TECHNICAL FIELD

[0001] The present invention relates to three dimensional (3D) ceramic matrix composite (CMC) components formed by pin weaving techniques, and more particularly, to components having a plurality of wall structures that include truss elements for reinforcing the wall structures wherein the wall structures and truss elements are unistructurally formed in CMC material.

BACKGROUND

[0002] In various multistage turbomachines used for energy conversion, such as gas turbines, a fluid is used to produce rotational motion An axial flow gas turbine includes a multi-stage compressor section, a combustion section, a multi stage turbine section and an exhaust system arranged along a center axis of the gas turbine Air at atmospheric pressure is drawn into the compressor section generally along the axial length of the turbine. The intake air is progressively compressed in the compressor section by rows of rotating compressor blades, thereby increasing pressure, and directed by mating compressor vanes to the combustion section, where it is mixed with fuel, such as natural gas, and ignited to create a combustion gas. The combustion gas, which is under greater pressure, temperature and velocity than the original intake air, is directed to the turbine section. The turbine section includes a plurality of airfoil shaped turbine blades arranged in a plurality of rows on a shaft that rotates about the center axis. The combustion gas expands through the turbine section where it is directed across the rows of blades by associated rows of stationary vanes. As the combustion gas passes through the turbine section, the combustion gas causes the blades and thus the shaft to rotate about the axis, thereby extracting energy from the flow to produce mechanical work.

[0003] A high efficiency is achieved by heating the gas flowing through the combustion section to as high a temperature as is practical. The hot gas, however, may degrade the various metal turbine components, such as the combustor, transition ducts, vanes, ring segments and turbine blades that it passes when flowing through the turbine. In order to enhance the durability of such components, high temperature materials adapted to withstand such extreme temperatures may be utilized in conjunction with cooling strategies to keep the components adequately cooled during operation. For example, ceramic matrix composite (CMC) materials have been developed with high temperature resistance. CMC materials include a ceramic or ceramic matrix reinforced with ceramic fibers.

[0004] Conventional two dimensional (2D) and three dimensional (3D) Oxide-Oxide (Ox-Ox) CMC structures have relatively moderate in-plane mechanical strength. This leads to components that have relatively thick cross-sections in order to withstand primary loads (e g., external aerodynamic loads and internal pressurization of airfoils) that the component is subjected to during operation. The thick cross-sections, combined with the relatively lower thermal conductivity of the CMC material, causes large thermal gradients to develop in applications above approximately 1200 degrees C, for example. This makes cooling of areas of a component, such as backside cooling, difficult to achieve. Backside cooling generally refers to the passage of a cooling fluid over a backside of a component that has a front side exposed to hot combustion gasses. The cooling fluid in backside cooling schemes may be compressed air that has been extracted from the compressor or steam that is available from other fluid loops in a combustion turbine power plant.

[0005] Further, conventional 2D Ox-Ox CMC structures have relatively low interlaminar strength. A technique of cooling such structures is to locate cooling holes or channels within a wall relatively close to a hot surface of a structure or component in order to provide near-wall cooling. However, such configurations are not desirable in 2D Ox-Ox CMC structures because high thermal stresses are generated in the weakest plane, resulting in potential interlaminar damage during operation.

[0006] As previously described, CMC materials are difficult to cool. Fig. 1 depicts an airfoil 10 formed from a CMC material having an outer wall 12 defining a large cavity 14 through which a cooling air may flow. During high temperature operation, the flow of cooling air through the cavity 14 results in a high pressure differential between the interior of the cavity 14 and an outside of the airfoil 10. The high internal pressure may damage the outer wall 12 or a trailing edge 16 of the airfoil 10. In addition, the flow of air through cavity 14 will have little effect on cooling the CMC material closest to an exterior 18 of the airfoil 10 since CMC materials have a low thermal conductivity.

[0007] In order to mitigate undesirable effects of the internal pressure, airfoils may be manufactured with one or more internal ribs. Fig. 2 depicts an airfoil 20 that includes an internal rib 22 which spans between a suction side 24 and a pressure side 26 of the airfoil 20. While the rib 22 assists in reducing the effects of stresses associated with high internal pressure, particularly at a leading edge 28 and a trailing edge 30 of the airfoil 20, relatively high interlaminar stresses occur at the joints where the rib 22 meets an outer wall 32 (i.e. the T- joints).

SUMMARY

[0008] A component fabricated from a three dimensional (3D) ceramic matrix composite (CMC) material is disclosed. The component includes an outer wall and an inner wall spaced apart from the outer wall to form a cooling channel that provides cooling of the outer wall wherein the outer wall and inner wall form a double walled structure. The component also includes a continuous truss fiber attached between the outer wall and the inner wall having portions that span the cooling channel wherein the fiber reinforces the outer wall and inner wall and wherein the truss fiber forms at least one space that enables crossflow of cooling air in the cooling channel and wherein the fiber, outer wall and inner wall are formed together as a unistructure in the CMC material.

[0009] In addition, a method is disclosed of forming a 3D CMC component by using a pin weaving technique. The method includes providing a plurality of outer wall reinforcement members arranged to form an outer wall of the component. The method also includes providing a plurality of inner wall reinforcement members arranged to form an inner wall of the component, wherein the inner wall members are spaced apart from the outer wall members for forming a cooling channel that provides near side cooling of the outer wall. A wall fiber is then woven about the outer wall reinforcement members for forming the outer wall and the inner wall reinforcement members for forming the inner wall. Further, the method includes weaving a truss fiber between the outer and inner wall reinforcement members wherein the truss fiber spans the first cooling channel and wherein the truss fiber forms at least one space that enables crossflow of cooling air in the cooling channel and wherein the outer and inner wall reinforcement members and the truss fiber are formed together as a unistructure in the CMC material.

