US2978061A

US2978061A - Jet propulsion nozzles

Info

Publication number: US2978061A
Application number: US646493A
Authority: US
Inventors: Keen John Michael Storer
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1956-03-16
Filing date: 1957-03-15
Publication date: 1961-04-04
Anticipated expiration: 1978-04-04

Description

April 4, 1961 Filed March 15, 1957 J. M, S. KEEN JET PROPULSION NOZZLES 6 Sheets-Sheet 1 April 1961 J. M. s. KEEN 2,978,061

JET PROPULSION NOZZLES Filed March 15, 1957 6 Sheets-Sheet 2 April 4, 1961 J. M. s. KEEN 2,978,061

JET PROPULSION NOZZLES Filed March 15, 1957 6 Sheets-Sheet 4 April 4, 1961 J. M. s. KEEN 2,978,061

JET PROPULSION NOZZLES Filed March 15, 1957 6 Sheets-Sheet 5 April 4, 1961 J. M. s. KEEN 2,978,061

JET PROPULSION NOZZLES Filed March 15, 1957 6 Sheets-Sheet 6 United States Patent JET PROPULSION NOZZLES John Michael Storer Keen, Allestree, England, assignor to Rolls-Royce Limited, Derby, England, a British com- P y Filed Mar. 15, 1957, Ser. No. 646,493

Claims priority, application Great Britain Mar. 16, 1956 Claims. (Cl. 181-41) This invention comprises improvements in or relating to jet propulsion nozzles, such for example as are employed in aircraft, and is concerned with silenced et propulsion nozzles.

Silenced jet nozzles as heretofore proposed have a fixed contour such that at least the peripheral portion of the gas jet issuing from the nozzle is divided into a' number of streams separated by spaces into which ambient air flows. Thus in one proposed construction, the

nozzle has a corrugated periphery at the outlet such that the issuing jet has in cross-section a central core and a series of circumferentially-spaced lobes, and the ambient air flows into the spaces between the lobes. In another proposed construction the outlet of the nozzle is afforded by a'series of angularly-spaced sector-shaped apertures so that the gas issues as acorresponding number of streams and so that air flows into the spaces between the streams.

It has now been found that, with such nozzles, a loss of thrust occurs as compared with an equivalent plain convergent nozzle and that such loss of thrust increases the specific fuel consumption. The increase in the specific fuel consumption is undesirable, particularly in th case of long range aircraft.

Accordingly, this invention provides a jet propulsion nozzle whereof the contour is adjustable between a first setting in which a marked silencing effect is obtained and a second setting in which a lower thrust loss is incurred as compared with the first setting.

According to a feature of this invention, a jet propulsion nozzle comprises a series of flaps which are disposed in annular assembly peripherally of the nozzle, are pivoted at their upstream ends to swing towards and away from the nozzle axis and co-operate with stationary structure to define in a first angular setting of the flaps a silenced nozzle having an outlet of corrugated contour or having a series of angularly-spaced outlet apertures,

and to define in a second angular setting of the flaps a' substantially frusto-conical nozzle or a nozzle having a corrugated contour whereof the radial depth of the corrugations is small compared with the depth of the corrugations in thefirst setting or with the radial extent of the outlet apertures in the first setting.

In preferred arrangements according to this invention, the nozzle fixed structure comprises a series of angularly spaced, axially extending radially inwardlyprojecting members, there being one such member between each pair of fiaps, and adjacent flaps are caused to-swing in opposite senses so that they are radially separated in the first setting and radially close in the second setting. The fixed members may be wedge-shaped so that each adjacent pair of such members have the facing,

to the circumferential dimension of the flaps which are" radially innermost in the first setting.

Some constructions of jet propulsion nozzle of this invention will now be described with reference to the accompanying drawings in which:

Figures 1 and 2 are axial views of a first construction, and showing the nozzle in the first and second settings respectively,

Figure 3 is a section on the line 3-3 of Figure l, and has parts broken away to show details of construction,

Figures 4 and 5 are views, corresponding to Figures 1 and 2, of a second construction,

Figures 6 and 7 are sections on the lines 66 and 7-7 respectively of Figure 4,

Figures 8 and 9 are diagrammatic views corresponding to Figures 1 and 2 of a third construction,

Figure 10 is an end view of part of yet another construction of nozzle according to this invention, and

Figures 11 and 12 are sections on the lines 11-41, 1212 of Figure 10.

Referring first to Figures 1 to 3, there is shown a jet pipe 10 at the outlet from which there is provided an adjustable silenced jet nozzle of this invention.

