US3025666A - Propelling nozzles for jet propulsion gas turbine engines - Google Patents

Description

J. M. s KEEN March 20, 1962 3,025,666

PROPELLING NOZZLES FOR JET PROPULSION GAS TURBINE ENGINES Filed May 6, 1960 z/OH/V M/CHAEZ S70E55 WEE /v I Attorney 3,25,5b6 Patented Mar. 20, 1962 3,025,666 PROPELLENG N OZZLES FOR JET PROPULSION GAS TURBINE ENGINES John Michael Storer Keen, Derby, England, assignor to Rolls-Royce Limited, Derby, England, a company of Great Britain Filed May 6, 1960, Ser. No. 27,336 Claims priority, application Great Britain June 12, 1959 3 Claims. (Cl. 60-35.6)

This invention relates to propelling nozzles for jet propulsion gas-turbine engines.

According to the present invention there is provided a propelling nozzle for a jet propulsion gas turbine engine comprising a main variable area nozzle adapted to be mounted at, or to form part of, the downstream end of the jet pipe of the said engine, an annular air duct surrounding said main nozzle or said jet pipe and provided with a secondary variable area nozzle such that air discharged through the secondary nozzle forms an annular stream closely surrounding the jet gases discharged through the main nozzle, and nozzle adjustment means for varying the effective areas of the main and secondary nozzles, said nozzle adjustment means being such as to permit the effective area of the secondary nozzle to be adjusted independently of that of the main nozzle when the latter area has a predetermined value.

Thus each of said nozzles may be provided with a series of circumferentially arranged flaps which may be moved so that the effective areas of the nozzles may be varied in accordance with different engine operating conditions. The flaps of the secondary nozzle preferably extend downstream of those of the main nozzle.

Preferably the main and secondary nozzles are provided with a common adjustment device operation of which effects simultaneous adjustment of both said nozzles at all times except when the effective area of the main nozzle is at the said predetermined Value.

Thus the adjustment device may comprise a cam member engaging a movable part or parts of the main nozzle, movement of said cam member effecting adjustment of said part or par-ts, whereby to adjust the effective area of the main nozzle, at all times except when a predetermined portion or portions of said cam member engages said movable part or parts.

Preferably the cam member is movable axially of the main nozzle, the said portion or portions of the cam member extending parallel to the axis of the main nozzle.

The invention also comprises a gas turbine jet propulsion engine comprising a main variable area nozzle mounted at the downstream end of the jet pipe of the engine, an annular passage surrounding the jet pipe and having at its downstream end a secondary variable area nozzle, said annular passages being arranged for the flow therethrough of air (e.g. ram air or compressed air from a compressor of the engine) which is discharged through the secondary nozzle as an annular stream closely sur rounding the jet gases discharged through the main nozzle, and nozzle adjustment means for varying the effective areas of the main and secondary nozzles, said nozzle adjustment means being such as to permit the effective area of the secondary nozzle to be adjusted independently of that of the main nozzle When the latter area has a predetermined value.

In order that the invention can be clearly understood and readily carried into effect one construction of a propelling nozzle in accordance with the invention will now be particularly described, by way of example only, with reference to the accompanying drawings, in which.

FIGURE 1 is a view showing a jet propulsion gas turbine engine having a propelling nozzle in accordance with the present invention, and

FIGURE 2 is an enlarged sectional view of a portion of the engine of FIGURE 1.

Referring to the drawings, 10 indicates a jet propulsion gas turbine engine having a compressor 12, combustion equipment and turbine equipment (not shown) and a jet pipe 14 whose downstream end is formed to provide a main, variable area, propelling nozzle 16.

The engine and jet pipe are enclosed within a nacelle 38 which extends from adjacent the compressor inlet to adjacent the nozzle outlet and is radially spaced therefrom whereby there is defined an annular by-pass passage 18 which surrounds the engine and the jet pipe. The bypass passage 18 is supplied, by means not shown, with air compressed by the compressor 12.

A secondary variable area nozzle 20 is provided at the downstream end of the passage 18 The arrangement i such that the air flowing through the passage 18 is discharged through the nozzle 20 as an annular stream closely surrounding the jet gases discharged through the nozzle 16. Reheat combustion equipment (not shown) is provided in the nozzle 16, the said equipment being adapted to injet fuel into, and to effect combustion of said fuel in, the exhaust gases passing through the nozzle 16, whereby to increase engine performance over a limited period.

The outlet end of the nozzle 16 is defined by a series of flap members 22 which are arranged in an annular assembly. The flap members 22 are supported on pivot members 24 which are arranged transversely of the longitudinal axis of the engine. The flap member 22 can thus be swung towards and away from the longitudinal axis 0f the engine so as to vary the effective outlet area of the nozzle 16.

Each flap member 22 is provided with a pair of upstanding, spaced apart flanges 26 on that face thereof which is remote from the gas flow passage through the nozzle 16, and carried between the flanges 26 is a roller 28 which is freely rotatable on a shaft, not shown, supported by the flanges 26.

Each of the rollers 28 engages with one face of a respective cam plate 30, each of the cam plates 30 being disposed in an inclined position and being carried on an axially movable externally screw threaded spindle 32. The latter form part of an actuating mechanism for turning the flap members 22 about their pivots 24 either towards or away from the longitudinal axis of the engine.

In order to ensure that all of the cam plates 30 move at the same time and the same distance when they are actuated they are all supported within two axially spaced apart frusto-conical rings 31 which are connected together.

Thus relative movements of the cam plates is prevented.

