US2715813A - Fuel injector and flame holder - Google Patents

Description

g- 23, 1955 F. T. HOLMES ET AL 2,715,813

FUEL INJECTOR AND FLAME HOLDER 3 Sheets-Sheet 1 Filed April 14, 1952 INVENTORS FREDER/ 7T LMES' ROB N E. 5 BY M YZW A TTORIVEYS 23, 1955 F. T. HOLMES ET AL FUEL INJECTOR AND FLAME HOLDER 5 Sheets-Sheet 2 Filed April 14, 1952 IN VEN TORJ' S n H M N L H 0H m MW m l 1 03 EN ww/A m 0 Y B 1955 F. HOLMES ET AL 2,715,813

FUEL INJECTOR AND FLAME HOLDER Filed April 14, 1952 3 Sheets-Sheet 3 IN VEN TORS FREDERICK 7. HOLMES ROB/IV E TABER 1 Q/ZWW ATTORNEYS Unite FUEL INJECTOR AND FLAME HOLDER Application April 14, 1952, Serial No. 282,144

11 Claims. (Cl. 60-356) This invention relates generally to aerial missiles. More particularly, the invention relates to burner assemblies for controlling the combustion of air fuel mixtures in rarnjet engines.

In the operation of ramjet engines, such as used with certain types of aerial missiles, it has been found desirable to have a constant application of driving energy or thrust in order that optimum range and accuracy can be obtained. It is, therefore, desirable that the driving energy be brought about by a smoothly-burning, constantly-ignited air fuel mixture which produces a substantially constant or at least a smoothly varying application of driving energy or thrust.

One of the major disadvantages heretofore found in the operation of ramjet engines has been a condition of improper burning commonly known as rough burning. Burning of this type is unsteady, irregular and variable. This type of undesirable burning results in bursts or rapidly varying applications of energy so that improper as well as inadequate thrust forces occur.

It is believed that the rough burning referred to, strangely enough, results from a smooth flow of the fuel mixture. When such rough burning occurs, the flame is not uniformly propagated and large quantities of uncombusted fuel mixture accumulate and then burn with explosive violence. This violent burning may result not only in an uneven application of driving or thrust force, but also, in some instances, it may damage the aerial missile itself.

Experimental investigations have indicated that smooth burning can best be obtained by providing turbulent flow of the air-fuel mixture at the point where ignition occurs. This type of flow gives a thorough mixing of the air and fuel, and thus effects rapid propagation of the flame.

Accordingly, it is one of the objects of this invention States Patent to provide a highly eflicient burner assembly for use in a ramjet engine.

Another feature of the invention is to provide an improved device for directing a flame into a combustible fuel mixture in a 'ramjet engine.

Still another object of the invention is to provide an igniter arrangement for constant ignition of fuel mixtures in ramjet engines.

To provide an injector arrangement for maintaining a fuel mixture flow adjacent an igniter arrangement, is also another object of the invention.

A further object of the invention is to provide an igniter arrangement, including a shield, for maintaining low turbulence flow of the air fuel mixture adjacent an igniter flame.

2,715,813 Patented Aug. 23, 1955 2 a ramjet engine, embodying the improved burner assembly; F Figl. 2 is an enlarged cross-section on the line 2-2 of Fig. 3 is an axial-section on the line 3-3 of Fig. 2;

Fig. 4 is an axial-section on the line 4-4 of Fig. .2 and Fig. 5 is a cross-section on the line 55 of Fig. 3.

In the design of ramjet engines and the like, it is necessary to determine the best relative positions of the pilot flames for the fuel used, the main fuel nozzle arrangement, and the fuel distributing vanes in order to create burning conditions which avoid the formation of large volumes of unburned fuel mixtures. Unburned fuel has a tendency to burn backward explosively when ignited,

and this results in uneven burning and possible damage or destruction of portions of ramjet engines.

