GB2435676A

GB2435676A - Exhaust nozzle for gas turbine aeroengine

Info

Publication number: GB2435676A
Application number: GB8903673A
Authority: GB
Inventors: John Matthew Hall
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1989-02-17
Filing date: 1989-02-17
Publication date: 2007-09-05
Anticipated expiration: 2009-02-17
Also published as: DE4004919A1; FR2894630A1; GB8903673D0; GB2435676B

Abstract

A nozzle is provided which is capable of varying its outlet area and varying the distribution of outlet area thereacross. The nozzle comprises a generally rectangular duct 32 and a parallelogram-shaped plug 40 which is expandable to vary the outlet area and translatable across the outlet 38 of the nozzle to vary the distribution of outlet area thereacross by means of independently actuatable ballscrews 66, 68. When the ballscrews 66,68 are rotated, as by motors 72, in the same direction, translation of the plug 40 across the outlet 38 occurs, whereas when they are rotated in opposite directions, a variation in width of the plug 40 occurs. The plug 40 is formed of four panels 42,44,46,48 hinged together at 54,56,58,60, and connected to sleeves 70 of the ballscrews 66,68. A pair of such nozzles spaced along an aircraft centreline can be used to provide both pitch and roll control.

Description

AN EXHAUST NOZZLE FOR A GAS TURBINE AEROENGINE

This invention relates to an exhaust nozzle for a gas turbine engine and relates particularly to an exhaust nozzle suitable for use in a vertical take off or landing (VTOL) type of aircraft.

Many types of nozzles are known in the gas turbine engine field. Perhaps one of the most well known is the rotatable bent nozzle used on the Rolls-Royce plc Pegasus engine which powers the British Aerospace plc Harrier aircraft. Two nozzles are provided on each side of the aircraft and all the nozzles are vectorable forwardly and rearwardly to provide pitch control, whilst small reaction jets provided towards the ends of the wings provide roll control during hover.

One disadvantage of the above mentioned arrangement is that the nozzles necessarily project beyond the surface of the fuselage and hence hinder the smooth flow of air over the aircraft particularly at high forward speeds.

Further to this, complex and expensive ducting is required to provide air to the reaction jets.

It is an object of the present invention to provide an exhaust nozzle suitable for use in an aircraft requiring both pitch and roll control which provides both types of control whilst presenting little or no obstruction to the airflow passing over the surface of the aircraft during forward flight. It will be appreciated that by providing both types of control with the nozzle itself no ducting or reaction jets are required although it will be appreciated that they may be employed to improve the role rate and controlability during hover.

The present invention provides a nozzle for a gas turbine engine having a longitudinally extending central axis, the nozzle comprising a duct having sidewalls terminating in an outlet having an outlet plane, a plug disposed within the nozzle and projecting through the outlet to define therewith a final outlet area of the nozzle, said plug being mounted so as to he capable of transverse movement in the plane of the outlet thereby to vary the distribution of outlet area thereacross and capable of varying its width thereby to vary the outlet area of the nozzle, and means for causing said movement and said expansion.

The present invention will now be more particularly described with reference to the accompanying drawings, in which: Figure 1 is a side elevation of an aircraft incorporating nozzles which are the subject of the present invention, Figure 2 is a cross sectional view of a gas turbine engine and two particular arrangements of nozzles, Figure 3 is a perspective view of one of the nozzles shown in figures 1 and 2 and, Figure 4 is a view in the direction of arrow A in figure 3.

Referring to figures 1 and 2, an aircraft shown generally at 10 is provided with a gas turbine engine 12 and a forward and a rearward nozzle 14, 16 respectively.

The engine shown is of a tandem fan arrangement comprising in flow series a first axial flow compressor 18, a fluid flow duct 20, a second axial flow compressor 22, combustion means 24 downstream of the compressor 22, turbine means 26 linked to drive the compressors 18, 22 and a rear exhaust duct 28 which terminates at one of said nozzles 16 positioned towards the rear of the aircraft. The forward nozzle 14 is positioned to receive air from the first compressor 18 via the fluid flow duct as and when required.

