U.S. patent application number 14/299890 was filed with the patent office on 2014-12-11 for fuel injector and a combustion chamber.
The applicant listed for this patent is ROLLS-ROYCE DEUTSCHLAND LTD & CO KG, ROLLS-ROYCE PLC. Invention is credited to Imon-Kalyan BAGCHI, Robert Anthony HICKS, Waldemar LAZIK, Ian James TOON, Michael WHITEMAN.
Application Number | 20140360202 14/299890 |
Document ID | / |
Family ID | 48875991 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140360202 |
Kind Code |
A1 |
TOON; Ian James ; et
al. |
December 11, 2014 |
FUEL INJECTOR AND A COMBUSTION CHAMBER
Abstract
A fuel injector includes pilot and main fuel injectors. The
pilot fuel injector includes at least one pilot air swirler and the
main fuel injector includes a main air blast fuel injector located
between inner main and outer main air swirlers. A first air
splitter is located between the pilot and inner main air swirlers
and a second air splitter is located between the pilot and inner
main air swirlers. The first air splitter has a downstream portion
converging to a downstream end. The second air splitter has a
downstream portion diverging to a downstream end. The second air
splitter downstream end is downstream of the first air splitter
downstream end and the ratio of the distance from the first air
splitter downstream end to the second air splitter downstream end
to the diameter of the second air splitter downstream end is in the
range of 0.22 to 0.30.
Inventors: |
TOON; Ian James; (Leicester,
GB) ; HICKS; Robert Anthony; (Derby, GB) ;
WHITEMAN; Michael; (Loughborough, GB) ; LAZIK;
Waldemar; (Teltow, DE) ; BAGCHI; Imon-Kalyan;
(Berlin, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROLLS-ROYCE PLC
ROLLS-ROYCE DEUTSCHLAND LTD & CO KG |
London
Blankenfelde-Mahlow |
|
GB
DE |
|
|
Family ID: |
48875991 |
Appl. No.: |
14/299890 |
Filed: |
June 9, 2014 |
Current U.S.
Class: |
60/776 ; 239/403;
60/735 |
Current CPC
Class: |
F23R 3/343 20130101;
F23D 11/107 20130101; F23R 3/346 20130101 |
Class at
Publication: |
60/776 ; 60/735;
239/403 |
International
Class: |
F23R 3/34 20060101
F23R003/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2013 |
GB |
1310261.1 |
Claims
1. A fuel injector comprising a pilot fuel injector and a main fuel
injector, the pilot fuel injector comprising at least one pilot air
swirler, the main fuel injector comprising a main air blast fuel
injector located between an inner main air swirler and an outer
main air swirler, a first air splitter located between the at least
one pilot air swirler and the inner main air swirler and a second
air splitter located between the at least one pilot air swirler and
the inner main air swirler, the first air splitter comprising a
downstream portion converging to a downstream end, the second air
splitter comprising a downstream portion diverging to a downstream
end, the downstream end of the second air splitter is downstream of
the downstream end of the first air splitter, the downstream end of
the second air splitter is downstream of the downstream end of a
member defining the outer surface of the outer main air swirler and
the ratio of the distance from the downstream end of the first air
splitter to the downstream end of the second air splitter to the
diameter of the downstream end of the second air splitter is in the
range of 0.22 to 0.30.
2. A fuel injector as claimed in claim 1 wherein the ratio of the
distance from the downstream end of the first air splitter to the
downstream end of the second air splitter to the diameter of the
downstream end of the second air splitter is in the range of 0.24
to 0.28.
3. A fuel injector as claimed in claim 1 wherein the ratio of the
distance from the downstream end of the first air splitter to the
downstream end of the second air splitter to the diameter of the
downstream end of the second air splitter is in the range of 0.25
to 0.27.
4. A fuel injector as claimed in claim 1 wherein the pilot fuel
injector comprising a pilot air blast fuel injector located between
an inner pilot air swirler and an outer pilot air swirler.
5. A fuel injector as claimed in claim 1 wherein the second air
splitter is located between the first air splitter and the inner
main air swirler, an additional air swirler is provided between the
first air splitter and the second air splitter to direct air over
the second air splitter.
6. A fuel injector as claimed in claim 1 wherein the outer main air
swirler comprises a plurality of swirl vanes arranged in an annular
duct, the annular duct is defined by a radially inner surface of an
outer wall and a radially outer surface of an inner wall.
7. A fuel injector as claimed in claim 6 wherein the radially inner
surface of the outer wall of the annular duct converges to a
minimum diameter downstream of the swirl vanes, the radial width of
the annular duct at the trailing edges of the swirl vanes is in the
range of 1.1 to 1.3 times the radial width of the annular duct at
the minimum diameter of the radially inner surface of the outer
wall of the annular duct.
8. A fuel injector as claimed in claim 7 wherein the radially outer
surface of the inner wall of the annular duct converges to a
minimum diameter downstream of the swirl vanes, the radial distance
of convergence of the radially outer surface of the inner wall is
in the range of 0.5 to 1.0 times the radial width of the annular
duct at the minimum diameter of the radially inner surface of the
outer wall of the annular duct.
