U.S. patent application number 10/893963 was filed with the patent office on 2004-12-23 for method of operating a gas-turbine power plant, and gas-turbine power plant.
Invention is credited to Braun, Jost.
Application Number | 20040255592 10/893963 |
Document ID | / |
Family ID | 4552106 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040255592 |
Kind Code |
A1 |
Braun, Jost |
December 23, 2004 |
Method of operating a gas-turbine power plant, and gas-turbine
power plant
Abstract
A method of operating a gas-turbine power plant, having a
gas-turbine plant (1) in which an oxygen-containing gas is drawn
in, compressed and fired and, after passing through a turbine
stage, is fed as discharging hot gas (8) to a waste heat boiler
(4), from which the cooled exhaust gas (9) is fed to an outlet (10)
and then to the free atmosphere. A specific reduction in the flow
velocity with which the exhaust gas (9) flows through the outlet
(10) is effected in the region of the latter, with a simultaneous
pressure increase downstream in the outlet (10), and in that the
pressure conditions occurring inside the outlet (10) are
transmitted free of losses between the gas turbine (1) and the
outlet (10) via a gas-tight flow path of the hot and exhaust gases
(8; 9).
Inventors: |
Braun, Jost;
(Waldshut-Tiengen, DE) |
Correspondence
Address: |
CERMAK & KENEALY LLP
P.O. BOX 7518
ALEXANDRIA
VA
22307
US
|
Family ID: |
4552106 |
Appl. No.: |
10/893963 |
Filed: |
July 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10893963 |
Jul 20, 2004 |
|
|
|
10157395 |
May 30, 2002 |
|
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Current U.S.
Class: |
60/772 ;
60/39.182 |
Current CPC
Class: |
Y02E 20/14 20130101;
F01D 25/30 20130101; Y02E 20/16 20130101; F02C 6/006 20130101 |
Class at
Publication: |
060/772 ;
060/039.182 |
International
Class: |
F02C 006/18 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2001 |
CH |
2001 1002/01 |
Claims
What is claimed is:
1. A method of operating a gas-turbine power plant, comprising:
drawing in an oxygen-containing gas; compressing and heating the
oxygen-containing gas while admixing a fuel; expanding the hot gas
produced in a gas turbine to perform work; discharging the hot gas
from the gas turbine and feeding the hot gas to an outlet via a
flow path; decelerating the exhaust-gas flow, at an essentially
constant flow rate, in the region of the outlet; and transmitting
the pressure conditions produced by decelerating upstream of the
region of the deceleration back via the flow path up to the outlet
of the gas turbine, wherein the flow path is gas-tight relative to
the atmosphere.
2. The method as claimed in claim 1, wherein decelerating comprises
decelerating the exhaust-gas flow in such a way that a low pressure
occurs relative to the atmospheric ambient pressure upstream of the
outlet.
3. A gas-turbine power plant, comprising: a device for compressing
an oxygen-containing gas; at least one combustion chamber for
heating the compressed gas; an outlet in fluid communication with
said at least one combustion chamber and including a flow-limiting
wall; a diffuser arranged at a position in the flow direction
selected from the group consisting of inside the outlet and
downstream of the outlet; at least one gas turbine in fluid
communication with said at least one combustion chamber and
including a flow path, an exit, and working stages, in which
turbine hot gas produced expands to perform work and is then
transferred into the flow path in which it passes through the
working stages, and discharged into the atmosphere via the outlet;
wherein the flow path between the exit of the gas turbine and the
outlet is essentially gas-tight relative to the atmosphere.
4. The gas-turbine power plant as claimed in claim 3, wherein the
outlet comprises a stack with a substantially uniform cross section
of flow, and the diffuser is mounted on the stack.
5. The gas-turbine power plant as claimed in claim 4, wherein the
diffuser comprises an axial diffuser.
6. The gas-turbine power plant as claimed in claim 3, further
comprising: a displacement body integrated at least approximately
centrally in the cross section of flow in the region of the outlet,
the displacement body having a spatial form so that it achieves a
diffuser effect in interaction with the flow-limiting wall; and
wherein the displacement body narrows in the direction of flow and
the flow-limiting wall adjacent to the displacement body is
essentially cylindrical.
7. The gas-turbine power plant as claimed in claim 3, wherein the
outlet comprises a stack with a substantially uniform cross section
of flow, and the diffuser comprises a radial diffuser.
8. The gas-turbine power plant as claimed in claim 7, wherein the
radial diffuser has a flow section arranged directly downstream of
the stack in the direction of flow having a cross section of flow
(D2) larger than portions upstream thereof, wherein the flow
section, at the larger cross section of flow (D2), includes
stationary flow surfaces deflecting the exhaust gas radially
outward.
