Abstract:
One embodiment of the present invention is a unique gas turbine engine case. Another embodiment is a unique method of manufacturing a gas turbine engine case. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engine cases. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith.

Description:
BACKGROUND 
       [0001]    Gas turbine engine cases 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 
       [0002]    One embodiment of the present invention is a unique gas turbine engine case. Another embodiment is a unique method of manufacturing a gas turbine engine case. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engine cases. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
           [0004]      FIG. 1  schematically illustrates some aspects of a non-limiting example of a gas turbine engine in accordance with an embodiment of the present invention. 
           [0005]      FIG. 2  schematically illustrates some aspects of a non-limiting example of a near net shape gas turbine engine case in accordance with an embodiment of the present invention. 
           [0006]      FIG. 3  depicts some aspects of a non-limiting example of a scalloped near net shape ring in accordance with an embodiment of the present invention. 
           [0007]      FIG. 4  depicts some aspects of a non-limiting example of a plurality of near net shape rings formed as a unit in accordance with an embodiment of the present invention. 
           [0008]      FIG. 5  depicts some aspects of a non-limiting example of a near net shape gas turbine engine case in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    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. 
         [0010]    Referring to the drawings, and in particular  FIG. 1 , a non-limiting example of some aspects of a gas turbine engine  10  in accordance with an embodiment of the present invention is schematically depicted. In one form, gas turbine engine  10  is an aircraft propulsion power plant. In other embodiments, gas turbine engine  10  may be a land-based or marine engine. In one form, gas turbine engine  10  is a multi-spool turbofan engine. In other embodiments, gas turbine engine  10  may take other forms, and may be, for example, a turboshaft engine, a turbojet engine, a turboprop engine, or a combined cycle engine having a single spool or multiple spools. 
         [0011]    As a turbofan engine, gas turbine engine  10  includes a fan system  12 , a bypass duct  14 , a compressor  16 , a diffuser  18 , a combustor  20 , a turbine  22 , a discharge duct  26  and a nozzle system  28 . Bypass duct  14  and compressor  16  are in fluid communication with fan system  12 . Diffuser  18  is in fluid communication with compressor  16 . Combustor  20  is fluidly disposed between compressor  16  and turbine  22 . In one form, combustor  20  includes a combustion liner (not shown) that contains a continuous combustion process. In other embodiments, combustor  20  may take other forms, and may be, for example and without limitation, a wave rotor combustion system, a rotary valve combustion system or a slinger combustion system, and may employ deflagration and/or detonation combustion processes. 
         [0012]    Fan system  12  includes a fan rotor system  30 . In various embodiments, fan rotor system  30  includes one or more rotors (not shown) that are powered by turbine  22 . Bypass duct  14  is operative to transmit a bypass flow generated by fan system  12  to nozzle  28 . Compressor  16  includes a compressor rotor system  32 . In various embodiments, compressor rotor system  32  includes one or more rotors (not shown) that are powered by turbine  22 . Each compressor rotor includes a plurality of rows of compressor blades (not shown) that are alternatingly interspersed with rows of compressor vanes (not shown). Turbine  22  includes a turbine rotor system  34 . In various embodiments, turbine rotor system  34  includes one or more rotors (not shown) operative to drive fan rotor system  30  and compressor rotor system  32 . Each turbine rotor includes a plurality of turbine blades (not shown) that are alternatingly interspersed with rows of turbine vanes (not shown). 
         [0013]    Turbine rotor system  34  is drivingly coupled to compressor rotor system  32  and fan rotor system  30  via a shafting system  36 . In various embodiments, shafting system  36  includes a plurality of shafts that may rotate at the same or different speeds and directions. In some embodiments, only a single shaft may be employed. Turbine  22  is operative to discharge an engine  10  core flow to nozzle  28 . In one form, fan rotor system  30 , compressor rotor system  32 , turbine rotor system  34  and shafting system  36  rotate about an engine centerline  48 . In other embodiments, all or parts of fan rotor system  30 , compressor rotor system  32 , turbine rotor system  34  and shafting system  36  may rotate about one or more other axes of rotation in addition to or in place of engine centerline  48 . Fan rotor system  30  loads, compressor rotor system  32  loads, turbine rotor system  34  loads and shafting system  36  loads are supported and reacted by a plurality of bearing systems, e.g., including bearing systems  50 ,  52  and  54 . 
