US2773350A - Combustion chamber assembly for ram jet fuel burner - Google Patents

Description

1956 H. E. BARRETT ET AL 2,773,350

COMBUSTION CHAMBER ASSEMBLY FOR RAM JET FUEL BURNER 2 Sheets-Sheet 1 Filed Jan. 31, 1950 MBUSTION CHAMBER ASSEMBLY FOR RAM JET FUEL BURNER Filed Jan. 31, 1950 Dec. 11, 1956 H. E. BARRETT ETAL 2 Sheets-Sheet 2 M TH United States Patent M COMBUSTION CHAMBER ASSEMBLY FOR RAM JET FUEL BURNER Hillard E. Barrett, East Orange, William S. Bower, Ridgewood, and William F. Payne, Cedar Grove, N. 3., assignors to the United States of America as represented by the Secretary of the Air Force Application January 31, 1950, Serial No. 141,562

7 Claims. (Cl. 60-35.6)

This invention relates to a combustion chamber assembly for a ram jet fuel burner. It is well known that great difficulty has heretofore been experienced through undesired extinguishment of the flame in burners of this class, especially at supersonic speeds and at extreme alti tudes.

One object of the present invention is to provide a burner assembly which produces a flame of extraordinary stability.

Another object is to provide a burner assembly which swirls the pilot flame in a different direction from the swirl of the first main flame and the second main flame swirls it counter to the first main flame.

Another object of the invention is to produce a burner assembly in which cold air flows through a jacket so that the walls of the combustion chamber will be protected from too high a temperature.

Referring to the drawings:

Fig. 1 is a perspective view of the burner assembly partly broken away longitudinally and wholly broken into two sections by a crosswise break to indicate that it can be made longer than shown.

Fig. 2 is a vertical section through the burner itself, and

Fig. 3 is a cross section of the complete burner taken on a line corresponding to the line 33 on Fig. 2.

is an outer metallic cylindrical shell, 11 is an in ner cylindrical metallic shell and 12-12 are metallic spacers between the outer and inner shells intended to space the outer shells sufliciently from the innershell to enable the entire device to be mounted in the neighborhood of inflammable materials without igniting them. In other words, the outer shell 10 is intended to remain cool although the inner shell 11 may have attained considerable temperature. Within the inner shell 11 there is a combustion chamber 13 which has a double wall, the outer wall which is 14. As shown in Fig. 1, the left hand end of the drawing is that end of the device which is intended to face in the direction of flight and thus receive ram air. It will hereinafter be referred to as the fore end of the device and the right hand end will be designated as the aft or tail end. The direction toward the tail end is designated downstream. The aft end of the chamber 13 and its second wall 14 are formed into a de Laval nozzle, the throat of which occurs at 15. The space between the walls 13 and 14 is designated 16 and terminates against a flange 17 in the fore end of the shells. A plurality of air holes 18 are drilled circumferentially about the flange 17 and are in direct communication with the space 16 to provide the latter with a flow of metered ram air, the volume of which is governed by the size of the holes 18. The volume of ram air desired is at least sufficient to prevent the shells 13 and 14 from melting or warping under the intense heat of the flames from the combustion ram. Air is admitted to the various burner structures, which will later be decribed, through a shroud 20 which is built through a flange 21 to a second 2,773,350 Patented Dec. 11, 1956 and inner shroud 22. The latter is attached to the flange 17 in such a manner that the holes 18 are not covered. Adjacent the flange 17 and encircling the shroud 22 are a pair of fuel annuli 23 and 24, the latter being innermost. These annuli may be supplied with liquid fuel through a pipe 25 from a reservoir, not shown. Within the space 26 between the shells 10 and 11 is contained an ignition coil and breaker assembly 27, a lead 28 from which supplies a spark plug 29 with current, the purpose of which is to ignite the pilot burner 30.

