Patent Application
20100254805
The subject matter disclosed herein relates to gas turbines, and more particularly to a gas turbine inner flow path cover piece.
Current solutions implement direct purging of air into the cavities between the rotor wheels. Other solutions implement an intermediate wheel that carries a platform to seal the hot gas path away from the wheel surfaces. Current solutions can incur a penalty in engine performance due to the parasitic use of compressor air to purge the cavities as to avoid ingestion. Also, the cavities eject air perpendicular to the main flow path, incurring mixing losses before the gas enters the blade or nozzle row.
According to one aspect of the invention, an apparatus in a gas turbine having a first turbine wheel and a second turbine wheel is provided. The apparatus includes a main body having a first surface and a second surface, side pieces disposed on the first surface of the main body and mating pairs disposed on the second surface of the main body.
According to another aspect of the invention, a gas turbine assembly is provided. The gas turbine assembly includes a first turbine wheel, a second turbine wheel and a gas turbine inner flow path cover piece disposed between the first turbine wheel and the second turbine wheel.
According to yet another aspect of the invention, a gas turbine is provided. The gas turbine includes a first turbine wheel, a second turbine wheel, a hot section turbine nozzle disposed between the first and second turbine wheels and a gas turbine inner flow path cover piece disposed between the first turbine wheel and the second turbine wheel.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
In exemplary embodiments, the turbine wheels 205, 210 each include at least one of male and female dovetail mating pairs 206, 211 (airfoil slots). As illustrated, the turbine wheels 205, 210 include female dovetail mating pairs 206, 211.
In exemplary embodiments, the gas turbine inner flow path cover piece 300 includes a main body 305 having an first (upper) surface 306 with a pre-defined contour matching that contour of a desired flow path within the upper cavity 225. In exemplary embodiments, the gas turbine inner flow path cover piece 300 can have any number of sealing mechanisms facing such flow path for mating with any sealing structure in order to prevent combustion gases from circumventing the stationary vane. In exemplary embodiments, a number of gas turbine inner flow path cover pieces 300 can be implemented to form a ring creating an annulus (upper cavity 225) between the hot section turbine nozzle 220 and the first surface 306 of the gas turbine inner flow path cover piece 300. In exemplary embodiments, the gas turbine inner flow path cover piece 300 can further include side pieces 310 configured to contact the turbine wheels 205, 210 when the gas turbine inner flow path cover piece 300 is affixed between the turbine wheels 205, 210. The side pieces 310 are contiguous with the first surface 306 and can be perpendicular to the first surface 306. In exemplary embodiments, the side pieces 310 can be perpendicular to the second (lower) surface 307 and further can be co-planar with the dove-tail mating pairs 301. In exemplary embodiments, the side pieces 310 are configured to deform at increased speeds of the turbine wheels 205, 210 forming a seal between the side pieces 310 and a blade section of the turbine wheels 205, 210.
In exemplary embodiments, the gas turbine inner flow path cover piece 300 can further include structural supports 315 disposed on the second surface 307 of the main body 305. The structural supports 315 are configured to provide a desired stiffness of the gas turbine inner flow path cover piece 300 in the radial direction. It is appreciated that the gas turbine inner flow path cover piece 300 can be fabricated using composite materials, frame techniques, plain material or any combination of other structural treatments to assure the desired stiffness in the radial direction. For example, in exemplary embodiments, the second surface 307 can include an isogrid pattern providing an isotropic support along the second surface 307.
The exemplary embodiments described herein eliminate or greatly reduce the cavity purges as there is no wheel cavity directly exposed to the hot gas path temperatures. Also, as no heavy purge is required, aero losses stemming from the purge flows used are greatly reduced resulting in a vast improvement in efficiency. Since the dovetail pairs 206, 211 on the turbine wheels 205, 210 are covered, cost advantages are realized because the turbine length is reduced. The presence of the gas turbine inner flow path cover piece 300 further prevents inter-stage leakage. Furthermore, the presence of the gas turbine inner flow path cover piece 300 can result in smaller bucket shanks leads to cost advantage. The complete elimination of diaphragms on the hot section turbine nozzle 220 also leads to cost advantage, which can lead to a higher hot section turbine nozzle life due to reduced plug load leads to cost advantage due to a reduced area subject to a differential pressure under the nozzle sections in comparison with convention configurations.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
