U.S. patent application number 12/224903 was filed with the patent office on 2009-05-07 for combustor and method of operating a combustor.
Invention is credited to Nigel Wilbraham.
Application Number | 20090117502 12/224903 |
Document ID | / |
Family ID | 36609522 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090117502 |
Kind Code |
A1 |
Wilbraham; Nigel |
May 7, 2009 |
Combustor and Method of Operating a Combustor
Abstract
A combustor comprises in flow series a burner, a transition
piece and a combustion chamber being of larger diameter than the
transition piece, the combustion chamber being connected to the
transition piece via a dome portion. In the dome portion are
located air injection openings. A method of operating the combustor
comprises the stop of introducing air from the dome portion by
means of air jets.
Inventors: |
Wilbraham; Nigel; (West
Midlands, GB) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Family ID: |
36609522 |
Appl. No.: |
12/224903 |
Filed: |
February 7, 2007 |
PCT Filed: |
February 7, 2007 |
PCT NO: |
PCT/EP2007/051141 |
371 Date: |
September 9, 2008 |
Current U.S.
Class: |
431/9 ;
431/352 |
Current CPC
Class: |
F23C 2202/40 20130101;
F23R 3/06 20130101; F23D 2206/10 20130101; F23C 7/00 20130101; F23D
2900/00015 20130101 |
Class at
Publication: |
431/9 ;
431/352 |
International
Class: |
F23C 6/04 20060101
F23C006/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 13, 2006 |
EP |
06005106.7 |
Claims
1.-7. (canceled)
8. A combustor for a gas turbine, comprising: a burner; a
transition piece arranged downstream of and adjacent to the burner
with respect to a flow direction; and a combustion chamber arranged
downstream of and adjacent to the transition piece with respect to
a flow direction, wherein the combustion chamber has a greater
diameter than the transition piece; and a dome portion that
connects the transition piece to the combustion chamber, the dome
portion having a plurality of air injection openings comprising a
first row of openings positioned on a circle of a first radius and
at least one further row of openings positioned on at least one
further circle of a second radius different that the first radius,
wherein all of the openings have an enlarged shape with a long
direction and a short direction, the long direction of the first
row being oriented essentially tangential an edge of the dome and a
tangential component portion of a respective opening's long
direction increases with the opening being positioned nearer the
innermost radius of the dome portion.
9. The combustor as claimed in claim 8, wherein the first row of
openings are arranged at a dome edge adjacent the transition
piece.
10. The combustor as claimed in claim 8, wherein the number of
openings of the first row is greater than the number of openings of
the further row.
11. The combustor as claimed in claim 10, wherein the openings of
the first row have a smaller diameter than a diameter of the
openings of the further row.
12. The combustor as claimed in claim 11, wherein duct portions of
ducts for feeding air to openings adjoining the air injection
openings have angles of inclination to the surface normal between
45 degrees and 80 degrees.
13. A method of operating a combustor for a gas turbine,
comprising: providing a burner, a transition piece arranged
downstream of and adjacent to the burner with respect to a flow
direction, and a combustion chamber arranged downstream of and
adjacent to the transition piece with respect to a flow direction,
wherein the combustion chamber has a greater diameter than the
transition piece; arranging a dome portion between the transition
piece and the combustion chamber that connects the transition piece
to the combustion chamber, where the dome portion has a plurality
of air injection openings comprising a first row of openings
positioned on a circle of a first radius and at least one further
row of openings positioned on at least one further circle of a
second radius different that the first radius, wherein all of the
openings have an enlarged shape with a long direction and a short
direction, the long direction of the first row being oriented
essentially tangential an edge of the dome and a tangential
component portion of a respective opening's long direction
increases with the opening being positioned nearer the innermost
radius of the dome portion; and introducing air into the combustion
chamber from the dome portion via air jets, wherein an air jet
without any tangential component streams through an air injection
opening of a row positioned at an outermost radius of the dome
portion, and wherein air jets with a tangential component that
increases with decreasing radial position flow through openings of
the other rows.
14. The method as claimed in claim 13, wherein the air is
introduced with an inclination to the surface normal of the dome
portion between 45 degrees and 80 degrees.
15. The method as claimed in claim 14, wherein the number of
openings of the first row is greater than the number of openings of
the further row.
16. The method as claimed in claim 15, wherein the openings of the
first row have a smaller diameter than a diameter of the openings
of the further row.
17. The combustor as claimed in claim 16, wherein the introduced
air is provided via duct portions of ducts for feeding air to
openings adjoining the air injection openings.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2007/051141, filed Feb. 7, 2007 and claims
the benefit thereof. The International Application claims the
benefits of European application No. 06005106.7 filed Mar. 13,
2006, both of the applications are incorporated by reference herein
in their entirety.
