US3647020A

US3647020A - Jet propulsion apparatus and operating method

Info

Publication number: US3647020A
Application number: US7520A
Authority: US
Inventors: Howard R Macdonald
Original assignee: Rohr Inc
Current assignee: Rohr Inc
Priority date: 1970-02-02
Filing date: 1970-02-02
Publication date: 1972-03-07
Anticipated expiration: 1989-03-07

Abstract

Vanes are mounted on jet engine nozzle or a plug associated therewith for movement between a position wherein they permit normal flow of the exhaust gas of the engine in a direction parallel with the longitudinal axis of the nozzle, and a position wherein they cause the exhaust gas to whirl about said nozzle axis as it travels longitudinally thereof. When the vanes whirl the exhaust gas its rate of mixing with atmospheric air is increased, thus suppressing jet noise.

Description

United States Patent MacDonald 5] Mar. 7, 1972 [54] JET PROPULSION APPARATUS AND OPERATING METHOD [72] Inventor: Howard R. MacDonald, San Diego, Calif.

[7 3] Assignee: Rohr Corporation, Chula Vista, Calif.

[22] Filed: Feb. 2, 1970 [21] Appl. No.: 7,520

[52] US. Cl. ..18l/33 HC, 181/33 HD, 239/127.3,

239/265.17 [51] Int. Cl. ..F0ln l/l4, FOln l/18, B64d 33/06 [58] FieldofSearch ..l8l/33,' 33.2, 33.221,33.222,

[56] References Cited UNITED STATES PATENTS 2,664,700 1/1954 Benoit ..l8l/33.222 2,944,623 7/1960 Bodine l 81/ 33.222 2,696,709 12/1954 Oulianoff ..181/33.222

3,036,429 5/1962 Schairer 1 81/3322] 3,550,721 12/1970 Bruner 181/51 FOREIGN PATENTS OR APPLICATIONS 874,496 8/1961 Great Britain ..239/265.39

885,093 12/1961 Great Britain... ..18l/33.222 1,525,355 4/1968 France ..181/33.222 1,524,105 4/1968 France ..l8l/33.221

Primary Examiner-Robert S. Ward, Jr. Anomey-George E. Pearson 571 ABSTRACT Vanes are mounted on jet engine nozzle or a plug associated therewith for movement between a position wherein they permit normal flow of the exhaust gas of the engine in a direction parallel with the longitudinal axis of the nozzle, and a position wherein they cause the exhaust gas to whirl about said noule axis as it travels longitudinally thereof. When the vanes whirl the exhaust gas its rate of mixing with atmospheric air is increased, thus suppressing jet noise.

3 Claims, 12 Drawing Figures PATENTEUHAR 11912 SHEET 1 UF 2 INVENTOR.

HOWARD R. MACDONALD BY EMQM AT TORN E Y PATENTEDMAR (I972 3,647,020

sum 2 [1F 2 INVENTO HOWARD R. MACDON BY EMDM ATTORNEY JET PROPULSION APPARATUS AND OPERATING METHOD SUMMARY OF THE INVENTION This invention relates to aircraft jet propulsion apparatus and a method of operating the same. More particularly, the invention provides means for suppressing noise generated by the flow of high-velocity jet engine exhaust gas through the atmosphere, as well as means for more rapidly decelerating an aircraft after it has landed.

