US2658333A

US2658333A - Variable area discharge nozzle for jet engines

Info

Publication number: US2658333A
Application number: US291518A
Authority: US
Inventors: Antoni J Smialowski
Original assignee: National Research Council of Canada
Current assignee: National Research Council of Canada
Priority date: 1952-06-03
Filing date: 1952-06-03
Publication date: 1953-11-10
Anticipated expiration: 1970-11-10
Also published as: GB739105A

Description

Nov. l0, 1953 A. J. sMlALowsKl VARIABLE AREA DISCHARGE NOZZLE FOR JET ENGINES 4 Sheets-Sheet l Filed June 3, 1952 A EN ml W www nu .n f i *mw s W IL W n mw o O T Q. QQ A Q o e 3Q) Nov. l0, 1953 A. J. sMlALowsKl VARIABLE AREA DISCHARGE NOZZLE FOR JET ENGINES 4 Sheets-Sheet 2 Filed June 3, 1952 Nov. 10, 1953 A. J. sMlALowsKl 2,658,333

VARIABLE AREA DISCHARGE NOZZLE FOR JET ENGINES Filed June 3, 1952 4 Sheets-Sheet I5 /A/VEN rox? Nov. 10, 1953 A. J. sMlALowsKl 2,658,333

VARIABLE AREA DISCHARGE NozzLE EoR JET ENGINES Filed June 3, 1952 4 Sheets-Sheet 4 Patented Nov. 10, 1953 VARIABLE AREA DISCHARGE N OZZLE FOR JET ENGINES Antoni J. Smialowski, Ottawa, Ontario, Canada., assigner to National Research Council, Ottawa, Ontario, Canada, a body corporate of Canada Application June 3, 1952, Serial No. 291,518

31 Claims. l

This invention relates to a variable area discharge nozzle for a jet engine.

Increased efliciency and better performance oi a jet engine can be achieved if means are provided for varying the size of the jet orifice. The efciency of the engine is improved if the outlet area is varied to give a reduced area at low speeds and a large area at high speeds as the optimum outlet area is related to the quantity of fuel supplied to the prime mover. There are additional advantages 'Where the jet engine is used as the motive power for an aircraft. When an after-burner is used to give extra thrust for take off and climbing the outlet area should be larger than under normal cruising conditions.

The outlet area should in general be large for starting and during low Velocity flight with low velocity requirements. A large nozzle exit area reduces the turbine back pressure and leads to easier starting at lower R. P. M. and a lower turbine inlet temperature than would normally be required. This is important in large engines where the mechanical power requirement for starting presents a serious problem. The use of a large outlet area enables the engine to accelerate faster to its rated speed. Furthermore, when a jet engine is operating in a low temperature atmosphere, such as that encountered at high altitudes, decreasing the outlet area will increase the back pressure in the engine; thus tending to increase the temperature of operation of the engine to a temperature at which the efciency is improved. Varying the size of the jet orifice achieves another improvement in performance in that this affords a thrust Controlling means which is more flexible and effective more quickly than modifying the fuel intake of the prime mover. The rotating parts of the engine do not have to undergo a large speed change where a variable discharge nozzle is used. The thrust can be changed as quickly as the tail adjustment can be moved.

A number of arrangements have previously been proposed for varying the outlet area of the discharge nozzle. Many of these involve the insertion of valves such as bullets or the closing of flaps partially to block the jet discharge. Such constructions are not suiliciently durable for operation oVer an extended period of time in view of the extremely high temperatures to which any structure in the direct path of the jet will be subject, or the mechanism for manipulating them is excessively bulky, heavy and complex, thus creating problems in streamlining. yIn U. S. Patent No. 2,546,293 which issued March 27,

1951, to Henry A. Berliner, it was proposed to deform a tail pipe by means of opposed cams bearing on the surface of the tail pipe. The construction proposed by Berliner is subject to a number of disadvantages which make it of doubtful practicability. The only means for restoring the deformed tail pipe to its former shape is the natural resiliency of the material of the tail pipe. In view of the high temperatures involved, the material is likely to assume a permanent set after a relatively short period of operation. The extent to which the area of the tail pipe can be reduced is limited by the longitudinal strains set up in the tail pipe when the material is deformed and by the inordinately large size of the cams which would be required to achieve a substantial deformation.