In order to overcome these disadvantages and also to effect smooth burning in the combustor of a ramjet engine, igniting or pilot flames have been provided which burn at a constant rate. These igniting or pilot flames are placed in a comparatively quiet area, but in close proximity to the intermingling fuel and air. structurally, the smooth burning is accomplished by the use of a novel flame holder, which is preferably in the form of a flared baflle arrangement. This baffle arrangement includes baffle wings or rake fingers, which cause the .air and fuel streams to mingle or uniformly mix, and, in addition, provide surfaces for directing the igniting flames into the fuel mixture.

The preferred embodiment of the invention is best illustrated in the drawing of Fig. l, which shows a ramjet engine, generally designated by reference numeral 11). This ramjet engine is usually a part of an aerial missile, and it has its body in the form of an elongated tubular duct which is open at both ends A and 10B. In the forward portion of the ramje't engine, there is located a diffuser usually of the 'frusto-conical type. This diffuser, which is commonly referred to as a ram channel, such as 12, delivers air in a substantially constant stream, as indicated by arrow 13, into a combustion chamber or combustor 14.

' This combustor 14 is located in the tailpipe section 14A of the ramjet engine. In the forward portion of the tailpipe section 14A, the air and burner fuel are 1 end of the combustor 14 in tailpipe section 14A.

1 body 15 is of ogival contour.

Other objects and many of the attendant advantages Fig. l is a fragmentary view partially in elevation of I This burner assembly 35 includes a substantially cylindrical body 15 which is anchored to the wall 11 of the ratnjet engine by means of four strut members 16, 17, 1'8 and 19. The forward or upstream end 15A of the The rearward or downstream end 158 of body 15 is constructed with a substantially flat burner face 20, as shown best in Fig. 4. This burner face is located at the forward or upstream end of the combustion chamber or tailpipe section .14.

As shown in Fig. 3, body 15 is provided with an axial bore 21 for the reception of a fuel injector 22. This fuel injector 22 is used for distributing fuel into the combustion chamber 14. Injector 22 fits snugly into bore 21. This injector 22 is provided with an axial fuel passageway or conduit 23. The conduit 23 communicates with another passageway, such as a pipe 24, located in the strut member 16 through inlet passages 24A and 2413 in the injector 22 and body 15, respectively, for supplying liquid fuel to the burner, such as kerosene or heptane, from a tank 29 located between inner wall 11 and outer wall 11A of the ramjet engine 10. This is best illustrated in Figs. 1 and 3. The outer or downstream end 22A of the injector 22 terminates substantially flush with the burner face 20. Injector 22 is counter-bored in end portion 22A to form a bore 228 so as to provide an air jacket 27 between a nozzle and the burner face 20. The surface of bore 22B is internally threaded, as shown at 22C. Nozzle 25 is connected to the injector 22 by means of a nipple 28 which is screwed into the internally threaded portion 22C of bore 22B. This is necessary so that nozzle 25 will be in communication with fuel conduit 23. Various lengths of nipples may be utilized for adjusting the position of the nozzle 25 with respect to the burner face 20 for different types or amounts of fuel or for various burner conditions.

The burner fuel, such as kerosene or heptane, from tank 29 is delivered through passageways 24, 24A, 24B, and 23 to nozzle 25. This nozzle 25, in turn, injects the fuel into combustion chamber 14 usually in a conical spray, although other types of sprays can be utilized.

The injected fuel is ignited by a number of pilot flames 30 arranged in a spaced annular series about the injector 22.

These pilot flames 30 are preferably of the self-sustaining type, that is, the flames 30 are fed by a mixture composed of a plurality of constituents. This mixture, when once ignited, will continue to burn, that is, it is self-sustaining. For example, such mixtures as (1) acetylene and oxygen, (2) hydrogen and air, and (3) chlorine and certain hydrocarbons, where one constitutent is the pilot fuel and the other a supporting medium, have been found to be highly satisfactory.

