US2638745A - Gas turbine combustor having tangential air inlets for primary and secondary air - Google Patents

Description

NATHAN GAS TURBINE COMBUSTOR HAVING TANGENTIAL AIR May 19, 1953 M.

INLETS FOR PRIMARY AND SECONDARY AIR 3 Sheets-Sheet 1 Filed Nov. 7, 1945 VIIIE M. L. NATHAN 2,638,745 GAS TURBINE COMBUSTOR HAVING TANG TIAL AIR INL S FOR PRIMARY AND SECOND AIR Filed Nov. 7, 1945 3 Sheets-Sheet 2 May 19, 1953 M. L. NATHAN GAS TURBINE COMBUSTOR HAVING TANGENTIAL AIR May 19, 1953 INLETS FOR PRIMARY AND SECONDARY AIR 3 Sheets-Sheet 5 Filed Nov. 7, 1945 Patented May 19, 1953 GAS "TURBINE JCOMBUSTOR HAVING :TA'N- .GENTIAL :Am :mm'rs iron PRIMARY: AND SECONDARY Am Matthew"Lewis Nathan, Gotlalming,-England, assigli'or to Power Jets (Research '& Development) Llmitedflzondon, England SectionLPubl-icLaw 690, Augusit 8, 15146 Patent expires April 1, 1963.

t 4 Claims. (.01. ,co ,-39.-65)

This invention relates to combustion arrangements-for burning flu-id fuel in an airastream. It -is applicable more particularly (though not exclusively) to l an arrangement for combustion tube as "being of two: or even "threewkintls; ":primary air .is that :proportion of the whole throughput"- Which is required to sustain :combus diluent, and "tertiary air if vprovided 101', is mainly air which is a diluent. Diluent lairzis, of

-course,: air overxand above that which is required iorcomhustion but which. is required to be heated for the operation OFT/he! power unitizor other pur- Thepresent invention comprises ine ifect aform oi fiame tube which Jhassshown' itself 1 in ;.:pra.ctise to meet actual requirements, :has 1a 1 reasonably a long life, is simpleto'make' andis light. in weight. -Aiunctional objectof theinventioni isxtoisohtain a correct 1 balance "between primary, secondary and tertiary air: flow and to so contro-lcthesethat the distribution of the flow isravourable forcom- "bu'stion inparticular it appears from' experiment thatthe arrangement permits the inject-edfuel in vaporizefthorough'ly' without being chilled.

-=Accorcling to the inventioma flame tnbeforuse with i one end open for emission .of combustion products and the other end closed except for minor; perforations, provision beingxmadeifor. the

introduction \of fuel into'the-tube in the region of of.1i i z -f d fuelin apcompressorand the closedeendtthevwall of the:tubein-this region gas-turbine power unit. The particular usewof (within whichiprimary combus on take P c the invention at present envisaged is as a flameham'l'lg openin s fi ed wlth mea s which ditube-in an aircraft propulsion. power unit comrect primaryairinto the tube -.in attangen-tial prising an air compressor; a plurality of combus- 'ensepwhi'ls o e op n s. arez tion chambers supplied thereby, and a gas turtube 'wallzfurther towardsithe openendlikewise bine driving thecompressor by power derived associatedwith-air directing:means-forsecondary from the combustion products one continuous air to enter theatubezin-a: tangential sense. :The basis. In such units it maybe assumed that each fuel is 2 preferably liquidiuehinjected intthemecombustion chamber comprises: a cylindrical gionnofthe closedend; theairdirectingmeans outer chamber t rw ia e ntersat one end are mainly external totheborezof the tube and and aninneriiame tubeofless diameter, into their purposeistocause the.enteringsairtoeswirl which the air passesirom the=annular spaceibe inthe bore in' vortex manner. The openings and tween the chamber and flametube; the latter associated air directing means inanyone axially disehargesfro-m one endpsubstantial'ly axially; :definedregion of .theitube are; provided asaring l'he achievement o'f efficient combustion over 2 or circumferentia1:series and evenly .spaced in a wide range of mixture strengths and. in various the circumferential .-sense. ..Beside the openings operating conditions is in itselfadifficult! techniwhich have air directing means other openings cal problem when limitations; o-favolume; highxair are preferably providedwhich; are. plain and these velocities, and-the-necessity'for:avoidingwcarbon "are distributed z'mainly towards .the open-lend of "deposition andexcessive local heating-vareutaken the tube. [Fl-1e airvdirectingmeans in one axially into account. Itistalsotdcemedito'he desirable located; region" may beroppositelyhanded in rotathat stratification of. gases in the outlet (i.-I8.-Wid6 tional sense'to those of an adjacent reg-1e11,. i.-,e. variations of temperature across; a' section ref-the one further up'or down stream. .The air'directfiow) is to'tbe'minimised. ing means may-comprise chutes of rectangular It-isusualto regard-theaflownf air: intoia fiame cross-section which are convergent in .thedirection of: airs flOWlBIld this. lends itself to their. :con-