The advantages of the invention may be attained through various embodiments thereof, all of which are arranged to induce, at a selected time, vortical motion in the exhaust gas discharged from an aircraft jet engine. In a preferred embodiment of the invention vanes are mounted within a jet engine thrust nozzle and project radially therefrom at the forward portion of the nozzle section, said vanes being rotatable between (I an inoperative position wherein they are feathered in the exhaust gas stream discharged through said nozzle and thus have little effect on the flow thereof and (2) an operative position wherein each vane is disposed. at an angle to the longitudinal axis of said nozzle so that exhaust gas impinges against one side thereof and is thereby deflected circumferentially of said nozzle (i.e., the deflected exhaust gas is given a velocity component in a direction transverse to the longitudinal axis of the nozzle). The portion of exhaust gas which is deflected by the vanesexerts deflecting force against the remainder of the exhaust gas, and thus the jetstream discharged to the atmosphere is whirled about the longitudinal axis of the thrust nozzle. The transverse velocity component of the exhaust gas causes the jetstream to flow away from the longitudinal axis of the nozzle when it reaches the atmosphere. Hence the angle at which the boundary of the jetstream diverges from the aft end of the nozzle is greater than that associated with normal linear flow of said jetstream (i.e., flow of the jetstream when the vanes are feathered and no vortical motion is imparted thereto). This increased angle of divergence of the jetstream and its whirling motion result in faster mixing of the hot, high-velocity exhaust gas with cool, relatively low-velocity atmospheric air and thereby suppresses the noise generated by the flow of the jetstream through the atmosphere. In a second embodiment oftheinvention vanes are pivotally mounted on a cone the base of which is fixedly attached to the aft bearing housing of a jet engine, and are movable between an inoperative position wherein they lie against the cone and an operative position wherein they extend radially from the latter and deflect exhaust gas circumferentially of a thrust nozzle as in the first described embodiment. In a third embodiment vanes are mounted on the aft edges of a lobed thrust nozzle and move between an inoperative position extending longitudinally from said edges and an operative position extending laterally therefrom both the exhaust gas streams which are discharged from the lobes of the nozzle and the airstreams which flow between said lobes being deflected by the respective vanes when the latter are in the operative position so that said streams whirl about a line coincident with the longitudinal axis of said nozzle and extending downstream therefrom. Thus the second and third embodiments are also adapted to vary the divergence of jet engine exhaust gas streams and impart vortical motion thereto and thereby suppress the noise of such streams at any selected time.

When apparatus in accordance with the invention is operated to impart vortical motion to ajetstream as described, the thrust of the stream is reduced. This result permits a jetengine to be operated at a high-power level during the landing approach of an aircraft, but without producing greater thrust than is usable at this time. After the aircraft has landed on a runway, thrust reversers can be deployed to reverse the thrust of the engine at the same time the apparatusof the invention is operated to provide normal flow of the jetstream. High reverse thrust is thus obtained as soon as the thrust reversers are deployed, whereas ordinarily maximum reverse thrust is .the term thrust nozzle,

reached only after some time has elapsed in increasing the thrust output of an engine while an aircraft is rolling down a runway. 1

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a jet engine housing and thrust nozzle assembly in which a first embodiment of the invention is incorporated, the drawing illustrating only the aft portion of said housing and components of the embodiment which are disposed within said nozzle being represented by broken lines;

FIGS. 2 and 3 are end elevations of the same apparatus, respectively illustrating inoperative and operative positions of vanes utilized therein; I

FIGS. 4-7 are corresponding views of another jet engine housing and thrust nozzle assembly in which a second embodiment of the invention is incorporated, FIGS. 4 and 5 respectively being side and end elevations which illustrate an in operative position of vanes utilized therein and FIGS. 6 and 7 respectively being side and end elevations which illustrate an" operative position of the same vanes:

FIGS. 8-10 are corresponding views'of still another jet engine housing and thrust nozzle assembly. in which a third embodiment of the invention is incorporated, FIGS. 8 and 9 respectively being side and end elevations which illustrate an inoperative position of vanes utilized therein and FIG. 10

being an end elevation which illustrates an operative position of the same vanes; v FIG. 11 is a fragmentary longitudinal section of a plug mounted at the aft endof the nozzle illustrated in FIGS. 8l0, together with typical parts of an actuating mechanism which moves components of the third embodiment; and

FIG. l2 is a fragmentary cross section of the same plug, illustrating the same parts of said mechanism.

