BACKGROUND
Embodiments presented herein relate generally to aerodynamic surfaces, and
more specifically to configuration of an aerodynamic surface, such as an airfoil, that
is resistant to high surface strains experienced during foreign object impacts.
Turbines include, but are not limited to, gas and steam turbine power
generation equipment and gas turbine aircraft engines. A turbine engine typically
includes a core engine having a high pressure compressor to compress the air flow
entering the core engine, a combustor in which a mixture of fuel and compressed air is
burned to generate a propulsive gas flow, and a high pressure turbine which is rotated
by the propulsive gas flow and which is connected by a larger diameter shaft to drive
the high pressure compressor. A typical front fan gas turbine engine adds a lowpressure
turbine (located aft of the high pressure turbine) which is connected by a
smaller diameter coaxial shaft to drive the front fan (located forward of the high
pressure compressor). The low-pressure compressor is sometimes called a booster
compressor or simply a booster.
The fan and the high and low pressure compressor of turbine engines have
turbine blades each including an airfoil portion attached to a shank or dovetail portion.
Conventional gas turbine blade designs typically have airfoil portions that are made
entirely of metal, such as titanium, or are made entirely of continuous fiber reinforced
composites (CFRC). The all-metal blades are heavier in weight which results in lower
fuel performance and requires sturdier blade attachments, while the lighter allcomposite
blades are more susceptible to damage from foreign object impacts, such as
bird ingestion events. Known hybrid blades include a composite blade having an
airfoil shape which is covered by a surface cladding (with only the blade tip and the
leading and trailing edge portions of the surface cladding comprising a metal) for
erosion and foreign object impacts. The gas turbine fan blades typically are the largest
(and therefore the heaviest) blades in a gas turbine aircraft engine and the front fan
blades are the first to be impacted by a bird strike. Composite blades have typically
2
been used in applications where weight is a major concern. However, composite
blades due to their thinness may develop high strain regions in the blade that may be
susceptible to failure during foreign object impact. To lower the strain levels in the
blades, it is desirable to change the dynamic response of the composite blade.
Accordingly, there is a need for an improved fan blade that provides a
lightweight airfoil that is resistant to high airfoil surface strains experienced during
foreign object impacts.
BRIEF DESCRIPTION
In accordance with one exemplary embodiment, an airfoil comprising a root
portion, a body portion and a tip portion, a suction side and a pressure side and a
compliant tip. The body portion is configured extending radially outward from the
root portion and wherein the tip portion is configured extending radially outward from
the root portion and the body portion. The suction side and the pressure side are
coupled together at a leading edge and a trailing edge spaced chord-wise and
downstream from the leading edge. The compliant tip extends along at least a portion
of the tip portion in a chord-wise direction and a span-wise direction. The compliant
tip is configured to provide wave propagation along the tip portion such that critical
strain proximate the tip portion and the trailing edge is reduced during a foreign object
impact.
In accordance with another exemplary embodiment, a fan assembly is
disclosed. The fan assembly comprising a disk; and a plurality of fan blades coupled
to the disk. Each blade of the plurality offan blades comprising a root portion, a body
portion and a tip portion, a suction side and a pressure side and a compliant tip. The
body portion is configured extending radially outward from the root portion and the
tip portion is configured extending radially outward from the root portion and the
body portion. The suction side and the pressure side are coupled together at a leading
edge and a trailing edge spaced chord-wise and downstream from the leading edge.
The compliant tip extends along at least a portion of the tip portion in a chord-wise
3
direction and a span-wise direction. The compliant tip is configured to provide wave
propagation along the tip portion such that critical strain proximate the tip portion and
the trailing edge is reduced during a foreign object impact.
In accordance with yet another exemplary embodiment, a fan engine is
disclosed. The fan engine comprising a core engine effective for generating
combustion gases passing through a main flow path, a power turbine aft of the core
engine and including first and second counter rotatable interdigitated turbine blade
rows effective for rotating a drive shaft, a fan section forward of the core engine
including a fan blade row connected to the drive shaft, the fan blade row including a
plurality of airfoils, each airfoil comprising: a root portion, a body portion and a tip
portion, a suction side and a pressure side and a compliant tip. The body portion is
configured extending radially outward from the root portion and the tip portion is
configured extending radially outward from the root portion and the body portion.
