US3837579A

US3837579A - Variable-geometry nozzle for a jet engine

Info

Publication number: US3837579A
Application number: US00371659A
Authority: US
Inventors: A Camboulives; Maout T Le; R Vandenbroucke; J Chambon; G Jourdain
Original assignee: Construct De Moteurs D Aviat S
Current assignee: Safran Aircraft Engines SAS
Priority date: 1972-06-19
Filing date: 1973-06-19
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24
Also published as: DE2330988C3; FR2189642B1; FR2189642A1; DE2330988B2; DE2330988A1

Abstract

A variable-geometry nozzle for a jet engine is of the type which comprises a fixed structure, flaps adjustable in position with respect to the fixed structure, and control means for adjusting the position of the flaps. A plurality of swivelling frames are arranged around the circumference of the nozzle and are separately hinged to the fixed structure for pivotal adjustment about axes perpendicular to the longitudinal direction of the nozzle. The control means comprise jacks operable to pivot the frames about their respective axes, and the adjustable flaps are connected to the frames. The flaps comprise, in resect of each frame, two flaps each of which is hinged to the corresponding frame for positional angular adjustment with reference to that frame about an axis which has a component perpendicular to the pivotal axis of the frame concerned.

Description

Unite States Patent Camboulives et al.

VARIABLE-GEOMETRY NOZZLE FOR A JET ENGINE Inventors: Andre Alphonse Mederic Leon Camboulives, Savigny-sur-Orge; Jean Francois Chambon, Le Mee-sur-Seine; Gerard Ernest Andre Jourdain, Evry; Theophile Francois Le Maout, Cesson; Roger Alfred Jules Vandenbroucke, Antony, all of France Societe Nationale DEtude et de Construction de Moteurs dAviation, Paris, France Filed: June 19, 1973 Appl. No.: 371,659

Assignee:

Foreign Application Priority Data June 19, 1972 France 72.22052 [451 Sept. 24, 1974 3,214,904 11/1965 Bailey et al. 239/265.41 X 3,243,126 3/1966 Kurti et al 239/265.39 3,531,049 9/1970 Hom 239/265.29

Primary ExaminerM. Henson Wood, Jr. Assistant Examiner-Michael Y. Mar

[57] ABSTRACT A variable-geometry nozzle for a jet engine is of the type which comprises a fixed structure, flaps adjustable in position with respect to the fixed structure, and control means for adjusting the position of the flaps. A plurality of swivelling frames are arranged around the circumference of the nozzle and are separately hinged to the fixed structure for pivotal adjustment about axes perpendicular to the longitudinal direction of the nozzle. The control means comprise jacks operable to pivot the frames about their respective axes, and the adjustable flaps are connected to the frames. The flaps comprise, in resect of each frame, two flaps each of which is hinged to the corresponding frame for positional angular adjustment with reference to that frame about an axis which has a component perpendicular to the pivotal axis of the frame concerned.

12 Claims, 16 Drawing Figures PAIENIEU SEPZ 41374 SHEET 2 [1F 9 PATENIE 59241974 SHEET 70F 9 VARlABLE-GEOMETRY NOZZLE FOR A JET ENGINE This invention relates to a variable-geometry nozzle for a jet engine, the nozzle being of the type which comprises a fixed structure, flaps adjustable in position with reference to the fixed structure, and control means for adjusting the position of the flaps. As is commonly known, such nozzles are used to achieve the optimum adaptation of a jet engine to a wide range of flight conditions.

One mandatory condition which a commercial jetdriven aircraft must observe is that its jet engines emit a minimum of noise at low altitudes, more especially in the course of take-off and landing, and likewise in the fly-over phase (a climb at full thrust followed by a reduction of thrust as soon as the aircraft has reached a safe height).

Various devices have already been proposed which achieve a reduction in the noise emitted by the jet-flow leaving a jet engine. These noise-reducing devices generally comprise special accessory parts which project into the said jet-flow, the contour of which they so modify as to increase the surface where this jet-flow mingles with the surrounding air.

These known devices, however, have the drawback that they bring about quite considerable losses in thrust, and it is therefore essential that they should be capable of retraction from the jet-flow as soon as their use is no longer necessary, a point which complicates the design and control of the nozzle.

