Abstract:
According to an exemplary embodiment of this disclosure, among other possible things a gas turbine engine includes a compressor section, a combustor in fluid communication with the compressor section, a turbine section in fluid communication with the combustor section, a plurality of turbine disks in at least one of the compressor section and the turbine sections, at least one cover plate corresponding to at least one of the turbine disks, each of the cover plates includes, at least two snaps connected via a webbing portion, and a bore region radially inward of the at least two snaps and connected to at least one of the at least two snaps via the webbing portion.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure is related to gas powered turbine engines and more specifically toward rotor disk cover plates for rotor systems in the same. 
       BACKGROUND OF THE INVENTION 
       [0002]    Gas power turbine engines, such as those used as commercial or military jet engines, utilize multiple stages including turbine stages and compressor stages. Compressor systems and turbine systems within a gas powered turbine engine are collectively referred to as rotor systems and include multiple rotating disks referred to as rotor disks. 
         [0003]    The rotor systems within the turbine engine use sealing mechanisms near a gas path rim of each of the rotor disks to prevent secondary air system air from entering the gas path. Typical sealing mechanisms involve a rotating to static hardware seal. The gap between the rotating piece and the static piece of the rotating to static seal directly affects the amount of gasses that across the gap and affect engine performance. 
         [0004]    One type of seal utilized in rotor systems is a knife edge seal having a knife edge protrusion as the rotating piece in the seal arrangement. The knife edge protrusion is connected to the rotor disk via a cover plate The knife edge protrusion interfaces with a corresponding static component to form a seal and minimize gas leakage between the secondary air systems and the gas path. The knife edge seals are connected to the rotor disks by the cover plate. The cover plates are intentionally made small relative to the rotor disks in order to minimize the centrifugal load imparted to the rotors on which the cover plates are attached. 
       SUMMARY OF THE INVENTION 
       [0005]    According to an exemplary embodiment of this disclosure, among other possible things a gas turbine engine includes a compressor section, a combustor in fluid communication with the compressor section, a turbine section in fluid communication with the combustor section, a plurality of turbine disks in at least one of the compressor section and the turbine sections, at least one cover plate corresponding to at least one of the turbine disks, each of the cover plates includes, at least two snaps connected via a webbing portion, and a bore region radially inward of the at least two snaps and connected to at least one of the at least two snaps via the webbing portion. 
         [0006]    In a further embodiment of the foregoing gas turbine engine, a first snap of the at least two snaps is tight fit with the rotor disk, and a second snap of the at least two snaps is loose fit when the cover plate is cool relative to the corresponding rotor disk and tight fit when the cover plate is hot relative to the corresponding rotor disk. 
         [0007]    In a further embodiment of the foregoing gas turbine engine, the bore region is axially thicker than the webbing, and the bore region provides mechanical restraint on radial growth and reduces load into rotor disk. 
         [0008]    In a further embodiment of the foregoing gas turbine engine, each of the snaps includes a contacting surface contacting the rotor disk, and the contacting surface is scalloped. 
         [0009]    In a further embodiment of the foregoing gas turbine engine, a scalloping on the first of the snaps contacting surface is a small scalloping. 
         [0010]    In a further embodiment of the foregoing gas turbine engine, the first of the snaps is a radially outermost snap. 
         [0011]    In a further embodiment of the foregoing gas turbine engine, a scalloping on the second of the snaps contacting surface is large scalloping. 
         [0012]    In a further embodiment of the foregoing gas turbine engine, the second of the snaps is a radially innermost snap. 
         [0013]    A further embodiment of the foregoing gas turbine engine includes at least one ducting gap between the cover plate and the rotor disk. 
         [0014]    In a further embodiment of the foregoing gas turbine engine, the at least one ducting gap comprises a first ducting gap radially outward of a first snap, a second ducting gap radially between the first snap and the second snap, and a third ducting gap radially inward of the second snap. 
         [0015]    In a further embodiment of the foregoing gas turbine engine, the first ducting gap is fluidly connected to the second ducting gap via scalloping on the first snap. 
         [0016]    In a further embodiment of the foregoing gas turbine engine, the second ducting gap is fluidly connected to the third ducting gap via scalloping on the second snap. 
         [0017]    In a further embodiment of the foregoing gas turbine engine, air in the duct region is scrub air, and the scrub air originates from a secondary air source. 
         [0018]    In a further embodiment of the foregoing gas turbine engine, scalloping on the first snap is a metering component operable to meter airflow into the ducting gaps. 
