U.S. patent application number 14/620612 was filed with the patent office on 2018-03-15 for combustor dome heat shield.
The applicant listed for this patent is Pratt & Whitney Canada Corp.. Invention is credited to MICHAEL PAPPLE.
Application Number | 20180073736 14/620612 |
Document ID | / |
Family ID | 56611661 |
Filed Date | 2018-03-15 |
United States Patent
Application |
20180073736 |
Kind Code |
A1 |
PAPPLE; MICHAEL |
March 15, 2018 |
COMBUSTOR DOME HEAT SHIELD
Abstract
A combustor dome heat shield has a heat shield panel adapted to
be mounted to a combustor dome with a back face of the heat shield
panel in spaced-apart facing relationship with an inner surface of
the combustor dome to define an air gap between the heat shield
panel and the combustor dome. Rails extend from the back face of
the heat shield panel across the air gap. An anti-rotation notch is
defined in at least one of the rails for receiving an anti-rotation
tab of an adjacent element, such as a fuel nozzle floating collar.
The rails include notch cavity rails extending on either side of
the anti-rotation notch. The notch cavity rails define a notch
cavity for capturing coolant air leaking through the anti-rotation
notch.
Inventors: |
PAPPLE; MICHAEL; (VERDUN,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pratt & Whitney Canada Corp. |
Longueuil |
|
CA |
|
|
Family ID: |
56611661 |
Appl. No.: |
14/620612 |
Filed: |
February 12, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23R 3/26 20130101; F23R
3/10 20130101; F23R 3/283 20130101; F23R 3/002 20130101; F23R 3/16
20130101 |
International
Class: |
F23R 3/00 20060101
F23R003/00; F23R 3/28 20060101 F23R003/28 |
Claims
1. A dome heat shield for a combustor of a gas turbine engine,
comprising a heat shield panel adapted to be mounted to a combustor
dome with a back face of the heat shield panel in spaced-apart
facing relationship with an inner surface of the combustor dome to
define an air gap between the heat shield panel and the combustor
dome, rails extending from the back face of the heat shield panel
across the air gap, and at least one anti-rotation notch defined in
a first one of the rails for receiving an anti-rotation tab of an
adjacent element, the rails further including notch cavity rails
extending from the first rail on either side of the at least one
anti-rotation notch, the notch cavity rails defining a notch cavity
in fluid flow communication with the anti-rotation notch, wherein
the cavity rails define a closed boundary about the anti-rotation
notch.
2. The dome heat shield defined in claim 1, wherein at least one
fuel nozzle opening is defined in the heat shield panel, and
wherein the first rail at least partly surrounds the at least one
fuel nozzle opening.
3. The dome heat shield defined in claim 2, wherein the rails
include inner and outer rings concentrically disposed about the at
least one fuel nozzle opening, and wherein the first rail in which
the anti-rotation notch is defined in the outer ring.
4. The dome heat shield defined in claim 1, wherein the at least
one fuel nozzle opening comprises first and second fuel nozzle
openings, wherein said at least one anti-rotation notch includes
first and second anti-rotation notches, and wherein said notch
cavity rails connect both said first and second anti-rotation
notches in fluid flow communication with said notch cavity.
5. The dome heat shield defined in claim 4, wherein said rails
include first and second rings respectively surrounding the first
and second fuel nozzle openings, wherein said first and second
anti-rotation notches are respectively defined in the first and
second rings, and wherein said notch cavity rails extend from said
first ring to said second ring.
6. The dome heat shield defined in claim 5, wherein said first and
second rings are outer rings respectively extending about first and
second inner rings, the first and second inner rings circumscribing
the first and second fuel nozzle openings.
7. The dome heat shield defined in claim 1, wherein effusion holes
extend through the heat shield panel within the confines of the
notch cavity.
8. The dome heat shield defined in claim 7, wherein heat transfer
augmentation features are provided within the notch cavity.
9. The dome heat shield defined in claim 8, wherein the heat
transfer augmentation features include at least one of a set of pin
fins and a set of trip-strips.
10. A gas turbine engine combustor comprising the dome heat shield
as defined in claim 1.
