U.S. patent application number 09/349966 was filed with the patent office on 2001-12-06 for method of operating a gas-turbine chamber with gaseous fuel.
Invention is credited to MULLER, GERHARD, REISS, FRANK, SCHIESSEL, PIRMIN, TSCHIRREN, STEFAN.
Application Number | 20010047650 09/349966 |
Document ID | / |
Family ID | 8236215 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010047650 |
Kind Code |
A1 |
MULLER, GERHARD ; et
al. |
December 6, 2001 |
METHOD OF OPERATING A GAS-TURBINE CHAMBER WITH GASEOUS FUEL
Abstract
In a method of operating a gas turbine, in which a gaseous fuel
is burned in a combustion chamber and the hot combustion gases
which are produced in the process are directed through the gas
turbine, and in which method the gaseous fuel is fed to the
combustion chamber via a plurality of controllable burners, working
in parallel and arranged on one or more concentric, essentially
circular rings, and is sprayed into the combustion chamber via fuel
holes, high safety and availability within various operating ranges
is achieved in a simple manner owing to the fact that the burners
are divided into at least two groups (40-42) of burners, these
groups in each case comprise the burners of one of the rings, and
these groups are individually activated as a function of the
operating state of the gas turbine.
Inventors: |
MULLER, GERHARD; (GERMERING,
DE) ; REISS, FRANK; (LAUCHRINGEN, DE) ;
SCHIESSEL, PIRMIN; (UNTEREHRENDINGEN, CH) ;
TSCHIRREN, STEFAN; (NUNNINGEN, CH) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
8236215 |
Appl. No.: |
09/349966 |
Filed: |
July 9, 1999 |
Current U.S.
Class: |
60/776 ;
60/39.465 |
Current CPC
Class: |
F02C 9/28 20130101; F23R
3/343 20130101; F23R 3/346 20130101; F02C 7/228 20130101 |
Class at
Publication: |
60/39.06 ;
60/39.465 |
International
Class: |
F02C 003/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 27, 1998 |
EP |
98 810 723.1 |
Claims
What is claimed as new and desired to be secured by Letters Patent
of the United States is:
1. A method of operating a gas turbine, in which a gaseous fuel is
burned in a combustion chamber and the hot combustion gases which
are produced in the process are directed through the gas turbine,
and in which method the gaseous fuel is fed to the combustion
chamber via a plurality of controllable burners (27), working in
parallel and arranged on one or more concentric, essentially
circular rings, and is sprayed into the combustion chamber via fuel
holes, wherein the burners (27) are divided into at least two
groups (40-42) of burners (27), these groups in each case comprise
the burners of one of the rings, and these groups are activated
individually as a function of the operating state of the gas
turbine.
2. The method as claimed in claim 1, wherein, during the run-up of
the gas turbine from the no-load idling operation to a full-load
operation, the at least two groups (40-42) are at least partly
ignited and/or started up one after the other in at least two
phases.
3. The method as claimed in claim 2, wherein the ignition and/or
start-up of the groups (40-42) in the different phases is effected
as a function of the speed of the gas turbine and/or of the load
applied to the gas turbine and/or of the emissions given off by the
gas turbine.
4. The method as claimed in either of claims 2 or 3, wherein the
fuel supply to the burners (27) of the individual groups (40-42) in
the different phases is effected as a function of the speed of the
gas turbine and/or of the load applied to the gas turbine and/or of
the emissions given off by the gas turbine.
5. The method as claimed in one of claims 1 to 4, wherein the
burners may be run in at least two operating modes (30, 31).
6. The method as claimed in claim 5, wherein at least one of the
groups (41) comprises the same burners (27) as another group (42),
wherein the groups differ, however, in the operating mode (30, 31)
of the burners (27).
7. The method as claimed in either of claims 5 or 6, wherein the
burners (27) may be operated in a premix mode (31), in which the
gaseous fuel is sprayed laterally into the burner via premix holes,
or in a pilot mode (30), in which the fuel is sprayed in via
central pilot-gas holes.
8. The method as claimed in claim 7, wherein only burners in the
pilot mode (30) are in operation within a lower load range (50,
60), wherein burners in both the pilot mode (30) and the premix
mode (31) are in operation within a moderate load range (51, 61),
and wherein only burners in the premix mode are in operation within
a top load range (53, 62).
9. The method as claimed in either of claims 7 or 8, wherein,
within the top load range (53, 62), the stability of the combustion
process is ensured by virtue of the fact that burners (40) in the
premix mode which are run on a lean mixture are externally piloted
by burners (41) in the premix mode which are run on a rich
mixture.
