U.S. patent application number 15/074218 was filed with the patent office on 2016-09-22 for part load performance improvement using deformable boreplugs.
The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Harish BOMMANAKATTE, Santhosh DONKADA, Sheo Narain GIRI, Krishna Kishore GUMPINA, Sanjeev Kumar JHA, Indrajit MAZUMDER, Bhaskar PEMMI, Rajarshi SAHA.
Application Number | 20160273377 15/074218 |
Document ID | / |
Family ID | 49447342 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160273377 |
Kind Code |
A1 |
GIRI; Sheo Narain ; et
al. |
September 22, 2016 |
PART LOAD PERFORMANCE IMPROVEMENT USING DEFORMABLE BOREPLUGS
Abstract
A cooling arrangement for a gas turbine engine includes a
discharge channel for airflow from a compressor, a first cooling
channel, and at least one aperture providing communication between
the flow of air through the discharge channel and the first cooling
channel. A restrictor device in the aperture regulates the flow of
air between the discharge channel and the first cooling channel.
The restrictor device deforms to vary air flowing through the
aperture in response to a physical condition of the engine. This
physical condition of the engine may be that of the temperature of
air flowing through the discharge channel or the power output of
the gas turbine engine. The restrictor device may be a boreplug,
which may be a two-way shape memory alloy.
Inventors: |
GIRI; Sheo Narain;
(Bangalore, IN) ; JHA; Sanjeev Kumar; (Bangalore,
IN) ; PEMMI; Bhaskar; (Bangalore, IN) ;
BOMMANAKATTE; Harish; (Bangalore, IN) ; DONKADA;
Santhosh; (Bangalore, IN) ; GUMPINA; Krishna
Kishore; (Bangalore, IN) ; MAZUMDER; Indrajit;
(Bangalore, IN) ; SAHA; Rajarshi; (Bangalore,
IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Family ID: |
49447342 |
Appl. No.: |
15/074218 |
Filed: |
March 18, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13654818 |
Oct 18, 2012 |
9297310 |
|
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15074218 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 5/082 20130101;
F02C 7/12 20130101; F02C 6/08 20130101; F05D 2300/504 20130101;
F05D 2220/32 20130101; F04D 29/582 20130101; F04D 29/522 20130101;
F05D 2260/20 20130101; F05D 2300/173 20130101; F01D 5/08 20130101;
F01D 25/08 20130101; F02C 7/141 20130101; F01D 17/10 20130101; F05D
2240/35 20130101; F02C 3/04 20130101; F02C 9/18 20130101; F01D
25/12 20130101; F05D 2300/502 20130101; F01D 25/14 20130101; F05D
2300/505 20130101; F02C 7/18 20130101; F01D 17/105 20130101 |
International
Class: |
F01D 17/10 20060101
F01D017/10; F02C 7/18 20060101 F02C007/18; F04D 29/58 20060101
F04D029/58; F01D 5/08 20060101 F01D005/08; F04D 29/52 20060101
F04D029/52; F02C 3/04 20060101 F02C003/04; F02C 7/141 20060101
F02C007/141 |
Claims
1. A cooling arrangement for a gas turbine engine, comprising: a
discharge channel for airflow from a compressor; a first cooling
channel; a compressor discharge case forming a boundary between the
discharge channel and the first cooling channel; at least one
aperture through the compressor discharge case providing
communication for flow of air between the discharge channel and the
first cooling channel; and at least one boreplug positioned within
the aperture that regulates the flow of air between the discharge
channel and the first cooling channel through the aperture in
response to a physical condition of the gas turbine engine; wherein
the boreplug deforms in response to the physical condition, thereby
regulating airflow through the at least one aperture; and wherein
the physical condition is selected from the group consisting of a
temperature of discharge air flowing through the discharge channel,
a power output of the gas turbine engine, and a combination
thereof.
2. The cooling arrangement of claim 1, wherein the boreplug is a
shape memory alloy.
3. The cooling arrangement of claim 2, wherein the shape memory
alloy is a two-way shape memory alloy.
4. The cooling arrangement of claim 3, wherein the two-way shape
memory alloy has the formula
(A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y wherein PGM is a platinum
group metal selected from the group consisting of Pt, Pd, Rh, Ru,
Ir, and combinations thereof.
5. The two-way shape memory alloy of claim 4 having the formula
(A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y, wherein A is selected
from the group consisting of Ni, Al, Nb, Ti, Ta, and combinations
thereof.
6. The two-way shape memory alloy of claim 5 having the formula
(A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y wherein B is selected
from the group consisting of Al, Cr, Hf, Zr, La, Y, Ce, Ti, Mo, W,
Nb, Re, Ta, V, and combinations thereof.
