Patent Description:
The high pressure turbine drives the high pressure compressor through an outer shaft to form a high spool, and the low pressure turbine drives the low pressure compressor through an inner shaft to form a low spool. The fan section may also be driven by the low inner shaft. A direct drive gas turbine engine includes a fan section driven by the low spool such that the low pressure compressor, low pressure turbine and fan section rotate at a common speed in a common direction.

<CIT> discloses a prior art gas turbine engine turbine vane airfoil as set forth in the preamble of claim <NUM>.

<CIT> discloses a prior art gas turbine vane with an integral cooling system.

<CIT> discloses a prior art core for forming a cooling microcircuit.

<CIT> discloses a prior art gaspath component including minicore plenums.

<CIT> discloses a prior art turbine airfoil with improved cooling.

In one aspect, there is provided a gas turbine engine turbine vane airfoil as set forth in claim <NUM>.

In another aspect, there is provided a gas turbine engine as set forth in claim <NUM>.

"Low corrected fan tip speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (<NUM> °R)]^ <NUM>.

<FIG> illustrates a representative example of a gas turbine engine article, namely a turbine airfoil <NUM> used in the turbine engine <NUM> (see also <FIG>). As shown, the turbine airfoil <NUM> is a turbine vane; however, it is to be understood that, although the examples herein may be described with reference to the turbine vane, this disclosure is also applicable to turbine blades, blade outer air seals, and combustor panels. The turbine airfoil <NUM> is also shown in a cross-sectioned view in <FIG>.

Referring to <FIG> and <FIG>, the turbine airfoil <NUM> includes an inner platform <NUM>, an outer platform <NUM>, and an airfoil section <NUM> that spans between the inner and outer platforms <NUM>/<NUM>. The airfoil section <NUM> includes an airfoil outer wall <NUM> that delineates the profile of the airfoil section <NUM>. The outer wall <NUM> defines a leading end (LE), a trailing end (TE), and first and second sides <NUM>/<NUM> that join the leading and trailing ends. In this example, the first side <NUM> is a pressure side and the second side <NUM> is a suction side. The outer wall <NUM> circumscribes an internal core cavity <NUM>, which in this example is partitioned by a rib <NUM> into a forward core cavity 74a and an aft core cavity 74b. As will be appreciated, there may alternatively be only a single core cavity or there may be additional ribs to partition additional core cavities.

There is at least one cooling passage flow circuit network <NUM> embedded in the airfoil outer wall <NUM> between inner and outer portions 68a/68b of the airfoil wall <NUM>. For example, as shown (<FIG>) one or more of the cooling passage networks <NUM> is embedded in the first side <NUM> of the outer wall <NUM>, although one or more cooling passage flow circuit networks <NUM> could additionally or alternatively be embedded in the first side <NUM>. The cooling passage flow circuit networks <NUM> may also be referred to as minicores, minicore passages, micro-cores, and/or micro channels. A "minicore", "minicore passage", "micro-core", and "micro-channels" are all terms used to describe and/or reference an inter-wall convective and/or convective and film cooled cooling passage or circuit that comprises of various inlet feed geometries, internal convective heat transfer augmentation features, and exit discharge features in order to produce high film cooling capability.

As stated a "minicore" is typically an "inter-wall" or "embedded" cooling passage or circuit, that may be fabricated using a variety of manufacturing techniques, including, but not limited to, ceramic silica or alumina cores bodies, fabricated from core dies and used in conjunction with a wax pattern, as part of the "lost wax" investment casting process. Alternatively, minicores may also be fabricated from RMC (Refractory Metal Core) material which provides added core stiffness and robustness for producibility purposes. Advanced manufacturing techniques may also be used to fabricate ceramic "minicore" geometries, such as those used in additive manufacturing laser powder bed processes, which are then integrated into a wax pattern, as part of the "lost wax" investment casting process. In yet another alternate embodiment the "minicore" geometries may be fabricated directly out of metal using a DMLS (Direct Metal Laser Sintering) additive manufacturing laser powder bed metal process. As such, the minicores are integrated to provide highly effective "inter-wall" thermal cooling effectiveness, and therefore the relative size of the minicore internal convective cooling geometries and passages are significantly smaller in comparison to those employed in a main body core that is used to form a main or central core cavity in an airfoil.

