U.S. patent application number 09/739283 was filed with the patent office on 2001-08-16 for drilled cooling air openings in gas turbine components.
Invention is credited to Haehnle, Hartmut, Weigand, Bernhard.
Application Number | 20010014282 09/739283 |
Document ID | / |
Family ID | 7934566 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014282 |
Kind Code |
A1 |
Haehnle, Hartmut ; et
al. |
August 16, 2001 |
Drilled cooling air openings in gas turbine components
Abstract
A blade component of a gas turbine is disclosed around the
outside of which hot air flows. The blade component is constructed
as a hollow profile having outside walls and a tip cover, and
having guiding walls arranged between the outside walls and
connecting said outside walls. The blade component is cooled on the
inside by cooling air flowing through cooling channels between the
outside walls and the guiding walls. Cooling air flows through
deflection areas in which the cooling air is deflected into flow
stagnation zones. An efficient cooling of the blade component in
the area of the stagnation zones is obtained in the area of the
flow stagnation zones which are located at the outer corner of the
deflection area. At least one drilled opening is provided in the
outside wall through which drilled opening cooling air is able to
flow at the stagnation zone from the cooling channel onto the
outside of the blade component.
Inventors: |
Haehnle, Hartmut;
(Kuessaberg, DE) ; Weigand, Bernhard;
(Filderstadt-Sielmingen, DE) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
7934566 |
Appl. No.: |
09/739283 |
Filed: |
December 19, 2000 |
Current U.S.
Class: |
415/115 ;
416/95 |
Current CPC
Class: |
F01D 5/186 20130101;
F01D 5/187 20130101; F05D 2260/202 20130101 |
Class at
Publication: |
415/115 ;
416/95 |
International
Class: |
B63H 001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 1999 |
DE |
199 63 099.2 |
Claims
What is claimed is:
1. A rotor blade for a gas turbine comprising: a hollow blade
having outside walls and a tip cover, and having first and second
internal guide walls arranged between the outside walls, said first
and second guide walls being spaced apart from each other and each
intersecting said tip cover, a central guide wall between the first
and second guide walls, said central guide wall being spaced from
said tip cover, thereby forming a cooling air passage extending in
sequence between the first guide wall and the central guide wall
and extending between the central guide wall and the tip cover and
extending between the central guide wall and the second guide wall,
the air cooling passage having flow stagnation zones adjacent the
intersection between the tip cover and the respective first and
second guide walls, and a plurality of openings in an outside wall
at at least one of said flow stagnation zones, whereby cooling air
is able to flow from the air cooling passage to the outside of the
blade to obtain a more efficient cooling effect.
2. The rotor blade as claimed in claim 1 wherein said openings are
drilled in the outside wall on the pressure side of the blade.
3. The rotor blade as claimed in claim 1 wherein said openings are
drilled in the outside wall on the suction side of the blade.
4. The rotor blade as claimed in claim 1 wherein said openings are
drilled in the tip cover and extend radially of the rotation axis
of the turbine rotor.
5. The rotor blade as claimed in claim 4 wherein the tip cover has
a tip extension on the outside of the tip cover adjacent said
openings in the tip cover.
6. The rotor blade as claimed in claim 1 wherein the openings are
cylindrical and extend perpendicular to the outside wall, the
openings being spaced apart from each other by at least one
diameter of the openings, and being arranged in rows, the openings
being spaced at least 5 diameters of the openings from the tip
cover and the openings being located adjacent the second guide
wall.
7. The rotor blade as claimed in claim 6 wherein the openings
include a conical portion adjacent the outside of one of the
outside walls.
8. The rotor blade as claimed in claim 1 wherein a guide rib is
mounted in the hollow blade between the central guide wall and the
tip cover.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the field of gas turbines and more
specifically to components in gas turbines that are exposed to hot
gases.
BACKGROUND OF THE INVENTION
[0002] The degree of efficiency of gas turbines depends to a
special degree on an efficient use of cooling air. Both operational
safety and the assurance of a justifiable life span of the
components heated during operation make adequate cooling
indispensable. Accordingly, there has always been a concentration
on optimizing the cooling of gas turbines.
[0003] Components that are surrounded by a flow of hot gases during
the operation of the gas turbine, and thus must be cooled
appropriately, can be cooled in several ways. On the one hand, it
is possible to provide a so-called film cooling, in which cooling
air is in a targeted manner passed around the outside surface of
the component. On the other hand, a so-called internal cooling can
be achieved, whereby the component has cooling channels inside,
through which a flow takes place. The internal cooling presupposes
that the components are hollow profiles or are at least provided
with channels, and that the latter permit good heat transfer from
the outside material parts to the cooling air. These two cooling
methods are frequently used in combination, since, on the one hand,
the internal cooling is only possible in areas where the thickness
of the material of the component permits construction as a hollow
profile or the attachment of drilled channel openings, and since,
on the other hand, an effective film cooling requires good
distribution of the cooling air on the outside surfaces. Effective
film cooling is only possible in the case of larger surfaces, a
strong flow, and, if possible, a low cooling air volume, if the
cooling air is supplied at least in part via internal cooling
channels.
