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>, <CIT> and <CIT> disclose prior art sealing arrangements.

A vane according to an aspect of the invention is provided by claim <NUM>.

In an optional embodiment of any of the foregoing embodiments, the axial leg defines an axial length, the radial leg defines a radial length, and the axial length is greater than the radial length.

In an optional embodiment of any of the foregoing embodiments, the seal is formed of a metallic material and has a thickness of <NUM> millimeters to <NUM> millimeters.

In an optional embodiment of any of the foregoing embodiments, the structural platform further comprises an axial seal slot extending from the radial seal slot.

In an optional embodiment of any of the foregoing embodiments, the radial leg and the axial leg form an angle of <NUM>° to <NUM>°.

A method for assembling a vane according to another aspect of the invention is provided by claim <NUM>.

In an optional embodiment of any of the foregoing embodiments, the axial leg defines an axial length, the radial leg defines a radial length, the axial length is greater than the radial length.

Terms such as "axial," "radial," "circumferential," and variations of these terms are made with reference to the engine central axis A.

"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 schematic view of a representative vane assembly, i.e., vane <NUM>, from the turbine section <NUM> of the engine <NUM>, although the examples herein may also be applied to vanes in the compressor section <NUM>. A plurality of vanes <NUM> are situated in a circumferential row about the engine central axis A. The vane <NUM> is comprised of a ceramic vane piece <NUM> and a structural platform <NUM>. In the illustrated example, the structural platform <NUM> is part of a spar piece <NUM>, but the structural platform <NUM> could alternatively be part of a case or other non-spar structure. The spar piece <NUM> includes the structural platform <NUM> and a hollow spar <NUM> that extends into the ceramic vane piece <NUM>. For example, the spar piece <NUM> is formed of a metallic material, such as a nickel- or cobalt-based superalloy, and is a single, monolithic piece. The ceramic vane piece <NUM> and the spar piece <NUM> may be clamped or otherwise held together in a known manner with a fastener (not shown), such as a tie rod.

The ceramic vane piece <NUM> includes several sections, including first (radially outer) and second (radially inner) platforms <NUM>/<NUM> and a hollow airfoil section <NUM> that joins the first and second platforms <NUM>/<NUM>. The first platform <NUM> includes a radially outer face 70a that defines a bearing surface 70b. The airfoil section <NUM> includes at least one internal passage <NUM>. The terminology "first" and "second" as 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 the embodiments herein in that a first component or feature could alternatively be termed as the second component or feature, and vice versa.

The ceramic vane piece <NUM> is formed of a monolithic ceramic or a ceramic matrix composite ("CMC"). Example ceramic materials may include, but are not limited to, silicon-containing ceramics. The silicon-containing ceramic may be, but is not limited to, silicon carbide (SiC) or silicon nitride (Si<NUM>N<NUM>). An example CMC may be a SiC/SiC CMC in which SiC fibers are disposed within a SiC matrix. The CMC nay be comprised of fiber plies that are arranged in a stacked configuration and formed to the desired geometry of the ceramic vane piece <NUM>. For instance, the fiber plies may be layers or tapes that are laid-up one on top of the other to form the stacked configuration. The fiber plies may be woven or unidirectional, for example. At least a portion of the fiber plies may be continuous through the first platform <NUM>, the airfoil section <NUM>, and the second platform <NUM>. In this regard, the ceramic vane piece <NUM> may be continuous in that the fiber plies are uninterrupted through the first platform <NUM>, the airfoil section <NUM>, and the second platform <NUM>.

<FIG> illustrates a more detailed view of a region R (indicated in <FIG>) at the leading end of the platforms <NUM>/<NUM> of the vane <NUM>. It is to be understood that the examples herein may additionally be applied to the trailing end of the platforms <NUM>/<NUM>. The structural platform <NUM> defines a seal slot <NUM>. In this example, the seal slot <NUM> has a radial seal slot 78a and an axial seal slot 78b that extends from the radial seal slot 78a.

The vane <NUM> further includes a seal <NUM>, which is also shown in an isolated view in <FIG>. The seal <NUM> is arced (i.e., an arc segment about engine central axis A) and has a radial leg 80a, an axial leg 80b, and a filet 80c that joins the radial and axial legs 80a/80b such that the seal <NUM> has an L-shaped cross-sectional shape. In one example, the radial leg 80a and the axial leg 80b form an angle (AN) of <NUM>° to <NUM>°.