The suction side and the pressure side are coupled together at a leading edge and a
trailing edge spaced chord-wise and downstream from the leading edge. The
compliant tip extends along at least a portion of the tip portion in a chord-wise
direction and a span-wise direction. The compliant tip is configured to provide wave
propagation along the tip portion such that critical strain proximate the tip portion and
the trailing edge is reduced during a foreign object impact.
These and other features and improvements of the present application will
become apparent to one of ordinary skill in the art upon review of the following
detailed description when taken in conjunction with the several drawings and the
appended claims.
DRAWINGS
The above and other features, aspects, and advantages of the present invention
will become better understood when the following detailed description is read with
reference to the accompanying drawings in which like characters represent like parts
throughout the drawings, wherein:
4
FIG. 1 is a schematic cross-section, illustrating a turbofan gas turbine engine
including airfoils having a compliant tip in accordance with an embodiment;
FIG. 2 is a schematic cross-section, illustrating an unducted contra-rotating fan
engine including airfoils having a compliant tip in accordance with an embodiment;
FIG. 3 is a perspective view of an airfoil showing a compliant tip in
accordance with an embodiment;
FIG. 4 is side view of an airfoil showing a compliant tip in accordance with an
embodiment;
FIG. 5 is a schematic exploded view of an exemplary airfoil including a
compliant tip, illustrating a pressure side, suction side and top portion in accordance
with an embodiment;
FIG. 6 is a schematic exploded view of an exemplary airfoil including a
compliant tip, illustrating a pressure side, suction side and top portion in accordance
with an embodiment;
FIG. 7 is a schematic exploded view of an exemplary airfoil including a
compliant tip, illustrating a pressure side, suction side and top portion in accordance
with an embodiment;
FIG. 8 is an exploded view of an exemplary airfoil including a compliant tip,
illustrating the manner in which the compliant tip is adjoined to the main airfoil in
accordance with an embodiment;
FIG. 9 is a schematic partial cross-section of the airfoil of FIG. 8 III
accordance with an embodiment;
FIG. 10 is an exploded view of an exemplary airfoil including a compliant tip,
illustrating the manner in which the compliant tip is adjoined to the main airfoil in
accordance with an embodiment;
5
FIG. 11 is a schematic partial cross-section of the airfoil of FIG. 10 in
accordance with an embodiment;
FIG. 12 is an exploded view of an exemplary airfoil including a compliant tip,
illustrating the manner in which the compliant tip is adjoined to the main airfoil in
accordance with an embodiment; and
FIG. 13 is a schematic partial cross-section of the airfoil of FIG. 12 in
accordance with an embodiment;
DETAILED DESCRIPTION
Generally provided are exemplary apparatus and methods for fabricating an
airfoil such as, but not limited to, for use in a device incorporating aerodynamic
surfaces, and more particularly for use in a rotary device. The embodiments described
herein are not limiting, but rather are exemplary only. It should be understood that the
exemplary apparatus and methods for fabricating an airfoil disclosed herein may
apply to any type of airfoil or aerodynamic surface, such as, but not limited to, fan
blades, rotor blades, ducted fan blades, unducted fan blades, turbine engine, and wind
turbines. More specifically, the exemplary apparatus and methods for fabricating an
airfoil disclosed herein may apply to any airfoil, or aerodynamic surface, that is
subject to impinging foreign objects.
Although the embodiments described herein are described in connection with
a turbofan engine, also referred to herein as a turbine engine, and an open rotor
propulsion system, also referred to herein as an unducted contra-rotating front fan
high bypass ratio engine, or UDF, it should be apparent to those skilled in the art that,
with appropriate modification, the apparatus and methods can be suitable for any
device including airfoils that are subject to impinging foreign objects and for which
resistance to high surface strains experienced during foreign object impacts is of
interest.
6
Referring now to FIG. 1, shown is a schematic illustration of an exemplary
turbofan gas turbine engine assembly 10 having a longitudinally extending axis or
centerline 12 that extends through the engine assembly 10 from front to back (from
left to right on FIG. 1). Flow through the illustrated exemplary engine is generally
from front to back. The direction parallel to the centerline toward the front of the
engine and away from the back of the engine will be referred to herein as the
"upstream" direction 14, while the opposite direction parallel to the centerline will be
referred to herein as the "downstream" direction 16.
