Patent Application
20160258295
Embodiments of the invention relate generally to rotary machines and, more particularly, to the reducing mixing of packing leakage and the main flow of hot gas or steam in gas and steam turbines, respectively.
As is known in the art, turbines employ rows of buckets on the wheels/disks of a rotor assembly, which alternate with rows of stationary vanes on a stator or nozzle assembly. These alternating rows extend axially along the rotor and stator and allow combustion gasses or steam to turn the rotor as the combustion gasses or steam flow therethrough.
Axial/radial openings at the interface between rotating buckets and stationary nozzles can allow hot combustion gasses or steam to exit the main flow and radially enter the intervening wheelspace between bucket rows. In gas turbines, cooling air or “purge air” is often introduced into the wheelspace between bucket rows. This purge air serves to cool components and spaces within the wheelspaces and other regions radially inward from the buckets as well as providing a counter flow of cooling air to further restrict incursion of hot gasses into the wheelspace. Nevertheless, incursion of combustion gasses or steam into the wheelspaces between bucket rows contributes to decreased turbine efficiency of between about 1% and about 1.5%.
In one embodiment, the invention provides a turbine bucket comprising: a platform portion; an airfoil extending radially outward from the platform portion; and at least one recess extending radially inward into the platform portion, the at least one recess being disposed at an angle relative to a leading edge of the platform portion.
In another embodiment, the invention provides a turbine comprising: a first turbine bucket including: a first platform portion; a first airfoil extending radially outward from the first platform portion; and at least one recess extending radially inward into the first platform portion, the at least one recess being disposed at an angle relative to a leading edge of the first platform portion; and a second turbine bucket including: a second platform portion; a second airfoil extending radially outward from the second platform portion; and at least one recess extending radially inward into the first platform portion, the at least one recess being disposed at an angle relative to a leading edge of the second platform portion.
These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which:
It is noted that the drawings of the invention are not to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements among the drawings.
Turning now to the drawings,
Shank portion 60 includes a pair of angel wing seals 70, 72 extending axially outward toward first stage nozzle 20 and an angel wing seal 74 extending axially outward toward second stage nozzle 22. It should be understood that differing numbers and arrangements of angel wing seals are possible and within the scope of the invention. The number and arrangement of angel wing seals described herein are provided merely for purposes of illustration.
As can be seen in
While
Recesses 192, 194, 294 may be machined into platforms 142, 242 according to any known or later-developed method. Alternatively, recesses 192, 194, 294 may be cast as part of platforms 142, 242.
The extent to which the swirl of hot gas 280, 380 is altered depends, for example, on the depth to which recesses 192, 294, 292, 394 extend radially inward into platforms 142, 242, 342. Typically, recesses 192, 294, 292, 394 extend radially inward into platforms 142, 242, 342 to a depth up to about 100 mil (i.e., about 0.1 inch), e.g., to a depth between about 10 mil and about 100 mil, or between about 20 mil and about 90 mil, or between about 30 mil and about 80 mil, or between about 40 mil and about 70 mil, or between about 50 mil and about 60 mil.
Similarly, the extent to which the swirl of hot gas 280, 380 is altered depends on the angles at which recesses 192, 294, 292, 394 are disposed relative to platform leading edges 146, 246, 346. Upstream recesses 192, 292, 392 are typically angled between about 45° and about 80° relative to platform leading edges 146, 246, 346. Downstream recesses 194, 294, 394 are typically angled between about 90° and about 120° relative to platform leading edges 146, 246, 346. As described herein and as shown in
The principle of operation of the platform recesses described above with respect to the operation of gas turbines may is also applicable to the operation of steam turbines. For example,
As noted above with respect to
As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any related or incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