In a general way, the present invention aims at providing a propulsion nozzle able, without the assistance of any accessory part, greatly to reduce the noise made by the jet-flow as it leaves a jet engine during take-off (or landing) phases and during fly-over phases, while still subsequently providing optimum thrust in all the other flight phases of the aircraft.

The invention also has the aim of providing an exhaust nozzle able selectively to reduce the noise emitted by the jet-flow in two given directions, namely in the horizontal plane of symmetry of the nozzle, during the take-off (or landing) phase, and in the vertical plane of symmetry of the nozzle during the fly-over phase.

According to the invention a variable-geometry nozzle, of the type which comprises a fixed structure, flaps adjustable in position with reference to the fixed structure, and control means for adjusting the position of the said flaps is notable in that it comprises, arranged on its periphery, at least two swivelling frames, each of which frames is hinged to said fixed structure in such a way as to be able to undergo angular adjustment in its position with reference to the fixed structure through rotation about an axis perpendicular to the longitudinal direction of the nozzle; in that said adjustable flaps are connected to swivelling frames and comprise, in respect of each frame, two actuated flaps each of which is itself hinged to the said frame in such a way as to be able to undergo angular adjustment in position with reference to said frame through rotation about an axis which possesses a component perpendicular to the axis of rotation of the frame; and in that the control means for the flaps comprise motor means, such as jacks, to cause each of said frames to turn with reference to the said fixed structure.

According to a preferred embodiment of the invention, the swivelling frames are distributed around the periphery of the nozzle and are at least equal to four in number. They are preferably even in number and are arranged so that the axes of rotation of two oppositely situated frames, on either side respectively of a longitudinal plane of symmetry of the nozzle, are parallel to each other.

According to one arrangement applicable in this case, the adjustable flaps comprise, in respect of each frame, three actuated flaps, namely a middle flap rigidly attached to the said frame and two side flaps which enframe the middle flap and are hinged to the frame, the arrangement being such that each side flap hinged to a frame is peripherally adjacent to a side flap hinged to the neighbouring frame. Peripherally adjacent side flaps are preferably inter-linked in their downstream portion by hinge means.

According to another embodiment of the invention, the swivelling frames are two only in number and are arranged oppositely, on either side respectively of a longitudinal plane of symmetry of the nozzle, in such a way that their respective axes of rotation are parallel to each other. In this case, the control means for the flaps also comprise motor means to cause each of the flaps to turn with reference to the frame to which it is hinged.

According to an arrangement applicable in this case, two actuated flaps which are peripherally consecutive and are hinged to one or other of the two swivelling frames, respectively, are interlinked by hinge means in such a way that one can turn in relation to the other about an axis which is virtually parallel to the respective axes of rotation of the said frames. The motor means to cause each of the flaps to turn with reference to the frame to which it is hinged, then comprise a motor device, such as a jack, which is associated with each group of two consecutive actuated flaps hinged to one or other of the said swivelling frames respectively, and which has one part integral with the said hinge means.

The invention applies more particularly to the case in which the fixed nozzle structure comprises a duct traversed by a gaseous flow, the said duct being terminated by a downstream edge. According to one arrangement of the invention applicable in this case, the adjustable flaps may, under the action of the aforementioned control means, take up an open position in which their upstream edge comes virtually into contact with the downstream edge of the said duct, the flaps then forming a downstream extension of this duct, and a closed position in which their upstream edge is at a distance from the downstream edge of the duct, in such a way as to define a passage through which a flow of atmospheric air (sometimes designated by the expression tertiary air flow) is able to penetrate the said gaseous efflux.

As will be seen hereinafter, a nozzle thus equipped makes it possible to achieve a selective noise reduction which is at its maximum in the horizontal plane of the nozzle during the take-off and landing phases, and also at its maximum in the vertical plane of symmetry of the said nozzle during the fly-over phase of the aircraft. in addition to its noise-reducing effect, this nozzle renders possible a selective supply of tertiary air, either mainly through or entirely through the upper and lower planes of the nozzle during take-off or landing, either mainly through or entirely through the lateral planes of the nozzle in the fly-over phase, or past the entire periphery of the nozzle when at subsonic cruising speed.

