Dual wall airfoil with stiffened trailing edge

An airfoil adapted for use in a gas turbine engine is disclosed herein. The airfoil includes a spar defining an interior space and a cover sheet extending around at least a portion of the spar. The cover sheet is bonded to the spar to define a cooling cavity between the spar and the cover sheet.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to gas turbine engines, and more specifically to airfoils used in gas turbine engines.

BACKGROUND

Various techniques are used to construct airfoils to achieve desired geometries at the trailing edges of the airfoils. Airfoil trailing edge thicknesses may impact the performance of gas turbine engine components including the airfoils. Constructing airfoils to achieve desired airfoil thicknesses and thereby improve the performance of such components remains an area of interest.

SUMMARY

An airfoil according to the present disclosure may include a spar. The spar may define an interior space and may include thickened portions creating tabs that define a plurality of outwardly-opening channels at the trailing edge of the airfoil along a suction side of the airfoil.

In illustrative embodiments, the airfoil may include a cover sheet. The cover sheet may extend around at least a portion of the spar. The cover sheet may be bonded to the tabs of the spar to create slots at the trailing edge of the airfoil.

In illustrative embodiments, the slots may open into a cooling cavity defined between the spar and the cover sheet. The cooling cavity may extend along the suction side of the airfoil forward of the tabs.

In illustrative embodiments, the spar may define a central cooling air plenum adapted to be pressurized with cooling air and may be formed to include cooling air passages fluidly coupling the central cooling air plenum to the cooling cavity.

In illustrative embodiments, the tabs may be spaced apart from one another in a radial direction extending along the trailing edge of the airfoil. One of the tabs may extend to an outward-most surface of the spar in the radial direction. Another of the tabs may extend to an inward-most surface of the spar in the radial direction arranged opposite the outward-most surface of the spar.

In illustrative embodiments, the tabs may be shaped so that the outwardly-opening channels diverge as they extend toward the trailing edge of the airfoil.

In illustrative embodiments, a thermal barrier coating may be applied to at least a portion of the cover sheet facing outwardly away from the cooling cavity. The portion of the cover sheet may extend to the trailing edge of the airfoil and forward of the tabs.

According to another aspect of the present disclosure, an airfoil may include a spar. The spar may terminate at a point located forward of a trailing edge of the airfoil.

In illustrative embodiments, the airfoil may also include a cover sheet coupled to the spar to form a cooling cavity between the spar and the cover sheet along at least a portion of a suction side of the airfoil and extending from the point to the trailing edge of the airfoil. The cover sheet may include a thickened portion along the trailing edge of the airfoil formed to include a plurality of slots that extend from the trailing edge of the airfoil to the cooling cavity to fluidly couple the cooling cavity to the trailing edge of the airfoil.

In illustrative embodiments, a thickness of the cover sheet measured forward of the point may be less than a thickness of the cover sheet measured at the trailing edge of the airfoil.

In illustrative embodiments, the slots may be spaced apart from one another in a radial direction extending along the trailing edge of the airfoil.

In illustrative embodiments, the spar may define a central cooling air plenum adapted to be pressurized with cooling air. The spar may be formed to include cooling air passages fluidly coupling the central cooling air plenum to the cooling cavity.

In illustrative embodiments, a notch may be formed in one of the spar and the thickened portion. The other of the spar and the thickened portion may be received by the notch to couple the thickened portion to the spar at the point.

In illustrative embodiments, a thermal barrier coating may be applied to the cover sheet opposite the cooling cavity.

In illustrative embodiments, a cooling path extending through the plurality of slots in a radial direction along the trailing edge of the airfoil may be defined by the thickened portion. In illustrative embodiments, the slots may diverge as they extend toward the trailing edge of the airfoil.

