US2801516A

US2801516A - Jet-nozzle arrangements with outlet area varying means

Info

Publication number: US2801516A
Application number: US437216A
Authority: US
Inventors: Battle Norman; Robinson Norman Robert
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1953-04-10
Filing date: 1954-06-16
Publication date: 1957-08-06
Anticipated expiration: 1974-08-06
Also published as: US2980395A; BE528164A; GB742194A; CH318642A; GB745069A; FR1097487A; BE529656A; FR1099272A; NL87657C; CH327869A; FR1107564A; CH325950A; GB820134A; DE928345C; FR1159179A; CH326650A; GB782493A

Description

Aug. 6, 1957 N. BATTLE ETAL JET-NOZZLE ARRANGEMENTS WITH OUTLET AREA VARYING MEANS Filed June 16, 1954 6 Shee ts-Sheet l Aug-6,1957 N. BATTLE ETAL 2,801,516

JET-NOZZLE ARRANGEMENTS WITH OUTLET AREA VARYING MEANS Filed June 16, 1954 e Sheets-Sheet z 55 J g 6&5 59 60 y as 9? 50 w flfia 92a 92 10695924 yaw 7 9293 4 1957 N. BATILE EI'AL 2,801,516

JET-NOZZLE ARRANGEMENTS WITH OUTLET AREA VARYING MEANS Filed June 1s, 19s4 e Sheets-Sheet 5 Aug. 6, 1957 N. BATTLE ETAL 2,801,516 JET-NOZZLE ARRANGEMENTS WITH 01mm AREA mama MEANS 6 Sheets-Sheet 6 Filed June 16, 1954 2,801,516 P e A g- 1.957.

Units SW68 Pa fi i JET-NOZZLE ARRANGEMENTS WITH OUTLET AREA VARYING MEANS Norman Battle, Chilwell, and Norman Robert Robinson, Quarndon, England, assignors to Rolls-Royce Limited, Derby, England, a British company Application June 16, 1954, Seriai No. 437,216 Claims priority, application Great Britain June 18, 1953 8 Claims. (Cl. 6035.6)

This invention comprises improvements in or relating to jet nozzle arrangements such as are employed in connection with gas-turbine engines for reaction propulsion purposes.

It is usual in jet nozzle arrangements employed with gas-turbine engines to arrange the effective area of the outlet orifice for the exhaust gases from the associated gas-turbine engine to be variable, so that, for instance, when the engine is fitted with after-burner equipment the effective area of the jet nozzle arrangement can be increased thereby to avoid overheating of the engine turbine.

This inventon has for an object to provide an improved valiable-orifice-area jet nozzle arrangement.

According to one aspect of this invention, there are provided a plurality of pivoted nozzle elements by means of which the effective area of the outlet orifice can be varied, and operating means by which the nozzle elements are interconnected and adapted to move the nozzle elements from one position to another, said operating means being mounted on the movable nozzle elements themselves.

Preferably, the operating means comprise a plurality of telescoping mechanisms, each of which mechanisms has a pair of elements adapted to telescope with respect to one another along a line which is directed circumferentially of the jet nozzle, one of said elements being connected to one nozzle element and the second of said telescoping elements being connected to an adjacent nozzle element.

In one arrangement according to this aspect of the invention, the operating means are fluid-operated rams which have circumferentially-directed lines of action, one part of the ram being attached to one nozzle element and a second and relatively movable part of the ram being-attached to an adjacent nozzle element. With such an arrangement on expansion of the ram the nozzle elements may conveniently be made to rock outwardly to increase the effective orifice area and on collapse of the rams the nozzle elements may be made to rock inwardly to decrease the effective orifice area.

In one construction the nozzle elements are axially elongated and are pivoted adjacent their forward ends and the operating means are hydraulic rams and the cylinders of the rams are attached in pairs to alternate nozzle elements and the pistons of the rams are con nected with the remaining nozzle elements through pivoted links. With such a construction there are conveniently a relatively large number of nozzle elements; for instance 16 such interconnected nozzle elements may be employed. In addition to these interconnected nozzle elements there may be provided sealing nozzle elements which overlap the circumferential edges of the main nozzle elements to prevent leakage of hot gas from the duct formed by the nozzle elements, and the parts of the sealing nozzle elements which overlap the main nozzle elements may be located with respect to themain nozzle elements adjacent one end thereof, say the forward ends thereof.

