Patent Description:
Gas turbine engines can include a fan for propulsion air and to cool components. The fan also delivers air into a core engine where it is compressed. The compressed air is then delivered into a combustion section, where it is mixed with fuel and ignited. The combustion gas expands downstream over and drives turbine blades. Static vanes are positioned adjacent to the turbine blades to control the flow of the products of combustion. The fan typically includes an array of fan blades having dovetails that are mounted in slots of a fan hub driven by a turbine.

<CIT> discloses a prior art turbine blade fastening apparatus.

<CIT> discloses a prior art fluid flow machine.

<CIT> discloses a prior art sealed airfoil blade and disc assembly for a rotor.

<CIT> discloses a prior art mounting arrangement for turbine or compressor blading.

According to a first aspect of the present invention, there is provided an airfoil assembly as set forth in claim <NUM>. According to a further aspect of the present invention, there is provided a gas turbine engine as set forth in claim <NUM>. According to a further aspect of the present invention, there is provided a method of assembly for a gas turbine engine as set forth in claim <NUM>. Further embodiments are provided as set forth in dependent claims <NUM> to <NUM>, <NUM> to <NUM> and <NUM>.

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of an embodiment.

The fan section <NUM> includes a rotor (or airfoil) assembly <NUM> including the fan <NUM> and a rotatable hub <NUM>. The fan <NUM> includes an array or row <NUM> of airfoils or fan blades <NUM>. The fan blades <NUM> extend circumferentially about and are carried or otherwise supported by the hub <NUM>. The fan blades <NUM> and hub <NUM> are rotatable about the engine longitudinal axis A. The hub <NUM> is mechanically attached to a fan shaft <NUM>, and the fan drive turbine <NUM> is mechanically coupled to the fan shaft <NUM> to drive the fan <NUM>.

<FIG> illustrates a rotor (or airfoil) assembly <NUM> according to another example. 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 original elements. The rotor assembly <NUM> can be incorporated into a gas turbine engine, such as the rotor assembly <NUM> or another portion of the engine <NUM> of <FIG>. Other portions of the engine <NUM> and other systems can benefit from the teachings disclosed herein, including rotatable and static airfoils in the compressor and turbine sections <NUM>, <NUM>.

The rotor assembly <NUM> includes an array or row <NUM> of rotatable airfoils <NUM> that extend circumferentially about and are supported by a rotatable hub <NUM> (see also <FIG>). In the illustrative example of <FIG>, the airfoils <NUM> are fan blades. Any suitable number of fan blades may be used in a given application, including <NUM> or fewer fan blades, such as between <NUM> and <NUM> fan blades. Although only one (e.g., forwardmost) row <NUM> of airfoils <NUM> is shown, the teachings herein can apply to engine arrangements having two or more rows of rotatable airfoils.

Each of the airfoils <NUM> includes an airfoil section <NUM> that extends in a radial or spanwise direction R from the hub <NUM> between a root section <NUM> and a tip portion <NUM>, in a chordwise direction X between a leading edge <NUM> and a trailing edge 168T, and in a thickness or circumferential direction T between a pressure sidewall (or side) 168P and a suction sidewall (or side) <NUM> (see <FIG> for directions R, X and T). The airfoil section <NUM> extends from the root section <NUM> in the radial direction R and terminates at a terminal end along the tip portion <NUM>. The airfoil section <NUM> and root section <NUM> are joined at a neck portion <NUM> (<FIG>). The pressure sidewall 168P and the suction sidewall <NUM> are spaced apart or separated in the circumferential direction T and generally meet together at both the leading and trailing edges <NUM>, 168T.

Each airfoil <NUM> has an exterior surface 168ES providing a contour that extends in the chordwise direction X from the leading edge <NUM> to the trailing edge 168T along the airfoil section <NUM>. The exterior surface 168ES generates lift based upon its geometry and directs flow along a gas path, such as the core flow path C and/or bypass flow path B of <FIG>. It should be understood that the airfoil profile including the contouring of the pressure and suction sides 168P, <NUM> is exemplary and other airfoil profiles can be utilized according to the teachings disclosed herein.

