Patent Description:
Airfoils in the turbine section are typically formed of a superalloy and may include thermal barrier coatings to extend temperature capability and lifetime. Ceramic matrix composite ("CMC") materials are also being considered for airfoils. Among other attractive properties, CMCs have high temperature resistance. Despite this attribute, however, there are unique challenges to implementing CMCs in airfoils. <CIT> discloses a vane arc segment according to the state of the art.

A vane arc segment according to the present invention includes a platform and an airfoil section that extends in a radial direction from the platform. The airfoil section has a pressure side and a suction side. The platform defines fore and aft axial sides, a core gaspath side, a non-core gaspath side, and first and second flanges that project from the non-core gaspath side. The first and second flanges define, respectively, first and second circumferential mate faces. The first and second flanges each are formed of upturned fiber plies from the platform such that the fiber plies in the first and second flanges are radially-oriented. The first and second circumferential mate faces have, respectively, first and second seal slots that each extend in a ply through-thickness direction across two or more of the fiber plies.

In a further embodiment of the foregoing embodiment, each of the first and second seal slots has a forward end that opens at the fore axial side of the platform and an aft end that opens at the aft axial side of the platform.

In a further embodiment of any of the foregoing embodiments, each of the first and second flanges has a radially outer face opposite the core gaspath side, each of the first and second flanges defines a flange radial span from the core gaspath side to the radially outer face with <NUM>% span at the core gaspath side and <NUM>% span at the radially outer face, and the first and second seal slots are located at greater than <NUM>% span.

In a further embodiment of any of the foregoing embodiments, the first and second seal slots are located at greater than <NUM>% span.

In a further embodiment of any of the foregoing embodiments, each of the first and second flanges has a radially outer face opposite the core gaspath side, the platform defines a platform thickness from the core gaspath side to the non-core gaspath side, the first and second flanges each define a flange thickness from the core gaspath side to the radially outer face, and the flange thickness is greater than the platform thickness by a factor of <NUM> or more.

In a further embodiment of any of the foregoing embodiments, the flange thickness is greater than the platform thickness by a factor of <NUM> or more.

In a further embodiment of any of the foregoing embodiments, the first and second seal slots each extend in the ply through-thickness direction across three or more of the fiber plies.

In a further embodiment of any of the foregoing embodiments, the first and second seal slots each terminate at an interface between two of the fiber plies.

A gas turbine engine according to an example of the present disclosure includes a compressor section, a combustor in fluid communication with the compressor section, and a turbine section in fluid communication with the combustor. The turbine section has vane arc segments as in any of the foregoing embodiments disposed in a circumferential row about a central axis of the gas turbine engine.

In a further embodiment of any of the foregoing embodiments, the first circumferential mate face of the one of the vane arc segments abuts the second circumferential mate face of the adjacent one of the vane arc segments.

In a further embodiment of any of the foregoing embodiments, each of the first and second seal slots has a forward end that opens at the fore axial side of the platform and an aft end that opens at the aft axial side of the platform.

In one disclosed embodiment, the engine <NUM> bypass ratio is greater than about ten (<NUM>:<NUM>), the fan diameter is significantly larger than that of the low pressure compressor <NUM>, and the low pressure turbine <NUM> has a pressure ratio that is greater than about five (<NUM>:<NUM>).

The engine parameters described above and those in this paragraph are measured at this condition unless otherwise specified. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about <NUM>, or more narrowly greater than or equal to <NUM>. The "Low corrected fan tip speed" as disclosed herein according to one non-limiting embodiment is less than about <NUM> ft / second (<NUM> meters/second), and can be greater than or equal to <NUM> ft / second (<NUM> meters/second).

<FIG> illustrates a representative portion of a vane ring assembly from the turbine section <NUM> of the engine <NUM>. The vane ring assembly is made up of a plurality of vane arc segments <NUM> that are situated in a circumferential row about the engine central axis A. <FIG> illustrates and isolated view of a representative one of the vane arc segments <NUM>. Although the vane arc segments <NUM> are shown and described with reference to application in the turbine section <NUM>, it is to be understood that the examples herein are also applicable to structural vanes in other sections of the engine <NUM>.

Referring to <FIG>, each vane arc segment <NUM> is a one-piece structure that is comprised of several sections, including first and second platforms <NUM>/<NUM> and an airfoil section <NUM> that extends between the platforms <NUM>/<NUM>. The airfoil section <NUM> in this example is hollow and defines a leading end 66a, a trailing end 66b, and pressure and suction sides 66c/66d. In this example, the first platform <NUM> is a radially outer platform and the second platform <NUM> is a radially inner platform. It is also contemplated, however, that in modified examples the vane arc segment <NUM> could alternatively have the first platform <NUM> as a single platform, with no second platform <NUM>, in which case the single platform may be at either the radially inner or outer end of the airfoil section <NUM>. Terms such as "inner" and "outer" used herein refer to location with respect to the central engine axis A, i.e., radially inner or radially outer. Moreover, the terminology "first" and "second" used herein is to differentiate that there are two architecturally distinct components or features. It is to be further understood that the terms "first" and "second" are interchangeable in that a first component or feature could alternatively be termed as the second component or feature, and vice versa.

