U.S. patent application number 11/856945 was filed with the patent office on 2009-03-19 for cooling circuit for enhancing turbine performance.
Invention is credited to Jeffrey John Butkiewicz, Biao Fang, Matthew Scott Kight, Tara McGovern, Omprakash Samudrala, Christopher Edward Wolfe.
Application Number | 20090074589 11/856945 |
Document ID | / |
Family ID | 40348783 |
Filed Date | 2009-03-19 |
United States Patent
Application |
20090074589 |
Kind Code |
A1 |
Fang; Biao ; et al. |
March 19, 2009 |
Cooling Circuit for Enhancing Turbine Performance
Abstract
In a gas turbine having a compressor discharge casing, a cooling
circuit diverts compressor discharge air toward a high pressure
packing (HPP) circuit. The cooling circuit includes an inlet pipe
that receives compressor discharge air. One or several cooled
cooling air pipes are in fluid communication with the inlet pipe
via a pipe manifold, which distributes the discharge air across the
cooled cooling air pipes. A seal is disposed upstream of an
entrance to the HPP circuit to limit flow into the HPP circuit, and
a second seal is disposed downstream of the HPP circuit at turbine
wheelspace to limit ingestion and thus the purge flow air required.
The circuit serves to reduce required purge flow in the HPP circuit
so that an amount of compressor discharge air can be put back to
the main flow path, thereby improving turbine performance.
Inventors: |
Fang; Biao; (Clifton Park,
NY) ; Wolfe; Christopher Edward; (Niskayuna, NY)
; Samudrala; Omprakash; (Niskayuna, NY) ; Kight;
Matthew Scott; (Greenville, SC) ; Butkiewicz; Jeffrey
John; (Greenville, SC) ; McGovern; Tara;
(Simpsonville, SC) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
40348783 |
Appl. No.: |
11/856945 |
Filed: |
September 18, 2007 |
Current U.S.
Class: |
416/97R |
Current CPC
Class: |
F02C 7/12 20130101; F01D
25/12 20130101 |
Class at
Publication: |
416/97.R |
International
Class: |
F01D 5/08 20060101
F01D005/08 |
Claims
1. A cooling circuit in a gas turbine for augmenting flow in a high
pressure packing (HPP) circuit of the turbine, the cooling circuit
comprising: an inlet pipe that receives compressor discharge air;
at least one cooled cooling air pipe in fluid communication with
the inlet pipe via a pipe manifold, the pipe manifold distributing
the discharge air across the at least one cooled cooling air pipe;
an upstream seal disposed upstream of an entrance to the HPP
circuit; and a downstream seal disposed downstream of the HPP
circuit.
2. A cooling circuit according to claim 1, further comprising a
cooling source in communication with the at least one cooled
cooling air pipe.
3. A cooling circuit according to claim 2, wherein the cooling
source comprises ambient air.
4. A cooling circuit according to claim 2, wherein the cooling
source comprises a heat exchanger.
5. A cooling circuit according to claim 2, wherein the cooling
source comprises an atomizer that sprays water droplets in contact
with one of the diverted air and the at least one cooled cooling
air pipe.
6. A cooling circuit according to claim 2, wherein the cooling
source comprises an ejector that mixes air from at least two
compressor stages including the compressor discharge.
7. A cooling circuit according to claim 1, wherein the cooled
cooling air pipes penetrate a vertical flange of the compressor
discharge casing and extend along a compressor discharge casing
strut at trailing edges.
8. A cooling circuit according to claim 1, further comprising a
valve disposed between the inlet pipe and the cooled cooling air
pipes, the valve adjusting mass flow and a temperature of the
diverted air based on a temperature of the HPP circuit.
9. A cooling circuit according to claim 1, further comprising
openings in an inner barrel to permit cooled cooling air from the
cooled cooling air pipes to reach at least one of a tie bolt and a
marriage flange in the turbine.
10. A cooling circuit according to claim 1, wherein the downstream
seal comprises an abradable angel wing seal.
11. A method of improving turbine performance using a cooling
circuit by augmenting flow in a high pressure packing (HPP) circuit
of the turbine, the method comprising: receiving compressor
discharge air in an inlet pipe; distributing the discharge air
across a plurality of cooled cooling air pipes; and disposing an
upstream seal upstream of an entrance to the HPP circuit to
regulate air entering the HPP circuit and disposing a downstream
seal downstream of the HPP circuit to regulate a need for
wheelspace purge air.
12. A method according to claim 11, further comprising actively
cooling the cooled cooling air pipes.
13. A method according to claim 12, wherein the actively cooling
step is practiced using ambient air.
14. A method according to claim 12, wherein the actively cooling
step is practiced using a heat exchanger.
15. A method according to claim 12, wherein the actively cooling
step is practiced using an atomizer that sprays water droplets in
contact with one of the diverted air and the cooled cooling air
pipes.
16. A method according to claim 12, wherein the actively cooling
step is practiced using an ejector that mixes air from at least two
compressor stages.