9. A fuel injector as claimed in claim 7 wherein the axial length
of the annular duct from the trailing edges of the swirl vanes to
the minimum diameter of the radially inner surface of the outer
wall of the annular duct is in the range of 1.7 to 2.5 times the
radial width of the annular duct at the minimum diameter of the
radially inner surface of the outer wall of the annular duct.
10. A fuel injector as claimed in claim 6 wherein the downstream
end of the second air splitter is downstream of the downstream end
of the inner wall of the annular duct.
11. A combustion chamber comprising at least one fuel injector as
claimed in claim 1.
12. A combustion chamber as claimed in claim 11 wherein the
combustion chamber comprises an igniter and the igniter is
positioned downstream of the at least one fuel injector.
13. A gas turbine engine comprising at least one fuel injector as
claimed in claim 1.
14. A gas turbine engine as claimed in claim 13 is a turbofan gas
turbine engine, a turbo-jet gas turbine engine, a turbo-shaft gas
turbine engine or a turbo-prop gas turbine engine.
15. A gas turbine engine as claimed in claim 14 wherein the gas
turbine engine is an aero gas turbine engine, a marine gas turbine
engine, an industrial gas turbine engine or an automotive gas
turbine engine.
16. A fuel injector comprising a pilot fuel injector and a main
fuel injector, the pilot fuel injector comprising at least one
pilot air swirler, the main fuel injector comprising a main air
blast fuel injector located between an inner main air swirler and
an outer main air swirler, a first air splitter located between the
at least one pilot air swirler and the inner main air swirler and a
second air splitter located between the at least one pilot air
swirler and the inner main air swirler, the first air splitter
comprising a downstream portion converging to a downstream end, the
second air splitter comprising a downstream portion diverging to a
downstream end, the downstream end of the second air splitter is
downstream of the downstream end of the first air splitter and the
ratio of the distance from the downstream end of the first air
splitter to the downstream end of the second air splitter to the
diameter of the downstream end of the second air splitter is in the
range of 0.22 to 0.30.
17. A method of operating a combustion chamber, the combustion
chamber comprising an igniter and at least one fuel injector, the
igniter being positioned downstream of the at least one fuel
injector, the fuel injector comprising a pilot fuel injector and a
main fuel injector, the pilot fuel injector comprising at least one
pilot air swirler, the main fuel injector comprising a main air
blast fuel injector located between an inner main air swirler and
an outer main air swirler, a first air splitter located between the
at least one pilot air swirler and the inner main air swirler and a
second air splitter located between the at least one pilot air
swirler and the inner main air swirler, the first air splitter
comprising a downstream portion converging to a downstream end, the
second air splitter comprising a downstream portion diverging to a
downstream end, the downstream end of the second air splitter is
downstream of the downstream end of the first air splitter, the
downstream end of the second air splitter is downstream of the
downstream end of a member defining the outer surface of the outer
main air swirler and the ratio of the distance from the downstream
end of the first air splitter to the downstream end of the second
air splitter to the diameter of the downstream end of the second
air splitter is in the range of 0.22 to 0.30, the method comprising
supplying pilot fuel to the pilot fuel injector and supplying main
fuel to the main fuel injector, atomising the pilot fuel using a
swirling flow of air from the at least one pilot air swirler,
atomising the main fuel using swirling flows of air from the inner
main air swirler and the outer main air swirler, producing an S
shaped flow path for the pilot fuel supplied from the pilot fuel
injector to the main fuel supplied by the main fuel injector, and
mixing the pilot fuel with the main fuel and air flow upstream of
the igniter.
18. A method as claimed in claim 17 wherein the combustion chamber
comprises a plurality of fuel injectors.
19. A method as claimed in claim 18 wherein the combustion chamber
is an annular combustion chamber.
20. A method as claimed in claim 17 wherein the pilot fuel injector
comprising a pilot air blast fuel injector located between an inner
pilot air swirler and an outer pilot air swirler.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a fuel injector and a
combustion chamber and in particular to a lean burn fuel injector
and a gas turbine engine combustion chamber.
BACKGROUND TO THE INVENTION
[0002] Conventionally fuel is supplied into a gas turbine engine
combustion chamber via a plurality of fuel injectors. In an annular
combustion chamber each fuel injector is located in a respective
one of a plurality of apertures in an upstream end of the
combustion chamber.
[0003] One type of gas turbine engine combustion chamber is known
as a rich burn combustion chamber and another type of gas turbine
engine combustion chamber is known as a lean burn combustion
chamber. In a lean burn type of combustion chamber the fuel and air
is mixed such that the fuel to air equivalence ratio is less than
one.
[0004] Conventionally gas turbine engine combustion chambers use
rich burn technology, however rich burn gas turbine engine
combustion chambers will not be able to achieve future nitrous
oxide (NOx) emission requirements.