10. The method as claimed in one of claims 7 to 9, wherein a first
group (40) comprises less than half the total number of burners
(27), and the burners of this first group (40) are operated in the
premix mode (31), and wherein a second group (41) is formed by the
rest of the burners (27) of the combustion chamber, and the burners
(27) of this second group (41) are operated in the premix mode
(31), and wherein a third group (42) is formed by the burners (27)
of the second group, and wherein the burners (27) of the third
group, however, are operated in the pilot mode (30).
11. The method as claimed in claim 10, wherein the combustion
chamber contains a total of 72 burners, wherein the first group
(40) comprises 18 burners, which are distributed essentially
uniformly all round on the rings, and the second and the third
group comprise the remaining 54 burners.
12. The method as claimed in claim 11, wherein, during the run-up
from the no-load idling operation to the load operation of the gas
turbine, only the third group (42) is active in a first phase (50,
60) between preferably 0 and 20% relative load, and this third
group (42) is increasingly supplied with fuel during increasing
load, wherein all three groups (40-42) are active in a second phase
(51, 61) up to a changeover point (52) between preferably 20% and
53.5% load, and wherein, in this second phase (51, 61), the third
group (42) is supplied with fuel to a decreasing extent during
increasing load, while the first group (40) and the second group
(41) are increasingly supplied with fuel and in the process the
first group is run on a richer mixture than the second group, and
wherein the third group (42) is completely shut down in a third
phase (53, 62) above the changeover point (52) of 53.5%, and the
first group (40) is run on a lean mixture and the second group (41)
is run on a rich mixture, and wherein the first group (40) is
supplied with a richer fuel mixture and the second group (41) is
supplied with a leaner fuel mixture in this third phase (53, 62)
during increasing load.
13. A method of operating a gas turbine, in which a gaseous fuel is
burned in a combustion chamber and the hot combustion gases which
are produced in the process are directed through the gas turbine,
and in which method the gaseous fuel is fed to the combustion
chamber via a plurality of controllable burners (27), working in
parallel and arranged on one or more concentric, essentially
circular rings, and is sprayed into the combustion chamber via fuel
holes, wherein the burners (27) are divided into at least two
groups (40-42) of burners (27), these groups in each case comprise
the burners of at least one of the rings, and these groups are
individually activated as a function of the operating state of the
gas turbine.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the field of gas turbines.
It relates to a method of operating a gas turbine, in which a
gaseous fuel is burned in a combustion chamber and the hot
combustion gases which are produced in the process are directed
through the gas turbine, and in which method the gaseous fuel is
fed to the combustion chamber via a plurality of controllable
burners, working in parallel and arranged on one or more
concentric, essentially circular rings, and is sprayed into the
combustion chamber via fuel holes.
[0003] 2. Discussion of Background
[0004] Gas turbines are being increasingly equipped with multiple
burners having a leaner premix technique. In this case, the fuel
and the combustion air is premixed as uniformly as possible and is
only then fed to the flame. If this is carried out with high excess
air, relatively low flame temperatures and thus low nitrogen-oxide
formation result.
[0005] In accordance with the geometry of gas turbines, the
majority of burners are often arranged in an annular shape in the
form of annular combustion chambers. EP-0 597 137 B1 and EP-0 597
138 B1, for example, have disclosed such annular combustion
chambers. In this case, the liquid or gaseous fuels are fed via
fuel-feed rings to the burners arranged in multiple rings, where
they are sprayed into the annular combustion chamber and burned.
Likewise, the water feed to the burners is ensured via water rings,
which are arranged next to the fuel-feed rings.
[0006] When gaseous fuel is used, different operating modes of the
individual burners may be more or less advantageous depending on
the type of loading state, the number of burners in operation, the
emission values or similar characteristic quantities of the gas
turbine. In the case of double-cone burners, the gaseous fuel, for
example in the so-called pilot mode, may be admixed to the
combustion air in the center at the base of the double-cone burner
through the so-called pilot-gas holes. The burners run in this way
are distinguished by a very stable flame with high flame
temperature, although this is a factor which also entails
disadvantageous emission values. On the other hand, in the
so-called premix mode, the gaseous fuel, in double-cone burners, is
admixed laterally to the combustion air in the cone region through
the premix-gas holes. The flames of burners in the premix mode are
distinguished by a low flame temperature and the advantageous
emission values associated therewith, but are substantially less
stable than burners operated in the pilot mode. A double-cone
burner may in principle be constructed in such a way that both of
the above operating modes may be run, in succession and in
parallel, and the gaseous fuel is accordingly sprayed in through
the one or the other set of holes.