In illustrative embodiments, the cover sheet may be constructed of one or more ceramic matrix composite materials. In some embodiments, the spar may be constructed of one or more metallic materials. In some embodiments, the spar may be constructed of one or more ceramic matrix composite materials

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now toFIG. 1, a vane segment10illustratively configured for use in a gas turbine engine is shown. The segment10is illustratively embodied as a single vane adapted for use in a turbine or in a compressor. In other embodiments, however, the segment10may be embodied as a multi-vane segment adapted for use in a turbine or in a compressor.

The segment10illustratively includes a platform12and a platform14spaced from the platform12in a radial direction indicated by arrow R as shown inFIG. 1. The platforms12,14are interconnected by an airfoil16that extends between the platforms12,14. The airfoil16may include features that are configured to interface with corresponding features of the platforms12,14to couple the airfoil16to the platforms12,14.

Referring now toFIG. 2, the illustrative airfoil16is shown in greater detail. The airfoil16includes a suction side22and a pressure side24arranged opposite the suction side22. The suction and pressure sides22,24are interconnected by a leading edge26and a trailing edge28arranged opposite the leading edge26.

The airfoil16illustratively includes a spar30that extends from the leading edge26to the trailing edge28and defines an interior space32as shown inFIG. 1. The airfoil16also includes a cover sheet34that extends around the spar30at the leading edge26. Along the pressure side24of the airfoil16, the cover sheet34terminates at a point36located forward of the trailing edge28. However, along the suction side22of the airfoil16, the cover sheet34extends to the trailing edge28. Because the illustrative airfoil16includes the spar30and the cover sheet34, the airfoil16may be referred to as a dual-wall airfoil.

The spar30includes thickened portions38that create tabs40at the trailing edge28of the airfoil16along the suction side22as best seen inFIGS. 4-5. The tabs40define outwardly-opening channels42at the trailing edge28of the airfoil16. The cover sheet34is bonded to the tabs40to create slots44at the trailing edge28of the airfoil16.

The illustrative airfoil16may provide a number of component features, which are described in greater detail below. The stiffness of the spar30included in the airfoil16may facilitate bonding with the cover sheet34and may control deformation of the airfoil16in response to experiencing operational loads. The relatively thin thickness of the trailing edge28of the airfoil16allowed by the disclosed design may facilitate cooling of the airfoil16and allow operating efficiency gains for a gas turbine engine including the airfoil16.

In the illustrative embodiment, the outwardly-opening channels42of the spar30are features provided solely by the spar30as shown inFIG. 4. In contrast, the slots44are features cooperatively provided by the outwardly-opening channels42of the spar30and the cover sheet34. Put another way, when the cover sheet34is not bonded to the tabs40of the spar30, the outwardly-opening channels42are bounded on three sides and are open along the suction side22of the airfoil16as shown inFIGS. 4-5. When the cover sheet34is bonded to the tabs40as shown inFIGS. 2-3, the cover sheet34closes off the outwardly-opening channels42along the suction side22of the airfoil16to create the slots44bounded on four sides.

Referring back toFIG. 2, the cover sheet34and the spar30illustratively extend forward of the tabs40to the leading edge26and therefrom to the point36to define a cooling cavity46therebetween. The cooling cavity46does not extend to the trailing edge28. Rather, the cooling cavity46terminates at the tabs40as shown inFIGS. 2-3.

The spar30is illustratively formed to include cooling air passages48that extend from the interior space32to the cooling cavity46as shown inFIG. 2. The interior space32is embodied as, or otherwise includes, a central cooling air plenum50adapted to be pressurized with cooling air. The cooling air passages48fluidly couple the plenum50to the cooling cavity46to conduct cooling air provided to the plenum50to the cooling cavity46to cool the airfoil16during operation of the gas turbine engine.

The cover sheet34is illustratively formed to include film cooling holes35extending therethrough to fluidly couple the cover sheet34to the cooling cavity46as shown inFIG. 2. The film cooling holes35may be located along the suction and pressure sides22,24between the leading and trailing edges26,28in a number of suitable positions, such as the positions shown inFIG. 2.

