U.S. patent application number 11/497094 was filed with the patent office on 2008-02-07 for airfoil with customized convective cooling.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to Matthew A. Devore, Corneil S. Paauwe.
Application Number | 20080031739 11/497094 |
Document ID | / |
Family ID | 38457756 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080031739 |
Kind Code |
A1 |
Devore; Matthew A. ; et
al. |
February 7, 2008 |
Airfoil with customized convective cooling
Abstract
An airfoil suitable for use in the turbine section of a jet
engine. Said airfoil contains a core having a passage for
conducting a coolant through said airfoil and discharging the
coolant through a radially disposed slot at the trailing edge of
the airfoil. A flow barrier is mounted adjacent to the discharge
slot within the flow passage which contains openings for tailoring
the coolant flow distribution profile in the trailing edge region
based upon some identifiable airfoil property such as the airfoil's
pressure and/or temperature profile, or a combination of the
pressure and temperature profiles.
Inventors: |
Devore; Matthew A.;
(Manchester, CT) ; Paauwe; Corneil S.;
(Manchester, CT) |
Correspondence
Address: |
MARJAMA MULDOON BLASIAK & SULLIVAN LLP
250 SOUTH CLINTON STREET, SUITE 300
SYRACUSE
NY
13202
US
|
Assignee: |
United Technologies
Corporation
|
Family ID: |
38457756 |
Appl. No.: |
11/497094 |
Filed: |
August 1, 2006 |
Current U.S.
Class: |
416/97R |
Current CPC
Class: |
F01D 5/28 20130101; F05D
2240/122 20130101; Y02T 50/60 20130101; F05D 2240/304 20130101;
F01D 5/188 20130101; Y02T 50/676 20130101 |
Class at
Publication: |
416/97.R |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0001] The United States Government has certain rights in this
invention pursuant to Contract No. N00019-02-C-3003 between the
United States Navy and United Technologies Corporation.
Claims
1. An airfoil having a core containing passage for conducting a
coolant through the airfoil and discharging the coolant through a
slot extending radially along the trailing edge of the airfoil,
wherein said airfoil further includes: a flow barrier mounted
adjacent to said slot for presenting blockage to coolant moving
through the trailing edge region of the airflow; and said flow
barrier having openings therein for tailoring the coolant trailing
edge flow profile along the radial span of the airfoil.
2. The airfoil of claim 1, wherein said barrier is fabricated of
the same material as the airfoil core.
3. The airfoil of claim 1, wherein said barrier is fabricated of a
material that is different from the core material.
4. The airfoil of claim 1, wherein said barrier is constructed of a
ceramic material.
5. The airfoil of claim 1, wherein the barrier is constructed of a
material containing a refractory metal.
6. The airfoil of claim 1, wherein said coolant is air.
7. The airfoil of claim 1, wherein the coolant trailing edge flow
profile is based upon the pressure profile along the radial span of
the airfoil.
8. The airfoil of claim 1, wherein the coolant trailing edge flow
profile is based upon the temperature profile along the radial span
of the airfoil.
9. The airfoil of claim 1, wherein said barrier contains a
plurality of spaced apart cylindrical pedestals that are mounted
perpendicularly to the coolant trailing edge flow.
10. The airfoil of claim 9, wherein the coolant flow profile is
generated by varying the gap between the adjacent pedestals.
11. The airfoil of claim 9, wherein the coolant flow profile is
generated by varying the pedestal diameters.
12. The airfoil of claim 1, wherein the coolant trailing edge flow
profile is based upon both the pressure profile and the temperature
profile along the radial span of the blade.
13. The airfoil of claim 1, wherein said barrier is at least one
wall that is mounted adjacent to the trailing edge slot, said wall
containing holes passing there through for tailoring the trailing
edge flow distribution profile of the coolant.
14. The airflow of claim 13, wherein the coolant flow profile is
generated by varying the size or shape of said openings.
Description
FIELD OF THE INVENTION
[0002] This invention relates to the internal cooling of an airfoil
employed in a rotary machine and, in particular, to controlled
internal cooling of a jet engine turbine blade. Background of the
Invention
[0003] The term airfoil, as herein used, refers to either a rotor
blade or a stator vane of the type employed in many types of rotary
machine such as gas turbines, compressors, and the like. In the
case of a jet engine turbine blade, for example, a coolant is
typically introduced into the core of the blade through the blade
root and is circulated through a core passage and finally
discharged through a radially extended window or slotted opening
located along the trailing edge of the airfoil. As disclosed in
U.S. Pat. No. 6,637,500 to Shah et al., pedestals fabricated of
core materials are placed in the coolant flow passage near the
discharge slot to meter flow, augment the flow, provide convective
surface area and provide additional strength in this area. The
pedestals are generally spaced apart at the same distance and the
coolant flow at the trailing edge of the blade is generally uniform
over the radial span of the blade.
