Patent Application
20140363279
The present invention relates generally to seals related to the flow of combustion gases in turbomachines, and specifically, to cover plates supporting seals (for example, so-called “angel-wing” seals) that over-lie the root portions of blades or buckets in the compressor and/or turbine sections of such machines.
Cover plates are generally used on turbomachine wheels, along the upstream and downstream faces of buckets or blades mounted on the wheels. The cover plates often support axially-projecting seals, generally referred to as angel-wings seals, that interact with seal lands on adjacent stationary and/or rotating hardware. These seals are intended to prevent both the ingress of hot gases into the rotor wheelspace radially inward of the buckets or blades, and the egress of the cooler wheelspace air into the hot gas path. The angel-wing seals may be integrally cast with the bucket or blade, or may comprise non-integral, separate plates mechanically assembled along axial faces of the wheel so as to cover one or more root portions of the buckets or blades. Examples of non-integral cover plates formed with integral angel-wing seals are disclosed in, for example, U.S. Pat. No. 6,190,131 and in U.S. Published Application 2010/0232938 A1.
There are occasions, however, when it is desired to utilize bucket or blade designs that are unable to accommodate the usual angel-wing seal configurations. For example, in a short-shank bucket or blade design, the shorter shank portions adjacent the bucket or blade root portions do not provide sufficient room for conventional angel-wing seals which, in many applications, are provided in a double-stacked arrangement with radially-spaced inner and outer seal elements.
There remains a need, therefore, for a unique turbomachine angel-wing seal arrangement conducive to the use of various bucket and blade designs.
In one exemplary but nonlimiting embodiment, the invention relates to a cover plate adapted to axially overlie root and/or shank portions of one or more buckets or blades secured to a turbomachine wheel comprising an arcuate cover plate body adapted to be secured to the turbomachine wheel so as to cover a root and/or shank portion of at least one of the turbine buckets or blades; and at least one arcuate angel-wing seal segment detachably secured to one side of the arcuate cover plate body.
In another exemplary aspect the invention provides a wheel for a turbomachine rotor rotatable about an axis, the wheel comprising a plurality of circumferentially-spaced bucket or blade slots receiving generally complimentary-shaped end portions of turbomachine buckets or blades, the buckets or blades each comprising a shank, a root portion and an airfoil portion; a circumferential array of cover plate segments axially overlying at least part of the shanks and the root portions of the buckets or blades, each of the cover plate segments comprising a cover plate body attached to the wheel; and one or more fastening elements provided on one side of the cover plate body for securing at least one seal segment on the one side of the cover plate body, the seal segment having at least one seal flange extending in a generally axial direction.
In still another aspect the invention provides a wheel for a turbomachine rotor rotatable about an axis, the wheel comprising a plurality of circumferentially-spaced, substantially axially-extending bucket or blade slots receiving generally complementary-shaped mounting portions of turbomachine buckets or blades; a circumferential array of a cover plate segments overlying end portions of the buckets or blades and portions of a face surface of the wheel; each cover plate segment comprising a cover plate body having at least one arcuate flange extending from one side of the cover plate for securing the cover plate in a generally complementary-shaped slot in the wheel; and a plurality of arcuate angel-wing seal segments detachably secured to respective cover plate bodies.
The invention will now be described in greater detail in connection with the drawings identified below.
It will be appreciated that the term “bucket” usually refers to the airfoil-shaped vanes (and associated mounting portion) employed in the turbine section(s) of turbomachines, while the term “blade” usually refers to the airfoil-shaped vanes (and associated mounting portions) typically employed in the compressor section of the machines. While the description below refers to “buckets”, it is to be understood that the seal configurations are applicable to both buckets and blades in the respective turbine and compressor sections of turbomachines.
The axially-facing sides of the shank and dovetail or root portions 16, 18, respectively, of buckets 14 are typically covered by cover plates 20, 22, each of which may have no angel-wing seals, or may be provided with one or more angel-wing seals. In the example shown, two such seals 24, 26 are provided on the upstream cover plate 20 and two similar seals 28, 30 are provided on the downstream cover plate 22. It will be appreciated that in other examples, one or more than two such seals may be employed. Additional seals 32, 34 may be located between the cover plates and the wheel. The cover plates 20, 22 may be secured to the wheel 12 in various ways, for example, by means of of a hook and slot arrangement shown at 36, 38, or by other conventional means such as, for example, bolts, pins, bayonet-type retaining ring or any combination thereof. Angel wing seals 24, 26 and 28, 30 typically cooperate with seal lands 40, 42 and 44, 46, respectively, formed on the adjacent nozzle diaphragms and support rings, or other turbomachinery hardware, to form a tortuous path that limits ingestion of the combustion gases flowing along the hot gas path 48 (and across the airfoil portions 49 of the buckets 14) into the wheel space radially inward of the buckets. At the same time, the angel-wing seals control/minimize the amount of purge/cooling air (see flow arrows 50, 52) in the radially-inner wheelspace from escaping into the hot gas path.
In conventional arrangements, the cover plates 20, 22 may be provided in the form of one or more arcuate segments which combine to form a substantially complete 360° cover plate assembly. In those arrangements where cover plates are formed with angel-wing seals, the seals will also be segmented, and will also together form 360° seals.
In an exemplary but nonlimiting embodiment of the invention, the angel-wing seals are provided as discrete seal elements detachably mounted on respective cover plate segments. It will be appreciated that the discussion below applies to the cover plates on both the upstream and downstream sides of the buckets, but for convenience only one cover plate/angel-wing seal configuration will be described in detail.
With reference now to
In this exemplary embodiment, the rail 64 of the angel-wing seal segment 66 supports a single angel-wing seal flange 74 of otherwise conventional size and shape.
In a variation illustrated in
In another variation shown in
It will be appreciated that the invention contemplates any suitable fastening arrangement between the angel-wing seal segment and the cover plate segment, as well as providing more than two radially-spaced angel-wing seals on an angel-wing seal segment.
For all of the described embodiments, it will be understood that the arcuate extent of the cover plate/angel-wing seal segments may vary. For example, the bucket or blade edges, cover plate edges, and seal edges may all be aligned; the cover plate edges and seal edges may be aligned but overlap the edges of one or more of the buckets or blades; or the the bucket or blade edges and cover plate edges may be aligned, with the seal edges overlapping one or more of the bucket or blade and cover plate edges
It is also contemplated that the cover plates and angel-wing seal segments may be locked in desired circumferential positions by means of axially-extending pins, other hard stops, or other known retention methods which need not be described.
In addition, the non-inegral arrangements described herein permit the use of different materials for the cover plates and angel-wing seal segments. For example, higher temperature-capable material may be used for the angel-wing seals and lower temperature-capable materials used for the cover plates.
While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within 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 essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best modes contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