The airfoil section <NUM> extends radially outward from at least one platform <NUM>, which provides an inner flow path or gas path surface GS. The platform <NUM> may be integral with the airfoil <NUM>. In the illustrative example of <FIG>, the rotor assembly <NUM> includes a pair of platforms <NUM> secured to each respective airfoil <NUM> (indicated at <NUM>-<NUM>, <NUM>-<NUM> in <FIG>). A geometry of the platforms <NUM>-<NUM>, <NUM>-<NUM> can be the same or can differ to complement a geometry of the airfoil <NUM>. Each platform <NUM> is a separate and distinct component from the airfoil <NUM>. The platform <NUM> can include a surface fairing <NUM> that defines the gas path surface GS. Each surface fairing <NUM> can have a generally wedge shaped geometry and can be dimensioned to slope in the chordwise direction X such that the gas path surface GS is generally inclined from an axially forward position to an axially aft position relative to the assembly axis AA, as illustrated by the surfaces fairings <NUM> of <FIG>. The surface fairing <NUM> can be formed from sheet metal and contoured to the predefined geometry of the gas path surface GS, for example. Respective pairs of the surface fairings <NUM> can be positioned between adjacent airfoils <NUM> to establish a generally conical aero flowpath, as illustrated by the fairings <NUM>, <NUM> of <FIG> and <FIG>.

The hub <NUM> is rotatable in a direction DR about an assembly (or longitudinal) axis AA. The assembly axis AA can be collinear or substantially parallel to the engine longitudinal axis A of <FIG>. The direction DR can be clockwise or counter-clockwise with respect to the assembly axis AA.

Referring to <FIG>, with continuing reference to <FIG>, the hub <NUM> includes an array of slots <NUM> defined about an outer periphery 166P of the hub <NUM>. The hub <NUM> can include an array of annular flanges 166F that extend about the assembly axis AA. The hub <NUM> includes an array of annular channels 166C established between adjacent pairs of the flanges 166F. In other examples, the channels 166C are omitted. The channels 166C can be dimensioned extend inwardly from and intersect the slots <NUM>.

Each channel 166C can be dimensioned to receive a reinforcement member <NUM>. Each reinforcement member <NUM> can have an annular geometry and is dimensioned to extend about an inner periphery 166I of the respective channel 166C.

Various materials can be utilized to form the reinforcement members <NUM>. The reinforcement members <NUM> can include metallic and/or composite materials. For example, each reinforcement member <NUM> can be made of a composite material including at least one composite layer LL that is formed to extend about the hub <NUM>. In the illustrative example of <FIG>, the reinforcement member <NUM> includes a plurality of composite layers LL in a stacked relationship. Various materials and constructions can be utilized to form the composite layers LL, including carbon and ceramic matrix composite (CMC) materials. For example, the reinforcement member <NUM> can be a carbon tape having uni-directional fibers and that is continuously wound around the hub <NUM> two or more times to define the composite layers LL, such as a total of three layers LL. It should be understood that the reinforcement member <NUM> can have fewer or more than three layers LL. The tape can be a dry form and impregnated or injected with an epoxy or resin after formation along the hub <NUM>, and then cured to fabricate the reinforcement member <NUM>, for example, which can reduce creep. The reinforcement members <NUM> can at least partially reinforce or support the hub <NUM> to react centrifugal forces and carry relatively high hoop loads during engine operation, and can reduce an overall weight of the hub <NUM>, for example. In other examples, the reinforcement members <NUM> are omitted.

Referring to <FIG>, with continuing reference to <FIG>, a pair of platforms <NUM> are secured to the airfoil <NUM> (indicated at <NUM>-<NUM>, <NUM>-<NUM>). The platforms <NUM>-<NUM>, <NUM>-<NUM> are arranged on opposed sides of the respective airfoil <NUM>. In other examples, the platforms <NUM>-<NUM>, <NUM>-<NUM> are a single component. Each platform <NUM> includes a first portion 176A and a second portion 176B. The platform portions 176A, 176B are separate and distinct components mechanically attached or otherwise secured to the root section <NUM> of the respective airfoil <NUM>.