         [0019]    According to an exemplary embodiment of this disclosure, among other possible things, a cover plate for a rotor disk includes, at least two snaps connected via a webbing portion, and a bore region radially inward of the at least two snaps and connected to at least one of the at least two snaps via the webbing portion. 
         [0020]    In a further embodiment of the foregoing cover plate for a rotor disk, the bore region is axially thicker than the webbing, and the bore region provides mechanical restraint on radial growth and reduces load into rotor disk. 
         [0021]    In a further embodiment of the foregoing cover plate for a rotor disk, each of the snaps includes a contacting surface contacting the rotor disk, and the contacting surface is scalloped. 
         [0022]    In a further embodiment of the foregoing cover plate for a rotor disk, a scalloping on the first of the snaps contacting surface is a small scalloping. 
         [0023]    In a further embodiment of the foregoing cover plate for a rotor disk, the first of the snaps is a radially outermost snap. 
         [0024]    In a further embodiment of the foregoing cover plate for a rotor disk, a scalloping on the second of the snaps contacting surface is large scalloping. 
         [0025]    In a further embodiment of the foregoing cover plate for a rotor disk, the second of the snaps is a radially innermost snap. 
         [0026]    These and other features may be best understood from the following specification and drawings, the following which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  schematically illustrates a gas powered turbine engine for an aircraft. 
           [0028]      FIG. 2  schematically illustrates a partial cross-sectional view of a rotor disk assembly. 
           [0029]      FIG. 3  schematically illustrates a three-dimensional isometric view of the cover plate of the rotor disk assembly of  FIG. 2 . 
           [0030]      FIG. 4  schematically illustrates a cross-sectional view of the cover plate of the rotor disk assembly of  FIG. 2 . 
           [0031]      FIG. 5  schematically illustrates airflow through a rotor disk assembly during operation of a gas turbine engine. 
           [0032]      FIG. 6   a  schematically illustrates a thumbnail scalloping of a radially outer snap of the cover plate of  FIG. 2 . 
           [0033]      FIG. 6   b  schematically illustrates a thumbnail scalloping of a radially inner snap of the cover plate of  FIG. 2 . 
           [0034]      FIG. 7   a  schematically illustrates a cross-sectional view of the rotor disk cover of  FIG. 2 . 
           [0035]      FIG. 7   b  schematically illustrates a three-dimensional isometric view of a slot portion of the bore region of  FIG. 7   a.    
           [0036]      FIG. 7   c  schematically illustrates the slot portion of  FIG. 7   b  in an assembled position. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]      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 might include an augmentor section (not shown) among other systems or features. The fan section  22  drives air along a bypass flowpath while the compressor section  24  drives air along a core flowpath for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a turbofan gas turbine engine 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 including three-spool architectures, ground based turbine engines, or military engines. 
         [0038]    The engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0039]    The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  and a low pressure turbine  46 . The inner shaft  40  is connected to the fan  42  through a geared architecture  48  to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  and high pressure turbine  54 . A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . A mid-turbine frame  57  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  57  further supports bearing systems  38  in the turbine section  28 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via bearing systems  38  about the engine central longitudinal axis A which is collinear with their longitudinal axes. The systems connected to, and rotating along with, the inner shaft  40  and the outer shaft  50  are collectively referred to as rotor systems. 
         [0040]    The core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed and burned with fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  57  includes airfoils  59  which are in the core airflow path. The turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. 
         [0041]    The engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the engine  20  bypass ratio is greater than about six (6), with an example embodiment being greater than ten (10), the geared architecture  48  is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine  46  has a pressure ratio that is greater than about 5. In one disclosed embodiment, the engine  20  bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor  44 , and the low pressure turbine  46  has a pressure ratio that is greater than about 5:1. Low pressure turbine  46  pressure ratio is pressure measured prior to inlet of low pressure turbine  46  as related to the pressure at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. The geared architecture  48  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 2.5:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans. 
         [0042]      FIG. 2  illustrates a cross-sectional view of a rotor disk  100  that can be used in the rotor systems of the gas turbine engine illustrated in  FIG. 1 . The rotor disk  100  includes multiple snap retaining features  102 , and a rotor disk interlocking feature  104 . The rotor disk  100  also includes a blade connection region  106  at a radially outward edge of the rotor disk  100 . 
