Patent Description:
Gas turbine engines are known, and typically include a fan delivering air into a bypass duct for propulsion, and into a core engine where it is compressed. The compressed air is delivered into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate. The turbine rotors, in turn, drive compressor rotors and the fan. Shafts connect the turbine rotors to the compressor and fan rotors.

Bearings support these shafts. The bearings may be provided with lubricant, and thus it is desirable to seal a compartment on each axial side of the bearings.

Face seal arrangements are utilized in the prior art. A seal seat rotates with the shaft on each side of the bearing. A face seal is biased in contact with the seal seat.

Typically a spring force biases the face seal against the seal seat. Pressurized air acting on a surface of the face seal also provides a bias force.

In the prior art the balance ratio, which is the area over which the pressurized air acts on the face seal taken as a ratio to the entire sealing face area of the face is relatively high. In addition, with this arrangement the spring force has been relatively high. This has resulted in challenges for operation of the prior face seal arrangements. A high axial closing force results in high heat generation, and sometimes oil coking and result in reduced service life.

<CIT> discloses a prior art seal assembly for arranging between a stator and a rotor.

<CIT> discloses a prior art mechanical seal with a balance ratio.

<CIT> discloses a prior art face seal arrangement comprising a seal support, a seal housing, and a carbon seal.

<CIT> discloses a prior art balanced mechanical seal assembly for providing a fluid-tight seal between a rotating shaft and a stationary housing.

<CIT> discloses a prior art oil weepage return for carbon seal plates.

<CIT> discloses a prior art mechanical seal for sealing a fluid that may leak from a sliding face.

<CIT> discloses a prior art self-aligning spiral groove face seal.

<CIT> discloses a prior art non-contacting mechanical end face seal.

According to a first aspect of the present invention, there is provided a face seal arrangement as set forth in claim <NUM>.

In another embodiment according to the previous embodiment, the balance ratio is between <NUM> and <NUM>.

In another embodiment according to any of the previous embodiments, the seal housing is formed of one of a titanium alloy and a ceramic.

In another embodiment according to any of the previous embodiments, the seal seat has a radially outermost surface and the sealing ring has a radially outermost surface. The seal seat radially outermost surface extends radially outward of the sealing ring radially outermost surface.

In another embodiment according to any of the previous embodiments, the seal seat has a radially outermost surface and the sealing ring has a radially outermost surface. The seal seat radially outermost surface is radially inward of the sealing ring radially outermost surface.

In another embodiment according to any of the previous embodiments, the seal seat has an inner diameter and an outer diameter. There is a plurality of slots circumferentially spaced and have an inlet to receive oil from an inner diameter of the seal seat and a circumferentially spaced outlet to outlet oil to an outer diameter of the seal seat and a plurality of drain grooves circumferentially spaced and radially inward of the slots. A supply groove connects the inner diameter to the inlet in the slots and a discharge groove connects the outlet of the slots to the outer diameter. A drain groove discharge groove communicates the drain grooves to the outer diameter.

In another embodiment according to any of the previous embodiments, the supply groove, the discharge groove and the drain groove discharge groove all extend at an angle that is not directly radially outward of a rotational axis of the seal seat. The seal seat rotates in a first circumferential direction. The angles of each of the supply groove, the discharge groove and the drain groove discharge groove have a radially outward component and a component in a circumferential direction opposed to the first circumferential direction.

According to a further aspect of the present invention, there is provided a gas turbine engine as set forth in claim <NUM>.

In another embodiment according to any of the previous embodiments, the at least one compressor rotor includes a high speed compressor rotor and a low speed compressor rotor. The at least one turbine rotor includes a high speed turbine rotor and a low speed turbine rotor. A low speed turbine rotor drives the low speed compressor rotor through a low speed shaft. The high speed turbine rotor drives the high speed compressor rotor through a high speed shaft.

In another embodiment according to any of the previous embodiments, the high speed shaft is the shaft supported by the bearing.

In another embodiment according to any of the previous embodiments, the low speed shaft is the shaft supported by the bearing.

In another embodiment according to any of the previous embodiments, the low speed shaft also drives the fan rotor through a gear reduction, and the gear reduction drives a fan shaft. The fan shaft is the shaft supported by the bearing.

The fan section <NUM> of the engine <NUM> is designed for a particular flight conditiontypically cruise at about <NUM> Mach and about <NUM>,<NUM> feet (<NUM>,<NUM> meters). "Low corrected fan tip speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (<NUM> °R)]<NUM> (where °R = K × <NUM>/<NUM>).

In an engine such as <FIG> bearings <NUM> support the shafts. <FIG> shows one such bearing <NUM> supporting the shaft <NUM> of the high speed spool. A face seal arrangement <NUM> is shown at each of two sides of a bearing compartment <NUM>. As known, bearing compartment <NUM> may be supplied with lubricant, and the face seal arrangements <NUM> seal the compartment to resist migration of the lubricant outwardly of the compartment <NUM>.