The first portion 176A of the platform <NUM> extends circumferentially from the second portion 176B to a respective mate face <NUM> (<FIG>). A respective surface fairing <NUM> can be secured to the second portion 176B to establish the gas path surface GS. The gas path surface GS can establish at least a portion of an inner diameter flow path boundary of the fan section <NUM> of <FIG>, for example. In other examples, the surface fairing <NUM> is incorporated into the second portion 176B.

Each mate face <NUM> can be dimensioned to establish a platform interface <NUM> with the mate face <NUM> of an adjacent one of platforms <NUM>, as illustrated in <FIG> (see also <FIG>). The platforms <NUM> can be dimensioned to at least partially yield in response to relative circumferential movement between adjacent airfoils <NUM> and can dimensioned to react aero-bending and bias the airfoils <NUM> back toward a neutral position. Adjacent platforms <NUM> can cooperate along the platform interface <NUM> to dampen movement of the respective airfoil <NUM> in response to relative circumferential movement between the airfoils <NUM>. In the illustrative example of <FIG>, the platforms <NUM> include circumferentially overlapping portions that establish the mate faces <NUM>. In the illustrative example of <FIG>, platforms <NUM>' include a tongue-and-groove arrangement to establish a platform interface <NUM>'. Damping can be established by frictional contact between surfaces of the platforms <NUM> along the platform interface <NUM>. Seal members <NUM> can be positioned relative to adjacent platforms <NUM> to limit the flow of fluid between intersegment gaps established by the respective mate faces <NUM> (shown in dashed lines in <FIG> for illustrative purposes). In other examples, the seal member <NUM> is omitted.

The second portion 176B of the platform <NUM> extends radially inwardly from the first portion 176A. The second portion 176B is dimensioned to follow a contour of the root section <NUM> of the airfoil <NUM>.

Referring to <FIG>, with continuing reference to <FIG>, the rotor assembly <NUM> includes one or more root mounts <NUM> for securing respective airfoils <NUM> to the hub <NUM>. Each root mount <NUM> includes first and second mount (or interface) members <NUM>, <NUM> arranged along and secured to circumferentially opposed sides 170C of the root section <NUM>. Each mount member <NUM>/<NUM> has an elongated main body 180B/182B extending between an inner circumferential face 180R/182R and an outer circumferential face 180C/182C. The inner circumferential faces 180R, 182R are dimensioned to at least partially follow a contour of the platform portions 176B. The outer circumferential faces 180C, 182C are dimensioned to mate with opposing surfaces of the respective slot <NUM>. The outer circumferential faces 180C, 182C can have a substantially arcuate shaped geometry and are dimensioned to pivotably mount the root section <NUM> in the respective slot <NUM> of the hub <NUM> in an installed position. For the purposes of this disclosure, the term "substantially" means ±<NUM>% of the stated relationship or value unless otherwise disclosed.

In the illustrative example of <FIG>, the circumferential face 180C of the first mount member <NUM> and the circumferential face 182C of the second mount member 182C are dimensioned to substantially follow an interface profile PF established by a common radius RM swept about a mount axis MA extending through the root section <NUM> (see also <FIG> and <FIG>). The interface profile PF is shown in dashed lines in <FIG> and <FIG> for illustrative purposes.

The respective slot <NUM> includes an interface region RI dimensioned to mate with the circumferential faces 180C, 182C. The interface region RI is dimensioned to extend along a substantially cylindrical projection that spans across at least some or all of the arcuate flanges 166F of the hub <NUM> (region RI illustrated in dashed lines in <FIG>, see also <FIG>). The mount members <NUM>, <NUM> cooperate to establish a pinned interface along the respective slot <NUM>.

Opposing walls of the slot <NUM> are dimensioned to substantially follow a contour of the circumferential faces 180C, 182C of the mount members <NUM>, <NUM> to establish a hinge joint arrangement in an installed position. Each slot <NUM> is dimensioned to at least partially follow a contour and encircle the circumferential faces 180C, 182C to establish the hinge joint arrangement and limit relative radial movement between the airfoil <NUM> and hub <NUM>.

