Patent Description:
Gas turbine engines are known and typically include a compressor compressing air and delivering it into a combustor. The air is mixed with fuel in the combustor and ignited. Products of the combustion pass downstream over turbine rotors, driving them to rotate.

It is desirable to ensure that the bulk of the products of combustion pass over turbine blades on the turbine rotor. As such, it is known to provide blade outer air seals radially outwardly of the blades. Air flowing through the combustor and turbine has very high temperatures. Some of the components in these high temperature areas, such as the combustor segments and the blade outer air seals have been proposed made of ceramic matrix composite fiber layers.

<CIT> describes a method of manufacturing transformer windings embedded in casting resin which utilizes an integrated winding mandrel for producing a non-standard oval shaped epoxy encapsulated low voltage coil for dry type distribution transformers. <CIT> describes an assembly adapted for use in a gas turbine engine which has a carrier component, a supported component, and a seal adapted to resist the flow of gasses between the supported component and the carrier component. <CIT> describes a component for a gas turbine. The component includes a component wall having a radially inner surface, a radially outer surface, a first circumferential surface, and a second circumferential surface.

According to an aspect of the invention, there is provided a method of manufacturing a component as recited in claim <NUM>.

In a further embodiment of the above, the method includes removing the mandrel and the rods.

In a further embodiment of any of the above, the method includes densifying the body.

In a further embodiment of any of the above, the densifying comprises injecting an infiltrant into the body to fill voids formed by the rods.

In a further embodiment of any of the above, the machining comprises removing at least <NUM>% of the outer wall.

In a further embodiment of any of the above, the machining includes removing a portion of the first and second walls to form a trailing edge platform.

In a further embodiment of any of the above, the machining is performed by an ultrasonic machine.

In a further embodiment of any of the above, the inner and outer wraps are formed from fibrous braided or woven plies.

In a further embodiment of any of the above, the inner wrap is formed from at least two plies.

In a further embodiment of any of the above, the body has between <NUM> and <NUM> plies.

In a further embodiment of any of the above, the rods extend along an axial length of the first and second walls.

In a further embodiment of any of the above, one rod is arranged at the first wall and configured to form a protrusion. Two rods are arranged at the second wall and configured to form a groove.

In a further embodiment of any of the above, each of the rods has a diameter of at least <NUM> inches (<NUM>).

In a further embodiment of any of the above, the body is formed from a ceramic matrix composite material.

In a further embodiment of any of the above, at least one of the rods comprises an inner rod and an outer rod. The outer rod is removed before the step of forming features in the circumferential sides.

According to an aspect of the present invention, there is provided a gas turbine engine as recited in claim <NUM>.

In a further embodiment of any of the above, the protrusion or groove is configured to engage with an adjacent segment.

In a further embodiment of any of the above, at least one segment is a ceramic matrix composite material.

The inner shaft <NUM> is connected to the fan <NUM> through a speed change mechanism, which in the exemplary gas turbine engine <NUM> is illustrated as a geared architecture <NUM> to drive a fan <NUM> at a lower speed than the low speed spool <NUM>. A combustor <NUM> is arranged in the exemplary gas turbine engine <NUM> between the high pressure compressor <NUM> and the high pressure turbine <NUM>.

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 fan section <NUM> of the engine <NUM> is designed for a particular flight conditiontypically cruise at about <NUM> Mach and about <NUM>,<NUM> feet (<NUM>,<NUM> meters).

<FIG> shows a portion of an example turbine section <NUM>, which may be incorporated into a gas turbine engine such as the one shown in <FIG>. However, it should be understood that other sections of the gas turbine engine <NUM> or other gas turbine engines, and even gas turbine engines not having a fan section at all, could benefit from this disclosure. The turbine section <NUM> includes a plurality of alternating turbine blades <NUM> and turbine vanes <NUM>.

A turbine blade <NUM> has a radially outer tip <NUM> that is spaced from a blade outer air seal assembly <NUM> with a blade outer air seal ("BOAS") <NUM>. The BOAS <NUM> may be made up of a plurality of seal segments <NUM> that are circumferentially arranged in an annulus about the central axis A of the engine <NUM>. The BOAS segments <NUM> may be monolithic bodies that are formed of a high thermal-resistance, low-toughness material, such as a ceramic matrix composite ("CMC").