DETAILED DESCRIPTION First Embodiment In FIG. 1 reference number 20 designates generally a tubular housing enclosing a jet engine 22 andhaving a frustoconica] thrust nozzle 24 coaxially mounted on the aft end 26 thereof. Housing 20.may be the fuselage or an engine nacelle of an aircraft, and engine .22 may be either a turbojet or a turbofan engine (although to simplify the drawings the engine is illustrated schematically as a turbojet engine). Hence it should be pointed out that the term exhaustgas, as. used in the followingdescription and inclaims appended hereto, is to be considered to apply to either the combustion gas of a turbojet engine or a mixture of. both the combustion gas andfan air of a turbofan engine. Furthermore, it shouldbe understood that as used in the description and claims, is intended to apply to the entire length of av conduit through which exhaust gas of ajetengine is discharged to the atmosphere. This definition of thrust nozzle" is made because vanes 28 which are mounted in the forward portion of nozzle 24 may, in some embodiments of the invention, be located in a duct which in a strict technicalsense does not constitute part. of a thrust nozzle butonly serves to conduct gas from a jet engine tothe nozzle. As can be seen in FIGS. 2 and 3, there are a plurality of vanes 28 each fixedly attached at one end to a rod 30 .which passes through a hole in the wall of nozzle 24 and which is rotatable about the longitudinal axis of said hole. More specifically, each rod 30 is coaxial with the vane mounted thereon, and the longitudinal axes of the rodvane assemblies lie in a plane perpendicular-to the longitudinal axis of the nozzle and are evenly spaced aroundand extend radially from said axis as illustrated. An arm 32 extends laterally from the outer end of-each rod 30 and is connected at its frceend to the drive shaft 34 of an actuator 36 mounted on housing 20 adjacent the aft end thereof. Actuators 36 may be of any suitable type and are adapted to be operated from a point remote from the engine housing so as to move drive shafts 34 longitudinally of said housing and thereby simultaneously rotate vanes 28 between the inoperative position illustrated in FIG. 2 and the operative position illustrated in FIG. 3. Operation of the First Embodiment When the vanes are in the inoperative position their sides extend longitudinally of nozzle 24, and therefore there is virtually no interference with the linear flow through the nozzle of exhaust gas discharged from engine 22. However, when the vanes are rotated to the operative position they are all disposed at a predetermined angle relative to the longitudinal axis of the nozzle (all vanes being turned in the same direction) and exhaust gas impinges upon the sides of the vanes and is thereby deflected in a circumferential direction relative to the. nozzle. The portion of exhaust gas which is deflected by the vanes exerts deflecting force against the remainder of said gas, and thus the jet stream comprised of said gas is whirled about the longitudinal axis of nozzle 24 as it flows rearwardly. When the exhaust gas reaches the aft end of the nozzle its velocity component transverse to the longitudinal axis of the nozzle causes the gas to flow away from said axis (i.e., away from a line which is coincident with the iongitudinal axis of the nozzle and which extends rearwardly from said nozzle). Hence, as pointed out hereinbefore, when the vanes are rotated to their operative position the angle of divergence of the jetstream from the nozzle is increased. The whirling motion of the jetstream and the resultant increase in its frontal area increase the volume of atmospheric air that is contacted with the exhaust gas at any given distance downstream from the thrust nozzle, and consequently the rate of mixing of the hot, high-velocity exhaust gas with the cool, relatively low-velocity air is greater than it is when the exhaust gas is discharged in a narrow laminar jetstream. It will be understood by persons skilled in the art of jet propulsion that this increase in the rate of mixing of the exhaust gas with atmospheric air suppresses the noise associated with the operation of a jet engine. Sound suppression of the engine, or engines, of an aircraft is generally most needed at the time the aircraft is taking off and climbing from conjested airports when high thrust is being produced by said engines. Thus actuators 36 are operated to move vanes 28 to their operative position as the aircraft equipped therewith is taking off. Since the velocity component of the exhaust gas which is transverse to the longitudinal axis of nozzle 24 does not provide thrust, the vortical motion induced in the jetstream to achieve sound suppression is accompanied by a decrease in thrust. The decrease in thrust at the time of takeoff is a disadvantage but is outweighed by the reduction in the noise produced by an aircraft which must by necessity fly at a low altitude over urban areas surrounding airports at major cities.

