Patent Description:
A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section may include low and high pressure compressors, and the turbine section may also include low and high pressure turbines.

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 prior art assembly having the features of the preamble of claim <NUM>. <CIT>, <CIT> and <CIT> disclose prior art seal assemblies.

An assembly according to an aspect of the present invention is provided in accordance with claim <NUM>.

A gas turbine engine according to another aspect of the present invention is provided in accordance with claim <NUM>.

Embodiments are set forth in the dependent claims.

<FIG> illustrates a line representation of an axial view of an assembly <NUM> from the turbine section <NUM> of the engine <NUM> (see also <FIG>) to demonstrate an example implementation of a spring device <NUM>. It is to be understood that although the examples herein are discussed in context of a vane from the turbine section, the spring device <NUM> can be applied to other components such as, but not limited to, blade outer air seals, other core gaspath walls, or components that would benefit from spring biasing.

In the illustrated implementation, the assembly <NUM> includes first and second airfoil fairings <NUM>. Each airfoil fairing <NUM> is comprised of an airfoil section <NUM> and first and second platforms <NUM>/<NUM> between which the airfoil section <NUM> extends. The airfoil section <NUM> generally extends in a radial direction relative to the central engine axis A. 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.

The airfoil fairings <NUM> are continuous in that the platforms <NUM>/<NUM> and airfoil section <NUM> constitute a unitary body. As an example, the airfoil fairings are formed of a ceramic matrix composite, an organic matrix composite (OMC), or a metal matrix composite (MMC). For instance, the ceramic matrix composite (CMC) is formed of ceramic fiber tows that are disposed in a ceramic matrix. The ceramic matrix composite may be, but is not limited to, a SiC/SiC ceramic matrix composite in which SiC fiber tows are disposed within a SiC matrix. Example organic matrix composites include, but are not limited to, glass fiber tows, carbon fiber tows, and/or aramid fiber tows disposed in a polymer matrix, such as epoxy. Example metal matrix composites include, but are not limited to, boron carbide fiber tows and/or alumina fiber tows disposed in a metal matrix, such as aluminum. A fiber tow is a bundle of filaments. As an example, a single tow may have several thousand filaments. The tows may be arranged in a fiber architecture, which refers to an ordered arrangement of the tows relative to one another, such as, but not limited to, a 2D woven ply or a 3D structure. Alternatively, the airfoil fairing <NUM> may be formed of a homogenous polymer, metal alloy, or ceramic material.

The airfoil section <NUM> circumscribes an interior through-cavity <NUM>. The airfoil section <NUM> may have a single through-cavity <NUM>, or the cavity <NUM> may be divided by one or more ribs. The airfoil fairings <NUM> are mechanically supported by support hardware, generally shown at <NUM>. In this example, the support hardware <NUM> includes spars <NUM>. Each spar <NUM> includes a spar platform 72a adjacent the airfoil platforms <NUM> and a spar leg 72b that extends from the spar platform 72a into the respective through-cavity <NUM>. Although not shown, the spar platform 72a includes attachment features that secure it to a fixed support structure, such as an engine case. The spar leg 72b may include an interior through-passage for transmitting cooling air to downstream locations.

The spar legs 72b extend past the platforms <NUM> of the airfoil fairings <NUM> so as to protrude from the airfoil fairings <NUM>. The support hardware <NUM> in this example additionally includes a support platform <NUM> adjacent the platforms <NUM> of the airfoil fairings <NUM>. Although not shown, the support platforms <NUM>, the platforms <NUM>/<NUM> of the airfoil fairings <NUM>, and the spar platform 72a may have flanges or other mating features through which the fairing platforms <NUM>/<NUM> interface with the platforms 72a/<NUM> to react out aerodynamic loads.

