Patent Description:
Gas turbine engines are known to include fan cases, which surround one or more arrays of fan blades and stator vanes. Fan cases are typically cylindrically shaped, and are known to be made of temperature resistant materials such as metals or composites. An example of such a fan case is described in <CIT>. This document describes an airflow-straightening structure for an aircraft engine which includes a hoop inside which there are arranged a plurality of flow-straightening vanes bearing a hub of a fan. The hoop and plurality of vanes are formed in one piece and at least partially formed of a composite material.

A further example is described in <CIT> which describes a containment case for a gas turbine engine. That case comprises a composite core with an inner and outer surface, and at least one puncture resistant layer bonded to the inner surface of the composite core and at least one energy capture layer bonded to the outer surface of the composite core. The puncture resistant layer has a high through-thickness shear strength and high interlaminar toughness at impact. The energy capture layer having a high in-plane tensile strength and low resistance to delamination and fiber-matrix debonding at impact. A method of fabricating a containment case is described which includes the steps of disposing one or more layers of a puncture resistant material on a layup mandrel, disposing one more layers of a structural composite material on an exterior surface of the puncture resistant material, disposing one or more layers of an energy capture material on an exterior surface of the structural material and curing a resin in the plurality of layers.

According to a first aspect of the present invention there is provided a gas turbine engine comprising, a fan case and a plurality of stator vanes integrally formed with the fan case, and the fan case is configured to radially surround fan blades of the gas turbine engine. The fan case and stator vanes are integrally molded of a composite material, the composite material is a polymer matrix composite material, and the polymer matrix composite material comprises reinforcing fibers bound together by a polymer matrix.

In an embodiment of the above embodiment, the plurality of stator vanes includes an array of stator vanes.

In an embodiment of any of the above embodiments, each stator vane in the array projects radially inward from the case.

In an embodiment of any of the above embodiments, the engine includes an inner platform, and each stator vane in the array projects radially inward from the case to the inner platform.

In an embodiment of any of the above embodiments, the inner platform is integrally formed with each of the stator vanes in the array.

In an embodiment of any of the above embodiments, the fan case and stator vanes are formed using a resin transfer molding process.

In an embodiment of any of the above embodiments, the polymer matrix is provided by a polyimide material.

In an embodiment of any of the above embodiments, the polymer matrix is provided by a bismaleimide (BMI) material.

In an embodiment of any of the above embodiments, the reinforcing fibers comprise one of carbon fibers, aramid fibers, glass fibers, and ceramic fibers.

In an embodiment of any of the above embodiments, the plurality of stator vanes comprises a first array of stator vanes and a second array of stator vanes axially spaced-apart from the first array of stator vanes.

In an embodiment of any of the above embodiments, the fan case includes a fore section integrally formed with the first array of stator vanes and an aft section integrally formed with the second array of stator vanes.

In an embodiment the reinforcing fibers are arranged differently in the fan case and the stator vanes. In an embodiment of the previous embodiment the fan case includes a plurality of first fibers extending in a direction parallel to the engine central longitudinal axis and a plurality of second fibers interwoven with the first fibers and extending circumferentially about the engine central longitudinal axis.

A method according to a second aspect of the present invention comprising,
inserting a reinforcement structure into a mold cavity, and injecting a polymer resin into the mold cavity to integrally form a fan case of a gas turbine engine with a plurality of stator vanes, and allowing the polymer resin and reinforcement structure to cool such that the polymer resin and the reinforcement structure form a polymer matrix composite (PMC) material comprising reinforcing fibers bound together by a polymer matrix.

In an embodiment of the above embodiment, the polymer resin is one of polyimide and bismaleimide (BMI).

In an embodiment of any of the above embodiments, the reinforcement structure comprises one of carbon fibers, aramid fibers, glass fibers, and ceramic fibers.

The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

Referring to <FIG>, a gas turbine engine <NUM> includes a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM>, and a turbine section <NUM>. Air entering into the fan section <NUM> is initially compressed and fed to the compressor section <NUM>. In the compressor section <NUM>, the incoming air from the fan section <NUM> is further compressed and communicated to the combustor section <NUM>. In the combustor section <NUM>, the compressed air is mixed with gas and ignited to generate a hot exhaust stream E. The hot exhaust stream E is expanded through the turbine section <NUM> to drive the fan section <NUM> and the compressor section <NUM>. The exhaust gasses E flow from the turbine section <NUM> through an exhaust liner assembly <NUM>. Although a specific engine is depicted in <FIG>, it should be understood that the concepts described may be applied to other types of turbine engines.

