Ring seal for a turbine engine

Abstract

Aspects of the invention are directed to a ceramic matrix composite ring seal segment. The ring seal segment according to aspects of the invention includes a relatively simple body that is circumferentially curved. At least a portion of the hot gas path surface of the ring seal segment can be coated with a thermal insulating. material. In one embodiment, each ring seal segment can be operatively connected to a stationary support structure, such as by way of isolation rings. The ring seal segments and/or the isolation rings can be configured so as to restrain the ring seal segments in the axial, radial and/or circumferential directions. The ring seal segments can be attached to the isolation rings so that the support points act opposite the operating pressure loads. Thus, the ring seal segments carry these loads in compression, a strong direction of the CMC fibers.

1 . A turbine engine ring seal system comprising:
 a ceramic matrix composite ring seal segment having a first circumferential end and a second circumferential end, the ring seal segment being circumferentially curved as it extends between the first and second circumferential ends, the ring seal segment further having an axial forward end, an axial aft end, a radially outer surface and a radially inner surface, the radially inner surface being radially inwardly concave; and   a stationary support structure, wherein the ring seal segment is operatively connected to the stationary support structure at the axial forward end and at the axial aft end.   
     
     
         2 . The system of  claim 1  wherein the ceramic matrix composite is an oxide-oxide ceramic matrix composite. 
     
     
         3 . The system of  claim 1  further including a thermal insulating material attached to the radially inner surface of the ring seal segment. 
     
     
         4 . The system of  claim 3  wherein the thermal insulating material is a friable graded insulation. 
     
     
         5 . The system of  claim 3  further including a forward isolation ring and an aft isolation ring attached to the stationary support structure, wherein the thermal insulating material is recessed from the axial forward end of the ring seal segment so that a forward shelf is formed, and wherein the thermal insulating material is recessed from the axial aft end of the ring seal segment so that an aft shelf is formed, and wherein the forward shelf engages the forward isolation ring and the aft shelf engages the aft isolation ring, whereby the ring seal segment is indirectly connected to the stationary support structure by the isolation rings. 
     
     
         6 . The system of  claim 5  wherein each of the forward and aft isolation rings includes a radially extending body and a ledge that extends substantially axially, wherein the ledge includes a radially inner surface and a radially outer surface, wherein the forward shelf engages the ledge of the forward isolation ring and the aft shelf engages the ledge of the aft isolation ring, and wherein the thermal insulating material is substantially flush with the radially inner surface of each of the ledges. 
     
     
         7 . The system of  claim 1  wherein the ring seal segment operatively engages the stationary support structure so as to be restrained in the radially outward direction. 
     
     
         8 . The system of  claim 7  further including a forward isolation ring and an aft isolation ring attached to the stationary support structure, wherein each of the isolation rings has an elongated channel therein, wherein a portion of the ring seal segment including the axial forward end is received within the channel in the forward isolation ring, and wherein a portion of the ring seal segment including the axial aft end is received in the channel in the aft isolation ring, whereby the ring seal segment is restrained in at least the radially outward direction. 
     
     
         9 . The system of  claim 1  wherein the ring seal segment operatively engages the stationary support structure so as to be substantially circumferentially restrained. 
     
     
         10 . The system of  claim 9  further including a forward isolation ring and an aft isolation ring attached to the stationary support structure, each of the isolation rings providing an axially extending protrusion, wherein each of the axial forward and aft ends of the ring seal segment include a notch, wherein the protrusion of the forward isolation ring is received in the notch in the forward end of the ring seal segment, and wherein the protrusion of the aft isolation ring is received in the notch in the aft end of the ring seal segment, whereby the ring seal segment is restrained in the circumferential direction. 
     
     
         11 . The system of  claim 1  wherein the ring seal segment is circumferentially curved relative to an axis, wherein the ceramic matrix composite of the ring seal segment includes a ceramic matrix with a plurality of fibers therein, wherein at least a substantial majority of the fibers are oriented parallel to the axis. 
     
     
         12 . A turbine engine ring seal system comprising:
 a stationary support structure;   a forward isolation ring;   an aft isolation ring opposite the forward isolation ring, the forward and aft isolation rings attached to the stationary support structure and extending substantially radially inward therefrom; and   a ceramic matrix composite ring seal segment having a first circumferential end and a second circumferential end, the ring seal segment being circumferentially curved as it extends between the first and second circumferential ends, the ring seal segment further having an axial forward end, an axially aft end, a radially outer surface and a radially inner surface, the radially inner surface being radially inwardly concave, wherein at least a portion of the radially inner surface of the ring seal segment is coated with a thermal insulating material,   wherein the axial forward end of the ring seal segment is operatively attached to the forward isolation ring and the axial aft end of the ring seal segment is operatively attached to the aft isolation ring.   
     
     
         13 . The system of  claim 12  wherein the ceramic matrix composite is an oxide-oxide ceramic matrix composite. 
     
     
         14 . The system of  claim 12  wherein the thermal insulating material is a friable graded insulation. 
     
     
         15 . The system of  claim 12  wherein the thermal insulating material is recessed from the axial forward end of the ring seal segment so that a forward shelf is formed, and wherein the thermal insulating material is recessed from the axial aft end of the ring seal segment so that an aft shelf is formed, and wherein the forward shelf operatively engages the forward isolation ring and the aft shelf operatively engages the aft isolation ring. 
     
     
         16 . The system of  claim 12  wherein each of the isolation rings has a radially inner surface, wherein the thermal insulating material is substantially flush with the radially inner surface of each of the isolation rings. 
     
     
         17 . The system of  claim 12  wherein each of the isolation rings has an elongated channel therein, wherein a portion of the ring seal segment including the axial forward end is received within the channel in the forward isolation ring, and wherein a portion of the ring seal segment including the axial aft end is received in the channel in the aft isolation ring, whereby the ring seal segment is restrained in at least the radially outward direction. 
     
     
         18 . The system of  claim 17  wherein each of the isolation rings providing an axially extending protrusion, wherein each of the axial forward and aft ends of the ring seal segment includes a notch, wherein the protrusion of the forward isolation ring is received in the notch in the forward end of the ring seal segment, and wherein the, protrusion of the aft isolation ring is received in the notch in the aft ring seal segment, whereby the ring seal segment is restrained in the circumferential direction. 
     
     
         19 . The system of  claim 18  wherein the protrusion is located within the channel. 
     
     
         20 . The system of  claim 12  wherein the ring seal segment is circumferentially curved relative to an axis, wherein the ceramic matrix composite of the ring seal segment includes a ceramic matrix with a plurality of fibers therein, wherein at least a substantial majority of the fibers are oriented parallel to the axis.