US2770095A

US2770095A - Jet deflector having curved guide wall for aircraft

Info

Publication number: US2770095A
Application number: US357117A
Authority: US
Inventors: Ashwood Peter Frederick; Fletcher Philip John
Original assignee: Power Jets Research and Development Ltd
Current assignee: Power Jets Research and Development Ltd
Priority date: 1952-05-30
Filing date: 1953-05-25
Publication date: 1956-11-13
Anticipated expiration: 1973-11-13
Also published as: NL94757C; DE1043824B; BE520316A; CH317635A; GB724011A

Description

1956 P. F. ASH-WOOD ET AL 2,770,095

JET DEFLECTOR HAVING CURVED GUIDE WALL FOR AIRCRAFT Filed May 25, 1955 2 She'ets-Sheet l Inven ors 1956 P. F. ASHWOOD ET AL 2,770,095

JET DEFLECTOR HAVING CURVED GUIDE WALL FOR AIRCRAFT Filed May 25, 1955 2 Sheets-Sheet 2 iinited States Patent JET DEFLECTOR HAVING CURVED GUIDE WALL FOR AIRCRAFT Peter Frederick Ashwood, Farnham, and Philip John Fletcher, Farnborough, England, assignors to Power Jets (Research and Development) Limited, London, England, a British company Application May 25, 1953, Serial No. 357,117

Claims priority, application Great Britain May 30, 1952 9 Claims. (Cl. 60-3554) When a high speed jet-propelled aircraft is landing, it is desirable to reduce the landing speed to a minimum by defecting the jet to destroy the propulsive thrust. It may also be desirable to deflect the jet downwards towards the ground to produce an upthrust on the aircraft to compensate for loss of lift due to reduction of speed and furthermore it may be desirable to be able to deflect the jet through various angles, to give some desired combination of partial forward thrust and partial upthrust.

The present invention makes use of the fact that a stream of fluid emerging from the open end of a duct having one side wall extending beyond the orifice as'a guide and curved away from the axis of the duct can be caused to follow a path along said curved wall by setting up, at the orifice, a pressure gradient across the stream from a minimum on the guide wall to a maximum at the free surfiace of the emerging stream. Thus according to the invention a nozzle unit has such a curved guiding side wall extending beyond the nozzle orifice on that side of the nozzle towards which it is desired to deflect the jet, in combination with means operable at will to cause the issuing jet to follow, or to prevent it from following, the curvature of said guide wall into a path transverse to the direction of the nozzle. In particular the said means can set up or destroy a pressure gradient across the stream.

The guide wall or at least some part thereof may be pivoted or hinged for movement to different positions. In particular there may be an element on said curved wall but movable from a position in which it guides the jet in the undeflected direction or otherwise separates the jet from the curved wall to one in which it leaves the jet free to follow the curvature of the said curved wall. Thus the curved wall may have a part which is cylindrical about an axis extending across the nozzle and projecting into the jet to eonstrict it and thus produce the pressure gradient, and said movable element may be a tangential projection from said cylinder movable about the axis of the cylinder. Alternatively the movable element may be a retractable projection from the guide wall.

The invention is illustrated by the accompanying drawings, of which:

Fig. 1 is a view of a nozzle unit in longitudinal crosssection;

Fig. 2 is an external side elevation of the same unit;

Fig. 3 is a view looking on Fig. 1 or Fig. 2 from the rear, in the direct-ion of the arrow A of Fig. 1;

Fig. 4 is an enlarged View of a portion of the deflector;

Fig. 5 is a view corresponding to Fig. 1 of a modification.

In the construction shown in Figs. 14 the connector pipe 1, flanged for attachment to the rear of the jet pipe of a jet engine, changes progressively in internal section rearwardly from a circular to a rectangular section.

ice

tached to the rear of this pipe is the nozzle member 2 terminating in a rectangular rear jet orifice. This member 2 is bounded on four sides by

walls

2a, 2b, 2c, and 2d. The wall 2a on the unde:rsidei.e. the side to which the jet is to be deflectedis curved at 2e to semi-cylindrical shape, the axis of the cylinder lying across the width of the nozzle. The opposite wall 2b is straight and terminates substantially opposite the nearest point of the semi-cylinder. The rectangular nozzle orifice from which the jet will emerge is formed between the crest of wall 2e and the end of wall 2b, and is of a width of about eight times its depth, or even more.

Side plates

20 and 2d extend beyond the other plates, as shown, to a distance beyond the orifice at least equal to the depth of the orifice.

The arrangement so far described could cause a jet issuing from the orifice to follow the curvature of the rear quadrant of the wall part 22 as a guide, and so turn through substantially as described below. To prevent this deflection, a movable guide flap 3 is provided for separating the jet from the curved guiding wall 2e; this flap 3 is in the form of a thin plate extending from Wall 2c to wall 2d and projecting smoothly tangentially or substantially tangentially from the semi-cylindrical wall.

