U.S. patent application number 12/185593 was filed with the patent office on 2009-02-12 for turbine blade with internal cooling structure.
This patent application is currently assigned to ALSTOM TECHNOLOGY LTD. Invention is credited to Alexander Khanin, Maxim Konter, Anton Sumin, Sergey Vorontsov.
Application Number | 20090041587 12/185593 |
Document ID | / |
Family ID | 38805662 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090041587 |
Kind Code |
A1 |
Konter; Maxim ; et
al. |
February 12, 2009 |
TURBINE BLADE WITH INTERNAL COOLING STRUCTURE
Abstract
A rotating blade (1) for a gas turbine comprises an internal
cooling structure having at least three cooling air passages (5, 6,
7) in fluid connection with one another by turns (9, 10). An
opening (12) provides an outlet for dissolved core material to be
removed from the blade following casting of the cooling structure
without any residue remaining within. According to the invention,
the cooling structure comprises trip strips (13, 15) in the first
and second passage (5, 6) with specified ratio of height to
distance between trip strips and the trip strips (13) in the first
passage being arranged at 90.degree. with respect to the direction
of airflow. In a particular embodiment, the trip strips (15) in the
second passage (6) are arranged at angle of 45.degree.. The design
according to the invention assures sufficient airflow through first
and second air passages (5, 6).
Inventors: |
Konter; Maxim; (Klingnau,
CH) ; Sumin; Anton; (Moscow, RU) ; Vorontsov;
Sergey; (Moscow, RU) ; Khanin; Alexander;
(Moscow, RU) |
Correspondence
Address: |
Volpe and Koenig, P.C.;Dept. Alstom
30 South 17th Street, United Plaza, Suite 1600
Philadelphia
PA
19103
US
|
Assignee: |
ALSTOM TECHNOLOGY LTD
Baden
CH
|
Family ID: |
38805662 |
Appl. No.: |
12/185593 |
Filed: |
August 4, 2008 |
Current U.S.
Class: |
416/97R ;
415/115 |
Current CPC
Class: |
F05D 2260/2212 20130101;
F05D 2230/211 20130101; F01D 5/187 20130101; F05D 2250/313
20130101; F05D 2260/22141 20130101 |
Class at
Publication: |
416/97.R ;
415/115 |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2007 |
EP |
07113996.8 |
Claims
1. A rotating blade (1) for a gas turbine comprising a blade root
(2), a blade tip (3) and an internal cooling structure, the
internal cooling structure comprising: a first cooling air passage
(5) extending generally in the longitudinal direction of the blade
from a plenum (4) in the blade root (2) to the blade tip (3), a
second cooling air passage (6) extending from the blade tip (3) to
the blade root (2) and a third cooling air passage (7) extending
from the blade root (2) to the blade tip (3), the first passage (5)
being in fluid connection with the second passage (6) by a first
turn (9) and the second passage (6) being in fluid connection with
the third passage (7) by a second turn (10), and an opening (12)
extending from the second turn (10) to the plenum (4) providing a
direct outlet for fluids from the blade, the first and second
cooling air passages (5, 6) each comprising a plurality of trip
strips (13, 15), the trip strips (13) in the first cooling passage
(5) being arranged at an angle (.alpha.) of
90.degree..+-.10.degree. to a direction of cooling fluid flow in
the first passage (5), the trip strips (15) in the second passage
(6) being arranged at an angle (.beta.) of 45.degree..+-.10.degree.
in relation to the cooling fluid flow direction, and the trip
strips (13, 15) in the first and second passages (5, 6) have a
height (h) and a distance (d) between adjacent trip strips (13,
15), the ratio between the height (h) and the distance (d) being
10.+-.2.
2. The rotating blade (1) according to claim 1, wherein the third
passage (7) comprises a plurality of trip strips (17) arranged at
an angle (.delta.) of 45.degree..+-.10.degree..
Description
FIELD OF INVENTION
[0001] The present invention relates to cast rotating blades for a
gas turbine, and in particular to the design of an internal cooling
structure within the blade in view of blade manufacturability.
BACKGROUND
[0002] Turbine blades for gas turbines are designed and
manufactured to withstand high temperatures during the gas turbine
operation. Such turbine blades comprise an internal cooling
structure through which a cooling fluid, typically air, is passed.
Cooling air is typically bled from a compressor of the gas turbine
engine. This extraction of air however, reduces the overall
performance of the engine. In order to minimize the effect on
engine performance by minimizing the air consumption and yet assure
sufficient cooling of the blade, the internal blade cooling
structure is designed for optimal cooling efficiency. Such designs
are disclosed for example in U.S. Pat. No. 6,139,269 and U.S. Pat.
