Airfoil trailing edge cooling

A turbine airfoil for a gas turbine engine includes a pressure sidewall extending along a spanwise direction, and from a leading edge of the airfoil towards the trailing edge of the airfoil. The turbine airfoil additionally includes a suction sidewall also extending along the spanwise direction, and from the leading edge towards the trailing edge. The pressure sidewall and suction sidewall define a cooling air cavity therebetween, and one or both of the pressure sidewall and suction sidewall define a trailing edge cooling channel extending from the cooling air cavity substantially to the trailing edge. Additionally, one or both of the pressure sidewall and suction sidewall include a plurality of pressure drop members extending partially into the trailing edge cooling channel for reducing an amount of cooling air flowing therethrough from the cooling air cavity.

FIELD OF THE INVENTION

The present subject matter relates generally to a cooling channel within an airfoil of a gas turbine engine.

BACKGROUND OF THE INVENTION

A gas turbine engine generally includes a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine general includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided from the fan to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gasses through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to atmosphere.

The turbine section typically includes a plurality of sequentially arranged stage(s) of turbine nozzles and turbine rotor blades. Each of the turbine nozzles within the various stages of turbine nozzles and each of the turbine rotor blades within the various stages of turbine rotor blades include an airfoil. These airfoils are typically actively cooled by flowing cool air into a central cavity of the airfoil and through a variety of cooling holes arranged in various locations on the airfoil. For example, an airfoil may include a variety of cooling holes at a leading edge, a variety of cooling holes along a pressure side and a suction side, and a variety of cooling holes at a trailing edge.

Given the nature of the airfoil, cooling air within the central cavity of the airfoil generally experiences the greatest pressure drop through the cooling holes at the trailing edge of the airfoil. For example, the trailing edge is desired to be as thin as possible in order to minimize aerodynamic losses. Accordingly, a section forming the trailing edge may also be relatively long, making it difficult to cast or machine small cooling holes through the length. Such a configuration may result in larger than desirable cooling holes allowing more cooling fluid flow than required or desired.

Accordingly, an airfoil having a trailing edge cooling channel with additional means for controlling an amount of airflow therethrough would be useful. More particularly, an airfoil having a trailing edge cooling channel including a metering section along with additional means for controlling an amount of airflow therethrough would be particularly beneficial.

BRIEF DESCRIPTION OF THE INVENTION

In one exemplary embodiment of the present disclosure, a turbine airfoil for a gas turbine engine is provided. The turbine airfoil defines a spanwise direction, a leading edge, and a trailing edge. The turbine airfoil includes a pressure sidewall extending along the spanwise direction and from the leading edge towards the trailing edge. The turbine airfoil also includes a suction sidewall extending along the spanwise direction and from the leading edge towards the trailing edge. The pressure sidewall and the suction sidewall define a cooling air cavity therebetween. One or both of the pressure sidewall and suction sidewall define a trailing edge cooling channel extending from the cooling air cavity substantially to the trailing edge. One or both of the pressure sidewall and suction sidewall include a plurality of pressure drop members extending partially into the trailing edge cooling channel for reducing an amount of cooling air flowing therethrough from the cooling air cavity.

In another exemplary aspect of the present disclosure, a method of manufacturing a gas turbine engine turbine airfoil defining a leading edge and a trailing edge is provided. The method includes forming a body section of the airfoil extending from the leading edge of the airfoil towards the trailing edge of the airfoil. The body section defines a cooling air cavity located proximate the trailing edge. The method also includes forming a trailing edge section of the airfoil using an additive manufacturing process. The trailing edge section is formed integrally with or attachable to the body section of the airfoil. The trailing edge section at least partially defines a trailing edge cooling channel extending from the cooling air cavity defined by the body section substantially to the trailing edge of the airfoil. The trailing edge section including a plurality of pressure drop members extending partially into the trailing edge cooling channel for reducing an amount of cooling air flowing therethrough.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,FIG. 1is a schematic cross-sectional view of a turbomachine in accordance with an exemplary embodiment of the present disclosure. More particularly, for the embodiment ofFIG. 1, the turbomachine is configured as a gas turbine engine, or rather as a high-bypass turbofan jet engine12, referred to herein as “turbofan engine12.” As shown inFIG. 1, the turbofan engine12defines an axial direction A (extending parallel to a longitudinal centerline13provided for reference), a radial direction R, and a circumferential direction (not shown) extending about the axial direction A. In general, the turbofan12includes a fan section14and a core turbine engine16disposed downstream from the fan section14.

