U.S. patent number RE33,896 [Application Number 07/415,997] was granted by the patent office on 1992-04-21 for combustion chamber apparatus for combustion installations, especially for combustion chambers of gas turbine installations, and a method of operating the same.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Bernard Becker, Helmut Maghon.
United States Patent |
RE33,896 |
Maghon , et al. |
April 21, 1992 |
**Please see images for:
( Certificate of Correction ) ** |
Combustion chamber apparatus for combustion installations,
especially for combustion chambers of gas turbine installations,
and a method of operating the same
Abstract
In a combustion chamber having a substantially cylindrical
housing and a flame tube .[.therein at an annular gap from a
housing of the chamber,.]. .Iadd.with an end face, the flame tube
being thermally movable and disposed in the combustion chamber and
the flame tube being spaced from the cylindrical housing defining
an annular gap therebetween, the improvement includes .Iaddend.a
burner apparatus .Iadd.having a burner axis and .Iaddend.including
at least one pilot burner .[.near an.]. .Iadd.having a head and
being disposed in the vicinity of the .Iaddend.end face of the
flame tube for generating a pilot flame .[.from.]. .Iadd., the
pilot burner operating with at least one fuel from the group
consisting of .Iaddend.natural gas .[.and/or.]. .Iadd.and
.Iaddend.heating oil, an air supply channel surrounding the head
.[.of the pilot burner.]., a premixing device for .[.natural gas.].
.Iadd.mixing gas and air .Iaddend.in the form of a ring channel
system surrounding the head.Iadd., the ring channel system
.Iaddend.including flow conduction walls defining an inflow cross
section at an air inflow side of the ring channel system
.Iadd.being .Iaddend.open toward the annular gap for conducting a
majority of .Iadd.available .Iaddend.combustion air .Iadd.in a
given flow direction .Iaddend.from the annular gap to a combustion
zone developing downstream of the burner head in the flame tube,
the combustion air having flow vectors with components entering the
combustion zone in directions .Iadd.ranging .Iaddend.from parallel
to the burner axis to an acute angle .Iadd.relative .Iaddend.to the
burner axis, the combustion air components having swirl components
superimposed thereon .[.tangentially relative.].
.Iadd.circumferentially .Iaddend.to the burner axis .[.acting.].
.Iadd., using the burner axis .Iaddend.as a swirl center, .[.a
multiplicity of nozzle tubes penetrating the inflow cross section
in a direction substantially transverse to the flow direction, the
nozzle tubes each having a side with nozzle openings facing away
from the air inflow side of the ring channel system,.]. .Iadd.a
device defining nozzle openings disposed in the ring channel
system, .Iaddend.and a .[.natural.]. gas feeding system
.[.substantially concentrically surrounding the pilot burner and.].
connected to .[.one end of each nozzle tube, and a method of
operating the same.]. .Iadd.the nozzle openings for feeding gas
thereto.Iaddend..
Inventors: |
Maghon; Helmut (Mulheim am
Ruhr, DE), Becker; Bernard (Mulheim am Ruhr,
DE) |
Assignee: |
Siemens Aktiengesellschaft
(Munich, DE)
|
Family
ID: |
6264092 |
Appl.
No.: |
07/415,997 |
Filed: |
October 2, 1989 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
836232 |
Mar 4, 1988 |
04701124 |
Oct 20, 1987 |
|
|
Foreign Application Priority Data
Current U.S.
Class: |
431/284;
60/39.826; 60/746; 60/748; 431/185; 60/39.55; 431/183; 60/747 |
Current CPC
Class: |
F02C
3/30 (20130101); F23D 14/02 (20130101); F23D
17/002 (20130101); F23C 7/004 (20130101); F23L
7/00 (20130101); F23D 2900/00008 (20130101) |
Current International
Class: |
F23D
14/02 (20060101); F23D 17/00 (20060101); F02C
3/20 (20060101); F23L 7/00 (20060101); F02C
3/30 (20060101); F23C 7/00 (20060101); F23Q
009/00 () |
Field of
Search: |
;431/4.9,174,175,177,284,285 ;60/39.55,39.826,733,746,747,748 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
US. Publication ASME 82-GT-29, article "Alternative Fuels: Burner
Concepts and Emission Characteristics of a Silo Combustor", by W.