A strut 34 is provided on each cam plate 30 on that face thereof which is remote from the face engaged by the roller 28. The strut 34 carries at its downstream end a roller 35 which is movable in a track 36. The track 36 is mounted on a further flap member 37 which is pivotally supported on the nacelle 38 enclosing the en gine. The flap members 37 are disposed in an annular array, a flap member 37 being provided for each of the flap members 22.

Whilst the track 36 shown in the drawings is straight it can if desired be curved so that when the flaps 22 and 37 are actuated their relative positions are varied.

Each flap member 37 is spaced downstream of the respective flap member 22 whereby a duct 40 is defined therebetween, the duct 40 communicating with the bypass passage 18.

The said actuating mechanism for causing axial movements of each spindle 32 comprises a screw jack 42 having an axially extending screw threaded bore in which the spindle 32 is disposed.

It will thus be seen that when the screw jack 42 is rotated, the spindle 32, which is held against rotation by its connection to the cam plate 30, will be caused to move axially. The cam plate will therefore also move axially whereby the associated flap 22 will (according to the direction of movement of the cam plate 30) either be moved inwardly towards the axis of the nozzle 16 or will be permitted to move away from this axis under the action of the gas pressure.

In order that all of the flap members 22 shall move in unison and in the same direction, all of the screw jacks 42 are rotated by a common mechanism, the said mechanism comprising a fully annular member 44, only part of which is shown in the drawings, the member 44 being provided with gear teeth 45 on its inner periphery.

The gear teeth 45 engage with corresponding gear teeth 46 formed on the exterior of each jack 4-2, and thus when the annular member 44 is rotated the jacks 42 are all rotated in a common direction, at the same speed whereby the movement of all the flaps 22 is equal.

The annular member 44 is supported in a ball race 46 as shown in FIGURE 2 of the drawings.

With the two sets of flaps 2'2 and 37 in the position shown in FIGURE 2 of the drawings, the outlet area of the nozzle 16 is reduced to its permissible minimum to obtain maximum thrust for take off and a convergent nozzle is defined.

As can be seen from FIGURE 2 of the drawings, each cam plate 30 is provided with a portion, indicated at 48, which is parallel with the axis of the nozzle 16 whereby it is possible to adjust the position of the flaps 37 without moving the iiaps 22.

Such an arrangement enables the area of the duct defined by the flaps 37 to be adjusted finely to reduce thrust losses.

When the nozzle above described is in use, air from the by-pass passage 18 flows through the duct 49 between the two sets of flaps to surround the exhaust gasses and prevent premature expansion thereof, whereby thrust losses are reduced or obviated.

It will be appreciated that instead of having a flat portion at one end only of each cam plate 30 such a portion may be provided at both ends. Thus when the said reheat combustion equipment is in use and the flaps 22, 37 are moved to define a convergent-divergent nozzle, fine adjustment may be made of the position of the flaps 37 without moving the flaps 22.

If desired a flat portion may also be formed on each cam plate 30 at a point substantially midway of its length whereby fine adjustment of the position of the flaps 37 may be made when the flaps 22 and 37 are positioned for normal cruise conditions.

I claim:

1. A gas turbine jet propulsion engine having a jet pipe for discharging jet gases and an annular air duct surrounding the jet pipe for discharging an annular stream of air closely'surrounding the discharge jet gases, the improvement comprising: a main variable area nozzle mounted at the downstream end of the jet pipe, said main nozzle including a series of circumferentially arranged flaps pivotally mounted on the jet pipe for varying the effective area of the same; a secondary variable area nozzle mounted at the downstream end of the annular air duct, said secondary nozzle including a series of circumferentially arranged flaps pivotally connected to the downstream end of said air duct for varying the effective area of the same; means operatively connected respectively to and intermediate of the flaps of said main and secondary nozzles and movable axially with respect thereto through a predetermined range, said last-mentioned means including a first means to vary the effective area of said secondary nozzle through the entire predetermined range and a cam means to vary the main nozzle simultaneously with the variance of the secondary nozzle through a portion of the predetermined range while maintaining the effective area of the main nozzle constant during at least another portion of the predetermined range; and an actuator member operatively connected to said first means and said cam means for axially moving the same to actuate the respective flaps of said main and secondary nozzles.

2. A propelling nozzle for a gas turbine jet propulsion engine comprising: a main nozzle, an annular air duct surrounding said main nozzle, a secondary nozzle carried by said air duct for discharging air through said secondary nozzle in an annular stream closely surrounding jet gases discharged through the main nozzle, said main nozzle and said secondary nozzle each comprising a series of circumferentially arranged pivotally mounted flaps which are movable to vary effective areas of the respective nozzles, a common adjustment device for varying the effective areas of said main nozzle and said secondary nozzle, said device comprising a member movable parallel to the axis of the main nozzle, said member having a plurality of camming surfaces and a plurality of arms, the flaps of said main nozzle having cam followers for engaging said oamming surfaces and the flaps of said secondary nozzle having guide tracks slidably engaging said arms, said camming surfaces each having at least one portion extending parallel to the axis of the main nozzle and enabling the effective area of said main nozzle to remain constant while the effective area of said secondary nozzle is varied during a predetermined portion of the range of axial movement of said member.

3. A propelling nozzle, as claimed in claim 1, includa plurality of circumferentially spaced screw jacks operatively connected to said member, and a common opera ing annular gear ring for engaging and operating said screw jack simultaneously to impart movement to said member parallel to the axis of the main nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 2,846,844 ORourke Aug. 12, 1958 2,931,169 Glenn Apr. 5, 1960 2,932,163 Hyde Apr. 12, 1960 OTHER REFERENCES Pearson: Exhaust Nozzles for Supersonic Aircraft, Journal of the Royal Areonautical Society, vol. 62; No. 573; September 1958, pp. 658-662; page 662 relied on.

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