U.S. patent application number 11/858333 was filed with the patent office on 2009-03-26 for method for making a composite airfoil.
This patent application is currently assigned to General Electric Company. Invention is credited to Joseph L. Moroso, Thomas R. Tipton.
Application Number | 20090077802 11/858333 |
Document ID | / |
Family ID | 40384618 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090077802 |
Kind Code |
A1 |
Moroso; Joseph L. ; et
al. |
March 26, 2009 |
METHOD FOR MAKING A COMPOSITE AIRFOIL
Abstract
A method of manufacturing a composite airfoil includes the step
of providing a core made of a metal or ceramic material. A plastic
airfoil portion is molded to envelope at least a portion of the
core.
Inventors: |
Moroso; Joseph L.;
(Greenville, SC) ; Tipton; Thomas R.; (Greer,
SC) |
Correspondence
Address: |
GE ENERGY GENERAL ELECTRIC;C/O ERNEST G. CUSICK
ONE RIVER ROAD, BLD. 43, ROOM 225
SCHENECTADY
NY
12345
US
|
Assignee: |
General Electric Company
|
Family ID: |
40384618 |
Appl. No.: |
11/858333 |
Filed: |
September 20, 2007 |
Current U.S.
Class: |
29/889.71 ;
264/271.1; 264/313 |
Current CPC
Class: |
B29C 2045/14327
20130101; B29L 2031/7504 20130101; F05D 2300/603 20130101; B29K
2705/00 20130101; B29C 70/70 20130101; B29C 45/14311 20130101; F04D
29/388 20130101; Y10T 29/49337 20150115; F04D 29/324 20130101; Y02T
50/60 20130101; F01D 5/147 20130101; F05D 2300/21 20130101; Y02T
50/672 20130101; B29C 45/14778 20130101; F05D 2300/43 20130101;
Y02T 50/673 20130101; F05D 2260/95 20130101; B29C 70/72 20130101;
F04D 29/023 20130101 |
Class at
Publication: |
29/889.71 ;
264/271.1; 264/313 |
International
Class: |
B21D 53/78 20060101
B21D053/78; B21K 3/04 20060101 B21K003/04 |
Claims
1. A method of manufacturing a composite airfoil, the method
comprising the steps of: providing a core made of a metal or
ceramic material; and molding a plastic airfoil portion to envelope
at least a portion of the core.
2. The method of claim 1 further including the step of providing at
least one opening in the core and the molding step includes filling
the at least one opening with the plastic material of the airfoil
portion to retain the airfoil portion in a position relative to the
core.
3. The method of claim 1 wherein the core is provided with a
leading edge and the molding step comprises injection molding the
airfoil portion to envelope the leading edge of the core.
4. The method of claim 1 wherein the molding step comprises
injection molding the airfoil portion to completely envelope the
core.
5. The method of claim 4 wherein the injection molding step
includes the step of providing a final shape and finish to the
airfoil portion.
6. The method of claim 1 wherein the providing step comprises
providing a metal core by a process selected from die casting,
investment casting and forging.
7. A method of manufacturing a composite airfoil, the method
comprising the steps of: providing a core made of a metal or
ceramic material, the core provided with a leading edge; and
molding a plastic airfoil portion to envelope at least the leading
edge of the core.
8. The method of claim 7 further including the step of providing at
least one opening in the core and the molding step includes filling
the at least one opening with the plastic material of the airfoil
portion to retain the airfoil portion in a position relative to the
core.
9. The method of claim 7 wherein the molding step comprises
injection molding the airfoil portion.
10. The method of claim 7 wherein the molding step comprises
injection molding the airfoil portion to completely envelope the
core.
11. The method of claim 10 wherein the injection molding step
includes the step of providing a final shape and finish to the
airfoil portion.
12. The method of claim 7 wherein the providing step comprises
providing a metal core by a process selected from die casting,
investment casting and forging.
13. A method of manufacturing a composite airfoil, the method
comprising the steps of: forming a metal core by die casting,
investment casting or forging; and injection molding a plastic
airfoil portion to envelope at least a portion of the core.