Krockow et al, pp. 1-10; FIG. 1 (date unknown)..
|
Primary Examiner: Dority; Carroll B.
Attorney, Agent or Firm: Lerner; Herbert L. Greenberg;
Laurence A.
Claims
We claim:
1. In a combustion chamber having a substantially cylindrical
housing and a flame tube with an end face, the flame tube being
thermally movable and .[.centered.]. .Iadd.disposed .Iaddend.in the
combustion chamber and the flame tube being spaced from the
cylindrical housing defining an .[.annular gap.]. .Iadd.air chamber
.Iaddend.therebetween, the improvement comprising a burner
apparatus having a burner axis and including at least one pilot
burner having a head and being disposed in the vicinity of the end
face of the flame tube for generating a pilot flame, said pilot
burner operating with at least one fuel from the group consisting
of .[.natural.]. gas and heating oil, an air supply channel
surrounding said head, a premixing device for .[.the combustion of
natural gas.]. .Iadd.mixing gas and air .Iaddend.in the form of a
ring channel system surrounding said head, said ring channel system
including flow conduction walls defining an inflow cross section at
an air inflow side of said ring channel system being open toward
the .[.annular gap.]. .Iadd.air chamber .Iaddend.for conducting a
majority of available combustion air in a given flow direction from
the .[.annular gap.]. .Iadd.air chamber .Iaddend.to a combustion
zone developing downstream of said burner head in the flame tube,
.Iadd.means for producing in .Iaddend.the combustion air
.[.having.]. flow vectors with components entering said combustion
zone in directions ranging from parallel to said burner axis to an
acute angle relative to said burner axis, said .[.combustion air.].
.Iadd.flow vector .Iaddend.components having swirl components
superimposed thereon .[.tangentially relative.].
.Iadd.circumferentially .Iaddend.to said burner axis, using said
burner axis as a swirl center, .[.a multiplicity of nozzle tubes
penetrating said inflow cross section in a direction substantially
transverse to said given flow direction, said nozzle tubes each
having ends and having a side with.]. .Iadd.means defining
.Iaddend.nozzle openings .[.facing away from said air inflow side
of.]. .Iadd.disposed in .Iaddend.said ring channel system, and a
.[.natural.]. gas feeding system .[.substantially concentrically
surrounding said pilot burner and being connected to one of said
ends of each of said nozzle tubes.]. .Iadd.connected to said nozzle
openings for feeding gas thereto.Iaddend..
2. Burner apparatus according to claim .[.1.]. .Iadd.15.Iaddend.,
wherein said pilot burner has an axis, and said .[.natural.]. gas
feeding system has an annular inlet chamber with a connecting wall
for said nozzle tubes being conically bevelled relative to said
axis of said pilot burner.
3. Burner apparatus according to claim .[.2.]. .Iadd.16.Iaddend.,
wherein said flow conduction walls are in the form of inner and
outer walls bounding said ring channel system, each of said inner
and outer walls being disposed at least approximately on a
respective conical surface .[.having conical axes coinciding with
with said axie of said pilot burner, said walls being mutually
axially offset along said pilot burner axis, and said conically
bevelled connecting wall of said annular inlet chamber being
extended along the same direction as said inner conical
wall.]..
4. Burner apparatus according to claim 3, .Iadd.wherein said pilot
burner has an axis, and said gas feeding system has an annular
inlet chamber with a connecting wall for said nozzle tubes
conically bevelled relative to said axis of said pilot burner, and
.Iaddend.wherein said conically bevelled connecting wall of said
annular inlet chamber at least partially coincides with said inner
conical wall.
5. Burner apparatus according to claim 3, including a cylinder wall
surrounding said pilot burner coaxially and defining a ring niche
along with said inner flow conduction wall, said annular inlet
chamber being disposed in said ring niche.
6. Burner apparatus according to claim .[.1.]. .Iadd.3.Iaddend.,
wherein said nozzle tubes have axes, and including a swirl vane
system disposed downstream of said nozzle tubes having longitudinal
guide vane axes extending substantially parallel to said axes of
said nozzle tubes.