The nozzle comprises a series of six pairs of hollow members 11 which are fixed to the outlet end of the jet pipe 10 and project axially downstream therefrom. The pairs of members 11 are equi-angularly spaced around the jet pipe. The downstream portion of each member 11 is wedge-shaped so as to have a pair of mutually

inclined walls

11a, 11b, and each wall 11a is parallel to the facing wall 11b of next adjacent member 11, so that the members 11 define between them a series of twelve

spaces

12, 13 with parallel walls. Alternate spaces 12 have a greater circumferential extent than the remaining spaces 13. The walls 11a, 1121 project within a geometrical projection of the jet pipe 10 and have an inward dimension which increases from their upstream ends to their downstream ends, so that the inner edges of the

walls

11a, 11b of each member 11 are inclined towards the nozzle axis.

The nozzle also comprises two series of six

flaps

14, 15 respectively which extend longitudinally downstream from pivotal connections 16 between their upstream edges and the jet pipe 10, the pivotal axes being at right angles to a plane containing the nozzle axis.

Each flap 14 has a longitudinally and circumferentiallyextending Wall 14a and a pair of radially-projecting side walls 14b which increase in depth from the upstream to the downstream ends of the flaps. As will be seen, the flaps 14 occupy the spaces 13 with their side walls 14b co-operating in a gas sealing manner with the

walls

11a, 11b of the members 11 which bound the spaces 13, and they swing from a first setting (Figure l) in which they project substantially radially inwards from the spaces 13 to a second setting (Figure 2) in which their walls 14a are level with the inner edges of the wedge members.

The flaps 15 are in the form of plates of arcuate section and they occupy the spaces 12 with their edges in gas sealing co-operation with the

walls

11a, 11b bounding these spaces. The flaps 15 swing from a first setting (Figure l) in which they occupy the radially outer portion of the spaces are level with the inner edges of the wedge members and thus form with the walls 14a of the flaps 14 a substantially frustoconical nozzle of circular outlet contour. As will be seen from Figure 1 in the first setting of the

flaps

14, 15, the flaps and wedge members co-operate to define angularly-spaced deep corrugations and so provide a silenced nozzle.

The flaps are caused to swing by a series of rams 1-7 housed in the members 11 and connected with a ring 18 encircling the nozzle. The ring carries a series of rollers 19, 20-, of which the rollers 19 run on the walls 14a of the flaps 14 and" ofwhich the rollers 20 run on ramps 21.

12 and a second setting in which they inwards, and such that, on movement to the left of ring 18, the flaps 14 are forced inwards and the flaps 15 are allowed to swing outwards under the gas pressure. The ring 18 is guided in slots 22 in the members 11;

In this construction, the total outlet area of the nozzle in the first setting (Figure 1) in which a silencing effect is obtained, is somewhat greater than the area in the second setting (Figure 2) in which loss of thrust is reduced.

Referring now to Figures 4 to 7, there is illustrated a nozzle in which in the second setting (Figure 5) the depth of the corrugations is substantially smaller than in the first setting (Figure 4).

In these figures, a indicates the 'jet pipe. The jet pipe is enclosed in a fairing 25 and has secured to it a series of circumferentially-spaced members 26 axially-projecting beyond the end of the jet pipe, which members are wedge-shaped in transverse cross-section so as to provide a pair of mutually

inclined walls

26a, 26b, whereof each wall'26a faces and is parallel to the nearer wall 26b of' the adjacent member 26. The members 26 are stiffened at their downstream ends by straight parts 27 of a polygonal ring.

The members 26 define between them twelve similar spaces, alternate spaces being occupied by flaps 28 and the remainder by flaps 29.

The flaps 28 are similar to the flaps 14 above described having a circumferential wall 28a and side walls 28b which co-operate with the walls 26a. The flaps also have outer walls 28c which at their upstream ends co-operate with the fairing 25 to form in some positions a smooth continuation thereof and at their downstream ends meet the inner wall 28a so that the flaps have outwardly facing channels open to atmosphere. The flaps 28 are mounted on the jet pipe by pivots 30.

The flaps 29 are similar to the flaps 28 and have outer circumferential walls 29a forming continuations of the fairing 25, side walls 29b projecting inwards from the edges of walls 29a and co-operating with the walls 26a, and inner circumferential walls 290 which extend from pivots 30 on the jet pipe to the downstream edges of the walls 29a so that the flaps 29 have inwardly facing channels.

a As will be seen from Figures 4 and 5, the

flaps

28, 29 are caused to swing from a first setting (Figure 4) in which the walls 28a are spaced radially inwards of the walls 296 to a larger extent giving large depth corrugations, to a second setting in which these walls 28a, 29c are less spaced. In the first setting, a well silenced nozzle is obtained, and in the second setting less silencing is obtained but a substantially lower thrust loss is experienced. The areas of the nozzle in the two settings are substantially equal.