[0010] A further method is disclosed of forming a 3D CMC component by using a pin weaving technique. The method includes providing pairs of outer wall reinforcement members arranged for forming an outer wall of the component and providing pairs of inner wall reinforcement members arranged for forming an inner wall of the component, wherein the inner wall members are spaced apart from the outer wall members for forming a first cooling channel that provides near side cooling of the first outer wall. The method also includes weaving a wall fiber between a first pair of inner wall reinforcement members and subsequently between a first pair of outer wall reinforcement members in a first pass wherein the wall fiber bypasses a second pair of outer wall reinforcement members. In addition, the method includes weaving the wall fiber between the first pair of outer wall reinforcement members and subsequently between the first pair of inner wall reinforcement members to form a first cross-tie portion in a second pass wherein the wall fiber bypasses a second pair of inner wall reinforcement members. Next, the wall fiber is woven between the second pair of outer wall reinforcement members and subsequently between the second pair of inner wall reinforcement members in a third pass wherein the first pair of outer wall reinforcement members is bypassed. Further, the method includes weaving the wall fiber between the second pair of inner wall reinforcement members and subsequently between the second pair of outer wall reinforcement members to form a second cross-tie portion in a fourth pass wherein the first pair of inner wall reinforcement members is bypassed and wherein the first and second cross-tie portions form a staggered cross tie configuration.

[0011] Those skilled in the art may apply the respective features of the present invention jointly or severally in any combination or sub-combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is explained in the following description in view of the drawings that show:

[0013] Fig. 1 illustrates an embodiment of a prior art airfoil.

[0014] Fig. 2 illustrates another embodiment of a prior art airfoil.

[0015] Fig. 3 illustrates a schematic of a gas turbine engine that incorporates a reinforced woven CMC component in accordance with an aspect of the present invention.

[0016] Fig. 4 illustrates a reinforced woven CMC component in accordance with an aspect of the present invention.

[0017] Fig. 5 is a cross sectional view of an airfoil portion along view line 5-5 of Fig. 4 that depicts a double walled structure fabricated from a three dimensional (3D) Oxide-Oxide (Ox- Ox) CMC material by using a pin weaving technique in accordance with an aspect of the invention.

[0018] Fig. 6A is an enlarged view of an exemplary section of outer and inner wall fibers and selected outer and inner wall pins.

[0019] Fig. 6B shows a first truss fiber woven between exemplary outer wall pins and inner wall pins.

[0020] Fig. 7 is a partial cross sectional view along view line 7-7 of Fig. 6B and depicts spaces created by spaced apart truss fiber portions.

[0021] Fig. 8A depicts an embodiment of a wall pin comprising a solid material.

[0022] Fig. 8B depicts an embodiment of a wall pin having a bore. [0023] Fig. 8C depicts a wall pin having a bore filled with a fugitive material prior to heat treating.

[0024] Fig. 8D depicts a wall pin having a pin cooling channel wherein a fugitive material is removed.

[0025] Fig. 9A depicts an embodiment of an outer wall pin that includes a pin cooling channel to enable cooling flow nearest a hot surface such as a first outer wall section.

[0026] Fig. 9B depicts a cooling tube located between overlap sections at an approximate mid wall position.

[0027] Fig. 9C depicts an embodiment of at least one outer wall pin that includes a pin cooling channel wherein a first cooling channel is not formed between a first outer wall section and first inner wall.

[0028] Fig. 9D depicts an embodiment wherein alternate outer and inner wall pins include a pin cooling channel.

[0029] Fig. 10A depicts an alternate embodiment of outer and inner wall pins and wall fiber for forming an alternate 3D CMC double walled structure by using an alternate pin weaving technique

[0030] Fig. 10B depicts first and second passes of the wall fiber of the embodiment of Fig. 10 A.

[0031] Fig. IOC depicts third and fourth passes of the wall fiber of the embodiment of Fig. 10 A.

[0032] Fig. 11 depicts a still further alternate embodiment of outer and inner wall pins and wall fiber for forming an alternate 3D CMC double walled structure having angled truss elements by using an alternate pin weaving technique. [0033] Fig. 12 depicts an embodiment of the airfoil portion having an alternate cooling arrangement.

[0034] Fig. 13 depicts an embodiment of the airfoil portion having a still further alternate cooling arrangement.

[0035] Fig. 14 depicts an embodiment of the airfoil portion having an additional cooling arrangement.

[0036] Fig. 15A illustrates a pin weaving pattern for forming the first and second outer wall sections and the first and second inner walls for the airfoil portion shown in Fig. 14.

[0037] 15B illustrates use of a single continuous fiber to connect the first outer wall section to the first inner wall and the second outer wall section to the second inner wall for the airfoil portion shown in Fig. 14

[0038] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale.

DETAILED DESCRIPTION

[0039] Although various embodiments that incorporate the teachings of the present disclosure have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The scope of the disclosure is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings The disclosure encompasses other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of“including,” “comprising,” or“having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms“mounted,”“connected,” “supported,” and“coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further,“connected” and“coupled” are not restricted to physical or mechanical connections or couplings.