FIELD OF INVENTION
[0002] The present invention relates to a combustor comprising in
flow series a burner, a transition piece and a combustion chamber
being of larger diameter than the transition piece, the combustion
chamber being connected to the transition piece via a dome portion.
In addition, the invention relates to a method of operating a
combustor, especially a combustor of a gas turbine.
BACKGROUND OF THE INVENTION
[0003] Modern gas turbine engines use the concept of premixing air
and fuel in lean stoichiometry before the combustion of the
fuel/air mixture. Usually, the pre-mixing takes place by injecting
fuel into an air stream in a swirling zone of a combustor which is
located upstream from the combustion zone. The swirling leads to a
mixing of fuel and air before the mixture enters the combustion
zone.
[0004] U.S. Pat. No. 6,532,726 B2 describes a gas turbine engine
system having a combustor with a burner head having injection
arrangements for gas- and liquid-fuel operations. During both gas-
and liquid-fuel operations the flame front face is located close to
the burner head and, during liquid-fuel operations, air is forced
across the downstream face to cool the head.
[0005] The aerodynamics in the combustor dome comprise of a annular
recirculation bubble that has a helical flow pattern in the
circumferential sense. This recirculation bubble is driven by the
swirling flow emerging from the pre-chamber. Currently, it is known
that at low machine loads the highest combustion efficiency can be
achieved if the flame front is fully stabilised in the dome
recirculation bubble. Poor efficiency is associated with a flame
front stabilised in the central recirculation bubble, which is
predominantly located in the pre-chamber area. At high machine
loads, the central recirculation bubble has sufficient swirl and
intensity for the flame front to be fully held.
[0006] However, the combustion system has relatively poor
combustion efficiency at low loads and at starting conditions. This
problem exists for liquid and gas operation, although it is most
noticeable on liquid.
SUMMARY OF INVENTION
[0007] With respect to the mentioned state of the art it is an
objective of the invention to provide a combustor, in particular a
gas turbine combustor, and a method of operating a combustor,
especially a gas turbine combustor which is advantageous in
providing a combustion efficiency at low loads and starting.
[0008] This objective is solved by a combustor according to the
claims and a method according to the claims. The dependent claims
describe advantageous developments of the invention.
[0009] The inventive combustor comprises in flow series a burner, a
transition piece and a combustion chamber being of larger diameter
than the transition piece. The combustion chamber is connected to
the transition piece via a dome portion. Air injection openings are
located in the dome portion. In particular, the transition piece
may also be referred to as a pre-chamber in regard to the
combustion chamber.
[0010] It is believed that the state of the art dome recirculation
bubble strength is only marginally insufficient and that limited
additional air directed the appropriate way will improve the
efficiency of the combustion system. To improve the dome
recirculation efficiency where a machine would be operating
predominantly in the low load regime, it is therefore proposed that
air is introduced across the dome to supplement the existing
aerodynamics and enhance stability.
[0011] In an advantageous embodiment of the present invention the
openings comprise a first row of openings being positioned at a
circle of a first radius of the dome portion and at least one
further row of openings being positioned at least one further
circle of a second radius of the dome portion being different to
the first radius. Advantageously, the openings have an elongated
shape with a long direction and a short direction. Especially, the
openings have a shape of an ellipse. However, the openings can be
of any other shape.
[0012] The openings of the first and the at least one further row
can have a defined orientation e.g. such as the openings being
positioned at an innermost circle of the dome portion are oriented
tangentially with their elongated direction and the openings being
positioned at the outermost circle of the dome portion have no
tangential component in their elongated direction. The orientation
of openings being arranged in further rows lying between the rows
being positioned at the innermost and the outermost radius may be
then dependent on the radius at which they are positioned.
Especially, the tangential component proportion of an openings long
direction increases as nearer the opening is positioned at the
innermost radius of the dome portion and decreases as nearer the
opening is positioned at the outermost radius of the dome portion.
In addition duct portions of ducts for feeding the air to the
opening adjoining the air injection openings are designed so that
they have angles of inclination to the surface normal of the dome
surface greater than 45 degrees and less than 80 degrees. When
angled jets have angles of inclination to the surface front to
which they emerge of less than 11 degrees (i.e. of more than 80
degrees relative to the surface normal) it will be difficult to
attach them to the surface of the surface.
[0013] With the described configuration of the openings, an air jet
streaming through an opening of a row being positioned at the
outermost radius of the dome portion has no tangential component.
