The subject matter disclosed herein generally relates to airflow in components of gas turbine engines and, more particularly, to pedestals and slots in a trailing edge cavity of an airfoil in components of gas turbine engines.
Airfoils, and particularly airfoils of gas turbine engines, may include internal flow passages to enable cooling of the airfoils. The supply of the cooling air through cavities of the airfoils may be carefully designed so as to provide an efficient cooling configuration. However, various structures and/or features of the airfoils may impact cooling schemes, thus reducing the efficiency and/or effectiveness of a cooling scheme.
According to some embodiments, airfoils for gas turbine engines are provided. The airfoils include an airfoil body having a leading edge and a trailing edge extending in a radial direction, a cooling cavity defined within the airfoil body at the trailing edge, and a plurality of angled pedestals arranged along the trailing edge, wherein the plurality of angled pedestals define a plurality of angled trailing edge slots therebetween. Adjacent angled pedestals of the plurality of angled pedestals define a meter section of a respective angled trailing edge slot and a diffuser section of the respective angled trailing edge slot, wherein the meter section is defined by parallel sides of the adjacent angled pedestals, wherein the parallel sides of the adjacent angled pedestals are oriented at a bleed direction that is less than 90° with respect to a feed direction through the cooling cavity.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the bleed direction is between 40° and 70° with respect to the feed direction.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the meter section has a length that is a minimum of one and a half times a hydraulic diameter.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include an upstream heat transfer augmentation feature arranged within the cooling cavity upstream relative to the plurality of angled pedestals in a flow direction through the cooling cavity.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the upstream heat transfer augmentation feature comprises a plurality of pedestals.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the upstream heat transfer augmentation feature comprises an impingement rib.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the diffuser section is defined between tapering walls of adjacent elongated pedestals of the plurality of angled pedestals, the diffuser section extending from the meter section to the trailing edge, wherein a downstream side defining the diffusion section has an angle β and an upstream side defining the diffusion section has an angle γ.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the angle β is greater than the angle γ.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the angle β is between 0° and 20°.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the angle γ is between 0° and 7°.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include a dividing rib separating the cooling cavity into a first cooling cavity and a second cooling cavity, wherein the dividing rib extends in an axial direction from a radially extending rib of the airfoil through the cooling cavity toward the trailing edge, wherein a first set of angled pedestals of the plurality of pedestals is located within the first cooling cavity.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the second cooling cavity includes a second set of angled pedestals.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the dividing rib extends a full distance from the radially extending rib to the trailing edge.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the first cooling cavity is fed cooling air from a first end of the airfoil and the second cooling cavity is fed cooling air from a second end of the airfoil.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include a rib flow control feature located at a trailing edge end of the dividing rib.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the rib flow control feature is hollow.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the trailing edge is a bowed trailing edge.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that each angled pedestal of the plurality of angled pedestals is the same length.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the angled pedestals of the plurality of angled pedestals having varying lengths.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that each angled pedestal of the plurality of angled pedestals is teardrop-shaped.
In addition to one or more of the features described above, or as an alternative, further embodiments of the airfoils may include that the plurality of angled pedestals are arranged parallel to each other.
The foregoing features and elements may be executed or utilized in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, that the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting.
The subject matter is particularly pointed out and distinctly claimed at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The gas turbine engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine centerline longitudinal axis A. The low speed spool 30 and the high speed spool 32 may be mounted relative to an engine static structure 33 via several bearing systems 31. It should be understood that other bearing systems 31 may alternatively or additionally be provided.
The low speed spool 30 generally includes an inner shaft 34 that interconnects a fan 36, a low pressure compressor 38 and a low pressure turbine 39. The inner shaft 34 can be connected to the fan 36 through a geared architecture 45 to drive the fan 36 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 35 that interconnects a high pressure compressor 37 and a high pressure turbine 40. In this embodiment, the inner shaft 34 and the outer shaft 35 are supported at various axial locations by bearing systems 31 positioned within the engine static structure 33.
A combustor 42 is arranged between the high pressure compressor 37 and the high pressure turbine 40. A mid-turbine frame 44 may be arranged generally between the high pressure turbine 40 and the low pressure turbine 39. The mid-turbine frame 44 can support one or more bearing systems 31 of the turbine section 28. The mid-turbine frame 44 may include one or more airfoils 46 that extend within the core flow path C.
