Patent Application
20170044923
The present invention is directed to turbine components. More particularly, the present invention is directed to turbine components having an inner shroud loaded to an outer shroud.
In gas turbines, certain components, such as the shroud surrounding the rotating components in the hot gas path of the combustor, are subjected to extreme temperatures, chemical environments and physical conditions. Inner shrouds are subjected to further mechanical stresses from pressures applied to load the inner shroud to the outer shroud, pushing against the pressure of the hot gas path. Pressurizing the space between the inner shroud and the outer shroud leaks high pressure fluid into the hot gas path, decreasing efficiency of the turbine. Further, mechanisms for mechanically loading the inner shroud against the outer shroud, such as springs, exhibit decreased effectiveness at high temperatures, and the springs themselves may creep over time, leading to insufficient loading pressure.
In an exemplary embodiment, a turbine shroud assembly includes an inner shroud having a surface adjacent to a hot gas path, an outer shroud, and a biasing apparatus. The biasing apparatus is arranged and disposed to bias the inner shroud in a direction away from the hot gas path, loading the inner shroud to the outer shroud.
In another exemplary embodiment, a turbine shroud assembly includes an inner shroud having a surface adjacent to a hot gas path, an outer shroud, and a springless biasing apparatus. The springless biasing apparatus includes at least one bellows, at least one thrust piston, or a combination of at least one bellows and at least one thrust piston, and is arranged and disposed to bias the inner shroud in a direction away from the hot gas path, loading the inner shroud to the outer shroud.
In another exemplary embodiment, a method for loading a turbine shroud assembly includes biasing an inner shroud having a surface adjacent to a hot gas path in a direction away from the hot gas path toward an outer shroud. Biasing the inner shroud includes a biasing force exerted by a biasing apparatus.
Other features and advantages of the present invention will be apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.
Provided is a turbine shroud assembly. Embodiments of the present disclosure, for example, in comparison to concepts failing to include one or more of the features disclosed herein, increase efficiency, increase durability, increase temperature tolerance, reduce the possibility of loss of load, reduce overall cost, and eliminate the need for pressurizing the shroud, produce other advantages, or a combination thereof.
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In one embodiment, the biasing apparatus 106 exerts a biasing force on the inner shroud 102 sufficient to dampen vibrations of the inner shroud 102 against the outer shroud 104. Without being bound by theory, it is believed that the vibrations of the inner shroud 102 are caused in part by the varying pressure field resulting from buckets/blades rotating in close proximity to the inner shroud 102. In another embodiment, contact between the inner shroud 102 and the outer shroud 104 reduces ingestion of hot gasses from the hot gas path 110 into the shroud assembly 100.
In one embodiment, either or both of the inner shroud 102 and the outer shroud 104 includes a ceramic matrix composite, a metal, a monolithic material, or a combination thereof. As used herein, the term “ceramic matrix composite” includes, but is not limited to, carbon-fiber-reinforced carbon (C/C), carbon-fiber-reinforced silicon carbide (C/SiC), and silicon-carbide-fiber-reinforced silicon carbide (SiC/SiC).
In one embodiment, the surface 108 includes an environmental barrier coating (EBC) which protects the surface 108 from water vapor, heat, and other combustion gases. In another embodiment, the surface 108 includes a thermal barrier coating (TBC) which protects the surface 108 from heat. In yet another embodiment, at least one of the EBC and the TBC coats the exterior 130 of the inner shroud 102, including both the surface 108 as well as the distal surface 132.
In one embodiment, the turbine shroud assembly 100 includes a springless biasing apparatus 106. As used herein, a “springless” biasing apparatus 106 is a biasing apparatus 106 in which the biasing force loading the inner shroud 102 against the outer shroud 104 is not generated by a spring. In certain embodiments, a springless biasing apparatus 106 may include a spring provided that any included spring does not generate a biasing force loading the inner shroud 102 against the outer shroud 104.
In one embodiment, the biasing apparatus 106 is driven by a pressurized fluid 114. The pressurized fluid 114 may be any fluid, including, but not limited to, air. Suitable sources for pressurized air include air from a gas turbine compressor.
In one embodiment, the biasing apparatus 106 includes at least one bellows 116. In a further embodiment, the at least one bellows 116 includes a first end 118 attached to the outer shroud 104 and a second end 120 configured to expand away from the hot gas path 110 in response to an increased internal pressure within the at least one bellows 116. The second end 120 of the at least one bellows 116 may be attached to at least one pin 122 which connects to at least one projection 124 of the inner shroud 102. In one embodiment, the second end 120 is attached to the at least one pin 122 by a stanchion 126.
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In one embodiment, loading a turbine shroud assembly 100 by biasing the inner shroud 102 in a direction 112 away from the hot gas path 110 toward the outer shroud 104 reduces damaging vibrations in the inner shroud 102, in comparison to a turbine shroud assembly 100 in which the inner shroud 102 is biased in a direction toward the hot gas path 110 away from the outer shroud 104. Without being bound by theory, it is believed that such damaging vibrations may be exacerbated in a turbine shroud assembly 100 in which the space between the inner shroud 102 and the outer shroud 104 is not pressurized by a fluid, such as, by way of example only, pressurized fluid 114.
While the invention has been described with reference to one or more embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
