US2920445A - Flame holder apparatus - Google Patents

Description

Jan. 12, 1960 F. w. BAILEY 2,92

FLAME HOLDER APPARATUS Filed Jan. 15, 1957 2 Sheets-Sheet l JNVENTFE' FRANK w BAILEY H I 5 ATT EIRNEY Jan. 12, 1960 F. w. BAILEY FLAME HOLDER APPARATUS 2 Sheets-Sheet 2 Filed Jan. 15, 1957 INVENTOR. FRANK w. BAILEY ms LATTDRNEY flame holder.

. flame is spread bustion flame holder apparatus 22. From chamber the gases discharge rearwardly United States Patent 2,920,445 FLAME HOLDER APPARATUS Frank W. Bailey,

Curtiss-Wright Corporation, a corporation of Delaware Application January 15, 1957, Serial No. 634,254 Claims. (Cl. 6035.6)

flame holder apparatus comprising some form of bluff object is generally disposed across the flow path of combustible gases for stabilizing the flame in the wake of the Combustion is commonly initiated by igniting pilot fuel in a flame holder whereupon the pilot to a main combustible air fuel mixture. Although combustion is stabilized in the wake of a flame holder because of the eddying of burning or hot gases in this region, nevertheless the phenomenon of flame blow-out wherein both the main flame and pilot flame may be extinguished under various operating conditions is well known.

. It is an object of this invention to provide a flame holder of the described type particularly adapted to maintain a pilot flame therein under severe conditions of operation.

It is a further object of the invention to promote eflicient operation of such a flame holder and improve flame stabilization in the wake of the flame holder by providing a-uniquely constructed device wherein provision is made for preheating fuel within the flame holder.

Other objects and advantages of the invention will become apparent upon reading the-annexed detailed description in connection with the drawings in which: 7

Fig. 1 is a schematic view of a ram jet engine provided with combustion apparatus embodying the features of the invention; Fig. 2 is an enlarged end view of the combustion apparatus of Fig. 1 taken on the line 22 of Fig. 1;

Fig. 3 is a sectional view taken on the line 33 of Fig. 2;

Fig. 4 is an enlarged sectional view of a flame holder unit of Figs. 1-3 showing flow conditions therein;

.Fig. 5 is a schematic view of a gas turbine engine illustrating application of the flame holder of the invention to an afterburner;

Fig. 6 is a view similar to Fig. 4 showing a modified form of flame holder and flow conditions therein.

Referring to Fig. 1 of the drawings, there is shown a ram jet engine 10 comprising a duct-like member 12 having a center body 14 supported therein by struts 16 adjacent the foiward end of the engine. The engine has an annular air inlet passage 18 and a combustion chamber 20 to which air is supplied from the passage 18 and to whichfuel is supplied from fuel nozzles 19 and comthe combustion from the duct member 12 through a nozzle 24 into the surrounding atmosphere to provide the engine with forward propulsive thrust.

: The ram jet enginelil described is conventional except Wayne Township, NJ., assignor to for the details of the structureof its combustion flame -holder apparatus hereinafter described. The use of such 'fuel in atomized form. A

is ignited by the spark plug 521 2,920,445. Cg P;tented Jan. 12, 1969 flame holder apparatus is however not limited in application to ram jet engines but is of general use for stabilizing combustion in high velocity gas streams. The flame holder of the invention may, for example, be used in combustion chambers for gas turbine engines, or it may be used as shown in Fig. 5 of the drawings to promote com bustion in the after-burner of a gas turbine engine.

As best seen in Figs. 2 and 3, the flame holder apparatus 22 comprises a plurality of flame holders 26 which are preferably non-uniform in cross-section and may for example be conical in form as shown in Figs. 1-5. Each flame holder 26 is associated with a pair of fuel supply lines 28 and 30. As will hereinafter become apparent the flame holders 26 and associated fuel supply system therefor represent only one form of combustion apparatus constructed in accordance with the invention, and the apparatus may take other forms such as that shown, for example in Fig. 6 and described in a subsequent portion of this specification. As shown in Figs. 1-5, the flame holders 26 are arranged in a symmetrical pattern and are interconnected by channels 32 which promote combustion by the creation of eddy currents in the wake of each channel and function to spread a flame to the several flame holders from one or more ignition sources. The channels also structurally tie the flame holders together.

The flame holders 26 are all alike and only one such unit will therefore be described in detail. Referring to Fig. 4 it will be seen that the flame holder comprises a wall structure 34 defining a conically shaped chamber having an opening 36 at the converging end. A cover plate 38 closes off the diverging end of the unit except for an annular passage 40 between the side edge 42 of the cover plate and wall structure 34. The opening 36 provides for the admission of air to the flame holder, and annular passage 40 permits the escape of hot and burning gases. The normal disposition of the flame holder in a gas stream is as shown in Figs. 1 and 5, that is, with the converging end of the unit located upstream relative to the main direction of flow of the gases and with the diverging end disposed downstream.