Air jets flowing through openings of the other rows have tangential
components that increase with decreasing radial position.
[0014] Advantageously, the first row of openings is arranged close
to a dome edge, where the dome portion is adjacent the transition
piece.
[0015] The number of openings of the first row may be greater than
the number of openings of the at least one further row. The higher
number of openings ensures a sufficient introduction of air near
the transition piece due to provision of greater air
penetration.
[0016] Further, the openings of the first row are advantageously
each smaller than openings of the at least one further row. Due to
the greater number and the smaller diameter of these openings, an
even introduction of air to the partially premixed gases leaving
the transition piece is achieved.
[0017] The inventive combustor is particularly adapted to perform
the inventive method.
[0018] The inventive method of operating a combustor which
comprises in flow series a burner, a transition piece and a
combustion chamber being of larger diameter than the transition
piece and being connected to it via a dome portion comprises the
step of introducing air from the dome portion of the combustor.
[0019] In an advantageous embodiment of the present invention, the
air is introduced by an inclination angle to the surface normal of
the dome surface greater than 45 degrees and less than 80
degrees.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Further features, properties and advantages of the present
invention will become clear from the following description of
embodiments of the invention in conjunction with the accompanying
drawings.
[0021] FIG. 1 shows a combustor according to the invention;
[0022] FIG. 2 shows a dome plate according to the present
invention; and
[0023] FIG. 3 shows another dome plate according to the present
invention.
DETAILED DESCRIPTION OF INVENTION
[0024] FIG. 1 shows a combustor according to the invention. The
combustor comprises in flow direction series a burner 10 with
swirler portion 12 and a burner-head portion 11 attached to the
swirler portion 12, a transition piece being referred as combustion
pre-chamber 13 and a main combustion chamber 4. The main combustion
chamber 4 has a diameter being larger than the diameter of the
pre-chamber 13. The main combustion chamber 4 is connected to the
pre-chamber 13 via a dome portion 30 comprising a dome plate 38. In
general, the transition piece 13 may be implemented as a one part
continuation of the burner 10 towards the combustion chamber 4, as
a one part continuation of the combustion chamber 4 towards the
burner 10, or as a separate part between the burner 10 and the
combustion chamber 4.
[0025] The combustor is adapted to be operated with either liquid
or gaseous fuel and comprises a gas-fuel injection system, a
liquid-fuel injection system and an air injection system.
[0026] The gas-fuel injection system comprises main gas-fuel
openings 23 and a pilot gas system. The main gas-fuel openings 23
are located at an air-inlet region of a burner head face 16, i.e.
of the swirler portion 12, i.e. adjacent a radially outer part of
passages 14 which are defined between a number of vanes of the
swirler portion 12 and are fed from connectors 24. The pilot gas
system comprises in flowing direction of pilot gas a connector 18
at the burner head 11, an annular gallery 19, gas outlets 32, a lip
20 extending radially inwards towards the longitudinal axis 21 of
the combustor, and a central part 22 being arranged on a burner
head face 16.
[0027] The liquid-fuel injection system comprises liquid-fuel pilot
openings 25 and main liquid-fuel openings 27. The liquid-fuel pilot
openings 25 can inject liquid fuel fed from connections 26 through
appropriate ducts extending through the burner head 11 into the
pre-chamber 13. The pilot openings 25 are positioned in the central
part 22 of the burner head face 16 outside the outer circumference
of the combustion flames front FF. The main liquid-fuel openings 27
are fed from fuel connectors 28 through appropriate passageways
extending through the burner head 11. The main liquid-fuel openings
27 are situated in the burner head face 16 at or near the air-exit
region of the swirler 12, i.e., near a radially inner portion of
the swirler passages 14.
[0028] The air injection system comprises air ducts 36 leading to
openings 40, 42, 44 in the dome plate 38. The exit parts of the
ducts, i.e. the parts adjoining the openings, are inclined with
respect to the surface normal of the dome pate 38 by an inclination
angle .alpha..
[0029] In operation, compressed air 15 is supplied to the burner 10
and streams through the swirler passages 14. The in streaming air
mixes with fuel injected into the compressed air streams through
the passages from injection openings located in a peripheral
section of the burner head face 16. On arriving in the pre-chamber
13, the mixture is ignited by an igniter unit 17. Once lit, the
flame continuous to burn so that a further ignition is not
required.
[0030] When the engine is started in gas-fuel mode of operation,
the pilot gas supplied through the connector 18 at the burner head
11 streams through passages in the burner head 11 arriving at the
annular gallery 19. From there the pilot gas is directed via the
gas outlets 32 to the underside of a directing means in the form of
the lip 20 extending radially inwards towards the longitudinal axis
21 of the combustor. The lip 20 deflects the pilot gas across the
central portion 22. However, as engine load and speed increase, the
pilot gas supply is reduced and the main gas-fuel supply is
increased. The main gas-fuel exits the main gas-fuel openings 23.