7. Burner apparatus according to .[.claims.]. .Iadd.claim
.Iaddend.1, wherein said pilot burner includes a swirl star on the
side of said burner head defining a flow space, a central burner
tube for supplying .[.heating.]. oil, a first burner jacket
surrounding said burner tube at a distance defining a first annular
space for feeding .[.natural.]. gas, a nozzle wall connecting said
first annular space with said flow space of said swirl star in the
vicinity of said burner head, a second burner jacket in the form of
an outer cylinder wall surrounding said first burner jacket at a
distance defining a second annular space coaxial with said burner
acting as an air supply channel of said pilot burner, said second
annular space also being connected to said flow space of said swirl
star.[., and means for feeding an inert substance into said
combustion zone.]..
8. Burner apparatus according to claim .[.2,.]. .Iadd.17, wherein
said pilot burner has an axis, and said feeding system has an
annular inlet chamber with a connecting wall for said nozzle tubes
conically bevelled relative to said axis of said pilot burner, and
.Iaddend.including a .[.natural.]. gas feedline connected to said
annular inlet chamber, said annular inlet chamber being steadily
tapered from a larger starting cross section following said
.[.natural.]. gas feedline down to a smaller end cross section,
said .Iadd.means defining said .Iaddend.nozzle .[.tubes.].
.Iadd.openings .Iaddend.being in the form of a nozzle tube ring, a
plurality of said nozzle .[.tubes.]. .Iadd.openings .Iaddend.being
connected to said end cross section of said annular inlet
chamber.
9. Burner apparatus according to claim .[.7,.]. .Iadd.3, wherein
said pilot burner includes a swirl star on the side of said burner
head defining a flow space, and .Iaddend.including a plurality of
gas inlets distributed over the periphery of said pilot burner for
supplying gas to said pilot burner, said gas inlets being fed and
controlled separately and being disposed in .[.said.]. .Iadd.an
.Iaddend.air supply channel at a distance upstream from said swirl
star.
10. Burner apparatus according to claim 9, .Iadd.wherein said pilot
burner includes a burner tube for supplying oil, and a first burner
jacket surrounding said burner tube at a distance defining a first
annular space for feeding gas, and .Iaddend.wherein said gas inlets
are formed of a plurality of additional tubes passing through said
first burner jacket and being distributed over the periphery of
said air supply channel.
11. Burner apparatus according to claim 10, wherein said additional
tubes include tube sections extending over a given distance into
said air supply channel.
12. Burner apparatus according to claim 11, wherein said tube
sections include a plurality of gas outlet openings within said air
supply channel.
13. Burner apparatus according to claim 12, wherein said gas outlet
openings are substantially perpendicular to said given flow
direction.
14. Burner apparatus according to claim 9, .Iadd.wherein said pilot
burner includes a burner tube for supplying air, a first burner
jacket surrounding said burner tube at a distance defining a first
annular space for feeding gas, and a second burner jacket
surrounding said first burner jacket at a distance defining a
second annular space serving as an air supply channel of said pilot
burner, and .Iaddend.including a ring canal concentric to said air
supply channel and having a separate gas feedline, said gas inlets
being in the form of holes formed in said .[.one of said.].
.Iadd.first .Iaddend.burner .[.jackets.]. .Iadd.jacket
.Iaddend.communicating with said ring canal. .Iadd.
15. Burner apparatus according to claim 1, including a plurality of
nozzle tubes formed with said nozzle openings and penetrating said
inflow cross section in a direction substantially transverse to
said given flow direction. .Iaddend. .Iadd.
16. Burner apparatus according to claim 15, wherein each of said
nozzle tubes has an end, and wherein said gas feeding system
surrounds said pilot burner substantially concentrically and is
connected to the ends of said nozzle tubes. .Iaddend. .Iadd.17.
Burner apparatus according to claim 1, wherein said nozzle openings
face away from said air inflow side. .Iaddend. .Iadd.18. Burner
apparatus according to claim 1, including means for feeding an
inert substance, selected from the group consisting of water and
steam, into said combustion zone. .Iaddend.
Description
.Iadd.This is a reissue of application Ser. No. 836,232 filed Mar.
4, 1986, which became U.S. Pat. No. 4,701,124, and is now
surrendered. .Iaddend.
