US2984979A - Vortex pilot flame source for ramjet engines - Google Patents

Description

May 23, 1961 E. R. BABCOCK ET AL 2,984,979

VORTEX PILOT FLAME SOURCE FOR RAMJET ENGINES 6 Sheets-Sheet 1 Filed March 27, 1951 INVENTORS. ELDON R. BABGOCK BY SEYMOUR D. ZWE/GORON Zidw ATTORNEY May 23, 1961 E. R. BABcocK ET AL 2,984,979

VORTEX PILOT FLAME SOURCE FOR RAMJET ENGINES Filed March 27, 1951 6 Sheets-Sheet 2 FIG 2 .I I a I I (o I N a Q l' b l I "3 INVENTOR. '1 ELDON R. BABG'OCK I BYSEYMOUI? QZWE/GORO/V ATTORNEY May 23, 1961 E. R. BABCOCK ETAL 2,934,979

VORTEX PILOT FLAME SOURCE F OR RAMJET ENGINES Filed March 27, 1951 s Sheets-Sheet s IN VEN TORS. EL DON R. BAB606K SEYMOUR D. ZWEIGORON ATTORNEY May 23, 1961 E. R. BABCOCK ET AL 2,984,979

VORTEX PILOT FLAME SOURCE FOR RAMJET ENGINES 6 Sheets-Sheet 4 Filed March 27, 1951 INVENTORS. ELDO/V R. BABCOCK SEYMOUR D. I'VE/60.90 /./(fl@fi4w- ATTORNEY May 23, 1961 Filed March 2'7, 1951 E. R. BABCOCK ET AL 2,984,979

VORTEX PILOT FLAME SOURCE FOR RAMJET ENGINES 6 Sheets-Sheet 5 INVENTORS. E'LOO/V R. EABCOCK SEYMOUR D. ZWEIGORO/V ATTORNEY May 23, 1961 E. R. BABCOCK ET AL 2,984,979

VORTEX PILOT FLAME SOURCE FOR RAMJET ENGINES Filed March 27, 1951 6 Sheets-Sheet 6 INVENTOR. ELDOIV R. BABCOC $EYMOUR D. ZWEIG 0N BY A TTORNE Y United States Patent VORTEX PILOT FLAlVIE SOURCE FOR RAMJET ENGINES Eldon R. Babcock, Midway, N.C., and Seymour D. Zweigoron, Chicago, Ill., assignors to the United States of America as represented by the Secretary ofthe Navy Filed Mar. 27, 1951, Ser. No. 217,814

2 Claims. (Cl. 60 39.82)

The present invention relates to a ramjet device and particularly to a pilot igniter for initiating combustion in a ramjet missile.

In the operation of ramjet devices such as missiles, the air received by the ram flows in a stream through the interior or Working passage of the ramjet and fuel is introduced and mixed with air to produce an air-fuel mixture stream which flows from a mixing area or chamber into a combustion area or chamber. It has been customary to initiate combustion of the air-fuel mixture by means of various kinds of igniter devices which have usually been placed in the air-fuel mixture stream in the area where the air-fuel flows from the mixing chamber into the combustion chamber. Considerable difliculty has heretofore been encountered in properly igniting and maintaining the ignition of the air-fuel mixture as it flows into the combustion chamber. For comparatively short flight intervals it has been customary to ignite the mixture by means of pyrotechnic flares, electric sparks or the like. Such systems of ignition have not been completely satisfactory and it is desirable to utilize a pilot igniter having a longer burning interval than is co'nveniently practical with flares, and particularly it is desirable to have a pilot igniter which is self-sustaining in operation, is comparatively immune to any reaction from the combustion chamber and which will continuously ignite the air-fuel mixture flowing into the combustion chamber.

The pilot igniter of the present invention secures substantially co'nstant, long life ignition by providing a tapering or frustro-conical shaped ignition channel in which a small quantity of fuel is burned under very favorable conditions as to stability and flame propagation. Air and fuel or an air-fuel mixture is introduced into the smaller end of the channel, either from an auxiliary source of igniter fuel or by bleeding a portion of the air-fuel mixture of the ramjet into the pilot igniter, after which the fuel mixture in the igniter channel is igited by any suitable means. Preferably the introduction of air or the air-fuel mixture is provided by intakes communicating with the main air or air-fuel stream flowing past the pilot igniter. The air and fuel or air-fuel mixture introduced into the pilot igniter is directed by a plurality of nozzles in a tangential direction so that the air-fuel mixture creates a vortex or cyclone effect within the igniter channel. The vortex or cyclone effect maintains the pilot combustion Within the pilot channel so that it is substantially impossible for it to be blown out because of any action in the combustion chamber. The pilot igniter is particularly simple, having no internal baflles but depending entirely upon the vortex or cyclone effect to cause mixing of the combusted and uncombusted fuel within the igniter channel and producing at the downstream end thereof a constant ignition flame commingling with the main air-fuel stream for propagating flame into the air-fuel mixture.

