rocking of lever 32 about pivot point 33, in a clockwise direction as viewed in Fig. 1, moves lever 32 to a position approximating that shown in chain dotted lines and, results in doors 16, 1 8 moving to positions also shown in chain dotted lines. Such positions effectively cause restriction of the nozzle outlet 1 2 and therefore, ensure a greater proportion of gas flow from nozzle outlet 14. Pivoting lever 32 in an anti-clockwise direction, changes over the outputs from the respective nozzles 12, 14.

In order to achieve appropriate pivoting of lever 32, upper link 34 is extended to the right as viewed in Fig. 1, and its end connected to the upper end 39 of a further lever 40 which is carried by sleeve 30 and is pivotally mounted thereon, at 42.

The lower end of lever 40 is connected via a link 43 to a pilot's or operator's control lever 44, so that manipulation of control lever 44, e.g. in an anti-clockwise direction, will react on levers 40 and 32 and links 34, 36 to move doors 16, 1 8 into the positions shown in chain dotted lines.

In may be necessary to simultaneously move doors 16, 1 8 into respective positions wherein both nozzle outlets 1 2 and 1 6 are constricted or even blocked. This can be achieved by maintaining control lever 44 in a fixed position and rotating shaft 22 by any suitable power means 46 e.g. an electric motor. The direction of rotation will depend on the hand of the screw threads, but in the example sleeves 28, 30 must be caused to move to the right as viewed in Fig. 1.

On sleeve 28, 30 moving along shaft 22, lever 40 will pivot about its connection 50 with link 43, to the position shown in chain dotted lines. Such movement is transmitted via link 34 to the upper end of lever 32 which therefore attempts to pivot in like manner.

However, the pitch of screw thread 24 which has a greater pitch than screw thread 26, moves sleeve 28 and consequently, lever 32, along shaft 22 at a rate sufficient to cancel the pivoting effect that lever 40 has on lever 32. Equal pulling forces are therefore exerted on doors 1 6, 18 via links 34, 36 with the result that both nozzle outlets 1 2, 1 4 are constricted or totally blocked, as required.

In the embodiment described herein, levers 32 and 40 are shown to be equal in length.

Therefore, the ratio of the two thread pitches should be 2:1.

In Fig. 2 an operating mechanism identical to that described in Fig. 1 is used, to manipulate a pair of clamshell doors 52, 54 which are arrangec' adjacent the outer wall of a single nozzle 56, and connected to it via a common pivot axle 58. Operation of the mechanism is also identical with the operating of the mechanism in Fig. 1 and therefore will not be described in detail. However, it will be clear that thrust vectoring and nozzle area varying can be achieved, where the present invention is utilised on a nozzle having a single outlet.

The invention could be adopted for utilisation with puff pipes i.e. conduits leading from engine bleed points, to aircraft wing tips (not shown) and/or fuselage extremities (not shown) for the purpose of attitude control during hovering of the aircraft, because the degrees of nozzle outlet area variation and directional discharge variation enables thrust vectoring through 180 to be achieved.

Claims (8)

1. A gas turbine engine, the exhaust duct of which terminates in at least one gas outlet, which duct includes a pair of doors pivotally connected thereto for movement between a position wherein said doors lie adjacent the wall of said duct and a position wherein at least one of the doors obstructs the or one of said gas outlets, door moving means comprising a shaft supported by the gas turbine engine, a first lever carried by said shaft and movable and pivotable relative thereto, said first lever being connected via its ends to said doors, a second lever carried by said shaft and movable and pivotable relative thereto, the end of said second lever being connected to one end of said first lever and the other end of said second lever being connected to lever pivoting means and means for bodily moving said first and second levers relative to the shaft, said pivoting and movement bodily of the levers being such as to achieve the desired positioning of the doors relative to the exhaust duct gas outlet.

2. A gas turbine engine as claimed in claim 1 wherein said shaft is screw threaded and is rotatable about its longitudinal axis so as to displace said first and second levers along said axis by means of force exerted via said screw threads, said screw threads comprising two portions, one having a greater pitch than the other and moving said first lever, the other moving the second lever.

3. A gas turbine engine as claimed in claim 1 or claim 2 including a pair of opposed gas outlets with the two doors pivotally mounted between them and within the confines of the duct, such that pivoting of the doors in either direction will cause obstruction of at least one gas outlet.

4. A gas turbine engine as claimed in claim 1 or claim 2 including only a single gas outlet with said doors pivotally mounted one either side thereof such that pivoting of the doors in either direction will result in obstruction of at least one side of said single gas outlet.

5. A gas turbine engine as claimed in any previous claim wherein the lever pivoting means comprises a manually operated lever, connected to the second lever at the end remote from the connection of the second lever to the first lever.

6. A gas turbine engine as claimed in any of claims 1 to 4 wherein the lever pivoting means comprises a power operated lever, connected to the second lever at that end remote from the connection of the second lever to the first lever.

7. A gas turbine engine substantially as described in this specification, with reference to Fig. 1 of the drawings.

8. A gas turbine engine substantially as described in this specification, with reference to Fig. 2 of the drawings.