17. A method according to claim 11, wherein the discharge air is
regulated by a valve.
18. A cooling circuit in a gas turbine for augmenting flow in a
high pressure packing (HPP) circuit of the turbine, the cooling
circuit comprising: an inlet pipe that receives compressor
discharge air; at least one cooled cooling air pipe in fluid
communication with the inlet pipe via a pipe manifold, the pipe
manifold distributing the discharge air across the at least one
cooled cooling air pipe; a cooling source in direct contact with
one of the at least one cooled cooling air pipe and the diverted
air; a valve disposed between the inlet pipe and the at least one
cooled cooling air pipe, the valve adjusting mass flow and a
temperature of the diverted air based on a temperature of the HPP
circuit; an upstream seal disposed upstream of an entrance to the
HPP circuit; and a downstream seal disposed downstream of the HPP
circuit.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a structure and method for
enhancing turbine performance and, more particularly, to a cooling
circuit that diverts compressor discharge air to supplement the
total required purge flow and cool critical turbine components.
[0002] The compressor discharge air leaking past the high pressure
packing (HPP) of a gas turbine is typically returned to the primary
gas path via the first forward wheelspace, between the first stage
nozzles and first stage buckets. This secondary flow path is
referred to as the HPP circuit. This air is used for two purposes:
(1) it is used as purge flow in the first wheelspace to prevent hot
gas ingestion; and (2) it cools critical components in the HPP
circuit. Some of the critical components in the HPP circuit include
the compressor tie bolts, marriage joint, nozzle support ring and
first stage wheel.
[0003] In some designs, the flow level in the HPP circuit is higher
than the wheelspace purge requirement because of component
temperature requirements. Therefore, an ideal solution should
reduce the total circuit flow to a level that satisfies the
wheelspace purge requirements while keeping all critical components
in the circuit under desired temperature requirements. Furthermore,
a preferred solution may also be able to handle robustly varying
ambient and turbine operation conditions. Finally, the solution
should be able to retrofit in the existing hardware.
[0004] In a previous General Electric turbine design (the 9H
turbine), an HPP circuit utilized a cooled cooling air bypass
system. The circuit used a heat exchanger to cool the extracted
compressor discharge air and bring the cooled cooling air to the
front of the HPP circuit to not only cool the last stages of the
compressor components but also prevent a later stage flow from
coming into the HPP circuit. This system uses conventional sealing
that the HPP and makes no attempt to regulate the purge flow
required beyond conventional angel wing seals. The cooled cooling
air is not adjustable.
[0005] Brush seals have been implemented in other turbine designs
to reduce the purge flow. No cooled cooling air is needed there,
however, because of lower compressor discharge temperatures and
consequently lower temperatures in the HPP circuit resulting in
adequate wheelspace temperature margins.
BRIEF DESCRIPTION OF THE INVENTION
[0006] In an exemplary embodiment, a cooling circuit in a gas
turbine serves to augment flow in a high pressure packing (HPP)
circuit of the turbine. The cooling circuit includes an inlet pipe
that receives compressor discharge air, and at least one cooled
cooling air pipe in fluid communication with the inlet pipe via a
pipe manifold. The pipe manifold distributes the discharge air
across the at least one cooled cooling air pipe. An upstream seal
is disposed upstream of an entrance to the HPP circuit, and a
downstream seal is disposed downstream of the HPP circuit.
[0007] In another exemplary embodiment, a method of improving
turbine performance using a cooling circuit by augmenting flow in a
high pressure packing (HPP) circuit of the turbine includes the
steps of receiving compressor discharge air in an inlet pipe;
distributing the discharge air across a plurality of cooled cooling
air pipes; and disposing an upstream seal upstream of an entrance
to the HPP circuit to regulate air entering the HPP circuit and
disposing a downstream seal downstream of the HPP circuit to
regulate a need for wheelspace purge air.
[0008] In still another exemplary embodiment, the cooling circuit
includes an inlet pipe that receives compressor discharge air; at
least one cooled cooling air pipe in fluid communication with the
inlet pipe via a pipe manifold, the pipe manifold distributing the
discharge air across the at least one cooled cooling air pipe; a
cooling source in direct contact with one of the at least one
cooled cooling air pipe and the diverted air; a valve disposed
between the inlet pipe and the at least one cooled cooling air
pipe, the valve adjusting mass flow and a temperature of the
diverted air based on a temperature of the HPP circuit; an upstream
seal disposed upstream of an entrance to the HPP circuit; and a
downstream seal disposed downstream of the HPP circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows the cooling circuit of an exemplary embodiment;
and
[0010] FIG. 2 shows the cooling circuit of an alternative exemplary
embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0011] With reference to FIG. 1, the system utilizes a seal 12 such
as a brush seal, adjustable seal, or the like to prevent excessive
flow from the compressor discharge air and secondary (bypass)
cooled cooling air system to supplement the total required purge
flow and cool critical components. An adjustable seal can be one
that is retracted during engine transients to minimize wear or
damage to the seal, or one that allows for adjustment in service to
accommodate seal performance degradation.
