U.S. patent application number 09/835426 was filed with the patent office on 2002-10-17 for thin walled cooled hollow tip shroud.
Invention is credited to Balkcum, J. Tyson III, Liang, George, Przirembel, Hans R., Remley, Timothy J., Williams, Christopher Charles.
Application Number | 20020150474 09/835426 |
Document ID | / |
Family ID | 25269479 |
Filed Date | 2002-10-17 |
United States Patent
Application |
20020150474 |
Kind Code |
A1 |
Balkcum, J. Tyson III ; et
al. |
October 17, 2002 |
Thin walled cooled hollow tip shroud
Abstract
The present invention relates to a lightweight shrouded turbine
blade. The turbine blade comprises an airfoil section and a hollow
blade tip shroud joined to the airfoil section. The hollow tip
shroud is preferably a cast, compartmentalized structure and has a
plurality of ribs acting as load bearing structures and defining a
plurality of shroud core sections. Each of the shroud core sections
communicates with a supply of cooling fluid and has a plurality of
apertures for supplying cooling fluid to exterior portions of the
shroud.
Inventors: |
Balkcum, J. Tyson III;
(Taylors, SC) ; Liang, George; (Palm City, FL)
; Remley, Timothy J.; (Jupiter, FL) ; Williams,
Christopher Charles; (Lake Worth, FL) ; Przirembel,
Hans R.; (Monterey, TN) |
Correspondence
Address: |
Barry L. Kelmachter
BACHMAN & LaPOINTE, P.C.
900 Chapel Street, Suite 1201
New Haven
CT
06510-2802
US
|
Family ID: |
25269479 |
Appl. No.: |
09/835426 |
Filed: |
April 16, 2001 |
Current U.S.
Class: |
416/97R ;
416/191; 416/192 |
Current CPC
Class: |
F05D 2260/201 20130101;
F05D 2260/203 20130101; F01D 5/225 20130101; F01D 5/186 20130101;
F05D 2240/81 20130101; F05D 2260/202 20130101; F05D 2230/21
20130101 |
Class at
Publication: |
416/97.00R ;
416/191; 416/192 |
International
Class: |
F01D 005/18 |
Claims
What is claimed is:
1. A shrouded turbine blade comprising an airfoil section and a
hollow blade tip shroud joined to said airfoil section.
2. A shrouded turbine blade according to claim 1, wherein said
hollow blade tip shroud is a cast, compartmentalized structure.
3. A shrouded turbine blade according to claim 1, wherein said
hollow blade tip shroud has a plurality of ribs acting as load
bearing structures and defining a plurality of hollow shroud core
sections.
4. A shrouded turbine blade according to claim 3, further
comprising means for supplying cooling fluid to each of said shroud
core sections and each of said shroud core sections having at least
one aperture for allowing said cooling fluid to flow over an
exterior portion of said shroud.
5. A shrouded turbine blade according to claim 4, wherein each of
said shroud core sections has a plurality of apertures in a density
sufficient to create a desired cooling effect.
6. A shrouded turbine blade according to claim 4, wherein said
cooling fluid supplying means comprises means for supplying cooling
air to said shroud core sections.
7. A shrouded turbine blade according to claim 4, further
comprising said airfoil having a plurality of hollow airfoil core
sections through which said cooling flows and each of said shroud
core sections communicating with a respective one of said airfoil
core sections via at least one metering hole.
8. A shrouded turbine blade according to claim 1, further
comprising an airfoil to shroud fillet for reducing stress
concentration.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a lightweight shrouded
turbine blade for use in gas turbines having a thin walled cooled
hollow tip shroud.
[0002] The use of shrouded gas turbine blades is known in the art.
In these blades, the tip shroud of each blade is formed from a
solid construction. As a result, the blades are quite heavy.
Further, cooling of the tip shroud is very difficult.
SUMMARY OF THE INVENTION
[0003] It is an object of the present invention to provide a
hollow, lightweight shrouded turbine blade.
[0004] It is a further object of the present invention to provide a
turbine blade as above having an improved system for cooling the
tip shroud.
[0005] The foregoing objects are attained by the shrouded turbine
blade of the present invention.
[0006] In accordance with the present invention, a shrouded turbine
blade comprises an airfoil section and a cored, hollow blade tip
shroud joined to the airfoil section. The hollow tip shroud is
preferably a cast structure and has a plurality of ribs acting as
load bearing structures and defining a plurality of shroud core
sections. Each of the shroud core sections communicates with a
supply of cooling fluid and has a plurality of apertures for
supplying cooling fluid to exterior portions of the shroud.
[0007] Other details of the lightweight shrouded turbine blade of
the present invention, as well as other objects and advantages
attendant thereto, are set forth in the following detailed
description and the accompanying drawings wherein like reference
numerals depict like elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a sectional view of a turbine blade in accordance
with the present invention having a hollow tip shroud; and
[0009] FIG. 2 is a sectional view of a hollow tip shroud taken
along line 2-2 in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0010] Referring now to the drawings, FIG. 1 illustrates a shrouded
turbine blade 10 in accordance with the present invention. The
turbine blade 10 has a root portion 12, a platform 14, an airfoil
section 16, and a hollow tip shroud 18 adjacent an end of the
airfoil section 16. The airfoil section 16 has a plurality of
cooling holes 20 by which a cooling fluid, such as air, is fed over
surfaces of the airfoil section to cool same. The shroud 18 is
preferably a cast, compartmentalized structure.