SUMMARY OF THE INVENTION
[0004] It is therefore an object of this invention to improve the
internal convective cooling of an airfoil employed in a rotary
machine.
[0005] It is a further object of the present invention to improve
the internal convective cooling of a turbine blade utilized in a
jet engine.
[0006] A still further object of the present invention is to tailor
the flow profile of a coolant moving through the core of an airfoil
to provide controlled cooling to regions of the airfoil which
require more or less cooling.
[0007] Another object of the present invention is to contour the
trailing edge flow of a cooling that is moving internally through
an airfoil with particular regard to the temperature or pressure
profile over the span of the airfoil or a combination of the
two.
[0008] These and other objects of the invention are attained by
means of an airfoil having an internal flow passage for routing a
coolant through the core of the airfoil and discharging the coolant
through a slot or window radially extended along the trailing edge
of the airfoil. In the practice of the present invention, the
trailing edge flow is governed by the pressure ratio over the
trailing edge of the airfoil and a control barrier that is placed
in the edge flow to selectively distribute the flow over the radial
span of the airfoil in response to some identifiable characteristic
of the airfoil such as the radial pressure or temperature profile
of the airfoil or both.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] For a better understanding of these and other objects of the
invention, reference will be made to the following detailed
description of the invention, which is to be read in association
with the following drawings, wherein:
[0010] FIG. 1 is a side elevation in section illustrating the
component parts of a jet engine;
[0011] FIG. 2 is an enlarged partial view showing a turbine vane
located in the first stage of the turbine section of the
engine;
[0012] FIG. 3 is an enlarged sectional view taken along lines 3-3
in FIG. 2;
[0013] FIG. 4 is a partial sectional view taken along line 4-4 in
FIG. 3 illustrating a plurality of pedestals mounted within the
trailing edge flow region of the airfoil which are placed in the
coolant flow path to control the distribution of flow within the
airflow;
[0014] FIG. 5 is an enlarged top view illustrating the spacing
between a pair of adjacent pedestals;
[0015] FIG. 6 is a chart illustrating a typical trailing edge
pressure profile over the radial span of an airfoil;
[0016] FIG. 7 is a chart illustrating a typical temperature profile
over the radial span of an airfoil;
[0017] FIG. 8 is a diagram illustrating how blockages within a base
line system can be employed to vary the flow distribution through
an airfoil;
[0018] FIG. 9 is a graphic illustration in which the trailing edge
flow of a base line system is plotted against pressure ratio.
[0019] FIG. 10 is a graphic illustration in which the trailing edge
Mach number of a base line system is plotted against pressure
ratio; and
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring initially to FIG. 1, there is shown the main
components of a jet engine, generally referenced 10 in schematic
outline. The engine includes a diffuser section 12 having a conical
inlet 13 in which RAM air is initially compressed and then passed
on to an axial compressor 14 by means of a fan 16 located at the
entrance to the compressor. Compressed air from the last stage of
the compressor is fed into a series of combustion chambers, one or
which is depicted as 17, where the compressed air is mixed with
fuel and is ignited. Gases from the combustors are passed on to the
turbine section of the engine 18 where the hot gases are expanded.
The turbine section of the engine is coupled directly to the
compressor by a common shaft 19. The power developed in the turbine
is thus utilized to drive the compressor and other auxiliary engine
components. Gases leaving the turbine are further expanded in the
exhaust nozzle 20 of the engine and are ejected at a velocity
greater than the flight velocity to product thrust.
[0021] FIG. 2 is an enlarged view of an airfoil 23 located in the
first stage of the turbine, which is exposed to gases from the
combustion chamber that are at relatively high temperatures and
pressures. Accordingly, airfoil cooling in this region is at a
premium. FIG. 3 is a section taken through the airfoil further
illustrating the internal construction of the airfoil. The airfoil
includes a core fabricated of any type of material or materials as
presently known and used in the art. These materials may include
but are not limited to ceramics, refractory metals, or a
combination of the two materials. A pair of interconnected radially
disposed passages 25 and 26 are provided in the core that are
connected to a coolant entrance located in the root of the airfoil.
