U.S. patent application number 13/350313 was filed with the patent office on 2013-07-18 for diffuser for a gas turbine.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is Jonathan Glenn Luedke, Deepesh Dinesh Nanda. Invention is credited to Jonathan Glenn Luedke, Deepesh Dinesh Nanda.
Application Number | 20130180246 13/350313 |
Document ID | / |
Family ID | 47631262 |
Filed Date | 2013-07-18 |
United States Patent
Application |
20130180246 |
Kind Code |
A1 |
Nanda; Deepesh Dinesh ; et
al. |
July 18, 2013 |
DIFFUSER FOR A GAS TURBINE
Abstract
A diffuser for a gas turbine includes an inlet adapted for
coupling to the gas turbine. The diffuser also includes at least
one outlet located proximate a diffuser end, wherein the diffuser
end is located downstream of the inlet. The diffuser further
includes an outer wall and an inner barrel that extends
substantially to the diffuser end.
Inventors: |
Nanda; Deepesh Dinesh;
(Bangalore, IN) ; Luedke; Jonathan Glenn;
(Simpsonville, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nanda; Deepesh Dinesh
Luedke; Jonathan Glenn |
Bangalore
Simpsonville |
SC |
IN
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
47631262 |
Appl. No.: |
13/350313 |
Filed: |
January 13, 2012 |
Current U.S.
Class: |
60/697 |
Current CPC
Class: |
F01D 25/30 20130101 |
Class at
Publication: |
60/697 |
International
Class: |
F01D 25/30 20060101
F01D025/30 |
Claims
1. A diffuser for a gas turbine comprising: an inlet adapted for
coupling to the gas turbine; at least one outlet located proximate
a diffuser end, wherein the diffuser end is located downstream of
the inlet; an outer wall; and an inner barrel extending
substantially to the diffuser end.
2. The diffuser of claim 1, wherein the outer wall and the inner
barrel define a varying radius along a length of the diffuser
between the inlet and the outlet.
3. The diffuser of claim 2, wherein the varying radius defined by
the outer wall and the inner barrel is greater at the outlet than
at the inlet.
4. The diffuser of claim 2, wherein the varying radius defined by
the outer wall and the inner barrel includes an outer radius
location.
5. The diffuser of claim 4, further comprising a midpoint located
relatively halfway between the inlet and the outlet, an inlet
portion defined by the inlet and the midpoint, and an outlet
portion defined by the midpoint and the outlet, wherein the outer
radius location is proximate the inlet portion.
6. The diffuser of claim 1, in combination with an axial-flow
turbine.
7. The diffuser of claim 1, wherein the outlet is adapted for
coupling to an adjacent object.
8. An exhaust gas diffuser comprising: an inlet; an outlet; an
inner barrel extending from substantially the inlet to
substantially the outlet; and an outer wall radially spaced apart
from the inner barrel, wherein the outer wall and the inner barrel
define a varying radius along a length of the diffuser between the
inlet and the outlet.
9. The diffuser of claim 8, wherein the varying radius defined by
the outer wall and the inner barrel is greater at the outlet than
at the inlet.
10. The diffuser of claim 8, wherein the varying radius defined by
the outer wall and the inner barrel includes an outer radius
location.
11. The diffuser of claim 10, further comprising a midpoint located
relatively halfway between the inlet and the outlet, an inlet
portion defined by the inlet and the midpoint, and an outlet
portion defined by the midpoint and the outlet, wherein the outer
radius location is proximate the inlet portion.
12. The exhaust gas diffuser of claim 8, in combination with an
axial-flow gas turbine.
13. The exhaust gas diffuser of claim 12, wherein the inlet is
adapted for coupling to the axial-flow gas turbine.
14. The exhaust gas diffuser of claim 12, wherein the outlet is
adapted for coupling to an adjacent object.
15. A gas turbine comprising: a turbine casing that surrounds a
portion of the gas turbine; and an exhaust gas diffuser coupled to
the turbine casing, the diffuser including: an inlet adapted for
coupling to the gas turbine, an outer wall, an inner barrel and a
diffuser end downstream from the inlet, the inner barrel extending
substantially to the diffuser end.
16. The gas turbine of claim 15, wherein the exhaust gas diffuser
further comprises an outlet located proximate the diffuser end.
17. The gas turbine of claim 16, wherein the outer wall and the
inner barrel define a varying radius along a length of the diffuser
between the inlet and the outlet.
18. The gas turbine of claim 17, wherein the varying radius defined
by the outer wall and the inner barrel is greater at the outlet
than at the inlet.
