U.S. patent application number 12/073620 was filed with the patent office on 2008-09-11 for turbine blade with micro-turbine nozzle provided in the blade root.
Invention is credited to Richard Whitton.
Application Number | 20080219855 12/073620 |
Document ID | / |
Family ID | 39544953 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080219855 |
Kind Code |
A1 |
Whitton; Richard |
September 11, 2008 |
Turbine blade with micro-turbine nozzle provided in the blade
root
Abstract
A turbine blade, in the blade root (2) of which a curved and
converging micro-turbine nozzle is provided, includes a passage
duct (6) with large diameter originating at a cooling-air chamber
(3) in the blade root, with a separately prefabricated
micro-turbine nozzle element (7) with minimized flow cross-section,
that is variably adaptable in size to the respective operating
conditions, being fitted into said passage duct (6). Due to the
reducible air mass flow that is adaptable to the actual
requirements in the space between the turbine rotor wheels, air
losses are reduced and efficiency is enhanced.
Inventors: |
Whitton; Richard; (Berlin,
DE) |
Correspondence
Address: |
Harbin King & Klima
500 Ninth Street SE
Washington
DC
20003
US
|
Family ID: |
39544953 |
Appl. No.: |
12/073620 |
Filed: |
March 7, 2008 |
Current U.S.
Class: |
416/97R |
Current CPC
Class: |
F01D 5/081 20130101;
F05D 2250/713 20130101; F05D 2220/40 20130101; F05D 2210/43
20130101; F05D 2250/232 20130101; F01D 5/087 20130101; F05D
2240/303 20130101; F05D 2230/238 20130101; F01D 5/048 20130101;
F01D 5/187 20130101; F05D 2250/141 20130101; F05D 2250/184
20130101; F05D 2240/81 20130101; F02C 7/18 20130101 |
Class at
Publication: |
416/97.R |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2007 |
DE |
10 2007 012 320.7 |
Claims
1. A turbine blade, comprising: an airfoil: a blade root connected
to the airfoil; a cooling air chamber positioned in the blade root
and connected between a cooling air supply and the airfoil; a
passage duct connected between the cooling air chamber and an
exterior of the blade to a space between turbine rotor wheels; a
separately prefabricated micro-turbine nozzle element having a
portion positioned in the passage duct and attached to the blade
root, the micro-turbine nozzle element having a duct for directing
cooling air flow from the cooling air chamber to the space between
the turbine rotor wheels in a direction opposite to a direction of
rotation of the turbine rotor wheels, the duct of the micro-turbine
nozzle element having a flow cross-section smaller than a flow
cross-section of the passage duct and which is selectable in size
depending on respective operating conditions.
2. The turbine blade of claim 1, wherein the prefabricated
micro-turbine nozzle element is attached to the blade root by a
joining process.
3. The turbine blade of claim 2, wherein the prefabricated
micro-turbine nozzle element is attached to the blade root by
brazing.
4. The turbine blade of claim 1, wherein the micro-turbine nozzle
element is a machined component fabricated from a non-machined but
shaped blank.
5. The turbine blade of claim 1, wherein the micro-turbine nozzle
element is injection molded.
6. The turbine blade of claim 1, wherein the passage duct is a cast
duct.
7. The turbine blade of claim 1, wherein the passage duct is a
drilled duct.
8. The turbine blade of claim 1, wherein the micro-turbine nozzle
element fits entirely within the passage duct.
9. A method for producing a turbine blade having an airfoil and a
blade root connected to the airfoil, comprising: forming a cooling
air chamber in the blade root and connected between a cooling air
supply and the airfoil; forming a passage duct connected between
the cooling air chamber and an exterior of the blade to a space
between turbine rotor wheels; separately fabricating a
micro-turbine nozzle element having a duct for directing cooling
air flow from the cooling air chamber to the space between the
turbine rotor wheels in a direction opposite to a direction of
rotation of the turbine rotor wheels, the duct of the micro-turbine
nozzle element having a flow cross-section smaller than a flow
cross-section of the passage duct; varying the flow cross-section
of the duct of the micro-turbine nozzle element depending on
respective operating conditions; positioning the micro-turbine
nozzle element so that at least a portion thereof is placed in the
passage duct; attaching the micro-turbine nozzle element to the
blade root.
10. The method of claim 9, wherein the micro-turbine nozzle element
is attached to the blade root by a joining process.
11. The method of claim 10, wherein the micro-turbine nozzle
element is attached to the blade root by brazing.
12. The method of claim 9, wherein the micro-turbine nozzle element
is fabricated in a cutting shaping process from a blank produced by
non-cutting shaping.
13. The method of claim 9, wherein the micro-turbine nozzle element
is injection molded.
14. The method of claim 9, wherein the passage duct is integrally
cast when casting the turbine blade.
15. The method of claim 9, wherein the passage duct is drilled into
the turbine blade.
16. The method of claim 9, wherein the micro-turbine nozzle element
is positioned entirely within the passage duct.
Description
[0001] This application claims priority to German Patent
Application DE 102007012320.7 filed Mar. 9, 2007, the entirety of
which is incorporated by reference herein.
[0002] This invention relates to a turbine blade having a curved
and converging micro-turbine nozzle in its blade root which
originates at a cooling-air chamber in the blade root and issues
downstream opposite to a direction of rotation of a turbine rotor
wheel.
[0003] On a gas-turbine engine known from specification U.S. Pat.
