US2771740A

US2771740A - Afterburning means for turbo-jet engines

Info

Publication number: US2771740A
Application number: US196040A
Authority: US
Inventors: Clarence L Johnson
Original assignee: Lockheed Aircraft Corp
Current assignee: Lockheed Corp
Priority date: 1950-11-16
Filing date: 1950-11-16
Publication date: 1956-11-27
Anticipated expiration: 1973-11-27

Description

Nov. 27, 1956 c. JOHNSON AFTERBURNING MEANS FOR TURBO-JET ENGINES Filed Nov. 16, 1950 3 Sheets-Sheet 1 INVENTOR. CLARENCE L. JOHNSON k Agent Nov. 27, 1956 c. L. JOHNSON 2,771,740

AFTERBURNING"MEANS FOR TURBO-JET ENGINES Filed Nov. 16, 1950' s Sheets-Sheet 2 18 a I O g INVENTOR.

* CLARENCE L. JOHNSON BY I \2 8 8 I WM 2 Agent Nov. 27, 1956 c. L. JOHNSON 2,771,740

AFTERBUR'NING MEANS FOR TURBO-JET ENGINES Filed Nov. 16, 1950 3 Sheets-Sheet 3 INVENTOR. CLARENCE L. JOHNSON Agent tall AFTERBURNING MEANS FOR TURBO-JET ENGINES Clarence L. Johnson, Encino, Califi, assignor to Lockheed Aircraft Corporation, Burbank, Calif.

Application November 16, 1950, Serial No. 196,040

12 Claims. (Cl. 6035.6)

This invention relates to turbo jet engines useful in the propulsion of aircraft, and the like, and relates more particularly to engines of this class incorporating afterburning means for effecting an increase in the propulsive thrust or power output.

Gas turbine powerplants, as employed for the propulsion of aircraft, embody nozzles for discharging the high Velocity propulsive jet of the products of combustion and compressed air. In order to obtain a substantial increase in the thrust for tactical operations, high speed, climb, take-offs, etc. it is more or less common practice to employ an after-burner in which fuel is introduced into the stream of combustion products and air at a point or region downstream from the turbine and this fuel is consumed to materially increase the volumetric flow and thus increase the reactive thrust. In such installations it is the practice to equip the nozzle with means for varying or changing its effective area to adapt the nozzle for the normal and afterburning operations, and this means has usually consisted of eyelids or clam shells pivoted at the aft end of the nozzle and movable between a closed or nearly closed position when not afterburning to an open position for afterburning. These nozzle eyelid-s thus increase the diameter of the propulsive jet and their design or configuration is such that they cause substantial drag when not afterburning and, accordingly reduce the efiiciency of the powerplant.

The typical afterburners also include fuel injecting pipes or nozzles projecting into the afterburning chamber and a flameholder arranged downstream from these fuel nozzles to prevent the afterburning flame from advancing upstream. The fuel nozzles and flame-holders, although they are not in use during the normal or non-afterburning opera-tions of the powerplant, offer substantial drag to the stream of gases and air during these normal operations and, therefore, reduce the propulsive efficiency of the powerplant.

It is an object of the present invention to provide a turbo-jet engine embodying a practical, improved and efficient afterburning arrangement which introduces or creates a minimum of drag or interference with the propulsive jet gases and compressed air.

Another object of the invention is to provide an afterburning means characterized by a variable area propulsive nozzle which maintains the full or maximum jet diameter at all times, that is, during normal powerplant operation as well as during the afterburning operations.

It is another object of the invention to provide an after burning means of the character mentioned embodying a central needle or plug movable axially in the nozzle and af-terburner between a position where it protrudes through or into the exit of the propulsive nozzle to reduce the effective area of the same for normal or non-afterburning powerplant operations and a position where it is retracted forwardly entirely clear of the nozzle exit to provide for the maximum volumetric discharge of the jet during afterburning operations. When, in its retracted or forward position, this plug or needle is clear of the tes atent 2 afterburning flame and heat generated behind the flameholder and is, therefore, substantially unaffected by the high afterburning temperatures. This is a radical departu're from the conventional clam shell or eyelid propulsive nozzle arrangement where the area controlling elements of the nozzle are directly exposed to the flame and high temperatures of the afterburner.

