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Publication Date: 2014-Nov-24
Document File: 5 page(s) / 118K

Publishing Venue

The Prior Art Database


An AFS including a diverging feed hole is described herein. An AFS including a multiple stepped feed hole is also described herein.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 26% of the total text.

Page 01 of 5



    Aspirating face seals (AFSs) are non-contacting hydrostatic seals designed to improve the performance of a turbine engine by maintaining constant clearance at an air bearing surface defined between the stator and rotor during operation. For turbine engines, clearance is maintained using air flow from a high pressure area to the air bearing surface, and the performance of the turbine engine may be reduced when larger amounts of air flow are required. Moreover, operating conditions sometimes result in contact between the stator and rotor, despite the AFS. This contact is sometimes referred to as rub, and an AFS design must account for rub to ensure reliable operation over the lifetime of the engine.

    FIG. 1 is a cut-away view of a turbine engine including an AFS. FIG. 2 is a cut-away view of a known AFS design for use in the turbine engine shown in FIG. 1. Referring to FIGS. 1 and 2, the turbine engine includes a stator, a rotor, and an air bearing surface defined between the stator and the rotor. The AFS includes a straight feed hole extending through a stator face and coupling a high pressure area (PHIGH) with the air bearing surface. Air flow from the high pressure area generates pressure at the air bearing surface, the pressure resulting in a force on the stator face at the air bearing surface urging the stator face away from the rotor. The AFS also includes a bias element (e.g., a spring) for exerting a force urging the stator face toward the rotor. During operation, as the stator face moves further from the rotor, the force resulting from air flow is reduced and the force exerted by the bias element is increased. An equilibrium exists where the two forces cancel and the stator face is maintained a distance from the rotor.

    In the known design, the AFS suffers leakage at the air bearing surface due to the straight feed hole, and a larger amount of air is required to maintain air bearing pressure and clearance between the stator and rotor. The turbine engine's performance is reduced based on the larger amount of air required.

    Another known design of an AFS includes a counter-bored feed hole rather than a straight feed hole. FIG. 3 includes a simplified cut-away view of the counter-bored feed hole. The counter-bored feed hole enables the AFS to maintain air pressure at the air bearing surface with reduced air flow. Specifically, the counter-bored feed hole provides steep pressure- clearance characteristics at higher clearances, and double metering restriction based on operating clearance. However, an AFS including a counter-bored feed hole is susceptible to compromise

FIG. 2

FIG. 1

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over the life of the turbine engine due to rub. During operation, the stator face and rotor contact (or rub) which, over time, wears away the stator surface, effectively reducing the depth of the counter-bore. The AFS may be compromised when the stator surface is worn past the coun...