11. A gas turbine engine combustor comprising: a shell having a
dome, at least one dome heat shield mounted to an inner surface of
the dome, at least one fuel nozzle opening defined in the dome heat
shield, at least one fuel nozzle component mounted to the dome, the
at least one fuel nozzle component having an anti-rotation tab
engaged in an anti-rotation notch defined in a first rail extending
from a back face of the dome heat shield, the anti-rotation notch
leading to a notch cavity defined on the back face of the dome heat
shield by notch cavity rails extending from the first rail, the
notch cavity rails and the first rail forming a boundary on all
sides of a perimeter of the notch cavity.
12. The gas turbine engine combustor defined in claim 11, wherein
the at least one fuel nozzle component comprises at least one
floating collar mounted between the dome and the at least one dome
heat shield, the anti-rotation tab forming part of the at least one
floating collar.
13. The gas turbine engine combustor defined in claim 12, wherein
the at least one fuel nozzle opening comprises first and second
fuel nozzle openings, wherein the at least one floating collar
comprise first and second floating collars, the anti-rotation tab
of the first floating collar being engaged in the anti-rotation
notch of the first rail, the anti-rotation tab of the second
floating collar being engaged in the anti-rotation notch of a
second rail, and wherein the notch cavity rails extend from said
first rail to said second rail, the anti-rotation notches of the
first and second rails both leading to said notch cavity.
14. The gas turbine engine combustor defined in claim 11, wherein
effusion holes extend from the back face to a front face of the
dome heat shield within the confines of the notch cavity.
15. The gas turbine engine combustor defined in claim 11, wherein
pins and/or trip-strips are provided within the notch cavity.
16. The gas turbine engine combustor defined in claim 13, wherein
the first and second rails are provided in the form of annular
rails respectively surrounding the first and second fuel nozzle
openings, said annular rails defining an annular collar cavity
about each of the first and second fuel nozzle openings, said
annular collar cavities being connected in flow communication with
the notch cavity via the anti-rotation notches.
Description
TECHNICAL FIELD
[0001] The application relates generally to gas turbine engine
combustors and, more particularly, to combustor dome heat
shields.
BACKGROUND OF THE ART
[0002] Heat shields such as those used to protect the combustor
shells, are exposed to hot gases in the primary combustion zone.
The amount of coolant available for cooling the heat shields must
be minimized to improve the combustion efficiency and to reduce the
smoke, unburned hydrocarbon and CO/NOx emission.
[0003] There is a continuing need for improved heat shields and
targeted cooling schemes.
SUMMARY
[0004] In one aspect, there is provided a dome heat shield for a
combustor of a gas turbine engine, comprising a heat shield panel
adapted to be mounted to a combustor dome with a back face of the
heat shield panel in spaced-apart facing relationship with an inner
surface of the combustor dome to define an air gap between the heat
shield panel and the combustor dome, rails extending from the back
face of the heat shield panel across the air gap, and at least one
anti-rotation notch defined in a first rail of said rails for
receiving an anti-rotation tab of an adjacent element, the rails
further including notch cavity rails extending from the first rail
on either side of the at least one anti-rotation notch, the notch
cavity rails defining a notch cavity in fluid flow communication
with the anti-rotation notch.
[0005] In a second aspect, there is provided a gas turbine engine
combustor comprising: a shell having a dome, at least one dome heat
shield mounted to an inner surface of the dome, at least one fuel
nozzle opening defined in the dome heat shield, at least one fuel
nozzle component, such as a floating collar, mounted to the dome,
the fuel nozzle component having an anti-rotation tab engaged in an
anti-rotation notch defined in a first rail extending from a back
face of the dome heat shield, the anti-rotation notch leading to a
notch cavity defined on the back face of the dome heat shield by
notch cavity rails extending from the first rail.
DESCRIPTION OF THE DRAWINGS
[0006] Reference is now made to the accompanying figures, in
which:
[0007] FIG. 1 is a schematic cross-section view of a turbofan
engine having a reverse flow annular combustor and dome heat
shields;
[0008] FIG. 2 is an isometric view of a dome portion of the
combustor of the engine shown in FIG. 1;
[0009] FIG. 3 is an enlarged isometric view of the dome portion of
the combustor shown in FIG. 2 and illustrating the assembly of a
dome heat shield to the radially inner and outer shells of the
combustor;
[0010] FIG. 4 is a rear view of the dome heat shield shown in FIG.