No. 6,290,464 B1, the blade roots of the turbine blades of the
turbine rotor wheel of the first stage are each provided with a
cooling-air duct which branches off a cooling-air chamber and
issues downstream and through which part of the cooling air fed
into the turbine blade is supplied to the next turbine stage. This
cooling-air duct, which originates at a cooling-air chamber in the
blade root, converges and continuously curves towards the air exit
side such that the cooling air exits opposite to the direction of
rotation of the turbine rotor wheel. Because of the curvature and
convergence of the cooling-air duct resulting in continuous
deflection of the cooling air opposite to the direction of rotation
of the rotor wheel and the expansion of the cooling air, the
cooling air produces power. The micro-turbine so provided in the
blade roots is an additional propulsive element for the first
turbine rotor wheel. Simultaneously, the cooling air is cooled
according to the turbine principle, thus being available with
improved cooling effect for the cooling of the turbine wheel of the
following turbine stage.
[0004] Manufacture of a cooling-air duct of such curvature and
convergence towards the air exit side in the blade roots is,
however, problematic in that the very slender and also brittle
ceramic cores applied in precision casting of turbine blades by the
lost-wax process for forming the very thin cooling-air ducts are
liable to failure, rendering manufacture by conventional precision
casting processes impossible. Also, manufacture of the converging
and curved cooling-air duct by cutting machining directly in the
blade root is only possible to a limited extent and confined to
larger diameters, especially as the smaller diameter is formed by
the exit opening. Directly in the blade root, the known casting and
mechanical machining processes are only appropriate for the
manufacture of cooling-air ducts with larger diameter. However,
such larger diameters will entail high cooling-air losses and
decrease the efficiency of the turbine. Disposing the micro-turbine
nozzles in turbine holding or cover plates, which is also proposed
in specification U.S. Pat. No. 6,290,464, is restricted to the
design provided for these plates. This bears on the efficiency of
the micro-turbine nozzles.
[0005] It is a broad aspect of the present invention to provide the
micro-turbine nozzle in the blade root such that small duct
cross-sections and, thus, low cooling-air losses and improved
engine efficiency can be obtained.
[0006] The essence of the present invention is that the turbine
blade does not form one part with the micro-turbine nozzle, but
that a passage duct with large diameter is formed in the area of
the blade root provided for the micro-turbine nozzle, which extends
from the cooling-air chamber to the downstream side of the blade
root, and that said passage duct is produced by drilling, machining
or integrally in the casting process, and that a separately
produced micro-turbine nozzle element is partly or also completely
fitted into this duct, has a converging nozzle with a cross-section
which is minimised in size and is flexible, i.e. is adapted to the
required operating conditions.
[0007] The known precision casting processes for the manufacture of
turbine blades whose blade root forms one integral part with the
micro-turbine nozzle, only allows large nozzle cross-sections which
affect the efficiency of the turbine. An essential advantage of the
turbine blade in accordance with the present invention lies in the
flexible cross-sectional size of the micro-turbine nozzle which is
adaptable to the respective operating conditions by way of a
separately produced micro-turbine nozzle element fitted into the
passage duct. Other than in the state of the art, the nozzle
cross-section is reducible, as a result of which an
efficiency-reducing decrease of the pressure of the cooling air
supplied is not necessary. The cooling-air mass flow introduced
into the space between the two turbine rotor wheels can be set as
low as necessary, thereby avoiding cooling air losses and a
reduction of turbine efficiency.
[0008] FIG. 1 shows a turbine blade with a micro-turbine nozzle
integrated into the blade root by way of a separately produced
component according to the present invention.
[0009] FIG. 1 shows a turbine blade 1 of the first turbine stage
with a cooling-air chamber 3 provided in the blade root 2, this
cooling-air chamber 3 being continuously supplied with cooling air
via an opening 4 in the blade root 2. While part of the cooling air
is used for cooling the airfoil 5, another part of the cooling air
flows, via the passage duct 6 branching off the cooling-air chamber
3 and through a duct 9 of a micro-turbine nozzle element 7 partly
integrated into the passage duct 6, into the space 8 between the
first and the second turbine stage and, from there, into the blade
root of the turbine blades of the second stage (not shown).
[0010] The turbine blades 1 are produced in a casting process,
actually with passage ducts 6 having a sufficiently large diameter.
With its correspondingly large diameter, the ceramic core for
casting the passage duct 6 will have adequate strength and will,
therefore, not be damaged or destroyed during casting. The passage
duct can also be produced by drilling the blade root. The
micro-turbine nozzle element 7 is a separate component which is
produced in a simple manner, for instance, in a cutting shaping
process from a blank which is formed by machining or in a
non-cutting shaping process, or by injection molding, or by other
methods, and is fitted completely or, as shown here, partly into
the passage duct 6 and attached therein by known joining processes,
such as brazing. The flow area of the duct 9 of the nozzle element
7 according to the present invention is no longer dictated by the
passage duct 6, and can be selectively varied as desired.
[0011] Besides reduced manufacturing cost, the now freely
selectable size of the flow area of the micro-turbine nozzle allows
the cooling air supply to the following turbine stage to be
optimally and variably set in accordance with the required
operating conditions, at least without unnecessary cooling air
losses.
LIST OF REFERENCE NUMERALS
[0012] 1 Turbine blade [0013] 2 Blade root [0014] 3 Cooling-air
chamber [0015] 4 Opening [0016] 5 Airfoil [0017] 6 Passage duct
[0018] 7 Micro-turbine nozzle element [0019] 8 Space between
turbine rotor wheels [0020] 9 Duct of nozzle element
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