Patent Application
20070140835
The invention relates in general to turbine engines and, more specifically, to cooling systems for stationary airfoils in a turbine engine.
During the operation of a turbine engine, turbine vanes, among other components, are subjected to the high temperatures of combustion. The vanes can be made of materials that are suited for high temperature applications, such as composite matrix composites (CMC). However, material selection alone will not enable the vanes to withstand such an environment. The vanes need to be cooled. Though a variety of systems can adequately cool a vane, manufacturing capabilities and other considerations can render a number of cooling systems infeasible or otherwise not possible in a CMC vane. Thus, there is a need for a CMC vane construction that facilitates the inclusion of intricate three dimensional cooling passages using relatively conventional manufacturing and assembly techniques.
Aspects of the invention relate to a turbine vane assembly having a first cooling system. The vane is formed by a radial stack of laminates that have an airfoil-shaped outer periphery. The vane has a planar direction and a radial direction; the radial direction is substantially normal to the planar direction. Each of the laminates is made of an anisotropic CMC material such that the planar tensile strength of the vane is substantially greater than the radial tensile strength of the vane. The vane can include an outer peripheral surface, which can be substantially covered by a thermal insulating material.
One or more first laminates have a outer airfoil-shaped wall enclosing an inner wall. The inner wall, which can be airfoil-shaped, encloses a central opening that defines a plenum. The inner wall is spaced from the outer wall so as to define a cooling passage therebetween. The spacing between the outer and inner walls in the first laminate can be substantially constant. Alternatively, the spacing between the outer and inner walls can be substantially constant in a forward portion of the laminate and increase in at least a part of the aft portion of the laminate. In such case, the laminate can have a substantially hollow trailing edge.
The inner wall is connected to the outer wall by at least one rib. The rib divides the cooling passage into a set of discrete cooling passages. The plenum can be in fluid communication with one or more of the discrete cooling passages through one or more supply openings provided in the inner wall. In one embodiment, the supply opening can be provided near either the trailing edge or the leading edge of the laminate. During engine operation, the vane can have a pressure side and a suction side. In one embodiment, the ribs can be provided solely on the suction side of the laminates.
One or more of the laminates can include a discharge opening extending through the outer wall of the laminate and substantially in the planar direction. The discharge opening can extend from one of the cooling passages and out the trailing edge of the laminate. As a result, a coolant in the cooling passages can be discharged from the vane assembly at the trailing edge of the vane.
The stack of laminates can further include a second laminate. The second laminate can have a outer airfoil-shaped wall that encloses an inner wall, which may be airfoil-shaped. The inner wall can be spaced from the outer wall so as to define a cooling passage therebetween. The inner wall can be joined to the outer wall by one or more ribs. These ribs can divide the cooling passage into a set of discrete cooling passages. The inner wall can include a central opening that defines a plenum. When a second laminate is provided, the vane can be formed by an alternating arrangement of the first laminates and the second laminates. The cooling passages in the first laminates can offsettingly overlap the cooling passages in the second laminate so as to be in fluid communication. Thus, a weaved cooling path can be established within the vane.
In another respect, aspects of the invention relate to a turbine vane assembly having a second cooling system. The vane is formed by a radial stack of laminates that have an airfoil-shaped outer periphery. The outer periphery of the laminates can form in part the outer peripheral surface of the vane. The vane has a planar direction and a radial direction. The radial direction is substantially normal to the planar direction. The laminates are made of an anisotropic ceramic matrix composite (CMC) material such that the planar tensile strength of the vane is substantially greater than the radial tensile strength of the vane.
The stack of laminates includes alternating large laminates and small laminates. The large laminates peripherally overhang the small laminates about the entire outer periphery of the small laminate. Consequently, a series of recesses are formed about the outer peripheral surface of the vane. Each recess is defined by the outer peripheral edge of at least one small laminate and the adjacent overhanging portions of two large laminates. An outer covering is secured to the outer peripheral surface of the vane so as to close the recesses to form a series of cooling channels extending about the outer peripheral surface of the vane.