When an aircraft equipped with the described sound suppressing apparatus is in cruise flight or when full power is needed for emergency conditions during take off or landing, vanes 28 are placed in their inoperative position so that the exhaust gas flows linearly through nozzle 24 and develops full thrust. During normal landing approach the vanes are preferably again rotated to their operative position, which reduces the exhaust noise and thrust produced by engine 22 while permitting it to be operated at a higher power level than would be possible for the same engine during landing approach in an aircraft having conventional propulsion apparatus. As soon as the aircraft lands on a runway thrust reversers associated with housing and nozzle 24 (which may be of any conventional type and therefore are not illustrated) are deployed to reverse the direction of travel of the exhaust gas issuing from said nozzle and actuators 36 are simultaneously operated to rotate vanes 28 to their inoperative position. Thus the thrust of engine 22 at high power level is immediately available to decelerate the aircraft when it lands on a runway. This is not possible in the operation of conventional propulsion apparatus, wherein an engine must be operated at a reduced power level during landing approach so as to produce less thrust and then stepped up in rotational speed after the aircraft has landed in order to developed maximum reverse thrust in conjunction with thrust reversers. It should be noted in connection with this use of vanes 28 that the amount of thrust loss which results from the vortical motion imparted to the exhaust gas by said vanes depends upon the amount of deflection of said gas circumferentially of nozzle 28. Therefore actuators 36 can be arranged to rotate the vanes to different angles during takeoff and landing approach, so as to thereby make the thrust loss resulting from the aforesaid vortical motion less during takeoff than during landing approach, while still inducing sufficient vortical motion at takeoff to provide adequate sound suppression. Furthermore, there is laminar flow in ajet engine only at certain optimum operating conditions and at other times there is swirl in the exhaust gas which reduces thrust. However, vanes 28 can be rotated as required to eliminate this undesirable swirling of exhaust gas during cruise flight, thus increasing thrust and reducing fuel consumption. Second Embodiment of the Invention In FIG. 4 reference number designates generally a second tubular aircraft housing enclosing a jet engine 122 which may be of either the turbojet or turbofan type (the drawings being simplified by illustrating a turbojet engine). As in the case of the first described apparatus, housing 120 has a frustoconical thrust nozzle 124 coaxially mounted on the aft end 126 thereof. In addition, a conical nozzle plug 128 is fixedly mounted on the aft bearing housing 130 of engine 122, this plug being hollow and coaxial with nozzle 124. Vanes 132 are pivotally mounted on the plug for movement between I) an inoperative position (illustrated in FIGS. 4 and 5) wherein the vanes are disposed adjacent said plug and extend axially thereof and (2) an operative position (illustrated in FIGS. 6 and 7) wherein the vanes extend laterally from said plug and deflect exhaust gas of engine 122 circumferentially of nozzle 124 to thereby impart vortical motion thereto. More specifically, each vane 132 is fixedly and coaxially mounted on one end of a bar 134, and the other end of this bar is in turn pivotally connected to plug 128 for rotation about an axis tan-' gential to the forward portion of the wall thereof, the axes of rotation of all of the bars 134 and vanes 132 thereon lying in a common plane perpendicular to the longitudinal axis of nozzle 124. Bars 134 are evenly spaced apart circumferentially of plug 128, and the vanes are respectively attached thereto so that when the bars are moved to the position illustrated in FIGS. 6 and 7 said vanes are disposed at a predetermined angle relative to the longitudinal axis of the nozzle (all vanes of course being turned in the same direction). The movement of the bars and vanes between the aforesaid inoperative and operative positions is effected by means of amechanism such as that described and illustrated in US Pat. No. 3,572,464, issued on Mar. 30, 1971, by the inventor of the herein disclosed invention and assigned by him to Rohr Corporation, the assignee of the present application. This mechanism comprises arms which are respectively fixedly attached to bars 134, links respectively pivoted to the free ends of said arms and to a ring coaxially disposed within plug 128, and an actuator which is also disposed within the plug and connected to said ring and adapted to move the same axially of said plug to thereby swing the vanes between their inoperative and operative positionsv Since the components associated with the drive mechanism for the vanes are fully described and illustrated in the identified patent application, the teachings of which are by this reference incorporated herein, they are not illustrated in the accompanying drawings for the sake of simplification. Preferably plug 128 is formed with elongate, shallow recesses 136 in which vanes 132 are respectively received when they are retracted. Operation of the Second Embodiment It will be understood from the foregoing description that vanes 132, when in the operative position, induce vortical motion in the exhaust gas of engine 122. Hence, the mechanism which moves said vanes can be operated at any selected time to suppress the noise generated by the flow of the exhaust gas through the atmosphere. Third Embodiment of the lnverltion In FIG. 8 reference number 220 designates generally a third tubular aircraft housing enclosing a jet engine 222 which again may be either the turbojet or the turbofan type (a turbojet engine being illustrated). Coaxially mounted on the aft end 224 of housing 220 is a longitudinally corrugated thrust nozzle which is designated generally by reference number 226. More explicitly, the wall of the nozzle is formed with longitudinally extending corrugations, or indentations, which gradually increase in depth in the downstream direction, the nozzle being cylindrical at its forward end to match the aft end of housing 220 and having a daisy-petal configuration at its aft end, as illustrated in FIGS. 9 and 10. The innermost portions of the aft edge of the nozzle are fixedly secured to a tear-shaped nozzle plug 228, the latter being coaxial with the nozzle and housing 220. Each lobe 230 of the nozzle comprises a pair of sidewalls which extend radially from the innermost curved portions of the nozzle wall, and a pair of