[0005] Gas turbine engine combustion chambers are being developed
which use lean burn technology to reduce the emissions of nitrous
oxides (NOx). Lean burn gas turbine engine combustion chambers have
lean burn fuel injectors, each of which comprises a pilot fuel
injector and a main fuel injector, to enable lean combustion at
higher air to fuel ratios than the stoichiometric air to fuel
ratio, and to provide high thrusts with low NOx and to supply fuel
to the pilot fuel injector at low thrusts to achieve required
combustion efficiency, lean blow out margin and altitude relight
capability.
[0006] One type of fuel injector for a lean burn type of combustion
chamber comprises a pilot fuel injector and a main fuel injector.
The pilot fuel injector is provided between two sets of air
swirlers and the main fuel injector is provided between a further
two sets of air swirlers. Generally the pilot fuel injector and the
main fuel injector are arranged concentrically and the main fuel
injector is arranged around the pilot fuel injector. The first two
sets of air swirlers provide swirling flows of air which atomise
the fuel from the pilot fuel injector and the second two sets of
air swirlers provide swirling flows of air which atomise the fuel
from the main fuel injector. Each air swirler comprises a plurality
of circumferentially spaced radially extending swirl vanes and the
swirl vanes extend between concentric members. The four sets of air
swirlers are arranged concentrically. This type of fuel injector is
also provided with first and second air splitters between the pilot
fuel injector and the main fuel injector. The first air splitter
has a converging downstream portion and the second air splitter has
a diverging downstream portion.
[0007] There have been problems with obtaining satisfactory
ignition of the fuel in the combustion chamber or problems with
unacceptably high temperatures of the second air splitter and
unacceptably low combustion efficiency when the pilot fuel injector
only is used.
[0008] Therefore the present invention seeks to provide a novel
fuel injector for a gas turbine engine combustion chamber which
reduces or overcomes the above mentioned problem.
STATEMENTS OF INVENTION
[0009] Accordingly the present invention provides a fuel injector
comprising a pilot fuel injector and a main fuel injector, the
pilot fuel injector comprising at least one pilot air swirler, the
main fuel injector comprising a main air blast fuel injector
located between an inner main air swirler and an outer main air
swirler, a first air splitter located between the at least one
pilot air swirler and the inner main air swirler and a second air
splitter located between the at least one pilot air swirler and the
inner main air swirler, the first air splitter comprising a
downstream portion converging to a downstream end, the second air
splitter comprising a downstream portion diverging to a downstream
end, the downstream end of the second air splitter is downstream of
the downstream end of the first air splitter, the downstream end of
the second air splitter being downstream of the downstream end of a
member defining the outer surface of the outer main air swirler,
and the ratio of the distance from the downstream end of the first
air splitter to the downstream end of the second air splitter to
the diameter of the downstream end of the second air splitter is in
the range of 0.22 to 0.30.
[0010] The ratio of the distance from the downstream end of the
first air splitter to the downstream end of the second air splitter
to the diameter of the downstream end of the second air splitter
may be in the range of 0.24 to 0.28.
[0011] The ratio of the distance from the downstream end of the
first air splitter to the downstream end of the second air splitter
to the diameter of the downstream end of the second air splitter
may be in the range of 0.25 to 0.27.
[0012] The pilot fuel injector may comprise a pilot air blast fuel
injector located between an inner pilot air swirler and an outer
pilot air swirler.
[0013] The second air splitter may be located between the first air
splitter and the inner main air swirler, an additional air swirler
is provided between the first air splitter and the second air
splitter to direct air over the second air splitter.
[0014] The outer main air swirler may comprise a plurality of swirl
vanes arranged in an annular duct, the annular duct is defined by a
radially inner surface of an outer wall and a radially outer
surface of an inner wall.
[0015] The radially inner surface of the outer wall of the annular
duct may converge to a minimum diameter downstream of the swirl
vanes, the radial width of the annular duct at the trailing edges
of the swirl vanes is in the range of 1.1 to 1.3 times the radial
width of the annular duct at the minimum diameter of the radially
inner surface of the outer wall of the annular duct.
[0016] The radially outer surface of the inner wall of the annular
duct may converge to a minimum diameter downstream of the swirl
vanes, the radial distance of convergence of the radially outer
surface of the inner wall is in the range of 0.5 to 1.0 times the
radial width of the annular duct at the minimum diameter of the
radially inner surface of the outer wall of the annular duct.
[0017] The axial length of the annular duct from the trailing edges
of the swirl vanes to the minimum diameter of the radially inner
surface of the outer wall of the annular duct may be in the range
of 1.7 to 2.5 times the radial width of the annular duct at the
minimum diameter of the radially inner surface of the outer wall of
the annular duct.
[0018] The downstream end of the second air splitter may be
downstream of the downstream end of the inner wall of the annular
duct.
[0019] The fuel injector may be provided in a combustion chamber.
The combustion chamber may comprise an igniter and the igniter is
positioned downstream of the at least one fuel injector. The
combustion chamber may be a gas turbine engine combustion
chamber.