3 and illustrating the engagement of an anti-rotation tab of a fuel
nozzle floating collar in a corresponding anti-rotation notch
defined in an outer ring projecting from the back face of the dome
heat shield;
[0011] FIG. 5 is a rear view of the dome heat shield and
schematically illustrating coolant air leaking over the top of the
rails on the back face of the dome heat shield;
[0012] FIG. 6 is a rear enlarged view of the dome heat shield
illustrating a notch cavity defined between notch cavity rails
extending between outer rings projecting from the back face of the
dome heat shield; and
[0013] FIG. 7 is a rear view of a further embodiment of the dome
heat shield wherein each anti-rotation notch has its own notch
cavity.
DETAILED DESCRIPTION
[0014] FIG. 1 illustrates a gas turbine engine 10 of a type
preferably provided for use in subsonic flight, generally
comprising in serial flow communication a fan 12 through which
ambient air is propelled, a multistage compressor 14 for
pressurizing the air, a combustor 16 in which the compressed air is
mixed with fuel and ignited for generating an annular stream of hot
combustion gases, and a turbine section 18 for extracting energy
from the combustion gases.
[0015] The combustor 16 is housed in a plenum 17 supplied with
compressed air from compressor 14. The combustor 16 comprise an
annular combustor shell 20 including a radially inner shell 20a and
a radially outer shell 20b, defining a combustion chamber 22. While
the illustrated combustor is a flow-through combustor, it is
understood that it could also take the form of a reverse-flow
combustor or any other type of gas turbine engine combustors. The
combustor 16 has a bulkhead or inlet dome portion 24. The combustor
16 further has an exit portion 26 for communicating combustion
gases with the turbine section 18. A plurality of circumferentially
distributed fuel nozzles 28 are mounted to extend through the dome
portion 24 of the combustor 20 to deliver a fuel-air mixture to the
combustion chamber 22.
[0016] A plurality of impingement holes 29 (see FIG. 3) are defined
in the inner and outer shells 20a and 20b for cooling purposes, and
dilution holes (not shown) may also be provided for combustion
purposes. It is understood that the inner and outer shells 20a and
20b may adopt various configurations. The inner and outer shells
20a and 20b are typically made out of sheet metal, though any
suitable material(s) and manufacturing method(s) may be used. Heat
shields, such as inner front heat shield 82 an outer front heat
shield 84 shown in FIG. 2, may be mounted to the hot inner surface
of the combustor shell 20. A thermal barrier coating (not shown)
may be applied to the inner or combustion facing surfaces of the
inner and outer front heat shields 82 and 84 to protect them
against the high temperatures prevailing in the combustion chamber
22.
[0017] Referring concurrently to FIGS. 2 and 3, it can be
appreciated that circumferentially distributed dome heat shields 40
may be mounted to the dome portion 24 of the inner and outer shells
20a, 20b inside the combustion chamber 22 to protect the dome
portion 24 from the high temperatures in the combustion chamber 22.
The dome heat shields 40 are typically castings made out of high
temperature capable materials. Each dome heat shield 40 has a
plurality of threaded studs 42 (six according to the examples shown
in FIGS. 4, 5 and 7) extending from a back face of the heat shield
and through corresponding mounting holes (not shown) defined in the
combustor dome. Self-locking nuts 41 are threadably engaged on the
studs 42 from outside of the combustion chamber 22 for holding the
dome heat shields 40 tightly against the combustor dome.
[0018] As shown in FIGS. 2 and 3, circumferentially spaced-apart
fuel nozzle openings 48 are defined through the combustor dome
portion 24 for allowing mounting of the fuel nozzles 28 to the
combustor 16. At least one corresponding fuel nozzle opening 52
(two in the examples illustrated in FIGS. 2-7) is defined in each
of the dome heat shields 40 and is aligned with a corresponding
fuel nozzle opening 48 in the combustor dome portion 24 for
accommodating an associated fuel nozzle therein. The provision of
two or more fuel nozzle openings 52 in each heat shield 40 reduces
the number of heat shields required to cover the dome portion 24,
the number of studs 42, rails, air coolant leakage, cost and weight
when compared to dome heat shields for a single fuel nozzle.
