Patent Description:
The compressor and turbine sections include alternating stages of rotating blades and fixed vanes. The vanes direct flow at a desired angle into the rotating blade stage. The rotating blade rows rotate within an engine case. A blade outer air seal is provided at each rotating blade stage to establish an outer radial flow path boundary. Moreover, the blade outer air seal provides a clearance between a tip of the rotating blade stages and the outer radial flow path boundary.

Turbine engine manufacturers continue to seek improvements to engine performance including improvements in engine assembly, material capabilities, and thermal, transfer and propulsive efficiencies.

<CIT>] <NUM> A discloses a blade outer air seal including a plurality of layers formed of a ceramic matric composite material.

In one aspect, a blade outer air seal (BOAS) is provided as claimed in claim <NUM>.

In another embodiment according to any of the previous embodiments, the first preform and the second preform define a curved surface defining a first slot on the first end and a second slot on the second end.

In another embodiment according to any of the previous embodiments, the first preform and the second preform have primary fibers substantially following a contour of a corresponding one of the first slot and the second slot.

In another embodiment according to any of the previous embodiments, includes at least one insert for each of the first preform and the second preform supporting a portion of the corresponding one of the first preform and the second preform.

In another embodiment according to any of the previous embodiments, each of the first end and the second end includes an end groove for a seal.

In another embodiment according to any of the previous embodiments, the tube has primary CMC fibers form one of a three-dimensional braid, a plurality of two-dimensional layers and a three-dimensional weave.

In another embodiment according to any of the previous embodiments, the tube has primary CMC fibers substantially following a longitudinal length of the BOAS.

In another aspect, a gas turbine engine is provided, as claimed in claim <NUM>.

In another aspect, a method of forming a blade outer air seal (BOAS) is provided as claimed in claim <NUM>.

In another embodiment according to any of the previous embodiments, the first preform and the second preform are formed separate from the tube to define a respective first slot and second slot and forming of the first preform and the second preform includes orientating primary fibers to substantially follow a contour of the respective first slot and the second slot.

In another embodiment according to any of the previous embodiments, assembling the first preform into the first end and the second preform into the second end includes installing at least one insert for supporting a portion of each of the first preform and the second preform.

The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans, land based turbine engines utilized for power generation as well as turbine engines for use in land based vehicles and naval propulsion.

The example gas turbine engine includes the fan <NUM> that comprises in one non-limiting embodiment less than about twenty-six fan blades. In another non-limiting embodiment, the fan section <NUM> includes less than about twenty fan blades. Moreover, in one disclosed embodiment the low pressure turbine <NUM> includes no more than about six turbine rotors schematically indicated at <NUM>. In another non-limiting example embodiment the low pressure turbine <NUM> includes about three turbine rotors. A ratio between the number of fan blades <NUM> and the number of low pressure turbine rotors is between about <NUM> and about <NUM>. The example low pressure turbine <NUM> provides the driving power to rotate the fan section <NUM> and therefore the relationship between the number of turbine rotors <NUM> in the low pressure turbine <NUM> and the number of blades in the fan section <NUM> disclose an example gas turbine engine <NUM> with increased power transfer efficiency.

Referring to <FIG> with continued reference to <FIG>, a portion of the turbine section <NUM> is schematically illustrated and includes a turbine rotor blade <NUM> rotating relative to a radial surface <NUM> defined by a plurality of blade outer air seals (BOAS) <NUM>. The turbine blade <NUM> includes a tip <NUM> that rotates proximate to the radial surface <NUM> defined by the BOAS <NUM>. The example shown in <FIG> is of a single, rotating turbine blade stage and may also be utilized within the compressor section <NUM>.

The BOAS <NUM> are supported within an engine case <NUM> with a mount <NUM>. The mount <NUM> may be an integral part of the case <NUM> or may be a separate part attached to the case <NUM>. A plurality of BOAS <NUM> form a full hoop circumferentially about the engine axis A to surround the blades <NUM>. The BOAS <NUM> control leakage of core flow C in the gap <NUM> between the tips <NUM> and the inner surface <NUM>. The illustrated mount <NUM> is disposed between each BOAS <NUM> and is one of a plurality of such mounts <NUM> disposed within the engine case <NUM>. The gap <NUM> between each of the BOAS <NUM> is bridged by a feather seal <NUM> that is assembled between adjacent BOAS <NUM>.

