BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the bucket vibration damping system as is described herein.
FIG. 2 is a side plan view of bucket vibration damping system of FIG. 1 as positioned within two adjoining buckets.
FIG. 3 is a perspective view of an alternative embodiment of a bucket vibration damping system as is described herein.
FIG. 4 is a side plan view of bucket vibration damping system of FIG. 3 as positioned within two adjoining buckets.
DETAILED DESCRIPTION
Referring now to the drawings, in which like numerals refer to like elements throughout the several views, FIGS. 1 and 2 illustrate a bucket damping system 100 as is described herein. The bucket damping system 100 includes a number of buckets 105. The buckets 105 may include a bucket airfoil 110, a platform 120, a shank 130, a dovetail 140, and other elements. It will be appreciated that the bucket 105 shown is one of a number of circumferentially spaced buckets 105 secured to and about the rotor of a turbine. As described above, turbines generally have a number of rotor wheels having axial or slightly off axis dovetail-shaped openings for receiving the dovetail 140 of the bucket 105. Likewise, the airfoils 110 project into the gas stream so as to enable the kinetic energy of the stream to be converted into mechanical energy through the rotation of the rotor.
The airfoil 110 includes a convex side 150 and a concave side 155. Likewise, the airfoil platform 120 includes a leading edge 160 and a trailing edge 165 extending between the convex side 150 and the concave side 155. A pair of generally axially spaced support ledges 170 may be positioned along the convex side 155 of the bucket 105. Likewise, an undercut 180 may be positioned within the bucket platform 120 from the leading edge 160 to the trailing edge 165 along the concave side 150 on the other end. The undercut 180 includes an angled surface 190 that may extend the full axial length of the bucket 105.
FIGS. 1 and 2 also show a damper pocket 200 as is described herein. The damper pocket 200 may be positioned just above the support ledges 170 on the convex side 150. The damper pocket 200 may have a tangential depth that may vary within the bucket platform 120. The variable tangential depth accommodates effective damping while minimizing bucket stresses. The pocket 200 may be deeper at the leading and trailing ends 160, 165 away from the load path of the airfoil 110. Specifically, the damper pocket 200 may be shallower under the airfoil hi-C location. (The point at which the gas flow reverses its direction on the convex side 150 of the airfoil 110 is known as the hi-C point.) Stress at this location is generally higher than surrounding locations. As such, a decrease in the depth of the damper pocket 200 at this location would assist in reducing overall bucket stress. Other shapes and depths may be used herein so as to accommodate the bucket 105 as a whole.
The pocket 200 also may have an angled surface 210 on one end. The angled surface 210 ensures proper installation of a damper pin as will be described in more detail below. The damper pocket 200 may be machined within the platform 120. Other types of manufacturing techniques may be used herein as will be explained in more detail below.
FIG. 2 shows the use of the bucket 105 with an adjoining bucket 220. Likewise, positioned within the damper pocket 200 may be a damper pin 230. As is shown, the damper pin 230 may be an elongated, generally triangularly shaped element with a pair of axially spaced bosses 240 on either end. The bosses 240 may be positioned on the support ledges 170. The damper pine 230 may have any convenient shape. The damper pin 230 is positional within the damper pocket 200 of the bucket 105 and underneath the angled surface 190 of the undercut 180 of the adjoining bucket 220. As is shown, the pocket 200 and the undercut 180 only partially enclose the damper 230. As such, it is possible to confirm that the damper pin 230 has been installed properly therein after assembly. The damper pin 230 also may have an angled surfaced 250 on one end. The angled surface 250 is designed to accommodate the angled surface 210 of the damper pocket 200 so as to ensure proper installation.
The damper pin 230 may have some play or space within the damper pocket 200 and the undercut 180. Once the bucket 100 obtains full speed, however, the damper pin 230 will engage the upper surface of the damper pocket 200 and the undercut 180 via centrifugal force such that both buckets 105, 220 are engaged. As such, the vibration of the buckets 105, 220 is dissipated by the contact between the damper pin 230 and the buckets 105, 220.
The damper pocket 200 thus radially and axially restrains the damper pin 230 in its proper position. Likewise, the support ledges 170 support the damper pin 230 when the bucket 105 is not rotating and under centrifugal force. The angled surface 210 of the damper pocket 200 also ensures proper installation of the damper pin 230. The variable tangential depth of the damper pocket 200 allows improved damping at the leading and trailing ends 160, 165 of the bucket 105 while minimizing the stress concentrations at the hi-C location.
FIGS. 3 and 4 show a further embodiment of a bucket damping system 300 as is described herein. As above, the bucket damping system 300 includes a bucket 305 with a damper pocket 310. The damper pocket 310 is largely similar to the damper pocket 200 with the exception that the damper pocket 310 is cast as opposed to machined. The bucket pocket 310 also fully encloses the damper pin 230. Specifically, the damper pocket has an enclosure 320 on the leading end 160 and on the trailing end 165. The enclosures 320 restrain the damper pin 230 axially and also minimize the cross shank leakage area. The damper pin 230, however, can still be seen so as to allow visual inspection and confirmation that the damper pin 230 has been properly installed.
It should be readily apparent that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
Patent Application
20070286734
