US2585270A

US2585270A - Adjustable jet nozzle for aircraft propulsion

Info

Publication number: US2585270A
Application number: US582257A
Authority: US
Inventors: Plath Robert
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 1945-03-12
Filing date: 1945-03-12
Publication date: 1952-02-12
Anticipated expiration: 1969-02-12

Description

Feb. 12, 1952 R, P'LATH 2,585,270

ADJUSTABLE JET NOZZLE FOR AIRCRAFT PROPULSION Filed March 12, 1945 INVENTOR. ROBE/PT PLA TH BY A TTORNEKS Patented Feb. 12, 1952 ADJUSTABLE JET NOZZLE FOR AIRCRAFT PROPULSION Robert Plath, Seattle, Wash., assignor to Boeing Airplane Company, a corporation of Delaware Application March 12, 1945, Serial No. 582,257

9 Claims.

My invention relates to a reactive jet structure capable of adjustment to vary the effective size of the jet orifice for regulating the action of the jet. The improvement is particularly applicable to jet motors for aircraft propulsion purposes.

Sometimes it is desirable to alter the eifective area of the orifice through which the jet of a jet motor is projected, but any mechanism intended for such adjustment should be rugged and reliable.

It is the principal object of my invention to provide jet orifice adjusting mechanism which is simple, effective, and easy tooperate, and a further object is to shield such mechanism from direct exposure to the intense heat of the gases projected through the orifice.

Another object of my invention is to enable the size of the jet orifice to be varied within wide limits by comparatively little movement of the adjusting mechanism. My structure may be designed, however, to require a greater or lesser movement of the adjusting mechanism in order to obtain a given variation in size of orifice.

Two representative forms of my adjustable orifice nozzle are shown in the accompanying drawing, and additional advantages of these particular embodiments will be discussed hereafter.

Figure 1 is a side elevation view of one type of adjustable orifice jet nozzle incorporating my invention, and Figure 2 is an' end elevational view thereof.

Figure 3 is a view similar to Figure 1 showing the parts in different adjusted positions, and Figure 4 is an end elevational view of the nozzle with the parts in such different positions.

Figure 5 is an end elevational view of a different form of adjustable orifice jet nozzle, and Figure 6 is a longitudinal sectional view of the same nozzle taken on line 6-43 of Figure 5.

Conventional reaction jet nozzles used for propulsion purposes include a tubular portion I, which may be cylindrical and terminate in a constricted tip ll] of rearwardly tapering frustoconical shape. The body I and tip 10, however, invariably are integrated into a single continuous tube. In the present structure the main tube I and its tip are preferably circular in cross section, although they may be of other shape, and likewise are integrated in the forms shown in Figures 1 to 4, inclusive, to the extent that they constitute a single integral structure when the nozzle has been completed. Thus the tip is secured to the tube I and supported from it. by connecting bars Il, spaced circummmntiany I 2 about the tube and extending lengthwise of it. These bars may be welded or otherwise rigidly and permanently attached to each nozzle part.

The wall of the nozzle tube is not continuous despite its integral construction, the rear edge l2 of the cylindrical tube section I and the forward edge [3 of the frusto-conical tubular tip 10 being arranged in axially spaced relationship to define an annular aperture between the tube parts. Such aperture between the nozzle tube parts is not left unrestricted in a radial direction, however, but can be closed completely by an encircling tube or sleeve arranged telescopically and concentrically relative to the inner tube. Such sleeveis similar to the inner tube in cross-sectional shape and includes a cylindrical section 14, fitting snugly over the cylindrical portion l of the nozzle tube, and a rearwardly tapered frustoconical tubular portion 15 having a cone angle equal to the cone angle of tip Hi. The length of the frusto-conical portion of the outer tube is sufiiciently great to bridge'between the rear edge l2 of the cylindrical nozzle portion and the forward end iii of the tip portion.

Although the encircling sleeve I4, l5 fits snugly over nozzle tube I it is slidable axially relative to it to vary the opening between the tube proper andtip It. In the position of the sleeve closing the nozzle aperture the rearward end of the outer .tube l5 will engage contiguously the forward portion of the outer surface of the inner tip tube It, so that the wall of the composite jet nozzle will be continuous from tube I to the rearward end of tip 10. With the adjustable tube in such closed position the nozzle functions in the conventional manner. 1

As the outer tube 14, l 5 is slid lengthwise rearwardly relative to tube l and tip I 0 from the position shown in Figures 1 and 2 into a position such as shown in Figures 3 and 4, the annular aperture between the nozzle tube and its tip is between the rearward end of sleeve l4 and the adjacent portion of the inner tube.