The flaps are caused to swing by rams 31 which move axially a ring 32 surrounding the jet pipe, and the ring is connected by links 33 to pins 34 running in

slots

35, 36 respectively in the walls 28b, 29b. The pins 34 are guided by slots 37 in the wedge members 26. The

slots

35, 36, are oppositely inclined to the slots 37 so that as one set of

flaps

28 or 29 swings outwards the

second set

29 or 28 respectively swings inwardly.

Referring now to Figures 8 and 9, the nozzle illustrated has a tubular outer casing 35 with a series of inwardlyprojecting walls 36. The walls 36 are contained in axial planes and increase in depth from their upstream ends to their downstream ends. Each wall carries a pair of sealing

elements

37, 38 which extend one on each surface of the wall along its longitudinal center line the purpose of which will be described below. 7 e

The nozzle also comprises two sets of six

flaps

39, 40 of arcuate cross-section; The flaps are pivoted to the easing 35 at their upstream ends, the pivots being adjacent the upstream ends of the walls 36.

The flaps 39 are arranged each to swing from a first setting (Figure 8) in which it joins the inner edges of a pair of the walls 36, to a second setting (Figure 9) in which it abuts by its edges the sealing strips 37 on the pair of walls 36.

The flaps 40 are arranged to swing from a first setting (Figure 8) in which they lie against the casing 35, to a second setting (Figure 9) in which each abuts by its edges the sealing strips 38 on a pair of adjacent walls 36.

Thus in the first setting, there is provided a silenced nozzle with a. deeply corrugated contour and in the second setting there is provided substantially a plain convergent nozzle, the strips 37 being offset radially from the strips 38 for the purpose of allowing the outlet ends of the flaps to lie on a common circle.

Referring now to Figures l0, l1 and 12 the embodiment illustrated again shows a nozzle 10b in which, in the setting for silencing, the depth of the corrugations is substantially greater than in the setting for normal 10w thrust-loss operation. The nozzle is also designed to be of the convergent/ divergent kind in the normal low thrust setting. Such a nozzle is desirable for high efliciency operation of high-speed aircraft.

Referring to Figure 10 the silenced setting of the nozzle is illustrated. As in the construction of Figures 4 to 7 a jet-pipe has secured to it a series of members 40'axially projecting beyond the end of the pipe, which members are wedge-shaped in cross-section so as to provide a pair of mutually-inclined circumferentially-facing walls 41, 41a corresponding to the

walls

26a, 26b of the previous construction. The members 40 are stiffened at their downstream ends by being joined together by parts 42 of a polygonal ring.

The members 40 define between them twelve similar spaces of which a number are shown in Figure 10. Alternate spaces are occupied by flaps 43 and the remainder walls of the flap 43 indicated at 43a co-operate with the side walls of the members 40 in gas sealing engagement. The flaps 44 are generally of arcuate cross-section having plane side walls 44a co-operating with the side walls 41 of the members 40. The flaps 44 are pivoted on the members 40 at 47 for angular movement, as more clearly shown in Figure 12. The leading edge 47b of each flap member 44 is formed as a part-spherical surface about a centre lying on the pivot axis 47. This leading edge surface co-operates with a fairing surface 48 forming a smooth continuation of the jet-pipe in the region of each of the flaps 44.

As in the previous construction mentioned, the

flaps

43 and 44 are caused to swing from a first setting shown in Figure 10 in which the depth of corrugations is large,

giving a well-silenced nozzle, to a low thrust operating setting, in which the flaps 43 are swung inwards, and the flaps 44 are swung outwards to the positions shown in dotted lines respectively in Figures 11 and 12.

Operating mechanism similar to that described in connection with previous embodiments, may be used.

In this construction in the silenced setting the nozzle throat is located at or towards the plane of the exit area, and in the low thrust loss setting the nozzle throat is located upstreamof the exit nozzle area substantially in the plane of the pivots 47 as indicated by the dotted line T--T on Figures 11 and 12. It will be noted in these figures and referring to the dotted positions of the

flaps

43 and 44, that the duct conveying the hot gas diverges after the plane of T--T, since in both cases the operative duct-defining walls of the

flaps

43 and 44 diverge away from the axis of the jet-pipe. In the full line position of the

flaps

43 and 44 as shown in Figures 11 and 12, i.e. in the silencing setting, the substantial inclination of the gas-defining surface of the flaps 44 provides a convergence which effectively with the divergence of the gas-defining surface of the flaps 43 causes the throat area to be defined substantially in the plane of exit to atmosphere.

While in the embodiments described above it is arranged that the effective areas of the nozzles in the two settings are substantially equal, it may in certain cases be desirable to provide that in the silencing setting the effective area is less than that in the low loss setting. Such an arrangement may be useful to increase the thrust available at take-off to compensate in part at least for losses which may be attributable to the silencing of the nozzle. Under the cruise condition, when the low loss setting is used, greatest economy in operation may be obtainable with a somewhat greater area exit nozzle.