Fig. 4 is an enlarged detail which shows the curved wall 2e and the tapering of the guide flap 3 at 3a adjacent to the curved wall so that it merges into this wall, which it may rub against, or may pass with small clearance as the flap turns around the axis of the cylinder. For rotating the guide flap 3, the latter is provided at each end with integral radial arms 3b.

Crank arms

4 and 5 extending parallel to the arms 3b are mounted for turning about the cylinder axis in bearings 6 carried on the outside of each of the

walls

26 and 2d, the outer ends of

arms

4 and 5 having

projections

4a and 5a making rigid driving connections fitting in slots in the outer ends of the arms 3b. The crank arm 4 is a bell-crank having an arm 41) Linked to the hydraulic or other actuator 7-pivoted in usual manner on the bracket 8 on the member 1for turning the crank arm 4 and hence the guide flap 3 through about 90.

An advantage of this construction as compared with possibly making the curved wall 26 a complete hollow cylinder, with end discs, and with the radially'projecting guide flap 3 a fixed part thereof, the whole being rotatable about the cylinder axis between the

walls

20 and 2d, is the reduction of space and of leakage problems.

For normal flight the guide flap 3 is as shown in Fig. l or in full lines in Fig. 4. The jet flowing through the nozzle flows over a quarter cylindrical surface formed by part of the wall part 2e as it emerges from the jet orifice, but it follows the flat surface of the flap 3 and continues in the same general rearward direction. The jet thus produces a forward thrust. When it is desired to reduce the forward propulsive thrust and introduce an upthrust component, the guide flap 3 is turned about its axis of rotation to tilt downwardly. It is then found that a jet at subsonic speed, as it moves clear of the upper wall 2b and emerges into the atmosphere, will flow over rather more than the quarter cylindrical surface on to the downwardly inclined flat surface of the flap 3 and will then leave the curved surface tangentially, thereby being deflected downwardly to produce an upwardly inclined reaction. By turning the flap 3 through 90 to the position shown in chain lines in Fig. 4 the jet can be deflected downwardly to produce substantially only upthrust.

Consider conditions when the guide flap 3 is in the latter position. The jet flowing through the nozzle will be constricted, as it comes to the jet orifice, by the curved wall part 2e. Accordingly the velocity, at leastifit be adjacent to the wall 2e and the pressure there will be decreased. In this way a pressure gradient will be set up across the stream; the maximum eflect occurs just as the jet is emerging from the orifice, when the pressure on the top free surface of the stream is substantially atmospheric and the pressure in the layer in contact with wall la is well below atmospheric. Due to this difference of pressure between the two sides of the stream the jet will be deflected towards the low pressure side and will follow the curvature of the curved wall.

Any destruction of the pressure gradient, either by preventing the unsymmetrical constriction of the jet or by separating the jet stream from the curved wall and so allowing the pressure adjacent to that wall to become atmospheric pressure, will prevent this deflection of the jet. It seems that the guide flap 3 separates the stream from the wall part 2e and, by letting air in, brings the pressure below the jet stream up to atmospheric pressure; the jet will accordingly continue in Whatever was its instantaneous direction when it was separated from the curved wall. The extension of

walls

20 and 2d 'beyond the orifice prevents atmospheric air from entering sideways and causing premature separation.

Although each nozzle orifice should have a width equal to several times its depth, the ratio of total width to depth of the complete nozzle unit can be considerably reduced by dividing the rear of the nozzle into separate passages, one above another. Such a modification is shown in section in Fig. 5 in which the connecting pipe 11, which reduces from circular to rectangular cross section, discharges into

separate nozzles

14 and 24 each of which is bounded by similar side walls to the nozzle 4 of Figs. 1-3 and each of which is provided with the movable guide flap 3 as in those figures. The line joining the pivot axes of these movable elements 3 lies obliquely across the nozzle unit, sloping forwardly and downwardly at about 45; due to this stagger the guide flaps 3, when moved to point downwardly, will lie along spaced parallel lines so that the jet will be deflected in non-interfering layers.

When there is a single nozzle unit in an aircraft, it is so located in the aircraft that when the jet is deflected downward the line of action of the upthrust passes through or very near to the centre of gravity. When there are several units they are so disposed about the centre of gravity that the resultant upthrust passes through it or very near thereto.

When the deflector device is used during landing of the aircraft the throttle is first closed to'reduce the fuel supply to the power unit and so initiate speed reduction; the guide flap, or each guide flap, is rotated, possibly only gradually, from the rearward-guiding position to the position in which the jet is fully deflected downwards, after which the throttle is re-opened to give full jet upthrust. There may be a single operating member to close the throttle during the first part of its movement, then effect the guide vane rotation, and finally, during the last part of its movement, re-open the-throttle. If however it is desired to be able to re-open the throttle to get full jet thrust in an oblique direction the throttle and the guide vane actuator are preferably independ ently controlled.