The face seal arrangements <NUM> include a rotating seal seat <NUM> which rotates with the shaft <NUM>, and a non-rotating face seal <NUM>.

While the shaft <NUM> is disclosed as part of the high speed spool, the seals of the disclosure could provide benefits at any of the bearing locations shown in <FIG>. That is, the seals could be associated with bearings supporting the low speed spool or the gear reduction and fan shaft.

<FIG> shows details of face seal arrangement <NUM> having the seal seat <NUM> and the face seal <NUM>. Non-rotating face seal <NUM> includes a sealing ring <NUM> having a sealing face <NUM> biased into contact with the seal seat <NUM>. The sealing ring <NUM> includes a mount portion <NUM>, a first groove <NUM> on an opposed side of the sealing face <NUM> from the seal seat <NUM>. As known, the groove <NUM> provides a bias area that will see high pressure air and will bias the sealing face <NUM> against the seal seat <NUM>. A second groove <NUM> is shown radially outwardly of the sealing face <NUM>.

The groove <NUM> results in a sealing face <NUM> of a desired size. A proud face <NUM> also remains in the sealing ring <NUM> forward of a forward end <NUM> of a seal housing <NUM>. With wear on the sealing face <NUM> the proud face will prevent contact between the forward end <NUM> of seal housing <NUM> and the seal seat <NUM>.

Generally the seal seat is formed of a metal such as steel, titanium or nickel based alloys. However, ceramics or molybdenum alloys may also be utilized.

A chamber <NUM> associated with the pressure face provided by groove <NUM> is at relatively high air pressure. A compartment <NUM> associated with the groove <NUM> and proud face <NUM> is at relatively low air pressure.

A seal housing <NUM> carries the sealing ring <NUM> and provides a mount area for a coil spring <NUM>. Coil spring <NUM> is mounted about a spring guide <NUM>.

The air pressure force from the pressure face created by the groove <NUM> and the force of the coil springs <NUM> bias the sealing ring sealing face <NUM> against the rotating seal seat <NUM>.

Note, this Figure is not drawn to scale.

<FIG> shows an exploded view of the support case <NUM>, coil springs <NUM>, seal housing <NUM>, sealing ring <NUM>, and the seal seat <NUM>.

<FIG> shows a face seal arrangement <NUM>. Face seal arrangement <NUM> includes a seal housing <NUM> mounting coil springs <NUM>. The sealing ring <NUM> has the mount portion <NUM>, a sealing face <NUM> and grooves <NUM> and <NUM>. A balance ratio can be defined between an area A<NUM>, which is the area of the face created by the groove <NUM> against which high pressure air in compartment <NUM> biases the sealing ring <NUM> sealing face <NUM> against seal seat <NUM>, and area A<NUM> which is the contact area of the sealing face <NUM>.

In this embodiment, the radially outer surface <NUM> of the seal seat <NUM> is shown extending radially outwardly of a radially outermost portion <NUM> of the proud face <NUM> of the sealing ring <NUM>.

In the prior art this balance ratio has been relatively high, and typically between <NUM> and <NUM>. Applicant has determined that reducing this balance ratio will reduce some of the concerns in the Background of the Invention section above. This reduction in the balance ratio reduces seal axial closing force and heat generation, resulting in lower component temperatures. This will mitigate and reduce oil coke formation, resulting in reduced seal wear and improved seal reliability. Thus, as shown in <FIG>, the balance ratio is reduced. In embodiments, the balance ratio may be between <NUM> and <NUM>. More narrowly, the balance ratio might be between <NUM> and <NUM>. In one seal embodiment the balance ratio was <NUM>.

However, to allow the reduction and balance ratio, other changes may be suggested.

<FIG> shows another embodiment <NUM>. The sealing ring <NUM> has the mount portion <NUM>, the groove <NUM> associated with a compartment <NUM> receiving high pressure air, a sealing face <NUM> and a groove <NUM>. Here, the balance ratio between areas A<NUM> and A<NUM> may be in the same ranges as in the <FIG> embodiment. However, as can be appreciated by comparing the two Figures, the area A<NUM> and the area A<NUM> are each smaller than in <FIG>. This may provide even greater advantages, such as reducing overall seal axial closing force and heat generation, thus resulting in lower component temperatures. This should mitigate and reduce oil coke formation. Resulting benefits include reduced seal wear, and improves seal reliability.

According to the invention, a width quantity is defined that speaks to the relative sizes of the sealing faces in the <FIG> and <FIG> sealing ring embodiments. The width quantity is:
WIDTH QUANTITY = (BR×W)/D; wherein BR is the balance ratio, W is the radial width of the sealing face and D is the outer diameter.

