CA2499258C

CA2499258C - Combustor assembly and method

Info

Publication number: CA2499258C
Application number: CA002499258A
Authority: CA
Inventors: Jan Honza Stastny
Original assignee: Pratt and Whitney Canada Corp
Current assignee: Pratt and Whitney Canada Corp
Priority date: 2001-06-04
Filing date: 2002-04-10
Publication date: 2009-10-13
Anticipated expiration: 2022-04-10
Also published as: CA2499258A1

Abstract

An improved assembly and method is provided for attaching the inner and outer liner of a aircraft engine combustor, using heat shields located inside the combustor.

Description

COMBUSTOR ASSEMBLY AND METHOD
FIELD OF THE INVENTION
[0001] The present invention re1 ates to a gas turbine engine combustor.

BACKGROUND OF THE INVENTION

[0002] Gas turbine engine comk-)ustors in use in aircraft engine applications often inc':ude an inner and outer liner which are joined to enclc:ae a space to provide a combustion chamber. Typicaliy, little attention is paid to how the inner and outer ccmbustor liners are attached, however. Since it is well-known that unnecessary weight is to be avoided in aircraft. applications, opportunities for weight reduction should no.: be ignored.

SUNIlMARY OF THE INVENTION

[0003] One object of the preserIt invention is to provide a low cost combustor burner co-Llar assembly which positions a fuel burner in a passage opf~ning in an upstream end wall of a combustor and permits the thermal expansion and contraction thereof with respect to the upstream end wall of the combustor.

[0004] Another object of the present invention is to provide a head part of a gas engine combustor wherein a single piece fuel burner collar is radial-displaceably secured to the combustor only by a heat shield attached to the combustor wall.

[0005] In accordance with one aspect of the present invention, there is provided a head part of an annular combustor for a gas turbine engine having an upstream end wall with passage openings each of which accommodates a fuel burner. The head part comprises a heat shield detachably secured to a downstream side of the upstream end wall and covering an inner surface thereof, and a burner collar positioned w=ithin each of the passage openings and accommodating a corresponding one of the fuel burners. The burner collar has a radial flange with opposed first and second annular radial surfaces. The burner collar is axially restrained directly by the upstream end wall and the hea'_- shield in a manner wherein a radial surface of the dowristream side of the upstream end wall abuts the first annular radial surface of the flange, and a radial surface of an upstream side of the heat shield abuts the second annular radial surface of the flange, such that the b:zrner collar is radially displaceable with respect to the upstream end wall.

[0006]The burner collar preferably includes an annular cylinder, and the radial f'-ange extends radially and outwardly from the external periphery of the annular cylinder.

[0007] In one embodiment of the present invention the burner collar includes an annular cylinder and a skirt portion having an outer diameter sma::ler than a diameter of the passage opening in the upstream end wall of the combustor.

The flange preferably extends radially and outwardly from a downstream end of the annular cylinder and has an outer diameter greater than the dianieter of the passage opening.
The heat shield preferably has threaded studs which are integrated with the heat shield and extend through openings in the upstream eiid wall of the combustor.
Self-locking nuts are used to engage the respective threaded studs in order to secure the heat shield to the upstream end wall. The heat shield has a configuration such that when the heat shield is secured to the upstream end wall the radial surface of the heat shield is axially spaced a predetermined distance apart from the radial surface of the downstream sidE~ of the upstream end wall to form a gap for fittably and radial-displaceably accommodating the flange of the burner collar therein.

[0008] In accordance with another aspect of the present invention, there is provided a method for securing a burner collar to a gas turbine engine combustor for accommodating a fuel burner r,adial-displaceably positioned in a passage opening in an upstream end wall of the combustor. The method coniprises a step of axially restraining the burner collar in the passage opening by using a heat shield which is detachably secured to a downstream side of the upstream end wall and covering an inner surface thereof, to directly abut a radial flange of the burner collar against a radial surface of the upstream end wall of the combustor suc:~h that the burner collar is radially displaceable with respect to the upstream end wall of the combustor.

