U.S. patent application number 13/614580 was filed with the patent office on 2013-03-28 for method of operating a combustion chamber.
This patent application is currently assigned to ROLLS-ROYCE PLC. The applicant listed for this patent is Anthony PIDCOCK. Invention is credited to Anthony PIDCOCK.
Application Number | 20130078582 13/614580 |
Document ID | / |
Family ID | 44994018 |
Filed Date | 2013-03-28 |
United States Patent
Application |
20130078582 |
Kind Code |
A1 |
PIDCOCK; Anthony |
March 28, 2013 |
METHOD OF OPERATING A COMBUSTION CHAMBER
Abstract
A method of operating a "rich burn" combustion chamber includes
supplying 10% of the air through an inlet in an upstream wall;
supplying 64% to 80% of the air for mixing and supplying 10% to 26%
of the air for cooling at least one double skin wall and the
upstream wall; supplying a first portion of the 64% to 80% of the
air for mixing through mixing ports into the combustion chamber;
supplying a second portion of the 64% to 80% of the air for mixing
to provide convective cooling of the at least one double skin wall
before being supplied through additional mixing ports into the
combustion chamber; and supplying the 10% to 26% of the air for
cooling the at least one double skin wall and the upstream wall to
provide convective and/or effusion cooling of the at least one
double skin wall and the upstream wall.
Inventors: |
PIDCOCK; Anthony; (Derby,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PIDCOCK; Anthony |
Derby |
|
GB |
|
|
Assignee: |
ROLLS-ROYCE PLC
London
GB
|
Family ID: |
44994018 |
Appl. No.: |
13/614580 |
Filed: |
September 13, 2012 |
Current U.S.
Class: |
431/12 |
Current CPC
Class: |
F23R 3/06 20130101; F23R
3/50 20130101; F23R 3/04 20130101 |
Class at
Publication: |
431/12 |
International
Class: |
F23N 1/02 20060101
F23N001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2011 |
GB |
1116608.9 |
Claims
1. A method of operating a combustion chamber, the combustion
chamber comprising an upstream wall having at least one inlet for a
fuel injector and primary air, at least one double skin annular
wall, the at least one double skin annular wall comprising an inner
wall and an outer wall, the at least one double skin annular wall
having at least one mixing port extending there-through, the inner
wall or the outer wall having at least one additional mixing port
extending there-through adjacent the mixing port, the method
comprising supplying air for the combustion chamber, the method
comprising supplying 10% of the air for the combustion chamber
through the inlet in the upstream wall, supplying 64% to 80% of the
air for mixing, and supplying 10% to 26% of the air for cooling the
at least one double skin annular wall and the upstream wall, the
method further comprising supplying a first portion of the 64% to
80% of the air for mixing through the at least one mixing port into
the combustion chamber and supplying a second portion of the 64% to
80% of the air for mixing to provide convective cooling of the at
least one double skin annular wall before being supplied through
the additional mixing port into the combustion chamber and
supplying the 10% to 26% of the air for cooling the at least one
double skin annular wall and the upstream wall to provide
convective cooling and/or effusion cooling of the at least one
double skin annular wall and the upstream wall.
2. A method as claimed in claim 1 wherein the at least one mixing
port extending through the at least one double skin annular wall
comprising at least one primary mixing port extending through the
at least one double skin annular wall and at least one secondary
mixing port extending through the at least one double skin annular
wall and arranged downstream of the at least one primary mixing
port, the at least one additional mixing port in the inner wall or
outer wall comprising at least one additional primary mixing port
extending through the inner wall or the outer wall adjacent the
primary mixing port and at least one additional secondary mixing
port extending through the inner wall or the outer wall adjacent
the secondary mixing port, the method comprising supplying 10% of
the air for the combustion chamber through the inlet in the
upstream wall, supplying 32% to 40% of the air for primary mixing,
supplying 32% to 40% of the air for secondary mixing and supplying
10% to 26% of the air for cooling the at least one double skin
annular wall and the upstream wall, the method further comprising
supplying a first portion of the 32% to 40% of the air for primary
mixing through the at least one primary mixing port into the
combustion chamber and supplying a second portion of the 32% to 40%
of the air for primary mixing to provide convective cooling of the
at least one double skin annular wall before being supplied through
the at least one additional primary mixing port into the combustion
chamber, supplying a first portion of the 32% to 40% of the air for
secondary mixing through the at least one secondary mixing port
into the combustion chamber and supplying a second portion of the
32% to 40% of the air for secondary mixing to provide convective
cooling of the at least one double skin annular wall before being
supplied through the at least one additional secondary mixing port
into the combustion chamber and supplying the 10% to 26% of the air
for cooling the at least one double skin annular wall and the
upstream wall to provide convective cooling and/or effusion cooling
of the at least one double skin annular wall and the upstream
wall.