The BOAS <NUM> may be mounted to an engine case or structure, such as engine static structure <NUM> via a control ring or support structure <NUM> and/or a carrier <NUM>. The engine structure <NUM> may extend for a full <NUM>° about the engine axis A. The engine structure <NUM> may support the support structure <NUM> via a hook or other attachment means. The engine case or support structure holds the BOAS <NUM> radially outward of the turbine blades <NUM>. Although a BOAS <NUM> is described, this disclosure may apply to other components, such as a combustor, inlet, exhaust nozzle, or vane, for example.

<FIG> shows a portion of an example BOAS assembly <NUM>. The assembly <NUM> includes seal segments 105A, 105B mounted on carriers <NUM>. Each seal segment 105A, 105B is a body that defines radially inner and outer sides R1, R2, respectively, first and second axial sides A1, A2, respectively, and first and second circumferential sides C1, C2, respectively. The radially inner side R1 faces in a direction toward the engine central axis A. The radially inner side R1 is thus the gas path side of the seal segment <NUM> that bounds a portion of the core flow path C. The first axial side A1 faces in a forward direction toward the front of the engine <NUM> (i.e., toward the fan <NUM>), and the second axial side A2 faces in an aft direction toward the rear of the engine <NUM> (i.e., toward the exhaust end). In one example, the seal segments 105A, 105B are arranged in the turbine section <NUM> such that the blades <NUM> pass from the first circumferential side C1 to the second circumferential side C2, or left to right in the illustrated embodiment.

In the illustrated example, each BOAS segment <NUM> includes a first wall <NUM> and a second wall <NUM> that extend radially outward from a base portion <NUM>. The first and second walls <NUM>, <NUM> extend along the base portion <NUM> in a generally axial direction, and are circumferentially spaced from one another. The base portion <NUM> extends between the first and second axial sides A1, A2 and defines a gas path on a radially inner side and a non-gas path on a radially outer side. In this disclosure, forward, aft, upstream, downstream, axial, radial, or circumferential is in relation to the engine axis A unless stated otherwise. The base portion <NUM> may extend axially forward and/or aft of the first and second walls <NUM>, <NUM>, and provides a surface for sealing of the BOAS first and second axial sides A1, A2. For example, the base portion <NUM> includes a portion <NUM> axially aft of the first and second walls <NUM>, <NUM> for sealing the trailing edge. That is, the walls <NUM>, <NUM> may extend less than the full length of the seal segment <NUM> in the axial direction.

The walls <NUM>, <NUM> include hooks <NUM>, <NUM>, respectively at a radially outermost portion. The hooks <NUM>, <NUM> extend circumferentially inward towards one another. The hooks <NUM>, <NUM> are configured to secure the seal segment <NUM> to the carrier <NUM>. The hooks <NUM>, <NUM> extend towards the matefaces, or first and second circumferential sides C1, C2.

The carrier <NUM> has a platform <NUM> with axially extending hooks <NUM>, <NUM>. The hooks <NUM>, <NUM> extend radially outward from the platform <NUM> for attaching the carrier <NUM> and seal segment <NUM> to the support structure <NUM> (shown in <FIG>). A portion of the platform <NUM> engages with the hooks <NUM>, <NUM>. The platform <NUM> is generally parallel to the base portion <NUM> of the seal segment <NUM>. In an example, the platform <NUM> of the carrier <NUM> has a width WC in the circumferential direction. The carrier hooks <NUM>, <NUM> have a width WH in the circumferential direction. The width WC is greater than the width WH to permit the platform <NUM> to engage with the hooks <NUM>, <NUM> of the seal segment <NUM>. In the illustrated example, the hooks <NUM>, <NUM> extend in a direction perpendicular to the walls <NUM>, <NUM>. In other examples, the hooks <NUM>, <NUM> may extend at an angle relative to the walls <NUM>, <NUM>. The axially extending hooks <NUM>, <NUM> provide engagement with the carrier <NUM> along all or most of the axial length of the carrier <NUM>. The carrier hooks <NUM>, <NUM> extend generally perpendicular to the seal segment hooks <NUM>, <NUM>. That is, the carrier hooks <NUM>, <NUM> extend generally circumferentially, while the seal segment hooks <NUM>, <NUM> extend generally axially.

