Abstract:
A cover plate for use with a rotor disk in a gas turbine engine includes an enclosed chamber associated with a web on the rotor disk. The enclosed chamber ensures that adequate cooling air is delivered by rotation of the cover plate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a cover plate for a turbine rotor disk in a gas turbine engine, wherein the cover plate has an enclosed pumping chamber for moving a cooling air from a central location to a cooling passage for delivering the air to a turbine blade. 
         [0002]    Gas turbine engines are known, and typically include a compressor for delivering air downstream to a combustion section. The air is mixed with fuel and burned in the combustion section, and the products of combustion move downstream over turbine rotors, driving the turbine rotors to rotate. The turbine rotors typically include a rotor disk, and a plurality of circumferentially spaced removable turbine blades. Since the rotor disk and turbine blades are subject to extreme temperatures, cooling air is typically delivered to these components to cool them. 
         [0003]    Some of the cooling air is delivered from a central location in the rotor disk radially outwardly to the interior of a disk slot in the rotor disk. The disk slot receives a root section from the turbine blade. The air then communicates into cooling air passages in the turbine blade. 
         [0004]    To seal the cooling passages, cover plates are typically attached to the rotor disk. Cover plates that form a small gap by following the contour of the disk create a boundary layer effect that pumps cooling air from a central location to the radially outward location when the cover plate and rotor rotate. The cover plates have been formed with internal fins which increases the pumping effectiveness. However, these fins have been somewhat ineffective at locations where the rotor may bend away from the cover plate. As an example, a central web of the rotor may be thinner than radially inner and outer portions of the rotor. This may be due to a desire to reduce the weight of the rotor, or for other reasons. In the past, the cover plate has been ineffective in moving cooling air when it is spaced from this central web. 
         [0005]    On the other hand, a cover plate that it is formed to follow the central web of the rotor, might well cause stress concentrations which would require the cover plate to be unduly large and heavy. 
       SUMMARY OF THE INVENTION 
       [0006]    In the disclosed embodiment of this invention, a cover plate for a rotor disk and a gas turbine engine has a pumping chamber on an interior face, wherein the pumping chamber is enclosed between axially inner and outer walls. The enclosed chamber is associated with an axially smaller web of the rotor disk. 
         [0007]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic view of a gas turbine engine. 
           [0009]      FIG. 2  is a cross-sectional view through a rotor having a cover plate according to this invention. 
           [0010]      FIG. 3  is an enlarged view of the  FIG. 2  cover plate. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0011]    A gas turbine engine  10 , such as a turbofan gas turbine engine, circumferentially disposed about an engine centerline  11 , is shown in  FIG. 1 . The engine  10  includes a fan  12 , a compressor  16 , a combustion section  18  and turbine sections  20 . As is well known in the art, air compressed in the compressor  16  is mixed with fuel which is burned in the combustion section  18  and expanded across turbines  20 . The turbines  20  includes rotors that rotate in response to the expansion, driving the compressor  16  and fan  14 . The turbines  20  comprises alternating rows of rotary airfoils or blades  24  and static airfoils or vanes  26 . This structure is shown somewhat schematically in  FIG. 1 . While one example gas turbine engine is illustrated, it should be understood this invention extends to any other type gas turbine engine for any application. 
         [0012]      FIG. 2  shows a rotor section  50  having a rotor disk  52 . As known, a disk slot receives a root of a turbine blade  54 . The disk slot is formed by circumferentially spaced and alternating slots and solid sections. The turbine blades  54  are received in the slots. The aspect is shown somewhat schematically. 
         [0013]    A cover plate  56  is secured to the rotor disk  52 . This connection may be as known in the art. As examples, a retaining ring, a bolt at the inner portion of the disk, or a clamp against the disk through various means may be used. 
         [0014]    A cooling air supply  58  supplies cooling air to a surface between an axially downstream side of the cover plate  56  and an axially upstream face  62  of the rotor disk  52 . In order to improve air pumping effectiveness, fins may be incorporated into the cover plate  56 . The fins can be located on the lower portion of the cover plate  56  or inside the chamber  68  or both. Fins need not extend along the entirety of these portions or be continuous. The fin geometry shown in  FIG. 2  and  FIG. 3  is only one potential embodiment. 
         [0015]    A portion  59  of the cover plate may have a plurality of fins  60  which are closely spaced from the surface  62 . As the rotor disk  52  and cover plate  56  are driven to rotate by the products of combustion, these fins  60  pump air radially outwardly. This portion of the illustrated embodiment is generally as known in the art. 
         [0016]    As shown, the cover plate  56  diverges axially upstream away from the central web  64  of the rotor  52 . At this portion  67  of the cover plate, an axially downstream wall  66  is spaced from the wall  67  to define an intermediate chamber  68 . The chamber  68  may be provided with fins, like the radially inner portion  59  of the cover plate. Now, even though the web  64  is spaced from the cover plate, there will still be pumping through chamber  68 . A downstream end  70  of the chamber  68  empties adjacent an outer face  72  of the rotor  52  and into a passage  74  leading to the disk slot which receives the turbine blade  54 . As shown, the turbine blade  54  has a flow passage  100  to deliver the cooling air outwardly to its airfoil. Again, this structure is shown schematically. 
         [0017]    By enclosing the chamber  68  along the web  64 , there is still adequate pumping of the cooling air. In the prior art, since the cover plate is further spaced from the thinner web  64 , adequate pumping may not have occurred. 
         [0018]      FIG. 3  shows another feature  80 , which is formed on the face  62 . Feature  80  bends the air flow upwardly into the chamber  68 , and further serves as a bumper for positioning the cover plate  56 . This feature  80  is optional and need not be included in all embodiments of this invention. 
         [0019]    As shown in  FIG. 2 , a radially outermost end of the cover plate  56  is beyond a radially innermost end  55  of the root of the turbine blade  54 . As is known, a main purpose of the cover plate  56  is to seal the air and gas flow passages that are formed between the rotor and disk slot. 
         [0020]    The cover plate can be formed by machining operations in an integral component to create the chamber  68 . On the other hand, a downstream wall can be attached to a main cover plate body by methods including, but not limited to, brazing or bonding. An integral cover plate could also be cast with the chamber built into the casting. These methods do not exclude other methods of manufacturing. 
         [0021]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.