Abstract:
One embodiment of the present invention is an integrated aero-engine flowpath structure. Another embodiment is a method of manufacturing integrated aero-engine flowpath structure. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for aero-engine flowpath structures. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application 61/290,807, filed Dec. 29, 2009, and is incorporated herein by reference. 
    
    
     GOVERNMENT RIGHTS 
     The present application was made with United States government support under Contract No. F33615-03-D-2357, awarded by the United States Air Force. The United States government may have certain rights in the present application. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to aero-engines, and, more particularly, to an integrated aero-engine flowpath structure. 
     BACKGROUND 
     Aero-engine structures remain an area of interest. Some existing systems have various shortcomings, drawbacks, and disadvantages relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     One embodiment of the present invention is an integrated aero-engine flowpath structure. Another embodiment is a method of manufacturing integrated aero-engine flowpath structure. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for aero-engine flowpath structures. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  schematically depicts an aero-engine in accordance with an embodiment of the present invention. 
         FIG. 2  depicts a cross section of a ramburner/nozzle in accordance with an embodiment of the present invention. 
         FIGS. 3A-3C  depict the alignment of composite fiber plies at some bond joints of the ramburner/nozzle embodiment of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nonetheless be understood that no limitation of the scope of the invention is intended by the illustration and description of certain embodiments of the invention. In addition, any alterations and/or modifications of the illustrated and/or described embodiment(s) are contemplated as being within the scope of the present invention. Further, any other applications of the principles of the invention, as illustrated and/or described herein, as would normally occur to one skilled in the art to which the invention pertains, are contemplated as being within the scope of the present invention. 
     Referring now to the drawings, and in particular  FIG. 1 , a non-limiting example of an engine  10  in accordance with an embodiment of the present invention is depicted. In one form, engine  10  is an aero-engine, such as a dual-mode gas turbine ramjet engine capable of operating as a gas turbine engine and a ramjet engine. In other embodiments, engine  10  may be a gas turbine engine, a ramjet engine, a scramjet engine, a rocket engine or any combination thereof. In the form of a gas turbine engine, engine  10  may be a single or multi-spool engine aero, land-based or marine engine, and may be a turbofan, turbojet, turboshaft, or turboprop engine. Embodiments of the present invention include case structures, flowpath structures, and combined case/flowpath structures formed of composite materials that do not employ or require metal or metallic backing structure in order to sustain both aerodynamic and structural loads. 
     Engine  10  includes a compressor  12 , a combustor  14  and a turbine  16 . A ramburner added to the rear of engine  10  may increase thrust at supersonic speeds, e.g., Mach 3.0 to Mach 4.0+ in one form, although greater or lesser speeds may be applicable to other embodiments. In one form, engine  10  includes an integrated composite ramburner/nozzle  18 , hereinafter referred to as ramburner  18 . Ramburner  18  may, in some embodiments, provide additional thrust capability relative to an air breathing gas turbine engine without the potentially significant cycle penalty due to pressure loss that may be seen in some conventional augmenter designs having mechanical flame holder features, or with a reduced such penalty. In one form, ramburner  18  is a flowpath structure that does not employ or require a metal or metallic backing structure in order to withstand both aerodynamic and structural loads. In one form, the composite material used to form ramburner  18  is carbon-carbon, although other composites may be used in other embodiments. For example and without limitation, other applicable composite materials may include other ceramic matrix composites (CMC&#39;s) than carbon-carbon, metal-matrix composites (MMC&#39;s) and/or intermetallic-matrix composites (IMC&#39;s) in addition to or in place of carbon-carbon. Non-limiting examples of applicable metallic materials include, without limitation, niobium alloys. In addition, the present invention is equally applicable to other flowpath structures, e.g., such turbine flowpath structures. 