The pilot burner is supplied with liquid fuel by a tube 31 which delivers liquid from the annulus 23 to a point axially concentric with a conical inner shroud 32 and a frustro-conical outer shroud 33, the latter being positioned by struts 34 anchored to the shroud 20. The tip of shroud 32 and the edge of shroud 33 are spaced apart to receive ram air which can find its way into the interior of the pilot burner structure 30 through a plurality of louvers 35 which are canted to produce a counterclockwise swirl in the air current and consequently in the burner flame. A nozzle 36 for fuel injection is located axially in the tip of the shroud 32 and concentrically with a cylindrical extension 33a of the shroud 33. This extension is also substantially an extension of the conical shroud 32, hence the shrouds 32 and 33 are welded together at the beginning of the cylindrical section 33a. At least four short gutters 37 made of sheet metal are mounted within the extension 33a to produce a cross section such as shown at the center of Fig. 3. The gutters 37 are short pieces of sheet metal which are bent into a 60 degree V shape and then end welded to the extension 33a so that they will project into the path of the pilot flame from the pilot burner assembly 30.

The shroud extension 3312- projects into a second shroud 38 which is cylindrical and concentric with the extension 33a. Shroud 38 is spaced from extension 33a by a multiplicity of vanes 39 which are canted to a 35 degree angle to produce a clockwise swirl in a main flame, the fuel for which is supplied from four burner nozzles, only one of which 40 is shown in Fig. 1, two of which are shown in Fig. 2. Four or more gutters 41 which are somewhat larger than the gutters 37 are positioned by end-welding to the. interior of shroud 38 so that they will project toward the axis of the entire burner assembly at points midway between the positions occupied by the gutters 37. Such positioning insures that each flame will contact at least one set of gutters. Both the gutters 37 and the gutters .41 are preferably perforated, the smaller gutters 37 having only one hole 4-2 while the gutters 41 have preferably two holes 42.

Mounted on the outside of the shroud 33 are eight fuel nozzles 43, which are positioned aft of the vanes 44. These vanes also have a 35 degree cant but in clockwise direction. The vanes 44 space the shroud 38 from the wall of the combustion chamber 13. The vanes are end-welded between the shroud 38 and the chamber 13. Tube 45 supplies each nozzle 43 with liquid fuel from the annulus 24. The degree of cant of the vanes 44 is preferably equal to the degree of cant of the vanes 39 and produces a swirl of the flame in a contrary direction which is however the same as that produced in the pilot flame by the cant of the louver 35. It has been found that the contrary direction of swirl of the pilot flame and of the main flames produces an exceptionally high eflicientcy of combustion. Fuel droplets as swirled by the pilot burner are subject to impact between its flame and the first counter rotating main flame and atomized.

Likewise liquid fuel droplets produced between first set of main burners are projected into the outside of the first tense and complete combustion is promoted. The flames are not readily extinguished at supersonic speeds and at very high altitudes.

High (supersonic) velocity is imparted to the combustio'n gases by the de Laval nozzlewhich is formed at the aft end of the combustion chamber 13. Vibration between the combustion chamber walls 1.3 and 14 and the cylindrical shell 11- is diminished by the use of a braided metallic seal or packing 46 which is positioned just forward to the nozzle throat between these shells. The packing 46 also acts as anair seal to prevent air leakage so that there is an adequate flow of cooling air through the jacket around the nozzle. Adjustable spacers 43 may be provided on the aft end of shell 11 to diminish oscillation of that shell. A tail. ring 49 may be threadedly attached or Welded to the extreme aft end of the outer shell 10.

Referring. now to Fig. 3, it'will be seen that a schematic disposition of air and flame directing vanes and gutters has been provided. The gutters 37 and 41 do not serve any swirling function but they do provide localized turbulent regions in which the flame can propagate to the incoming fuel-air mixture. The vanes 39 and 44 fulfill a swirling and mixing function which promotes fuel atomization as previously described. The shrouds 33a and 38 perform the function of directing the air blast and of holding the gutter surfaces whereon atomization and volatilizationmay take place. They also establish the swirl boundaries of their respective flames.

Shroud 3% also serves as a support for clips 5t which support the burner nozzles 43.

The spark plug 29 is of a special type which has an arcuate electrode 5i. it is mounted behind one of the gutters 3'7 and is so arranged that the spark from the electrode Sll will jump to the shroud extension 33a. Better ignition and a steadier flame has been obtained by this arrangement. it is not necessary that the spark plug 29 should function at all times while the pilot burner is in operation.

Numerous changes may be made without departing from the spirit of the invention. 1

For example, the pilot flame may be arranged to swirl clockwise, the first main flame to swirl counterclockwise and the second main flame to swirl clockwise. The fuel supply may be arranged to be fed from a tank or other structure separate from the structure herein shown. The number of main burner nozzles may be varied. Other changes will occur to those skilled in the art.