         [0014]    Discharge duct  26  extends between a discharge portion  40  of turbine  22  and engine nozzle  28 . Discharge duct  26  is operative to direct bypass flow and core flow from a bypass duct discharge portion  38  and turbine discharge portion  40 , respectively, into nozzle system  28 . In some embodiments, discharge duct  26  may be considered a part of nozzle  28 . Nozzle  28  is in fluid communication with fan system  12  and turbine  22 . Nozzle  28  is operative to receive the bypass flow from fan system  12  via bypass duct  14 , and to receive the core flow from turbine  22 , and to discharge both as an engine exhaust flow, e.g., a thrust-producing flow. In other embodiments, other nozzle arrangements may be employed, including separate nozzles for each of the core flow and the bypass flow. 
         [0015]    During the operation of gas turbine engine  10 , air is drawn into the inlet of fan  12  and pressurized by fan  12 . Some of the air pressurized by fan  12  is directed into compressor  16  as core flow, and some of the pressurized air is directed into bypass duct  14  as bypass flow, and is discharged into nozzle  28  via discharge duct  26 . Compressor  16  further pressurizes the portion of the air received therein from fan  12 , which is then discharged into diffuser  18 . Diffuser  18  reduces the velocity of the pressurized air, and directs the diffused core airflow into combustor  20 . Fuel is mixed with the pressurized air in combustor  20 , which is then combusted. The hot gases exiting combustor  20  are directed into turbine  22 , which extracts energy in the form of mechanical shaft power sufficient to drive fan system  12  and compressor  16  via shafting system  36 . The core flow exiting turbine  22  is directed along an engine tail cone  42  and into discharge duct  26 , along with the bypass flow from bypass duct  14 . Discharge duct  26  is configured to receive the bypass flow and the core flow, and to discharge both as an engine exhaust flow, e.g., for providing thrust, such as for aircraft propulsion. 
         [0016]    Referring to  FIGS. 2-4 , some aspects of a non-limiting example of an engine case  60  in accordance with an embodiment of the present invention are schematically illustrated. Engine  10  includes a plurality of engine cases, such as engine case  60  for housing and supporting various components of engine  10 . In one form, engine case  60  houses and supports components of fan system  12 . In other embodiments, case  60  may be configured to house other engine  10  components in addition to or in place of fan system  12  components. For example and without limitation, case  60  may be an inner case and/or an outer case for compressor  16 , diffuser  18 , combustor  20 , turbine  22  and/or nozzle  28 . 
         [0017]    Engine case  60  is a near net shape unitary annular engine case, e.g., generally revolved about engine centerline  48 . Internal lines in  FIG. 2 , e.g., lines L 1 , L 2  and L 3 , illustrate the net shape features of engine case  60 , whereas external lines, e.g., L 4 , L 5  and L 6 , represent the raw near net shape of engine case  60 , illustrating the material to be removed to yield the final net shape of engine case  60 . Although depicted in cross-section, it will be understood that the depiction of  FIG. 2  is schematic in nature, and that cross-hatching is not shown for purposes of clarity. In one form, engine case  60  is formed of a two annular case sections  62  and  64  that are electron beam welded to each other at a weld joint  66  to form an intermediate unitary annular case structure  68 . In some embodiments, one or more of annular case sections  62  and  64  may be formed of one or more plates that are rolled or otherwise formed to the desired dimensions, and then seam welded, e.g., from the forward end to the aft end, to form the case sections, and in some embodiments case structure  68 . A plurality of near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88  are electron beam welded to intermediate unitary annular case structure  68 , e.g., annular case sections  62  and  64 , at weld joints  90 ,  92 ,  94 ,  96 ,  98 ,  100 ,  102 ,  104  and  106 , to form unitary annular engine case  60 . As illustrated in  FIG. 2 , some of the near net shape rings are electron beam welded to an outer surface  108  of case structure  68 , some are electron beam welded to an inner surface  110  of case structure  68 , and some are welded to end portions of case structure  68 , e.g., at weld joints  90  and  106 . In various embodiments, engine case  60  may be formed of any number of annular case sections and near net shape rings that are electron beam welded to each other at any number of weld joints to form a unitary annular engine case. In one form, the electron beam welds between the near net shape rings and case structure  68  extend circumferentially along (around) case structure  68 . In other embodiments, the electron beam welds may extend only partially along case structure  68 . In one form, the near net shape rings are 360° rings. In other embodiments, the near net shape rings may be any arc length. In addition, in some embodiments, near net shape linear or other segments may be electron beam welded to case structure  68 , e.g., in an axial direction parallel to engine centerline  48 . 