         [0043]    Connected to the aft side of the rotor disk  100  is a rotor disk cover plate  110 . The rotor disk cover plate  110  includes two snaps  116  for retaining the cover plate  110  in position and preventing the cover plate  110  from shifting radially during operation of the gas turbine engine  20 . The cover plate  110  also includes two knife edges  114  for a standard knife edge sealing arrangement and a webbing  112  connecting the snaps  116  and the knife edges  114 . Connected to the radially innermost snap  116  is a bore region  119  of the cover plate  110 . The bore region  119  is axially thicker than the remainder of the cover plate  110 . The additional mass of the bore  119  provides mechanical restraint on the radial growth of the cover plate  110 , reducing the radial load it imparts to the rotor disk  100 . In an alternate example, the bore region  119  is separate from the radially inner snap  116  and connected to the snap  116  via additional webbing  112 . Alternate coverplates can have “HALO” seals, brush seals, or no seal other than the disk rim sealing. 
         [0044]    Multiple duct regions  120 ,  122 ,  124  are defined and bounded by the webbing  112  of the cover plate  110  and the aft surface of the rotor disk  100 . Each of the ducted regions  120 ,  122 ,  124  is fluidly connected to the adjacent ducted regions  120 ,  122 ,  124  via a scalloping feature  118  on a contact surface of the snap  116 . 
         [0045]    The bore region  119  interfaces with a rotor disk interlocking slot feature  104  to prevent the rotor disk cover plate  110  from rotating about the engine center line axis. In some examples, the rotor disk interlocking slot feature  104  also interfaces with an interlocking feature on an adjacent rotor disk. The interfacing with an adjacent rotor disk is described below with regards to  FIGS. 7   a ,  7   b , and  7   c.    
         [0046]      FIG. 3  schematically illustrates a three-dimensional isometric view of the cover plate  110 . The cover plate  110  is a generally cylindrical shape with a central opening  130 . The central opening  130  is coaxial with the cover plate  110 . The cover plate  110  includes multiple slots  132  corresponding to the rotor disk interlocking slot retention feature  104 . The slots  132  are distributed about the inner radius of the cover plate  110  and allow for a locking feature to prevent the cover plate  110  from rotating relative to the rotor disk  100  as described below with regards to  FIGS. 7   a ,  7   b , and  7   c.    
         [0047]    The three-dimensional view of  FIG. 3  also illustrates knife edges  114  for the knife edge sealing arrangement, the webbing  112  and the bore region  119 . Each of these features is continuous radially about the cover plate  110 . Each of the snap features  116  is located on the reverse side of  FIG. 3 . Each of the snap features  116  is also continuous radially about the cover plate  110 . 
         [0048]      FIG. 4  schematically illustrates a cross-section of the cover plate  110  isolated from the rotor disk  100 , with like numerals indicating like elements. Each of the snaps  116  includes a scalloped surface  118  that directly contacts an opposing surface on the snap retaining features  102 . The scalloping dent, or thumbnail indent, in the scalloped surface  118  allows air to pass between the snap  116  and the opposing surface of the corresponding snap retaining feature  102  while still maintaining contact between the snap  116  and the snap retaining feature  102 . While illustrated herein as raised surfaces for illustrative purposes, in a practical implementation the scalloping of the scalloped surface  118  protrudes into the snap. 
         [0049]    During standard operation of the turbine engine  10 , engine components heat up to extreme temperatures. As the engine heats up, the components expand due to thermal expansion. Engine components with a smaller mass heat up and expand faster than engine components with a larger mass. The cover plate  110  has a significantly smaller mass than the rotor disk  100  to which it is attached, and thus expands and contracts faster than the rotor disk  100 , leading to excessive loading into the rotor disk  100 . This disparity in temperature response is partially offset by the bore region  119  which adds mass to the part, decreasing the rate of heat up and expansion, thus reducing the load into the rotor disk  100 . 
         [0050]    When the turbine engine  20  is off, or cool, the radially outer snap  116  is tight against the corresponding snap retaining feature  102  due to a preload. The radially inner snap  116 , on the other hand, is loose against the corresponding snap retaining feature  102  while the engine  20  is off or cool. As the engine  20  winds up, the engine  20  gets hotter and the cover plate  110  expands. As the cover plate  110  expands, the snaps  116  get tighter against the contact surfaces of the corresponding snap retaining feature  102 . When the radially inner snap  116  becomes tight due to thermal expansion, the load on the radially outward snap  116  is partially transferred to the radially inward snap  116 , thereby preventing the radially outward snap from overloading and breaking. 
         [0051]    A secondary effect of the inclusion of the cover plate  110  is that the cover plate  110  of standard arrangements shields the rotor disk  100  from exposure to airflow from a secondary air source while simultaneously exposing the cover plate  110  to the airflow. This airflow is referred to as scrub air, and is typically at a different temperature than the gas path air. Because the scrub air only scrubs the cover plate  110  in a standard cover plate arrangement, the disparity in thermal expansion between the rotor disk  100  and the cover plate  110  is exacerbated. 
         [0052]      FIG. 5  illustrates an airflow path of scrub air  402  passing through the rotor disk assembly of  FIG. 1 . Initially the scrub air  402  flows into the blade connection region  106  of the rotor disk  100 , in the blade connection region  106 , a portion  404  of the scrub air is directed to the blades (not pictured) connected to the radially outward region of the rotor disk  100  via the blade connection region  106 . This portion of the scrub air  402  passes over the outside of the cover plate  110  and does not contact the surface of the rotor disk  100 . The remainder of the scrub air  402  follows a ducting flow path  406 ,  408 ,  410 ,  412  into a first ducting gap  120  between the cover plate  110  and the rotor disk  100 . The scrub air  402  then passes through the scalloping  118  on the radially outward snap  116  into a second ducting region  122 . The scrub air  402  then passes through the scalloping  118  on the radially inward snap  116  into a third ducting region  124 . Scrub air  402  then flows away from the ducting gap  124  through the rotor disk interlocking slots  104  to an adjacent rotor disk. 
         [0053]    By passing the scrub air  402  through the ducting regions  120 ,  122 ,  124  both the rotor disk  100  and the cover plate  110  are exposed to the same airflows and the thermal expansion disparity between the rotor disk  100  and the cover plate  110  due to the scrub air is minimized. 
         [0054]    The size and depth of the scalloping  118  of the snaps  116  is designed to further improve gas flow through the ducting regions  120 ,  122 ,  124 .  FIG. 6   a  and  FIG. 6   b  illustrate the scalloping on the scalloped surface  118  of each of the snaps  116 , with  FIG. 6   a  illustrating a scalloping feature  510  of the radially outward snap  116  scalloped surface  118  and  FIG. 6   b  illustrating a scalloping feature  520  of the radially inward snap  116  scalloped surface  118 . Each of the scalloping features  510 ,  520  is a thumbnail groove in the scalloped snap surface  118 . The thumbnail grooves are reiterated across the entire scalloped surface  118  of the snaps  116 . 
         [0055]    In order to meter, or control, scrub air  402  flow through the scalloped surfaces  118 , the scalloping features  510  of the radially outward snap  116  are small (have a short arc length  512  and a short radial depth) and restrict the volume of gas that can pass through the scalloped feature  510 . In contrast, the scalloping feature  520  of the radially inward snap  116  is significantly larger (has a long arc length  522  and/or a large radial depth relative to the radially outward scalloping  118 ) than the scalloping feature  510  of the radially outward snap  116  and does not provide a meaningful limit on gas flow. Thus, the flow of gas is metered, or controlled, via the scalloping features  510  of the radially outward snap  116 . 
         [0056]      FIGS. 7   a ,  7   b  and  7   c  illustrate the rotor disk interlocking slot features  104  of  FIG. 2  in greater detail.  FIG. 7   a  illustrates a cross-sectional view of the cover plate  110 ,  FIG. 7   b  illustrates a zoomed in view of the radially inward edge of the bore region  119  of the cover plate  110 , and  FIG. 7   c  illustrates the view of  FIG. 7   b  in an installed arrangements. 
         [0057]    The bore region  119  of the cover plate  110  includes multiple slots  710  with the interlocking portion of the bore region  119 . To install the cover plate  110 , tabs  712  are slid through slots  730  and the rotor disk  100  interlocking region. The cover plate  110  is then rotated about the engine centerline axis, and the tabs  712  are aligned with and blocked by portions of the rotor disk interlocking slots  104 . A locking component  720  is then placed in the slots  730  to prevent the cover plate  110  from rotating out of position. In some examples, the locking component  720  is a plurality of tabs  722  on an adjacent rotor disk. 
         [0058]    While the above disclosure is described with regards to a cover plate  110  in a rotor system for a turbine engine  20 , it is understood that the cover plate design can be used in other rotating systems and still fall within this disclosure.