structionlfrom sheet metal. The extent to which air directing means: project into the bore of 'the tube is small and: the nature of anvsuch-projeo- "tlOIIiSIiSUCh'thBItJ it does not substantially interffere with the air :flo'w within the tube .vso \that serious local turbulence caused thereby is avoided and alsopthe susceptibility of theimeans to damage by the impin'gement of flame orrhotxlgasis which IFig. 1 l is a sectional :views showingaiflamettribe and: associated parts together witht-themethodtof mountingosandi locating.

Fig. :2 is: a .partiy sectioned: illustrationwshowing the externalrappearance ofzza flame tube.

Fig; '3 iswawsectdonal. fragmentary viewcofzone air directingrmeans.

Fig.4 isa representationiof a :power unitfor; i at propulsion :intended. for *use on aan zaircrait and is an .exampleiofronercasei inawhiohvthe' invention may be applied.

' tends.

Referring first to Fig. 4, a compressor rotor 22 of a double sided centrifugal compressor draws in air through double air intakes 23 and the compressed air is delivered from the compressor casing 24 through outlets 25 to a plurality of interconnected combustion chambers or air casings I arranged symmetrically in a circular series around the axis of the compressor 22. Each chamber I comprises a flame tube 8 provided with suitable apertures through which the air enters and by means of a fuel injector 4 fuel under pressure from a supply source and pump 26 is sprayed into the flame tube 8 and the gaseous mixture ignited, for example by means of an electric spark plug. The gaseous products are then delivered through elbow ducts to the nozzle assembly 6 of a turbine 3| mounted on the same shaft 32 as the compressor rotor 22. The hot gases thus drive turbine 3| which in turn drives the rotor 22, and the gases after passing through the turbine 3| flow into an annular duct 33 formed between a conical fairing 34 and a jet pipe 35, being finally ejected to atmosphere through the outlet 36 of jet pipe 35 and forming in this way a main propulsive jet stream.

The flame tube 8 is illustrated on a larger scale in Fig. 1. Each combustion chamber consists of a cylindrical wall I, with an air entry 2 and with one end closed by a hemispherical end 3 through which extends axially a fuel injector 4 the purpose of which is to inject liquid fuel in at atomised state.' From the interior of the combustion chamber I there leads an elbowed receiving duct 5 to lead combustion products laterally out of the chamber I to the nozzles 6 of the gas turbine 3| (Fig. 4). The lateral air duct 1 leads from the combustion chamber I to an identical neighbouring chamber.

Coaxially within the chamber I is mounted the flame tube. This consists of a sheet metal body 8 made in the form of a tubular cylinder with an open end at 9 which fits spigot-wise into the corresponding open end of the receiving duct 5, and is a sliding fit therein. The

other end of the flame tube 8 is virtually closed by a dished end closure II] which has minor perforations through it arranged as a ring at II. The closure II] also has an axial central hole provided with an inwardly extending mounting sleeve, through which the fuel injector 4 ex- Out side-the closure III there is also provided a frusto conical screen I2 with a comparatively large central aperture. The space between the elements II] and I2 serves as a distributing duct to lead primary air to the entrance I3 of air directing chutes I4 which are arranged as a ring or circumferential series equally spaced around the flame tube and terminating in openings in the wall of the flame tube, the direction of the chutes being tangential. The air entering chutes I4 when it reaches the interior or bore of the flame tube 8 constitutes a now of vortex nature and it will be appreciated that this air mixing with the injected fuel burns in the region of the closed end of the flame tube; this combustion being relatively rich mixture combustion which is self-sustaining in all intended operational conditions is the primary combustion. The fact that it is self-sustaining appears to be due largely to the fact that the vorticity produces a reversal of flow or reversed core whereby a certain amount of flame is always sustained in the region of fuel injection. Beyond the region of primary combustion openings are provided in the flame tube wall for the introduction of sec- '4 ondary air. Some of these simply constitute rings of plain holes I5 but other openings I6 and I1 are associated with air directing chutes ISA, HA. The openings I6 are arranged in a ring and it has been found successful to arrange these with an opposite rotational direction to the chutes I4. The chutes I'IA again arranged as a ring and axially spaced from the chutes I 6A are again oppositely handed, that is to say they are of the same hand as the chutes I4. The last openings in the downstream direction are somewhat elongated holes I8 this shape having been found most suitable for the introduction of tertiary air in this region.

