U.S. patent application number 10/880463 was filed with the patent office on 2005-02-17 for double wall combustor tile arrangement.
This patent application is currently assigned to Rolls-Royce plc. Invention is credited to Close, Desmond, Pidcock, Anthony.
Application Number | 20050034399 10/880463 |
Document ID | / |
Family ID | 34137734 |
Filed Date | 2005-02-17 |
United States Patent
Application |
20050034399 |
Kind Code |
A1 |
Pidcock, Anthony ; et
al. |
February 17, 2005 |
Double wall combustor tile arrangement
Abstract
A double wall structure (22) for a combustor (15) of a gas
turbine engine (10) comprising an inner wall (28) and an outer wall
(27), the inner wall (28) comprising a plurality of main tiles
(50), the main tiles (50) are secured to the outer wall (27) by a
securing means (35), wherein the inner wall (28) further comprises
a plurality of edge tiles (52) which are secured to the outer wall
(27) by securing means (35), each edge tile (52) overlapping at
least one edge (30, 31, 54, 61) of a main tile (50) thereby further
securing the main tiles (50) to the outer wall (27).
Inventors: |
Pidcock, Anthony; (Derby,
GB) ; Close, Desmond; (Derby, GB) |
Correspondence
Address: |
MANELLI DENISON & SELTER
2000 M STREET NW SUITE 700
WASHINGTON
DC
20036-3307
US
|
Assignee: |
Rolls-Royce plc
|
Family ID: |
34137734 |
Appl. No.: |
10/880463 |
Filed: |
July 1, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10880463 |
Jul 1, 2004 |
|
|
|
10330329 |
Dec 30, 2002 |
|
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Current U.S.
Class: |
52/506.1 |
Current CPC
Class: |
F23R 3/60 20130101; F23R
2900/03041 20130101; F23R 3/002 20130101 |
Class at
Publication: |
052/506.1 |
International
Class: |
E04B 002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 15, 2002 |
GB |
0200778.9 |
Claims
We claim:
1. A double wall structure for a combustor of a gas turbine engine
comprising an inner wall and an outer wall, the inner wall
comprising a plurality of main tiles, the main tiles being secured
to the outer wall by securing means, wherein the inner wall further
comprises a plurality of edge tiles which are secured to the outer
wall by securing means, each edge tile overlapping at least one
edge of a main tile thereby further securing the main tiles to the
outer wall, the edge tiles being narrower than the main tiles in a
dimension perpendicular to the overlapping edge.
2. A double wall structure as claimed in claim 1 wherein the
dimension of at least one of said edge tiles is between 50 and 5%
that of the main tile.
3. A double wall structure as claimed in claim 1 wherein the
dimension of at least one of said edge tiles is between 25 and 20%
that of the main tile.
4. A double wall structure as claimed in claim 1 wherein the
dimension of at least one of said edge tiles is between 50 and 10%
that of the main tile.
5. A double wall structure as claimed in claim 1 wherein the edge
of the main tile comprises a stepped edge having a leg portion
extending from the main tile towards the outer wall and a foot
portion extending from a distal end of the leg portion, the edge is
arranged to space apart the main tile from the outer wall, the foot
portion being in slideable contact with the outer wall and the
overlapping edge tile.
6. A double wall structure as claimed in claim 1 wherein the edge
of the main tile comprises a leg portion extending from the main
tile towards the outer wall, the edge is arranged to space apart
the main tile from the outer wall, the leg portion having a distal
end in slideable contact with the outer wall, the overlapping edge
tile being in slideable contact with the edge.
7. A double wall structure as claimed in claim 1 wherein the
securing means is a stud, the stud comprises a threaded plug and a
nut, in use the threaded plug is secured to the tile and extends
through a hole defined in the outer wall and onto which the nut is
fastened.
8. A double wall structure as claimed in claim 7, wherein the
threaded plug of the stud further comprises a thickened portion,
the thickened portion is disposed between the tile and the outer
wall and defines the space therebetween.
9. A double wall structure as claimed in claim 1 wherein the edge
tile overlaps adjacent edges of adjacent main tiles, the edges
being generally aligned with a principal axis of the engine.
10. A double wall structure as claimed in claim 1 wherein the edge
tile overlaps adjacent edges of adjacent main tiles, the edges
being generally circumferentially aligned with respect to a
principal axis of the engine.
11. A double wall structure as claimed in claim 1 wherein the edge
tile overlaps adjacent edges of adjacent main tiles, the edges
being generally axially aligned with a principal axis of the engine
and the edges being generally circumferentially aligned to the
principal axis.
