Abstract:
An assembly line is disclosed for economically and efficiently assembling a core into a recuperator. The assembly line has an inlet end, an assembly station, a welding station, a control station and an outlet end. The inlet end has a plurality of the cores to be used for assembly thereat. The core is positioned within the assembly station and an assembly fixture locates a ducting structure in a preestablished relationship to the core. The control station using a plurality of sensors sends an input to a controller and the welding station performs a weld fixedly securing the ducting structure to the core.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates generally to a heat exchanger or more explicitly to a recuperator and more particularly to an apparatus and method for assembling the recuperator.  
         BACKGROUND  
         [0002]    Many application use the recuperator which is a specific type of heat exchanger to extract heat from a fluid. One such application is that of a gas turbine engine. For example, to increase the operation efficiency of the gas turbine engine, heat is extracted from the exhaust gas and used to preheat the intake air. Typically, the recuperator for a gas turbine engine must be capable of operating at temperatures of between about 500 degrees C. and 700 degrees C. and internal pressures of between approximately 450 kPa and 1400 kPa under operating conditions involving repeated starting and stopping cycles.  
           [0003]    Many recuperators are of a primary surface construction. In a primary surface recuperator, a plurality of thin sheets are stacked in a spaced apart configuration to form a cell. The cells are assembled, such as by welding, to form a core. The spacing within the core forms a plurality of donor passages and a plurality of recipient passages. In applying the recuperator to the gas turbine engine, the hot exhaust gas is passed through the donor passages and an atmospheric temperature intake air is passed through the recipient passages. Heat from the hot exhaust is transferred through the sheet and absorbed by the cooler intake air increasing the efficiency of the gas turbine engine.  
           [0004]    In most applications the primary surface sheet used in forming the cell is very thin, flimsy and difficult to maintain a uniform cross sectional area of the passages between the sheets. To enhance the rigidity of the thin sheets, the sheets are formed into an accordion type configuration forming peaks or crests and valleys forming a plurality of upwardly and downwardly opening, transversely extending, relatively deep grooves being relatively closely spaced and having substantially vertical side walls or fins. In forming the recuperator using such sheets, the peeks of alternate sheets are aligned and the valleys of alternate sheets are aligned to form the donor passages and the recipient passages. Additionally, many of the sheets are formed with a serpentined configuration to enhance a controlled turbulent which increases heat conductivity and resulting efficiency. In manufacturing such recuperators, the component parts are fixedly attached together by a welding process to prevent leakage from the respective donor passages and recipient passage. To insure the integrity of the recuperator, the welding process and technique used is very critical to maintaining a sealed separation between the plurality of donor passages and the plurality of recipient passages.  
           [0005]    U.S. Pat. No. 5,060,721 issued on Oct. 29, 1991 to Charles T. Darragh discloses an example of one such recuperator. The recuperator disclosed in this patent has a circular configuration. The recuperator has a plurality of cells made from a pair of primary surface sheets, a plurality of spacer bars and a plurality of guide strips. The component parts are welded together to form the recuperator. The welding of these thin sheet and component parts into a cell having a sealed interface is difficult to accomplish in a cost effective and efficient manner.  
           [0006]    After the assembly of the sheets and component parts into the cell and the assembly of the cells into the core, additional component, such as ducts, must be added to the core. The ducts direct the hot exhaust gas to and through the donor passages and direct the intake air to and thorough the recipient passages. These ducts are also welded to the core. The welding of these thin sheets of the core to the ducts and the relative positioning thereof with a sealed interface is difficult to accomplish in a cost effective and efficient manner.  
           [0007]    The present invention is directed to overcome one or more of the problems as set forth above.  