3. A method as claimed in claim 2 comprising supplying 10% of the
air for the combustion chamber through the inlet in the upstream
wall, supplying 35% to 40% of the air for primary mixing, supplying
35% to 40% of the air for secondary mixing and supplying 10% to 20%
of the air for cooling the at least one double skin annular wall
and the upstream wall, the method further comprising supplying a
first portion of the 35% to 40% of the air for primary mixing
through the at least one primary mixing port into the combustion
chamber and supplying a second portion of the 35% to 40% of the air
for primary mixing to provide convective cooling of the at least
one double skin annular wall before being supplied through the at
least one additional primary mixing port into the combustion
chamber, supplying a first portion of the 35% to 40% of the air for
secondary mixing through the at least one secondary mixing port
into the combustion chamber and supplying a second portion of the
35% to 40% of the air for secondary mixing to provide convective
cooling of the at least one double skin annular wall before being
supplied through the at least one additional secondary mixing port
into the combustion chamber and supplying the 10% to 20% of the air
for cooling the at least one double skin annular wall and the
upstream wall to provide convective cooling and/or effusion cooling
of the at least one double skin annular wall and the upstream
wall.
4. A method as claimed in claim 2 comprising supplying 10% of the
air for the combustion chamber through the inlet in the upstream
wall, supplying 40% of the air for primary mixing, supplying 40% of
the air for secondary mixing and supplying 10% of the air for
cooling the at least one double skin annular wall and the upstream
wall, the method further comprising supplying a first portion of
the 40% of the air for primary mixing through the at least one
primary mixing port into the combustion chamber and supplying a
second portion of the 40% of the air for primary mixing to provide
convective cooling of the at least one double skin annular wall
before being supplied through the at least one additional primary
mixing port into the combustion chamber, supplying a first portion
of the 40% of the air for secondary mixing through the at least one
secondary mixing port into the combustion chamber and supplying a
second portion of the 40% of the air for secondary mixing to
provide convective cooling of the at least one double skin annular
wall before being supplied through the at least one additional
secondary mixing port into the combustion chamber and supplying the
10% of the air for cooling the at least one double skin annular
wall and the upstream wall to provide convective cooling and
effusion cooling of the at least one double skin annular wall
and/or the upstream wall.
5. A method as claimed in claim 2 comprising supplying half of the
air for primary mixing through the at least one primary mixing port
into the combustion chamber and supplying half of the air for
primary mixing to provide convective cooling of the at least one
double skin annular wall before being supplied through the at least
one additional primary mixing port into the combustion chamber.
6. A method as claimed in claim 2 comprising supplying half of the
air for secondary mixing through the at least one secondary mixing
port into the combustion chamber and supplying half of the air for
secondary mixing to provide convective cooling of the at least one
double skin annular wall before being supplied through the at least
one additional secondary mixing port into the combustion
chamber.
7. A method as claimed in claim 2 wherein the at least one double
skinned annular wall comprises a plurality of circumferentially
spaced primary mixing ports and a plurality of circumferentially
spaced secondary mixing ports.
8. A method as claimed in claim 2 wherein the at least one double
skinned annular wall comprises a plurality of circumferentially
spaced additional primary mixing ports and a plurality of
circumferentially spaced additional secondary mixing ports.
9. A method as claimed in claim 2 wherein the at least one
additional primary mixing port is arranged around the at least one
primary mixing port.
10. A method as claimed in claim 2 wherein the at least one
additional secondary mixing port is arranged around the at least
one secondary mixing port.
11. A method as claimed in claim 1 comprising supplying half of the
air for mixing through the at least one mixing port into the
combustion chamber and supplying half of the air for mixing to
provide convective cooling of the at least one double skin annular
wall before being supplied through the at least one additional
mixing port into the combustion chamber.
12. A method as claimed in claim 1 wherein the combustion chamber
is an annular combustion chamber comprising a radially inner double
skinned annular wall and a radially outer double skinned annular
wall.
13. A method as claimed in claim 1 wherein the combustion chamber
is a tubular combustion chamber comprising a single double skinned
annular wall.
14. A method as claimed in claim 1 wherein the combustion chamber
is a gas turbine engine combustion chamber.
Description
[0001] The present invention relates to a method of operating a
combustion chamber and in particular to a method of operating a gas
turbine engine combustion chamber.
[0002] Most gas turbine engine combustion chambers use a
"rich-burn" design. In these "rich-burn" design combustion chambers
the fuel injectors supply a mixture of air and fuel at a ratio that
is much richer than the stoichiometric value of approximately 15.