The inner shaft 34 and the outer shaft 35 are concentric and rotate via the bearing systems 31 about the engine centerline longitudinal axis A, which is co-linear with their longitudinal axes. The core airflow is compressed by the low pressure compressor 38 and the high pressure compressor 37, is mixed with fuel and burned in the combustor 42, and is then expanded over the high pressure turbine 40 and the low pressure turbine 39. The high pressure turbine 40 and the low pressure turbine 39 rotationally drive the respective high speed spool 32 and the low speed spool 30 in response to the expansion.
The pressure ratio of the low pressure turbine 39 can be pressure measured prior to the inlet of the low pressure turbine 39 as related to the pressure at the outlet of the low pressure turbine 39 and prior to an exhaust nozzle of the gas turbine engine 20. In one non-limiting embodiment, the bypass ratio of the gas turbine engine 20 is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor 38, and the low pressure turbine 39 has a pressure ratio that is greater than about five (5:1). It should be understood, however, that the above parameters are only examples of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines, including direct drive turbofans.
In this embodiment of the example gas turbine engine 20, a significant amount of thrust is provided by the bypass flow path B due to the high bypass ratio. The fan section 22 of the gas turbine engine 20 is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. This flight condition, with the gas turbine engine 20 at its best fuel consumption, is also known as bucket cruise Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust.
Fan Pressure Ratio is the pressure ratio across a blade of the fan section 22 without the use of a Fan Exit Guide Vane system. The low Fan Pressure Ratio according to one non-limiting embodiment of the example gas turbine engine 20 is less than 1.45. Low Corrected Fan Tip Speed is the actual fan tip speed divided by an industry standard temperature correction of [(Tram ° R)/(518.7° R)]0.5, where T represents the ambient temperature in degrees Rankine. The Low Corrected Fan Tip Speed according to one non-limiting embodiment of the example gas turbine engine 20 is less than about 1150 fps (351 m/s).
Each of the compressor section 24 and the turbine section 28 may include alternating rows of rotor assemblies and vane assemblies (shown schematically) that carry airfoils that extend into the core flow path C. For example, the rotor assemblies can carry a plurality of rotating blades 25, while each vane assembly can carry a plurality of vanes 27 that extend into the core flow path C. The blades 25 of the rotor assemblies create or extract energy (in the form of pressure) from the core airflow that is communicated through the gas turbine engine 20 along the core flow path C. The vanes 27 of the vane assemblies direct the core airflow to the blades 25 to either add or extract energy.
Various components of a gas turbine engine 20, including but not limited to the airfoils of the blades 25 and the vanes 27 of the compressor section 24 and the turbine section 28, may be subjected to repetitive thermal cycling under widely ranging temperatures and pressures. The hardware of the turbine section 28 is particularly subjected to relatively extreme operating conditions. Therefore, some components may require internal cooling circuits for cooling the parts during engine operation. Example cooling circuits that include features such as airflow bleed ports are discussed below.
Although an aero or aircraft engine application is shown and described above, those of skill in the art will appreciate that airfoil configurations as described herein may be applied to industrial applications and/or industrial gas turbine engines, land based or otherwise.
Turning now to
As shown, the airfoil 200 has an airfoil body 202 extending radially from a first end 204 (e.g., an inner diameter or root region) to a second end 206 (e.g., an outer diameter or tip region). An inner platform 208 is shown at the inner diameter (e.g., first end 204), with the airfoil body 202 extending radially therefrom, and an outer platform 210 is located at the outer diameter (e.g., second end 206) of the airfoil body 202. As shown, the airfoil body 202 define one or more cavities and/or flow paths therein that are configured to enable cooling of the airfoil 200.