         [0018]    The near net shape rings may vary with the needs of the particular application. In one form, near net shape rings  72  and  88  are forged near net shape into the form of a flange, e.g., for attaching engine case  60  to other structures. In one form, near net shape rings  74 ,  80 ,  82  and  84  are formed, e.g., by forging, near net shape into the form of external stiffening rings configured to add stiffness to engine case  60 . In one form, near net shape rings  78  and  86  are formed, e.g., by forging, near net shape into the form of internal retaining flanges configured to support engine  10  components positioned inside engine case  60 . In one form, near net shape ring  76  is formed, e.g., by forging, near net shape into the form of an accessory attachment ring configured for attaching accessories externally to engine case  60 . In one form, near net shape rings  76  and  88  are scalloped, e.g., in order to reduce weight. The scallops, e.g., depicted in  FIG. 3  as scallops  110  and  112 , may be formed by various means, including machining and/or may be formed, e.g., forged, near net shape. In one form, a plurality of near net shape rings may be formed as a unit, e.g., as a single forging, which may be subsequently cut into individual near net shape rings. For example, as depicted in  FIG. 4 , near net shape rings  80  and  82  may be formed as a unit  114 , which may be cut along a parting line  116  to yield individual near net shape rings  80  and  82 . 
         [0019]    Engine case  60  may be manufactured by forming one or more annular case sections, e.g., annular case sections  62  and  64 . In one form, case sections  62  and  64  are formed by forging into near net shape. In other embodiments, other forming techniques may be employed to yield a final shape and/or near net shape. Faying surfaces are machined on both annular case sections  62  and  64  at the location of intended weld joints, e.g., weld joint  66 , and then annular case sections  62  and  64  are electron beam welded together at the faying surfaces to form unitary annular case structure  68 . In some embodiments, annular case sections  62  and  64  may be temporarily tack welded together, e.g., to aid in final electron beam welding of the two sections together. Although described herein as being electron beam welded together prior to attaching near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88 , it will be understood that in various embodiments, any one or more of near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88  may be attached to annular case sections  62  and/or  64  prior to electron beam welding annular case sections  62  and  64  together. 
         [0020]    In one form, near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88  are formed by forging. In other embodiments, one or more of near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88  may be formed via another manufacturing technique, e.g., extrusion, casting, or machining of bar-stock and/or tube-stock, depending upon the needs of the application, e.g., including the desired size of the rings. In some embodiments, near net shape rings may be forged as rings, or formed as straight pieces, which are rolled into rings and then welded by electron beam, laser welding or flash butt welding (preferred). Faying surfaces are machined into each of near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88  and on case structure  68  at the locations intended for weld joints  90 ,  92 ,  94 ,  96 ,  98 ,  100 ,  102 ,  104  and  106 . For example, referring to  FIG. 5 , a faying surface  118  is machined into near net shape ring  82 , and a faying surface  120  is machined into annular case section  64  of intermediate case structure  68 . In the depiction of  FIG. 5 , dashed lines generally represent raw near net shape surfaces, as formed e.g., by forging, whereas solid lines represent machined surfaces, including machined faying surfaces  118  and  120 . In other embodiments, faying surfaces may not be machined into either of near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88 , and case structure  68 . In another manufacturing step, near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88  are tack welded onto intermediate case structure  68 . For example, in the depiction of  FIG. 5 , near net shape ring  82  is tack welded to case structure  68  with a tack weld  122 . In other embodiments, any one or more of near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88  may not be tack welded in place. Once tack welded into place on case structure  68 , near net shape rings  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88  are electron beam welded to case structure  68 . In one form, the electron beam welds extend circumferentially around case structure  68 , e.g., along circumferential direction  124  ( FIG. 3 ). In other embodiments, the electron beam welds may extend intermittently or only partially around case structure  68 . Whereas near net shape rings  74 ,  76 ,  80 ,  82  and  84  are electron beam welded to outer surface  108  of case structure  68 , near net shape rings  78  and  86  are electron beam welded to inner surface  110 , and near net shape rings  72  and  88  are welded to ends of case structure  68  at the location of weld joints  90  and  106 . 
