Abstract:
An extended impingement cooling structure to cool outside an air supply plenum comprises an inner wall; an impingement sheet; a series of supports to maintain the inner wall in spaced relation to the impingement sheet, and a baffle supported between the inner wall and the impingement sheet. The baffle has a collector plenum area that receives impingement cooling air from the air supply plenum and a channel in fluid communication with the collector plenum and extending outside the air supply plenum with openings to allow impingement cooling air to pass therethrough and having a series of lands extending into the channel wherein the lands are located in proximity to impingement cooling air outlets in the inner wall.

Description:
[0001]     This invention was made under a United States Government Contract No. F33657-01-C-1240 and the United States Government may have certain rights to this invention. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to cooling of portions of a gas turbine engine. More particularly this invention relates to impingement cooling of portions of a liner outside of an air supply plenum.  
       BACKGROUND ART  
       [0003]     Impingement cooling has been used in gas turbine engines for some time. Relatively cooler air is taken from the compressor of the engine and passed through a series of holes in an impingement sheet to direct jets of cool air directly onto a surface in need of cooling. For instance in the area downstream from the combustor section of turbine engines impingement cooling has been used to cool the liner to protect parts that may be damaged by high heat from the core gas flow passes over the surface of the liner. The liner has a series of larger holes that are offset from the first series of holes to create a pressure drop that facilitates the airflow across the hot surfaces of the liner. See for instance U.S. Pat. No. 5,782,294.  
         [0004]     Certain areas of these liners cannot be adequately cool by impingement air flow because the air supply plenum is blocked by other equipment or structures located in proximity to the impingement sheet. In the past, there have been various structures proposed to indirectly cool the blocked areas. One such structure includes a series of apertures in the sidewall of a cast heat shield that in turn has a second series of apertures in the surface that is co-linear with the liner.  
       SUMMARY OF THE INVENTION  
       [0005]     One aspect of the present invention comprises an extended impingement cooling structure to cool outside an air supply plenum that comprises an inner wall; an impingement sheet; and a series of supports to maintain the inner wall in spaced relation to the impingement sheet. The structure also includes a baffle supported between the inner wall and the impingement sheet that has a collector plenum area that receives impingement cooling air from the air supply plenum and a channel in fluid communication with the collector plenum and extending outside the air supply plenum with openings to allow impingement cooling air to pass therethrough and having a series of lands extending into the channel wherein the lands are located in proximity to impingement cooling air outlets in the inner wall.  
         [0006]     A further aspect of the present invention is a baffle to direct impingement cooling air to portions of an inner wall comprises a collector plenum area that receives impingement cooling air from an air supply plenum and a channel in fluid communication with the collector plenum and extending beyond the air supply plenum. The channel has openings to allow impingement cooling air to pass therethrough; and a series of lands that extend into the channel wherein the lands are located in proximity to impingement cooling air outlets in the inner wall.  
         [0007]     A still further aspect of the present invention comprises a method of impingement cooling an area of an inner wall beyond an air supply plenum that includes the steps of receiving impingement cooling air in a collector plenum and transferring the impingement cooling air from the collector plenum through a channel to an opening beyond the air supply plenum. Next the impingement cooling air is passed through the opening onto the inner wall; and then the impingement cooling air is passed out through openings in the inner wall.  