Another object of the invention is to provide an afterburning means characterized by pipes, tubes, or nozzles for introducing the fuel for the afterburning operations which are retracted clear or substantially clear of the propulsive stream of gases and air during normal or nonafterburning powerplant operations. In accordance with this invention these tubes or fuel injecting nozzles are associated with the abovementioned plug or needle to be automatically extended or projected to the operative fuel introducing positions when the needle is retracted forwardly from the propulsive nozzle for the afterburning operations and they are automatically retracted to offer a minimum of resistance or interference to the flow of the combustion gases and air when the plug or needle is moved rearwardly into the propulsive nozzle for normal powerplant operations.

A further object of the invention is to provide an afterburning means of this class in which the flame-holder is automatically projected to the operative flame-holding position when the aforesaid needle or plug is retracted from the propulsive nozzle for the afterburning operations and that is automatically retracted to a position where it creates little or no drag or resistance to flow of the gases and air when the plug is extended into the propulsive nozzle for the normal or non-afterburning operations.

A still further object of the invention is to provide an afterburning arrangement of this character having simple, effective means for cooling the movable needle or plug and associated parts.

Other objectives and features will become apparent from the following detailed description ofa typical preferred embodiment of the invention wherein:

Figure 1 is a more or less diagrammatic side elevation of a turbo-jet powerplant embodying the afterburning means of the invention with internal elements of the powerplant and certain elements of the afterburning means appearing in broken lines;

Figure 2 is an enlarged longitudinal detailed sectional view of the afterburning means showing the plug or needle in the retracted position and the flame-holder and fuel injecting tubes extended, with arrows indicating the direction of flow of the actuating air and cooling air;

Figure 3 is a fragmentary longitudinal sectional view similar to Figure 2 illustrating the needle or plug in its extended or operative position with the flame-holder and afterburning fuel injecting tubes retracted;

Figures 4 and 5 are transverse detailed sectional views taken substantially as indicated by

lines

44 and 55 respectively, on Figure 2;

Figure 6 is an enlarged transverse detailed sectional view taken substantially as indicated by line 66 on Fig ure 3;

Figure 7 is an enlarged fragmentary sectional view taken substantially .as indicated by line 77 on Figure 9 illustrating the means for projecting and retracting the fuel injecting tubes with said tubes in the retracted positions;

Figure 8 is a view similar to Figure 7 showing the fuel injecting tubes in the extended positions; and

Figure 9 is an enlarged fragmentary transverse sectional view of a portion of the afterburning means taken on line 9-9 of Figure 7, illustrating one of the afterburning fuel introducing assemblies.

. The afterburning means of the invention is capable of wane so incorporation in or use with turbo-jet and turbo-propeller engines of various classes and types and, of course, may be altered or varied considerably to adapt it for use on given or specific powenplants. In Figure 1 of the drawings, I have illustrated the invention applied to or used with a more or less typi-cal type of turbo-jet powerplant, it being understood that this is merely an illustrative form and application of the invention. The particular powerplant illustrated includes a compressor of the axial flow type having a ram air inlet 11 at its forward end. The compressor 10 supplies the compressed air to a primary combustion chamber 12 which, in turn, supplies hot gases of combustion and the unconsurned compressed air to a turbine 13 to drive the same. The turbine 13 includes a bladed rotor 14 which drives the rotor 15 of the compressor lil throu gh the medium o f' a shaft 16. The turbine rotor '14 is conoidal or of rearwardly decreasing diameter and such rotors usuallyv have a rather pointed rear end or apex. However, as best illustrated in Figure 2 this apex portionof theturbine rotor 14 is preferably omittedandi the rotor presents a flat normal rear surface. Thefgases of combustion and the excess or unconsumed compressed air which drive the turbine 13 discharge rear: wardly from around the turbine rotor 14 in an annular stream and are received by the afterburning means of the invention. 7 i i The afterburning means is contained or housed in what may be termed a tail pipe 17 which extends rearwardly from the turbine 13. The forward end of the tail. pipe 17. is suitably anchored or secured at the turbine 1:3 and its forward portion may gradually flare rearwardly. The aft or rear portion of the tail pipe 17 gradually reduces in diameter to form a nozzle 18 for discharging the turbine. exhaust gases and air in the form of a high velocity propulsion jet. It is to be observed that the nozzle 18 presents smooth, clean, external and internal surfaces and end devoid of projecting eyelids, or the like. The afterburner includes an elongate tube 19 for receiving and slidably supporting the aforementioned needle or plug 20.

