Patent Description:
A gas turbine engine includes seals for separating different cavities within the gas turbine engine. The condition of each of these seals may affect gas turbine engine operation and/or efficiency. Various methods are known in the art for testing the condition of a seal. While these known testing methods have various benefits, there is still room in the art for improvement. There is a need in the art therefore for improve methods and systems for testing a condition and/or an effectiveness of a seal.

<CIT> discloses a prior art method, having the features of the preamble of claim <NUM>, for testing an annular seal within a gas turbine engine.

According to an aspect of the present disclosure, a method is provided for testing an annular seal within a gas turbine engine in accordance with claim <NUM>.

According to still another aspect of the present disclosure, a system is provided for testing an annular seal arranged in situ within a structure of a gas turbine engine in accordance with claim <NUM>.

<FIG> illustrates a portion of a rotating structure <NUM> of a gas turbine engine; e.g., an engine spool assembly. This rotating structure <NUM> is rotatable about a rotational axis <NUM>, which rotational axis <NUM> may also be an axial centerline of the gas turbine engine. The rotating structure <NUM> of <FIG> includes a bladed rotor <NUM>, a first engine component <NUM> and a second engine component <NUM>. This rotating structure <NUM> of <FIG> also includes a seal <NUM> configured to seal a (e.g., annular) gap between the first engine component <NUM> and the second engine component <NUM>.

The bladed rotor <NUM> may be configured as a compressor rotor or a turbine rotor within the gas turbine engine. The bladed rotor <NUM> of <FIG>, for example, includes a plurality of rotor blades <NUM> and at least one rotor disk <NUM>. The rotor blades <NUM> are distributed circumferentially around an outer periphery of the rotor disk <NUM>. The rotor blades <NUM> are connected to the rotor disk <NUM>. The rotor blades <NUM>, for example, may be formed integral with the rotor disk <NUM>, or mechanically fastened, welded, brazed, adhered and/or otherwise attached to the rotor disk <NUM>.

The rotor disk <NUM> of <FIG> includes a disk hub <NUM>. This disk hub <NUM> extends axially along the rotational axis <NUM> to an axial end <NUM> of the bladed rotor <NUM> and its disk hub <NUM>. The disk hub <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The disk hub <NUM> extends radially between and to an inner side <NUM> of the bladed rotor <NUM> and its disk hub <NUM> and an outer side <NUM> of the disk hub <NUM>. The disk hub <NUM> of <FIG> is configured with outer threads <NUM> (schematically shown in <FIG>) along at least a portion of the hub outer side <NUM> at (e.g., on, adjacent or proximate) the rotor end <NUM>.

The first engine component <NUM> may be configured as an inner nut for the rotating structure <NUM>. The first engine component <NUM> of <FIG> includes a tubular member <NUM> (e.g., an extension, a sleeve, etc.) and an inner seal land <NUM>. The tubular member <NUM> extends axially along the rotational axis <NUM>. The tubular member <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The tubular member <NUM> extends radially between and to an inner side <NUM> of the first engine component <NUM> and its members <NUM> and <NUM> and an outer side <NUM> of the tubular member <NUM>.

The inner seal land <NUM> is connected to (e.g., formed integral with) the tubular member <NUM>. The inner seal land <NUM> projects axially along the rotational axis <NUM> out from the tubular member <NUM> to an axial end <NUM> of the first engine component <NUM> and its inner seal land <NUM>. The inner seal land <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The inner seal land <NUM> extends radially between and to component inner side <NUM> and an outer side <NUM> of the inner seal land <NUM>. The inner seal land <NUM> of <FIG> includes a seal receptacle <NUM> (e.g., a groove) configured to receive the seal <NUM>. This seal receptacle <NUM> extends radially into the inner seal land <NUM> from the land outer side <NUM> to a radial side <NUM> of the seal receptacle <NUM>. The seal receptacle <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM> within the inner seal land <NUM>. The seal receptacle <NUM> extends axially along the rotational axis <NUM> within the inner seal land <NUM> between opposing axial ends <NUM> and <NUM> of the seal receptacle <NUM>.

