Patent Description:
Many seals are utilized in gas turbine engines to isolate various parts of the gas turbine engine. One example of a sealing location is in a high speed rotor of the gas turbine engine, where a piston ring seal is utilized to seal between a rotor tie shaft and a rotor disc, to isolate adjacent cavities. During operation of the gas turbine engine, the tie shaft and the rotor disc experience relative motion, such as relative axial or radial motion, due to operating conditions such as pressure, temperature and centripedal forces. The piston ring seal is a split ring, which cannot support its own centripedal weight and therefore must transfer that force to the rotor disc radially outboard of the piston ring seal. The relative motion causes the piston ring seal to be dragged against these mating parts under significant force causing damaging wear to the piston ring seal and/or to the tie shaft or rotor disc, and deterioration of function of the seal over time.

<CIT> discloses a rotating assembly of a gas turbine engine comprising the features of the pre-characterizing portion of claim <NUM>.

According to a first aspect of the present invention, there is provided a rotating assembly of a gas turbine engine according to claim <NUM>. Optionally an axial distance between the first axial stop and the second axial stop is greater than an axial length of the shuttle located therebetween.

Optionally the shuttle extends circumferentially unbroken around the second rotating component.

Optionally the shuttle is formed from a material having similar thermal properties to the second rotating component.

Optionally the piston ring has a split ring configuration.

According to another aspect of the present invention, there is provided a rotor assembly of a gas turbine engine according to claim <NUM>. The rotor assembly includes a plurality of rotors arranged along an engine central longitudinal axis between a forward rotor hub and an aft rotor hub. A tie shaft is located radially inboard of the plurality of rotors and rotatable therewith about the engine central longitudinal axis. A seal assembly is configured to seal between a rotor of the plurality of rotors and the tie shaft. The seal assembly includes a shuttle located on a radial outer surface of the tie shaft and freely axially movable along the radial outer surface, and a piston ring seal retained in the shuttle and engaged with the rotor. Axial motion of the rotor relative to the tie shaft urges movement of the shuttle along the radial outer surface of the tie shaft, while the position of the piston ring seal remains stationary relative to the rotor.

Optionally a first axial stop and a second axial stop are located at the tie shaft between which the shuttle is axially retained.

According to another aspect of the present invention, there is provided a gas turbine engine including a combustor and a rotor assembly operably connected to the combustor, according to claim <NUM>. The rotor assembly includes a plurality of rotors arranged along an engine central longitudinal axis between a forward rotor hub and an aft rotor hub, and a tie shaft located radially inboard of the plurality of rotors and rotatable therewith about the engine central longitudinal axis. A seal assembly is configured to seal between a rotor of the plurality of rotors and the ties shaft. The seal assembly includes a shuttle located on a radial outer surface of the tie shaft and freely axially movable along the radial outer surface, and a piston ring seal retained in the shuttle and engaged with the rotor. Axial motion of the rotor relative to the tie shaft urges movement of the shuttle along the radial outer surface of the tie shaft, while the position of the piston ring seal remains stationary relative to the rotor.

The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans.

Referring now to <FIG>, illustrated is a partial view of an embodiment of the high speed spool <NUM> with the high pressure compressor <NUM> and the high pressure turbine <NUM>. The high pressure compressor <NUM> includes a plurality of compressor rotors <NUM> located between a forward compressor hub <NUM> and an aft compressor hub <NUM>. A high pressure compressor (HPC) tie shaft <NUM> extends radially inboard of the compressor rotors <NUM> and engages the forward compressor hub <NUM> and the aft compressor hub <NUM>. In some embodiments, a high pressure turbine (HPT) tie shaft <NUM> extends radially inboard of high pressure turbine rotors <NUM> of the high pressure turbine <NUM> and engages the HPC tie shaft <NUM>. A spanner nut <NUM> engages an axially downstream end of the HPC tie shaft <NUM> to compress the plurality of compressor rotors <NUM> between the forward compressor hub <NUM> and the aft compressor hub <NUM>.

The structure defines two or more rotor compartments between the HPC tie shaft <NUM> and the compressor rotors <NUM>, for example, a first rotor compartment <NUM> and a second rotor compartment <NUM>. Referring now to <FIG>, it may be desired to isolate the first rotor compartment <NUM> from the second rotor compartment <NUM>, and thus a seal assembly <NUM> is located at a compressor rotor <NUM>, for example, a sixth stage compressor rotor <NUM> of the compressor rotors <NUM> and extends between the compressor rotor <NUM> and the HPC tie shaft <NUM>. While in the embodiment of <FIG>, the seal assembly <NUM> is located at the sixth stage compressor rotor <NUM>, one skilled in the art will readily appreciate that the seal assembly <NUM> may be located at other locations along the HPC tie shaft <NUM>, for example other compressor rotors <NUM>, and that in some embodiments multiple seal assemblies <NUM> may be utilized.

The seal assembly <NUM> is illustrated in more detail in <FIG>. As shown, the seal assembly <NUM> includes a piston ring seal <NUM> engaging the compressor rotor <NUM>, in some embodiments an inner bore surface <NUM> of the compressor rotor <NUM>. In some embodiments, two piston ring seals <NUM> may be utilized. The piston ring seals <NUM> are circumferentially split rings, and thus a configured to radially "grow" during operation of the gas turbine engine <NUM> into engagement with the compressor rotor <NUM>.

