Abstract:
A case for a gas turbine engine incudes a radial flange with a partial scallop along an inner diameter of the radial flange. A case assembly for a gas turbine engine incudes a first case with an a first radial flange with a partial scallop along an inner diameter of the first radial flange, the partial scallop adjacent to a first aperture thorough the first radial flange and a second case with an a second radial flange with a second aperture thorough the second radial flange the second radial flange mountable to the first radial flange at an interface such that the second aperture is axially aligned with the first aperture and a seal lip that extends from the second case interfaces with said first case at a longitudinal interface

Description:
BACKGROUND 
       [0001]    The present disclosure relates to a gas turbine engine and, more particularly, to a case flange therefor. 
         [0002]    An engine case assembly for a gas turbine engine includes multiple cases that are secured to one to another at an external flange joint. The multiple cases facilitate installation of various internal gas turbine engine components such as a diffuser assembly, rotor assemblies, vane assemblies, combustors, seals, etc. Each external flange joint includes flanges that extend radially outwardly from an outer surface of the outer engine case. 
         [0003]    The multiple external bolted flange joints have a specific fatigue life and may provides a potential leak path. 
       SUMMARY 
       [0004]    A case for a gas turbine engine according to one disclosed non-limiting embodiment of the present disclosure can include a radial flange with a partial scallop. 
         [0005]    A further embodiment of the present disclosure may include, wherein the partial scallop is along an inner diameter of the radial flange of an outer engine case. 
         [0006]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the partial scallop is along an outer diameter the radial flange of an inner engine case. 
         [0007]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the partial scallop forms a radius of about 0.25 inch (6.35 mm). 
         [0008]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the partial scallop forms an inner radius of about 0.25 inch (6.35 mm) formed from a face of the radial flange portion. 
         [0009]    A further embodiment of any of the embodiments of the present disclosure may include a scallop along an outer diameter of the radial flange. 
         [0010]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the scallop forms a radius of about 0.25 inch (6.35 mm). 
         [0011]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the partial scallop forms a radius of about 0.25 inch (6.35 mm). 
         [0012]    A further embodiment of any of the embodiments of the present disclosure may include, wherein a circle defined around an aperture in the radial flange tangentially interfaces with the inner diameter of the radial flange, the outer diameter of the radial flange, the partial scallop and the scallop. 
         [0013]    A further embodiment of any of the embodiments of the present disclosure may include, wherein a web thickness around an aperture in the radial flange is approximately equivalent with respect to the inner diameter of the radial flange, the outer diameter of the radial flange, the partial scallop and the scallop. 
         [0014]    A case assembly for a gas turbine engine according to another disclosed non-limiting embodiment of the present disclosure can include a first case with an a first radial flange with a partial scallop along an inner diameter of the first radial flange, the partial scallop adjacent to a first aperture thorough the first radial flange; and a second case with an a second radial flange with a second aperture thorough the second radial flange the second radial flange mountable to the first radial flange at an interface such that the second aperture is axially aligned with the first aperture and a seal lip that extends from the second case interfaces with said first case at a longitudinal interface. 
         [0015]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the seal lip that extends from the second case includes an undercut adjacent to the longitudinal interface. 
         [0016]    A further embodiment of any of the embodiments of the present disclosure may include, wherein a web thickness around an aperture in the radial flange is approximately equivalent with respect to the inner diameter of the first radial flange, an outer diameter of the first radial flange, and the partial scallop. 
         [0017]    A further embodiment of any of the embodiments of the present disclosure may include a scallop along an outer diameter of the radial flange. 
         [0018]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the scallop forms a radius of about 0.25 inch (6.35 mm). 
         [0019]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the partial scallop forms a radius of about 0.25 inch (6.35 mm). 
         [0020]    A further embodiment of any of the embodiments of the present disclosure may include, wherein the partial scallop forms an inner radius of about 0.25 inch (6.35 mm) formed from a face of the radial flange portion. 
         [0021]    A further embodiment of any of the embodiments of the present disclosure may include, wherein a circle defined around the first aperture in the first radial flange tangentially interfaces with the inner diameter of the radial flange, the outer diameter of the radial flange, and the partial scallop. 
         [0022]    A further embodiment of any of the embodiments of the present disclosure may include a heat shield that includes a distal end that interfaces with a step in the first case forward of the radial flange interface. 
         [0023]    A further embodiment of any of the embodiments of the present disclosure may include a fastener with a “D” head that is received through the first and second aperture. 