         SUMMARY OF THE INVENTION  
         [0008]    In one aspect of the invention, a recuperator assembly line is adapted to assemble a core. The core has a plurality of donor passages therein and a plurality of recipient passages. The recuperator assembly line has an assembly station including an upper stacking portion defining a first side and a second side. The upper stacking portion is rotatable between a first position and a second position. The core is positioned in the upper stacking portion. An assembly fixture is positioned at one of the first side and the second side. The assembly fixture has a plate having a bore therein. A plurality of locating members are positioned in one of the assembly fixture and the assembly station. The plurality of locating members define a preestablished relationship between the assembly fixture and the assembly station. A locating mechanism is positioned in the bore, the locating mechanism has a first end having a positioning portion located near said first end. A one of a plurality of ducting structures is attached to the positioning portion of the locating mechanism. The one of the plurality of ducting structures is positioned in a preestablished position relative to one of the plurality of donor passages and the plurality of recipient passages. A welding station has a welding head and forms a weld. A control station has a plurality of sensors, a plurality of switches and a controller operatively receiving an input from the plurality of sensors and the plurality of switches. The controller defines a relative position of the one of the plurality of ducting structures and the core. And, the one of the plurality of ducting structures is attached to the core with the weld.  
           [0009]    In another aspect of the invention, a method of assembling a core into a recuperator has the steps of positioning the core in an upper stacking portion; securing the core within the upper stacking portion; positioning one of a plurality of ducting structures within an assembly fixture; positioning the assembly fixture relative to the upper stacking portion in a preestablished relationship; and welding the one of a plurality of ducting structures to the core.  
           [0010]    In another aspect of the invention, a circular recuperator assembly line has an assembly station defining an axis and having a core defining an axis “A” being aligned about the axis of the assembly station and is removably positioned within the assembly station. An assembly fixture defines an axis and has a ducting structure removably positioned therein relative to the axis of the assembly fixture. The assembly fixture is position in axial alignment with the axis “A” of the core. A control station has a controller, a plurality of switches and a plurality of sensors defining an input to the controller of the relative position of the core within the assembly station and the ducting structure relative to the core. A welding station has a welding head and a lead. The welding station is operatively connected to the control station and the assembly station. And, a weld is interposed the core and the ducting structure. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a sectional view of a partially assembled recuperator taken through a plurality of cells;  
         [0012]    [0012]FIG. 2 is a schematically representation of a manufacturing system or line;  
         [0013]    [0013]FIG. 3 is a detailed sectional view of a work station of the manufacturing line of FIG. 2; and  
         [0014]    [0014]FIG. 4 is a top view of the work station of FIG. 3. 
     
    
     DETAILED DESCRIPTION  
       [0015]    [0015]FIG. 1 shows a partially assembled recuperator  10 . In the application shown, the recuperator  10  is that of a circular core  12 . The core  12  is formed from a plurality of cells  14 . The core  12  has a plurality of donor passages  15  formed therein and a plurality of recipient passages  16  formed therein. The core  12  has a plurality of donor inlet portions  17  positioned at a first side  18  of the core  12 , best shown in FIG. 3. And, a plurality of donor outlet portions  19  are positioned at a second side  20  of the core  12 , best shown in FIG. 3. The plurality of cells  14  are formed from a plurality of primary surface sheets  21  having a serpentined pleat  22  thereon, a plurality of spacer bars  24  and a plurality of guide vanes  26 . The primary surface sheets  21  are very thin in thickness, for example, in this application the thickness is about 2.3 mm. However, as an alternative, the thickness can be larger or possibly thinner which out changing the jest of the invention. Respective ones of the plurality of guide vanes  26  are positioned in a donor inlet end  28  of the respective plurality of donor passages  15  and positioned in a recipient inlet end  40  of the respective plurality of recipient passages  16 . The respective plurality of primary surface sheets  21  and the respective plurality of spacer bars  24  of the respective plurality of cells  14  are fixedly attached by a welding station  42 . The plurality of cells  14  are also fixedly attached by the welding station  42 . The welding process and procedures used in each of the assembly of the plurality of sheets  21  and the plurality of spacer bars  24 , and the plurality of cells  14  are very critical to maintain the integrity of the recuperator  10 . After the plurality of cells  14  have been assembled, a plurality of recipient air ducting structures  43  and a plurality of donor gas ducting structures  44  are added to complete the recuperator  10 . The plurality of donor gas ducting structures  44  and the plurality of recipient air ducting structures  43  are also fixedly connected by the welding station  42 . In this application, with the core  12  being circular, the plurality of donor gas ducting structures  44  defines an axis, an inner surface  45  and an outer surface  46  thereon and the plurality of recipient air ducting structures  43  defines an axis, an inner surface  47  and an outer surface  48  thereon.  
