Patent Description:
Gas turbine engines typically comprise tierods to provide structural support for various components of the gas turbine engine. In aircraft having smaller sized engines, the loss of volume can negatively impact the engine design and performance. For example, the loss of volume can result in less volume available for other cooling fluid to circulate.

<CIT> relates to a gas turbine engine with a mid turbine frame disposed between turbine rotor assemblies. The mid turbine frame includes hollow airfoils radially extending through an annular gas path duct. The airfoils each include a double-walled leading edge structure to define a front chamber separated from a rear chamber defined in the remaining space within the airfoil. <CIT> relates to a turbine housing section including a radially inner case centered on a first axis, and a radially outer case spaced radially outwardly of the inner case, and centered on a second axis. The first and second axes are offset relative to each other. A plurality of tie rods include a threaded nut received on a tie rod, with the plurality of tie rods connecting the inner and outer cases. The plurality of tie rods are spaced circumferentially about both of the first and second axes, and extend for distinct lengths between the inner and outer cases such that the inner and outer cases are held at a position wherein the first and second axes are offset.

According to a first aspect, there is provided an assembly for a gas turbine engine according to claim <NUM>.

The tierod may comprise a base comprising the base flange, a rod extending from the base, and a head opposite the base and extending from the rod. The bearing mounting ring may comprise at least one aperture for receiving the tierod. The joint may be configured to increase a volume of a bearing compartment on an inner surface of the bearing mounting ring. The joint may couple an outer surface of the base flange to the inner surface of the bearing mounting ring. The rod may extend through an aerodynamic fairing. The head may be configured to be mechanically coupled to an annular outer structure. A coefficient of thermal expansion of the bearing mounting ring may be substantially the same as the coefficient of thermal expansion of the tierod. The joint may be configured to decrease a thickness of the base flange. The tierod may comprise a cast nickel alloy.

From a further aspect of the invention, a gas turbine engine as claimed in claim <NUM> may be provided.

The tierod may comprise a base comprising the flange, a rod extending from the base, and a head opposite the base and extending from the rod. The tierod may extend radially from the bearing mounting ring, through the fairing structure, to the annular outer structure. The head of the tierod may be configured to be mechanically coupled to the annular outer structure. A coefficient of thermal expansion of the tierod may be the same as a coefficient of thermal expansion of the bearing mounting ring. Brazing the tierod to the bearing mounting ring may be configured to increase a volume of a bearing compartment.

According to a further aspect of the disclosure there is provided a method as claimed in claim <NUM> of assembling an assembly of a gas turbine engine.

The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in, and constitute a part of, this specification, illustrate various embodiments, and together with the description, serve to explain the principles of the disclosure.

The detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical, chemical, electrical, and mechanical changes may be made without departing from the scope of the disclosure.

For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full, and/or any other possible attachment option.

For example, in the context of the present disclosure, methods, systems, and articles may find particular use in connection with gas turbine engines. However, various aspects of the disclosed embodiments may be adapted for optimized performance in a variety of engines or other systems. As such, numerous applications of the present disclosure may be realized.

Referring to <FIG>, a gas turbine engine <NUM> (such as a turbofan gas turbine engine) is illustrated according to various embodiments. Gas turbine engine <NUM> is disposed about axial centerline axis <NUM>, which may also be referred to as axis of rotation <NUM>. Gas turbine engine <NUM> may comprise a fan <NUM>, compressor sections <NUM> and <NUM>, a combustion section <NUM>, and turbine sections <NUM>, <NUM>. The fan <NUM> may drive air into compressor sections <NUM>, <NUM>, which further drive air along a core flow path for compression and communication into the combustion section <NUM>. Air compressed in the compressor sections <NUM>, <NUM> may be mixed with fuel and burned in combustion section <NUM> and expanded across the turbine sections <NUM>, <NUM>. The turbine sections <NUM>, <NUM> may include high pressure rotors <NUM> and low pressure rotors <NUM>, which rotate in response to the expansion. The turbine sections <NUM>, <NUM> may comprise alternating rows of rotary airfoils or blades <NUM> and static airfoils or vanes <NUM>. Cooling air may be supplied to the turbine sections <NUM>, <NUM> from the compressor sections <NUM>, <NUM>. A plurality of bearings <NUM> may support spools in the gas turbine engine <NUM>. <FIG> provides a general understanding of the sections in a gas turbine engine, and is not intended to limit the disclosure. The present disclosure may extend to all types of applications and to all types of turbine engines, including turbofan gas turbine engines and turbojet engines.