The spar30and the cover sheet34may have a variety of constructions. In the illustrative example, the cover sheet34is constructed of ceramic matrix composite materials and the spar30is constructed of metallic materials. In another example, the spar30and/or the cover sheet34may be constructed of ceramic matrix composite materials. In yet another example, the spar30and/or the cover sheet34may be constructed of metallic materials. In yet another example still, the spar30and the cover sheet34may have other suitable constructions.

The airfoil16further illustratively includes a thermal barrier coating52as shown inFIG. 2. The thermal barrier coating52is applied to the cover sheet34opposite the cooling cavity46so that the coating52extends from the trailing edge28to the leading edge26and therefrom to the point36shielding the outer surface of the cover sheet34. The thermal barrier coating52is illustratively embodied as an environmental barrier coating adapted to create a temperature barrier to help the airfoil16withstand operating temperatures encountered during operation of the gas turbine engine.

Referring now toFIG. 3, the interface between the cooling cavity46and the slots44at the trailing edge28of the airfoil16is shown in greater detail. Each of the slots44illustratively opens into and is thereby fluidly coupled to the cooling cavity46. As such, cooling air may be provided to the slots44from the cooling cavity46and conducted by the slots44through the trailing edge28of the airfoil16during operation of the gas turbine engine.

Referring now toFIGS. 4-5, the tabs40of the spar30and the outwardly-opening channels42defined by the tabs40are shown in greater detail. The tabs40are illustratively spaced apart from one another in the radial direction indicated by arrow R along the trailing edge28of the airfoil16. The tabs40are interconnected with and extend outwardly from an exterior wall54of the spar30as best seen inFIG. 5. Each of the outwardly-opening channels42is arranged between two of the tabs40as best seen inFIG. 4.

In the illustrative embodiment, the tabs40and the outwardly-opening channels42have a generally trapezoidal shape as shown inFIGS. 4-5. In other embodiments, however, the tabs40and the outwardly-opening channels42may take the shape of other suitable geometric forms.

Referring now toFIG. 4, the tabs40illustratively include a radially outward-most tab56that extends to an outward-most surface58of the spar30in the radial direction indicated by arrow R. Additionally, the tabs40include a radially inward-most tab60that extends to an inward-most surface62of the spar30in the radial direction indicated by arrow R. The surfaces58,62are arranged opposite one another. Each of the surfaces58,62extends substantially in an axial direction indicated by arrow A that is substantially orthogonal to the radial direction indicated by arrow R.

The radially outward-most tab56illustratively includes a planar top wall64that is directly interconnected with the radially outward-most surface58as best seen inFIG. 5. The top wall64extends substantially parallel to the surface58in the axial direction indicated by arrow A. The tab56further includes a planar bottom wall66that is arranged opposite the top wall64. The top and bottom walls64,66are interconnected by planar side walls68,70that are arranged opposite one another. The top and bottom walls64,66and the side walls68,70are interconnected with a planar front wall72.

As best seen inFIG. 5, the top and bottom walls64,66of the radially outward-most tab56do not extend parallel to one another in the axial direction indicated by arrow A. Rather, unlike the top wall64, the bottom wall66illustratively extends both in the axial direction indicated by arrow A and the radial direction indicated by arrow R from the side wall68to the side wall70. Specifically, the bottom wall66extends aftward in the axial direction indicated by arrow A and outward in the radial direction indicated by arrow R from the side wall68to the side wall70.

The radially inward-most tab60illustratively includes a planar bottom wall74that is directly interconnected with the radially inward-most surface62as shown inFIG. 4. The bottom wall74extends substantially parallel to the surface62in the axial direction indicated by arrow A. The tab60further includes a planar top wall76that is arranged opposite the bottom wall74. The bottom and top walls74,76are interconnected by planar side walls78,80that are arranged opposite one another. The bottom and top walls74,76and the side walls78,80are interconnected with a planar front wall82.