         [0016]    In this application, the circular core  12  has an inner diameter “ID” and an outer diameter “OD”. The circular core  12  is centered about an axis “A”. The inner diameter “ID” has a preestablished diameter and the outer diameter “OD” has a preestablished diameter.  
         [0017]    As shown in FIG. 2, a manufacturing or assembly line  50  is shown. The manufacturing or assembly line  50  has an inlet end  52  having a flat or tub  54  positioned at the inlet end  52  on which is positioned a plurality of partially assembled cores  12 . For example, the partially assembled cores  12  have the respective plurality of cells  14 , plurality of spacer bars  24 , and the plurality of guide vanes  26  assembled one to another by the welding station  42 . Positioned at an outlet end  56  being opposite the inlet end  52  is a flat or tub  58  on which is positioned assembled cells  12 , or the recuperator  10 , having the respective plurality of donor gas ducting structures  44  and the plurality of recipient air ducting structures  43  connected thereto by the welding station  42 . Interposed the inlet end  52  and the outlet end  56  is an assembly station  60  being centered about an axis, which in operation coincides with the axis “A” of the core  12 . The welding station  42  is operatively attached to the assembly station  60  and is positioned within the manufacturing or assembly line  50 . A control station  66  is operatively attached to the assembly station  60  and the welding station  42 . The control station  66  has a controller  68  which operatively receives inputs from a plurality of sensors  70  and a plurality of switches  72 .  
         [0018]    As best shown in FIGS. 3 and 4, the assembly station  60  includes a table  74  having an inner chucking portion  76  which is movable between a lower position  78 , shown in phantom, and an upper position  80  by a cylinder  82 . The cylinder  82  is hydraulically actuated but as an alternative could be electrically or pneumatically actuated. The table  74  also has an upper stacking portion  84  which defines a first side  86  and a second side  88 . The upper stacking portion  84  is movable between a loading position  90 , shown in phantom, and a clamping position  92 . The upper stacking portion  84  is rotatable between a first position  94  and a second position  96  as is partially shown in phantom. The upper stacking portion  84  is rotatable 360 degrees and the first position  94  is indexed 180 degrees from the second position  96  by a motor  98  which in this application is hydraulically actuated. As an alternative, the motor could be electrically or pneumatically actuated. The upper stacking portion  84  is lockable at either of the first position  94  and the second position  96 . The inner chucking portion  76  is expandable between a retracted position  110 , shown in phantom, and an expanded position  112 . Each of the first side  86  and the second side  88  of the upper stacking portion  84  have a plurality of locating members  114  such as dowels extending therefrom in a preestablished position. Each of the inner chucking portion  76  and the upper stacking portion  84  define an axis which with the core  12  positioned about the inner chucking portion  76  and the core  12  positioned within the upper chucking portion  84  aligns with the axis “A” of the core  12 .  
         [0019]    An assembly fixture  120  is orientated by the plurality of locating members  114 . The assembly fixture  120  is adapted to be positioned on either of the first side  86  or the second side  88 . The assembly fixture  120  includes a plate  122  defining a first side  124  and a second side  126 . At least a pair of locating holes  128  which align with the plurality of locating members  114  extend between the first side  124  and the second side  126 . As an alternative, the dowels could be positioned in the assembly fixture  120  the holes could be positioned in the inner chucking portion  76 . A bore  140  is positioned in the plate  122  and extends between the first side  124  and the second side  126 . The bore  140  defines an axis which with the locating holes  128  and the plurality of locating members  114  are aligned with the axis “A” of the core  12 . A locator mechanism  142  is positioned in the bore  140 . The locator mechanism  142  has a positioning portion  144  located near a first end  146 . In this application, the locator mechanism  142  is hydraulically activated and has a hose  147  extending from a second end  148 . The hose  146  is operatively attached to a source of fluid pressure  150 . The source of fluid pressure  150  is operatively connected and controlled by the control station  66 . The positioning portion  144  is expandable between a retracted position  152  and an expanded position  154 .  
