U.S. patent application number 12/514511 was filed with the patent office on 2010-02-18 for film cooling structure.
This patent application is currently assigned to IHI CORPORATION. Invention is credited to Yoji Ohkita.
Application Number | 20100040459 12/514511 |
Document ID | / |
Family ID | 39401434 |
Filed Date | 2010-02-18 |
United States Patent
Application |
20100040459 |
Kind Code |
A1 |
Ohkita; Yoji |
February 18, 2010 |
FILM COOLING STRUCTURE
Abstract
A film cooling structure 10 includes a structural wall 11 that
has an outer surface 12 exposed to combustion gas and an inner
surface 13 positioned opposite to the outer surface 12, and film
cooling holes 14 are formed at the structural wall 11 and introduce
cooling air from the inner surface 13 toward the outer surface 12
in order to perform film cooling. The film cooling hole 14 includes
an introducing portion 14a that extends to a middle position in the
structural wall 11 from the inner surface 13 toward the outer
surface 12, an enlarged portion 14b of which the cross-sectional
area is gradually increased toward the outer surface 12 from an end
of an outer surface side of the introducing portion 14a and which
is opened at the outer surface 12, and a partition portion 16 that
partitions the inside of the enlarged portion 14b into a plurality
of spaces in a width direction of the hole perpendicular to a flow
direction of the combustion gas.
Inventors: |
Ohkita; Yoji; (Tokyo,
JP) |
Correspondence
Address: |
GRIFFIN & SZIPL, PC
SUITE PH-1, 2300 NINTH STREET, SOUTH
ARLINGTON
VA
22204
US
|
Assignee: |
IHI CORPORATION
Tokyo
JP
|
Family ID: |
39401434 |
Appl. No.: |
12/514511 |
Filed: |
March 13, 2007 |
PCT Filed: |
March 13, 2007 |
PCT NO: |
PCT/JP2007/054910 |
371 Date: |
May 12, 2009 |
Current U.S.
Class: |
415/177 |
Current CPC
Class: |
F05D 2260/202 20130101;
F05D 2250/52 20130101; F01D 5/186 20130101 |
Class at
Publication: |
415/177 |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 2006 |
JP |
2006/306538 |
Claims
1. A film cooling structure, comprising: a structural wall that has
an outer surface exposed to combustion gas and an inner surface
positioned opposite to the outer surface, wherein film cooling
holes being formed at the structural wall and introducing cooling
air from the inner surface toward the outer surface in order to
perform film cooling of the outer surface, the film cooling hole
includes an introducing portion that extends to a middle position
in the structural wall from the inner surface toward the outer
surface, an enlarged portion of which the cross-sectional area is
gradually increased toward the outer surface from an end of an
outer surface side of the introducing portion and which is opened
at the outer surface, and a partition portion that partitions the
inside of the enlarged portion into a plurality of spaces in a
width direction of the hole perpendicular to a flow direction of
the combustion gas.
2. The film cooling structure according to claim 1, wherein the
partition portion is formed at a middle position of the inside of
the film cooling hole in the width direction of the hole
perpendicular to the flow direction of the combustion gas, and the
partition portion protrudes from one of the wall surfaces facing
upstream and downstream sides in the flow direction of the
combustion gas toward the other thereof, and extends over the
entire inside of the hole from the inner surface of the structural
wall toward the outer surface.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field of the Invention
[0002] The present invention relates to a film cooling structure
that is suitable for film cooling of the surface of a component
(turbine blade or the like) of a gas turbine engine.
[0003] 2. Description of the Related Art
[0004] The efficiency of a gas turbine engine is increased as
combustion gas temperature rises. However, the combustion gas heats
a structural wall of a component (a combustor liner, a turbine
blade, a turbine shroud, or the like), that is disposed on a flow
passage for combustion gas, to high temperature. Accordingly, in
order to efficiently cool the structural wall of such the
component, there is employed a film cooling structure. In the
cooling structure, a cooling passage is formed therein, convection
cooling is performed by making cooling air flow through the cooling
passage, and film cooling is performed by making the cooling air be
ejected from film cooling holes onto a surface, which is exposed to
high-temperature combustion gas, in the shape of a film (for
example, see the following Patent Documents 1 to 5).
