US3081596A

US3081596A - Variable area nozzle and shroud combination

Info

Publication number: US3081596A
Application number: US357074A
Authority: US
Inventors: Hillard E Barrett; Elia A Gallo
Original assignee: Curtiss Wright Corp
Current assignee: Curtiss Wright Corp
Priority date: 1953-05-25
Filing date: 1953-05-25
Publication date: 1963-03-19
Anticipated expiration: 1980-03-19

Description

March 19, 1963 Hmmm NNNNNNN R5 I LA March 19, 1963 VARIABLE AREA NOZZLE AND SHROUD COMBINATION l Filed May 25, 1955 2 Sheets-Shea?l 2 3,0SL596 VARIABLE AREA NDZZLE AND SHRGUD CMBNATIQN Hillard E. Barrett, East Grange, and Elia A. Gallo, En-

glewood, NJ., assignors to Curtiss-Wright Corporation, a corporation of Delaware Filed May 25, 1953, Ser. No. 357,074 7 Claims. (Cl. 60-35.6)

This invention relates to variable area nozzle and nozzle shroud combinations and is particularly directed to a jet engine exhaust nozzle and nozzle shroud construction for aircraft.

An object of the invention comprises the provision of a novel jet engine exhaust nozzle and nozzle shroud combination in which the shroud is movable with lthe nozzle to reduce the base drag area of the engine. ln accordance with the invention, as the nozzle exit diameter is decreased the diameter of the aft end of the nozzle shroud also decreases whereby the base drag area of lthe engine is less than it would be if said nozzle shroud had a fixed diameter. A further object of the invention comprises the provision of a novel adjustable convergent-divergent nozzle and shroud combination in which the shroud follows movement of the nozzle.

Specifically the nozzle-shroud combination -of the present invention comprises a plurality of circumferentially overlapping segments which are pivotally supported at their upstream ends and are surrounded by a plurality of circumferentially overlapping shroud segments which are also pivotally supported at their upstream ends. A further object of the invent-ion comprises the provision of a novel actuator mechanism for pivotally moving said overlapping nozzle and shroud segments. A still further object of the invention comprises the provision of a novel segmented nozzle construction in which novel means are provided vfor minimizing leakage flow between the nozzle segments.

Other objects of the -invention will become apparent upon reading the annexed detailed description in connection with the drawing in which:

FIG. l is an axial sectional view through a turbo-jet engine embodying the invention with the nozzle in its maximum open position;

FIG. 2 is a fragmentary view of the nozzle portion of FIG. l but illustrating the nozzle in its minimum open position;

FIG. 3 is an enlarged partial axial sectional view of the nozzle;

FlGS. 4, 5, 6, 7 and 8 are sectional views taken along lines 4 4, 5 5, 6-6, 7 7 and 8-8 respectively of FlG. 3; and

FIG. 9 is a fragmentary sectional view of the nozzle illustrating a modilied construction.

Referring now to FIGS. l and 2 of the drawing, a turbo-jet engine l@ is illustrated as comprising an air compressor l2, a combustion chamber ld and a turbine 16 drivably connected -to the compressor l2. Said compressor, combustion chamber and turbine are housed within an inner casing or duct i8 which provides the compressor with a forward-ly directed air inlet opening Ztl. In general the duct 1b is surrounded by an outer casing 22 to form a hollow double wall housing structure having an annular spacev 23 between its walls. The compressor 12 delivers compressed air to the combustion chamber lli where heat energy is added to said air by burning fuel therein, the Afuel nozzles or burners being indicated at 24. The heated gases discharge from the combustion chamber 14 lbetween the blades of the turbine 16 to drive said turbine. lFrom the turbine i6 the lgases exhaust through the duct 18 and discharge rearwardly 3,08l,596 Patented Mar. 19, 1963 into the surrounding atmosphere through a nozzle 26. Between the nozzle 26 and the turbine i6, the turbo-jet engine may also include a second combustion chamber 28 generally termed an afterburner, the fuel nozzles or burners of the afterburner being indicated at 30. The structure of the turbo-jet engine `so far described is conventional. As will appear, the nozzle structure of the present invention is not limited to use with an afterburning turbo-jet engine, like the engine l0, but can also be used with non-afterburning turbo-jet engines as well as with other jet engines, as for example a `ram jet engine.