     Referring now to  FIG. 2 , ramburner  18  includes an integrated primary structure  20  formed of a composite outer flowpath wall  22 , a composite inner flowpath wall  24  and a plurality of composite linking structures  26 . Linking structures  26  extend between outer flowpath wall  22  and inner flowpath wall  24 . In one form, linking structures  26  are attached to both outer flowpath wall  22  and inner flowpath wall  24 , and are structured to separate outer flowpath wall  22  and inner flowpath wall  24  to form a primary flowpath  28  therebetween, i.e., a flowpath for the primary working fluid of engine  10 , and to transfer mechanical loads between outer flowpath wall  22  and inner flowpath wall  24 . 
     In one form, linking structures  26  include a plurality of vanes  30 , such as turbine exit vanes, and a plurality of aft support struts  32 . In other embodiments, linking structures  26  may take other forms that link outer flowpath wall  22  to inner flowpath wall  24  in addition to or in place of vanes  30  and struts  32 . In still other embodiments, linking structures  26  may be of a single common form in place of both forms manifested by vanes  30  and struts  32 . Such linking structures  26  may be located at a common axial location, or may be located at more than one axial location. 
     In one form, integrated primary structure  20  includes a nozzle  34 , e.g., a plug nozzle, which in some embodiments may be formed as part of inner flowpath wall  24 . In other embodiments, nozzle  34  may be a separate piece that is co-bonded with one or more features of integrated primary structure  20 . In still other embodiments, nozzle  34  may not be considered part of integrated primary structure  20  and may or may not be attached to integrated primary structure  20 . In one form, integrated primary structure  20  also includes a center hub  36  to secure the inner ends of struts  32  and additional stiffness and stability to integrated primary structure  20 . In other embodiments, center hub  36  may not be considered part of integrated primary structure  20 . 
     A weakness of the carbon-carbon material system is relatively low inter-laminar shear strength. A fairly simple structural joint to produce in a carbon-carbon assembly is a stab-through joint where one element passes through a second element with an effective bond applied to the mating surfaces. If carbon-carbon elements are bonded in this fashion, high inter-laminar shear stresses may be generated from the mismatch in coefficient of thermal expansion between the intersecting plies. This may result from the fact that the coefficient of thermal expansion for carbon-carbon varies significantly in the longitudinal direction versus the through-the-thickness direction. In order to reduce or eliminate high inter-laminar shear stresses, the carbon fiber plies of the mating components in embodiments of the invention are aligned in the structural bond joints of primary structure  20 , i.e., are oriented in the same direction. In one form, these joints include the turbine exit vane  30  to outer flowpath wall  22  bond joints, the turbine exit vane  30  to inner flowpath wall  24  bond joints, the aft strut  32  to outer flowpath wall  22  bond joints, the aft strut  32  to inner flowpath wall  24  bond joints, and the aft strut  32  to center hub  36  bond joints. 
     For example, vanes  30  include segments  30 A and  30 B extending from the airfoil portion in a direction approximately parallel to outer flowpath wall  22  and inner flowpath wall  24 , respectively. Segments  30 A and  30 B may be formed by rolling the carbon-fiber plies at the ends of each vane  30  in a direction approximately parallel outer flowpath wall  22  and inner flowpath wall  24 , respectively. The carbon-fiber plies of vanes  30  transition from extending along the airfoil span to extending approximately parallel to the plies in outer flowpath wall  22  and inner flowpath wall  24 , respectively. Hence, the plies of vanes  30  are aligned with the plies of outer flowpath wall  22  and inner flowpath wall  24 , which may reduce inter-laminar shear stresses at the bond joints. For example, as depicted in  FIG. 3A , plies  30 P of vane  30  in segment  30 A are aligned approximately parallel to plies  22 P of outer flowpath wall  22 . Similarly, as depicted in  FIG. 3B  the plies  30 P of vane  30  in segment  30 B are aligned approximately parallel to plies  24 P of inner flowpath wall  24 . In one form, the plies are not only aligned in one plane, e.g., as depicted in  FIG. 3A , but are also aligned in a second plane. For example,  FIG. 3C  depicts plies  30 P of vane  30  aligned in a second plane with plies  22 P of outer flowpath wall  22 . In the depiction of  FIG. 3C , plies  30 P are hidden, and hence are indicated with dashed lines, whereas plies  22 P are indicated with solid lines. In one form, the plane of  FIG. 3C  is perpendicular to the plane of  FIG. 3A . 