A tandem fan type engine 12 is capable of operating in two distinct modes namely series and parallel flow. In series flow mode, used during forward flight, all the flow from the first compressor 18 is directed into the second compressor 22 to supercharge it. In parallel flow mode used during hover or vertical take off or landing, all the air from the first compressor 18 is directed to the forward nozzle 14 and an auxiliary air intake (not shown) is opened up to provide air to the second axial flow compressor 22. A valve shown diagramatically at 30 is provided in the fluid flow duct to prevent air from the first compressor 18 entering the second compressor 22 during the parallel mode of operation whilst a valve not shown is generally provided to obstruct the outlet to the forward nozzle 14 during operation in series mode. It will be appreciated that the nozzles 14, 16 to be described in detail below may -be used in conjunction with many other types of gas turbine engines and consequently the scope of use of the present invention is not intended to be limited to use on tandem fan type engines.

Referring now more particularly to figures 3 and 4, each nozzle 14, 16 comprises a duct 32 of generally rectangular cross sectional form having sidewalls 34, 36 terminating in an outlet 38 having an outlet plane P, and a plug 40 dispersed within the nozzle and projecting through the outlet 38 to define therewith a final outlet area of the nozzle. The sidewalls are divided into a first and a second pair of mutually confronting sidewalls the first pair 34 of which extend across the width W of the nozzle whilst the second pair 36 extend in the direction of the nozzles depth D between said first pair. The plug 40 comprises four plates 42, 44, 46 and 48 provided in two side plate pairs 50, 52 hinged to each other to form a parallelogram shaped obstruction in the outlet of the nozzle 14, 16. The hinges 54, 56 which join the plates of each side plate pair 50, 52 are arranged to extend longitudinally between the first pair of sidewalls 34, parallel to each other, and in the same plane as the outlet plane P. The remaining two hinges 58, 60 extend parallel to said first two hinges 54, 56 and act to join the plate pairs together. An actuation mechanism 62 in the form of two baliscrews 64, 66 is provided to facilitate transverse movement of the plug across the width W of the nozzle in the plane of the outlet P thereby to vary the distribution of outlet area A thereacross and to expand the plug 40 bodily thereby the vary the outlet area A. The baliscrews 64, 66 are arranged on opposite sides of the nozzle 40 to each other and extend axially along one or other of the first pair of sidewalls 34 adjacent the outlet 38 of the nozzle 14, 16. Each ballscrew 64, 66 comprises a central shaft 68, an outer sleeve 70 and an actuation motor 72 connected to drive its associated shaft 68 in a rotary manner. The outer sleeve 70 of the first baliscrew 64 is connected to the first plate pair 50 adjacent their common hinge joint 54 whilst the outer sleeve 70 of the second baliscrew 66 is similarly connected to the second plate pair 52. The sleeves 70 may be connected to their respective plate pairs on the same side of the nozzle 14, 16 other or on opposite sides to each other as shown in figures 3 and 4.

The operation of baliscrews is well known in the prior art and therefore not described in detail herein however, for the purposes of clarity, rotation of the shaft 68 acts to move the outer sleeve 70 along the shaft 68 thereby converting rotational motion into linear motion. The motors 72 provided to rotate each shaft are reversible thereby allowing movement of the sleeve 70 up and down the shaft 68 as and when required.

It will be appreciated that alternative actuators may be used such as hydraulic rams or pneumatic cylinders all of which are well known for use in similar applications.

In operation the outlet area of the nozzle may be varied by increasing or decreasing the width of the plug.

The width of the plug is increased by rotating the shafts 68 of each ballscrew 64, 66 such that the two outer sleeves 70 move away from each other in the direction of arrows I and I2 It will be appreciated that this movement acts to draw the upstream and downstream ends 72, 74 respectively of the plug 40 together and the two sides are pulled apart thereby decreasing the outlet area A. Movement of the two sleeves in the opposite direction namely in the direction of arrows D1, D2 in fig 3 will decrease the width W of the plug 40 and hence increase the outlet area A. In order to vary the distribution of the outlet area across the nozzle 14, 16 it is necessary to move the plug 40 transversely in the plane of the outlet.