Conveniently where a large number of pivotednozzle elements are provided means is also provided to constrain the pivoted nozzle elements to move through equal angular extents. In one particular arrangement such means comprises pairs of links, each pair being between a pair of adjacent nozzle elements and one link of each pair being pivoted to a corresponding one of the nozzle elements, the pairs being pivoted together at their opposite ends. The pivotal axes of the connections between the links and the nozzle elements are preferably radial.

According to another aspect of this invention, there is provided a jet nozzle arrangement which is readily attachable to and detachable from an associated aircraft and jet pipe structure.

In one arrangement according to this aspect of the invention, there is provided a mounting structure which is adapted to encircle the downstream end of the jet pipe leading from an associated gas-turbine engine, and which is readily attachable to supporting structure for the engine, for instance to a structural member of an aircraft wing, and the nozzle elements for varying the effective area of the outlet orifice are pivoted to the mounting structure so that on detachment of the mounting structure the pivoting nozzle elements are also detached from the associated jet pipe. In such an arrangement the mounting structure may also carry a ring element which mates with the end of the jet pipe on attachment of the mounting structure to the supporting structure, to determine the effective throat area of the nozzle in the maximum orifice area position of the adjustable nozzle elements.

One embodiment of nozzle arrangement of this invention for use with a gas-turbine engine will now be described With reference to the accompanying drawings in which:

Figure 1 is an axial section through a part of the nozzle arrangement, the figure being divided into two parts 1A and 1B, of which the part 1B is immediately. to the right of the part 1A, the line of junction of the parts being indicated by the reference 10,

Figure 2 is a section on the line IIII of Figure 1, and the figure has the plane of section of Figure l indicated on it by the line I -I,

Figure 3 is a view corresponding to Figure 2 but with the parts in diflierent positions,

Figure 4 is a section on the line IV-IV of Figure 1,

Figure 5 is a view to a larger scale of part of Figure 1,

Figure 6 is a section on the line VI--VI of Figure 5,

Figure 7 is a section on the line VII'-VII of Figure 6 and has the plane of section of Figure 5 indicated thereon by the line V---V,

Figure 8 is a section on the line VIII -VIII of Figure 1,

Figure 9 is a detail view,

Figure 10 is a section on the line X--X of Figure 9 "and has the plane of section of Figure 9'indicated on it by the section line IX--IX,

Figure 11 is a View corresponding to Figure 10 with the parts in another position,

Figure 12 is a section on the line XII-*XII of Figure 8, and

Figure 13 is a diagrammatic View of part of the arrangement.

Referring first to Figure l, the jet nozzle arrangement illustrated is suitable for use either with a gas-turbine engine accommodated within a nacelle forming part of an aircraft wing structure or with a gas-turbine engine accommodated within a fuselage and having its jet pipe opening to atmosphere through the after end of the fuselage.

In Figure 1, the jet pipe is illustrated as having an inner skin 20 which defines the exhaust gas duct leading from the gas-turbine engine to the jet nozzle arrangement, and the inner skin has at its outlet end a frusto-conical portion 21 terminating in an annular end fitting 22 having an axially-extending portion 22a of slightly larger diameter, and an outer skin 23 surrounding the inner skin 20 and held in spaced relation thereto by means of a muif 24 to aflord a passage for cooling air. The outer skin 23 has welded on its downstream end an outwardly-flanged end ring 25 and the mufl 24 is flared outward at its downstream end to provide a flange 24a which lies against the flange of the flanged end ring 25. Secured to the flanged end ring 25 is a further ring member 26 having an axial extension 26a the purpose of which will appear below. The upstream end of muir 24 is formed as a number of circumferentially-extending strips 24b which are bent inward to have their free ends welded to the inner skin 20. The outer skin 23 of the jet pipe terminates at a position somewhat upstream of the frusto-conical portion 21. r

The downstream end of the fuselage or nacelle in which the gas-turbine engine is located is indicated at 27 and there is indicated at 28 a structural member of the fuselage or wing structure, which member is capable of carrying high loads. 7

The jetnozzle arrangement which is associated with the jet pipe 20, 23, comprises a mounting structure generally indicated at 29, by which the jet nozzle arrangement is attached to the aircraft structure in juxtaposition to the jet pipe, anda multiplicity of jet nozzle elements by which the eflective area of the outlet orifice of the nozzle arrangement can be varied. The jet nozzle arrangement also COHlPl'iSES motor means fOI moving the nozzle elements to vary the effective orifice area of the nozzle and the motor means is carried solely by the moving nozzle elements.