Because of the larger. area through which the gases can escape'their velocity will be less than when the sleeve. is in the fully closed position of Figure 1. Moreover, the farther sleeve I4 is slid rearwardly the greater will be the radial width of the annular opening between the telescoping tubes, and consequently the larger will be the aggregate nozzle discharge area. The jet orifice will reach its maximum size, equal to the area of the rearward end of outer tube l4, l5, when such rearward end has been moved rearward far enough to lie in the same plane transversely of the nozzle tubes as the rearward end of the inner tube Hi.

When the nozzle area adjustment is effected by an external sliding sleeve, such as the tube l4, IS, the cylindrical portion in engagement with tube l is not exposed directly to the jet gases, and consequently such portion will remain comparative- 1y cool. Moreover the nozzle in that event is not obstructed by mechanism required to control the sliding of the orifice adjusting tube. The particular type of adjusting mechanism employed is not of great importance, a rod is pivotally connected to the cylindrical portion of the outer tube being illustrated as a representative type of operator.

In the form of nozzle shown in Figures 5 and 6 the rearward taper of the nozzle 2 is relatively gradual and extends over a considerable distance. Consequently the external adjusting tube of the type described above and shown in Figures 1 to 4 is not well adapted to effect the adjustment of the orifice area in such a nozzle. In this instance, therefore, the orifice adjusting tube is received telescopically and concentrically within the end of the nozzle 2. Such tube is of rearwardly tapered frusto-ccnical shape, preferably having the same cone angle as that of the main nozzle tube 2.

The tube 2!) is supported for adjustment lenthwise of nozzle 2 by a rod 2f, carrying plates 22 which are disposed radially of the adjustable tube. Four such plates arranged mutually perpendicular are suificient to interconnect the tube 20 and rod 2| securely. The sup-porting rod is received slidably in a block 23, which is protected from contact with the hot reaction jet gases by a conical shield 24 located concentrically within the outer tube 2.

If the adjustable tube 29 is in its rearmost position its wall will engage the tip of the nozzle 2 and will extend unbrokenly in continuation of the nozzle wall. As the rod 2| is slid forward an annular space is formed between the rearward end of nozzle 2 and the wall of tube 20. The farther the rod is pulled forward the greater becomes the space between the nozzle and the adjustable tube, and the effective radial width of the annular jet space increases correspondingly. The aggregate jet area is thus progressively enlarged even though the discharge aperture centrally of tube 20 remains constant in size. The adjustable tube may be moved forwardly sufilciently far to bring its rearward end into the same plane transversely of the nozzle tube as the tip of the outer nozzle tube, thus establishing the maximum annular jet space. In such position the effective jet area will be the area of the end of the outer or principal jet tube 2.

It will be appreciated that with either of my arrangements of composite telescoping tube jet nozzles the size of the effective escape orifice for the gases may be varied between a minimum size, equal to the tip area of the inner tube, and a maximum size, equal to the tip area of the outer tube, by lengthwise movement of the adjustable tube. As the effective area of the composite jet aperture is increased the discharge velocity of the gases will be decreased, (assuming acQIlSWRt volumetric flow) and consequently the thrust force produced will not be as great, but the efficiency of operation will be higher. On the contrary the effective area of the composite orifice may be decreased, resulting in a greater velocity of the jet gases emitted from the nozzle and a corresponding thrust increase, although the efficiency of the jet operation will not be as great.

The only difference in manipulation of the two types of adjustable nozzle described is that the efiective jet area is increased in the outer adjustable tube type by shifting the movable tube rearwardly, whereas in the inner adjustable tube type the movable tube must be shifted forwardly to increase the jet area. Consequently the impact force of the jet gases against the adjustable tube tending to shift it rearward tends to increase the area of the jet orifice when the outer tube is shiftable, whereas such force tends to reduce the jet orifice area in the shiftable inner tube type. In either structure the variation in jet area effected by a given movement of the adjustable tube lengthwise of the stationary tube can be decreased by reducing the cone angle of both tubes, and vice versa. Also the proportional variation in the composite jet orifice will be affected by the size of the orifice through the inner tube.

