U.S. patent application number 12/812301 was filed with the patent office on 2010-12-23 for burner and method for reducing self-induced flame oscillations.
Invention is credited to David Barkowski, Matthias Hase, Jaap Van Kampen, Berthold Kostlin, Werner Krebs, Martin Lenze, Martin Stapper.
Application Number | 20100323309 12/812301 |
Document ID | / |
Family ID | 39420374 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100323309 |
Kind Code |
A1 |
Barkowski; David ; et
al. |
December 23, 2010 |
Burner and Method for Reducing Self-Induced Flame Oscillations
Abstract
A method for reducing self-induced flame oscillations is
provided. In a first fluid mass flow flowing through a jet nozzle
from a fluid inlet opening to a fluid outlet opening, a second
fluid mass flow is injected on an axial position of the jet nozzle
positioned downstream from the fluid inlet opening. One fluid mass
flow includes air, and the other fluid mass flow includes a fuel. A
second method for reducing self-induced flame oscillations is also
provided. In a first fluid mass flow flowing through a jet nozzle
from a fluid inlet opening to a fluid outlet opening, a second
fluid mass flow is injected on a radial position of the jet nozzle
in relation to the circumference of the jet nozzle. One mass flow
includes air and the other fluid mass flow includes a fuel. Burners
which ensure the execution of the method are also provided.
Inventors: |
Barkowski; David;
(Hamminkeln, DE) ; Hase; Matthias; (Mulheim,
DE) ; Krebs; Werner; (Mulheim an der Ruhr, DE)
; Kostlin; Berthold; (Duisburg, DE) ; Lenze;
Martin; (Essen, DE) ; Stapper; Martin;
(Kamp-Lintfort, DE) ; Kampen; Jaap Van; (Roermond,
NL) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Family ID: |
39420374 |
Appl. No.: |
12/812301 |
Filed: |
April 24, 2008 |
PCT Filed: |
April 24, 2008 |
PCT NO: |
PCT/EP2008/054969 |
371 Date: |
August 20, 2010 |
Current U.S.
Class: |
431/8 ;
431/278 |
Current CPC
Class: |
F23R 2900/00014
20130101; F23R 2900/03282 20130101; F23R 3/286 20130101 |
Class at
Publication: |
431/8 ;
431/278 |
International
Class: |
F23R 3/36 20060101
F23R003/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 11, 2008 |
EP |
08000497.1 |
Claims
1.-27. (canceled)
28. A method for reducing self-induced flame oscillations,
comprising: injecting a second mass flow of fluid that includes a
fuel into a first mass flow of fluid comprising air and flowing
through a jet nozzle from a fluid inlet opening to a fluid outlet
opening wherein the second mass flow of fluid is injected at an
axial position on the jet nozzle downstream of the fluid inlet
opening; and injecting a third mass flow of fluid into the first
mass flow of fluid from the fuel line from which the first mass
flow of fluid flows into the jet nozzle wherein the third mass flow
of fluid is injected at a first plurality of positions disposed
mutually offset in an axial direction around a circumference of the
jet nozzle.
29. A method for reducing self-induced flame oscillations,
comprising: injecting a second mass flow of fluid comprising a fuel
into a first mass flow of fluid comprising air and flowing through
a jet nozzle from a fluid inlet opening to a fluid outlet opening
wherein the second mass flow is injected at a radial position on
the jet nozzle with respect to a circumference of the jet nozzle;
and injecting a third mass flow into the first mass flow of fluid
from the fuel line from which the first mass flow of fluid flows
into the jet nozzle, wherein the third mass flow is injected at a
second plurality of positions disposed mutually offset in an axial
direction around a circumference of the jet nozzle.
30. The method as claimed in claim 29, wherein a plurality of
different radial fuel distributions are implemented.
31. The method as claimed in claim 28, wherein the second mass flow
of fluid is injected into the first mass flow of fluid at a second
plurality of positions around the circumference of the jet
nozzle.
32. The method as claimed in claim 29, wherein the second mass flow
of fluid is injected into the first mass flow of fluid at a second
plurality of positions around the circumference of the jet
nozzle.
33. The method as claimed in claim 32, wherein the second mass flow
of fluid is injected into the first mass flow of fluid at the
second plurality of positions disposed mutually offset in the axial
direction around the circumference of the jet nozzle.
34. The method as claimed in claim 28, wherein the second mass flow
of fluid is an air/fuel mixture.