In order to have effective ignition flames, a plurality of manifolds, such as 31 and 32, are formed in the body 15 adjacent the burner face 20, as shown in Figs. 3 and 4. These manifolds or cavities 31 and 32 are preferably formed by machining annular cavities or chambers in the body 15. These cavities are shown as concentrically arranged, with the innermost cavity 31 being formed adjacent the central or axial bore 21 for injector 22, while manifold cavity 32 is adjacent the exterior portion of the body 15.

More specifically, the inner manifold cavity 31 is in the form of an annular groove, with wall surfaces 33A, 33B, and 33C of fuel injector 22 and the exterior surface of the fuel injector 22. The outer manifold cavity 32 is formed by an annular groove in body 15, the outer wall of which is constituted by a sleeve 36 and wall surfaces 34A, 34B, and 34C of fuel injector 22. Sleeve 36 is applied over a cut-away portion 37 of body 15, and is secured in any desired manner, such as welding, so as to become substantially integral therewith.

Preferably, various constituents, such as a pilot fuel and a supporting medium, as pointed out above, are introduced into the manifold cavities 31 and 32, respectively, as just described through passageways or pipes 38 and 39, as best shown in Fig. 4, in struts 17 and 19. These passageways are connected to sources, such as 40, which contain either the pilot fuel or the supporting medium. Passageways or pipes 38 and 39 are connected to suitable entrances 41 and 42 in the side of the body 15. Between entrances 41 and 42 and manifold cavities 31 and 32 there are located suitable passageways 43 and 44, such as bores within the body 15. For simplicity, only two manifolds 31 and 32 are shown but obviously a larger number may be employed if it is desired to use more than two pilot fuel constituents.

Referring again to Fig. 3, a plurality of jet forming passageways 45 and 46, hereinafter to be called orifices, are provided between each of the manifolds 31 and 32, and the burner face 20 so that the constituents within the manifold cavities 31 and 32 can flow through orifices and 46 to the burner face 20.

For properly utilizing the various constituents for sustaining a flame, the orifices 45 and 46 are arranged in groups, herein shown as pairs, in which the orifices extending from the several manifolds 31 and 32 reach the burner face 20 in an arrangement so that the constituents flowing from the several manifolds 31 and 32 are commingled into a single stream. In the paired orifices shown, each pair of orifices 45 and 46 are inclined so that they converge at the burner face 20, and the streams of constituents flowing through the separate manifolds 31 and 32 impinge to provide a single jet.

In order to maintain an optimum burning condition in the vicinity of the pilot flames 30, a shield 48 is provided around the burner face and extending axially past the face 20 to provide a zone of comparative quiet where the pilot flames 30 will be substantially undisturbed by the flow of air through the ram channel or diffuser 12 or by the burner fuel flow from the injector 22. The shield 48 is preferably constructed so as to have an annular tubular body portion 50 surrounding the body 15, and extending past the burner face 20 thereof so that the shield 48, aids in controlling the flow of air to the burner face 20. A different length of shield 48 may be desired for different operating conditions. The tubular body portion 50 is shown in telescoping relation to the exterior surface of the body 15, and is secured thereto by suitable means such as set screws 51 which may engage spaced sockets 52 in the lateral surface of the burner body 15.

To assure a thorough mixing of burner fuel and air adjacent the forward or upstream region of the combustion chamber 14, the shield 48 is further provided with rake fingers 55, formed on the end of the tubular body portion 50. These rake fingers 55 produce a turbulent flow of the air being delivered through the ram channel 12, and, consequently, a rapid intermixing or commingling of the main burner fuel spray 26 and the air delivered by the ram channel 12. The rake fingers 55 are in the form of segments of a conical shell. These fingers 55 also serve as flame holders in that they provide sheltered surfaces behind which the ignition flames 39 can linger, so that the flame is much more readily communicated to or propagated into the fuel mixture adjacent the forward end of the combustion chamber 14. The maintenance of the constant igniter flames 30 adjacent the commingling surface of the air and fuel, and the utilization of the rake fingers 55 to carry the flame into proximity with the air fuel mixture, produces substantially constant combustion and therefore substantially constant delivery of propulsion energy to the ramjet device 10.