As shown inFIG. 4, the bottom and top walls74,76of the radially inward-most tab60do not extend parallel to one another in the axial direction indicated by arrow A. Rather, unlike the bottom wall74, the top wall76illustratively extends both in the axial direction indicated by arrow A and the radial direction indicated by arrow R from the side wall78to the side wall80. Specifically, the top wall76extends aftward in the axial direction indicated by arrow A and inward in the radial direction indicated by arrow R from the side wall78to the side wall80.

The tabs40further illustratively include central tabs84that are spaced from one another in the radial direction indicated by arrow R between the radially outward-most and radially inward-most tabs56,60as shown inFIG. 4. The central tabs84are substantially identical to one another. As such, reference numerals used to describe one of the tabs84(with the exception of the numerals86,88discussed below) are applicable to each of the tabs84.

The central tabs84illustratively include a tab86that is positioned closer to the radially outward-most tab56than any of the other tabs84as best seen inFIG. 5. Additionally, the central tabs84include a tab88that is positioned closer to the radially inward-most tab60than any of the other tabs84as shown inFIG. 4.

The tab86of the central tabs84illustratively includes a planar top wall90and a planar bottom wall92that is arranged opposite the top wall90as shown inFIG. 5. The top and bottom walls90,92are interconnected by planar side walls94,96that are arranged opposite one another. The top and bottom walls90,92and the side walls94,96are interconnected with a planar front wall98.

As best seen inFIG. 5, the top and bottom walls90,92of the tab86extend toward one another. Specifically, the top wall90extends aftward in the axial direction indicated by arrow A and inward in the radial direction indicated by arrow R from the side wall94to the side wall96. The bottom wall92extends aftward in the axial direction indicated by arrow A and outward in the radial direction indicated by R from the side wall94to the side wall96.

The outwardly-opening channels42illustratively include a radially outward-most channel100, a radially inward-most channel102, and central channels104as shown inFIG. 4. The radially outward-most channel100is positioned closer to the radially outward-most tab56than any of the other channels42. The radially-inward most channel102is positioned closer to the radially inward-most tab60than any of the other channels42. The central channels104are spaced from one another in the radial direction indicated by arrow R between the radially outward-most and radially inward-most channels100,102. The central channels104are substantially identical to one another.

The radially outward-most channel100is illustratively defined by the radially outward-most tab56, the tab86, and a surface106that interconnects the tabs56,86as best seen inFIG. 5. Specifically, the channel100is defined by the bottom wall66of the tab56, the top wall90of the tab86, and the surface106interconnecting the walls66,90. The channel100extends aftward in the axial direction indicated by arrow A and both inward and outward in the radial direction indicated by arrow R toward the trailing edge28of the airfoil16. As such, the channel100may be said to diverge as the channel100extends toward the trailing edge28of the airfoil16.

The radially inward-most channel102is illustratively defined by the radially inward-most tab60, the tab88, and a surface108that interconnects the tabs60,88as shown inFIG. 4. Specifically, the channel102is defined by the top wall76of the tab60, the bottom wall92of the tab88, and the surface108interconnecting the walls76,92. The channel102extends aftward in the axial direction indicated by arrow A and both inward and outward in the radial direction indicated by arrow R toward the trailing edge28of the airfoil16. As such, the channel102may be said to diverge as the channel102extends toward the trailing edge28of the airfoil16.

The central channels104are illustratively defined by the central tabs84and surfaces110that interconnect the tabs84as shown inFIG. 4. Specifically, the channels104are defined by the top walls90of the tabs84, the bottom walls92of the tabs84, and the surfaces110interconnecting the walls90,92. The channels104extend aftward in the axial direction indicated by arrow A and both inward and outward in the radial direction indicated by arrow R toward the trailing edge28of the airfoil16. As such, the channels104may be said to diverge as the channels104extend toward the trailing edge28of the airfoil16.