The engine assembly 10 has an outer shell, or nacelle 18, that generally
defines the engine. The engine assembly 10 also includes an intake side 20, a core
engine exhaust side 22, and a fan exhaust side 24. The intake side 20 includes an
intake 26 located at front opening of the nacelle 18, and flow into the engine enters
through the intake 26. The fan exhaust side 24 includes an exhaust, or nozzle, (not
shown) located at the aft end of the nacelle 18. Flow exits the engine assembly 10
from the exhaust.
A core engine is disposed inside the nacelle 18 and includes a fan assembly
30, a booster compressor 32, a core gas turbine engine 34, and a low-pressure turbine
36 that is coupled to the fan assembly 30 and the booster compressor 32. The fan
assembly 30 includes a plurality of fan blades 40, or airfoils, that extend substantially
radially outward from a fan rotor disk 42. As described below, the fan blades 40 may
be configured to include a compliant tip as described herein, to resist high surface
strains experienced during foreign object impacts.
The core gas turbine engine 34 includes a high-pressure compressor 44, a
combustor 46, and a high-pressure turbine 48. The booster compressor 32 includes a
plurality of blades 50 that extend substantially radially outward from a compressor
rotor disk 52 coupled to a first drive shaft 54. The high-pressure compressor 44 and
the high-pressure turbine 48 are coupled together by a second drive shaft 56.
During operation, air entering the engine assembly 10 through the intake side
20 is compressed by the fan assembly 30. The airflow exiting the fan assembly 30 is
7
split such that a portion of the airflow, and more particularly a compressed airflow 58
is channeled into the booster compressor 32 and a remaining portion 59 of the airflow
bypasses the booster compressor 32 and the core turbine engine 34 and exits the
engine assembly 10 through a stationary vane row, and more particularly an outlet
guide vane assembly 38, comprising a plurality of airfoil guide vanes 39, at the fan
exhaust side 24. More specifically, a circumferential row of radially extending airfoil
guide vanes 39 are utilized adjacent fan assembly 30 to exert some directional control
of the air flow 59. The plurality of rotor blades 50 compress and deliver the
compressed airflow 58 towards the core gas turbine engine 34. The airflow 58 is
further compressed by the high-pressure compressor 44 and is delivered to the
combustor 46. The airflow 58 from the combustor 46 drives the rotating turbines 36
and 48 and exits the engine assembly 10 through the core exhaust side 22.
Referring now to FIG. 2, illustrated is an unducted contra-rotating fan engine
60 including airfoils having a compliant tip in accordance with an embodiment. More
specifically, illustrated is an engine assembly 60 including a longitudinal center line
axis 62 that extends through the engine assembly 60 from front to back (from left to
right on FIG. 2). Flow through the illustrated exemplary engine is generally from
front to back. The direction parallel to the center line axis 62 toward the front of the
engine and away from the back of the engine will be referred to herein as the
"upstream" direction 64, while the opposite direction parallel to the center line axis 62
will be referred to herein as the "downstream" direction 66.
The engine assembly 60 has an outer shell, or an outer casing 68 disposed coaxially
about center line axis 62. Outer casing 68 is conventionally referred to as a
nacelle and is nonstructural in that it does not support any of the engine components.
It can therefore be constructed of thin sheet metal such as aluminum and/or composite
material.
Engine assembly 60 also includes a gas generator referred to as core engine
70. Such core engine includes a compressor 72, a combustor 74 and a high pressure
turbine 76, either singular or multiple stages.
8
At the forward part of the engine 60, there is provided a front fan section 78.
Fan section 78 includes a first fan blade row 80 connected to a forward end of an
inner contra-rotating shaft 82 which extends between a power turbine 84 and the fan
section 78. Front fan section 78 includes a second fan blade row 86 connected to the
forward end of an outer drive shaft 88 also connected between the power turbine 84
and the fan section 78. Each of the first and second fan blade rows 80 and 86
comprise a plurality of circumferentially spaced airfoils 90, or fan blades. Fan blade
rows 80 and 86 are contra-rotating which provides a higher disk loading and
propulsive efficiency. It should be appreciated that the contra-rotating fan blade row
86 serves to remove the swirl on the circumferential component of air imparted by the
contra-rotating fan blade row 80. As described below, the airfoils 90 in blade row 80
and 86 may be configured to include a compliant tip as described herein, to resist high
surface strains experienced during foreign object impacts and provide a more robust
fan blade.