[0005] FIGS. 1A to 1C show an example of a film cooling structure
30 of the related art. FIG. 1B is a cross-sectional view taken
along a line 1B-1B of FIG. 1A, and FIG. 1C is a cross-sectional
view taken along a line 1C-1C of FIG. 1B.
[0006] In FIGS. 1B and 1C, a structural wall 31 has an outer
surface 32 that is exposed to combustion gas 1, and an inner
surface 33 that is positioned opposite to the outer surface 32.
Film cooling holes 34 are formed at the structural wall 31 so as to
be inclined with respect to the outer surface 32 by a predetermined
angle, and introduce cooling air 5 from the inner surface 33 toward
the outer surface 32 in order to perform the film cooling of the
outer surface 32. The film cooling hole 34 includes an introducing
portion 34a that extends to a middle position in the structural
wall 31 from the inner surface 33 toward the outer surface 32, and
an enlarged portion 34b (diffuser) of which the cross-sectional
area is gradually increased toward the outer surface 32 from an end
of the introducing portion 34a facing the outer surface 32 and
which is opened at the outer surface 32. As shown in FIG. 1B, a
wall surface 35 of the enlarged portion 34b facing an upstream side
in the flow direction of the combustion gas 1 is formed in a linear
shape. Further, as shown in FIG. 1C, both wall surfaces 36 and 36
of the enlarged portion 34b in a direction perpendicular to the
flow direction of the combustion gas 1 are formed in a linear
shape.
[0007] [Patent Document 1]
[0008] Japanese Patent Application Laid-Open No. 2006-9785
[0009] [Patent Document 2]
[0010] Japanese Patent Application Laid-Open No. 2005-90511
[0011] [Patent Document 3]
[0012] Japanese Patent Application Laid-Open No. 2003-41902
[0013] [Patent Document 4]
[0014] Japanese Patent Application Laid-Open No. 2001-173405
[0015] [Patent Document 5]
[0016] Japanese Patent Application Laid-Open No. 10-89005
SUMMARY OF THE INVENTION
[0017] As for film cooling, it is preferable to spread the cooling
air 5 on the outer surface 32, which is to be cooled, as thinly and
broadly as possible, and to attach the cooling air to the outer
surface 32 as close as possible. Accordingly, in order to spread
the cooling air 5 thinly and broadly on the outer surface 32, it is
effective to increase an enlarged angle of the enlarged portion 34b
as much as possible.
[0018] However, the cross-sectional area of the hole is linearly
increased at the enlarged portion 34b of the above-mentioned film
cooling structure 30 in the related art. Accordingly, if an
enlarged angle of the enlarged portion 34b is excessively large,
the separation of the cooling air 5 occurs in the hole. For this
reason, there have been problems that the cooling air 5 is not
effectively diffused and it is difficult to improve average film
cooling efficiency.
[0019] The invention has been made in consideration of the
above-mentioned problems, and an object of the invention is to
provide a film cooling structure that can increase an enlarged
angle of an enlarged portion and improve average film cooling
efficiency.
[0020] In order to solve the above-mentioned problems, the film
cooling structure according to the invention includes the following
means.
[0021] According to the invention, a film cooling structure
includes a structural wall that has an outer surface exposed to
combustion gas and an inner surface positioned opposite to the
outer surface, and film cooling holes are formed at the structural
wall and introduce cooling air from the inner surface toward the
outer surface in order to perform film cooling of the outer
surface. The film cooling hole includes an introducing portion that
extends to a middle position in the structural wall from the inner
surface toward the outer surface, an enlarged portion of which the
cross-sectional area is gradually increased toward the outer
surface from an end of an outer surface side of the introducing
portion and which is opened at the outer surface, and a partition
portion that partitions the inside of the enlarged portion into a
plurality of spaces in a width direction of the hole perpendicular
to a flow direction of the combustion gas.