The outer covering can be a thermal insulating material. Alternatively, the outer covering can be a CMC wrap. The fibers of the CMC wrap can be oriented so as to be substantially parallel to the outer peripheral surface of the vane. In one embodiment, the CMC wrap can be substantially surrounded by a thermal insulating material.
The laminates can include radial cutouts so as to form a coolant supply plenum in the vane. The coolant supply plenum can be in fluid communication with the series of cooling channels. Thus, a coolant introduced in the coolant supply plenum can flow into the series of cooling channels so as to cool the outer peripheral surface of the vane. The vane can have a leading edge and a trailing edge. In one embodiment, the plenum can be provided in the laminate substantially adjacent the leading edge. One or more exit passages can extend from the cooling channel through the outer covering and out the trailing edge of the vane. As a result, coolant can be dumped at the trailing edge after the coolant has passed through the cooling channels.
Aspects of the invention further relate to a turbine vane having a third cooling system. The vane is formed by a radial stack of laminates. Each laminate has an airfoil-shaped outer periphery. The outer periphery transitions from a forward portion that includes a leading edge to an aft portion that includes a trailing edge. The vane has a planar direction and a radial direction; the radial direction is substantially normal to the planar direction. Each of the laminates is made of an anisotropic CMC material such that the planar tensile strength of the vane is substantially greater than the radial tensile strength of the vane.
The radial stack of laminates include at least a first laminate and an adjacent second laminate. The first laminate has a series of cooling slots in the aft portion of the laminate. The cooling slots extend radially through the first laminate. The second laminate has a series of cooling slots in the aft portion of the laminate. The cooling slots extending radially through the second laminate. The cooling slots in the first laminate are overlappingly offset from the cooling slots in the second laminate so as to be in fluid communication with at least one slot in the second laminate. Thus, a tortuous coolant path is created in the aft portion of the vane such that a coolant must move in the planar and radial directions through the vane assembly.
In one embodiment, the final cooling slot in the first laminate can open to the trailing edge of the laminate, and the final cooling slot in the second laminate can terminate prior to the trailing edge of the second laminate. Thus, a coolant traveling through the overlapping cooling slots can exit the vane through the final slot in the first laminate.
A series of cooling slots can be provided in the forward portion of the first laminate. The cooling slots can extend radially through the first laminate. The cooling slots can be proximate to and can generally follow the outer peripheral surface of the first laminate. Similarly, a series of cooling slots can be provided in the forward portion of the second laminate. The cooling slots can extend radially through the second laminate. The cooling slots can be proximate to and can generally follow the outer peripheral surface of the second laminate. The cooling slots in the forward portion of the first laminate can be overlappingly offset from the cooling slots in the forward portion of the second laminate. As a result, a cooling slot in the forward portion of the first laminate can be in fluid communication with at least one slot in the forward portion of the second laminate. Such an arrangement can create a tortuous coolant path in the forward portion of the vane such that a coolant must move in the planar and radial directions through the forward portion of the vane.
Again, the laminates are made of a CMC material that can include a ceramic matrix and a plurality of fibers therein. In one embodiment, the fibers can be substantially oriented in two planar directions. A first portion of the fibers can extend in a first planar direction, and a second portion of the fibers can extend in a second planar direction. The first and second planar directions can be oriented at about 90 degrees relative to each other. At least one of the cooling slots can have ends that are filleted so as to substantially correspond to the orientation of the fibers.
Various cooling systems according to embodiments of the invention will be explained herein in the context of one possible stacked laminate turbine vane construction, but the detailed description is intended only as exemplary. Embodiments of the invention are shown in
The individual laminates 12 of the vane assembly 10 can be substantially identical to each other; however, one or more laminates 12 can be different from the other laminates 12 in the vane assembly 10. Each laminate 12 can be airfoil-shaped. The term airfoil-shaped is intended to refer to the general shape of an airfoil cross-section and embodiments of the invention are not limited to any specific airfoil shape. Design parameters and engineering considerations can dictate the needed cross-sectional shape for a given laminate 12.
