Patent Description:
Gas turbine engines, such as those utilized in commercial and military aircraft, include a compressor section that compresses air, a combustor section in which the compressed air is mixed with a fuel and ignited, and a turbine section across which the resultant combustion products are expanded. The expansion of the combustion products drives the turbine section to rotate. As the turbine section is connected to the compressor section via a shaft, the rotation of the turbine section further drives the compressor section to rotate. In some examples, a fan is also connected to the shaft and is driven to rotate via rotation of the turbine as well.

Gas turbine engines include rotating components and static components, with the rotating components being supported interior to the static components via one or more bearings. The bearings are supported within bearing support structures, and allow the rotating components to rotate relative to the static components.

<CIT> discloses a ducted fan gas turbine engine, wherein the shafts of the engine are mounted on roller bearings. The bearings are attached to a structure which comprises an axial sleeve, a front frustoconical portion and a rear radially stiff but axially flexible frustoconical portion and is attached to the engine casing.

The present invention provides a gas turbine engine as set forth in claim <NUM>.

In an example of the above described gas turbine engine the inlet case flange is oblique to an axis defined by the gas turbine engine.

In another example of any of the above described gas turbine engines the pedestal is oblique to an axis defined by the gas turbine engine.

In another example of any of the above described gas turbine engines the bearing support portion is connected to the radially inward ring via an inlet case flange and the inlet case flange is normal to the axis defined by the gas turbine engine.

A method for supporting a bearing system in a gas turbine engine according to the invention includes defining a radially outer ring connected to a radially inner ring by a plurality of struts using a unitary body, supporting the bearing system relative to a static structure via a bearing support portion of the unitary body, the bearing support portion protruding radially inward from the radially inner ring and including a radially outward facing sealing surface of a radially outward flange and a radially inward facing surface of a radially inner flange, the radially outward flange being connected to the radially inward flange by a pedestal, and supporting at least one bearing system case component via a plurality of fasteners connecting the at least one bearing system case component to an inlet case flange portion of the unitary body, the inlet case flange portion being a flange connecting the bearing support portion to the radially inner ring.

An example of the above described exemplary method for supporting a bearing system in a gas turbine engine further includes forming the unitary body as a single component via at least one of a casting process, a composite material forming process, a combination of a bonded metal and composite material forming process, and an additive manufacturing process.

In another example, the teachings disclosed herein can be applied to a fain inlet case (FIC) on a non-high bypass engine including engine case struts positioned forward of the fan.

The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>: <NUM>.

"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 x <NUM>/<NUM>).

Multiple static components of a gas turbine engine, such as a fan inlet case <NUM>, are maintained in a static position relative to an airframe. The static components support rotating components such as the inner shaft <NUM> and the outer shaft <NUM> through bearing structures <NUM>. The fan inlet case <NUM> is an annular body that typically includes a radially outer wall connected to a radially inner wall by multiple struts. The struts have a leading edge at a foreword end of the fan inlet case <NUM> and are generally airfoil shaped. In existing systems, the radially inner wall is structurally connected to a bearing support via a radially inward protruding flange. The flange includes a radially inward facing contact surface resulting in an interference fit between the radially inward facing contact surface of the flange and a radially outward facing contact surface of the bearing support. The interference fit provides a robust load path and radially maintains the position of the centerline of the damper and rotating hardware relative to the fan inlet case. A bolt, or other fastener, is aligned with an axis defined by the fan inlet case <NUM> and protrudes through the bearing support and the flange. The bolt assists in maintaining the bearing support in position axially within the engine <NUM>. The bolt can be threaded into another engine component, as shown in the example embodiment, of can be engaged with a nut. In addition to the provided load path, the interference fit provides a seal between the contacting surfaces.

In some examples, an anti-icing system is incorporated within the fan inlet case <NUM>. One example anti-icing system uses a hot airflow to heat the struts and other leading edge portions of the fan inlet case <NUM>. In alternative examples, alternative systems for heating the fan inlet case <NUM> can be used by alternative anti-icing systems. The heating melts ice that may have accumulated at the leading edge of the engine <NUM> and allows unimpeded operation. However, due to the heating from the anti-icing systems, as well as the disparate materials used to create the bearing support and the fan inlet case <NUM>, a large thermal gradient occurs between the fan inlet case <NUM> and the bearing support.

The large thermal gradient causes the fan inlet case <NUM> to expand more, and at a faster rate, than the bearing support. The expansion disparity results in a potential radial separation between the radially inward facing surface of the flange and the bearing support. The separation breaks the seal and can allow leakage into or out of the bearing systems <NUM>. Further, the separation applies a shearing stress to the bolt, or other fastener, and can decrease the expected lifespan of the system.

With continued reference to <FIG>, <FIG> and <FIG> schematically illustrates a cross sectional view of a fan inlet case and bearing support body <NUM> provided as a single unitary body. As used herein a "unitary body" refers to a single structure that is either formed as a single structure or is a single structure made up of multiple segments that are permanently bonded together. The fan inlet case and bearing support body <NUM> (referred to alternately as the body <NUM>) is illustrated in the context of adjacent components included in the engine <NUM> of <FIG>, and isolated from that context in <FIG>. The body <NUM> is an annular component defining an axis A and including an outer ring portion <NUM> connected to an inner ring portion <NUM> via multiple struts <NUM>. Incorporated in each of the struts <NUM> may be an anti-icing system <NUM>, illustrated schematically herein as an internal passage. One of skill in the art will appreciate that any anti-icing system could be incorporated in the strut <NUM>, and the anti-icing system is not limited to the illustrated internal passage <NUM>.

Protruding radially inward from the inner ring <NUM> is a bearing support structure <NUM>. The bearing support structure <NUM> includes a first platform <NUM> and a second platform <NUM> connected to each other by a pedestal <NUM>. The first platform <NUM> has a radially outward facing surface <NUM> that forms a sealing surface contacting a housing <NUM>. Embedded within the radially outward facing surface <NUM> are multiple squeeze film dampers <NUM>. The squeeze film dampers <NUM> dampen vibrational translation from the bearing compartment <NUM> to the body <NUM>. The first platform <NUM> is connected to the inner ring <NUM> via an inlet casing flange <NUM>, and the housing <NUM> is maintained in contact with the inlet casing flange <NUM> via one or more fasteners <NUM> protruding through corresponding axially aligned through holes <NUM> in the inlet casing flange <NUM>.

The through holes <NUM> in the inlet casing flange <NUM> are, in one example, circumferentially distributed approximately evenly about the inlet case flange <NUM>. As used herein, "approximately evenly" refers to a generally even circumferential distribution inclusive of minor variations (to the order of <NUM> degrees or less) to accommodate varying engine structures and manufacturing tolerances. In alternative examples, the circumferential distribution can be uneven, depending on the structure and needs of a given engine. In the example illustrated at <FIG>, the inlet case flange <NUM> is normal to the axis A. In alternative examples, such as those illustrated in <FIG>, the inlet case flange <NUM> can be oblique to the axis A and achieve similar effects.

The radially inward facing surface <NUM> of the radially inward platform <NUM> contacts an outer race <NUM> of a bearing <NUM>, and the outer race <NUM> is connected to the housing <NUM>. Radially inward of the outer system race is an exemplary bearing <NUM>. Radially inward of the exemplary bearing <NUM> is an inner race <NUM>. The disclosed integrated fan inlet case and bearing support body <NUM> can be utilized in alternate configurations with other bearing system, with the radially inward facing surface <NUM> of the radially inward platform <NUM> contacting an outer race.

Due to the unitary nature of the body <NUM>, the body <NUM> can be formed as a single structure. By way of example, the body <NUM> can be cast in a single casting step, additively manufactured as a single component, created using a composite forming process, created using a combination of bonded metal and a composite forming process, or created using any other technique configured to create a single unitary body. In alternative examples, the body <NUM> can be created as multiple radial segments, with the segments being permanently bonded together, such as by welding or any other similar bonding process to form the annular shape. The resultant structure of either is a single annular body <NUM> that includes both the fan inlet case <NUM> and the bearing support <NUM>.

During operation of the gas turbine engine <NUM>, vibrational loads, and other similar loads are transferred from the bearing system <NUM> into the body <NUM>, and into other static structures of the gas turbine engine <NUM>. The utilization of a unitary structure for the body <NUM> improves the damper performance by reducing closures due to interference, and thereby reducing a nominal damper gap and improving the performance of the squeeze film dampers <NUM>.

In some examples, normal orientation of the flange <NUM> relative to the axis A provides less than ideal translation of loads, such as vibrational loads, from the bearing and provides compliance with stresses associated with a thermal gradient between the compartment <NUM> and the static structures of the engine. With continued reference to <FIG>, and with like numerals indicating like elements, <FIG> schematically illustrates an alternate example configuration that improves load transfer characteristics of a unitary annular body <NUM> and reduces stresses introduced due to thermal gradient, relative to the example of <FIG>.