<FIG> shows an "inverse" or negative view of a representative one of the cooling passages flowing circuit networks <NUM>. The inverse view is also representative of an investment core that may be used in an investment casting process to form the network <NUM> in the airfoil <NUM>. Most typically, the investment casting core is injection molded from a material that contains ceramic or metal alloy. The investment core is shaped to form the cooling passage flow circuit network <NUM>. In the inverse view, solid structures of the investment core produce void structures in the cooling passage flow circuit network <NUM> and void structures of the investment core produce solid structures in the cooling passage flow circuit network <NUM>. Thus, the investment core has the negative of the structural and internal convective heat transfer features of the cooling passage flow circuit network <NUM>. It is to be understood that although the inverse views presented herein may be used to describe features of the network <NUM>, each negative view also represents an investment core and a corresponding cavity in a molding tool and/or core die that is operable to molding and fabricating the investment core.

The cooling passage flow circuit network <NUM> includes at least one inlet orifice <NUM> through the inner portion 68a of the airfoil outer wall <NUM> (<FIG>) to receive cooling air from the internal core cavity <NUM>. The inlet orifice <NUM> may be, but is not limited to, round, rectangular, oval (racetrack) and may be sized appropriately to achieve desired flow and fill characteristics in the cooling passage flow circuit network <NUM>. Most typically, the cooling passage flow circuit network <NUM> will include <NUM> inlet orifices <NUM>. A single, exclusive inlet orifice <NUM> is also contemplated, as well as more than <NUM> inlet orifices <NUM>, although fabrication may be challenging. The size, location, and arrangement of the inlet apertures may vary depending on air flow and thermal cooling effectiveness requirements necessary to meet local metal temperature and durability life objectives.

The inlet orifices <NUM> open into a radially-elongated manifold region <NUM>, which serves to distribute the cooling air to a downstream sub-passage region <NUM>. Stated differently, the inlet flow apertures are arranged laterally within the minicore cooling circuit in order to optimize internal backside impingement and convective cooling flow characteristics, and mitigate local cooling flow recirculation zones and/or eliminate regions of internal flow separation which exhibit poor convective cooling characteristics. One of the inlet orifices <NUM> is located in the radially upper half of the manifold region <NUM> and the other of the inlet orifices <NUM> is in the radially lower half of the manifold region <NUM>. Most typically, the radially upper and lower halves of the network <NUM> are mirror images, i.e., symmetric relative to the midline of the network between the two inlet orifices <NUM>.

In this example, the region <NUM> includes an array of pedestals 82a that defines a plurality of sub-passages 82b there between. For instance, the pedestals 82a are provided in radially-aligned rows and may include up to <NUM> rows that are staggered relative to each other, although in the illustrated example there are <NUM> rows. The pedestals 82a as shown have a lobed-diamond cross-sectional geometry in which each of the faces of the diamond are concave such that the tips of the diamond form rounded projections, i.e., lobes. It is to be understood, however, that the pedestals 82a may alternatively be, but are not limited to, diamond or other polygonal shape, round, oval, or elliptical. The size of the pedestals 82a and sub-passages 82b may be determined based on achieving the desired cooling air flow, pressure loss, and convective heat transfer characteristics required across the minicore flow circuit network <NUM>.

It should be recognized by those skilled in the art that the axial or streamwise length of the minicore circuit network <NUM> and the number of pedestal rows and blockage requirements are also a strong function of the available pressure ratio across the minicore cooling passage flow circuit network <NUM>. The available pressure ratio is defined as the ratio of the supply pressure feeding the inlet orifices <NUM>, divided by the downstream minicore circuit slot exit region <NUM> static pressure sink or discharge pressure. The sink or discharge pressure is a function of the local airfoil surface Mach number, temperature, pressure gradient, and velocity, all of which are dictated by the aerodynamic shape and the amount of turning of the freestream air induced by the airfoil geometry.

The management of pressure ratio and the pressure losses within the minicore cooling passage flow circuit network is essential to achieving optimal thermal performance and convective efficiency. Therefore evaluating the pressure losses across each of the elements comprising the minicore cooling passage flow circuit must be evaluated. There are typically <NUM> main elements or regions within each of the minicore cooling passage flow circuits <NUM>, the inlet orifices or supply feeds <NUM> (region <NUM>), the internal heat transfer cooling features, i.e. trip strips, pedestals, pin fins, divots, hemispherical protrusions, etc, (region <NUM>), and the downstream plurality of exit flow features (region <NUM>).