The ends of the spar legs 72b are secured to the support platforms <NUM>. For example, the ends of the spar legs 72b have a clevis mount that includes two spaced-apart prongs that have aligned holes, and there is a pin that extends through the holes. The pins prevent the spar legs 72b from being retracted through the support platform <NUM>, thereby locking the support platforms <NUM> to the spar legs 72b and trapping the airfoil fairings <NUM> between the spar platforms 72a and the support platforms <NUM>. It is to be understood that other mechanisms may alternatively be used to lock the spar legs 72b with the support platforms <NUM>. Moreover, the example configuration could also be inverted, with the spar platform 72a being adjacent the platform <NUM> and the support platform <NUM> being adjacent the platform <NUM>.

Turning again to the airfoil fairings <NUM>, each of the fairing platforms <NUM> is a core gaspath wall that defines a core gas path side 66a and a non-core gas path side 66b. The airfoil fairings <NUM> are arranged circumferentially next to each other such that the fairing platforms <NUM> define a gap G therebetween. There is a seal <NUM>, such as a feather seal, arranged on the non-core gas path sides 66b. The seal <NUM> bridges over the gap G to seal the core gas path from the space between the fairing platforms <NUM> and the spar platforms 72a. The surfaces of the fairing platforms <NUM> that are in contact with the seal <NUM> may include a coating, for thermal considerations, to smooth the surface for better sealing contact with the seal <NUM>, and/or reduce wear. For example, the coating is selected of a composition that is thermally insulating in comparison to the CMC (if used) of the airfoil fairings, to thermally insulate the seal <NUM>. The coating may be composed of elemental silicon, silicate, silica, hafnia, zirconia, or combinations thereof. The spring device <NUM> is located adjacent the seal <NUM>. The spring device <NUM> is retained in a slot <NUM> in the spar platforms 72a, but other support structure than the spar platform 72a may be used in implementations of the spring device <NUM> in other components.

The spring device <NUM> biases the seal <NUM> against the non-core gas path sides 66a of the airfoil fairings <NUM> to facilitate sealing of the seal <NUM> against the non-core gas path sides 66a. The biasing also facilitates attenuation of radial tolerances in the assembly in that dimensional variations in the components is taken up by compression of the spring device <NUM>. Moreover, the biasing also facilitates proper positioning of the components during assembly, idle, and engine shut-down by urging the airfoil fairings <NUM> toward the support platforms <NUM>. As will be appreciated, a seal <NUM> and a spring device <NUM> may also be provided, or alternatively be provided, at the gap between the fairing platforms <NUM>. Moreover, it is also contemplated that the spring device <NUM> be used without the seal <NUM>, to serve the tolerance and positioning functions.

<FIG> illustrates an isolated view of an example of the spring device <NUM>. The spring device <NUM> is generally axially elongated and, relative to <FIG>, runs axially along the seal <NUM> (perpendicular to the plane of <FIG>). The spring device <NUM> includes a plurality of spring elements <NUM> that serve to provide the bias force on the seal <NUM>. The spring elements <NUM> are finger springs. For example, the finger springs <NUM> are formed of sheet metal, but could alternatively be formed by casting, additive manufacturing, or other process. A "finger spring" is generally a curved elongated body that is elastically flexible under the applied loads. Each of the finger springs <NUM> includes a base portion 82a, a finger portion 82b, and an acute elbow portion 82c that connects the base portion 82a and the finger portion 82b. The base portion 82a is bonded to a common backing plate <NUM>, such as by welding or other metallurgical bonding. The backing plate <NUM> is received in to the slot <NUM> in the spar platforms 72a to retain the spring device <NUM> in place.

The finger portion 82b in this example is substantially planar. The tip end of the finger portion 82b turns so as to form a bearing surface 82d that bears against the seal <NUM> (or other structure if a seal is not used). The bearing surface 82d provides an area contact over which the spring force is distributed, as opposed to a point or line of contact that would otherwise concentrate the force. The distribution of the force serves to facilitate reduction in wear and stress loads on the seal <NUM>.

The acute elbow portion 82c includes a turn that serves as a transition between the base portion 82a and the finger portion 82b. The turn is acute in that an angle defined between the base portion 82a that lies flat against the backing plate <NUM> and the finger portion 82b is less than <NUM>°. The acute elbow portion 82c serves as a flexible joint between the base portion 82a and the finger portion 82b such that when compressed between the spar platforms 72a and the fairing platforms <NUM>, the finger springs <NUM> deflect about the acute elbow portions 82c.