A first cooling cavity 216 is located proximate the leading edge 212 of the airfoil 200 and a second cooling cavity 218 is located proximate the trailing edge 214 of the airfoil 200. The first cooling cavity 216 is fluidly separated from the second cooling cavity 218 by a rib 220. In the embodiment of
Cooling air enters the first cooling cavity 216 through a first feed supply 222 that is formed in the first platform 208. The air will then flow from the first end 204 toward the second end 206 of the airfoil body 202. As the air flows through the first cooling cavity 216, a portion of the air may be expunged or bled through one or more apertures within the surfaces of the airfoil body 202 and thus be ejected into a gaspath. Cooling air enters the second cooling cavity 218 through a second feed supply 224 that is formed in the second platform 210. The air will then flow from the second end 206 toward the first end 204 of the airfoil body 202. As the air flows through the second cooling cavity 218, a portion of the air will exit through the trailing edge 214 of the airfoil body 202 and thus be ejected into the gaspath. In some embodiments, the flow directions of the cooling flow into the first and second cooling cavities 216, 218 may be the opposite of that shown in
As shown in the example embodiment of
Turning to
As shown in
The meter section 234 is defined between parallel walls or sides of the adjacent elongated pedestals 226, as shown. That is, the trailing edge slots 231 have uniform widths 236 along the meter section 234 defined by adjacent elongated pedestals 226. Each of the trailing edge cooling flow slots 231 further includes a tapering diffuser section 238 formed aft of the meter section 234 of a given trailing edge cooling flow slot 231. The tapering diffuser section 238 expands outward from the meter section 234 to the trailing edge 214. As such, the trailing edge slots 231 widen in the streamwise direction of cooling flow toward the trailing edge 214. The uniform width 236 of the meter sections 234 of the trailing edge cooling flow slots 231 may have a length (i.e., streamwise length) based on the hydraulic diameter, typically greater than one and a half times the hydraulic diameter (1.5 Dh). The incorporation and utilization of a flow development length along the metering section 234, within the trailing edge cooling flow slot(s) 231, enables the cooling flow structure to be more stable and uniformly aligned, thereby improving the convective and film cooling characteristics by reducing and/or eliminating the local vortices within the cooling flow, which inherently induce more turbulent mixing and entrainment of hot gas.
However, as illustratively shown in
Although illustrated in
As discussed, the shape and orientation of the elongated pedestals is selected to improve flow as it exits through the trailing edge slot of the airfoil. However, these optimized and oriented elongated pedestals may still have flow inefficiencies and/or losses due to the turning of cooling flow required.
For example, turning now to
Cooling air enters the cooling cavity 318 through the feed supply 322 and flows radially outward from the first end 304 toward a second end of the airfoil in the feed direction Df. As the air flows through the cooling cavity 318, a portion of the air will exit through the trailing edge 314 of the airfoil and thus be ejected into the gaspath. As shown, the trailing edge 314 is configured with a plurality of elongated pedestals 326 similar to that described above. Each elongated pedestal 326 has an upstream side 348 and a downstream side 350. The cooling flow 346 flows in the feed direction Df and will turn to flow between the elongated pedestals 326 in a bleed direction Db. In this configuration, as shown, the cooling flow 346 will turn at a bleed angle α of about 90° when entering the trailing edge slots 331 defined between adjacent elongated pedestals 326. The bleed angle α is the angle of change in direction of the cooling flow 346 as it turns from the feed direction Df to the bleed direction Db. The upstream side 348 and the downstream side 350 of the elongated pedestals 326 is based on the feed direction Df, as shown.
Due to the high velocity air in the cooling cavity 318, from the feed supply 322, and the angle in which the cooling flow is bled off from the cooling cavity 318 (i.e., bleed direction Db), the pressure feeding the trailing edge slots 331 of the airfoil is closer to static pressure than total pressure. Further, because the cooling flow 346 will turn at the bleed angle α of about 90° when entering the trailing edge slots 331, a flow separation will result off the downstream side 350 generating local flow vorticities 340, as illustratively shown. The local flow vorticities 340 create regions of local flow separation and recirculation. As will be appreciated by those of skill in the art, these undesirable cooling flow characteristics, produce increased pressure loss and significantly reduce the internal convective heat transfer and film cooling effectiveness, resulting in lower thermal cooling performance in the airfoil trailing edge region. Further, as shown, when the airfoil 300 is a blade that is rotated within a gas turbine engine, the rotational effects cause the cooling flow 346 within the trailing edge slots 331 to be centrifuged outward causing flow separation 354 adjacent to the downstream side 350 of the elongated pedestal, as the cooling flow is expanded through the tapering diffusing section 338 at the outlets of the trailing edge slots 331. This flow separation 354 may be most apparent along the tapering diffuser sections of the elongated pedestals 326 in the diffusing section of the trailing edge slots 331.