12. A double wall structure as claimed in claim 1 wherein the edge
tile comprises a plurality of angled effusion cooling holes.
13. A double wall structure as claimed in claim 1 wherein the edge
tile comprises a plurality of pedestals, each pedestal extending
from the edge tile toward the outer wall.
14. A double wall structure as claimed in claim 1 wherein the
securing means is located generally centrally of the main
tiles.
15. A gas turbine engine comprising a combustor wherein the
combustor comprises a double wall structure as claimed in claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation in part of Ser. No.
10/330,329 filed Dec. 30, 2002.
FIELD OF THE INVENTION
[0002] This invention relates to improvements to a combustor of a
gas turbine engine and in particular to an arrangement of heat
resistant tiles of a double wall of a combustor.
BACKGROUND OF THE INVENTION
[0003] In a double walled combustor of a gas turbine engine it is
known to provide an inner wall which comprises heat resistant tiles
with pedestals, which extend toward the outer wall thereby
improving heat removal by a cooling air flow between the walls. The
tiles are secured to the outer wall by integral studs, which are
intended to allow the tiles to expand and contract with the thermal
cycle of the engine. However, it is known that the studs lock-up
and prevent thermal movement of the tiles. This damages the tiles
and leads to large gaps around the tiles and an undesirable
increase in the amount of cooling air required.
[0004] One way of reducing combustion product emissions is to
employ lean-burn combustion which limits the peak flame temperature
and hence production of nitrides of oxygen (NOx). To achieve
lean-burn most of a compressed air flow from a compressor of the
engine has to be committed to fuel/air mixing modules, with little
compressed air remaining for cooling the combustor walls.
[0005] Employing the most advanced double wall cooling designs
possible for lean-burn combustors is hence very beneficial to NOx
control to minimise the cooling air quantity required. This enables
the fuel/air mixing modules to be run even leaner and hence further
reduces NOx emissions.
SUMMARY OF THE INVENTION
[0006] It is therefore an object of the present invention to
provide a combustor double wall arrangement, which minimises the
amount of cooling fluid used and allows tiles to expand and
contract with the thermal cycle of the engine.
[0007] According to the present invention a double wall structure
for a combustor of a gas turbine engine comprising an inner wall
and an outer wall, the inner wall comprising a plurality of main
tiles, the main tiles are secured to the outer wall by a securing
means, wherein the inner wall further comprises a plurality of edge
tiles which are secured to the outer wall by securing means, each
edge tile overlapping at least one edge of a main tile thereby
further securing the main tiles to the outer wall, the edge tile
being narrower than the main tile in a dimension perpendicular to
the overlapping edge.
[0008] Preferably, the dimension of the edge tile is between 50 and
5% of the width of the main tile and more preferably, between 25
and 20% the width of the main tile. It will be understood that
dimensions from 50 to 10% of the width of the main tile may also be
used.
[0009] Preferably, the edge of the main tile comprises a stepped
edge having a leg portion extending from the main tile towards the
outer wall and a foot portion extending from a distal end of the
leg portion, the edge is arranged to space apart the main tile from
the outer wall, the foot portion being in slideable contact with
the outer wall and the overlapping edge tile.
[0010] Alternatively, the edge of the main tile comprises a leg
portion extending from the main tile towards the outer wall, the
edge is arranged to space apart the main tile from the outer wall,
the leg portion having a distal end in slideable contact with the
outer wall, the overlapping edge tile being in slideable contact
with the edge.
[0011] Preferably, the securing means is a stud, the stud comprises
a threaded plug and a nut, in use the threaded plug is secured to
the tile and extends through a hole defined in the outer wall and
onto which the nut is fastened.
[0012] Preferably, the threaded plug of the stud further comprises
a thickened portion; the thickened portion is disposed between the
tile and the outer wall and defines the space therebetween.
[0013] Preferably, the edge tile overlaps adjacent edges of
adjacent main tiles, the edges being generally aligned with a
principal axis of the engine.
[0014] Preferably, the edge tile overlaps adjacent edges of
adjacent main tiles, the edges being generally circumferentially
aligned with respect to a principal axis of the engine.
[0015] Preferably, the edge tile overlaps adjacent edges of
adjacent main tiles, the edges being generally axially aligned with
a principal axis of the engine and the edges being generally
circumferentially aligned to the principal axis.
[0016] Preferably, the edge tile comprises a plurality of angled
effusion cooling holes.
[0017] Alternatively, the edge tile comprises a plurality of
pedestals, each pedestal extending from the edge tile toward the
outer wall.
[0018] Preferably, the securing means is located generally
centrally of the main tiles. Preferably, the securing means is
tightly secured to the main tiles. Preferably, further securing
means are provided, the further securing means are loosely secured
to the main tiles.