[0012] The seal 12 is placed upstream or adjacent the HPP circuit
entrance before all critical components and the existing honeycomb
seal. As noted, the seal can be a conventional brush seal, an
adjustable seal with an actuating system, or the like.
[0013] An inlet tube or pipe 14 is positioned to receive compressor
discharge air. Preferably, the circuit includes two inlet tubes or
pipes 14 of about 3'' diameter.
[0014] Diverted air in the inlet pipe 14 is flowed to a plurality
of cooled cooling air pipes 16 via a pipe manifold 18. The pipe
manifold 18 distributes the discharge air from the inlet pipes 14
across the cooled cooling air pipes 16. The cooled cooling air
pipes 16 direct the compressor discharge air to the HPP
circuit.
[0015] In a preferred arrangement, the cooling circuit includes 12
cooled cooling air pipes that penetrate at the compressor discharge
case vertical flange and run along the compressor discharge case
strut at trailing edges. The cooled cooling air pipes are
preferably 3/4'' or 1'' in diameter. The positioning via the
compressor discharge case struts serves to minimize the aerodynamic
impact on the main gas flow. A computational fluid dynamics
analysis has been conducted to ensure that the added tubing system
has a negligible impact on the main gas flow. The tubes 16 further
penetrate the compressor discharge casing inner barrel flange via
suitable apertures.
[0016] The circuit preferably additionally includes a cooling
source in communication with either or both of the inlet pipe 14
and the cooled cooling air pipes 16. In one arrangement, the
cooling source comprises ambient air that serves to cool the air
flow as it travels through the cooled cooling air pipes 16.
Alternatively, the cooling source may comprise a heat exchanger 20
such as a tube-shell type heat exchanger or the like.
[0017] Still another alternative for the cooling source is an
atomizer 22 that sprays water droplets in contact with either the
diverted air or the cooled cooling air pipes 16. The atomizer 22
preferably generates micro-level water droplets that are sprayed
directly to cool the extracted air. The amount of water required to
cool the flow by 150.degree. F. will elevate the main gas path flow
moisture level by only 2%. Locally in the HPP circuit, the specific
humidity will typically be 4-5 times compared to the condition at
the inlet. This higher humidity in general is harmless to the
circuit components.
[0018] FIG. 2 illustrates an alternative to the heat exchanger 20
or atomizer 22 shown in FIG. 1. FIG. 2 illustrates an ejector 24
that mixes air from the 13.sup.th stage of the compressor, or other
suitable compressor extraction port, with the compressor discharge
air. The 13.sup.th stage air is directed to the ejector via
suitable tubing 26 or the like. The combined 13.sup.th stage and
compressor discharge air at the ejector exit will have a desired
temperature and lower than the compressor discharge air pressure.
Because relatively cheaper air from stage 13, cheaper in that less
work has been done on the air to compress and heat it, is used,
additional turbine performance can be gained.
[0019] The exit temperature and mass flow can be tuned by a valve
28 disposed between the inlet pipe 14 and the cooled cooling air
pipes 16. An additional valve may be provided to control water mass
when using the atomizer 22. The two valves can be operated either
manually or automatically by control signals. Preferably, the
valves can be automatically adjusted for desired mass flow and
temperature of cooled cooling air based on a temperature
measurement at the HPP circuit. Such valves can be used to regulate
the CCA circuit regardless of the cooling mechanism used. These
valves should be controlled based on temperature measurements made
in the HPP circuit; these are typically made at several locations
in the wheelspace, but can also be made at any critical location in
the HPP circuit. Temperature measurements can be used to both
determine that the cooling air is adequately cool, and to identify
the hot gas ingestion into the wheelspace.
[0020] The cooled cooling air pipes 16 deliver the cooling air at
various locations relative to the HPP circuit. As shown in FIGS. 1
and 2, openings 30 are preferably provided in the inner barrel in
order to supply cooled cooling air to the tie bolt and marriage
flange of the turbine. The remainder of the CCA is fed directly
into the first forward wheelspace.
[0021] The system and method described endeavor to save the amount
of compressor discharge air required in the HPP circuit and
redirect it back to the main flow path to enhance turbine
performance. This can be achieved robustly by introducing a
secondary flow system to bring cooled cooling air in the circuit.
The amount of the total flow required in the circuit is dictated by
the wheelspace purge requirement. The difference between the
wheelspace purge requirement and current flow is significant enough
to justify the implementation of the secondary cooled cooling air
circuit. A seal limits the air entering the HPP circuit to the
minimum possible so that as much of the required purge air as
possible is supplied by the cooled cooling air circuit. Improved
sealing at the wheelspace via abradable angel wing seals reduces
the amount of purge air required. The mixed compressor discharge
air and cooled cooling air should be sufficient to prevent the
wheelspace hot gas ingestion while keeping the critical components
in the circuit under temperature limits.
[0022] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not to be
limited to the disclosed embodiments, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *