US2548087A - Vaporizer system for combustion chambers - Google Patents

Description

April 1951 F. D. M. WILLIAMS VAPORIZER SYSTEM FOR COMBUSTION CHAMBERS 2 Sheets-Sheet 1 Filed Jan. 21, 1950 April 0, 1951 F. D. M. WILLIAMS VAPORIZER' SYSTEM FOR COMBUSTION CHAMBERS 2 sheets sheec 2 Filed Jan. 21, 1950 uvvclvron A'DM w/Lu/ms Ar'rohNEx Patented Apr. 10, 1951 VAPORIZER SYSTEM FOR COMBUSTION CHAMBERS Frederick Denison Morgan- Williams, Nobel, n-

tario, Canada, assignor to A. V. Roe Canada Limited, Malton, Ontario, Canada Application January 21, 1950, Serial No. 139,843 a 14 Claims.

This invention relates to fuel vapourizing systems. for combustion chambers, and. particularly for combustion chambers of gasturbine engines.

In order to introduce fuel into the flame: tube of a combustion chamber. in the form of a vapour which can be readily ignited, a well-established practice of the art has used vapourizer tubes, mounted at their forward or upstream ends. in a tube plate and. extending as cantilevers into the flame. zone. These tubes extend from the front face of the tube plate, the. remainder of which forms a closure near the upstream end of the flame tube, so that air flowing into the upstream end or inlet of the flame tube is directed into the vapourizer tubes and flows through them into the flame tube. The downstream ends of the vapourizer tubes are curved through 180 to discharge the: air upstream into the flame zone.

Liquid fuel is introduced into the upstream ends of the vapourizer tubes through. suiablejets and is. carried down. the tubes by the flow of air. Since. the greater part of, the outer surfaces ofthe vapourizer tubes is exposed to the combustion in the flame zone the tubes become very hot: the liquid fuel flowing through the tubes is vapourized so that a mixture of air and fuel vapour is discharged as a combustible gas. In the process of vapourization the tubes undergo some beneficial cooling.

According to the above mentioned prior art difficult. The principal object of this invention lie to eliminatev the need for great accuracy in they distribution of, the fuel. to the. individual vapourizer tubes.

In the prior art construction comprising individual vapourizer tubes great care has to be exercised in arranging the regions of reverse air flow whereby the extra oxygen necessary for effective combustion is furnished tothe rich mixture emerging from thevapourizer tubes to ensure stabilitv of. combustion- Therefore. another object. of this. invention is to produce a relatively simple and easily controlled flow pattern for. the air which. supplies. extra oxygen.

Furthermore, the unsupported vapourizer tubes .of. the prior art, subject as. they areto vibration, to extremely high'temperatures externally and to indifferent distribution of internal cooling by the liquid. fuel, are prone to failures which may result in costly-damage to the turbine into which the. combustion, system discharges. quently a further object of this invention is to prevent such failures by providing mutual support for the, vapourizer tubesat their downstream ends.

The primary object of this invention is there fore to provide a uniform distribution of the combustible gases emerging from the vapourizer system and to ensure that they are thoroughly mixed before emerging into the flame zone, while the secondary objects include the provision of improved cooling of the vapourizer system, an improved supply of extra oxygen, and adequate support for the vapourizer tubes at their downstream ends. Other objects and advantages of the invention will be apparent fromthe following description of the preferred application of the invention. to a tube type combustion chamber. Combustion chambers of gas turbine engines may be of the tube type or of theannular type and, although the invention is described herein as ap-- plied to a tube type combustion chamber, it will be understood that it can be applied with but minor adaptation to the annu ar type and is in no wa restricted to the particular application described herein. v

In the accompanying drawings forming a part of this application and in which like reference characters designate like parts throughout the same:

Fig. 1 is alongitudinal section through a typical gas turbine engine combustion chamber embodying the invention;

Fig. 2 is an enlarged sectional view of the vapourizer system illus rated in Fig. 1; and

Fig. 3 is a. fragmentary view of the vapourizer nozzle and a portion of the vapourizer tubes,

viewed, in the, direction of the arrows III-III. in Fig. 2..