The tube 19 is centrally or coaxially supported in the tail pipe 17 by a forward set of struts 21 and a rear series of struts 22. The struts '21 and 22, which are preferably streamlined project inwardly from the pipe 17 to rigidly mount the tube 19 in the pipe. The forward end of the tube 19 is preferably of substantially the same external. diameter as the aft end of the turbine rotor 14 and lies immediately adjacent the same, as illustrated in Figure 2. Thc aft end of the tube 26 is spaced a considerable distance forwardly from the nozzle 18. and the supporting struts 22 may have their rear edges at the same plane. An internal annular hearing or guide 24 is secured in the rear end ofthe tube 19 to assist in slidably supporting the needle or plug 20.

The needle or plug is movable axially to regulate orvarythe effective diameter of thepropulsive nozzle 18. 'A s' illustrated in Figures 2 and 3, the plug 20-,is.

shiftable between the retracted position where it is sub: stantially entirely within the stationary tube 19 aud.the extended position where it projects into or through the nozzl'e 18. The plug 20 may be in the nature of a hollow shell or tube internally reinforced by longitudinally spaced ribs orhoops 25. An annular hearing or guide 26 on the forward end of the plug 20 rides on the internal surface of the tub-e 19, the plug being guided and supportedlinfthe tube. by the above mentioned bearing 24fahdthe guide 26. The aft end oftheplu-g ZlLhasa pointed or substantially conical cap 27 which may project rearwardly beyond the nozzle 18 when the plug is inthe extended position for normal powerplan-t operation, or

it may be partial-lyextended to vary the final-outlet nozzle.

area as desired.

The means for operating or moving the plug 20 includes a: cylinder 28secured within the stationarystube. 19. The forward endof the .cylin-der.28..is.fixed.,to. a. fitting29which, in. turn, issecured to a bulkhead.

closing the forward end of the tube. The cyiindeg' 2Q extehds rearwardly into the tubular needle or plug 20 with clearance and terminates adjacent the plane occupied by the aft end of the supporting tube 19. A tubular piston rod 31 is secured to the cap 27 of the plug 20 and extends into the cylinder 28. A head or piston 32 is secured to the forward end of the rod 31 and operates in the cylinder 28. In accordance with the invention the needle or plug 20 is preferably operated by compressed air bled from the compressor 10 of the power; plant. A duct 33. leads through one of the struts 2'1 and extends through the forward portion of the supporting e 9 t mmu ca h e. orwa d end f. the cylinder 28. A similar duct 34 leads through a strut 21 and the tube 29 to have communication with the aft end of the cylinder 28. Pipes '35 and 36 which may be external of the engine, extend from the ducts 3'3 and 34 respectively, to a valve 37 and a compressed air supply pipe 38 extends from the compressor 10 to the valve, The valve 37 is operable manually, or by other means, between the position illustrated in Figure 1 where it pilaces the pipe 35 in communication with the pressure supply. pipe 38 and puts the pipe 36 in communioatipn with: anoutlet 3'9 exhausting to the atmosphere and a position where the pipe 36 has communication with the. pressure supply pipe 38 and the pipe 35 discharges to the atmosphere. It is believed that it will be apparent how the valve 37 may be opera-ted to cause the plug. 20 to be moved rearwandly into the nozzle 18 for normal powerplant operation or to be moved forwardly free of the nozzlejwhere it is substantially entirely housed within the stat-ionarysupporting tube 19.