The invention relates to a burner apparatus for combustion
installations, especially for combustion chambers of gas turbine
installations, the combustion chamber including a substantially
cylindrical housing and a flame tube thermally movable and centered
therein with an annular gap, and the burner apparatus including at
least one pilot burner disposed in the vicinity of the end face of
the flame tube for generating a pilot flame, the pilot burner being
operated with natural gas and/or heating oil as a fuel, an air
supply system and a ring channel system surrounding the head of the
pilot burner with flow conduction walls for the supplying the main
portion of the combustion air from the annular gap to a combustion
zone developing downstream of the burner head in the flame tube,
the combustion air having flow vectors with components leading into
the combustion zone in directions from parallel to an acute angle
relative to the burner axis, and the the combustion air components
having swirl components superimposed thereon being tangentially
directed relative to the burner axis acting as a swirl center.
Such a burner apparatus must meet a number of requirements so that
the operation thereof is assured even when considering more
stringent environmental protection regulations: Thus, the NO.sub.x
content in the exhaust gas must not exceed upper limits. This means
that the temperatures in the combustion zone must not be too high
and sufficient amounts of combustion air must be fed to the
combustion zone, an excess of air being generally maintained. It
should be possible to operate the burners not only with heating
oil, but also with natural gas.
Another special problem is the retrofitting of burner apparatus
which, while they meet present NO.sub.x limits, will not meet
future NO.sub.x limits.
It is accordingly an object of the invention to provide a
combustion chamber apparatus for combustion installations,
especially for combustion chambers of gas turbine installations,
which overcomes the hereinaforementioned disadvantages of the
heretofore known apparatus of this general type, and to do so in
such a way that it ensures operation with low NO.sub.x contents in
the exhaust gas in accordance with the requirements indicated
above, and which permits retrofitting of existing burner apparatus
in order to reduce the NO.sub.x exhaust gas values, without having
to replace the entire burner apparatus. A further object of the
invention is to provide a suitable method for operating the burner
apparatus which causes a production of NO.sub.x that is as small as
possible.
With the foregoing and other objects in view there is provided, in
accordance with the invention, in a combustion chamber, especially
of a gas turbine installation, having a substantially cylindrical
housing and a flame tube with an end face, the flame tube being
thermally movable and centered in the combustion chamber and the
flame tube being spaced from the cylindrical housing defining an
annular gap therebetween, the improvement comprising a burner
apparatus having a burner axis and including at least one pilot
burner having a head and being disposed in the vicinity of the end
face of the flame tube for generating a pilot flame, the pilot
burner operating with at least one fuel from the group consisting
of natural gas and/or heating oil, an air supply channel
surrounding the head, a premixing device for the combustion of
natural gas in the form of a ring channel system surrounding the
head, the ring channel system including flow guide or conduction
walls defining an inflow cross section at an air inflow side of the
ring channel system being open toward the annular gap for
conducting a majority or main portion of available combustion air
in a given flow direction from the annular gap to a combustion zone
developing downstream of the burner head in the flame tube, the
combustion air having flow vectors with components entering the
combustion zone in directions ranging from parallel to the burner
axis to an acute angle relative to the burner axis, the combustion
air components having swirl components superimposed thereon
tangentially relative to the burner axis, using the burner axis as
a swirl center, a multiplicity of nozzle tubes penetrating the
inflow cross section in a direction substantially transverse to the
given flow direction, the nozzle tubes each having ends and having
a side with nozzle openings facing away from the air inflow side of
the ring channel system, and a natural gas feeding system
substantially concentrically surrounding the pilot burner and being
connected to one of the ends of each of the nozzle tubes.
In accordance with another feature of the invention, the pilot
burner has an axis, and the natural gas feeding system has an
annular inlet chamber with a connecting wall for the nozzle tubes
being conically bevelled relative to the axis of the pilot
burner.
In accordance with an added feature of the invention, the flow
conduction walls are in the form of inner and outer walls bounding
the ring channel system, each of the inner and outer walls being
disposed at least approximately on a respective conical surface
having conical axes coinciding with with the axis of the pilot
burner, the walls being mutually axially offset along the pilot
burner axis, and the conically bevelled connecting wall of the
annular inlet chamber being extended along the same direction as
the inner conical wall.
In accordance with a further feature of the invention, the
conically bevelled connecting wall of the annular inlet chamber at
least partially coincides with the inner conical wall.
