US2978868A

US2978868A - Concentric combustion system with cooled dividing partition

Info

Publication number: US2978868A
Application number: US861075A
Authority: US
Inventors: Samuel R Puffer
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1959-12-21
Filing date: 1959-12-21
Publication date: 1961-04-11
Anticipated expiration: 1978-04-11

Description

April 11, 1961 s. R. PUFFER 2,978,868

CONCENTRIC- COMBUSTION SYSTEM WITH COOLED DIVIDING PARTITION Filed Dec. 21, 1959 INVENTOR. 5.444051 E PflFF-E United States Patent CONCENTRIC COMBUSTION SYSTEM WITH COOLED DIVIDING PARTITION Samuel R. Puffer, Hartland, Vt., assignor to General Electric Company, a corporation of New York Filed Dec. 21, 1959, Ser. No. 861,075

7 Claims. (CI. 60-356) This invention relates to concentric combustion systems of the kind in which a central combustion passage is surrounded by an annular supplementary combustion passage, these passages being separated by an annular dividing partition. Systems of this kind find their principal application in those jet propulsion engines of the bypass or ducted fan type in which afterburners are provided in both a main propulsion conduit and a bypass conduit.

A principal problem in such a system is the cooling of the annular dividing partition, which is subjected to high temperatures of combustion both internally and externally. It is an object of my invention to provide a concentric combustion system having improved means for cooling a dividing partition thereof. It is a further object of my invention to provide a concentric combustion system having an improved dividing partition, which is cooled by vaporization of fuel and which aflords improved means for injection of fuel into concentric combustion passages of the system.

Further objects and advantages of my invention will become apparent as the following description proceeds.

Briefly stated, in accordance with one aspect of my invention, I provide a concentric combustiousystem withan annular dividing partition having inner and outer radially spaced walls to enclose an annular fuel-vaporizing chamber, and form a plurality of fuel injection orifices spaced along both the inner and outer walls of the dividing partition. I further provide means for supplying streams of fuel into the fuel-vaporizing chamber. By these means, fuel is vaporized in the chamber for cooling of the internal wall surfaces. A mixture of vaporized fuel is injected through the orifices in both walls to institute combustion in the central and supplementary combustion passages, sweeping the outer surfaces of the'walls toprovide further cooling of the dividing partition. The partition is thus cooled internally and externally, and

protected from the high temperatures of combustion in the concentric combustion passages; also, vaporized fuel is injected into the combustion passages in a series of streams spaced along the partition, so that combustion occurs with evenly increasing intensity as it proceeds downstream.

In a preferred embodiment of my invention, 1 divide the fuel-vaporizing chamber into concentric annular portions by means of an annular baflle radially spaced between the walls of the partition. By these means, pressure differentials existing between the concentric combustion passages are prevented from interfering with the desired division of fuel flow between them, or starving one of the passages. However, the use of the annular bafile is not essential to the practice of my invention.

In an alternative embodiment of my invention, I form openings between upstream ends of the walls to admit streams of diluent fluid into the fuel-vaporizing chamber, to assist in complete evaporation of the fuel streams.

: The diluent fluid is drawn from that one of the central or supplementary combustion passages in which the higher pressure exists, so that reverse flow is avoided. However, the temperature of the diluent fluid must not be sufliciently high to produce ignition within the fuelvaporizing chamber.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which I regard as my invention, it is believed that the invention will be better understood from the following detailed description thereof, taken in connection with the accompanying drawing, in which:

Fig. l is an elevation view, partially in section, of one embodiment ofmy improved combustion system as applied to a jet propulsion engine;

Fig. 2 is a pictorial view of a fragmentary portion of the combustion system; n

Fig. 3 is a pictorial view of a fragmentary portion of a modified embodiment of the combustion system; and

Fig. 4 is an elevation, partially in section, of a further modification of the combustion system as applied to a jet propulsion engine.

Referring to Fig. 1, my improved concentric combustion system is shown in operative relation to a conventional' bypass jet propulsion engine generally designated l. The engine is of the bypass or ducted fan type, illustrating one of the uses to which the system can be adapted. Engine 1 includes concentric annular main and bypass fluid conduits 2 and 3, respectively, which are formed by concentric annular casings 5 and 6. Each of the conduits receives working fluid, ordinarily atmospheric air, in streams flowing in the direction shown by the arrows. A compressor (not shown) is rotatably mounted upstream in conduit 2 for compression of the working fluid, and is drivingly connected to a turbine 7 by means of a shaft 8. A fuel combustor 9 of well-known type injects and ignites fuel in the working fluid stream, from which energy is extracted by turbine 7 to drive the compressor. In the bypass engine shown, an additional turbine 10 receives working fluid exhausted from turbine 7, extracting further energy therefrom to drive a fan 11 in conduit 3. As shown, the blades'of fan 11 are directly mounted upon a shroud ring 12 attached to the buckets of turbine 10. Fan 11 operates in a well known manner to accelerate the flow of working fluid in conduit 3, for augmentation of the thrust produced by working fluid exhausted from conduit 2.

