Blade outer air seal with non-linear response
A blade outer air seal (BOAS) for a gas turbine engine includes a seal ring body having a radially inner face and a radially outer face that axially extend between a leading edge portion and a trailing edge portion and a segmented spline that extends from the radially outer face of the seal ring body, the seal secured to the radially inner face of the seal ring body.
1. A blade outer air seal (BOAS) for a gas turbine engine, comprising:
a full ring hoop seal ring body having a radially inner face and a radially outer face;
a honeycomb seal secured to the radially inner face of the seal ring body adjacent to a turbine rotor; and
a segmented spline that extends radially outward from the radially outer face of the seal ring body, the segmented spline comprises slots to permit communication of a purge airflow between the radially outer face and a turbine exhaust case, a spacing between the segmented spline and a machined pad on the turbine casing set at assembly to provide a tolerance-controlled interface between the BOAS and the turbine casing that sets the non-linear thermal expansion response of the blade outer air seal (BOAS) with respect to the turbine rotor during engine operation
a seal secured to the radially inner face of the seal ring body.
2. The blade outer air seal (BOAS) as recited in claim 1 , further comprising a thermal barrier coating applied to at least a portion of a radially inner face of the seal.
3. The blade outer air seal (BOAS) as recited in claim 1 , wherein the seal is brazed to the radially inner face.
4. The blade outer air seal (BOAS) as recited in claim 1 , wherein the radially inner face and the radially outer face of the seal ring body axially extends between a leading edge portion and a trailing edge portion.
5. The blade outer air seal (BOAS) as recited in claim 4 , wherein the honeycomb seal extends at least partially between the leading edge portion and the trailing edge portion.
6. The blade outer air seal (BOAS) as recited in claim 1 , wherein the segmented spline abuts a power turbine engine casing of a turboshaft engine.
7. A non-linear response system, comprising:
a turbine rotor along an axis;
a turbine exhaust case comprising a pad at least partially around the axis; and
a blade outer air seal (BOAS) with a segmented spline that extends radially outward from a radially outer face of a full hoop seal ring body and a honeycomb seal secured to the radially inner face of the seal ring body adjacent to the turbine rotor, the segmented spline includes slots to permit communication of a purge airflow between the radially outer face and the turbine exhaust case, a spacing between the segmented spline and the pad on the turbine casing set at assembly to provide a tolerance-controlled interface between the BOAS and the turbine casing that sets the non-linear thermal expansion response of the blade outer air seal (BOAS) with respect to the turbine rotor during engine operation.
8. The non-linear response system in claim 7 , wherein the blade outer air seal (BOAS) comprises a honeycomb seal that extends radially inward from the full hoop seal ring body.
9. The non-linear response system in claim 8 , wherein the turbine rotor comprises rotor blades with knife edges that interface with the honeycomb seal.
10. The non-linear response system in claim 7 , wherein the pad is a machined surface.
11. A method of controlling a specific rate of thermal change to match a corresponding blade design with a blade outer air seal (BOAS) for a gas turbine engine, comprising:
setting a spacing between a segmented spline that extends radially outward from a radially outer face of a full hoop seal ring body and a machined pad on a turbine casing at assembly to provide a tolerance-controlled interface between a blade outer air seal (BOAS) and the turbine casing that sets a predefined non-linear thermal expansion response of the blade outer air seal (BOAS) with respect to the turbine rotor;
securing a honeycomb seal to a radially inner face of the seal ring body adjacent to the turbine rotor; and
selectively abutting the segmented spline that extends from the radially outer face of a full hoop seal ring body with the machined pad during engine operation resulting in the non-linear thermal expansion response reducing a tip clearance between the turbine rotor and the honeycomb seal of the blade outer air seal (BOAS).
12. The method as recited in claim 11 , further comprising controlling a purge airflow between the radially outer face and the engine casing.
13. The method as recited in claim 12 , further comprising controlling the airflow through slots in the segmented spline.
14. The blade outer air seal (BOAS) as recited in claim 1 , wherein the pad is machined into the turbine exhaust casing.
15. The blade outer air seal (BOAS) as recited in claim 1 , wherein the honeycomb seal interfaces with a knife edge that extends from a blade tip of the turbine rotor.
16. The blade outer air seal (BOAS) as recited in claim 1 , wherein the segmented spline extends radially outward about 0.04-0.06 inches (1.02-1.5 mm) to provide an assembly gap of 0.005-0.020 inches (0.127-0.508 mm) within the turbine exhaust case which results in a 0.01-0.03 inch (0.025-0.08 mm) running gap during operation.