Each laminate 12 can be substantially flat. Each laminate 12 can have a top surface 26 and a bottom surface 28 as well as an outer peripheral edge 30, as shown in
As will be described in greater detail below, the laminates 12 can be made of a ceramic matrix composite (CMC) material. A CMC material comprises a ceramic matrix 32 that hosts a plurality of reinforcing fibers 34, as shown in
A CMC laminate 12 having anisotropic strength characteristics according to embodiments of the invention can be made of a variety of materials, and embodiments of the invention are not limited to any specific materials so long as the target anisotropic properties are obtained. In one embodiment, the CMC can be from the oxide-oxide family. In one embodiment, the ceramic matrix 32 can be, for example, alumina. The fibers 34 can be any of a number of oxide fibers. In one embodiment, the fibers 34 can be made of Nextel™ 720, which is sold by 3M, or any similar material. The fibers 34 can be provided in various forms, such as a woven fabric, blankets, unidirectional tapes, and mats. A variety of techniques are known in the art for making a CMC material, and such techniques can be used in forming a CMC material having strength directionalities in accordance with embodiments of the invention.
As mentioned earlier, fiber material is not the sole determinant of the strength properties of a CMC laminate. Fiber direction can also affect the strength. In a CMC laminate 12 according to embodiments of the invention, the fibers 34 can be arranged to provide the vane assembly 10 with the desired anisotropic strength properties. More specifically, the fibers 34 can be oriented in the laminate 12 to provide strength or strain tolerance in the direction of high thermal stresses or strains. To that end, substantially all of the fibers 34 can be provided in the in-plane direction 14 of the laminate 12; however, a CMC material according to embodiments of the invention can have some fibers 34 in the through thickness direction as well. “Substantially all” is intended to mean all of the fibers 34 or a sufficient majority of the fibers 34 so that the desired strength properties are obtained. Preferably, the fibers 34 are substantially parallel with at least one of the top surface 26 and the bottom surface 28 of the laminate 12.
When discussing fiber orientation, a point of reference is needed. For purposes of discussion herein, the chord line 36 of the laminate 12 will be used as the point of reference; however, other reference points can be used as will be appreciated by one skilled in the art and aspects of the invention are not limited to a particular point of reference. The chord line 36 can be defined as a straight line extending from the leading edge 22 to the trailing edge 24 of the airfoil shaped laminate 12. In the planar direction 14, the fibers 34 of the CMC laminate 12 can be substantially unidirectional, substantially bi-directional or multi-directional.
In a bi-directional laminate, like the laminate 12 shown in
As noted earlier, the fibers 34 can be substantially unidirectional, that is, all of the fibers 34 or a substantial majority of the fibers 34 can be oriented in a single direction. For example, the fibers 34 in one laminate can all be substantially aligned at, for example, 45 degrees relative to the chord line 36, such as shown in the laminate 12a in
Aside from the particular materials and the fiber orientations, the CMC laminates 12 according to embodiments of the invention can be defined by their anisotropic properties. For example, the laminates 12 can have a tensile strength in the in-plane direction 14 that is substantially greater than the tensile strength in the through thickness direction 15. In one embodiment, the in-plane tensile strength can be at least three times greater than the through thickness tensile strength. In another embodiment, the ratio of the in-plane tensile strength to the through thickness tensile strength of the CMC laminate can be about 10 to 1. In yet another embodiment, the in-plane tensile strength can be from about 25 to about 30 times greater than the through thickness tensile strength. Such unequal directionality of strengths in the laminates 12 is desirable for reasons that will be explained later.
One particular CMC laminate 12 according to embodiments of the invention can have an in-plane tensile strength from about 150 megapascals (MPa) to about 200 MPa in the fiber direction and, more specifically, from about 160 MPa to about 184 MPa in the fiber direction. Further, such a laminate 12 can have an in-plane compressive strength from about 140 MPa to 160 MPa in the fiber direction and, more specifically, from about 147 MPa to about 152 MPa in the fiber direction.