The details of the nozzle 26 are best seen in FIGS. 3-8. As illustrated the nozzle 26 has a variable area construction and comprises a plurality of circumferentially-overlapping axially-extending nozzle segments or members 32 with the upstream end of each nozzle member 32 terminating in a hollow hinge pin 34.. As Seen in FIG. 3, the individual hinge pins 34- of the nozzle members 32 are pivotally journaled between annular members 36 and 33 co-axially secured together and to the duct i8, the member 36 forming a continuation of the `duct i8.

The nozzle 26 is surrounded by an annular movable shroud or fairing comprising circumferentially-overlapping axially extending shroud segments or members 4l) each having .its upstream end terminating in a hinge pin 42. The individual hinge pins 42 of the shroud members 4b are pivotally journaled between annular members 44 and '46 forming a ring disposed in the annular space 23 between the inner wall or duct 18 and the outer wall 22 of the housing for the engine l0. There is one shroud member du for each nozzle member 32. The overlapping arrangement of the nozzle members 32 and the shroud members 4@ is best seen in FIGS. 4 to 8.

Each nozzle member 32 has a longitudinally extending rib 48 on its outer side from which a pair of

axiallyspaced projections

49 and 50 extend radially outwardly, the

projections

49 and 50 having cam follower rollers 52 and S4 respectively at their outer ends. Each shroud member 4u has a pair of circumferentially-spaced radially inwardly extending flanges 56 and S8 between which the projections 49 and 5u of the associated nozzle mem ber 32 extend. Each

shroud member flange

56 and 58 has a similar pair of cam slots or

tracks

60 and 62 within which .are received the

cam follower rollers

52 and 54 respectively. The

cam tracks

60 and 62 `are so disposed and orientated that axial movement of the composite ring 44, 46, in a rearward direction, causes the downstream ends of the nozzle members 32 to swing inwardly to reduce the minimum or throat area of the nozzle and at the same time causes the downstream ends of the shroud members 40 to swing inwardly. The two extreme positions of the nozzle members 32 and the accompanying .extreme positions of the shroud members 4l) are illustrate-d in FIGS. l and t2. Since the shroud members 40 form a substantially streamline continuation of the outer engine housing 22 in all positions of nozzle adjustment, the inward swinging movement of the shroud members 4@ accompanying inward swinging movement of the nozzle members 32 serves to reduce the base drag area of the engine 10 from what it would be if the nozzle members 32 had a fixed annular shroud.

A plurality of interconnected uid motors 70 are mounted in the annular space 23 between the duct 18 and the outer housing 22. Each of the motors 70 is connected to the ring 44, 46 by a piston rod 72 for axially moving said ring to vary the minimum or throat .area of the nozzle. Obviously the nozzle motors 70 may be subject to manual or automatic control. Because the ring 44, 46 is connected to all the shroud members 40 and thence to all the nozzle members 32 all motion of said ring, except axial motion, is opposed by the pivotal sup ports for the nozzle members 32. Accordingly, the ring 44, 46 does not require any axial guideway to limit its motion to axial motion and therefore no such guideway is illustrated. Obviously, however, an axial guideway may be provided for the ring 44, 46 to reduce the forces on `the pivotal supports of the nozzle members 32. Thus the internal surface of the housing 22 may form such a guideway.

Each nozzle member 32 is designed to maintain contact with the adjacent nozzle members throughout their length to prevent leakage of the hot exhaust gases out therebetween from inside the nozzle. However, because of manufacturing tolerances, thermal distortions etc. some leakage passages may exist between adjacent nozzle members 32. Any leakage of the jet engine exhaust gases outwardly between the nozzle members 32 decreases the mass iioW of exhaust gases discharging axially from the nozzle and therefore decreases the engine thrust. In addition, when the engine afterburner 28, 3h is operating the temperature of the exhaust gases is very high and may be more than 2500 F. so that any leakage of the exhaust gases between the nozzle members 32 results in extremely high temperatures on both sides of the nozzle members thereby reducing the useful life of said nozzle members.

