GB2241021A

GB2241021A - Variable area jet nozzle.

Info

Publication number: GB2241021A
Application number: GB8103026A
Authority: GB
Inventors: Clifford Stanley Woodward
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1981-01-31
Filing date: 1981-01-31
Publication date: 1991-08-21
Anticipated expiration: 2001-01-31
Also published as: DE3202450C1; FR2664656A1; GB2241021B

Description

VARIABLE AREA JET NOZZLE.

DESCRIPTION This invention relates to jet propulsion power plant for aircraft.

A known such power plant comprises a curved jet pipe supported on fixed structure for rotation about the axis of the pipe at the upstream end thereof thereby to vary the direction of discharge of fluid from the free or downstream end of the pipe, and varying means for varying the flow area of a nozzle provided at said other end of the pipe, said varying means comprising a driving part mounted on the fixed structure and drivingly connected to a driven part mounted on the pipe.

The present invention is concerned with the problem of designing the connection between the driving and driven parts in such a way that the rotation of the pipe is accommodated.

It has been proposed to connect the driving and driven parts by a flexible drive, i.e. a flexible shaft in a flexible sheath, but this is not always appropriate because of the limitations of such drives as regards curvature and length. Friction and stress increase with the acuteness of the curve through which the drive is routed. Torsional deflection increases with the length of the shaft which, being stranded, is relatively suceptible to such deflection and is, for the same reason, limited as regards torque transmitted. Thus the flexible drive is useful only for relatively shallow curves and relatively short lengths or low torque.

It has been proposed to allow the flexible drive to become wrapped around the jet pipe as the latter rotates and accommodate the resulting axial movement of the shaft by permitting axial sliding of the shaft through the torque-transmitting connection to an input gear. But that proposal introduces complexities of its own without removing the earlier mentioned difficulties especially those arising from undue length of shaft.

It is an object of this invention to provide a connection between said driving and driven parts which overcomes or reduces those difficulties.

According to this invention there is provided a jet propulsion powerplant for aircraft comprising a curved jet pipe supported on fixed structure for rotation about the axis of the pipe at the upstream end thereof thereby to vary the direction of discharge of fluid from the free or downstream end of the pipe, varying means for varying the flow area of a nozzle provided at said downstream end of the pipe, said varying means comprising a driving part mounted on the fixed structure, a driven part mounted on the pipe, and a drive connection between said parts, characterized in that the drive connection comprises two elongate member pivotally connected at adjacent ends thereof and AonnecieX at their mutually remote ends to the fixed structure and to the jet pipe respectively, said members being. adapted to transmit rotation between the driving and driven parts.

An example of a powerplant according to this invention will now be described with reference to the accompanying drawings wherein: Fig. 1 is a plan view of the powerplant as installed in an aircraft.

Fig. 2 is an enlarged detail of Fig. 1.

Fig. 3 is a section on the line III-III in Fig. 2.

The powerplant is a gas turbine engine 10 having a pair of curved jet pipes 11 projecting laterally from a fuselage 12 of an aircraft not otherwise indicated.

Each jet pipe 11 is supported at its upstream end on fixed structure, constituted by the fuselage 12, by a bearing 13. This enables rotation of the jet pipe about the axis 14 at said upstream end thereof thereby to vary the direction of discharge of fluid from the downstream end of the jet pipe. At said downstream end the jet pipe has a nozzle 15. Means for varying the flow area of the nozzle 15 comprise petals 16 embodied in the nozzle and a drive mechanism 17 for pivoting the petals.

The mechanism 17 comprises an air motor 18 mounted on the fueselage 12 and connoted by a shaft 19, extending generally transversely to the main axis, 20, of the engine, to respective gearboxes 21 mounted on the fuselage at positions adçacent the respective bearings 13. In each gearbox 21 the shaft 19 is connected by bevel gearing to a shaft 22 (Figs. 2,3) and the gearbox 21 is supported on the shaft 19 so as to enable the shaft 22 to pivot about the shaft 19 and in a plane perpendicular to the axis 14. The shaft 22 is connected through bevel gearing in a gearbox 23 to a short shaft 24 in turn connected through bevel gearing in a gearbox 25 to a shaft 26.The gearboxes 23,25 are rotatable one relative to the other about the shaft 24 and the arrangement is such that the shaft 26 can pivot relative to the shaft 22 about the shaft 24 and in a plane perpendicular to the axis 14.

