The invention generally relates to a gas turbine engine, and more particularly to a seal component between a transition and a turbine of such engine.
In gas turbine engines, air is compressed at an initial stage, then is heated in combustion chambers, and the hot gas so produced passes to a turbine that, driven by the hot gas, does work which may include rotating the air compressor.
In a typical industrial gas turbine engine a number of combustion chambers combust fuel and hot gas flowing from these combustion chambers is passed via respective transitions (also referred to by some in the field as ducts and tail tubes) to respective entrances of the turbine. More specifically, a plurality of combustion chambers commonly are arranged radially about a longitudinal axis of the gas turbine engine, and likewise radially arranged transitions comprise outlet ends that converge to form an annular inflow of hot gas to the turbine entrance. Each transition exit is joined by a number of seals each of which bridges a gap between a portion of the exit and one or more turbine components. The latter, in various designs, are identified as row 1 vane segments. Adjacent component growth variances due to thermal expansion, mechanical loads, and vibrational forces from combustion dynamics all affect design criteria and performance of such a seal, referred to herein as a transition-to-turbine seal. Maintenance of component temperatures below particular limits is also desired and this may affect design of the seal and adjacent components. Consequently, the design of such seals has presented a challenge resulting in various approaches that attempt to find a suitable balance between seal cost, reliability, durability, installation and repair ease, performance, and effect on adjacent components.
For example, U.S. Pat. No. 6,751,962, issued Jun. 22, 2004 to Kuwabara et al., provides inclined cooling fluid holes drilled in a tail tube seal in addition to conventionally existing cooling fluid holes. These cooling fluid holes exit into the hot gas path, and are stated to cool the hot gas side of a downstream groove of the seal due to film effect. This is stated to increase reliability and decrease wear. A different approach is taken to cool the transition side of the seal in U.S. Pat. No. 6,769,257, issued Aug. 3, 2004 to Kondo et al. In this patent are disclosed cooling medium and heating medium channels provided in the outlet structure of a transition. Various embodiments are described that are stated to reduce the temperature difference of a flange formed at the downstream end of the transition, which attaches to a sealing component connecting to the turbine. Finally, in U.S. Pat. No. 6,860,108, issued Mar. 1, 2005 to Soechting et al., a seal was directed to prevent the outer and inner shrouds of the turbine's first stationary blade (i.e., row 1 vane segment) from heat damage and wear. The seal comprised a downstream portion having an inclined surface (inclining outwardly from the hot gas path) so that the cross-sectional area defined within the seal increased from an upstream point to a downstream point. Also, outlets for ejecting cooling air were provided that were disposed to release cooling air at the downstream end of the seal. Further, bleed holes were provided toward an upstream end section of the seal, near a front corner of the seal in the hot gas path. The latter are stated to “cool the film” [sic] of the parallel (non-inclined, more upstream) and the inclined (more downstream) surfaces of the seal that are in the hot gas path.
Despite the respective features of these and other transition-to-turbine seals and temperature equilibrating approaches known in the art, there remains a need for an improved transition-to-turbine seal.
The invention is explained in the following description in view of the drawings that show:
Embodiments of the invention provide a number of advances over known transition-to-turbine seals, providing enhanced durability by reducing transition metal temperatures and lowering wear rates of adjacent components such as the transition outlet flange. The inventors have developed a transition-to-turbine seal that takes into account pressure impacts of the more downstream row 1 vanes, in particular that a bow wake from the vanes may provide a slight but significant higher pressure region adjacent to an upstream gap between a flange of a transition and the seal. Appreciating that this could result in a circumferential deflection of cooling fluid flows from the seal through the gap, the inventors obviated such possible impacts in embodiments of the present invention, and thereby advanced the art.
More particularly, embodiments of the present invention comprise a transition-to-turbine seal that comprises a means for keeping a cooling fluid flow in a substantially radial direction after it emanates from the seal, into the gap, and then travels in the gap toward the hot gas path. One disclosed embodiment provides a plurality of flow partitions along a seal wall designed to partially engage the first flange, wherein the flow partitions comprise a plurality of spaced apart recesses, separated by intervening walls, with each recess comprising one or more cooling apertures, so that the presence of the partitions more clearly assures that respective flows will be directed along the entire inside edge of the gap (i.e., in the hot gas path). Such embodiment, and the invention in general, provide a seal that is multi-purpose: it not only achieves a primary sealing function, but it also cools the transition outlet flange and more uniformly purges hot gases from the gap. The cooling of the flange includes both impingement type and convective type cooling, and the flow further provides uniform gap purging and film cooling. The seal achieves these purposes while providing a robust mechanical junction between the seal and the transition outlet flange, this being due in part to the intervening walls that distribute wear load while still providing for unobstructed outflow of cooling fluids from the cooling apertures in the recesses. As a result of reducing the transition outlet flange and seal metal temperatures, a lower wear at this interface is expected. Additionally, the intervening walls will prevent the recesses to collapse from the mechanical and thermal loads imposed on the seal.