The following description, with reference to the accompanying drawings and given by way of nonlimitative example, brings out how the invention may be put into effect, In the drawings:

FIG. 1 is a longitudinal sectional view, taken along the line I-I in FIG. 3, of a variable-geometry nozzle according to a first embodiment of the invention, the nozzle being shown in the completely open position;

FIG. 2 is a view similar to that in FIG. 1, but here the nozzle is in partly closed position;

FIG. 3 is a cross-sectional view, taken along the line IIIIII in FIG. 1, of the nozzle illustrated in FIG. 1;

FIG. 4 is a part sectional view, taken along the line IV-IV in FIG. 3, of the nozzle shown inFIG. 3;

FIG. 5 is a part sectional view, taken along the line V-V in FIG. 4, of the nozzle shown in FIG. 4;

FIG. 6 is a fractional view, looking in the direction of the arrow VI in FIG. 4, of the nozzle shown in FIG. 4;

FIG. 7 is a diagrammatic view similar to FIG. 3 and showing a modification of the first embodiment of the invention;

FIG. 8 is a diagrammatic view similar to FIG. 3 and showing a second modification of the first embodiment of the invention;

FIGS. 9, 10, 11 and 12 provide diagrammatic illustrations in cross-section of the various shapes which may be given to the exhaust section area of an improved nozzle in accordance with the invention;

FIG. 13 is a view in longitudinal section, taken along the line XIIIXIII in FIG. 15, of a variable geometry nozzle in accordance with a second embodiment of the invention, the nozzle being shown in a completely open position and the inner wall of the nozzle being assumed to be transparent;

FIG. 14 is a side elevation view, looking in the direction of the arrow XIV in FIG. 15, of the same nozzle;

FIG. 15 is a cross-sectional view, taken along the line XV-XV in FIG. 13, of the nozzle illustrated in FIG. 13, and

FIG. 16 is a plan view, looking in the direction of the arrow XVI in FIG. 15, of the nozzle shown in FIG. 15, here the upper wall of the said nozzle being assumed to be transparent.

FIGS. 1 to 6 refer to a first embodiment of the invention and in these figures the general reference numeral 1 denotes an exhaust assembly for a jet propulsion engine. This exhaust assembly is of the type known as composite or ejector, comprising at the least a primary jet-pipe (not shown) traversed by a primary gaseous flow F and terminating in a secondary nozzle 2. This secondary nozzle will in the following part of the description be designated simply by the term nozzle.

The nozzle 2 comprises, more especially, a fixed structure 3 which bounds a duct 4 traversed by a flow of secondary air F the duct 4 terminating a downstream edge 5. The fixed structure 3 is extended in the downstream direction by means of brackets 6 spaced apart peripherally.

On the periphery of the nozzle 2 there are arranged four

swivelling frames

101, 102, 103, 104, each one constituted by a hoop each end of which is hinged to a corresponding bracket 6 by a bell joint 7. As is shown in FIG. 3, each of the frames is thus hinged to the fixed structure 3 and may be adjusted angularly in position with reference to the fixed structure by rotation about an axis perpendicular to the longitudinal direction X-X of the nozzle. The axes of rotation of the four

frames

101, 102, 103, 104 are respectively denoted by A -A A -A A A A A and it will be seen that the axes of rotation (such as A,-A and A -A of the two frames (such as 101 and 103) which are oppositely situated on either side respectively of a longitudinal plane of symmetry of the nozzle are parallel to each other, and that two non-parallel axes, such as A,-A, and A,- A meet at a point 0.

With each of the

swivelling frames

101, 102, 103, 104 there is associated motor means, such as a control jack V V V or V.,, which has a rod t t or t, the end of which is hinged to the corresponding frame. It is therefore sufficient, to make a frame, such as 101, turn about its axis A -A to actuate the corresponding jack V,. It is advantageous though this is not mandatory that the jacks V and V should be mutually synchronized, and similarly the jacks V and V To each swivelling frame, such as 101, there are connected three actuated flaps, namely a middle flap 201a and two side flaps 201b, 201e, the latter two enframing the middle flap. The middle flap 201a is rigidly fixed to the frame 101, for example by bolt means, by riveting or by welding, as indicated by the reference numeral 8 in FIG. 1 in respect of the frame 103.

