US2720080A

US2720080A - Combustion equipment for gas-turbine engines with support means for supporting the flame tube from an air casing

Info

Publication number: US2720080A
Application number: US332812A
Authority: US
Inventors: Oulianoff George; Evans Jeffrey
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1952-02-01
Filing date: 1953-01-23
Publication date: 1955-10-11
Anticipated expiration: 1972-10-11
Also published as: FR1073579A; GB715909A; CH309297A

Description

O 11 1955 G. OULIANOFF ET AL 2,720,080

COMBUSTION EQUIPMENT FOR GAS-TURBINE ENGINES WITH SUPPORT MEANS FOR SUPPORTING THE FLAME TUBE FROM AN AIR CASING 4 Sheets-Sheet 1 Filed Jan. 23, 1953 1955 G. OULIANOFF ETAL 20,080

CQMBUSTION EQUIPMENT FOR GAS-TURBINE ENGINES WITH SUPPORT MEANS FOR SUPPORTING THE FLAME TUBE FROM AN AIR CASING Filed Jan. 25, 1953 4 Sheets-Sheet 2 Oct. 1., 1955 e. OULIANOFF ET AL COMBUSTION EQUIPMENT FOR GAS-TURBINE ENGINES WITH SUPPORT MEANS FOR SUPPORTING THE I FLAME TUBE FROM AN AIR CASING 4 Sheets-Sheet 3 Filed Jan. 23, 1953 A E W HW Wm llllllll 1 Z A g O 1955 v G. OULIANOFF ET AL COMBUSTION EQUIPMENT FOR GAS-TURBINE ENGINES WITH SUPPORT MEANS FOR SUPPORTING THE FLAME TUBE FROM AN AIR CASING F iled Jan. 25, 1953 United States Patent fitice 2,720,080 Patented Oct. 11, 1955 COMBUSTION EQUIPMENT FOR GAS-TURBINE ENGINES WITH SUPPORT MEANS FOR SUP- PORTING THE FLAME TUBE FROM AN AIR CASING George Oulianotf, Allestree, and Jeffrey Evans, Alvaston,

England, assignors to Rolls-Royce Limited, Derby, England, a British company Application January 23, 1953, Serial No. 332,812

Claims priority, application Great Britain February 1, 1952 Claims. (31. Gil-39.36)

This invention relates to combustion equipment of gasturbine engines of the kind (hereinafter referred to as the kind specified) which comprises an annular air casing afforded by inner and outer coaxial casing walls, and within the annular space between these walls a flame tube also having inner and outer coaxial walls which are also coaxial with the walls of the air casing and in spaced relation thereto.

This invention has for an object to provide improved means for supporting the annular flame tube structure in position within the annular space between the walls of the air casing.

According to this invention, combustion equipment of the kind specified comprises a plurality of struts extending between and interconnecting the inner and outer walls of the air casing at a location so as to overlap axially the inlet end of the flame tube, which overlap is accommodated by complementary inter-engaging notchlike features extending from the leading end of the flame tube and from the trailing end of the struts respectively, and a plurality of pins each arranged to extend through aligned bores in a strut and an adjacent portion of the flame tube, thereby to locate the flame tube with respect to the struts.

Preferably the struts are of aerofoil section and are those normally provided to divide the inlet section of the air casing into a plurality of axially-extending diffuser passages preferably the flame tube extends from the trailing edge of each strut part-way only towards its leading edge.

In one preferred embodiment, the entry portion of a flame tube is annular and of wedge section with the apex of the wedge facing the inlet of the air casing and with the surfaces of the wedge substantially parallel to the inner and outer walls of the expansion chamber section of the air casing, which walls diverge in the direction of flow of air therethrough. In this preferred embodiment the trailing edge of each strut is, in effect, cut away towards its leading edge to form two surfaces respectively parallel to the inner and outer walls of the flame tube, and the flame tube is cut away to a shape to conform closely to the shape of the adjacent portion of the strut. Secured to the flame tube to extend between its inner and outer walls adjacent the downstream end of each cutaway there is a member having a radial bore therethrough, which bore is aligned with bores in the parts of the co-operating strut which lie radially inwards and radially outwards of its cutaway portion of the strut. An elongated pin is provided for each set of bores to extend therethrough to locate the flame tube with respect to the strut, and the head of the pin may be received in a socket which is grooved to receive a circlip for retaining the pin in position.