rectangular vanes

232, 234 are respectively pivotally mounted at the aft edges of these radially projecting sidewalls of each lobe. More particularly, each vane is mounted on a rod 236 (see FIGS. 11 and 12) which in turn is journaled in an aperture in the forward portion of the wall of plug 228, and the rods are spaced apart circumferentially of said plug and arranged so that their longitudinal axes are respectively in parallel, adjacent relation with the radially projecting portions of the aft edges of lobes 230. Fixedly mounted within the plug is an actuator 238 which can be operated to move the drive shaft 240 thereof in opposite directions axially of said plug. A plurality of struts 242 are fixedly connected at one end to the free end of drive shaft 240 and at the other end to a ring 244 which coaxially disposed with the plug. Each rod 236 projects into the interior of the plug and has a pinion gear 246 on its inner end, and a plurality of gear racks 248 are fixedly mounted on ring 244 and project rearwardly therefrom the respectively engage gears 246. Operation of the Third Embodiment During cruise flight of the aircraft equipped with the abovedescribed

propulsion apparatus vanes

232 and 234 are in the inoperative position illustrated in FIGS. 8 and 9, wherein they extend downstream from the aft edges of the lobes 230 of nozzle 226 and their sides are coplanar with the surfaces of the radially extending sidewalls of said lobes. When in this position the vanes obviously have no effect on the flow of exhaust gas from the nozzle lobes or the flow of slipstream air therebetween. Prior to or during takeoff of the aircraft actuator 238 is operated to move ring 244 toward the forward end of plug 228, whereupon gear racks 248 turn pinion gears 246 so that

vanes

232 and 234 are rotated to the operative position illustrated in H6. 10. Exhaust gas flowing through lobes 230 is then deflected laterally thereof, and slipstream air flowing through the valleys between said lobes is also deflected in the same direction, thereby imparting vortical motion to the combined streams of exhaust gas and slipstream air and thereby increasing the rate of mixing of said exhaust gas with atmospheric air.

Vanes

232 and 234 may of course also be placed in the operative position as the aircraft is landing, so as to permit operation of the associated jet engine 222 at high rotational speed while reducing thrust until thrust reversers are deployed, as described hereinbefore.

Other embodiments of the invention and modifications of the disclosed embodiments will be obvious in view of the disclosure made herein. The scope of the invention should there fore be considered to be limited only by the terms of the appended claims.

What is claimed as new and useful and desired to the secured by US. Letters Patent is: V

1. In an aircraft having a jet engine, the combination comprising:

a thrust nozzle through which exhaust gas of said engine is discharged; plurality of rotatable vanes for whirling said exhaust gas about the longitudinal axis thereof at any selected time, whereby the divergence of the jetstream discharged from said nozzle can be varied, said vanes being disposed adunct to said thrust nozzle and positioned upstream of the discharge portion thereof, said vanes having a greater surface area radially transverse to the direction of exhaust flow than longitudinal of said flow, said transverse surface area of said vanes being substantially equal to the radius of said exhaust nozzle, and said vanes being rotatable between (1) an inoperative position wherein they permit normal flow of said exhaust gas substantially parallel with the longitudinal axis of said nozzle and (2) an operative position wherein they are spaced apart around said axis in oblique angular relation thereto and disposed within said exhaust gas to deflect impinging portions thereof circumferentially of said nozzle; and

means connected to said vanes for moving them between said inoperative and operative positions thereof.

2. The combination defined in claim 1 wherein said vanes are feathered in said exhaust gas when in said inoperative positron.

3. The combination defined in claim 1 wherein said vanes are mounted on said nozzle for rotation about axes disposed radial to the longitudinal axis thereof.

Claims

1. In an aircraft having a jet engine, the combination comprising: a thrust nozzle through which exhaust gas of said engine is discharged; a plurality of rotatable vanes for whirling said exhaust gas about the longitudinal axis thereof at any selected time, whereby the divergence of the jetstream discharged from said nozzle can be varied, said vanes being disposed adjunct to said thrust nozzle and positioned upstream of the discharge portion thereof, said vanes having a greater surface area radially transverse to the direction of exhaust flow than longitudinal of said flow, said transverse surface area of said vanes being substantially equal to the radius of said exhaust nozzle, and said vanes being rotatable between (1) an inoperative position wherein they permit normal flow of said exhaust gas substantially parallel with the longitudinal axis of said nozzle and (2) an operative position wherein they are spaced apart around said axis in oblique angular relation thereto and disposed within said exhaust gas to deflect impinging portions thereof circumferentially of said nozzle; and means connected to said vanes for moving them between said inoperative and operative positions thereof.

2. The combination defined in claim 1 wherein said vanes are feathered in said exhaust gas when in said inoperative position.