14. The method of claim 13 further including the step of forming at
least one opening in the core and the injection molding step
includes filling the at least one opening with the plastic material
of the airfoil portion to retain the airfoil portion in a position
relative to the core.
15. The method of claim 13 wherein the core is provided with a
leading edge and the injection molding step comprises enveloping
the leading edge of the core with plastic material.
16. The method of claim 13 wherein the injection molding step
comprises completely enveloping the core.
17. The method of claim 13 wherein the injection molding step
includes the step of providing a final shape and finish to the
airfoil portion.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to turbo-machinery. In
particular, the invention relates to making a turbo-machine airfoil
with components of different materials.
[0002] Turbo-machinery may take many forms or be applied in various
uses. These forms and uses may include steam turbines for power
generation, gas turbines for power generation, gas turbines for
aircraft propulsion and wind turbines for power generation.
[0003] In a gas turbine, typically there are numerous rotating
blades and stationary vanes. The blades and vanes are arranged in
alternating circumferential arrays that are spaced longitudinally
along the turbine. Each of the blades and vanes includes an airfoil
portion attached to a mounting portion.
[0004] A conventional gas or stream turbine blade or vane design
typically has its airfoil portion made entirely of an alloy of a
metal, such as titanium, aluminum or stainless steel. The
conventional gas or steam turbine compressor blade or vane design
may also be made entirely of a composite, such as fiber reinforced
plastic. The all-metal blades are relatively heavy in weight that
can result in lower fuel economy and require robust mounting
portions. In a gas turbine application, the lighter all-composite
blades are susceptible to damage and wear from foreign object
ingestion.
[0005] Known hybrid blades include a composite airfoil portion
having a metal leading edge to protect the airfoil from wear and
impact from foreign object ingestion. The gas turbine first stage
blades typically are the largest and the heaviest blades and are
generally the first to be subject to foreign object ingestion.
Composite blades have typically been used in turbine applications
where weight is a major concern.
[0006] On a typical gas turbine compressor airfoil, the overall
geometry is a compromise between structural and aerodynamic needs.
Structural needs and ability to withstand damage due to foreign
object ingestion are in direct conflict with airfoil geometry
optimized for aerodynamic performance. For example, an
aerodynamically desirable airfoil is relatively thin with a
relatively sharp leading edge. Whereas, a structurally desirable
airfoil is relatively thick with a robust leading edge. The final
design is typically a compromise between the opposing structural
and aerodynamic needs with neither being optimum.
[0007] Current manufacturing processes for an all-metal airfoil
requires milling and hand polishing of the airfoil to achieve the
desired geometry. The polishing operation is labor intensive to
achieve critical airfoil dimensions and surface finish. This
requires usage of materials that are easily machined and polished
to minimize cost. This typically restricts material selection and
increases the cost of manufacturing.
[0008] During operation of a gas turbine for power generation, dirt
and debris accumulate on the airfoil surface resulting in a loss of
designed performance. Water washing is typically used to remove
this accumulated dirt and debris. Such washing may erode and
corrode the metal material of the airfoil. Compressor tip
clearances are typically not optimized to preclude the chance of
rotor blade tips rubbing on the case or stator blade tips rubbing
on the rotor.
[0009] Accordingly, there is a need for an improved turbine airfoil
for a gas turbine blade that is lighter in weight than an all-metal
airfoil, possesses desirable structural and aerodynamic properties,
withstands foreign objects ingestion, be cost effective and resist
erosion and corrosion.
SUMMARY
[0010] A method of manufacturing a composite airfoil according to
one aspect of the invention includes the step of providing a core
made of a metal or ceramic material. A plastic airfoil portion is
molded to envelope at least a portion of the core.
[0011] Another aspect of the invention is a method of manufacturing
a composite airfoil. The method includes the step of providing a
core made of a metal or ceramic material. The core is provided with
a leading edge. A plastic airfoil portion is molded to envelope at
least the leading edge of the core.