[0019] Preferably, a gas turbine engine comprising a combustor
wherein the combustor comprises a double wall structure as
hereinbefore described.
[0020] Preferably, a method of assembling a double wall structure
of a combustor of a gas turbine engine, the wall structure
comprising an outer wall and an inner wall, the method comprising
the steps of: securing a plurality of main tiles to the outer wall
by a first securing means; securing a plurality of edge tiles to
the outer wall by securing means so that each edge tile overlaps at
least one edge of a main tile thereby further securing the main
tile to the outer wall.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Embodiments of the invention will now be described by way of
example only, with reference to the accompanying diagrammatic
drawings, in which:
[0022] FIG. 1 is a sectional side view of a gas turbine engine
incorporating a combustor in accordance with the present
invention.
[0023] FIG. 2 shows a sectional side view of part of a combustor of
the engine shown in FIG. 1;
[0024] FIG. 3 shows a prior art sectional side view of a part of a
radially outer wall structure of a combustor showing a wall
element;
[0025] FIG. 4 is a sectional side view A-A on FIG. 2 showing part
of a radially outer wall structure of a combustor double wall
element of a first embodiment of the present invention;
[0026] FIG. 5 is a sectional side view A-A on FIG. 2 showing part
of a radially outer wall of a combustor double wall element of a
second embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0027] With reference to FIG. 1, a ducted fan gas turbine engine
generally indicated at 10 has a principal axis X-X. The engine 10
comprises, in axial flow series, an air intake 11, a propulsive fan
12, an intermediate pressure compressor 13, a high-pressure
compressor 14, combustion equipment 15, a high-pressure turbine 16,
an intermediate pressure turbine 17, a low-pressure turbine 18 and
an exhaust nozzle 19.
[0028] The gas turbine engine 10 works in the conventional manner
so that air entering the intake 11 is accelerated by the fan 12 to
produce two air flows, a first air flow into the intermediate
pressure compressor 13 and a second air flow which provides
propulsive thrust. The intermediate pressure compressor 13
compresses the airflow directed into it before delivering that air
to the high-pressure compressor 14 where further compression takes
place.
[0029] The compressed air exhausted from the high-pressure
compressor 14 is directed into the combustion equipment 15 where it
is mixed with fuel and the mixture combusted. The resultant hot
combustion products then expand through, and thereby drive, the
high, intermediate and low-pressure turbine 16, 17 and 18 before
being exhausted through the nozzle 19 to provide additional
propulsive thrust. The high, intermediate and low-pressure turbines
16, 17 and 18 respectively drive the high and intermediate pressure
compressors 14 and 13 and the fan 12 by suitable interconnecting
shafts (not referenced).
[0030] Referring to FIG. 2, the combustor 15 is constituted by an
annular combustion chamber 20 having radially inner and outer wall
structures 21 and 22 respectively. The combustor 15 is secured to a
wall 23 by a plurality of pins 24 (only one of which is shown).
Fuel is directed into the chamber 20 through a number of fuel
nozzles 25 located at an upstream end 26 of the chamber 20. The
fuel nozzles 25 are circumferentially spaced around the engine 10
and serve to spray fuel into air derived from the high-pressure
compressor 14. The resultant fuel/air mixture is then combusted
within the chamber 20.
[0031] The combustion process takes place within the chamber 20 and
naturally generates a large amount of heat. It is necessary
therefore, to arrange that the inner and outer wall structures 21
and 22 are capable of withstanding the heat.
[0032] The radially inner and outer wall structures 21 and 22 each
comprise an outer wall 27 and an inner wall 28. The inner wall 28
is made up of a plurality of discrete wall elements in the form of
tiles 29A and 29B.
[0033] Each of the tiles 29A, 29B has circumferentially extending
edges 30 and 31, and the tiles are positioned adjacent each other,
such that the edges 30 and 31 of adjacent tiles 29A, 29B overlap
each other. Alternatively, the edges 30, 31 of adjacent tiles can
abut each other. Each tile 29A, 29B comprises a base portion 32
which is spaced from the outer wall 27 to define therebetween a
space 44 (see FIG. 3) for the flow of cooling fluid in the form of
cooling air as will be explained below. Heat removal features in
the form of pedestals 45 (see FIG. 3) are provided on the base
portion 32 and extend into the space 44 towards the outer wall
27.
[0034] Conventionally, and as shown in the arrangement of FIG. 2,
(first) securing means (35) are in the form of studs 35 comprising
threaded plugs 34 and nuts 36. Each tile 28 has a plurality of
threaded plugs 34 extending from the base portions 32 of the tiles
29A, 29B through apertures in the outer wall 27. Nuts 36 are
screwed onto the plugs 34 to secure the tiles 29A, 29B to the outer
wall 27.