The mounting structure 29 comprises a pair of axiallyspacedannular end walls 30a, 30b secured to an axiallyexten'ding inner wall 31, the upstream end 31a of :which is capable of sliding engagement with the axial extension 26a of the ring member 26, and the downstream end 31b of which is frusto-conical and is securedto the inner edge of the downstream wall 30a. Another frustoconical member 310 connects the wall 31 to the outer edge of annular wall 30a. The upstream end wall 30b is connected with the axially-extending wall 31 by means of fabricated sheet metal brackets 32, and these brackets 32 have projecting from them lugs 33 which project between pairs of lugs 28a on the structural member 28 to enable the jet nozzle arrangement to be secured in position by means of pins or the like passing through aligned holes 34 in the lugs 33 and the co-operating lugs 28a.

The mounting structure 29 also comprises an outer wall 35 adapted to form a smooth continuation of the fuselage or nacelle 27. The upstream end of the wall 35 is formed with a radial, inwardly-directed flange 336 having at its inner edge an axially-extending portion 37 to seat on an axial flange 38 on the outer edge of the upstream wall 30b, and the downstream edge of the wall 35 is headed as indicated at 39 and engages a cylindrical seating 40 of a seal member 41, thepurpose of which will appear below. The seal member 41 is carried by a ring 41a secured to the outer edge of the downstream wall 30a.

The inner wall 31, as has been said, has sliding engagement with the axial extension 26a of the ring member 26 and the wall 31 is radially spaced from the downstream portion of the inner wall 20 of the jet pipe and its conical end portion' 21, so affording a downstream extension of the annular air passages between the jet pipe walls 20, 23.

The mounting structure 29 also comprises a number of brackets 42 (see Figures 5, 6, 7) fabricated from sheet metal, which brackets 42 support bushes 43 to receive the ends of pivot pins 44 by which the nozzle elements areconnectedto the mounting structure 29.

The pivot pins 44 have heads 44a which limit the extent to which the pivot pins can pass in one direction through the bushes 43 and disengagement of the pins 44 from the bushes 43 is prevented by flanges 45 forming parts of union connections 46 in a pressure fluid system for supplying pressure fluid tooperating rams (described below) for moving the nozzle elements.

The nozzle elements are of two kinds, of which one kind, referred to hereinafter as the main nozzle elements, are indicated at 47, and of which the other kind, which will be referred to as the sealing nozzle elements, are indicated at 48 (see especially Figures 2, 3 and 4).

The main nozzle elements 47 (of which there may for instance be 16) are divided into two categories which alternate around the nozzle orifice, but each category comprises the following general structure.

Each main nozzle element comprises a load-bearing structure including an outer sheet-metal wall 49, a sheetmetal inner wall 50 and sheet-metal side walls 51 which are secured together to form an axially-extending tapering tube-like structure. Each main nozzle element 47 also comprises at its upstream end an end wall 52 and a forwardly-extending bracket structure 53 carrying bushes 54, which fit between the pairs of bushes 43 (see Figures 6 and 7) and also receive the pivot pins 44. Each main nozzle element 47 is also strengthened internally at its upstream and downstream ends by centrally-arranged tapering channel members 55 which have the base of the channel secured to the inner wall 50 and flanges 551; secured to the outer wall 49.

The motor means for causing the main nozzle elements 47 to pivot relative to the mounting structure 29 is in the form of fluid-operated motors such as hydraulic or pneumatic rams, and the motor structure forms part of the main nozzle elements 47.

The first category of main nozzle element 47 has located between its pair of members 55 a block 56 (Figures 1B, 2 and 3) having formed in it pressure fluid supply channels 57, and the block carries four ram cylinders 58. The ram cylinders 58 are arranged in two pairs, the one pair having a larger diameter than the other pair, and the larger-diameter pair being disposed nearer the pivot for the nozzle element than the smaller-diameter pair. One ram cylinder 58 of each pair is mounted on each side of the block 56 to extend towards an adjacent main nozzle element 47. The outer end of each ram cylinder 58 is closed by a bored plug 59.

