U.S. patent application number 14/265584 was filed with the patent office on 2015-11-05 for burner with adjustable radial fuel profile.
This patent application is currently assigned to SIEMENS AKTIENGESELLSCHAFT. The applicant listed for this patent is SIEMENS AKTIENGESELLSCHAFT. Invention is credited to Mariano CANO WOLFF, Andreas DIEBELS, Boris Ferdinand KOCK, Jurgen MEISL, Bernd PRADE, William R. RYAN.
Application Number | 20150316266 14/265584 |
Document ID | / |
Family ID | 53724271 |
Filed Date | 2015-11-05 |
United States Patent
Application |
20150316266 |
Kind Code |
A1 |
PRADE; Bernd ; et
al. |
November 5, 2015 |
BURNER WITH ADJUSTABLE RADIAL FUEL PROFILE
Abstract
A burner (1) with a longitudinal burner axis (2) and a mixing
channel (3, 4), formed in an annular manner around the longitudinal
burner axis (2), for the mixing of fuel and air. Each mixing
channel is bounded radially on the inside by a channel hub (5, 6)
and radially on the outside by a channel outer wall (7, 8). A fuel
concentration distribution in the mixing channel (3, 4) from the
channel hub (5, 6) to the channel outer wall (7, 8) being
adjustable by adjusting the introduction of fuel to provide an
adjustable fuel concentration distribution at respective radial
locations across each mixing claimed. Also a combustion system (20)
with a burner (1) and to a method for operating a burner (1).
Inventors: |
PRADE; Bernd; (Mulheim,
DE) ; CANO WOLFF; Mariano; (Ratingen, DE) ;
KOCK; Boris Ferdinand; (Ratingen, DE) ; MEISL;
Jurgen; (Mulheim an der Ruhr, DE) ; DIEBELS;
Andreas; (Bottrop, DE) ; RYAN; William R.;
(Oviedo, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SIEMENS AKTIENGESELLSCHAFT |
Munchen |
|
DE |
|
|
Assignee: |
SIEMENS AKTIENGESELLSCHAFT
Munchen
DE
|
Family ID: |
53724271 |
Appl. No.: |
14/265584 |
Filed: |
April 30, 2014 |
Current U.S.
Class: |
60/776 ; 60/737;
60/742 |
Current CPC
Class: |
F23R 2900/00013
20130101; F23C 2900/07001 20130101; F23N 5/16 20130101; F23R 3/286
20130101; F23R 2900/03343 20130101; F23R 3/14 20130101; F23R 3/34
20130101 |
International
Class: |
F23R 3/28 20060101
F23R003/28; F23R 3/34 20060101 F23R003/34 |
Claims
1. A burner having a longitudinal burner axis; a first mixing
channel extending annularly around the longitudinal burner axis,
and the first mixing channel being configured and operable for
mixing of fuel and air in the burner; a channel hub bounding the
first mixing channel radially on an inward side thereof, and a
channel outer wall bounding the first mixing channel radially on an
outward side thereof; and a device in the first mixing channel
configured for providing an adjustable fuel concentration
distribution in the first mixing channel radially from the channel
hub to the channel outer wall.
2. The burner as claimed in claim 1, further comprising a burner
stage comprising a first and a second distribution system for the
mixing channel; respective first fuel jets of the first
distributing system being arranged at at least one of substantially
radially inward and substantially radially outward in the first
mixing channel; and respective second fuel jets of the second
distributing system being arranged substantially radially in a
middle region in the first mixing channel between radially inward
and radially outward sides of the first mixing channel.
3. The burner as claimed in claim 2, further comprising a second,
annular mixing channel which is surrounded by the first mixing
channel; a third distributing system in the second annular mixing
channel, the third distributing system having third fuel jets and
the third fuel jets are arranged substantially in a radially middle
region to a radially outward region in the second annular mixing
channel; and a fourth distributing system having fourth fuel jets
and the fourth fuel jets are arranged substantially in the radial
middle region of the second annular mixing channel to a radially
inward region in the second annular mixing channel.