7. The cooling arrangement of claim 2, wherein the shape memory
alloy is responsive to a temperature experienced by the gas turbine
engine.
8. The cooling arrangement of claim 1, wherein the at least one
aperture comprises a plurality of apertures providing communication
between the discharge channel and the first cooling channel.
9. The cooling arrangement of claim 8, wherein the at least one
boreplug comprises a plurality of boreplugs, the boreplugs being
positioned in at least some of the plurality of apertures.
10. The cooling arrangement of claim 9, wherein the boreplugs are
shape memory alloys.
11. The cooling arrangement of claim 10, wherein the shape memory
alloys are two-way shape memory alloys having the formula
(A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y, wherein PGM is a
platinum group metal selected from the group consisting of Pt, Pd,
Rh, Ru, Ir, and combinations thereof.
12. The two-way shape memory alloys of claim 11 having the formula
(A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y, wherein A is selected
from the group consisting of Ni, Al, Nb, Ti, Ta, and combinations
thereof.
13. The two-way shape memory alloys of claim 12 having the formula
(A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y, wherein B is selected
from the group consisting of Al, Cr, Hf, Zr, La, Y, Ce, Ti, Mo, W,
Nb, Re, Ta, V, and combinations thereof.
14. The cooling arrangement of claim 11, wherein: when the
temperature of airflow of the discharge air is below a first
preselected temperature for the boreplug, each of the two-way shape
memory alloys assumes a first shape such that the boreplug is in a
closed state and little or no air flows through the aperture; and
when the temperature of airflow of the discharge air reaches the
first preselected temperature for the boreplug, each of the two-way
shape memory alloys assume a second shape such that the boreplug is
in an open state to allow air to flow freely through the aperture
such that airflow is regulated by the temperature of the discharge
air.
15. The cooling arrangement of claim 10, wherein: the boreplugs
comprise a first portion of boreplugs of a first two-way shape
memory alloy and a second portion of boreplugs of a second two-way
shape memory alloy; when the temperature of airflow of the
discharge air is below a first preselected temperature, each of the
first two-way shape memory alloys assumes a first shape such that
the first portion of boreplugs is in a closed state and little or
no air flows through the aperture; when the temperature of airflow
of the discharge air reaches the first preselected temperature,
each of the first two-way shape memory alloys assumes a second
shape such that the first portion of boreplugs is in an open state
to allow air to flow freely through the aperture such that airflow
is regulated by the temperature of the discharge air; when the
temperature of airflow of the discharge air is below a second
preselected temperature, each of the second two-way shape memory
alloys assumes a third shape such that the second portion of
boreplugs is in a closed state and little or no air flows through
the aperture; when the temperature of airflow of the discharge air
reaches the second preselected temperature, each of the second
two-way shape memory alloys assumes a fourth shape such that the
second portion of boreplugs is in an open state to allow air to
flow freely through the aperture such that airflow is regulated by
the temperature of the discharge air; and the first preselected
temperature and the second preselected temperature are
different.
16. The cooling arrangement of claim 15, wherein: the boreplugs
comprise a third portion of boreplugs of a third two-way shape
memory alloy; when the temperature of airflow of the discharge air
is below a third preselected temperature, each of the third two-way
shape memory alloys assumes a fifth shape such that the third
portion of boreplugs is in a closed state and little or no air
flows through the aperture; and when the temperature of airflow of
the discharge air reaches the third preselected temperature, each
of the third two-way shape memory alloys assumes a sixth shape such
that the third portion of boreplugs is in an open state to allow
air to flow freely through the aperture such that airflow is
regulated by the temperature of the discharge air.
17. The cooling arrangement of claim 10, wherein: each boreplug
positioned in at least some of the plurality of apertures comprises
a different shape memory alloy; each shape memory alloy assumes a
first shape such that each boreplug is closed when the temperature
of airflow of the discharge air is below a first preselected
temperature so that little or no air flows through the aperture;
each shape memory alloy assumes a second shape such that each
boreplug is open to allow air to flow freely through the aperture
when the temperature of airflow of the discharge air is at least at
a second preselected temperature; the first preselected temperature
and the second preselected temperatures of each of the different
shape memory alloys is different; and the second preselected
temperature is greater than the first preselected temperature for
each of the different shape memory alloys; whereby airflow from the
discharge channel into the first cooling channel is modulated over
a range of temperatures.
18. The cooling arrangement of claim 17, wherein: each boreplug
assumes the first shape and is closed when the temperature of
airflow of the discharge air is below the first preselected
temperature; each boreplug assumes the second shape and is fully
open when the boreplug is at least at the second preselected
temperature; and each boreplug assumes an intermediate shape
between the first shape and the second shape when the temperature
of airflow of the discharge air is between the first preselected
temperature and the second preselected temperature.