The manifold region <NUM> and region <NUM> may also include additional heat transfer augmentation features such as dimples, trip-strips, pedestals, pin fins, hemispherical protrusions, etc. depending on the desired pressure losses, cooling air temperature heat pickup, as well as, local convective heat transfer and thermal cooling requirements necessary to achieve the desired local metal temperature and film cooling effectiveness requirements immediately adjacent to and downstream of the minicore flow circuit. In addition, the radial (or lateral) and axial (or streamwise) spacing of these internal features may also vary to achieve the desired cooling flow rate, pressure loss, cooling air temperature heat pickup, internal Reynolds number, and corresponding convective heat transfer, and heat conduction required to achieve the optimal local thermal cooling effectiveness. The tailoring of internal pressure loss and convective heat transfer within the minicore cooling circuit network <NUM> is contingent on the local external heat flux distribution.

The sub-passages 82b are circuitous but extend generally axially from the manifold region <NUM> and inlet orifices <NUM> to a downstream exit region <NUM>. In this example, the exit region <NUM> includes a plurality of flow guides 84a. For instance, the flow guides 84a have a teardrop shape and facilitate the lateral distribution, straightening and guiding cooling air flow into one or more outlet orifices <NUM> (<FIG> and <FIG>) through the outer portion 68b (<FIG> and <FIG>) of the airfoil wall <NUM>. The axial extent of the regions <NUM>/<NUM>/<NUM> may be varied based on desired heat transfer, pressure loss, overall size (i.e. height or lateral distance in the radial direction, and width in the streamwise axial flow direction) of the minicore cooling passage flow circuit network <NUM>, and manufacturability.

<FIG> shows an example configuration of an arrangement of minicore cooling passages flow circuit networks <NUM> on the first side <NUM> of the airfoil <NUM> with a mid-span portion surface <NUM> that comprises a total surface area that may range between <NUM>%-<NUM>% of the surface area on the first side <NUM> of the airfoil section <NUM> and is spaced inward from the LE, TE, and opposing radial edges of the airfoil section <NUM>. The mid-span portion includes an area of the first side <NUM> of the airfoil section <NUM> experiencing the highest external heat flux and gas temperatures and must have adequate coverage of the minicore cooling passage flow circuit networks <NUM> to ensure optimal distribution of interface and post spall metal temperatures along the first side <NUM> of the airfoil <NUM> in order to meet durability oxidation and thermal mechanical fatigue life requirements. Ideally, it is desired to maximize the coverage of the airfoil surface portion <NUM> with the minicore footprint in order to ensure the required or optimal distribution inter-wall internal convective and film cooling provided by the cooling air through each of the minicore cooling passage flow circuit networks <NUM>. However, due to minicore manufacturing and producibility concerns associated with core breakage, core assembly, and wall control the overall physical geometric size (i.e. height or lateral distance in the radial direction, and width in the streamwise axial flow direction) of the minicore cooling passage flow circuit network <NUM> has to be considered in the overall design and size of each of the minicore cooling passage flow circuit networks <NUM> on the first side <NUM> within the airfoil <NUM>, the inner diameter platform <NUM>, and the outer diameter platform <NUM> endwall geometry surfaces. In addition to casting and core manufacturing producibility concerns there are also both local and bulk thermal airfoil cooling design factors and requirements that need to be considered and evaluated to ensure the optimal number and distribution of minicore cooling passage flow circuit networks <NUM> are being utilized.