The flame tube of which the open end 9 is supported against all movement except axial by its sliding fit, is supported towards its closed end by various means which may be used together or alternatively. In some cases it may be supported by and located with respect to the fuel injection 4 or any tubular fuel injector mounting such as 4A. Again it may be supported by an igniter plug exemplified at I9 or in the case of a combustion chamber not having such a plug a dummyv plug occupying the place of an igniter plug, and further it may be supported by a tubular element 20 which constitutes a branch connection between the interior of the flame tube 8 and a like adjacent flame tube in an adjacent combustion chamber. connection 20 lies within the branch duct I and may be supported therein by a perforated plate 7 2I interposed in an assembly joint of the duct I.

The general form of the chutes is illustrated by Fig. 3 in which it can be seen that the air passage of a chute is convergent in the direction of flow and that the structure of the chute lies mainly external to the bore of the flame tube the only internal projection being so inclined to the direction of whirl of the gases within the flame tube and so adequately cooled by the air flow in the chute that the structure is not susceptible to damage due to the combustion nor is it such as to promote any substantial amount of turbulence within the bore. The chutes at I4 only differ from the form represented in Fig. 3 by having the air entrance to the chute somewhat differently disposed as can be seen most clearly at I3 in Fig. 2.

In the construction described it can be seen that the flame tube as a whole can be mounted within the combustion chamber I prior to final assembly and sufficiently supported therein for the combustion chamber with flame tube complete to be assembled to the other parts. In general so far as the flame tube itself is concerned the closed end is regarded as the upstream end and the open end 9 the downstream end.

I claim:

1. In combustion apparatus for the combustion of fuel in a combustion supporting gas supplied as a high velocity stream, and of the kind comprising a flame tube which is open at its downstream end for emission of combustion products and is provided with swirl inlets at its upstream end constituting main primary combustion supporting gas entries from said stream and with additional inlets downstream of said primary entries constituting secondary combustion supporting gas entries, in combination with a fuel injector which enters the upstream end of said flame tube along the axis of the tube, and which accordingly directs the fuel into the core of reverse flow which will be formed by the primary combustion supporting gas entering by said swirl inlets and swirling around the axis of the tube, the improve- As is apparent the branch ment that said flame tube is made up of a peripheral wall and an upstream end closure wall and said swirl inlets are ports formed in said peripheral wall, adjacent to said end closure wall and around said fuel injector, and are shaped to direct the air into the flame tube substantially tangentially on to the inner surface of the said peripheral wall.

2. Combustion apparatus according to claim 1 wherein said inlets for secondary combustion supporting gas are also located to direct the combustion supporting gas inward substantially tangentially to the periphery of said tube.

3. Combustion apparatus according to claim 2 wherein the said inlets for primary combustion supporting gas are located to direct said primary combustion supporting gas to swirl around the axis of the tube in one sense and the inlets for secondary combustion supporting gas are located to direct said secondary combustion supporting gas to swirl in the opposite sense around the axis of said tube.

4. Combustion apparatus according to claim 3 in which there are inlets downstream of the inlets for secondary combustion supporting gas, said 6 downstream inlets being located to direct additional secondary combustion supporting gas to swirl in the same sense as the primary air.

MATTHEW LEWIS NATHAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,322,999 Bester Nov. 25, 1919 1,451,063 Anthony Apr. 10, 1923 1,603,032 Elze et a1 Oct. 12, 1926 1,618,808 Burg Feb. 22, 1927 1,657,698 Schutz Jan. 31, 1928 2,107,365 Bray Feb. 8, 1938 2,110,209 Engels Mar. 8, 1933 2,195,025 Couzinet Mar. 26, 1940 2,268,464 Seippel Dec. 30, 1941 2,273,406 Lasley Feb. 17, 1942 2,286,909 Goddard June 16, 1942 2,398,654 Lubbock Apr. 16, 1946 2,404,334 Whittle July 16, 1946 2,404,335 Whittle July 16, 1946 2,440,491 Schwander Apr. 2'7, 1948

Images