In accordance with an additional feature of the invention there is
provided a cylinder wall surrounding the pilot burner coaxially and
defining a ring niche along with the inner flow conduction wall,
the annular inlet chamber being disposed in the ring niche.
In accordance with yet another feature of the invention, the nozzle
tubes have axes, and including a swirl vane system disposed
downstream of the nozzle tubes having longitudinal guide vane axes
extending substantially parallel to the axes of the nozzle
tubes.
In accordance with yet a further feature of the invention, the
pilot burner includes a swirl star on the side of the burner head
defining a flow space, a central burner tube for supplying heating
oil, a first burner jacket surrounding the burner tube at a
distance defining a first annular space for feeding natural gas, a
nozzle wall connecting the first annular space with the flow space
of the swirl star in the vicinity of the burner head, a second
burner jacket in the form of an outer cylinder wall surrounding the
first burner jacket at a distance defining a second annular space
coaxial with the burner acting as an air supply channel of the
pilot burner, the second annular space also being connected to the
flow space of the swirl star, and means for feeding an inert
substance into the combustion zone.
In accordance with yet a further feature of the invention, there is
provided a natural gas feedline connected to the annular inlet
chamber, the annular inlet chamber being steadily tapered in the
shape of a snail shell from a larger starting cross section
following the natural gas feedline down to a smaller end cross
section, the nozzle tubes being the form of a nozzle tube ring
including last nozzle tubes to be acted upon, the last nozzle tubes
being connected to the end cross section of the annular inlet
chamber.
In accordance with yet another feature of the invention, there is
provided a plurality of gas inlets distributed over the periphery
of the pilot burner for supplying gas to the pilot burner, the gas
inlets being fed and controlled separately and being disposed in
the air supply channel at a distance upstream from the swirl
star.
In accordance with still an added feature of the invention, the gas
inlets are formed of a plurality of additional tubes passing
through the first burner jacket and being distributed over the
periphery of the air supply channel.
In accordance with still an additional feature of the invention,
the additional tubes include tube sections extending over a given
distance into the air supply channel.
In accordance with still another feature of the invention, the tube
sections include a plurality of gas outlet openings within the air
supply channel.
In accordance with again an added feature of the invention, the gas
outlet openings are substantially perpendicular to the given flow
direction.
In accordance with again another feature of the invention, there is
provided a ring channel being concentric to the air supply channel
and having a separate gas feedline, the gas inlets being in the
form of holes formed in the one of the burner jackets communicating
with the ring canal.
In accordance with again a further mode of the invention, there is
provided a method of operating a burner apparatus of a combustion
chamber having a substantially cylindrical housing and a flame tube
having an end face and being disposed in the housing at a distance
from the housing defining a ring gap therebetween, which comprises
feeding a given amount of at least one fuel from the group
consisting of natural gas and heating oil to a pilot burner having
a head and being disposed in the vicinity of the end face of the
flame tube, feeding combustion air from the ring gap through an air
supply channel surrounding the head and through a ring channel
system developing a combustion zone downstream of the burner head
in the flame tube, as seen in flow direction of the combustion air,
and feeding a quantity of inert substances to the combustion zone
equal to substantially between 50% and 120% of the given amount of
fuel fed to the pilot burner, forming as large a portion of inert
substances in a flame of the pilot burner as possible during
operation near a given design point.
In accordance with again an additional mode of the invention, there
is provided a method which comprises adjusting the quantity of
inert substances to 100% of the given amount of fuel fed to the
pilot burner.
In accordance with again a further mode of the invention, there is
provided a method, which comprises feeding a substance from the
group consisting of water and steam as the inert substance.
In accordance with still an added mode of the invention, there is
provided a method, which comprises changing the ratio of fuel to
air at the pilot burner as a function of the total quantity of
fuel.
In accordance with still another mode of the invention, there is
provided a method, which comprises increasingly feeding gas
quantities into the air supply channel with decreasing total fuel
quantity, in order to stabilize the flame of the burner apparatus
by intentional inhomogeneity, and operating the pilot burner at an
approximate air number of .lambda.=1.4.+-.0.4.