         [0021]    Embodiments of the present invention include a method of manufacturing a gas turbine engine case, comprising: forming a first annular case section; forging a first near net shape ring; machining a faying surface on at least one of the first near net shape ring and the first annular case section; and electron beam welding the first near net shape ring to the first annular case section at the faying surface. 
         [0022]    In a refinement, the electron beam welding is performed circumferentially around the first annular case section. 
         [0023]    In another refinement, the first annular case section is formed by forging. 
         [0024]    In yet another refinement, the method further comprises: forming a second annular case section; machining a second faying surface on the second annular case section; machining a third faying surface on the first annular case section; and electron beam welding the first annular case section to the second annular case section at the third faying surface and the second faying surface. 
         [0025]    In still another refinement, the first near net shape ring is forged into the form of a flange. 
         [0026]    In yet still another refinement, the flange is electron beam welded to an end of the first annular case section. 
         [0027]    In a further refinement, the method further comprises: forming a second near net shape ring; machining a fourth faying surface on at least one of the second near net shape ring and the first annular case section for joining the second near net shape to one of an inner surface and an outer surface of the first annular case section; and electron beam welding the second near net shape ring to the first annular case section at the one of the inner surface and the outer surface of the first annular case section. 
         [0028]    In a yet further refinement, the method further comprises forming the first near net shape ring as a stiffening ring configured to add stiffness to the first annular case section. 
         [0029]    In a still further refinement, the method further comprises forming the first near net shape ring as an accessory attachment ring. 
         [0030]    In a yet still further refinement, the method further comprises forming scallops in the first near net shape ring. 
         [0031]    In additional further refinement, the method further comprises: forging a plurality of near net shape rings in a single forging; and machining the single forging to separate the plurality of near net shape rings. 
         [0032]    Embodiments of the present invention include a gas turbine engine case, comprising: a plurality of individual annular case sections electron beam welded to each other to form a unitary annular case structure; and at least one near net shape ring electron beam welded to the unitary annular case structure to form a unitary annular engine case. 
         [0033]    In a refinement, the gas turbine engine case further comprises at least another near net shape ring electron beam welded to the unitary annular case structure. 
         [0034]    In another refinement, the at least one near net shape ring is forged into the form of a flange. 
         [0035]    In yet another refinement, the at least one near net shape ring is forged into the form of a stiffening ring. 
         [0036]    In still another refinement, the at least one near net shape ring is forged into the form of an accessory attachment ring. 
         [0037]    In yet still another refinement, the at least one near net shape ring is forged into the form of an internal retaining flange. 
         [0038]    In a further refinement, an electron beam weld between the at least one near net shape ring and the unitary annular case structure extends circumferentially along the unitary annular case structure. 
         [0039]    Embodiments of the present invention include a method for manufacturing a gas turbine engine, comprising: forming an engine case for at least one of a fan, a compressor, a diffuser, a combustor, a turbine and a nozzle of the gas turbine engine by: forming an first near net shape annular case section; forging a first near net shape ring; machining a faying surface on at least one of the first near net shape ring and the first near net shape annular case section; and electron beam welding the first near net shape ring to the first near net shape annular case section at the faying surface. 
         [0040]    In a refinement, the method further comprises at least one of: forming a second near net shape annular case section; machining a second faying surface on the second near net shape annular case section; machining a third faying surface on the first near net shape annular case section; and electron beam welding the first near net shape annular case section to the second near net shape annular case section at the third faying surface and the second faying surface; and forming a second near net shape ring; machining a fourth faying surface on at least one of the second near net shape ring and the first near net shape annular case section or the second near net shape annular case section for joining the second near net shape to at least one of an inner surface and an outer surface of the first near net shape annular case section or the second near net shape annular case section; and electron beam welding the second near net shape ring to the first near net shape annular case section or the second near net shape annular case section at the at least one of the inner surface and the outer surface. 
         [0041]    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.