The invention further includes means for introducing fuel into the tail pipe 17, that is into the afterburning passage or chamber defined by thepipe 17. This means i s characterized by the automatic projection and retrac,-. tion of fuel injecting tubes or nozzles 45 simultaneou siy with movement of the above described needle or plug 20, to the end that the nozzles 45 are retracted when the plug is in. the normal powerplant operating position of Figure. 3 and are extended to the fuel injecting positions whenthe plug is in the retracted afterburning condition of Figure 2.. The tubes or nozzles 45 for introducing the afterburning fuel are secured to tubular shafts 41 which extend throughthe above described struts 22. These shafts 41 extendjadiallyinward from the exterior of the tail pipe 17 toth e stationary supporting tube19 and are carried or supported by bearings 42 .for angular movement about. their individuallongitudinal axes, Theinner-ends oi -the shafts. 41 are closed while the outer ends of thesha fts; are provided; with fittings 43 which connect the shafts with flexible helically curved fuel supply tubes 44. Each shaft 41 i sprovided with longitudinally spaced projeet: ing tubes or nozzles 45. The nozzles 45 project from op posite. sidesof; their respective shattsfll and receiyethe ts ibu a na. fuel. tsmth n ri rs. f. he. a ts.- he h' fiwli ars mwm be tur d hrush apnrqa m tsla 9O .degrees to move the no zzles-45 between pqsitions where they lie against the opposite sides of the struts22. and po; sitions where they projectlaterally from the struts to be Within theafterburning chamber. The sides-of the struts 22 preferably have groovesordepressious 46 for receiving or housing the nozzles 45 when the latter areinjl enrce tracted positions sotl at the nozzl es lie substantially flush with the surfaces of thestruts to create little or no drag duringv normal powerplant operations. The; nozzles/15; extend through slots 43 in the walls of the struts 22 .soas to .be movable between their extended I and retract flxpg sitions. Each nozzle 45/.is provided with a plupalityt of. longitudinally spaced fuel discharging orifices 47. As il lustrated in Figure 4, the orifices 47 are directed axially. oi theafterburning chamber and face downstream, it .being understood that .the orifices may be directed upstream .01: in directions normal to the flow of the. airand 1 gases through the afterburning chamber. Figure-,tillustrates the positions of the nozzles 45 when extended and it will be observed from this disclosure that the nozzles 45 provide for a substantially uniform distribution of the fuel throughout the cross sectional area of the annular afterburning chamber. Figures 3 and 7 show the manner in which the nozzles 45 are received in the depressions 46 to lie substantially flush with the surfaces of the struts 22 where they create little or no drag.

The means for moving or turning the fuel injecting shafts 41 through substantially 90 degrees to project and retract the nozzles 45 include longitudinally extending flange members 48 fixed on the exterior of the movable needle or plug 20. Each member 48 carries a pin 50 which projects substantially radial with respect to the wall of the needle or plug 20. As best illustrated in Figures 7, 8 and 9, the pins 50 move adjacent the inner ends of the fuel supply shafts 41 and each shaft is provided at its inner end with a cam or pawl 51 for cooperating with the adjacent pin 50. The pawls 51 are fixed to their respective shafts 41 and each presents two

surfaces

52 and 53 extending at right angles to one another. These

surfaces

52 and 53 are adapted to alternately engage with the axially extending surfaces of the adjacent flange members 48. Each pawl 51 has a slot 54 at the junction of its two

surfaces

52 and 53. The slots 54 are adapted to receive the related or adjacent pins 50 upon movement or reciprocation of the plug 20, the arrangement being similar to a Geneva movement. The engagement of the pins 50 in the slots 54 serves to turn the pawls 51 and their fuel shafts 41 through approximately 90 degrees, the angle members 48 being provided with depressions or recesses 55 to permit the pointed pawls to turn or reverse their positions.

With the arrangement just described the cam or pawl surfaces 53 are engaged with the angle members 48 so long as the needle or plug 20 remains in the extended position of Figure 3 and this engagement holds the shafts 41 in the positions where the fuel tubes or nozzles 45 are retracted in their grooves 46. Figure 7 illustrates one of the afterburning fuel units in this condition. Upon movement of the plug 20 from the projected position of Figure 3 to the retracted or afterburning position of Figure 2, the pins 50 cooperate with the slots 54 to turn the pawls 51 approximately 90 degrees to bring the surfaces 52 against the angle members 48. This swings the fuel nozzles 45 to the projected positions illustrated in Figures 4 and 8. Thus the fuel nozzles 45 are automatically moved to their projected positions for the introduction of the afterburning fuel when the plug 20 is retracted. When the plug 20 is moved from the retracted position of Figure 2 to the extended position of Figure 3 for normal powerplant operation, the pins 56 cooperate with the slots 54 to swing the pawls 51 to the positions where their surfaces 53 engage angle members 48 and where the nozzles 45 are again retracted into their grooves 46. From the foregoing, it will be seen that the means for introducing the afterburning fuel is fully retracted to leave the afterburning chamber clear and unobstructed during normal powerplant operation, and yet provides for the effective distribution of the fuel across the chamber during the afterburning operations.