This particular CMC laminate 12 can be relatively weak in tension in the through thickness direction. For example, the through thickness tensile strength can be from about 3 MPa to about 10 MPa and, more particularly, from about 5 MPa to about 6 MPa, which is substantially lower than the in-plane tensile strengths discussed above. However, the laminate 12 can be relatively strong in compression in the through thickness direction. For example, the through thickness compressive strength of a laminate 12 according to embodiments of the invention can be from about −251 MPa to about −314 MPa.
The above strengths can be affected by temperature. Again, the above quantities are provided merely as examples, and embodiments of the invention are not limited to any specific strengths in the in-plane or through thickness directions.
As noted earlier, a vane assembly 10 according to embodiments of the invention can be formed by a stack of CMC laminates 12. Up to this point, the terms “in-plane” and “through thickness” have been used herein to facilitate discussion of the anisotropic strength characteristics of a CMC laminate in accordance with embodiments of the invention. While convenient for describing an individual laminate 12, such terms may become awkward when used to describe strength directionalities of a turbine vane 10 formed by a plurality of stacked laminates according to embodiments of the invention. For instance, the “in-plane direction” associated with an individual laminate generally corresponds to the axial and circumferential directions of the vane assembly 10 in its operational position relative to the turbine. Similarly, the “through thickness direction” generally corresponds to the radial direction of the vane assembly 10 relative to the turbine. Therefore, in connection with a turbine vane 10, the terms “radial” or “radial direction” will be used in place of the terms “through thickness” or “through thickness direction.” Likewise, the terms “planar” or “planar direction” will be used in place of the terms “in-plane” and “in-plane direction.”
With this understanding, the plurality of laminates 12 can be substantially radially stacked to form the vane assembly 10 according to embodiments of the invention. The outer peripheral edges 30 of the stacked laminates 12 can form the exterior surface 20 of the vane assembly 10. As noted earlier, the individual laminates 12 of the vane assembly 10 can be substantially identical to each other. Alternatively, one or more laminates 12 can be different from the other laminates 12 in a variety of ways including, for example, thickness, size, and/or shape.
The plurality of laminates 12 can be held together in numerous manners. For instance, the stack of laminates 12 can be held together by one or more fasteners including tie rods 38 or bolts, as shown in
The fastener can be closed by one or more retainers to hold the laminate stack together in radial compression. The retainer can be a nut 42 or a cap, just to name a few possibilities. The fastener and retainer can be any fastener structure that can carry the expected radial tensile loads and gas path bending loads, while engaging the vane assembly 10 to provide a nominal compressive load on the CMC laminates 12 for all service loads so as to avoid any appreciable buildup of interlaminar tensile stresses in the radial direction 15, which is the weakest direction of a CMC laminate 12 according to aspects of the invention. The fastener and retainer can further cooperate with a compliant fastener, such as a Belleville washer 44 or conical washer, to maintain the compressive pre-load, while permitting thermal expansion without causing significant thermal stress from developing in the radial direction 15. To more evenly distribute the compressive load on the laminates 12, the fastener and/or retainer can cooperate with a load spreading member 45, such as a washer. The load spreading member 45 can be used with or without a Belleville washer 44 or other compliant fastener.
In addition or apart from using fasteners, at least some of the individual laminates 12 can also be bonded to each other. Such bonding can be accomplished by sintering the laminates or by the application of a bonding material between each laminate. For example, the laminates 12 can be stacked and pressed together when heated for sintering, causing adjacent laminates 12 to sinter together. Alternatively, a ceramic powder can be mixed with a liquid to form a slurry. The slurry can be applied between the laminates 12 in the stack. When exposed to high temperatures, the slurry itself can become a ceramic, thereby bonding the laminates 12 together.