4. The burner as claimed in claim 3, further comprising blades in
each of the mixing channels, the blades having inner fuel passages
of the blades and the inner fuel passages located in the respective
mixing channel in which the blades are located, and the fuel
passages are configured and operable for injection of fuel by at
least one of the distributing systems for the respective mixing
channel.
5. The burner as claimed in claim 4, further comprising a plurality
of the blades in each of the mixing channels, wherein successive
blades of the plurality of the blades in each mixing channel are
neighboring one another, and different ones of the respective
distributing systems of each mixing channel are assigned to
neighboring blades in the mixing channels.
6. The burner of claim 4, wherein each of the blades is
respectively assigned to and configured to receive fuel from at
least two of the distributing systems.
7. A combustion system including a burner as claimed in claim 2;
the combustion system further comprising a combustion chamber
having a first end, a burner arranged in the first end of the
combustion chamber; and a device configured for measuring
alternating pressure amplitudes or accelerations in individual
frequency bands in at least one of the combustion chamber and the
burner.
8. A method for operating a burner in which fuel is injected into a
mixing channel for mixing of fuel and air, the method comprising:
injecting fuel of one burner stage via at least two distributing
systems, each distributing system having a different fuel profile
over a cross-section of the mixing channel; and selectively
influencing operation-restricting or operating-enhancing
oscillation modes in corresponding load ranges in fuel distribution
to the distributing systems for changing the fuel distribution over
the cross-section of the mixing channel.
9. The method as claimed in claim 8, further comprising:
continuously measuring alternating pressure amplitudes or
accelerations in individual frequency bands in a combustion chamber
or at the burner; upon an increase in an amplitude of a mode above
a fixed limit value, changing the fuel of one of the distributing
systems as a proportion of the total amount of the fuel being
injected by the two distributing systems for adjusting for the
increase in the amplitude of the mode.
10. The method of claim 8, wherein the mixing channel is an annular
channel and the method further comprising changing the fuel
distribution in the mixing channel such that a selected radial fuel
profile is altered.
11. The method as claimed in claim 10, further comprising changing
the fuel distribution such that a proportion of fuel in a radial
middle region of the annular mixing channel is changed with respect
to a radially inner and a radially outer region of the annular
mixing channel.
12. The method as claimed in claim 10, further comprising changing
the fuel distribution such that a proportion of fuel in a radially
inner region of the annular mixing channel is changed with respect
to a proportion of fuel in a radially outer region of the annular
mixing channel.
13. The method as claimed in claim 11, further comprising: changing
fuel distribution in an annular main channel such that a
proportional distribution of fuel in a radial middle region in the
main channel is changed with respect to a proportional distribution
of fuel to a radially inner and a radially outer regions of the
main channel; and changing fuel distribution in an annular pilot
channel that is surrounded by the main channel so that a proportion
of fuel in a radially inner region of the pilot channel is changed
with respect to a proportion of fuel in a radially outer region of
the pilot channel.
14. A method for operating a burner according to claim 1, in which
fuel is injected into a mixing channel for mixing of fuel and air,
the method comprising: injecting fuel of one burner stage via at
least two distributing systems, each distributing system having a
different fuel profile over a cross-section of the mixing channel;
and selectively influencing operation-restricting or
operating-enhancing oscillation modes in corresponding load ranges
in fuel distribution to the distributing systems for changing the
fuel distribution over the cross-section of the mixing channel.
Description
TECHNICAL FIELD
[0001] The invention relates to a burner with a radially adjustable
fuel profile. The invention also relates to a combustion system
with such a burner and to a method for operating such a burner.
TECHNICAL BACKGROUND
[0002] The operation of gas turbines is influenced more and more
frequently by changing boundary conditions. Apart from the usual
changes, such as ambient conditions, these changing conditions also
take the form of increasingly greater and more frequent load
changes, including sometimes sustained operation under partial
load, as well as a varying gas composition, i.e. a varying
calorific value or Wobbe index.
[0003] Since gas turbines, and in particular also the combustion
system, often used to be designed in particular for the rated power
output, increasing `off-design` operation sometimes has side
effects that may lead to operational restrictions.