No. 5,403,159. U.S. Pat. No. 6,139,269 discloses a serpentine
cooling structure having several passages extending in the blade
longitudinal direction and connecting to either an inlet opening at
the blade root, to an outlet opening at the blade tip, or to a
further longitudinal passage by a turn or bend of approximately
180.degree.. The cooling structure furthermore comprises on the
walls of the longitudinal passages a multitude of trip strips,
oriented at approximately 45.degree. to the direction of flow
through the passage. The particular construction in U.S. Pat. No.
6,139,269 comprises furthermore at each 180.degree.-turn near the
blade root an air re-supply passage allowing air to enter into the
passage from the blade root.
[0003] Turbine blades with internal cooling structure of this type
are cast, as a rule, by an investment casting process using a core
defining the cooling structure. The core is made of a leachable
material such as ceramic. Following the molding process, the
ceramic core is removed by a leaching process.
[0004] The leaching process is difficult in regard to the removal
of core material in the region of the 180.degree.-turns, and a risk
remains that residual core material stays behind in the blade
cooling channels and thus obstructing the flow of cooling media
through the cooling passage. In order to reduce this risk, an
opening is provided in the cooling structure wall in the region of
the 180.degree. turn for remaining core material to leach out. In
some known gas turbine blades, this opening is again closed by a
plate or plug as disclosed for example in U.S. Pat. No.
6,634,858.
SUMMARY
[0005] The invention relates to a rotating blade for a gas turbine.
The rotating blade includes a blade root, a blade tip and an
internal cooling structure. The internal cooling structure includes
a first cooling air passage extending generally in the longitudinal
direction of the blade from a plenum in the blade root to the blade
tip. The internal cooling structure also includes a second cooling
air passage extending from the blade tip to the blade root and a
third cooling air passage extending from the blade root to the
blade tip. The first passage is in fluid connection with the second
passage by a first turn and the second passage being in fluid
connection with the third passage by a second turn. Further, the
internal cooling structure includes an opening extending from the
second turn to the plenum providing a direct outlet for fluids from
the blade. The first and second cooling air passages each include a
plurality of trip strips. The trip strips in the first cooling
passage are arranged at an angle of 90.degree..+-.10.degree. to a
direction of cooling fluid flow in the first passage. The trip
strips in the second passage are arranged at an angle of
45.degree..+-.10.degree. in relation to the cooling fluid flow
direction. Finally, the trip strips in the first and second
passages have a height and a distance between adjacent trip strips,
the ratio between the height and the distance being 10.+-.2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 shows a side view of an exemplary gas turbine blade,
to which the invention may be applied;
[0007] FIG. 2 shows a cross-sectional view of the blade of FIG. 1
along II-II showing the internal blade cooling structure according
to the invention;
[0008] FIGS. 3a and 3b show respectively, a cross-section of the
trip strips along IIIa-IIIa in FIG. 2 and the trip strips in
detail, in particular the arrangement and relative dimensions of
turbulators in the first cooling passage of the blade cooling
structure;
[0009] FIGS. 3c and 3d show respectively, a cross-section of the
trip strips along IIIc-IIIc in FIG. 2 and the trip strips in
detail, in particular the arrangement and relative dimensions of
turbulators in the second cooling passage of the blade cooling
structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Introduction to the Embodiments
[0010] The invention is directed to a gas turbine rotating blade
with an internal cooling structure having a design that allows
improved manufacturability over those of the state of the art while
at least maintaining the existing cooling performance of the
internal cooling structure.
[0011] A gas turbine rotating blade comprises an internal cooling
structure having at least three cooling passages extending in the
blade longitudinal direction, at least one inlet opening in the
region of the blade root, and at least one outlet opening in the
region of the blade tip leading from a cooling passage out of the
blade. The blade furthermore comprises in its root region a plenum
for cooling air, the inlet opening extending from this plenum to a
cooling passage. The first cooling passage extends, in the
direction of cooling fluid, from the blade root region to the blade
tip region. The second cooling passage extends from the tip to the
root region. First and second cooling passages are in fluid
connection with one another in the region of the blade tip by a
bend or turn in the region of the blade tip. The third cooling
passage again extends from the root to the tip, while second and
third cooling passages are in fluid connection with one another by
a turn or bend in the region of the blade root. In order for a core
material to be removed from the bend by leaching out with a reduced
risk of core material remaining in the bend, an opening is provided
in the cooling structure wall extending from the plenum to the bend
or turn in the blade root region from the second to the third
cooling passage. The opening provides a direct fluid connection
from the bend to the root of the blade and to the exterior of the
blade. In particular, the opening and root region of the blade is
such that a liquid fluid is allowed to flow directly and generally
in the longitudinal blade direction out of the blade internal
cooling structure. This allows the fluid core material to exit the
blade completely without having to pass through any back turns or
dead zones. Thus, it is prevented that fluid core material remains
in the structure as residual fluid. The flow of cooling air through
the internal cooling structure when the blade is in operation is
thus assured.