In addition to sintering and bonding, the laminates 12 can be joined together through co-processing of partially processed individual laminates using such methods as chemical vapor infiltration (CVI), slurry or sol-gel impregnation, polymer precursor infiltration & pyrolysis (PIP), melt-infiltration, etc. In these cases, partially densified individual laminates are formed, stacked, and then fully densified and/or fired as an assembly, thus forming a continuous matrix material phase in and between the laminates.
It should be noted that use of the phrase “at least one of co-processing, sintering and bonding material,” as used herein, is intended to mean that only one of these methods may be used to join individual laminates together, or that more than one of these methods can be used to join individual laminates together. Providing an additional bond between the laminates (whether by co-processing, sintering or having bonding material between each laminate 12) is particularly ideal for highly pressurized cooled vanes where the cooling passages require a strong seal between laminates 12 to contain pressurized coolant, such as air, flowing through the interior of the vane assembly 10.
The airfoil-shaped CMC laminates 12 according to embodiments of the invention can be made in a variety of ways. Preferably, the CMC material is initially provided in the form of a substantially flat plate. From the flat plate, one or more airfoil shaped laminates can be cut out, such as by water jet or laser cutting.
The operation of a turbine is well known in the art as is the operation of a turbine vane. During operation, a turbine vane can experience high stresses in three directions—in the radial direction 15 and in the planar direction 14 (which encompasses the axial and circumferential directions of a vane relative to the turbine). A vane according to aspects of the invention is well suited to manage such a stress field.
In the planar direction 14, high stresses can arise because of thermal gradients between the hot exterior vane surface and the cooled vane interior. The thermal expansion of the vane exterior and the thermal contraction of the vane interior places the vane in tension in the planar direction 14. However, a vane assembly 10 according to embodiments of the invention is well suited for such loads because, as noted above, the fibers 34 in the CMC are aligned in the planar direction 14, giving the vane 10 sufficient planar strength or strain tolerance. Such fiber alignment can also provide strength against pressure stresses that can occur in the turbine.
In the radial direction 15, thermal gradients and aerodynamic bending forces can subject the vane 10 to high radial tensile stresses. While relatively weak in radial tension, a vane 10 according to embodiments of the invention can take advantage of the though thickness compressive strength of the laminates 12 (that is, the radial compressive strength of the vane 10) to counter the radial forces acting on the vane 10. To that end, the vane 10 can be held in radial compression at all times by tie bolts 38 or other fastening system. As a result, radial tensile stresses on the vane 10 are minimized.
During operation, the vane assembly 10 can be exposed to high temperatures, so the vane assembly 10 may require cooling. A stacked laminate vane construction as discussed above can permit the inclusion of cooling systems that would not otherwise be possible or practical in a conventional CMC vane design.
Embodiments of one cooling system according to aspects of the invention are shown in
The inner wall 52 can be spaced from the outer wall 50 so as to define a cooling passage 54 therebetween. The outer and inner walls 50, 52 can be connected by one or more ribs 56 that can extend in the in-plane direction 14 of the laminate 12. The ribs 56 can be provided at various locations between the outer and inner walls 50, 52. Embodiments of the invention are not limited to any particular quantity, shape or thickness of the ribs 56. In the case of two or more ribs 56, the ribs 56 can be substantially identical in size and shape, or they can be different in at least one of these respects.
The ribs 56 can provide structural support to accommodate, among other things, the non-relenting mechanical loads on the vane assembly 10. For instance, the ribs 56 can support the outer wall 50 against the pressure load of the combustion gases in the turbine. The ribs 56 can also provide compliance for thermal loads. In operation, the vane assembly 10 and each laminate 12 can have a pressure side P and a suction side S. The pressure side P generally faces the oncoming combustion gases whereas the suction side S generally faces away from the oncoming combustion gases. In some instances, there may not be any ribs 56 on the pressure side P of the laminate 12, as shown in
For each laminate 12 in a vane assembly 10 configured with a cooling system according to aspects of the invention, the location, shape, thickness and quantity of ribs 56 can be identical, or they can be different in one or more of these and other respects. Similarly, the design of the laminates 12 and arrangement of the laminates in the stack can vary in each vane assembly 10 in the turbine.