The object of the present invention is to provide a variable area discharge nozzle of the type in which the tail pipe is deformed in which positively acting means are provided both for decreasing and restoring the outlet area so as to diminish the possibility of the occurrence of a permanent set.

A further object of the present invention is to provide a discharge nozzle which can be continuously varied over a wide range of areas.

Another object is to achieve deformation of the tail pipe conveniently and readily by means of a construction which does not include a large ramount of outwardly extending structure such as would tend materially to increase the resistance to air flow where this invention is used in conjunction with an aircraft.

In accordance with this invention regarded in its broadest aspect a tubular tail pipe of deformably metal is adapted to be secured to the preceding tubular duct as a continuation thereof. An outwardly extending ilange is disposed around the edge of the tail pipe, which is adjacent yto the tubular duct. Means are provided for simultaneously twisting opposite portions of the flange in one direction about substantially parallel axes within the tail pipe and tubular ducts to change the outlet area of the tail pipe. This has the' effect of deforming the tail pipe to change the outlet area while maintaining a constant periphery. Means are also provided for simultaneously twisting the opposite portions of the flange in a direction opposite to the previously mentioned direction about the same axes to restore the outlet area of the tail pipe to its former area. Thus there is a positive action, not only when the tail pipe is being deformed, but also when it is being restored to its former shape. This prevents the permanent set which would otherwise result from the use of imperfectly resilient material, and even enables materials which are not appreciably resilient to be used for the tail pipe. A connecting means is disposed between the duct and the tail pipe, capable of conforming to changes in the distances between portions of the inner edge of the tail pipe and opposing portions of the edge of the tubular duct. This prevents the setting up of the severe strain which would otherwise be present when the tail pipe was deformed. Other inventive features will hereinafter be apparent from the detailed description.

In the drawings which illustrate the preferred embodiment of this invention:

Figure 1 shows an elevation view partly in section,

Figure 2 is a sectional view on the line 2--2 in Figure 1,

Figure 3 is a perspective elevation view showing the tail pipe subject to deformation,

Figure 4 is a detailed sectional view of the stitlening members,

Figure 5 is a diagrammatic elevation view of another embodiment of this invention,

Figure 6 is a diagrammatic plan view of the embodiment shown in Figure 5,

Figure 7 is a diagrammatic elevation view similar to Figure 5, but showing the tail pipe in distorted position,

Figure 8 is a diagrammatic plan view of Figure 7,

Figure 9 is a perspective elevation view showing another embodiment of this invention; Figure 9 is partly broken away to show this embodiment in section,

Figure 10 is an elevation view of another embodiment,

Figure 11 is a plan view of the embodiment shown in Figure 10.

In the drawings in which like numerals indicate like parts there is illustrated a. tubular duct I0 through which the jet gases are expelled. Duct III has longitudinal ribs II to support the biasing means subsequently to be described in detail, and terminates in an annular outwardly turned flange I2. A tubular tail pipe I3 of resilient materia] is joined to duct I0 as a continuation thereof by a connecting piece capable u Referring now to tail pipe I3 in greater detail, tail pipe I3 is preferably slightly inwardly converging toward its outer end I5 and is normally circular in shape. At its inner edge there is an outwardly turned annular flange IB. Bellows Il extend between and are joined to flanges I2 and I6. The end of duct I0 preferably cornprises a separate portion Ia rigidly joined to the main portion I0 at flange Iza. End portion Na extends past flange I2 within the bellows so as to afford an inner lining which prevents the jet gases from impinging directly upon bellows I4. One end of portion Illa is anchored to flange I2a. The other end slidably engages the interior edge of tail pipe I3 so that these can move relative to each other when the tail pipe is deformed.