In either of the illustrated forms it will be evident that turbulence of flow is inappreciable, and that the relative velocities of gases emerging from the inner and outer orifice portions remains substantially unaltered throughout a wide range of positional adjustment between inner and outer tubular members.

I claim as my invention:

1. In a jet motor for aircraft propulsion, a jet nozzle comprising an inner tube includin a forward'portion of constant exterior cross-sec tional shape lengthwise thereof and a rearwardly tapered rearward portion spaced lengthwise to define a circumferential aperture therebetwee'm, an outer tube including a forward outer tube portion of constant interior cross-sectional shape lengthwise thereof, slidably encircling the forward portion of said inner tube and a rearward outer tube portion rearwardly tapered and adjoining said forward outer tube portion and of a length greater than the length of the circum-' ferential aperture between the forward ancitapered rearward portions of said inner tube, and means operable to shift one of said outer and inner tubes relative to the other length-wise between a position in which the tapered rearward portion of said outer tube closes the circumferential aperture between the forward and rearward portions of said inner tube, and a position in which the tapered rearward portion of said outer tube is spaced outward from the tapered rearward portion of said inner tube to define an orifice opening between the rearward end of said outer tube and the outer surface of the tapered rearward portion of said inner tube, which orifice opening communicates with such circumferential aperture of said inner tube.

2. In a jet motor for aircraft propulsion, a jet nozzle comprising an inner tube including a cylindrical forward portion and a rearwardly tapered frusto-conical rearward portion spaced lengthwise to define an annular aperture therebetween, an outer tube including a cylindrical forward portion slidably encirclin the cylindrical forward portion of said inner tube, and a rearward outer tube portion rearwardly tapered frustomonically and'adjoining said forward outer tu e po on and of a l ng h g eater than the annular aperture between the forward and tapered rearward portions of said inner tube, and means operable to shift said outer tube lengthwise relative to said inner tube between a forward position in which the frusto-conicalrearward portion of said outer tube closes the annular aperture between the forward and rearward portions of said inner tube and the frusto-conical portions of said inner and outer tubes are disposed in substantially unbroken continuation, and a rearward position in which the frustoconical rearward portion of said outer tube is spaced outward from the frusto-conical rearward portion of said inner tube to define an annular orifice opening between the rearward end of said outer tube and the outer surface of the frustoconical rearward portion of said inner tube, which orifice opening communicates with such annular aperture of said inner tube.

3. An aircraft propulsion jet comprising an inner cylindrical shell communicating internally with the aircraft jet-motor combustion chamber and forming a substantially continuous duct tapered at its exhaust end to define an inner jet orifice at such end, the tapered end portion of said inner shell having a discharge aperture therein by passing said inner jet orifice, spaced from its exhaust end, and an outer cylindrical shell closely encircling said inner shell and having a rearward end portion tapered rearwardly to define an outer jet orifice duct encircling said inner orifice duct and communicating therewith through said aperture.

4. An aircraft propulsion jet comprising an inner cylindrical shell communicatin internally with the aircraft jet-motor combustion chamber and forming a substantially continuous duct tapered at its exhaust end to define an inner jet orifice at such end, the tapered end portion of said inner shell having a discharge aperture therein by-passing said inner jet orifice, spaced from its exhaust end, an outer cylindrical shell closely encircling said inner shell and having a rearward end portion tapered rearwardly at substantially the same angle as said inner shell to define an end-opening cuter jet orifice duct encircling said inner orifice duct and communicating therewith through said aperture, means guiding said outer shell for adjustment endwise relative to said inner shell to vary the radial width of said outer jet orifice duct, and thereby the outer orifice area, and adjustment means operatively connected with said outer shell and located wholly outside said outer shell and out of the path of heated gases therein, and operable to shift said outer shell endwise to vary the area of said outer orifice.

