Blade outer air seal arrangement and method of sealing

A flow path component assembly includes a flow path component having a plurality of segments that extend circumferentially about an axis and mounted in a support structure. At least one of the plurality of segments have a first wall and a second wall that extend radially outward from a base portion. The first wall is axially spaced from the second wall. A coating is on a portion of the first wall and a portion of the second wall. The coating is in contact with a feature on the support structure.

BACKGROUND

This application relates to a blade outer air seal arrangement and method of sealing a blade outer air seal assembly.

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. Some gas turbine engine components are formed from ceramic materials.

SUMMARY OF THE INVENTION

In one exemplary embodiment, a flow path component assembly includes a flow path component having a plurality of segments that extend circumferentially about an axis and mounted in a support structure. At least one of the plurality of segments have a first wall and a second wall that extend radially outward from a base portion. The first wall is axially spaced from the second wall. A coating is on a portion of the first wall and a portion of the second wall. The coating is in contact with a feature on the support structure.

In a further embodiment of any of the above, the coating is a silicon metal coating.

In a further embodiment of any of the above, the coating extends to at least part of the base portion.

In a further embodiment of any of the above, the feature is a rounded protrusion that extends in an axial direction.

In a further embodiment of any of the above, the feature contacts the second wall.

In a further embodiment of any of the above, a w-seal contacts the coating.

In a further embodiment of any of the above, the w-seal contacts the coating on the first wall.

In a further embodiment of any of the above, a seal plate abuts the support structure and contacts the w-seal.

In a further embodiment of any of the above, a seal plate contacts the coating.

A w-seal is arranged between the support structure and the seal plate.

In a further embodiment of any of the above, the coating is machined to provide a smooth contact area.

In a further embodiment of any of the above, the coating is machined to provide dimensional control.

In a further embodiment of any of the above, the at least one segment has a first aperture and the support structure has a second aperture. A pin extends through the first and second apertures.

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

In one exemplary embodiment, a method of assembling a flow path component assembly includes providing a component segment that has a first wall and a second wall that extends radially outward from a base portion. The first wall is axially spaced from the second wall. A coating is applied to a portion of the segment. The coating is machined to form a smooth contact surface. The segment is mounted to a support structure such that a feature on the support structure contacts the smooth contact surface.

In a further embodiment of any of the above, the coating is a silicon metal coating.

In a further embodiment of any of the above, the coating is applied to a portion of the first wall and a portion of the second wall.

In a further embodiment of any of the above, the coating is machined on the second wall to form the smooth contact surface. The coating on the first wall is machined to form a second smooth contact surface.

In a further embodiment of any of the above, a w-seal is arranged in contact with the second smooth contact surface.

In a further embodiment of any of the above, the mounting the segment to the support structure comprises inserting a pin through a first aperture on the segment and a second aperture on the support structure.

In a further embodiment of any of the above, the segment is formed from a ceramic material.

DETAILED DESCRIPTION

FIG. 2shows a portion of an example turbine section28, which may be incorporated into a gas turbine engine such as the one shown inFIG. 1. However, it should be understood that other sections of the gas turbine engine20or other gas turbine engines, and even gas turbine engines not having a fan section at all, could benefit from this disclosure. The turbine section28includes a plurality of alternating turbine blades102and turbine vanes97.

A turbine blade102has a radially outer tip103that is spaced from a blade outer air seal (“BOAS”) assembly104. The BOAS assembly104may include a plurality of seal segments105that are circumferentially arranged in an annulus about the central axis A of the engine20.

The BOAS segments105may be mounted to an engine case or structure, such as engine static structure36via a control ring or support structure110. The support structure110may extend for a full 360° about the engine axis A. The engine case or support structure holds the BOAS segments105radially outward of the turbine blades102. Although a BOAS assembly104is described, this disclosure may apply to other components, and particularly flow path components. For example, this disclosure may apply to combustor liner panels, shroud, transition ducts, exhaust nozzle liners, or other CMC components.

Each seal segment105is a body that defines radially inner and outer sides R1, R2, respectively, and first and second axial sides A1, A2, respectively. The radially inner side R1faces in a direction toward the engine central axis A. The radially inner side R1is thus the gas path side of the seal segment105that bounds a portion of the core flow path C. The first axial side A1faces in a forward direction toward the front of the engine20(i.e., toward the fan42), and the second axial side A2faces in an aft direction toward the rear of the engine20(i.e., toward the exhaust end).

In the illustrated example, each BOAS segment105includes a first wall120axially spaced from a second wall122. The first and second walls120,122extend generally radially outward from a base portion124. The first and second walls120,122may extend along an entire circumferential length of the seal segment105, or may terminate circumferentially inward of the base portion124. In this example, the first and second walls120,122are generally parallel to one another and perpendicular to the base portion124. In other examples, the first and second walls120,122may be angled. An aperture130extends through the first and second walls120,122, and receives a pin132for securing the seal segment105to a support structure110. In some examples, multiple apertures130circumferentially spaced apart extend through the first and second walls120,122.

The base portion124extends between the first and second axial sides A1, A2and defines a gas path on a radially inner side and a non-gas path on a radially outer side. The first wall120is spaced from the first axial side A1to form a forward portion126, and the second wall122is spaced from the second axial side A2to form an aft portion127. In this disclosure, forward, aft, upstream, downstream, axial, radial, or circumferential is in relation to the engine axis A unless stated otherwise.

The BOAS segments105may be formed of a ceramic matrix composite (“CMC”) material. Each seal segment105is formed of a plurality of CMC laminate sheets. The laminate sheets may be silicon carbide fibers, formed into a braided or woven fabric in each layer. In other examples, the BOAS segments105may be made of a monolithic ceramic.

CMC components such as BOAS segments105are formed by laying fiber material, such as laminate sheets or braids, in tooling, injecting a gaseous infiltrant into the tooling, and reacting to form a solid composite component. The component may be further processed by adding additional material to coat the laminate sheets. In some examples, the base portion124and first and second walls120,122may be formed from the same number of laminate plies, and thus have substantially the same thickness. The simple arrangement of the base portion124and first and second walls120,122allows for a simple ply layup.

The seal segment105is received radially within the support structure110, and secured in position by a pin132that extends through the support structure110and through the first and second walls120,122. The pin132extends through the aperture130on the BOAS segment105and through an aperture134on the support structure110. The pin132retains the BOAS segment105in the circumferential and radial directions. A seal plate140may secure the pin132in place. The seal plate140may secure to the support structure110or other engine structure via a snap fit, for example.

The seal segment105has a coating at a first portion160and a second portion162. The coating may be a silicon metal coating. In one example, the coating may be an Air Plasma Spray (APS) silicon metal coating. The coating bonds well to the CMC material, and behaves similarly to CMC under varying temperatures. The first portion160is on the first wall120, and the second portion162is on the second wall122. In some examples, the first portion160and/or the second portion162may extend onto the base portion124. The coating may be machined to provide a smooth sealing area. The machined silicon metal coating may provide a smoother surface than CMC for sealing. The coating may also be machined to tightly controlled dimensions and mitigate surface tolerance variation.

The support structure110has a rounded feature142that protrudes axially toward the BOAS segment105. The feature142may be machined into the support structure110, for example. The feature142contacts the coating. In the illustrated example, the feature142contacts the coating at the second portion162on the second wall122. The rounded shape of the feature142may provide line contact between the support structure110and the BOAS segment105, which may minimize heat transfer between the support structure110and the BOAS segment105. Case feature142could be omitted in another embodiment where a local case surface could be flat or have another shape.

A W-seal150may be arranged between the BOAS segment105and the seal plate140. The W-seal150contacts the seal plate140at a point144, which may be radially inward of the support structure110. In the illustrated example, the W-seal150contacts the coating at the first portion160on the first wall120. The W-seal150biases the BOAS segment105axially to keep the BOAS segment105seated against the feature142.

The assembly104forms several cavities having air at different pressures. For example, high pressure air may be at locations170and176, while lower pressure air is present at locations172and174. The sealing provided by the feature142and the w-seal150in contact with the coating at portions160,162prevents leakage between these high and low pressure locations.

FIG. 3illustrates another example BOAS assembly204. In this example, the seal plate240has a radial inner portion243that forms a rounded feature241. The seal plate240may provide a land243that positions a W-seal250radially. The seal plate240is positioned by a land239, which is tightly clearance to land238on the support structure210. The rounded features241contacts the coating at the first portion260, while the rounded feature242on the support structure210contacts the coating at the second portion262. The W-seal250is arranged between the seal plate240and a portion245of an engine structure, such as engine structure36. In this example, the seal plate240is not snapped into a supporting structure, and is instead biased axially by the W-seal250. The W-seal250biases the seal plate240into contact with the BOAS segment105, which biases the BOAS segment105into contact with the feature242. In some examples, a second W-seal280may be used aft of the feature242. The second W-seal280may be arranged between the support structure210and a structure298of a vane assembly297, for example.

FIG. 4illustrates a side view of an example BOAS assembly104. The blade outer air seal assembly104includes a feather seal slot180. The feather seal slot180may be about halfway between the radially inner and outer sides R1, R2of each BOAS segment105, for example. The slot180may include an axial portion182and a radial portion184. The radial portion184may extend up one or both of the walls120,122. The axial portion182may extend into the base portion124forward and aft of the walls120,122, for example. A feather seal190may be arranged in the slot180. The feather seal190may include an axial portion192and a radial portion194to engage with the axial and radial portions182,184of the slot180, for example. The axial portion192and radial portions194may be a single unitary piece, or may separate pieces. Although a particular feather seal190is shown, other intersegment seal configurations may be utilized. The feather seal190may be a metallic component, for example. An intersegment seal, such as the feather seal190may be used in combination with the forward and aft sealing embodiments described above.

BOAS require sealing between secondary flow paths and the gas path in order to maintain BOAS supply pressure and to minimize leakage. The disclosed arrangement provides axial sealing on both the front and rear sides of the BOAS, and may be used with intersegment seals between adjacent BOAS segments. The machinable coating provides a high surface finish which may improve sealing performance at front and rear sealing points. Machining the coating also allows for tighter tolerance control of the axial width of the BOAS, which may improve the distribution of contact between the W-seal and the BOAS segments for proper sealing. The W-seal provides a preload that maintains the BOAS segment in contact with the rounded support structure feature. The W-seal and rounded feature provide minimized surface area of the BOAS exposed to high velocity cooling air, which may impart high thermal stress on the BOAS segment. The disclosed arrangement provides a low-complexity sealing solution for a CMC BOAS.

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.