The first engine component <NUM> is mated with the bladed rotor <NUM>. The first engine component <NUM> of <FIG>, for example, is received within (e.g., extends axially within) an inner bore of the bladed rotor <NUM>. The inner seal land <NUM> of <FIG> projects out of the inner bore to its inner seal land end <NUM>. An inner bore of the first engine component <NUM> may receive another component <NUM> of the rotating structure <NUM> or another rotating structure of the gas turbine engine. The component <NUM> of <FIG> is configured as an engine shaft that projects axially along the rotational axis <NUM> through the inner bore of the first engine component <NUM>.

The second engine component <NUM> may be configured as an outer nut for the rotating structure <NUM>. The second engine component <NUM> of <FIG>, for example, includes a component base <NUM> and an outer seal land <NUM>. The component base <NUM> extends axially along the rotational axis <NUM> between opposing axial ends <NUM> and <NUM> of the second engine component <NUM> and its component base <NUM>. The component base <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The component base <NUM> extends radially between and to an inner side <NUM> of the component base <NUM> and an outer side <NUM> of the second engine component <NUM> and its component base <NUM>. The component base <NUM> of <FIG> is configured with inner threads <NUM> (schematically shown in <FIG>) along at least a portion of the base inner side <NUM> at (e.g., on, adj acent or proximate) the component end <NUM>.

The outer seal land <NUM> is connected to (e.g., formed integral with) the component base <NUM>. The outer seal land <NUM> projects radially inward from the component base <NUM> to an inner side <NUM> of the second engine component <NUM> and a radial distal end <NUM> of the outer seal land <NUM>. This outer seal land <NUM> extends axially along the rotational axis <NUM> (at the distal end <NUM>) between opposing axial sides of the outer seal land <NUM>. The outer seal land <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>.

The second engine component <NUM> is mated with the bladed rotor <NUM> and the first engine component <NUM>. The component base <NUM> of <FIG>, for example, is mounted (e.g., threaded) onto the disk hub <NUM> where the inner threads <NUM> engage the outer threads <NUM>. The inner seal land <NUM> is received within (e.g., extends axially within) an inner bore of the second engine component <NUM> and its outer seal land <NUM>. The seal receptacle <NUM> is axially aligned with a (e.g., cylindrical) inner surface of the outer seal land <NUM> at component inner side <NUM>. The component inner side <NUM> is radially spaced from the component outer side <NUM> by a (e.g., annular) radial gap.

The seal <NUM> may be configured as an annular seal element (e.g., a piston seal, a ring seal, etc.) or an annular seal assembly. The seal <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The seal <NUM> is mounted to the first engine component <NUM> radially between the inner seal land <NUM> and the outer seal land <NUM>. The seal <NUM> of <FIG>, for example, is seated within the seal receptacle <NUM>, and the seal <NUM> is sealingly engaged with (e.g., radially contacts) the inner surface of the outer seal land <NUM> and is sealingly engaged with (e.g., axially contacts) a (e.g., annular) side surface of the inner seal land <NUM> at one of the receptacle sides <NUM>, <NUM>. The seal <NUM> may thereby substantially (or completely) seal the gap between the first engine component <NUM> and the second engine component <NUM>.

Following assembly of the rotating structure <NUM> (e.g., during a manufacturing inspection process, following use of the gas turbine engine or otherwise), the seal <NUM> may be tested to evaluate a condition of seal <NUM> and/or an effectiveness of the seal interface between the first engine component <NUM> and the second engine component <NUM>. <FIG> illustrates a system <NUM> which may be used for testing the seal <NUM> of <FIG> (or other seals) during such an evaluation. This testing system <NUM> includes a vacuum pump <NUM>, a vacuum circuit <NUM> and a measurement system <NUM>. The testing system <NUM> of <FIG> also includes a compressed gas circuit <NUM> and an exhaust circuit <NUM>.

The vacuum pump <NUM> is configured to generate suction at a vacuum inlet <NUM>. The vacuum pump <NUM> may be configured as a venturi pump operable to generate suction by flowing compressed gas (e.g., compressed air) therethrough. The vacuum pump <NUM> of <FIG> includes the vacuum inlet <NUM>, a compressed gas inlet <NUM> and an exhaust outlet <NUM>.

The vacuum circuit <NUM> includes a vacuum tool <NUM> and a vacuum conduit <NUM>. The vacuum circuit <NUM> of <FIG> also includes a vacuum circuit valve <NUM>; e.g., a shutoff valve.

Referring to <FIG>, the vacuum tool <NUM> is configured as an annular cap and/or plug. The vacuum tool <NUM> of <FIG> includes a tool base <NUM>, tool flanges <NUM> and <NUM> and one or more seals <NUM> and <NUM>; e.g., annular seal elements.

The tool base <NUM> extends axially along the rotational axis <NUM> between and to an interior end <NUM> of the tool base <NUM> and an exterior end <NUM> of the vacuum tool <NUM>. The tool base <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The tool base <NUM> extends radially between and to an inner side <NUM> of the vacuum tool <NUM> and an outer side <NUM> of the vacuum tool <NUM>. The tool base <NUM> of <FIG> includes a conduit adaptor <NUM>; e.g., a quick release nipple.

The tool inner flange <NUM> is connected to (e.g., formed integral with) the tool base <NUM> at the tool inner side <NUM>. The tool inner flange <NUM> projects axially out from the tool base <NUM> along the rotational axis <NUM> to an interior end <NUM> of the vacuum tool <NUM>. The tool inner flange <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. This tool inner flange <NUM> includes an (e.g., annular) inner flange seal land <NUM> at the tool interior end <NUM>. The inner flange seal land <NUM> of <FIG>, for example, projects axially out from an intermediate member <NUM> of the tool inner flange <NUM> along the rotational axis <NUM> to the tool interior end <NUM>. This inner flange seal land <NUM> extends radially between and to the tool inner side <NUM> and an outer side <NUM> of the inner flange seal land <NUM>. The inner flange seal land <NUM> of <FIG> includes an inner flange seal receptacle <NUM> (e.g., a groove) configured to receive the tool inner seal <NUM>. This inner flange seal receptacle <NUM> extends radially into the inner flange seal land <NUM> from the land outer side <NUM> to a radial side <NUM> of the inner flange seal receptacle <NUM>. The inner flange seal receptacle <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM> within the inner flange seal land <NUM>. The inner flange seal receptacle <NUM> extends axially along the rotational axis <NUM> within the inner flange seal land <NUM> between opposing axial ends <NUM> and <NUM> of the inner flange seal receptacle <NUM>.

The tool outer flange <NUM> is connected to (e.g., formed integral with) the tool base <NUM> at the tool outer side <NUM>. The tool outer flange <NUM> projects axially out from the tool base <NUM> along the rotational axis <NUM> to an interior end <NUM> of the tool outer flange <NUM>, which flange interior end <NUM> may be recessed axially from the tool interior end <NUM>. The tool outer flange <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The tool outer flange <NUM> includes a component seal land <NUM> (e.g., an annular rim) at the flange interior end <NUM>. The component seal land <NUM> of <FIG>, for example, projects axially out from an intermediate member <NUM> of the tool outer flange <NUM> along the rotational axis <NUM> to the flange interior end <NUM>. This component seal land <NUM> extends radially between and to the tool outer side <NUM> and an inner side <NUM> of the component seal land <NUM>, where the land inner side <NUM> is radially recessed outward from an inner side <NUM> of the intermediate member <NUM>. The tool outer flange <NUM> also includes an outer flange seal receptacle <NUM> (e.g., a groove) configured to receive the tool outer seal <NUM>. This outer flange seal receptacle <NUM> is disposed at an axial interface between the component seal land <NUM> and the intermediate member <NUM>. The outer flange seal receptacle <NUM> extends radially into the component seal land <NUM> from the inner sides <NUM> and <NUM> to a radial side <NUM> of the outer flange seal receptacle <NUM>. The outer flange seal receptacle <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM> within the component seal land <NUM>. The outer flange seal receptacle <NUM> extends axially along the rotational axis <NUM> within the component seal land <NUM> between opposing axial ends <NUM> and <NUM> of the outer flange seal receptacle <NUM>.