The invention further provides retractable flame-holding means associated with the movable needle or plug 20. This means includes a plurality of flame arresting or holding members 69 pivoted at 61 to the above described cap 27 of the plug 29. The members 60 may be simple elongate parts of V-shaped transverse cross section and their rear ends are pivoted at 61 adjacent the aft pointed end of the cap 27. Axial rearwardly converging slots 62 are provided in the wall of the cap 27 to receive the flameholding members 60, the slots being such that the members may lie substantially flush with the exterior of the cap when in the retracted positions. In accordance with the invention, the flame-holding members 60 are extended laterally or radially from the cap 27 when the plug 20 is moved to the retracted position of Figure 2.

The means for extending and retracting the members 60 includes a collar 63 slidable on the piston rod 31 of the plug 20 and links 64 extending between and pivotally connected with the collar 63 and the members 60. A tube 65 is secured to the collar 63 and extends forwardly in spaced surrounding relation to the piston rod 31. The tube 65 passes through a guide or bearing 66 on the aft end of the cylinder 28 and is provided at its forward end with a piston-like head 67. Spaced axially ports 68 are provided in the head 67 to permit the direct application of the actuating air pressure to the piston 32 of the needle or plug 20. The assembly of the head 67, tube 65, and flame-holding members 60 has a slack or lost motion connection with the piston rod assembly of the plug 20 to provide the relative movement for extending and retracting the members 60. The head 67 is engageable by the piston 32 to limit rearward movement of the plug assembly relative to the flameholding assembly, that is the parts are related and proportioned so that the piston 32 and plug 20 are movable rearwardly some distance before the piston 32 engages the head 67 to transmit rearward motion to the tube 65 and other elements of the flame-holding assembly. An external collar 70 is fixed on the rear end of the tube 65 and is engageable with the above mentioned bearing or guide 66 to limit forward movement of the flame arresting assembly. The head 67 of the tube 65 is engageable with the forward end of the stationary guide 66 to limit the rearward movement of the flame-holding assembly and the plug 20. When the actuating air under pressure is delivered to the above described duct 34 through the valve 37 it acts on the head 67 and piston 32 to simultaneously move the plug 20 and the tube 65 forwardly. As the tube 65 moves forwardly together with the needle or plug 20, the flame-holding members 60 remain in their retracted positions substantially flush with the surface of the cap 27. However, before the piston 32 reaches the forward end of its stroke the collar 70 engages the stationary guide 66 to stop forward movement of the tube 65. The actuating air under pressure acting through the ports 65 continues to move the piston 32 forwardly so that the forward motion of the plug 20 is continued. This forward movement of the needle or plug 20 relative to the tube 65 results in lateral pivoting or projection of the flame-holding members 60 from the positions of Figure 3 to the positions of Figure 2, the action being similar to the opening of an umbrella. It is to be observed that this lateral projection of the flame-holding members 60 to the operative positions occurs during the final phase of forward motion of the plug 20 and takes place after the cap 27 has moved clear of the nozzle 18 so that the members 60 cannot interfere with the propulsive nozzle. A stop collar is fixed on the piston rod 31 within the cap 27 and is engageable by the collar 63 to limit the outward or rearward pivoting of the flame-holding members 60.

