Abstract:
A gas turbine engine is provided with turbine sealing structures including knife edge seals which extend at an angle relative to an axial center line of the engine. Each knife edge seal is associated with a control pocket defined between a radially inner surface and a spaced radially outer surface. The control pockets and their associated knife edge seals create a difficult flow path to prevent leakage into radially inner portions of the turbine section.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to canted knife edge seals which rotate with a gas turbine rotor, and are associated with canted pockets in a stationary sealing surface. 
         [0002]    Gas turbine engines are known, and typically include a series of sections. A fan may deliver air to a compressor section. Air is compressed in the compressor section, and delivered downstream to a combustor. In the combustor, air and fuel are combusted. The products of combustion then pass downstream over turbine rotors. The turbine rotors rotate to create power, and also to drive the fan and compressors. 
         [0003]    The turbine rotors typically are provided with a plurality of removable blades. The blades are alternated with stationary vanes. It is desirable to limit leakage of the products of combustion radially inwardly of the turbine blades. Thus, the turbine rotors are provided with knife edge seals which are spaced closely from sealing surfaces on the static members. 
         [0004]    Labyrinth seal structures are known. Generally, the sealing surfaces have been formed as cylindrical surfaces at a plurality of different radial distances from an engine centerline. The combination of these different radial distances, and a plurality of associated knife edge blades create a labyrinth path to limit leakage fluid. Even so, some leakage does occur, and it would be desirable to further reduce leakage. 
       SUMMARY OF THE INVENTION 
       [0005]    In a disclosed embodiment of this invention, the generally cylindrical sealing surfaces of the prior art are replaced by canted pockets. The pockets generally are defined between a radially inner surface spaced from a radially outer surface. An angled face connects the inner and outer surfaces. 
         [0006]    At the same time, in a disclosed embodiment, knife edge seals are associated with the pockets. The knife edge seals extend at an angle in the same general direction as the angled face. The combination of the canted knife edge seals and the pockets limit leakage. 
         [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  schematically shows a gas turbine engine. 
           [0009]      FIG. 2  shows a sample sealing location with a gas turbine engine of the present invention. 
           [0010]      FIG. 3A  shows a prior art seal. 
           [0011]      FIG. 3B  shows a first sealing arrangement. 
           [0012]      FIG. 4  shows one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    A gas turbine engine  10 , such as a turbofan gas turbine engine, circumferentially disposed about an engine centerline, or axial centerline axis  12  is shown in  FIG. 1 . The engine  10  includes a fan  14 , compressors  15  and  16 , a combustion section  18  and turbines  20  and  22 . As is well known in the art, air compressed in the compressors  15  and  16 , and is mixed with fuel and burned in the combustion section  18  and expanded in turbines  20  and  22 . The turbines include rotors which rotate in response to the expansion, driving the compressors  15  and  16  and fan  14 . The turbines comprise alternating rows of rotary airfoils or blades  24  and static airfoils or vanes  26 . In fact, this view is quite schematic, and blades  24  and vanes  26  are actually removable. It should be understood that this view is included simply to provide a basic understanding of the sections in a gas turbine engine, and not to limit the invention. This invention extends to all types of turbine engines for all types of applications. 
         [0014]      FIG. 2  is an enlarged view of turbine blade  24 , and stationary vane  26 . As known, sealing surfaces  34  are associated with knife edge seals  36 . As can be seen in this figure, in the present invention, these knife edge seals extend at an angle relative to the axial centerline  12  of the jet engine. Also, the knife edge seals are associated with canted pockets  38 , as will be explained in more detail below. As can be appreciated, there may be a plurality of radially spaced pockets and associated knife edge seals. 
         [0015]    As shown in  FIG. 3A , in the prior art, a labyrinth seal was created by cylindrical sealing surfaces  49  and  51  spaced at different radial positions, and knife edge seals  50  spaced from the associated static sealing surfaces  51  and  49 . As known, an abradable sealing material may actually be positioned at surfaces  49 ,  51  to allow the knife edge seal to wear the surfaces and provide a close fit. With the radially distinct sealing surfaces  49  and  51 , a labyrinth leakage path  54  is presented to any fluid which may leak radially inwardly of the rotor. The labyrinth seal path does provide a good restriction to linkage fluid. However, it would be desirable to even further improve the resistance of this path. 
         [0016]    Thus, as shown in  FIG. 3B , fluid can be forced into vortices  40  and  42  by angling the knife edge seals  36  relative to axis  12  of the gas turbine engine, and creating pockets  38  from radially inner walls  39  and a radially outer wall  34 . A vortex  42  is created in the pocket  38 , and the angled knife edge seal  36  creates yet another vortex  40 . The combination of the vortices  40  and  42  present a great resistance to fluid leakage. This is particularly true when there are additional knife edge seals at different radial positions, and positioned along a path of the fluid flow, as shown in  FIG. 3B . In  FIG. 3B , the knife edge seals  36  are angled into the pockets  38 . This basic arrangement is disclosed in co-pending patent application Ser. No. 11/605,678, entitled “Gas Turbine Engine With Concave Pocket With Knife Edge Seal,” filed on 29 Nov. 2006. 
         [0017]    This application relates to an even more restrictive pocket and seal arrangement, one embodiment of which is illustrated in  FIG. 4 . As shown in  FIG. 4 , a stationary seal  100  is positioned adjacent to a rotating rotor  102 , with the rotor  102  having a plurality of knife edge seals  104  extending at a non-perpendicular angle relative to a flow path of products of combustion across the turbine rotor. The stationary seal  100  has a plurality of sealing surfaces  106 ,  108 , and  110  associated with the knife edge seals  104 . As shown, connecting faces  112  connect the sealing surfaces to define pockets  114 . These connecting faces  112  extend at an angle from a radially inner seal portion to a radially outer seal portion, with the angle being into the direction of flow X. Thus, the angle of the surface  112  and the angle of the knife edge seal  104  both extend into the flow direction X, but are non-perpendicular to direction X. The angles selected for the two surfaces may be the same, or they may be selected to be different to achieve various manufacturing and performance goals. Stated another way, the angled surface  112  and the knife edge seals  104  extend in a direction having a component extending in an upstream direction, or toward the combustion section. Now, a very close spacing is provided between the knife edge seals  104  and the sealing surfaces  106 ,  108 , and  110 . A more restrictive flow path is presented to prevent fluid from leaking between these surfaces. 
         [0018]    Although preferred embodiments of this invention have 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.