[0022] Since the film cooling hole includes the partition portion
that has been formed as described above, an effective area
expansion ratio may be reduced. Accordingly, even though the
enlarged angle of the enlarged portion in a transverse direction is
large, the separation of the cooling air is suppressed. Therefore,
since it is possible to effectively diffuse cooling air as compared
to the related art, the enlarged angle of the enlarged portion in
the transverse direction can be made large. As a result, it is
possible to spread the cooling air thinly and broadly on the outer
surface of the structural wall, and to improve average film cooling
efficiency. Meanwhile, the definition of the average film cooling
efficiency will be described below.
[0023] Further, since it is possible to spread the cooling air
thinly and broadly as compared to the related art, the number of
film cooling holes formed at the structural wall may be reduced.
Accordingly, the number of processes for manufacturing the film
cooling structure can be reduced. Furthermore, as the number of
film cooling holes is reduced, the amount of cooling air extracted
from the compressor of the gas turbine engine can be decreased.
Therefore, engine efficiency can be improved.
[0024] In addition, in the film cooling structure, the partition
portion is formed at a middle position of the inside of the film
cooling hole in the width direction of the hole perpendicular to
the flow direction of the combustion gas, protrudes from one of the
wall surfaces facing upstream and downstream sides in the flow
direction of the combustion gas toward the other thereof, and
extends over the entire inside of the hole from the inner surface
of the structural wall toward the outer surface.
[0025] As described above, the partition portion does not
completely partition the film cooling hole in the transverse
direction, and extends over the entire structural wall in a
thickness direction. Therefore, it is easy to form the film cooling
hole.
[0026] From the above description, according to the invention, it
is possible to obtain advantages of increasing an enlarged angle of
an enlarged portion and improving average film cooling
efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1A is a plan view of a film cooling structure in the
related art.
[0028] FIG. 1B is a cross-sectional view taken along a line 1B-1B
of FIG. 1A.
[0029] FIG. 1C is a cross-sectional view taken along a line 1C-1C
of FIG. 1B.
[0030] FIG. 2 is a perspective view of a turbine rotating blade to
which a film cooling structure according to the invention is
applied.
[0031] FIG. 3A is a plan view of a film cooling structure according
to an embodiment of the invention.
[0032] FIG. 3B is a cross-sectional view taken along a line 3B-3B
of FIG. 3A.
[0033] FIG. 3C is a cross-sectional view taken along a line 3C-3C
of FIG. 3B.
[0034] FIG. 4 is a perspective view showing the shape of a film
cooling hole of the film cooling structure according to the
embodiment of the invention.
[0035] FIG. 5 is a view illustrating the physical action of a
partition portion.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] A preferred embodiment of the invention will be described in
detail below with reference to accompanying drawings. Meanwhile,
the same reference numerals are given to common portions in each
drawing, and redundant description thereof will be omitted.
[0037] A film cooling structure according to the invention is
applied to a component that is disposed on a flow passage for
combustion gas in a gas turbine engine. Examples of this component
include a combustor liner, a turbine nozzle vane, a turbine nozzle
band, a turbine rotating blade, a turbine stator blade, a turbine
shroud, and a turbine outlet liner.
[0038] FIG. 2 is a perspective view of a turbine rotating blade 2
to which the film cooling structure 10 according to the invention
is applied. The turbine rotating blade 2 includes a blade portion 3
that serves as a structural wall having an outer surface 12 exposed
to combustion gas 1, and a base portion 4 that is used to mount the
blade portion 3 on a rotor of an engine. A cooling circuit (not
shown) through which cooling air flows is formed in the blade
portion 3. This cooling air is extracted from a compressor of a gas
turbine engine, and flows into the cooling circuit through a flow
passage (not shown) that is formed in the base portion 4. The
cooling air, which has flown into the cooling circuit, is ejected
from a plurality of film cooling holes 14 that is formed on an
outer surface 12 of the blade portion 3, and performs film cooling
on the outer surface 12 of the blade portion 3. The film cooling
structure 10 according to an embodiment of the invention will be
described below.