Referring to the drawings, air from the compressor enters the combustion chamber 6 inthe direction of the arrow l. Part of the said air passes as a cooling medium through, the annular space 8 between the combustion chamber 6 and flame. tubev 9 and the remainder enters the up.- stream end 9 of the flame tube. A transverse bafile. Hisupports a tube plate H to which the vapourizer tubes l2 are secured and it a so directs the air into the open upstream ends I2. of. the tubes l2. Liquid fuel is introduced through the pipe. line H leading into the burner M, which may be of the. torch'igniter type described in my (Lo-pending application No. 67,118 filed December 24, 1948, now Patent No. 2,541,900, and an ignition lead for the torch igniter is carried in the tube l5 from the external terminal IS. The jets I1, provided in the burner l4 inject fuel-into the upstream ends l'2 of the vapourizer tubes i2.

Conse Since the jets I! are slightly offset from the axes of their respective vapourizer tubes they present relatively little obstruction to the free entry of air. the head 14, serves as a torch igniter, the discharge therefrom being directed upon electrodes l which form a spark gap energized from the terminal [6.

Downstream of the tube plate I I the vapourizer tubes [2 arcuately diverge from the common axis of their mounting in the tube plate H and subsequently converge, entering a plane transverse to the axis of the combustion chamber and converging into a common nozzle l8.

The vapourizer tubes enter the nozzle substantiall tangentially or at least non-radially as shown in Figs. 2 and 3. In this preferred arrangement the nozzle comprises an annulus which is substantiall U-shaped in section and is coaxial with the combustion chamber. The discharge port of the nozzle, corresponding in section to the open top of the U, faces upstream and the inner and outer walls I 8 and l8 respectively of the annular discharge port are arranged for mutual support through the medium of a series of small, symmetrically disposed swirl vanes 19 extending from the inner to the outer wall.

In operation the greater portion of the air entering the combustion chamber flows into the annular space 8 between the combustion chamber 6 and the flame tube 9 and thence, through the various stages of the orifices into the said flame tube opposite or downstream of the vapourizer tubes l2; the remainder enters the upstream end 9 of the flame tube 9 and is directed into the vapourizer tubes through the openings 12 Since liquid fuel is injected by the jets I 1 into these same openings, a mixture of fuel and air flows down into the vapourizer system. The vapourizer tubes l2 are situated in the flame zone and are therefore subjected to considerable external heat, resulting in the vapourization of the liquid fuel and. the preheating of the fuel-air mixture: this vapourization taking place within the tubes, together with the flow of relatively cold air, serves to cool the said tubes and protect them against burning. The foregoing is the normal function of vapourizer tubes which will be familiar to those skilled in the art.

The preheated mixture emerges from the vapourizer tubes into the nozzle l8 and, due to its substantially tangential entry, it generates a circumferential swirl around the annulus, thereby ensuring thorough mixing of the gases before they are discharged in the form of a vortex into the flame zone. An additional supply of air, which has entered the flame tube 9 through the orifices 20 flows forwardly into the low pressure area in the wake of the baflie l9 introducing extra oxygen to promote combustion, It is a feature of this preferred construction that. because the vortex of combustible gases emerging from the nozzle l8 induces a further depression at its centre, a portion of the said additional air flows strongly through the centre of the nozzle, injecting oxygen to the core of the flame zone where the combustible mixture is relatively rich.

Initial ignition is effected by the torch igniter unit 14 playing a flame upon the nozzle l8.

When a flame has been established, in the flame zone it envelops the vapourizer tubes [2 and thereafter the combustion is self-propagating.