         [0024]    The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
           [0026]      FIG. 1  is a schematic cross-sectional view of an example geared architecture gas turbine engine; 
           [0027]      FIG. 2  is an exploded view of an engine case assembly of the example geared architecture gas turbine engine; 
           [0028]      FIG. 3  is a cross-sectional view through an example case flange; 
           [0029]      FIG. 4A  is a perspective view of a flange for an outer case; 
           [0030]      FIG. 4B  is a perspective view of a flange for an inner case; 
           [0031]      FIG. 5  is a face view of a flange; 
           [0032]      FIG. 6  is a sectional perspective view of the flange joint; 
           [0033]      FIG. 7  is a perspective view of a fillet radius at the partial scallop; and 
           [0034]      FIG. 8  is a sectional top view of the flange joint. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines architectures such as a low-bypass turbofan may include an augmentor section (not shown) among other systems or features. Although schematically illustrated as a turbofan in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines to include, but not limited to, a three-spool (plus fan) engine as well as other engine architectures such as turbojets, turboshafts, open rotors and industrial gas turbines. 
         [0036]    The fan section  22  drives air along a bypass flowpath and a core flowpath. The compressor section  24  compresses air along the core flowpath for communication into the combustor section  26  then expansion through the turbine section  28 . The engine  20  generally includes a low spool  30  and a high spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine case assembly  36  via several bearing compartments  38 . 
         [0037]    The low spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low-pressure compressor (“LPC”)  44  and a low-pressure turbine (“LPT”)  46 . The inner shaft  40  drives the fan  42  either directly or through a geared architecture  48  to drive the fan  42  at a lower speed than the low spool  30 . The high spool  32  includes an outer shaft  50  that interconnects a high-pressure compressor (“HPC”)  52  and high-pressure turbine (“HPT”)  54 . A combustor  56  is arranged between the HPC  52  and the HPT  54 . Core airflow is compressed by the LPC  44  then the HPC  52 , mixed with fuel and burned in the combustor  56 , then expanded over the HPT  54  and the LPT  46 . The HPT  54  and the LPT  46  drive the respective high spool  32  and low spool  30  in response to the expansion. The inner shaft  40  and the outer shaft  50  are concentric and rotate about the engine central longitudinal axis A that is collinear with their longitudinal axes. 
         [0038]    In one example, the gas turbine engine  20  is a high-bypass geared architecture engine in which the bypass ratio is greater than about six (6:1). The geared architecture  48  can include an epicyclic gear system  48 , such as a planetary gear system, star gear system or other system. The example epicyclic gear train has a gear reduction ratio of greater than about 2.3, and in another example is greater than about 2.5 with a gear system efficiency greater than approximately 98%. The geared turbofan enables operation of the low spool  30  at higher speeds which can increase the operational efficiency of the LPC  44  and LPT  46  and render increased pressure in a fewer number of stages. 
         [0039]    A pressure ratio associated with the LPT  46  is pressure measured prior to the inlet of the LPT  46  as related to the pressure at the outlet of the LPT  46  prior to an exhaust nozzle of the gas turbine engine  20 . In one non-limiting embodiment, the bypass ratio of the gas turbine engine  20  is greater than about ten (10:1), the fan diameter is significantly larger than that of the LPC  44 , and the LPT  46  has a pressure ratio that is greater than about five (5:1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans. 
         [0040]    In one non-limiting embodiment, a significant amount of thrust is provided by the bypass flow due to the high bypass ratio. The fan section  22  of the gas turbine engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. This flight condition, with the gas turbine engine  20  at its best fuel consumption, is also known as bucket cruise Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust. 
         [0041]    Fan Pressure Ratio is the pressure ratio across a blade of the fan section  22  without a Fan Exit Guide Vane system. The low Fan Pressure Ratio according to one non-limiting embodiment of the example gas turbine engine  20  is less than 1.45. Low Corrected Fan Tip Speed is the actual fan tip speed divided by an industry standard temperature correction of (“T”/518.7) 0.5  in which “T” represents the ambient temperature in degrees Rankine. The Low Corrected Fan Tip Speed according to one non-limiting embodiment of the example gas turbine engine  20  is less than about 1150 fps (351 m/s). 
         [0042]    With reference to  FIG. 2 , the engine case assembly  36  generally includes a plurality of cases, including a fan case  60 , an intermediate case  62 , a Low Pressure Compressor (LPC) case  64 , a High Pressure Compressor (HPC) case  66 , a diffuser case  68 , a High Pressure Turbine (HPT) case  70 , a mid-turbine frame (MTF) case  72 , a Low Pressure Turbine (LPT) case  74 , and a Turbine Exhaust Case (TEC) case  76 . It should be appreciated that additional or alternative cases might be utilized. 
         [0043]    With reference to  FIG. 3 , each case is assembled to an adjacent case at a respective flange  80 ,  82 , via a plurality of fasteners  100  (one shown) that are installed in respective apertures  120 ,  122  to form flanged joint  78 . It should be appreciated that although a single flange joint interface  130  between an example diffuser flange  80 , of the diffuser case  68  and an adjacent HPT flange  82  of the HPT case  70  are illustrated in this example, any flange joint interface  130  such as between each or any of the above delineated cases will benefit herefrom. 