We claim as our invention:

1. In a fuel burner adapted for ram jet operation a combustion chamber comprising a substantially cylindrical open end casing, a pilot burner mounted axially at one end of said casing, a first shroud surrounding said pilot burner, a plurality of gutters symmetrically mounted on the inner surface of said first shroud downstream from said burner said first shroud having also a plurality of openings between said gutters, louvers in said shroud adjacent to said openings disposed to give the flame of said burner a counterclockwise swirl, a pair of fuel annuli surrounding said first shroud, a plurality of main burner nozzles mounted exteriorly to but adjacent to said first shroud slightly downstream from the gutters therein, a second shroud concentric with said first shroud and extending downstream therefrom, said second shroud being attached to said first shroud by angled fins adapted to give the flame from said main burner nozzles a clockwise swirl, a third shroud mounted concentrically upon the downstream end of said second shroud and attached thereto by angled vanes, a larger number of main burner nozzles between said vanes than the first mentioned set of main burner nozzles, said vanes being angled to impart to the flame from said second set of main burners a clockwise swirl, connections from all 4; of the aforesaid burners to at least one of said fuel annuli, and a plurality of structural members attached by one of their ends to a shroud for concentrically mounting said shroud assembly within said casing.

2. A ram jet fuel burner according to claim 1 having a casing about and concentric with the casing set forth in that claim, spacing means between the two casings arranged to permit a flow of ram air between them, a flange joining said casings at the upstream end thereof, said flange having a plurality of. metered openings therein disposed about the upstream face of said flange whereby to admit ram air to the space between said casings to cool the latter.

3. A ram jet fuel burner according toclaim 2 having the two casings formed into a de Laval. nozzle at the downstream end thereof, the spaced concentricity of said casings being maintained to the end of said nozzle.

4. in a fuel burner assembly adapted for ram jet operation a substantially cylindrical double walled combustion chamber, a forward flange spacing said walls apart and having a multiplicity of metered openings to admit ram air to the space between the walls to cool the casings, a forward shroud mounted on said flange to admit ram air to said combustion chamber, fuel annuli in said shroud adjacent said flange, a pilot burner mounted axially at the fore end of said combustion chamber said pilot burner comprising a conical shroud, a fuel nozzle mounted in the tip of said shroud, a frustoconical shroud encircling said conical shroud, air swirling means in the latter, a cylindrical shroud extension joining both conical and frustoconical shrouds, a plurality of short gutters mounted in said shroud extension to project into the flame path, a multiplicity of angled vanes mounted on the aft end of the shroud extension, a plurality of first burner nozzles amounted forward of said vanes and disposed to project fuel between them, a second cylindrical shroud mounted aft of the first cylindrical shroud and concentric therewith, a plurality of short gutters mounted interiorily of said shroud and projecting into the flame stream. of said first main burner, a multiplicity of angled vanes mounted between the aft end of said second shroud and the interior wall of said combusion chamber, a plurality of second main burner nozzles mounted between said vanes and disposed to project fuel aft, ignition means for said pilot burner and a fuel connection for each burner nozzle from one of said fuel annuli.

5. A fuel burner assembly according to claim 4 including a tail end in the shape of a de Laval nozzle for said combustion chamber, an outer cylindrical casing for said chamber and air sealing means between the outer wall of said combustion chamber and said casing just forward of the throat of said de Laval nozzle shaped tail end.

6. A fuel burner assembly according to claim 4 in which the louvers of the conical shroud of the pilot burner and the vanes of the second main burner are disposed to swirl the flames from said burners in a direction opposite to the direction in which the vanes of the first main burner are disposed to swirl the flame from that burner.

7. A fuel burner assembly according to claim 6 in which the main burner vanes are disposed at about 35 from the axis ofv the combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,398,654 Lubbock et a1. Apr. 16, 1946 2,404,335 Whittle July 16, 1946 2,417,445 Pinkel Mar. 18, 1947 2,500,925 Bonvillian et al. Mar. 21, 1950 2,560,223 Hanzalek -a July 10, 1951 FOREIGN PATENTS 376,570 Germany May 30, 1923

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