What we claim is:

l. A jet nozzle unit for a jet propelled aircraft, for directing the jet rearwardly or deflecting the jet and comprising walls constituting a nozzle, and defining a nozzle orifice discharging to atmosphere, a guiding boundary wall extending outside the nozzle beyond the said nozzle orifice to form a smooth continuation of that one of said nozzle walls which is on that side of the nozzle towards which it is desired to deflect the jet, said guiding wall curving round into a direction transverse to the direction of the nozzle walls, and means operable" at will to cause the issuing jet to separate from said guiding wall or to follow the curvature of said guiding Wall into a path transverse to the direction of the nozzle walls.

2. A jet nozzle unit according to claim 1 comprising, in engagement with and forming part of said curved guiding wall outside the nozzle, an element for separating the jet from the said wall, and means for moving said element around the curvature of said curved wall to a position in which it leaves the jet free to follow at least part of the curvature of said curved guiding wall.

3. A jet nozzle unit for a jet propelled aircraft, for directing the jet rearwardlyjof deflecting the jet and comprising walls constituting a nozzle and defining a nozzle orifice discharging to atmosphere, a guiding boundary wall outside the nozzle extending beyond the said nozzle orifice to form a smooth continuation of that one of the said nozzle Walls" which is o'nthat side of the nozzle towards which it is desired to deflect the jet, said guiding wall curving round into a direction transverse to the direction of the nozzle walls, aridmeans operable at will to set up and destroy a pressure gradient across the jet stream where it issues through said nozzle orifice, by varying the pressure in the jet stream where it is in contact with the said wall onthe said side of the nozzle, to and from a value below the pressure on the free surface of the jet stream issuing from the said nozzle orifice.

4. A jet nozzle unit for a jet-propelled aircraft, for directing the jet rearwardly or deflecting the jet and comprising a nozzle, means forming a partly curved guiding boundary wall outside the nozzle, extending beyond the nozzle orifice and on that side of the nozzle towards which it is desired to deflect the jet, means inside the nozzle for constricting the jet at the orifice and from the said side of the nozzle adjacent to the said outside curved guiding wall, the fluid pressure in the jet on that side beingaccordingly reduced and a pressure gradient set up across the jet stream at the orifice by virtue of the said constriction, and means operable at will to destroy said pressure gradient.

5. A jet nozzle unit according to claim 4 wherein the said means for destroying the pressure gradient consists of a movable element on said'cu'rved guiding wall for separating the jet from said wall at a chosen point thereon, and means for moving said element around the curvature of said curved guiding wall.

6. A'jet nozzle unit for a' jet-propelled aircraft, for directing the jet rearwardlyor deflecting the jet and comprising a' nozzle, and means forming'a guiding boundary Wall extending beyondthe nozzle orifice on that side of the nozzle towards which it is desired to deflect the jet, which wall has asurface partly cylindrical about an axis extending across the nozzle at the nozzle discharge orifice and which projects into the issuing jet path to constrict the jet, at the orifice, in combination with a movable'element for separating'the jet from the cylindrical surface of said guiding wall'at a chosen point rearward of the orifice.

7. A jet nozzle unit according to claim 6 wherein the said jet sepai-ating elenient comprises amovable element forming a tangential projection from the saidcyli'ndrical' surface in conibinatiori with means'for moving said ele ment about the axis of the cylinder to positio'ns Whereit points tangentially from the cylindrical surface in different directions according to how it is required to direct the issuing jet. l

8. A jet no'zzlun'it acc'ordirig "t'o clairri 7 wherein" said cylindrical guiding wall is fixed andin whichsaid'movahle tangentially projecting element is movable relatively to the cylindrical surface about the axis thereof.

9. A jet nozzle unit for a jet propelled aircraft, for directing'the jet rearwardly or deflecting the jet and comprising walls con'stitutinga' plurality of' nozzles, and defining a plurality of shallow elongatednozzle orifices discharging to atmosphere, one above die other, each said orifice except the lowest being at some distance to the References Cited in the file of this patent rearof the orifice immediately beneath it, a plurality of UNITED STATES PATENTS guiding boundary walls outside the nozzles, forming a smooth continuation of each one of the first said walls 2418488 Th(.)mpson 1947 defining the lower boundary of a nozzle orifice and eX- 5 10 195,0 tending beyond the orifice, said guiding boundary walls 2637164 Robbon et a1 May 1953 curving smoothly from the rearward to the downward FOREIGN PATENTS direction to define a numb-er of downward paths, one

behind the other, and means operable at will to cause the 4322 Great Bntam 1876 issuing jet to separate from each said guiding wall and 10 272464 swltzerland 1951 continue rearwardly, or to follow the curvature of each said guiding wall into a number of parallel downward paths.