US2625792A - Flame tube having telescoping walls with fluted ends to admit air - Google Patents

Description

Jan. 2 0, 1953 D MCCARTHY ETAL 2,625,792 I ING TELESCOPING WALLS FLAME 'ruE HAV WITH FLUTED ENDS TO ADMIT AIR' Filed Sept. 2, 1948 4 Sheets-Sheet l i 4 Amer/me! DEN/S M ammy ,4. a I? SM/TV Jan. 20, 1953 D. M CARTHY ET AL 2,625,792

FLAME TUBE HAVING TELESCOPING WALLS 7 WITH FLUTED ENDS TO ADMIT AIR 4 Sheets-Sheet 2 Filed Sept. 2. 1948 M ra/me; 051w: MtAkT/IY A. a. E sM/m E Jan. 20, 1953 MccARTHY ETAL 2,625,792

- FLAME TUBE HAVING TELESCOPING WALLS WITH FLUTED ENDS TO ADMIT AIR Filed Sept. 2, 1948 4 Sheets-Sheet 3 E WWW Ami-n Jan. 20, 1953 D. MCCARTHY ET AL 2,625,792

FLAME TUBE HAVING TELESCOPING WALLS WITH FLUTED ENDS T0 ADMIT AIR 4 Sheets-Sheet 4 Filed Sept. 2. 1948 HL GO TM R w wwww w mw Mir, My m MN m Patented Jan. 20, 1953 FLAME TUBE HAVING TELESCOPING WALLS WITH FLUTED ENDS TO ADMIT AIR Denis McCarthy, and Alan Douglas French Smith,

Derby, England, assignors to Rolls-Royce Limited, Derby, England, a British company Application September 2,1948, Serial No. 47,398 In Great Britain September 10, 194! Claims. 1

This invention relates to gas-turbine engines and more particularly concerns combustion equipment for said engines.

A typical gas-turbine engine, as illustrated in Figure 1, comprises a compressor driven by a turbine through a shaft connecting them and delivering air to combustion equipment 12 in which fuel is burnt in the air and from which the combustion products pass to the turbine to drive it.

In the embodiment illustrated the combustion equipment comprises a series of combustion chambers 13 disposed in a, ring around the shaft connecting the turbine with the compressor and each combustion chamber comprises an outer casing or air casing within which a flame tube of cylindrical or part conical form is positioned so as to be spaced from the air casing. In alternative arrangements of combustion equipment the series of outer casings are replaced by an annular air casing formed by inner and outer substantially cylindrical walls surrounding the shaft interconnecting the turbine and compressor; in such an arrangement a series of flame tubes of cylindrical or part conical form may be accommodated within the annular air casing, or alternatively the flame tube itself may be of annular form being constituted by inner and outer flame tube walls spaced respectively from the inner and outer air casing walls. The present invention is generally applicable to flame tube arrangements, such as those of substantially cylindrical or part conical form or those providing an annular flame tube space.

In combustion equipment comprising an air casing and flame tube arrangement such as outlined, fuel is delivered into the flame tube and the air entering the combustion equipment .flow partly as primary air directly into the flame tube and partially around it; in addition apertures are usually provided in the wall or walls in the flame tube to allow the air flowing around the flame tubes to pass into them to provide "secondary or tertiary and possibly additional "primary air supplies thereto.

One known construction of flame-tube comprises two or more substantially frusto-conical elements disposed end to end and connected together by flanges on them so that the flame-tube had a stepped formation. Air inlet apertures are formed in the walls of the frusto-conical sections and in the flanges which extend transversely of the air stream around the flame-tube.

One object of this invention is to provide a flame-tube having rigidity of-structure and also 2 giving rise to improved combustion. Another object of the invention is to reduce the pressure loss attributable to the passage of air into the interior of the tube.

Another object of the invention is to provide a flame tube having degree of flexibility, accommodating expansion differences arising from 10- cal temperature variations, and thereby reduce the tendency of the flame-tube to buckle.

