Fatigue resistant blade outer air seal

A blade outer air seal segment including a radially outward surface, a radially inward surface oriented away from the radially outward surface, and a cooling channel located between the radially outward surface and the radially inward surface. The blade outer air seal segment also including a stress-relief boss extending into the cooling channel and an inlet orifice fluidly coupled to the cooling channel through the stress-relief boss. The blade outer air seal segment further including a stress-relief recess. The stress-relief boss being located within the stress relief recess.

BACKGROUND

The subject matter disclosed herein generally relates to gas turbine engines and, more particularly, to a blade outer air seal (BOAS) having fatigue resistant cooling inlets and methods of forming the same.

A gas turbine engine generally includes a fan section, a compressor section, a combustor section, and a turbine section. The fan section drives air along a bypass flow path and a core flow path. In general, during operation, air is pressurized in the compressor section and then mixed with fuel and ignited in the combustor section to generate combustion gases. The combustion gases flow through the turbine section, which extracts energy from the combustion gases to power the compressor section and generate thrust.

The blade assemblies of the turbine section generally include a BOAS to reduce flow leakage over the blade tips. The BOAS is subjected to extremely hot combustion gases. To cool the BOAS, cooling air from a secondary air flow system may be provided to internal cooling channels formed within the body of the BOAS. The cooling air may enter the internal cooling channels through inlet holes formed through the BOAS. The inlet holes tend to experience increased fatigue due to the tensile stresses resulting from the temperature difference between the flow-path side of the BOAS and the cooled side of the BOAS (i.e., the side proximate the combustion gases and the side proximate the cooling flow).

SUMMARY

According to an embodiment, a blade outer air seal segment is provided. The blade outer air seal segment including a radially outward surface, a radially inward surface oriented away from the radially outward surface, and a cooling channel located between the radially outward surface and the radially inward surface. The blade outer air seal segment also including a stress-relief boss extending into the cooling channel and an inlet orifice fluidly coupled to the cooling channel through the stress-relief boss. The blade outer air seal segment further including a stress-relief recess. The stress-relief boss being located within the stress relief recess.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the cooling channel is defined, at least partially, by a radially outward channel surface and a radially inward channel surface. The stress-relief boss extends away from the radially outward channel surface to a surface of the stress-relief boss.

In addition to one or more of the features described above, or as an alternative, further embodiments may include a raised portion of the radially outward surface. The radially outward channel surface is located radially outward of the radially inward channel surface. The inlet orifice extends from the raised portion of the radially outward surface to the surface of the stress-relief boss.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the surface of the stress-relief boss is about parallel to at least one of the radially inward channel surface and the radially outward channel surface.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the stress-relief boss extends to a surface of the stress-relief boss. A radial height of the cooling channel between the radially outward channel surface and the radially inward channel surface is greater than a radial height of the cooling channel between the surface of the stress-relief boss and the radially inward channel surface.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the stress-relief boss is concentric to the inlet orifice.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the stress-relief boss is concentric to the stress-relief recess.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the cooling channel is defined, at least partially, by a radially outward channel surface and a radially inward channel surface. The stress-relief recess extends into the radially outward channel surface to a base of the stress-relief recess.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that a radial height of the cooling channel between the radially outward channel surface and the radially inward channel surface is less than a radial height of the cooling channel between the base of the stress-relief recess and the radially inward channel surface.

According to another embodiment, a turbine section of a gas turbine engine is provided. The turbine section including: a blade configured to rotate about an axis and a blade outer air seal segment radially outward of the blade. The blade outer air seal segment including a radially outward surface, a radially inward surface oriented away from the radially outward surface, and a cooling channel located between the radially outward surface and the radially inward surface. The blade outer air seal segment also including a stress-relief boss extending into the cooling channel and an inlet orifice fluidly coupled to the cooling channel through the stress-relief boss. The blade outer air seal segment further including a stress-relief recess. The stress-relief boss being located within the stress relief recess.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the cooling channel is defined, at least partially, by a radially outward channel surface and a radially inward channel surface; and wherein the stress-relief boss extends away from the radially outward channel surface to a surface of the stress-relief boss.

In addition to one or more of the features described above, or as an alternative, further embodiments may include a raised portion of the radially outward surface. The radially outward channel surface is located radially outward of the radially inward channel surface. The inlet orifice extends from the raised portion of the radially outward surface to the surface of the stress-relief boss.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the surface of the stress-relief boss is about parallel to at least one of the radially inward channel surface and the radially outward channel surface.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the stress-relief boss extends to a surface of the stress-relief boss. A radial height of the cooling channel between the radially outward channel surface and the radially inward channel surface is greater than a radial height of the cooling channel between the surface of the stress-relief boss and the radially inward channel surface.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the stress-relief boss is concentric to the inlet orifice.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the stress-relief boss is concentric to the stress-relief recess.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that the cooling channel is defined, at least partially, by a radially outward channel surface and a radially inward channel surface. The stress-relief recess extends into the radially outward channel surface to a base of the stress-relief recess.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that a radial height of the cooling channel between the radially outward channel surface and the radially inward channel surface is less than a radial height of the cooling channel between the base of the stress-relief recess and the radially inward channel surface.

According to another embodiment, a method of forming a blade outer air seal segment is provided. The method including that a blade outer air seal material is deposited around a core. The core being configured to form a cooling channel in the blade outer air seal segment. The core includes a raised section and a recess within the raised section. A thickness of the core at the recess is less than a thickness of a channel portion of the core and a thickness of the core at the raised section is greater than the thickness of the channel portion of the core. The method also including that an inlet orifice is formed through the blade outer air seal material in a location of the recess.

In addition to one or more of the features described above, or as an alternative, further embodiments may include that forming the inlet orifice includes using electrical discharge machining to form the inlet orifice.

The detailed description explains embodiments of the present disclosure, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION

Referring now toFIG.2, with continued reference toFIG.1, a portion of the high pressure turbine54is illustrated, in accordance with an embodiment of the present disclosure. The high pressure turbine54may include vane assemblies100and blade assemblies102(one shown) axially interspersed with the vane assemblies100. The vane assemblies100do not rotate and the blade assemblies102rotate. The vane assemblies100each include a plurality of vanes106positioned about the engine central longitudinal axis A. Each of the vanes106may extend between an inner vane platform112and an outer vane platform114. The outer vane platform114may be configured to couple, or otherwise support attachment of, the vane assemblies100to a turbine case structure116. The turbine case structure116may form a portion of the engine static structure36illustrated inFIG.1. The vane assemblies100comprise static structures that do not rotate relative to the engine central longitudinal axis A. The vane assemblies100may help direct the flow of fluid (i.e., airflow along core flow path C) received by and output from the blade assemblies102.

The blade assemblies102each include a plurality of blades110configured for rotation about the engine central longitudinal axis A. For example, the blades110may rotate in response to receiving a flow of fluid (e.g., combustion gases) from the combustor56ofFIG.1. Power from the flow may be converted to mechanical power, or torque, by the blades110. The blade assemblies102may also include a blade outer air seal120(BOAS120). A blade outer air seal support122(BOAS support122) may couple, or otherwise secure, the BOAS120to the turbine case structure116.

The BOAS120is disposed radially outward of the blades110. The BOAS120is configured to provide a seal to reduce or prevent hot gases from leaking over the tips of the blades110. In various embodiments, the BOAS120may be segmented. For example, the BOAS120may comprise a plurality of arcuate BOAS segments arranged in circumferential series around the engine central longitudinal axis A.

Referring now toFIG.3, with continued reference toFIGS.1-2, a BOAS segment130of the BOAS120is illustrated, in accordance with an embodiment of the present disclosure. The BOAS segment130includes a radially inward (or first) surface134and a radially outward (or second) surface136. The radially inward surface134is oriented away from the radially outward surface136. When installed in the blade assemblies102ofFIG.2, the radially inward surface134of the BOAS segments130is oriented toward blades110.

The BOAS segment130includes a forward wall140and an aft wall142opposite the forward wall140. The forward wall140extends in a radially outward direction and may define a forward edge144of BOAS segment130. The aft wall142extends in a radially outward direction and may define an aft edge146of the BOAS segment130. In various embodiments, the aft wall142may include one or more aftward extending flange(s)154and one or more forward extending flange(s)156. The forward wall140may include one or more aftward extending flange(s)158. The aftward extending flanges158may extend aftward from an aftward oriented surface148of the forward wall140. In various embodiments, the forward wall140may also or alternatively include one or more forward extending flange(s)147. The forward extending flange(s)147of the forward wall140may extend forward from a forward oriented surface145of the forward wall140.

The BOAS segment130includes a first circumferential wall150and a second circumferential wall152opposite the first circumferential wall150. The first circumferential wall150extending from the forward wall140to the aft wall142. The second circumferential wall152extending from the forward wall140to the aft wall142. The BOAS segment130may be arranged in circumferential series with a plurality of BOAS segments130such that the first circumferential wall150of a first BOAS segment130is circumferentially adjacent to the second circumferential wall152of a second BOAS segment130.

In an embodiment, the BOAS segment130includes one or more inlet orifice(s)170. Stated differently, BOAS segment130defines the inlet orifices170. In various embodiments, inlet orifices170are formed in the radially outward portion136of the BOAS segment130. In this regard, the inlet orifices170may be formed through radially outward portion136of the BOAS segment130. The inlet orifices170may be formed through raised portions172of the BOAS segment130.