One embodiment of this invention will now be described by way of example, reference being made in the description to the accompanying drawings, in which- Figure l is a part-axial section through a construction of combustion equipment of the kind specified and embodying the invention,

Figure 2 is a section of which the right hand portion is taken on the line 2--2 of Figure 3, and of which the left hand portion is taken on the line 2A-2A of Figure 4,

Figure 3 is a section on the line 3-3 of Figure 1,

Figure 4 is an enlarged view of the pin and socket connection between the strut and the inlet section of the flame tube, and

Figure 5 illustrates a modification.

The combustion equipment comprises an air casing and a flame tube and each of these parts is formed in a number of sections joined end to end.

The air casing comprises an expansion chamber section 10 and a main flame-tube-enclosing section 11 con nected to the downstream end of the expansion-chamber section 10. Downstream of the section 11 there is located the nozzle box assembly 12 of the gas-turbine engine.

The expansion-chamber section 10 comprises an outer annular wall 10a and coaxially within it an inner wall 1% and these two walls are connected together by a plurality of hollow, circumferentially-spaced, radiallyextending, aerofoil-section struts 100. The walls 10a and 10b and the struts 10c are conveniently formed in one piece as a casting. As will best be seen from Figure 1, the walls 10a and 10b diverge in the direction of air flow through the expansion-chamber section and, as will best be seen from Figures 2 and 31', the aerofoil struts divide the annular space between the walls 10a and 10b into a plurality of axially-extending air passages.

The main flame-tube-enclosing section 11 comprises an outer wall 11a and an inner wall 11b. The upstream end of the outer wall 11a is secured as by bolts to the outlet end of the outer wall 10a of the expansion-chamber section 10 and the downstream end is inwardly flanged, as indicated at 13, so that the wall may be bolted to the outer casing member 12a of the nozzle box structure. The outer wall 11a can be withdrawn axially to expose the flame tube by unbolting it from the other wall parts 10a, 12a and withdrawing it axially over the nozzle box structure 12.

The inner wall 11b is formed from sheet metal and has a strengthening ring 14 secured to its upstream end, which ring has. a sliding engagement with a part carried by the outlet end of the wall 10b of the expansionchamber section 10. The downstream end of the Wall 11b is connected with adjacent structure in any convenient manner.

The flame tube is formed from sheet metal and comprises an inlet section 15, an outer annular wall 16 and an inner annular wall 17. The inlet section 15 is of hollow wedge form, and the two divergent surfaces thereof may either form continuations of the annular walls 16, 17, or as shown they may be separately formed so that the sections 16, 17 are separate from section 15. The annular walls 16, 17 are perforated to permit air flowing in the air casing to pass into the flame tube. The inlet section 15, and walls 16, 17 may be formed as continuous annular parts, or may be formed of segmental sections suitably secured together. Preferably the inlet section 15 is a continuous annular part and the walls 16, 17 are formed in a number, say four, of segmental sections.

The inlet section 15 of the flame tube extends from within the main flame-tube-enclosing section 11 of the the expansion-chamber section 10 is such that the inlet 1 section- 15.. of. theflametube overlaps axially the hollow aerofoil-section struts 100.

The inlet section of the flame tube is formed of upstream: anda'clown strearn, sheet-metal; annular parts. The

upstreampartmisroughly of V--'section and provides therapexr end of the section :15; and the'd'ownstrearn part 18 is trough-like in section and provides=outer andwinner Walliextensions 18a, 18b of the outer and innerwalls-of the: upstream part.19.

Thewall extensions

18a, 18b are joggled;attlieir-upstream ends to-provide locating seats for the upstream part 19, and the downstream part 18-also' comprises} a radial; wall' 18%: interconnecting the upstream ends-of. the::wall; extensions: 18a, 18b.

Eittett within the: trough of the downstream part 18,

there is an annular series of wall parts 20, each' of'which is basically in the form of-afrustum of a cone but is formed.- at: its: larger-diameter end with: diametrically-opposed:flats,. 'which. conform with the curvature of

walls

18a, 18b respectively, and is cut away. along planes which are-.normalto; thewalls'18a, 18b atztheir points of intersection. Eacht-walbpartr 20., asseen looking along the axisofthe. cone, therefore occupiesasector of the annulus lying between walls18a, 18b, and. each part 20 is joined, asby Welding, .to the-adjacentparts 20;

Each conical wall part 20 is formed at its smallerdiameter end with a cylindrical portion 20a terminating in. an. outwardly-directed. flange. 20b which surrounds a circular hole-in theradialwalL18c.