At its end remote from the gearbox 25 the shaft 26 is connected by bevel gearing in a gearbox 27 to a short shaft 28 in turn connected by bevel gearing in a gearbox 29 to a shaft 30. The gearbox 29 and shaft 30 are mounted on the pipe 11. The shafts 19 and 30 constitute a driving and a driven member mounted respectively on fixed structure and on the pipe 11.

It will be clear that the connection between the shafts 19,30 is such that during rotation of the pipe 11 about the axis 14 any change in relative position of the shafts 19,30 is accommodated by the pivoting of the shafts 22,26 about the shafts 19,24 and 28.

The shaft 30 is a flexible shaft curved around the pipe 11 and connected by spur gearing in a gearbox 31 to a flexible shaft 32 extending around the pipe 11 at the downstream end thereof in a plane perpendicular to the axis, 36, of the pipe 11 at said downstream end.

The shaft 32 is connected through three gearboxes 33 (only one shown) to respective screwjacks 34 themselves connected to a shroud 35. Rotation of the shaft 32 moves the shroud 35 along the axs 36 and pivots the petals 16 in a manner known per se.

The gearboxes 25,27 are secured together by a tube 26A surrounding the shaft 26 (Fig. 2) and a correspcnding tube 22A connects the gearboxes 21,23.

When the jet pipe 11 is rotated about the axis 14, the gear pairs in the respective boxes 21,23,25,27 make a certain amount of epicyclic motion resulting in axial movement of the shroud 36. However, in practice the amount of movement of the shroud in these circumstances can be made to be negligible. This is done by making the speed of the 'shaft relatively high and provide a substantial speed reduction between the shaft 32 and the screw of the screwjack 31c. It can be shown that, with these provisions, the movement of the shroud 35 would only be a few thousands of an inch for the maximum of 900 of the jet pipe 11.

Claims

1. Jet propulsion power plant for aircraft comprising a curved jet pipe supported on fixed structure for rotation about the axis of the pipe at the upstream end thereof thereby to vary the direction of discharge of fluid from the free or downstream end of the pipe, varying means for varying the flow area of a nozzle provided at said downstream end of the pipe, said varying means comprising a driving part mounted on the fixed structure, a driven part mounted on the pipe, and a drive connection between said parts, characterized in that the drive connection comprises two elongate members pivotally connected at adjacent ends thereof and pivotally connected at their mutually remote ends to the fixed structure and to the jet pipe respectively, said members being adapted to transmit rotation between the driving and driven parts.

2. Powerplant according to claim 1 wherein the two elongate members are defined by two shafts connoted respectively to each other, to said fixed structure and to said jet pipe by gearing adapted. to accommodate said pivotal connection.

3. Jet propulsion powerplant for aircraft substantially as described herein with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. Jet propulsion powerplant for aircraft comprising a curved jet pipe supported on fixed structure for rotation about the axis of the pipe at the upstream end thereof thereby to vary the direction of discharge of fluid from the free or downstream erid of the pipe, varying means for varying the flow area of a nozzle provided at said downstream end of the pipe, said varying means comprising a driving part mounted on the fixed structure, a driven part mounted on the pipe, and a drive connection between said parts, characterized in that the drive connection comprises two elongate members pivotally connected at adjacent ends thereof, the other end of one said meniber being so connected to the driving part that said one member is pivotable with respect to the fixed structure, the other end of the other said member being so connected to the driven part that said ottler member is pivotable with respect to the jet pipe, said members being adapted to transmit rotation between the driving and driven parts.

2. Jet propulsion powerplant according to Claim 1, wherein the two elongate members are arranged adjacent the upstream end of the pipe and in a plane perpendicular to said axis about which the pipe is rotatable.

3. Jet propulsion powerplant according to Claim 1 or Claim 2 wherein the two elongate members are defined by two rotatable shafts drivably connected to eacll other and drivably connected to the driving part and the driven part respectively, the connections being made by gearing adapted to accommodate pivoting of tie elongate members.

4. Jet propulsion powerplant according to Claim 3 wherein the shafts are supported in respective tubes, the tubes being pivotably connected to each other and pivotable with respect to the fixed structure and the jet pipe respectively.

5. Jet propulsion powerplant according to Claim 3 or Claim 4, comprising a third rotatable shaft located at said adjacent ends of the first two shafts, and geared thereto to provide the drivable connection between therm, the first two shafts being pivotable about the axis of the third shaft.

6. Jet propulsion powerplant according to any one of the preceding claims, wherein the driven part comprises a flexible shaft connected between the drive connection and the nozzle.

7. Jet propulsion powerplant: substantially as described herein with reference to the accompanying drawings.