9. The gas-turbine power plant as claimed in claim 3, wherein the
outlet comprises a stack with a flow-limiting wall and a
substantially uniform cross section of flow, and the diffuser
comprises a semiaxial diffuser.
10. The gas-turbine power plant as claimed in claim 9, wherein the
semiaxial diffuser includes a displacement body integrated
centrally in the cross section of flow, and the contour of the
displacement body extends along the flow-limiting wall in such a
way that a continuously widening cross section of flow is produced
in the direction of flow.
Description
[0001] This application is a Divisional of U.S. application Ser.
No. 10/157,395, filed May 30, 2002, the entirety of which is
incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a method of operating a gas-turbine
power plant, essentially comprising a device for compressing an
oxygen-containing gas, at least one combustion chamber for heating
the compressed gas, at least one gas turbine in which the hot gas
produced is expanded to perform work, a flow path in which the
expanded hot gas, if need be while passing a number of further
working stages for energy and/or material recycling, such as, for
example, a waste heat boiler for the generation of steam, is fed to
an outlet into the atmosphere. Furthermore, the invention relates
to a corresponding gas-turbine power plant.
[0004] 2. Brief Description of the Related Art
[0005] A gas-turbine power plant of the generic type is described
in publication DE 199 05 818 A1, this gas-turbine power plant
providing a stationary gas turbine which has an open cycle and in
which the atmospheric circulating air is drawn in, compressed,
mixed with fuel and ignited, and the hot gases produced in the
process are expanded in a turbine stage and are then directed into
a waste heat boiler for further recycling of the inherent thermal
energy.
[0006] The output of a gas-turbine power plant also depends to a
certain extent on the losses in the flow path of the hot gases.
Firstly, the output is reduced by exhaust-gas pressure losses in
the downstream plants. Secondly, the exhaust gases largely recycled
thermally discharge via the stack into the atmosphere with flow
velocities of 10 m/s to 30 m/s, that is to say with a considerable
content of kinetic energy.
[0007] To increase the overall efficiency of the gas-turbine power
plant known per se, it is proposed in the abovementioned
publication to utilize the kinetic energy of the thermally recycled
exhaust gas flowing through the outlet of the waste heat boiler. To
this end, a fluid-flow prime mover which is designed like a turbine
as used occasionally for utilizing wind power is provided inside
the outlet designed as a stack. Such a fluid-flow prime mover has
propeller or turbine rotors which are set in rotation inside the
outlet when subjected to the flow of the exhaust gas. To generate
electricity, the rotor shaft of such a fluid-flow prime mover is
connected to a generator, which is driven in a similar manner to a
wind power plant, so that electrical energy can accordingly be
obtained from the loss of flow energy.
[0008] A disadvantage of this known apparatus for utilizing the
kinetic energy inherent in the exhaust gas is the relatively high
complexity of the fluid-flow machine provided in the outlet region
of the stack, this fluid-flow machine additionally being subject to
a high maintenance cost and comparatively high investment costs. In
addition, typical fluid-flow machines for the flow conditions
present inside the stack, with flow velocities of between 10 m/s
and 30 m/s, generally have a markedly lower working potential than
the gas turbine connected upstream in the flow, so that the energy
conversion also takes place at an efficiency which tends to be
lower than is possible in the upstream gas turbine.
SUMMARY OF THE INVENTION
[0009] In a development of the prior art, the object of the
invention is to reduce the total pressure loss in the flow path of
the exhaust gas between the discharge from the gas turbine and the
entry into the atmosphere, in which case the reduced flow losses
are to directly benefit the gas turbine as increased output.
[0010] According to the invention, the object is achieved by a
method of operating a gas-turbine power plant and by a gas-turbine
power plant
[0011] The basic idea of the inventions consists in utilizing the
kinetic energy of the exhaust gas, discharging via an outlet into
the atmosphere, specifically for producing a low pressure within
the flow path of the exhaust gas and in maintaining this low
pressure over the entire flow path downstream of the gas turbine in
order to build up in this way a lower back pressure behind the
turbine. In this way, the gas turbine does not have to perform work
against atmospheric pressure or an even higher pressure--as is
normal in conventional plants. The higher pressure difference
available at the gas turbine as a result of this measure is
reflected in an increased output and thus increased overall
efficiency of the gas-turbine power plant.