An annular exhaust collector duct 13 of substantial axial length is provided to accommodate reheat or afterburning combustion in the working fluid streams exhausted from engine 1. A flange 14 is formed on an upstream end of duct 13, and is secured to a mating flange 15 of casing 6 by means of a circumferential row of fasteners 16. At its downstream end, duct 13 is formed with an exhaust nozzle 17 for discharge of the working fluid streams to generate propulsive thrust.

Duct 13 also serves to support turbine 10 and fan 11 rotatably therein. For this and other purposes, a circumferential row of hollow struts 18 are welded or otherwise suitably secured in the duct, and secured at their inner extremities to an exhaust bullet 19. Turbine 10 is rotatably mounted in suitable bearings (not shown) in the exhaust bullet. The structure thus far described is conventional, and no further detailed description is believed necessary.

In order to carry out my invention in a preferred embodiment thereof, I provide an annular dividing partition generally designated .24, to divide the fluid streams exhausted from ducts 2 and 3 into central and supplementary combustion passages 25 and 26, respectively. Rather than being a single wall member, partition 24 comprises inner and outer radially spaced annular walls 27 and 28, respectively, enclosing an annular fuel-vapor izing chamber 29. The walls are joined at a common 3 downstream end 30, and upstream ends 31 and 32 thereof. In order to support the partition concentrically Within duct 13, upstream ends 31 and 32 are welded .or otherwise suitably secured to struts v18. The walls are extended upstream in close proximity to shroud ring 12, to divide the fluid streams received from conduits 2 and 3.

Fuel is injected into chamber 29 by means of suitable nozzles 34, which are supplied with fuel through one or more tubes 35 passing through one or more of hollow struts 18 to the exterior of duct 13. Any desired number of nozzles 34 may be spaced about chamber 29, to establish a desired degree of uniformity of fuel distribution. Fuel injected into the chamber vaporizes by abso'rbing heat from walls 27 and 28, and this process of evaporation cools the interior surfaces of the walls.

As shown in Figs. 1 and 2, chamber 29 is divided into concentric segmental portions by means of an annular baflie element 36, in order to prevent differences in pressure in passages 26 and 27 from causing an imbalance in the desired division of fuel supply between them, with a resulting starvation" of one passage. The chamber is also divided into arcuate segmental portions by means of radial baflle elements 37 and 38. At least one fuel nozzle 34 is provided for each division of the chamber. 7

In order to inject vaporized fuel evenly into passages 25 and 26, and to cool the exterior surfaces of walls 27 and 28, I form the walls with a plurality of axiallyspaced rows of circumferentially-extending louvres 39, having upstream surfaces 40 which are inclined downstream from a radial inclination, and downstream surfaces 41 extending generally in radial planes. A plurality of fuel orifices 42 are circumferentially spaced about surfaces 41, and serve to inject vaporized fuel generally parallel to walls 27 and 28, into passages 25 and 26, at spaced intervals along the passages. As shown by the direction of the arrows in Fig. l, vaporized fuel injected into the passages sweeps over and cools the external surfaces of the walls, and is deflected toward the centers of the passages by successive downstream surfaces 40, to promote effective mixing with working fluid flowing therein. The working fluid stream in central passage 25 comprises hot combustion products, which automatically ignite the fuel injected therein. In supplementary passage 26, combustion of fuel is initiated by means of one or more circumferentially-spaced conventional ignitors 43, and one or more pilot fuel injection nozzles 44.

A modified form of partition 48 is shown in Fig. 3, having circumferential rows of individual tetrahedral louvres 49 struck up from the surfaces of walls 27' and 28'. Louvres 49 are formed with inclined upstream surfaces 50 and generally radially-extending downstream surfaces 51, the latter being provided with fuel injection orifices 52. The partition functions in essentially the same manner as that of Figs. land 2. The baflle elements shown are similar, and are similarly numbered, with prime superscripts.