For the <FIG> embodiment, the width quantity ranges between <NUM> and <NUM>. For the <FIG> embodiment, the width quantity ranges between <NUM> and <NUM>. The benefits such as mentioned above flow from the other aspects disclosed in this application, but also the reduced width quantity for the <FIG> embodiment compared to <FIG>.

In the embodiment of <FIG>, the radially outermost surface <NUM> of the seal seat <NUM> is radially inward of the radially outermost portion <NUM> of the proud face <NUM> sealing ring <NUM>.

While the sealing ring may be described as a carbon ring, this should not be interpreted as requiring the ring to be formed of carbon. Note sealing rings may include graphitic carbon or electrographitic carbon. However, ceramics and metallics may also be utilized within the scope of this disclosure.

Details of the seal seat <NUM>/<NUM> are illustrated in <FIG>. A sealing face <NUM> would be in contact with the sealing faces <NUM>/<NUM>. There is an inner diameter <NUM> and an outer diameter <NUM>. The ring is shown having a counter-clockwise direction of rotation in this Figure. There are a plurality of slots <NUM>, which may be called oil slots or pools. In addition, each slot <NUM> has an inlet <NUM> and an outlet <NUM>. Outlet <NUM> is spaced from the inlet <NUM> in a direction opposed to the direction of rotation. An oil slot or groove <NUM> extends from an inlet associated with the inner diameter <NUM> and communicates with the inlet <NUM> in the oil slots <NUM>. An outlet drain hole <NUM> carries oil from outlet <NUM> to the outer diameter <NUM>.

A plurality of drain grooves <NUM> are positioned radially inward of the slots <NUM>. Discharge grooves <NUM> extend from a downstream circumferential end of the grooves <NUM> to the outer periphery <NUM>. Discharge grooves <NUM> could be at the other circumferential locations in grooves <NUM>.

Grooves and drain holes <NUM>, <NUM> and <NUM> extend at an angle that is not directly radially outwardly relative to a rotational or central axis of the seal seat <NUM>/<NUM>. The angle extends with a radially outward component, but also with a circumferential component opposed to the direction of rotation. In alternative embodiments, the grooves may extend at different angles, including directly radially outwardly, or any number of angles include <NUM> degrees, <NUM> degrees, <NUM> degrees, <NUM> degrees, etc..

The provision of the oil to the interface between the sealing faces <NUM>/<NUM> and the seal seat is particularly important given the reduced balance ratio of this disclosure.

This structure would also be preferably found in the seal seat <NUM>.

With either embodiment further enhancements might improve the functioning of the face seal arrangements. As an example, the moment of inertia of the seal housing and the sealing ring may be reduced. A reduced density may be utilized for the sealing ring than has been the case in the prior art. Further, the weight of the seal housing may be reduced. Typically in the prior art, the seal housings were formed of steel or nickel. The seal housing <NUM> may be formed of titanium alloy or ceramics, thus reducing the weight and the moment of inertia. All of these changes allow a reduction in the spring force provided by the coil spring <NUM> compared to the prior art.

Claim 1:
A face seal arrangement (<NUM>) for a gas turbine engine, the face seal arrangement comprising:
a seal seat (<NUM>) configured for rotating with a shaft;
a seal housing (<NUM>); and
a non-rotating face seal, said non-rotating face seal including a sealing ring (<NUM>) mounted to said seal housing (<NUM>), said sealing ring (<NUM>) including a mount portion mounted to said seal housing (<NUM>) and a sealing face (<NUM>) biased into contact with said seal seat (<NUM>), said sealing ring (<NUM>) also having a groove (<NUM>) defined remote from said seal face relative to said seal seat (<NUM>), and said groove (<NUM>) providing a pressure face that will be exposed to high pressure air, and a coil spring (<NUM>) biasing said seal housing (<NUM>) towards said seal seat (<NUM>), such that said sealing face (<NUM>) of said sealing ring (<NUM>) is biased into contact with seal seat (<NUM>) by air pressure against said pressure face, and said coil spring (<NUM>); and
a balance ratio defined between an area (A<NUM>) of said pressure face created by the groove (<NUM>) against which high pressure air biases said sealing face (<NUM>) of said sealing ring (<NUM>) into contact with said seal seat (<NUM>), and an area (A<NUM>) of said sealing face (<NUM>), which is the contact area of the sealing face (<NUM>),
characterized in that:
said balance ratio is between <NUM> and <NUM>; and
a width quantity is defined as the balance ratio multiplied by a radial width of the sealing face (<NUM>) divided by an outer diameter of the sealing ring (<NUM>) at the sealing face (<NUM>), and said width quantity being between <NUM> and <NUM> or between <NUM> and <NUM>.