However, it is understood that the features of the present
disclosure are equally applicable to dome heat shield segments
having a single fuel nozzle opening.
[0019] As can be appreciated from FIGS. 2-4, a floating collar 54
is mounted in each nozzle opening 48 to provide sealing between the
combustor shell 20 and the fuel nozzles 28 while allowing relative
movement therebetween. The fuel nozzle collars 55 of the nozzles 28
are slidably received in the floating collars 54. The floating
collars 54 are axially trapped between the dome heat shields 40 and
the dome portion 24 of the inner and outer combustor shells 20a,
20b. The fuel nozzle openings 48 are slightly oversized relative to
the floating collars 54, thereby allowing limited radial movement
of the collars 54 with the fuel nozzles 28 relative to the
combustor shell 20.
[0020] As shown in FIG. 3, the dome heat shields 40 are spaced from
the dome portion 24 so as to define a heat shield back face cooling
air space or air gap 60. Relatively cool air from plenum 17 is
admitted in the air gap 60. Impingement hole patterns are arranged
in the dome portion 24 of the combustor shell 20 to optimize the
heat shield cooling. As will be seen hereinafter, heat exchange
promoting structures and rails may be strategically positioned on
the back face of the heat shields 40 to locally promote enhance
cooling in targeted or most thermally solicited areas of the heat
shields.
[0021] Now referring concurrently to FIGS. 4 and 5, it can be seen
that each individual heat shield 40 may be provided in the form of
a panel 40a, more particularly a circular sector, having radially
inner and outer edges 41, 43 extending between lateral edges 45,
47. Rails integrally extend from the back face of the heat shields
40 to strengthen the heat shields and direct the flow of cooling
air as desired. Some of the rails may extend from the heat shield
panel back face all the way into sealing contact with the inner
surface of the combustor dome portion 24 and, thus, more or less
act as sealing rails to compartmentalize the air gap 60, thereby
directing the cooling air to targeted regions of the dome heat
shields.
[0022] For instance, the rails may include lateral rails 66a, 66b
extending along lateral edges 45, 47 between radially inner and
outer rails 66c, 66d. These peripheral rails 66a, 66b, 66c, 66d
form a closed perimeter at the back of the heat shield 40. The
peripheral rails 66a, 66b, 66c, 66d extend across the air gap 60
into sealing contact with the inner surface of the dome portion 24
of the combustor 16.
[0023] The rails may also include concentric inner and outer rings
66e, 66f about each fuel nozzle opening 52. As can be appreciated
from FIG. 3, the height of the inner rings 66e is less than the
height of the outer rings 66f and the peripheral rails 66a, 66b,
66c, 66d. The rings 66e do not extend completely across the gap 60.
As shown in FIG. 3, the inner rings 66e seal against the floating
collars 54. Each pair of inner and outer rings 66e, 66f subdivides
the air gap 60 into a collar cavity 60a. As shown in FIG. 3,
cooling air A1 passes through a gap between the floating collar 54
and the outer shell 20b to cool each collar cavity 60a of the dome
heat shield 40. Impingement cooling is not available in this area
in view of the presence of the fuel nozzles 28 and the floating
collars 54. A circular row of effusion holes 61 may be provided in
the annular collar cavity 60a concentrically about each fuel nozzle
opening 52 for allowing at least part of the coolant air flowing
into the collar cavity 60a to flow thought the dome heat shield 40
to provide for the formation of a cooling film over the front face
of the dome heat shield 40. Such dual use of the coolant air
advantageously contributes to minimize the amount of cooling air
required for the heat shields 40.
[0024] As shown in FIG. 4, an anti-rotation notch 70 is defined in
each outer ring 66f for engagement with a corresponding
anti-rotation tab 72 projecting from each floating collar 54. While
in the example depicted the anti-rotation tab is on a floating
collar, the skilled reader will appreciate that the described
structure can be applied to anti-rotation feature(s) on any
suitable adjacent structure. Coolant air in each collar cavity 60a
can leak through the gap between the anti-rotation notch 70, the
outer shell 20b and the anti-rotation tab 72. This leakage air is
undesirable in that it weakens the impingement cooling of air
passing through the inner and outer shell impingement holes 29
(FIG. 3) used to cool the main surface area of the dome heat shield
outside the collar cavity area.