<FIG> illustrates an engine component <NUM> according to this disclosure from a perspective view, and <FIG> illustrates the engine component <NUM> from a front view. With joint reference to <FIG> and <FIG>, the engine component <NUM> is a fan case <NUM> and provides a portion of the fan section <NUM> of the engine <NUM>. In this disclosure, a plurality of stator vanes <NUM> are integrally formed with the fan case <NUM>. In <FIG> and <FIG>, a first array <NUM> of stator vanes <NUM> is shown, and each of the stator vanes <NUM> is integrally formed with the fan case <NUM>.

In <FIG> and <FIG>, the fan case <NUM> extends approximately <NUM>° about the engine central longitudinal axis A. Specifically, the engine component <NUM> provides about half of the fan case <NUM> and first array <NUM>, and the engine <NUM> includes a similar engine component which is arranged relative to the engine component <NUM> and completes the fan case <NUM> and the first array <NUM>. In another embodiment the fan case <NUM> forms a complete circumferential hoop about the engine central longitudinal axis A and provides an entire fan case. In this other embodiment, the first array <NUM> of stator vanes <NUM> also extends about the entirety of the engine central longitudinal axis A.

While only one array of stator vanes is shown in <FIG> and <FIG>, there could be a second array of stator vanes integrally formed with the fan case <NUM> and axially spaced-apart from the first array <NUM>. As is known, arrays of fan blades or other rotatable blades are configured to rotate about the engine central longitudinal axis A within the fan case <NUM> and adjacent the array(s) of stator vanes <NUM>.

Again, in this disclosure, the fan case <NUM> is integrally formed with the stator vanes <NUM>. Integrally formed means that the components are formed into one piece. In particular, the components that are referred to herein as integrally formed are formed together as part of the same manufacturing process and, when formed, provide a unitary structure without any joints or seams. Integrally forming the engine component <NUM> provides a number of benefits, including reducing weight of the engine <NUM>, and reducing the number of component parts. Additional benefits will be appreciated from the below.

In a particular aspect of this disclosure, not only are the fan case <NUM> and stator vanes <NUM> integrally formed, but the engine component <NUM> also includes an inner platform <NUM> which is also integrally formed with each of the stator vanes <NUM>. In particular, each stator vane <NUM> projects radially inward, relative to the radial direction R, which is normal to the engine central longitudinal axis A and labeled in the figures for reference, from the fan case <NUM> to the inner platform <NUM>. The platform <NUM> is configured to connect to a structure of the engine <NUM>, as is known in the art.

In this disclosure, the engine component <NUM> (i.e., the fan case <NUM>, stator vanes <NUM>, and inner platform <NUM>) is integrally formed of a composite material. According to the invention, the engine component <NUM> is integrally formed of a polymer matrix composite (PMC) material including reinforcing fibers bound together by a polymer matrix. A polymer matrix composite (PMC) is a composite material composed of a variety of short or continuous fibers bound together by an organic polymer matrix. PMCs are designed to transfer loads between fibers through the matrix. PMCs are lightweight, exhibit high stiffness, and exhibit high strength along the direction of the reinforcing fibers. Other advantages are good abrasion resistance and good corrosion resistance.

The PMC material provides weight and cost benefits, and the fan case <NUM> may also exhibit enhanced containment capabilities relative to prior designs, in particular in the event of a blade out condition wherein the fan case <NUM> is relied upon to prevent a blade or fragments of a blade from being expelled outside the engine <NUM>.

Example PMC materials which may be used to form the engine component <NUM> will now be described. In one example, the engine component <NUM> may be formed of a reinforcing structure bound together by polyimide or bismaleimide (BMI), both of which are polymer materials with high temperature resistance capabilities and which may provide enhanced containment capabilities. The reinforcing structure can be any known type of fiber material, including carbon fibers, aramid fibers, ceramic fibers, and glass fibers, as examples.

Polyimides are polymers of imide monomers. Polyimides exhibit high temperature resistance and also exhibit high strength and rigidity at elevated temperatures. One known type of polyimide is AFR-PE-<NUM> made commercially available by Renegade Materials. BMIs are high performance thermosetting addition-type polyimides. Their characteristics are similar to those of polyimides, which exhibit high strength and high temperature resistance. One known BMI is CYCOM <NUM>-<NUM> manufactured by Solvay.

The engine component <NUM> is manufactured by a resin transfer molding process in one example. In that example, the engine component <NUM> is formed first by inserting the reinforcing structure (i.e., the carbon, aramid, ceramic, or glass fibers) into a mold cavity, and then injecting polymer resin into the mold cavity. Again, the polymer resin is one of polyimide and bismaleimide (BMI). Following injection, the part is allowed to cool, and then it is removed from the mold.

In one example, the reinforcement structure is arranged differently in the fan case <NUM> and the stator vanes <NUM>. In particular, relative to <FIG>, the fan case <NUM> includes a plurality of first fibers <NUM> extending in a direction parallel to the engine central longitudinal axis A and a plurality of second fibers <NUM> interwoven with the first fibers <NUM> and extending circumferentially about the engine central longitudinal axis A, which is represented as in-and-out of the page relative to <FIG>. This arrangement of fibers, which may be braided and/or 3D-woven, relative to the fan case <NUM> provides enhanced containment capabilities. To this end, the fan case fiber arrangement shown in <FIG> may be limited to areas in the engine <NUM> where containment is needed. Relative to the stator vanes <NUM>, the reinforcement structure includes a plurality of first fibers <NUM> extending in a direction parallel to radial direction R and a plurality of second fibers <NUM> interwoven with the first fibers <NUM> and extending in a direction parallel to the engine central longitudinal axis A. This fiber arrangement relative to the stator vanes <NUM> provides for optimum vane performance.

<FIG> schematically illustrates another engine component <NUM>' according to this disclosure. In <FIG>, the fan case <NUM>' includes a first array <NUM> of stator vanes <NUM> and a second array <NUM> of stator vanes <NUM> axially spaced-apart from the first array <NUM> along the engine central longitudinal axis. In this example, the fan case <NUM>' includes two sections, namely a fore section <NUM> and an aft section <NUM>. The fore section <NUM> is integrally formed with the first array <NUM> of stator vanes <NUM>, and the aft section <NUM> is integrally formed with the second array <NUM> of stator vanes <NUM>. The fore section <NUM> is made of a polymer matrix composite including reinforcing fibers held together by a matrix provided by a bismaleimide (BMI) material, in one example. In this example, the aft section <NUM> is made of another material, which may be of higher temperature capability and greater cost, as examples, than the material forming the fore section <NUM>. The arrangement of <FIG> provides the fore section <NUM> with enhanced containment capabilities, high temperature resistance, and high strength, while saving on cost. While the fan case <NUM>' in <FIG> is not a unitary, seamless structure, it still reduces the number of component parts relative to traditional designs, and provides enhanced material properties in the fore section <NUM>, which is the section most likely to need such enhanced properties in some scenarios.

It should be understood that terms such as "fore," "aft," "axial," "radial," and "circumferential" are used above with reference to the normal operational attitude of the engine <NUM>. Further, these terms have been used herein for purposes of explanation, and should not be considered otherwise limiting. Terms such as "generally," "substantially," and "about" are not intended to be boundaryless terms, and should be interpreted consistent with the way one skilled in the art would interpret those terms.

In addition, the various figures accompanying this disclosure are not necessarily to scale, and some features may be exaggerated or minimized to show certain details of a particular component or arrangement.

Claim 1:
A gas turbine engine (<NUM>), comprising:
a fan case (<NUM>); and
a plurality of stator vanes (<NUM>) integrally formed with the fan case (<NUM>), and the fan case (<NUM>) is configured to radially surround fan blades of the gas turbine engine (<NUM>), characterised in that the fan case (<NUM>) and stator vanes (<NUM>) are integrally molded of a composite material, the composite material is a polymer matrix composite material, and the polymer matrix composite material comprises reinforcing fibers bound together by a polymer matrix.