When the needle or plug 20 is to be moved rearwardly for normal powerplant operation, that is operation without after-burning, the actuating air under pressure is sup plied to the duct 33 and the forward end of the cylinder 28. The air under pressure acts upon the piston 32 to move the plug 20 rearwardly. During the initial phase of this motion the head 67 and the tube 65 remain stationary and the rearward movement of the plug cap 27 relative to the tube 65 results in inward pivoting or retraction of the members 60 into the slots 62. Thus the flame-holding members 60 are retracted during the initial phase of rearward travel of the plug 20 so they cannot interfere with the propulsive nozzle 18. The piston 32 engages the head 67 to move the tube 65 rearwardly together with the plug 20 during the balance of the rearward travel which is terminated when the head 67 engages the stationary bearing or guide 66. From the foregoing itwill beseen that the flame-holding: members 60 remain retracted and substantially flush with thesurface of the cap 27 during normal powerplant operations where they offerlittle orno drag in the propulsive jet of gases and air and are automatically projected to the operative flame-holding posit-ions when the plug 20 is retracted forwardly for the after-burning operations. The flamerholders 60 are automatically retracted into their slots 65 in the head 27 when the needle orplug 20 is restored to its projected normal position.

I-t'ispreferred to circulate cooling air through the afterburning apparatus to prevent overheating. A cooling air duct 80- extends through aforward supporting strut 21 to communicate with the forward end of the tubular plug 20; The duct 80 is supplied with air under pressure by a pipe- 8-1, which bleeds the air from the engine compressor 10' and which is equipped with a suitable control valve 82; The cooling air supplied to the forward end of the plug 29 flows rearwardly through the plug to cool the assembly and to ultimately discharge from the slots 62f of -the cap 27-. These slots 62- are formed and proportioned' to allow the discharge of'cooling air in reasonable volumes even when the flame-holding members 60 are retracted in the slots. During the after-burning operations when the temperatures in the after-burner region are increased, the members 60 are clear of the slots 62, as above described, so that a larger volume of air is free to how through the plug 20 and slots. Thus the flameholding members 60- serve as valves to automatically regulate the amount of cooling air flowing through the apparatus.

It is believed that the operation ofthe after-burning apparatus of the invention will be understood from the foregoing detailed description wherein the functioning of the several instrumentalities has been fully set forth. The present invention completely avoids the necessity for installing eyelid-type nozzle controls, or the like, on the propulsive nozzle 18, permitting the use of a smooth, clean, eliicient nozzle. The needle or plug-20 operates to-vary the effective area of the nozzle 18 without altering the external diameter of the propulsive jet. During thenormal powerplant operations the needle or plug 20 is extended rearwardly into or through the nozzle 18, asillustrated in Figures 1' and 3. At this time both the after-burner fuel nozzles 45 and the flame-holding members 60 are retracted out of the path of the high velocity gases and create little or no turbulence or drag. Accordingly, as distinguished from prior afterburning apparatus, the fuel injecting means and the flame-holding means do not detract from or reduce the efficiency during normal powerplant operations. When it is desired to operate the after-burning means the valve 37 isturnedto direct air under pressure from the compressor 10' to the duct 34 to move the plug 20 to the retracted position illustrated in Figure 2. Aspreviously-described, the fuel nozzles 45 and the flame-holding members 60are automatically projected into the afterburning chamber when the plug 29 moves forwardly. Fuel discharged from the nozzles 45' is ignited in the high temperature gas stream and the resultant flame forms behind the fiame-holders 60. It is to be particularly observedthat during the after-burning operations the plug 21) is retracted-forwardly to be almost entirely housed within the supporting tube 19 and to,be entirely forward ofthe after-burning flame and its high temperature. Thus the needle or plug 20 and the parts associated therewith are not subjected to the high after-burning tempera tures. In fact, there need be no elements, with the exception of. the nozzle 18, and fiame-holderstit) directly exposed to the high temperatures in the region of the after burning flame.

Having described-only a typical form of'the invention, Ldo not Wishto belimited to the specificdetails herein set forth, butwish-i to reservetomyself any variations 8 or modifications that may appear to those skilled in the art or fall within the scope of thefollowing claims.

I. Iii-combination; apipe for discharging astream of gases and air, a nozzle at the aft end of the pipe for discharging the stream in the form of a propulsive jet, a member movable axially in the pipe between a first position where it extends into the nozzle to reduce the cross sectional area of the same and a second position spaced forwardly from the nozzle, means for moving the member, movable fuel injecting means movable between a retracted position to a position projecting into the pipe, and means actuated upon movement of said member to said second position for moving the fuel injecting means to said projecting position.