     Each vane  30  interfaces with outer flowpath wall  22  at a radial interface  38  and an axial interface  40 , which respectively position each vane  30  radially and axially with regard to outer flowpath wall  22 . In one form, radial interface  38  includes an outer pilot diameter on each vane  30  and an inner pilot diameter in outer flowpath wall  22 . In other embodiments, other radial positioning interface types may be employed. Axial interface  40  includes a shoulder in outer flowpath wall  22  abutted by the shroud end face (segment  30 A) of each vane  30 . In one form, the interface features are machined. In other embodiments, other forming processes may be employed. 
     Each vane  30  interfaces with inner flowpath wall  24  at a radial interface  42  and an axial interface  44 , which respectively position each vane  30  radially and axially with regard to inner flowpath wall  24 . In one form, radial interface  42  includes an outer pilot diameter on each vane  30  and an inner pilot diameter in inner flowpath wall  24 . In other embodiments, other radial positioning interface types may be employed. Axial interface  44  includes a shoulder in inner flowpath wall  24  abutted by the platform end face (segment  30 B) of each vane  30 . In one form, the interface features are machined. In other embodiments, other forming processes may be employed. 
     Similar to vanes  30 , each strut  32  includes a segment  32 A extending in a direction approximately parallel to outer flowpath wall  22 . The plies of each strut  32  transition from extending along the strut span to extending approximately parallel to the plies in outer flowpath wall  22 , and are aligned with the plies in outer flowpath wall  22  in a manner similar to that described with respect to segments  30 A of vanes  30  and depicted in  FIG. 3A . Primary structure  20  includes a transition structure  46 , which may be in the form of a collar extending around each strut  32 . Transition structure  46  includes plies extending along the strut span and aligned with the plies of strut  32 . Transition structure  46  also includes plies extending approximately parallel to inner flowpath wall  24  and aligned with the plies of inner flowpath wall  24 . 
     Each strut  32  interfaces with outer flowpath wall  22  at an interface  48 , which positions each strut  32  circumferentially, radially and axially with regard to outer flowpath wall  22 . In one form, interface  48  includes a pad formed into outer flowpath wall  22 , into which strut  32  is fitted. In other embodiments, other radial positioning interface types may be employed. In one form, the interface features are machined. In other embodiments, other forming processes may be employed. 
     Each strut  32  is fitted through a slot  50  in inner flowpath wall  24  and into a pocket  52  in center hub  36 . The slot dimensions are sufficiently larger than the strut dimensions so as to avoid undesirable contact between the strut and inner flowpath wall as might induce undesirable stresses, e.g., due to thermal expansion. Center hub  36  is of a laminated construction to provide near parallel ply orientation between each strut  32  and the corresponding center hub strut pocket  52 . To eliminate high inter-laminar tensile stresses at the foot of the strut, the strut is cut short at the inner end and a radial gap  54  is provided between the strut foot and the hub. 
     Once components  22 - 38  are assembled together, they are co-bonded to form the unitized integral primary structure  20 , which is designed to withstand the thermal and mechanical loading encountered during the operation of engine  10  and the vehicle into which engine  10  is installed, without additional structural backing/support. Co-bonding may be performed, for example and without limitation, by applying a film of carbon resin (and any other suitable materials desired for the particular application, e.g., silicon carbide (SiC) particulates) to bond surface(s) of one or more of the carbon-carbon parts to be joined. The carbon-carbon parts are then held together at the bond surfaces, with the carbon resin contacting the bond surfaces of each of the carbon-carbon parts to be joined. Heat is then applied, during which time the resin infiltrates into the carbon-carbon parts, creating a bond between the carbon-carbon parts at the location of the bond surfaces. 