<FIG> illustrates a view of the first platform <NUM>. The first platform <NUM> includes fore and aft axial sides 62a/62b, a core gaspath side 62c, and a non-core gaspath side 62d. The platform <NUM> has first and second flanges <NUM>/<NUM> that project radially from the non-core gaspath side 66d. The flanges <NUM>/<NUM> define, respectively, first and second circumferential mate faces <NUM>/<NUM>. In this example, the flanges <NUM>/<NUM> are exclusive in that they are the only radial projections from the non-core gaspath side of the platform <NUM>. The flanges <NUM>/<NUM> are generally elongated and run along the full fore-aft extent of the platform <NUM>. The flanges <NUM>/<NUM> define respective radial faces 68a/70a (here radially outer) and inside faces 68b/70b. The inside faces 68b/70b face circumferentially toward each other (i.e., toward the central region of the platform <NUM>).

The vane arc segment <NUM> is continuous in that the platforms <NUM>/<NUM> and airfoil section <NUM> constitute a single, uninterrupted body. As an example, the vane arc segment <NUM> is formed of a ceramic matrix composite (CMC). In the illustrated example in <FIG>, referring to cutaway section B, the CMC includes ceramic fibers 76a that are disposed in a ceramic matrix 76b. The CMC may be, but is not limited to, a SiC/SiC composite in which SiC fibers are disposed within a SiC matrix. The ceramic fibers 76a are provided in fiber plies (see <FIG> at 76c). The fiber plies 76c may be woven or unidirectional and may collectively include plies of different fiber weave configurations. The fiber plies 76c are continuous through at least the platform <NUM>, including the flanges <NUM>/<NUM>, the airfoil section <NUM>, and the second platform <NUM>. As shown, the fiber plies 76c are laid-up in a laminate configuration. At the edges of the platform <NUM>, the fiber plies 76c are upturned to form the flanges <NUM>/<NUM>. The fiber plies 76c in the flanges <NUM>/<NUM> are thus radially-oriented in that they lie in planes that are substantially radially-oriented.

The first and second circumferential mate faces <NUM>/<NUM> have, respectively, first and second seal slots <NUM>/<NUM> that retain a feather seal <NUM>. A feather seal is a relatively long, narrow, thin strip of metal alloy, which under pressure can conform to a surface to provide sealing. Each of the seal slots <NUM>/<NUM> (see <FIG>) has a forward end 84a that opens at the forward axial side 62a of the platform <NUM> and an aft end 84b that opens at the aft axial side 62b of the platform <NUM>. The seal slots <NUM>/<NUM> thus extend the full distance from the axial side 62a to the axial side 62b.

In general, feather seals have been used for sealing between metallic components. However, CMC challenges the use of feather seals. For instance, the properties of CMCs substantially differ in-plane versus out-of-plane of the fiber plies, whereby a CMC is relatively strong in in-plane tension and relatively weak in interlaminar tension. The use of CMCs may thus be limited by its interlaminar properties. Additionally, due to their thermal resistance, CMCs can be used at temperatures that may exceed the operating temperature of metallic alloys, such as that of a feather seal. In these regards, as will be discussed below, the flanges <NUM>/<NUM> and seal slots <NUM>/<NUM> are adapted for use of feather seals with CMCs.

The seal slots <NUM>/<NUM> extend into the respective flanges <NUM>/<NUM> in a ply through-thickness direction, i.e., generally orthogonal to the radial direction and thus also generally orthogonal to the planes of the fiber plies 76c. Each of the seal slots <NUM>/<NUM> extends across two or more of the fiber plies 76c, for example across three or more plies. The seal slots <NUM>/<NUM> each terminate at an interface between two of the fiber plies 76c. That is, the seal slots <NUM>/<NUM> stop at the face of a fiber ply 76c rather than extending partially through the fiber ply 76c. Although not limited, the seal slots <NUM>/<NUM> may be formed by machining, such as waterjet-guided laser machining.

As shown in <FIG>, the feather seal <NUM> is partially disposed in seal slot <NUM> and partially disposed in slot <NUM>. The radial height and the circumferential depth of the seal slots <NUM>/<NUM> are larger, respectively, than the radial height and circumferential width of the feather seals <NUM> so that the feather seals <NUM> have space to shift somewhat during engine operation as the vane arc segments <NUM> move relative to each other. The circumferential depth of the seal slots <NUM>/<NUM> is selected such that the feather seals <NUM> are unable to fall out of the seal slots <NUM>/<NUM> at a condition of maximum separation between the mate faces <NUM>/<NUM> during engine operation.