[0009] In contrast to multi-part assemblies of burner collars in the prior art, the present invention advantageously provides a single piece configuration of a burner collar which needs no additional parts to hold the burner collar in position. Lnstead, the axial flange of the burner collar is sirnply clamped between the conventional heat shield and the upstream end wall of the combustor. Therefore, the burner collar can be manufactured economically and. the overall weight of the gas turbine engine combustor can be reduced, which is also a desirable advantage especially when the gas turbine engine is used in aircraft.

[0010] Other advantages and features of the present invention will be better understood with reference to a preferred embodiment of the present invention described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing a preferred embodiment by way of illustration, in which:

[0012] Fig. 1 is a partial cross-sectional view of a gas turbine engine, showing an annular combustor incorporating an embodiment of the present invention;

[0013] Fig. 2 is a partial cross-sectional view of an annular combustor in an enlarged scale, illustrating details of the embodiment shown in Fig. 1;

[0014] Fig. 3 is a front view of a heat shield used in the embodiment in Fig. 1, showincx the upstream side thereof;
and [0015] Fig. 4 is a rear view of a burner collar used in the embodiment of Fig. 1, showing the downstream side thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] Referring to the drawings, particularly to Fig. 1, an annular combustor 10 is shown. The inner casing 12 of the annular combustor 10 includes radially spaced annular inner and outer walls 14 and 16 respectively, interconnected at their upstream ends by means of an annular upstream end wall, u:_,ually called a bulkhead 18, to form an annular combustor cnamber 20.

5 [0017] A plurality of passage openings 22 (only one shown) are provided in the bulkhead 18, each one receiving the outlet end of a fuel burner 24 which is suspended from an outer casing structure 26 for delivery of fuel and air into the combustion chamber 2~0. The passage openings 22 are equally spaced around the bulkhead 18.

[0018]As more clearly shown in Fig. 2, the bulkhead 18 has a first annular section 30 which integrally extends radially and inwardly from the annular outer wall 16 of the combustor 10, and a secc>nd annular section 32 which integrally extends radially and outwardly from the annular inner wall 14 of the combustc:>r 10. The first and second sections 30, 32 are overlapped in part, adjacent to the annular inner wall 14, and art:, secured together by locking means which are described with details hereinafter. The plurality of passage openings 22 are located in the first annular section 30 of the bulr":head 18.

[0019]The bulkhead 18 is part_icularly vulnerable to over heating as a result of the combustion process which takes place within the combustor chamber 20. In order to provide thermal shielding of the bulkhead 18, segmented heat shields 34 are attached to the downstream side of the first annular section 30 of the bulkhead 18, covering an inner surface 36 thereof. Heat shields 38, 40 are also provided to cover the inner surfaces of the respective annular inner and outer walls 14, 16 at an area adjacent to the bulkhead 18.

[0020]As more clearly shown in Fig. 3, each heat shield 34 is of generally truncated sectorial configuration, having ridges 41, 42, 44 and 46 projecting from the shield plate 48. The shield plate 48 has a circular opening 50 having a diameter smaller than the passage openings 22 of the bulkhead 18 and greater than the periphery of the outlet end of the fuel bur.-ner 24 (see Fig. 2). The ridge 41 is circular and defines the periphery of the opening 50, and includes a radial surface 52. The ridge 42 is also circular, radially spaced apart from the ridge 41, and as more clearly shown in Fig. 2, the ridge 42 has a thickness greater than the thickness of ridge 41. Ridges 44, 46 havf~ the same thickness as that of ridge 42 so that the ridiges 42, 44 and 46 provide an equal spacing between the shield plate 48 and the inner surface 36 of the first section 30 of the bulkhead 18 when the heat shield 34 is secured to the bulkhead 18.