This effect can be obtained in the various embodiments illustrated by selecting the respective increase and decrease of areas by inward and outward movement of adjacent flaps to be of a differential nature. Thus for example in the construction of Figures 4 to 7 the increase of area afforded by outward movement of flaps 28 may be greater than the decrease of area afforded by inward movement of flaps 29. Thus the effective area in the silenced setting (Figure 4) may be less than in the loss setting (Figure I claim:

1. A jet propulsion nozzle for a continuous combustion jet propulsion engine, said nozzle comprising a rigid tubular structure and first and second sets of flaps defining the nozzle outlet by their downstream ends, the flaps of the first set alternating around the nozzle with the flaps of the second set, each of said flaps having a longitudinallyand circumferentially-extending wall defining a part of a gas passage through the nozzle, pivot means connecting each flap at the upstream end of its longitudinally and circumferentially-extending wa l to the tubular structure to swing about an axis which is at right angles to a plane containing the nozzle axis, and operating means connected to said sets of flaps and in operation effecting swinging of said first and second sets of flaps in opposite directions between a first setting in which the downstream ends of the walls of the first set of flaps are at a substantially smaller radial distance from the nozzle axis than the downstream ends of the walls of the second set of flaps and the nozzle outlet has a corrugated contour, and a second setting in which the downstream ends of the first and second flaps are radially closer together, said rigid tubular structure comprising a series of angularly-spaced, longitudinally extending, radially-inwardlyprojecting fixed members, there being one such fixed member between each pair of adjacent flaps, and the flaps have circumferentially-spaced edge portions cooperating in gas-sealing manner with the fixed members.

2. A jet propulsion nozzle as claimed in claim 1 in which the fixed members are wedge-shaped in cross section, each adjacent pair of said fixed members having their facing walls parallel.

3. A jet nozzle according to claim 2, wherein each flap of the first set has a pair of outwardly extending side walls at the edges of its circumferentially extending wall,

which side walls cooperate with the wedge-shaped fixed members, these flaps swinging between a position in the first setting in which they project inwardly from the wedge-shaped members and a position in the second setting in which their circumferentially-extending walls are substantially level with the inner edges of the wedge shaped members, and the flaps of the second set have the edges of their circumferentially-extending walls cooperating with the adjacent wedge-shaped members and swing from a position in the first setting in which their walls are spaced radially outwards from the inner edges of the wedge-shaped members and a position in the second setting in which their walls are radially nearer sm'd inner edges.

4. A jet nozzle according to claim 3, wherein, in the second setting, said flaps of the second set have their circumferentially-extending walls substantially radially level with the inner edges of the wedge-shaped members.

5. A jet nozzle according to claim 3, wherein flaps of the second set have side walls projecting inwards from the edges of their circumferentially-extending walls, and in the second setting have the inner edges of their side walls substantially level with the inner edges of the wedgeshaped members.

6. A jet nozzle according to claim 3 wherein said flaps of the first set have a longitudinal extent less than said flaps of the second set, the downstream ends of the flaps being coplanar, and fairing means is provided to extend from the upstream ends of the wedge-shaped members to the upstream ends of the said flaps of the first set.

7. A jet nozzle according to claim 6, wherein at least in the second setting the flaps define a part at least of a convergent/ divergent nozzle.

8. A jet nozzle according to claim 1, comprising a fairing surrounding the tubular structure, the flaps having outer walls forming continuations of the fairing.

9. A jet nozzle according to claim 1, wherein the fixed members are radial walls projecting inwardly from the tubular structure, said radial walls carrying sealing strips extending along the longitudinal center line of the wall with which the flaps cooperate in their second setting, and said radial walls having a spacing at their inner radius equal to the circumferential extent of the said walls of the first set of flaps.

10. A jet nozzle according to claim 1, wherein the operating means effects simultaneous swinging of the first and second sets of flaps and comprises a ring encircling the nozzle, ram means connected to move the ring longitudinally of the nozzle, and camming means conmeeting the ring with each flap.

References Cited in the file of this patent UNITED STATES PATENTS 2,569,497 Schiesel Oct. 21, 1951 2,669,834 Helms Feb. 23, 1954 2,693,078 Laucher Nov. 2, 1954 2,865,165 Kress Dec. 23, 1958 FOREIGN PATENTS 1,084,419 France July 7, 1954 1,102,597 France May 11, 1955 1,111,867 France Nov. 2, 1955 766,985 Great Britain Jan. 30, 1957 766,986 Great Britain Jan. 30, 1957 768,553 Great Britain Feb. 20, 1957 781,661 Great Britain Aug. 21, 1957 1,164,936 France May 19, 1958