Each of the

side flaps

201b, 201c is hinged to the frame 101 by means of a pin 9 so as to be capable of angular positional adjustment with reference to the frame by rotation about an xis B (C,) which has one component perpendicular to the axis of rotation A,-A of the frame. In the example shown in FIG. 3, the axes B, and C are perpendicular to the axis A -A but this arrangement is not mandatory, as will be seen hereinafter.

In a similar manner, the

reference numerals

202a, 203a and 204a have been used to denote the middle flaps rigidly fixed to the

frames

102, 103 and 104 respectively, and the reference numbers 202b (2026), 203b (203C) and 204b (2040) to denote the side flaps hinged to the frames so as to be able to turn about axes B (C B (C and B (C respectively.

As shown in FIG. 3, each side flap (such as 201b) hinged to an swivelling frame (such as 101) is peripherally adjacent to a side flap (such as 204c) hinged to a neighbouring frame (such as 104). It will also be observed that the axes B, and C have the same geometrical support, as do the axes C and B B and C and C and 13,. It will finally be noted that two axes (such as B, and C associated respectively with two side flaps (such as 201b and 204C) which are peripherally adjacent meet at the point 0 situated at the point of convergence of the axes of rotation (such as A -A and A -A.,) of the frames (such as 101 and 104) to which the flaps are hinged.

As is shown in FIGS. 4 to 6, two peripherally adjacent side flaps (such as 201e, 20222) are joined together, at their downstream part, by a swivel-type hinge 10.

Fluid tightness between peripherally consecutive flaps is ensured by the mutual overlapping of these flaps. If, for example, the overlapping of two flaps, such as 201a and 201b, is taken into consideration (see FIG. 3), it will be observed that the female portion of one of the flaps (in this instance flap 201a) must have a geometrical form which is that of the volume produced by the rotation about the axis B of the section of the flap 201b through a plane (in this instance, the plane of FIG. 3) containing the said axis (a field of application of Guldins theorem).

An examination will now be made of the operation of the nozzle 2 just described, while also referring to FIGS. 9 to 12.

On take-off of the aircraft, the jacks V and V are actuated so as to cause the swivelling frames 101 and 103 to turn about their respective axes A -A and A A;,. As a consequence of this movement, the

middle flaps

201a and 203a, supported by the said frame respectively, turn through the same angle and move to close the nozzle 2 partially along its two horizontal sides. According to whether the jacks V and V, are either not actuated or actuated in the direction of opening, the swivelling frames 102 and 104, as well as the

middle flaps

202a and 204a, either remain immobile or are set to an angular open position determined by the optimum nozzle cross-section requirements.

As to the side flaps hinged to the four swivelling

frames

101, 102, 103 and 104, they turn with reference to the frames about their respective axes so as to maintain the continuity of the angular areas of the nozzle. In this connection, it is pointed out that in the course of this manoeuvre relative movement between the peripherally adjacent flaps occurs.

The nozzle 2 thus assumes the configuration shown in FIGS. 2 and 9, with an oblong or flattened exhaust crosssection (See FIG. 9) the long side of which is virtually parallel to the horizontal plane of symmetry of the nozzle. The jet-flow leaving the nozzle 2 is therefore mechanically pinched in a corresponding manner, and it has been established that such a pinching effect is accompanied by a modification to the spatial distribution of the noise energy emitted by the jet-flow of such a kind that, in the horizontal plane of symmetry of the nozzle, the more pronounced the pinching effect on the jet, the greater the noise reduction in the noise pattern. Thus, in particular, disturbance at groundlevel owing to the noise made by the jet-flow at take-off is decreased.

It will be further noted that, in this configuration, the upstream edge of the

middle flaps

201a and 203a is at such a distance from the downstream edge 5 of the duct 4 as to define passages 11 through which a flow F of atmospheric air, called tertiary air, is able to penetrate through the upper and lower planes of the nozzles into the flow of secondary air F so as to mingle with the said flow and favourably modify its pressure level. This air also, as is already known, plays a useful part in the process of reducing the noise produced by the jet.