[0039] FIGS. 3A to 3C show the film cooling structure 10 according
to the invention. FIG. 3A is a plan view of the film cooling
structure 10. FIG. 3B is a cross-sectional view taken along a line
3B-3B of FIG. 3A. FIG. 3C is a cross-sectional view taken along a
line 3C-3C of FIG. 3B. Further, FIG. 4 is a perspective view
showing the shape of the film cooling hole 14 of the film cooling
structure 10 according to the embodiment of the invention.
[0040] As described above, the film cooling structure 10 is applied
to a component such as a turbine rotating blade that is disposed on
a flow passage for combustion gas 1 in a gas turbine engine. As
shown in FIGS. 3B and 3C, the film cooling structure 10 includes a
structural wall 11 that has the outer surface 12 exposed to the
combustion gas 1 and an inner surface 13 positioned opposite to the
outer surface 12. If the component of the gas turbine is, for
example, a turbine rotating blade, a wall forming the blade portion
of the turbine rotating blade is the structural wall 11. Cooling
air 5 flows into the inner surface 13 of the structural wall
11.
[0041] The film cooling hole 14, which introduces the cooling air 5
from the inner surface 13 to the outer surface 12 in order to
perform the film cooling of the outer surface 12, is formed in the
structural wall 11. As shown in FIG. 3B, an axis of the film
cooling hole 14 is inclined with respect to the outer surface 12 of
the structural wall 11 by a predetermined angle so that the cooling
air 5 is blown from the film cooling hole 14 in a direction
corresponding to the flow of the combustion gas 1.
[0042] The film cooling hole 14 includes an introducing portion 14a
that extends to a middle position in the structural wall 11 from
the inner surface 13 toward the outer surface 12, and an enlarged
portion 14b of which the cross-sectional area is gradually
increased toward the outer surface 12 from an end of an outer
surface side of the introducing portion 14a and which is opened at
the outer surface 12.
[0043] The film cooling hole 14 further includes a partition
portion 16 that partitions the inside of the enlarged portion 14b
into a plurality of spaces in a width direction of the hole
perpendicular to the flow direction of the combustion gas 1. In
this case, the "width direction of the hole perpendicular to the
flow direction of the combustion gas 1" is a direction
perpendicular to the plane of in FIG. 3B, and is a horizontal
direction in FIG. 3C.
[0044] In the embodiment shown in FIGS. 3A to 3C and 4, the
partition portion 16 is formed at a middle position of the inside
of the film cooling hole 14 in the width direction of the hole
perpendicular to the flow direction of the combustion gas 1,
protrudes from the wall surface facing an upstream side in the flow
direction of the combustion gas 1 toward the upstream side in the
flow direction of the combustion gas 1, and extends over the entire
inside of the hole from the inner surface 13 of the structural wall
11 toward the outer surface 12. A gap is formed between the
partition portion 16 and a wall surface facing a downstream side in
the flow direction of the combustion gas 1.
[0045] One partition portion 16 has been formed in the embodiment
shown in FIGS. 3A to 3C and 4, but a plurality of partition
portions may be formed at intervals in the width direction of the
hole.
[0046] Further, in the embodiment shown in FIGS. 3A to 3C and 4,
the partition portion 16 has protruded from the wall surface facing
the upstream side in the flow direction of the combustion gas 1
toward the upstream side in the flow direction of the combustion
gas 1. However, in contrast to this, the partition portion may
protrude from the wall surface facing a downstream side in the flow
direction of the combustion gas 1 toward the downstream side in the
flow direction of the combustion gas 1. In this case, a gap is
formed between the partition portion 16 and a wall surface facing
the upstream side in the flow direction of the combustion gas
1.
[0047] According to this embodiment, it is possible to obtain the
following effects.