35. The method as claimed in claim 28, wherein the second and/or
the third mass flow of fluid is injected into the first mass flow
of fluid at an angle of between 0.degree. and 90.degree..
36. The method as claimed in claim 35, wherein the second mass flow
of fluid is injected into the first mass flow of fluid at the angle
of 90.degree., and wherein the third mass flow of fluid is injected
into the first mass flow of fluid at the angle of 45.degree..
37. A burner, comprising: a jet nozzle with a main fluid inlet
opening and a fluid outlet opening, wherein the main fluid inlet
opening is connected to a first fluid supply line which is an air
supply line, wherein fuel may be injected into the jet nozzle
either via a fuel nozzle which is disposed in or immediately
preceding the main fluid inlet opening or via a first secondary
fluid inlet opening connected to a fluid supply line, the first
fluid inlet is disposed in an axial position on the jet nozzle
downstream of the main fluid inlet opening, and wherein a plurality
of second secondary fluid inlet openings are connected to the first
fluid supply line and disposed at a plurality of positions disposed
in a mutually offset manner in an axial direction along a
circumference of the jet nozzle.
38. A burner, comprising: a jet nozzle with a main fluid inlet
opening and a fluid outlet opening, wherein the main fluid inlet
opening is connected to a first fluid supply line which is an air
supply line, wherein fuel may be injected into the jet nozzle
either via a fuel nozzle which is disposed in or immediately
preceding the main fluid inlet opening, or via first secondary
fluid inlet opening connected to a fluid supply line from a radial
position of the jet nozzle with respect to a circumference of the
jet nozzle, and wherein a plurality of second secondary fluid inlet
openings are connected to the first fluid supply line and disposed
at a first plurality of positions disposed in a mutually offset
manner in an axial direction along the circumference of the jet
nozzle.
39. The burner as claimed in 37, wherein the plurality of first
fluid inlet openings or the plurality of second secondary fluid
inlet openings are disposed at a second plurality of positions
along the circumference of the jet nozzle.
40. The burner as claimed in claim 39, wherein the plurality of
first fluid inlet openings or the plurality of second secondary
fluid inlet openings are disposed at the second plurality of
positions disposed in a mutually offset manner along the
circumference of the jet nozzle.
41. The burner as claimed in claims 37, wherein the plurality of
first secondary fluid inlet openings or the plurality of second
secondary fluid inlet openings and the main fluid inlet opening
each include a central axis, and wherein the plurality of central
axes of the plurality of first fluid inlet opening or the plurality
of second secondary fluid inlet openings are at an angle of between
0.degree. and 90.degree. to the central axis of the main fluid
inlet opening and/or to the central axis of the jet nozzle.
42. The burner as claimed in claim 41, wherein the plurality of
central axes of a first portion of the plurality of first or second
secondary fluid inlet openings are at the angle of 90.degree. to
the central axis of the main fluid inlet opening and/or to the
central axis of the jet nozzle, and wherein the plurality of
central axes of a second portion of the plurality of first or
second secondary fluid inlet openings are at an angle of 45.degree.
to the central axis of the main fluid inlet opening and/or to the
central axis of the jet nozzle.
43. The burner as claimed in claim 37, wherein the plurality of
first or second secondary fluid inlet openings and the main fluid
inlet opening each include a central axis, and wherein the
plurality of central axes of the plurality of first or second
secondary fluid inlet openings are at the angle of between
0.degree. and 90.degree. to a radial direction with respect to the
central axis of the main fluid inlet opening.
44. The burner as claimed in claim 37, wherein a plurality of fluid
supply lines connected to the plurality of first secondary fluid
inlet openings are interconnected via an annular distributor
disposed along the circumference of the jet nozzle.
45. The burner as claimed in claim 37, wherein the fuel nozzle
comprises a fuel distributor which is disposed in or immediately
preceding the main fluid inlet opening.
46. The burner as claimed in claim 37, wherein the second secondary
fluid inlet opening is implemented as an annular gap running along
the circumference of the jet nozzle.
47. The burner as claimed in claim 46, wherein the burner is
implemented as a jet burner and comprises a plurality of jet
nozzles, and wherein a plurality of annular gaps of the plurality
of different jet nozzles are disposed at different axial positions
in each case.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2008/054969, filed Apr. 24, 2008, and claims
the benefit thereof. The International Application claims the
benefits of European Patent Office application No. 08000497.1 EP
filed Jan. 11, 2008. All of the applications are incorporated by
reference herein in their entirety.