In this example, the finger springs <NUM> are arranged as two oppositely-oriented groups. For instance, the three finger springs <NUM> on the left-hand side in <FIG> form a first group and the three finger springs <NUM> on the right-hand side form a second group. The finger springs <NUM> of the first group are oriented such that the acute elbow portions 82c open toward the left and the finger springs <NUM> of the second group open toward the right. The base portions 82a each include a downturned tab 82e that abuts the acute elbow portion 82c of the adjacent one of the finger springs <NUM> of the group. Thus, in the depicted configuration, the acute elbow portion 82c of the middle one of the finger springs <NUM> nests with the tab 82e of the inner-most one of the finger springs <NUM>, and the acute elbow portion 82c of the end one of the finger springs <NUM> nests with the tab 82e of the middle one of the finger springs <NUM>. The two inner-most ones of the finger springs <NUM> of the groups are situated back-to-back such that the acute elbow portions 82c abut one another.

Such a configuration facilitates rotational stabilization of the finger springs <NUM>. For instance, compression of the spring device <NUM> causes the bearing surfaces 82d to apply force on the seal <NUM>. Each of the finger springs <NUM> flexes about its acute elbow portion 82c, causing a rotation moment there about. However, with the aforementioned nesting, the tab 82e supports the acute elbow portion 82c of the next finger spring <NUM> to thereby stabilize the finger spring <NUM> against rotation. Such loads may ultimately be transmitted to the middle ones of the finger springs <NUM> where they oppose and substantially cancel due to the opposed orientation of the back-to-back acute elbow portions 82c. Moreover, should one of the finger springs <NUM> dislodge from the backing plate <NUM>, the above nesting may also facilitate maintaining the dislodged finger spring <NUM> in position. Any portions of the spring device <NUM> that are in friction contact, such as the bearing surfaces 82d and/or acute elbows 72c, may be provided with a lubricious coating. For example, the lubricious coating may be, but is not limited to, graphite, chromium carbide, chromia, or alumina.

As shown in the further example in <FIG>, the slot <NUM> additionally includes a tang 80a that projects into the open space in the slot <NUM>. The tang 80a serves to capture the tab 82e of the end one of the finger springs <NUM> to facilitate retaining the spring device <NUM> in the slot <NUM>. The tang 80a serves as an anti-rotation feature against the tendency of the finger springs <NUM> to rotate when under compression.

<FIG> illustrates a further example in which the slot <NUM> additionally includes a keystone element <NUM>. The keystone element <NUM> is a projection in the slot <NUM> that extends between the inner-most ones of the finger springs <NUM>. In this example, the keystone element <NUM> is substantially triangular in cross-section and extends between the adjacent finger portions 82b of the inner-most ones of the finger springs <NUM> such that the sides of the triangular cross-section bear against the finger portions 82b. The keystone element <NUM> serves as a further anti-rotation feature against the tendency of the finger springs <NUM> to rotate when under compression. For instance, under compression, the right-hand one of the inner-most finger spring <NUM> has a tendency to rotate counter-clockwise in the illustrated example. However, since the side of the keystone element <NUM> bears against the finger portion 82b, the keystone element <NUM> limits the deflection of the finger spring <NUM> and its ability to rotate in place. Likewise, the keystone element <NUM> also limits the left-hand side one of the inner-most finger springs <NUM>. Moreover, as the loads of the groups of the finger springs <NUM> are transmitted to the inner-most finger springs <NUM>, the keystone element <NUM> may also indirectly serve for anti-rotation of the middle and outer ones of the finger springs <NUM>.