Divergence of the channels100,102,104as they extend toward the trailing edge28of the airfoil16may impact the amount of heat transferred from the airfoil16to the cooling air conducted through the channels100,102,104. As the channels100,102,104diverge toward the trailing edge28, the area bounded by the channels100,102,104increases. The amount of cooling air occupying the area bounded by the channels100,102,104may therefore increase. Because heat transfer from the airfoil16to the cooling air contained in the channels100,102,104increases as the channels100,102,104diverge, the divergence of the channels100,102,104may lead to lower operating temperatures of the airfoil16.

Referring back toFIG. 3, the spar30illustratively has a thickness T1of about 0.020 inches at the trailing edge28of the airfoil16. The cover sheet34illustratively has a thickness T2of about 0.010 inches at the trailing edge28of the airfoil16. The thermal barrier coating52illustratively has a thickness T3of about 0.006 inches at the trailing edge of the airfoil16. As a result, the trailing edge28of the illustrative airfoil16has a thickness T4of about 0.036 inches. In other embodiments, however, the spar30, the cover sheet34, and the thermal barrier coating52may have other suitable thicknesses. In those embodiments, the trailing edge28of the airfoil16may have another suitable thickness.

Referring toFIGS. 1-5, the spar30of the illustrative airfoil16may have a greater stiffness at the trailing edge28than the stiffnesses of components of other airfoils at the trailing edges thereof. The stiffness of the spar30at the trailing edge28of the airfoil16may facilitate bonding of the cover sheet34to the tabs40of the spar30. In other airfoils, the stiffnesses of the airfoil components at the trailing edges thereof may not facilitate bonding to the degree that it is facilitated by the stiffness of the spar30at the trailing edge28of the airfoil16. Additionally, the stiffness of the spar30at the trailing edge28of the airfoil16may facilitate controlled deformation of the spar30in response to experiencing operational loads. In other airfoils, the stiffnesses of the airfoil components at the trailing edges thereof may not facilitate deformation of the components to the degree that it is facilitated by the stiffness of the spar30at the trailing edge28of the airfoil16.

Referring again toFIGS. 1-5, the thickness T4of the trailing edge28of the illustrative airfoil16may be smaller than the thicknesses of trailing edges of other airfoils. The benefits associated with the thickness T4of the trailing edge28of the airfoil16are twofold. First, the smaller thickness T4of the airfoil16may facilitate cooling of the airfoil16, thereby reducing the operating temperature of the gas turbine engine component including the airfoil16compared to other components including different airfoils. Second, because airfoil thickness reductions may result in efficiency improvements for gas turbine engine components including the airfoils, the gas turbine engine component including the airfoil16may achieve a greater efficiency than other components including different airfoils. Such efficiency improvements may be particularly achieved by gas turbine engine components receiving air at very high sonic or even supersonic speeds, such as “high work” turbines.

Referring yet again toFIGS. 1-5, the airfoil16may be made by forming the tabs40, and thus the outwardly-opening channels42defined by the tabs40, in the spar30. The tabs40may be machined into the spar30. In one example, the tabs40may be machined into the spar30by an electrical discharge machining (EDM) process, such as a plunge-EDM or wire-EDM process. In another example, the tabs40may be machined into the spar30by another suitable process, such as a laser-machining process.

Referring still toFIGS. 1-5, the airfoil16may be made by machining the cover sheet34. Specifically, the cover sheet34may be machined from a thickness of between about 0.015 inches to 0.020 inches to 0.010 inches before being bonded to the tabs40of the spar30. In one example, the cover sheet34may be machined by an electrical discharge machining (EDM) process, such as a plunge-EDM or wire-EDM process. In another example, the cover sheet34may be machined by another suitable process, such as a laser-machining process.