During the fly-over phase, the jacks V and V, are actuated so as to cause the swivelling frames 102 and 104 to turn about their respective axes A -A and A -A As a consequence of this movement, the

middle flaps

202a and 204a supported by these swivelling frames respectively, turn through the same angle and move to close the nozzle 2 partially along its two vertical sides. According to whether the jacks V and V are either not actuated or actuated in the direction of opening, swivelling

frames

101 and 103, as well as the

middle flaps

201a and 203a, either remain immobile or are set to an angular open position determined by the optimum nozzle cross-section requirements.

The nozzle 2 thus assumes the configuration shown in FIG. 10, with an oblong or flattened exhaust crosssection the long side of which is virtually parallel to the vertical plane of symmetry of the nozzle. The jet-flow leaving the nozzle 2 is therefore mechanically pinched in a corresponding manner, so that now a noisereduction in the noise pattern is achieved in the vertical plane of symmetry of the nozzle. Thus, in particular, disturbance at ground-level owing to the noise made by the jet during fly-over is decreased. It will also be noted that, in this configuration, a flow of tertiary air is able to penetrate into the flow F of secondary air through passages (similar to the passages 11) formed through the side planes of the nozzle between the downstream edge 5 of the divergent duct 4 and the upstream edge of the

middle flaps

202a and 204a.

In subsonic flight, the four jacks V V V V, are actuated simultaneously so as simultaneously to alter the position of the four

middle flaps

201a, 202a, 203a, 204a. The nozzle 2 then assumes the configuration shown in FIG. 11, with a virtually square exhaust crosssection, and a supply of tertiary air around its whole periphery. Thus external and internal drag effects along the nozzle are reduced. By way of modification, the four jacks could be uncoupled from the frames they control so as to allow the flaps to shift freely about and to assume a position corresponding to the balance of internal and external pressures on either side of the flaps. It will also be noted that it would be possible to control the jacks in a differential manner so as to obtain a directional effect.

When flying in the supersonic cruise mode, the four jacks V V V V, are actuated in such a way that the four

middle flaps

201a, 202a, 203a, 204a are completely open. The nozzle 2 then assumes the configuration shown in FIGS. 1 and 12, with an exhaust crosssection which is homothetic to the one shown in FIG. 11. The flaps then occupy a position in which their upstream edge virtually comes into contact with the downstream edge 5 of the duct 4, the flaps thus forming a downstream extension of the duct, being either aligned with the duct or otherwise. As the passages 11 are then blocked, the nozzle is no longer supplied with tertiary air.

It has been indicated hereinbefore that it was not mandatory for two converging axes, such as B, and C to be perpendicular to each other.

FIG. 7 is a simplified diagrammatic view similar to FIG. 3 and specifically showing an arrangement in which the above-mentioned converging axes form between them an angle other than of In this figure, for denoting similar parts (the swivelling frames, middle flaps, hinged side flaps, axes of rotation of the frames and flaps) use has again been made of the same reference numerals as in FIG. 3. As in the case of FIG. 3, the axes of rotation of two consecutive swivelling frames (for instance, the axes of rotation A -A and A.,-A of the frames 101 and 104) and the axes of rotation of two adjacent side flaps supported by the said frames respectively (in the present case, the axes of rotation B and C of the side flaps 2011; and 204C) converge at the same point 0.

When FIG. 7 is examined, the special shape (an inverted V) given to the

middle flaps

201a, 202a, 203a, 204a will also be noted. A nozzle fitted out thus will therefore in cross-section have a polygonal form with a large number of sides and one approaching the conventional circular form. The junction of the nozzle with an upstream fairing arrangement having a circular cross-section, or with the remainder of the jet engine, can therefore be easily effected.

Up to now it has been assumed that the swivelling frames 101, 102, 103, 104 were four in number, distributed virtually around a square. But this arrangement is not limitative. Thus it would be possible to conceive other arrangements comprising, for example, six or eight swivelling frames distributed virtually in accordance with a hexagon or an octogon.

