Abstract:
An apparatus and system for thermally isolating a gas turbine housing from the significantly high temperatures associated with the combustion gases flowing through the housing. A floating liner is assembled within the housing with an outer baffle surrounding the floating liner and an inner baffle disposed within the floating liner. The floating liner creates a thermally isolated device to cover and protect the housing from high temperature. Openings formed in the outer baffle, floating liner and inner baffle create a single, continuous cooling passageway within the housing for collecting heat from adjacent the surfaces of the floating liner and expelling the heat into the combustion exhaust stream.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention is directed to a gas turbine engine assembly of a type capable of operating at elevated temperatures. In particular, the present invention is directed to an assembly creating a single cooling circuit for thermally isolating the turbine housing from high temperatures that would otherwise adversely impact the delivery of cooling air/oil through the high temperature gas path to cool bearings, seals, nozzles and other engine components as well as maintaining the housing structural integrity.  
           [0002]    Recent advances in turbine engine technology utilize ceramic combustor technology which can operate at temperatures exceeding even 2500° F. It is essential that some housings must be cooled effectively and efficiently. Cooling the engine components while maintaining and even increasing engine efficiency and power are possible by operating at such higher temperatures without compromising the system.  
           [0003]    Typically, such high temperature gas turbine engines require many complex cooling circuits to isolate the housing from high temperature gases. Separate cooling circuits are often utilized to cool the gas path liner and air/oil passages extending through the struts as required for lubrication of bearings, seals, turbine blades and associated engine components.  
           [0004]    To insure adequate cooling, engine assemblies currently may utilize a circular inner hub and outer housing or shroud joined by a number of radially-extending support struts passing through the hot gas flow path. The struts may have hollow core areas extending lengthwise through the core for delivering air/oil to cool the bearings, nozzles and other components. The design of such inner hubs may accommodate bearings and various seal arrangements, while the outer shroud supports other ancillaries. The separate cooling circuits required for such shroud and hub assemblies are complex and expensive to fabricate and maintain.  
           [0005]    There clearly is a need for an apparatus capable of creating a single cooling circuit which is simply supported within the engine compartment and capable of successfully isolating the entire engine housing from the high temperatures created by the gas combustion process, thereby enabling the housing to deliver cooling air to the bearings, seals, nozzles and other engine components.  
         SUMMARY OF THE INVENTION  
         [0006]    In one aspect of the present invention, an apparatus is disclosed for thermally isolating a turbine engine housing from high temperatures created by combustion gases flowing through the engine. The apparatus includes a floating liner assembly that may be positioned within the engine housing, with a plurality of openings extending through the baffles. An outer baffle assembly may surround the floating liner assembly, with a plurality of openings extending through the outer baffle assembly. An inner baffle assembly may-be arranged within the floating liner assembly, with a plurality of openings extending through the inner baffle. The floating liner assembly, the outer baffle assembly and the inner baffle assembly may be arranged to form a single passageway for conveying a stream of compressed, cooling air against said floating liner to extract heat from said floating liner by both conduction and convection. The cooling air after extracting heat is then expelled into a stream of combustion gases flowing through turbine engine.  
           [0007]    In another aspect of the invention, a system is disclosed for thermally isolating a gas turbine engine housing having an outer ring-shaped housing member and an inner hub attached by housing struts from high temperatures created by combustion gases flowing through the turbine engine. The system includes a floating liner assembly that may be disposed between the inner hub and the outer ring-shaped housing member and may further include a plurality of liner struts enclosing the housing struts, with a plurality of openings extending through the floating liner. An outer baffle assembly may surround the floating liner assembly, with a plurality of openings extending through portions of the outer baffle assembly. An inner baffle assembly may be disposed within the floating liner assembly, with a plurality of openings extending through portions the inner baffle. A continuous stream of pressurized air may enter the outer ring-shaped housing member and may flow through the openings in the outer baffle assembly. The air stream may be directed against the floating liner to collect heat from the floating liner and expel the heat to a stream of combustion gases flowing through the gas turbine engine.  