It will be understood that in a construction made according to this invention the life of the The jet Il embodied centrally in vapourizer system is prolonged by the improved cooling inherent in the construction, apart from the benefit of mutual support afforded by the vapourizer tubes meeting, at their extremities, in a common nozzle. The forward portions of the tubes are cooled by the vapourization of the liquid fuel flowing over their inner surfaces, while the divergence of the tubes farther downstream results in their being situated in a relatively cool region of the flame zone. The inner wall of the nozzle annulus is not subjected to direct contact with the flame since it furnishes the main passage of the additional supply of air into the centre of the flame zone as hereinbefore described. Furthermore the outer wall and the downstream closure of the nozzle annulus are subjected to the scrubbing of the fuel-air mixture entering tangentially and at high velocity from the vapourizer tubes, so that adequate internal cooling is assured.

It is to be understood that the form of the invention herewith shown and described, is to be taken as a preferred example of the same, and that various changes in the shape, size and arrangement of the parts may be resorted to, without departing from the spirit of the invention or the scope of the claims.

What I claim as my invention is:

1. In a vapourizer system for a combustion chamber in which liquid fuel is burned in an air stream flowing in the combustion chamber, vapourizer tubes having inlet ends and outlet ends, said tubes being secured with their inlet ends facing the air stream and the outlet ends of the tubes converging into a common outlet facing the air stream.

2. In a vapourizer system for a combustion chamber in which liquid fuel is burned in an air stream flowing in the combustion chamber, vapourizer tubes having inlet ends and outlet ends, said tubes being mounted with their inlet ends facing the air stream, and a nozzle having an outlet facing the air stream, the outlet ends of the vapourizer tubes converging into the nozzle to provide a common outlet for the vapourizer tubes.

3. In a vapourizer system for a combustion chamber in which liquid fuel is burned in an air stream flowing in the combustion chamber, vapourizer tubes having inlet ends and outlet ends, said tubes being mounted with their inlet ends facing the air stream, and a tubular nozzle having an outlet facing the air stream, the outlet ends of the vapourizer tubes converging nonradially into the side wall of the tubular nozzle.

4. In a vapourizer system for a combustion chamber in which liquid fuel is burned in an air stream flowing in the combustion chamber, vapourizer tubes having inlet ends and outlet ends, said tubes being mounted with their inlet ends facing the air stream, and a nozzle having an annular outlet facing the air stream, the outlet ends of the vapourizer tubes converging into the nozzle.

5. In a vapourizer system for a combustion chamber in which liquid fuel is burned in an air stream flowing in the combustion chamber, vapourizer tubes having inlet ends and outlet ends, said tubes being mounted with their inlet ends facing the air stream, and an annular nozzle having an outlet facing the air stream, the outlet ends of the vapourizer tubes converging non-radially and in a plane substantially transverse to the air stream into the nozzle.

6. In a vapourizer system for a combustion chamber in which liquid fuel is burned in an air stream flowing in the combustion chamber, comprising vapourizer tubes having inlet ends and outlet ends, said tubes being mounted with their inlet ends facing the air stream, an annular nozzle having an outlet facing the air stream, means for introducing fuel to the vapourizer tubes, the outlet ends of the vapourizer tubes converging non-radially into the sides of the nozzle to provide a common outlet wherein the fuel air mixture flowing through the vapourizer tubes will form a vortex prior to discharge, and means for igniting the fuel-air mixture discharged from the nozzle.

'7. A vapourizer system for a combustion chamber in which fuel is burned in an air stream flowing through the combustion chamber, the said system comprising, a bafile disposed transversely of the air stream, a plurality ofvapourizer tubes extending through the baffle and downstream thereof, a nozzle situated in the wake of the baffle and discharging in a direction opposed to the direction of the air stream, the downstream terminal portions of the vapourizer tubes converging into the nozzle, means for introducing fuel to the vapourizer tubes and means for igniting the fuel-air mixture discharged from the nozzle.

8. A vapourizer system for a combustion chamher in which fuel is burned in a high velocity 2 air stream flowing through the combustion chamber, the said system comprising, a baffle disposed transversely of the said air stream, a plurality of vapourizer tubes extending through the baffle downstream thereof, an annular nozzle situated in the wake of the bafiie and discharging in a direction opposed to the direction of the air stream, the downstream terminal portions of the vapourizer tubes converging into the nozzle, means for introducing fuel to the vapourizer tubes, and means for igniting the fuel-air mixture discharged from the nozzle.