5. An aircraft propulsion jet comprising an inner cylindrical shell communicating internally with the aircraft jet-motor combustion chamber and forming a substantially continuous duct tapered at its exhaust end to define an inner jet orifice at such end, the tapered end portion of said inner shell having an annular discharge aperture therein by-passing said inner jet orifice spaced from its exhaust end, an outer cylindrical shell telescoping slidably over the end portion of said inner shell and having a rearward end portion rearwardly tapered at substantially the same angle as said inner shell to define an outer jet orifice duct encircling said inner orifice duct, communicating therewith through said aperture, and adjustable in crosssectional area by telescoping movement of one shell efiected relative to the other, the inside dimension of the rearward tip of the tapered end portion of the outer shell being less than the corresponding outer dimension of the inner shell at the rearward edge of the aperture therein so as to close substantially completely said aperture in the forward limit position of the outer shell relative to the inner shell, and adjustment means disposed outside of both shells and operatively connected with said outer shell to shift said outer shell endwise from said limit position; to increase progressively the opening area of said outer orifice.

6. An aircraft propulsion jet comprising an inner substantially continuous duct communicating with the aircraft's jet-motor combustion chamber and tapered rearwardly at its exhaust end to define an inner jet orifice, the ducts tapered wall portion having an externally-communicating aperture therein, occupying a substantial wall area and spaced forwardly of the rearward, or exhaust, end of such wall portion, an outer duct at least partly surrounding, and communication with, said inner duct through said aperture and paralleling the tapered wall portion of said inner duct to the exhaust end of said outer duct to define an outer jet orifice adjacent to said inner orifice, and means operable, while maintaining said parallel relationship, to adjust the spacing between the outer ducts inner wall and the inner ducts outer wall to vary the outer ducts jet orifice opening and thereby the effective opening of the composite jet formed by both ducts.

7. An aircraft propulsion jet comprising an inner substantially continuous duct communicating with the aircrafts jet-motor combustion chamber and tapered rearwardly at its exhaust end to define an inner jet orifice, the ducts tapered wall portion having an externally-communicating aperture therein, occupying a substantial wall area and spaced forwardly of the rearward, or exhaust, end of such wall portion, an outer duct at least partly surrounding, and communicating with, said inner duct through said aperture and paralleling the tapered wall portion of said inner duct to the exhaust end of said outer duct to define an outer jet orifice adjacent to said inner orifice, means operable, while maintaining said parallel relationship, to adjust the spacing between the outer ducts inner wall and the inner ducts outer wall to vary the outer ducts jet orifice opening and thereby the effective opening of the composite jet formed by both ducts, and means mounting said adjusting means wholly externally of both ducts.

8. An aircraft propulsion jet comprising an inner cylindrical shell defining a substantially continuous duct communicating with the aircrafts jet-motor combustion chamber and tapering at its exhaust end to define an inner jet orifice, said shell being articulated in its tapered end portion to define a substantially full annular aperture whose rearward annular boundary is of substantially lesser diameter than its forward annular boundary because of the taper, effectively to provide a direct by-pass path for gases passing through said duct toward said inner jet orifice, an adjustable outer shell encircling the taper end of said inner shell, comformably tapered and overlying said aperture to define an annular outer by-pass duct and jet orifice adapted to discharge gases into a stream converging with the inner orifice expelled stream, and adjustment means operable to shift said outer shell axially between a forward position blocking flow through said aperture and substantially closing said'outer jet orifice, and a rearward position defining a relatively large outer jet orifice, the structure thus defined providing a velocity relationship between the inner and outer jet substantially uncharged throughout adjustment of. the outershell.

9. 'An aircraft propulsion jet comprising an inner cylindrical shell defining a substantially continuous inner duct communicating with the aircraft's jet-motor combustion chamber and tapering at its rearward or exhaust end to define an inner jet orifice, a tapered outer shell of substantially equal taperangle, surrounding said inner shell and movable axially thereof to define, between said shells, an annular duct of an adjustable width which is substantially constant over the overlapping tapered lengths of the shells, the rearward end of .said outer shell defining an outer jet orifice and being larger than the corresponding end of the innershell, an annular aperture located in the tapered portion of said inner shell and underlying said outer shell, thereby communicating with said outer duct, and means operable to adjust the position of said outer shell axially relative to said inner shell to vary the width of said outer duct between said aperture and outer jet orifice, thereby to preserve substantially the same relative jet velocities through said outer orifice and adjacent inner orifice.

ROBERT PLATH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 576,259 Diamond Feb. 2, 1897 658,586 Reiling Sept. 25, 1900 20 1,319,782 Maul Oct. 28, 1919 1,536,630 Reinecke May 5, 1925 2,408,099 Sherman Sept. 24, 1946