           [0008]    In a yet further aspect of the present invention, an apparatus and system are disclosed for thermally isolating an outer ring-shaped housing member of gas turbine engine having a number of inlets and an inner hub attached the outer ring-shaped housing member by a plurality of separate housing struts, from high temperatures created by combustion gases flowing through the turbine engine. The apparatus and system may include a floating liner assembly disposed between the inner hub and the outer ring-shaped housing member. The floating ring may include separate, radially-disposed inner and outer ring-shaped members, with each ring-shaped member having a number of openings. This may form a cooling air passageway adjacent each of the floating liner ring-shaped inner and outer members. An outer baffle assembly may be formed of two similar, generally cylindrically-shaped members attached to one another and surrounding the floating liner outer ring-shaped member, with a plurality of openings extending through each outer baffle member. An inner baffle assembly may be formed of two similar, generally cylindrically-shaped members arranged within the floating liner inner ring-shaped member, with a plurality of openings extending through each inner baffle member. A single, continuous air cooling circuit may extend through the outer ring-shaped housing member and may flow through the openings in the outer and inner baffle assemblies, impacting on each of the floating liner inner and outer ring-shaped members. The stream may collect heat from each of the floating liner inner and outer ring-shaped members and expel the heat to a stream of combustion gases flowing through the gas turbine engine  
           [0009]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a schematic view of a gas turbine engine having a thermally cooled housing assembly formed in accordance with the present invention;  
         [0011]    [0011]FIG. 2 is a perspective view of one-half the thermally cooled housing assembly formed in accordance with the present invention;  
         [0012]    [0012]FIG. 3 is an exploded view taken along the lines A-A in FIG. 2;  
         [0013]    [0013]FIG. 4 is an exploded view taken along the lines B-B in FIG. 2;  
         [0014]    [0014]FIG. 5 is a perspective view of the thermally cooled housing assembly formed in accordance with the present invention;  
         [0015]    [0015]FIG. 6 is a perspective view of the thermally isolated housing without the liner assembly formed in accordance with the present invention;  
         [0016]    [0016]FIG. 7 shows an isometric view of the floating liner assembly formed in accordance with the present invention;  
         [0017]    [0017]FIGS. 8 a  and  8   b  show perspective views of portions of the inner and outer baffle members;  
         [0018]    [0018]FIG. 9 a  shows an exploded perspective view of the thermally isolated housing, baffles and floating liner assembly formed in accordance with the present invention; and  
         [0019]    [0019]FIG. 9 b  shows a view of the floating liner and baffle assembled into the thermally isolated housing as formed in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    The following detailed description is of the best currently contemplated modes of carrying out the present invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.  
         [0021]    The gas turbine engine formed in accordance with the present invention includes an assembly and system for thermally isolating housing from high temperatures in the gas path that otherwise adversely affect the housing and its cooling passages. The apparatus allows the turbine engine to function without thermal interference of the type caused by transient conditions existing during system startup and shutdown. Referring now to FIG. 1, a thermally isolated housing assembly is shown at  10 . An inlet pipe  12  can be attached to housing  10  and may deliver a quantity of relatively cool, compressed air through a number of inlets  14  extending through housing  10 . As shown by the arrows  16 , a portion of the compressed cooling air may circulate in a forward direction through the housing until reaching typical metal seals  18  located at the forward end  20  of the turbine engine. The cool air  16  continues to flow through a cavity created between the liner  35  and strut  48  to the hub of the housing  10 . A further portion of the cooling air  16  also flow towards forward end  20  of the turbine engine to cool the hub of the housing  10  prior to flow toward the rear end of the engine housing. The cooling air  16  may pass adjacent the rear metal air seals  24  before being expelled from the air circuit through one or more outlets  25 . The expelled cooling air can mix with the turbine gas  30  flowing through the exhaust nozzle  28 .  
         [0022]    As shown in FIGS. 2 and 5 and  6 , thermally isolated housing  10  encloses a cooling apparatus  11  that can include a number of radially-aligned components. Among the components can be a floating liner  32  that may be formed as a single assembly or, preferably, constructed from outer and inner ring members  33   a  and  33   b , respectively. When assembled, the outer ring member  33   a  may surround and can be radially-spaced from the inner ring member  33   b . A number of hollow liner struts  35  may extend between the ring members. A number of openings  34  may extend through each of the outer and inner ring-shaped members  33   a  and  33   b  to form an air flow passageway through outer ring member  33   a , strut  35  and inner ring member  33   b , allowing a single stream of cooling air to circulate adjacent each floating liner ring member as will become clear.  
         [0023]    Cooling apparatus  11  can also include an outer baffle assembly  36  that may be formed as a single, cylindrically-shaped member or, preferably, may be formed from two separate, cylindrically-shaped portions  37   a  and  37   b , respectively. Portions  37   a  and  37   b  may be welded together to form a closed cylinder during assembly. When assembled, outer baffle assembly  36  can enclose floating liner outer ring member  33   a  and  33   b . A plurality of circumferentially-spaced openings  38  and  40  extend through outer baffle portion  37   a , allowing cooling air to pass through baffle portion  37   a  and flow adjacent to floating liner  32 . Each of the portions  37   a  and  37   b  further includes aligned slot portions  41  that engage one another to form enlarged openings as baffle portions  37   a  and  37   b  are assembled. As will be explained, the enlarged openings formed by slots  41  enclose strut-shaped connecting members forming additional air passageways through the baffle assembly  36 .  