To produce optimum shielding of the pilot flames 30 and to facilitate the communication of flame behind the flame holding rake fingers 55, it is sometimes desirable to provide groups of the orifices 45 and 46, corresponding in number to the number of rake fingers 55, and to center each of the groups of orifices on the center line of its corresponding rake finger 55.

Recapitulating, an aerial missile including a ramjet engine 10 and a launching carriage means such as rockets (not shown) or the like, is launched from a launching platform. After the launching carriage means has substantially spent its power the ramjet engine then furnishes the necessary thrust to move the aerial missile along its trajectory.

The entering air stream flows through the ram channel or diffuser 12, Where velocity energy is converted to pressure energy, and it is then mixed with the burner fuel injected therein by nozzle 25. The airstream and the injected burner fuel are mixed together by means of the rake fingers 55. The air-fuel mixture is then ignited by flames 30 and burned in the combustion chamber 14. The products of combustion generated, i. e., the liberated gases, are then expanded through an exit nozzle arrangement located in the furthermost portion of the tailpipe section 14A at a Y 5 velocity considerably higher than the velocity of the entering air stream to furnish the thrust forces required to propet the aerial missile along its trajectory.

Obviously, many modifications and variations of the present invention are possible in view of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be prae tieed otherwise than as specifically described.

claimed is:

'L Inan aerial missile having a body in the form of an elongated'tlibulai duct, a'dirruser and a combustor iii said duct, and a burner assembly mounted at the entrance of said combustor, said burner assembly, comprising, a body having a burner face, at least two manifolds in said body, a pilot fuel in one of said manifolds and a supporting medium in the other, paired orifices extending between said manifolds and said face to provide a plurality of pilot burners due to the commingling of said pilot fuel and supporting medium, said body having a passage for delivery of burner fuel to said combustor.

2. In an aerial missile having a ramjet engine with a ram channel for supplying air to a combustion chamber; in combination with a burner assembly mounted at the exit of said ram channel, said burner assembly, comprising, a body having a burner face at its downstream end, means for distributing burner fuel into said combustion chamber, and pilot flame means for maintaining a plurality of pilot flames around said distribution means and at said burner face, said pilot flame means being constituted by a plurality of manifolds located in the body of the burner assembly, at least one of said manifolds containing a pilot fuel and another a supporting medium, and a plurality of orifices between each of said manifolds and said burner face, said orifices being arranged in a plurality of groups, each group including an orifice from each manifold.

3. In an aerial missile having a ramjet engine with a ram channel for supplying air to a combustion chamber; in combination with a burner assembly mountedat the exit of said ram channel, said burner assembly, comprising, a body having a burner face at its downstream end, means for distributing burner fuel into said combustion chamber, pilot flame means for maintaining a plurality of pilot flames around said distribution means and at said burner face, said pilot flame means being constituted by 1- a plurality of concentric and annular manifolds located in the body of said burner assembly, at least one of said manifolds containing a pilot fuel and another a supporting medium, a plurality of orifices between each of said manifolds and said burner face, said orifices being arranged in a plurality of groups, each group including an orifice from each manifold, and a plurality of rake fingers secured to said body and extending in an outwardly flaring relation to said burner face.

4. A burner arrangement, comprising, a body having a i 7 central passageway extending from one end thereof along a portion of its axis, manifolds arranged concentrically and annularly about said passageway and having paired orifices in the walls thereof adjacent that end of said body having the opening therein, at least one of said manifolds arranged to contain a pilot fuel and another a supporting medium, a separate passageway connected to each of said manifolds and to said central passageway, a fuel injection nozzle detachably mounted in the open end of said central passageway and a shield slidably mounted on said body for shielding said orifices.

5. The arrangement set forth in claim 4, wherein said shield comprises a frusto-conical skirt divided into a plurality of fingers which are aligned with said orifices.