The unitary annular body <NUM> includes an inner ring <NUM> connected to a bearing support portion <NUM> via an inlet case flange <NUM>. The inlet case flange <NUM> is angled relative to an axis B defined by the annular body <NUM>. This angling is referred to as the inlet case flange <NUM> being oblique to the axis B. In addition to angling the inlet case flange <NUM>, the pedestal <NUM> connecting the first platform <NUM> and the second platform <NUM> is provided with a similar angling feature. While illustrated herein as the same angle, it is appreciated that the pedestal <NUM> and the inlet case flange <NUM> can be at distinct angles from each other, and still both be oblique to the axis B.

In order to facilitate mounting the bearing system case <NUM>, as well as any other static components <NUM> to the unitary body <NUM>, a mounting block <NUM> is included at the angled inlet case flange <NUM> and provides surfaces normal to the axis B, through which the bearing case <NUM> and the additional static components <NUM> can be interfaced to the unitary body <NUM>.

With continued reference to <FIG>, and with like numerals indicating like elements, <FIG> illustrates another example configuration that incorporates at least a portion of the benefits from the angled inlet case flange <NUM> and the angled pedestal <NUM> without requiring the incorporation of the mounting block <NUM>. In the example of <FIG>, the singular annular body <NUM> includes an inner ring <NUM> connected to a bearing support portion <NUM> via an inlet case flange <NUM>. The inlet case flange <NUM> is normal to the axis C defined by the annular body <NUM>. Unlike the inlet case flange <NUM>, the pedestal <NUM> connecting the first platform <NUM> and the second platform <NUM> is oblique to the axis C. The angled pedestal provides at least a portion of the vibrational benefits and thermal gradient stress reduction benefits of the configuration illustrated in <FIG>, while the normal inlet case flange <NUM> allows for simplified interconnections with the bearing case <NUM> and the additional engine components <NUM>.

With continued reference to <FIG>, <FIG> schematically illustrates the example of <FIG> with the addition of a distinct damping sleeve <NUM> attached to the bearing support <NUM>. The damping sleeve <NUM> is attached via a radial interference fit and axial retention of the damping sleeve <NUM> is achieved using a nut, a retaining ring, or any similar feature. In the example of <FIG>, the radial surface <NUM> is part of the damping sleeve <NUM> instead of part of the bearing support <NUM>, <NUM>, <NUM> as shown in <FIG>. This configuration allows for improved modularity of the assembly. In the case of damage to the damper surface, only the damping sleeve <NUM> must be replaced or repaired instead of repairing or replacing the entirety of the fan inlet case. Further, the damping sleeve <NUM> can be incorporated with each of the alternative examples of <FIG> to achieve the same effect.

In yet further examples, the bearing support <NUM>, <NUM><NUM> can include any conventional anti-rotation feature to prevent rotation of the damping sleeve <NUM>.

Claim 1:
A gas turbine engine (<NUM>) comprising:
a compressor section (<NUM>);
a combustor section (<NUM>) fluidly connected to the compressor section (<NUM>) via a primary flowpath;
a turbine section (<NUM>) fluidly connected to the combustor section (<NUM>) via the primary flowpath;
a fan (<NUM>) mechanically connected to at least one turbine (<NUM>) in the turbine section (<NUM>) via a shaft (<NUM>), the shaft (<NUM>) being supported relative to at least one static structure (<NUM>) of the gas turbine engine (<NUM>) via a bearing system (<NUM>), the at least one static structure (<NUM>) including a fan inlet casing and bearing support defined by an annular body (<NUM>; <NUM>; <NUM>) having a radially inward ring (<NUM>; <NUM>; <NUM>) connected to a radially outward ring (<NUM>) via a plurality of struts (<NUM>), a bearing support portion (<NUM>; <NUM>; <NUM>) protruding radially inward from the radially inward ring (<NUM>; <NUM>; <NUM>) and including an axially aligned outer flange (<NUM>; <NUM>; <NUM>) connected to an axially aligned inner flange (<NUM>; <NUM>; <NUM>) via a pedestal (<NUM>; <NUM>; <NUM>), the axially aligned outer flange (<NUM>; <NUM>; <NUM>) including a radially outward facing contact surface (<NUM>) and the axially aligned inner flange (<NUM>; <NUM>; <NUM>) including a radially inward facing contact surface (<NUM>), and the fan inlet casing and bearing support is a single unitary structure, wherein the bearing support portion (<NUM>; <NUM>; <NUM>) is connected to the radially inward ring (<NUM>; <NUM>; <NUM>) via an inlet case flange (<NUM>; <NUM>; <NUM>) and further includes a bearing system case (<NUM>; <NUM>; <NUM>) connected to the inlet case flange (<NUM>; <NUM>; <NUM>) via a plurality of fasteners (<NUM>).