The radial leg 80a extends in the radial seal slot 78a and the axial leg 80b extends along the axial seal slot 78b in an expansion gap <NUM> at an interface <NUM> between the structural platform <NUM> and the first vane platform <NUM> (<FIG>). In this regard, the axial seal slot 78b opens toward the first platform <NUM> and may be considered to be part of the interface <NUM>. The seal <NUM> may extend in the circumferential direction the full or substantially full circumferential extent of the first platform <NUM>. In this example, the axial leg 80b defines an axial length (L1), the radial leg defines a radial length (L2), and the axial length (L1) is greater than the radial length (L2). In one example, the lengths L1 and L2 refer to the minimum length along the extent of the radial leg 80a and axial leg 80b, respectively. The radial leg 80a extends from the filet 80c to a tip edge 80d (radial face). As shown, the tip edge 80d has a concavity 80e in that the circumferential ends of the radial leg 80a have a greater radial length (L2) than the circumferentially central portion of the radial leg 80a.

The vane <NUM> further includes a pressure tap <NUM> that opens to the seal <NUM>. For instance, the pressure tap <NUM> includes one or more passages through the structural platform <NUM> that open into the seal slot <NUM>, such as to the radial seal slot 78a. Pressurized fluid (P), such as bleed air from the compressor section <NUM>, is provided through the pressure tap <NUM> and into the seal slot <NUM>. The pressurized fluid provides a back-pressure behind the seal <NUM> that biases the radial leg 80a of the seal <NUM> toward a seated sealing position against the side of the radial seal slot 78a and the axial leg 80b against the bearing surface 70b of the first platform <NUM>. The seal <NUM> may be further configured to conform to the side of the radial seal slot 78a and to the bearing surface 70b. For instance, the seal <NUM> is formed of a metallic sheet material that is relatively thin to allow the seal <NUM> to deflect or deform to the local contours of the side of the radial seal slot 78a and the bearing surface 70b. In one example, the walls of the seal <NUM> have a thickness of <NUM> millimeters to <NUM> millimeters to permit such conformance while also maintaining sufficient stiffness to prevent the radial leg 80a of the seal <NUM> from folding or "extruding" into the interface <NUM>.

The structural platform <NUM> also includes one or more purge holes <NUM> that allow the pressurized fluid to exit from the seal slot <NUM>. For example, the purge hole(s) <NUM> are axial holes that open to the forward face of the structural platform <NUM>. In the seal slot <NUM>, the purge holes <NUM> open at a location that corresponds to the concavity 80e of the radial leg 80a. That is, the concavity 80e is shorter in radial length (L2) so that the radial leg 80a does not obstruct the purge hole(s) <NUM>.

During operation of the engine <NUM> cooling air, such as bleed air from the compressor section <NUM>, is provided through the structural platform <NUM> into the internal passage <NUM> of the ceramic vane piece <NUM>. The seal <NUM> serves to facilitate a reduction in air leakage from the internal passage <NUM> through the interface <NUM> as well as limit combustion gases from the core flow passage C from infiltrating into the interface <NUM>.

The configuration of the seal <NUM> facilitates maintaining sealing over a range of relative radial and axial motion between the ceramic vane piece <NUM> and the structural platform <NUM>. For example, the ceramic vane piece <NUM> and the structural platform <NUM> can move radially and axially relative to one another due to differences in thermal expansion/contraction and/or shifting from aerodynamic forces. <FIG> illustrate example relative motions to demonstrate the operation of the seal <NUM> over a range of motions. In <FIG> the gap <NUM> between the ceramic vane piece <NUM> and the structural platform <NUM> is in a maximum expanded state in comparison to the gap shown in <FIG>. For instance, in the maximum expanded state, the gap <NUM> may be up to five times greater in size (radial height between the ceramic vane piece <NUM> and the structural platform <NUM>) than in a default or non-expanded state (<FIG>). As shown, the radial length of the radial leg 80a is such that at least a portion of the radial leg 80a remains in the radial seal slot 78a in the maximum expanded state so that sealing is maintaining in the maximum expanded state.