6. In an aerial missile of the ramjet type having a ram channel delivering an air stream to a combustion chamber, a burner assembly mounted in said ram channel in the flow path of the air stream, the downstream end of said assembly constituting a burner face, said assembly having a plurality of concentric manifolds therein, pas- 6 sageways connected to said manifolds for delivering a pilot fuel to at least one of said manifolds and a supporting medium to another, said assembly having a plurality" burner face.

7. In an aerial missile of the ramjet type having a ram channel delivering an air stream to a combustion chamber, a burner assembly, comprising, pilot flame means mounted in said ram channel in the flow path of the air stream, the downstream end of the said pilot flame means constituting a burner face, said pilot flame means having a pair of concentric, annular manifolds therein, means connected to said manifolds for delivering at least a pilot fire! to one of said manifolds and a supporting medium to another, said pilot flame means having a plurality of paired orifices extending from said burner face to the respective manifolds, said orifices converging toward each other to provide impinging jets of said pilot fuel and said s;:pporting medium to form a ring of pilot flame when ignited, and shielding means surrounding said burner face and including a plurality of diverging rake fingers.

8. In an aerial missile of the ramjet type having a ram channel delivering air into a combustion chamber, a

urncr assembly, comprising, a body having a burner face defining the forward end of said combustion chamber, means defining manifolds in said body at least one of said manifolds arranged to contain a pilot fuel and another a supporting medium, there being a plurality of paired oriices extending between said manifolds and said burner face to provide a plurality of pilot flames, means for delivering a burner fuel stream adjacent said burner face, and shielding means adjacent said pilot flames.

9. A burner assembly comprising, a body having a burner face, said body having a plurality of concentric manifolds therein, at least one of said manifolds arranged to contain a pilot fuel and another a supporting medium, there being a plurality of orifices in each of said manifolds, said orifices being arranged in proximity to provide a plurality of commingling jets of said pilot fuel and supporting medium, noule means directing a fuel spray adjacent said pilot flames, and shielding means surrounding said body.

10. In an aerial missile of the ramjet type having a ram channel and a combustion chamber, a burner assembly located in said ram channel at the forward end of said combustion chamber, said assembly, comprising, a body secured substantially axially in said ram channel, said body having an axial passageway therein, means for sugpiying burner fuel through said passageway into said combustion chamber, a plurality of manifolds in saidbody, passageways for supplying a pilot fuel to at least one of said manifolds and a supporting medium to another, there being a plurality of outlet orifices in each oisaid manifolds, the orifices being arranged in a plurality of groups, each group includingan orifice from each, manifold, the orifices of a group being arranged so that said pilot fuel and supporting medium from the several manifolds are intermingled to sustain pilot flames, a shield about said pilot flames, and a plurality of outwardly flaring rake fingers extending from said shield in annular arrangement about said body.

11. In combination, with a ramjet type of aerial missile having a ram channel supplying a stream of air to a combustion chamber, a burner assembly, comprising, a substantially cylindrical body secured axially in said ram channel adjacent the upstream end of said combustion chamber, the downstream end of said body constituting a burner face, said body having an axial passage terminating at said burner face, means for delivering burner fuel through said axial passage, nozzle means connected to said axial passage in proximity to said burner face for delivering said burner fuel from said axial passage into said combustion chamber, a pair of manifolds around said axial passage, one of said manifolds containing a pilot fuel and the other a supporting medium, there being a plurality of pairs of pilot flame orifices in said burner face connected to said manifolds to provide streams of said pilot fuel and supporting medium therefor, shielding means around said body extending axially beyond said burner face to provide a shielded area adjacent said pilot orifices, and a plurality of rake fingers formed onsaid shield and extending in divergent frusto-conical relation to said burner face.

References Cited in the file of this patent UNITED STATES PATENTS 1,924,400 Forney Aug. 29, 1933 2,214,568 Thomas Sept. 10, 1940 2,439,554 Anderson Apr. 13, 1948 2,518,000 Goddard Aug. 8, 1950 2,547,936 Grow Apr. 19, 1951 2,618,928 Nathan Nov. 25, 1952

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