In accordance with a concomitant mode of the invention, there is
provided a method, which comprises adjusting the quantity of gas
being fed in the vicinity of the design point forming an
approximately uniform mixture at the outlet of the pilot burner
with about the same air number as in an outer main flow.
Among others, the advantages obtainable with the invention are that
the ring channel system which is already present is constructed in
such a way that the flow conduction walls serve as the support of a
premixing burner device which permits retrofitting of existing
burner apparatus. The methods for operating a retrofitted burner
apparatus described above permit a mode of operation in which the
NO.sub.x emission is minimized without an excessive increase of the
consumption of additives, particularly water. The invention begins
from the insight that without suitable counter measures, by far the
largest part of the NO.sub.x production takes place in the pilot
flame of the pilot burner, although the fuel share of this flame is
only about 5 to 10% of that of the entire burner apparatus. A
decisive reduction of the NO.sub.x emission can therefore be
achieved by suitably influencing the pilot flame. The quantities of
the substance consumed, which may be water or water vapor, are in
the order of magnitude of about 100% of the amount of fuel of the
pilot burner, which are still relatively small.
The relocation of the gas inlets into the channel originally
serving for the air supply permits quasi-operation of the pilot
burner as a premixer burner. A load-dependent change of the ratio
of fuel to air, permits the stability of the pilot flame and
therefore of the entire burner flame to be maintained. In regions
in which the burner flame already burns in a stable manner
(.lambda.=1.8.+-.0.4), the pilot flame can be operated with such a
ratio of fuel and air. If the total load is reduced, i.e. with a
decreasing total amount of fuel, the fuel portion in the pilot
flame must be increased (for instance to .lambda.=1.4.+-.0.4). This
intended inhomogeneity stabilizes the entire flame configuration of
the burner. The advantage of this procedure is that it produces a
lowering of the NO.sub.x emission in the vicinity of the design
point by reducing the NO.sub.x generation in the pilot flame and
that it produces an extension of the operating range of the burner
apparatus in the direction toward smaller air numbers. In the
partial-load range, the NO.sub.x emission can be kept low by
additional admisture of water or steam in spite of the
inhomogeneity of the mixture field. In this connection it is
important for the admixed inert substances to be present in the
pilot flame as completely as possible. In the vicinity of the
design region, i.e. in the preferred operating range of the
apparatus, the admixture of inert substances can generally be
dispensed with.
Other feathers which are considered as characteristic for the
invention are set forth in the appended claims.
Although the invention is illustrated and described herein as
embodied in a combustion chamber apparatus for combustion
installations, especially for combustion chambers of gas turbine
installations, and a method of operating the same, it is
nevertheless not intended to be limited to the details shown, since
various modifications and structural changes may be made therein
without departing from the spirit of the invention and within the
scope and range of equivalents of the claims.
The construction and method of operation of the invention, however,
together with additional objects and advantages thereof will be
best understood from the following description of specific
embodiments when read in connection with the accompanying drawings,
in which:
FIG. 1 is a fragmentary, diagrammatic, axial-sectional view of a
burner apparatus according to the invention, omitting parts of the
burner not necessary for an understanding of the invention, as well
as a combustion chamber;
FIG. 2 is a diagram in which, for instance, the NO.sub.x content in
mg/m.sup.3 is plotted on the ordinate axis as a function of the gas
turbine entrance temperature .theta..sub.TI of the combustion gas
on the abscissa axis;
FIG. 3 is an enlarged view of a portion of FIG. 1 illustrating the
placement of gas inlets in the air supply canal of the pilot
burner; and
FIG. 4 is a view similar to FIG. 3, illustrating another embodiment
of the gas inlets thereof;
Referring now to the figures of the drawings in detail and first,
particularly, to FIG. 1 thereof, there is seen a burner apparatus B
which is part of a gas turbine installation that is the preferred
application of the invention. However, the burner apparatus B is
also suitable for gas-fired combustion systems of boilers.
A corresponding combustion chamber BK includes an approximately
cylindrical housing 1 shown in a detailed axial section and a flame
tube 2, which is held therein with an annular gap So, in a
thermally movable and centered manner. The housing 1 is
diagrammatically illustrated, it is not drawn to scale and the
embodiment is not limited to the burner apparatus B with a single
burner; as a rule, the combustion chamber BK includes six burners
which are disposed in a hexagonal configuration or eight in an
octagonal configuration.