         [0024]    A further part of cooling apparatus  11 , inner baffle assembly  42 , may be arranged within floating liner inner ring member  33   b . Inner baffle assembly  42  may be formed as a single, cylindrically-shaped member or, preferably, may be formed from separate, cylindrically-shaped members  43   a  and  43   b , respectively. Further, each of the cylindrical members  43   a  and  43   b  may, itself, be formed by a number of arc-shaped segments welded to form the continuous cylinder. The number of segments can depend on the number of struts and contour shape. By forming the inner baffle cylindrical portions from a number of arc-shaped segments, ease of assembly is assured. A number of openings  44  extend through inner baffle assembly  42 , allowing cooling air to circulate through the inner baffles  42  and adjacent floating liner inner ring member  33   b.    
         [0025]    Referring now to FIGS. 3 and 6, thermally isolated housing assembly  10  can further include a number of radially-disposed hollow housing struts  48  extending between and joining an outer shroud ring-shaped housing member  50  and a cylindrically-shaped inner hub member  52 . This assembly allows cooling air/oil to be circulated between outer housing member  50  and inner hub  52 , for cooling the bearings and seal assemblies contained within hub  52 . When assembled, cooling apparatus  11  having floating liner assembly  32  and associated outer baffle assembly  36  and inner baffle assembly  42 , is positioned between outer housing member  50  and inner hub  52 , with floating liner struts  35  encasing the housing struts  48  and creating an air flow passageway  49  there between.  
         [0026]    Referring again to FIG. 1, a number of circumferentially-spaced clocking or dowel pins  54  may extend between housing  10  and a forward portion of floating liner  32  for properly orienting floating liner  32  within housing  10 . Controlling circumferential expansion and orientation are particularly important during the engine operating thermal cycle.  
         [0027]    The present invention may provide a single air circuit capable of circulating compressed air within the engine housing compartment adjacent floating liner outer and inner rings  33   a  and  33   b , respectively. As shown in FIGS.  2 - 4 , a stream of compressed cooling air  16  enters housing  10  via a number of the inlet openings  14 . As the compressed air impinges on the outer baffle assembly  36 , it diffuses, with most of the cooling air  16  moving toward the forward end  20  of housing  10 , while the remaining cooling air  16  moves toward the aft end  23  of housing  10 . The cooling air stream  16  may move through the openings  38  and  40  in outer baffle  36  and flow adjacent to the surface of floating liner outer ring  33   a  in both axial and circumferential directions. This extracts heat from all outer surfaces of floating liner outer ring  33   a  forming a boundary with the hot flow gases  30 . A further portion of cooling air  16  may flow inwardly through the openings in floating liner outer ring  33   a  and into the through passageway  49  defined by housing strut  48  and floating liner strut  35 . The cooling air exits via additional openings  34  in the floating liner inner ring member  33   b  and is directed between inner baffle  42  and floating liner inner ring  33   b . The cooling stream of air can collect heat from the floating liner inner ring  33   b  and expel it through outlets  25  into the stream of combustion gases  30  flowing through exhaust  28 .  
         [0028]    Cooling apparatus  11  including floating liner  32 , outer baffle assembly  36  and inner baffle assembly  42  is specifically designed to isolate the thermal interference which may arise in housing  10  and otherwise prevent delivery of cooling air to the engine components that must be cooled, i.e., seals, bearings, turbine blades during thermal transient cycles. The forward and aft portions of the floating liner  32  and baffles  36  and  42  are protected against axial thermal expansion by the seal assemblies  22  and  24  which may take the form of typical metal seals such as W, C configuration or piston seals. Because floating liner  32  can be circumferentially clocked at the forward end by the three dowel pins  54  radially piloted within the aft end of housing  10 , it can remain in its pre-determined location in the flow path  30  of the hot engine gases. Floating liner  32  along with its single cooling circuit extending between liner  32  and both baffles  36  and  42  serves to extract and expel heat from liner  32  which would otherwise damage the housing shroud  50  and its ability to deliver cooling air/oil to hub  52  to cool bearings, nozzles and other components.  
         [0029]    It should be understood, of course, that the foregoing relates to preferred embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention. For example, the floating liner  32 , outer baffle  36  and inner baffle  42  may each be formed from a single member rather than from a number of separate members. The location of the openings extending through floating liner  32  and the baffles  36  and  42  may be altered to adjust the flow path for the compressed cooling air  16  and thereby maximize its cooling affect. These any other modifications should in no way limit the scope of the invention, which should only be determined based on the following claims.