         [0044]    The diffuser flange  80  generally includes a radial flange portion  140  and a seal lip  142  that extend transverse thereto. In this embodiment, the seal lip  142  extends longitudinally with respect to the engine axis A and is perpendicular to the radial flange portion  140 . The seal lip  142  is arranged to at least partially overlap the HPT case  70  and is directed in a downstream direction to interface with the HPT case  70  at a longitudinal interface  144  to seal a radial interface  146  between the flanges  80 ,  82 . That is, the longitudinal interface  144  extends axially beyond the radial interface  146 . The seal lip  142  may include an undercut  188  to ensure the seal snap occurs on the uninterrupted (in circumferential direction) surface  189  ( FIG. 6 ). Alternatively, or in addition, an undercut  191  may be located on the flange  82  ( FIG. 7 ). 
         [0045]    In one example, the radial flange portion  140  defines a thickness of about 0.26 inch (6.6 mm). Such a thickness facilitates coating repair, such as via plasma spray, which may be required whenever the diffuser case  68  and the HPT cases  70  are separated. 
         [0046]    In this disclosed non-limiting embodiment, a heat shield  210  includes a distal end  212  that interfaces with a step  214  in the diffuser case  68  forward of the radial flange portion  140 . The interface location of the heat shield  210  thereby facilitates shielding of the radial interface  146  from high speed/high pressure flow to minimize heat transfer at flange. That is, the heat shield  210  is radially inboard of the seal lip  142 . 
         [0047]    With reference to  FIG. 4A , a radial flange portion  148  includes a scallop  150  along an outer diameter  160  to flank each aperture  122 . This facilitates a reduction of the stress on the aperture  122  near the outer diameter  160 . Each aperture  120 ,  122 , in one example, is about 0.34 inch (8.6 mm) in diameter. Although primarily illustrated with respect to an outer case  70 , an inner case  70 ′ ( FIG. 4B ) with a flange  82 ′ that extends radially inboard and has partial scallops  180  on an inner diameter will also benefit herefrom. 
         [0048]    Each scallop  150  extends for the entire thickness of the radial flange portion  148  and, in one example, defines a radius of about 0.25 inch (6.35 mm). That is, the scallop  150  is of a most generous radius related to the number of apertures and space therebetween to provide a desired web thickness. The radial flange portion  148  further includes a partial scallop  180  along an inner diameter  190  of the radial flange portion  148  to flank each aperture  122 . This further facilitates a reduction of the stress on the flange  82 . 
         [0049]    Each partial scallop  180  is about half the thickness of the radial flange portion  148 . As defined herein, “partial” refers to the partial scallop  180  that does not extend through the entirety of the thickness of the radial flange portion  148 . Each partial scallop  180 , in one example, also defines a radius of about 0.25 inch (6.35 mm). In one example, the generosity of the scallop  150 , and the partial scallop  180 , may be sized to form a circle “C” that surrounds the aperture  122  and extends from the outer diameter  160  to the inner diameter  190  ( FIG. 5 ). That is, a web thickness around the aperture  122  in the radial flange is approximately equivalent with respect to the inner diameter  190 , the outer diameter  160 , the partial scallops  180  and the scallops  150 . It should be appreciated that various other radiuses may be provided. 
         [0050]    An inner scallop fillet radius  186 , in one example, is about 0.25 inch (6.35 mm) is also formed from a face  192  of the radial flange portion  148  (also shown in  FIG. 6  and  FIG. 7 ). The inner scallop fillet radius  186  is also provided as a generous radius that, in one example, is about 0.5 that of the depth of the partial scallops  180 . That is, the inner scallop fillet radius  186  is a relatively large transition to minimize stress formations and may essentially form a semi-spherical shape. The partial scallops  180 , readily increase Low Cycle Fatigue (LCF) life of the apertures  122 . 
         [0051]    With reference to  FIG. 8 , the apertures  120 ,  122  receives the respective fastener  100  that, in one example, includes a “D” head bolt  202  that is 0.3125″ (7.9 mm) in diameter. The “D” head bolt  202  facilitates a reduced radial height of the radial flange portions  140 ,  148  and operates as an anti-rotation feature to facilitate receipt and removal of a nut  204 . 
         [0052]    The use of the terms “a,” “an,” “the,” and similar references in the context of description (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or specifically contradicted by context. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. It should be appreciated that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to normal operational attitude and should not be considered otherwise limiting. 
         [0053]    Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
         [0054]    It should be appreciated that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be appreciated that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
         [0055]    Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
         [0056]    The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.