[0040] Fig. 3 illustrates a gas turbine engine 40 that includes one or more hybrid components formed from a ceramic matrix composite (CMC) material and a metal material as described herein. The gas turbine engine 40 includes a compressor section 42, a combustor section 44, and a turbine section 46. The turbine section 46 includes alternating rows of stationary airfoils 48 (i e. "vanes") and rotating airfoils 50 (i.e. "blades"). Each row of blades 50 is formed by a circular array of airfoils connected to an attachment disc 52 disposed on a rotor 54 having a rotor axis 56. The airfoils 48, 50 extend substantially spanwise along a radial direction of the axis 56 of the gas turbine engine 40. The blades 50 extend radially outward from the rotor 54 and terminate in blades tips. The vanes 48 extend radially inward from an inner surface of vane carriers 58, 60 that are attached to an outer casing 62 of the gas turbine engine 40. A ring seal 64 is attached to an inner surface of the vane carrier 58 and between the rows of vanes 48. The ring seal 64 is a stationary component that acts as a hot gas path guide between the rows of vanes 48 at the locations of the rotating blades 50. The ring seal 64 is commonly formed by a plurality of ring segments that are attached either directly to the vane carriers 58, 60 or indirectly such as by attachment to metal isolation rings attached to the vane carriers 58, 60. During engine operation, high-temperature/high-velocity gases 66 flow primarily axially with respect to the rotor axis 56 through the rows of vanes 48 and blades 50 in the turbine section 46

[0041] Referring to Fig. 4, a reinforced component 68 is shown in accordance with an aspect of the current invention which may comprise a gas turbine component described in connection with Fig. 3. In the embodiment of Fig. 4, the component 68 comprises a vane 48. The vane 48 includes an elongated airfoil portion 70 having a body 72 that extends in a substantially spanwise or radial direction R. The body 72 is defined between a leading edge 76 and a trailing edge 78, and further includes an outer wall 80. The outer wall 80 may have a substantially concave-shaped portion 82 defining a pressure side 84 and a substantially convex shaped portion 86 on an opposite side defining a suction side 88. The airfoil portion 70 is disposed between an outer platform 90 at a first end 92 of the vane 48 and an inner platform 94 at a second end 96 of the vane 48. Although a vane 48 is shown, it is appreciated that the component 68 is not limited to a vane 48, but may include any component for high temperature use, such as another component of a gas turbine engine 40 shown in Fig. 3, e.g., a turbine blade 50 having an airfoil portion 70.

[0042] Referring to Fig. 5, a cross sectional view of the airfoil portion 70 along view line 5-5 of Fig. 4 is shown. In accordance with an aspect of the invention, the airfoil portion 70 includes a double walled structure fabricated from a three dimensional (3D) Oxide-Oxide (Ox-Ox) CMC material by using a pin weaving technique as will be described. In an embodiment, the 3D CMC material may an Oxide-Oxide (Ox-Ox) CMC. The convex 86 and concave 82 portions of the outer wall 80 are defined by first 100 and second 102 outer wall sections having substantially convex and concave shapes, respectively. The airfoil portion 70 also includes first 104 and second 106 inner walls having substantially convex and concave shapes that correspond in shape to the first 100 and second 102 outer wall sections, respectively. It is understood that other shapes may be used for the first 104 and second 106 inner walls. The first 104 and second 106 inner walls extend through a portion of the interior of the airfoil portion 70 and are separated by a main cavity 108 through which a cooling fluid such as cooling air may flow. The first 100 and second 102 outer wall sections are separated from the first 104 and second 106 inner walls by first 110 and second 112 gaps, respectively, to form an airfoil portion 70 having a double walled structure 114. In certain embodiments, the first 110 and second 112 gaps comprise radially extending first 110 and second 112 cooling holes or channels that enable passage of cooling fluid such as cooling air therethrough in the radial direction R. The first 100 and second 102 outer wall sections are sufficiently thin such that cooling air flowing through the first 110 and second 112 cooling channels provides near wall cooling of the first 100 and second 102 outer wall sections, respectively. In addition, the first 100 and second 102 outer wall sections and the first 104 and second 106 inner walls are sized to provide sufficient load bearing capability, including being able to withstand bending forces.

[0043] The airfoil portion 70 includes first 116 and second 1 18 pluralities of outer wall reinforcement members or pins 120 positioned in a substantially convex and concave shaped arrangements used for forming a perimeter of the first 100 and second 102 outer wall sections, respectively. The airfoil portion 70 also includes third 122 and fourth 124 pluralities of inner wall reinforcement members or pins 126 positioned in substantially convex and concave arrangements, respectively, used for forming a perimeter of the first 104 and second 106 inner walls. Referring back to Fig. 4 in conjunction with Fig. 5, the outer 120 and inner 126 wall pins extend through the body 72 of the airfoil portion 70 in the radial direction R between a root 128 and a tip 130 of the airfoil portion 70 In an embodiment, the outer 120 and inner 126 wall pins may be substantially evenly spaced relative to each other