In some examples, a wear liner may be arranged between the seal segment <NUM> and the carrier <NUM>. The wear liner may be a metallic material such as cobalt, for example. The wear liner may be formed from sheet metal. The carrier <NUM> may be segmented, with each segment engaged with a seal segment <NUM>.

<FIG> is a portion of the BOAS assembly <NUM>. The first and second circumferential sides C1, C2 are configured to mate with adjacent seal segments <NUM>. In the illustrated example, the first circumferential side C1 of each seal segment 105A, 105B has a protrusion <NUM> extending circumferentially outward from the seal segment 105A, 105B. The second circumferential side C2 of each seal segment 105A, 105B has a groove <NUM> extending circumferentially inward toward the seal segment <NUM>. The protrusion <NUM> of a seal segment 105A is configured to engage with the groove <NUM> of an adjacent seal segment 105B. The protrusion <NUM> and groove <NUM> may extend along an axial length of the first and second walls <NUM>, <NUM>. The protrusion <NUM> and groove <NUM> provide sealing between the first and second circumferential sides C1, C2 of each seal segment 105A, 105B.

In some examples, a seal segment <NUM> may have either grooves <NUM> or protrusions <NUM> at both the circumferential sides C1, C2 for engagement with an adjacent seal segment <NUM>. For example, a first seal segment 105A may have protrusions <NUM> at both circumferential sides C1, C2, while a second seal segment 105B may have grooves <NUM> at both circumferential sides C1, C2.

In one example, the protrusion <NUM> has a height <NUM>, and the groove has a height <NUM> (shown in <FIG>). The height <NUM> is greater than the height <NUM>. The groove <NUM> forms an inner portion <NUM> and an outer portion <NUM> of the second wall <NUM>. The second circumferential side C2 has a thickness T, which includes the inner and outer portions <NUM>, <NUM>, and the groove <NUM>. The first circumferential side C1 has a thickness H. In some examples, the thickness H is the same as the thickness T. The thicknesses H and T may be between about <NUM> and <NUM> inches (<NUM>-<NUM>), for example.

The BOAS <NUM> may be formed of a ceramic matrix composite ("CMC") material. Each seal segment <NUM> is formed of a plurality of CMC laminates. The laminates may be silicon carbide fibers, formed into a braided or woven fabric in each layer. The fibers may be coated by a boron nitride. In other examples, the BOAS <NUM> may be made of a monolithic ceramic.

CMC components such as BOAS segments <NUM> are formed by laying fiber material, such as laminate sheets or braids, in tooling, injecting an infiltrant into the tooling, and curing to form a solid composite component. The component may be densified by adding additional material to further stiffen the laminates.

In an embodiment, the BOAS segment <NUM> is formed from fiber material such as silicon carbide (SiC) braids. In one example, the protrusion <NUM> and groove <NUM> are integrally formed from the construction. The protrusion <NUM> and groove <NUM> may be formed by wrapping braided plies about a mandrel, then pulling the laminates in the circumferential direction to form the protrusion <NUM> and groove <NUM> in one example. In another example, the protrusion <NUM> and groove <NUM> may be formed using inner and outer molds that form the protrusion <NUM> and groove <NUM>.

<FIG> summarizes an example method of forming a component, such as the seal segment <NUM>. An inner wrap is formed about a mandrel at step <NUM>. An outer wrap is formed about the inner wrap and one or more rods at step <NUM>. The rods are used to form features in the circumferential sides of the outer wrap at step <NUM>. The seal segment <NUM> may be densified at step <NUM>. The seal segment <NUM> may be machined to form the final shape at steps <NUM> and <NUM>. Each of these steps is further described herein.