[0035] Referring to FIG. 3, during engine operation, some of the
air exhausted from the high-pressure compressor 14 is permitted to
flow over the exterior surfaces of the chamber 20. The air provides
the chamber 20 with cooling with some of this air being directed
into the interior of the chamber 20 to assist in the combustion
process. First and second rows of mixing ports 38, 39 are provided
in the tiles 29B and are axially spaced from each other. The ports
38 correspond to apertures 40 in the outer wall 27, and the ports
39 correspond to apertures 41 in the outer wall 27.
[0036] Referring particularly to the tiles 29B, arrow A in FIG. 3
indicates air exiting via the open upstream edge 30 of the tile 29B
and mixing with downstream air flowing from the upstream adjacent
tile 29A, as indicated by arrow B. Arrow C indicates the resultant
flow of air. Angled effusion holes 46 are provided centrally of the
tile 29B between the ports 38 and 39. Arrow D indicates a flow of
air exiting from the space 44 through the effusion cooling holes
46. Also, a flow of downstream air exits from the open downstream
edge 31 of the tile 29B after mixing with upstream air flowing from
the adjacent tile 29A, as indicated by arrow E. Air flows indicated
by arrows C and E provide a film of cooling air over the interior
surface of the tiles 29A and 29B thereby preventing overheating
caused by the combustion of gases in the chamber 20.
[0037] During a normal operation cycle of the engine 10 the
combustor 20 will be subject to varying amounts of combustion heat.
This causes the tiles 29A and 29B to thermally expand relative to
the outer wall 27. The studs 35 which allow the tiles 29A and 29B
to slide usually accommodate these thermal expansions. However, it
is known that some of the studs 35 prevent the tiles 29A and 29B
from sliding particularly at extreme engine 10 operating
conditions. This leads to high stresses in the tile 29A, 29B at
elevated temperatures and subsequently premature failure thereof.
Furthermore, if the nuts 36 are over-tightened the tiles 29A, 29B
will lock-up against the studs 35 as they thermally expand causing
distortion, leading to fatigue and cracking. If the nuts 36 are
loose then both frettage and cooling flow leakage around the tiles
29A, 29B edges 30, 31 will occur. These problems are more severe
where advanced high-temperature alloys are used for the tiles 29A,
29B, because, although the alloys have superior oxidation
properties they have inferior strength, when compared to
conventional tile material.
[0038] To obviate these problems it would be easy to think that one
solution would be to use a central stud 35 in each tile 29A, 29B
thereby allowing the tile to be unconstrained at the
(circumferential) edges 30, 31, as well as axially aligned edges
(54, 61 in FIG. 4). However, it is likely that there would be
significant and uncontrolled cooling fluid leakage around the
(circumferential) edges 30, 31 and 54, 61 in FIG. 4, which in turn
would lead to a reduced amount of coolant flow through the effusion
cooling holes 46 and subsequent over-heating of the tiles 29A, 29B.
An additional concern is that should the stud 35 fail the whole
tile 29A, 29B would be released into the combustor 15 and passes
downstream into the high-pressure turbine 16.
[0039] Referring now to FIG. 4, the outer wall structure 22
comprises the inner wall 28 arranged in accordance with a first
embodiment of the present invention. The inner wall 28 comprises
main tiles 50 and edge tiles 52. The main tiles 50 are bolted to
the outer wall 27 by a generally centrally located stud 35. The
stud 35 is similar to that hereinbefore referred to and in use the
threaded plug 34 is cast integrally with the tile 50, 52 and
extends through a hole 33 defined in the outer wall 27 and onto
which the nut 36 is fastened. Alternatively, the threaded plug 34
may be brazed to the tile 50, 52. This generally centrally located
stud 35 tightly secures the main tile 50, as there is little or no
relative movement at the centre of the tile 50.
[0040] Main tiles 50 are generally similar to the tiles 29A, 29B
having pedestals 45 and effusion cooling holes 46, however, the
tiles 50 further comprise stepped edges 54. The stepped edge 54
comprises a leg portion 58 and a foot portion 56. The leg portion
58 extends from the main tile 50 towards the outer wall 27 and at
its distal end 55 the foot portion 56 extends away from and in
generally the same plane as the main tile 50. The foot portion 56
is arranged to seal against the outer wall 27 and is in slideable
contact therewith.