[0004] When constructing such components as hollow profiles, a
problem that occurs frequently is that the channels have areas in
which the cooling air is deflected, resulting in so-called flow
stagnation areas in which the flow becomes distinctly
three-dimensional, and in which the cooling then becomes less
efficient (so-called "dead water areas"). Such flow stagnation
areas in most cases result necessarily from the geometric
parameters of the components and channels on the one hand, and, on
the other hand, from the fact that a design of the cooling channels
that would guide the flow in an optimal way, especially in the
deflection areas, would require rounded areas in the corners. But
such massive rounded areas, i.e. constructed by filling them with
material, would however cause the corners to become heavier, which
means that moving components, such as turbine blades, would become
less economical and deflection areas and bends in such corners
would be cooled even less well. The formation of such flow
stagnation areas is often counteracted by integrating ribs or guide
plates that specifically supply and remove the cooling air to/from
such areas, but such means are often not sufficient to make cooling
in the deflection areas efficient enough.
SUMMARY OF THE INVENTION
[0005] The invention therefore is based on the objective of
providing a component for gas turbines that has internal cooling,
in which during operation of the gas turbine, i.e. while hot air
flows around the component, and while cooling air simultaneously
flows through the component, efficient cooling is made possible in
the deflection areas of the cooling air.
[0006] This objective is achieved by an arrangement of drilled
openings in the flow stagnation zones on the outflow sides of the
deflection areas so that these zones are no longer actual dead
water areas. The drilled openings provided there cause a flow
through the zones and thus have the result that the cooling air is
not retained too long in these zones. The cooling efficiency in
these areas improves according to the reduced staying time of the
cooling air in the flow stagnation zones. The cooling air flowing
out of the drilled opening or openings onto the outside, then can
simultaneously still be utilized for film cooling on the outside of
the component if the drilled opening has been located at a suitable
place. The drilled opening or openings can preferably be located on
the pressure side in the outside wall facing the flowing air. The
exiting cooling air in this way flows around the outside surface to
the suction side of the component and acts not only as a
ventilation of the flow stagnation zones but also as a film cooling
along the path around the component on the suction side.
[0007] A preferred embodiment of the invention includes a turbine
blade around which a hot working air stream flows. The guide walls
in the turbine blade are arranged essentially radially of the
rotation axis of the turbine rotor and essentially vertically to
the plane of the turbine blade outside surface between the outside
walls. The radially extending cooling channels formed in this way
are connected in pairs at the tip of the turbine blade in a flow
connection; and that in this connection a deflection area of the
cooling channels is arranged in the area of the tip. Especially in
components designed in this way, the problem of cooling is
manifested particularly in the deflection areas. The tips of the
turbine blades are exposed to a high mechanical and thermal load
during operation, and without sufficient cooling a severe fatigue
and wear of the materials in the tip area can hardly be prevented.
On the other hand, the geometry of the tips is more or less
determined by the function of the blades, and the design of the
channels therefore must adapt to it. Especially in the deflection
area of the cooling channels that are supplied with cooling air
from the hub area, and through which the cooling air flows in a
U-shape, significant stagnation zones form; but their cooling
efficiency-reducing effect can be prevented or at least greatly
reduced by drilled openings.
[0008] The arrangement of the drilled openings in the flow
stagnation zone on the outflow side is found to be particularly
advantageous in combination with, for example, drilled openings
arranged on the inflow side and extending essentially radially to
the rotation axis of the turbine motor through a tip cover that
closes off the hollow profile of the component radially.