The mount members <NUM>, <NUM> of the root mount <NUM> together with the root section <NUM> and platforms <NUM> are slidably received in a respective one of the slots <NUM> in the hub <NUM> to establish the hinge joint arrangement that mounts the respective airfoil <NUM> to the hub <NUM>. The airfoil <NUM> is pivotable about a hinge line established along the mount axis MA. A projection of the mount axis MA extends between opposed ends of the respective slot <NUM> in the installed position, as illustrated by <FIG>. The second portion 176B of each platform <NUM> is trapped or sandwiched between the root section <NUM> and a respective one of the mount members <NUM>, <NUM>.

The neck portion <NUM> is situated between opposed circumferential walls 166W of the respective slot <NUM>. The neck portion <NUM> is pivotable in a direction RR about the mount axis MA established by the root mount <NUM>. The circumferential walls 166W are dimensioned to limit rotation of the neck portion <NUM> in the direction RR about the mount axis MA. In examples, the circumferential walls 166W are dimensioned to abut the second portion 176B of a respective one of the platforms <NUM> to limit rotation of the airfoil <NUM> about the mount axis MA (illustrated in dashed lines at 176B' for illustrative purposes). In other examples, circumferential walls 166W are dimensioned to directly abut against surfaces of the airfoil <NUM> to limit rotation of the airfoil <NUM> about the mount axis MA.

The root section <NUM> extends radially inwardly from the airfoil section <NUM> to a radially inner face 170F. The root section <NUM> can include a key portion <NUM> dimensioned to extend radially inwardly from the mount members <NUM>, <NUM> to the radially inner face 170F of the root section <NUM>. The second portion 176B of each platform <NUM> can be dimensioned to follow the key portion <NUM> between the respective mount member <NUM>/<NUM> and the radially inner face 170F.

In the illustrative example of <FIG>, the root section <NUM> is dimensioned such that the radially inner face 170F is situated outside of a boundary of the interface profile PF. The key portion <NUM> together with the adjacent portions of the platforms <NUM> are slidably received in a keyway region RK of the slot <NUM> (see also <FIG>) to limit rotation of the root section <NUM> about the mount axis MA in the installed position. An angle established between opposed walls of the slot <NUM> along the keyway region RK can be the same or can differ from an angle established between the circumferential walls 166W adjacent the neck portion <NUM> of the airfoil <NUM>.

Various materials can be utilized or incorporated in the rotor assembly <NUM>. The root section <NUM> of the airfoil <NUM> includes a first material. Each platform <NUM> includes a second material. Each of the mount members <NUM>, <NUM> of the root mount <NUM> includes a third material. The first, second and/or third materials can be the same or can differ in construction and/or composition. In examples, at least one of the first, second and/or third materials is a composite material, and another one of the first, second and/or third materials is a metallic material. For example, the first material can include a composite material, and the second and/or third materials can include a metallic material. Example metallic materials include steel or an aluminum or titanium alloy.

Example composite materials include organic matrix composites. The organic matrix composite can include a matrix material and reinforcement fibers distributed through the matrix material. The reinforcement fibers can be discontinuous or continuous, depending upon the selected properties of the organic matrix composite. Example matrix materials include thermoset polymers or thermoplastic polymers. Example reinforcement fibers include carbon graphite, silica glass, and silicon carbide. Pre-pregs can also be utilized. Given this description, one of ordinary skill in the art will recognize that other types of matrix materials and reinforcement fibers can be utilized, including ceramic matrix composite materials.

The airfoil <NUM> may be constructed from a composite material, a metal material such as an aluminum or titanium alloy, or a combination of one or more of these, for example. Abrasion-resistant coatings or other protective coatings may be applied to the airfoil <NUM>. The airfoil section <NUM> can be substantially solid or can be hollow. In examples, the airfoil <NUM> includes a composite (e.g., carbon-based) core and a metallic sheath <NUM> including a pair of skins <NUM> that form an external surface of the airfoil section <NUM>, as illustrated in <FIG>. In the illustrative example of <FIG>, the skins <NUM> are dimensioned to extend from the airfoil section <NUM> at least partially along the root section <NUM> to establish a load path between the mount members <NUM>, <NUM>, as illustrated in <FIG>.