Another object of the invention is to provide a construction of flame tube which permits flow of the primary and/or secondary and/ or tertiary air to enter the interior of the flame tube without undue turbulence.

Constructions of flame-tube embodying the invention will now be described by way of example with reference to Figures 2-7 of the accompanying drawings, of which:

Figure 1 is a side elevational view of a gasturbine engine constructed in accordance with the present invention.

Figure 2 illustrates one construction of combustion equipment with parts broken away.

Figure 3 is a fragmentary view of part of Fig. 2 to a larger scale.

Figure 4 is a section taken on the line 4-4 in Figure 3.

Figure 5 illustrates another construction of combustion equipment with a part broken away.

Figure 6 is a fragmentary view of part of Figure 5 to a larger scale.

Figure '7 is a section on the line in Figures 5 and 6.

The embodiment of the invention illustrated in Figures 2, 3 and 4 of the accompanying drawings comprises a domed end-member IQ of known construction with a snout portion ISA through which primary air enters the flame-tube, and through which a fuel nozzle (not shown) extends to inject fuel into the interior of the flame tube. The flame tube additionally comprises an intermediate tubular member 2| with aperatures for receiving interconnector tubes and a substantially frusto-conical tubular discharge member 21 with apertures 26 for the introduction of tertiary air, these members being secured together in line.

The junction between the intermediate member 2| and the frusto-conical member 21 (Figure 3 and 4) is arranged to be at the desired point for the introduction of secondary air into the flame-tube and they are secured together by tubular, slightly- tapering extensions 22, 24 thereon of a heat-resistant metal, the extension 22 on the intermediate member 2| engaging by its 3 end within the extension 24 on the frusto-conica'l member 27.

The extension 22 of the intermediate member 2| is formed with a number of circumferentiallyspaced longitudinal inwardly-indented flutes or corrugations 2.3; so that the-.- extension 22 is; grooved on its outer surface and ridged on its inner surface. The flutes or corrugations 23 decrease in depth from the end by which it is:

engaged in the extension 2-ofthe-frusto-conical member 2! to that by which it is secured. to the intermediate member 2|.

The extension 24 of thefrusto-conical'member 21 is formed with oppositely-directedflutes or corrugations 28, so that the outer surface thereof is ridged and the inner surface.- grooved these flutes or corrugations 28 being likewisecircumferentially-spaced and tapered. so that when the extensions 22, 24 are interengaged the flutes or corrugations 23, 28 thereon register with one another and form ducts 29F of a cross-section tapering slightly from their-inlet.

ends to their outlet ends. The portionsof the extensions 22, 24 between the flutes or corru- 1 gations are in contact and are conveniently secured together by welding.

It will be clear that by reason of the flutes or corrugations tapering in depth the ducts 29- will be directed inwardly at an angle to the wall of the flame tube and towards the axis thereof in the direction of flow of gases through the flame-tube.

This flow of air is shown generally by the arrows of'Fi'gs. 2 and 3.

The angle, spacing, length, positionandicrosssectional area of the duct-like air inlets'will be selected to give the greatest efficiency ofrmixing of the air and gases;

The embodiment of the invention shown in Figures -7 of the accompanying drawings is illustrative of a number of' ways in whichthe' invention can be applied. shown the flame tube comprises a domed tubular end: member 3'! of' known construction with a shout. portion 31A throughwhich primary air enters the. flame-- tube and through which. a fuel nozzle: (not' shown) extends to spray fuel into theinterior The flame tube additionally of the flame tube. comprises two intermediate tubular members 69,- M and a fmsto-conical' tubular discharge member 32, these members being secured togetherin line.

As shown in greater detail in Figs. 6 and 'T the domed end-member 37 comprises two'tubular members 38, 39 and compressed air from the:

compressor of the engine. has access: between; these two members through snout'portiont 37A...

