Patent Application
20070286732
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
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 on the convex side 150 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 convex 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.
Positioned within the damper pocket 200 may be a damper pin 230. As is shown in
The damper pin 230 also has a pair of axially spaced bosses 240, 250 on either end. The leading boss 240 may include a contact prong 260. The contact prong 260 includes a rounded crown 270 on one side thereof. Other shapes may be used herein. The use of the contact prong 260 prevents the damper 230 from sliding forward due to centrifugal force. The rounded crown 270 prevents any sharp edged snags and allows free sliding in the radial direction. The trailing end boss 250 may include an angled surface 280 with a short protrusion 290. The angled surface 280 comports with the angled surface 210 of the damper pocket 200 so as to ensure proper installation of the damper pin 230.
The damper pin 230 may have some play or space within the damper pocket 200 and the undercut 180. As described above, 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 once the buckets 105, 220 are at full speed. This contact is aided by the offset center of gravity 235. The frictional force between the damper pin 230 and the buckets 105, 220 thus dissipates the vibrational energy from the buckets 105, 220. Because the contact between the damper pin 230 and the buckets 105, 220 are at an incline from the trailing edge 165 to the leading edge 160, the damper pin 230 has a tendency to slide forward. The contact prong 260 of the leading boss 240 therefore restrains the damper pin 230 in its proper axial position.
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 when taken in conjunction with the angled surface 280 of the damper pin 230. The bucket damping system 100 thus provides improved damping effectiveness, minimizes the chances of lockup due to frictional forces, avoids interference with adjacent buckets, and prohibits rotation of the damper pin 230 during startups and shutdowns.
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.