FIG. 8 is specifically an illustration of an arrangement comprising six swivelling

frames

101, 102, 103, 104, 105, 106, these being able to turn about axes A A,, A -A A -A respectively. Each of these frames has connected to it, as described hereinbefore, three flaps, namely a middle flap 201a (202a 206a) which is fixed with reference to the said frame, and two side flaps 20lb (202b 206b) and 201C (2026 206C) hinged to the said frame. The respective axes of rotation of these side flaps have been denoted by the references B,, B B and C,, C C Here too it will be noted that, as in the case of FIGS. 3 and 7, the axes of rotation of two consecutive swivelling frames (for example, the axes of rotation A,-A, and A -A of the frames 101 and 106) and the axes of rotation of two adjacent side flaps supported by the said frames respectively (in the present case, the axes of rotation B, and C of the side flaps 20lb and 2060) converge at the same point 0.

FIGS. 13 and 14 relate to a second embodiment of the invention. In these figures, as hereinbefore the reference numeral 2 denotes a secondary nozzle with an axis X-X and comprising a fixed structure 3 which bounds a duct 4 traversed by a flow of secondary air F the duct 4 terminating in a downstream edge 5. The flow F surrounds in an already known manner a primary gaseous flow F, emitted by a primary nozzle (not shown here). The fixed structure 3 is extended downstream by two diametrically opposite brackets 20.

On the periphery of the nozzle there are oppositely arranged, on either side respectively of a longitudinal plane of symmetry of the nozzle, two swivelling

frames

51, 52, each of them constituted by a hoop each end of which is hinged to a bracket 20 by means ofa ball joint 23. As is shown in FIG. 14, each of the two

frames

51, 52 is thus hinged to the fixed structure 3 and may be adjusted angularly in its position with reference to the said fixed structure by rotation about an axis C,-C, (C C perpendicular to the longitudinal direction X-X of the nozzle. The axes C,-C, and C -C are parallel to each other.

With each of the two swivelling

frames

51, 52 there is associated motor means, such as a control jack W, (W,,) which as a rod s, the end of which is hinged at 50 to the corresponding frame. It is therefore sufficient, to make a frame 51 (52) turn about its axis C,-C, (C -C to actuate the corresponding jack W (W To each of the two

frames

51, 52 there are connected two actuated flaps 61, 62 (63, 64), each one of which is attached to the corresponding frame with the aid of hinge means 24 (preferably of the type involving a ball joint so as to be capable of angular adjustment in its position with reference to the frame by rotation about an axis D, (D D,, D,) perpendicular to the axis of rotation C,-C, (C -C of the said fitting. The axes D, and D, have the same geometrical support, as do the axes D and D The peripherally consecutive flaps 61 and 63 (62 and 64) which are hinged to the swivelling frames 51 and 52 respectively are inter-linked by means of a ball joint 25 which comprises a pin 26 that is virtually parallel to the axes of rotation C,-C, and C -C of the

frames

51 and 52. The flaps 61 and 63 (62 and 64) are therefore able to turn in relation to each other about the pin 26. The pins 26 relating to the

flaps

61 and 63 on the one hand, and to the

flaps

62 and 64 on the other, have the same geometrical support.

With each group of two consecutive actuated flaps 6163 (or 62-64) which are hinged to one or other of the two swivelling

frames

51 and 52 respectively there is associated motor means, such as a jack W (W which has a rod s (s attached to the ball joint 25 of the said group of flaps. Thus, when, for example, the jack W is actuated, the two

flaps

61 and 63 turn simultaneously, each with reference to the frame 51 (52) to which it is hinged, moving about axes D, and D, respectively. Likewise, when the jack W is actuated, the two

flaps

62 and 64 turn simultaneously about axes D and B, respectively.

It is advantageous though this is not mandatory that the jacks W, and W, should be mutually synchronized, and similarly the jacks W and W Each of the

flaps

61, 62, 63, 64 is pivotally attached by a hinge pin 28 to one of the ends of an arm 29. The other end of this arm is pivotally attached by a hinge pin 30 to two parallel link-

rods

31, 32. The latter are themselves pivotally attached about a pin 33 to a yoke 34 integral with the swivelling frame 51 (involving the flaps 61 and 62) or with the swivelling frame 52 (involving the flaps 63 and 64). The hinge pins 28, 30 and 33 are perpendicular to the axes of rotation C,-C, and C -C of the swivelling frames 51 and 52. This arrangement relieves the hinge means 24 by facilitating the guidance of the flaps and resisting the moments which are due to the pressure of gases against the flaps.