[0041] Where two circumferentially adjacent tiles 50 meet, an edge
tile 52 is positioned to overlap the foot portion 58 of each
adjacent tile 50. It is preferable for the edge tile 52 to be in
slideable contact with the main tiles 50 so that the main tiles
29A, 29B are able to thermally expand and contract in their main
plane. However, a small clearance may be provided between the foot
portion 56 and both the outer wall 27 and the edge tile 52.
[0042] An expansion gap 48 is defined between the main tile 50 and
the edge tile 52 to accommodate the thermal expansion of the main
tile 50. Similarly, a second expansion gap 47 is defined between
the stud 35 and the foot portion 56 to accommodate the thermal
expansions.
[0043] A stud 35 has its threaded plug 34 cast integrally with the
edge tile 52 and is secured by the nut 36 in conventional manner to
the outer wall 27. The edge tile 52 may be provided with more than
one stud 35 along its axial length. The outer wall 27 is provided
with apertures 60 (not shown where the edge tile is) to allow
cooling fluid into the space 44 between the tiles 52, 50 and the
outer wall 27.
[0044] In addition, the edge tiles 52 represent only a small
fraction of the total wall 22 area so a relatively large amount of
cooling air may be used, compared to that supplied to the larger
main tiles 29A, 29B. The edge tiles 52 can hence be operated at
relatively cool temperatures, enabling minimal distortion thereof,
therefore providing good location and slideable sealing engagement
with the main tiles 29A, 29B. Therefore the edge tiles 52 may be
made of a lower temperature capable and lower cost material than
the larger main tiles 29A, 29B.
[0045] A further improvement of the arrangement of the present
invention is the ease of assembly. The large main tiles 50 are
assembled to the combustor outer wall 27 when cold and secured by
their central stud 35 fixing, followed by fitting of the edge tiles
52. The conventional alternative approach of using edge-sealing
strips (not shown, but commonly known in the art) that slide into
slots on the tile edges present considerable assembly problems and
even greater dismantling problems after service.
[0046] Importantly, should the main tile's 50 centre stud 35 fail,
the tile 50 will remain secured to the outer wall 27 by the edge
tiles and so cannot be released into the combustor 15. For safety
reasons it may still be prudent to provide additional studs 35 near
to the edges 30, 31, 54, 61 of the main tile 50, however these
additional studs 35 would be relatively loosely fitted so as to not
restrain the thermal growth of the main tiles 50.
[0047] Referring now to FIG. 5, a second embodiment of the present
invention relates to the arrangement of the main tile 50 edges and
the edge tile 52. The main tile 50 comprises an edge 61 and the leg
portion 58, the leg portion 58 extending from the edge 61 toward
the outer wall 27. The distal end of the leg portion is in
slideable contact with the outer wall 27. The edge tile 52 is
arranged to overlap the edges 61 of two adjacent main tiles 50,
thereby securing the main tiles 50 to the outer wall 27. The edge
tile 52 comprises a rim 64, which is in slideable contact with
edges 61. The rim 64 comprises cooling holes 65. The threaded plug
34 further comprises a thickened portion 62 arranged to space apart
the edge tile 52 and the outer wall 27.
[0048] It should be apparent to one skilled in the art that not
only may the edge tiles 52 secure the main tiles 50 along their
generally axially aligned edges 54, 61, but may also secure the
main tiles 50 along their circumferential edges 30, 31.
[0049] The present invention is realized where the edge tile 52 is
narrower than the main tile 50. In particular, the edge tile 52 is
as narrow as possible so that thermal distortions are minimized so
its edges do not distort in a similar way to the aforementioned
edges of the prior art tiles. By way of exemplary embodiment, each
edge tile 52 is between 25 and 20% narrower than the main tile 50,
narrower being defined as a dimension perpendicular to the
overlapping edges. Without departing from the scope of the present
invention, it is particularly advantageous that the edge tile 52 is
between 50 and 5% the width of the main tile and more particularly
between 50 and 10% the width of the main tile.
[0050] Although the main tiles 50 have been described with
reference to having pedestals 45, impingement cooling may
alternatively cool the tiles 50. A configuration of an
impingement-cooling tile (or wall element) is described and
incorporated herein with reference to European Patent EP0576435 of
the present Applicant. The edges of the wall elements described in
EP0576435 are intended to be of a similar configuration as
described herein. Furthermore and in accordance with the present
invention the inner wall of EP0576435 is provided with edge
tiles.
[0051] Whilst endeavouring in the foregoing specification to draw
attention to those features of the invention believed to be of
particular importance it should be understood that the Applicant
claims protection in respect of any patentable feature or
combination of features hereinbefore referred to and/or shown in
the drawings whether or not particular emphasis has been placed
thereon.
* * * * *