     In one form, the bonded integrated primary structure  20  is treated to reduce or prevent oxidation damage, e.g., which may occur during high temperature operation. In one form, integrated primary structure  20  is coated with SiC as an oxidation protection treatment, although other treatments may be employed in other embodiments. For example and without limitation, other treatments that provide oxidation resistance may include silicon nitride (Si3N4), tetraethylorthosilicate (TEOS) and/or dichroic glass in addition to or in place of SiC. In other embodiments, part or all of integrated primary structure  20  may not be coated or treated for oxidation resistance, or may be coated or treated for purposes other than oxidation resistance in addition to or in place of treatment for oxidation resistance. As an integrated structure, integrated primary structure  20  is single, one-piece, co-bonded, unitary structure not susceptible to nondestructive disassembly. 
     Ramburner  18  may also include additional components, which may be in the form of prefabricated secondary elements that are added to integrated primary structure  20  after co-bonding. Alternatively, one or more of the additional components may be included as part of integrated primary structure  20  in some embodiments. The additional components may include, for example, a forward guide structure  56 , a screech cover  58  and a tail cone  60 . In other embodiments, tail cone  60  may be included as part of nozzle  34 . In one form, the prefabricated secondary elements are glassed in place through a heat treat cycle. This glassing provides a leak free weak bond at the mating faces. Glassing may be performed, for example and without limitation, by applying an SiC coating to the surfaces to be joined, holding the parts together, and heating the parts to form silica glass from the SiC coating. In other embodiments, other glassing materials and/or glassing techniques may be employed. In still other embodiments, other processes and/or other techniques may be employed to hold the prefabricated secondary elements in place in addition to or in place of glassing. 
     Ramburner  18  also includes a flange  62  for attachment to engine  10 , e.g., via an axial clamping arrangement, and via a radial and circumferential positioning arrangement, e.g. a cross key arrangement. Although the present embodiment includes each component/feature  54 - 60 , it will be understood that other embodiments may not include each such component/feature, and/or may include other components/features. For example, other embodiments may or may not include various elements, such as, for example, screech cover  58 . In addition, other embodiments may include additional elements, such as a T-shield to protect each strut  32 . Each such component, e.g., each of components  54 - 60 , is prefabricated and formed to interface with each adjoining component to yield the structure depicted in  FIG. 2 . 
     Forward guide structure  56  interfaces with inner flowpath wall  24  at a radial interface  64  and an axial interface  66 , which respectively position forward guide structure  56  radially and axially with regard to inner flowpath wall  24 . In one form, radial interface  64  is a threaded joint, i.e., with mating threads formed on each of forward guide structure  56  and inner flowpath wall  24 . In other embodiments, other radial positioning interface types may be employed. Axial interface  66  includes a shoulder in inner flowpath wall  24  abutted by the end face of forward guide structure  56 . In one form, the interface features are machined. In other embodiments, other forming processes may be employed. In one form, the carbon-fiber plies in forward guide feature  56  are aligned with the carbon fiber plies of inner flowpath wall  24 . 
     Screech cover  58  is pinned in place on outer flowpath wall  22 . In one form, the carbon-fiber plies in screech cover  58  are aligned with the carbon fiber plies of outer flowpath wall  22 . 
     Tail cone  60  interfaces with nozzle  34  at a radial interface  68  and an axial interface  70 , which respectively position tail cone  60  radially and axially with regard to nozzle  34 . In one form, radial interface  68  is a threaded joint, i.e., with mating threads formed on each of tail cone  60  and nozzle  34 . In other embodiments, other radial positioning interface types may be employed. Axial interface  68  includes a shoulder in nozzle  34  abutted by the end face of tail cone  60 . In one form, the interface features are machined. In other embodiments, other forming processes may be employed. In one form, the carbon-fiber plies in tail cone  60  are aligned with the carbon fiber plies of nozzle  34 . 