[0004] For example, in certain power output ranges that have
previously not been used on a sustained basis, combustion
oscillations or increased pollutant emissions occur, possibly
restricting sustained operation in those cases. A change of the
fuel composition also leads to disturbances, such as for example
combustion oscillations, increased emissions and thermal loading of
components.
[0005] In the system-specific fine-tuning of parameters (tuning),
adjustments that are dependent on the ambient conditions and are
sometimes complex, e.g. of the amount of pilot gas, the inlet guide
vane (IGV) positioning, and consequently the exhaust gas
temperature, are respectively provided in different power output
ranges, possibly even differently for subjecting the gas turbine to
loading and relieving the gas turbine of loading. This may under
some circumstances require that, when there are changing operating
requirements, a readjustment of control parameters must be made.
The exhaust gas emissions may possibly not be adjusted as
desired.
[0006] EP 1 394 471 A1 discloses a burner with a fuel concentration
distribution that is not constant in a plane perpendicular to the
direction of flow of the fuel, in particular changes in the radial
direction, in order to avoid combustion instabilities during
operation of the burner.
[0007] A disadvantage of this is that, when there is a change in
concentration, the fuel mass flow as a whole is also changed, and
the relative concentration at the fuel jets involved remains
substantially the same.
SUMMARY OF THE INVENTION
[0008] The object of the invention is therefore to provide a
burner, a combustion system and a method for operating a burner
with which the best possible tuning of the fuel injection can be
performed.
[0009] This object is achieved by the burner, the combustion system
and the method according to the invention. The following is
achieved in the case of a burner with a longitudinal burner axis
and a mixing channel, which is formed in an annular manner around
the longitudinal burner axis, for the mixing of fuel and air, and
which is bounded radially on the inside by a channel hub and
radially on the outside by a channel outer wall, wherein a fuel
concentration distribution in the mixing channel from the channel
hub to the channel outer wall is adjustable.
[0010] The fuel profile, and consequently the flame geometry, can
be adapted to the operational requirements during the operation of
the fuel profile. Neutral adjustment of the fuel flows, i.e. a
uniform distribution of the fuel from the channel hub to the
channel outer wall, produces a homogeneous field, which is
preferred for low fuel emissions, with a high power output, in the
case of a high part load, for example, a profile with fuel
reduction in the middle of the channel. Depending on the form of
the flame, and consequently on the delay time distribution of the
fuel/air mixture up to the reaction zone, the strength of the
feedback of thermoacoustic oscillations to the flow of the fuel/air
mixture can consequently be changed.
[0011] "Radially" is understood here as meaning a direction from
the channel hub to the channel outer wall in the plane
perpendicular to the direction of flow of the fuel/air mixture. If
the mixing channel formed in an annular manner around the
longitudinal burner axis is conical, then "radially" is not
understood as meaning strictly mathematically perpendicular to the
longitudinal axis of the burner, but an appropriate inclination is
assumed.
[0012] In an advantageous embodiment of the invention, the burner
comprises a burner stage with two distributing systems, first fuel
jets of a first distributing system being arranged substantially
radially on the inside and/or radially on the outside in the mixing
channel and second fuel jets of a second distributing system being
arranged substantially radially in the middle in the mixing
channel.
[0013] By increasing or reducing the fuel of one distributing
system as a proportion of the total amount of fuel in the mixing
channel, it is possible in the case of this embodiment to adjust a
fuel/air profile in the radial middle of the channel that can be
freely changed from lean in fuel to rich in fuel (with respect to
the integral mean value of the fuel/air mixture).
[0014] The radial positioning (and number) of the freely
activatable distributing systems may be chosen according to
expediency.
[0015] This allows the radial position of the minimum or maximum
fuel concentration to be varied, there being the possibility in
particular of achieving a local maximum or minimum of the injected
amount of fuel within the channel and not only at the peripheries
of the channel.
[0016] In a further advantageous embodiment of the invention, the
burner also comprises a further annular mixing channel, which is
surrounded by the mixing channel and has a third distributing
system and a fourth distributing system. Third fuel jets of the
third distributing system are arranged substantially in the region
of a radial middle to radially on the outside in the further mixing
channel and fourth fuel jets of the fourth distributing system are
arranged substantially in a region of the radial middle to radially
on the inside in the further mixing channel.