In addition to structural support, the ribs 56 can divide the cooling passage 54 into a set of discrete cooling passages 54a, 54b. The ribs 56 can allow the cooling channels 54 to be positioned closer to the hot outer peripheral surface 58 for cooling effectiveness while retaining structural rigidity and robustness of a thick-walled structure. As shown in
Such a core-less arrangement can avoid potentially detrimental thermal growth issues that may otherwise occur. More particularly, if the outer wall 50 enclosed a central airfoil-shaped solid mass (not shown) as opposed to the relatively thin inner wall 52 according to aspects of the invention, differences in thermal inputs on these portions of the laminate could possibly jeopardize the integrity of the laminate 12 and possibly the vane assembly 10 itself. For example, the outer wall 50 experiences larger heat inputs than the central mass because the outer wall 50 is in contact with the hot combustion gases. If the outer wall 50 attempts to expand outward, the cooler solid central mass would resist such outward growth, potentially causing breakage of the connecting ribs 56 and separation of the solid inner mass. Thus, the inner wall 52 of an airfoil laminate 12 according to embodiments of the invention can be sized to account for the unequal thermal expansion and contraction between the hot outer wall 50 and the relatively cool inner wall 52.
The plenum 60 can be in fluid communication with at least some of the cooling passages 54 by one or more supply openings 62 extending through the inner wall 52. Thus, a coolant 64 supplied to the plenum 60 can flow through the supply opening 62 and into the cooling passages 54. The supply opening 62 can be provided in various locations about the laminate 12. For instance, the supply opening 62 can be proximate the leading edge 66. Alternatively, the supply openings 62 can be provided closer to the trailing edge 68, as shown in
A laminate 12 according to embodiments of the invention can include any quantity of supply openings 62. In the case of two or more supply openings 62, the supply openings 62 can be substantially identical to each other, or they can be different. Embodiments of the invention are not limited to any particular configuration, size or shape for the supply openings 62. In some laminates, there may not be any supply openings 62, as shown in
In general, each laminate 12 has a forward region 70 that includes the leading edge 66 and an aft region 72 that includes the trailing edge 72. The location of a supply opening 62 can affect the effectiveness of the coolant 64 in the cooling passages 54. For example, in the case of the laminate 12 shown in
The laminates 12 according to embodiments of the invention and any of the above described features therein—ribs, plenum, supply openings, and cooling passages—can be made using various machining techniques including, for example, laser cutting and water jet cutting.
In one embodiment, shown in
The first and second laminates 74, 76 may be a unique pair of laminates in the vane assembly 10. Alternatively, the first and second laminates 74, 76 can be provided in various alternating arrangements in the vane assembly 10. It should be noted that the term “alternating” is intended to broadly mean any alternating arrangement of the first and second laminates 74, 76. Embodiments of the invention are not limited to any particular manner of alternating the first and second laminates 74, 76. For instance, using the letter A to designate the first laminate 74 and the letter B to designate the second laminate 76, the laminates 74, 76 can be stacked in various manners such as ABABAB, AABBMBB, and ABBABBABBA, just to name a few possibilities. The vane assembly 10 may include a third laminate, which can be, for example, a substantially solid laminate with no cooling features or passages other than a plenum. Labeling such a laminate as C, the laminates can be stacked, for example, according to the pattern ABCABCABC.