As shown, the flame holders 26 connect by lengths of tubing 44 and 46 with fuel lines 28 and 30 respectively. The tube length 44 extends within the flame holder chamber and connects at the end thereof with cover plate 38. Openings 48 are provided in the tubing 44 in close proximity to the cover plate 38 for the purpose of discharging plate 50 is attached to tubing 44 in fixed spatial relationship tocover plate 38. The plate 50 which is disposed in fairly close proximity to cover plate 38 serves to confine fuel discharged from openings 48 and to direct such fuel to annular passage 40. The tubing 46 which connects with fuel line 30 encases and is concentric with a portion of tube length 44. As shown such tubing 46 extends only a short distance into flame holder 26 and has openings 51 for discharging fuel therefrom in atomized form. A spark plug 52 is provided in one unit 26 for igniting the fuel in the combustion space 53. Additional igniting elements are generally unnecessary since the channels 32 serve'to spread a flame from the one unit to the several flame holders. While it is generally intended that fuel be introduced into an engine both upstream of the flame holders as for example at nozzles 19, and through the flame holders, this does not preclude the possibility of introducing all of the fuel through'the flame holders.

In operation of the flame holders 26, air including fuel which may have been introduced upstream of the flame holders enters through opening 36 and passes through converging nozzle 54 where it picks up fuel discharged through the openings 51 in tubing 46. This fuel is carried into combustion space 53 where the air fuel mixture The fuel air ratio witha, r in space 53 may be controlled to a desired value by regulating the quantity of fuel fed to the flame holder through line 30. Preferably the fuel flow through line is regulated to provide. a substantially stoichiometric mixture in space 53. With the maintenance of such stoichiometric mixture, the intensity of the flame in the space 53 is pro 'portional to the mass flow velocity of the gas mixture entering the flame holder.

Hot and burning gases discharge from combustion space 53 through annular passage 40, and are mixed at the entrance of such passage with fuel which issues from the openings 48 in line 44, such fuel being directed to the passage 40 between end cover 38 and plate 50, Fuel discharged from the passage 40 together with fuel in the main gas stream burns in the wake of the flame holder where a zone 56 of eddy currents exists, and the flame is thereafter propagated across and downstream in the main gas stream. It is desirable to control fuel flow through line 44 to maintain a substantially stoichiometric mixture in the wake of the flame holder to thereby provide a flame in the wake of the flame holder having an intensity which is proportional to mass flow velocity of the main gas stream. The arrangement of several flame holders as hereinbefore described for use in a ram-jet engine assures burning across substantially the entire cross section of the combustion chamber. The fuel in line 44 is of course heated by the flame in space 53 since the length of tube 44 passes through this combustion space 53 in the flame holder. This preheating of this fuel is an important feature of the invention in that it makes for an eflicient device and promotes stabilization of the flame in the wake of the flame holder.

Burning within the space 53 is stabilized by reason of the ring vortex type of flow promoted by the flame holder construction. By reason of the vertical plate which serves as a deflector and diverging wall 34 of the flame holder, the flow which is illustrated in Fig. 4 is a vortiginous type of flow wherein rotation is about a circular axis having a substantially fixed position. This is in contrast to a swirl type of flow in which rotation is about an unstable axis. With the described ring vortex flow, increased velocity of air entering the flame holder increases the strength of the ring vortex so that the flame is not readily blown out even in an unusually high velocity gas stream such as may occur in a jet engine under certain operating conditions. An additional advantage of the vortex type of flow as contrasted to the swirl type of flow is the tendency of the vortex to retain fuel particles rather than to centrifuge fuel to the walls of the flame holder.

Reference is made to Fig. 5 for the application of flame holder '26 to the afterburner of a gas turbine engine 58. Such engine includes as essential components, a compressor 60, combustion chamber 62 and turbine 64 within housing 66, The engine has an afterburner 68 only a portion of which is illustrated and fuel supply means therefor including fuel nozzles 69. As shown, a flame holder 26 may be mounted in the aft end of the diffuser center body 70 of such engine and air supplied to the unit as for example from compressor 60 through supply line 72. Operation of the flame holder is similar to the operation hereinbefore described in connection with its use in the main combustion chamber of a ram jet engine. However the provision of air line 72 which connects with the flame holder 26 renders control of air to the flame holder possible. Any suitable means, such as valve 74, may be utilized for controlling the quantity of air to the flame holder. The fuel air ratio within the flame holder may be readily maintained constant at a desired value by proper control of the air fed to the flame holder through line 72 and of the quantity of fuel fed through line 76, and such fuel air ratio is substantially independent of gas flow through the engine. As shown, the fuel lines 76 and 78 respectively are conveniently disposed for a Portion of their length withl aeaonas in air supply line 72 to enter the flame holder 26 through opening 36. If desired provision might readily be made for supplying the flame holder 26 with an oxygen en riched mixture instead of air. The use of such oxygen enriched mixture would be particularly desirable at high altitudes.