Referring still to the embodiment ofFIG. 1, the fan section14includes a variable pitch fan38having a plurality of fan blades40coupled to a disk42in a spaced apart manner. As depicted, the fan blades40extend outwardly from disk42generally along the radial direction R. Each fan blade40is rotatable relative to the disk42about a pitch axis P by virtue of the fan blades40being operatively coupled to a suitable pitch change mechanism44configured to collectively vary the pitch of the fan blades40in unison. The fan blades40, disk42, and pitch change mechanism44are together rotatable about the longitudinal axis12by LP shaft36across a power gear box46. The power gear box46includes a plurality of gears for adjusting the rotational speed of the fan38relative to the LP shaft36to a more efficient rotational fan speed. More particularly, the fan section includes a fan shaft rotatable by the LP shaft36across the power gearbox46. Accordingly, the fan shaft may also be considered a rotary component, and is similarly supported by one or more bearings.

It should be appreciated, however, that the exemplary turbofan engine12depicted inFIG. 1is provided by way of example only, and that in other exemplary embodiments, the turbofan engine12may have any other suitable configuration. It should also be appreciated, that in still other exemplary embodiments, aspects of the present disclosure may be incorporated into any other suitable gas turbine engine. For example, in other exemplary embodiments, aspects of the present disclosure may be incorporated into, e.g., a turboprop engine, a turboshaft engine, or a turbojet engine. Further, in still other embodiments, aspects of the present disclosure may be incorporated into any other suitable turbomachine, including, without limitation, a steam turbine, a centrifugal compressor, and/or a turbocharger.

Referring now toFIG. 2, a close-up view of the exemplary turbofan engine12ofFIG. 1is provided. More particularly,FIG. 2provides a close-up view of the turbine section, including the HP turbine28and a first rotor blade stage of the LP turbine30. The HP turbine28is positioned downstream of a combustor (not shown) of the combustion section26and upstream of the LP turbine30. As discussed above, the combustion section26, or rather the combustor, mixes fuel with pressurized air for generating hot combustion gases which flows in a downstream direction D through the turbines.

The HP turbine28includes a first turbine nozzle stage80located upstream of a first rotor blades stage82. The first turbine nozzle stage80includes a plurality of circumferentially spaced nozzles sections84. Each of the nozzle sections84includes an airfoil86configured for directing an airflow through the HP turbine28. Similarly, the first rotor blade stage82includes a plurality of circumferentially spaced HP turbine rotor blades88. Each of the HP turbine rotor blades88includes a turbine airfoil90integrally formed with a platform92and an axial entry dovetail94, which is used to mount the HP turbine rotor blade88on a perimeter of a supporting rotor disk96.

Referring now toFIG. 3, providing a perspective view of a HP turbine rotor blade88, the airfoil90extends outwardly along a spanwise direction S (and along a radial direction R when installed in a gas turbine engine) from an airfoil base98on the blade platform92to an airfoil tip100. During operation, hot combustion gases are generated in the combustor and flow downstream D over the turbine airfoil90which extracts energy therefrom for rotating the rotor disk96supporting the HP turbine rotor blade88. The rotor disk96may, in turn, rotate a shaft or spool (e.g., HP shaft34, not shown) for powering, e.g., a compressor. A portion of pressurized air102, e.g., from the compressor section of the turbofan engine12, may be directed to the HP turbine rotor blade88for cooling thereof during operation.