In accordance with the present invention any such leakage of gases out between the nozzle members is prevented or minimized by providing a high pressure about the outside'of the nozzle members opposing any such leakage flow. For this purpose one side of each longitudinal rib 48 of each nozzle member 32 is provided with a pair of sheet metal leaves 85) and 82 and the facing side of the longitudinal rib of the ,adjacent nozzle member 32 has a single sheet metal leaf 84 which slidably extends between the leaves Si) and 82 kthereby forming a passage 86 extending along the outside of the overlapping junction of said nozzle members.

The hollow hinge pin 34 of each nozzle member 32 has a pair of openings 88 on opposite ysides of the rib 48 of said nozzle member. In addition the annular member 38 has an annular extension 90 extending upstream therefrom in spaced relation to the duct 18 to provide an annular space or chamber 92 therebetween. A plurality of circumferentially-spaced ducts 94 extend upstream from the chamber 92, said ducts communicating with the interior of the jet engine duct 18 at a point downstream of the turbine 16 and upstream of the after burner combustion chamber28. With this arrangement the ducts 94 bleed off gases under pressure from the turbo-jet engine at a point downstream of its turbine and upstream of the engine afterburner. These gases are supplied to the annular chamber `92 from which they ow through the hinge openings 38 into the passages 86. The downstream or discharge ends of the passages 86 are restricted, as provided by the flange 96 on each leaf 84, to control the rate of flow through said passages and to provide a fluid pressure in the passage 86 opposing leakage ilow from inside the nozzle through the junctions between overlapping nozzle members. The gas ilow `through the nozzle passages 86 also serves to cool the nozzle during afterburner operation. Obviously if a cooler gas ow is desired through the pasages 86 the ducts 94 could bleed off air from the compressor 12 instead of bleeding gases from the turbine exhaust upstream of theafterburner.

The passages 86 do not need to extend completely to the discharge "end of thenozzle members since the pressure 'in 'the nozzle 26 drops to that of the surrounding atmosphere at the discharge end of the nozzle. Hence the pressure in the nozzle is relatively low adjacent to its discharge end and therefore the pressure differential available for producing leakage flow outwardly between the overlapping nozzle members is relatively low adjacent to the nozzledischarge end.

The afterburner combustion chamber 28 preferably has a liner construction providing an annular space between said liner and the adjacent wall of the duct 18 to protect said duct from the hot gases in the afterburner chamber during afterburner operation. The liner 11G extends from-the upstream end of the afterburner chamber 28 and terminates at the nozzle 26 whereby the relatively cool gases flowing between the liner l110 and the duct 18 discharges therefrom against the upstream end of said nozzle. Although this thin layer of cool gas probably will not follow the inner surface of the nozzle 26 throughout its entire length nevertheless said cool gas will cool the upstream ends of the nozzle members 32 where their stresses are the greatest.

As illustrated each nozzle member 32 has a curved profile in an axial direction, said members being convex when viewed from inside the nozzle. The invention however is not limited to such curved nozzle members. With the nozzle members 32 having the curvature illustrated, the crossesectional area of the nozzle 26 progressively converges in a downstream direction when the nozzle is adjusted to its minimum open position FIG. 2 or to positions adjacent to said minimum open position and said nozzle has a converging-diverging cross-sectional area when it is adjusted toA its maximum open position or to positions adjacent thereto. In the case of an after-burning turbo-jet engine, when the afterburner is operating, rela tively large nozzle throat areas are required and in general large nozzle pressure ratios exist. For maximum nozzle efliciency at high nozzle pressure ratios the nozzle should have a converging-diverging flow passage. Accordingly the curved prole of the nozzle members 32 is important in the case of an afterburning turbo-jet engine.

As further illustrated, the nozzle shroud members 4i) extend downstream of the nozzle members 32 whereby the gases discharging through the nozzle 26 act as an ejector to draw air through the annular space between said nozzle members 32 and shroud members. The upstream end of the annular space between the nozzle members 32 land the shroud members 4G communicates with the annular space 23 between the duct 18` and the outer housing 22. The forward end of the annular space 23 may communicate with the compressor inlet 2'through openings 112 or the forward end of said space may cornmunicate directly with the surrounding atmosphere. With this arrangement the ejector `action of the exhaust gases helps to draw cooling `air through the annular space 23 and thence through the annular space between the nozzle 26 and the shroud members 40. This air helps to cool the actuator portions of the nozzle 26. At the discharge end of the nozzle 2,6, the gas ow through the annular space between the nozzle members 32 and the shroud members 40 discharges about the nozzle exhaust jet and the combined jet then discharges through the circular opening formed by the 4aft end of the shroud members. This has an effect on nozzle performance which is equivalent to increasing the divergence of the exit portion of the nozzle as is highly desirable during afterburner operation.