Turning now to
As the cooling air flows through the trailing edge cooling cavity 418, a portion of the air will exit through one or more trailing edge slots 431 at the trailing edge 414 of the airfoil 400 and then discharge into the gaspath. The trailing edge slots 431 are defined by a plurality of elongated pedestals 426 similar to that described above. Each elongated pedestal 426 has an upstream side 448 and a downstream side 450. Further, similar to the elongated pedestals described above, the elongated pedestals 426 have a meter section 434 and a diffuser section 438. The meter section 434 of the elongated pedestals 426 are relatively oriented to define parallel walls that define a constant width (e.g., constant flow area) trailing edge slot 431. The diffuser sections 438 define tapering walls that expand the width of the trailing edge slots 431 as the trailing edge slots 431 approach the trailing edge 414 of the airfoil 400.
Continuing with reference to
The bleed angle α is defined by the angle of the trailing edge slots 431 defined between angled elongated pedestals 426. The slanted elongated pedestals 426 are oriented at the bleed angle α such that the meter sections 434 of the angled elongated pedestals 426 incorporate parallel metering wall features that are oriented in a direction parallel to the bleed angle α. The diffuser sections 438 extend toward the trailing edge 414 from the ends of the metered sections 434. Airfoils of the present disclosure include a plurality of angled elongated pedestals 426 with each elongated pedestal being substantially oriented similar to either adjacent angled elongated pedestal, thereby creating parallel meter sections 434 that are present through the plurality of angled elongated pedestal features.
The meter sections 434 have uniform width and have a length (i.e., streamwise length) based on the hydraulic diameter. In some embodiments, the streamwise length of the meter section 434 may be greater than one and a half times the hydraulic diameter (1.5 Dh). The streamwise distance of the meter section 434 provides a development length necessary to “condition” the cooling flow within the trailing edge cooling flow slots 431. The ability to “condition” the cooling flow ensure a more stable and uniformly distributed flow structure is achieved within the cooling flow slots 431, thereby maximizing the local convective heat transfer, film cooling, and thermal cooling effectiveness characteristics immediately adjacent to the airfoil trailing edge. In this embodiment, as noted above, the meter sections 434, and the walls or portions of the slanted elongated pedestals 426 are parallel.
Because the angle in which flow is bled off from the cooling cavity 418 into the trailing edge slots 431 (i.e., at the bleed angle α) is less than 90°, the pressure feeding the trailing edge slots 431 is closer to total pressure than static pressure. Further, because the trailing edge slots 431 are angled at the bleed angle α in the same direction that rotational centrifugal effect cause cooling flow to be urged radially outward, the flow separation described above may be significantly minimized or eliminated. Moreover, the local flow vorticities and region of flow separation described above that typically occurs along the elongated pedestals at the entrance to the trailing edge slots 431 due to the high rate of flow turning associated with the bleed angle α that is more consistent with 90°, may be reduced or eliminated due to the decreased relative turning of the cooling airflow flow 446 associated with the incorporation of angled elongated pedestals of the present disclosure.
Turning now to
As shown in
Turning now to
Turning now to
Turning now to
The diffuser sections 838 of some embodiments of the present disclosure may have differing diffusion angles (i.e., the change in wall angle after the meter section 834 ends). As shown in
Depending on a desired diffusion to be achieved, the first diffusion angle β and the second diffusion angle γ may be different, producing a non-axisymmetric tapered geometry feature. For example, in some embodiments, the first diffusion angle β may be an angle between 0° and about 20° and the second diffusion angle γ may be an angle between 0° and about 7°. In rotating airfoil designs, centrifugal forces allow for the diffusion angles to be larger on the upstream side 848 as compared to the downstream side 850 of the angled elongated pedestals 826. In reference to the trailing edge slot 831, larger radial slot diffusion angles are acceptable due to rotational inertial forces which inherently “push” the flow toward the radially outboard or downstream side of the trailing edge slot 831. Conversely, the radially inboard or upstream side of the trailing edge slot 831 requires “smaller” diffusion angles in order to mitigate the potential for cooling flow separation due to the rotational inertial forces, which “pulls” the flow away from the upstream side of the trailing edge slot 831, generating local flow vortices that can entrain hot freestream gas reducing the local thermal performance of the airfoil trailing edge.