Turning now to FIGs. 3 and 4 illustrated is an exemplary fan blade configured
to resist high surface strains experienced during foreign object impacts according to
an embodiment. In particular, FIG. 3 is a perspective view of an embodiment of an
aerodynamic surface, and more particularly the fan blade embodying an airfoil
including the compliant tip as disclosed herein. FIG. 4 is a side view of a pressure
side of the airfoil of FIG. 3 wherein like parts are identically referenced. More
particularly, illustrated is a fan blade 100, generally similar to the fan blades 40, 80
and 86 of FIGs. 1 and 2, respectively that may be used in a turbofan gas engine
assembly, generally similar to the engine assembly 10 of FIG. 1 or an open rotor
engine assembly, generally similar to the engine assembly 60 of FIG. 2. In a
preferred embodiment, fan blade 100 may reside in a forward or aft positioned
bladerow. In an embodiment, the fan blade 100 includes an airfoil 102, a platform
104 and a root portion 106. Alternatively, the airfoil 102 may be used with, but not
limited to, rotor blades, and/or turbine blades. The airfoil 102 further includes a body
portion 105 and a tip portion 118, wherein the body portion 105 is configured
extending radially outward from the root portion 106 and wherein the tip portion 118
9
is configured extending radially outward from the root portion 106 and the body
portion 105.
In an embodiment, the root portion 106 includes an integral dovetail 108 that
enables the airfoil 102 to be mounted to a disk, such as a fan rotor disk. The airfoil
102 includes a first contoured sidewall 110 and a second contoured sidewall 112.
Specifically, in an embodiment, the first contoured sidewall 110 defines a suction side
III of the airfoil 102, and the second contoured sidewall 112 defines a pressure side
113 of the airfoil 102. The sidewalls 110 and 112 are coupled together at a leading
edge 114 and at an axially-spaced trailing edge 116. The trailing edge 116 is spaced
chord-wise and downstream from the leading edge 114. The airfoil 102 includes a
thickness measured between the pressure side 113 and the suction side 111 extending
from the leading edge 114 to the trailing edge 116, whereby the airfoil thickness
varies in a span-wise direction. The pressure side 113 and the suction side 111, and
more particularly first contoured sidewall 110 and second contoured sidewall 112,
respectively, each extend longitudinally, or radially outward, from the root portion
106 to the tip portion 118. Alternatively, the airfoil 102 may have any conventional
form, with or without the dovetail 108 or platform portion 104. For example, the
airfoil 102 may be formed integrally with a rotor disk in a blisk-type configuration
that does not include the dovetail 108 and the platform portion 104.
In an embodiment, the airfoil 102 includes a compliant tip 120 at the tip
portion 118. The compliant tip 120 extends along at least a portion of the tip portion
118 in a chord-wise direction, indicated by "x" and in a span-wise direction, indicated
by "y". The compliant tip 102 is configured to provide wave propagation along the
tip portion 118 such that critical strain proximate the tip portion 118 and the trailing
edge 116 is reduced during a foreign object impact.
In an embodiment, the compliant tip 120 is defmed by a portion of the airfoil
102 that is comprised of a compliant material 122 (shown in hidden line), such as, but
not limited to, polyurethane, po1yurea, fluoroe1astomer (FPM), nitrile rubber, ethylene
propylene diene monomer (M-c1ass) rubber (EPDM) rubber, epoxy, or combinations
thereof. In an embodiment, the material may contain some fiber reinforcement (e.g.
10
•
glass fiber) for additional strength or stiffness. The compliant material 122 has a
lower stiffness compared to a base material 124 that forms the body portion 105 the
airfoil 102. In addition, the compliant material 122 has an increased strain capability,
thereby providing for a more robust airfoil 102.
In an exemplary embodiment, the compliant tip 120 changes the dynamics of
the airfoil 102, and more particularly the fan blade 100 when under an impact
condition so that a wave propagation along the tip region 118 occurs in such a way
that the critical strain near the tip region 118 and trailing edge 116 is reduced. Wave
speed, Cg, for bending waves in thin plates is given as:
1
.-- ( Eh
2 )4
CB = ...jw 12(1-v2)p
where, w: frequency
h: plate thickness
E, p , v: Modulus, density and Poisson's ratio of the medium (plate),
respectively.