[0017] Consequently, a burner with two concentric mixing channels
for the at least partial premixing in each case of air with fuel is
obtained. This makes it possible for the air and the fuel to be fed
to a pilot flame in the inner channel (pilot channel).
[0018] It is advantageous if fuel jets are provided in blades with
inner fuel passages in the mixing channel for the injection of fuel
of at least one distributing system. This allows on the one hand
fuel to be injected into an air stream at exactly the desired
locations in the mixing channel and on the other hand a swirl to be
imparted to the fuel/air stream to improve the mixing.
[0019] The fuel ports may be positioned on the blades on either of
the suction side or on the pressure side or on both sides.
[0020] For a solution that can be realized in a mechanically simple
form, it is expedient if neighboring blades are assigned to
different distributing systems.
[0021] However, the variant in which the blades are respectively
assigned to at least two distributing systems offers a greater
potential with regard to achievable fine mixing and is therefore
advantageous.
[0022] In the case of an advantageous alternative embodiment, fuel
jets are provided on the channel hub and/or the channel outer wall
for the injection of fuel for at least one distributing system.
This makes it possible to dispense with the blades with inner fuel
passages, at least for one distributing system.
[0023] A further advantageous alternative embodiment provides small
tubes with fuel jets for the injection of fuel, the small tubes
extending from the channel hub in the direction of the channel
outer wall. The small tubes are easier to produce, and consequently
less costly, than blades with inner fuel passages.
[0024] At the same time, it may be expedient with regard to
improved flow control if the small tubes are profiled on their
outer wall.
[0025] In order to be able to adapt the depth of penetration of the
individual distributing systems in a specific manner, it is
advantageous if at least one diameter for a fuel jet of one
distributing system differs from a second diameter of a fuel jet of
another distributing system of the same mixing channel.
[0026] The combustion system according to the invention comprises a
burner according to the invention as well as a combustion chamber,
at one end of which the burner is arranged, and comprises a device
for measuring alternating pressure amplitudes in individual
frequency bands in the combustion chamber. By means of the device
for measuring alternating pressure amplitudes in individual
frequency bands, it can be established specifically which pressure
or flame oscillations occur in the combustion chamber, so that fuel
can be suitably supplied to the distributing systems of the burner
in order to reduce the disturbances occurring.
[0027] In the inventive method, for operating a burner in which
fuel is injected into a mixing channel for fuel and air, the fuel
of one burner stage is injected by way of at least two distributing
systems with a different fuel profile over a cross section of the
mixing channel and, for influencing operation-restricting or
operation-enhancing oscillation modes in corresponding load ranges,
the fuel distribution to the distributing systems is changed.
[0028] It is particularly advantageous in this respect if
alternating pressure amplitudes in individual frequency bands in a
combustion chamber are continuously measured and, in the case of an
increase in the amplitude of a mode above a fixed limit value, the
fuel of one distributing system as a proportion of the total amount
of fuel is changed.
[0029] In this respect, it is advantageous with regard to the
suppression of combustion oscillations if the fuel distribution in
a mixing channel configured as an annular channel is changed such
that a radial fuel profile changes.
[0030] In particular, it may be advantageous with regard to the
suppression of combustion oscillations if the fuel distribution is
changed such that a proportion of fuel in a radial middle of the
annular channel is changed with respect to radially inner and outer
regions of the annular channel.
[0031] Furthermore, it may be advantageous with regard to the
suppression of combustion oscillations if the fuel distribution is
changed such that a proportion of fuel in a radially inner region
of the annular channel is changed in comparison with a radially
outer region of the annular channel.
[0032] It is most particularly advantageous if the fuel
distribution in an annular main channel is changed such that a
proportion of fuel in a radial middle of the main channel is
changed with respect to radially inner and outer regions of the
main channel and the fuel distribution in an annular pilot channel
that is surrounded by the main channel is changed such that a
proportion of fuel in a radially inner region of the pilot channel
is changed in comparison with a radially outer region of the pilot
channel.
[0033] The respective shifting of the proportions of fuel makes it
possible to compensate partially or completely for the influence on
the combustion behavior of further operating parameters, such as
for example the Wobbe index or gas temperature, and ambient
conditions.