The airfoil90includes widthwise spaced apart generally concave pressure sidewall104and convex suction sidewall106. The pressure and suction sidewalls104,106extend outwardly along the spanwise direction S from the airfoil base98to the airfoil tip100. The sidewalls104,106also extend generally along a chordwise direction C (and along an axial direction A when installed in a gas turbine engine) from a leading edge108towards an opposing trailing edge110. The exemplary airfoil90depicted is hollow with the pressure and suction sidewalls104,106being spaced widthwise or laterally apart between the leading and trailing edges108,110to define an internal cooling air cavity112or circuit therein. The cooling air cavity112may circulate the pressurized cooling air102, e.g., from the compressor section, and inject such cooling air102onto a hot side surface of the airfoil90as film cooling during operation.

The exemplary turbine airfoil90depicted increases in width W or widthwise from the leading edge108to a maximum width aft therefrom and then converges to a relatively thin or sharp trailing edge110. The size of the internal cooling air cavity112therefore varies with the width W of the airfoil90, and is relatively thin immediately forward of the trailing edge110where, for the embodiment depicted, the two sidewalls104,106integrally join together and form a thin trailing edge section114of the airfoil90(located aft or downstream D from a body section116of the airfoil90, the body section116defined by both the pressure sidewall104and suction sidewall106). One or both of the pressure sidewall104and suction sidewall106additionally define a trailing edge cooling channel118extending from the cooling air cavity112substantially to the trailing edge110. More particularly, for the embodiment depicted, one or both of the pressure sidewall104and suction sidewall106define a plurality of trailing edge cooling channels118, the plurality of trailing edge cooling channel118spaced along the spanwise direction S of the airfoil90. Each of the plurality of trailing edge cooling channels118is configured to cool the trailing edge110of the airfoil90.

Referring now also toFIGS. 4 and 5, close-up views of one or more trailing edge cooling channels118are provided. Specifically,FIG. 4provides a close-up view of three of the plurality of spanwise spaced apart trailing edge cooling channels118; andFIG. 5provides a close-up, side, cross-sectional view of one of the plurality of trailing edge cooling channels118, taken along Line5-5ofFIG. 4. As is depicted, the trailing edge cooling channels118each extend along the chordwise direction C substantially to the trailing edge110. Additionally, the trailing edge cooling channels118are spaced along the spanwise direction S and are in flow communication with the cooling air cavity112for discharging the cooling air102therefrom during operation.

Each trailing edge cooling channel118includes in serial flow relationship, an inlet120, an interior portion122, and a trailing edge cooling slot124. With such an embodiment, cooling air102may flow through the interior portion122of the trailing edge cooling channel118to the trailing edge cooling slot124. The trailing edge cooling slot124, sometimes referred to as the pressure side bleed slot, begins at a breakout126at a downstream end128of the interior portion122and, for the embodiment illustrated, diverges spanwise. Such a configuration may allow for a flow of cooling air102through the plurality of trailing edge cooling channels118to disperse and more effectively cool the trailing edge110of the airfoil90in the spanwise direction S. It should be appreciated, however, that in other embodiments, the cooling channels118may not include the trailing edge cooling slot124, and instead the cooling channels118may extend directly to the trailing edge110. With such an embodiment, the trailing edge cooling channel118may instead be referred to a trailing edge ejection hole. Additionally, although for the embodiment depicted the trailing edge cooling channels118each extend generally along the chordwise direction C, in other embodiments, the cooling channels118may instead have any other suitable orientation, and may define an angle relative to the chordwise direction C.

Further, for the embodiment depicted, one or both of the pressure sidewall104and suction sidewall106include a plurality of pressure drop members130extending partially into each of the trailing edge cooling channels118for reducing an amount of cooling air102flowing therethrough from the cooling air cavity112. More specifically, for the embodiment depicted, the suction sidewall106includes the plurality of pressure drop members130extending partially into each of the trailing edge cooling channels118(seeFIG. 5). Each of these pressure drop members130are configured as a semi-circular, rounded protrusion extending partially into the trailing edge cooling channel118. The semi-circular protrusions may each be substantially the same size. It should be appreciated, however, that although each of the plurality of pressure drop members130have a substantially consistent size and shape for the embodiment depicted, in other exemplary embodiments, a size and/or shape of the pressure drop members130may vary in any suitable manner. It should also be appreciated that as used herein, “extending partially into” refers to the pressure drop member130extending from one wall, into the cooling channel118, but not across the cooling channel118. For example, in the embodiment depicted, the pressure drop members130extend from suction sidewall106into the cooling channel118, but do not connect to the pressure sidewall104.