FIELD OF INVENTION
[0002] The present invention relates to a method for reducing
self-induced flame oscillations and to a burner with which this
method can be carried out.
BACKGROUND OF INVENTION
[0003] Self-induced flame oscillations frequently occur in
combustion chambers and in this context are also known as
combustion hum. Combustion chamber oscillations are caused by
feedback between pressure changes in the combustion chamber and
fluctuations in the mass flow of fuel and air. The combustion
chamber oscillations constitute an undesirable side-effect of the
combustion process, as they place increased mechanical and thermal
stress on the burner components and the combustion chamber
components. In addition, combustion hum produces increased levels
of noise pollution in the vicinity of the combustion chamber in
question.
[0004] Reducing combustion hum, i.e. minimizing self-induced flame
oscillations, has hitherto been achieved in some cases with the aid
of Helmholtz resonators. Another possibility is to supply an
increased amount of pilot gas to the burner used. Pilot gas, i.e.
pilot fuel, is normally used to stabilize the flame. However,
increasing the pilot gas supply results in higher NO.sub.X
emissions.
SUMMARY OF INVENTION
[0005] The object of the present invention is therefore to provide
an advantageous method for reducing self-induced flame
oscillations. Another object of the present invention is to provide
an advantageous burner.
[0006] The first object is achieved by a method as claimed in the
claims. The second object is achieved by a burner as claimed in the
claims. The dependent claims contain further advantageous
embodiments of the invention.
[0007] In the method according to the invention for reducing
self-induced flame oscillations, into a first mass flow of fluid
flowing through a jet nozzle from a fluid inlet opening to a fluid
outlet opening, there is injected a second mass flow of fluid at
least one axial position on the jet nozzle downstream of the fluid
inlet opening, one of the two mass flows of fluid being air. The
other mass flow of fluid comprises a fuel. By injecting the fuel
and/or air at a plurality of axial positions into a main mass flow
of fluid flowing through the jet nozzle, the response e.g. of the
mass flow of fuel can be smeared such that resonance can only occur
for a small portion of the mass flow. Smearing of the delay between
injection and combustion is achieved by the method according to the
invention. The method according to the invention can be used in
particular for operating a jet burner, while still retaining the
positive characteristics of a jet burner.
[0008] Alternatively or additionally, the second mass flow of fluid
can be injected at at least one radial position on the jet nozzle
with respect to the circumference of the jet nozzle.
[0009] This likewise achieves the smearing of the delay time
between injection and combustion as described above.
[0010] Different radial fuel distributions are preferably
implemented. Here it is advantageous e.g. during part-load
operation to run the inner areas richer, i.e. the areas leading to
the center of a housing, thereby enabling flame extinction and CO
emissions to be prevented.
[0011] The second mass flow of fluid can preferably be injected
into the first mass flow of fluid at a plurality of positions
around the circumference of the jet nozzle. In particular, the
second mass flow of fluid can be injected into the first mass flow
of fluid at a plurality of positions disposed mutually offset in
the axial direction around the circumference of the jet nozzle. As
a result, the flow in the jet nozzle is not always attenuated at
the same circumferential position.
[0012] The mass flow of fluid comprising a fuel can be, for
example, an air/fuel mixture. The fuel used can, in particular, be
gaseous fuel, such as natural gas or a synthesis gas. For natural
gas, as the mass flows of fuel are much smaller than the air mass
flows, there is unlikely to be a significant increase in pressure
loss even in the case of injection perpendicular to the flow
direction of the air. Moreover, the method can also be applied to
liquid fuels.
[0013] In addition to the second mass flow of fluid, a third mass
flow of fluid can be injected into the first mass flow of fluid.
For example, the second mass flow of fluid can comprise a fuel and
the first mass flow of fluid can comprise air. The third mass flow
of fluid can likewise comprise air, steam or another gas, e.g. an
inert gas. The second and/or the third mass flow of fluid can be
injected into the first mass flow of fluid at an angle of between
0.degree. and 90.degree.. For example, the second mass flow of
fluid can be injected into the first mass flow of fluid at an angle
of 90.degree. and the third mass flow of fluid can be injected into
the first mass flow of fluid at an angle of 45.degree.. Said first
and third mass flow of fluid can be, for example, a mass flow of
air, and the second mass flow of fluid can be a mass flow of fuel.
The advantage of jet-in-crossflow injection is that it helps to
increase the mixing of the air/fuel mixture, while wall film
formation is primarily a measure to counteract flashback.