[0011] As can be seen from FIGS. 1 and 2, a plurality of ribs 22
extend within the airfoil section 16 of the turbine blade 10 to the
hollow tip shroud 18. The ribs 22 form a plurality of hollow
airfoil core sections 24, 26, 28, 30, and 32. Each of the hollow
core sections 24, 26, 28, 30, and 32 communicates with a passageway
34 through which cooling fluid flows from a source of cooling fluid
(not shown). Each of the airfoil core sections 24, 26, 28, 30, and
32 acts as a cooling passageway and communicates with its own set
of cooling holes 20. Some of the cooling fluid passing through the
core sections 24, 26, 28, 30, and 32 exits via the cooling holes
20, while the remaining portion of the cooling fluid is transmitted
to the hollow tip shroud 18.
[0012] Referring now to FIG. 2, the hollow tip shroud 18 has a
compartmentalized structure in which a plurality of ribs 40 form a
plurality of hollow shroud core sections or compartments 42, 44,
46, 48, 50, and 52. The ribs 40 act as load bearing structures.
[0013] Each of the shroud core sections 42, 44, 46, 48, 50, and 52
is in fluid communication with one of the airfoil core sections 24,
26, 28, 30, and 32 via at least one metering hole. For example,
shroud core sections 42 and 44 communicate with airfoil core
section 24 via metering holes 54 and 56. Similarly, shroud core
section 46 communicates with airfoil core section 26 via metering
hole 58, shroud core section 48 communicates with airfoil core
section 28 via metering hole 60, shroud core section 50
communicates with airfoil core section 30 via metering hole 62, and
shroud core section 52 communicates with airfoil core section 32
via metering hole 64.
[0014] While the present invention has been illustrated with just
one metering hole between a respective shroud core section and an
airfoil core section, it should be recognized that more than one
metering hole can be used to place a respective shroud core section
in fluid communication with a respective airfoil core section.
Further, the amount of cooling fluid delivered from each respective
airfoil core section to each respective shroud core section can be
regulated by controlling the size and/or the density of the
metering hole(s).
[0015] As can be seen from FIG. 2, each shroud core section is
provided with a plurality of apertures or cooling holes 66. The
size, shape, and density of the apertures or cooling holes 66 in
each shroud core section may be varied to achieve one or more
desired exterior surface cooling effects. For example, the
apertures or cooling holes 66 may be designed to perform cooling of
exterior portions of the shroud 18 by film, transpiration,
localized impingement, and convection techniques. It can be said
that the shroud core sections allow a great deal of cooling design
flexibility.
[0016] The turbine blade design of the present invention provides
numerous advantages. For example, the hollow tip shroud 18 is very
efficient and provides the same strength as solid tip shrouds at a
lower weight penalty. The reduced weight of the shroud 18 permits a
lower stage airfoil count which leads to lower cost and a more
robust blade. The rib geometry through the hollow shroud 18 act as
load bearing structures that take the place of the traditional
solid shroud geometry. Still further, because of the hollow shroud
structure, the airfoil to shroud fillet 68 can be increased to
reduce stress concentration with no increase in weight.
[0017] The localized compartments or shroud core sections in the
shroud provide cooling design flexibility. Local airfoil and shroud
metal temperatures can be tailored to the engine thermal
environment by (1) a redistribution of coolant flow in each shroud
core section or compartment, or (2) a change in metering hole size
and/or density. Additionally, the cooling chamber
compartmentalization provided by the shroud core sections minimizes
the coolant flow demand that would normally be required by the
large gas side pressure gradient. Still further, the
compartmentalization in the shroud allows different compartments to
be pressurized at different pressures and also allows cooling fluid
to flow into and out of the compartments at different rates. The
ribs forming the compartments prevent a continuous flow of fluid
from the leading edge to the trailing edge of the shroud.
[0018] Other benefits provided by the present invention are that
the shroud contact face 70 cooling through the cooling holes 66 in
core sections 46 and 48 can be tailored and optimized for specific
hardface materials, which is highly desirable since temperature
drives a material's wear and extrusion characteristics. When used,
film hole sizes in one or more of the shroud core sections are 40%
smaller in diameter than plugging hole size limits. This is
possible because cooling fluid exiting to the flowpath is
contamination free due to particle centrifugation. The smaller film
holes reduce overall cooling flow while maintaining cooling
effectiveness.
[0019] Transpiration cooling may be utilized with the hollow shroud
structure of the present invention to overcome the highly
fluctuating velocity and pressure gradients existing on the hot
flowpath side of the tip shroud. This cooling approach provides a
very high cooling capacity and eliminates the need for extensive
backside convection. This, in turn, simplifies the cooling
configuration and reduces the shroud weight and subsequent airfoil
load. The shroud structure of the present invention operates in a
cooling fluid purged pocket behind a vane platform and
attachment.
[0020] As can be seen from the foregoing discussion, there has been
provided a lightweight shrouded turbine blade 10 that is cooled
sufficiently to survive excessive turbine temperatures.
[0021] It is apparent that there has been provided in accordance
with the present invention a thin walled cooled hollow tip shroud
which fully satisfies the objects, means and advantages set forth
hereinbefore. While the present invention has been described in the
context of specific embodiments thereof, other variations,
alternatives, and modifications will become apparent to those
skilled in the art having read the foregoing description.
Accordingly, it is intended to embrace those variations,
alternatives, and modifications which fall within the broad scope
of the appended claims.
* * * * *