19. A gas turbine engine comprising: a combustor for combusting
fuel with compressed air; a turbine for generating power; and a
compressor for compressing air, the compressor comprising: a
discharge channel for directing compressed air from the compressor
downstream for combustor and cooling; a cooling channel to provide
cooling for cooling flow to turbine buckets; a compressor discharge
case forming a boundary between the cooling channel and the
discharge channel; at least one aperture in the compressor
discharge case providing communication between airflow through the
discharge channel and the first cooling channel; and a restrictor
device positioned in the aperture to regulate the airflow between
the discharge channel and the cooling channel through the aperture
in response to a physical condition of the gas turbine engine;
wherein the restrictor device deforms in response to at least one
of a temperature of the airflow through the discharge channel and a
power output of the gas turbine engine, thereby regulating the
opening for airflow through the at least one aperture.
20. The gas turbine engine of claim 19, wherein the restrictor
device is a boreplug positioned in the aperture.
21. The gas turbine engine of claim 20, wherein the boreplug is a
shape memory alloy.
22. The gas turbine engine of claim 21, wherein the shape memory
alloy is a two-way shape memory alloy.
23. The gas turbine engine of claim 22, wherein the two-way shape
memory alloy has the formula
(A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y wherein PGM is a platinum
group metal selected from the group consisting of Pt, Pd, Rh, Ru,
Ir and combinations thereof.
24. The gas turbine engine of claim 21, wherein the shape memory
alloy is responsive to an ambient temperature experienced by the
gas turbine engine compressor inlet, wherein airflow temperature in
the discharge channel from the compressor is directly related to
the ambient temperature at the compressor inlet, wherein the shape
memory alloy assumes a first shape when the shape memory alloy is
in a martensitic state below a first temperature so as to
substantially prevent airflow into the cooling channel, and wherein
the shape memory alloy assumes a second shape when the shape memory
alloy is in an austenitic state at or above the first temperature
so as to substantially admit airflow into the cooling channel.
25. The gas turbine engine of claim 24, wherein cross shank leakage
across bucket shanks is reduced when the shape memory alloy is in
the martensitic state below the first temperature, thereby
preventing airflow into the cooling channel.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Utility
Application No. 13/654,818, filed on Oct. 18, 2012, and entitled
"PART LOAD PERFORMANCE IMPROVEMENT USING DEFORMABLE BORE PLUGS",
the disclosure of which is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention is directed generally to the use of
shape memory alloys in gas turbine engine components, and
specifically to the use of shape memory alloys to control cooling
of turbine engine components with changing temperature.
BACKGROUND OF THE INVENTION
[0003] Gas turbine engines operate by burning fuel and extracting
energy from the combusted fuel to generate power. Atmospheric air
is drawn into the engine from the environment, where it is
compressed in multiple stages to significantly higher pressure and
higher temperature. A portion of the compressed air is then mixed
with fuel and ignited in the combustor to produce high energy
combustion gases. The high energy combustion gases then flow
through the turbine section of the engine, which includes a
plurality of turbine stages, each stage comprising turbine vanes
and turbine blades mounted on a rotor. The high energy combustion
gases create a harsh environment, causing oxidation, erosion and
corrosion of downstream hardware. The turbine blades extract energy
from the high energy combustion gases and turn the turbine shaft on
which the rotor is mounted. The shaft may produce mechanical power
or may directly generate electricity. A portion of the compressed
air is also used to cool components of the turbine engine
downstream of the compressor, such as combustor components, turbine
components and exhaust components.
[0004] In some gas turbine engines, the compressor discharge casing
is a complex cast iron structure that locates the combustion
hardware (e.g. fuel nozzle, combustion liner and transition pieces)
between the compressor exit and the turbine inlet. Air from the
compressor is a permitted to leak around the compressor discharge
casing to cool the region in front of the first rotor and turbine
blade set mounted on the rotor, also referred to as the first
forward wheelspace (1 FWSP). Of course, the amount of cooling air
is determined based on the pressure of the compressor discharge
air, which can vary at fixed load conditions based on ambient air
temperature. To provide additional cooling, boreplugs are provided
in the compressor discharge casing that permits additional
compressor discharge air to flow into 1 FWSP to provide additional
cooling. The number of boreplugs to be opened is based on
anticipated cooling flow requirements. If the anticipated cooling
flow is incorrect, then cooling either will be inadequate, causing
the temperatures in the 1 FWSP to be too high, which can result in
shortened life expectancy of the components being cooled, or will
be excessive, resulting in the unnecessary diversion of compressor
air that can result in operational inefficiency. Of course, because
the boreplugs are opened or removed on installation based on
anticipated cooling flow, correction of the cooling flow by
addition or removal of plugs must await maintenance, as removal of
a gas turbine from service to accomplish this modification is not
cost effective.