         [0020]    The welding station  42  includes a welding head  160  having a lead  162  connected thereto. The welding head  160  and the lead  162  are of conventional construction. The welding head  160 , in this application, has the ability of be manually controlled by an operator and to be automatically controlled. The welding head  160  produces a weld  164 .  
       INDUSTRIAL APPLICABILITY  
       [0021]    In operation, the recuperator assembly line  50  is used to manufacture the recuperator  10 . The partially manufactured core  12  is available to the recuperator assembly line  50  at the input end  52 . In this application, the operator removes the core  12  from the flat  54 . Or, as an alternative, an automated process, such as a robot could perform the operator functions. With the inner chucking portion  76  in the upper position  80  and the upper stacking portion  84  in the loading position  90  the core  12  is positioned therein. The upper stacking portion  84  has the first side  86  up and the core  12  has the first side  18  up. The upper chucking portion  76  is moved into the clamping position  92  and the axis of the inner chucking portion  76 , upper stacking portion  84  and the core  12  are aligned.  
         [0022]    With the positioning portion  144  of the locating mechanism  142  in the retracted position  152 , one of the donor gas ducting structures  44  is positioned about the positioning portion  144 . The source of pressure  150  is actuated and the positioning portion  14  is moved into the expanded position  154 .  
         [0023]    With the positioning portion  144  of the locating mechanism  142  in the retracted position  152 , one of the recipient air ducting structures  43  is positioned about the positioning portion  144 . The source of pressure  150  is actuated and the positioning portion  14  is moved into the expanded position  154 . The positioning portion  144  is positioned above the upper stacking portion  84 , the pair of locating holes  128  are aligned with the plurality of locating members  114  and lowered until the recipient air ducting structure  43  is in contact with the first side  18  of the core  12 . By using the locating holes  128  and the locating members  114  the axis of the recipient air ducting structure  43  and the axis “A” of the core  12  are aligned.  
         [0024]    The plurality of sensors  70  monitor the position of the respective parts and when aligned or mated sends a signal to the controller  68  of the control station  66 . The controller  68  signals the operator that a weld  164  of the welding station  42  can be welded. The welding head  160  is positioned relative to the recipient air ducting structure  43  and the core  12  and a plurality of tack welds  164  are initiated. For example, about six locations are used to secure the recipient air ducting structure  43  to the core  12 . With the tack welds  164  completed, the interface of the recipient air ducting structure  43  and the core  12  at the outer surface  46  and the inner diameter “ID” respectively are completely welded  164 . With the tack welds  164  complete, the locating member  114  can be removed to provide additional room for easier welding  164 . With the first side  18  of the core  12  up any additional ducting structure  43 , 44  can be welded  164  thereto in a similar manner. During the welding process, caution must be taken to prevent burning through of the thin sheets  21  of which the core  12  is made which would result in a defective core  12 . It should be noted that the welding operation can be done manually or with an automated process.  
         [0025]    With the welds  164  complete on the first side  18  of the core  12 , the upper stacking portion  84  is indexed or rotated from the first position  94  into the second position  96  and locked into the second position  96 . Thus, any remainder of the welding can be welded  164  to the second side  20  of the core  12  in a similar manner and process.  
         [0026]    With the welding of the ducting structures  43 , 44  to the core  12  complete, the upper stacking portion  84  is moved into the loading position  90  and the core  12  and ducting structures  43 , 44  are removed from the upper stacking portion  84 . With the core  12  and the ducting structures  43 , 44  clamped in the upper stacking portion  84 , if desired, a shipping band or bands can be added to the structure to maintain the outer diameter “OD” within it diameter. Such a band can also be added to the core  12  prior to rotating the upper stacking portion  84  from the first position  94  to the second position  96 , if desired.  
         [0027]    Thus, an effective and efficient assembly of the core  12  and the ducting structures  43 , 44  is accomplished. The ducting structures  43 , 44  are properly aligned with the core  12 . And, the relationship of the ducting structures  43 , 44  to there defined relationship with the completed recuperator  10  is maintained for further use and assembly of the recuperator&#39;s  10  future application. With the relationship of the ducting structures  43 , 44  and the core  12  maintained the welding of the interface is made easier, more efficient and effective. And, results in a high quality, lower maintenance, more efficient recuperator  10 .