19. The gas turbine of claim 17, wherein the varying radius defined
by the outer wall and the inner barrel includes an outer radius
location.
20. The gas turbine of claim 19, wherein the exhaust gas diffuser
further comprises a midpoint located relatively halfway between the
inlet and the outlet, an inlet portion defined by the inlet and the
midpoint, and an outlet portion defined by the midpoint and the
outlet, wherein the outer radius location is proximate the inlet
portion.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to turbines and,
in particular, to diffusers for use with gas turbines and steam
turbines.
[0002] Typical gas turbines include a diffuser cone, or diffuser,
coupled to the last stage bucket of the rotor. The diffuser serves,
generally, to increase static pressure of the exhaust gas by
decreasing the kinetic energy of the exhaust gas. Generally, this
may be achieved by increasing the cross-sectional area of the
diffuser in the direction of exhaust gas flow.
[0003] Often, gas turbines are not operated at full load, but are
designed for efficiency under such a full load. Therefore, part
load performance efficiency is sacrificed, based on the full load
design. Such inefficiencies are due, at least in part, to flow
separation on the diffuser inner barrel, leading to tip strong flow
profiles. Other factors, such as operation of the last stage of the
turbine, may influence the flow profile. Additionally, flow passing
over a center body of the diffuser generates large vortices that
result in yet further system inefficiency.
BRIEF DESCRIPTION OF THE INVENTION
[0004] According to one aspect of the invention, a diffuser for a
gas turbine includes an inlet adapted for coupling to the gas
turbine. The diffuser also includes at least one outlet located
proximate a diffuser end, wherein the diffuser end is located
downstream of the inlet. The diffuser further includes an outer
wall and an inner barrel extending substantially to the diffuser
end.
[0005] According to another aspect of the invention, an exhaust gas
diffuser includes an inlet and an outlet. The exhaust gas diffuser
also includes an inner barrel extending from substantially the
inlet to substantially the outlet. The diffuser further includes an
outer wall radially spaced apart from the inner barrel, wherein the
outer wall and the inner barrel define a varying radius along a
length of the diffuser between the inlet and the outlet.
[0006] According to yet another aspect of the invention, a gas
turbine includes a turbine casing that surrounds a portion of the
gas turbine. The gas turbine also includes an exhaust gas diffuser
coupled to the turbine casing. The diffuser includes an inlet
adapted for coupling to the gas turbine, an outer wall, an inner
barrel and a diffuser end downstream from the inlet, the inner
barrel extending substantially to the diffuser end.
[0007] These and other advantages and features will become more
apparent from the following description taken in conjunction with
the drawings.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The subject matter, which is regarded as the invention, is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
features and advantages of the invention are apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which:
[0009] FIG. 1 is a side, cross-sectional view of a diffuser
according to one aspect of the invention;
[0010] FIG. 2 illustrates a flow profile associated with the
diffuser illustrated in FIG. 1;
[0011] FIG. 3 illustrates a diffuser flow profile exhibiting flow
separation; and
[0012] The detailed description explains embodiments of the
invention, together with advantages and features, by way of example
with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0013] FIG. 1 illustrates one aspect of a diffuser 200 according to
one embodiment of the present invention. In operation, exhaust gas
from the gas turbine flows through the diffuser 200 in the
direction shown by arrow A. In this description, an object is
"downstream" of another object or location if it is displaced from
it in the direction of arrow A and is "upstream" if it is displaced
from it in a direction opposite of arrow A.
[0014] The diffuser 200 includes an inner barrel 202 that includes
an inner wall 204 that forms an inner chamber 208 through which a
portion of a rotor may pass. The diffuser 200 includes an inlet 211
located proximate a diffuser entry end 210 and an outlet 220
located proximate a diffuser exit end 222. The inlet 211 may be
coupled to a turbine, while the outlet 220 may be coupled to an
adjacent object, such as a silencer. The diffuser also includes an
outer wall 206 radially spaced from the inner wall 204 of the inner
barrel 202. The area between the inner wall 204 and the outer wall
206 allows fluid or gas to flow downstream therethrough from the
inlet 211 to the outlet 220 of the diffuser 200.
[0015] The diffuser 200 may also include one or more struts 216
formed between the inner wall 204 and the outer wall 206. The strut
216 serves to hold the inner wall 204 and the outer wall 206 in a
fixed relationship to one another, as well as providing bearing
support. The number of struts 216 is variable and commonly ranges
from about four to about ten.