In the current embodiment described herein, multiple minicores are needed to properly cover the entire airfoil surface and provide optimal cooling. In particular, as the minicore cooling passage flow circuit networks <NUM> become increasingly larger, they are subject to potential producibility and yield issues associated with core breakage during the injection, core firer, and core assembly processes. Conversely as the minicore cooling passage flow circuit networks <NUM> become smaller, the surface area that each of the minicore cooling passage flow circuit networks <NUM> protects or "covers" may be considerably reduced. The significant reduction in the "covered" surface area due to the smaller minicore cooling passage flow circuit networks <NUM> footprint size, will result in a significant reduction in the relative percentage that the total mid span portion surface <NUM> will be covered for an equivalent number of minicore cooling passage flow networks <NUM>. Therefore a greater number of the smaller minicore cooling passage flow circuit networks <NUM> would be required to maintain the same relative coverage of the total mid span portion surface <NUM>. The increased number of smaller minicore cooling passage flow circuit networks <NUM> will increase producibility costs from a core manufacturing and assembly perspective, as well as, increase the overall cooling airflow flow requirements, which negate the intent of implementing the minicore cooling passage flow circuit networks <NUM> concepts described within this embodiment. By limiting the number of unique minicores, the producibility costs are reduced.

To maintain optimal cooling, the minicore cooling passage flow circuit networks <NUM> are generally <NUM> inches (<NUM>) thick which limits the networks <NUM> radially to between <NUM> inches (<NUM>) and <NUM> inches (<NUM>) and axially between <NUM> inches (<NUM>)and <NUM> inches (<NUM>). Additionally, it is also desirable to minimize the number of unique minicores used to effectively cool the airfoil surface <NUM> in order to minimize cost associated with manufacturing minicores for the turbine article such as airfoil.

In the illustrated example shown in <FIG>, the first column <NUM> of minicore cooling networks <NUM> includes two minicore cooling passage flow circuit networks <NUM>-<NUM> with each having the same radial and axial dimensions, and the second column <NUM> of minicore cooling networks <NUM> includes three minicore cooling passage flow circuit networks <NUM>-<NUM> with each having the same radial and axial dimensions. In this sense there are only two sizes of minicore networks <NUM>-<NUM> and <NUM>-<NUM> that are utilized to cool the first side <NUM>. The networks <NUM>-<NUM> include outlet orifices <NUM>-<NUM> that are radially aligned with mid-span walls <NUM> located between adjacent minicore networks <NUM>-<NUM> in the second column <NUM> to provide cooling to the first side <NUM> of the airfoil section <NUM> between the minicore networks <NUM>-<NUM>. The minicore networks <NUM>-<NUM> also include outlet orifices <NUM>-<NUM>. It is important to recognize that within this embodiment that both minicore cooling passage flow networks, <NUM>-<NUM> and <NUM>-<NUM> each span across a nearly equivalent radial distance that is defined by the mid-span portion surface <NUM>, of the first side <NUM>, of the airfoil section <NUM>.

Additionally, a mid-span wall <NUM> is located between the networks <NUM>-<NUM> and is not cooled by the networks <NUM>-<NUM> or <NUM>-<NUM> but is still within the mid-span portion <NUM> of the airfoil section <NUM>. To cool the mid-span wall <NUM>, cooling holes <NUM> are located upstream and radially aligned with the mid-span wall <NUM>. The cooling holes <NUM> provide cooling for the mid-span wall <NUM> because the airfoil section <NUM> is sized such that it cannot accommodate an additional column of networks <NUM> upstream of the minicore cooling passage flow circuit networks <NUM>-<NUM> that could provide cooling to the mid-span wall <NUM>. The cooling holes <NUM> are also located downstream of the leading edge LE. The cooling holes <NUM> are in fluid communication with the forward core cavity 74a. The networks <NUM>-<NUM> can also be in fluid communication with the forward core cavity 74a and the networks <NUM>-<NUM> can be in fluid communication with the aft core cavity 74b.

<FIG> illustrates another example configuration of minicore cooling passage flow circuit networks <NUM> on the first side <NUM> of the airfoil section <NUM> located within the mid-span portion <NUM>. The configuration of minicore cooling passage flow circuit networks <NUM> includes a first column <NUM> having a single minicore cooling network <NUM>-<NUM> and a pair of minicore cooling networks <NUM>-<NUM> and a second column <NUM> includes one single minicore cooling network <NUM>-<NUM> and another pair of minicore cooling networks <NUM>-<NUM>. <FIG> illustrates yet another example configuration of minicore cooling passage flow circuit networks <NUM> that is similar to the configuration in <FIG> but with the order of individual networks in the first and second columns <NUM>, <NUM> reversed.

