Reverse Pressure Capable Finger Seal

To extend the benefits of finger seals to applications that may have reversing pressures, a new design is required that prevents air from traveling directly from the low side to the high side by passing through the pressure balance circuit. This can be accomplished by designing a seal that includes two separate stacks of laminates, oriented so that air passing between the two cavities on either side of the seal must pass through both sets of laminates. A cavity exists between the two sets of laminates and a plate may be installed between them. This intermediate plate between each stack of laminates is optional, and omitting it does not change the overall function of the seal. Cover plates are installed at either end of this seal, which each contains a pressure balance cavity and dam.

When pressure is applied to the reverse capable finger seal design, the upstream set of laminates (the set of laminates on the side of the seal facing the high pressure) is pushed away from the dam on its cover plate. As air leaks past the upstream laminates, it flows into the pressure balance cavity, through the pressure balance circuit, and into the cavity between the two sets of laminates, causing it to pressurize. Due to the rising pressure in the cavity between the sets of laminates, the downstream set is axially loaded into the dam on the downstream cover plate.

The direction of pressure applied to the seal can be reversed, and the two sets of laminates will also reverse roles, with the set formerly acting as the upstream laminates becoming the downstream, and vice versa. In this reversed pressure case, the one set again will be pushed away from its dam, allowing leakage to occur, while the other set will be pressed into the dam on its cover plate. This allows the seal to function equally well in either direction.

This work was done by Nathan Gibson and Joe Yanof of Honeywell International for the Air Force Research Laboratory. AFRL-0215