[0020] The gas turbine engine may be a turbofan gas turbine engine,
a turbo-jet gas turbine engine, a turbo-shaft gas turbine engine or
a turbo-prop gas turbine engine. The gas turbine engine may be an
aero gas turbine engine, a marine gas turbine engine, an industrial
gas turbine engine or an automotive gas turbine engine.
[0021] The present invention also provides a method of operating a
combustion chamber, the combustion chamber comprising an igniter
and at least one fuel injector, the igniter being positioned
downstream of the at least one fuel injector, the fuel injector
comprising a pilot fuel injector and a main fuel injector, the
pilot fuel injector comprising at least one pilot air swirler, the
main fuel injector comprising a main air blast fuel injector
located between an inner main air swirler and an outer main air
swirler, a first air splitter located between the at least one
pilot air swirler and the inner main air swirler and a second air
splitter located between the at least one pilot air swirler and the
inner main air swirler, the first air splitter comprising a
downstream portion converging to a downstream end, the second air
splitter comprising a downstream portion diverging to a downstream
end, the downstream end of the second air splitter is downstream of
the downstream end of the first air splitter, the downstream end of
the second air splitter is downstream of the downstream end of a
member defining the outer surface of the outer main air swirler and
the ratio of the distance from the downstream end of the first air
splitter to the downstream end of the second air splitter to the
diameter of the downstream end of the second air splitter is in the
range of 0.22 to 0.30, the method comprising supplying pilot fuel
to the pilot fuel injector and supplying main fuel to the main fuel
injector, atomising the pilot fuel using a swirling flow of air
from the at least one pilot air swirler, atomising the main fuel
using swirling flows of air from the inner main air swirler and the
outer main air swirler, producing an S shaped flow path for the
pilot fuel supplied from the pilot fuel injector to the main fuel
supplied by the main fuel injector, and mixing the pilot fuel with
the main fuel and air flow upstream of the igniter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The present invention will be more fully described by way of
example with reference to the accompanying drawings, in
which:--
[0023] FIG. 1 is partially cut away view of a turbofan gas turbine
engine showing a combustion chamber having a fuel injector
according to the present invention.
[0024] FIG. 2 is an enlarged cross-sectional view of a combustion
chamber having a fuel injector according to the present
invention.
[0025] FIG. 3 is an enlarged cross-sectional view of a fuel
injector according to the present invention.
[0026] FIG. 4 is an enlarged cross-sectional view of a fuel
injector having a half of the fuel injector according to the
present invention and a half of the fuel injector not according to
the present invention.
[0027] FIG. 5 is an enlarged cross-sectional view of a fuel
injector having a half of the fuel injector according to the
present invention and a half of another fuel injector not according
to the present invention.
[0028] FIG. 6 is an enlarged cross-sectional view of a fuel
injector according to the present invention.
[0029] FIG. 7 is a further enlarged cross-sectional view of a main
outer air swirler of a fuel injector according to the present
invention.
DETAILED DESCRIPTION
[0030] A turbofan gas turbine engine 10, as shown in FIG. 1,
comprises in flow series an intake 11, a fan 12, an intermediate
pressure compressor 13, a high pressure compressor 14, a combustion
chamber 15, a high pressure turbine 16, an intermediate pressure
turbine 17, a low pressure turbine 18 and an exhaust 19. The high
pressure turbine 16 is arranged to drive the high pressure
compressor 14 via a first shaft 26. The intermediate pressure
turbine 17 is arranged to drive the intermediate pressure
compressor 13 via a second shaft 28 and the low pressure turbine 18
is arranged to drive the fan 12 via a third shaft 30. In operation
air flows into the intake 11 and is compressed by the fan 12. A
first portion of the air flows through, and is compressed by, the
intermediate pressure compressor 13 and the high pressure
compressor 14 and is supplied to the combustion chamber 15. Fuel is
injected into the combustion chamber 15 and is burnt in the air to
produce hot exhaust gases which flow through, and drive, the high
pressure turbine 16, the intermediate pressure turbine 17 and the
low pressure turbine 18. The hot exhaust gases leaving the low
pressure turbine 18 flow through the exhaust 19 to provide
propulsive thrust. A second portion of the air bypasses the main
engine to provide propulsive thrust.
[0031] The combustion chamber 15, as shown more clearly in FIG. 2,
is an annular combustion chamber and comprises a radially inner
annular wall structure 40, a radially outer annular wall structure
42 and an upstream end wall structure 44. The radially inner
annular wall structure 40 comprises a first annular wall 46 and a
second annular wall 48. The radially outer annular wall structure
42 comprises a third annular wall 50 and a fourth annular wall 52.
The second annular wall 48 is spaced radially from and is arranged
radially around the first annular wall 46 and the first annular
wall 46 supports the second annular wall 48. The fourth annular
wall 52 is spaced radially from and is arranged radially within the
third annular wall 50 and the third annular wall 50 supports the
fourth annular wall 52. The upstream end of the first annular wall
46 is secured to the upstream end wall structure 44 and the
upstream end of the third annular wall 50 is secured to the
upstream end wall structure 44. The upstream end wall structure 44
has a plurality of circumferentially spaced apertures 54 and each
aperture 54 has a respective one of a plurality of fuel injectors
56 located therein. The fuel injectors 56 are arranged to supply
fuel into the annular combustion chamber 15 during operation of the
gas turbine engine 10.
