Patent Description:
Gas turbine engines typically contain bearing compartments, or other wetted chambers. The bearing compartments contain oil and typically include dynamic seals with an air buffered cavity to retain the oil within the bearing compartment. Typically, seal systems are positioned to prevent the high temperature and pressure air from flowing into sensitive areas.

Loss of oil from the bearing compartments, at the location of the seals in particular, can have negative consequences to engine performance, durability, or operation. Oil that weeps through the seal system may also seep into the compressor system or turbine. Oil weepage into the compressor may lead to imbalance concerns or customer bleed contamination while bleeding into the turbine may lead to thermal operational effects. <CIT>, <CIT> and <CIT> disclose systems of the prior art.

A seal system for a bearing compartment of a gas turbine engine according to an aspect of the invention is provided by claim <NUM>.

A further embodiment of the foregoing embodiment includes that the oil return passageway is arranged about an engine central longitudinal axis, the oil return passageway angled with respect to the engine central longitudinal axis at an angle from between <NUM> - <NUM> degrees.

A further embodiment of any of the foregoing embodiments includes that the oil return passageway is arranged about an or the engine central longitudinal axis, the oil return passageway skewed at an angle from between <NUM> - <NUM> degrees.

A further embodiment of any of the foregoing embodiments includes that the oil return passageway is one of an array of oil return passageways arranged about an or the engine central longitudinal axis.

A further embodiment of any of the foregoing embodiments of the present invention includes that the dry seal interface is formed in part by an annular ridge of the annular seal element.

A further embodiment of the present invention includes that the outward facing shoulder of the annular rotating seal seat defines a radius R1 and the inwardly facing shoulder defines a radius R2; the annular rotating seal seat having an array of oil return passageways through the rotating seal seat around an engine longitudinal axis to provide the communication path from the dry zone annular space outboard of the rotating component back to the oilwetted zone, and that each of the array of oil return passageways being angled with respect to the engine central longitudinal axis at an angle from between <NUM> - <NUM> degrees and skewed at an angle from between <NUM> - <NUM> degrees.

A further embodiment of the present invention includes that the oil return passageway defines an inlet at an intersection between the outward facing shoulder of the annular rotating seal seat and the recessed face.

A further embodiment of the present invention includes that an inward facing seal edge of the seal element defines a radius R3 between R1 and R2.

A further embodiment of the present invention includes that the dry seal interface is formed in part by an annular ridge of the annular seal element, the annular ridge of the annular seal element defines a radial inner face outboard of the inward facing seal edge of the seal element.

A method for communicating wept oil back to an oil-wetted zone in a bearing compartment of a gas turbine engine according to another aspect of the invention is provided by claim <NUM>.

These features and elements as well as the operation of the invention will become more apparent in light of the following description and the accompanying drawings. It should be appreciated; however, the following description and drawings are intended to be exemplary in nature and non-limiting.

Alternative engine architectures might include an augmentor section and exhaust duct section among other systems or features.

The fan section <NUM> drives air along a bypass flowpath while the compressor section <NUM> drives air along a core flowpath for compression and communication into the combustor section <NUM> then expansion through the turbine section <NUM>. Although depicted as a turbofan in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines such as a low bypass augmented turbofan, turbojets, turboshafts, and three-spool (plus fan) turbofans wherein an intermediate spool includes an intermediate pressure compressor ("IPC") between a low pressure compressor ("LPC") and a high pressure compressor ("HPC"), and an intermediate pressure turbine ("IPT") between the high pressure turbine ("HPT") and the low pressure turbine ("LPT").