In order to achieve the desired effect, the compliant tip 120 is comprised of the
compliant material 122 chosen such that the wave speed is changed by at least two
times of that in the base material 124 of the blade 100. In an embodiment, the
compliant tip 120 is comprised of a material 122 having a wave speed at least two
times smaller than the base blade material 124. In yet another embodiment, the
compliant tip 120 is comprised of a material 122 having a wave speed at least two
times larger than the base blade material 124. In addition, the compliant tip 120 is
comprised of a high strain-to-failure material as compared to the base blade material
124. In an embodiment, the compliant material122 includes a stiffness parameter
that is approximately 8-10 times more compliant that the base blade material 124.
The novel compliant tip 120 as disclosed herein enables the airfoil 102 to resist high
surface strains experienced during foreign object impacts. The inclusion of the
compliant material 122 to form the compliant tip 120 changes the dynamic response
ofthe fan blade 102 under an impact event. Analysis has shown that this may
11
minimize any whipping action of the trailing edge 116, more particulalry at a tailing
edge comer 119, during an impact scenario. This in tum may reduce the strain
concentrations developed along the trailing edge 116. By reducing the strain at the
trailing edge 116, the fan blade 102 is more robust and less prone to failure during an
impact event.
As best illustrated in FIG. 4, the airfoil 102 may further include a hybrid
trailing edge material 117 (shown in dotted line) at trailing edge 116. More
specifically, the airfoil 102 may include a material such as, but not limited to, S-glass
to form the trailing edge 116 having a higher strain capability. In addition, the airfoil
102 may further include a metal leading edge 115.
Referring now to FIGs. 5-10, illustrated are various configurations of a blade
including a compliant tip portion, similar to blade 100 of FIGs. 3 and 4, for use in an
engine assembly, such as engine assembly 10 of FIG. 1 or engine assembly 60 of FIG.
2. FIGs. 5-7 illustrate in schematic exploded views, exemplary airfoils including a
compliant tip, illustrating a pressure side, suction side and top portion in accordance
with embodiments. Figs. 8-13 illustrate side views of an airfoil suction side and
schematic partial sectional end views showing attachment configurations of the
compliant tip to the body portion of the airfoil. It should be understood that like
elements have like numbers throughout FIGs. 5-10 and the disclosed embodiments.
Illustrated in FIG. 5 is a blade 130, such as a fan blade, including a compliant
tip. More specifically, illustrated is the blade 130, having a blade pressure side 132, a
blade suction side 134 and a blade top side 136. The blade 130 is configured to
include a compliant tip 138, comprised of a compliant material 140 that is disposed
within a tip cap 142, such as a metal tip cap, formed as a part of the blade 130. The
compliant material 140 is exposed on the blade top side 136. The blade 130 is further
comprised of a base material 144, typically comprised of a composite material, such
as those well known in the art. As used herein, the term "composite material" refers
to a material containing high strength fibers in a thermosetting or thermoplastic resin
12
matrix. The blade 130 may further comprise a metal leading edge 146, a hybrid
trailing edge 148, a pressure side cladding ISO, and a composite body portion 152.
Illustrated in FIG. 6 is another embodiment, illustrating a blade 160, such as a
fan blade, including a compliant tip. More specifically, illustrated is the blade 160,
showing a blade pressure side 162, a blade suction side 164 and a blade top side 166.
The blade 160 is configured to include a compliant tip 138, comprised of a compliant
material 140. The compliant material 140 is exposed on the blade top side 166, the
blade pressure side 162 and the blade suction side 164 along at least a portion of the
airfoil length in a span-wise direction and along at least a portion of the airfoil chord
length in a chord-wise direction. The blade 130 is further comprised of a tip cap 142,
typically comprised of a metal material and a base material 144, typically comprised
of a composite material, such as those well known in the art. The blade 130 may
further comprise a metal leading edge 146, a hybrid trailing edge 148, a pressure side
cladding 150, and a composite body portion 152.
Illustrated in FIG. 7 is yet another embodiment of a blade 170, such as a fan
blade, including a compliant tip. More specifically, illustrated is the blade 170,
showing a blade pressure side 172, a blade suction side 174 and a blade top side 176.
The blade 170 is configured to include a compliant tip 138, comprised of a compliant
material 140. The compliant material 140 is exposed on the blade top side 176 and the
blade suction side 174 along at least a portion of the airfoil length in a span-wise
direction and along at least a portion of the airfoil chord length in a chord-wise
direction. The compliant material 140 is covered on the blade pressure side 172 by a
tip cap 142, typically comprised of a metal material. The blade 130 is further
comprised of a base material 144, typically comprised of a composite material, such
as those well known in the art. The blade 130 may further comprise a metal leading
edge 146, a hybrid trailing edge 148, a pressure side cladding ISO, and a composite
body portion 152.