[0021] As illustrated in Fig. 2, the heat shield 34 includes a plurality of threaded studs 54 extending from a thickened portion 56 (see Fiq. 3) of the shield plate 48.
The thickened portion 56 has a thickness equal to or slightly less than the thickness of the ridges 42, 44 and 48 to maintain the equal and even spacing. Small holes 58 and 60 in the respective shield 34 and the bulkhead 18 form cooling air passages to direct pressurized cool air from outside of the combustor chamber 20, through the space between the heat shield 34 and the bulkhead 18, entering the combustor chamber 20 to cool the bulkhead 18 and the heat shield 34. A plurality of pins 62 integrally project from the shield plate 48 to increase air contacting surfaces of the heat shield 34 for a better cooling result. The heat shield 34 further includes inner and outer ridgt:--~s 64, 66 extending outwardly from the shield plate 48 t.owards the inside of the combustor chamber 20 to form air channels adjacent to the heat shields 38, 40 for a better cooling result.

[0022] When the heat shielk:i 34 is mounted to the bulkhead 18, the threaded studs 54 positioned close to the annular outer wall 16 extend through mounting holes in the first annular section 30 and engage with self-locking nuts 68 and washers 70 to secure the heat shield 34 to the downstream side of the bulkhead 18. The threaded studs 54 positioned close to the arinular inner wall 14 extend through mounting holes in the first and second annular sections 30, 32 to engage with self-locking nuts 68 washers 70 to not only secure the heat shield 34 to the downstream side of the bulkhead 18, but also to securely join together the overlappec3 portions of the first and second annular sections 30, 32 to form the assembled bulkhead 18.

[0023] The annular radial surface 52 of the annular ridge 41 is spaced apart from the inner surface 36 of the first annular section 30 of the bulkhead 18 because the thickness of the ridge 41 is less than the thickness of the spacing ridges 42, 44 arid 46, forming a gap between the radial surface 52 of the heat shield 34 and the inner surface 36 of the bulkhead 18, to fittably accommodate a radial flange 72 of a burner collar 74.

[0024] The burner collar 74 includes an annular cylinder 76.
The annular radial flange 72 extends radially and outwardly from a downstream erid of the annular cylinder 76 and has an outer diameter greater than the passage opening 22 of the bulkhead 18. A skirt portion 78 extends radially, axially and outwardly from an upstream end of the annular cylinder 76 and has an outer diameter smaller than a diameter of the passage opening 22 of the bulkhead 18. Thus the buriier collar 74 is positioned within the passage opening 22 of the bulkhead 18 to accommodate the fuel burner 4, the inner surface of the annular cylinder 76 sealir:3ly contacting the outer periphery of the burner 24 to inhibit pressurized air outside the combustor chamber 20 from uncontrollable admission into the combustor chamber 20.

[0025] The distance between the annular radial surface 52 of the heat shield 34 and the inner surface 36 of the bulkhead 18 can be predetermined to a high degree of accuracy during the machinin(.j process. Thus, the radial inner surface 36 of the bulkhead 18 closely abuts the radial surface of the annular flange 72 at the upstream side thereof and the radial surface 52 of the heat shield 34 closely abuts the radial surface of the annular flange 32 at the downstream side thereof. Such a configuration axially restra-ins the position of the burner collar 74 with respect to t:ie bulkhead 18 and minimizes air leakage between the burner collar 74 and the respective heat shield 34 and the bulkhead 18, while permitting radial displacement of the burner collar 74 with respect to the bulkhead 18 and the heat shield 34.

[0026] As more clearly shown in Figs. 3 and 4, the radial flange 72 of the burner collar 74 further includes a tab 80 projecting radially and outwardly with a pair of side surfaces 82. The tab 80 fits into an axial recess 84 in ridge 42 with a pair of side walls 86. Thus, the interfaces 82 and 86 between the tab 80 and the recess 86 inhibit rotational movement of the burner collar 74 with respect to the bulkhead 18.