Typically, coolant is air that is bled from the compressor section
of the engine. The coolant, however, may be any fluid that is known
and used in the art for providing convection type cooling to an
airfoil surfaces.
[0022] With further reference to FIG. 4, the coolant flow conducted
through passage 26 is discharged from the airfoil via a radially
extended slot or window 27 located along the trailing edge of the
airfoil. As noted above, the trailing edge flow is governed by the
pressure ratio over the trailing edge of the airfoil and the amount
of blockage that is present within the trailing edge flow
region.
[0023] Blockage is the ratio of closed to open areas within the
flow path in the trailing edge region. The external discharge
pressure can vary significantly along the radial span of the
airfoil, and as a result, the flow field along the trailing edge
will be non-uniform where the blockage in the trailing edge region
is relatively constant. The heat loading upon the airfoil can also
vary significantly along the radial span. Accordingly, the amount
of convective cooling required at various span locations will vary
with respect to the temperature and pressure trailing edge profiles
of the airfoil. Additionally, the amount of convective cooling
potential, as a function of mass flow rates at various span
locations, will vary with respect to the external trailing edge
pressure profile. Typical pressure and temperature profiles are
depicted in FIGS. 6 and 7.
[0024] With further reference to FIGS. 3 and 4, the trailing edge
flow distribution profile is contoured in this embodiment of the
invention by placing a barrier in the flow path within the trailing
edge region. The barrier is arranged to provide a blockage to flow
that is tailored to control the coolant flow distribution based
upon either the pressure profile or temperature profile of the
airfoil or a combination of both. The trailing edge flow is
tailored to provide more or less convection to certain regions of
the airfoil.
[0025] In this embodiment of the invention, banks of cylindrical
pedestals 50-50 that are fabricated of the core material extend
perpendicularly across the trailing edge flow path adjacent to the
discharge window or slots. As illustrated in FIG. 5, the amount of
blockage can be varied by altering the gap between adjacent
pedestals or by changing the diameters of the pedestals. By varying
the amount of blockage in various regions over the radial span of
the airfoil, the trailing edge flow distribution profile can be
tailored in regard to either the pressure or the temperature
profiles of the airfoil, or a combination of both. Blockage is
minimized in regions where more convective heat transfer is
required and maximized in regions where less convective heat
transfer is needed. Although true in the design used for FIG. 5,
this may not be applicable for applications where pressure drop is
managed differently and/or the design relies heavily on fin
conduction effects.
[0026] The profile of the trailing edge flow is tailored in the
embodiment of the invention such that internal convection levels
result in metal temperatures which meet oxidation, creep, and
thermal mechanical fatigue life requirements. Conversely, the flow
distribution may be varied to reduce convection so that coolant
heatup along a passage is minimized, and thus allowing for more
available heat flux potential in downstream regions.
[0027] Although cylindrical pedestals are employed in this
embodiment of the invention to establish blockage within the
trailing edge flow, any type of barrier may be used in the practice
of the invention which serves to tailor the flow distribution into
a desired profile. For example, a wall or a series of walls can be
erected in the discharge flow path having openings of various sizes
and/or shapes located within the wall which serve to tailor the
flow distribution into a desired profile. Here again, the barrier
or barriers may be fabricated of any known core material.
[0028] As illustrated in FIGS. 5 and 8, the design of a basic
pedestal system without flow control that has thirty-five percent
blockage can be modified by varying either the pitch between
pedestals and/or the diameter of the pedestals to vary the amount
of blockage over the span of the airfoil and thus control the
coolant flow distribution within the airfoil. Using the pedestal
feature size to increase the gap size between pedestals will reduce
the susceptibility of the trailing edge of the airfoil to become
placed with dirt or the like. This method of increasing blockage in
selected regions thus allows the core to better withstand the
stresses involved in the casting processes.
[0029] Customizing of the above noted basic system provides for
trailing edge flow reduction and Mach number benefits. As
illustrated in FIG. 9, the customization of the trailing edge
features allow for a net reduction in cooling air. This reduction
in cooling air increases engine performance by reducing pressure
and enthalpy losses associated with coolant being introduced into
engine pass flow stream. As illustrated in FIG. 10, the
customization of the trailing edge flow further allow for a net
increase in the cooling air exit Mach number. This increase in Mach
number results in more effective mixing of the coolant with the
gases in the engine flow stream and thus serves to further increase
engine performance.
[0030] While this invention has been particularly shown and
described with reference to the preferred embodiment in the
drawings, it will be understood by one skilled in the art that
various changes in its details may be effected therein without
departing from the teachings of the invention.
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