The other category of main nozzle element 47 has lo.- cated between its members 55 a block 60 having therein a recess of part-spherical form to receive part-spherical heads 61 of a pair of rocking arms 62 extending circumferentially from the block 6% through apertures 63 to form the outer ends of links which connect the nozzleelement 47 to the pistons 64 which work in the ram cylinders 58 of the nozzle element next adjacent to it. The opposite ends of the links are formed by rods 65 having heads 66 formed with part-spherical convex and concave surfaces which co: operate respectively with a part-spherical recess in thepiston 64 and a domed element 67 carried by a cap member 68 bolted to the head of the piston 64. The stem 64a of the piston 64 is hollow to allow angular movement of the rod 65 within it and the end of rod 65 remote from'the head 66 is secured by a length-adjusting arrangement 69 to the corresponding rocking arms 62. A spherical-surfaced plug 70 retains the heads 61 of the arms 62 in position in the recess and the plug 70 is retained in position within the block 60 by a plate 71 bolted to the block 60. The plate 71 has a stem 72 carrying a cover plate 73 closing an aperture in the outer wall 49 of the nozzle element, .By removal of the cover plate 73 access can be had to the block 60.

It will be, appreciated that by supplying pressure fluid to one end of the ram cylinders 58, i. e. the end adjacent their supporting block 56, the nozzle elements 47 will be constrained to open up to increase the effective area oiffthe' nozzle orifice and that on supply of pressure fluid to the opposite end of the ram cylinders 58 the nozzle elements 47 will rock inwardly to reduce the effective orifice area of the nozzle arrangement.

Each main nozzle element 47 also comprises a removable protective wall 74, the lateral edges 74asof which, as will best be seen from Figure 2, are joggled to co-operate with parts of the sealing nozzle elements 48 ina manner to be described below. The. removable protective wall 74 has secured to its outer surface an I-section member 75 the radially outer flange 75a of which is employed to connect the protective wall 74 to the inner Wall 50 of the nozzle element. The flange 75a engages in channels formed by Z-section elements 76 secured to the inner surface of the wall 50 and extending axially thereof (see particularly Figures 2 and 3). The protective wall 74 is retained against disengagement from its associated nozzle element 47 by means of a retaining member 77 which projects from a plate secured by set-screws 77a to the inner wall 50 of the nozzle element 47 and which engages in a hole in the forward end of the radially-outer flange of the I.-section member 75 (see Figures 5.; and 6). It will be. clear that since the wall 74 is only located adjacent its for-.

ward end, it is capable of expanding relatively to the load bearing structure of the nozzle element 47.

The forward edge of the protective wall 74 bears against the downstream edge of a seal member 78 carried by the load-bearing structure of the main nozzle. element 47 and the sealing element 78 is curved about the pivotal axis of the nozzle element and about the nozzle axis. The seal! ing element 78 co-operates with a sealing pad 79 provided externally of a ring element 80 for the jet pipe, whichelement 80 is secured through ring members 81 to the end wall 30a of the mounting structure 29. j The element 80 is provided externally with a grooved land, 82 accommodatinga sealing ring 83. which bears on the axial extension 2211 of the end ring 22 carried by the frusto conical por= tion 21 of the inner wall of the jet pipe. It will be clear that when the jet nozzle arrangement is. being detached from the aircraft structure, the element 80 will be removed with the jet nozzle arrangement. The sealing ring 83 prevents leakage of hot gas from the jet pipe.

Cooling air which has flowed between the walls 20, 23 of the jet pipe (see Figures 1A and 1B) and through the, space between the inner wall 31 of the mounting structure 29 and the jet pipe wall passes outside the ring element 80, through apertures in ring member 81, and outside the sealing member 78 into the spaces between the protective Walls 74 of the nozzle elements 47 and the inner walls 50 of their load-bearing structure.

Each main nozzle element 47 also comprises an outer seal member 84 which is curved about the pivot axis of its associated nozzle member and about the nozzle axis and co-operates through its external surface with the seal member 41 above referred to.

The main nozzle elements 47 are constrained to move inwardlyand outwardly to the same angular extents bylinking them together. Referring now more particularly to Figures 113, 8 and 12, there are provided between each pair of main nozzle elements 47 a pair of links 85 of triangular form which are pivoted both to the adjacent nozzle elements 47 and to one another. Each link 85 is. pivoted to its associated nozzle element 47 by having one side of it formed as an elongated boss. 85a to receive a pivot pin 86 engaging in sockets 87 secured to. the edges of the outer and inner walls 49and 50 of the load-bearing structure of the nozzle element47. The apices of the triangulated links 85 are radially aligned and are interconnected through a ball and socket joint (Figure 12), the ball 88 of the joint having a threaded stem 89 to engage in a threaded boss 90 on the apex of the outer link 85 and the socket of the joint being provided in a boss 91 at the apex of the other link 85. It will be appreciated that this arrangement prevents relative radial movement of adjacent nozzle elements 47 It will be appreciated that when the main nozzle elements 47 move outwardly their lateral edges tend to move the joggled edge portions 74a of the protective walls 74 and it is preferably arranged that in the minimum area position of the nozzle elements 47, 48 a substantially smooth frusto-conical wall is provided, the joggled portions 74a of the protective walls 74 being completely covered by the inner sealing wall 92. The sealing strips 93 are retained between flanges 92a at the edges of the inner walls 92 and flanged strips 108 which are welded to the outer surface of the wall 92 (see Figures 2, 3, 4, 6 and 8). The forward ends of the strips 108 have lugs 108a (see Figure 6) which engage in notches in side flanges of the protective wall 74 thereby to retain the inner sealing walls 92 axially in position. i