If desired the nozzle shroud members 4u may terminate short of the nozzle members so as not to affect the gases discharging front the nozzle. Such an arrangement-is illustrated in FIG. 9. The parts of FIG. 9 have been designated yby `the same reference numerals but with a subscript a added thereto as the corresponding parts of FIGS. l to 8. Except for shortening the nozzle shroud members, the modification of FIG. 9 is like that of FIGS. 1 to 8 so that no further description or" FIG. 9 is deemed necessary.

With the nozzle and shroud construction illustrated, rearward motion of the shroud segments 4d produces inward movement of the nozzle segments 32 against the pressure of the exhaust gases within the nozzle. Accordingly the portion of each shroud segment 40 between its connection to a nozzle segment and the actuator ring 44, 46 is in compression. Obviously however the slots 66 and 62 could be oriented so that forward, instead of rearward, movement of the shroud segments 40 produced inward movement of the nozzle segments whereupon the shroud segments would be in tension, Furthermore the relative positions of each cam slot I60 or 62 and its cam follower on the nozzle and shroud segments could be reversed if desired.

While we have described our invention Vin detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modifications may be made therein without departing from the spirit or scope there of. We aim in the appended claims to cover all such modifications.

We claim as our invention:

l. A combination fluid nozzle and shroud construction comprising a plurality of circumferentially overlapping nozzle members disposed to form a substantially annular nozzle surface; a plurality of circumferentially overlapping shroud members forming a substantially annular shroud `co-axial with and about -said nozzle; means supporting said nozzle members for inward and outward movement to vary the nozzle uid flow area; and means operatively interconnecting each shroud member with Va nozzle member comprising ia pair of cam and cam follower combinations with each cam being connected to one of said members and with its cam follower being connected to the other of said members so that said shroud members move inwardly and outwardly with inward and outward movement respectively of said nozzle members.

2. A combination fluid nozzle `and shroud construction comprising a plurality of circumferentially overlapping nozzle members disposed to form a substantially annular nozzle surface; means pivotally supporting said nozzle members adjacent to their upstream ends for pivotal movement to vary the nozzle tiuid ow area downstream of said pivotal supports; a plurality of circumferentially overlapping shroud members forming a substantially annular shroud co-axial with and about said nozzle; axially movable annular means co-axial with said nozzle; means pivotally connecting the upstream ends of said shroud members to said annular means; and means operatively interconnecting each shroud member with a nozzle member comprising a pair of cam and cam follower combinations with each cam being connected to one of said members and with the follower of said cam being connected to the other of said members so that axial movement of said annular means is operative to pivotally move the downstream ends of said nozzle and shroud members inwardly and outwardly in the same direction.

3. A combination fluid nozzle and shroud construction comprising a plurality of circumferentially overlapping nozzle members disposed to form a substantially annular nozzle surface; means pivotally supporting said nozzle members adjacent to their upstream ends for pivotal movement to vary the nozzle fluid ow area downstream of said pivotal supports; a plurality of circum-ferentially overlapping shroud members forming a substantially annular shroud co-axial with and about said nozzle; axially movable annular means co-axial with said nozzle; means pivotally connecting the upstream ends of said shroud members to said annular means; and means operatively interconnecting each shroud member with a nozzle memer comprising a pair of cam tracks connected to said shroud member and a pair of cam followers connected to said nozzle member with the one cam track and its follower being disposed downstream of the other relative to the liow direction through the nozzle and with said cam tracks being shaped so that axial movement of said annular means in a downstream direction is operative to pivotally move the downstream ends of said nozzle members inwardly to decrease the effective nozzle fluid flow area and is operative to pivotally move the downstream ends of said shroud members inwardly.