[0014] The burner according to the invention comprises at least one
jet nozzle with a main fluid inlet opening and a fluid outlet
opening, the main fluid inlet opening being connected to a fluid
supply line. The burner according to the invention is characterized
in that at least one secondary fluid inlet opening connected to a
fluid supply line is disposed at least one axial position on the
jet nozzle downstream of the main fluid inlet opening.
[0015] The fluid supply line connected to the main fluid inlet
opening can be implemented, for example, as a fuel supply line, as
an air supply line or as a fuel/air mixture supply line. The main
fluid inlet opening is preferably connected to an air supply line.
Although the fluid supply line connected to at least one secondary
fluid inlet opening can preferably be implemented as a fuel supply
line, it can also be implemented as an air supply line, as a steam
supply line, as a nitrogen supply line or as an air/fuel mixture
supply line.
[0016] It is basically advantageous if the secondary fluid inlet
openings are disposed at a plurality of axial positions on the jet
nozzle. The secondary fluid inlet openings, which can be disposed
at different axial positions, can be, in particular, air inlet
openings. In addition, secondary fluid inlet openings can be
disposed at a plurality of positions along the circumference of the
jet nozzle. In this case it is advantageous if secondary fluid
inlet openings are disposed at a plurality of positions disposed
mutually offset in the axial direction along the circumference of
the jet nozzle. This means that the flow in the jet nozzle is not
always attenuated at the same circumferential position.
[0017] The main fluid inlet opening can preferably be connected to
an air supply line and a portion of the secondary fluid inlet
openings can be connected to a fuel supply line. In particular, a
first portion of the secondary fluid inlet openings can be
connected to a fuel supply line and a second portion of the
secondary fluid inlet openings can be connected to an air supply
line.
[0018] In addition, the secondary fluid inlet openings and the main
fluid inlet opening can have a central axis in each case. Said
central axes of the secondary fluid inlet openings can be at an
angle of between 0.degree. and 90.degree. to the central axis of
the main fluid inlet opening and/or to the central axis of the jet
nozzle. Advantageously, the central axes of a first portion of the
secondary fluid inlet openings can be at 90.degree. to the central
axis of the main fluid inlet opening and/or to the central axis of
the jet nozzle, and the central axes of a second portion of the
secondary fluid inlet openings can be at 45.degree. to the central
axis of the main fluid inlet opening and/or to the central axis of
the jet nozzle. The advantage of jet-in-crossflow injection is that
it helps to increase the mixing of the air/fuel mixture, while wall
film formation is primarily a measure to counteract flashback.
[0019] The secondary fluid inlet openings and the main fluid inlet
opening may have a central axis in each case and the central axes
of the secondary fluid inlet openings can be at an angle of between
0.degree. and 90.degree. to a radial direction with respect to the
central axis of the main fluid inlet opening. This enables
injection to take place tangentially along the circumference of the
jet nozzle, thereby producing a wall film on the inner surface of
the jet nozzle. Injection along the circumference of the jet nozzle
can also be used to produce swirl in the jet nozzle.
[0020] A plurality of fluid supply lines connected to secondary
fluid inlet openings can be interconnected via an annular
distributor disposed along the circumference of the jet nozzle.
[0021] In addition, a fuel nozzle can be disposed in the main fluid
inlet opening or immediately preceding the main fluid inlet
opening. The fuel nozzle can comprise a fuel distributor which is
disposed in or immediately preceding the main fluid inlet
opening.
[0022] At least one secondary fluid inlet opening can be
implemented as an annular gap running along the circumference of
the jet nozzle. In this case the burner according to the invention
can comprise a plurality of jet nozzles, the annular gaps of the
different jet nozzles being disposed at different axial positions
in each case. Varying the axial positions of the annular gaps
provides an additional design parameter for counteracting
thermoacoustic flame oscillations.
[0023] The burner according to the invention can comprise a
plurality of jet nozzles disposed e.g. annularly with respect to
the central axis of the burner. It can also incorporate one or more
pilot burners.
[0024] The burner according to the invention is preferably used in
a gas turbine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Further features, characteristics and advantages of the
present invention will now be described in greater detail using
exemplary embodiments and with reference to the accompanying
drawings in which:
[0026] FIG. 1 schematically illustrates a section through a jet
burner at right angles to its longitudinal direction.
[0027] FIG. 2 schematically illustrates a section through another
jet burner at right angles to its longitudinal direction.