[0032] Each fuel injector 56 comprises a fuel feed arm 58 and a
fuel injector head 60, as shown in FIG. 2. The fuel feed arm 58 has
a first internal passage 62 for the supply of pilot fuel to the
fuel injector head 60. The fuel feed arm 58 has a second internal
fuel passage 64 for the supply of main fuel to the fuel injector
head 60. Each fuel injector head 60 locates coaxially within a
respective one of the apertures 54 in the upstream end wall 44 of
the combustion chamber 15. The fuel injector head 60 has an axis Y
and the fuel feed arm 58 extends generally radially with respect to
the axis Y of the fuel injector head 60 and also generally radially
with respect to the axis X of the turbofan gas turbine engine 10.
The axis Y of each fuel injector head 60 is generally aligned with
the axis of the corresponding aperture 54 in the upstream end wall
44 of the combustion chamber 15.
[0033] A fuel injector 56 according to the present invention is
shown more clearly in FIG. 3. The fuel injector head 60 comprises a
first generally cylindrical member 66, a second generally annular
member 68 spaced coaxially around the first member 66 and a third
generally annular member 70 spaced coaxially around the second
member 68. A plurality of circumferentially spaced swirl vanes 72
extend radially between the first member 66 and the second member
68 to form a first air swirler 71. The second member 68 has a
greater axial length than the first member 66 and the first member
66 is positioned at an upstream end 68A of the second member 68 and
a generally annular duct 74 is defined between the first member 66
and the second member 68 and the swirl vanes 72 extend radially
across the annular duct 74. A generally cylindrical duct 76 is
defined radially within the second member 68 at a position
downstream of the first member 66. The second member 68 has one or
more internal fuel passages 78 which are arranged to receive fuel
from the first internal fuel passage 62 in the fuel feed arm 58.
The one or more fuel passages 78 are arranged to supply fuel to a
fuel swirler 80 which supplies a film of fuel onto a radially inner
surface 82 at a downstream end 68B of the second member 68. A
plurality of circumferentially spaced swirl vanes 84 extend
radially between the second member 68 and the third member 70 to
form a second air swirler 83. The second member 68 has a greater
axial length than the third member 70 and the third member 70 is
positioned at the downstream end 68B of the second member 68 and a
generally annular duct 86 is defined between the second member 68
and the third member 70 and the swirl vanes 84 extend across the
annular duct 86. The downstream end 70B of the third member 70 is
conical and is convergent in a downstream direction. The radially
inner surface 82 of the second member 68, the radially outer
surface of the second member 68 and the radially inner surface of
the third member 70 are all circular in cross-section in a plane
perpendicular to the axis Y of the fuel injector head 60 of the
fuel injector 56. The downstream end 70B of the third member 70 is
downstream of the downstream end 68B of the second member 68 and
the downstream end 68B of the second member 68 is downstream of the
downstream end 66B of the first member 66. In operation the pilot
fuel is supplied by the internal fuel passages 78 and the fuel
swirler 80 onto the radially inner surface 82 of the second member
68 and the pilot fuel is atomised by swirling flows of air A and B
from the swirl vanes 72 and 84 of the first and second air swirlers
71 and 83 respectively. The first member 66, the second member 68,
the third member 70, the first swirler 71 and the second swirler 83
form the pilot fuel injector 59 and in this case the pilot fuel
injector 59 is a pilot air blast fuel injector. The first and
second air swirlers 71 and 83 are the inner and outer pilot air
swirlers respectively for the pilot air blast fuel injector 59.
[0034] The fuel injector head 60 also comprises a fourth generally
annular member 88 spaced coaxially around the third member 70, a
fifth member 90 spaced coaxially around the fourth member 88 and a
sixth member 92 spaced coaxially around the fifth member 90. A
plurality of circumferentially spaced swirl vanes 94 extend
radially between the fourth member 88 and the fifth member 90 to
form a third air swirler 93. The fifth member 90 has a greater
axial length than the fourth member 88 and the fourth member 88 is
positioned at the downstream end 90B of the fifth member 90 and a
generally annular duct 96 is defined between the fourth member 88
and the fifth member 90 and the swirl vanes 94 extend across the
annular duct 96. The fifth member 90 has one or more internal fuel
passages 98 which are arranged to receive fuel from the second
internal fuel passage 64 in the fuel feed arm 58. The one or more
fuel passages 98 are arranged to supply fuel to a fuel swirler 100
which supplies a film of fuel onto the radially inner surface 102
at the downstream end 90B of the fifth member 90. A plurality of
circumferentially spaced swirl vanes 104 extend radially between
the fifth member 90 and the sixth member 92 to form a fourth air
swirler 103. A generally annular duct 106 is defined between the
downstream end 90B of the fifth member 90 and the sixth member 92
and the swirl vanes 104 extend across the annular duct 106. The
downstream end 88B of the fourth member 88 is conical and is
divergent in a downstream direction. In operation the main fuel
supplied by the internal fuel passages 98 and fuel swirler 100 onto
the radially inner surface 102 of the fifth member 90 is atomised
by swirling flows of air C and D from the swirl vanes 94 and 104 of
the third and fourth air swirlers 93 and 103 respectively. The
fourth member 88, the fifth member 90, the sixth member 92, the
third swirler 93 and the fourth swirler 103 form the main fuel
injector 61 and in this case the main fuel injector 61 is a main
air blast fuel injector 61. The third and fourth air swirlers 93
and 103 are the inner and outer main air swirlers respectively for
the main air blast fuel injector 61.