The mount members <NUM>, <NUM> can have a unitary construction, as illustrated in <FIG>. In the illustrative example of <FIG>, mount member <NUM>'/<NUM>' includes a main body 180B'/182B' extending between the inner circumferential face 180R'/182R' and the outer circumferential face 180C'/182C'. A first coating <NUM>' can be disposed along the inner circumferential face 180R'/182R'. A second coating <NUM>' can be disposed along the outer circumferential face 180C'/182C'. The first and second coatings <NUM>', <NUM>' can be made of a material that differs from a material of the main body 180B'/182B', such as a different modulus or strain to distribute loads between the root section <NUM> and hub <NUM> and/or vary the amount of rotational deflection of the airfoil <NUM> upon impact by foreign object debris (FOD).

In examples, the hub <NUM>, mount portions <NUM>, <NUM> and platform portions <NUM> are formed from a metallic material, including any of the materials disclosed herein such as titanium. The platform portions <NUM> may be formed from sheet metal, for example.

In the illustrative example of <FIG>, the airfoil <NUM> is formed of a composite material including a plurality (or first set) of plies P1 arranged in a layup. The plies P1 are arranged to extend from the root section <NUM> at least partially into the neck portion <NUM> and airfoil section <NUM> of the airfoil <NUM>. At least some of the plies P1 can establish the radially inner face 170F of the root section <NUM>. The composite material can include wedge region P2 arranged in a root section <NUM> between adjacent plies P1, as illustrated in <FIG>. The wedge region P2 can include any of the materials and constructions disclosed herein. For example, the wedge region P2 can include a composite material that is co-cured with the plies P1. The plies P1 and wedge region P2 are arranged to establish sloped circumferential sides 270C along the root section <NUM>.

The rotor assembly <NUM> can be assembled as follows. Referring to <FIG>, the pair of platforms <NUM> can be moved in respective directions D1, D2 and into abutment with opposed sides of the root section <NUM>. Direction D1 can be generally opposed to direction D2. The platforms <NUM> can be bonded or otherwise secured to the root section <NUM> with one or more layers <NUM>. The layers <NUM> can be an adhesive or epoxy, for example.

The mount members <NUM>, <NUM> of the root mount <NUM> can be moved in respective directions D1, D2 and into abutment with the second portion 176B of the respective platforms <NUM> such that the root section <NUM> is captured between the mount members <NUM>, <NUM>. The mount members <NUM>, <NUM> can be mechanically attached to the platforms <NUM> and root section <NUM> with one or more fasteners F to establish an assembly, as illustrated by <FIG> and <FIG>. The fasteners F can include bolts, pins, clips and rivets, for example. In the illustrative example of <FIG>, the fastener F is a bolt that is threadably attached to the mount members <NUM>, <NUM>. In other examples, each mount member <NUM>, <NUM> is integrally formed with a respective one of the platform portions <NUM>.

Referring to <FIG>, an outer diameter of each reinforcement member <NUM> can be positioned radially inward of a radially innermost portion of the mount members <NUM>, <NUM> with respect to the assembly axis AA, as illustrated by <FIG>. The mount members <NUM>, <NUM> of the root mount <NUM> together with the captured root section <NUM> of the airfoil <NUM> and platforms <NUM> are moved as an assembly or unit in a direction D3, which can be substantially parallel to the assembly axis AA, and at least partially or completely into the respective slot <NUM> to mount the airfoil <NUM> to the hub <NUM>. In the installed position, the mount axis MA extends longitudinally along the respective slot <NUM> to establish the hinge joint arrangement, as illustrated by <FIG> and <FIG>. A respective surface fairing <NUM> can be secured to the second portion 176B of the platform <NUM> to establish the gas path surface GS subsequent to positioning the captured root section <NUM> in the respective slot <NUM>, as illustrated in <FIG>. Various techniques can be utilized to secure the surface fairing <NUM> to the second portion 176B, such as bonding the surfaces with an adhesive or mechanically attaching one or more fasteners.

<FIG> illustrates a rotor assembly <NUM> according to another example. Root section <NUM> is dimensioned such that a radially inner face 270F of the root section <NUM> is dimensioned to substantially follow an interface profile PF established by the root mount <NUM>. Opposing walls of a respective slot <NUM> are dimensioned to substantially follow a contour of the radially inner face 270F and circumferential faces 280C, 282C of mount members <NUM>, <NUM> to establish a hinge joint arrangement.