[0012] For purposes of simplified and thus cost efficient
manufacture of the gas turbine rotating blade, the opening at the
bend or 180.degree. turn of the internal structure is not closed up
again prior to the operation of the blade in the turbine. Since
said opening at the 180.degree. turn has an effect on the
aerodynamics of the internal cooling structure and distribution of
the cooling air, the design of the cooling passages is adapted and
optimized accordingly in view of cooling function and
efficiency.
[0013] According to the invention, the first cooling passage
extending, in the direction of cooling fluid from the plenum in the
root region to the tip region of the blade, comprises a plurality
of turbulators or trip strips arranged at an angle of
90.degree..+-.10.degree. to the direction of flow of the cooling
fluid. Additionally, the second cooling passage, in fluid
connection with the first cooling passage by a turn, comprises a
plurality of trip strips or turbulators. Finally, in combination
with the specific orientation of the trip strips in the first
cooling passage, the trip strips in the first and second cooling
passages are arranged and dimensioned such that the ratio between
their height and the distance between adjacent trip strips is
10.+-.2.
[0014] In an exemplary embodiment of the invention, the trip strips
in the second cooling passage are arranged at an angle of
45.degree..+-.10.degree. in relation to the flow direction. In a
further exemplary embodiment, the third cooling passage comprises a
plurality of trip strips arranged at an angle of
45.degree..+-.10.degree. from the direction of flow to the
direction of the trip strip.
[0015] As mentioned above, the opening at the turn from the second
to the third passage affects the cooling air distribution in the
cooling structure. In particular, a non-plugged opening at that
location would result in a reduction of the airflow from the plenum
in the root region through the first and second passage and an
increase of airflow from the plenum through the opening directly to
the third passage. The design measures according to the invention
in the form of a particular arrangement of trip strips in the first
and second passage allow an optimization of the cooling airflow and
re-establishment of the airflow through the first and second
passage. It thereby assures sufficient and uniform cooling of the
entire blade. The design of the trip strips according to the
invention allows compensation of very small hydraulic pressure
losses from the beginning of the first passage to the beginning of
the third passage. Compensation of the low-pressure losses is
achieved by pumping forces in the first and second passages due to
a convective temperature increase of the cooling air along these
passages.
[0016] The flow dynamics of the cooling air are elaborated in
connection with the following figures.
[0017] As mentioned above, the design of the blade cooling
structure according to the invention allows for optimized
manufacturing due to the opening provided in the turn near the root
of the blade. The design requires no measures following the casting
for closing of the opening. The specific design of the trips strips
in the cooling passages compensates for hydraulic pressure losses
and thereby assures sufficient cooling within the first and second
passages. The design therefore allows improved and simplified
manufacturing while maintaining cooling performance.
DETAILED DESCRIPTION
[0018] FIG. 1 shows a rotating gas turbine blade 1 extending
longitudinally from a root 2 to a tip section 3.
[0019] FIG. 2 shows the internal cooling structure of the blade
having a plenum 4 within the root region for cooling air entering
the cooling structure, a plurality of at least three longitudinal
cooling passages 5, 6, 7 extending from the plenum 4 at the root 2
to the tip 3 and from the tip 3 to the root 2 respectively. The
longitudinal passages are in fluid connection with one another by
turns of approximately 180.degree..
[0020] The airflow passes, as indicated by arrows, from the plenum
4 through an inlet opening 8 at the beginning of the first cooling
passage 5 to the end of the first passage at the tip of the blade,
and around a turn 9 of approximately 180.degree.. It then flows
along the second cooling passage 6 to a further 180.degree.-turn 10
connecting the second cooling passage 6 with the third cooling
passage 7. The cooling air finally flows through the third cooling
passage 7 to the tip of the blade and exits the cooling structure
through the outlet opening 11 at the tip of the blade.
[0021] At the turn 10 near the root of the blade, an opening or
channel 12 is provided for leaching out core material after casting
and allowing all of the dissolved core material to run out of the
cooling structure via the plenum 4 such that no core material
remains in the turn 10. Due to this opening 12, cooling air could
pass more readily from the plenum 4 directly to the third cooling
passage 7 rather than through first and second cooling passages 5
and 6. However, due to the particular design of the first and
second cooling passages according to the invention, the pressure
drop between position A and position B is such that a cooling
airflow is assured through passages 5 and 6.