The main gas-fuel and the air mix together as they pass the swirler
passages 14 on their way to a combustion flame within pre-chamber
13 and main-chamber 4.
[0031] Further, air jets 34 are supplied by the air openings 36
into main combustion chamber 4. Therein, they mix in dependence of
engine load with either with the pilot gas, the fuel-air mixture
and/or the combustion products of them so as to improve the dome
recirculation efficiency by providing sufficient swirl and
intensity for the flame front. The injected air jets 34 have an
inclination angle .alpha. in relation to the surface normal of the
dome surface being shown as dashed line.
[0032] When the engine is started in the liquid-fuel mode of the
combustor, pilot liquid-fuel is injected from pilot openings 25
into the pre-chamber 13 in an axial direction which is at least
approximately parallel to the central longitudinal axis 21, where
it mixes with air 15 exiting the swirler passages 14. The obtained
mixture of air and fuel is ignited by the igniter unit 17. And
further mixtures of air and fuel are fed to the so obtained flame
F.
[0033] Additionally, the air jets 34 are supplied by the air
openings 36 into the main combustion chamber 4. Therein, they mix
with the mixture which leaves the pre-chamber 13. This mixture can
comprise the pilot fuel, the air-fuel mixture being introduced into
the combustor and/or their combustion products. Due to the
orientation of the exit parts of the ducts 36 the air jets 34 have
an inclination angle .alpha. in relation to the surface normal of
the dome surface being shown as dashed line to compliment the
existing aerodynamics and enhance the stability, especially, when
the gas turbine is operating in the low load regime.
[0034] As engine load increases from start-up to approximately 70%
full load, the supply of liquid pilot fuel is reduced, and main
liquid fuel is introduced from the main liquid-fuel openings 27
which are located on the burner face in the air exit region of the
swirler passages 14 and inject main liquid fuel in a direction
approximately perpendicular to the air stream flow 15. The supply
of air jets 34 can either be continued or stopped.
[0035] FIG. 2 shows a dome portion according to the present
invention. The dome portion comprises a plate 200 having a first
row of openings 202, a second row of openings 204 and a third row
of openings 206. All openings have an elongated shape defining a
long direction of the openings.
[0036] The openings 202 are positioned at the innermost radius of
the plate 200 and closest to the dome edge 208. They are oriented
near tangential to the dome edge 208 with their long direction. The
openings 204 are arranged at radius being greater than the previous
radius. Their orientation is less tangential than that of the
openings 202 of the first row. The openings 206 are situated at the
outermost radius and are oriented radially inwards with no
tangential component of their long direction.
[0037] Through openings 202, 204 and 206 air is introduced in the
dome of the combustor. The air jets stream out the openings 202,
204 and 206 have an inclination in regard to a surface normal of a
dome surface from which they emerge (see FIG. 1). The inclination
angle .alpha. lies in the range of
45.degree.<.alpha.<80.degree.. The jets streaming out
openings 206 do not have a tangential component in regard to the
dome edge 208, while the others have a tangential component. The
flow direction of the air jets is shown by arrows.
[0038] FIG. 3 shows another dome portion according to the present
invention. The dome portion comprises a plate 300 having a first
row of openings 302, a second row of openings 304 and a third row
of openings 306.
[0039] The openings 302 are positioned at the innermost radius of
the plate 300 and closest to the dome edge 308 and are oriented
near tangential to the dome edge 308. The openings 304 are arranged
at radius being greater than the previous radius and are oriented
less tangential than the openings 302. The openings 306 are
situated at the outermost radius and are oriented radially inwards
with no circumferential component.
[0040] The number of openings 302 is greater as the number of
openings 304 or the number of openings 306 Further, the diameters
of the openings 302 are smaller than the diameters of the openings
304 or 306. Thereby, an even introduction of air to the fuel and/or
gases being introduced in the dome portion of the combustor is
ensured and a greater air penetration is provided.
[0041] Through openings 302, 304 and 306 air is introduced in the
dome of a combustion system. The air jets stream out the openings
302, 304 and 306 by an inclination angle .alpha., wherein
45.degree.<.alpha.<80.degree., wherein .alpha. is defined in
regard to a surface normal of a dome surface front from which the
air jets emerge (see FIG. 1). The jets streaming out openings 306
do not have a tangential component in regard to the dome edge
308.
* * * * *