[0035] The third member 70 and the fourth member 88 are first and
second splitters respectively and are used to separate, or split,
the flows of fuel and air from the pilot fuel injector 59 from the
fuel and air from the main fuel injector 61.
[0036] The fuel injector head 60 also comprises a plurality of
circumferentially spaced swirl vanes 108 which extend radially
between the third member 70 and the fourth member 88 to form a
fifth air swirler 107. In operation the swirl vanes 108 of the
fifth air swirler 107 provide a swirling flow of air E over the
radially inner surface of the fourth member 88.
[0037] The sixth member 92 has a radially inner surface 110, the
radially inner surface 110 of the sixth member 92 is generally
circular in cross-section in a plane perpendicular to the axis Y of
the fuel injector head 60 of the fuel injector 56. The radially
inner surface 110 of the downstream end 92B of the sixth member 92
converges to a minimum diameter 114 at a plane arranged
perpendicular to the axis Y of the fuel injector head 60 containing
the downstream end 90B of the fifth member 90 and then the radially
inner surface 110 of the downstream end 92B of the sixth member 92
diverges downstream of the downstream end 90B of the fifth member
90. In particular the radially inner surface 110 of the downstream
end 92B of the sixth member 92 downstream of the swirl vanes 104
converges to the minimum diameter 114.
[0038] The fifth member 90 has a radially outer surface 112, the
radially outer surface 112 of the fifth member 90 is generally
circular in cross-section in a plane perpendicular to the axis Y of
the fuel injector head 60 of the fuel injector 56. The radially
inner surface 102 of the fifth member 90 is generally circular in
cross-section in a plane perpendicular to the axis Y of the fuel
injector head 60 of the fuel injector 56. The radially outer
surface 112 of the downstream end 90B of the fifth member 90
converges to a minimum diameter 116 at a plane arranged
perpendicular to the axis Y of the fuel injector head 60. The
minimum diameter 116 of the radially outer surface 112 of the
downstream end 90B of the fifth member 90 is positioned upstream of
the minimum diameter 114 of the radially inner surface 110 of the
downstream end 92B of the sixth member 92.
[0039] FIG. 4 shows a fuel injector 56 having a half of the fuel
injector according to the present invention and a half of the fuel
injector not according to the present invention. In particular in
FIG. 4 the upper half of the fuel injector head 60 of the fuel
injector 56 is according to the present invention whereas the lower
half of the fuel injector head 60 is not according to the present
invention. The lower half of the fuel injector head 60 of the fuel
injector 56 has the downstream end 70B of the third member 70
positioned too far downstream relative to the downstream end 88B of
the fourth member 88 and this results in the pilot fuel Fp from the
pilot fuel injector 59 being directed and contained along the axis
Y of the fuel injector head 60 and mixing with the main fuel from
the main fuel injector 61 downstream of the igniter I location.
Supplying the pilot fuel Fp to the main fuel and air flow
downstream of the igniter I makes ignition of the fuel not
possible. The upper half of the fuel injector 60 of the fuel
injector 56 has the downstream end 70B of the third member 70
positioned so as to produce an "S" shaped flow path for the pilot
fuel Fp' supplied from the pilot fuel injector 59 to the main fuel
supplied by the main fuel injector 61. The "S" shaped flow path for
the pilot fuel Fp' to the main fuel is necessary to minimise
emissions and maximise combustion efficiency when the pilot fuel
mixes with the main fuel and air flow. The "S" shaped flow path for
the pilot fuel Fp' to the main fuel is necessary to achieve relight
ignition capability by providing a suitable main fuel and air flow
cone angle and entrainment of the pilot fuel into the main fuel and
air flow upstream of the igniter location I. The "S" shaped flow
path for the pilot fuel Fp' to the main fuel and air flow provides
an acceptable temperature at the downstream end 88B of the fourth
member 88.