[0028] FIG. 3 schematically illustrates a section through part of a
jet burner in the longitudinal direction.
[0029] FIG. 4 schematically illustrates a section through part of
another jet burner in the longitudinal direction.
[0030] FIG. 5 schematically illustrates a section through part of
an alternative jet burner in the longitudinal direction.
[0031] FIG. 6 schematically illustrates a section in the
longitudinal direction through another jet burner.
[0032] FIG. 7 schematically illustrates a section through part of a
jet burner in the longitudinal direction.
[0033] FIG. 8 schematically illustrates a jet burner having an
annular gap, in the longitudinal direction,
[0034] FIG. 9 schematically illustrates an alternative arrangement
of the annular gap of the jet burner shown in FIG. 8.
[0035] FIG. 10 shows a cross-section of a jet burner and of the
annular distributor with a plurality of radial secondary fluid
inlet openings.
DETAILED DESCRIPTION OF INVENTION
[0036] A first exemplary embodiment of the invention will now be
explained in greater detail with reference to FIGS. 1 to 4. FIG. 1
schematically illustrates a section through a jet burner 1
perpendicular to a central axis 4 of the burner 1. The burner 1
comprises a housing 6 having a circular cross-section. Inside the
housing 6, a particular number of jet nozzles 2 are disposed in an
essentially annular manner. Each of said jet nozzles 2 has a
circular cross-section. The burner 1 can also incorporate a pilot
burner.
[0037] FIG. 2 schematically illustrates a section through a jet
burner 101, said section running perpendicular to the central axis
of the burner 101. The burner 101 likewise has a housing 6 of
circular cross-section in which are disposed a number of inner and
outer jet nozzles 2, 3. The jet nozzles 2, 3 each have a circular
cross-section, said outer jet nozzles 2 having a cross-sectional
area that is the same size as, or larger than, that of the inner
jet nozzles 3. The outer jet nozzles 2 are disposed in an
essentially annular manner inside the housing 6 and form an outer
ring. The inner jet nozzles 3 are likewise disposed in an
essentially annular manner inside the housing 6. The inner jet
nozzles 3 fond an inner ring which is disposed concentrically to
the outer jet nozzle ring.
[0038] FIGS. 1 and 2 merely show examples of the arrangement of jet
nozzles 2, 3 inside a jet burner 1, 101. Alternative arrangements,
as when using a different number of jet nozzles 2, 3, are
self-evidently possible.
[0039] FIG. 3 schematically illustrates a section through part of a
jet burner 1 according to the invention in the longitudinal
direction, i.e. along the central axis 4 of the burner 1. The
burner 1 has at least one jet nozzle 2 disposed in a housing 6. The
central axis of the jet nozzle 2 is identified by the reference
character 5. The jet nozzle 2 comprises a main fluid inlet opening
8 and a fluid outlet opening 9. The combustion chamber 18 is
connected to the fluid outlet opening 9. In addition, the jet
nozzle 2 is disposed in the housing 6 such that the main fluid
inlet opening 8 faces the back wall 24 of the burner 1. The housing
6 also comprises an outer housing section 27 disposed radially with
respect to the central axis 4 of the burner 1.
[0040] The jet nozzle 2 is fluidically connected to a compressor.
The compressed air from the compressor is conveyed via an annular
gap 22 to the main fluid inlet opening 8 and/or is conveyed
radially with respect to the central axis 5 of the jet nozzle 2 via
an air inlet opening 23 to the main fluid inlet opening 8. In the
event that the compressed air is supplied through the annular gap
22 of the jet nozzle 2, said compressed air flows through the
annular gap 22 in the direction of the arrow identified by the
reference character 15, i.e. parallel to the central axis 5 of the
jet nozzle 2. The air flowing in the direction of the arrow 15 is
then deflected through 180.degree. at the back wall 24 of the
burner 1 and then flows through the main fluid inlet opening 8 into
the jet nozzle 2. The flow direction of the air inside the jet
nozzle 2 is indicated by an arrow 10.
[0041] Additionally or alternatively to feeding the compressed air
through the annular gap 22, the compressed air from the compressor
can also be supplied through an opening 23 disposed radially in the
housing 6 of the burner 1 with respect to the central axis 5 of the
jet nozzle 2. The flow direction of the compressed air flowing
through the opening 23 is indicated by an arrow 26. In this case
the compressed air is then deflected through 90.degree. and then
flows into the jet nozzle 2 through the main fluid inlet opening
8.
[0042] The burner according to the invention 1 can basically also
be implemented without the outer housing section 27, i.e. without
an external casing 27. In this case the compressed air can flow
directly into the "plenum", i.e. the area between the back wall 24
and the main fluid inlet opening 8. The burner according to the
invention 1 can also be implemented even without the back wall
24.
[0043] The jet nozzle 2 is encircled radially by an annular
distributor 7 which is supplied with fuel 12 via a fuel supply line
13. The annular distributor 7 has a number of secondary fluid inlet
openings 14 through which fuel can be injected into the mass flow
of air flowing through the jet nozzle 2. The secondary fluid inlet
openings 14 can be implemented as a slit or an oval nozzle. This is
particularly advantageous for synthesis gas injection, as it means
that a smaller inflow surface is offered to the flow of air. This
also results in a lesser tendency to recirculation downstream of
fuel injection. The flow direction of the fuel 12 injected into the
jet nozzle 2 through the secondary fluid inlet openings 14 is
indicated by arrows 17. Said flow direction 17 of the injected fuel
12 runs perpendicular to the central axis 5 of the jet nozzle 2 and
therefore also perpendicular to the main flow direction 10 of the
compressed air 11 flowing through the jet nozzle 2.
[0044] In FIG. 3, secondary fluid inlet openings 14 are disposed at
three different axial positions, two secondary fluid inlet openings
14 being disposed opposite one another at each axial position. A
number of secondary fluid inlet openings 14 are advantageously
disposed along the circumference of the jet nozzle 2. These can in
particular also be disposed in an axially offset manner with
respect to one another. Secondary fluid inlet openings 14 can
basically be disposed at only one or at additional axial positions
along the circumference of the jet nozzle 2.
[0045] Inside the jet nozzle 2, the injection of fuel 12 into the
compressed air 11 flowing through the jet nozzle 2 creates a
fuel/air mixture which leaves the jet nozzle 2 through the fluid
outlet opening 9 in the direction of the combustion chamber 18.
[0046] FIG. 4 schematically illustrates a section through a burner
201 which constitutes a development of the burner 1 shown in FIG.
3. The compressed air 11 from a compressor can again either be
supplied to the jet nozzle 2 via an annular gap 22 or, as shown in
FIG. 3, injected via an air inlet opening perpendicularly to the
central axis 5 of the jet nozzle. In this variant, the compressed
air 11 is preferably supplied to the jet nozzle 2 via an annular
gap 22. Injection perpendicular to the central axis 5 is therefore
only denoted by a dashed arrow 26.
[0047] In addition to the features already described in connection
with FIG. 3, the burner 201 shown in FIG. 4 not only has the
secondary fluid inlet openings 14 through which fuel is injected
into the jet nozzle 2, but also secondary fluid inlet openings 25
through which the additional compressed air is injected into the
jet nozzle 2 in the flow direction indicated by the arrows 16. Said
additional secondary fluid inlet openings 25 are connected to the
annular gap 22. This means that a portion of the compressed air 11
coming from the compressor is conveyed through the annular gap 22
to the back wall 24 of the burner where it is deflected through
180.degree. and is then fed through the main fluid inlet opening 8
into the jet nozzle 2. This mass flow of air flows through the jet
nozzle 2 in the direction indicated by the arrow 10. Another
portion of the compressed air from the compressor is injected from
the annular gap 22 into the jet nozzle 2 through the secondary
fluid inlet openings 25 in the flow direction indicated by the
arrows 16. Said secondary fluid inlet openings 25 can be disposed
at different axial positions around the jet nozzle 2. In FIG. 4,
the secondary fluid inlet openings 25 through which compressed air
is injected into the jet nozzle 2 are disposed such that a
secondary fluid inlet opening 25 is disposed in each case in the
flow direction 10 downstream of a secondary fluid inlet opening 14
through which fuel 12 is injected into the jet nozzle 2. Any other
arrangements are self-evidently also possible. However, it is
advantageous if the secondary fluid inlet openings 25 are disposed
in a radial offset manner along the circumference of the jet nozzle
2. This means that the flow is not always attenuated at the same
circumferential position.
[0048] In FIG. 4, the secondary fluid inlet openings 14 and 25 are
disposed such that the fuel 12 is injected through the secondary
fluid inlet openings 14 perpendicularly to the flow direction 10 of
the compressed air 11 flowing through the main fluid inlet opening
8 into the jet nozzle 2. Further compressed air is injected into
the jet nozzle 2 through the secondary fluid inlet openings 25 at
an angle of about 45.degree. to the main flow direction 10. Both
the fuel 12 and the additional compressed air can be injected into
the jet nozzle 2 at any other angle of between 0.degree. and
90.degree. to the main flow direction 10 at different axial
positions. As e.g. for natural gas, the mass flows of fuel are much
smaller than the mass flows of air, a significant increase in the
pressure loss is unlikely to occur even in the case of
perpendicular fuel injection. The fuel 12 can also be injected
against the air flow direction 10.
[0049] The fuel can basically be supplied via one or more fuel
supply lines 13 and transported to the individual jet nozzles 2 via
an annular distributor 7. If a plurality of fuel supply lines 13
are present, these can be advantageously disposed along the
circumference of the burner. It is further advantageous if the
injection of the fuel into the air jet is carried out at more than
one axial position of the jet pipe 2. In addition, to ensure better
mixing, injection can take place at a plurality of circumferential
positions on the jet pipe 2.
[0050] A second exemplary embodiment will now be described in
greater detail with reference to FIGS. 5 to 7. Elements
corresponding to elements already described in the first exemplary
embodiment are provided with the same reference characters and will
not be described again in detail.
[0051] FIGS. 5 to 7 each show sections through part of a burner 301
along the central axis 4 of the burner 301. The burner 301 has at
least one, but advantageously a plurality of jet nozzles 2 disposed
in an essentially annular manner about the central axis 4. For
possible arrangements of the jet nozzles 2, 3, please refer to
FIGS. 1 and 2 and the statements made in that context.
[0052] In FIGS. 5 to 7, a fuel nozzle 19 is disposed in the region
of the main fluid inlet opening 8 of the jet nozzle 2. Through said
fuel nozzle 19, fuel 12 is injected into the jet nozzle 2. The fuel
12 is preferably injected at an angle of about 45.degree. to the
flow direction 10 of the compressed air 11 flowing into the jet
nozzle through the main fluid inlet opening 8. The flow direction
of the fuel 12 injected through the fuel nozzle 19 is indicated by
arrows 17. The fuel 12 can also be injected into the jet nozzle 2
at an angle of between 0.degree. and 90.degree. with respect to the
flow direction 10 of the compressed air 11.
[0053] Disposed at different axial positions on the jet nozzle 2
are further secondary fluid inlet openings 25 through which
compressed air can be injected into the jet nozzle 2. Said
compressed air is fed to the secondary fluid inlet openings 25 via
an annular gap 22. In FIGS. 5 and 6, the compressed air is injected
through the secondary fluid inlet openings 25 into the jet nozzle 2
perpendicularly to the central axis 5 of the jet nozzle. In FIG. 5,
said compressed air from a compressor flows through the annular gap
22 in the direction of the arrow 15.
[0054] In FIG. 6, the compressed air coming from a compressor is
injected into the burner 301 perpendicularly to the central axis 5
of the jet nozzle 2 through an air inlet opening 23. The flow
direction of the compressed air 11 passing through the opening 23
is indicated by an arrow 26. The compressed air 11 now flows
through the annular gap 22 to the secondary fluid inlet openings 25
and is fed via the latter into the jet nozzle 2. However, the main
portion of the compressed air 11 is introduced into the jet nozzle
2 though the main fluid inlet opening 8 in the flow direction
10.
[0055] FIG. 7 shows an alternative embodiment of the burner 301
shown in FIG. 5. Unlike in FIG. 5, in FIG. 7 the secondary fluid
inlet openings 25 are disposed such that the compressed air
injected into the jet nozzle 2 through the secondary fluid inlet
openings 25 is injected into said jet nozzle at an angle of
approximately 45.degree. to the central axis 5 of the jet pipe 2.
Another injection angle between 0.degree. and 90.degree. is
basically possible and practical.
[0056] The air used for the axially stepped air injection in this
exemplary embodiment can either be extracted from the annular gap
22 or directly from a plenum surrounding the burner 301 and
injected into the fuel/air mixture in the jet nozzle. Said air can
be introduced as a jet into the crossflow or as a wall film. The
advantage of jet-in-crossflow injection is that it helps to
increase the mixing of the fuel/air mixture, while wall film
formation is primarily a measure to counteract possible flashback.