[0007] If a gas turbine of the type mentioned at the beginning is
run up from idling to load operation, undesirable effects often
occur. Inter alia, pronounced development of smoke and nitrogen
oxide is possible in certain phases of the run-up and at part-load
operation, burners may be extinguished, and disadvantageous
pulsating of the gas turbine may also occur.
SUMMARY OF THE INVENTION
[0008] Accordingly, one object of the invention is to provide a
novel method and a novel apparatus with which both run-up and
part-load operation of a gas turbine operated with gaseous fuel is
possible in a reliable, uncomplicated and low-pollution manner.
[0009] This object is achieved in a method of the type mentioned at
the beginning in that the burners are divided into at least two
groups of burners, these groups in each case comprise the burners
of one of the rings, and these groups are individually activated as
a function of the operating state of the gas turbine. By the use
according to the invention of burner groups which can be activated
individually with gaseous fuel, the conditions in the combustion
chamber can be adapted in an optimum manner to the operating state
of the gas turbine, a factor which makes possible run-up and
part-load operation under controlled combustion and flow conditions
in the gas turbine.
[0010] A first preferred embodiment of the method according to the
invention is distinguished by the fact that the burners of the gas
turbines are ignited and/or started up one after the other in at
least two phases, i.e. they are supplied with gaseous fuel. In this
case, the start-up is advantageously effected as a function of the
speed of the gas turbine, of the load applied to the gas turbine,
or of the flue gases emitted by the gas turbine. In addition, the
feed of gaseous fuel may be designed to be variable likewise as a
function of the abovementioned characteristic quantities. In this
way, depending on the basic conditions, an optimum combustion
behavior of the annular combustion chamber can be set in a simple
manner.
[0011] A preferred development of this embodiment is distinguished
by the fact that the abovementioned groups, in their arrangement,
differ at least partly in their operating mode, i.e. that certain
burners are operated in several different operating modes. In
particular, division into premix mode and pilot mode permits an
extremely suitable setting of the combustion behavior in the
annular combustion chamber, and this setting allows the compromise
between the prevention of the formation of smoke and nitrogen oxide
and flames which are nonetheless stable and safe from extinction to
be regulated in an optimum manner.
[0012] If the gas turbine is run up from idling to load or
part-load operation, the groups are preferably started up one after
the other in different phases of the run-up. In this case, the
limits between the different phases are again preferably determined
as a function of the speed of the gas turbine, the load applied to
the gas turbine, and/or as a function of the emissions given off by
the gas turbine.
[0013] Further embodiments follow from the dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0015] FIG. 1 shows a schematic representation of fuel system and
burner;
[0016] FIG. 2 shows a schematic representation of the annular
combustion chamber in a view against the direction of the gas
flow;
[0017] FIG. 3 shows a representation of the relative fuel
distribution to the three burner rings in percentage (ordinate) as
a function of the load (abscissa) applied to the gas turbine in
percentage relative to the full load, and
[0018] FIG. 4 shows a representation of the fuel/air ratio 0
(ordinate) as a function of the load (abscissa) measured relative
to the full load and applied to the gas turbine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Referring now to the drawings, wherein like reference
numerals designate identical or corresponding parts throughout the
several views, FIG. 1 indicates a schematic representation of the
activation according to the invention of an annular combustion
chamber. Such activation is possible, for example, in the GT 13E2
gas turbine from ABB having the known EV17 burner from ABB. The
gaseous fuel is fed to the burner system via the feeder line 11, in
which case the feed may be controlled by a main shut-off valve 12.
The fuel is first cleaned in a filter 13 and then with a screen 14
and then enters regions close to the burners in a controllable
manner via a quick shut-off valve 15. In accordance with the
division of the burner groups 40-42, the burner line is then
divided into fuel-feed rings 21-23, which can be activated
individually via control valves 18-20. The fuel-feed rings 21-23
have fuel-feed-ring outlets 24-26, via which the burners 27 of the
respective group 40-42 are supplied with the gaseous fuel.
Depending on the mode of operation 30, 31 of the burners 27 of the
group 40-42 considered, the burners 27 are activated differently.