Referring to Fig. 4, a modification in which diluent fluid is drawn from the by-pass fluid conduit is shown. Parts similar to those of the embodiment of Fig. l are similarly numbered, with double prime superscripts. In this,modification, end 31" of inner wall 27" of partition 24" is extended upstream in close proximity to shroud ring 12", and end 32" of outer wall 28" is terminated in the region of struts 18". An opening 56 is thus formed to admit working fluid to chamber 29" from the bypass conduit. This arrangement provides diluent air to aid in fuel evaporation and may be utilized to prevent carbonization of the nozzles 34, or in applications in which complete evaporation cannot be achieved within chamber 29" through absorption of heat by the fuel stream from walls 27" and 28" alone. The pressure in the bypass fluid conduit must be higher than that 4 I in the main fluid conduit, in order to insure flow of vaporized fuel ms both conduits. In the event that the pressure in the main conduit is .the higher, diluent fluid may be drawn therefrom by terminating end 31" of wall 27'. in the region of struts l8", and extending wall 28" upstream. However, the latter arrangement should not be used in applications for which the main fluid stream is at a fuel-igniting temperature, because of the danger of ignition in chamber 29". Therefore, an additional ignitor should be provided within passage 25" in applications suitable for the latter arrangement. Alternatively, compressed air may be bled from themgine compressor (not shown) and supplied to chamber 29" through suitable conduit means (not shown) for the purpose of preventing carbonization of fuel nozzles 34. I

It will be apparent from the foregoing description that I have provided an improved concentric combustion system which utilizes the evaporation of fuel in a new manner to cool a hollow dividing partition internally and externally. My improved system extends the useful life of the partition, situated between high temperature combustion passages, by providing effective cooling of all surfaces of the partition.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention,

What I claim and desire to secure by Letters Patent of the United States is:

1. In a ducted fan type turbine engine including an afterburner, a concentric fuel combustion system comprising, in combination; a cylindrical duct, an annular partition concentrically spaced within said duct to divide and maintain the separation of the fluid exhausted by said turbine from the working fluidexhausted by said fan, said partition including a pair of concentric radially spaced-apart cylindrical walls enclosing an annular fuelvaporizing chamber, and means for supplying streams of fuel to said chamber, said walls each being formed with a plurality of spaced-apart orifices for injection of vaporized fuel into said passages from said chamber, such that said walls are cooled internally by vaporization of fuel and cooled externally by vaporized fuel injected into said passages through said orifices.

2. A concentric fuel combustion system as recited in claim 1, together with baflie elements mounted on said walls within said "chamber to divide said chamber into segmental portions each communicating with the orifices of only one of said walls.

3. A concentric fuel combustion system as recited in claim 1, said walls further forming an opening at an upstream end of said chamber for receiving said fluid exhausted by said turbine.

4. In a ducted fan type turbine engine including an afterburner, a concentric fuel combustion system comprising, in combination; a cylindrical duct, an annular partition concentrically spaced within said duct to divide and maintain the separation of the fluid'exhausted by said turbine from the working fluid exhausted by said fan, said partition including a pair of concentric radially spaced-apart annular walls enclosing an annular fuelvaporizing chamber, and means for injecting streams of fuel into said chamber for vaporization by said fluid to cool said walls in said chamber, said walls each being formed with a plurality of spaced-apart orificesfor injection of vaporized fuel into said passages from said chamber for cooling said walls in said passages and. for combustion therein. 1

5. A concentric fuel combustion system adapted to receiveconcentric streams of working fluid from a jetpropulsion engine of the kind having concentric main and bypass fluid conduits, said combustion system comprising, in combination; a cylindrical duct, an annular partition concentrically spaced within said duct to form a central combustion passage and a divided supplementary combustion passage concentrically within said duct, said passages adapted to receive the streams of working fluid from the main and bypass conduits, respectively, said partition including a pair of concentric radially spacedapart cylindrical walls enclosing an annular fuel-vaporizing chamber, means for injecting streams of fuel into said chamber for vaporization therein to cool said walls in said chamber, said walls each being formed with a plurality of axially spaced-apart circumferential rows of orifices for injection of vaporized fuel into said passages from said chamber for cooling said walls in said passages and for combustion therein, and fuel ignition means in said supplementary combustion passage.

6. A concentric fuel combustion system as recited in claim 4, together with baflie elements mounted on said 6 walls within said chamber to divide said chamber intosegmented portions each communicating with the orifices of only one of said walls.

7. A concentric fuel combustion system as recited in.

claim 5, said walls further forming an opening at an upstream end of said chamber for receiving a stream of fluid from the engine for vaporization of the streams of fuel in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS