Patent Description:
A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section.

The compressor section can include rotors that carry airfoils to compress the air entering the compressor section. A shaft may be coupled to the rotors to rotate the airfoils.

<CIT> discloses a composite face seal having an annular seal rotor which has a metal base portion and a radially extending flange. The flange has first and second axially facing surfaces. A first ceramic ring may be mounted to the first surface of the flange of the seal rotor by a first braze joint. A second ceramic ring may be mounted to the second surface of the flange of the seal rotor by a second braze joint. Each of the braze joints may include a molybdenum ring disposed between two braze rings. <CIT> discloses a seal assembly comprising a split seal ring, the split seal ring extending at least partially into a groove and positioned between first and second components.

A rotor assembly for a gas turbine engine according to the present invention is presented in claim <NUM>.

In a further embodiment of any of the foregoing embodiments, the first layer comprises copper.

In a further embodiment of any of the foregoing embodiments, the first layer has a composition, by weight percent, <NUM>% to <NUM>% copper, and aluminum.

In a further embodiment of any of the foregoing embodiments, the first layer has a composition, by weight percent, <NUM>% to <NUM>% aluminum, and at least <NUM>% copper.

In a further embodiment of any of the foregoing embodiments, the substrate comprises a nickel alloy.

In a further embodiment of any of the foregoing embodiments, the annular seal extends about an outer diameter portion of the shaft.

In a further embodiment of any of the foregoing embodiments, the first layer has a composition, by weight percent, <NUM>% to <NUM>% copper, and at least <NUM>% aluminum.

In a further embodiment of any of the foregoing embodiments, the annular seal is a split ring including a seal body extending between a first end and a second, opposed end that engages with the first end.

In a further embodiment of any of the foregoing embodiments, the integrally bladed rotor is a compressor rotor, and the substrate of the annular seal is seated in an annular groove extending inwardly from the outer diameter portion of the shaft, and the second layer abuts against an inner diameter portion of the hub.

In a further embodiment of any of the foregoing embodiments, the molybdenum trioxide (MoO<NUM>) is formed from molybdenum disulfide (MoS<NUM>).

A gas turbine engine according to an the present invention is presented in claim <NUM>.

In a further embodiment of any of the foregoing embodiments, the compressor section includes a low pressure compressor and a high pressure compressor, and the integrally bladed rotor is a high pressure compressor rotor of the high pressure compressor.

A method of sealing for a gas turbine engine according to the present invention is presented in claim <NUM>.

In a further embodiment of any of the foregoing embodiments, the step of forming includes depositing the second layer directly on the first layer.

In a further embodiment of any of the foregoing embodiments, the step of forming includes depositing molybdenum disulfide (MoS<NUM>) on the first layer, and heating the molybdenum disulfide (MoS<NUM>), e.g. to a predetermined temperature threshold, to form the solid lubricant.

In a further embodiment of any of the foregoing embodiments, the piston ring includes a seal body extending between a first end and a second, opposed end that engages with the first end along an outer diameter portion of the shaft.

In a further embodiment of any of the foregoing embodiments, the hub defines a seal land that establishes the sealing relationship with the second layer.

In a further embodiment of any of the foregoing embodiments, the second layer is dimensioned to abut against an inner diameter portion of the hub to establish the sealing relationship.

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description.

<FIG> illustrates a rotor assembly <NUM> for a section <NUM> of a gas turbine engine, such as the compressor section <NUM> of <FIG>. Although the disclosure primarily refers to the compressor section <NUM>, other portions of the engine <NUM> may benefit from the teachings disclosed herein, such as the fan and turbine sections <NUM>, <NUM>, towershafts and auxiliary systems. Other systems may also benefit from the teachings herein, including marine systems, and ground-based systems lacking a fan for propulsion.

The section <NUM> includes a plurality of rotors <NUM> each including a disk or hub <NUM> that carries one or more rotatable blades or airfoils <NUM>. The airfoils <NUM> are rotatable about the engine axis A in a gas path GP, such as core flow path C. Each airfoil <NUM> includes a platform 64A and an airfoil section 64B extending in a spanwise or radial direction R from the platform 64A to a tip 64C. A root section 64D of each airfoil <NUM> extends outwardly from, and is mounted to, a respective hub <NUM>. In some examples, the root section 64D is received in a slot defined by the hub <NUM>. In the invention, as illustrated in the example of <FIG>, the rotor <NUM> is a blisk or integrated bladed rotor (IBR) in which the airfoils <NUM> are integrally formed with the hub <NUM>. In examples, the IBR is a compressor rotor, such as a high pressure compressor rotor of the high pressure compressor <NUM> coupled to the high pressure turbine <NUM>, or such as a low pressure compressor rotor of the low pressure compressor <NUM> coupled to the low pressure turbine <NUM>. Various techniques can be utilized to form the IBR, such as casting, additive manufacturing, machining from a solid work piece, or welding individual airfoils <NUM> to the hub <NUM>.

One or more rows of vanes <NUM> are positioned along the engine axis A and adjacent to the airfoils <NUM> to direct flow in the gas path GP. The vanes <NUM> can be mechanically attached to the engine static structure <NUM> (<FIG>). An array of seals <NUM> are distributed about each row of airfoils <NUM> to bound the gas path GP.

One or more of the rotors <NUM> are mechanically attached or otherwise fixedly secured to an elongated, rotatable shaft <NUM>. The shaft <NUM> is rotatable about the engine axis A. In examples, the shaft <NUM> interconnects a turbine and a compressor, such as one of the shafts <NUM>, <NUM> of <FIG>.

The rotor assembly <NUM> includes at least one annular seal <NUM>. The seal <NUM> can be located at one or more of the stages of the section <NUM>, such as an intermediate stage as illustrated by seal <NUM>, and/or a forwardmost or aftmost stage indicated by seals <NUM>', <NUM>" of rotor assemblies <NUM>', <NUM>" (<NUM>', <NUM>" shown in dashed lines for illustrative purposes). Each rotor assembly <NUM> can have a single seal as illustrated by seals <NUM>, <NUM>' or can have multiple seals as illustrated by seals <NUM>" of rotor assembly <NUM>".

<FIG> illustrates an enhanced view of a portion <NUM> of the rotor assembly <NUM>. The annular seal <NUM> is carried by, and extends about, an outer diameter portion 70A the shaft <NUM> for establishing a sealing relationship between the hub <NUM> of the rotor <NUM> and the shaft <NUM> to block or otherwise reduce communication of flow between adjacent cavities defined by the rotor <NUM> and shaft <NUM>. A cross section of the shaft <NUM> can have a circular or otherwise generally elliptical geometry.

The seal <NUM> can be a piston ring having a generally hoop-shaped geometry, as illustrated in <FIG>. In the illustrated example of <FIG>, the seal <NUM> is a split ring including a main body 74A extending between opposed first and second ends 74B, 74C. The first end 74B engages with the second end 74C at an interface along the outer diameter portion 70A of the shaft <NUM>. In other examples, the body 74A is continuous to form a full hoop.

The seal <NUM> is dimensioned to extend about a circumference of the shaft <NUM>. The shaft <NUM> includes an annular groove <NUM> extending inwardly from the outer diameter portion 70A. The groove <NUM> is dimensioned to receive at least a portion of the seal <NUM>. The seal <NUM> is seated in the groove <NUM> to establish a sealing relationship with an inner diameter portion 63A of the hub <NUM>. The seal <NUM> can be arranged such that the first end 74B engages with the second end 74C along the outer diameter portion 70A of the shaft <NUM>. The seal <NUM> can be exposed to relatively high temperatures due to proximity to the gas path GP and other portions of the engine <NUM>.

Referring to <FIG>, with continuing reference to <FIG>, the seal <NUM> has a multi-layer construction including a substrate <NUM> and a coating <NUM> including a plurality of layers. The coating <NUM> can include at least a first layer 80A and a second layer 80B. At least a portion of the substrate <NUM> is seated in the groove <NUM>, and the coating <NUM> is situated between the substrate <NUM> and the hub <NUM>. The second layer 80B can define an external surface of the seal <NUM>. The inner diameter portion 63A of the hub <NUM> defines a counter face or seal land. The second layer 80B can be dimensioned to abut against the hub <NUM> to establish a sealing relationship with the seal land. In the illustrative example of <FIG>, the second layer 80B is dimensioned and arranged to abut against or contact the inner diameter portion 63A of the hub <NUM>, or is otherwise in close proximity to the seal land, to establish the sealing relationship with the hub <NUM> along an interface <NUM>.

The first layer 80A can be disposed directly on the substrate <NUM>. The second layer 80B is disposed on the first layer 80A. In other examples, one or more layers of material are formed between the substrate <NUM> and first layer 80A and/or between the first and second layers 80A, 80B. The hub <NUM> can include a third layer <NUM> (shown in dashed lines for illustrative purposes) disposed on surfaces of the inner diameter portion 63A along the interface <NUM> to establish the seal land. In other examples, the third layer <NUM> is omitted.

Various materials can be utilized to form the rotor assembly <NUM>. The first layer 80A can be made of a first material, the second layer 80B can be made of a second material, and the substrate <NUM> can be made of a third material. The first, second and/or third materials can differ in composition and/or construction.