Fluid tightness between successive controlled flaps is ensured by four slaved flaps each one of which is composed of an outer plate 35a and an inner plate 35b, these plates being inter-connected by hinge means at their downstream edge 36. Each slaved

flap

35a, 35b is fitted at its downstream part with pivot means 37 to which two link

rods

38, 39 are each pivotally attached by one of their ends. These link rods are pivotally attached at their other ends to two adjacent actuated flaps, respectively. Each slaved flap therefore undergoes displacement downstream at the time of the rotating movement of the two actuated flaps which enframe it (see FIG. 14).

With reference more especially to the two slaved flaps arranged between the two actuated flaps 61 and 63 (or 62 and 64) that both pivot about a hinge pin 26, it will be noted that each of them includes, in its upstream part, a slot 40 (see FIG. 14) made in the plate 35a and through which the pin 26 passes. As will be readily understood, this arrangement facilitates the centering of these two slaved flaps.

The operation of the nozzle 2 just described will now be considered, with due reference to FIGS. 9 to 12, as in the preceding case.

On take-off of the aircraft, the rods of the jacks W, and W move out, so causing the two swivelling

frames

51 and 52 to turn about their respective axes C -C and C -C The rods of the jacks W and W retract, so that the pins 26 with which they are integral are placed in a position which is determined by the optimum-section conditions for the nozzle. As a consequence of the movement of the jacks W, and W the four

flaps

61, 62, 63, 64 undergo displacement along with the

frames

51 and 52, turning about the pins 26, which are parallel to the axes C -C and C -C The nozzle 2 thus shifts from the configuration shown in full lines to the one indicated by broken lines in FIG. 14, with an exhaust cross-section which is oblong or flattened (see FIG. 9), its long side being virtually parallel to the horizontal plane of symmetry of the nozzle. The jet-flow leaving the nozzle is therefore mechanically pinched in a corresponding manner, this achieving a reduction in the noise pattern in the horizontal plane of symmetry of the nozzle.

In this configuration, the upstream edge of the flaps is at such a distance from the downstream edge of the duct 4 as to define passages through which a flow of tertiary air F is able to penetrate through the upper and lower planes of the nozzle into the flow of secondary air F so mixing with the latter flow and favourably modifying its pressure level.

In the fly-over phase, the rods of the jacks W and W move out. The rods of the jacks W and W retract, so that the swivelling frames 51 and 52 are placed in a position determined by the optimum nozzle-section requirement. As a consequence of the movement of the jacks W and W.,, the four

flaps

61, 62, 63, 64 undergo displacement with reference to the

frames

51 and 52, turning about axes D D D D, which are perpendicular to the axes of rotation C ,-C 1 and C -C of the said frames.

The nozzle 2 thus assumes the configuration shown in FIG. 10, with an oblong or flattened exhaust crosssection area the long side of which is virtually parallel to the vertical plane of symmetry of the nozzle. The jetflow leaving the nozzle is therefore mechanically pinched in a corresponding manner, this now achieving a reduction in the noise pattern in the vertical plane of symmetry of the nozzle. In this configuration, a flow of tertiary air is able to penetrate into the flow of secondary air F, by way of passages formed along the side planes of the nozzle, between the downstream edge of the duct 4 and the upstream edge of the flaps.

In subsonic flight, the four jacks W W W and W, are actuated simultaneously in the same direction. The nozzle 2 then assumes the configuration shown in FIG. 11, with a virtually square exhaust cross-section and a supply of tertiary air around its entire periphery.

As in the case of the first embodiment, the four jacks could be uncoupled so as to allow the flaps to shift about freely and to assume a position which corresponds to the balance of the internal and external pressures on either side of the said flaps. It would also be possible to control these jacks in a differential manner to obtain a directional effect.

When flying in the supersonic cruise mode, the rods of the four jacks W W W and W, are completely retracted. The nozzle 2 then assumes the configuration shown in FIG. 12, with an exhaust cross-section which is similar in shape to that shown in FIG. 11. The four

flaps

61, 62, 63, 64 then occupy a position in which they form a downstream extension of the duct 4, and are aligned with the said duct or otherwise. In this configuration, the nozzle 2 is no longer supplied with tertiary air.