Referring now toFIGS.4A and4B, with continued reference toFIGS.1-3, additional details of the inlet orifice170formed through the radially outward portion136of the BOAS segment130are illustrated, in accordance with an embodiment of the present disclosure.

The inlet orifices170formed through the raised portion172of the BOAS segment130are illustrated, in accordance with various embodiments. A radial height, or thickness, H7 of the BOAS segment130at the raised portion172is greater than the radial height H2 of the BOAS segment130at the radially outward surface136. The radial height H7 is measured between the radially inward surface134of the BOAS segment130and the surface174of the raised portion172. The surface174of the raised portion172is oriented opposite, or generally away from, radially the inward surface134. In various embodiments, the radial height H7 of the BOAS segment130at the raised portion172is less than the radial height H1 of BOAS segment130at the first circumferential wall150.

A radial height, or thickness, H1 of the BOAS segment130at the first circumferential wall150is equal to or greater than a radial height, or thickness, H2 of the BOAS segment130at the radially outward surface136. The radial height H1 is measured between the radially inward surface134of the BOAS segment130and the surface160of the first circumferential wall150. The surface160of the first circumferential wall150is oriented opposite, or generally away from, the radially inward surface134. The radial height H2 is measured between the radially inward surface134and the radially outward surface136of the BOAS segment130. In an embodiment, the second circumferential wall152includes a radial height equal to the radial height H1 of first circumferential wall150.

The BOAS segment130defines one or more internal cooling channel(s)180. The cooling channels180may form a cooling circuit through the BOAS segment130. Cooling airflow in the space over (i.e., radially outward from) radially outward surface136may be provided to the cooling channels180through the inlet orifices170. Stated differently, cooling airflow may flow through the inlet orifice170and into the cooling channel180.

The cooling channel180is enclosed within the BOAS segment130between the radially outward surface136and the radially inward surface134. The cooling channel180may be defined, at least partially, by a radially outward channel surface182and a radially inward channel surface184opposite the radially outward channel surface182. The radially outward channel surface182is located radially outward of the radially inward channel surface184. The radially outward channel surface182may be located at a radial height H3 away from the radially inward channel surface184. Stated differently, the radial height H3 is a height or thickness of the cooling channel180.

A stress-relief boss162extends into the cooling channel180. The stress-relief boss162extends to a surface164, as shown inFIG.4B. The inlet orifice170extends from the surface174of the raised portion172to the surface164of the stress-relief boss162. In an embodiment, the surface164of the stress-relief boss162may be about parallel with at least one of the radially inward channel surface184and the radially outward channel surface182. The stress-relief boss162may be formed on the radially outward channel surface182. The stress-relief boss162extends away from the radially outward channel surface182into the cooling channel180and towards the radially inward channel surface184. The stress-relief boss162is located proximate the inlet orifice170. In an embodiment, the inlet orifice170may be formed through the stress-relief boss162of BOAS segment130. The inlet orifices170are fluidly coupled to cooling channels180. In an embodiment, the inlet orifice170is fluidly coupled to the cooling channel180through the stress-relief boss162.

The radial height H3, H4, H8 of the cooling channel180decreases proximate the stress-relief boss162. Stated differently, the radial height H3 of the cooling channel between the radially outward channel surface182and the radially inward channel surface184is greater than the radial height H4 of the cooling channel between a surface164of the stress-relief boss162and the radially inward channel surface184.

The BOAS segment130includes a radially outward wall163interposed between the radially outward surface136and radially outward channel surface182. The radially outward wall163also extends between the radially outward surface136and a surface164of the stress-relief boss162. A thickness H6 of the radially outward wall163between the radially outward surface136and a surface164of the stress-relief boss162is greater than a thickness H5 of the radially outward wall163between the radially outward surface136and radially outward channel surface182. In other words a thickness of the radially outward wall163increases proximate the stress-relief boss162.

In an embodiment, the BOAS segments130includes a stress-relief recess190. The stress-relief is formed in the radially outward channel surface184. The stress-relief boss162is located within the stress relief recess190. The stress-relief recess190may encircle the stress-relief boss162, as illustrated inFIG.4B. The stress-relief recess190extends into the radially outward channel surface182to a base192of the stress-relief recess190. Stated differently, the stress-relief recess190bottoms out at the base192. The stress-relief recess190may extending into the radially outward channel surface182a radial height H9, as illustrated inFIG.4B. The radial height H3, H4, H8 of the cooling channel180increases at the stress-relief recess190. Stated differently, the radial height H3 of the cooling channel between the radially outward channel surface182and the radially inward channel surface184is less than the radial height H8 of the cooling channel between the base192of the stress-relief recess190and the radially inward channel surface184.