[0034] What is essential here is the adjustability of a radial
fuel-air mixture profile during operation by integration of two or
more fuel passages that can be activated separately from one
another, by way of corresponding distributing systems. This takes
place by the radial arrangement of the individual stages in the
mixing channel, preferably on each swirl blade or each fuel
injection element.
[0035] The arrangement allows in particular a local maximum or
minimum of the injected amount of fuel to be achieved within the
mixing channel and not only at the peripheries of the channel.
[0036] The invention is explained in more detail by way of example
on the basis of the drawings, which are schematic and not to scale
and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 shows a cross-section of a burner according to the
invention,
[0038] FIG. 2 shows schematically a combustion system according to
the invention,
[0039] FIGS. 3-5 show an example of the changing of the fuel
profile over the main channel,
[0040] FIGS. 6-8 show a further example of the changing of the fuel
profile over the pilot channel,
[0041] FIG. 9 shows blades of a burner according to the invention
with fuel jets of two distributing systems each,
[0042] FIG. 10 shows blades of a burner according to the invention
that are assigned to different distributing systems,
[0043] FIG. 11 shows a possible arrangement of the fuel jets of the
distributing systems on a blade in section,
[0044] FIG. 12 shows a view of a blade with the arrangement of the
fuel jets from FIG. 11,
[0045] FIG. 13 shows a further arrangement of the fuel jets of the
distributing systems on a blade in section and
[0046] FIG. 14 shows an alternative arrangement of the fuel jets of
the distributing systems on a blade in section.
DESCRIPTION OF EMBODIMENTS
[0047] FIG. 1 shows schematically and by way of example a section
through a burner 1 according to the invention. The burner 1 has a
longitudinal axis 2, and also mixing channels, formed in an annular
manner around the longitudinal burner axis 2, a main channel 3 and
a pilot channel 4, for the mixing of fuel 24 and air 25. Two
concentric, annular mixing channels are illustrated. But, the
invention may be used for as few as one mixing channel or for more
than two of the elements, as a particular burner is designed and as
such control over the distribution of fuel is required in an
embodiment of a burner.
[0048] Arranged centrally along the longitudinal burner axis 2 is a
pilot burner 23. In premixing operation, the pilot burner 23 is
operated to support the main burner 9.
[0049] The mixing channels 3, 4 of the burner stage 9, which is
also referred to as the main burner, and of the pilot burner 23 are
bounded radially on the inside by a channel hub 5, 6 and radially
on the outside by a channel outer wall 7, 8. Arranged in the mixing
channels 3, 4 are blades 18, which extend from the hub 5, 6 to the
channel outer wall 7, 8. The blades 18 have inner fuel passages 19,
which are assigned to different distributing systems 10, 11, 14,
15. Each distributing system comprises an annular passage extending
circumferentially around the inward wall of the respective mixing
channel 3, 4. The respective distributing system brings fuel to the
inward end of all of the blades radially outward of the
distributing system. The distributing system is in turn supplied
its fuel from a source, not illustrated. During operation, fuel 24
from the blades is injected by fuel jets 12, 13, 16, 17 into the
respective mixing channel 3, 4.
[0050] FIG. 2 shows a combustion system 20 according to the
invention, with a burner 1 according to the invention and a
combustion chamber 21, at the one end of which the burner 1 is
arranged. The combustion system 20 also comprises a device 22 for
measuring alternating pressure amplitudes or accelerations in
individual frequency bands in the combustion chamber 21. Such a
device 22 at the burner 1 is likewise conceivable. In the inventive
method, alternating pressure amplitudes in the individual frequency
bands in the combustion chamber 21 are continuously measured. If
the amplitude of a mode increases above a fixed limit value, the
fuel of one distributing system 10, 11, 14, 15 as a proportion of
the total amount of fuel is changed, i.e. increased or reduced. If
the amplitude in the corresponding frequency band falls again below
the adjusted limit value, the distribution of fuel can be restored
to a basic setting.