At the junction. of the member: 39' and upstream intermediate member 40 (Figures 6 'and' 7), the end-portion of the member 39.xwhich: is. received within the end-portion 44' of, the

upstream intermediate member, is formed with inwardly indented flutes or longitudinal .corruegations' 43 and the adjacent end-portion 44 of:v

the upstream-intermediate. memhenisacylinderz' Secondary diluting air passing through these ducts" is thus'introduced into the There are thus provided between the flutes 43 and the cylindrical end-portion 44 duct-like air-passages to introduce cooling air.

The invention is not limited to the details of construction described above and a number of modificationsz-will be apparent to' those well skilled in the art, which may be employed without departing from the scope of the invention.

The flutes or corrugations in accordance with the invention may have any suitable crosssection,. for example they may be substantially semi-circular to form substantially semi-circular-sectioned; or, when registering with similar flutes on another part, substantially circularsectioned ducts, or they may be such as to form substantially square or rectangular ducts.

It willbeclear moreover, that the fluted or corrugated formation gives mechanical strength to" the flame-tube which is relatively simple to manufacture.

Moreover,. constructions of flame tube in accordance with the invention can be of' the type providing an annular combustion space within an annular'air casin'g'structure. Such a flame tube" may be constituted by substantially oylin drical or frusto-conical walls respectively of. greater" and less meanv diameter; and one" orrboth of the walls. may comprise tubular flame tube' wall members secured: together in line, with the end portion or one member engaged within the end portion of the other member, either orboth of the" tubular members being corrugatedor fluted in a. manner such as described in'relation: to. the. substantially cylindrical: and: part-conical flame tubes described; above; In such annular flame tube: constructions the, duct-like passages associated with theouter flame tube wall may be inclinedin the'directionrof flow towards the aXis-ofthe tubular member, whilst the. passages associated with the-inner flame tube wall may" be inclined in the direction'of flowaway from; the axis of'the tubular members. In this mannerair introduced bythe duct passages into theinterior of the flame tube space will penetrate towards the mean radius of the annulus of flame longitudinal corrugations, asecond flame tubewall-member arranged in line with said first flame tube-wall-memberand having an integral end'portion engaged within and secured to'saidiintegral end portion of said first wall member; inwardlyindented flutes orlongitudinal oorruga.- tions formed in said integral end'portion. of said second wall member; and. registering with said' outwardly indented .flut'es' or longitudinal corrugations. to provide between them duct-like: airpassages to the interiorroftheflame-tube; which air passages. have their inlet ends: facing upstream-.to. thee air-flow exterior to" the flamertube? wall.

2. A- flame-tube as claimed in claim 1 in whichthe inner end-portion has inwardly indented flutes or. corrugations and. the outer'end portion has outwardly indented flutes or corrugationa.

3. In aflame tube for use with the combustion: equipment of a gas: turbine engine,- a pair of tubular flame tube- Wallv members arranged; in;

line with the integral end portion of one member engaged within, and secured to, the adjacent integral end portion of the other member, each of which members has its engaging end portion formed with flutes or longitudinal corrugations to co-operate with the end portion of the other tubular member to provide between them duct-like air passages to the interior of the flame tube, which air passages have their inlet ends facin upstream to the air flow exterior to the flame tube wall and have a slightly convergent crosssection throughout their length in the direction of air flow through them.

4. In a flame tube for use with the combustion equipment of a gas-turbine engine, a first tubular flame-tube wall member having an integral endportion, a second tubular flame-tube wail member arranged in line with said first wall member and having an integral end portion formed with in- Wardly indented flutes or longitudinal corrugations, which end portion is received within said first mentioned integral end portion, engages therewith and is secured thereto, said flutes or longitudinal corrugations co-operating with said REFERENCES CITED The following references are of record in the file of this patent: j

UNITED STATES PATENZIS Number Name Date 20 2,268,464 Seippel Dec. 30, 1941 2,448,561 Way Sept. 7, 1948 2,510,645 McMahan June 6, 1950 2,549,858 Sforzini Apr. 24, 1951

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