The minicore cooling network <NUM>-<NUM> includes an outlet orifice <NUM>-<NUM> that is radially aligned with a mid-span wall <NUM> located between the pair of minicore cooling networks <NUM>-<NUM> in the second column <NUM>. And a middle one of the pair of minicore cooling networks <NUM>-<NUM> include outlet orifices <NUM>-<NUM> with at least one of the outlet orifices <NUM>-<NUM> that is radially aligned with a mid-span wall <NUM> located between the minicore cooling network <NUM>-<NUM> in the network <NUM>-<NUM> in the second column <NUM>.

Cooling holes <NUM> are located upstream and radially aligned with a mid-span wall <NUM> located between the pair of networks <NUM>-<NUM> in the first column <NUM> and a mid-span wall <NUM> located between the network <NUM>-<NUM> and one of the pair of networks <NUM>-<NUM> in the first column <NUM>. This allows for the mid-span walls <NUM> and <NUM> in the mid-span portion <NUM> of the airfoil section <NUM> to receive sufficient cooling. The cooling holes <NUM> are located in fluid communication with the forward core cavity 74a. The cooling holes <NUM> are also located downstream of the leading edge LE.

By having a minimum of three minicores in the second column <NUM>, it enables the distance between the outlet orifices <NUM> to the airfoil trailing edge TE to be minimized in order to mitigate local airfoil trailing edge oxidation. By reducing the distance between the outlet orifices <NUM> and the airfoil trailing edge TE, the level of film cooling effectiveness will remain relatively high, providing a better insulating boundary of film cooling air to reduce the local trailing edge heat flux and local operating metal temperatures for improved part durability capability.

Additionally, by having a minimum of three minicores in the second column <NUM>, it enables local tailoring of the cooling flow from any one of the three minicore cooling networks <NUM>-<NUM>-<NUM>-<NUM>. In this sense, the radial distribution of cooling flow from any of the three minicore cooling networks can be increased and or decreased through modifications of the supply feeds. The optimization and tailoring of cooling flow distribution in any of the three minicore cooling networks enables increased robustness of the cooling design in that the cooling flows can be tailored to better align with changes in radial temperature profile and heat flux distributions. Since there are three minicore networks in the second column <NUM>, the cooling flow increase to one of the three minicore circuits will be reduced relative to a second column <NUM> comprising of only two minicore circuits covering the same radial extent of mid span portion surface <NUM>. In this sense local durability life shortfalls can be addressed with lower levels of cooling flow that are more isolated and targeted. The reduced level of cooling flow required to address local durability life shortfalls minimizes the adverse impacts associated with aerodynamic cooling flow mixing losses and the impact to both stage and turbine efficiency.

Claim 1:
A gas turbine engine turbine vane airfoil (<NUM>) comprising:
an article wall (<NUM>) having an inner portion (68a) at least partially defining a cavity (<NUM>) and an outer portion (68b);
a plurality of first cooling passage networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>) each defining first dimensions and embedded in the article wall (<NUM>) between the inner portion (68a) and the outer portion (68b) of the article wall (<NUM>); and
a plurality of second cooling passage networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>) each defining second dimensions and embedded into the article wall (<NUM>) between the inner portion (68a) and the outer portion (68b) of the article wall (<NUM>), wherein the plurality of first and second cooling passage networks (<NUM>; <NUM>-<NUM>, <NUM>-<NUM>; <NUM>-<NUM>, <NUM>-<NUM>) are arranged in one of a first column (<NUM>; <NUM>) of radially positioned networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>, <NUM>-<NUM>) and a second column (<NUM>; <NUM>) of radially positioned networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>, <NUM>-<NUM>), wherein each of the first cooling passage networks (<NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>) have an outlet orifice (<NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>) radially aligned with a second mid-span wall (<NUM>; <NUM>; <NUM>) between adjacent networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>) in the second column (<NUM>; <NUM>);
characterised by comprising
a plurality of cooling holes (<NUM>; <NUM>) located upstream of the first column (<NUM>; <NUM>) of radially positioned networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>, <NUM>-<NUM>) and radially aligned with at least one first mid-span wall (<NUM>; <NUM>, <NUM>) between adjacent networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>, <NUM>-<NUM>) in the first column (<NUM>; <NUM>) of networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>, <NUM>-<NUM>),
wherein the airfoil is sized such that it cannot accommodate an additional column of cooling passage networks upstream of the first cooling passage networks (<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>).