To meet emission requirements and engine operating requirements,
the rich mixture of air and fuel is then diluted with air supplied
through rows of mixing ports in the walls of the combustion
chamber. The walls of combustion chambers have been provided with
one, two or three rows of mixing ports. The total flow of air to
the combustion chamber is divided and a first portion is supplied
to the fuel injector, a second portion is supplied to the mixing
ports and a third portion is supplied to cool the walls of the
combustion chamber.
[0003] A problem with the "rich-burn" design is that as the gas
turbine engine operating cycle has become more arduous, additional
air is required to cool the walls of the combustion chamber and
additional air is required to be supplied to the fuel injectors.
Thus, "rich burn" combustion chambers have an insufficient amount
of air for the mixing ports once the requirements of the fuel
injectors and the wall cooling have been fulfilled. This results in
a reduction in the amount of air available for the mixing ports,
which therefore reduces the ability to reduce, or minimise, the
emissions from the combustion chamber.
[0004] Accordingly the present invention seeks to provide a novel
method of operating a combustion chamber which reduces, preferably
overcomes, the above mentioned problem.
[0005] Accordingly the present invention provides a method of
operating a combustion chamber, the combustion chamber comprising
an upstream wall having at least one inlet for a fuel injector and
primary air, at least one double skin annular wall, the at least
one double skin annular wall comprising an inner wall and an outer
wall, the at least one double skin annular wall having at least one
mixing port extending there-through, the inner wall or the outer
wall having at least one additional mixing port extending
there-through adjacent the mixing port,
[0006] the method comprising supplying air for the combustion
chamber,
[0007] the method comprising supplying 10% of the air for the
combustion chamber through the inlet in the upstream wall,
supplying 64% to 80% of the air for mixing, and supplying 10% to
26% of the air for cooling the at least one double skin annular
wall and the upstream wall,
[0008] the method further comprising supplying a first portion of
the 64% to 80% of the air for mixing through the at least one
mixing port into the combustion chamber and supplying a second
portion of the 64% to 80% of the air for mixing to provide
convective cooling of the at least one double skin annular wall
before being supplied through the additional mixing port into the
combustion chamber and supplying the 10% to 26% of the air for
cooling the at least one double skin annular wall and the upstream
wall to provide convective cooling and/or effusion cooling of the
at least one double skin annular wall and the upstream wall.
[0009] The method may comprise supplying half of the air for mixing
through the at least one mixing port into the combustion chamber
and supplying half of the air for mixing to provide convective
cooling of the at least one double skin annular wall before being
supplied through the at least one additional mixing port into the
combustion chamber.
[0010] The at least one mixing port extending through the at least
one double skin annular wall comprising at least one primary mixing
port extending through the at least one double skin annular wall
and at least one secondary mixing port extending through the at
least one double skin annular wall and arranged downstream of the
at least one primary mixing port, the at least one additional
mixing port in the inner wall or outer wall comprising at least one
additional primary mixing port extending through the inner wall or
the outer wall adjacent the primary mixing port and at least one
additional secondary mixing port extending through the inner wall
or the outer wall adjacent the secondary mixing port, [0011] the
method comprising supplying 10% of the air for the combustion
chamber through the inlet in the upstream wall, supplying 32% to
40% of the air for primary mixing, supplying 32% to 40% of the air
for secondary mixing and supplying 10% to 26% of the air for
cooling the at least one double skin annular wall and the upstream
wall, [0012] the method further comprising supplying a first
portion of the 32% to 40% of the air for primary mixing through the
at least one primary mixing port into the combustion chamber and
supplying a second portion of the 32% to 40% of the air for primary
mixing to provide convective cooling of the at least one double
skin annular wall before being supplied through the at least one
additional primary mixing port into the combustion chamber,
supplying a first portion of the 32% to 40% of the air for
secondary mixing through the at least one secondary mixing port
into the combustion chamber and supplying a second portion of the
32% to 40% of the air for secondary mixing to provide convective
cooling of the at least one double skin annular wall before being
supplied through the at least one additional secondary mixing port
into the combustion chamber and supplying the 10% to 26% of the air
for cooling the at least one double skin annular wall and the
upstream wall to provide convective cooling and/or effusion cooling
of the at least one double skin annular wall and the upstream
wall.