The tool inner seal <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The tool inner seal <NUM> is mounted to the tool inner flange <NUM>. The tool inner seal <NUM> of <FIG>, for example, is seated within the inner flange seal receptacle <NUM>.

The tool outer seal <NUM> extends circumferentially about (e.g., completely around) the rotational axis <NUM>. The tool outer seal <NUM> is mounted to the tool outer flange <NUM>. The tool outer seal <NUM> of <FIG>, for example, is seated within the outer flange seal receptacle <NUM>.

Referring to <FIG>, the vacuum tool <NUM> is configured to mate with the rotating structure <NUM>. The tool inner flange <NUM>, for example, is received within (e.g., projects axially into) an inner bore of the inner seal land <NUM>. The tool inner seal <NUM> is disposed radially between the inner flange seal land <NUM> and the inner seal land <NUM>. More particularly, the tool inner seal <NUM> sealingly engages (e.g., radially contacts) a (e.g., cylindrical) outer surface of the tool inner flange <NUM> at the receptacle side <NUM> and a (e.g., cylindrical) inner surface of the inner seal land <NUM> at the side <NUM>. The second engine component <NUM> is received (e.g., projects axially into) an inner counterbore of the component seal land <NUM>. The tool outer seal <NUM> is disposed axially between the second engine component <NUM> and the tool outer flange <NUM>. More particularly, the tool outer seal <NUM> sealingly engages (e.g., axially contacts) an (e.g., annular) end surface of the component base <NUM> at the base end <NUM> and an (e.g., annular) end surface of the tool outer flange <NUM> at the receptacle end <NUM>.

With the foregoing arrangement, the vacuum tool <NUM> forms an enclosed exterior volume <NUM> (e.g., a cavity, a chamber, a plenum, etc.) with the rotating structure <NUM>. This exterior volume <NUM> extends axially between the tool base <NUM> and the seal lands <NUM> and <NUM>. The exterior volume <NUM> extends radially between the component base <NUM> and the tool inner flange <NUM>, and radially between the inner seal land <NUM> and the tool inner flange <NUM>. The seal <NUM> of <FIG> is between and is configured to substantially (or completely) fluidly separate (e.g., isolate, decouple, etc.) the exterior volume <NUM> from an enclosed interior volume <NUM> (e.g., a cavity, a chamber, a plenum, etc.) within the rotating structure <NUM> formed by and between, for example, the rotating structure components <NUM>-<NUM>.

Referring to <FIG>, the vacuum conduit <NUM> may be configured as or otherwise include a length of hose, pipe or any other type of tubing. The vacuum conduit <NUM> extends longitudinally between and is fluidly coupled with the vacuum tool <NUM> and the vacuum pump <NUM>. A first end of the vacuum conduit <NUM> of <FIG>, for example, is fluidly coupled with the conduit adaptor <NUM>, which fluidly couples an internal passage of the vacuum conduit <NUM> with the exterior volume <NUM>. A second end of the vacuum conduit <NUM> of <FIG> is fluidly coupled with the vacuum circuit valve <NUM> through an intermediate fitting <NUM>. The vacuum circuit valve <NUM> is between and is fluidly coupled with the vacuum conduit <NUM> and, more particularly, the intermediate fitting <NUM> and the vacuum pump <NUM> and its vacuum inlet <NUM>.

The measurement system <NUM> includes one or more pressure measurement devices <NUM> and <NUM>. The vacuum circuit measurement device <NUM> is configured as a vacuum pressure gauge 166A. This vacuum pressure gauge 166A is configured to measure vacuum pressure within the vacuum circuit <NUM> and its vacuum conduit <NUM> / the vacuum inlet <NUM>. The vacuum pressure gauge 166A of <FIG>, for example, is fluidly coupled with the intermediate fitting <NUM>. The gas circuit measurement device <NUM> is configured as a compressed gas pressure gauge 168A. This gas pressure gauge 168A is configured to measure gas pressure within the compressed gas circuit <NUM> / the compressed gas inlet <NUM>. The gas pressure gauge 168A of <FIG>, for example, is fluidly coupled with an intermediate fitting <NUM> in the compressed gas circuit <NUM>. While these pressure measurement devices <NUM> and <NUM> are shown as analog devices in <FIG>, one or more of these pressure measurement devices <NUM>, <NUM> may alternatively be configured with digital sensors.

The compressed gas circuit <NUM> of <FIG> includes a compressed gas source <NUM> and a source conduit <NUM>. The compressed gas circuit <NUM> of <FIG> also includes a compressed gas circuit valve <NUM> (e.g., a shutoff valve) and/or a compressed gas circuit flow regulator <NUM>.

The compressed gas source <NUM> is configured to provide and contain compressed gas. The compressed gas source <NUM>, for example, may include a compressor <NUM> (e.g., a pump) and a reservoir <NUM>. The compressor <NUM> is configured to compress gas (e.g., air) and direct that compressed gas into the reservoir <NUM> for storage. The reservoir <NUM> may be configured as a tank, a cylinder or any other pressure vessel. An example of the compressed gas source <NUM> is a shop air source.

The source conduit <NUM> may be configured as or otherwise include a length of hose, pipe or any other type of tubing. The source conduit <NUM> extends longitudinally between and is fluidly coupled with the compressed gas source <NUM> and the vacuum pump <NUM>. An end of the source conduit <NUM> of <FIG>, for example, is fluidly coupled with the gas circuit valve <NUM>. The gas circuit valve <NUM> is between and is fluidly coupled with source conduit <NUM> and the flow regulator <NUM>. The flow regulator <NUM> is between and is fluidly coupled with the gas circuit valve <NUM> and the vacuum pump <NUM> and its compressed gas inlet <NUM> through the intermediate fitting <NUM>.

The exhaust circuit <NUM> of <FIG> includes an exhaust conduit <NUM> and a muffler <NUM>. The exhaust conduit <NUM> may be configured as or otherwise include a length of hose, pipe or any other type of tubing. The exhaust conduit <NUM> extends longitudinally between and is fluidly coupled with the muffler <NUM> and the vacuum pump <NUM> and its exhaust outlet <NUM>.

The testing system <NUM> is described above with certain exemplary components and circuits. The testing system <NUM> of the present disclosure, however, is not limited to such an arrangement. For example, in some embodiments, one or more of the valves <NUM> and <NUM> may be omitted. In some embodiments, the muffler <NUM> may be omitted, or the conduit <NUM> between the muffler <NUM> and the vacuum pump <NUM> may be omitted. In some embodiments, the compressed gas circuit <NUM> may be omitted where the vacuum pump <NUM>, for example, is configured as an electrically powered vacuum pump. In some embodiments, the vacuum tool <NUM> may have different configurations to mate with different rotating structures and/or to test seals in other locations of a gas turbine engine.

<FIG> is a flow diagram of a method <NUM> for testing a seal such as the seal <NUM> of <FIG>. For ease of description, this seal testing method <NUM> is described below with reference to the testing system <NUM> of <FIG>. The seal testing method <NUM>, however, may alternatively be performed with other testing system arrangements.

In step <NUM>, the vacuum tool <NUM> is mated with the rotating structure <NUM>.

In step <NUM>, a vacuum is applied to the exterior volume <NUM>. The compressed gas circuit <NUM>, for example, may direct compressed gas from the compressed gas source <NUM> to the vacuum pump <NUM> through its compressed gas inlet <NUM>. The flow regulator <NUM> may be set (or adjusted) such that the compressed gas received by the vacuum pump <NUM> at its compressed gas inlet <NUM> is at a predetermined compressed gas pressure. This compressed gas pressure may be less than (or equal to) a pressure of the compressed gas output by the compressed gas source <NUM>. The compressed gas flows through the vacuum pump <NUM> (e.g., a venturi vacuum pump) to the exhaust outlet <NUM> to generate suction at the vacuum inlet <NUM> using known fluid principles. The compressed gas is subsequently exhausted from the testing system <NUM> through the exhaust circuit <NUM> and its muffler <NUM>.