Referring now particularly toFIG. 5, the interior portion122of each of the cooling holes30includes height132defined between the pressure sidewall104and suction sidewall106. As is depicted, the height132of each of the trailing edge cooling channels118is substantially constant for the interior portions122of the respective channels118. Moreover, with the exception of the plurality of pressure drop members130extending partially into the trailing edge cooling channels118, the interior portions122of the trailing edge cooling channels118define a substantially constant cross-sectional flow area (i.e., an area defined in a plane perpendicular to a centerline of the respective cooling channels118). For example, the exemplary trailing edge cooling channel118depicted defines a first cross-sectional flow area A1immediately upstream of the plurality of pressure drop members130, e.g., proximate the inlet120of the trailing edge cooling channel118. The trailing edge cooling channel118additionally defines a second cross-sectional flow area A2immediately downstream of the plurality of pressure drop members130, and immediately upstream of the trailing edge cooling slot124. For the embodiment depicted, the first cross sectional flow area A1is substantially the same as the second cross sectional flow area A2. Additionally, although not marked in the FIGS., the interior portion122of the trailing edge cooling channel118defines a variety of intermediate cross-sectional flow areas between adjacent pressure drop members130. Each of these intermediate cross-sectional flow areas is substantially the same as the first and second cross-sectional flow areas A1, A2. It should be appreciated, that as used herein, terms of approximation, such as “about” or “substantially,” refer to being within a 5% margin of error.

Within the interior portions122of the trailing edge cooling channels118, the trailing edge cooling channel118defines a primary metering section134. The primary metering section134refers to a minimum cross-sectional flow area for a given trailing edge cooling channel118. For the embodiment depicted, one of the plurality of pressure drop members130is located at the primary metering section134, and at least partially defines the primary metering section134. Notably, for the embodiment depicted, each of the plurality of pressure drop members130within the interior portion122of the trailing edge cooling channels118are substantially the same size, and the interior portion122of the trailing edge cooling channel118defines a substantially constant cross-sectional flow area (save for the pressure drop members130). The pressure drop member130located proximate the inlet120(i.e., an upstream pressure drop member) is located at, and at least partially defines, the primary metering section134.

Although the exemplary trailing edge cooling channel118may define substantially the same cross-sectional area at each of the plurality of pressure drop members130, the downstream pressure drop members130are not be considered the primary metering section (as there is no reduction in cross-sectional area). However, the downstream pressure drop members130may still assist in controlling a flow of cooling airflow therethrough by effecting a pressure drop of the cooling air102flowing therethrough. Accordingly, such a configuration may further reduce a flowrate of the cooling air102flowing therethrough without requiring additional reductions to the cross-sectional area of the primary metering section134. More particularly, by including the one or more pressure drop members130downstream of, and in addition to, the primary metering section134, the primary metering section134may include a larger opening that may be easier to manufacture accurately.

It should be appreciated, however, that in other exemplary embodiments, the trailing edge cooling channels118may have any suitable configuration. For example, although for the embodiments depicted, the interior portions122of the trailing edge cooling channels118each define a substantially consistent height132(and cross-sectional area), in other exemplary embodiments the interior portions122of the trailing edge cooling channels118may vary in height132, and may, e.g., diverge or converge, along a length thereof. Further, in other exemplary embodiments, the trailing edge cooling channels118may define any suitable cross-sectional shape. For example, in the embodiments depicted, the trailing edge cooling channels may define a circular cross-sectional shape, or alternatively may define a squared or rectangular cross-sectional shape, or any other suitable cross-sectional shape.