Referring now to Figure 4, it will be seen that the inner wall 92 of the sealing nozzle element 48 is supported from the adjacent main nozzle elements 47. The inner sealing wall 92 has secured to it a bracket 94 having at its outer end a short, axially-extending T-section rail 95 engaging in an undercut channel section member 96. The channel section member 96 is carried at the inner end of a pivot pin 97 connecting a pair of links 98 which are formed with sleeves surrounding the pin 97. The opposite ends of links 98 carry balls 99 received in sockets 100- mounted in the side walls 51 of the adjacent main nozzle elements 47. j

The outer end 101 of the pivot pin 97 of each sealing nozzle element 48 is of T-form and engages an axiallyextending undercut channel formed by a. pair of Z strips 102 secured to the, inner side of the outer wall 103 of the sealing nozzle element 48, thereby to support the outer wall 103. The lateral edges of each of the outer walls 103 of the sealing nozzle element 48 overlie the outer walls 49 of the adjacent main nozzle elements 47 and, as the nozzleis opened and closed, slide over them.

The forward end of the outer wall 103 of each sealing nozzle element 48 has secured to it a pair of Z-shaped lugs 104. (see Figures 9, 10, 11) which engage with the flanges 105 of a curved member 106 secured to the mounting structure 29 and affording guides to control the movement of the forward ends of the sealing nozzle elements 48. The outer walls 103 of the sealing nozzle elements 48 are retained against axial disengagement from the associated main nozzle elements 47 by having flanges of the Z-shaped lugs 104 engaged in notches 107 (Figure 9-).in. the circumferentially-spaced edges of the outer walls 49 of the main nozzle elements 47. The guiding effect of the flanges 105 of the curved members 106 is illustrated by Figures 10 and 11, the parts being shown in the maximum orifice area position in Figure 10 and in the minimum orifice areaposition in Figure 11.

The supply of operating pressure fluid to the rams 58 is efiected in any convenient manner and. in the arrangement illustrated is effected through flexible supply pipes 109 leading from manifolds 110 in the mounting structure 29 to the unions 46 which are carried on the end walls 52 of themain nozzle elements 47 and through flexible pipes 111 which lead from the unions 46 to the rams 58. Each set of rams 58 has associated with it a pair of supply pipes 109 from manifolds 110 and a pair of supply pipes 111, and one of the supply pipes 111 leads to the block 56 to deliver pressure fluid into the supply channel 57 and the other supply pipe 111 is provided with branches 111a which lead to the opposite ends of the rams 58. When the pressure fluid is supplied through channel 57 to the adjacent ends of the rams 58 from one manifold 110 the rams expand so opening up the nozzle, the maximum efiective area of the 'nozzle elements being the position shown in full lines in Figure 1B, and when the pressure fluid is supplied from the other manifold 110 to theremote ends of the rams 58, the ram pistons'are retracted and the nozzle elements 47 are moved to reduce the effective area, the minimum area position being shown in dotted lines in Figure 1B.

We claim:

' 1. A variable-area nozzle for a circular-section jet pipe comprising circular-section fixed structure at the down stream end of said jet-pipe, two series of nozzle elements together forming an annular nozzle outlet, said nozzle elements alternating with one another around the nozzle and said nozzle elements projecting downstream fromand being pivotally connected to said fixed structure to pivot about axes substantially tangential of said fixed structure, each nozzle element of one of said series of nozzle elements having connected thereto a pair of oppositelyfacing circumferentially-extending cylinders, and each nozzle element of the other of said series of nozzle elements having connected thereto a pair of oppositelyfacing circumferentially-extending pistons one of which pistons slides in one of the pair of cylinders associated with the next adjacent nozzle element on 'one side and the other of which pistons slides in one of the pair of cylinders associated with the next adjacent nozzle element on the other side, means to supply pressure fluid sclectively to opposite ends of said cylinders thereby to cause the pistons to telescope in the said cylinders so that the nozzle elements pivot inwardly and to cause the pistons to move outwardly in said cylinders so that the nozzle elements pivot outwardly respectively.