The engine <NUM> generally includes a low spool <NUM> and a high spool <NUM> mounted for rotation about an engine central longitudinal axis A relative to an engine static structure <NUM> via several bearing compartments <NUM>. The low spool <NUM> generally includes an inner shaft <NUM> that interconnects a fan <NUM>, a low pressure compressor <NUM> ("LPC") and a low pressure turbine <NUM> ("LPT"). The inner shaft <NUM> drives the fan <NUM> directly or through a geared architecture <NUM> to drive the fan <NUM> at a lower speed than the low spool <NUM>. An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system. The high spool <NUM> includes an outer shaft <NUM> that interconnects a high pressure compressor <NUM> ("HPC") and high pressure turbine <NUM> ("HPT"). A combustor <NUM> is arranged between the HPC <NUM> and the HPT <NUM>. The inner shaft <NUM> and the outer shaft <NUM> are concentric and rotate about the engine central longitudinal axis A which is collinear with their longitudinal axes.

Core airflow is compressed by the LPC <NUM> then the HPC <NUM>, mixed with fuel and burned in the combustor <NUM>, then expanded over the HPT <NUM> and the LPT <NUM>. The turbines <NUM>, <NUM> rotationally drive the respective low spool <NUM> and high spool <NUM> in response to the expansion. The main engine shafts <NUM>, <NUM> are supported at a plurality of points by respective bearing compartments <NUM>.

With reference to <FIG>, each of the multiple of bearing compartments <NUM> include one or more bearings <NUM> (one bearing of a bearing compartment illustrated schematically) and one or more seal system <NUM> (only the rear seal of the bearing compartment illustrated schematically). The bearing <NUM> and seal system <NUM> respectively support and interface with the shafts <NUM>, <NUM> (<FIG>) along the engine central longitudinal axis A.

The seal system <NUM> can include carbon seals, mechanical seals, brush seals, etc. The seal system <NUM> operates to seal the bearing compartments <NUM>, i.e., an oil-wetted zone <NUM> from a buffer air cavity <NUM>. So, for example, the interior of each bearing compartment <NUM> may be referred to as the oil-wetted zone while the region external thereto may be referred to as the dry zone. The bearings <NUM> support the low spool <NUM> and the high spool <NUM> and the seal system <NUM> separate the oil-wetted zone <NUM> from the dry zone <NUM> to define the boundaries of each bearing compartment <NUM>. Oil and air are typically exposed to the higher pressure which is typically present in the buffer air cavity <NUM>. A pump scavenges oil from the oil-wetted zone <NUM> which can then be introduced back into the oil-wetted zone <NUM> through a flow passage via spray nozzles N and the like which communicate with an annulus <NUM> in an outer diameter annular rotating seal seat <NUM> adjacent to an annular seal element <NUM> of the seal system <NUM>. Although particular bearing compartments and bearing arrangements are illustrated in the disclosed non-limiting embodiment, other bearing compartments and bearing arrangements in other engine architectures will also benefit herefrom.

With reference to <FIG>, the seal system <NUM> includes the annular seal element <NUM> and the annular rotating seal seat <NUM>. The seal system <NUM> is configured as a dry seal assembly; e.g., a dry face seal. The seal system <NUM> is configured with a substantially dry seal interface <NUM> between the seal element <NUM> and the rotating seal seat <NUM> to minimize oil weepage at the seal interface <NUM> between the seal element <NUM> and the rotating seal seat <NUM>.

The dry seal interface <NUM> minimizes the oil loss from the oil-wetted zone <NUM> when operable under a positive pressure differential during normal engine operation. The dry seal interface <NUM> is typically subject to low or zero pressure during engine start which may lead to oil loss from the oil-wetted zone <NUM>.

The rotating seal seat <NUM> is mounted for rotation with a rotating component <NUM> and may be axially located between an inner race <NUM> of the bearing <NUM> and another rotating component <NUM>; e.g., a tubular sleeve, slinger, etc. The rotating seal seat <NUM> may extend circumferentially at least partially around the rotating component <NUM>.

The seal element <NUM> has a radial seal surface <NUM> which is in interfacial contact with a radial seal face <NUM> (also shown in <FIG>). The seal element <NUM> is retained by a seal carrier <NUM> with the assembly being urged by spring system <NUM> (<FIG>) to maintain the sealing contact at the dry seal interface <NUM>.