Accordingly, an object of the invention is to provide a simple long life igniter arrangement for a ramjet.

it is a further object of the invention to provide a self sustaining pilot igniter.

A further object of the invention is to provide a pilot igniter having no internal bafiies o'r moving parts.

Still another object of the invention is to produce a pilot igniter in which the flame is maintained by means of a vortex action within the igniter channel.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

Fig. 1 is an elevation of the vortex pilot in place in a ramjet device, portions of the pilot and the ramjet being broken away;

Fig. 2 is an axial section through the vortex pilot itself;

Fig. 3 is a section taken along the line 3-3 of Fig. 2 and showing the igniter arrangement at the working end of the vortex channel;

Fig. 4 is a section taken on the line 4-4 of Fig. 3, and illustrating the arrangement of one of the passages for producing the tangential flow of the air-fuel mixture;

Fig. 5 is a diagrammatic illustration of the vortex action within the pilot channel;

Fig. 6 is an elevation, partially in section, through a modified embodiment of the invention; and

Fig. 7 is an end view looking into the outlet end of the vortex pilot igniter of Fig. 6.

In the exemplary embodiment of the invention, the ramjet device 10 is provided with an air-fuel mixing chamber 11 from which the air-fuel mixture flows into a combustion chamber 12 where it is ignited by means of the pilot igniter presently to be described.

In the embodiment according to Figs. 1 to 4, the pilot igniter comprises an igniter body 13 having therein a tapering channel 14, preferably in the form of a truncated cone-shaped igniter channel having its smaller end lo'cated upstream in the air or air-fuel mixture stream of the ramjet and with the larger rearward or outlet end adjacent to the forward portion of the combustion chamber 12. The igniter body 13 is also preferably constructed in the form of a truncated cone having a cap or closure 15 applied to' the smaller end. The control elements of the pilot igniter are usually constructed as component parts of the closure 15. The pilot igniter is anchored to the interior of the ramjet body 10 by means of struts 16 attached to the closure 15.

Obviously many arrangements may be utilized for producing a tangential vortex flow in the igniter channel 14. A simplified arrangement is shown in Fig. 4, in which the closure 15 for the body 13 is provided with a substantially straight passage 21 which can conveniently be constructed by drilling a hole from the base to the forward wall of said closure 15 to provide a scoop inlet 29 and a passage 21. Usually a plurality, in this instance two, of the inlet passages 21 are provided. In order to direct the air-fuel mixture tangentially within the channel 14, there is provided a nozzle disc 23 having a plurality of obliquely directed nozzle passages 22 which are in communication with the passages 21 in the closure 15, and which direct the fuel mixture generally tangentially toward the walls of the igniter channel 14. As shown in Fig. 3, the nozzle disc 23 is screwed into place and then locked by a plurality of machine screws 24 passing through the nozzle disc 23 and screwed into a po'rtion of the closure 15.

In this simplified embodiment of the pilot igniter, auxiliary fuel for the igniter channel 14 is supplied through a fuel line 25 which extends along the axis of the closure 15 and has its forward end connected to a suitable fuel supply (not shown). The fuel supply line 25 has its rear end connected to an axial bore 26 in the closure 15 which registers with a bore 27 in the disc 23. The bore. 27 is enlarged and threaded to receive a spray jet 28, preferably of the type which produces a cone shape spray. The jet 28, as will be seen, is in the upstream, or front end of the channel 14.

Intermediately along the closure 15 there are provided radially extending passages 29 for supplying auxiliary fuel outside the cone-shaped member 13 and below the scoop inlet 20 thereof. Usually the main fuel is directed upstream in the ramjet device a substantial distance ahead of the pilot igniter by outlets 30, so that an air-fuel mixture of substantially the content of the main air-fuel mixture stream entering the combustion chamber 12 is supplied to the igniter channel 14 by the scoop inlets 20. i The air-fuel mixture within the channel 14 is ignited by any desired means such as pyrotechnic flare 31, or an electric ignition device 134 (Fig. 6). For most operations a supply of auxiliary fuel is unnecessary and the pilot will operate quite satisfactorily with just the introduction of the air-fuel mixture to the channel 14 through the passages 21 and nozzle passages 22.