The fuel injectors 34 are. located coaxially within the smallerrdiameterends. of the. parts 20, the atomising'oritherebetween. The shroud members are mounted. from.

the. conical wall parts. 20 by means of. indentations 37 which extend across the annular passage and are secured.

as by welding.

In an alternative. construction (Figure 5.) the wall parts 20 may be omitted and the shroud members 36.- secured:

directly. to the wall 18c.

The. flame-tubeis supported at; its inlet end by having the. inlet section 15. secured. to the struts. 100 in the fol-.-

lowing manner.

The. trailing edge of each strut-is formed with a notchlike feature (see Figures 1 and 4) having, a radially outer surface 21 parallel to the adjacent portion of the.-

outer. wall 18a of. section; 15, a radially-inner. surface; 22

parallel. to; the adjacent. portion of the innerywall'. 18bof the. section 15, and a connecting surface 23' which. isv The.-

parallel to but axially spaced from the wall 18c. connectingsurface. 23- is axially about half-way between the apex of the section. 15. and thetrailing edge of the:

strut.

The upstream part'19 of'the. section 15 is. formed. with,

a series of circumferentially-spaced notch-like cut-away recesses 24 (Figure 3), one adjacent each strut 10c, and the part 19'is shaped'with the inner and outer side edges of the'recesses' 24 conforming to the adjacent circumferentially-facing surfacesof-the strut-10c andthe inner and outer bottom edges lying close to the surface 23.

Sheet-metal blanking pieces 25 are secured tothe part- 19 to stiffen it at the cut-awaymecesses 24 and' to seal otf the aperturesformed; by: the cut-away recesses.

the hole 27.

Each blanking-.pieceZS. has secured to.it'.a: short-peg 26 which. projects :into: a. hole. 27. inthe: surface. 23.: of the: adj acentstrutilom. The:v peg26 :has,=a clearance.-from:.the. edges: of:

The'section 15 is disposed relative'to the trailing edges" of the struts by inter-engaging the notch-like cut-away recesses 24 with the notch-like features (21, 22, 23) of the struts, and there is provided locating means by means of which the section 15 is located axially with respect to the struts 10c and is centred relative'thereto while. being;

capable of relative thermal expansion with respect-.to the struts.

The locating means comprises a series of socket'members 28, one for each strut 100, each of which. socket. members 28 is secured to the wall 18c on the side thereof-facing the surface 23 of the associated strut 10'c and extending from close to surface 21 of the associated strut 100 to close to its surface 22. Each socket member 28 has a bore 28a running through it and with the flame tube in position in the combustion. equipment the bore lines up with

radial bores

29, 30 in the strut 100, of which bore 29 extends from the outer surface of wall 10a to the surface 21 and of which the bore 30 is blind and extends inwards from surface 22.

The locating means also comprises a series of pins 31,. one for each strut 10c, and each pin 31 extends through. a set of aligned bores 29, 28a, 30. Each pin- 31 has a: head 31a received in a socket 32 mounted on the outer. Wall 10a of the air casing and the. socket is internallygrooved to'receive a retaining circlip 33- for holding,the pin in position.

The

walls

18a, 18b have a-clearance from the

surfaces

21, 22 of the strut 10c, the larger clearanceon. assem-- bly, when the flame tube is cold, being between wall. 18a and surface 21. In operation, the flame-tube is: heated to a greater extent thanthe struts 10c, and expands relative to the struts and this expansion is accommodated by the socket members 28 slidingradially with respect to the pins 31. In this Way the concentricityof the flame tube is maintained.

The. flame tube sections 16, 17 may be of any convenient construction and one suitable construction isdc.-

scribed in the specification of co-pending application Serial No. 332,811 filed January 23, 1953, of; the same.

applicants, now Patent No. 2,709,894, issued June 7, 1955.

