Blade outer air seal with multi impingement plate assembly

A multi impingement plate assembly for a Blade Outer Air Seal (BOAS) includes a first impingement plate which defines a multiple of first impingement plate holes and a second impingement plate attached to the first impingement plate. The second impingement plate includes a platform section spaced away from the multiple of first impingement plate holes to define a plate cavity.

BACKGROUND

The present application relates to a blade outer air seal (BOAS) and more particularly to a multi impingement plate assembly therefor.

Gas turbine engines generally include fan, compressor, combustor and turbine sections along an engine axis of rotation. The fan, compressor, and turbine sections each include a series of stator and rotor blade assemblies. A rotor and an axially adjacent array of stator assemblies may be referred to as a stage. Each stator vane assembly increases efficiency through the direction of core gas flow into or out of the rotor assemblies.

An outer case includes a blade outer air seal (BOAS) to provide an outer radial flow path boundary for the core gas flow. A multiple of BOAS segments are typically provided to accommodate thermal and dynamic variation typical in a high pressure turbine (HPT) section of the gas turbine engine. The BOAS segments are subjected to relatively high temperatures and receive a secondary cooling airflow for temperature control.

SUMMARY

A multi impingement plate assembly for a Blade Outer Air Seal (BOAS) according to an exemplary aspect of the present disclosure includes a first impingement plate which defines a multiple of first impingement plate holes and a second impingement plate attached to the first impingement plate. The second impingement plate includes a platform section spaced away from the multiple of first impingement plate holes to define a plate cavity.

A blade outer air seal assembly according to an exemplary aspect of the present disclosure includes a body that defines a first cavity separated from a second cavity by a circumferential rib. A multi impingement plate assembly defines a plate cavity, the multi impingement plate assembly circulates a secondary cooling air flow between the first cavity and the second cavity through the plate cavity.

A method of communicating a secondary cooling airflow within a gas turbine engine according to an exemplary aspect of the present disclosure includes segregating a first cavity from a second cavity by a circumferential rib and communicating the secondary cooling airflow between the first cavity and the second cavity through a plate cavity of a multi impingement plate assembly.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT

FIG. 1schematically illustrates a gas turbine engine20, illustrated partially herein as a High Pressure Turbine (HPT) section22disposed along a common engine longitudinal axis A. The engine20includes a Blade Outer Air Seal (BOAS) assembly24to provide an outer core gas path seal for the turbine section22. It should be understood that although a BOAS assembly for a HPT of a gas turbine engine is disclosed in the illustrated embodiment, the BOAS assembly may be utilized in any section of a gas turbine engine. The BOAS segment may find beneficial use in many industries including aerospace, industrial, electricity generation, naval propulsion, pumping sets for gas and oil transmission, aircraft propulsion, vehicle engines, and stationary power plants.

The HPT section22generally includes a rotor assembly26disposed between forward and aft stationary vane assemblies28,30(illustrated schematically). Outer vane supports28A,30A attach the respective vane assemblies to an engine case32(illustrated schematically). The rotor assembly26generally includes a multiple of airfoils34circumferentially disposed around a disk36. The distal end of each airfoil34may be referred to as an airfoil tip34T which rides adjacent to the BOAS assembly24.

The BOAS assembly24is disposed in an annulus radially between the engine case32and the airfoil tips34T. The BOAS assembly24generally includes a blade outer air seal (BOAS) support38and a multiple of blade outer air seal (BOAS) segments40mountable thereto (also seeFIG. 2). The BOAS support38is mounted within the engine case32to define forward and aft flanges42,44to receive the BOAS segments40. The forward flanges42and the aft flanges44may be circumferentially segmented to receive the BOAS segments40in a circumferentially rotated and locked arrangement as generally understood.

Each BOAS segment40includes a body46which defines a forward interface48and an aft interface50. The forward interface48and the aft interface50respectively engage the flanges42,44to secure each BOAS segment40thereto. It should also be understood that various interfaces and BOAS assemblies may alternatively be provided.

With reference toFIG. 2, each BOAS segment40includes at least two cavities52A,52B to receive a secondary cooling airflow S. In the disclosed non-limiting embodiment, the cavity52A is axially forward of cavity52B but separated therefrom by a circumferential rib56. That is, the circumferential rib56essentially surrounds the engine longitudinal axis A. Each cavity52A,52B may be formed through, for example, an investment casting process then closed by a multi impingement plate assembly54(FIG. 3).