In the modification shown in Fig. 6, the. nozzle disc 23 has been replaced by a plate 123 having a plurality of angularly-directed tubes forming nozzle passages 122 attached thereto and communicating with a chamber 121 which in turn communicates with a plurality of scoop openings 120 in the closure 115 of the igniter body 113. The angularly-directed nozzle passages 122 serve exactly the same purposes as the obliquely-directed nozzle passages 22 in the disc 23. Nozzles 122 inclined at an angle of the order of 45 have produced very satisfactory vortex action.

: After ignition, the air-fuel mixture, as best seen in Fig. 5,, flows spirally within the chamber 14 against the inner wall thereof, as shown in broken lines at 35. Arrows 36 show the returning flow of the burning mixture axially through said chamber 14. Thus it will be seen that the burning air-fuel mixture is recirculated by the well known vortex action.

" In the operation, it has been found that the air-fuel mixture within the channel 14 is substantially immune to any action such as air blasts or other detrimental action within the combustion chamber 12. Also it has been found that the ignited air-fuel mixture stays in the open end of the igniter channel 14 substantially in the form of a white-hot ball of flame.

' It has been found that the air-fuel mixture is in general sufficient to maintain combustion within the channel 114 without the introduction of any auxiliary fuel, so in Fig. 6, the auxiliary fuel supply has been omitted, although it could be supplied if found desirable.

' Usually it is desirable to provide flame-holding gutters 37 adjacent to and slightly downstream from the open end of the channel 14. In the pilot igniter of Fig. 1, the flame holding gutters 37 are shown as simple cross-gutters. However, in many instances, it is desirable to have a more complicated gutter construction in order to secure faster and more evenly distributed combustion. This is particularly advantageous in larger ramjets.

In the modification shown in Fig. 6, an annular flame holder or gutter 137 is placed slightly down stream from and around a pilot. Igniter channel 114 and radial gutters 139 extend from the mouth or outlet end of the pilot igniter and connect with the annular gutter 137. The radial gutters 139 may if desired communicate with the channel 114 or may be fed over the end of the igniter :body 113. A plurality of radial flame spreaders in the form of rake fingers 138 are usually attached to the gutter 137 to increase the turbulence of the air-fuel mixture stream and expedite the propagation of flame into the air- 4 .a fuel mixture. In the larger size ramjets, rake fingers 141 may likewise be placed at the lower end of the pilot igniter body 113 and extend radially from the body 113 toward the gutter 137.

A supporting ring 132 is anchored inside the body 10 and a plurality of radial struts 116 firmly connect the body 113 to the ring 132. The closure 115 may be closed at its forward end but in most cases will connect with an inner body (not shown).

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that (within the scope of the appended'claims) the invention maybe practiced otherwise than as specifically described.

What is claimed is:

1. A vortex pilot flame source for an engine, comprising, a frustum shaped body placed in an air-fuel stream entering the combustion chamber of said engine and having its larger downstream end open, an ogival shaped body spaced upstream from said frustum shaped body, said ogival shaped body having a plurality of scoop inlets at its ogival end for admitting portions of the flow of said air-fuel stream, a disc shaped closure secured to the upstream end of said frustum shaped body and to the downstream end of said ogival shaped body, said disc shaped body having a plurality of passages communicating with said inlets in said ogival shaped body and arranged to direct said admitted air-fuel portions for producing a vortex flow within said frustum shaped'body, a fuel injecting nozzle in said disc shaped closure arranged to inject fuel into said frustum shaped body, and means in said frustum shaped body for igniting the air-fuel mixture introduced therein.

2. A vortex pilot flame source for an engine, comprising, a frustum shaped hollow body located in an air-fuel stream entering said engine, said body being arranged substantially parallel to the direction of flow of said stream and having a threaded portion at its smaller, upstream end, a closure having a threaded end applied to said upstream end of said body, the downstream end of said body being open, an ogival shaped body spaced upstream in contact with said closure and having a plurality of scoop inlets formed in the ogival end thereof for diverting portions of the air-fuel mixture from said air-fuel stream, said closure having a plurality of inclined passages therein communicating with said scoop inlets and connected to the interior of said hollow shaped body to control the direction of flow of said diverted air-fuel portions to produce a vortex flow in said hollow shaped body, a fuel injecting nozzle mounted in said closure for injecting fuel into said hollow shaped body to commingle with said diverted air-fuel portions, and means for initiating burning of the air-fuel mixture in said hollow shaped body.

References Cited in the file of this patent UNITED STATES PATENTS

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