If a burner 27 is operated in pilot mode 30, the fuel first flows
through a burner valve 29 and is then sprayed in centrally through
the pilot-gas holes directly at the base of the cone burner 27. On
the other hand, if a burner 27 is operated in the premix mode 31,
the gaseous fuel is sprayed downstream of the burner valve 29 in
the cone region through the premix-gas holes into the
combustion-air flow.
[0020] FIG. 2 shows a section through the annular combustion
chamber with the division of the burner groups 40-42, against the
direction of the gas flow. The three groups 40-42 of 72 burners are
identified by appropriate marking. Solid circles designate the 18
burners 27 of the 1/4 premix burner group 40, empty circles
designate the 54 burners which, if operated in the premix mode 31,
make up the 3/4 premix burner group 41 and, if operated in the
pilot mode 30, form the 3/4 internally piloted burner group 42. In
other words, the two groups 41 and 42 are formed by the same
burners, and the two groups differ only in the type of activation
of the burners 27, as shown in FIG. 1.
[0021] FIG. 3 shows the gas distribution in % to the respective
burner groups as a function of the load applied to the gas turbine
in percentage relative to the full load during run-up from idling
operation to full load (100%) or even to overload operation
(>100%).
[0022] The run-up of the gas turbine from shutdown to idling
operation is simple when using gaseous fuel. In this case, the gas
turbine is accelerated externally to about 600 rpm; at this speed,
the fuel is sprayed in as a function of the turbine outlet
temperature and is then ignited. In the process, only the 54
burners of the 3/4 internally piloted burner group 42 are used. In
this case, typical gas flows of 600-700 gr/s are advantageous for
the gas turbine specified above.
[0023] In the first phase 50 of the run-up from idling to full-load
operation of the gas turbine, the operation is the same as during
the run-up to idling, i.e. only the 54 burners of the 3/4
internally piloted burner group 42 are used and simply increasingly
supplied with gaseous fuel. The stability of the flames within the
low load range is thus ensured.
[0024] At about 20% load the other two groups 40 and 41 are now
started up. Thus all three groups 40-42 are active in the second
phase 51, which means that the burners of groups 41 and 42 run in
parallel in both operating modes. The gas feeding of the three
groups is different in the second phase 51. The 3/4 internally
piloted group 42 is continously activated with less gaseous fuel,
and, at the changeover point 52, i.e. preferably at around 50%
load, only about 25% of the entire gas flow is fed to the 3/4
internally piloted group 42. On the other hand, the premix burner
groups 40 and 41 are correspondingly activated with increasing gas
quantity. The 3/4 premix burner group 41 ends at the changeover
point 52 with a relative gas quantity of about 40%, i.e. the fuel
feed to the burners of groups 41 and 42 is increasingly displaced
from the internally piloted operating mode to the premix
activation. In the second phase 51, the 1/4 premix burner group 40
is also additionally started up, specifically in a substantially
more intensive manner than that of the 3/4 premix burner group 41.
This is because, at the changeover point 52, about 36% of the fuel
quantity is fed to the burners of the 1/4 premix burner group 40,
of which there are only 18, i.e. this burner group is operated on a
very rich mixture. This can also be seen in particular from FIG. 4,
where the fuel-to-air ratio .O slashed. is plotted as a function of
the load applied to the gas turbine. In the first phase 60, the
burners of the 3/4 internally piloted burner group 42 are activated
on a fairly lean but increasing mixture .O slashed. increases from
about 0.18 to 0.3); in the second phase 61, however, the mixture
density up to the changeover point 52 decreases again to about
0.13. In the second phase 61, the premix burner groups are started
up but are supplied with fuel to a very different extent. Within
this range, the 3/4 premix burner group 41 is run up on a
relatively lean mixture to a value of about .O slashed.=0.2 at the
changeover point 52, whereas the 18 burners of the 1/4 premix
burner group 40 are run on a relatively rich mixture to about .O
slashed.=0.55 at the changeover point 52 (in the case of the
abovementioned special burners about 2.2 kg/s of fuel gas is fed
into the burners of the 1/4 premix burner group 40). This
combination of internally piloted burners (group 42) and externally
piloted burners of group 40 (group 40 is externally piloted, as it
were, by the burners of group 41) is the basis for optimized
emissions of nitrogen oxide within this load range of about 20-50%
without the disadvantages of extinction.