Referring now to Figs. 8-13, illustrated in schematic exploded side views and
schematic partial sectional end views are a plurality of configurations for an airfoil
13
with a compliant tip in accordance with embodiments. It should be understood that
like elements have like numbers throughout the disclosed embodiments.
Illustrated in FIGs. 8 and 9 is an airfoil 180, including a compliant tip 182.
Airfoil 180 is configured generally similar to airfoil 160 of FIG. 6 wherein a
compliant material 184 that forms the compliant tip 182 is exposed on a pressure side
186, a suction side 188 and on a blade top side 190. In the embodiment illustrated,
the compliant tip 182 and an uppermost part of the body portion 192 of the airfoil 180
are formed having a tongue-in-groove cooperating configuration as best illustrated in
FIG. 9 in a partial cross-sectional end view. More specifically, the compliant tip 182
includes a protruding lower portion 194 that is configured to seat within a groove 196
formed on an uppermost edge 198 of the body portion 192 the airfoil 180. The
compliant tip 182 may be formed of a polyurethane material that when positioned
relative to the body of the airfoil 180 seats into the groove 187 formed in a composite
material that comprises the base material of the airfoil 180. Such configuration
increases contact surface between the compliant tip 182 and the underlying base
material thus increasing the bonding between these components. It is also preferable
from manufacturing perspective. Illustrated in FIGs. 10 and 11 is an airfoil 200,
including a compliant tip 202. Airfoil 200 is configured generally similar to airfoil
160 of FIG. 6 wherein a compliant material 204 that forms the compliant tip 202 is
exposed on a pressure side 206, a suction side 208 and on a blade top side 210. In the
embodiment illustrated, the compliant tip 202 and an uppermost part of the body
portion 212 of the airfoil 200 are formed having a tongue-in-groove cooperating
configuration as best illustrated in FIG. 11 in a partial cross-sectional end view. More
specifically, the body portion 212 of the airfoil 200 includes a protruding edge 214
that is configured to seat within a groove 216 formed in the compliant tip 202. The
compliant tip 202 may be formed of a polyurethane material that when positioned
relative to the body of the airfoil 200, seats onto the protruding edge 214 formed in a
composite material that comprises the base material of the airfoil 200. Similar to
aforementioned configuration, this configuration provides increased bonding between
compliant tip 202 and base material and may be preferable from fabrication point of
view.
14
Illustrated in FIGs. 12 and 13 is an airfoil 220, including a compliant tip
222. Airfoil 220 is configured generally similar to airfoil 160 of FIG. 6 wherein a
compliant material 224 that forms the compliant tip 222 is exposed on a pressure side
226, a suction side 228 and on a blade top side 230. In the embodiment illustrated,
the compliant tip 222 and an uppermost part of the body portion 232 of the airfoil 200
are formed having a tongue-in-groove cooperating configuration as best illustrated in
FIG. 13 in a partial cross-sectional end view, and generally configured in the same
manner as the embodiment illustrated in FIGs. 10 and 11. In contrast to the
previously described embodiment, in this particular configuration, the uppermost part
of the body portion 232 of the airfoil 230 includes a protruding edge 234 that while
configured to seat within a groove 236 formed in the compliant tip 222, is shaped to
have a similar overall edge configuration to that of the compliant tip 222, providing
for a compliant tip trailing edge 240 that is comprised solely of the compliant
material, and thus having altered dynamic responses than compliant tip 202 of FIGs.
10 and 11. As previously described, the compliant tip 232 may be formed of a
polyurethane material that when positioned relative to the body of the airfoil 220,
seats onto the protruding edge 234 formed in a composite material that comprises the
base material of the airfoil 220. While this configuration provides the same benefit in
fabrication and bondability as the previous two configurations, such gradual transition
between compliant tip 222 and body portion 232 ensures no elevated strains in the
transition region. An airfoil including a compliant tip configured in this manner
addresses the unsteady aerodynamics that result in blade strain and unsteady whipping
action of the trailing edge in response to a foreign object impact. More specifically,
the airfoil including a compliant tip configured as described herein facilitates a
reduction in unsteady airfoil response of the foreign object impinging on the airfoil
such that the strain and wave propagation are facilitated to be reduced. By reducing
the strain at the trailing edge, and more particularly, the trailing edge comer, the fan
blade is less prone to failure during an impact event. The reduction in strain on the
airfoil resulting from a trailing edge oscillating in response to an upstream impinging
foreign object and thereby generating high unsteady pressure fluctuations on the
airfoil may facilitate engine system performance improvements such as reducing the
overall weight of the airfoils while providing a more robust response at the trailing
15
edge. As a result, engine efficiency and performance are facilitated to be improved in
comparison to engines using standard airfoils without a compliant tip. The reduction
in airfoil strain and aeromechanicalloading are achieved without an increase in blade
or vane weight, without substantially decreasing aerodynamic performance, and
without any otherwise impact on the overall engine system (length, weight, structure,
etc.).