The piston ring seals <NUM> reside in a shuttle <NUM> located at the HPC tie shaft <NUM>. The HPC tie shaft <NUM> includes a radial shaft surface <NUM> on which a complementary shuttle base <NUM> of the shuttle <NUM> rests. The shuttle <NUM> further includes a forward axial leg <NUM> and an aft axial leg <NUM> extending from the shuttle base <NUM> and defining a shuttle pocket <NUM> therebetween. The piston ring seals <NUM> are at least partially inserted into the shuttle pocket <NUM>. The HPC tie shaft <NUM> includes a shoulder <NUM> located at a first end of the shuttle <NUM>, for example axially forward of the shuttle <NUM>, and a retainer <NUM> installed to the HPC tie shaft <NUM> at a second end of the shuttle <NUM>, for example axially aft of the shuttle <NUM>. While in some embodiments, such as shown in <FIG>, the shoulder <NUM> is located axially forward of the shuttle <NUM> and the retainer <NUM> is installed to the HPC tie shaft <NUM> axially aft of the shuttle <NUM>, in other embodiments the configuration may be substantially mirrored or reversed. In some embodiments, the shoulder <NUM> may be located axially aft of the shuttle <NUM> and the retainer <NUM> is located axially forward of the shuttle <NUM>. The shoulder <NUM> and the retainer <NUM> define a shaft pocket <NUM> in which the shuttle <NUM> resides. A shaft pocket axial width <NUM> is greater than a shuttle width <NUM> such that the shuttle <NUM> is axially movable along the radial shaft surface <NUM> between the shoulder <NUM> and the retainer <NUM>. The shuttle <NUM> includes a forward arm <NUM> extending axially forward from the forward axial leg <NUM> at least partially over the shoulder <NUM>, and an aft arm <NUM> extending axially aft from the axial aft leg <NUM> at least partially over the retainer <NUM>, to act as a radial locator for the shuttle <NUM> and a guide during axial movement of the shuttle <NUM>, and to further reduce leakage across the shuttle <NUM>.

The shuttle <NUM> is a full hoop component extending entirely circumferentially unbroken around the HPC tie shaft <NUM>, and formed from a material with similar thermal properties as the HPC tie shaft <NUM> such that during operation the shuttle <NUM> maintains a close clearance to the HPC tie shaft <NUM> to prevent leakage. The shuttle <NUM> is axially retained between the shoulder <NUM> and the retainer <NUM>, and is freely axially movable therebetween. During operation of the gas turbine engine <NUM>, the piston ring seals <NUM> will establish an equilibrium position relative to the compressor rotor <NUM> and engage the compressor rotor <NUM>, and the shuttle <NUM> will likewise be axially positioned by the position of the piston ring seals <NUM>. Based on movement of the HPC tie shaft <NUM> relative to the compressor rotor <NUM>, however, the axial position of the shuttle <NUM> between the shoulder <NUM> and the retainer <NUM> will vary. As the relative motion of the compressor rotor <NUM> and the HPC tie shaft <NUM> changes, the shuttle <NUM> will move axially between the shoulder <NUM> and the retainer <NUM>, while the piston ring seals <NUM> remain engaged in a same position to the compressor rotor <NUM>. Since the piston ring seals <NUM> remain stationary relative to the compressor rotor <NUM> to which it is engaged, wear of the piston ring seals88 and the compressor rotor <NUM> is greatly reduced, while the seal of the piston ring seals <NUM> to the compressor rotor <NUM> is maintained.

Claim 1:
A rotating assembly of a gas turbine engine, comprising:
a first rotating component (<NUM>, <NUM>);
a second rotating component (<NUM>) disposed radially inboard of the first rotating component, relative to an engine central longitudinal axis; and
a seal assembly (<NUM>) configured to seal between the first rotating component and the second rotating component, the seal assembly including:
a shuttle (<NUM>) disposed on a radial outer surface (<NUM>) of the second component and freely axially movable along the radial outer surface; and
a piston ring seal (<NUM>) retained in the shuttle and engaged with the first rotating component;
a first axial stop (<NUM>) and a second axial stop (<NUM>) at the second rotating component (<NUM>) between which the shuttle (<NUM>) is axially retained;
wherein the shuttle comprises a forward axial leg (<NUM>) and an aft axial leg (<NUM>) extending from the shuttle base (<NUM>) and defining a shuttle pocket (<NUM>) therebetween and into which the piston ring is installed; and
wherein axial motion of the first rotating component (<NUM>, <NUM>) relative to the second rotating component (<NUM>) urges movement of the shuttle (<NUM>) along the radial outer surface (<NUM>) of the second rotating component, while the position of the piston ring seal (<NUM>) remains stationary relative to the first rotating component;
characterized in that the shuttle further comprises a forward arm (<NUM>) extending axially forward from the forward axial leg (<NUM>) and an aft arm (<NUM>) extending axially aft from the aft axial leg (<NUM>); the forward arm at least partially overlapping one of the first axial stop or the second axial stop and the aft arm at least partially overlapping the other of the first axial stop and the second axial stop, wherein the first axial stop is a shoulder (<NUM>) formed on the second rotating component (<NUM>), and the second axial stop is a retainer (<NUM>) secured to the second rotating component.