[0044] The airfoil portion 70 also includes outer 132 and inner 134 wall fiber materials that are woven around the outer 120 and inner 126 wall pins, respectively, as will be described. In certain embodiments, the outer 132 and inner 134 wall fibers are each continuous fiber bundles woven about the outer 120 and inner 126 wall pins, respectively, on a layer by layer basis to build the airfoil portion 70. In this way, the outer 132 and inner 134 wall fibers for each layer are each provided as a single piece or unit, cutting of the wall fibers 132, 134 is eliminated, and the mechanical strength of CMC material used to form the airfoil portion 70 may be uniform throughout with no relative weak points. In an aspect, the outer 132 and inner 134 wall fibers may be woven about the outer 120 and inner 126 wall pins, respectively, in an axial direction 98 of the airfoil portion 70 that extends in a direction between the leading 76 and trailing 78 edges In other embodiments, the axial direction 98 may instead extend in a direction between the pressure 84 and suction 88 sides. The axial direction 98 may extend at any angle tangential to the radial direction R extending through the airfoil portion 70 and may also comprise a component perpendicular to the radial direction R.

[0045] Further, the airfoil portion 70 includes first 136 and second 138 truss fiber materials woven between the outer 120 and inner 126 wall pins and across first 110 and second 12 cooling channels, respectively, as will be described. In an aspect of the invention, the first 136 and second 138 truss fibers and the outer 132 and inner 134 wall fibers may be in the form of unidirectional fibers, fiber bundles, braided fiber material, ropes, or the like. The outer 132 and inner 134 wall fibers and first 136 and second 138 truss fibers are hosted within ceramic matrix material 140, impregnated with the ceramic material 140 and subjected to a sintering process to form a CMC material 142 having a single integrated structure or unistructure 145 that forms the airfoil portion 70.

[0046] In an aspect of the invention, the outer wall fiber 132 may be woven about the outer wall pins 120 such that a portion of the outer wall fiber 132 travels over at least one pin in a first step or pass of a pin weaving technique and a portion of the outer wall fiber 132 is under the same pin in a second pass. Further, the inner wall fiber 134 is woven about the inner wall pins 126 such that a portion of inner wall fiber 134 travels over at least one pin in a first pass and a portion of the inner wall fiber 34 is under the same pin in a second pass.

[0047] Figs. 6A and 6B depict a pin weaving technique used to form the 3D CMC double walled structure 114 and the first 136 and second 138 truss fibers in accordance with an aspect of the invention. Referring to Fig. 6A, an enlarged view of an exemplary section of outer 132 and inner 134 wall fibers, outer wall pins 120 and corresponding inner wall pins 126 relative to the first cooling channel 110 is shown. In an embodiment, each outer wall pin 120 is aligned with an inner wall pin 126. The first truss fiber 136 is not shown in Fig. 6A for purposes of clarity. The outer 132 and inner 134 wall fibers form a wall fiber layer. The structure 1 14 includes exemplary first 120A, second 120B, third 120C, fourth 120D and fifth 120E outer wall pins and corresponding first 126A, second 126B, third 126C, fourth 126D and fifth 126E inner wall pins. In an aspect of the invention, the outer wall fiber 132 may be woven about the outer wall pins 120A-120E such that a portion of the outer wall fiber 132 travels over at least one pin in a first pass 144 and a portion of the outer wall fiber 132 travels under the same pin in a second pass 146. In an embodiment, the outer wall fiber 132 travels over a selected pin and under a successive pin. In particular, the outer wall fiber 132 travels over the first outer wall pin 120A and under the second outer wall pin 120B. The pattern is then repeated such that the outer wall fiber 132 travels over the third 120C and fifth 120E outer wall pins and under the fourth outer wall pin 120D in a first pass 144. In a return or second pass 146, the position of the outer wall fiber 132 relative to the pins is reversed, i.e. the outer wall fiber 132 travels under the fifth 120E, third 120C and first 120A outer wall pins and over the fourth 120D and second 120B outer wall pins.

[0048] The inner wall fiber 134 is woven about successive inner wall pins 126A-126E in the same manner as the outer wall fiber 132 and outer wall pins 120A-120E. In particular, inner wall fiber 134 travels over the first 126 A, third 126C and fifth 126E inner wall pins and under the second 126B and fourth 126D inner wall pins in a first pass 148 of the inner wall fiber 134. In a return or second pass 150 of the inner wall fiber 134, the inner wall fiber 134 travels under the fifth 126E, third 126C and first 126A inner wall pins and over the fourth 126D and second 126B inner wall pins. [0049] The first truss fiber 136 is woven between the outer wall pins 120 and inner wall pins 126 such that the truss fibers span the first cooling channel 110. In an embodiment, the first truss fiber 136 is woven or travels over at least one selected outer wall pin 120 and at least one inner wall pin 126 such that the first truss fiber 136 spans across the first cooling channel 110. Fig. 6B shows the first truss fiber 136 woven between the exemplary outer wall pins 120A- 120E and inner wall pins 126A-126E such that the truss fibers span the first cooling channel 110. In particular, the first truss fiber 136 travels over the first outer wall pin 120 A, across the first cooling channel 110 and subsequently under the second inner wall 126B pin. The pattern is then repeated such that the first truss fiber 136 travels over the third 120C and fifth 120E outer wall pins and under the fourth inner wall pin 126D in a first pass 152 of the first truss fiber 136. In a return or second pass 154 of the first truss fiber 136, the first truss fiber 136 travels under the fifth 126E, third 126C and first 126A inner wall pins and over the fourth 120D and second 120B outer wall pins.