A secondary seal such as a piston ring <NUM> (<FIG>) seals the inner circumference of the seal carrier <NUM> while permitting axial movement thereof under the bias of the spring system <NUM>. An inward facing seal edge <NUM> of the seal element <NUM> is displaced from a radial inner face <NUM> of an annular ridge <NUM> that forms the radial seal surface <NUM> to interface with the radial seal face <NUM>. The inner face <NUM> of the annular ridge <NUM> is adjacent to a dry zone annulus <NUM> adjacent to the dry seal interface <NUM>.

An inwardly facing shoulder <NUM> of the rotating seal seat <NUM> has a radius of R1. The radius of an outward facing shoulder <NUM> indicated as R2 while radius R3 at the inward facing seal edge <NUM> of the seal element <NUM>. A recessed face <NUM> is thereby formed between the inwardly facing shoulder <NUM> and the outward facing shoulder <NUM> of the rotating seal seat <NUM>. A ratio between R1 and R2 is thereby provided to facilitate startup oil to return back to the oil-wetted zone <NUM>.

The rotating seal seat <NUM> is configured with at least one oil return passageway <NUM>. Each oil return passageway <NUM> is formed from an inlet <NUM> at the intersection of the inwardly facing shoulder <NUM> and the recessed face <NUM> to an outlet <NUM> through an outwardly facing surface <NUM> of the seal seat <NUM>.

The oil return passageways <NUM> are arranged in an annular array about the engine axis A. Each oil return passageway <NUM> of the array may be angled with respect to the axis A at an angle W from between <NUM> - <NUM> degrees as well as being skewed (e.g. radially inclined) at an angle T from between <NUM> - <NUM> degrees (<FIG>). That is, the oil return passageways <NUM> provide a communication path for weepage oil from the dry zone annular space <NUM> outboard of the rotating component <NUM> back to the oil-wetted zone <NUM>.

Weepage oil from the seal interface <NUM> may collect within the dry zone annular space <NUM> when the engine is not in operation. The dry zone annulus <NUM> terminates with the dry zone annular space <NUM> which may be generally rectilinear in cross-sectional shape and adjacent to the rotating seal seat <NUM>. The oil return passageway <NUM> communicates oil weepage from the dry zone annular space <NUM> adjacent to the seal interface <NUM> between the seal element <NUM> and the rotating seal seat <NUM> to return the oil to the oil wetted zone <NUM>. The oil return passageways <NUM> provide substantial pumping action from the dry zone annular space <NUM> because of the centrifugal action thereon during engine operation. This ratio has been found to optimize the dry zone annular space <NUM> geometry within the rotating seal seat <NUM> to reduce the boundary layer and provide substantial pumping action from the dry zone annular space <NUM> without otherwise compromising the dry seal interface <NUM>. The oil return passageway <NUM> allows startup oil to return back to the oil-wetted zone <NUM>. This minimizes oil weepage from the compartment and potential leakage into the gaspath.

Although the different non-limiting embodiments have specific illustrated components, the embodiments are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.

It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.

Claim 1:
A seal system for a bearing compartment of a gas turbine engine comprising:
an annular seal element (<NUM>);
a rotating component (<NUM>) adjacent the seal element (<NUM>); characterised by
an annular rotating seal seat (<NUM>) in contact with the seal element (<NUM>) to form a dry seal interface (<NUM>) therebetween to separate an oil-wetted zone (<NUM>) from a dry zone (<NUM>), the annular rotating seal seat (<NUM>) forming a dry zone annular space (<NUM>) adjacent to the annular seal element (<NUM>) and the rotating component (<NUM>); and
the annular rotating seal seat (<NUM>) having an oil return passageway (<NUM>) through the rotating seal seat (<NUM>) to provide a communication path from the dry zone annular space (<NUM>) outboard of the rotating component (<NUM>) back to the oil-wetted zone (<NUM>);
wherein the dry zone annular space (<NUM>) is formed in part by a recessed face (<NUM>) between an inwardly facing shoulder (<NUM>) and an outward facing shoulder (<NUM>) of the annular rotating seal seat (<NUM>).