[0048] FIG. 5 is a graph where a length ratio is represented on a
horizontal axis in logarithmic scale, a value obtained by
subtracting 1 from an inlet-outlet area ratio is represented on a
vertical axis in logarithmic scale, and a pressure recovery rate
(reduction rate) Cp is used as a parameter, as for a diffuser. In
this case, if inlet-outlet area ratios are equal to each other, an
enlarged angle is smaller when a length ratio is larger. Further,
when a pressure recovery rate is high, separation hardly does
occur. A straight line, which is represented by a pressure recovery
rate Cp** of the drawing, is obtained by connecting points where
the maximum pressure recovery rate is obtained when an inlet-outlet
area ratio of a diffuser is constant. Meanwhile, a straight line of
Cp* is a line where the maximum pressure recovery rate is obtained
when a length ratio is constant. Accordingly, it is found out that
if an inlet-outlet area ratio is constant, when an enlarged angle
is small, a pressure recovery rate is high and separation hardly
does occur. If a passage of the diffuser is divided into two or
three equal parts, an enlarged angle of each of the small passages
becomes a half or a third and becomes smaller than an enlarged
angle determined by Cp*. For this reason, a high pressure recovery
rate is obtained over the entire passage.
[0049] Accordingly, according to this embodiment, if the film
cooling hole 14 includes the partition portion 16 formed as
described above, an effective area expansion ratio is suppressed.
Therefore, even though an enlarged angle of the enlarged portion
14b is increased in a transverse direction, the separation of the
cooling air 5 is suppressed. For this reason, since it is possible
to effectively diffuse the cooling air 5 as compared to the related
art, the enlarged angle of the enlarged portion 14b in the
transverse direction can be increased. Accordingly, it is possible
to spread the cooling air 5 thinly and broadly on the outer surface
12 of the structural wall 11, and to improve average film cooling
efficiency. In this case, the average film cooling efficiency is
given by (fuel gas temperature-surface temperature of structural
wall)/(combustion gas temperature-cooling air temperature).
[0050] Further, since it is possible to spread the cooling air 5
thinly and broadly on the outer surface 12 of the structural wall
11 as compared to the related art, the number of film cooling holes
14 formed at the structural wall 11 can be reduced. For this
reason, the number of processes for manufacturing the film cooling
structure 10 can be reduced. Further, as the number of film cooling
holes 14 is reduced, the amount of cooling air extracted from the
compressor of the gas turbine engine can be decreased. Therefore,
engine efficiency can be improved.
[0051] When the film cooling holes 14 are formed using a method
such as electric discharge machining, an electric discharge
machining electrode needs to be inserted into each of the divided
holes in order to form holes if the partition portion 16 completely
partitions the film cooling hole 14 in a transverse direction.
Further, if the partition portion 16 is formed in a shape that is
broken at a position in a thickness direction of the structural
wall 11, a plurality of processes is required to form one film
cooling hole 14 (for example, electric discharge machining
electrodes need to be inserted from the outer surface 12 and the
inner surface 13 in order to form the hole.) Furthermore, even
though other machining means is used, forming processes are
complicated likewise.
[0052] In contrast, in this embodiment, the partition portion 16
does not completely partition the film cooling hole 14 in the
transverse direction, and extends over the entire structural wall
11 in the thickness direction. Accordingly, if an electric
discharge machining electrode, which is formed to form the film
cooling hole 14 shown in FIGS. 3A to 3C and 4, is inserted from the
outer surface 12, it is possible to form the film cooling hole 14
by a single process. Therefore, it is easy to form the film cooling
hole 14.
[0053] Meanwhile, the embodiment of the invention has been
described above. However, the above-mentioned embodiment of the
invention is only illustrative, and the scope of the invention is
not limited to the embodiment of the invention. For example, the
invention has been applied to the turbine rotating blade 2 in the
above-mentioned embodiment, but may be applied to other components,
such as a combustor liner, a turbine nozzle vane, a turbine nozzle
band, a stationary turbine blade, a turbine shroud, and a turbine
outlet liner, which are disposed on a flow passage for combustion
gas in a gas turbine engine.
[0054] The scope of the invention is defined by the description of
claims, and includes all modifications that are in a meaning and a
scope equivalent to the description of claims.
* * * * *