In addition, the air can be injected into the jet nozzle 2
tangentially to the circumference thereof. Said wall film can be
produced over the entire inner surface of the jet nozzle 2.
Tangential injection can also be used to generate swirl in the jet
nozzle 2.
[0057] It is also conceivable for jet-in-crossflow injection to be
combined with wall film injection by disposing the nozzles in very
close succession. Jet-in-crossflow injection ensures improved
mixing, particularly also in the core region of the jet, and the
film of the second nozzle strengthens the flow boundary layer,
thereby preventing flashback. This design is particularly
advantageous for central co-flow injection into the main fuel
injection, e.g. for synthesis gas. If there is a high proportion of
air in the axial stepping, it is possible to adjust the nozzle
diameter of the jet nozzle such that the flow rate in the nozzle
remains essentially the same.
[0058] A third exemplary embodiment will now be explained in
greater detail with reference to FIGS. 8 and 9. Elements
corresponding to elements already described in the first exemplary
embodiment are provided with the same reference characters and will
not be described again in detail.
[0059] FIGS. 8 and 9 schematically illustrate different variants of
a burner 401 in the longitudinal direction along the central axis 4
of the burner 401. The burner 401 has a number of jet nozzles 2
which are disposed in an essentially annular manner about the
central axis 4 of the burner 401. For possible arrangements of the
jet nozzles 2, 3, please refer to FIGS. 1 and 2 and the statements
made in that context.
[0060] Each jet nozzle 2 comprises a main fluid inlet opening 8 and
a fluid outlet opening 9. The fluid outlet opening 9 leads into the
combustion chamber 18. A fuel nozzle 19 is disposed in the main
fluid inlet opening 8. The fuel nozzle 19 comprises a fuel
distributor 20 which enables fuel 12 to be injected into the jet
nozzle 2 at different radial positions and different
circumferential positions of the main fluid inlet opening 8. The
flow direction of the injected fuel 12 is indicated by arrows
17.
[0061] An annular gap 21 is disposed at another axial position on
the jet nozzle 2 downstream in respect of the flow directions 10
and 17. Air is injected into the jet nozzle 2 through the annular
gap 21. The flow direction of the injected air is indicated by
arrows 16. Said air is injected into the jet nozzle 2 virtually
parallel to the central axis 5 thereof. In contrast to the variant
shown in FIG. 8, in FIG. 9 the annular gap 21 is disposed at a
position further downstream of the main fluid inlet opening 8. In
the two variants shown in FIGS. 8 and 9, the compressed air used
from a compressor can be either passed through an annular gap 22 in
the flow direction 15 to the main fluid inlet opening 8 of the jet
nozzle 2 and/or injected perpendicularly to the central axis 5 in
the flow direction 26.
[0062] The variants shown in FIGS. 8 and 9 include the possibility
of inserting into the burner 401, from the back wall 24 of the
burner, the nozzle section located downstream in terms of the flow
direction 15 of the compressed air coming from the compressor and
on which the fuel distribution also depends, and positioning it by
means of the front combustion-chamber-side section, e.g. by means
of spacers in the annular space. In the extreme case, the
downstream nozzle section sits directly in the bottom of the fire
tube.
[0063] FIG. 10 shows a cross-section of a jet burner 1 and of the
annular distributor 7 with a plurality of radial secondary fluid
inlet openings 14. Said annular distributor 7 comprises a complete
annulus of jet nozzles 2. Radiating from the annular distributor 7
are secondary fluid inlet openings 14 which meet the jet nozzles 2
at different circumferential positions. Long secondary fluid inlet
openings 14 can be used. Secondary fluid inlet openings 14 can also
be at an angle to the jet nozzle 2. The jet nozzles 2 can be
disposed in any manner. It is also conceivable merely for an
annular distributor 7 with fuel to be present and the jet nozzles
to be disposed in any manner within it (central jet burner 1).
[0064] In all the exemplary embodiments and variants, the inventive
burner 1, 101, 201, 301, 401 can also be implemented without the
outer housing section 27 or rather without an outer casing 27. In
this case, the compressed air can flow directly into the "plenum",
i.e. the area between the back wall 24 and the main fluid inlet
opening 8. The inventive burner 1, 101, 201, 301, 401 can also be
implemented without the back wall 24.
[0065] Varying the axial positions of the annular gaps 21 provides
an additional design parameter to guard against thermoacoustic
flame oscillations. It is also possible to provide different jet
nozzles 2 of a burner 401 with annular gaps 21 at different axial
positions.
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