[0012] The method according to the invention of operating a
gas-turbine power plant, an oxygen-containing gas being drawn in,
compressed and heated while admixing a fuel, and the hot gas
produced being expanded in a gas turbine to perform work and then
discharging from the gas turbine and being fed to an outlet via a
flow path, is characterized according to the invention in that the
hot-gas flow, at an essentially constant flow rate, is decelerated
in the region of the outlet, and the pressure conditions produced
as a result upstream of the region of the deceleration are
transmitted back via the flow path of the hot gases up to the exit
of the gas turbine.
[0013] A gas-turbine power plant designed for realizing this method
is equipped with a diffuser unit in the region of the outlet, which
as a rule is designed as a stack, by means of which diffuser unit
the exhaust gas is decelerated in its flow velocity with low losses
by means of a specific widening of the cross section of flow, in
the course of which the pressure prevailing in the region of the
decelerated exhaust gas increases. This in turn, relative to the
atmospheric pressure which adjoins the diffuser unit downstream,
leads to a considerable pressure reduction upstream of the diffuser
unit inside the outlet. By the flow path between the turbine exit
and the outlet equipped with the diffuser unit being at the same
time designed so as to be gas-tight relative to the ambient
pressure, the reduced pressure occurring upstream of the diffuser
unit inside the outlet is able to spread right up to the turbine
exit. Thus the gas turbine works against a lower back pressure, as
a result of which the efficiency of the gas turbine can be
increased inasmuch as the latter does not have to work against
atmospheric pressure, as in the case of conventional gas-turbine
plants of open design, but against a pressure level which is
markedly reduced compared with the atmospheric pressure.
[0014] By means of suitable diffuser units, a selection (by no
means exhaustive) of which is explained in the exemplary
embodiments below with reference to the drawings, an energy
recovery efficiency of over 70% can be achieved from the specific
deceleration of the exhaust-gas velocity.
[0015] The overall efficiency, which is relatively high anyway, of
a gas-turbine power plant known per se is further increased by the
measure according to the invention for utilizing the kinetic energy
inherent in the exhaust-gas flow, it not being necessary to use any
technically complex, movable components susceptible to wear for
realizing the increased technical overall efficiency, as is the
case, for example, with a fluid-flow machine installed in the
exhaust-gas duct.
[0016] In the process, the utilization of the kinetic energy
directly benefits the generation of electricity with a relatively
high efficiency. In this case, the relevant measures require low
investment costs. The associated maintenance cost is exceptionally
low. Finally, it is worth mentioning that the measures according to
the invention for the technical utilization of the kinetic energy
inherent in the exhaust gas can be integrated not only in plants to
be newly erected but also, with an extremely low investment cost,
in already existing plants.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The invention is described by way of example below, without
restricting the general idea of the invention, with the aid of
exemplary embodiments and with reference to the drawings, in
which:
[0018] FIG. 1 shows a schematic overall view of a gas-turbine power
plant designed according to the invention,
[0019] FIG. 2 shows a schematic representation of an axial
diffuser,
[0020] FIG. 3 shows a schematic representation of an axial diffuser
arranged at an angle,
[0021] FIG. 4 shows a schematic representation of a radial
diffuser,
[0022] FIG. 5 shows a schematic representation of a semiaxial
diffuser, and
[0023] FIG. 6 shows a schematic representation of the outlet as the
complete diffuser.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Shown in FIG. 1 in a highly schematic manner is a
gas-turbine power plant which is designed like a combined-cycle
plant or a cogeneration plant; that is to say that the hot gases
leaving the gas turbine are thermally recycled in a waste heat
boiler before being discharged into the atmosphere.
[0025] The stationary gas turbine 1, from its downstream region,
discharges hot gases 8, which in modem plants may reach
temperatures of over 600.degree. C., which hot gases 8 pass through
downstream process stages 2, 3 into a waste heat boiler 4 and
discharge a proportion of the inherent thermal energy there by
indirect heat transfer for the purpose of the generation of steam.
The generated steam feeds a steam turbine or is utilized in another
manner, which is not of interest in the context in question
here.
[0026] The exhaust gas 9, largely recycled thermally, now passes
via transition pieces 5 and 6 into the outlet 10, which is designed
as a stack of approximately constant cross section of flow along
its extent. As termination, the stack 10 is equipped according to
the invention with a diffuser 7, which brings about a specific
deceleration in the flow velocity.
[0027] A feature which all the diffusers 7 explained below have in
common is the fact that they have no movable parts, as a result of
which they can be manufactured in a technically and financially
favorable manner on the one hand and they also require no
maintenance or only little maintenance.
[0028] A longitudinal section through a diffuser 7 directly
attached to the outlet 10 in the direction of flow is shown in FIG.
2. As already explained, the stack 10 has an essentially uniform
cross section of flow D1, adjoining which is a flow section, an
"axial diffuser", widening conically to a cross section of flow D2.