2. A variable-area nozzle as claimed in claim 1 comprising also a plurality of sealing elements, one between each pair of said nozle elements, and comprising means to support said sealing elements from said nozzle elments.

' 3. A variable-area nozzle for a circular-section jet pipe comprising a circular-section fixed structure having an inner skin forming the boundary of the downstream end of the jet pipe and an outer skin surrounding the inner skin, two series of nozzle elements together forming an annular nozzle outlet, said nozzle elements alternating with one another around the nozzle, and said nozzle elements being elongated axially of the nozzle and projecting downstream from said circular-section fixed structure and being pivotally connected to said fixed structure at their upstream ends to pivot about axes substantially tangential of said fixed structure, each of said nozzle elements having an inner skin and an outer skin and intermediate structure extending between and interconnecting said inner and outer skins of the nozzle elements, each nozzle element of one of said series of nozzle elements having mounted on its intermediate structure a pair of oppositely-facing circumferentially-extending cyclinders, and each nozzle element of the other series of said nozzle elements having mounted on its intermediate structure a pair of oppositelyfacing circumferentially extending pistons one of which pistons slides in one of the pair of cylinders on the nozzle element of the one series next adjacent on one side, and the other of which pistons slides in one of the pair of cylinders on the nozzle element of said one series next adjacent on the other side, and means to supply pressure fluid selectively to opposite ends of said cylinders, thereby to cause the pistons to telescope in the said cylinders so that the nozzle elements pivot inwardly and to cause the pistons to move outwardly in said cylinders so that the nozzle elements pivot outwardly respectively. Y j

4. A variable-area nozzle as claimed in claim 3 comprising also stabilizing means interconnecting each nozzle element and its next adjacent nozzle element to constrain the nozzle elements to pivot through substantially equal angular extents.

5. A variable-area nozzle as claimed in claim 4, wherein the stabilizing means comprises a plurality of pairs of links, each pair extending between an associated pair of adjacent nozzle elements, each link of each pair being pivoted at one end to a corresponding one of the associated pair of nozzle elements and the links of each pair being pivoted together in a manner to restrain relative radial displacement.

6. A variable-area nozzle as claimed in claim 5, where in the pivotal axes between the links and the nozzle elements are radial to the nozzle axis and each pair of links are connected through a ball and socket connection.

7. A variable-area nozzle as claimed in claim 3, cornprising also a number of sealing elements, one between each pair of said nozzle elements, and comprising means to support said sealing elements from said nozzle elements.

8. A variable-area nozzle for a circular-section jet pipe of a jet-propulsion engine comprising a circular-section fixed structure adapted to be mounted on the downstream end of said jet pipe and being supported in gas-sealing relation with the end of the jet pipe, supporting structure externally of the jet pipe, a plurality of lugs secured to and projecting from said circular-section fixed structure, readily-detachable means securing said lugs to said supporting structure, whereby the fixed structure of said nozzle may be readily detached from the supporting structure of the engine, two series of nozzle elements together forming an annular'nozzle outlet, said nozzle elements alternating with one another around the nozzle, each of which nozzle elements projects downstream from said fixed structure and is pivotally mounted on the fixed structure to pivot about axes substantially tangential thereto, whereby on detachment of the fixed structure from said supporting structure the nozzle elements are detached therewith, each nozzle element of one series of nozzle elements having connectedthereto a pair of oppositely-facing circumferentially-extending cylinders, and each nozzle element of the other series of nozzle elements having connected thereto a pair of oppositely-facing circumferentially-extending pistons one of which pistons slides in one of the pair of cylinders associated with the next adjacent nozzle element on one side and the other of i which pistons slides in one of the pair of cylinders assopivot inwardly and to cause the pistons to move outwardly in the cylinders so that the nozzle elements pivot outwardly respectively.

References Cited in the file of this patent UNITED STATES PATENTS 2,411,895 Poole Dec. 3, 1946 2,462,953 Eaton et al. Mar. 1, 1949 2,603,062 Weiler et al. July 15, 1952 2,634,578 Kallal Apr. 14, 1953 2,682,147 Ferris June 29, 1954 2,697,907 Gaubatz Dec. 28, 1954