[0009] These radial drilled openings can also be arranged in an
approximate L-shape, i.e. both next to each other, parallel to the
tip cover, as well as next to each other, radially along the rear
guide wall, around the corner on the outflow side. A group of
drilled openings arranged in a two-dimensional, for example
triangular, shape that covers an area of the stagnation zone and,
for example, in a way connects the two legs of the L's with each
other, can also be advantageous.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A preferred embodiment of the invention is illustrated in
the drawing, in which:
[0011] FIG. 1 is a cross-sectional view of a turbine blade
essentially tangential in relation to the rotor axis;
[0012] FIG. 2 is a cross-sectional view of the turbine blade along
the line Y-Y in FIG. 1; and
[0013] FIG. 3 is a cross-sectional view of the turbine blade along
the line X-X in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0014] FIG. 1 shows a section, essentially tangential in relation
to the rotor axis of the turbine rotor, through a turbine blade 10
constructed as a hollow profile. A hot working air stream 11 blows
against the rotor blade 10 on the pressure side, setting this rotor
blade into motion. The outside shape of the blade 10 is formed by
the outside wall 12 on the pressure side, the outside wall 13
facing away from the air flow on the suction side, and a tip cover
21 (FIGS. 2 and 3) that forms the radially outside border of the
blade 10. The walls 12, 13, and 21 are connected via guide walls
14, 15, and 16 that extend radially in relation to the rotor axis
and vertically in relation to the rotor blade plane with each
other. These guide walls not only stabilize the blade but also
simultaneously act as guide walls for the cooling air 17, 18
flowing through the hollow profile. Normally, the cooling air 17 is
blown from the hub side into a cooling channel 19 with ascending
ventilation and is guided to the tip. Each tip is provided with a
break-through to an adjoining cooling channel 20, through which the
cooling air 18 is again passed after a 180.degree. deflection in
zone 22 radially in the direction towards the hub. In this way,
pairs of channels 19 and 20 are connected with each other in
accordance with the flow, and the cooling air is able to either
consecutively flow through the pairs inside blade 10 in the manner
of a meander or can be supplied individually.
[0015] The cooling channels can be provided with ribs 23 or
baffles, which, for the purpose of better heat transfer between the
housing--i.e. the walls 12-16 and 21--and the cooling air, either
force the latter, for example in a meander shape, so that it will
impact the walls, or enable an optimum flow even in deflection
areas. The blade 10 also can be provided additionally with
independent means or means following the internal cooling for a
film cooling of the outside (not shown in FIG. 1).
[0016] When the cooling air 17 is deflected at the tip of the
blade, this will in most cases result in flow stagnation zones at
the corners of the deflection area. One of these occurs mostly on
the side of the incoming flow 29, i.e. at the corner at the inlet
into the deflection area 22, and another one on the outflow side
30, at the corner at the outlet of deflection area. The cooling
medium remains longer in zones 29 and 30 than in other areas, and a
less efficient heat exchange takes place. Guide ribs 23 that guide
the cooling medium in a specific manner also are not able to really
prevent such dead water areas, and the guide walls 14 and 15,
outside walls 12 and 13, as well as the tip cover 21 are heated
more in these zones than at other places.
[0017] In order to better ventilate the zone 30 on the inflow side,
a drilled opening 25, for example, can be provided in the tip cover
21, and radially ventilate the cooling channel there. It is useful
that this drilled opening 25 merges into an outside recess in the
tip cover 21.
[0018] In order to better ventilate the zone 30 on the outflow side
(or, if applicable, analogously on the inflow side), drilled
openings 24 are now provided in the outside wall 12 on the pressure
side. These drilled openings 24 result in a flow of cooling air
through the bores onto the outside. On the outside, the cooling air
27 then flows around the tip of the blade onto the suction side of
the rotor and hereby cools the tip in the manner of a film cooling.
The tip of the rotor blade hereby can be constructed either in a
simple manner or may be provided with, for example, rib extensions
26 at the tip for a seal between the rotor and the housing.
Especially in the latter case, the additional film cooling effect
may turn out to be particularly advantageous. Naturally, the
drilled openings 24 also can be provided on the suction side of the
blade 10, but the advantageous film cooling effect is hereby
essentially eliminated.
[0019] The drilled openings 24 can be arranged parallel to the
direction of the tip cover 21, next to each other in a row or
offset from each other, and/or analogously parallel to the rear
guide wall 15. It was found that in particular the row of drilled
openings parallel to the guide wall 15, i.e. essentially radial to
the axis of the rotor, was effective for ventilating the flow
stagnation zones. The drilled openings 24, as shown in FIG. 2), can
be arranged in an L-shaped row or two-dimensionally, i.e. in
several rows arranged next to each other so as to ventilate an
entire area. The area may hereby have a triangular shape, i.e.
connect the legs of the above L-shaped arrangement, or may cover
another area on the outside wall relative to the flow stagnation
zone.
[0020] These drilled openings can be constructed cylindrically or
so as to be flared towards the outside, the latter in particular
for those extending radially and not located directly at the tip
cover (see extension 28), i.e. in a sort of tube shape, in order to
ensure improved flow behavior. The drilled openings may extend
vertically to the plane of the blade 10, but can also be drilled at
an angle, slightly radial towards the outside. The drilled holes
may have different or identical diameters. To prevent obstructions,
at least one large drilled opening may also be provided. The
drilled openings should be spaced apart from each other by at least
one opening diameter, and a first row of drilled openings 24 should
be arranged not more than five opening diameters from the tip cover
21 in respect to the rear guide wall 15.
* * * * *