[0051] In an exemplary embodiment of the invention, in the main
channel 3 a fuel-air profile in the radial middle of the channel
can be freely changed from lean in fuel to rich in fuel (with
respect to the integral mean value of the fuel/air mixture) by two
separately adjustable distributing systems 10, 11.
[0052] By analogy, the fuel injection of the inner pilot channel 4
can likewise be realized by two separately adjustable distributing
systems 14, 15. In the pilot channel 4, it is particularly
advantageous to set up the arrangement of the third and fourth fuel
jets 16, 17 such that a fuel-air profile that allows an adjustment
between preferred radially outer or radially inner injection can be
produced. Neutral adjustment of the flows then produces a
homogeneous field, which is preferred for low fuel emissions, with
a high power output, in the case of a high part load and low part
load preferably a profile that is relatively lean in fuel in the
outer section.
[0053] There follows a more detailed description of the operating
behavior for the setup described above (main burner lying
concentrically on the outside and pilot burner lying on the inside,
with in each case two distributing systems 10, 11, 14, 15 that are
adjustable independently of one another). In this case, the
arrangement of the distributing systems 10, 11, 14, 15 allows a
shifting of the proportion of fuel radially in the mixing channel 3
from the middle to the inside (hub 5) and outside (cone or channel
outer wall 7) in the main burner 9 and radially in the mixing
channel 4 from the inside (hub 6) to the outside (cone or channel
outer wall 8) in the pilot burner 23.
[0054] FIG. 3 shows plotted on the right the entire nominal
proportion of fuel of the two distributing systems 10, 11. This
basic setting is optimized for the compromise between emissions and
performance of the burner 1.
[0055] FIG. 4 shows in comparison with FIG. 3 an increased
proportion of fuel in the radial middle of the mixing channel 3,
for influencing an operation-restricting or operation-enhancing
mode in certain load ranges or possibly to easily influence the
NO.sub.x emissions.
[0056] FIG. 5 correspondingly shows a reduced proportion of fuel in
the radial middle of the mixing channel 3.
[0057] A similar situation applies to the pilot burner 23, the
mixing channel 4 of which is shown in FIG. 6 with a nominal fuel
distribution of the two distributing systems 14, 15 in the basic
setting, which is optimized for the compromise between emissions
and performance/stability of the burner.
[0058] FIG. 7 shows, in comparison, the case of an increased
proportion of fuel radially on the inside (i.e. at the hub 6). This
changing of the fuel profile also serves for influencing an
operation-restricting or operation-enhancing mode in certain load
ranges, or can contribute to improving the NO.sub.x emissions in
certain load ranges. The starting behavior of the burner 1 is also
possibly improved.
[0059] FIG. 8 shows a proportion of fuel that is reduced radially
on the inside (hub 6) in comparison with FIG. 7.
[0060] The degree of shifting of the proportions of fuel is freely
selectable within the operating limits. Depending on the operating
state of the machine (starting, part load, base load, etc.), the
combination of these cases that is expedient in each case is
likewise freely selectable.
[0061] FIG. 9 shows a detail as seen when looking into a mixing
channel 3 along the longitudinal burner axis. In the exemplary
embodiment of FIG. 9, the blades 18 have fuel jets 12, 13 of
different distributing systems 10, 11. As an alternative to this,
FIG. 10 shows an exemplary embodiment in which neighboring blades
18 are exclusively assigned to different distributing systems 10,
11.
[0062] FIGS. 11 and 12 show an embodiment of a blade 18 of a burner
1 according to the invention. FIG. 11 shows the respective section
through the plane of the inner fuel passage 19 in the blade 18 that
belongs to the respective distributing system 10, 11. FIG. 12 shows
the plan view of the blade 18 with the arrangement of the fuel jets
12, 13 corresponding to FIG. 11. It can be seen that the fuel jets
12, 13 can be provided both on the suction side and on the pressure
side of the blade 18 and that the pattern of the fuel jets 12, 13
does not have to be symmetrical.
[0063] Further alternative arrangements of the fuel jets 12, 13 of
the distributing systems 10, 11 are shown in FIGS. 13 and 14,
embodiments of the invention that produce fuel profiles other than
those shown in FIGS. 3 to 8, as shown in FIG. 14, also being
covered by the invention.
* * * * *