[0022] A pressure loss is due to hydraulic resistance and depends
on the square of the air velocity, the shape of the channel, the
degree of smoothness of the passage walls as well as the shape of
turbulators or trip strips. All these features according to the
invention result in that the air pressure at position B at the
beginning of the third passage 7 is lower than at position A at the
beginning of the first passage 5.
[0023] Additionally, a pumping effect occurs due to the rotation of
the blade. Due to the pumping effect the air pressure increases
with increasing radius of the passage, specifically in proportion
to the difference of the squares of the radii at a given angular
speed. In the first passage 5 therefore, the pressure increases
with increasing radius from position A to position B. In the second
passage 6, the pressure decreases with decreasing radius from
position B to position C, decreasing by the same magnitude as it
increased in passage 5. The final effect would therefore be zero.
Additionally however, a heat flux is picked up by the cooling air
from the heat convective walls of the passages increasing the
temperature of the cooling air. As a result, the temperature of the
cooling air in the second passage 6 is higher than in the first
passage 5. This temperature change also affects the pumping effect
in the first and second passages. The higher temperature in the
second passage results in that the pumping effect along the second
passage 6 is smaller than in the first passage 5. Therefore, the
pressure at position B is lower compared to that at position A,
resulting in an effective cooling airflow along passages 5 and
6.
[0024] As mentioned above, the hydraulic resistance of a cooling
passage depends from, among others, on the design of the passage,
in particular the design of the turbulators or trip strips 13. FIG.
2 shows an embodiment of the invention comprising in the first
cooling passage 5 turbulators or trip strips 13 arranged at
90.degree..+-.10.degree. in relation to the direction of cooling
flow, as indicated by the arrow. FIG. 3a shows in cross-section the
arrangement and relative dimensions of the trip strips. Each trip
strips has a height h measured from the wall 14 of the passage 5,
and each trip strip 13 is arranged at a distance d from the
adjacent trip strip. The height h and distance d are at a ratio of
10.+-.2. The trip strips are shown having a rectangular shape.
However, they can be of any other aerodynamically suitable
cross-sectional shape as well. FIG. 3b shows the orientation of the
trip strips in relation to the direction of cooling air flow. The
angle a is 90.degree..+-.10.degree..
[0025] FIG. 2 further shows the second cooling passage 6 having
trip strips 15. Similarly as in passage 5, the trip strips 15 in
passage 6 are designed having a height h measured from the wall 16
of the passage 6 and distance d between them such that the ratio of
height h to distance d is 10.+-.2, as shown in FIG. 3c. Height h is
measured from the wall of the passage, and distance d is measured
between adjacent trip strips along the direction of cooling
airflow.
[0026] The trip strips 15 in cooling passage 6 as shown in FIG. 2
are at a greater distance from each other compared to the distance
between adjacent trip strips 13 in passage 5. However, the
essential design features of cooling passages in order to assure a
sufficient cooling air flow through passages 5 and 6 include the
specific orientation of the trip strips in passage 5 and the ratio
of height h to distance d between adjacent trip strips of 10.+-.2
for both passages 5 and 6.
[0027] A further design feature, which enhances the effect includes
the specific orientation of the trip strips in passage 6. The trip
strips are arranged at an inclination angle .beta. of
45.degree..+-.10.degree. in relation to the direction of airflow,
as shown in FIG. 3d. The angle is measured in counter-clockwise
direction from the direction of the trip strips to the direction of
airflow.
[0028] The third passage 7, can also have turbulators 17 of any
design in order to enhance cooling efficiency along that passage.
In the exemplary embodiment shown, they are arranged at an
inclination angle .delta. to the direction of airflow, the angle
being 45.degree..+-.10.degree. in relation to the direction of
airflow.
Terms Used in Figures
[0029] 1 rotating blade [0030] 2 blade root [0031] 3 blade tip
[0032] 4 plenum for cooling air [0033] 5 first cooling air passage
[0034] 6 second cooling air passage [0035] 7 third cooling air
passage [0036] 8 inlet opening [0037] 9 turn [0038] 10 turn [0039]
11 outlet opening [0040] 12 outlet opening for core material [0041]
13 trip strips in first passage [0042] 14 cooling passage wall
[0043] 15 trip strips in second passage [0044] 16 wall of second
cooling passage [0045] 17 trip strips in third passage [0046] h
trip strip height [0047] d distance between adjacent trip strips
[0048] .alpha. orientation angle of trip strips 13 [0049] .beta.
orientation angle of trip strips 15 [0050] .delta. orientation
angle of trip strips 17 [0051] A position at beginning of cooling
passage 5 [0052] B position at end of cooling passage 5 [0053] C
position at bend from second passage 6 to third passage 7
* * * * *