Referring yet still toFIGS. 1-5, the airfoil16may be made by bonding the machined cover sheet34to the tabs40. Specifically, the machined cover sheet34may be bonded to the tabs40so that the cover sheet34closes off the outwardly-opening channels42to create the slots44and the cooling cavity46is defined between the spar30and the cover sheet34. The thermal barrier coating52may then be applied to the cover sheet34.

Referring now toFIG. 6, a vane segment210illustratively configured for use in a gas turbine engine is shown. The segment210is illustratively embodied as a single vane adapted for use in a turbine or in a compressor. In other embodiments, however, the segment210may be embodied as a multi-vane segment adapted for use in a turbine or in a compressor.

The segment210illustratively includes an airfoil212as shown inFIGS. 6-7. The airfoil212includes a suction side214and a pressure side216arranged opposite the suction side214. The suction and pressure sides214,216are interconnected by a leading edge218and a trailing edge220arranged opposite the leading edge218.

The airfoil212illustratively includes a spar222that extends from the leading edge218to a point224located forward of the trailing edge220and defines an interior space226as best seen inFIG. 7. The airfoil212also includes a cover sheet228that extends around the spar222at the leading edge218. Along the pressure side216of the airfoil212, the cover sheet228terminates at a point230located forward of the trailing edge220. However, along the suction side214of the airfoil212, the cover sheet228extends from the point224to the trailing edge220. Because the illustrative airfoil212includes the spar222and the cover sheet228, the airfoil212may be referred to as a dual-wall airfoil.

The cover sheet228and the spar222are illustratively coupled together to form a cooling cavity232between the cover sheet228and the spar222as shown inFIGS. 6-7. The cover sheet228includes a thickened portion234along the trailing edge220that is formed to include slots236. The slots236extend from the trailing edge220to the cooling cavity232to fluidly couple the cooling cavity232to the trailing edge220.

The slots236are illustratively spaced apart from one another in a radial direction indicated by arrow R extending along the trailing edge220as shown inFIG. 6. Additionally, as best seen inFIG. 6, the slots236diverge as they extend toward the trailing edge220. In the illustrative embodiment, the slots236are generally trapezoidal-shaped. In other embodiments, however, the slots236may take the shape of other suitable geometric forms.

Divergence of the slots236as they extend toward the trailing edge220of the airfoil212may impact the amount of heat transferred from the airfoil212to the cooling air conducted through the slots236. As the slots236diverge toward the trailing edge220, the area bounded by the slots236increases. The amount of cooling air occupying the area bounded by the slots236may therefore increase. Because heat transfer from the airfoil212to the cooling air contained in the slots236increases as the slots236diverge, the divergence of the slots236may lead to lower operating temperatures of the airfoil212.

The illustrative airfoil212may provide a number of component features, which are described in greater detail below. The stiffness of the spar222included in the airfoil212may facilitate bonding with the cover sheet228and may control deformation of the airfoil212in response to experiencing operational loads. The relatively thin thickness of the trailing edge220of the airfoil212allowed by the disclosed design may facilitate cooling of the airfoil212and allow operating efficiency gains for a gas turbine engine including the airfoil212.

The cover sheet228and the spar222illustratively extend forward of the point224to the leading edge218and therefrom to the point230to define the cooling cavity232therebetween as shown inFIGS. 6-7. The cooling cavity232does not extend to the trailing edge220. Rather, the cooling cavity232terminates adjacent the point224as shown inFIGS. 6-8.

Referring now toFIG. 7, the spar222is illustratively formed to include cooling air passages238that extend from the interior space226to the cooling cavity232. The interior space226is embodied as, or otherwise includes, a central cooling air plenum240adapted to be pressurized with cooling air. The cooling air passages238fluidly couple the plenum240to the cooling cavity232to conduct cooling air provided to the plenum240to the cooling cavity232to cool the airfoil212during operation of the gas turbine engine.