At least one damping member <NUM> can be positioned between a neck portion <NUM> of the airfoil <NUM> and a respective one of the circumferential walls 266W of the slot <NUM>. The damping member <NUM> is deformable or crushable in response to rotation of the airfoil section <NUM> about a mount axis MA established by the root mount <NUM>. In examples, the damping member <NUM> is positioned on only one side of the neck portion <NUM>. In other examples, another damping member <NUM>' is positioned on an opposed side of the neck portion <NUM> (shown in dashed lines for illustrative purposes). The assembly <NUM> can include a plurality of damping members <NUM> uniformly or non-uniformly axially distributed along a portion or entirety of the slot <NUM>.

Various materials can be utilized to form the damping member <NUM>. The damping member <NUM> can have a honeycomb construction, as illustrated by <FIG>. The honeycomb construction can be additively manufactured, for example. The damping member <NUM> can be a replaceable, one-event component that is permanently deformable in response to an impact or impulse by FOD such as during a bird strike event, for example. The damping member <NUM> can serve to absorb the impact or impulse, limit bending and more uniformly distribute torque loads. In other examples, the damping member <NUM> is made of an elastic material such as rubber that is temporarily deformable. The damping member <NUM> can be bonded or otherwise secured to the circumferential wall 266W of the slot <NUM>.

The arrangements disclosed herein including the hinge joint or pivotable interface between the airfoils and hub can be utilized to reduce stress concentrations in the airfoil including the root section that may be otherwise caused by an impact by FOD such as during a bird strike event. The root mounts can be slidably received in the respective slots to mount the airfoils, which may reduce installation and maintenance complexity. The airfoils can incorporate composite materials, which may reduce weight of the assembly. The platforms can be exclusively mounted to the hub via retention in the slots, which may reduce the need for separate mounting features on the hub (e.g., tombstones and fasteners) and which may reduce weight of the assembly.

Claim 1:
An airfoil assembly (<NUM>; <NUM>) for a gas turbine engine (<NUM>) comprising:
an airfoil (<NUM>; <NUM>) including an airfoil section (<NUM>; <NUM>) extending from a root section (<NUM>; <NUM>), the airfoil section (<NUM>; <NUM>) extending between a leading edge (<NUM>) and a trailing edge (168T) in a chordwise direction and extending between a tip portion (<NUM>) and the root section (<NUM>; <NUM>) in a radial direction, and the airfoil section (<NUM>; <NUM>) defining a pressure side (168P) and a suction side (<NUM>) separated in a circumferential direction;
a root mount (<NUM>; <NUM>) including first and second mount members (<NUM>, <NUM>; <NUM>, <NUM>) secured to circumferentially opposed sides of the root section (<NUM>), wherein arcuate circumferential faces (180C, 182C; 280C, 282C) of the first and second mount members (<NUM>, <NUM>) are dimensioned to pivotably mount the root section (<NUM>) in respective slots (<NUM>) defined about an outer periphery of a hub (<NUM>) in an installed position, each of the fan blades (<NUM>) includes a neck portion (<NUM>; <NUM>) joining the airfoil section (<NUM>; <NUM>) and the root section (<NUM>; <NUM>), the airfoil (<NUM>; <NUM>) is configured to be pivotable about a hinge line established along a mount axis (MA), the mount axis (MA) established by the root mount (<NUM>; <NUM>) in the installed position, the neck portion (<NUM>; <NUM>) is configured to be situated between opposed circumferential walls (180R, 182R; 280R, 282R) of the respective slot that are dimensioned to limit rotation of the neck portion (<NUM>; <NUM>) about the mount axis (MA), and a projection of the mount axis (MA) extends between opposed ends of the respective slot in the installed position; and characterised in that
at least one platform (<NUM>) including a first portion (176A) and a second portion (176B), the first portion (176A) extending circumferentially from the second portion (176B), and the second portion (176B) trapped between the root section (<NUM>; <NUM>) and a respective one of the first and second mount members (<NUM>, <NUM>; <NUM>, <NUM>).