The suction at the vacuum inlet <NUM> draws gas (e.g., air) out of the exterior volume <NUM> through the vacuum circuit <NUM>. This drawing of the gas applies a vacuum to the exterior volume <NUM> as well as the vacuum circuit <NUM>. A pressure of the gas within the exterior volume <NUM> and the vacuum circuit <NUM>, for example, is less than a pressure of ambient (e.g., room) air at standard atmosphere; e.g., <NUM> psi (<NUM> kPa) at sea level. The vacuum pressure of the gas within the exterior volume <NUM> and the vacuum circuit <NUM> may be expressed as a positive number (e.g., a number below <NUM> psi (<NUM> kPa)) or a negative number (e.g., a number to be subtracted from <NUM> psi (<NUM> kPa)). For ease of description, the vacuum pressure is expressed below as a positive number.

In step <NUM>, the vacuum pressure within the vacuum circuit <NUM> and its vacuum conduit <NUM> is measured. This vacuum pressure (e.g., a gas pressure below <NUM> psi (<NUM> kPa)) may be measured using the vacuum pressure gauge 166A.

In step <NUM>, the measured vacuum pressure is analyzed to determine a characteristic about the seal <NUM> and/or the seal interface between the first engine component <NUM> and the second engine component <NUM>. The measured vacuum pressure is compared to a predetermined threshold vacuum pressure. This threshold vacuum pressure may be related to a (e.g., acceptable) vacuum pressure that is expected to be measured within the vacuum circuit <NUM> and its vacuum conduit <NUM> when the seal <NUM> is configured and operating according to a specification; e.g., a design specification. The threshold vacuum pressure, for example, may be equal to an expected vacuum pressure with an allowable leakage factor. The expected vacuum pressure may be a pressure that is expected to be measured within the vacuum circuit <NUM> and its vacuum conduit <NUM> when the seal <NUM> is fully operational. The allowable leakage factor may be a vacuum pressure loss to account for a maximum allowable leakage flow across the seal <NUM> from the interior volume <NUM> to the exterior volume <NUM>. For example, where (A) a pressure that is expected to be measured within the vacuum circuit <NUM> and its vacuum conduit <NUM> when the seal <NUM> is fully operational is X psi (<NUM> psi = <NUM> kPa) and (B) there can be at most Y psi leakage across the seal <NUM>, then (C) the threshold vacuum pressure may be equal to (X + Y) psi; e.g., <NUM> psi + <NUM> psi = <NUM> psi (<NUM> kPa + <NUM> kPa = <NUM> kPa). The present disclosure, of course, is not limited to the foregoing exemplary values.

Where the measured vacuum pressure (Z) is less than (or equal to) the threshold vacuum pressure (e.g., Z ≤ (X + Y)), it may be determined that the seal <NUM> and/or the seal interface between the first engine component <NUM> and the second engine component <NUM> satisfy the standard; e.g., the design standard. However, where the measured vacuum pressure is greater than the threshold vacuum pressure (e.g., Z > (X + Y)), it may be determined that the seal <NUM> and/or the seal interface between the first engine component <NUM> and the second engine component <NUM> do not satisfy the standard; e.g., the design standard. The seal testing method <NUM> may thereby facilitate testing of the seal <NUM> and/or the seal interface between the first engine component <NUM> and the second engine component <NUM> while the seal <NUM> is in situ; e.g., while the rotating structure <NUM> is completely assembled and/or in an otherwise operational state. The seal testing method <NUM> therefore may not require partial disassembly or reconfiguring of the rotating structure <NUM> (or at least its rotating structure components <NUM>-<NUM> and <NUM>) for the testing.

<FIG> is a side sectional illustration of an example of the gas turbine engine with which the rotating structure <NUM> of <FIG> may be included. This gas turbine engine of <FIG> is configured as a turboprop gas turbine engine <NUM>. This gas turbine engine <NUM> extends axially along the rotational axis <NUM> between a forward end <NUM> of the gas turbine engine <NUM> and an aft end <NUM> of the gas turbine engine <NUM>. The gas turbine engine <NUM> of <FIG> includes an airflow inlet <NUM>, an exhaust <NUM>, a propulsor (e.g., a propeller) section <NUM>, a compressor section <NUM>, a combustion section <NUM> and a turbine section <NUM>.