2. In combination; a pipe for discharging a stream of gases and air, a nozzle at the aft endof the pipe for dischargingthe stream in the formof a propulsive jet, a member movable axially in the pipe between a first position whereit extends into the nozzle to reduce the crosssectional areaof the same and a second position spacedforwardly from the nozzle, means for moving the member, fuel injecting means movable between a retracted position toa position projecting into the pipe, means actuated upon movement of said member to said second position for moving the fuel injecting means from its retracted position to said projecting position, a fiameholder on themernbermovablefrom a retracted position to-a posit-ion projecting intosaid stream, and means actuated upon movement of said member to said second position for movingthe flame-holder to the projecting position.

3. Afterburning apparatus for use with a turbo engine having a compressor and discharging a stream of combustiongases'andaircomprising a tail pipe receiving said stream, a' nozzle at'the aftend of the pipe for discharging the stream in the form of a propulsive jet, a tube spaced within the forward portion ofthe pipe, a plug movable between a; first position where it extends into the nozzle and asecond position where its major portion is protected within the tube, means actuated by air pressure from the compressor for moving the'plug, means for introducing fuel into the pipe, a movable flame-holder on the plug, and means actuated upon movement of the plug from saidfirst position, to said second position for moving the flame-holder from a contracted position against the plug to anextended position where itprojects-into thestream aftof the fuel introducing means;

4. Afterburningapparatus for use with a turbo engine having a compressor and discharging a stream of combustion gases-and'air comprising a tailpipe receiving said stream, a nozzle at the aftend of the pipe for discharging the stream in the form of a' propulsive jet, a tube spaced within the-forward portion of the pipe, a plug movable between a first position Where it extends into the nozzle and'-a=secondposition where its majorportion is protected within-.thetube, meansactuated by. air pressure from the compressor for moving the plug, means for introducing fuelinto the pipe, including fuel nozzlesmovable between retracted: positions and: positions where they project into the stream, means actuated upon movement; of the plug from saidfirstposition tosaid second position for moving the fuel nozzlesstoithe projecting positions, a movable flame-holder on the'plug, and means actuated upon movement of'the plug from said first position to said second positionfor moving the flame-holder from acontracted position-against: the plug to an extended position where it projects intolhe stream aft of the fuel introducing means.

5. In combination; a pipe for discharging a stream-of gases=and air,- anozzle at the aft end of the pipe for discharging-the-stream in the form of a propulsive jet,.a membermovable axially in the pipe between. avfirst po sitionwhereit extends-intothe nozzle to reducethe-cross sectional area of the same and a second position spaced forwardly from the nozzle, the member having a tapered cap on its aft end provided with slots, means for moving the member between said positions, flame-holders pivoted to the cap to be movable between retracted positions in said slots and active positions projecting from said cap, and means operated upon movement of the member to said second position for moving the flameholders to said active positions and for moving the flameholders to said retracted positions upon movement of said member to said first position.

6. Afterburning apparatus for use with a turbo engine having a compressor and discharging a stream of combustion gases and air comprising a tail pipe receiving said stream, a nozzle at the aft end of the pipe for discharging the stream in the form of a propulsive jet, a tube spaced within the forward portion of the pipe, a plug movable between a first position where it extends into the nozzle and a second position where its major portion is protected within the tube, cylinder and piston means actuated by air pressure from the compressor for moving the plug, flame-holders arranged on the aft end of the plug for movement between retracted and projected positions, means associated with the cylinder and piston means for retracting the flame-holders when the plug is moved to said first position and for projecting the flame-holders when the plug is moved to said second position, and means for injecting fuel into the tail pipe.

7. Afterburning apparatus for use with a turbo engine having a compressor and discharging a stream of combustion gases and air comprising a tail pipe receiving said stream, a nozzle at the aft end of the pipe for discharging the stream in the form of a propulsive jet, a tube spaced within the forward portion of the pipe, a plug movable between a first position where it extends into the nozzle and a second position where its major portion is protected within the tube, means actuated by air pressure from the compressor for moving the plug, means for introducing fuel into the pipe, a movable flame-holder on the plug, means for circulating cooling air through said tube, and means actuated upon movement of the plug from said first position to said second position for moving the flame-holder from a contracted position against the plug to an extended position where it projects into the stream aft of the fuel introducing means.