Exemplary embodiments of airfoils including fan blades are described above
in detail. The airfoils are not limited to the specific embodiments described herein, but
rather, may be applied to any type of airfoil that are subjected to foreign object
impacts, such as a fan blade, stator, airframe, or an unsteady fluid flow. The airfoils
described herein may be used in combination with other blade system components
with other engines.
While the disclosure has been illustrated and described in typical
embodiments, it is not intended to be limited to the details shown, since various
modifications and substitutions can be made without departing in any way from the
spirit of the present disclosure. As such, further modifications and equivalents of the
disclosure herein disclosed may occur to persons skilled in the art using no more than
routine experimentation, and all such modifications and equivalents are believed to be
within the spirit and scope of the disclosure as defined by the subsequent claims.
16
10 engine assembly
12 longitudinal center line axis
14 upstream direction
16 downstream direction
18 outer shelllncelle
20 intake side
22 core engine exhaust side
24 fan exhaust side
26 intake side
28
30 fan assembly
32 booster compressor
34 core gas turbine engine
36 low-pressure turbine
38 outlet guide vane assembly
39 airfoil guide vanes
40 plurality of fan blades
42 fan rotor disk
44 high-pressure compressor
46 combustor
48 high-pressure turbine
50 plurality of blades (booster compressor)
52 compressor rotor disk
54 first drive shaft
56 second drive shaft
58 compressed airflow
59 remaining portion of the airflow
60 engine assembly
62 longitudinal center line axis
64 upstream direction
66 downstream direction
68 outer shell/nacelle
70 core engme
72 compressor
74 combustor
76 high-pressure turbine
78 front fan section
80 first fan blade row
82 inner contra-rotating shaft
84 power turbine
86 second fan blade row
88 outer drive shaft
17
90 plurality of circumferentially spaced airfoils/fan blades
100 fan blade
102 airfoil
104 platform
105 body portion
106 root portion
108 integral dovetail
110 first contoured sidewall
111 suction side
112 second controured sidewall
113 pressure side
114 leading edge
115 metal leading edge
116 trailing edge
117 hybrid trailing edge material
118 tip portion
119 trailing edge comer
120 compliant tip
122 compliant material
124 base material
126
128
130 fan blade
132 blade pressure side
134 blade suction side
136 blade top side
138 compliant tip
140 compliant material
142 tip cap
144 base material - composite
146 metal leading edge
148 hybrid trailind edge
150 pressure side cladding
152 composite base portion
154
156
158
160 blade
162 blade pressure side
164 blade suction side
166 blade top side
168
170 blade
172 blade pressure side
174 blade suction side
176 blade top side
178
180 blade
182 compliant tip
184 compliant tip material
186 blade pressure side
188 blade suction side
190 blade top side
192 tip region
194 protruding lower edge
196 groove
198 uppermost edge of airfoil 180
200 blade
202 compliant tip
204 compliant tip material
206 blade pressure side
208 blade suction side
210 blade top side
212 tip region
214 protruding lower edge
216 groove
218 uppermost edge of airfoil 180
220 blade
222 compliant tip
224 compliant tip material
226 blade pressure side
228 blade suction side
230 blade top side
232 tip region
234 protruding lower edge
236 groove
238 uppermost edge of airfoil 180
240 thicker trailing edge 240

WE CLAIM :
1. An airfoil (102) comprising:
a root portion (106), a body portion (105) and a tip portion (118), wherein the
body portion (105) is configured extending radially outward from the root portion
(106) and wherein the tip portion (118) is configured extending radially outward from
the root portion (106) and the body portion (105);
a suction side (111, 134) and a pressure side (113, 132) coupled together at a
leading edge (114) and a trailing edge (116) spaced chord-wise and downstream from
the leading edge (114); and
a compliant tip (120) extending along at least a portion of the tip portion (118)
in a chord-wise direction and a span-wise direction,
wherein the compliant tip (118) is configured to provide wave propagation
along the tip portion (118) such that critical strain proximate the tip portion (118) and
the trailing edge (116) is reduced during a foreign object impact.