Referring to <FIG>, according to various embodiments, a schematic diagram of an assembly <NUM> for gas turbine engine <NUM> is depicted. Assembly <NUM> may be situated in a midturbine frame situated between turbine sections <NUM> and <NUM> of gas turbine engine <NUM>. With reference to <FIG>, assembly <NUM> may be disposed about axial centerline axis <NUM> of gas turbine engine <NUM>.

Referring now to <FIG> and <FIG>, <FIG> depicts a cross-sectional view of assembly <NUM> along section line <NUM>-<NUM>. <FIG> depicts an axial view of assembly <NUM>. Assembly <NUM> may comprise tierod <NUM>, fairing structure <NUM>, bearing mounting ring <NUM>, and annular outer structure <NUM>. Fairing structure <NUM> may comprise a plurality of aerodynamic fairings <NUM> extending radially within fairing structure <NUM>. The aerodynamic fairings <NUM> of fairing structure <NUM> may comprise an aperture <NUM> configured to receive tierod <NUM>. Tierod <NUM> may extend radially from bearing mounting ring <NUM> to annular outer structure <NUM>. As will be discussed in further detail with reference to <FIG> and <FIG>, tierod <NUM> is brazed to bearing mounting ring <NUM> and mechanically coupled to annular outer structure <NUM>. Bearing mounting ring <NUM> comprises bearing compartment <NUM> on its inner surface.

With reference now to <FIG>, assembly <NUM> is depicted in greater detail. Tierod <NUM> may comprise a base <NUM> comprising a base flange <NUM>. Base flange <NUM> may extend around an outer portion of base <NUM>, comprising a relatively wider surface area than base <NUM>. The base flange <NUM> may be integral with base <NUM>. In various embodiments, base flange <NUM> may be coupled to base <NUM> by other methods, including but not limited to welding, brazing, and/or sintering. Base flange <NUM> comprises an outer surface <NUM> configured to be brazed to an inner surface <NUM> of the bearing mounting ring <NUM>. Tierod <NUM> may further comprise a rod <NUM> extending from the base <NUM> and a head <NUM> extending from the rod <NUM> and opposite the base <NUM>. In various embodiments, base <NUM>, rod <NUM>, and head <NUM> may be integral with each other. In various embodiments, base <NUM>, rod <NUM>, and head <NUM> may be separate components coupled together.

Tierod <NUM> extends through fairing structure <NUM> and may be coupled to the bearing mounting ring <NUM> and annular outer structure <NUM>. For example, tierod <NUM> may extend through fairing structure <NUM> and coupled to annular outer structure <NUM> utilizing a mechanical coupling. Outer surface <NUM> of the flange <NUM> is brazed to inner surface <NUM> of bearing mounting ring <NUM>. Outer surface <NUM> and inner surface <NUM> may be brazed throughout an entirety of their mating surfaces or a portion of their mating surfaces.

Tierod <NUM> and bearing mounting ring <NUM> may be the same or similar materials. For example, tierod <NUM> and bearing mounting ring <NUM> may be a cast nickel alloy, a nickel chromium alloy (such as that sold under the mark INCONEL, e.g., INCONEL <NUM>, <NUM>, <NUM>, <NUM>, X-<NUM>, and the like) and/or the like. Tierod <NUM> and bearing mounting ring <NUM> may have a substantially similar coefficient of thermal expansion (CTE). For example, a CTE of tierod <NUM> may be within +/- <NUM>% of a CTE of bearing mounting ring <NUM>. Tierod <NUM> and bearing mounting ring <NUM> comprising materials with substantially similar CTEs allows tierod <NUM> and bearing mounting ring <NUM> to expand at similar rates in response to changes in temperature, thereby making structural failure of joints <NUM> and assembly <NUM> less likely.

With reference now to <FIG>, joints <NUM> are shown connecting outer surface <NUM> of flange <NUM> and inner surface <NUM> of bearing mounting ring <NUM>. Joints <NUM> may result from various brazing processes, including but limited to torch brazing, furnace brazing, silver brazing, braze welding, cast iron welding brazing, vacuum brazing, dip brazing, or other brazing techniques. Various materials may be used for brazing of joints <NUM>, including but not limited to nickelboron pastes, nickel-silicon pastes, nickel-phosphorus pastes, gold pastes or other any other material capable of withstanding high temperatures in the gas turbine engine <NUM>. While joints <NUM> are shown only between a portion of outer surface <NUM> and inner surface <NUM> on flange <NUM> in <FIG>, joints <NUM> are not limited in this regard. Alternative embodiments of assembly <NUM> may comprise one joint <NUM> extending an entire length of a mating surface between outer surface <NUM> and inner surface <NUM>, for example. In this regard, base <NUM> may be a separate component from rod <NUM> and joint <NUM> may couple base <NUM> to rod <NUM> and bearing mounting ring <NUM>. Further embodiments may comprise multiple joints <NUM> along the entire length of the mating surface between outer surface <NUM> and inner surface <NUM>.

Brazing tierod <NUM> to bearing mounting ring <NUM> results in numerous advantages. In this regard, assembly <NUM> utilizing joints <NUM> between tierod <NUM> and bearing mounting ring <NUM> can limit additional weight to gas turbine engine <NUM> and limit the occupied space in bearing compartment <NUM> by reducing a thickness of the flange <NUM>. This allows bearing compartment <NUM> to better accommodate oil routing components and cooling applications such as oil scavenging, for example. Additional space in bearing compartment <NUM> can be seen in <FIG> and <FIG>. as indicated by shaded region <NUM>.

A block diagram illustrating a method <NUM> for assembling a assembly, such as assembly <NUM>, is depicted in <FIG>, in accordance with various embodiments. Method <NUM> comprises positioning a fairing structure within an annular outer structure. Method <NUM> further comprises inserting a tierod through a bearing mounting ring. The method further comprises inserting the tierod through the fairing structure. The method further comprises coupling the tierod to the annular outer structure and brazing the tierod to the bearing mounting ring. Method <NUM> is not intended to be limited in this regard. For example, in various embodiments, method <NUM> may comprise brazing the tierod to the bearing mounting ring prior to coupling the tierod to the annular outer structure.

Different crosshatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials.

Methods, systems, and computer-readable media are provided herein. In the detailed description herein, references to "one embodiment", "an embodiment", "various embodiments", etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic.

Claim 1:
An assembly (<NUM>) for a gas turbine engine (<NUM>), comprising:
a tierod (<NUM>);
wherein the tierod (<NUM>) comprises a base flange (<NUM>),
the assembly further comprising:
a brazed joint (<NUM>),
a fairing structure (<NUM>) positioned within an annular outer structure (<NUM>); and
a bearing mounting ring (<NUM>) defining a bearing compartment (<NUM>) on its inner surface,
wherein the brazed joint is located between mating surfaces of the tierod base flange (<NUM>) and the bearing mounting ring (<NUM>),
wherein the tierod extends through the bearing mounting ring and the fairing structure,
wherein the brazed joint (<NUM>) is between an outer surface (<NUM>) of the base flange (<NUM>) and an inner surface (<NUM>) of the bearing mounting ring (<NUM>) that defines a boundary of the bearing compartment (<NUM>).