[0005] Due to rising fuel costs, natural gas fired power plants
that were designed to operate at mostly full power output are now
being operated on a intermittent basis. Coal and nuclear energy now
generally make up the majority of stable power output. Gas turbines
are being increasingly used to make up the difference during peak
demand periods. For example, a gas turbine may be used only during
the daytime and then taken off line during the night time when the
power demand is lower. During load reductions or "turndowns", gas
turbines typically can remain in emissions compliance down to about
forty to forty-five percent (40% to 45%) of full rated load output.
Below this load, carbon monoxide (CO) emissions can increase
exponentially and cause the system as a whole to go out of
emissions compliance. Generally described, emissions compliance
requires that the turbine as a whole to produce less than the
guaranteed or predetermined minimum emissions levels. Such levels
may vary with the ambient temperature, system size, and other
variables. Especially the turndown capability of the gas turbine
goes down in cold ambient, i.e. as the ambient temperature falls,
the minimum load for CO compliance rises steeply. If a gas turbine
has to be shutdown because it cannot remain in emissions compliance
due to a low power demand, the other equipment in a combined cycle
application also may need to be taken offline. This equipment may
include a heat recovery steam generator, a steam turbine, and other
devices. Bringing these other systems online again after a gas
turbine shutdown may be expensive and time consuming. Such startup
requirements may prevent a power plant from being available to
produce power when the demand is high. There may be a strategic
operational advantage in being able to keep a gas turbine online
and in emissions compliance during periods of low power demand so
as to avoid the start up time and expense. The above defined
minimum load is a function of combustion temperature. If the
combustion temperature drops down below a predetermined value, the
CO emission increases. This temperature is a function of fuel air
ratio in the combustor. So during gas turbine load reduction the
fuel and air flow has to be reduced proportionately to maintain
required combustion temperature. Current gas turbine design have
several limitation on minimum allowable airflow to the combustor
below a predetermined gas turbine load which impacts the fuel air
ratio also the combustion temperature and increases the emission at
lower gas turbine load. There is a desire therefore for methods to
minimize the airflow to the combustor further as function of fuel
flow at lower loads and extending gas turbine emissions compliance
during periods of reduced loads.
[0006] Shape memory alloys (SMA), sometimes referred to as smart
materials, have the ability to change shape based on microstructure
and composition. SMAs take advantage of the transition of the
microstructure from a low temperature martensitic structure to a
high temperature austenitic structure (and back) in a predictable
manner. The SMAs may provide the ability to regulate the airflow
through boreplugs by opening, closing (or partially opening) the
bore apertures thereby increasing or decreasing airflow. And while
one well-known SMA, nitinol, or NiTi having roughly an equal atomic
percentage of Ni and Ti, is unsuitable for use as a boreplug
opening due to the high temperatures experienced in the operation
in a gas turbine engine, other SMAs having the ability to survive
high temperatures of operation as well as the corrosive, oxidative
environment of a gas turbine engine may be suitable. Thus, a shape
memory alloy suitable for use in the high temperature, oxidative
and corrosive environment of a gas turbine engine may find use as a
component for the regulation of cooling flow based on changing
operational conditions.
SUMMARY OF THE INVENTION
[0007] A cooling arrangement for a gas turbine engine is set forth.
The gas turbine engine comprises a compressor for compressing air,
a combustor for combusting fuel with compressed air and a turbine
for generating power. A discharge channel from the compressor
directs compressed air from the compressor downstream for use in
the combustor and for cooling hot sections of the engine such as
portions of the combustor and the turbine. One of the cooling
apparatus of the engine is a cooling channel that provides cooling
for cooling flow to turbine buckets. Cooling air for the cooling
channel is provided from the discharge channel. A compressor
discharge case forms a boundary between the cooling channel and the
discharge channel to prevent unrestricted flow of air between the
cooling channel and the discharge channel. Flow between the
discharge channel and the cooling channel is restricted by at least
one aperture in the compressor discharge case, which provides
communication between the flow of air through the discharge channel
and the first cooling channel. A restrictor device within the at
least one aperture further regulates the flow of air between the
discharge channel and the cooling channel in response to a physical
condition of the gas turbine engine. The restrictor device is
positioned in the at least one aperture. The restrictor device
deforms in response to at least one of a temperature of the air
flowing through the discharge channel and a power output of the gas
turbine engine, thereby regulating the opening for airflow through
the at least one aperture.