The BOAS <NUM> encounter extreme pressures and temperatures and therefore it is desirable to utilize materials that are capable of operating in the harsh environments encountered within a gas turbine engine <NUM>. In this disclosed example, each of the BOAS <NUM> are formed from a ceramic matrix composite material. CMC materials include a plurality of fibers suspended within a ceramic matrix. The fibers can, for example, be ceramic fibers, silicon fibers, carbon fibers, and or metallic fibers. The ceramic matrix material can be any known ceramic material such as silicon carbide. The ceramic matrix composite material provides the desired thermal capabilities to operate within the harsh environment of the turbine section <NUM>.

Referring to <FIG>, the example BOAS <NUM> comprises a tube <NUM> with open ends <NUM> into which are assembled and mounted preforms <NUM>. In this example, the tube <NUM> comprises an open structure having a substantially rectangular shape in cross-section. However, the tube <NUM> may be shaped differently and remain within the contemplation of this disclosure. The preforms <NUM> define first and second slots <NUM> that correspond with a shape and contour of the mount <NUM>. The example disclosed mount <NUM> includes outward extending arms <NUM> that fit within the slots <NUM> defined by the preforms <NUM>. Each of the open ends <NUM> also includes a groove <NUM> for the feather seal <NUM>.

The open ends <NUM> each have a corresponding cutout <NUM> within the top surface <NUM> that is open the corresponding end <NUM>. The cutouts <NUM> corresponds with a profile of the mount <NUM> such that the mount <NUM> may extend into the open ends <NUM> of the tube <NUM>. The tube <NUM> may also include an opening <NUM> along the top surface <NUM> utilized to provide cooling air or to reduce the total weight of the BOAS <NUM>. One or several openings <NUM> may be utilized and are within the contemplation of this disclosure. The preform <NUM> is formed separate from the tube <NUM> and assembled into each of the open ends <NUM>.

Referring to <FIG> with continued reference to <FIG>, an interface between adjacent BOAS <NUM> is shown with arms <NUM> of the mount <NUM> extending into corresponding slots <NUM> defined by preforms <NUM> within separate BOAS <NUM>. It should be appreciated that each BOAS <NUM> includes first and second open ends <NUM> that correspond with the mount <NUM> provided in the engine case <NUM>. The preforms <NUM> are formed separately from the tube <NUM> and installed to define the slots <NUM> that correspond with the mount <NUM>.

Inserts <NUM> are provided along with each of the preforms <NUM> to support curved portions on a back side <NUM> of each preform <NUM>. Each of the preforms <NUM> is formed from a plurality of fibers that substantially follow a contour of the desired slot <NUM>. In this disclosed example, the slot <NUM> comprises a substantially c-shaped contour in cross-section that corresponds with arms <NUM> of the example mount <NUM>. It should be appreciated that other shapes and contours could be utilized and are within the contemplation of this disclosure. Moreover, the specific fit between the preform <NUM> and the arms <NUM> of the mount <NUM> are such that excessive movement is prevented while accommodating relative thermal expansion between the case <NUM>, mount <NUM> and the BOAS Additionally, each of the BOAS <NUM> is designed and dimensioned to accommodate thermal expansion and movement relative to the rotating turbine blade <NUM>.

Referring to <FIG> with continued reference to <FIG>, a schematic illustration of a method of fabricating the example disclosed BOAS <NUM> is shown and generally indicated at <NUM>. The method <NUM> includes an initial step <NUM> of forming the tube <NUM>. The tube <NUM> will include a width <NUM> and a longitudinal length <NUM>. A plurality of fibers will be included along the length <NUM> to provide the substantial structure of the tube <NUM>.

Referring to <FIG>, the example tube <NUM> is formed from a plurality of fibers <NUM> disposed within a ceramic matrix that are provided at a defined orientation. The desired orientation of the fibers <NUM> can be one orientation or a combination of orientations determined to provide the desired mechanical properties of the tube <NUM>.

In the example illustrated in <FIG>, the primary fibers <NUM> are orientated in a three dimensional braid.

Referring to <FIG>, the primary fibers <NUM> are layered in a two-dimensional layers that extend substantially along the longitudinal length <NUM> of the tube <NUM>.

Referring to <FIG>, a schematic view of another fiber orientation is illustrated and shows the primary fibers <NUM> orientated in a substantially three-dimensional woven mat that extends in the direction of the longitudinal length of the tube <NUM>.