The substrate <NUM> and/or rotor <NUM> can comprise a high temperature metal or metal alloy, such as a nickel alloy. Example nickel alloys include nickel chromium alloy sold under the tradename INCONEL® alloy <NUM> (IN718) and Direct Age Processed Alloy <NUM> (DA718). In the illustrated example of <FIG>, the substrate <NUM> is made of IN718 and at least the inner diameter portion 63A of the hub <NUM> is made of DA718. In other examples, the substrate <NUM> comprises a cobalt alloy, e.g. a cobalt alloy sold under the tradename STELLITE® 6B, and the first layer 80A can be omitted.

The first layer 80A may be a relatively soft metal or metal alloy coating comprising copper or a copper alloy including aluminum or nickel, for example. In other examples, the first layer 80A is a nickel-based or molybdenum-based metal or metal alloy. In examples, the first layer 80A has a composition, by weight percent, of about <NUM>% to about <NUM>% copper, and aluminum, e.g. the balance is aluminum. In further examples, the first layer 80A has a composition, by weight percent, of about <NUM>% to about <NUM>% copper, and at least <NUM>% aluminum. In examples, the first layer 80A has a composition, by weight percent, <NUM>% to <NUM>% aluminum, and at least <NUM>% copper. In further examples, the first layer 80A has a composition, by weight percent, of about <NUM>% copper, and about <NUM>% aluminum. In other examples, the first layer 80A has a composition of copper including any of the weight percentages disclosed herein, and the balance is aluminum or nickel. For the purposes of this disclosure, the term "about" means ±<NUM>% of the disclosed weight percent value unless otherwise stated.

The second layer 80B can be a low friction coating comprising a solid lubricant. The second layer 80B can have a lesser hardness than the first layer 80A. Hardness of the layers 80A, 80B can be measured by means of nanoindentation.

In the illustrated example of <FIG>, the first layer 80A of the coating <NUM> is a layer of copper alloy disposed on the substrate <NUM>, and the second layer 80B is a solid lubricant disposed on the first layer 80A. A hardness of the copper-based coating can be relatively lower than other materials to reduce wear of the counter face and the solid lubricant that may otherwise occur due to the interface <NUM>. The second layer 80B provides a self-lubricating feature and can reduce frictional heating along the interface <NUM>.

The solid lubricant of the second layer 80B includes molybdenum trioxide (MoO<NUM>). The second layer 80B can be formed utilizing any of the techniques disclosed herein, including applying a solid lubricant such as molybdenum disulfide (MoS<NUM>) on the first layer 80A or substrate <NUM> and heat treating the solid lubricant to form MoOs. The solid lubricant can reduce a coefficient of friction (COF) between the seal <NUM> and the rotor <NUM> along the interface <NUM>, which can reduce wear and improve durability of the components of the rotor assembly <NUM>, including the seal <NUM> and rotor <NUM>. The second layer 80B can have a relatively lower COF than the first layer 80A of the coating <NUM>.

The third layer <NUM> of the hub <NUM> can be a solid lubricant, which can be the same or can differ from the solid lubricant of the second layer 80B. The solid lubricant of the third layer <NUM> can comprise MoS<NUM>, MoOs, boron nitride, tungsten disulfide, and carbon-based and graphite-based materials, for example. Applying a solid lubricant to the inner diameter portion 63A of the hub <NUM> can reduce leakage along the interface <NUM>.

During operation, the shaft <NUM> and each rotor <NUM> rotate as an assembly about the engine axis A. The seal <NUM> may move relative to the hub <NUM> along the interface <NUM> in axial, radial and/or circumferential directions X, R, C. The axial direction X can be coincidental or parallel to the engine axis A. Sliding or movement of the seal <NUM> along the interface <NUM> in the axial and/or circumferential directions X, C may occur due to relatively high vibratory energy in the system. The solid lubricant can reduce the COF and frictional heating along the interface <NUM>, which can reduce galling and other wear along the adjacent surfaces and can increase durability of the seal <NUM> and the rotor <NUM>. Reduced wear can reduce overhaul costs that may otherwise be associated with replacement or refurbishment of the seal <NUM>, shaft <NUM> and/or rotor <NUM>.

<FIG> illustrate example plots of COF versus cycles of rotor assemblies. The x-axis corresponds to the number of cycles of movement of the respective seal relative to the interface. The y-axis corresponds to the average COF. Values along the y-axis correspond to movement of the seal in a first direction. <FIG> illustrates curve <NUM> corresponding to average COF values for a seal having a copper-based coating free of a solid lubricant. <FIG> illustrates curve <NUM> corresponding to average COF values for the seal <NUM> having a copper-based coating and a MoOs-based solid lubricant. The MoOs-based solid lubricant can be formed from a MoOs-based solid lubricant utilizing any of the techniques disclosed herein.