[0013] The method may comprise supplying 10% of the air for the
combustion chamber through the inlet in the upstream wall,
supplying 35% to 40% of the air for primary mixing, supplying 35%
to 40% of the air for secondary mixing and supplying 10% to 20% of
the air for cooling the at least one double skin annular wall and
the upstream wall, [0014] the method further comprising supplying a
first portion of the 35% to 40% of the air for primary mixing
through the at least one primary mixing port into the combustion
chamber and supplying a second portion of the 35% to 40% of the air
for primary mixing to provide convective cooling of the at least
one double skin annular wall before being supplied through the at
least one additional primary mixing port into the combustion
chamber, supplying a first portion of the 35% to 40% of the air for
secondary mixing through the at least one secondary mixing port
into the combustion chamber and supplying a second portion of the
35% to 40% of the air for secondary mixing to provide convective
cooling of the at least one double skin annular wall before being
supplied through the at least one additional secondary mixing port
into the combustion chamber and supplying the 10% to 20% of the air
for cooling the at least one double skin annular wall and the
upstream wall to provide convective cooling and/or effusion cooling
of the at least one double skin annular wall and the upstream
wall.
[0015] The method may comprise supplying 10% of the air for the
combustion chamber through the inlet in the upstream wall,
supplying 40% of the air for primary mixing, supplying 40% of the
air for secondary mixing and supplying 10% of the air for cooling
the at least one double skin annular wall and the upstream wall,
[0016] the method further comprising supplying a first portion of
the 40% of the air for primary mixing through the at least one
primary mixing port into the combustion chamber and supplying a
second portion of the 40% of the air for primary mixing to provide
convective cooling of the at least one double skin annular wall
before being supplied through the at least one additional primary
mixing port into the combustion chamber, supplying a first portion
of the 40% of the air for secondary mixing through the at least one
secondary mixing port into the combustion chamber and supplying a
second portion of the 40% of the air for secondary mixing to
provide convective cooling of the at least one double skin annular
wall before being supplied through the at least one additional
secondary mixing port into the combustion chamber and supplying the
10% of the air for cooling the at least one double skin annular
wall and the upstream wall to provide convective cooling and
effusion cooling of the at least one double skin annular wall
and/or the upstream wall.
[0017] The method may comprise supplying half of the air for
primary mixing through the at least one primary mixing port into
the combustion chamber and supplying half of the air for primary
mixing to provide convective cooling of the at least one double
skin annular wall before being supplied through the at least one
additional primary mixing port into the combustion chamber.
[0018] The method may comprise supplying half of the air for
secondary mixing through the at least one secondary mixing port
into the combustion chamber and supplying half of the air for
secondary mixing to provide convective cooling of the at least one
double skin annular wall before being supplied through the at least
one additional secondary mixing port into the combustion
chamber.
[0019] The at least one double skinned annular wall may comprise a
plurality of circumferentially spaced primary mixing ports and a
plurality of circumferentially spaced secondary mixing ports.
[0020] The at least one double skinned annular wall may comprise a
plurality of circumferentially spaced additional primary mixing
ports and a plurality of circumferentially spaced additional
secondary mixing ports.
[0021] The at least one additional primary mixing port may be
arranged around the at least one primary mixing port.
[0022] The at least one additional secondary mixing port may be
arranged around the at least one secondary mixing port.
[0023] The combustion chamber may be an annular combustion chamber
comprising a radially inner double skinned annular wall and a
radially outer double skinned annular wall.
[0024] The combustion chamber may be a tubular combustion chamber
comprising a single double skinned annular wall.
[0025] The present invention will be more fully described by way of
example with reference to the accompanying drawings, in
which:--
[0026] FIG. 1 is a cross-sectional view through a turbofan gas
turbine engine having a combustion chamber according to the present
invention.
[0027] FIG. 2 is an enlarged cross-sectional view through the
combustion chamber shown in FIG. 1.
[0028] FIG. 3 is an enlarged cross-sectional view of a wall and a
mixing port in the wall of the combustion chamber shown in FIG.
2.
[0029] FIG. 4 is an alternative enlarged cross-sectional view of a
wall and a mixing port in the wall of the combustion chamber shown
in FIG. 2.
[0030] FIG. 5 is another enlarged cross-sectional view of a wall
and a mixing port in the wall of the combustion chamber shown in
FIG. 2.
[0031] A turbofan gas turbine engine 10, as shown in FIG. 1,
comprises in flow series an inlet 12, a fan section 14, a
compressor section 16, a combustion section 18, a turbine section
20 and an exhaust 22. The fan section 14 comprises a fan 24. The
compressor section 16 comprises in flow series an intermediate
pressure compressor 26 and a high pressure compressor 28. The
turbine section 20 comprises in flow series a high pressure turbine
30, an intermediate pressure turbine 32 and a low pressure turbine
34. The fan 24 is driven by the low pressure turbine 34 via a shaft
40. The intermediate pressure compressor 26 is driven by the
intermediate pressure turbine 32 via a shaft 38 and the high
pressure compressor 28 is driven by the high pressure turbine 30
via a shaft 36. The turbofan gas turbine engine 10 operates quite
conventionally and its operation will not be discussed further. The
turbofan gas turbine engine 10 has a rotational axis X.