<FIG> illustrates a method step <NUM> in forming the seal segment <NUM>. An inner wrap <NUM> is formed about a mandrel <NUM>. The inner wrap <NUM> is formed by wrapping a plurality of woven or braided plies <NUM> about the mandrel <NUM> to form the base portion <NUM>, the first and second walls <NUM>, <NUM>, an outer wall <NUM>, and a passage <NUM>. The shape of the mandrel <NUM> generally defines the shape of the passage <NUM>. In one example, the inner wrap <NUM> is formed from at least two plies <NUM>. In a further example, the inner wrap <NUM> is formed from three or four plies <NUM>. In some examples, additional plies <NUM> may be used to form the inner wrap <NUM>. The plies <NUM> may be a silicon carbide matrix composite, for example.

In some examples, the inner wrap <NUM> is formed by draping woven plies <NUM> around the mandrel <NUM> without forming a full loop. In this example, there may be less machining needed after the seal body is formed.

<FIG> illustrates a subsequent method step <NUM> in forming the seal segment <NUM>. Dowels or rods <NUM>, <NUM>, <NUM> are placed adjacent the inner wrap <NUM> near the first and second walls <NUM>, <NUM>, or first and second circumferential sides C1, C2. The rods <NUM>, <NUM>, <NUM> extend substantially parallel to the mandrel <NUM> along the axial length of the seal body. In one example, a single rod <NUM> is arranged at the first circumferential side C1. The rod <NUM> is configured to form the protrusion <NUM> (shown in <FIG>). Two rods, <NUM>, <NUM> are arranged at the second circumferential side C2. The rods <NUM>, <NUM> are configured to form the groove <NUM> (shown in <FIG>). In one example, the rods <NUM>, <NUM>, <NUM> have a diameter of at least <NUM> inches (<NUM>). In an example, the rods <NUM>, <NUM>, <NUM> have a diameter of less than about <NUM> inches (<NUM>). The rods <NUM>, <NUM>, <NUM> may all have the same diameter, or may have different diameters. Once the rods <NUM>, <NUM>, <NUM> are placed, an outer wrap <NUM> is formed about the inner wrap <NUM> and rods <NUM>, <NUM>, <NUM>. The outer wrap <NUM> is formed from ideally at least two braided plies <NUM>. In one example, the inner and outer wraps <NUM>, <NUM> together have between <NUM> and <NUM> plies <NUM>. In another example, the inner and outer wraps <NUM>, <NUM> together have between <NUM> and <NUM> plies <NUM>.

<FIG> illustrates a subsequent method step <NUM> in forming the seal segment <NUM>. In step <NUM>, the rods <NUM>, <NUM>, <NUM> are pulled outward from the seal body. The rods <NUM>, <NUM>, <NUM> are pulled in a generally circumferential direction relative to the seal body. In one example, the rods <NUM>, <NUM>, <NUM> are pulled in a direction substantially perpendicular to the length of the rods <NUM>, <NUM>, <NUM>. As the rods <NUM>, <NUM>, <NUM> are pulled outward, the outer wrap <NUM> is also pulled outward to form the protrusion <NUM> and groove <NUM>. The groove <NUM> is formed by the rods <NUM>, <NUM> forming outer and inner portions <NUM>, <NUM> adjacent the second wall <NUM>.

In some embodiments, the rods <NUM>, <NUM>, <NUM> are removed after the step <NUM>. When the rods <NUM>, <NUM>, <NUM> are removed following step <NUM>, a gap may be left behind in the seal body. In other embodiments, the gap is filled with material added to the seal body.

In another example, the rods <NUM>, <NUM>, <NUM> are larger than the desired protrusion <NUM> and groove <NUM>. The rods <NUM>, <NUM>, <NUM> are then removed, and the excess material in the plies <NUM> is pressed to form the protrusion <NUM> and groove <NUM>. In this embodiment, the rods <NUM>, <NUM>, <NUM> may have a diameter that is between about <NUM>% and <NUM>% of a desired circumferential width of the protrusion <NUM> and groove <NUM>.