[0050] Referring back to Fig. 5, it is understood that the weaving pattern described above for the first truss fiber 136 relative to the outer 120 and inner 126 wall pins and first cooling channel 110 is also applicable to the second truss fiber 138 relative to the inner 126 and outer 120 wall pins such that the second truss fiber 138 spans the second cooling channel 112. In an embodiment, the second truss fiber 138 travels over at least one selected inner wall pin 126 and at least one outer wall pin 120 such that the second truss fiber 138 spans across the second cooling channel 112.

[0051] As previously described, cooling air flows through the first 1 10 and second 1 12 cooling channels to provide near wall cooling of the first 100 and second 102 outer wall sections, respectively The air flow may result in an undesirable high pressure differential either between the first cooling channel 110 and adjacent walls 100, 104 or between the second cooling channel 1 12 and adjacent walls 102, 106 or between both the first 1 10 and second 1 12 cooling channels and respective walls 100, 104 and 102, 106.

[0052] In accordance with an aspect of the invention, the first 136 and second 138 truss fibers are each formed as a single piece or unit that forms a continuous fiber with no relative weak points. Thus, the first 136 and second 138 truss fibers each provide uniform mechanical strength that reinforces the first outer wall section 100 and first inner wall 104 and the second outer wall section 102 and second inner wall 106, respectively, such that the first outer wall section 100 and first inner wall 104 and the second outer wall section 102 and second inner wall 106 withstand the loads generated by the high pressure differential.

[0053] Referring to Fig. 7, an exemplary partial cross sectional view along view line 7-7 of Fig. 6B is shown. In Fig. 7, an exemplary single pass of outer 132 and inner 134 wall fibers is shown for purposes of clarity. The first truss fiber 136 is woven such that truss fiber portions 136A of the first truss fiber 136 are spaced apart by the outer 132 and inner 134 wall fibers to form at least one pair of truss fiber portions 136A forming a space 160. In an embodiment, a plurality of truss fiber portions 136A are formed to form a plurality of spaces 160. In accordance with an aspect of the invention, the spaces 160 enable airflow 162 (see Fig. 6B) in the first cooling channel 110 in a direction substantially transverse to the radial direction R (i.e. crossflow direction 162). A plurality of overlap sections 156 of the first truss fiber 136 is formed due to the first 152 and second 154 passes wherein portions of the first truss fiber 136 are adjacent each other. In an alternate embodiment, a portion of the first truss fiber 136 may crossover another portion of the first truss fiber 136 in a respective overlap section 156.

[0054] The outer 120 and inner 126 wall pins may comprise any material having a rigidity effective to provide at least a degree of reinforcement to the body 72 of the airfoil portion 70 in the radial direction against internal pressure forces (see arrows in Figs. 1-2) and/or compressive forces. In certain embodiments, as shown in Fig. 8A, at least one of the outer 120 and inner 126 wall pins comprise a solid material 162. In particular, the outer 120 and inner 126 wall pins comprise a ceramic material, a ceramic matrix, or a CMC material. In other embodiments, the outer 120 and inner 126 wall pins may comprise a carbon material. In accordance with another aspect and as shown in Fig. 8B, at least one of the outer 120 and inner 126 wall pins comprise a pin body 166 that defines a bore 168 extending therethrough in the radial direction (R). The bore 168, in turn, defines a pin cooling channel 170 for each respective wall pin 120, 126. The wall pins 120, 126 comprising a pin cooling channel 170 may similarly be formed of a carbon material, a ceramic material, a ceramic matrix material, or a CMC material as with a solid wall pin 120, 126.

[0055] In certain embodiments, the wall pins 120, 126 themselves may comprise a fiber material such as the outer 132 and inner 134 wall fibers. The outer 132 and inner 134 wall fibers may be in any suitable form that provides sufficient rigidity or reinforcement as discussed above, such as in the form of unidirectional fibers, fiber bundles, braided fiber material, ropes, or the like. In an embodiment, the wall pins 120, 126 comprise at least one of a braided ceramic rope or a hollow braided ceramic rope having a bore 168 (pin cooling channel 170) extending therethrough in a lengthwise or spanwise dimension of the fiber material. In certain embodiments, as shown in Fig. 8C, the wall pins 120, 126 may be provided with a bore 168 which, prior to a heat treatment (firing), is filled with a fugitive material 172. In this way, the wall pins 120, 126 comprise an added degree of structural strength to the body 72 before firing of the same. The fugitive material 172 may comprise a wax material or a low melting temperature polymer (at least having a lower melting point than the body 166), for example. In any case, the fugitive material 172 may be melted and removed from the body 166 during heat treatment to leave behind pin cooling channel 170 in selected wall pins 120, 126 as shown in Fig. 8D.

[0056] The wall pins 120, 126 may be distributed in any suitable arrangement throughout a body 72 of the airfoil portion 70. In addition, any suitable number or concentration of wall pins 120, 126 may be provided. It is appreciated that any given number of the wall pins 120, 126 may be provided in any desired location to provide a desired degree of reinforcement to the airfoil portion 70. For example, the wall pins 120, 126 may be provided with any desired spacing between adjacent wall pins. In certain embodiments, the spacing between wall pins 120, 126 aids in defining a density of the wall pins 120, 126 in a given region of the airfoil 70. In particular embodiments, the density of the wall pins 120, 126 is greater (e g., more wall pins 120, 126 per a given unit of area) at the trailing edge 54 of the airfoil portion 72 relative to a remaining portion of the airfoil portion 72.