The feather seal <NUM> facilitates sealing the interface between the mate faces <NUM>/<NUM> of adjacent vane arc segments <NUM> to limit leakage of gases from the core gaspath of the engine <NUM>. For instance, the feather seal <NUM> is pressurized from the non-core gaspath side to contact, and thus seal against, the surfaces of the seal slots <NUM>/<NUM>. Similar to the seal slots <NUM>/<NUM>, the feather seal <NUM> extends the full distance from the axial side 62a to the axial side 62b to provide sealing along the entire interface.

The pressurized loading of the feather seals <NUM> against the surfaces of the seal slots <NUM>/<NUM> may cause radial loads through the flanges <NUM>/<NUM>. By having the seal slots <NUM>/<NUM> extend across the fiber plies 76c in the through-thickness direction, the radial loads are applied in the in-plane direction, thereby avoiding interlaminar tension as discussed above. Additionally, as the seal slots <NUM>/<NUM> extend across several of the fiber plies, the radial loads are distributed through the ends of the fiber plies 76c over multiple fiber plies 76c.

In order to address high temperatures, the seal slots <NUM>/<NUM> are also offset from the core gaspath side 62c of the platform <NUM> so as to be closer to the radial faces 68a/70a of the flanges <NUM>/<NUM> than to the core gaspath side 62c. For example, each of the flanges <NUM>/<NUM> defines a flange radial span RS (<FIG>) from the core gaspath side 62c to the radially outer face 68a/70a, with <NUM>% span at the core gaspath side 62c and <NUM>% span at the radially outer face 68a/70a. The seal slots <NUM>/<NUM> are located at greater than <NUM>% span.

The CMC from which the platform <NUM> is formed transmits heat at the core gaspath side 62c, although it is generally a poor heat conductor in comparison to metals. Given this poor thermal conductivity, offsetting the seal slots <NUM>/<NUM> to be closer to the radial faces 68a/70a, even by a small amount of the radial span RS, facilitates lowering the temperature at the location of the seal slots <NUM>/<NUM>. For instance, at flow path temperatures above <NUM>, the temperature at the seal slots <NUM>/<NUM> is expected to be lowered by <NUM> or more in comparison to a seal slot that is located at less than <NUM>% span. As the thermal gradient from the core gaspath side 62c is expected to be high, increasingly further offsets from the core gaspath side 62c provide increasingly lower exposure temperatures at the seal slots <NUM>/<NUM>. In further examples, the seal slots <NUM>/<NUM> are located at greater than <NUM>% span, or at greater than <NUM>% span.

In order to facilitate locating the seal slots <NUM>/<NUM> a desired distance away from the core gaspath side 62c given an expected thermal gradient, the flanges <NUM>/<NUM> are relatively thick in the radial direction as compared to the radial thickness of the platform <NUM>. For example, the platform <NUM> defines a platform thickness PT (<FIG>) from the core gaspath side 62c to the non-core gaspath side 62d, the flanges <NUM>/<NUM> each define a flange thickness (FT) from the core gaspath side 62c to the radial face 68a/70a, and the flange thickness is greater than the platform thickness by a factor of <NUM> or more, for example by a factor of <NUM> or more, or of <NUM> or more. As will be appreciated, increasing the factor enables the seal slots <NUM>/<NUM> to be located further away from the core gaspath side 62c at higher percent spans.

In addition to the feather seals <NUM>, the circumferential mate faces <NUM>/<NUM> also provide sealing. As shown in <FIG>, the mate faces <NUM>/<NUM> may abut one another. Such contact further limits escape of gases from the core gaspath. Furthermore, the contact also serves for transfer of aerodynamic loads and/or other loads. For instance, the inside face 68b of the flange <NUM> abuts a structural support <NUM>. Loads are driven from flange <NUM> of one vane arc segment <NUM>, into the flange <NUM> of the adjacent vane arc segment <NUM>, and then into the support <NUM>. This also serves to distribute the loads over the two flanges <NUM>/<NUM> rather than through a single flange, thereby enhancing durability.

Claim 1:
A vane arc segment (<NUM>) comprising:
a platform (<NUM>) and an airfoil section (<NUM>) extending in a radial direction from the platform (<NUM>),
the airfoil section (<NUM>) having a pressure side (66c) and a suction side (66d),
the platform (<NUM>) defining fore and aft axial sides (62a, 62b), a core gaspath side (62c), a non-core gaspath side (62d), and first and second flanges (<NUM>, <NUM>) projecting from the non-core gaspath side (62d), the first and second flanges (<NUM>, <NUM>) defining, respectively, first and second circumferential mate faces (<NUM>, <NUM>),
the first and second flanges (<NUM>, <NUM>) each being formed of upturned fiber plies (76c) from the platform (<NUM>) such that the fiber plies (76c) in the first and second flanges (<NUM>, <NUM>) are radially-oriented, and
the first and second circumferential mate faces (<NUM>, <NUM>) having, respectively, first and second seal slots (<NUM>, <NUM>) characterised in that each slot extends in a ply through-thickness direction across two or more of the fiber plies (76c).