[0032] The combustion section 18 comprises an annular combustion
chamber 42, which is shown more clearly in FIG. 2. The annular
combustion chamber 42 has a radially inner annular wall 44, a
radially outer annular wall 46 and an upstream wall 48 connecting
the upstream ends of the radially inner annular wall 44 and the
radially outer annular wall 46. The annular combustion chamber 42
is surrounded by a casing 50. The upstream wall 48 has a plurality
of circumferentially spaced fuel injector apertures 52 and each
fuel injector aperture 52 has a respective one of a plurality of
fuel injectors 54. The upstream wall 48 also has a plurality of
smaller diameter cooling apertures 56 through which a flow of
coolant, air, is arranged to flow in operation. The radially inner
annular wall 44 has a plurality of circumferentially spaced mixing
ports 58 through which a flow of mixing air is arranged to flow
into the annular combustion chamber 42 in operation. The radially
outer annular wall 46 has a plurality of circumferentially spaced
mixing ports 62 through which a flow of mixing air is arranged to
flow into the annular combustion chamber 42 in operation. The fuel
injector apertures 52 in the upstream wall 48 define inlets for
primary air for the annular combustion chamber 42.
[0033] The radially inner annular wall 44 is a double skin annular
wall and the radially outer annular wall 46 is a double skin
annular wall. The radially inner annular wall 44 comprises a
radially inner wall 66 and a radially outer wall 68 and the
radially outer annular wall 46 comprises a radially inner wall 70
and a radially outer wall 72. The radially outer wall 68 of the
radially inner annular wall 44 comprises a plurality of tiles 68A
and 68B and the radially inner wall 70 of the radially outer
annular wall 46 comprises a plurality of tiles 70A and 70B. The
double skin radially inner annular wall 44 has a plurality of
circumferentially spaced primary mixing ports 58A extending
there-through and a plurality of circumferentially spaced secondary
mixing ports 58B extending there-through and the secondary mixing
ports 58B are arranged downstream of the primary mixing ports 58A.
The double skin radially outer annular wall 46 has a plurality of
circumferentially spaced primary mixing ports 62A extending
there-through and a plurality of circumferentially spaced secondary
mixing ports 62B extending there-through and the secondary mixing
ports 62B are arranged downstream of the primary mixing ports 62A.
The radially outer wall 68 of the double skin radially inner wall
44 has a plurality of circumferentially spaced additional primary
mixing ports 74A extending there-through adjacent the primary
mixing ports 58A, the radially outer wall 68 of the double skin
radially inner wall 44 also has a plurality of circumferentially
spaced additional secondary mixing ports 74B extending
there-through adjacent the secondary mixing ports 58B. The radially
inner wall 70 of the double skin radially outer wall 46 has a
plurality of circumferentially spaced additional primary mixing
ports 76A extending there-through adjacent the primary mixing ports
62A, the radially inner wall 70 of the double skin radially outer
wall 46 also has a plurality of circumferentially spaced additional
secondary mixing ports 76B extending there-through adjacent the
secondary mixing ports 62B. Each of the additional primary mixing
ports 74A is arranged around the respective primary mixing port 58A
and each of the additional secondary mixing ports 74B is arranged
around the respective secondary mixing port 58B. Similarly each of
the additional primary mixing ports 76A is arranged around the
respective primary mixing port 62A and each of the additional
secondary mixing ports 76B is arranged around the respective
secondary mixing port 62B.
[0034] The radially inner wall 66 of the double skin radially inner
annular wall 44 also has a plurality of smaller diameter cooling
apertures 60 through which a flow of coolant, air, is arranged to
flow in operation. The coolant, air, is arranged to flow through
the apertures 60 into chambers 80 defined between the radially
inner wall 66 and the tiles 68A and 68B of the radially outer wall
68 of the double skin radially inner wall 44. The coolant is
arranged to impinge upon the radially inner surfaces 82 of the
tiles 68A and 68B to provide impingement cooling and then to flow
over the radially inner surfaces 82 of the tiles 68A and 68B to
provide convective cooling of the tiles 68A and 68B. The tiles 68A
and 68B of the radially outer wall 68 of the double skin radially
inner annular wall 44 have a plurality of effusion cooling
apertures 78 through which a flow of coolant, air, is arranged to
flow in operation from the chambers 80 and over the radially outer
surfaces 84 of the tiles 68A and 68B. Some of the coolant in the
chambers 80 is arranged to flow through the additional primary
mixing ports 74A and the additional secondary mixing ports 74B.