[0040] FIG. 5 shows a fuel injector 56 having a half of the fuel
injector according to the present invention and a half of the fuel
injector not according to the present invention. In particular in
FIG. 5 the upper half of the fuel injector head 60 of the fuel
injector 56 is according to the present invention whereas the lower
half of the fuel injector head 60 is not according to the present
invention. The lower half of the fuel injector head 60 of the fuel
injector 56 has the downstream end 70B of the third member 70
positioned too far upstream relative to the downstream end 88B of
the fourth member 88 and this results in the pilot fuel Fp from the
pilot fuel injector 59 being directed radially outwards away from
the axis Y of the fuel injector head 60 and towards and onto the
downstream end 88B of the fourth member 88 producing unacceptable
temperature for the downstream end 88B of fourth member 88 due to
the impingement of the pilot flame on the downstream end 88 of the
fourth member 88. In addition the combustion efficiency when only
pilot fuel is supplied to the fuel injector 56 is unacceptably low
due to the high level of air flowing from the third and fourth air
swirlers 93 and 103 back along the axis Y of the fuel injector head
60 to mix with the pilot fuel Fp.
[0041] FIG. 6 shows that the downstream end 88B of the fourth
member 88 of the fuel injector head 60 has a diameter D and the
axial distance between the downstream end 70B of the third member
70 and the downstream end 88B of the fourth member 88 of the fuel
injector head 60 has a distance L. An acceptable location for the
downstream end 70B of the third member 70 and the downstream end
88B of the fourth member 88 is one where the ratio of the axial
distance L to the diameter D is in the range of 0.22 to 0.3 to
achieve the required "S" shape flow path for the pilot fuel Fp' to
the main fuel and air flow in order to achieve the required
combustion characteristics discussed previously. Thus, the ratio of
the distance from the downstream end 70B of the first air splitter
70 to the downstream end 88B of the second air splitter 88 to the
diameter of the downstream end 88B of the second air splitter 88 is
in the range of 0.22 to 0.30. Preferably the ratio of the axial
distance L to the diameter D is in the range of 0.24 to 0.28 to
achieve the required "S" shape flow path for the pilot fuel Fp' to
the main fuel and air flow and more preferably the ratio of the
axial distance L to the diameter D is in the range of 0.25 to 0.27
to achieve the required "S" shape flow path for the pilot fuel Fp'
to the main fuel and air flow.
[0042] The advantage of the present invention is that the required
aerodynamics are achieved for the fuel injector resulting in
minimisation of NOx, maximising combustion efficiency, achieving
the required ignition characteristics and lean blow out level and
the required temperature for the second splitter.
[0043] FIG. 7 shows the fourth swirler, the main outer air swirler,
103 of the fuel injector 56 in more detail. In order to maintain a
high velocity flow of air through the annular duct 106 and in
particular on the radially inner surface 110 of the sixth member 92
and on the radially outer surface 112 of the fifth member 90 the
radial width L2 of the annular duct 106 at the trailing edges of
the swirl vanes 104 is in the range of 1.1 to 1.3 times the radial
width T of the annular duct 106 at the minimum diameter 114 of the
radially inner surface 110 of the sixth member 92. The axial length
L1 of the annular duct 106 from the trailing edges of the swirl
vanes 104 to the minimum diameter 114 of the radially inner surface
110 of the sixth member 92 is in the range of 1.7 to 2.5 times the
radial width T of the annular duct 106 at the minimum diameter 114
of the radially inner surface 110 of the sixth member 92. The
radial distance L3 of convergence of the radially outer surface 112
of the fifth member 90 is in the range of 0.5 to 1.0 times the
radial width T of the annular duct 106 at the minimum diameter 114
of the radially inner surface 110 of the sixth member 92. The
length L4 of the radially inner surface 110 of the sixth member 90
downstream of the minimum diameter 114 is in the range of 1.0 to
1.2 times the radial width T of the annular duct 106 at the minimum
diameter 114 of the radially inner surface 110 of the sixth member
92. The axial length L5 from the position of minimum diameter 116
of the radially outer surface 112 of the fifth member 90 to the
position of minimum diameter 114 of the radially inner surface 110
of the sixth member 92 is in the range of 0 to 0.4 times the radial
width T of the annular duct 106 at the minimum diameter 114 of the
radially inner surface 110 of the sixth member 92.
[0044] The radius R1 of the radially inner surface 110 of the sixth
member 92 at the minimum diameter 114 is in the range of 0.9 to 1.1
times the radial width T of the annular duct 106 at the minimum
diameter 114 of the radially inner surface 110 of the sixth member
92. The radius R2 of the radially inner surface 110 of the sixth
member 92 at the trailing edges of the swirl vanes 104 is in the
range 0.9 to 1.1 times the radial width T of the annular duct 106
at the minimum diameter 114 of the radially inner surface 110 of
the sixth member 92. The radius R3 of the radially outer surface
112 of the fifth member 90 at the trailing edges of the swirl vanes
104 is in the range 0.9 to 1.1 times the radial width T of the
annular duct 106 at the minimum diameter 114 of the radially inner
surface 110 of the sixth member 92.