[0025] The detrimental effect of the collar cavity leakage air on
impingement cooling of the remainder of the dome heat shield can be
minimized by capturing at least a portion of the air escaping
through the anti-rotation notch 70 into a notch cavity 74. As shown
in FIG. 4, the notch cavity 74 may be formed by the addition of
notch cavity rails 76 between the outer rings 66f. According to the
embodiment shown in FIG. 4, the notch cavity rails 76 extend from a
first outer ring to a second outer ring on either side of the
anti-rotation notches 70 formed in the outer rings 66f.
Accordingly, both anti-rotation notches 70 lead to a common notch
cavity. In other words, both anti-rotation notches 70 are connected
in fluid flow communication with a same and unique notch cavity 74.
Effusion holes 78 may be provided in the bottom of the notch cavity
74 to evacuate coolant air from the notch cavity 74 and contribute
to the formation of a cooling film of air over the front face of
the dome heat shield 40. As shown in FIG. 6, heat transfer
augmentation features, such as pins 80 and trip-strips 82 may be
provided in the notch cavity 74.
[0026] The outer ring 66f, the peripheral rails 66a, 66b, 66c and
66d and the notch cavity rails 76 are in sealing contact with the
outer shell 20b. This contact is however not perfect and coolant
air can leak over the top of these rails as schematically depicted
by the flow arrows in FIG. 5. It is, thus, desirable to minimize
the length of the notch cavity rails 76 in order to reduce the air
leakage from the notch cavity 74 to the main cavity 60b defined
between the outer rings 66f and the peripheral rails 66a, 66b, 66c,
66d. The configuration of the notch cavity rails 76 extending
transversally between the adjacent outer rings 66f from one
anti-rotation notch to an opposed generally facing anti-rotation
notch as for instance shown in FIG. 4 contributes to minimize the
overall length of notch cavity rails 76.
[0027] Also, it is desirable to minimize the size of the notch
cavities 74 and maximize the size of the main cavity 60b since the
main cavity 60b can be impingement cooled efficiently through the
shell impingement holes 29. As shown in FIG. 7, each anti-rotation
notch 70 could have its own notch cavity 74'. According to this
alternative, the notch cavity size is minimized but the length of
the notch cavity rails is higher than in the embodiment shown in
FIGS. 4-6. This type of notch cavity is more suitable for dome heat
shields having only one fuel nozzle per heat shield (i.e. dome heat
shield with a single fuel nozzle opening and, thus, a single
anti-rotation notch).
[0028] As shown in FIG. 7, the notch cavity rails 76' have a
generally U-shaped configuration, including a first segment 76a'
extending from the associated outer ring 66f on a first side of the
anti-rotation notch, a second segment 76b' extending at generally
90 degrees from the first segment 76a' and a third segment 76c'
extending at generally 90 degrees from the opposed end of the
second segment 76b' to the outer ring 66f on a second side of the
anti-rotation notch 70, thereby forming a closed perimeter at the
exit of the anti-rotation notch 70.
[0029] The coolant air in the air gap 60 (i.e. the collar cavity
60a, the main cavity 60b and the notch cavities 74) can be
discharged through the effusion holes 61 in the collar cavity 60a,
the notch and main cavities 74 and 60b, as well as through holes
(not shown) defined in the peripheral rails 66a, 66b, 66c, 66d.
[0030] The above description is meant to be exemplary only, and one
skilled in the art will recognize that changes may be made to the
embodiments described without departing from the scope of the
invention disclosed. For example, the invention can be provided in
any suitable heat shield configuration and in any suitable
combustor configuration, and is not limited to application in
turbofan engines. Also, the anti-rotation notches could be defined
in other types of rails and are not limited to the outer rings as
shown in the exemplified embodiments. For instance, the
anti-rotation notches could be provided in semi-annular mid-rails
extending between the inner and outer rails. Still other
modifications which fall within the scope of the present invention
will be apparent to those skilled in the art, in light of a review
of this disclosure, and such modifications are intended to fall
within the appended claims.
* * * * *