In another example, the rods <NUM>, <NUM>, <NUM> comprise inner and outer rod portions. The inner rod portion fits within the outer rod portion. After the outer wrap <NUM> is formed about the rods <NUM>, <NUM>, <NUM>, the outer rod portion is removed. This creates some slack from excess material in the outer wrap <NUM>. The excess material in the outer wrap <NUM> is pressed to form the protrusion <NUM> and groove <NUM>. The rods <NUM>, <NUM>, <NUM> may have a diameter that is between about <NUM>% and <NUM>% of a desired circumferential width of the protrusion <NUM> and groove <NUM>. In this example, the inner portions of the rods <NUM>, <NUM>, <NUM> may help control the position of the component while the protrusion <NUM> and groove <NUM> are formed.

In each of these embodiments, the rods <NUM>, <NUM>, <NUM> may be composite, for example. Either triaxial or biaxial braid weave laminates or woven laminates may be used. Although cylindrical rods <NUM>, <NUM>, <NUM> are shown, the rods may have other shapes, such as a rounded rectangular shape. In particular, the rod shape may avoid sharp edges to prevent fiber breakage in the laminates <NUM>.

<FIG> illustrates a subsequent method step <NUM> in forming the seal segment <NUM>. In step <NUM>, the seal body may be densified. Densification generally includes adding additional material to make the laminates stiffer than their free laminated fiber state. Densification increases the density of the laminate material after assembly. An infiltrant is injected into the seal body and cured to form a solid composite component. The infiltrant may be a silicon carbide matrix material, for example.

<FIG> illustrates a subsequent method step <NUM> in forming the seal segment <NUM>. In step <NUM>, the seal body may be machined to form additional features. For example, the outer wall <NUM> may be machined to form the hooks <NUM>, <NUM> for engagement with the carrier <NUM>. In one example, at least <NUM>% of the outer wall <NUM> is removed to form the hooks <NUM>, <NUM>. In a further example, about <NUM>%-<NUM>% of the outer wall <NUM> is removed. This step <NUM> may be done using ultrasonic machining, for example. The first and second axial sides A1, A2 may also be machined to form a smooth surface. In one example, about <NUM> inches (<NUM>) is machined from the first and second axial sides A1, A2.

<FIG> illustrates a subsequent method step <NUM> in forming the seal segment <NUM>. In step <NUM>, additional features may be machined into the seal body to form the final seal segment configuration. In this example, a trailing edge platform <NUM> is formed near the second axial side A2. The trailing edge platform <NUM> may be machined, for example. The trailing edge platform <NUM> is used in the final assembly to seal the trailing edge of the seal segment <NUM>. The trailing edge platform <NUM> is machined by removing some of the first and second walls <NUM>, <NUM>. In some examples, a leading edge platform may be machined near the first axial side A1. This step <NUM> may be done using ultrasonic machining, for example.

The disclosed BOAS segment <NUM> and method of manufacture includes an integrated protrusion and groove arrangement for improved sealing between segments. This arrangement prevents a straight path to the gas path for improved sealing. This arrangement may also provide radiative and convective cooling, reducing the conducted temperature into the metallic carrier. This "shiplap" arrangement may further enable the use of additional flow discouragers or mateface seals. The rods used during manufacturing permit the protrusion and groove to be integrated into the laminate plies, allowing simplified manufacturing of the protrusion and groove features.

In this disclosure, "generally axially" means a direction having a vector component in the axial direction that is greater than a vector component in the circumferential direction, "generally radially" means a direction having a vector component in the radial direction that is greater than a vector component in the axial direction and "generally circumferentially" means a direction having a vector component in the circumferential direction that is greater than a vector component in the axial direction.

Claim 1:
A method of manufacturing a component for a gas turbine engine, comprising:
forming an inner wrap (<NUM>) about a mandrel (<NUM>), the inner wrap (<NUM>) having first and second walls (<NUM>, <NUM>) joined by a base portion (<NUM>) and an outer wall (<NUM>);
arranging a rod (<NUM>, <NUM>, <NUM>) at each of the first and second walls (<NUM>, <NUM>);
forming an outer wrap (<NUM>) about the inner wrap (<NUM>) and the rods (<NUM>, <NUM>, <NUM>) to form a body;
characterised by forming features in circumferential sides (C1, C2) of the outer wrap (<NUM>) using the rods (<NUM>, <NUM>, <NUM>); and
machining the body to form a blade outer air seal segment.