In an embodiment, the stress-relief boss162may be cylindrically shaped. In this regard, a cross-section of the stress-relief boss162taken along a plane generally parallel to the surface164may be circular. The inlet orifice170may be cylindrically shaped. In this regard, a cross-section of the inlet orifice170taken along a plane generally parallel to the surface164may be circular. In an embodiment, the stress-relief recess190may be cylindrically shaped. In this regard, a cross-section of the stress-relief recess190taken along a plane generally parallel to the base192may be circular. In various embodiments, a cross-section of the stress-relief boss162a cross-section the inlet orifice170, and/or the stress-relief recess190taken along a plane generally parallel to the base192may comprise an elliptical, an oval, a rectangular, a polygonal, or any other desired shape.

The stress-relief boss162may be concentric to the inlet orifice170such that a radius R1 of the inlet office170and a radius R2 of the stress-relief boss162are measured from the same axis B. A diameter D1 of inlet orifice170is less than a diameter D2 of stress-relief boss162.

The stress-relief recess190may be concentric to the inlet orifice170and the stress-relief boss162such that the radius R1 of the inlet office170, the radius R2 of the stress-relief boss162, and a radius R3 of the stress-relief boss162are measured from the same axis B. The diameter D1 of the inlet orifice170is less than a diameter D2 of the stress-relief boss162and the diameter D2 of stress-relief boss162is less than a diameter D3 of stress-relief recess162.

Advantageously, the stress-relief boss162and the stress-relief recess190tends to shield the inlet orifice170from the tensile stress field created by the thermal gradient between the radially inward surface134and the radially outward surface136. The stress-relief boss162may be subjected to the tensile stress field, but experiences a lower stress than the inlet orifice170alone extending to the radially outward channel surface182(i.e., cooling circuits which do not include stress-relief bosses162or the stress-relief recess190). The BOAS segment130tends to exhibit improved fatigue capability, which may allow the BOAS120to be employed in greater temperatures and/or exposed to increased temperatures for a longer durations of time. Also advantageously, decreasing the radial height (i.e., from H3 to H4) of the cooling channel180proximate the inlet orifice170improves the impingement coefficient of cooling air flow through the inlet orifice170towards the radially inward channel surface184. Also advantageously, by adding the stress-relief recess190the radial height H6 of the stress-relief boss162may be reduced, which reduces the impedance of the stress-relief boss162on lateral airflow within the cooling channel180.

Referring now toFIG.5, with continued reference toFIGS.1-4A, and4B, a core200configured to form the cooling channels180and the stress-relief boss162is illustrated, in accordance with an embodiment of the present disclosure. The core200may comprise metal, composite, or any other suitable material. In various embodiments, the core200may be a ceramic core. The core200includes one or more recesses202. The location of the recess202corresponds to the location of the inlet orifice170ofFIGS.3,4A, and4B. In various embodiments, the location of recesses202corresponds to the stress-relief bosses162of BOAS segment130, ofFIG.4. The recesses202are formed on the channel portions204of the core200. A thickness of core200at recess202is less than a thickness of core200at channel portion204. The thickness of core200at recess202is equal to the radial height H4 inFIG.4B. The thickness of core200at the channel portion204is equal to the radial height H6.

In an embodiment, the location of the raised section206corresponds to the stress-relief recess190of BOAS segment130, ofFIG.4. The raised section is formed on the channel portions204of the core200. A thickness of core200at the raised section is greater than a thickness of core200at channel portion204. The thickness of core200at raised section206is equal to the radial height H9 inFIG.4B. The thickness of core200at the channel portion204is equal to the radial height H6.

Referring now toFIG.6, with continued reference toFIGS.1-4A,4B, and5, a method250of forming a BOAS segment130having inlet orifices170that are fatigue resistant is illustrated, in accordance with an embodiment of the present disclosure. The method250may include the steps of depositing a BOAS material around a core200(step252). The core200being configured to form a cooling channel180in the BOAS segment130and including a raised section206and a recess202within the raised section206. The raised section206may encircle the recess206, as illustrated inFIG.5. A thickness of the core200is reduced at the recess202. A thickness of the core200is increased at the raised section206. The method250may further comprise removing the core200(step254). For example, the core200may be leached out of the BOAS material forming the BOAS segment130. The method250further comprises forming an inlet orifice170through the BOAS segment130(step256). In an embodiment, the inlet orifice170is formed within the recess202.

In various embodiments, step256may include forming the inlet orifice using electrical discharge machining (EDM). Using EDM to form the inlet orifices170tends to be associated with greater reductions in fatigue capability, as compared to milling or drilling the inlet orifices170. In various embodiments, step256may include forming the inlet orifice170using milling, drilling, or any other suitable technique.

While the inlet orifices170and method250are described in relation to a BOAS segment130, it is further contemplated and understood that the features and techniques described herein may be applied to other parts having cooling circuits. For example, the cooling channels180, and the inlet orifices170may be formed in the inner vane platform112and/or the outer vane platform114inFIG.2.