It should also be appreciated that the pressure drop members130may in other exemplary embodiments vary in size, shape, and/or number. For example, in other embodiments, one or more of the pressure drop members130may not have a rounded, semicircular shape, and each trailing edge cooling channel may only include two pressure drop members, or alternatively may include four or more pressure drop members. In one or more of the above embodiments, the primary metering section134in the trailing edge cooling channel118may not be defined at the upstream pressure drop member130, and instead may be defined at one of the intermediate or downstream pressure drop members130. Furthermore, in certain embodiments, the plurality of pressure drop members130may be sized such that a local effective cross-sectional area at the respective pressure drop members130allow two or more pressure drop members130to act equally as metering sections. For example, two separate pressure drop members130may each provide about half of an overall pressure loss through the trailing edge cooling channel118. By providing two or more pressure drop members130configured to effect a pressure drop, the metering function is distributed to more than a single cross sectional area, and hence may be more manufacturable (e.g., may allow for less restrictive size limitations) and may also be more robust to variations

Referring still toFIG. 5, as previously noted, the pressure sidewall104and suction sidewall106together define a body section116of the airfoil90. Additionally, for the embodiment depicted, both of the pressure sidewall104and suction sidewall106together define the trailing edge section114of the airfoil90. The trailing edge section114is formed separately from the body section116. The separately formed trailing edge section114may be attached to the body section116, for the embodiment depicted at the attachment line136(see alsoFIG. 4). For example, in certain exemplary embodiments, the body section116of the airfoil90may be formed at least partially by casting the body section116of the airfoil90, and the trailing edge section114of the airfoil90may be formed using an additive manufacturing process (also known as rapid prototyping, rapid manufacturing, and 3D printing). For example, in certain exemplary aspects, the trailing edge section114of the airfoil90may be manufactured using selective laser sintering (SLS), direct metal laser sintering (DMLS), electron beam melting (EBM), diffusion bonding, or selective heat sintering (SHS). Such an exemplary manufacturing process may allow for an airfoil90including the relatively fine details described in the exemplary trailing edge section114of the airfoil90. Alternatively, however, the trailing edge section114may be constructed (e.g., printed) directly onto the existing projection140.

It should be appreciated, however, that in other exemplary embodiments, the trailing edge section114may instead be manufactured in any other suitable manner. For example, referring now toFIG. 6, a close-up, side, cross-sectional view of a trailing edge cooling channel118of a trailing edge section114in accordance with another exemplary embodiment of the present disclosure is provided. The airfoil90of the exemplary embodiment ofFIG. 6may be configured in substantially the same manner as exemplary airfoil90depicted inFIG. 5. Accordingly, the same or similar numbering may refer to the same or similar part.

As is depicted, however, a pressure sidewall104and a suction sidewall106of the exemplary airfoil90ofFIG. 6do not together define a trailing edge section114of the exemplary airfoil90. Instead, as is indicated by an attachment line138, the pressure sidewall104defines the separately formed trailing edge section114of the airfoil90. With such an exemplary embodiment, the suction sidewall106includes a projection140extending along the spanwise direction S and extending along the chordwise direction C to which the trailing edge section114(defined by a portion of the pressure sidewall104) may be attached. The separately formed portion of the pressure sidewall104defining the trailing edge section114may be formed using an additive manufacturing process, and may include a plurality of pressure drop members130extending partially into the trailing edge cooling channel118once the trailing edge section114is attached to the body section116of the airfoil90. Notably, for the embodiment depicted, the trailing edge cooling channels118are together defined by the pressure sidewall104and the suction sidewall106(or rather the projection140of the suction sidewall106).

For the embodiment depicted, the separately formed trailing edge section114may be attached after constructing (e.g., “printing”) the trailing edge section. Alternatively, however, the trailing edge section114may be constructed (e.g., printed) directly onto the existing projection140. Regardless, it should be appreciated that the projection140of the suction sidewall106may be cast with the suction sidewall106and machined to a desired final definition (e.g., final desired thickness, etc.), and/or may undergo some other machining steps to, e.g., prepare a surface of the projection for joining or printing thereon.

Further, however, in still other exemplary embodiments, the trailing edge section114may be manufactured in any other suitable manner. For example, referring now toFIG. 7, a close-up, side, cross-sectional view of the trailing edge cooling channel118of a trailing edge section114in accordance with another exemplary embodiment of the present disclosure is provided. The airfoil90of the exemplary embodiment ofFIG. 7may also be configured in substantially the same manner as the exemplary airfoil90depicted inFIG. 5. Accordingly, the same or similar numbering may refer to the same or similar part.