Turning now to
Turning now to
As shown and described above, the angled elongated pedestals are all arranged to be parallel along the length of the trailing edge. However, in some embodiments, not all of the angled elongated pedestals need be angled at the same angle or even in the same direction. For example, in some configurations, a trailing edge cooling cavity may be fed cooling air from both the inner and outer diameters (e.g., in a vane). In some blade configurations, a serpentine flow can be employed to supply cooling air proximate the tip, and thus radially inward flowing, while a separate supply of cooling air can be provided from the root region, thus allowing for contra-sourced cooling flows in a blade.
For example, turning to
Turning to
Turning to
Although shown in the above illustrative embodiments of
In the embodiments described above, and variations thereon, the metering length (i.e., length of the meter section) between any two adjacent elongated pedestals features will have a minimum metering length (e.g., 1.5 Dh). In some embodiments, due to, for example, the curved nature of the trailing edge of the airfoil, the total metering length for one elongated pedestal to any adjacent elongated pedestal may be different because the relative orientation angle of the elongated pedestal features may differ. In some such embodiments, the elongated pedestal feature length may change as function of radial location along the airfoil trailing edge. However, the amount of “overlap” between adjacent metering sections must be maintained at a minimum of one and a half times the hydraulic diameter (1.5 Dh).
Moreover, in some embodiments, in order to achieve an adequate flow development length it may be necessary to modify the lengths of the metering section defined by any two adjacent angled elongated pedestals features. The overall length of the elongated pedestal feature and the meter length requirements for any two adjacent elongated pedestal features may be dictated by the shape of the airfoil trailing edge. For example, the shape of the airfoil trailing edge may be, without limitation, linear, tapered, concave curvature/bow, convex curvature/bow as a function of the airfoil true chord. The different meter lengths of any two adjacent angled elongated pedestals may also impact the relative taper angles to be unique for each upstream and downstream side of the of any two adjacent elongated pedestal features. Additionally the length of the elongated pedestal geometry may also be dictated by cooling air temperature heat pick considerations as well as internal convective metering slot heat transfer requirements in order to effectively cool the local airfoil trailing edge region.
Advantageously, embodiment described herein provide for improved cooling flow at trailing edges of airfoils. The improved cooling is achieved through the inclusion of a plurality of angled elongated pedestals that are parallel to each other and defining meter sections between adjacent angled elongated pedestals. The angled elongated pedestals reduce the angle that a cooling flow has to make to enter a trailing edge slot defined between adjacent angled elongated pedestals. Accordingly, flow separation may be minimized or eliminated, resulting in lower pressure loss and better convective cooling flow characteristics. Advantageously, in some embodiments, the angled elongated pedestal arrangements described herein may eliminate the need for additional upstream flow conditioning features, such as crossover holes and pedestals. Moreover, additional real estate may be freed up for the radially extending cooling cavity (e.g., feed passage) at the trailing edge of the airfoil. Moreover, the angling of the trailing edge slots reduces the axial length of the slots while maintaining the same meter section length, giving even more real estate for the radial feed passage and bringing a high heat transfer coefficient found in the slot meter section closer to the trailing edge.
The use of the terms “a,” “an,” “the,” and similar references in the context of description (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or specifically contradicted by context. The modifier “about” and/or “approximately” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. It should be appreciated that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” “radial,” “axial,” “circumferential,” and the like are with reference to normal operational attitude and should not be considered otherwise limiting.
While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions, combinations, sub-combinations, or equivalent arrangements not heretofore described, but which are commensurate with the scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments.
Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
The present application claims priority from U.S. Provisional Patent Application No. 62/701,024, filed Jul. 20, 2018. The content of the priority application is hereby incorporated by reference in its entirety.
This invention was made with Government support under W58RGZ-16-C-0046 awarded by the United States Army. The Government has certain rights in this invention.
Number | Date | Country | |
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62701024 | Jul 2018 | US |