A self-contained impact-type damper for a bellows-type face seals suppresses dynamic instability or chatter. In current practice, damping in a typical seal is accomplished through rubbing contact between a ground (a stationary member) and a bellows or carrier as the seal translates. Usually, the rubbing contact occurs through a third member. This contact results in the potential for the carrier to seize, with consequent limitation of axial travel. It also makes for a complicated assembly, susceptible to assembly error.

A Self-Contained Impact-Type Damper has been incorporated into an advanced bellows-type lift-off face seal in a high-pressure turbopump.

The self-contained impact-type damper (see figure) consists of a damping medium contained in a pocket in an insert carrier. The medium consists of particles. The cavity is filled to less than its full volume with the particles, leaving some room for motion. Damping is accomplished when the particles impinge on each other and the cavity walls, absorbing energy from the carrier when it begins to vibrate.

This work was done by Richard James Kloepfer and Michael Howard Dills of UTC/Pratt & Whitney, Government Engines & Space Propulsion, for Marshall Space Flight Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Mechanics category, or circle no. 198 on the TSPOrder Card in this issue to receive a copy by mail ($5 charge).

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