<FIG> illustrates an example spring device <NUM> outside the wording of the claims. In this disclosure, like reference numerals designate like elements where appropriate and reference numerals with the addition of one-hundred or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding elements. Here, the spring device <NUM> is the same as the spring device <NUM> except that it excludes the common backing plate <NUM>. In this regard, the finger springs <NUM> are provided as individual, separate pieces that are not commonly affixed. Although the finger springs <NUM> in this example are free-floating relative to one another, the compression of the finger springs <NUM> between the slot <NUM> and the seal <NUM> serves to maintain the finger springs <NUM> in place. Moreover, due to the aforementioned nesting via the tabs 82e and acute elbow portions 82c, the finger springs <NUM> are rotationally self-constraining. In this example, the keystone element <NUM> addition facilitates maintaining the finger springs <NUM> in place by supporting the inner-most ones of the finger springs <NUM> and preventing them from "collapsing" into the middle region between the inner-most finger springs <NUM>.

<FIG> illustrates another example of a spring device <NUM>. In this example, rather than the two groups of oppositely-oriented finger springs <NUM>, the spring device <NUM> includes a single group of commonly-oriented finger springs <NUM>. Here, although the finger springs <NUM> still nest as discussed above, the rotational stabilization may be somewhat less than in the two-group configuration because there are no back-to-back finger springs <NUM> for load cancellation. Thus, the loads here may ultimately be borne at the end of the slot <NUM>. In that regard, the end of the slot <NUM> may be adapted to support the last finger spring <NUM>, such as with an angled face.

As illustrated in <FIG>, the biasing force provided by the spring devices disclosed herein may also be used to facilitate positioning of adjacent seals. For instance, seal <NUM> is biased with force F by a spring device as disclosed herein. A portion of an adjacent seal <NUM>-<NUM> underlaps the seal <NUM>. Thus, the bias force applied to the seal <NUM> is transmitted also to the adjacent seal <NUM>-<NUM> to thereby provide a secondary bias force to facilitate maintaining the seal <NUM>-<NUM> in position. The secondary bias force applied to the seal <NUM>-<NUM> may also be used to provide a tertiary bias force. For instance, another adjacent seal <NUM>-<NUM> underlaps the seal <NUM>-<NUM>. Thus, the bias force applied to the seal <NUM>-<NUM> is transmitted also to the adjacent seal <NUM>-<NUM> to thereby provide a tertiary bias force to facilitate maintaining the seal <NUM>-<NUM> in position. The types of the seals <NUM>-<NUM>/<NUM>-<NUM> are not particularly limited. For example, the seals <NUM>-<NUM>/<NUM>-<NUM> may be, but are not limited to, feather seals and L-seals.

Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this invention.

In other words, a system designed according to an embodiment of this invention will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures.

Claim 1:
An assembly for a gas turbine, the assembly comprising:
first and second core gaspath walls (<NUM>), each of the core gaspath walls (<NUM>) defining a core gas path side (66a) and a non-core gas path side (66b), the first and second core gaspath walls (<NUM>) being arranged next to each other and defining a gap (G) therebetween;
a seal (<NUM>); and
a spring device (<NUM>; <NUM>) having a plurality of spring elements (<NUM>), wherein the spring elements (<NUM>) are finger springs (<NUM>) bonded to a common backing plate (<NUM>), each of the finger springs (<NUM>) including a base portion (82a), a finger portion (82b), and an acute elbow portion (82c) connecting the base portion (82a) and the finger portion (82b), the finger portion (82b) including a tip end having a bearing surface (82d) that bears against the seal (<NUM>), characterised in that:
the seal (<NUM>) is arranged on the non-core gas path side (66b), the seal (<NUM>) bridging over the gap (G) to seal the gap (G);
the spring elements (<NUM>) bias the seal (<NUM>) against the non-core gas path sides (66b) of the first and second core gaspath walls (<NUM>); and
the assembly further comprises support hardware (<NUM>, <NUM>) that defines a slot (<NUM>) in which the spring device (<NUM>; <NUM>) is disposed, the slot (<NUM>) including a tang (80a) retaining the spring device (<NUM>; <NUM>), and/or a keystone element (<NUM>) limiting rotation of the spring elements (<NUM>).