Abstract:
According to an embodiment disclosed herein, an apparatus for cooling a rotating part having cooling channels therein, the rotating part attaching to a disk rotating about an axis, the disk having a conduit for feeding a cooling fluid to the cooling channel is described. The apparatus has a first impeller rotating with the disk and in register with the conduit and an outer periphery of the disk, the impeller directing the cooling flow to the conduit.

Description:
TECHNICAL FIELD 
       [0001]    The invention is applicable to a gas turbine engine cooling system and more particularly to an improved apparatus for supplying cooling fluid to hot parts of the engine, specifically, the interior of the turbine blade. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is widely recognized that the efficiency and energy output of a gas turbine engine can be improved by increasing the operating temperature of the turbine. Under elevated operating temperatures, gas turbine engine components such as the turbine rotors and blades are cooled by a flow of compressed air discharged at a relatively cool temperature. The flow of coolant across the turbine rotor and through the interior of the blades removes heat so as to prevent excessive reduction of the mechanical strength properties of the blades and rotor. 
         [0003]    Therefore on the one hand the turbine operating temperature, efficiency and output of the engine are limited by the high temperature capabilities of the various turbine elements and the materials of which they are made. In general the lower the temperature of the elements the higher strength and resistance to operating stresses. On the other hand the performance of the gas turbine engine is very sensitive to the amount of air flow that is used for cooling the hot turbine components. The less air that is used for cooling functions the better the efficiency and performance of the engine. 
         [0004]    To cool the turbine blades, a flow of cooling air is typically introduced. There are two ways to deliver cooling air to turbine blades. One is from stationary part and other is from rotating part. From a stationary part, the cooling flow is introduced with a swirl or tangential velocity component through use of a tangential on board injector with nozzles directed at the rotating hub of the turbine rotor. From a rotating part, a flow of cooling air is typically introduced at a lower radius as close as possible to the engine shaft, such as underneath of the rotor disk bore. 
       SUMMARY OF THE INVENTION 
       [0005]    According to an embodiment disclosed herein, an apparatus for cooling a rotating part having cooling channels therein, the rotating part attaching to a disk rotating about an axis, the disk having a conduit for feeding a cooling fluid to the cooling channel is described. The apparatus has a first impeller rotating with the disk and in register with the conduit and an outer periphery of the disk, the impeller directing the cooling flow to the conduit. 
         [0006]    According to a further embodiment disclosed herein, an apparatus for directing a cooling fluid through a conduit to a rotating part, includes a first impeller in register with the conduit, the impeller having a shape that changes the direction of cooling fluid that is rotating tangentially relative to the conduit to flowing axially to the conduit. 
         [0007]    According to a further embodiment disclosed herein, a method of cooling a turbine blade disposed in a gas turbine engine is described. The method includes providing a broach slot for providing cooling air to a base of the turbine blade and turning cooling air from rotating tangentially relative to the slot to passing axially to the broach slot. 
         [0008]    These and other features of the invention would be better understood from the following specifications and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is an embodiment of a gas turbine engine employing an embodiment disclosed herein. 
           [0010]      FIG. 2  is a schematic depiction of a turbine section of the engine of  FIG. 1 . 
           [0011]      FIG. 3  is a schematic, cut-away view, partially in phantom of a disk of the turbine section of  FIG. 2 . 
           [0012]      FIG. 4  is a schematic sectional view of a further embodiment of the disk of  FIG. 3 . 
           [0013]      FIGS. 5A and 5B  are graphical depictions comparing a prior art disk with and embodiment of the present invention. 
           [0014]      FIGS. 6A and 6B  are graphical depictions comparing a prior art disk with and embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring to  FIG. 1 , a gas turbine engine  10 , such as a turbofan gas turbine engine  10 , circumferentially disposed about an engine centerline, or axial centerline axis  12 , is shown. The engine  10  includes a case  21 , a fan  14 , compressor sections  15  and  16 , a combustion section  18  and a turbine  20 . As is well known in the art, air compressed in the compressor  15 / 16  is mixed with fuel and burned in the combustion section  18  and expanded in turbine  20 . The turbine  20  includes high pressure and low pressure turbine rotors  22  and  24 , which rotate in response to the expansion. The turbine  20  comprises alternating rows of rotary airfoils or blades  26  and static airfoils or vanes  28 . 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. For example, while a fan  14  is shown, this invention may be used in turbines that do not include a fan section. 
         [0016]    Referring now to  FIGS. 2 and 3 , the high pressure turbine area  22  is shown in more detail. A combustion gas path  40  passes by stationary vanes  45  and rotatable turbine blades core  50 . Each turbine blade core  50  has an airfoil section  55  that has a hollow interior  60  and a base  65  shaped like an inverted Christmas tree or other shape that is known for holding the turbine blade core  50  within a disk  75 . A plurality of passageways  70  pass through the base  65  to deliver cooling to the hollow interior  60  of the turbine blade core  50 . Disk  75  has a plurality of cutouts  80  that have a shape to mate with the base  65  of each turbine blade cores  50 . A broach slot  85  forms an area beneath each installed blade and extends along a length L of the base  65  for sending a cooling fluid such as air through the passageways  70  into the hollow of interior  60  to cool the turbine blade core  50  that extends within the combustion gas path  40  to provide rotative force to the turbine blade cores  50 . 