[0057] Figs. 9A-9D depict alternate embodiments for the first truss fiber 136 and exemplary outer wall pins 120A-120E and inner wall pins 126A-126E. In Fig 9A, at least one outer wall pin 120A-120E includes the pin cooling channel 170 to enable cooling flow nearest a hot surface such as the first outer wall section 100 In this embodiment, the first cooling channel 110 may be filled with a ceramic material. In the embodiment shown in Fig. 9B, a cooling tube 174 having a cooling aperture 176 is located between each overlap section 156 at an approximate mid-wall position. Each cooling tube 174 extends radially within the airfoil portion 70. Each cooling aperture 176 enables passage of cooling air therethrough in the radial direction R to provide cooling of the airfoil portion 70. In the embodiment shown in Fig. 9C, at least one outer wall pin 120A-120E includes the pin cooling channel 170 as previously described whereas the first cooling channel 110 is not formed between the first outer wall section 100 and first inner wall 104 such that filling with ceramic is not required. Fig. 9D depicts an alternate configuration for the pins shown in Fig. 9C. In the embodiment shown in Fig. 9D, the pin cooling channel 170 is formed in alternate outer wall pins 120A-120E and inner wall pins 126A-126E. In particular, the outer wall pins 120A-120E and inner wall pins 126A-126E woven in the first pass 152 include the pin cooling channel 170 whereas the outer wall pins 120A-120E and inner wall pins 126A-126E woven in the second pass 154 do not include the pin cooling channel 170 to form an alternating pin cooling channel configuration that provides a balanced structure for the airfoil portion 70.

[0058] Referring to Fig. 10A, an alternate embodiment of outer and inner wall pins and wall fiber is shown for forming an alternate 3D CMC double walled structure 222 by using an alternate pin weaving technique. In an embodiment, the 3D CMC material may be an Oxide- Oxide (Ox-Ox) CMC. The structure 222 includes exemplary first 182, second 184, third 186, fourth 188 and fifth 190 outer pin pairs each including first 178 and second 180 outer wall pins for forming a perimeter of the first outer wall section 100. The structure 222 also includes exemplary first 192, second 194, third 196, fourth 198 and fifth 200 inner pin pairs each including first 202 and second 204 inner wall pins for forming a perimeter of the first inner wall 104. The first 182, second 184, third 186, fourth 188 and fifth 190 outer pin pairs may be evenly spaced in the first outer wall section 100 and the first 192, second 194, third 196, fourth 198 and fifth 200 inner pin pairs may be evenly spaced in the first inner wall 104. A continuous single wall fiber 206 is woven around the first 178, 180 outer wall pins of the 182, 184, 186, 188, 190 outer pin pairs and the first 202 and second 204 inner wall pins of the 192, 194, 196, 198, 200 inner pin pairs to eliminate cutting of the fiber such that the mechanical strength of the CMC material 140 is uniform throughout the airfoil portion 70 with no relative weak points.

[0059] Figs. 10B and IOC illustrate a plurality of passes of the wall fiber 206 relative to the first 178 and second 180 outer wall pins and first 202 and second 204 inner wall pins used in an alternate pin weaving technique for forming a 3D CMC double walled structure. In an aspect of the invention, the wall fiber 206 is woven in a staggered wall fiber configuration 220 such that an equal amount of fiber is provided at all locations of the wall fiber configuration. Referring to Fig. 10B, first 208 and second 210 passes of the wall fiber 206 are shown. In the first pass 208, the wall fiber 206 is first woven between the first 202 and second 204 inner wall pins of the first inner pin pair 192 and subsequently the first 178 and second 180 outer wall pins of the first outer pin pair 182. The wall fiber 206 then bypasses the second outer pin pair 184 and is subsequently woven between the first 178 and second 180 outer wall pins of the third outer pin pair 186 and then the first 202 and second 204 inner wall pins of the third inner pin pair 196. The wall fiber 206 then bypasses the fourth inner pin pair 198 and is subsequently woven between the first 202 and second 204 inner wall pins of the fifth inner pin pair 200 and then the first 178 and second 180 outer wall pins of the fifth outer pin pair 190.

[0060] In the second pass 210, the wall fiber 206 is first woven between the first 178 and second 180 outer wall pins of the first outer pin pair 182 and subsequently the first 202 and second 204 inner wall pins of the first inner pin pair 192. The wall fiber 206 then bypasses the second inner pin pair 194 and is subsequently woven between the first 202 and second 204 inner wall pins of the third inner pin pair 196 and then the first 178 and second 180 outer wall pins of the third outer pin pair 186. The wall fiber 206 then bypasses the fourth outer pin pair 188 and is subsequently woven between the first 178 and second 180 outer wall pins of the fifth outer pin pair 190 and then the first 202 and second 204 inner wall pins of the fifth inner pin pair 200.

[0061] Referring to Fig. IOC, third 212 and fourth 214 passes of the wall fiber 206 are shown. In the third pass 212, the wall fiber 206 bypasses the first outer pin pair 182 and is woven between the first 178 and second 180 outer wall pins of the second outer pin pair 184 and subsequently the first 202 and second 204 inner wall pins of the second inner pin pair 194. The wall fiber 206 then bypasses the third inner pin pair 196 and is subsequently woven between the first 202 and second 204 inner wall pins of the fourth inner pin pair 198 and then the first 178 and second 180 outer wall pins of the fourth outer pin pair 188. The wall fiber 206 then bypasses the fifth outer pin pair 190.