[0008] The cooling arrangement comprises a flow of air through a
discharge channel, a first cooling channel and at least one
aperture or borehole through the compressor discharge case
providing communication between the flow of air through the
discharge channel and the first cooling channel. A restrictor
device is placed within the at least one aperture to regulate the
flow of air between the discharge channel and the first cooling
channel. The restrictor device deforms in response to a physical
condition of the gas turbine engine. The physical condition may be
a temperature of the air flowing through the discharge channel, the
temperature in or adjacent to the cooling channel reflective of the
area to be cooled or a power output of the gas turbine engine. The
deformation of the restrictor device in or across the borehole
regulates the opening through the at least one aperture, which
controls the airflow between the discharge channel and the first
cooling channel.
[0009] The modulation of airflow by reducing the flow of air from
the discharge channel and through the cooling channel when it is
not needed will change the air pressure across bucket segments.
This change in air pressure across the bucket shanks should assist
in reducing cross shank leakage. In addition, by restricting the
flow of air through cooling channels when it is not needed, more
air will be available to support combustion to manage both CO and
NO.sub.x levels, particularly during turndown. Control of CO and
NO.sub.x are critical in controlling of emissions from gas
turbines.
[0010] Other features and advantages of the present invention will
be apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings which illustrate, by way of example, the principles of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross-section of a gas turbine engine utilizing
a compressor discharge case.
[0012] FIG. 2 is a cross section of a compressor discharge case
showing the path for cooling air for the 1 FWSP location.
[0013] FIG. 3 is a perspective view of the compressor discharge
case of FIG. 2 having 18 boreplugs.
[0014] FIG. 4 depicts a cross section of a bore hole of FIG. 2
showing a SMA boreplug at two different temperatures.
[0015] FIG. 5 depicts a cross section of a bore hole of FIG. 2
showing a second embodiment of a SMA boreplug at two different
temperatures.
[0016] FIG. 6 depicts the SMA operational envelope in a compressor
casing.
[0017] FIG. 7 depicts the increase in CO with gas turbine
turndown.
[0018] FIG. 8 represents the improvement due to reduction in CO
emissions at 0.degree. ambient temperature due to opening of three
boreplugs.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention utilizes the unique properties of SMAs
to provide cooling based on temperature. SMAs are characterized by
temperature-dependent phase changes, the phases generally being a
low temperature martensitic phase and an elevated austenitic phase.
While SMAs can exhibit one-way shape memory, two-way shape memory
of SMAs makes cooling modulation possible. Two-way shape memory is
characterized by a shape transition both upon heating from the
martensitic phase to the austenitic phase, as well as upon cooling
from the austenitic phase to the martensitic phase. Two-way shape
memory may be either extrinsic or intrinsic. Intrinsic behavior is
induced in SMAs through processing, which includes deformation of
the SMA material while in the martensitic phase, followed by
multiple heating and cooling cycles through the transformation
temperature range under constraint. Once processing is complete,
shape changes between the low temperature state and the high
temperature state is reversible. Extrinsic behavior combines a SMA
that exhibits one way behavior with another element that provides a
restoring force that recovers the shape after the one way
deformation.
[0020] Nitinol, Ni--Ti alloys having approximately equal atomic
percentages of nickel and titanium, are well known SMAs. However,
nitinol is not suitable in oxidizing, corrosive environments and
the transformation temperatures of martensite to austenite is
relatively low, the temperatures occurring over a range extending
up to about 100.degree. C. However, other suitable SMAs having
higher temperature capabilities include alloys having compositions
selected from the group consisting of Ni, Al, Nb, Ti, Ta and
combinations thereof and platinum group metals selected from the
group consisting of Pt, Pd, Rh, Ru, Ir and combinations thereof.
More specifically, suitable shape memory alloy compositions may
include nickel aluminum based alloys such as nickel aluminum alloys
including a platinum group metal (PGM). Because the behavior of the
SMA is very dependent on alloy composition, small changes in
composition and/or processing can be used to alter transformation
temperature, strain hysteresis, actuation force, yield strength,
damping ability, resistance to oxidation, hot corrosion, ability to
actuate through repeated cycles, capability to exhibit two-way
shape memory effect among other engineering attributes. More
specifically, the SMA alloy compositions may include alloys having
the formula (A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y, where A is
selected from the group consisting of Ni, Co, Fe and combinations
thereof; PGM is selected from the group consisting of Pt, Pd, Rh,
Ru, Ir and combinations thereof; and B is selected from the group
consisting of Al, Cr, Hf, Zr, La, Y, Ce, Ti, Mo, W, Nb, Re, Ta, V
and combinations thereof; x is greater than 0, y is from 0 to about
0.23. The SMA alloy may additionally include up to about 1 atomic %
of C or B.
[0021] Thus, it is clear that the behavior of SMAs is well-known,
and the behavior of SMAs can be varied to achieve two-way shape
memory behavior by modifying the composition of the alloy to
exhibit two-way shape memory at various temperatures. Furthermore,
the SMA alloy composition can be modified to also provide oxidation
resistance and corrosion resistance.