2. An airfoil in accordance with Claim 1, wherein the compliant tip (118)
is comprised of a compliant material (122).
3. An airfoil in accordance with Claim 2, wherein the compliant material
(122) is at least one of a polyurethane, a polyurea, a fluoroelastomer (FPM), a nitrile
rubber, ethylene propylene diene monomer (EPDM) rubber and an epoxy.
4. An airfoil in accordance with Claim 1, wherein the trailing edge (116)
is comprised of a hybrid material (117).
5. An airfoil in accordance with Claim 1, wherein the body portion (105)
is comprised of a composite material (140).
6. An airfoil in accordance with Claim 5, wherein the compliant tip (118)
is comprised of a compliant material (122) such that a wave speed traveling
therethrough the compliant tip (118) in response to a foreign object impact is changed
by at least two times a wave speed traveling therethrough the body portion (105) of
the airfoil (102).
7. An airfoil in accordance with Claim 1, wherein the airfoil (102) is one
of a fan blade, a rotor blade ducted fan blade, an unducted fan blade, or a wind turbine
blade.
8. A fan assembly comprising:
a disk (42,52); and
a plurality of fan blades (40, 50) coupled to the disk (42,52), each blade of the
plurality of fan blades comprising:
a root portion (106), a body portion (lOS) and a tip portion (118),
wherein the body portion (105) is configured extending radially outward from
the root portion (106) and wherein the tip portion (118) is configured
extending radially outward from the root portion (106) and the body portion
(105);
a suction side (111) and a pressure side (113) coupled together at a
leading edge (114) and a trailing edge (116) spaced chord-wise and
downstream from the leading edge (114); and
a compliant tip (120) extending along at least a portion of the tip
portion (118) in a chord-wise direction and a span-wise direction,
wherein the compliant tip (120) is configured to provide wave
propagation along the tip portion (118) such that critical strain proximate the
tip portion (118) and the trailing edge (116) is reduced during a foreign object
impact.
9. A fan assembly in accordance with Claim 8, wherein the each fan
blade (40, 50) is configured to facilitate a reduction in strain at the trailing edge (116)
associated with a foreign object impact.
10. A fan engine (60) comprising:
a core engine (70) effective for generating combustion gases passing through a
main flow path;
21
a power turbine (84) aft of the core engine (70) and including first and second
counter rotatable interdigitated turbine blade rows effective for rotating a drive shaft
(56, 82);
a fan section (78) forward of the core engine (70) including a fan blade row
(80, 86) connected to the drive shaft (82), the fan blade row (80, 86) including a
plurality of airfoils (102), each airfoil (102) comprising:
a root portion (106), a body portion (105) and a tip portion (118),
wherein the body portion (105) is configured extending radially outward from
the root portion (106) and wherein the tip portion (118) is configured
extending radially outward from the root portion (106) and the body portion
(105);
a suction side (111) and a pressure side (113) coupled together at a
leading edge (114) and a trailing edge (116) spaced chord-wise and
downstream from the leading edge(114); and
a compliant tip (120) extending along at least a portion of the tip
portion (118) in a chord-wise direction and a span-wise direction,
wherein the compliant tip (120) is configured to provide wave
propagation along the tip portion (118) such that critical strain proximate the
tip portion(118) and the trailing edge (116) is reduced during a foreign object
impact.
22. A fan engine in accordance with Claim 21, wherein the airfoil (l02) is
configured to facilitate a reduction in strain at the trailing edge (116) associated with a
foreign object impact.
23. A fan engine in accordance with Claim 21, wherein the compliant tip
(120) is comprised of a compliant material (122) such that a wave speed traveling
therethrough the compliant tip (120) is changed by at least two times a wave speed
traveling therethrough the body portion (105) of the airfoil (120).
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MANISHA SINGH NAIR
Agent for the Applicant [IN/PA-740]
LEX ORBIS
Intellectual Property Pnctice
709/710, Tolstoy House,
15-17, Tolstoy Marg,
New Delhi-II 000 I