For the exemplary airfoil90ofFIG. 7, the suction sidewall106defines the separately formed trailing edge section114of the airfoil90(as is indicated by the attachment line144. With such an exemplary embodiment, the pressure sidewall104includes a projection142extending along the spanwise direction S and along the chordwise direction C to which the trailing edge section114(defined by a portion of the suction sidewall106) may be attached. The separately formed portion of the suction sidewall106defining the trailing edge section114may be formed using an additive manufacturing process, and may include a plurality of pressure drop members130extending partially into a trailing edge cooling channel118once the trailing edge section114is attached to the body section116of the airfoil90. Notably, for the embodiment depicted, the trailing edge cooling channels118may be together defined by the suction sidewall106and the pressure sidewall104(or rather the projection142of the pressure sidewall104). Accordingly, as with the embodiments described above, the separately formed trailing edge section114may be fully constructed and then attached to the body section116. Alternatively, the trailing edge section114may be construction (e.g., printed) directly onto the projection142of the pressure sidewall104.

Referring now toFIG. 8, a flow diagram of an exemplary method (200) of manufacturing a turbine airfoil for a gas turbine engine is provided. The exemplary method (200) may be utilized to manufacture one or more of the exemplary turbine airfoils described above with reference toFIGS. 2 through 7. Accordingly, in certain exemplary aspects, the exemplary airfoil may define a leading edge, a trailing edge, and a span.

The exemplary method (200) includes at (202) forming a body section of the airfoil extending from the leading edge of the airfoil towards the trailing edge of the airfoil. The body section defines the cooling air cavity located proximate the trailing edge of the airfoil. Additionally, the exemplary method (200) includes at (204) forming a trailing edge section of the airfoil using an additive manufacturing process. The trailing edge section is formed integrally with or attachable to the body section the airfoil and at least partially defines a trailing edge cooling channel. The trailing edge cooling channel extends from the cooling air cavity defined by the body section substantially to the trailing edge of the airfoil. The trailing edge section is additionally formed such that the trailing edge section includes a plurality of pressure drop members extending partially into the trailing edge cooling channel for reducing an amount of cooling air flowing therethrough.

For the exemplary aspect depicted, forming the body section the airfoil at (202) may include forming the body section of the airfoil by casting the body section of the airfoil. With such an exemplary aspect, the trailing edge section may be formed at (204) separately from, but attachable to, the body section of the airfoil. Accordingly, with such an exemplary aspect, the exemplary method (200) further includes at (206) attaching the trailing edge section of the airfoil to the body section of the airfoil. Attaching the trailing edge section to the body section at (206) may include attaching by joining, brazing, diffusion bonding, etc. However, in other exemplary aspects, forming the body section of the airfoil at (202) may include forming the body section of the airfoil using an additive manufacturing process. With such an exemplary aspect, the trailing edge section may be formed at (204) integrally with the body section of the airfoil.

Furthermore, in certain exemplary aspects, the airfoil may include a pressure sidewall and suction sidewall. The pressure sidewall and suction sidewall may together define the body section of the airfoil. As is discussed with the various exemplary embodiments ofFIGS. 4 through 7, in certain exemplary aspects, forming the trailing edge section of the airfoil at (204) may include forming the trailing edge section the airfoil to include a portion of the pressure sidewall and a portion of the suction sidewall (seeFIG. 4). However, in other exemplary aspects, forming the trailing edge section of the airfoil at (204) may instead include forming the trailing edge section of the airfoil to include only a portion of one of the pressure sidewall or suction sidewall (seeFIGS. 6 and 7). In such an exemplary aspect, forming the body section of the airfoil at (202) may include forming an extension extending along the span of the airfoil for receiving the trailing edge section. Such an exemplary aspect may further include attaching the trailing edge section of the airfoil to the body section the airfoil, or more particularly, attaching the trailing edge section of the airfoil to the extension of the body section of the airfoil. Further, with such an exemplary aspect, the trailing edge section may define the trailing edge cooling channel with the extension of the body section of the airfoil.