Transverse movement of the plug may be achieved by actuating the baliscrews 64, 66 such that their outer sleeves 70 move in the same direction at the same time thereby moving the plug 40 sideways across the nozzle in the direction of either arrows or I. The front nozzle 14 shown in the drawings is fixed to point downwardly at all times whilst the rear nozzle is vectorable by pivoting it about point P in a manner well known in the art between a first position in which is discharges rearwardly and a second position shown in figure 2 in which it discharges downwardly. When the exhaust gases are being discharged downwardly slight movement of the plug 40 sideways will produce a differential in thrust across the nozzle 14, 16 and hence the aircraft will tend to roll towards the side having the least thrust. The use of this method of roll control eliminates the necessity for expensive and complicated roll reaction jets at the tips of the aircraft wings.

It will be appreciated that pitch control may be achieved during hover and low speed forward flight by varying the outlet areas of the two nozzles 14, 16 thereby to produce a difference in forward to rearward thrust distribution and producing a nose up or nose down attitude.

It will be further appreciated that the nozzle 14 may be incorporated in a conventional (NON VTOL) aircraft where it would be positioned to direct rearwardly at all times.

It will be still further appreciated that if the nozzle is incorporated in a conventional aircraft in the manner described above the nozzle may be positioned such that the plug translates in a generally vertical path rather than horizontally as disclosed above. Vertical movement of the plug will provide some degree of pitch control during forward flight.

Claims

CLAIMS

1. A nozzle for a gas turbine engine having a longitudinally extending central axis, the nozzle comprising a duct having sidewalls terminating in an outlet having an outlet plane, a plug disposed within the nozzle and projecting through the outlet to define therewith a final outlet area of the nozzle, said plug being mounted so as to be capable of transverse movement in the plane of the outlet thereby to vary the distribution of outlet area thereacross and capable of varying its width, thereby to vary the outlet area of the nozzle, and means are provided for causing said movement and said variation in width.

2. A nozzle as claimed in claim 1 in which the duct is generally rectangular in cross section having a first and a second pair of mutually confronting sidewalls, said first pair of sidewalls extending across the width at the nozzle whilst the second pair of sidewalls extend between said first sidewalls in the direction of the nozzle depth.

3. A nozzle as claimed in claim 2 in which the plug extends between the first pair of sidewalls thereby to bifurcate the duct.

4. A nozzle as claimed in claim 3 in which the plug comprises four plates hinged to each other to form a parallelogram shaped obstruction at the outlet of the nozzle.

5. A nozzle as claimed in claim 4 in which the four plates are arranged in a first and a second pair, the hinges which join the plates of each pair being arranged to extend longitudinally between the first pair of sidewalls, parallel to each other and in the same plane as the outlet plane whilst the remaining two hinges extend parallel to the first two hinges.

6. A nozzle as claimed in claim 5 in which the means for providing the transverse movement and the expansion of the plug comprises first and second baliscrew arrangements, each baliscrew having a control shaft an outer sleeve and a motor connected to drive said shaft in a rotary manner, the outer sleeve of the first ballscrew being connected to the first pair of plates adjacent their common hinged joint whilst the outer sleeve of the second baliscrew is connected to the second pair of plates adjacent their common hinged joint.

7. A nozzle as claimed in claim 6 in which the outer sleeve of the first baliscrew and the outer sleeve of the second ballscrew are connected to their respective plate pairs on opposite sides of the nozzle to each other.

8. A nozzle as claimed in claim 6 or claim 7 in which the motors of each baliscrew are operable in unison to move their respective sleeves in the same direction at the same time thereby to move the common hinged joint of each plate pair in the same direction at the same time.

9. A nozzle as claimed in any one of claims 6 to 8 in which the motors of each baliscrew are operable in unison to move their respective sleeves in opposite directions to each other simultaneously thereby to move the common hinged joints of each plate pair in opposite directions to each other simultaneously.

10. A nozzle as claimed in any one of claims 6 to 9 in which each baliscrews lies adjacent one of the sidewall of the fist sidewall pair and extend axially in a direction transverse to the engine axis.

11. A nozzle substantially as herein described with reference to figures 1 to 4 of the accompanying drawings.