[0027] In a disassembly process, the self-locking nuts 68 and washers 70 positioned close to the annular inner wall 14 are disengaged frorr the threaded studs 54 to permit removal of the annular inner wall 14 of the combustor 10. The self-locking nuts 68 and washers 70 positioned close to the annular outer wall 16 of the combustor 10 are then disengaged from the studs 54 permitting detachment of tkie heat shield 34 from the downstream side of the first annular section 16 of the bulkhead 18. Finally, the burner collar 74 can be withdrawn from the passage opening 22 of the bulkhead 18 towards the inside of the combustor chamber 20. The process is reversed in the assembly process thereof.

[0028] Modifications and improvements to the above described embodiment of the present invention may become apparent to those skilled in the art. The forgoing description is intended to be exemplary rather than limiting. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A combustor for a gas turbine engine, the combustor comprising radially spaced annular outer and inner walls and a heat shield disposed therebetween, a section of respective outer and inner walls positioned adjacent to one another to form a bulkhead of the combustor, the heat shield mounted to the bulkhead on an inside of the combustor and connecting the sections of the inner and outer walls to thereby secure the outer and inner walls together.

2. A combustor as claimed in claim 1, wherein the heat shield is mounted to the inner and outer walls by a plurality of studs

3. A combustor as claimed in claim 2, wherein the plurality of studs are integral to the heat shield

4. A combustor as claimed in claim 2, wherein the studs extend through openings defined in the bulkhead

5. The combustor as claimed in claim 1 wherein the heat shield includes an aperture for receiving a fuel nozzle.

6. An attachment arrangement of radially spaced annular outer and inner walls which defines therebetween an annular combustion chamber of a combustor for gas turbine engines, comprising a first annular section extending radially and inwardly from the outer wall at an upstream end thereof, a second annular section extending radially and outwardly from the inner wall at an upstream end thereof, the first and second sections overlapping in part to form a bulkhead of the combustor, and means for securing the first and second sections together at overlapping portions thereof, said means disposed inside the combustor and integral with a combustor heat shield.

7. The attachment arrangement as claimed in claim 6 wherein the means comprise threaded studs on the heat shield.

8. The attachment arrangement as claimed in claim 7 wherein the heat shield comprises a shield plate attached to a downstream surface of the bulkhead for providing thermal shielding of the bulkhead, the threaded studs extending from the shield plate through respective openings in the overlapping portions of the first and second sections to engage with self-locking nuts in order to secure the heat shield and the first and second sections of the outer and inner walls together.

9. The attachment arrangement as claimed in claim 7 wherein the threaded studs are integrated with a shield plate of the heat shield.

10. The attachment arrangement as claimed in claim 7 wherein the heat shield comprises means integrated with a shield plate of the heat shield for providing spacing between the shield plate and the downstream surface of the bulkhead, thereby defining a predetermined gap between the shield plate and the downstream surface of the bulkhead.

11. The attachment arrangement as claimed in claim 10 wherein the means comprise a plurality of ridges projecting from an upstream side of the shield plate.

12. The attachment arrangement as claimed in claim 7 wherein the shield plate comprises an aperture in line with an aperture defined in the first section, for receiving an outlet end of a fuel burner.

13. A method of connecting radially spaced annular outer and inner walls in order to define therebetween an annular combustion chamber of a combustor for gas turbine engines, the method comprising: (a) partially overlapping at an upstream end of the combustor, a first annular radial section of the outer wall with a second annular radial section of the inner wall, thereby forming a bulkhead of the combustor, and (b) securing overlapping portions of the first and second annular radial sections together.

14. The method as claimed in claim 13 wherein step (b) is practiced by use of a heat shield attached to a downstream surface of the bulkhead, functioning both for proving thermal shielding of the bulkhead and for securing the overlapping portions of the first and second annular radial sections.

15. The method as claimed in claim 13 wherein step (b) is practiced by use of a plurality of heat shield segments each having a plurality of integrated fastening studs, each of the heat shield segments being attached to a downstream surface of the bulkhead and the fastening studs extending through openings defined in the overlapping portions of the first and second annular radial sections to secure the heat shield segment and the first and second annular radial sections together.

16. The method as claimed in claim 15 wherein each of the fastening studs comprises threads engaging with a self-locking nut at an upstream side of the bulkhead.