     One embodiment of the present invention is an integrated aero-engine flowpath structure which may include a composite outer flowpath wall, a composite inner flowpath wall, and a composite linking structure extending between the composite outer flowpath wall and the composite inner flowpath wall. The composite linking structure is structured to separate the composite outer flowpath wall from the composite inner flowpath wall. The composite outer flowpath wall and the composite inner flowpath wall define therebetween a primary flowpath for a working fluid of the aero-engine. The composite outer flowpath wall, the composite inner flowpath wall, and the composite linking structure are co-bonded to form a unitary structure operable to withstand thermal and mechanical loading during the operation of the aero-engine without additional structural backing. 
     In one refinement of the embodiment the composite outer flowpath wall, the composite inner flowpath wall, and the composite linking structure are formed of a carbon-carbon material. 
     In another refinement of the embodiment plies of the carbon-carbon material in the composite linking structure are aligned with plies in at least one of the composite outer flowpath wall and the composite inner flowpath wall. 
     In another refinement of the embodiment the composite linking structure includes a segment extending parallel to at least one of the composite outer flowpath wall and the composite inner flowpath wall. 
     In another refinement of the embodiment the composite linking structure is a vane. 
     In another refinement of the embodiment the composite linking structure is a strut. 
     Another refinement of the embodiment the may include a carbon-carbon transition structure bonded to the composite linking structure and to at least one of the composite outer flowpath wall and the composite inner flowpath wall. The plies of the carbon-carbon transition structure are aligned with plies in the composite linking structure and aligned with plies in at least one of the composite outer flowpath wall and the composite inner flowpath wall. 
     Another refinement of the embodiment may include an integral carbon-carbon plug nozzle forming a portion of the composite inner flowpath wall. 
     Another refinement of the embodiment may include a carbon-carbon tail cone bonded to the carbon-carbon plug nozzle. 
     Another refinement of the embodiment may include a threaded bond joint between the carbon-carbon tail cone and the carbon-carbon plug nozzle. 
     Another refinement of the embodiment may include a carbon-carbon forward structure bonded to the composite inner flowpath wall. 
     Another refinement of the embodiment may include a threaded bond joint between the carbon-carbon forward structure and the composite inner flowpath wall. 
     Another embodiment of the present invention may include at least one of a carbon-carbon outer flowpath wall and a carbon-carbon inner flowpath wall. It may also include a carbon-carbon linking structure extending from the at least one of the carbon-carbon outer flowpath wall and the carbon-carbon inner flowpath wall, and a bond joint between the carbon-carbon linking structure and at least one of the carbon-carbon outer flowpath wall and the carbon-carbon inner flowpath wall. At the bond joint, plies in the carbon-carbon linking structure are aligned with plies in the at least one of the carbon-carbon outer flowpath wall and the carbon-carbon inner flowpath wall. 
     In one refinement of the embodiment the carbon-carbon linking structure includes a segment extending parallel to the at least one of the carbon-carbon outer flowpath wall and the carbon-carbon inner flowpath wall. 
     Another refinement of the embodiment may include a carbon-carbon transition structure bonded to the carbon-carbon linking structure and to the at least one of the carbon-carbon outer flowpath wall and the carbon-carbon inner flowpath wall. The plies of the carbon-carbon transition structure are aligned with plies in the carbon-carbon linking structure and aligned with plies in at least one of the carbon-carbon outer flowpath wall and the carbon-carbon inner flowpath wall. 
     Another embodiment of the present invention is a method of manufacturing an integrated aero-engine flowpath structure which include rolling composite plies of a first composite component to form a segment of the first composite component extending in a direction parallel to a second composite component. It may also include aligning the plies in the segment with plies of the second composite component, and bonding the segment to the second composite component. 
     In one refinement of the embodiment the aligning includes aligning the plies of the segment with the plies of the second composite component includes aligning in one plane. 
     In another refinement of the embodiment the aligning includes aligning the plies of the segment with the plies of the second composite component includes aligning in two planes. 
     Another refinement of the embodiment may include performing an oxidation protection treatment of the aero-engine flowpath structure. 
     In another refinement of the embodiment the oxidation protection treatment is performed after the bonding. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment(s), but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.