The airflow inlet <NUM> is towards the engine aft end <NUM>, and aft of the gas turbine engine sections <NUM>, <NUM>, <NUM> and <NUM>. The exhaust <NUM> is located towards the engine forward end <NUM>, and axially between the propulsor section <NUM> and the gas turbine engine sections <NUM>, <NUM> and <NUM>.

The propulsor section <NUM> includes a propulsor rotor <NUM>. The compressor section <NUM> includes a compressor rotor <NUM>. The turbine section <NUM> includes a high pressure turbine (HPT) rotor <NUM> and a low pressure turbine (LPT) rotor <NUM>, where the LPT rotor <NUM> may be referred to as a power turbine rotor and/or a free turbine rotor. Each of these gas turbine engine rotors <NUM>-<NUM> includes a plurality of rotor blades arranged circumferentially about and connected to one or more respective rotor disks or hubs. The bladed rotor <NUM> of <FIG> may be configured as or otherwise included as part of any one of the gas turbine engine rotors <NUM>-<NUM>, for example.

The propulsor rotor <NUM> of <FIG> is connected to the LPT rotor <NUM> sequentially through a propulsor shaft <NUM>, an epicyclic geartrain <NUM> and a low speed shaft <NUM>. The compressor rotor <NUM> is connected to the HPT rotor <NUM> through a high speed shaft <NUM>.

During gas turbine engine operation, air enters the gas turbine engine <NUM> through the airflow inlet <NUM>. This air is directed into a core flowpath which extends sequentially from the airflow inlet <NUM>, through the engine sections <NUM>, <NUM> and <NUM> (e.g., an engine core), to the exhaust <NUM>. The air within this core flowpath may be referred to as "core air".

The core air is compressed by the compressor rotor <NUM> and directed into a combustion chamber of a combustor <NUM> in the combustion section. Fuel is injected into the combustion chamber and mixed with the compressed core air to provide a fuel-air mixture. This fuel-air mixture is ignited and combustion products thereof flow through and sequentially cause the HPT rotor <NUM> and the LPT rotor <NUM> to rotate. The rotation of the HPT rotor <NUM> drives rotation of the compressor rotor <NUM> and, thus, compression of air received from the airflow inlet <NUM>. The rotation of the LPT rotor <NUM> drives rotation of the propulsor rotor <NUM>, which propels air outside of the gas turbine engine <NUM> in an aft direction to provide forward aircraft thrust.

Claim 1:
A method for testing an annular seal (<NUM>) within a gas turbine engine (<NUM>), the method comprising:
mounting a tool (<NUM>) to a structure (<NUM>) of the gas turbine engine (<NUM>), wherein a first volume (<NUM>) is between and is formed by the tool (<NUM>) and the structure (<NUM>);
applying a vacuum to the first volume (<NUM>) through a conduit (<NUM>), wherein the annular seal (<NUM>) is between the first volume (<NUM>) and a second volume (<NUM>), and the conduit (<NUM>) is connected to the first volume (<NUM>) through the tool (<NUM>);
measuring a vacuum pressure within the conduit (<NUM>) while the vacuum is applied; and
comparing the measured vacuum pressure to a threshold vacuum pressure, wherein a difference between the measured vacuum pressure and the threshold vacuum pressure is indicative of leakage across the annular seal (<NUM>) from the second volume (<NUM>) to the first volume (<NUM>), characterized in that:
the tool (<NUM>) extends circumferentially about an axis (<NUM>), and the tool (<NUM>) includes a base (<NUM>), an inner flange (<NUM>) and an outer flange (<NUM>);
the base (<NUM>) extends radially between the inner flange (<NUM>) and the outer flange (<NUM>); the inner flange (<NUM>) is connected to an inner end (<NUM>) of the base (<NUM>), the inner flange (<NUM>) projects axially out from the base (<NUM>), and the inner flange (<NUM>) is configured to axially overlap and seal against the structure (<NUM>); and
the outer flange (<NUM>) is connected to an outer end (<NUM>) of the base (<NUM>), the outer flange (<NUM>) projects axially out from the base (<NUM>), and the outer flange (<NUM>) is configured to axially overlap and seal against the structure (<NUM>).