         [0008]     Other aspects and advantages of the present invention will become apparent upon consideration of the following detailed description.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is an exploded isometric view showing one aspect of the cooling structure and baffle of the present invention;  
         [0010]      FIG. 2  is an isometric view of the cooling structure of  FIG. 1 ;  
         [0011]      FIG. 3  is a view taken generally along the line  3 - 3  in  FIG. 2 ;  
         [0012]      FIG. 4  is a view taken along the line  4 - 4  in  FIG. 2 ;  
         [0013]      FIG. 5  is a plan view of a portion of one embodiment of the baffle of present invention;  
         [0014]      FIG. 6  is a plan view of a portion of the opposite side of the baffle of  FIG. 5  attached to an impingement sheet; and  
         [0015]      FIG. 7  is a view similar to  FIG. 3  of an alternate embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Referring to  FIGS. 1 and 2 , a liner  100  for a high temperature application such as the exhaust area of a turbine engine has an inner wall  102 , an impingement sheet  104 , spacers  106  and  106   a , and an air supply plenum  108  having a seal  110 . In addition, portions of the liner  100  will have a baffle  112  to direct impingement air, as discussed below, to areas of the inner wall beyond the air supply plenum seal  108 . As shown in  FIG. 3 , an interfering structure  114  (shown in phantom lines), such as an air pump shroud, may prevent the air supply from within the air supply plenum  108  from reaching the portions of the inner wall  102  that lie beyond the extent of the area bounded by air supply plenum seal  110 . The structure also includes a tip (not shown) that forms a seal to further direct impingement air through the baffle  112 .  
         [0017]     The inner wall  102  has a series of apertures  120 . These apertures are located within a series of lands  122 . The lands  122  serve to meter the air flow along an inner surface  124  of the inner wall  102  so that the inner wall  102  is more efficiently cooled by the impinging air that strikes the inner surface  124 , travels along the inner surface  124  and then exits through apertures  120 . The apertures  120  and the lands  122  cover the entire inner wall  102 . Also as more clearly seen in  FIGS. 3 and 4 , the inner wall  102  can optionally have a heat resistant coating  126 . The coating  126  provides further heat protection to the liner  100 .  
         [0018]     The impingement sheet  104  has a series of apertures  130  located in a first area of the impingement sheet  104 . These apertures  130  direct cooling impingement air from air supply plenum  108  onto the inner surface  124  of the inner wall  102  in a conventional manner. The impingement sheet  104  has a second series of baffle supply apertures  132 . The baffle supply apertures  132  are located in proximity to the portion of the impingement sheet  104  near the air supply plenum seal  110 . The baffle supply apertures  132  are larger than the apertures  130  and the baffle supply apertures  132  are also spaced closer together than the apertures  120 . The reason for the size and spacing difference is that the baffle supply apertures  132  are supplying cooling air to a larger area to be cooled than the apertures  130  that are directly supplying cooling impingement air to the inner wall  102 . The impingement sheet  104  can also have an area  134  outside the air supply plenum seal  110 . The area  134  has no apertures  130  or  132 . This forms a seal with the tip structure to force the cooling air through the baffle  112 . The impingement sheet  104  also has a series of support clearance holes  136 . The area  134  will also have support clearance holes  136 .  
         [0019]     The inner wall  102  is spaced from the impingement sheet  104  by the supports  106 . The supports  106  are attached to the inner wall  102  in a conventional manner, such as by welding. The supports  106  have a shoulder  140  to support the impingement sheet  104  away from the inner wall  102 . A sealing washer  142  is placed over the support  106  on the shoulder  140 . The washer  142  forms a seal that prevents air from passing though the support clearance holes  136 . Allowing air to pass through the support clearance holes would reduce the cooling efficiency on the inner wall  102 . Even though the washer  142  is shown in direct contact with the shoulder  140 , the washer  142  can also be placed between the impingement sheet  104  and the baffle  112 . The location of the washer  142  is not particularly important as long as a good seal is formed. A proximal end  146  of the support  106  is shaped to receive a support nut  144  or other fastener. The support nut  144  can be either screwed into place with a locking screw arrangement or can be crimped into place. Also the support nut  144  can also be welded into place after it is in position. For those areas where there is a close clearance, a shorter support  106   a  also can be used. Support  106   a  is similar to support  106  except that the proximal end  146   a  of the support  106   a  is shorter than the proximal end  146  of the support  106 . The support  106   a  will have a close clearance fastener  148 . Typically the fastener  148  will be welded into place to securely hold the impingement sheet  104  against the washer  142  and in spaced relation to the inner wall  102 . Other forms of supporting structure can also be used such as a grid structure, integral support members, and the like.  