[0035] The radially outer wall 72 of the double skin radially outer
annular wall 46 also has a plurality of smaller diameter cooling
apertures 64 through which a flow of coolant, air, is arranged to
flow in operation. The coolant, air, is arranged to flow through
the apertures 64 into chambers 88 defined between the radially
outer wall 72 and the tiles 70A and 70B of the radially inner wall
70 of the double skin radially outer wall 46. The coolant is
arranged to impinge upon the radially outer surfaces 90 of the
tiles 70A and 70B to provide impingement cooling and then to flow
over the radially outer surfaces 90 of the tiles 70A and 70B to
provide convective cooling of the tiles 70A and 7013. The tiles 70A
and 70B of the radially inner wall 70 of the double skin radially
outer annular wall 46 have a plurality of effusion cooling
apertures 86 through which a flow of coolant, air, is arranged to
flow in operation from the chambers 88 and over the radially inner
surfaces 92 of the tiles 70A and 70B. Some of the coolant in the
chambers 88 is arranged to flow through the additional primary
mixing ports 76A and the additional secondary mixing ports 76B.
[0036] In operation 10% of the air for the combustion chamber 42 is
supplied through the inlets, the fuel injector apertures 52, in the
upstream wall 48, 32% to 40% of the air is supplied for primary
mixing, 32% to 40% of the air is supplied for secondary mixing and
10% to 26% of the air is supplied for cooling the double skin
radially inner annular wall 44 and the double skin radially outer
annular wall 46 and the upstream wall 48. A first portion A of the
32% to 40% of the air for primary mixing is supplied through the
primary mixing ports 58A and 62A in the double skin radially inner
annular wall 44 and the double skin radially outer annular wall 46
respectively into the combustion chamber 42. A second portion B of
the 32% to 40% of the air for primary mixing provides convective
cooling of the double skin radially inner annular wall 44 and the
double skin radially outer annular wall 46 before it is supplied
through the additional primary mixing ports 74A and 76A in the
radially outer wall 68 of the double skin radially inner annular
wall 44 and in the radially inner wall 70 of the double skin
radially outer annular wall 46 respectively into the combustion
chamber 42. A first portion C of the 32% to 40% of the air for
secondary mixing is supplied through the secondary mixing ports 58B
and 62B in the double skin radially inner annular wall 44 and the
double skin radially outer annular wall 46 respectively into the
combustion chamber 42. A second portion D of the 32% to 40% of the
air for secondary mixing provides convective cooling of the double
skin radially inner annular wall 44 and the double skin radially
outer annular wall 46 before it is supplied through the additional
secondary mixing ports 74B and 76B in the radially outer wall 68 of
the double skin radially inner annular wall 44 and in the radially
inner wall 70 of the double skin radially outer annular wall 46
respectively into the combustion chamber 42. In addition 10% to 26%
of the air is used for cooling the double skin radially inner
annular wall 44 and the double skin radially outer annular wall 46
and the upstream wall 48 provides convective cooling and/or
effusion cooling of the double skin radially inner annular wall 44,
the double skin radially outer annular wall 46 and the upstream
wall 48.
[0037] In an example, 35% to 40% of the air is supplied for primary
mixing, 35% to 40% of the air is supplied for secondary mixing and
10% to 20% of the air is supplied for cooling the double skin
radially inner annular wall 44 and the double skin radially outer
annular wall 46 and the upstream wall 48. A first portion A of the
35% to 40% of the air for primary mixing is supplied through the
primary mixing ports 58A and 62A in the double skin radially inner
annular wall 44 and the double skin radially outer annular wall 46
respectively into the combustion chamber 42. A second portion B of
the 35% to 40% of the air for primary mixing provides convective
cooling of the double skin radially inner annular wall 44 and the
double skin radially outer annular wall 46 before it is supplied
through the additional primary mixing ports 74A and 76A in the
radially outer wall 68 of the double skin radially inner annular
wall 44 and in the radially inner wall 70 of the double skin
radially outer annular wall 46 respectively into the combustion
chamber 42. A first portion C of the 35% to 40% of the air for
secondary mixing is supplied through the secondary mixing ports 58B
and 6213 in the double skin radially inner annular wall 44 and the
double skin radially outer annular wall 46 respectively into the
combustion chamber 42. A second portion D of the 35% to 40% of the
air for secondary mixing provides convective cooling of the double
skin radially inner annular wall 44 and the double skin radially
outer annular wall 46 before it is supplied through the additional
secondary mixing ports 74B and 76B in the radially outer wall 68 of
the double skin radially inner annular wall 44 and in the radially
inner wall 70 of the double skin radially outer annular wall 46
respectively into the combustion chamber 42. In addition 10% to 20%
of the air is used for cooling the double skin radially inner
annular wall 44 and the double skin radially outer annular wall 46
and the upstream wall 48 provides convective cooling and/or
effusion cooling of the double skin radially inner annular wall 44,
the double skin radially outer annular wall 46 and the upstream
wall 48.