[0022] Referring now to FIG. 1, which is a cross section of a gas
turbine engine 10, depicting the fan portion 12 of the engine, the
compressor portion 14 of the engine, the combustor portion 16 of
the engine, the turbine portion 18 of the engine and the exhaust
portion 20 of the engine. Air from the environment is inlet through
fan portion 12 and directed to compressor portion 14 where it is
compressed to high pressures, the temperature of the air also being
elevated by the compression process. Compressed air from compressor
portion is then used for combusting fuel, but also may be used for
other purposes such as active or passive cooling of various
components in the engine. Compressed air is mixed with fuel in
combustor portion 16 where the fuel is ignited and burned. The hot
gases of combustion, being energetic, travel at high velocity to
turbine portion 18, where energy is extracted the energy being
converted to electrical energy or mechanical energy. A portion of
the energy extracted by the turbine is utilized to turn compressor
portion 14 and fan portion 12. The less energetic exhaust gases are
then exhausted through exhaust portion 20 as exhaust gases which
may be treated before being returned to the environment.
[0023] FIG. 2 represents a cross-section of compressor portion 14
of gas turbine engine of FIG. 1. Some compressor air is channeled
through passageway 30, where it cools rotor 32 and turbine blades
34 mounted on rotor 32. The amount of cooling air required will
depend on a number of factors, including ambient air temperature
and the pressure of the compressor discharge air. Because ambient
air temperature can vary significantly, depending upon the location
of the gas turbine, by 110.degree. F. or more, provisions are
normally provided to increase cooling air volume at higher
operating temperatures.
[0024] FIG. 2 shows the flow of compressor discharge air as it is
funneled by compressor discharge case to the next stage of gas
turbine 10. Compressor discharge case includes a plurality of
boreholes 40. These boreholes 40 may be filled with boreplugs 42.
Prior art designs utilize boreplugs 42 to selectively fill
boreholes 40 based on anticipated cooling flow requirements, each
borehole providing additional cooling flow. The number of boreholes
40 with or without boreplugs 42 is dependent on the anticipated
cooling flow requirements, more anticipated cooling requiring the
removal of more boreplugs.
[0025] Cooling flow is channeled through boreholes 40 into second
channel 44 where additional cooling air is permitted to flow to
permit additional cooling to rotor 32 and to turbine blades 34
mounted on rotor 32. Unlike the prior art, which anticipated
cooling flow requirements at gas turbine installation or during
maintenance, the design of FIG. 2 includes a plurality of boreholes
40, each of boreholes 40 including a restrictor device positioned
within borehole 40 to control the flow of air between the discharge
panel and the first cooling channel. The restrictor device may be a
boreplug 42. FIG. 3 depicts such a casing showing 18 boreholes 40,
each with a boreplug 42.
[0026] Boreplugs 42 of the present invention may be installed in
all boreholes 40 or only in a predetermined number of boreholes 40.
The actual number of apertures or boreholes and boreplugs will
depend on the gas turbine design. Boreplugs 42 comprise a shape
memory alloy (SMA), the SMA selected based on its ability to
respond to changes in temperature by change of shape due to changes
in microstructure, for example, austenite to martensite and vice
versa. By careful selection of composition and heat treatment, the
SMA material can respond to changes in temperature. The selection
of composition and heat treatment to obtain the requisite behavior
is referred to as "training." As the temperature of compressor
discharge air changes, boreplugs 42 comprising SMA undergo a
modification in shape, thereby increasing, reducing or stopping the
flow of air through boreholes 40. The ability of boreplugs 42 to
change shape to increase or reduce the flow of air through
boreholes based on an increase or decrease in temperature
respectively means that the SMA exhibits bidirectional behavior,
and the SMA is bidirectional. Typically, the SMA assumes a first
shape in their martensitic condition. On reaching a predetermined
temperature, depending upon alloy composition and heat treat
condition, the SMA will convert to an austenitic condition. On
transforming to its austenitic condition, the SMA assumes a
different shape.
[0027] In a simple example, referring again to FIG. 3 as well as to
FIGS. 4 and 5, when ambient temperatures are low and pressure of
compressor discharge air is also low, the temperature range of the
compressor discharge air being known, there is no need for
additional cooling air to flow through boreholes 40 into channel
44. Within this temperature range, the SMA material comprising
boreplugs 42 are selected so that boreholes 40 are closed by
boreplugs 42 and remain closed within this temperature range. Thus,
compressor flow can be directed through compressor discharge case
without diversion into channel 44, as additional cooling is not
needed. As compressor discharge air increases, due to increased
turbine demand and higher ambient temperatures, there is a need for
increased airflow to cool the region referred to as first forward
wheelspace (1 FWSP), since air flowing in passageway 30 is
inadequate. The increased temperature of the compressor discharge
air flowing over boreplugs 42, of course, raises the temperature of
boreplugs 42. The SMA material comprising the boreplugs are
preselected to change shape as the temperature of the compressor
discharge air reaches a predetermined temperature, the change in
shape of the SMA material opening the boreholes 40 to allow
compressor discharge air to pass through boreholes 40 and into
channel 40.