8. In combination; a pipe for discharging a stream of gases and air, a nozzle at the aft end of the pipe for discharging the stream in the form of a propulsive jet, a member movable axially in the pipe between a first position where it extends into the nozzle to reduce the cross sectional area of the same and a second position spaced forwardly from the nozzle, the member having a tapered cap on its aft end provided with slots, means for moving the member between said positions, flame-holders pivoted to the cap to be movable between retracted positions in said slots and active positions projecting from said cap, means for circulating cooling air through the member to discharge from said slots, and means operated upon movement of the member to said second position for moving the flame-holders to said active positions and for moving the flame-holders to said retracted positions upon movement of said member to said first position.

9. Afterburning apparatus for use with a turbo engine having a compressor and discharging a stream of gases and air comprising a pipe receiving said streams, a propulsive nozzle on the aft end of the pipe, a tube spaced within the forward portion of the pipe, struts supporting the aft end of the tube in the pipe, a plug member movable from a retracted position where its major portion is received in the tube and a projected position where it extends into the nozzle, cylinder and piston means for moving the member, flame-holders pivoted on the aft end of the member to move between retracted positions substantially flush with the surface of the member and projected positions where they'project into the stream, means connected with the cylinder and piston means for moving the flame-holders to the retracted positions when the member is moved to the projected position and for moving the flame-holders to the projected positions where the member is moved to the retracted position, fuel nozzles movably supported on the struts, and means for moving the fuel nozzles from retracted positions substantially flush with the struts to positions projecting from the struts upon movement of the member to said retracted position.

10. Afterburning apparatus for use witha turbo engine having a compressor and discharging a stream of gases and air comprising a pipe receiving said streams, a propulsive nozzle on the aft end of the pipe, a tube spaced within the forward portion of the pipe, struts supporting the aft end of the tube in the pipe, a plug member movable from a retracted position where its major portion is received in the tube and a projected position where it extends into the nozzle, cylinder and piston means for moving the member, flame-holders pivoted on the aft end of the member to move between retracted positions substantially flush with the surface of the member and projected positions where they project into the stream, means connected with the cylinder and piston means for moving the flame-holders to the retracted positions when the member is moved to the projected position and for moving the flame-holders to the projected positions when the member is moved to the retracted position, fuel nozzles movably supported on the struts, and means for moving the fuel nozzles from retracted positions substantially flush with the struts to positions projecting from the struts upon movement of the member to said retracted position, the struts having grooves for receiving the fuel nozzles when in the retracted positions.

11. Afterburning apparatus for use with a turbo engine having a compressor and discharging a stream of gases and air comprising a pipe receiving said stream, a propulsive nozzle on the aft end of the pipe, a tube spaced within the forward portion of the pipe, struts supporting the aft end of the tube in the pipe, a plug member movable from a retracted position where its major portion is received in the tube and a projected position where it extends into the nozzle, cylinder and piston means for moving the member, means for conducting air from said compressor to the cylinder and piston means to actuate the same, flame-holders pivoted on the aft end of the member to move between retracted positions substantially flush with the surface of the member and projected positions where they project into the stream, means connected with the cylinder and piston means for moving the flameholders to the retracted positions when the member is moved to the projected position and for moving the flameholders to the projected positions when the member is moved to the retracted position, fuel nozzles movably supported on the struts, and means for moving the fuel nozzles from retracted positions substantially flush with the struts to positions projecting from the struts upon movement of the member to said retracted position.

12. Afterburning means for use in a tube having a discharge nozzle comprising a plug movable into and out of the nozzle, means for moving the plug, fuel injecting means movable between a retracted position and an 0perative position in the tube, and means actuated upon movement of the plug for moving the injecting means to the retracted position when the plug is moved into the nozzle and to the operative position when the plug is moved out of the nozzle, and means for moving the plug.

( nces on fol o p References Cited in the; file of this'patent U ITED STATES ATEN Bradbury June 18, 19.46 Bobier, Jr. Feb. 28, 1950 Redding May 23, 1950 Schmitt U-- Scpt. 5, 1950 Iohnstone et a1. Aug, 28, 1951 12 Schrasel Oct. '2, 1951 Hildestad Oct. 23, 1951 Imbert Mar. 18, 1952 Laucher -May 12, 1953 FOREIGN PATENTS France Ian. 20, 1947