         [0017]    Referring now to  FIGS. 3 and 4 , impellers  90  are machined into the disk  75  or into the bore cover plate  95  that attaches to the disk  75 . For ease of illustration, the impellers  90  are shown attached to either turbine disks  75  or bore cover plate  95 . However, one of ordinary skill in the art will recognize that the impellers may be placed in other areas and on other disks within the gas turbine engine  10  to cool components that may need cooling. A conduit  100  directs cooling air from the compressor  15 / 16  as is known in the art. 
         [0018]    Referring again to  FIGS. 3 and 4 , one can see a base  65  of a turbine blade core  50  disposed within a cutout  80  around the disk  75 . Broach slots  85  are shown below each base  65 . Impellers  90  are spaced apart to enable each impeller  90  to direct cooling air within the conduit  100  into the broach slots  85  to provide cooling air to the interior of the turbine blade cores  50  and airfoils  55 . 
         [0019]    Some impellers  90  have a J-shaped body  105  that has a radially extending part  107  that extends axially aft from bore cover plate  95 . The radially extending part  107  smooths into an extension  110  that is perpendicular to the part  107  and tangential to airflow  115  (moving counter-clockwise in this application though clockwise is possible in other applications) in the conduit  100 . The extensions  110  about the bore cover plate  95  form an imaginary perimeter  120  about the interior of the bore cover plate  95  and are disposed at an angle of 0-5 degrees relative thereto. Each of the part  107  and extension  110  smooth into the bore cover plate  95  by means of rounded beads  125 . The body  105  has a saddle  130  at an intermediary portion  135  thereof, at upper peak  140  and a lower peak  145 . The cover plate  95  conforms to the shape of the saddle  125 , the upper peak  140  and the lower peak  145  so that cooling air does not flow over the impellers  90 ,  150  only between them. 
         [0020]    Some impellers  150  do not have an extension  110  to save weight and may be interspersed between impellers  90  that have the extension  110 . Typically there is one impeller to direct air to each broach slot  85  (See  FIG. 5B ). The part  107  is the same in the impellers  90  and  150 . Each broach slot  85  is disposed between and in register with the upper peaks  140  of a pair of impellers  90  or impellers  90 ,  150 . 
         [0021]    Referring to  FIG. 5A , the effects of air flowing to each broach slot  85  are shown. Air enters the conduit  100  at a given pressure P that tends to diminish to P 1  in the conduit  100  as the volume of the conduit  100  increases towards the broach slots  85 . Referring now to  FIG. 5B , it is seen that with the impellers  90 ,  150  urging the cooling air into the broach slots  85 , pressure within the broach slot  85  increases radially outwardly within the conduit  100  along each pressure lines P 2 , P 3 , P 4 , P 5 , P 6 , P 7   7 , as an example, with the use of the impellers, thereby increasing the amount of cooling air passing through the blades  50 . If there are no impellers, pressure within the cavity defined by the conduit  100  is increased far less as one extends radially outwardly as the conduit gets closer to the broach slots. By adding the impellers, the pressure increases much more as the air approaches the broach slot. 
         [0022]    Referring to  FIGS. 6A and 6B , if impellers  90 ,  150  are not included in the conduit  100 , the cooling air rotates at a swirl ratio much less than  1 . Referring to  FIG. 6A , if the cooling air gets into the turbine blade broach  85  the swirl ratio is 1. The mismatch of the swirl ratios results in a large flow recirculation zone  160  which causes pressure loss and lower static pressure to feed the turbine blades for cooling thereof. Installing impellers  90 ,  150  on the bore cover plate  95  turns the cooling air flow  115  from tangential to the broach slots  85  to radially thereto before flow gets into the blade broach slot which thereby minimizes the large flow recirculating zone  160  inside the broach slot. The overall static pressure of cooling air supplied to the turbine blade cores  50  is higher and that can overcome the pressure fluctuations caused by engine operation to guarantee the cooling safety margin. 
         [0023]    By adding the impellers, the higher swirl ratio increases the pressure of the cooling air flow within the turbine rotor cavity before it enters a broach slot  85 . The low entrance angle of the extension  110  of the impellers  90  relative to the cooling air flow A is very small, between zero and five degrees since this arrangement will produce the least flow loss. The idea is to turn flow from tangential to radial with minimum flow loss minimal heat gain. The extension  110  and the beads  125  are shaped to turn the airflow  115  with minimal flow losses and heat gains. 
         [0024]    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.