[0028] FIGS. 3-5 represent the broad embodiment of the present
invention. There are a number of possible variations, all within
this broad embodiment. Referring to FIG. 3, which discloses 18
boreholes 40, all of the boreplugs 42 in boreholes 40 may comprise
the same SMA material composition, so that on reaching a
predetermined temperature, all boreplugs change shape identically
to change the flow of air from a minimum or zero to a maximum,
resulting in maximum airflow through boreholes 40 into channel 44
to provide cooling to 1 FWSP.
[0029] Alternatively, boreplugs 42 may comprise the same SMA
material composition. However, boreplugs 42 may change shape over a
range of temperatures, that is, boreplugs may convert from a
martensitic condition to an austenitic condition over a range of
temperatures. Thus, SMA material may be selected so that it moves a
predetermined amount over a range of temperatures, so that the
amount of air passing through boreholes 40 into channel 44 is
modulated over the temperature range. This allows the amount of air
admitted into channel 44 to increase as the temperature of the
compressor discharge air is increased.
[0030] Because SMA materials are very sensitive to temperature, and
can be trained to change shape on achieving a predetermined
temperature. Yet another embodiment utilizes a different SMA
material for boreplugs 42 in boreholes 40. A plurality of boreplugs
42 of the same SMA material may be utilized in a plurality of
boreholes 40, as illustrated in FIG. 4 in which boreplug 42 is
cylindrically shaped. It is within the scope of this invention to
utilize a different SMA material composition for a boreplug 42 in
each of boreholes 40. Because SMA materials can be trained to
change shape with changing temperature, different compositions or
heat treat conditions of SMA materials can be selected for use in
boreholes so that they change shape at different temperatures, i.e.
convert from martensitic condition to austenitic condition at
different temperatures. Thus, as the temperature changes in the
discharge channel, various boreplug or boreplugs 42 will change
shape to modulate airflow through boreholes into channel 44 as
needed based on the discharge temperature. A boreplug 42 in
individual boreholes may be further comprised of a plurality of
segments 48, as illustrated in FIG. 5.
[0031] SMA materials can be trained to modulate airflow in a number
of ways. Whatever method is used, the modulation should admit more
air into channel 44 as additional cooling air is required in the
cooling channel with increasing discharge channel air temperature.
Thus, boreplug 42 may be in a deformed position at cooler
temperatures, blocking borehole 40, and may straighten into an
undeformed position at a preselected temperature or temperature
range, thereby increasing airflow through borehole 40.
Alternatively, boreplug 42 may be in an undeformed position at
cooler temperatures, blocking borehole 40, and may deform at a
preselected temperature or temperature range, thereby increasing
airflow through borehole 40. FIGS. 4 and 5 illustrate a segmented
boreplug 42 installed in borehole 40, creating a varying area
orifice for regulating cooling flow. In these Figures, segmented
boreplug 42 is deformed at cooler temperatures, blocking airflow
into borehole 40. As shown in FIGS. 4 and 5, at cooler
temperatures, segmented boreplug 42 may be deformed to only
partially block airflow through borehole 40. However, it will be
understood by those skilled in the art that segmented boreplug 42
may be deformed so as to substantially block borehole 40. As the
ambient temperature increases, the SMA material straightens into an
undeformed position and occupies counterbore 46 in compressor
discharge case 36 so that maximum airflow occurs through borehole
40. As noted above, SMA material may be selected and trained so as
to change shape at a preselected temperature or over a preselected
temperature range. When selected to change shape over a preselected
temperature range, the airflow through borehole 40 will be
modulated as the temperature changes within the range. It also will
be understood by those skilled in the art with a segmented boreplug
42 having a plurality of segments, each of the segments may be
comprised of a different SMA material composition that changes
shape at a different preselected temperature, so that each boreplug
42 is self-modulating as temperature changes.
[0032] By modulating boreplug flow as a function of temperature,
reduction in the amount of air passing into channel 44 will reduce
air leakage across the blade shank when airflow into channel 40 is
reduced by the shape memory alloys as cooling demands decrease.