[0038] In a more specific example, 40% of the air is supplied for
primary mixing, 40% of the air is supplied for secondary mixing and
10% of the air is supplied for cooling the double skin radially
inner annular wall 44 and the double skin radially outer annular
wall 46 and the upstream wall 48. A first portion A of the 40% of
the air for primary mixing is supplied through the primary mixing
ports 58A and 62A in the double skin radially inner annular wall 44
and the double skin radially outer annular wall 46 respectively
into the combustion chamber 42. A second portion B of the 40% of
the air for primary mixing provides convective cooling of the
double skin radially inner annular wall 44 and the double skin
radially outer annular wall 46 before it is supplied through the
additional primary mixing ports 74A and 76A in the radially outer
wall 68 of the double skin radially inner annular wall 44 and in
the radially inner wall 70 of the double skin radially outer
annular wall 46 respectively into the combustion chamber 42. A
first portion C of the 40% of the air for secondary mixing is
supplied through the secondary mixing ports 58B and 62B in the
double skin radially inner annular wall 44 and the double skin
radially outer annular wall 46 respectively into the combustion
chamber 42. A second portion D of the 40% of the air for secondary
mixing provides convective cooling of the double skin radially
inner annular wall 44 and the double skin radially outer annular
wall 46 before it is supplied through the additional secondary
mixing ports 74B and 76B in the radially outer wall 68 of the
double skin radially inner annular wall 44 and in the radially
inner wall 70 of the double skin radially outer annular wall 46
respectively into the combustion chamber 42. In addition 10% of the
air is used for cooling the double skin radially inner annular wall
44 and the double skin radially outer annular wall 46 and the
upstream wall 48 provides convective cooling and/or effusion
cooling of the double skin radially inner annular wall 44, the
double skin radially outer annular wall 46 and the upstream wall
48.
[0039] In the examples given above half of the air for mixing is
supplied through the mixing ports 58A, 58B, 62A and 62B into the
combustion chamber 42 and half of the air for mixing is used to
provide impingement and/or convective cooling of the double skin
radially inner annular wall 44 and the double skin radially outer
annular wall 46 before being supplied through the additional mixing
ports 74A, 74B, 76A and 76B into the combustion chamber 42. In
particular half of the air for primary mixing A is supplied through
the primary mixing ports 58A and 62A into the combustion chamber 42
and half of the air for primary mixing B is used to provide
impingement and/or convective cooling of the double skin radially
inner annular wall 42 and the double skin radially outer annular
wall 46 before being supplied through the additional primary mixing
ports 74A and 76A into the combustion chamber 42 and half of the
air for secondary mixing C is supplied through the secondary mixing
ports 58B and 62B into the combustion chamber 42 and half of the
air for secondary mixing D is used to provide impingement and/or
convective cooling of the double skin radially inner annular wall
44 and the double skin radially outer annular wall 46 before being
supplied through the additional secondary mixing ports 74B and 76B
into the combustion chamber 42.
[0040] FIG. 3 shows an embodiment of the double skin radially outer
annular wall 46 and shows a tile 70A of the radially inner wall 70
and the radially outer wall 72. The radially outer wall 72 has
apertures 64 to provide impingement cooling of the radially outer
surface 90 of the tiles 70A, alternatively the radially outer
surface 90 of the tiles 70A may be convectively cooled or the
radially outer surface 90 of the tiles 70A may be provided with
radially outwardly extending ribs, or projections, to provide
cooling of the tiles 70A. Each mixing port 62A is defined by a boss
94 which is integral, e.g. cast integral, with the tile 70A and
abuts the radially inner surface of the radially outer wall 72.
Each additional mixing port 76A, or 76B, comprises one or more
slots in the tile 70A which are arranged around, e.g.
concentrically around, the boss 94.