Spacing members I1 are equally and symmetrically spaced about the periphery of tail pipe I3. These spacing members comprise four bolts rigidly connected to flanges I2 and I6. The bolts or spacing members II are of resilient metal, and are narrowed along one dimension as shown so that the bolts will be bendable in a direction tangential to the periphery of the tail pipe. To further facilitate bending of bolts I1 the ends of the bolts which are axed to flange I6 are held between supports I8, which extend from flange I6 in the approximate direction of the respective bolts I1.

Four elongated stiiening members I9a and I9b are equally and symmetrically spaced about the periphery of the tail pipe, and are longitudinally disposed with respect to the tail pipe. 'I'hese stiilening members are positioned so that the adjacent bolts I'I will be equally spaced from the stiffening members. Stiflening members I9a and I9b are connected to the surface of tail pipe I3 by a series of connecting pieces 20 at the inner ends of which are inwardly directed gripping members 2 I, shown in detail in Figure 4. Gripping members 2| embrace the outwardly diverging arms 22 of short rails 23 so as to permit relative movement of the stiiening members with respect to the tail pipe in a direction longitudinally along the surface of the tail pipe to compensate for temperature differentials. It will be noted in the drawings that stiffening members I9a and I9b extend substantially the full length of the tail pipe. Levers 24a and 2lb are joined to each of stiilening members I9a and lib respectively. These levers are disposed so as to diverge slightly upwardly from being in alignment with the corresponding stiffeners I9a and I9b. At the junction between each stiil'ener Isa and I9b and its corresponding lever 24a and 2lb flange I6 is gripped as shown at 25. A double acting hydraulic cylinder 26a is connected between the end 2'I of lever 24a and one of ribs II and similarly a hydraulic cylinder 2Gb acts on each of levers 24h. A stop limit 28 is Joined between rib II and an intermediate point on lever 24.

When it is desired to deform the outlet of tail pipe I3 hydraulic fluid is supplied to diametrically opposite hydraulic cylinders 26a in such a manner as to force levers 24a outwardly. As levers 24a are clamped to flange I6 at the junction between levers 24a and stifleners I9a the outward movement of levers 24a will have the eiect of twisting the opposite portions of nange I6, which are gripped by levers 2Ia, in the direction of outlet I5. The portions of flange I6 which are gripped by levers 24a will be twisted about axes passing through, respectively, the spacing members which are equidistant from levers 24a. Simultaneously, hydraulic iluid is supplied to the other two diametrically opposed hydraulic cylinders 2Gb to cause levers 2lb to be rotated inwardly, and the diametrically opposite portions of flange I6 which are gripped by levers 24h will be twisted in a direction opposite to that previously described in connection with levers 24a. The portions of flange I6 which are twisted by levers 24h will be twisted about axes passing through, respectively, spacing members equidistant from each of levers 2lb.

It will be appreciated that the effect of twisting portions of flange IB which are angularly spaced with respect to the central axis of the tail pipe at an angle of in opposite directions will be to exert on the portion of tail pipe I3 which is in longitudinal alignment with levers 2lb a. force which tends to rotate these portions of tail pipe I3 outwardly, and at the same time move these portions of the tail pipe in the direction of duct I. Similarly, the twisting action which has been applied to the portion oi flange I6 which is gripped by levers 24a will tend to rotate the portions of tail pipe I3 which are in longitudinal alignment with levers 24a inwardly and in a direction away from duct I0. Longitudinally extending portions of tail pipe I3 intermediate between levers 2da and 2d?) will be moved inwardly in a direction away from duct Iii or outwardly and in a direction toward duct Ii) to a degree which depends upon the distance of these portions from levers 24a and 24h. There will be a uniform gradation because flange I6 may be expected to twist in a uniform manner between the portions gripped by levers 24a and 24h, Bolts I? must be made bendable to accommodate the twisting of ange I5, as these bolts will be bent in a direction tangential to the periphery of flange i6 and in the general direction of levers 24h.