We claim:

1. A combustion chamber of the kind employedin an aircraft gas turbine engine comprising an air casing having. an. inlet end and an outlet end and including an inner. annular wall and an outer annular wall, a plurality. of; struts extendingbetween. andinterconnecting saidinner. and outer air casing Walls at the inlet end of the air: casing, a flame tube including aninner'annular. wall and anouter annular wall, said flame tube. walls beingspaced fromthe corresponding air casingwall over part.at'least. of their length and being. substantially coaxial therewith, and said' flame. tube Walls defining therebetween.

an annular combustion space, an inlet flame-tube sec. tion interconnecting said inner and outer flame tube walls at their ends adjacent the inlet endof the air casingaud. overlapping said struts axially of. said annular space,, means defining recesses in the ends of said strutsnearest the outlet end of the air casing, said; recesses being adapted to receive said inlet flame-tube section, a plurality of radially-extending boresin said struts, means defining a plurality of bores in said. inlet flame-tubesec tion adapted to be aligned with the boresin said struts when said inlet section is received in said recesses, and. a plurality of pins. each adapted to extend through a bore inone. of said struts and an aligned bore in. said flame-tube section.

2. A combustion chamber of the kind employed. in an aircraft gas turbine engine. comprising an air casing having an inlet end and an outlet end and includingan inner annular wall and an outer annular Wall,.said.walls being divergent at the inlet end of the air. casing, a plu-. rality ofv axially-extendingstruts having side surfaces -ex-' tending between leading and trailing edges and said struts interconnecting said inner and outer air casing walls at the inlet end of the air casing, a flame tube including an inner annular wall and an outer annular wall, said flame tube walls being spaced from the corresponding air casing wall ever part at least of their length, and being substantially coaxial therewith and said flame tube walls defining therebetween an annular combustion space, a wedge-shaped inlet flame tube section interconnecting said inner and outer flame tube walls at their ends adjacent to the inlet end of the air casing, the apex of the wedge being directed towards the inlet end of the air casing and the inner and outer surfaces of the wedgeshaped section being substantially parallel to the inner and outer Walls respectively of the air casing, the struts having at their trailing edges means defining notch-like recesses, each recess having a radially-extending surface forwardly of the trailing edge of the corresponding strut and having inner and outer surfaces which are parallel to the divergent inner and outer walls of the inlet end of the air casing respectively and extend rearwards from the radial surface to the trailing edge of the strut, the wedge-shaped inlet section of the flame tube comprising a series of notch-like recesses circumferentially spaced to be aligned with the struts and each of the notch-like recesses having a radially-extending surface and a pair of axially-extending surfaces which extend from said radially-extending surface of the wedge-shaped inlet section to the leading edge thereof, the notch-like recesses in the struts being adapted to receive the inlet flame tube section so that the radially-extending surfaces of the wedge-shaped inlet section and of the struts lie parallel to and adjacent to one another, and so that the axially-extending surfaces of the wedge-shaped inlet section lie alongside the side surfaces of the struts and the inner and outer surfaces of the recesses in the struts lie alongside the inner and outer surfaces of the wedgeshaped inlet section, a plurality of radially-extending bores in said struts opening into the recesses in the struts, means defining a plurality of bores in said wedge-shaped inlet section adapted to be aligned with the bores in said struts when said wedge-shaped inlet section is received in said recesses in the struts, and a plurality of pins each adapted to extend through a bore in one of said struts and an aligned bore in said wedge-shaped inlet section.

3. A combustion chamber as claimed in claim 2, wherein said radially-extending surfaces or" the notch-like recesses in the wedge-shaped inlet section carry each a short axially-extending peg, and wherein the radiallyextending surfaces in the recesses of the struts are formed each with an axially-extending hole to be engaged by a corresponding one of the pegs.

4. A combustion chamber as claimed in claim 2, wherein the means defining a plurality of bores in said wedgeshaped inlet section comprises in each of its notch-like recesses a socket member extending between the inner and outer surfaces of the wedge-shaped inlet section and having a bore adapted to be aligned with a corresponding radially-extending bore in one of the struts when the inlet section is received in said recesses in the struts, the pins being adapted each to extend through a bore in one of the struts and the bore in the socket member.

5. A combustion chamber as claimed in claim 4, wherein each pin has a head, and the outer end of each of the bores in the struts is formed as a recess to receive the head, and comprising means to retain the pin in position with its head in the recess.

References Cited in the file of this patent UNITED STATES PATENTS 2,552,851 Gist, II. May 15, 1951 FOREIGN PATENTS 620,270 Great Britain Mar. 22, 1949