[0012] Another aspect of the invention is a method of manufacturing
a composite airfoil. The method includes the step of forming a
metal core by die casting, investment casting or forging. A plastic
airfoil portion is injection molded to envelope at least a portion
of the core.
DRAWINGS
[0013] These and other features, aspects, and advantages of the
invention will be better understood when the following description
is read with reference to the accompanying drawings, in which:
[0014] FIG. 1 is a perspective illustration of a composite airfoil
according to one aspect of the invention, with an internal
component represented by dashed fines;
[0015] FIG. 2 is an exploded view of the composite airfoil
illustrated in FIG. 1; and
[0016] FIG. 3 is a cross-sectional view of the composite airfoil of
FIG. 1, taken approximately along line 3-3 in FIG. 1.
DETAILED DESCRIPTION
[0017] A composite airfoil 20 is illustrated in FIG. 1 as a part of
a blade 10 for a gas turbine used in a power generation
application, according to one aspect of the invention. It will be
appreciated that the composite airfoil 20 of the blade 10, in
various aspects of the invention, may be in the form of a
compressor blade, vane or turbine blade and may be used in steam
turbine, gas turbine or wind turbine applications. The composite
airfoil 20 of the blade 10, according to one aspect, includes a
core 22 and a plastic airfoil portion 24 completely enveloping and
encapsulating the core.
[0018] The composite airfoil 20 is made from at least two different
materials in a unique manner. As used herein, "composite" is
defined as having a plastic material form the finished airfoil
portion 24 located over a relatively strong structural material
that (such as, metal or ceramic) forms the core 22. The term
"plastic" is defined to mean capable of being melted at a
temperature relatively lower than the melting point of the material
of the core 22 so it can flow and easily be molded to a final
desired shape.
[0019] A root 26 is attached to the core 22 and is used to mount
the blade to turbine structure for operation. The root 26 can be
attached to the core by forming the core and root integrally as a
one-piece subcomponent, such as by forging or machining from a
single piece of raw material, such as metal or ceramic.
Alternatively the core 22 and root 26 could be made separately and
the core could be fastened, welded or otherwise attached to the
root. A tip 40 is located at the axially opposite end of the
composite airfoil 20 from the root 26. An axis A extends in a
direction along the length of the composite airfoil 20 from the
root 26 to the tip 40. As used herein, "axis" A refers to reference
axis and not a physical part of the blade 10 or composite airfoil
20.
[0020] The blade 10 and composite airfoil 20 are a designed to
operate at the typical temperature that the first few stages of a
turbine compressor would be exposed to according to one aspect of
the invention. In a gas turbine application for power generation
the "design operating temperature" is the maximum temperature the
blade 10 and airfoil portion 24 is expected to experience during
normal operation in the first few stages in a compressor. An
example of a typical gas turbine design operating temperature in
the first few stages is, without limitation, generally in the range
of 18.degree. C. to 200.degree. C.
[0021] Medium direction arrows M in (FIG. 3) indicate the general
direction of flow. The medium M typically comprises air in a gas
turbine application. The medium M in a gas turbine power generation
application is typically controlled. Specifically, the medium M is
inlet air filtered to remove many of the foreign objects, can be
chilled or heated to a desired temperature range and routed through
structure to remove moisture and salt.
[0022] In a compressor blade application of a gas turbine for the
composite airfoil 20, the root 26 typically includes a dovetail
portion 42 (FIGS. 1-2), to mount the blade 10 to a rotor disc (not
shown). The airfoil portion 24 has a leading edge 44 (FIG. 3) and a
trailing edge 46. The direction of medium M flow is generally from
the leading edge 44 to the trailing edge 46. The airfoil portion 24
of the composite airfoil 20 also has a pressure side surface 62 and
a suction side surface 64.
[0023] The airfoil portion 24 is a very complex surface defined by
a series of points at sections spaced along the axis A. The leading
edge 44 and trailing edge 46 are typically round surfaces defined
by relatively small radii according to one aspect of the invention.