In <FIG> the ceramic vane piece <NUM> is axially shifted relative to the structural platform <NUM> to a maximum axial shift state in comparison to the relative axial position shown in <FIG>. As shown, the seal <NUM> remains seated such that the axial leg 80a of the seal <NUM> maintains sealing with the bearing surface 70b of the first platform <NUM>.

As demonstrated in <FIG>, the seal <NUM> maintains sealing over a maximum expanded state and a maximum axial shift state. As can be appreciated, the seal <NUM> also maintains sealing over intermediate relative positions that are less than the maximum expanded state and less than the maximum axial shift state, as shown in <FIG>. Additionally, the axial length (L1) of the axial leg 80b being greater than the radial length (L2) of the radial leg 80a facilitates teetering of the seal <NUM>. For instance, as the ceramic vane piece <NUM> and the structural platform <NUM> move relative to one another, the seal <NUM> may teeter on the axial leg 80a to accommodate the movement, yet maintain contact with the bearing surface 70b for sealing.

<FIG> illustrates another example seal <NUM>. The seal <NUM> is the same as the seal <NUM> except that radial leg 180a is hooked. For instance, the radial leg 180a is hooked in a retrograde manner, i.e., back toward the axial leg 80b. The curvature of the hook shape of the radial leg 180a enables the seal <NUM> to maintain a circumferential line of contact with the side of the radial seal slot 78a in the event that the seal <NUM> tilts axially forward or aft.

As shown and described, the seal <NUM>/<NUM> facilitates sealing in a dynamic location over a range of radial and axial motion. Moreover, unlike simple feather seals or brush seals, the legs 80a/180a/80b of the seal <NUM>/<NUM> provide sealing in two dimensions - axial and radial.

The vane <NUM> also embodies a method of assembly. For example, the method includes providing the structural platform <NUM> and the ceramic vane piece <NUM> with the first platform <NUM>, and then introducing the seal <NUM>/<NUM> between the structural platform <NUM> and the first platform <NUM> such that the radial leg 80a/180a of the seal <NUM>/<NUM> extends in the radial seal slot 78a and an axial leg 80b of the seal <NUM>/<NUM> extends in the interface <NUM> between the structural platform <NUM> and the first platform <NUM>. As an example, the seal <NUM>/<NUM> may be placed between the structural platform <NUM> and the first platform <NUM> prior to bring the structural platform <NUM> and the first platform <NUM> together during assembly, i.e., inserting the spar <NUM> through the internal passage <NUM>. The method may be applied in an original manufacture of the vane <NUM> and/or as part of a repair or replacement process.

Claim 1:
A vane (<NUM>) comprising:
a ceramic vane piece (<NUM>) defining first and second vane platforms and a hollow airfoil section (<NUM>) joining the first and second vane platforms, the first vane platform (<NUM>) having a radially outer face (70a) defining a bearing surface (70b);
a structural platform (<NUM>) adjacent the radially outer face (70a), the structural platform (<NUM>) defining a radial seal slot (78a);
an expansion gap (<NUM>) along an interface (<NUM>) between the first vane platform (<NUM>) and the structural platform (<NUM>), the expansion gap (<NUM>) varying with relative movement between the ceramic vane piece (<NUM>) and the structural platform (<NUM>) such that there is a range of radial and axial motion;
a seal (<NUM>/<NUM>) having a radial leg (80a/180a) and an axial leg (80b), the radial leg (80a/180a) extending in the radial seal slot (78a) and the axial leg (80b) extending in the interface (<NUM>) along the bearing surface (70b); and characterised by
a pressure tap (<NUM>) opening to the seal (<NUM>/<NUM>), the pressure tap (<NUM>) configured to provide a pressurized fluid biasing the seal (<NUM>/<NUM>) toward a seated sealing position against the radial seal slot (78a) and the bearing surface (70b) over the range of radial and axial motion;
wherein the seal (<NUM>/<NUM>) includes a filet (80c) that joins the radial leg (80a/180a) and the axial leg (80b) such that the seal (<NUM>/<NUM>) has an L-shaped crosssection,
wherein the radial leg (80a/180a) extends from the filet (80c) to a tip edge (80d), and the tip edge (80d) has a concavity (80e); and
wherein the structural platform (<NUM>) defines a purge hole (<NUM>) that opens at the radial seal slot (78a) and exits over the concavity (80e) to allow the pressurized fluid to exit from the radial seal slot (78a).