The cover sheet228is illustratively formed to include film cooling holes229extending therethrough to fluidly couple the cover sheet228to the cooling cavity232as shown inFIG. 7. The film cooling holes229may be located along the suction and pressure sides214,216between the leading and trailing edges218,220in a number of suitable positions, such as the positions shown inFIG. 7.

The spar222and the cover sheet228may have a variety of constructions. In the illustrative example, the cover sheet228is constructed of ceramic matrix composite materials and the spar222is constructed of metallic materials. In another example, the spar222and/or the cover sheet228may be constructed of ceramic matrix composite materials. In yet another example, the spar222and/or the cover sheet228may be constructed of metallic materials. In yet another example still, the spar222and the cover sheet228may have other suitable constructions.

The airfoil212further illustratively includes a thermal barrier coating242as shown inFIG. 7. The thermal barrier coating242is applied to the cover sheet228opposite the cooling cavity232so that the coating242extends from the trailing edge220to the leading edge218and therefrom to the point230shielding the outer surface of the cover sheet228. The thermal barrier coating242is illustratively embodied as an environmental barrier coating adapted to create a temperature barrier to help the airfoil212withstand operating temperatures encountered during operation of the gas turbine engine.

The thickened portion234of the cover sheet228illustratively includes a segment244and a segment246interconnected with the segment244as shown inFIG. 7. Each of the segments244,246extends to the trailing edge220from the point224. The segments244,246are integral with one another and cooperate to define the slots236as best seen inFIG. 8.

Referring now toFIG. 8, the segment244is coupled to the spar222at the point224. In the illustrative embodiment, the spar222is formed to include a notch248, and the segment244is received by the notch248to couple the segment244to the spar222at the point224. In other embodiments, however, the segment244may be formed to include the notch, and the spar222may be received by the notch in the segment244to couple the segment244to the spar222at the point224. In any case, the segment244may be bonded to the spar222at the point224to couple the cover sheet228to the spar222.

The segments244and246of the thickened portion234illustratively cooperate to partially define a cooling path250as shown inFIG. 8. Specifically, a generally semicircular-shaped groove252formed in the segment244and a generally-shaped semicircular groove254formed in the segment246cooperate to partially define the cooling path250. In other embodiments, however, the grooves252,254may take the shape of other suitable geometric forms.

The cooling path250extends through the slots236in the radial direction indicated by arrow R along the trailing edge220of the airfoil212. Cooling air conducted to the cooling cavity232passes through the cooling path250as the cooling air is conducted by the slots236to the trailing edge220during operation of the gas turbine engine.

A thickness t1of the cover sheet228measured forward of the point224is illustratively different from a thickness t2of the cover sheet228measured at the trailing edge220of the airfoil212as shown inFIG. 8. The thickness t1of the cover sheet228is illustratively less than the thickness t2of the cover sheet228. The thickness t2represents the thickness of the thickened portion234of the cover sheet228.

The thickness t2of the cover sheet228at the trailing edge220of the airfoil212is illustratively about 0.033 inches. The thermal barrier coating242illustratively has a thickness t3of about 0.006 inches at the trailing edge220. As a result, the trailing edge220of the illustrative airfoil212has a thickness t4of about 0.039 inches. In other embodiments, however, the cover sheet228and the thermal barrier coating242may have other suitable thicknesses. In those embodiments, the trailing edge220of the airfoil212may have another suitable thickness.

Referring toFIGS. 6-8, the spar222of the illustrative airfoil212may have a greater stiffness at the trailing edge220than the stiffnesses of components of other airfoils at the trailing edges thereof. The stiffness of the spar222at the trailing edge220of the airfoil212may facilitate bonding of the cover sheet228to the spar222. In other airfoils, the stiffnesses of the airfoil components at the trailing edges thereof may not facilitate bonding to the degree that it is facilitated by the stiffness of the spar222at the trailing edge220of the airfoil212. Additionally, the stiffness of the spar222at the trailing edge220of the airfoil212may facilitate controlled deformation of the spar222in response to experiencing operational loads. In other airfoils, the stiffnesses of the airfoil components at the trailing edges thereof may not facilitate deformation of the components to the degree that it is facilitated by the stiffness of the spar222at the trailing edge220of the airfoil212.