Reference is made to Fig. 6 showing a modified form of flame holder 80 constructed in accordance with the invention. As shown the wall 82 of the flame holder is ogival in shape rather than conical, and the cover plate 84 has an annular lip 86 which extends in line with the wall 82. The flame holder has a central opening 88 through which a gas stream may enter the unit, and an annular opening 90 between the wall 82 and cover plate 84 from which hot and burning gases may escape. Fuel is supplied to the flame holder through a tube 92 surrounding the opening rather than through two separate lines as hereinbefore described. The tube is shielded as by an outer wall 91 and an inner wall 93 which inner wall defines an inlet nozzle 96. The tube 92 and nozzle wall 93 have aligned openings 94 and 95 respectively through which the fuel is discharged in atomized form into the nozzle 96. Such fuel is picked up in the gas stream entering the flame holder and is carried into combustion space 98. All of the fuel entering the flame holder impinges on cover plate 84 which acts as a deflector. Some of the fuel is recirculated within the flame holder in the desired ring vortex type of flow hereinbefore described, and the remainder is sloughed through opening 90 into the wake region of the flame holder. The recirculated fuel may be ignited as by a spark plug 100. By reason of the burning which takes place in space 98 fuel is heated therein before being discharged through opening 90. Such preheating of the fuel is desirable for reasons already noted in the description of the flame holder of Figs. 1-5. The cover plate 84 may include a number of circumferential perforations 102 such that a flame in the wake region of the flame holder may be drawn through the perforations for ignition and re-ignition purposes.

While I have described my invention in detail it will be appreciated that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit of the invention.

I claim as my invention:

1. In combination with a main combustion chamber having an entrance through which air is supplied for combustion and having a discharge end through which gases exhaust from said chamber; a flame holder disposed within said main combustion chamber and having a wall structure diverging for at least a portion of its length in the downstream direction and forming an auxiliary chamber, said auxiliary chamber having an air intake opening at the upstream end and on the axis thereof and an annular discharge opening at the downstream end and coaxial with said auxiliary chamber, a deflector element positioned within said auxiliary chamber and defining therewith a fire zone of vortiginous flow therein, a first fuel supply means adapted to discharge fuel at said air intake opening, a second fuel supply means extending through said fire zone and adapted to discharge fuel downstream from said deflector element, and means for igniting fuel in said auxiliary chamber.

2. In combination with an afterburner of a gas turbine engine: a flame holder disposed within said afterburner a substantial distance from the downstream end thereof relative to the direction of flow through the afterburner, said flame holder having a wall member defining a substantially conical combustion chamber having its larger end disposed downstream of its smaller end and having an opening at each end, a cover plate disposed within the downstream opening and defining an annular passage between said wall member and said cover plate, a deflector plate disposed within said chamber spaced from said cover plate and coaxial therewith and parallel thereto an defining with said wall member a fire zone of vortiginous flow, a conduit connected with said upstream opening adapted to supply combustion-supporting gas to said flame holder along the axis of said vortiginous fire zone, a first fuel supply means extending into said flame holder and adapted to discharge atomized fuel at the upstream end thereof, a second fuel supply means extending into said flame holder along the axis thereof and adapted to discharge atomized fuel between said deflector plate and said cover plate, and means for igniting fuel within said chamber.

3. The combination as defined in claim 2, wherein said conduit has valve means for controlling the flow therethrough.

4. In combination with a main combustion chamber having an entrance through which air is supplied for combustion and having a discharge end through which gases exhaust from said chamber; a flame holder comprising a wall member defining a substantially conical auxiliary chamber having open ends and disposed with its converging end upstream relative to the direction of flow through the main combustion chamber, a cover plate disposed within the opening at the diverging end of said auxiliary chamber coaxial therewith and defining an annular passage between said wall member and said cover plate, a deflector plate disposed within said auxiliary chamber spaced from said cover plate and coaxial therewith and parallel thereto and defining with said wall member a fire zone of vortiginous flow, said auxiliary chamber wall having at the converging end thereof a re-entrant air said cover plate, and means for igniting fuel within said auxiliary chamber.

5. The combination as defined in claim 4, wherein said cover plate has an annular flange extending therefrom in the downstream direction and parallel to said wall member and adapted to promote'vortiginous flow in the wake of said auxiliary chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,474,867 Walker Nov. 20, 1923 2,622,396 Clarke et a1. Dec. 23, 1952 2,734,341' Lovesey Feb. 14, 1956 2,771,743 Lovesey Nov. 27, 1956 2,780,916 Collins Feb. 12, 1957 FOREIGN PATENTS 1,085,458 France July 28, 1954 702,760 Great Britain Ian. 20, 1954

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