[0025] At the changeover point 52, the gas flows are shifted to a
great extent with the use of a certain logic circuit. The 3/4
internally piloted burner group 42 and the 1/4 premix burner group
40 are completely shut down, while the 3/4 premix burner group 41
is run up in a controlled manner to rich operation. During the
run-up, all the valves are operated simultaneously at preferably
around 53.5% relative load. Since the fuel gas pressure in the
lines to the 3/4 internally piloted burner group 42 is so high, so
much fuel still flows internally into the burners immediately after
the closing of the valves that the risk of extinction during this
control process, which is abrupt per se, is very low. During
reduction in output, however, a different procedure has to be used
in order to effectively prevent extinction; at around 53% relative
load, the fuel supply to the 3/4 premix burner group 41 is first
throttled back when the gas flow in the lines to the 3/4 internally
piloted burner group 42 has reached a sufficient value (this is
about 0.72 kg/s in the case of the burners specified above). During
reduction in output, the 1/4 premix burner group 40 is supplied
with fuel when the gas flow of the 3/4 internally piloted burner
group has already assumed a certain value (more than 0.12 kg/s for
0.05 s in the above example).
[0026] In the third phase 53, 62 above the changeover point 52, all
the burners run in the premix mode 31. only groups 40 and 41 are
active. During increasing load, the 1/4 premix burner group 40 is
increasingly supplied with gaseous fuel above the changeover point,
while the 3/4 premix burner group 41 is rather reduced in output
somewhat. In general, however, at average load above the changeover
point 52, the 3/4 premix burner group 41 is run on a rich mixture
and the 1/4 premix burner group 40 is rather run on a lean mixture
(see FIG. 4). At full load and in particular within the overload
range (>100%), however, the mixture densities are then very
similar and values of .O slashed. of about 0.5 apply to both groups
40 and 41.
[0027] Within the range between the changeover point 52 and full
load (100%), the fuel-to-air ratio .O slashed. is the most
important parameter which is relevant for the emissions of nitrogen
oxide. However, in order to continue to optimize the discharge of
nitrogen oxide from the gas turbine, it is advantageous, in
addition to varying the value of .O slashed., to also vary the
ratio between the 54 burners of the 3/4 premix burner group 41
(here the main premix burner group) and the 1/4 premix burner group
(here the externally piloted premix burner group). In this way, it
is possible to achieve fine setting of the emissions of nitrogen
oxide and the flame stability; in particular, it is possible to
react to changes in the gas-turbine hardware, to the ambient
conditions or to quick changes in the load applied to the gas
turbine.
[0028] In other words, If the gas turbine is running at full load
(100%), the emission of nitrogen oxide may be optimally set via the
fuel-activation ratio of the two groups 40 and 41. For homogeneous
operation, in particular ratios of 1/4 (group 40) to 3/4 (group 41)
of 0.1 to 0.25 are optimal.
[0029] In practice, the behavior during rapid load fluctuations is
especially important for the operation of a gas turbine. Precisely
at steep load gradients, there is in particular the risk of the
burners being extinguished. Within the load range below the
changeover point 52, this risk is reduced by at least some of the
burners (group 42) being run in the stable, internally piloted
operating mode. Above the changeover point 52, it is possible to
react to rapid load fluctuations in such a way that the 3/4 premix
burner group 41 is run on a richer mixture and supplied with a
considerable amount of fuel, while the 1/4 premix burner group 40
is reduced in output to a leaner operation. This leads to stable
flames which are not extinguished. It is therefore clear that, in
particular within the load range substantially above the changeover
point, this adaptation may be used ever more effectively, since the
1/4 premix burner group 40 there is supplied with a considerable
fuel quantity. In order to react to rapid load fluctuations in the
load applied to the gas turbine even within the range just above
the changeover point 52, slight throttling-back may be effected via
the VIGV (variable inlet guide vane) with the air flowing into the
burners, which likewise leads to a richer fuel-to-air ratio and
thus to more stable burner flames.
[0030] In summary, this complicated control of the runup is
advantageous for the following reasons:
[0031] Within all the load ranges, the burners of the gas turbine
can be set so as to be stable and safe from extinction.
[0032] Due to the mutual adjustability of different groups, which
is possible within all load ranges, the emission of nitrogen oxide
can be kept at an optimum level and can be controlled.
[0033] The division of the groups and the different operating modes
permit flexible reaction to rapid load fluctuations, which further
stabilizes the operation of the gas turbine.
[0034] The operating concept is simple and reliable.
[0035] High availability due to controlled run-up and controlled
reduction in output. obviously, numerous modifications and
variations of the present invention are possible in light of the
above teachings. It is therefore to be understood that, within the
scope of the appended claims, the invention may be practiced
otherwise than as specifically described herein.
* * * * *