Referring again toFIGS. 6-8, the thickness t4of the trailing edge220of the illustrative airfoil212may be smaller than the thicknesses of trailing edges of other airfoils. The benefits associated with the thickness t4of the trailing edge220of the airfoil212are twofold. First, the smaller thickness t4of the airfoil212may facilitate cooling of the airfoil212, thereby reducing the operating temperature of the gas turbine engine component including the airfoil212compared to other components including different airfoils. Second, because airfoil thickness reductions may result in efficiency improvements for gas turbine engine components including the airfoils, the gas turbine engine component including the airfoil212may achieve a greater efficiency than other components including different airfoils. Such efficiency improvements may be particularly achieved by gas turbine engine components receiving air at very high sonic or even supersonic speeds, such as “high work” turbines.

Referring yet again toFIGS. 6-8, the airfoil212may be made by forming the slots236in the spar222. The slots236may be machined into the spar222. In one example, the slots236may be machined into the spar222by an electrical discharge machining (EDM) process, such as a plunge-EDM or wire-EDM process. In another example, the slots236may be machined into the spar222by another suitable process, such as a laser-machining process.

Referring still toFIGS. 6-8, the airfoil212may be made by forming the cooling path250in the segments244,246of the thickened portion234of the cover sheet228. The cooling path250may be machined into the segments244,246. In one example, the cooling path250may be machined into the segments244,246by an electrical discharge machining (EDM) process, such as a plunge-EDM or wire-EDM process. In another example, the cooling path250may be machined into the spar222by another suitable process, such as a laser-machining process

Referring yet still toFIGS. 6-8, the airfoil212may be made by forming the notch248in the spar222. The notch248may be machined into the spar222. In one example, the notch248may be machined into the spar222by an electrical discharge machining (EDM) process, such as a plunge-EDM or wire-EDM process. In another example, the notch248may be machined into the spar222by another suitable process, such as a laser-machining process.

Finally, referring once more toFIGS. 6-8, the airfoil212may be made by positioning the segment244in the notch248. Additionally, the airfoil212may be made by bonding the segment244received in the notch248to the spar222to couple the cover sheet228to the spar222and define the cooling cavity232between the spar222and the cover sheet228.

Existing dual-wall airfoil fabrication methods may bond together airfoil spars and coversheets that may be thin and flexible at their trailing edges. Such flexibility may lead to unbonding of the airfoil components and undesirable airfoil trailing edge geometry following bonding.

The present disclosure may address the drawbacks associated with these existing methods. In one design contemplated by this disclosure, the spar of the airfoil, such as the spar30of the airfoil16, may be thickened at the trailing edge, such as the trailing edge28. In this design, the pattern layer, such as the cooling cavity46, may be prevented from contributing to the thickness of the airfoil at the trailing edge, such as the thickness T4of the airfoil16at the trailing edge28. In another design contemplated by this disclosure, the cover sheet of the airfoil, such as the cover sheet228of the airfoil212, may be thickened at the trailing edge, such as the trailing edge220. In this design, the pattern layer, such as the cooling cavity232, may be prevented from contributing to the thickness of the airfoil at the trailing edge, such as the thickness t4of the airfoil212at the trailing edge220.

The designs contemplated by this disclosure may provide a number of features. For instance, the designs may allow an airfoil having a stiffer trailing edge to be achieved than the airfoils produced using the existing methods. Additionally, the trailing edges of the airfoils contemplated by this disclosure may be thinner than the trailing edges of the airfoils produced using the existing methods. As a result, the airfoils contemplated by this disclosure may be operated at lower temperatures and may allow greater operating efficiencies to be achieved than the airfoils produced using the existing methods.