[0062] In the fourth pass 214, the wall fiber 206 bypasses the first inner pin pair 192 and is first woven between the first 202 and second 204 inner wall pins of the second inner pin pair 194 and subsequently the first 178 and second 180 outer wall pins of the second outer pin pair 184. The wall fiber 206 then bypasses the third outer pin pair 186 and is subsequently woven between the first 178 and second 180 outer wall pins of the fourth outer pin pair 188 and then the first 202 and second 204 inner wall pins of the fourth inner pin pair 198. The wall fiber 206 then bypasses the fifth inner pin pair 200.

[0063] Thus, portions of the wall fiber 206 extending between the first 178 and second 180 outer wall pins and the first 202 and second 204 inner wall pins (i.e. truss elements or cross-tie portions 216) provide uniform mechanical strength that reinforces the first outer wall section 100 and first inner wall 104 such that the first outer wall section 100 and first inner wall 104 withstand the loads generated by a high pressure differential. In addition, the cross-tie portions 216 and wall portions 215 of the wall fiber 206 extending between outer pin pairs 182 and 184, 184 and 186, 186 and 188, 188 and 190 in the first outer wall section 100 and inner pin pairs 192 and 194, 194 and 196, 196 and 198, 198 and 200 in the first inner wall 104 form cooling air channels 218 (see Fig 10A) that enable passage of cooling air therethrough in the radial direction R.

[0064] In accordance with an aspect of the invention, the cross-tie portions 216 are staggered such that two thicknesses or layers of wall fiber 206 are provided at all locations of the wall fiber configuration to provide a staggered wall fiber configuration 220. In an alternate embodiment, the cross-tie portions 216 are not staggered resulting in areas of the wall fiber configuration that have two thicknesses (i.e the cross-tie portions 216) while remaining areas only have one thickness. In this embodiment, the cross-tie portions 216 may be radially compacted (by battening the cross-tie portions 216, for example) such that the thickness of each cross-tie portion 216 is substantially similar to the thickness of the remaining areas of the wall fiber configuration.

[0065] Referring to Fig. 1 1, a still further alternate embodiment of outer and inner wall pins and wall fiber is shown for forming an alternate 3D CMC double walled structure 224 by using an alternate pin weaving technique. In an embodiment, the 3D CMC material may be an Oxide- Oxide (Ox-Ox) CMC. The structure 224 includes first 226 and second 228 truss elements that extend from the first outer wall section 100, taper toward each other and terminate at the first inner wall 104 to form a first triangular air channel 230A. The structure 224 also includes third 238 and fourth 240 truss elements that extend from the first outer wall section 100, taper toward each other and terminate at the first inner wall 104 to form a second triangular air channel 23 OB. A third air channel 242 is formed by the second 228 and third 238 truss elements and the first outer wall section 100 and first inner wall 104. The third air channel 242 has an inverted orientation relative to the first 230A and second 230B air channels.

[0066] The first outer wall section 100, first inner wall 104, first 226, second 228, third 238 and fourth 240 truss elements are formed by weaving a single continuous wall fiber 232 around spaced apart first 234A and second 234B outer wall pins and a first inner wall pin 236A for forming the first air channel 230A, a third outer wall pin 234C and spaced apart second 236B and third 236C inner wall pins for forming the second air channel 242 and spaced apart fourth 234D and fifth 234E outer wall pins and fourth inner wall pin 236D for forming the third air channel 230B.

[0067] The air channels 230A, 242, 230B enable passage of cooling air therethrough in the radial direction R. In accordance with an aspect of the invention, the truss elements 226, 228, 238, 240 are angled so as to withstand bending forces in the first outer wall section 100 and first inner wall 104 generated by a high pressure differential due to air flow in the air channels 230 A, 242, 230B.

[0068] Referring to Fig. 12, an embodiment of the airfoil portion 70 having an alternate cooling arrangement 244 is shown. As previously described, the main cavity 108 and first 110 and second 112 cooling channels enable passage of cooling air therethrough in the radial direction R In this embodiment, the airfoil portion 70 further includes leading 246 and trailing edge 248 cavities located near the leading 76 and trailing 78 edges, respectively, of the airfoil portion 70. A trailing edge passageway 250 extends between the trailing edge cavity 248 and the trailing edge 78 to provide fluid communication between the trailing edge cavity 248 and outside 75 the trailing edge 78. In operation, cooling air also flows through the leading edge cavity 246 in the radial direction R to assist in cooling of the airfoil portion 70. The cooling air flowing in the main cavity 108, leading edge cavity 246 and first 110 and second 112 cooling channels exits the main cavity 108, leading edge cavity 246 and the first 110 and second 1 12 cooling channels in a radial direction. The trailing edge cavity 248 receives cooling air from a radial direction but the cooling air then exits the trailing edge cavity 248 via the trailing edge passageway 250. [0069] Referring to Fig. 13, an embodiment of the airfoil portion 70 having a still further alternate cooling arrangement 252 is shown In this embodiment, the main cavity 108 is in fluid communication with the leading edge cavity 246 via leading edge passageways 254. In addition, the main cavity 108 is in fluid communication with the first 110 and second 1 12 cooling channels via first 256 and second 258 cooling channel passageways, respectively. The first 110 and second 112 cooling channels are also in fluid communication with the trailing edge cavity 248 via third 260 and fourth 262 cooling channel passageways, respectively. In operation, cooling air from the main cavity 108 is directed to the leading edge cavity 246 via the leading edge passageways 254. In addition, cooling air from the main cavity is directed to the first 110 and second 112 cooling channels via first 256 and second 258 cooling channel passageways, respectively. Cooling air from the first 110 and second 112 cooling channels is then directed to the trailing edge cavity 248 via the third 260 and fourth 262 cooling channel passageways, respectively. The cooling air then exits the trailing edge cavity 248 via the trailing edge passageway 250. Cooling air from the leading edge cavity 246 may be ejected as film cooling. Alternatively, cooling air from the leading edge cavity 246 may be directed to the main cavity 108 via the leading edge passageways 254, from the main cavity 108 to the trailing edge cavity 248 via the third 260 and fourth 262 cooling channel passageways and ultimately outside 75 of the trailing edge 78 via the trailing edge passageway 250.