9. A vapourizer system for a combustion chamber in which fuel is burned in a high velocity air stream flowing through the combustion chamber, the said system comprising, a baffle disposed transversely of the air stream, a plurality of vapourizer tubes extending through the bailie and downstream thereof, the said tubes diverging as they extend downstream of the baiiie, an annular nozzle situated in the wake of the said baffle, and discharging in a direction opposed to the direction of the air stream, the downstream terminal portions of the vapourizer tubes converging into the nozzle, means for introducing fuel to the vapourizer tubes, and means for igniting the fuel-air mixture discharged from the nozzle.

10. A vapourizer system for a combustion chamber in which fuel is burned in a high velocity air stream flowing through the combustion chamber, said system comprising, a baflie disposed transversely of the said air stream, a plurality of vapourizer tubes extending through the said baffle downstream thereof, the said tubes diverging as they extend downstream of the said baffle, an annular nozzle situated in the wake of the said baiile and discharging in a direction opposed to the direction of the air stream, the downstream terminal portions of the vapourizer tubes converging into the said nozzle in a plane substantially transverse to the air stream, means for introducing fuel to the vapourizer tubes and means for igniting the fuel-air mixture discharged from the nozzle.

11. A vapourizer system for a combustion chamber in which fuel is burned in a high velocity air stream flowing through the combustion chamber, the said system comprising, a baiile disposed transversely of the said air stream, a plurality of vapourizer tubes extending through the said baflle and downstream thereof, the said tubes diverging as they extend downstream of the said baffie, an annular nozzle situated in the wake of the said bafile and discharging in a direction opposed to the direction of the air stream. the downstream terminal portions of the vapourizer tubes converging into thesaid nozzle in a plane substantially transverse to the air stream and entering the said annular nozzle substantially tangentially, means for introducing fuel to the vapourizer tubes, and means for igniting the fuel-air mixture discharged from the nozzle.

12. A vapourizer system for a combustion chamber in which fuel is burned in a high veloc ity air stream flowing through the combustion chamber, the said system comprising, a baflle disposed transversely of the said air stream, a plurality of vapourizer tubes extending through the said bafile and downstream thereof, an annular nozzle situated in the wake of the bafile and discharging in a direction opposed to the direction of the air stream, a plurality of struts extending between the inner and outer walls of the annular nozzle, the downstream terminal portions of the vapourizer tubes converging into the nozzle, means for introducing fuel to the vapourizer tubes, and means for igniting the fuel-air mixture discharged from the nozzle.

13. A vapourizer system for a combustion chamber in which fuel is burned in a high velocity air stream flowing through the combustion chamber, the said system comprising, a baiile disposed transversely of the air stream, a plurality of vapourizer tubes mounted on the bafile and extending downstream thereof, means for introducing a flow of air into the said tubes, means for introducing fuel into the said tubes, an annular nozzle situated in the wake of the bafiie and discharging in a direction opposed to the direction of the air stream, the downstream terminal portions of the vapourizer tubes converging into the nozzle, and means for igniting the fuel-air mixture discharged from the nozzle. 14. A vapourizer system for a combustion chamber in which fuel is burned in a high velocity air stream flowing through the combustion chamber, the said system comprising, a baflie disposed transversely of the air stream, a plurality of vapourizer tubes mounted on the baiiie and extending downstream thereof, means for introducing a flow of air into the said tubes, means for introducing fuel into the said tubes, an annular nozzle situated in the wake of the baffle and discharging in a direction opposed to the di rection of the air stream, the downstream terminal portions of the vapourizer tubes converging non-radially and in a plane substantially transverse to the air stream into the nozzle, means for inducing a swirl of the fuel-air mixture within the said nozzle so that it emerges therefrom in the form of a vortex and means for igniting the said discharge. FREDERICK DEiNISON MORGAN WILLIAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,411,663 McCollum Nov. 26, 1946 2,522,081 Allen Sept. 12, 1950

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