Another pair of adjacent laminates 78 according to embodiments of the invention is shown in
A coolant 64 in the cooling passages 54 can be expelled from the vane assembly 10 in various ways. Referring to
The discharge openings 84 can have any of a number of shapes, but substantially circular discharge openings 84 are preferred. A plurality of discharge openings 84 can be provided in the vane assembly 10. The discharge openings 84 can be provided at a regular interval. For example, the discharge openings 84 can be provided in every other laminate 12, as shown in
In some instances, at least a portion of the outer peripheral surface 86 of the vane assembly 10 according to embodiments of the invention may need additional thermal protection. To that end, one or more layers of a thermal insulating material or a thermal barrier coating 88 can be applied around the outer peripheral surface 86 of the vane 10, as shown in
Embodiments of another cooling system according to aspects of the invention are shown in
For example, the vane 10 can be assembled so that large laminates 12L alternate with small laminates 12S to form the stepped outer surface. The large laminates 12L and the small laminates 12S can be substantially geometrically similar. The terms “large” and “small” are intended to refer to the relative size of the outer peripheral surface 30 of a laminate. The large laminates 12L can be slightly larger than the small laminates 12S, such that when stacked, the large laminates 12L can overhang the small laminates 12S from about 2 millimeters to about 3 millimeters. Such an overhang can span about the entire periphery 30 of the small laminate 12S. Preferably, the amount that a large laminate 12L overhangs a smaller laminate 12S is substantially constant about the periphery 30 of the small laminate 12S.
It should be noted that embodiments of the invention are not limited to laminates of just two sizes. The term “large laminates” can include laminates of various sizes so long as they are generally larger than the adjacent small laminates. Similarly, the term “small laminates” can include laminates of various sizes so long as they are generally smaller than the adjacent large laminates.
As noted above, the large laminates 12L can alternate with small laminates 12S. It should be noted that the term “alternate” is intended to broadly mean any alternating arrangement of the large laminates 12L and small laminates 12S. Embodiments of the invention are not limited to any particular manner of alternating the large laminates 12L and the small laminates 12S. For instance, using the letter A to designate the large laminates and the letter B to designate the smaller laminates, the laminates can be stacked in at least the following possible ways: ABABAB (see
Thus, it will be appreciated that the outer peripheral surface 20 of the vane 10 can be formed by the outer periphery 30 of each laminate 12L, 12S as well as the overhanging portions 120V of the large laminates 12L or other externally exposed portion of the laminates 12L, 12S in the vane stack 10. Referring to
An outer covering can be applied over or in substantially surrounding relation to the outer peripheral surface 20 of the vane 10 so as to close the open end of the recesses 90, thereby forming a series of individual cooling channels 92 extending about the vane 10. There can be any number of cooling channels 92 extending about the vane 10. The cooling channels 92 can be radially spaced from each other. Preferably, the cooling channels 92 are substantially parallel to each other. The cooling channels 92 can be substantially identical to each other, or at least one can be different in any of a number of ways including size or cross-sectional geometry.
Ideally, the outer covering is applied after the laminates 12S, 12L are at least partially cured or sintered. In order to form such channels 92, a sacrificial filler material can be included in the recesses 90 in the outer peripheral surface 20 of the vane 10 so as to substantially prevent any outer covering material from entering the recess 90. The vane 10 can then be heated to facilitate bonding between the outer covering and the outer peripheral surface 20 of the vane 10 such that the sacrificial filler material is destroyed, leaving the cooling channel 92 behind. Alternately and preferably, the filler material can be completely removed prior to the final curing and bonding steps.