A multiple of edge holes80and a multiple of film holes82provide flow communication for the secondary cooling air S from the cavities52A,52B into the core gaspath flow C. The multiple of edge holes80are arranged generally circumferentially and the multiple of film holes82are arranged generally radially with respect to the engine axis A. It should be understood that various numbers, sizes, orientations and arrangements may be provided and that the holes80,82are illustrated somewhat schematically.

The multi impingement plate assembly54generally includes a first impingement plate60and a second impingement plate62, however, any number of plates or plate sections may be utilized. The first impingement plate60and the second impingement plate62may be welded together as a unit then welded to the body46(FIG. 3). That is, the multi impingement plate assembly54facilitates retrofit for single impingement plate BOAS designs.

The first impingement plate60extends between a forward ledge64, and an aft ledge66over the circumferential rib56. The first impingement plate60generally includes a window67over the forward cavity52A and a multiple of impingement holes68over the aft cavity52B (FIG. 4). Alternatively, the first impingement plate60extends from the circumferential rib56to the aft ledge66to cover the aft cavity52B.

The second impingement plate62extends between the forward ledge64and the aft ledge66over the first impingement plate60. The second impingement plate62includes a platform section70which is displaced from a plane P2which defines a base section72. Plane P2is parallel to plane P1which is defined by the first impingement plate60. The platform section70is imperforate while the base section72includes a multiple of impingement holes74. The second impingement plate62may be welded along a periphery of the first impingement plate60to form a spaced relationship therebetween over the multiple of impingement holes68.

At least one passage76extends between the platform section70and the base section72beyond the circumferential rib56(best seen inFIG. 3). That is, the at least one passage76provides a transition between the platform section70and the base section72for communication of the secondary cooling air S from the forward cavity52A to a plate cavity78between the platform section70and the first impingement plate60. In the disclosed non-limiting embodiment, the passage76may include a set of passages76which may be generally U-shaped and is displaced from the plane P2which includes the base section72

The at least one passage76provides a fluid communication path S1(FIG. 4) for the secondary cooling air S which enters through the multiple of second impingement holes74into the forward cavity52A through the window67of the first impingement plate60. The secondary cooling air S provides impingement cooling of the BOAS surface in the forward cavity52A then exits out to the core gaspath flow C (FIG. 1) through the multiple of edge holes80and the multiple of film holes82.

The secondary cooling air S then enters into the plate cavity78through the passage76. From the plate cavity78, the secondary cooling air S exits through the multiple of first impingement holes68into the aft cavity52B to provides impingement cooling in the aft cavity52B then exits out to the core gaspath flow through the multiple of edge holes80. Approximately 80% of that secondary cooling air S flows out through the multiple of film holes82and 20% through the multiple edge holes80.

The multi impingement plate assembly54allows some of the forward cavity52A secondary cooling air S to be reused in the aft cavity52B which results in lower temperatures and relatively lower cooling flow requirements for the BOAS segment40. In the disclosed non-limiting embodiment, the secondary cooling air S gaspath pressure within the BOAS segment40is lower axially aft along the airfoil tips34T (FIG. 1). The forward cavity52A thus has a somewhat higher static pressure than the aft cavity52B due to the direction of primary core flow. This generates a higher pressure ratio across the BOAS and tends to “withdraw” air from the forward cavity52A to the aft cavity52B which facilitates operation of and cooling efficiency through the multi impingement plate assembly54. The higher static pressure in cavity52A also results in increased axial crossflow heat transfer coefficient (Hc) in the forward cavity52A which results in, for example, lower temperatures, and, thereby, longer operational life of the BOAS.

The multi impingement plate assembly54also provides additional cooling benefit by recirculating secondary cooling air from the forward cavity52A into the aft cavity52B without increased supply pressure. Estimation of cooling flow benefit through simulation is ˜0.06% turbine core flow (Wae). Thermal analysis of the multi impingement plate assembly54configuration provides a benefit of ˜0.06% cooling flow reduction relative to a conventional, single-plated design which equates to a flow reduction is equivalent ˜0.006% Thrust Specific Fuel Consumption (TSFC).