As will be seen, the nozzle according to the invention achieves a noise-reducing effect, when such is required, without it, however, being necessary to have recourse to special accessory parts: in fact, the very same flaps which simultaneously act to adjust the cross-section of the nozzle with a view to producing optimum thrust in all the flight phases of the aircraft are employed to give the nozzle a configuration which is favourable to the selective reduction of the noise from the jet in selected directions.

It is self-evident that the embodiments described are merely examples and that it would be possible to modify them, more especially by replacing them by technical means which are equivalent, without however departing from the scope of the invention.

We claim:

1. A variable-geometry nozzle for a jet engine, comprising a fixed structure, at least two swivelling frames arranged at the periphery of the nozzle and each of which is hinged to said fixed structure for positional angular adjustment with reference to the fixed structure by rotation about an axis perpendicular to the longitudinal direction of the nozzle, adjustable flaps connected to said swivelling frames and comprising, in respect of each frame, two actuated flaps each of which is itself hinged to the frame for positional angular adjustment with reference to the frame by rotation about an axis which possesses a component perpendicular to the axis of rotation of the frame, and control means for adjusting the position of the flaps and which comprise motor means operable to turn each of the frames relatively to the said fixed structure.

2. A nozzle according to claim 1, wherein said swivelling frames are distributed around the periphery of the nozzle and are at least four in number.

3. A nozzle according to claim 2, wherein said frames are even in number and are arranged so that the axes of rotation of two oppositely situated frames, on either side respectively of a longitudinal plane of symmetry of the nozzle, are parallel to each other.

4. A nozzle according to claim 2, wherein said adjustable flaps comprise, in respect of each swivelling frame, three actuated flaps, namely a middle flap rigidly attached to the frame and two side flaps which enframe the middle flap and are hinged to the frame, and each side flap hinged to a frame is peripherally adjacent to a side flap hinged to the immediately adjacent frame.

5. A nozzle according to claim 4, wherein said middle flap possesses, in section in a plane perpendicular to the longitudinal direction of the nozzle, the shape of an inverted V.

6. A nozzle according to claim 2, wherein the axes of rotation of two peripherally consecutive swivelling frames and the axes of rotation of two peripherally adjacent flaps supported by these frames respectively intersect at one and the same point.

7. A nozzle according to claim 2, wherein two peripherally adjacent flaps hinged respectively to two neighbouring frames are inter-linked at their downstream part by hinge means.

8. A nozzle according to claim 1, wherein said swivelling frames are two only in number and are arranged oppositely, on either side of a longitudinal plane of symmetry of the nozzle respectively, in such a way that 10. A nozzle according to claim 9, wherein the motor means operative to turn each of the flaps relatively to the frame to which it is hinged comprise a motor device which is associated with each group of two consecutive actuated flaps hinged to one or other of the said swivelling frames respectively, and which has one part attached to the said hinge means.

11. A nozzle according to claim 1, wherein the fixed structure comprises a duct traversed by a gaseous flow and terminating in a downstream edge, and wherein said adjustable flaps can, under the action of the said control means, take up an open position in which their upstream edges come virtually into contact with the downstream edge of the duct, the flaps then forming a downstream extension of the duct, or a closed position in which their upstream edges are at a distance from the downstream edge of the duct, in such a way as to define a passage through which a flow of atmospheric air is able to penetrate said gaseous flow.

12. A nozzle according to claim 11, wherein the flaps when forming a downstream extension of the duct are in alignment with the duct.

Claims

8. A nozzle according to claim 1, wherein said swivelling frames are two only in number and are arranged oppositely, on either side of a longitudinal plane of symmetry of the nozzle respectively, in such a way that their respective axes of rotation are parallel to each other, and the control means for the flaps also comprise motor means operative to turn each of the flaps relatively to the frame to which it is hinged.

9. A nozzle according to claim 8, wherein two peripherally consecutive actuated flaps hinged to one or other of the said swivelling frames, respectively, are inter-linked by hinge means in such a way that one can turn in relation to the other about an axis which is virtually parallel to the respective axes of rotation of the frames.

10. A nozzle according to claim 9, wherein the motor means operative to turn each of the flaps relatively to the frame to which it is hinged comprise a motor device which is associated with each group of two consecutive actuated flaps hinged to one or other of the said swivelling frames respectively, and which has one part attached to the said hinge means.