[0070] Referring to Fig. 14, an embodiment of the airfoil portion 70 having an additional cooling arrangement 264 is shown. In this embodiment, the airfoil portion 70 includes a single continuous wall cavity 266 that extends between the first outer wall section 100 and the first inner wall 104 and between the second outer wall section 102 and the second inner wall 106. The main cavity 108 is in fluid communication with the wall cavity 266 via impingement passageways 268 located in areas of the airfoil portion 70 having the highest temperature or heat flux, such as a leading edge stagnation point 270. Cooling air from the main cavity 108 is directed to the wall cavity 266 via the impingement passageways 268. Cooling air from the wall cavity 266 then travels aft and exits the wall cavity 266 via the trailing edge passageway 250.

[0071] Referring to Figs. 15A-15B, a method of constructing the airfoil portion 70 described in Fig. 14 is shown. In Fig. 15A, a pin weaving pattern 272 such as that described in relation to Figs. 5 and 6 A is used to form the first 100 and second 102 outer wall sections and the first 104 and second 106 inner walls. In accordance with an aspect of the invention, a single continuous wall fiber 274 is used for the pin weaving pattern. The pin weaving pattern may also include a transverse weaving pattern 276 wherein the wall fiber 274 crosses from a first side 278 of the trailing edge 78 to a second side 280 opposite the first side 278 of the trailing edge 278 in order to reinforce the trailing edge 78.

[0072] In Fig. 15B, the same wall fiber 274 used to construct the first 100 and second 102 outer wall sections and the first 104 and second 106 inner walls is used as a truss fiber 286 to connect the first outer wall section 100 to the first inner wall 104 and the second outer wall section 102 to the second inner wall 106. Alternatively, a separate truss fiber 286 having a size optimized for strength requirements may be used. The wall fiber 274 is used in connection with a pin weaving pattern 282 such as that described in relation to Figs. 5 and 6B to connect the first outer wall section 100 to the first inner wall 104 and the second outer wall section 102 to the second inner wall 106.

[0073] As previously described, CMC material 142 comprises the outer 132 and inner 134 wall fibers and first 136 and second 138 truss fibers (collectively“fiber material”) hosted within a ceramic matrix material 140. The fiber material may comprise an oxide material, a non-oxide material, or a combination thereof, such as alumina, mullite, aluminosilicate, ytrria alumina garnet, silicon carbide, silicon nitride, silicon carbonitride, and the like, and combinations thereof. It is appreciated that the CMC material 142 may combine a matrix composition with a reinforcing phase (fiber material) of a different composition (such as mullite/alumina), or may be of the same composition (alumina/alumina or silicon carbide/silicon carbide). In an embodiment, the CMC material 142 comprises an oxide-oxide (Ox-Ox) CMC material having oxide fibers disposed within an oxide matrix. The fibers of the fiber material may be continuous or long discontinuous fibers, and may be oriented in a direction generally parallel, perpendicular, or otherwise disposed relative to the major length of the CMC material. The (host) ceramic matrix material 140 may further contain whiskers, platelets, particulates, or fugitives, or the like for additional reinforcement.

[0074] To form the CMC material 142, the fiber material is impregnated with an effective amount of a ceramic or ceramic precursor material (ceramic material 140) as described herein. The fiber material may be impregnated with the ceramic material 140 by any suitable method. In certain embodiments, the fiber material is pre-impregnated with a ceramic material 140 prior to the weaving about the fiber material about the reinforcement members 55. In other embodiments, the fiber material is woven about the reinforcement members 55 in their desired position, impregnated with a ceramic or ceramic precursor material, and sintered to form the desired CMC material 142. The ceramic material 140 itself may comprise any suitable oxide, non-oxide material, or combinations thereof, such as one or more of alumina, mullite, aluminosilicate, yttria alumina garnet, silicon carbide, silicon nitride, silicon carbonitride, and the like, or a precursor thereof. In particular embodiments, the ceramic material 140 comprises an oxide material. In any case, once the fiber material is impregnated with the ceramic material 140, the impregnated fiber material may be subjected to a sintering process in order to provide a final CMC material 142 having a single integrated structure or unistructure. In an embodiment, the sintering is done at a temperature of from 500 to 1300° C, isocratic or with a gradient, for a duration of from 1 to 24 hours. [0075] While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.