As illustrated by <FIG>, the copper-based coating including a MoOs-based solid lubricant can reduce the average COF as compared to coatings free of a solid lubricant. In the illustrative example of <FIG>, the seal <NUM> has an average COF of less than <NUM>, such as less than <NUM> when the solid lubricant is first formed and between <NUM> and <NUM> subsequent to an initial break-in period of the seal <NUM>, whereas the average COF of curve <NUM> is greater than <NUM> for a comparable number of cycles. The combination of materials of the substrate <NUM>, layers 80A, 80B of coating <NUM> and/or hub <NUM> can reduce wear adjacent the first and second ends 74B, 74C of the seal <NUM> and adjacent portions of the hub <NUM>.

<FIG> illustrates a process in a flowchart <NUM> for forming a rotor assembly, including any of the seals and rotor assemblies disclosed herein. Reference is made to the seal <NUM> and rotor assembly <NUM> of <FIG> for illustrative purposes. In examples, a coating including one or more layers of material is removed from surfaces of substrate <NUM> at step <NUM>, including at least a previously applied second layer 80B comprised of a solid lubricant.

The first layer 80A is deposited or is otherwise disposed or formed on the substrate <NUM> at step <NUM>. The first layer 80A can be formed on the substrate <NUM> utilizing various techniques, such as by plasma spray deposition or another thermal spraying technique. Example techniques for forming the first layer 80A can include physical vapor deposition (PVD) and chemical vapor deposition (CVD). In examples, step <NUM> includes removing a previously applied first layer 80A such as a layer of copper alloy from the substrate <NUM> prior to step <NUM>. The previously applied first layer 80A may be removed after about <NUM>,<NUM>-<NUM>,<NUM> operating cycles of the engine, whereas a previously applied second layer 80B may be removed after a lesser number of operating cycles, such as approximately <NUM> operating cycles, for example.

At step <NUM> the second layer 80B comprising a solid lubricant such as MoOs is disposed or otherwise formed on the first layer 80A. Step <NUM> can include depositing the second layer 80B directly on the first layer 80A. In some examples, at step <NUM> the third layer <NUM> comprising a solid lubricant is deposited or otherwise formed on the hub <NUM>. A previously applied third layer <NUM> can be removed prior to steps <NUM>, <NUM>.

The second and third layers 80B, <NUM> can be applied utilizing various techniques, such as brushing, swabbing, or spraying including any of the spraying techniques disclosed herein. In examples, the second and/or third layers 80B, <NUM> are applied by PVD or CVD techniques.

Step <NUM> can include depositing a precursor on the first layer 80A at step <NUM>, and heating the precursor to a predetermined temperature threshold for a predetermined time threshold to form the solid lubricant at step <NUM>. In examples, the precursor is a solid lubricant such as MoS<NUM> and is applied by brushing, swabbing or spraying to obtain a thickness of about <NUM>-<NUM> (<NUM>-<NUM> inches) at step <NUM>, for example, and step <NUM> includes forming a solid lubricant comprising MoOs in response to heating the precursor to a predetermined temperature threshold of at least about <NUM>° C (<NUM>° F), including oxidation of the precursor such as MoS<NUM>. The MoS<NUM> or other solid lubricant can include a binder such as silicate. The MoS<NUM> applied to the first layer 80A at step <NUM> can be free of any MoO<NUM>. Forming the MoO<NUM> from MoS<NUM> can reduce manufacturing cost and complexity. In examples, step <NUM> includes pre-treating the coating <NUM> by heating the MoS<NUM> deposited on the substrate <NUM> or first layer 80A to about <NUM>° C (<NUM>° F) for about <NUM> hours to form the second layer 80B of MoOs. The solid lubricant may comprise no more than about <NUM>% of binder constituents such that a majority, such as at least <NUM>%, of the second layer 80B is MoOs. The predetermined time threshold can be greater than about <NUM> hours to increase a concentration of the MoO<NUM> forming the second layer 80B.

The first, second and/or third layers 80A, 80B, <NUM> may include one or more sublayers. One or more layers of material may be formed on and/or between the layers 80A, 80B, <NUM>. Various finishing operations can be applied to the seal <NUM> once the respective layers 80A, 80B, <NUM> are formed.

Claim 1:
A rotor assembly (<NUM>, <NUM>', <NUM>") for a gas turbine engine (<NUM>) comprising:
a rotor (<NUM>) including a hub (<NUM>) carrying one or more rotatable blades (<NUM>), the rotor (<NUM>) mechanically attached to a shaft (<NUM>); and
an annular seal (<NUM>, <NUM>', <NUM>") carried by the shaft (<NUM>), wherein the annular seal (<NUM>, <NUM>', <NUM>") comprises:
a substrate (<NUM>);
a first layer (80A) disposed on the substrate (<NUM>); and
a second layer (80B) disposed on the first layer (80A) and arranged to
establish a sealing relationship with the rotor (<NUM>), characterised by the second
layer (80B) comprising a solid lubricant including molybdenum trioxide (MoO<NUM>); and
wherein the rotor (<NUM>) is an integrally bladed rotor.