[0041] FIG. 4 shows another embodiment of the double skin radially
outer annular wall 46 and shows a tile 70A of the radially inner
wall 70 and the radially outer wall 72. The radially outer wall 72
has apertures 64 to provide impingement cooling of the radially
outer surface 90 of the tiles 70A, alternatively the radially outer
surface 90 of the tiles 70A may be convectively cooled or the
radially outer surface 90 of the tiles 70A may be provided with
radially outwardly extending ribs, or projections, to provide
cooling of the tiles 70A. The tiles 70A also have effusion cooling
apertures 86 at predetermined locations to cool hot spots on the
tiles 70A. Each mixing port 62A is defined by a boss 96 which
extends radially through the radially outer wall 72 and a tile 70A
of the radially inner wall 70 and the boss 96 has a flange 98 which
abuts, and is secured to, the radially outer surface of the
radially outer wall 72. Each additional mixing port 76A, or 76B,
comprises an annular slot defined between the tile 70A and the boss
96. Each additional mixing port 76A or 76B is concentric with the
boss 96.
[0042] FIG. 5 shows a further embodiment of the double skin
radially outer annular wall 46 and shows a tile 70A of the radially
inner wall 70 and the radially outer wall 72. The radially outer
wall 72 has apertures 64 to provide impingement cooling of the
radially outer surface 90 of the tiles 70A, alternatively the
radially outer surface 90 of the tiles 70A may be convectively
cooled or the radially outer surface 90 of the tiles 70A may be
provided with radially outwardly extending ribs, or projections, to
provide cooling of the tiles 70A. Each mixing port 62A is defined
by a boss 100 which extends radially through the tile 70A of the
radially inner wall 70 and the boss 100 has a flange 102 which
abuts, and is secured to, the radially inner surface of the
radially outer wall 72. Each additional mixing port 76A, or 76B,
comprises an annular slot defined between the tile 70A and the boss
100. Each additional mixing port 76A or 76B is concentric with the
boss 100. Each boss 100 has a portion 104 which extends radially
into the combustion chamber 42 and enhances mixing in the
combustion chamber 42. The portion 104 is chamfered such that the
downstream end 106 extends radially further into the combustion
chamber 42 than the upstream end 108. The additional mixing air
flowing through the additional mixing port 76A, 76B also cools the
portion of the boss 100 extending into the combustion chamber
42.
[0043] Although the present invention has been described with
reference to an annular combustion chamber comprising a radially
inner double skinned annular wall and a radially outer double
skinned annular wall, the present invention is equally applicable
to a tubular combustion chamber comprising a single double skinned
annular wall.
[0044] The present invention provides more air than is currently
supplied for mixing purposes. The present invention uses some, or
all, of the air currently used to provide film cooling of the inner
wall of the double skinned annular wall(s) to provide convection
cooling and/or effusion cooling of the double skinned annular
wall(s) and this air is then supplied through the additional mixing
port in the inner wall of the double skinned annular wall(s) to
function as mixing air to provide supplementary mixing air. The
present invention provides these additional mixing ports adjacent
to, around, the mixing ports. The additional mixing ports may be
concentric annular slots around the mixing ports or as a plurality
of slots arranged concentrically with the mixing ports. In
addition, the present invention uses some of the air currently
supplied through the mixing ports and used as mixing air to provide
convection cooling and/or effusion cooling of the double skinned
annular wall(s) and this air is then supplied through the
additional mixing port in the inner wall of the double skinned
annular wall(s) to function as mixing air to provide supplementary
mixing air.
[0045] In the present invention the air supplied through the mixing
ports is used as an ejector, or energiser, for the air supplied
through the corresponding additional mixing port.
[0046] The advantage of the present invention is that it increases
the amount of air available for mixing in a "rich burn" combustion
chamber and therefore improves the mixing process within the
combustion chamber and hence reduces engine emissions. In addition
the present invention significantly increases the amount of air
available for cooling of the double skinned annular wall(s)
compared to current designs. The increased mass flow of air for
cooling of the double skinned annular wall(s) reduces the level of
temperature rise in the cooling air, so improving the cooling
performance and at the same time any temperature rise that does
occur in the cooling air is beneficial in improving the mixing
performance in the combustion chamber, because this spent cooling
air is supplied through the additional mixing port(s). The supply
of mixing air through the double skinned annular wall(s) results in
a pressure drop in the cooling air and hence in the cooling air
supplied through the additional mixing port(s) as mixing air. This
pressure drop reduces the ability of the cooling air flowing
through the additional mixing port(s) to mix efficiently with the
combustion products in the combustion chamber. That is why the
present invention does not supply all the air required for mixing
through the double skinned annular wall(s) to cool the double
skinned annular wall(s) before being used as mixing air. An optimum
use of the air is to supply half of the air directly through the
mixing port(s) as mixing air and to supply half of the air for
cooling the double skinned annular wall(s) and then through the
additional mixing port(s) as mixing air so as to provide sufficient
momentum to achieve efficient mixing of the mixing air and
combustion products in the combustion chamber.
* * * * *