The axial diffuser 7 has an opening angle .alpha. which
continuously widens the original cross section of flow D1 to the
discharge cross section of flow D2. The flow velocity of the
exhaust gas 9 is reduced in proportion to the increase in the cross
section of flow, as a result of which the static pressure inside
the axial diffuser 7 is increased. This in turn leads to a pressure
reduction inside the flow region in the outlet 10. Of course, these
effects occur only on the precondition that the flow does not
separate from the flow-limiting wall to an appreciable degree.
Therefore, the opening angle .alpha. of the diffuser 7 should not
exceed a range of 5.degree. to 7.degree.. At larger opening angles,
the flow losses caused by wall separation increase so much that the
diffuser efficiency drops to a quantity that no longer permits any
significant pressure recovery. On account of the gas-tight design
of the flow path between the diffuser 7 and the exit of the gas
turbine 1, the reduced pressure conditions are transmitted via the
flow path virtually free of losses and become effective in the form
of a reduced back pressure at the exit of the turbine 1.
[0029] Shown in FIG. 3 is a further variant of an axial diffuser 7
in which the exhaust gas 9 flowing along the flow path of the
outlet 10 is deflected by an angle, here 90.degree., by means of
baffles 11, 12. Furthermore, a displacement body 13 is provided in
the region of the deflected exhaust gas 9, the spatial form of this
displacement body 13 being designed in such a way that the latter,
in combination with the contour of the flow-limiting wall of the
outlet 10, widens the cross section and thus exerts a decelerating
effect on the flow velocity of the exhaust gas 9. Simultaneous
coupling of the deceleration with a low-loss deflecting effect is
possible with this type of construction and is to be aimed at. It
goes without saying that, in this type of construction too, the
flow conditions are to be taken into account in such a way that
loss-inducing flow separation at the wall is largely prevented; the
flow-limiting contours of the displacement body 13 and of the
outlet 10 thus assume an appropriately small opening angle relative
to one another.
[0030] By the angled embodiment of the axial diffuser 7 shown in
FIG. 3, it is possible to integrate the diffuser 7 as a compact
construction unit in the interior of a stack or outlet 10 without
changing its type of construction and in particular its external
appearance. This type of construction is therefore especially
suitable for new plants.
[0031] Shown in FIG. 4 is a radially acting diffuser 7 which
directly adjoins the outlet 10 in the direction of flow. The radial
diffuser 7 has a constant increase in cross section of flow from
(D1).sup.2.pi./4 to (D2).pi.h and has deflecting surfaces 14
deflecting the exhaust-gas flow in the radial direction. The flow
velocity of the exhaust gas passing through the radial diffuser 7
is reduced by specific radial outflow of the exhaust gas along the
flow section h of the radial diffuser 7.
[0032] Shown in FIG. 5 is a "semiaxial diffuser" 7 which provides a
flow section 15, widening in a funnel shape, on the outlet 10 in
the direction of flow, in which flow section 15 a displacement body
16 is inserted centrally. Depending on its geometrical embodiment,
the displacement body 16 is able to decelerate the exhaust gas 9,
flowing through the flow section 15, in both the axial and radial
directions.
[0033] Finally, an embodiment of a diffuser unit 7 which extends
over the entire length of the stack itself can be seen from FIG. 6.
Here, the outlet or stack 10 is shown as a body 17 which widens in
the direction of flow and along the flow path of which the exhaust
gas is decelerated continuously by the cross section of flow
increasing continuously.
[0034] All the diffuser units described above are based on the
flow-dynamic principle of the specific reduction of the flow
velocity with a simultaneous increase in the static pressure, a
marked reduction in pressure occurring upstream of the diffuser
unit, this reduction in pressure being specifically transmitted
into the downstream region of the gas turbine, so that the back
pressure applied at the turbine exit is reduced and thus the
available pressure potential between turbine inlet and outlet is
increased.
1 List of designations 1 Gas-turbine stage 2 Diffuser of the gas
turbine 3 Transition piece, gas turbine, waste heat boiler 4 Waste
heat boiler 5, 6 Transition piece to the outlet 7 Diffuser unit 8
Hot gas 9 Exhaust gas 10 Outlet, stack 11, 12 Baffles 13
Displacement body 14 Deflecting surfaces 15 Flow section 16
Displacement body 17 Stack
[0035] While the invention has been described in detail with
reference to preferred embodiments thereof, it will be apparent to
one skilled in the art that various changes can be made, and
equivalents employed, without departing from the scope of the
invention. Each of the aforementioned documents is incorporated by
reference herein in its entirety.
* * * * *