[0045] The radially inner surface 110 of the sixth member 92 is
defined by a tangent connecting the radius R2 and the radius R1 and
the length L4 is the length of a tangent from the radius R2 at the
angle .alpha.1. The angle .alpha.1 of the divergent portion of the
radially inner surface 110 of the sixth member 92 downstream of the
position of minimum diameter 114 is in the range of 35.degree. to
45.degree.. The radially outer surface 112 of the fifth member 90
is defined by a tangent connecting the radius R3 and the minimum
diameter point 116.
[0046] The advantage of the arrangement of the arrangement of the
fourth swirler, the main outer air swirler, 103 of the fuel
injector 56 as described is that the aerodynamic flow of air from
the fourth swirler 103 attaches to the radially inner surface 110
of the sixth member 92 both upstream and downstream of the minimum
diameter 114 of the radially inner surface 110 and the air from the
fourth swirler 103 attaches to the radially outer surface 112 of
the fifth member 90. This maximises the mixing of the air from the
third and fourth swirlers 93 and 103 and hence maximises the mixing
of the fuel from the downstream end of the radially inner surface
102 of the fifth member 90 into the air from the third and fourth
swirlers 93 and 103 respectively. This minimises emission and
maximises combustion efficiency. The angle .alpha.1 of the
diverging portion of the radially inner surface 110 of the
downstream end 92B of the sixth member 92 is optimised to direct
the flow of fuel and air towards the igniter, to enable ignition of
the fuel and air. The presence of the diverging portion of the
radially inner surface 110 of the downstream end 92 of the sixth
member 92 downstream of the minimum diameter 114 of the radially
inner surface 110 of the sixth member 92 stabilises the flow cone
angle temporarily, which is beneficial in suppressing combustion
instabilities and producing consistent ignition. Thus, this
arrangement prevents flow separation of the air flow from, or
significant boundary layer thickness build up on, the radially
inner surface 110 of the sixth member 92 and the radially outer
surface 112 of the fifth member 90 which impair mixing of the air
from the third and fourth swirlers 93 and 103 respectively and the
mixing of the fuel into the air from the third and fourth air
swirlers 93 and 103.
[0047] As mentioned previously the pilot fuel is supplied by the
internal fuel passages 78 and the fuel swirler 80 onto the radially
inner surface 82 of the second member 68 and the pilot fuel is
atomised by swirling flows of air A and B from the swirl vanes 72
and 84 of the first and second air swirlers 71 and 83 respectively.
The first member 66, the second member 68, the third member 70, the
first swirler 71 and the second swirler 83 form the pilot fuel
injector 59 and in this case the pilot fuel injector 59 is a pilot
air blast fuel injector. In addition the main fuel supplied by the
internal fuel passages 98 and fuel swirler 100 onto the radially
inner surface 102 of the fifth member 90 is atomised by swirling
flows of air C and D from the swirl vanes 94 and 104 of the third
and fourth air swirlers 93 and 103 respectively. The fourth member
88, the fifth member 90, the sixth member 92, the third swirler 93
and the fourth swirler 103 form the main fuel injector 61 and in
this case the main fuel injector 61 is a main air blast fuel
injector 61. Thus, the pilot fuel and the main fuel are both
atomised by high air velocity accelerating the fuel from the
respective pre-filming surface, and thus the fuel pressure does not
affect the fuel atomisation. An advantage of this type of fuel
injector is that pilot fuel only is supplied to the pilot fuel
injector 59 for and during a "cold day" take-off, in order to
obtain satisfactory combustion efficiency. The pilot fuel injector
is provided with an increased number of fuel passages 78, fuel
passages 78 with a greater diameter etc. in order to provide a
greater flow of fuel to the pilot fuel injector 59 during a "cold
day" take off. On the contrary if pilot fuel is supplied to the
pilot fuel injector 59 and main fuel is supplied to the main fuel
injector 61 for and during a "cold day" take-off, unsatisfactory
combustion efficiency, lower than a predetermined level of
efficiency, is achieved. Unacceptable combustion efficiency is
obtained by supplying pilot fuel and main fuel to the fuel injector
because the temperature in the combustion chamber is not hot enough
for the main fuel to burn at lean conditions. The modified pilot
fuel injector 59 also enables relight ignition to be achieved by
supplying pilot fuel only to the pilot fuel injector 59.
[0048] Although the present invention has been described with
reference to the use of a separate first air splitter, a separate
second air splitter and an air swirler positioned between the first
and second air splitters it may be possible to provide an
arrangement in which the first air splitter and the second air
splitter diverge from a downstream end of a single annular
member.
[0049] Although the present invention has been described with
reference to a gas turbine engine combustion chamber it may be
possible to use the present invention in other types of combustion
chambers.
[0050] Although the present invention has been described with
reference to a turbofan gas turbine engine it is equally possible
to use the present invention on a combustion chamber of a turbo-jet
gas turbine engine, a turbo-shaft gas turbine engine or a
turbo-prop gas turbine engine. Although the present invention has
been described with reference to an aero gas turbine engine it is
equally possible to use the present invention on a combustion
chamber of a marine gas turbine engine, an industrial gas turbine
engine or an automotive gas turbine engine.
* * * * *