Prior to discussion of an exemplary embodiment, a discussion is provided of a common arrangement of elements of a prior art gas turbine engine.
Further to conventional aspects of seals provided at such junction 115 of
Also, notwithstanding the above specific embodiment, any number of outlets of cooling fluid holes may be provided in each of the recesses. Further, it is noted that the diameter of the cooling fluid holes may be increased relative to other holes and other recesses for the recesses that are positioned upstream of an airfoil of the adjacent row 1 vane segment, which therefore may be affected by a bow wake of the airfoil during operation. For example, if an airfoil as indicated by bold arrow 334 is directly downstream of the recess identified as 327-B, then a bow wake may present a higher pressure at the opening of the recesses 327-A, 327-B, and 327-C into hot gas path 170. In such case, to at least partially compensate for this, the cooling fluid holes for recesses 327-A, 327-B, and 327-C may be provided with larger diameters (example shown as dashed circles) than the other recesses 327 depicted in
Also shown in
Further to the cooling characteristics of cooling fluid holes 339, by viewing
Also, the cooling effect provided by such flow is a combination of impingement cooling and convective cooling, and this flow contrasts with expected low flow such as through the groove 335 which is restricted by the close proximity between the distal section 326 and a directly opposing distal section of the transition outlet flange downstream surface 417. Thus, the flow from the outlets 329 into a respective recess 327 provides a flow having an established flow velocity effective to provide a desired cooling greater than the expected flow rate through a relatively stagnant area bounded in part by the distal section 326 where the flow is directed toward the hot gas path 170 and establishes a film cooling flow across the exposed surface 332. Further, in various embodiments the respective outlets 329 provides a selected flow of cooling fluid into the recesses 327 that is effective to purge the gap 401 between the transition outlet flange 416 and the seal 320. This purging reduces the likelihood of hot gas ingestion due to a maintenance of recess-to-hot gas path local pressure gradients.
This approach contrasts with other approaches known in the art. Also, outlets such as these may be designed to be effective to provide an impingement cooling and a convective cooling of the transition outlet flange.
It is recognized that impingement cooling is achieved when a flow of sufficient force, directed toward a surface, is effective to disturb a thermal gradient over that surface. This increases the thermal transfer from the surface. In addition to impingement and convection cooling of the downstream surface 417 (which results in the overall flange 416 remaining cooler), the flow of cooling fluids out of the gap 401 and into the hot gas path 170 purges the gap 401, reducing or eliminating hot gas ingestion due to maintenance of desired local recess-to-hot gas path pressure gradients, and also provides a film cooling effect across the exposed surface 332. The partitioning of the gap 401 into a plurality of recesses 327 better assures the latter two functions.
The overall design, combining the noted features and relationships, provides beneficial cooling of both the transition outlet flange and the seal itself.
Also, the term “means for sealingly engaging a transition outlet flange” is taken to include all of the above structural elements of embodiments for effectuating a sealing engagement between the transition-to-turbine seal, of which this means is a portion, and a transition outlet flange. Also, it is recognized that various specific design modifications may be effectuated without departing from the scope of such means. For example, a complete U-shaped design need not be employed for a design of a means for sealingly engaging a transition outlet flange. The “means for directing cooling fluid flows” is taken to include the various depicted embodiments of pluralities of recesses comprising cooling fluid holes with outlets in respective recesses, or analogous defined partitioned areas, each separated by intervening wall structures. More particularly, “means for conveying a respective cooling fluid flow” is taken to include the various depicted embodiments, and variations based on design modifications, of one or more cooling fluid holes in a particular recess or analogous defined partition area. Similarly, “means for restricting” is taken to include the intervening wall structures and analogous structures. A “means for portioning” is taken to include any approach to provide a relatively greater flow to particular regions along a transition-to-turbine seal at the junction of the transition, such as for balancing overall flows given greater back pressures upstream of a turbine row 1 airfoil. Examples include, but are not limited to: greater diameter cooling fluid holes in such upstream areas relative to other areas; more cooling fluid holes in such upstream areas; and combinations thereof.
Also, a “a means for sealingly engaging an adjacent turbine component” is taken to include all of the above structural elements of embodiments for effectuating a sealing engagement between the transition-to-turbine seal, of which this means is a portion, and an adjacent transition component such as the lip of a row 1 vane segment, and various specific design modifications.
Having thusly described aspects and features of particular embodiments, it is appreciated that the invention relates not only to the transition-to-turbine seal apparatuses, such as those described and illustrated, but also to transition-to-turbine seal junctions comprising the transition-to-turbine seals of the present invention, and to gas turbine engines comprising the seals and the transition-to-turbine seal junctions of the present invention.
All patents, patent applications, patent publications, and other publications referenced herein are hereby incorporated by reference in this application in order to more fully describe the state of the art to which the present invention pertains, to provide such teachings as are generally known to those skilled in the art.
While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Moreover, when any range is described herein, unless clearly stated otherwise, that range includes all values therein and all sub-ranges therein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.