The outer covering can be a variety of materials or combinations of materials that can protect the outer peripheral surface 20 of the vane assembly 10. For example, the outer covering can be used to reduce thermal gradients across the CMC laminates 12 or to otherwise afford greater thermal protection for the vane assembly 10. In such case, one or more layers of a thermal insulating material or a thermal barrier coating 94 can be applied around the outside surface 20 of the vane 10, as shown in
In one embodiment, the outer covering can be one or more layers of a CMC wrap 96, as shown in
In one embodiment, the fibers of the CMC wrap 96 can be substantially aligned in the radial direction 15 of the vane 10. In such case, the fibers of the CMC wrap 96 can be substantially normal to the fiber orientation in the laminates 12. In one embodiment, the CMC wrap 96 can be substantially surrounded by a thermal insulating material or thermal barrier coating 98, as shown in
The coolant passages 92 can be supplied with a coolant 100, such as air, through a supply plenum. In one embodiment, the supply plenum can be formed by providing radial cutouts 102 at or near the leading edge of each laminate 12, as shown in
Regardless of the particular coolant supply arrangement, a coolant 100 introduced in the supply plenum can flow into the series of cooling channels 92 so as to cool the outer peripheral surface 20 of the vane 10. When the coolant 100 reaches the trailing edge 68, one or more exit passages 108 can be provided through the trailing edge 68 of at least one of the laminates 12 and the outer covering (see, for example,
It will be readily appreciated that the laminates 12 according to embodiments of the invention, generally shown in
Embodiments of another cooling system according to aspects of the invention are shown in
To form a trailing edge cooling system, a vane 10 can be formed by a radial stack of alternating laminates. One embodiment of a cooling system for the aft portion 72 of the vane 10, shown in
The first laminate 110 can have a series of discrete cooling slots 114 in the aft portion. There can be any number of slots 114 in the series. Each slot 114 can extend through the thickness of the laminate 110 at any of a number of angles, but at substantially 90 degrees to the surface 116 is preferred. The slots 114 can extend toward the trailing edge 68 of the laminate 110. The final slot 114f in the series can open to the trailing edge 68. The cooling slots 114 (including the final slot 114f) can have any of a number of shapes. For example, the cooling slots 114 can be generally rectangular, but other conformations are possible. The slots 114 can be substantially identical in size and shape, or at least one of the slots 114 can be different in either of these respects. Further, the cooling slots 114 can be shaped to take advantage of the orientation of the fibers in the laminate 110 to minimize the stress concentrations that may develop in slots 114 with sharp corners. To that end, the cooling slots 114 can be formed such that the ends of the slot 114 include fillets 118 that generally follow or substantially correspond to the fiber orientation in the laminate. For example, if the fibers 120 in the laminate 110 are oriented at +/−45 degrees relative to the chord line 122 of the laminate 110, the ends of the cooling slots 114 can include fillets 118 that generally extend at about +/−45 degrees relative to the chord line 122 of the laminate 110, as shown in
The slots 114 in each laminate can be substantially equally spaced from each other in the aft portion 72 of the laminate, or they can be unequally spaced. Further, it should be noted that the cooling slots 114 can be arranged in various ways. For instance, the slots 114 can be substantially aligned so as to form a row, as shown in
The second laminate 112 can also have a series of cooling slots 114 in the aft portion 72 of the laminate 112. The above discussion pertaining to slots 114 in the first laminate 110 is applicable to the slots 114 in the second laminate. However, unlike the final slot 114f in the first laminate 110, the final slot 114f in the second laminate 112f does not open to the trailing edge 68. That is, the final slot 114f can terminate prior to and proximate to the trailing edge 68. In addition, at least some of the slots 114 in the second laminate 112 are overlappingly offset from the slots 114 in the first laminate 110, as shown in
The first and second laminates 110,112 can be stacked in an alternating manner to form a vane 10. The previous discussion of “alternate” or “alternating” applies, and the following discussion will assume an ABABAB type arrangement. Thus, when the laminates are stacked, the slots 114 can be overlappingly offset so that the slots 114 in the first laminate 110 are in fluid communication with the slots 114 in the second laminate 112. In one embodiment, shown in
The arrangement shown in
For example,
Another embodiment of a cooling system according to embodiments of the invention is shown in
In some instances, the multiple cooling paths in a vane assembly pattern can be compartmentalized by using one or more solid laminates 146 without any slots, as shown in
While the described in connection with the aft portion 72 of the vane 10, any of the foregoing overlappingly offset cooling slot systems can be applied to the forward portion 70 of the vane 10 as well. For instance, as shown in
The foregoing description is provided in the context of one vane assembly according to embodiments of the invention. Of course, aspects of the invention can be employed with respect to myriad vane designs, including all of those described above, as one skilled in the art would appreciate. Embodiments of the invention may have application to other hot gas path components of a turbine engine. Thus, it will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the following claims.