4. A jet engine having an exhaust duct; a housing surrounding said duct; an exhaust nozzle at the discharge end of said duct, said nozzle comprising a plurality of circumferentially overlapping nozzle members disposed to form a substantially annular nozzle surface; means pivotally supporting said nozzle members adjacent -to their upstream ends for pivotal movement to vary the nozzle uid flow area downstream of said pivotal supports; a shroud surrounding said nozzle and forming a downstream continuation of said housing, said shroud comprising a plurality of circumferentially overlapping shroud members forming a substantially annular shroud co-axial with and abou-t said nozzle; axially movable annular means disposed within said housing co-axial with said nozzle; means pivotally connecting the upstream ends of said shroud members to said annular means; and means operatively interconnecting each shroud member with a nozzle member comprising a pair of cam and cam follower combinations with each cam being connected to one of said members 'and with the follower of said cam being connected -to the other of said members so that axial movement of said annular means is operative to pivotally move the downstream ends of said nozzle and shroud members inwardly and outwardly in the lsame direction.

5. A jet engine having an exhaust duct; a housing surrounding said duct; an exhaust nozzle at the discharge end of said duct, said nozzle comprising a plurality of circumferentially overlapping nozzle members disposed to form a substantially annular nozzle surface; means pivotally supporting said nozzle members adjacent to their upstream ends for pivotal movement to vary the nozzle flow area downstream of said pivotal supports; a shroud surrounding said nozzle and forming a smooth downstream continuation of said housing for flow of rthe airstream surrounding said jet engine thereover, said shroud comprising la plurality of circumferentially overlapping shroud members forming a substantially annular shroud co-axial with and about said nozzle; annular means disposed adjacent to the upstream end of said shroud and pivotally connected to the upstream ends of said shroud members for supporting the upstream ends of said shroud members; cam means operatively interconnecting said shroud and nozzle members so that inward and outward pivotal adjustment of said nozzle members is accompanied by a corresponding inward and outward pivotal adjustment of said shroud members; and in ywhich each overlapping pair of nozzle members has means connected thereto and bridging their junction to form an individual tubular passageway along the outer side of said junction for providing a fluid pressure along said outer side, one wall of each said passageway being formed by the overlapping portions of its associated pair of overlapping nozzle members.

6. In combination: a duct for flow therethrough of a liuid under pressure; a variable area nozzle at the discharge end of said duct, said nozzle comprising a plurality of circumferentially overlapping and contacting members disposed to form a substantially annular nozzle surface and pivotally movable to vary the nozzle area, each overlapping pair of nozzle members having means connected thereto and bridging across their junction to form an individual tubular passageway along the outer side of said junction, one wall of each said passageway being for-med by the overlapping portions of its associated pair of overlapping nozzle members and each said passageway communicating with said duct upstream of said nozzle members for providing a iuid pressure on the exterior side of and along the junction of its associated pair of overlapping nozzle members.

7. A turbojet engine comprising an exhaust duct having an end and an exhaust nozzle having a convergent coniiguration when closed and a convergent-divergent conguration when open, comprising a plurality of rigid aps each having a longitudinally arcuate inner sur-face, said aps being pivotally secured to said end for radial swinging movement to provide throat and outlet portions of .variable area downstream of said end.

References Cited in the le of this patent UNITED STATES PATENTS Melchior May 20, 1952 vWalker June 10, 1952 Brown July 15, 1952

Claims

1. A COMBINATION FLUID NOZZLE AND SHROUD CONSTRUCTION COMPRISING A PLURALITY OF CIRCUMFERENTIALLY OVERLAPPING NOZZLE MEMBERS DISPOSED TO FORM A SUBSTANTIALLY ANNULAR NOZZLE SURFACE; A PLURALITY OF CIRCUMFERENTIALLY OVERLAPPING SHROUD MEMBERS FORMING A SUBSTANTIALLY ANNULAR SHROUD CO-AXIAL WITH AND ABOUT SAID NOZZLE; MEANS SUPPORTING SAID NOZZLE MEMBERS FOR INWARD AND OUTWARD MOVEMENT TO VARY THE NOZZLE FLUID FLOW AREA; AND MEANS OPERATIVELY INTERCONNECTING EACH SHROUD MEMBER WITH A NOZZLE MEMBER COMPRISING A PAIR OF CAM AND CAM FOLLOWER