It will be noted that stiffeners ISD form exm tensions of levers 24h, and similarly stiifeners lea form extensions of levers Zta. Hence, when levers 2Gb are Jforced outwardly stifleners ld will be biased inwardly about axes passing through, respectively, the spacing members which are equidistant from stiifeners Ida. .Simultaneously, the inward rotation of levers 24h will cause stiifeners leb to be biased outwardly about axes passing through, respectively, the spacing members equidistant from each of stiffening msnm bers I9b.

It will be appreciated that the effect of biasing stiifeners ISb outwardly and stiffeners i3d inwardly will be to make the stiifeners follow the deformation of tail pipe I3 which has been caused by the twisting of flange I6. The biasing of the stiifeners will materially assist in the distortion of tail pipe I3, particularly where the material which comprises tail pipe I3 is somewhat resistant to distortion. The biasing of stiffeners ISa and I9?) could be used in the absence of twisting of flange I6 to achieve a Vcertain amount of distortion. However, the best results will be achieved by using both twisting of flange IB and biasing of the stiifeners. -Stiffeners ISa and I9b present the advantage of maintaining the tail pipe in the shape into `which it has been deformed by the twisting of flange i5. The stiffeners will absorb at least part of any unusual strain on the discharge nozzle, and these stiffeners have the advantage that 'they will tend to reduce any tendency of the tail pipe to flutter.

When it is desired to increase the outlet area of the discharge nozzle so as to restore it to its former area, the portions of flange I6 which are gripped by levers 24a are twisted in the direction of duct it, and at the same time'the portions of ange it gripped by levers Mb are twisted in the direction of outlet I5. Thus positive forces will be exerted upon tail pipe I3 until outlet i5 is again in the form of a circle. In the embodiment illustrated the outward rotation of levers Eib and the inward rotation of levers 24a partially resilient, it is not necessary that this material have a complete or indeed a substantial amount of resilience. It is sufficient that the material which forms the tail pipe be deformable without any pronounced tendency to crinkle.

In order to attain symmetry, spacing members II should be disposed equidistant between adjacent levers 2da and 24h. However, as a modiflcation spacing members I'I may be displaced somewhat from this position, provided that they are arranged so that adjacent spacing members I7 will be equidistant from the lever which lies between them. This is necessary to prevent severe strain from being exerted upon the tail pipe.

Preferably the sti'ening members I9 are exterior to tail pipe I3. It would be feasible to locate the stiffening members within the tail pipe, making other appropriate modifications to the structure which has been described. However, this is not the preferred embodiment, as the stifleners would then be subject to the direct action of the hot gases of the jet. In the preferred embodiments four stiff:eners have been used. As a modication, two diametrically opposite stiii'eners could be used. This would provide the same effect as four stifleners, except there would not be available the rigidifying influence of the other pair of stiffeners.

In the embodiments illustrated in Figures 5 to 8 inclusive tail pipe 3I is shaped to present a substantially elliptically shaped outlet 32, when ilange 33 is planar, as illustrated in Figures 5 and 6. When portions 34 of flange 33,' which are in alignment with the longitudinal axis of elliptically shaped outlet 32, are twisted in the direction of the outlet; and simultaneously portions 35, which are angularly removed with respect to the longitudinal axis of the tail pipe by from portions 34, are twisted in a direction away from outlet 32. The tail pipe will be deformed so that outlet 32 will be circular as illustrated in Figures 7 and 8. This construction has the advantage that a wide variation in outlet area can be obtained with 1less twisting of flange 33 than is necessary in the case of the embodiments illustrated in Figures 1 to 4 inclusive. It will be appreciated that the embodiment illustrated in Figures 1 to 4 inclusive is suitable for distortion in two directions, whereas the embodiment in Figures 5 to 8 inclusive is primarily designed for deformation in only one direction. This is not normally a disadvantage. The embodiment in Figures 5 to 8 inclusive includes a connecting piece 36 capable of conforming to changes in the shape of flange 33 adjoining tail pipe 3! to tubular duct 3l and spacing members 36 peripherally disposed midway between points 34 and 35.