         [0020]     As shown by FIGS.  1  to  6 , the baffle  112  has an air collector plenum area  150 . The baffle also has a series of lands  152  that are shaped and spaced to correspond with the shape and location of the lands  122  on the inner wall  102 . The lands  152  form a series of channels  154  that permit air to flow from the air collector plenum area  150  of the baffle  112  to the entire area of the baffle  112 . A series of apertures  156  are formed in the channels  154 . The apertures  156  provide impingement cooling air to flow through the baffle  112  directly onto the inner surface  124  of the inner wall  102 . There are no apertures  156  that directly align with baffle supply apertures  132 . The baffle  112  also has a series of support clearance holes  158  that are located in a corresponding series of support clearance lands  160 . The baffle  112  has a leading edge  162  with a sealing surface that is secured to the impingement sheet  104  to form an airtight seal by the supports  106  and a trailing edge (not shown) that is secured to the inner wall  102  by conventional methods to form an airtight seal so that the trailing edge of the baffle  112  is sealed to the inner wall  102 . The entire periphery of the baffle  112  forms a seal with the inner wall  102 , the impingement sheet  104  or both the inner wall  102  and the impingement sheet  104  to prevent air from escaping and not cooling the inner wall  104 . One advantage of the baffle  112  structure as shown is a compact structure that can be placed into a thin environment and provide edge cooling to structures that cannot receive direct impingement cooling air. By having the lands  152  conform to the shape of the lands  122  on the inner wall  102 , the cooling airflow is maximized allowing to increased air velocity for impingement cooling and better film cooling as the air travels over the inner surface  124  of the inner wall  102 .  
         [0021]     As noted previously, air is supplied to the air supply plenum by conventional means such as from an air compressor (not shown). The cooling air will flow from the air supply plenum  108  through the apertures  130  in the impingement sheet  104  onto the inner surface  124  of the inner wall  102  in the direction of arrow  200 . As in conventional impingement cooling, after the cooling air strikes the inner surface  124  it then flows along the inner surface  124  of the inner wall providing added cooling effect in the direction of arrows  202  until the air exits through the apertures  120  in the direction of arrows  204 .  
         [0022]     Air from the air supply plenum  108  also will pass through the baffle supply apertures  132 . As noted above, the baffle supply apertures  132  are larger than the apertures  130 . Typical sizes for apertures  130  are about 0.030-0.060 inch and for baffle supply apertures about 0.066-0.090 inch. Air will flow through the baffle supply apertures  132  in the direction of arrow  210  and then be directed through the channels  154  in the direction of arrow  212 . When the airflow reaches the apertures  156  in the baffle  112 , the air will flow directly onto the inner surface  124  of the inner wall  102  to provide cooling effect as above in the direction of arrow  214 . The impingement air will then flow along the inner surface  124  of the inner wall  102  in the direction of arrows  216  and exit through apertures  120  as above.  
         [0023]     The baffle  112  can be formed from any suitable material for use in a high temperature environment. Typical materials include Inconel 625 or similar malleable alloys with high formability to maximize the relative heights of the various lands in the baffle.  
         [0024]     As shown in  FIG. 7 , an alternate embodiment of a baffle  112   a  for use in high pressure environments has a series of projections  250  depending from the baffle  112   a  and contacting the inner surface  124  of the inner wall  104 . The projections  250  add structure and support to the baffle  112   a  so that the baffle  112   a  will not flex under high pressures that may be encountered in certain applications. The projections  250  are spaced to provide support without interfering with air flow. In all other respects the baffle  112   a  is similar to the baffle  112 .  
         [0025]     Numerous modifications to the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is presented for the purpose of enabling those skilled in the art to make and use the invention and to teach the best mode of carrying out same. The exclusive rights to all modifications which come within the scope of the appended claims are reserved.