[0016] The inner wall 204 of the inner barrel 202 extends from the
inlet 211, or diffuser entry end 210, to the outlet 220, or
diffuser exit end 222. The inner barrel 202, and hence the inner
wall 204, includes a first end 224 located proximate the inlet 211
and a second end 226 located proximate the outlet 220 and may take
on numerous longitudinal contours as the inner barrel 202 extends
from the first end 224 to the second end 226. The inner barrel 202
may slightly curve continuously from the first end 224 to the
second end 226, may curve slightly for only portions between the
first end 224 and the second end 226, may extend in a substantially
straight direction, or may comprise segmented portions, where the
overall longitudinal direction of the inner barrel 202 comprises
any combination of the curvilinear paths described above.
Irrespective of the shape of the inner barrel 202, and more
particularly the inner wall 204, the inner barrel 202 and inner
wall 204 extend to the diffuser outlet 220 or diffuser exit
222.
[0017] The outer wall 206 includes a first portion 230 that extends
from the inlet 211, or diffuser entry end 210, in a substantially
downstream direction, as well as in a direction away from the inner
wall 204. The sloping curvilinear direction of first portion 230 of
the outer wall 206 terminates at an outer radius location 232. The
outer wall 206 also includes a second portion 234 that extends from
the outer radius location 232 in a substantially downstream
direction to the outlet 220, or diffuser exit end 222. The first
portion 230 of the outer wall 206 angles away from the inner wall
204 more substantially than the second portion of the outer wall
206, with the outer radius location 232 being located further
upstream than a longitudinal midpoint 236 of the inner barrel 202.
The portion of the inner barrel 202 located upstream of the
longitudinal midpoint 236 is an inlet portion 238, while the
portion of the inner barrel located downstream of the longitudinal
midpoint 236 is an outlet portion 240. Therefore, the outer wall
206 is pushed to an outer radius further upstream than conventional
diffuser outer wall constructions.
[0018] FIG. 2 shows a flow path profile in diffuser 200 shown in
FIG. 1. As can be seen, the flow profile for the diffuser 200 of
FIG. 1 is strong throughout the entire radial area of the diffuser
200, even along the inner wall 204. The diffuser 200 reduces flow
separation, thereby improving diffuser performance over a diffuser
flow profile exhibiting flow separation, as shown in FIG. 3.
[0019] In addition to reducing flow separation by employing the
above-described diffuser 200 structure, the introduction of
secondary air flow may be injected into the diffuser 200. Such a
secondary air flow into the diffuser 200 and thereby a main
diffuser flow alters overall flow by energizing a shear layer that
is formed between the main flow and the inner wall 204 and/or outer
wall 206, causing a delay of the flow separation itself The main
flow widens and a larger static pressure recovery is achieved.
[0020] Various approaches to achieve introduction of the secondary
air flow are contemplated and one such approach is by installing a
flow manipulation device, such as a pump, within the inner barrel
202. The inner wall 204 of the inner barrel 202 includes one or
more actuator openings and one or more suction openings that are
located downstream of the one or more actuator openings. The
suction opening allows common weak flow that passes directly over
the inner wall 204 to enter the inner barrel 202 and pass through
the flow manipulating device with sufficient force to exit the
actuating opening in a manner that manipulates the flow profile of
the diffuser 200. The manipulation of flow reduces flow separation,
thereby increasing diffusion area.
[0021] Advantageously, diffuser 200 flow path is controlled by
focusing the diffusion gradient near the region of high velocity
and radially redistributing the flow. To reduce flow separation
within the diffuser 200, particularly during part load performance
of the overall system, the inner barrel 202 extends to the relative
outlet 220 of the diffuser 200. Additionally, an outer wall 206 of
the diffuser 200 extends radially away from the inner barrel 202 at
a rapid rate, starting upstream at the relative inlet 211 of the
diffuser 200. The result is a reduction in loss producing vortices
associated with wake and a significant improvement in diffuser
performance and thereby system heat rate gain. While the invention
has been described in detail in connection with only a limited
number of embodiments, it should be readily understood that the
invention is not limited to such disclosed embodiments. Rather, the
invention can be modified to incorporate any number of variations,
alterations, substitutions or equivalent arrangements not
heretofore described, but which are commensurate with the spirit
and scope of the invention. Additionally, while various embodiments
of the invention have been described, it is to be understood that
aspects of the invention may include only some of the described
embodiments. Accordingly, the invention is not to be seen as
limited by the foregoing description, but is only limited by the
scope of the appended claims.
* * * * *