Another embodiment of this invention is illustrated diagrammatically in Figure 9. In this embodiment a tubular tail pipe 58 is deformed by twisting an outwardly extending flange 39 in the manner described with reference to the embodiments shown in Figures l to 8 inclusive. Encircling tail pipe 33 are bracing members 40 and di. These bracing members are in the shape of a truncated cone. .Erasing member 4l) has a dihedral angle which is less than the dihedral angle of tail pipe iid with respect to a plane passing through the base of the tail pipe, and bracing member et is rigidly secured to flange 39 at a point 152 which is outwardly spaced from the junction d3 between tail pipe 33 and flange 39. The outer edge All of bracing member 4i) slidably engages the outer surface of tail pipe 38. Edge 44 is preferably spaced from the edge 45 of tail pipe 38. Similarly, bracing member 4l has a dihedral angle less than that of bracing member 44, and is secured to flange 39 at a position 48 which is outwardly spaced from junction 42. 'Ihe outer edge 41 of bracing member 4i is spaced from the edge 44 of bracing member 40, and slidably engages the outer surface of bracing member 44. When opposite quadrants of flange 39 are twisted in one direction and the remaining quadrants of flange 39 are twisted in the other direction, this will cause tail pipe 38 to be deformed to change the circular shape of edge 45 to an elliptical shape. Bracing members 40 and 4I will be deformed by the twisting of flange Il at the same time as and in the same manner as tail pipe 38 will be deformed. Their outer edges 44 and 41 will be constrained into elliptical shape. The deformed edge of member 40 will bear on the outer surface of tail pipe 3B and the deformed edge of member 4l will bear on the outer surface of member 40. These bracing members will thus assist in deforming tail pipe 3B and in maintaining the shape of tail pipe 38 when it has been deformed. If desired, provision may be made for the flow of cooling air in the spaces between tail pipe 3B, bracing member 40 and bracing member 4|, by providing pipes to convey cooling air communicating with these spaces and by providing outlet passages from these spaces to discharge air after it has performed its cooling function.

For supersonic application a Venturi shaped outlet will be desirable, and it will be appreciated that the embodiments of this invention which have been described can readily be modied by providing a flared structure at the outlet of the tail pipe. Deformation of the tail pipe will then have the effect of changing the area of the waist of the discharge nozzle. Such a construction is contemplated as falling within the ambit of the present invention. A suitable construction for supersonic applications is illustrated in Figures l0 and 11. In Figures 10 and l1 there is illustrated a tail pipe 48 which is deformed by the outward movement of levers 49 twisting flange 50 about spacing studs 5I. An auxiliary section of tail pipe 52 is secured to the outlet end of tail pipe 4l, with the edge 53 of the auxiliary section overlapping the edge 54 of tail pipe 48. It will be noted that tail pipe 48 converges towards its outlet and auxiliary section 52 diverges towards its outlet so that together the tail pipe and auxiliary section form a Venturi shaped discharge nozzle. Spacing studs 5| are made hollow and tie rods 55 tensioned by springs 56 pass through studs 5I. extend longitudinally to tail pipe 48 and are secured at 56 to the outer edge of section 52. Links 51 are disposed in longitudinal alignment with levers 49. Preferably these links are in the form of a V with its

legs

58 and 59 pivotally secured to the auxiliary section and to the tail pipe respectively and with its apex pivoted and outwardly directed.

The waist or the throat between tail pipe 43` and auxiliary section 52 is normally in the shape of an ellipse as shown in Figure 1l. When flange 50 is deformed the outlet of tail pipe 48 is forced into the shape of a circle. Because of the overlapping relationship between tail pipe 4B and auxiliary section 52 the auxiliary section is also at the same time deformed. The shape of the discharge nozzle after deformation is shown by dotted lines in Figures 10 and 11.

It will be apparent that a discharge nozzle in ill accordance with this invention is well adapted to achieve the objects set forth, and has other atidvantages apparent from the detailed descrip- I claim:

1. A discharge nozzle for a jet engine adapted to be secured to a tubular duct as a continuation thereof, comprising a tubular tail pipe of deformable metal having an outwardly extending flange around the edge of the tail pipe which is adjacent to the tubular duct, means for simultaneously twisting opposite portions of the flange in one direction about substantially parallel axes within the tail pipe and tubular duct to change the outlet area of the tail pipe, means for simultaneously twisting said opposite portions of the flange in a direction opposite to said one direction about said axes to restore the outlet area of the tail pipe to its former area, and connecting means between the duct and the tail pipe capable of conforming to changes in the distances between portions of the inner edges of the tail pipe and opposing portions of the edge of the tubular duct.

2. A discharge nozzle as in claim l in which each of the axes is equidistant from the central longitudinal axis of the tail pipe and from the portion of the flange which is located on a line passing perpendicularly through the centre of said axis about which the flange is twisted.

3. A discharge nozzle for a jet engine adapted to be secured to a tubular duct as a continuation thereof, comprising a tubular tail pipe of deformable metal, an outwardly extending flange around the edge of the tail pipe which is adjacent to the tubular duct, four spacing members connecting said ilange to the tubular duct, the spacing between adjacent spacing members being equal to the spacing between adjacent spacing members at the opposite side of the flange,

means for simultaneously twisting opposite portions of the ange in one direction about axes passing through the spacing members which are respectively adjacent to each of said portions, said portions of the flange being substantially midway between their adjacent spacing members, the twisting of the flange in said one direction having the effect of changing the outlet area of the tail pipe, means for simultaneously twisting portions of the flange which are angularly removed with respect to the longitudinal axis of the tail pipe by an angle of from the firstmentioned portions in a direction opposite to said one direction about axes passing through the spacing members adjacent to these portions twisted in said direction opposite to said one direction to assist in changing the outlet area of the tail pipe, portions of the flange being twisted in said one direction and in the opposite direction simultaneously, and means for twisting the aforesaid portions of the flange to their original positions to restore the outlet area of the tail pipe to its former area, and connecting means between the duct and the tail pipe capable of conforming to changes in the differences between portions of the inner edge of the tail pipe and opposing portions of the edge of the tubular duct.

4. A discharge nozzle as in claim 3 in which stiiiening members in longitudinal alignment with said portions of the ange and secured to the flange and to the surface of the tail pipe are biased inwardly where the flange is twisted in the direction of the outlet of the tail pipe, and biased outwardly where the ange is twisted in a direction away from the outlet of the tail pipe.

5. A discharge nozzle as in claim 3 in which the spacing members are equally spaced around the periphery of the flange.

6. A discharge nozzle as in claim 5 in which there is an outwardly extending flange round the edge of the tubular duct and in which the spacing members comprise bolts rigidly connecting the flanges, the axes of the bolts being substantially parallel to the axis of the tail pipe.

7. A discharge nozzle as in claim 6 in which the bolts are capable of resilient bending in a direction tangential to the periphery of the tail pipe.

8. A discharge nozzle as in claim 3 in which the connecting means comprises a bellows structure compressible and extensible in a direction parallel to the axis of the tail pipe.

9. A discharge nozzle as in claim 3 in which the means for twisting portions of the flange in one direction and in an opposite direction comprises a lever extending outwardly from each of said portions of the flange in a direction away from the outlet of the tail pipe and a double acting hydraulic cylinder mounted on the tubular duct to actuate the outer end of said lever.

10. A discharge nozzle for a jet engine adapted to be secured to a tubular duct as a continuation thereof, comprising a tubular tail pipe of deformable metal, said tail pipe having an outlet which is substantially elliptical in shape, a planar outo wardly extending flange around the edge of the tail pipe which is adjacent to the tubular duct, means for simultaneously twisting portions of the flange which are in alignment with the longitudinal axis of the ellipse in a direction towards the outlet, and means for simultaneously twisting portions of the ilange which are angularly removed with respect to the longitudinal axis of the tail pipe by an angle of 90 from the first mentioned portions in a direction away from the outlet, all of said portions being twisted simultaneously whereby the outlet area of the tail pipe will be increased, and means for twisting said portions of the flange in directions opposite to the previously mentioned directions to reduce the outlet area of the tail pipe.

ll. A discharge nozzle as in claim 10 in which four spacing members rigidly connecting said flange and tubular duct are disposed around the iiange so that each of said portions will have spacing members equally spa-ced from it.

l2. A discharge nozzle as in kclaim ll in which the spacing members are equally spaced with respect to each other.

13. A discharge nozzle as in claim 1G having connecting means between the duct and the tail pipe'capabie of conforming to changes in the distances between portions oi the inner edge oi the tail pipe and the opposing portions of the edge of the tubular duct.

14. A discharge nozzle for a jet engine adapted to be secured to a tubular duct as a continuation thereof, comprising a tubular tail pipe of deformable metal, an outwardly extending lange around the edge of the tail pipe adjacent to the tubular duct, a bracing member in the shape of a truncated cone coaxial with said tail pipe, the base of said bracing member being secured to said flange at a position spaced upon the base of the tail pipe and the outer end of the bracing member slidably engaging the outer surface of the tail pipe at a position spaced from the outlet of the tail pipe, means for simultaneously twisting opposite portions of the flange in one direction about substantially parallel axes within the tail pipe and tubular ducts to change the outlet area of the tail pipe, and means for simultaneously twisting said opposite portions of the flange in a direction opposite to said one direction about said axes to restore the outlet area oi the tail pipe to its former area.

l5. A discharge nozzle as in claim 14 in which portions of the ilange removed with respect to the longitudinal axis of the tail pipe from said opposite portions are simultaneously twisted in a direction opposite to the direction in which said opposite portions are being twisted at the same time that said opposite portions are being twisted.

16. A discharge nozzle as in claim 15 in which a second bracing member similar to the first mentioned bracing member is disposed with its base secured to the flange at a position outwardly spaced from the base of the rst bracing member and with its outer edge slidably engaging the outer surface of the first mentioned bracing member at a position spaced from the outer edge of the first mentioned bracing member. i

17. A discharge nozzle for a jet engine adapted to be secured to a tubular duct as a continuation thereof, comprising a tubular tail pipe of resilient material, four elongated stiffening members connected to a surface of the tail pipe and longitudnally disposed with respect to said tail pipe, said stiiening members being equally and symmetrically spaced about the periphery of the tail pipe, means for biasing two diametrically opposed stiffening members inwardly about axes adjacent to the junction between tail pipe and said duct and simultaneously biasing the other two diametrically opposed stiffening members outwardly whereby the outlet area of the tail pipe is decreased, and means for biasing the rst mentioned two stiiening members outwardly and for simultaneously biasing the said other two stifiening members inwardly to increase the outlet area of the tail pipe to its former area.

18. A discharge nozzle for a jet engine adapted to be secured to a tubular duct as a continuation thereof, comprising a tubular tail pipe of resilient material, four elongated stiifening members connected to a surface of the tail pipe and longitudinally disposedwith respect to said tail pipe, said stiiening members being equally and symmetrically spaced about the periphery of the tail pipe, a connecting piece between the tubular duct and the tail pipe capable of conforming to changes in the distances between portions of the inner edge of the tail pipe and the opposing portions of the edge of said tubular duct, spacing members rigidly connected between the inner edge of the tail pipe and the opposing edge of the tubular duct, said spacing members consisting of two members disposed at substantially an equidistance from one of the stiiiening members and two members disposed at substantially the same equidistance from the stifening member which is diametrically opposite to said one stiffening member, means for biasing two diametrically opposed stiiiening members inwardly about axes passing through, respectively, the spacing members equidistant from each of the last mentioned stiftening members and simultaneously biasing the other two diametrically opposed stiffening meinbers outwardly about axes passing through, respectively, the spacing members equidistant from each of the last mentioned stiffening members whereby the outlet area of the tail pipe is decreased and means for biasing the first mentioned two diametrically opposed stiffening members outwardly and for simultaneously biasing said 1 1 other two diametrically opposed stiiening members inwardly to increase the outlet area of the tail pipe to its former area.

19. A discharge nozzle as in claim 18 in which the spacing members are equally spaced about the periphery of the tail pipe.

20. A discharge nozzle as in claim 19. in which there are outwardly extending flanges around the opposing edges of the tail pipe and tubular duct, and in which the spacing members comprise bolts rigidly connecting said flanges, the axes ci the bolts being substantially parallel to the axis of the tail pipe.

21. A discharge nozzle as in claim 20 in which the stiieners are rigidly clamped to the iiange around the edge of the tail pipe whereby the twisting of the last mentioned ange assists in changing the outlet area of the tail pipe.

22. A discharge nozzle as in claim 21 in which the bolts are capable of resilient bending in a direction tangential to the periphery of the tail pipe.

23. A discharge nozzle as in claim 18 in which the connecting piece comprises a bellows structure compressible and extensible in a direction parallel to the axis of the tail pipe.

24. A discharge nozzle as in claim 18 in which the means for biasing each of the stiening members inwardly and outwardly comprises a lever outwardly extending from the end of each of the sti'ening members which is adjacent to the junction between tail pipe and tubular duct and a double acting hydraulic cylinder mounted on the tubular duct and actuating the outer end of said lever.

25. A discharge nozzle as in claim 18 in which the stiffening members extend substantially the full length of the tail pipe.

26. A discharge nozzle as in claim 18 in which the stiffening members are relatively movable with respect to the tail pipe in a direction longitudinally along the surface of the tail pipe to compensate for heat expansion differentials.

27. A discharge nozzle as in claim 18 in which the stiiening members are disposed exteriorly of the tail pipe.

28. A discharge nozzle for a jet engine adapted to be secured to a tubular duct as a continuation thereof, comprising a tubular tail pipe of deformable metal having an outwardly extending flange around the edge of the tail pipe which is adjacent to the tubular duct, means for simultaneously twisting opposite portions of the flange in one direction about substantially parallel axes within the tail pipe and tubular duct to change the outlet area of the tail pipe. means for simultaneously twisting said opposite portions of the ange in a direction opposite to said one direction about said axes to restore the outlet area of the tail pipe to its former area, connecting means between the duct and the tail pipe capable of conforming to changes in the distances between portions of the inner edges oi' the tail pipe and opposing portions of the edge of the tubular duct, an auxiliary section of tail pipe of deformable metal secured to the outlet end of said tail pipe and deformable with said tail pipe, said tail pipe having walls converging towards its outlet and said auxiliary section of tail pipe diverging towards its outlet so that said tail pipe and said auxiliary section of tail pipe together form a Venturi shaped discharge nozzle with a waist of variable area.

29. A discharge nomle as in claim 28 in which the adjacent edges of the tail pipe and auxiliary section of tail pipe are in overlapping relationship and which tensioned means retains said auxiliary section of tail pipe in position at the end of said tail pipe.

30. A discharge nozzle as in claim 28, in which one pair of diametrically oppositely disposed levers are actuated to twist the flange, tensioned tie rods disposed longitudinally of the tail pipe and equally spaced from said levers retain said auxiliary section of tail pipe in position at the end of said tail pipe with the adjacent edges of the tail pipe and auxiliary section ot the tail pipe overlapping and in which there are links in longitudinal alignment with each of the levers joining the tail pipe and the auxiliary section of tail pipe.

31. A discharge nozzle as in claim 30 in which the links are in the form of a V with its legs pivotally secured to the tail pipe and auxiliary tail pipe section respectively and with its apex pivoted and outwardly directed.

ANTONI J. SMIALOWSKI.

Name Date Berliner Sept. 2, 1952 Number