The complex surface, leading edge 44 and trailing edge 46 are
relatively difficult to manufacture. For aerodynamic reasons, it is
generally desirable to have a leading edge 44 with as small of a
radius as possible, for example 0.010 inch which has not been
practical previously. It is also desirable to have an extremely
smooth and precise final shape for the airfoil portion 24 that does
require machinery polishing or coating, which also has not been
practical previously. Being able to injection mold a plastic
airfoil portion 24 to a final or near-final shape overcomes
previous disadvantages.
[0024] Preferably, the airfoil portion completely envelopes the
core 22. In one aspect of the invention, the composite airfoil 20
is the plastic airfoil portion 24 enveloping at least a portion of
the metal or ceramic core 22. It will be apparent, however, that
the core 22 does not have to be completely enveloped by the airfoil
portion 24 and that the core may be partially covered according to
another aspect of the invention. The plastic airfoil portion 24 is
molded without the need for fiber reinforcement, preferably
injection molded, onto at least a portion of the core 22. The
injection molding process is capable of forming precise and
accurate parts of the airfoil portion 24, such as the pressure side
surface 62, suction side surface 64, leading edge 44 and trailing
edge 46.
[0025] With the multi-piece design the internal geometry of the
blade 10 in the form of the core 22 can be optimized for frequency
tuning and structural needs. The external surface can be tailored
for aerodynamic performance in the form of the injection molded
plastic airfoil portion 24.
[0026] In an exemplary aspect the core 22 has a plurality of
openings 82 extending through it between the pressure side surface
62 and suction side surface 64 of the airfoil portion 24. The
openings 82 are located in areas of the core 22 that do not need a
continuous solid structure for strength or function. The openings
82 lighten the core 22 for lower rotating mass which is generally a
desirable feature. The openings 82 receive a portion 84 of the
plastic material of the airfoil portion 24 during the injection
molding process to retain the airfoil portion in place relative to
the core 22. The openings 82 do not have to extend completely
through the core 22 but have a depth sufficient to receive portion
84 of the plastic material. The portion 84 of plastic material does
not have to completely fill the opening 82 but extend a sufficient
distance in to the opening to retain the airfoil portion 24 in
place relative to the core 22.
[0027] The core 22 has a tip portion 100 (FIG. 2). The core 22 has
a leading edge 102 (FIGS. 2 and 3) and a trailing edge 104. The tip
28 of the airfoil portion envelopes the tip portion 100 of the core
22. The airfoil portion 24 envelopes at least the leading edge 102
of the core 22 and preferably the entire outer surface of the core
including the trailing edge 104. The airfoil portion 24 has a
thickness t (FIG. 3) at a location spaced away from the openings 82
such as in the range of 0.020 to 0.100 inch to where it covers the
core 22 away from the openings 82. The thickness to does not have
to be uniform. The thickness t may gradually increase from one or
both edges 44, 46 towards the middle of the blade 10. The depth of
the opening 82 is preferably greater than the thickness t of the
airfoil portion 24 covering the core 22.
[0028] By creating the airfoil portion 24 from plastic, desired
final airfoil shape for aerodynamic performance can be incorporated
and preferably without the need form machinery, polishing or
coating. Since the airfoil portion 24 is separated from the
internal load carrying structure of the core 22 a design that is
more tolerant to damage from ingested debris is also possible. This
separation of load carrying structure of the core 22 from the
airfoil portion 24 also increases the number of material options
available for manufacturing the core to maximize structural
features and minimizing weight.
[0029] By disassociating the structural and aerodynamic components
of the design of the blade 10, a number of cost savings
opportunities arise. Tight manufacturing tolerances are no longer
required on the internal load carrying structure that now permits
the usage of nickel or ceramic materials for the core 22. The
materials with higher modulii can provide similar stiffness with
less mass reducing the overall weight of the blade 10. This also
opens up the potential for investment casting, die casting or
forging of the core 22 with limited machining. Injection molding
the plastic airfoil portion 24 to provide the final aerodynamic
shape can eliminate the entire hand polishing operation of previous
all-metal blade configurations. Injection molding the plastic
airfoil portion 24 also yields a very consistent airfoil shape with
an excellent surface finish eliminating the need for any surface
treatments after polishing.