Modulating secondary airflows may impact air available to the
combustor. Unlike the prior art schemes in which airflow was
determined on installation, the flow of air for cooling in the
present invention is determined modulated by the use of shape
memory alloys. Thus, except under those operating conditions in
which maximum cooling is required, under most conditions, more air
should be available to the combustor which should provide
additional flexibility to adjust combustion conditions to further
manage NO.sub.x, un unexpected additional benefit of air modulation
as more air can be provided for control of combustion at part load
conditions.
[0033] SMA materials, either as a cylindrical plug or as
cylindrical segments may be attached to compressor discharge case
36 by brazing, welding or other joining technique. It also may be
possible to mechanically lock plug 42 to compressor discharge case,
such as by a dovetail arrangement or other keyway/keyhole
arrangement that positively locks plug 42 to compressor discharge
case 36. The selected technique should not affect the temperature
behavior characteristics of the SMA material.
[0034] In another embodiment, installed boreplug 42 is installed in
counterbore 46 so that little or no air can pass through boreholes
40. As temperature is increased, boreplug 42 undergoes a shape
change so that air can pass around boreplug 42, through counterbore
46, into and through borehole 40 and into channel 44. The operation
of boreplug 42 in this embodiment once again depends on the shape
change characteristics of the SMA with temperature, although the
flow path of the cooling air through compressor discharge case, and
further illustrates the various ways in which the SMA material can
be used to modulate or regulate the flow of air to provide
additional cooling as needed as a result of part/full load
conditions, ambient air temperature etc.
[0035] While the present invention has been described in terms of
circular or cylindrical apertures or boreholes 40, and boreplugs 42
having a circular area profile matched to boreholes to provide the
desired airflow based on load conditions and/or ambient air
conditions, it will be recognized by those skilled in the art that
the shape of boreholes and boreplugs is not so restricted, and any
geometric shape, including but not limited to rectangular, square,
triangular, oval, hexagonal octangular etc. may be used.
[0036] FIG. 6 depicts load as a function of compressor discharge
temperature as well as ambient temperature using active cooling
such as the active boreplugs of the present invention. Ambient
temperature alone may affect compressor discharge temperature at 1
FWSP (where this designates the temperature of the compressor air
as it is discharged from the compressor) by a .DELTA.T.sub.1 which
is more than 100.degree. F., and gas turbine load combined with
ambient temperature can affect compressor discharge temperature at
1 FWSP by .DELTA.T.sub.3 which is more than 200.degree. F. FIG. 6
thus shows the importance of providing additional cooling to 1
FWSP, as without such cooling, temperatures could easily exceed
1000.degree. F.
[0037] In still another embodiment, SMA material can be used to
control cross shank leakage.
[0038] In yet another embodiment, SMA material can be used in
boreplugs to improve the turndown capability of a gas turbine
engine. At lower load levels during turndown, the amount of fuel
consumed is decreased and the amount of air provided for combustion
also changes, to maintain the emissions from combustion,
specifically NO.sub.x and CO, within prescribed, compliance limits.
As the ambient temperature falls, the compressor discharge
temperature also decreases, which may adversely affect emissions,
and the minimum load for CO compliance rises steeply, the ambient
air temperature being directly related to the compressor discharge
temperature of the air. This is shown in FIG. 7 which is a plot of
CO vs. combustion temperature. However, emissions can be improved
by modulating the flow of compressor discharge air through
boreholes 40 using SMA boreplugs 42. At high compressor discharge
temperatures, which occur at high ambient temperatures, the SMA
boreplug may be provided in a heat treatment condition such that
the bore opening is smaller. At low compressor discharge
temperatures, which occur at low ambient temperatures, the SMA
boreplug, due to its heat treatment condition, reacts to the low
temperature, by providing an enlarged bore opening. This results in
a reduction of airflow to the combustor and an increase in the
cooling flow air based on the compressor discharge temperature,
which is related to the ambient temperature. So for example,
boreplugs may be completely closed or partially closed at a high
compressor discharge temperature, for example about 750.degree. F.,
and may be completely open at a low compressor discharge
temperature, for example about 620.degree. F. The SMA boreplugs may
also undergo a gradual change in the opening as the temperature
varies between the extremes. Thus, boreplugs 42 may be completely
closed at 750.degree. F., completely open at 620.degree. F. and
open to bypass about 50% of air midway between these extreme
temperatures. Alternatively, boreplugs 42 may completely open to
bypass maximum air when a predetermined temperature is reached, for
example 650.degree. F. The operation of the boreplugs 42 in this
manner has been found to reduce the minimum emission compliant load
by up to 3% at 0.degree. F. ambient as indicated in FIG. 8. FIG. 8
represents the measured reduction in gas turbine turndown
capability of 3% at 0.degree. F. (ambient temperature). This
reduction means the gas turbine can run with an emission compliant
load of 37% rather than 40% load with a few (3 boreplugs) in the
open configuration.
[0039] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
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