Each individual burner apparatus B is formed of at least one pilot
burner PB which is disposed with fuel nozzles 3.1, 3.2 and with
swirl vanes swirl stars 4 of a burner head 3 thereof in the
vicinity of an an end face of the flame tube 2 and which can be
operated with natural gas E and/or heating oil H as the fuel. The
head 3 of the pilot burner PB is surrounded coaxially (relative to
a burner axis b) by a system of ring canals R with inner and outer
flow conduction walls r1 and r2. In this way, an annular canal
cross section 5 is formed which serves for supplying the main
portion of the combustion air L from the annular gap So to a
non-illustrated combustion zone which develops downstream of the
burner head 3. The pressurized combustion air L is fed to the
annular gap by the compressor of the gas turbine; the hot fuel
gases flow into the turbine blade system.
The combustion air L with admixed natural gas, if applicable,
passes from the annular canal cross section 5 into a circular cross
section 6 disposed downstream of the burner head 3, and leads into
a swirl zone with a recirculation region in the flame area,
together with air entering through an annular space 16 coaxial to
the burner. It is important that the local velocity in the rotary
flow which is formed is high enough to intermittently mix the
combustion air with the flame cone of the injected, finely atomized
heating oil H or the blown-in natural gas E, so that the dwelling
time of the reaction mixture is minimized in the area of
stoichiometric conditions in cooperation with the fuel supply of
the pilot flame, whereby the lowest possible NO.sub.x content is
assured. The NO.sub.x content can be reduced further by the
injection of water from water nozzles 7 or steam D from steam
nozzles 8 as indicated by broken lines. It is especially
advantageous if these inert substances are also present in the
pilot flame in particular, since otherwise most of the NO.sub.x is
generated there. The disposition of the nozzles 7, 8 in accordance
with the invention makes this possible.
According to the invention, the ring canal system R with its flow
conduction walls r1, r2 is furthermore constructed as a premixer
device VM for the combustion of natural gas E. To this end, the
inflow cross section 5 (which is also referred to as the canal
cross section) of the ring canal system R which is open toward the
ring gap. So, is penetrated by a multiplicity of nozzle tubes 9
aligned approximately transversely to the flow of the air L. The
ends of the nozzle tubes 9 facing the inner flow conduction wall r1
are connected to a natural gas feeding system EZ, which surrounds
the pilot burner PB approximately concentrically. As is illustrated
by the small natural gas flow arrows e, the nozzle openings of the
nozzle tubes 9 are disposed on the side of the nozzle tubes 9
facing away from the air inflow side of the ring canal system R.
Each of the nozzle tubes 9 which are distributed over the annular
canal cross section 5 and could be constructed as so-called "little
tubes" in comparison to the tube dimensions of a diffusion burner
DB, has five nozzle openings and the ring of nozzle tubes 9 in the
embodiment includes 24 "little tubes" which, however, still leave
still enough inflow cross section free for the combustion air L.
The ring of little tubes acts like a natural gas shower which
contributes to optimum mixing with the combustion air L.
The natural gas feeding system for the premixing burner VM has an
annular inlet chamber 10 with a connecting wall 10.1 for the nozzle
tubes 9, which is conically bevelled relative to the axis b of the
pilot burner PB. The inflow chamber 10 steadily tapers from a
larger starting cross section (at the left-hand side of FIG. 1)
connected to a natural gas feedline 11, down to a smaller final
cross section (at the right-hand side of FIG. 1) in the form of a
snail-shaped housing. The last of the nozzles tubes 9 of the nozzle
tube ring to be acted upon are connected in such a way that the
flow velocity of the combustion air is approximately the same at
all of the nozzle openings.
The ring channel or canal or canal system R is bounded by the
above-mentioned inner and outer flow conduction walls r1, r2, each
of which are located at least approximately on a conical surface,
the conical axes of which coincide with the axis b of the pilot
burner PB. The walls are mutually axially offset for forming the
annular canal cross section 5 in the direction of the pilot burner
axis. The conically bevelled connecting wall 10.1 of the inflow
chamber 10 follows the same direction as the conical flow
conduction wall r1 and partially coincides therewith, as can be
seen. A particularly space-saving measure which is advantageous for
the flow is achieved, if the inflow chamber 10 is disposed in a
ring niche which is defined by a cylinder wall 12 surrounding the
pilot burner PB and the inner flow conduction wall r1, as
shown.
A rotary component is impressed on the combustion air L flowing
into the premixing burner VM by a swirl vane 13 which is downstream
of the nozzle tubes 9. The longitudinal axis of the guide vanes of
the swirl vane 13 extend approximately parallel to the nozzle tube
axes.
The function of the pilot burner PB is supplemented by the
premixing burner VM, i.e. in natural gas operation, it is possible
to switch the premixer burner operation with its lower NO.sub.x
values, after the pilot burner is started and warmed up. The pilot
burner PB is ignited by an ignition burner Z thereof which has a
gas tube z1 and a rod or tube-shaped electrode configuration z2 for
this purpose. The ignition burner Z is extinguished if a permanent
flame burns at the burner head downstream thereof; the premixing
burner VM is ignited by the flame of the pilot burner PB. The flame
cannot flash back into the premixing burner region even without a
flame holder, if attention is paid to providing sufficient air
velocity. A central tube 30 of the pilot burner PB serves for
supplying heating oil H and a first burner jacket 31 surrounding
the central burner tube forms an annular space or channel 14 for
feeding the natural gas E. In the vicinity of the burner head 3,
the annular space 14 discharges through a conical nozzle wall 32
into a flow space 33 of the swirl vane or swirl star 4 on the side
of the burner head, which is held by its guide blades between the
inner nozzle wall 32 and an outer conical skirt 15. The outer
conical skirt 15 is fastened at the edge of a truncated conical
opening of the inner flow guide wall r1. A second burner jacket
concentrically surrounding the first burner jacket 31 is formed by
the outer cylinder wall 12 which defines a second annular space or
channel 16 coaxial with the burner. The ring space 16 likewise ends
in the flow space of the swirl vane or star 4 on the side of the
burner head and serves for supplying air to the pilot flame and
optionally for feeding-in water W through the nozzles 7 or steam D
through the nozzles 8 as already explained above. The entire burner
unit PB/VM is fastened at its lower end to a flange 2.1a of the end
face 7.1 of the flame tube 2 by means of a tube stub 17 with a
flange 17.1. The tube stub 17 is welded to the outer flow
conduction wall r2. Flange screws are designated with reference
numeral 18.
In the diagram of FIG. 2, an upper curve k1 shows the NO.sub.x
emission in the exhaust gas for 15% by volume O.sub.2 during
operation of the hybrid burner without H.sub.2 O injection and
without an activated premixing burner VM, as a function of the
temperature .theta..sub.TI, which is the gas turbine inflow
temperature of the working medium. A curve k1.1 shows the steep
drop of the NO.sub.x emission for a transition to the premixing
burner operation; and the curve k2 shows the further reduction of
the NO.sub.x content in the exhaust gas during operation of the
hybrid burner with H.sub.2 O injection.
FIG. 3 diagrammatically illustrates one possible embodiment for
changing the gas inlets or tube sections 36 to the pilot burner PB
in the second annular space 16 which is coaxial with the burner and
otherwise serves for the air supply. This is done for the
load-dependent change of the fuel/air mixture. The gas can be fed
into the annular space 16 through an additional pipeline or tube 35
which is fed and controlled separately and which is brought through
the inner wall 31 of the second annular space 16. Suitable outlet
openings 37 which are preferably located perpendicular to the
remaining air flow in the ring space 16, allow good mixing to take
place. In this manner, the pilot burner PB is no longer operated as
a diffusion burner but rather as a separately controlled
quasi-premixing burner. Basically, the path through which the
additional air is fed is of secondary importance, so that there are
many possibilities for installing the pipeline 35 and the gas
outlets 36, several of which are distributed over the
circumference.
FIG. 4 therefore diagrammatically illustrates another embodiment of
the gas inlets. A ring canal 38 is disposed concentric to the
second annular space 16. The ring canal 38 communicates with
several holes 39 passing through the wall 31 of the second annular
space 16, which are distributed over the circumference. The ring
canal 38 is supplied with gas through a pipeline 40, depending on
the load.
* * * * *