[0030] Creating a smooth surface for the plastic airfoil portion 24
from injection molding will reduce accumulation of debris on the
blade 10. This reduces the need for as frequent water washes. The
material for the plastic airfoil portion 24 is inherently corrosion
resistant. Additionally, additives such as PTFE can be introduced
into the airfoil portion 24 to further enhance the repelling of the
accumulation of debris on the airfoil portion.
[0031] By injection molding the tip 28 of the plastic airfoil
portion 24 the clearances relative to other turbine components can
be held tighter. In the event the plastic nibs against another
turbine component, it is a benign event and does not compromise the
structural components of the blade 10 or turbine. With the
composite airfoil 20 compressor clearances can be held tighter for
improved performance without the need of abradable surfaces or the
introduction of rub compliant coating.
[0032] The technical advantages are numerous. The composite airfoil
20 provides the opportunity to create more damage tolerant and
optimized airfoil portion 24 and a structurally optimized core 22.
Additionally the opportunity to optimize aerodynamic geometry of
the airfoil portion 24 results in increased performance of the gas
turbine. Reduction of compressor fouling of the airfoil portion 24
reduces the level of performance degradation. There are also
significant opportunities to reduce manufacturing costs.
[0033] The composite airfoil 20 of the blade 10, thus, provides an
optimal aerodynamic shape with the injection molded plastic airfoil
portion 24 and desired structural characteristics with the core 22.
The plastic material of the airfoil portion 24 may be any suitable
plastic material. The plastic material is selected to be able to
survive the design operating temperature of the particular stage of
the turbine that it is selected to operate in. For example, the
first stage of a gas turbine compressor operates at ambient air
temperatures and at relatively low pressures compared to other
later stages of the compressor.
[0034] The blade 10 can be manufactured according to another aspect
of the invention. The blade 10 is made with the composite airfoil
20 by first forming the metal core 22 by die casting, investment
casting or forging. The core 22 may also be made from a ceramic
material cast to final shape. The core 22 is formed with the root
26 and dovetail portion 42 in its final configuration.
[0035] The core 22 is then supported in a die 120 (FIG. 4) of an
injection molding apparatus (not shown). The die 120 of the
injection molding apparatus has a desired shape of half of the
airfoil formed in the die with allowances for shrinkage and
warping. The core 22 is supported in a predetermined position
within the die, as illustrated in FIG. 5. Locator pins 140 in the
die 120 assist in properly locating the core 22 in a predetermined
position relative to the airfoil shape. A vent 122 extends from the
interior of the die to the outside. The root 26 may be located
outside of the die 120 and have a surface that engages the die to
locate the core 22 axially relative to the die.
[0036] A second die 126 (FIG. 6) is provided. The second die 126 of
the injection molding apparatus has a desired shape of another half
of the airfoil formed in the die with allowances for shrinkage and
warping. A vent 122 extends from the interior of the second die 126
to the outside. The second die 126 is moved to engage the die 120
and enclose the core 22. A conduit 124 is provided to direct melted
material into the cavity created by the dies 120, 126.
[0037] The airfoil portion 24 is then injection molded to envelope
at least a portion of the core 22. The airfoil portion 24 is made
from a plastic material. The plastic material is melted in the
injection molding apparatus. The melted plastic is forced into the
dies 120, 126 through the conduit 124. The plastic material then
cools and hardens to form the desired shaped formed by the cavity
of the dies 120, 126 around the core 22.
[0038] The core 22 has a plurality of voids or openings 82 formed
in the core. During the injection molding process, the openings 82
in the core 22 are filled with the melted plastic material of the
airfoil portion 24. This retains the airfoil portion 24 in a
position relative to the core 22.
[0039] Specific terms are used throughout the description. The
specific terms are intended to be representative and descriptive
only and not for purposes of limitation. The invention has been
described in terms of at least one aspect. The invention is not to
be limited to the aspect disclosed. Modifications and other aspects
are intended to be included within the scope of the appended
claims.
* * * * *