Referring back to <FIG>, formation of the preforms <NUM> is schematically illustrated at <NUM> and also includes formation of the inserts <NUM>. Each of the preforms are formed with primary fibers <NUM> suspended in a ceramic matrix. The primary fibers <NUM> are orientated to follow a contour <NUM> that is utilized to define the slot <NUM>. In this example, the fibers <NUM> substantially follow the contour <NUM> of the slot <NUM>. The inserts <NUM> are formed from randomly orientated fibers or other compatible CMC material and fibers. The inserts <NUM> in this disclosed example are formed separate from the preforms <NUM> and are shaped to correspond with the back side <NUM> contour of the preform <NUM>. The inserts <NUM> engage the back side <NUM> of the preform <NUM> to reduce and eliminate any unsupported region or area once installed into the tube <NUM>. Although, the example inserts <NUM> are disclosed as separate parts, formation of the preform <NUM> to include integral structures on the back side <NUM> for support could be utilized and are within the contemplation of this disclosure.

The preforms <NUM> and inserts <NUM> can be formed using known CMC techniques including layering of a number of CMC sheets, polymer infiltration (PIP), chemical vapor infiltration (CVI) and chemical vapor deposition (CVD). In these processes the primary fibers are provided as a preform that is subsequently infiltrated with a ceramic matrix material. By forming the tube <NUM>, preform <NUM> and inserts <NUM> separately, the individual structures have increased quality and can be formed with densities and material properties that would be difficult to attain when forming the entire BOAS as a single structure.

Each of the preforms <NUM> are initially formed in a larger size than is required to fit within the tube <NUM>. As is shown at <NUM>, each of the preforms <NUM> is initially machined to provide a desired width <NUM>. The primary fibers <NUM> are orientated to define the slot <NUM> and once the preform <NUM> is initially machined to provide a desired width as indicated at <NUM>. The machining operation can include grinding, cutting or any other machining operations understood to be compatible with CMC materials.

As indicated at <NUM>, the height of the preform <NUM> is then adjusted to fit within the tube <NUM>. All machining operations on the preform <NUM> are made with respect to a datum schematically indicated at <NUM> that corresponds with the mount structure <NUM>. It is the slot <NUM> of the preform <NUM> that provides the origin to which all dimensions include the width <NUM>, height <NUM> along with the shape of the slot <NUM> are orientated such that the installed preform <NUM> corresponds with the features of the mount <NUM>.

Once the preform <NUM> is machined to the proper, desired size, it is installed within the tube <NUM> as schematically indicated at <NUM>. Installation of the preform <NUM> into the end of the tube <NUM> defines the slots <NUM> within the completed BOAS <NUM>. The preforms <NUM> are installed such that the slot <NUM> defined by the preform <NUM> corresponds with the open ends <NUM> and cut out <NUM> of the tube <NUM>.

Assembly of the preforms <NUM> and inserts <NUM> to the tube <NUM>, <NUM> can be accomplished by any means understood known by those skilled in the art for adhesion of CMC materials to one another. In one example embodiment, the tube <NUM> and preform <NUM> are assembled in a partially cured condition and then fully cured together to provide a desired adhesion and structure. In another example embodiment a ceramic matrix material is further infused into a partially cured tube <NUM>, preform <NUM> and inserts <NUM> once assembled and finally cured to form one continuous structure. Moreover, other known processes and methods of joining CMC parts could be utilized within the contemplation of this disclosure.

Accordingly, the example BOAS <NUM> includes separately formed CMC components to form different structures for mounting and definition of the boundary surface to increase build quality, strength and durability.

Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention.

Claim 1:
A blade outer air seal (BOAS) (<NUM>) comprising:
a tube (<NUM>) of a ceramic matrix composite (CMC) material; and
a preform (<NUM>) within the tube (<NUM>) configured to receive a mount (<NUM>) for the BOAS (<NUM>), wherein the preform (<NUM>) is of a CMC material,
wherein the tube (<NUM>) has a first open end (<NUM>) and a second open end (<NUM>) at opposite sides of the BOAS (<NUM>), and the preform (<NUM>) comprises a first preform (<NUM>) in the first open end (<NUM>) facing circumferentially outward and a second preform (<NUM>) in the second open end (<NUM>) facing circumferentially outward opposite the first preform (<NUM>), and
characterised in that
the tube (<NUM>) comprises a substantially rectangular shape with a radially inner surface (<NUM>) and a radially outer surface (<NUM>) joined by side surfaces, the radially outer surface including a first cutout (<NUM>) and a second cutout (<NUM>) at respective first and second ends (<NUM>).