Patent Publication Number: US-7584621-B2

Title: Radially expanding turbine engine exhaust cylinder interface

Description:
FIELD OF THE INVENTION 
     The invention relates in general to turbine engines and, more particularly, to the exhaust portion of turbine engines. 
     BACKGROUND OF THE INVENTION 
     The exhaust portion of a turbine engine typically includes an exhaust cylinder and an exhaust diffuser. During engine operation, hot exhaust gases pass through the exhaust cylinder and the exhaust diffuser, causing these components to thermally expand in the radial direction. However, the exhaust cylinder and the exhaust diffuser expand at different rates. In some engines, the interface between the exhaust cylinder and the exhaust diffuser is rigid at least in the radial direction, thereby inhibiting relative radial movement of these components. Consequently, stresses are placed on the interface, making it susceptible to low cycle fatigue (LCF), which can manifest as cracks, fractures or failures. 
     LCF failures of the exhaust cylinder and exhaust diffuser interface result in increased downtime to repair the interface and maintain the integrity of the turbine. Often, these repairs require the time-consuming and labor intensive disassembly of the external components surrounding the interface. Thus, there is a need for an interface between the exhaust cylinder and the exhaust diffuser that can minimize such concerns. 
     SUMMARY OF THE INVENTION 
     Aspects of the invention are directed to an interface between a first turbine engine component and a second turbine engine component that are substantially coaxial. In one embodiment, the first turbine engine component can be an exhaust cylinder, and the second turbine engine component can be an exhaust diffuser. 
     The first and second turbine engine components are operatively connected by a plurality of connecting members, which can be tied rods. Each connecting member has a first end and a second end. The first end of each connecting member is connected to the first turbine engine component, and the second end of each connecting member is connected to the second turbine engine component. 
     At least a portion of each of the ends is pivotable. To that end, at least one of the pivotable ends of the connecting member can include a bearing housing with a pivot bearing therein. In one embodiment, the first and second ends of each connecting member can be at least partially spherically pivotable. Thus, the connecting members can maintain a structural connection between the first and second turbine engine components while permitting relative radial movement of the components. 
     Each connecting member can be angled relative to a neighboring connecting member. The neighboring connecting members can be angled from about 25 degrees to about 165 degrees relative to each other. 
     In another respect, aspects of the invention are directed to a turbine engine interface between a first turbine engine component and a second turbine engine component. The first and second turbine engine components are substantially coaxial. The interface can permit relative radial movement of the first and second turbine engine components. In one embodiment, the first turbine engine component can be an exhaust cylinder, and the second turbine engine component can be an exhaust diffuser. The first turbine engine component has a plurality of first mounting posts connected thereto and extending therefrom; the second turbine engine component has a plurality of second mounting posts connected thereto and extending outward therefrom. 
     A plurality of connecting members operatively connect the first turbine engine component and the second turbine engine component. The connecting members can be, for example, tie rods. Each connecting member has a first end and a second end. At least a portion of each end is pivotable. In one embodiment, the first and second ends of the connecting members can be at least partially spherically pivotable. One or both ends of each connecting member can include a bearing housing with a pivot bearing therein. 
     Each first end is connected to one of the first mounting posts, and each second end is connected to one of the second mounting posts. The connecting members can be secured to each mounting post by lug nuts, friction fittings and/or welds. In one embodiment, each end of the connecting members can be secured to a respective mounting post by a lug nut and a retainer. The retainer can be one or more of the following: a lock nut, a lock washer, a spring washer, a wedge-lock washer, a cotter pin, a split pin or a weld. 
     Each connecting member can be angled relative to a neighboring connecting member. For instance, the neighboring connecting members can be angled from about 25 degrees to about 165 degrees relative to each other. 
     In yet another respect, aspects of the invention are directed to a radially expanding turbine engine exhaust cylinder interface. The interface includes an exhaust cylinder and an exhaust diffuser that are substantially coaxial. The exhaust cylinder has a plurality of mounting posts connected about and extending outward from the periphery of the exhaust cylinder. Likewise, the exhaust diffuser has a plurality of mounting posts connected about and extending outward from the periphery of the exhaust diffuser. 
     According to aspects of the invention, a plurality of tie rods operatively connect the exhaust cylinder and the exhaust diffuser. Each tie rod has a first end and a second end. At least a portion of each end is pivotable. In one embodiment, one or both ends of each tie rod can include a bearing housing with a pivot bearing therein. Each first end is connected to one of the mounting posts on the exhaust cylinder, and each second end is connected to one of the mounting posts on the exhaust diffuser. Thus, relative radial movement between the exhaust cylinder and the exhaust diffuser is permitted. In one embodiment, each tie rod can be angled relative to a neighboring tie rod from about 25 degrees to about 165 degrees. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exhaust cylinder-exhaust diffuser interface according to aspects of the present invention. 
         FIG. 2  is a close-up perspective view of a portion of the exhaust cylinder-exhaust diffuser interface of  FIG. 1 , showing an arrangement of a pair of connecting members according to aspects of the invention. 
         FIG. 3  is cutaway plan view of one embodiment of a connecting member according to aspects of the invention, wherein the connecting member is a tie rod. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Aspects of the invention are directed to an interface between two or more turbine engine components with different rates of thermal expansion. Embodiments of the invention will be explained in connection with an exhaust cylinder and an exhaust diffuser, but the detailed description is intended only as exemplary. Embodiments of the invention are shown in  FIGS. 1-3 , but the present invention is not limited to the illustrated structure or application. 
     It is noted that use herein of the terms “circumferential,” “radial” and “axial” and variations thereof is intended to mean relative to the turbine. An interface according to aspects of the invention allows relative radial movement between two or more turbine engine components. The interface can further be configured to minimize the relative axial and/or circumferential movement between the two or more turbine engine components. 
     Referring to  FIG. 1 , an exemplary radially expanding interface for the exhaust portion of a turbine engine is illustrated and generally referred to by reference numeral  10 . The interface  10  generally connects two or more turbine engine components, particularly those components that are substantially coaxial. For instance, the interface  10  according to aspects of the invention can be used to connect an exhaust cylinder  20  and an exhaust diffuser  22 . The exhaust cylinder  20  and the exhaust diffuser  22  can be substantially coaxial. Generally, the exhaust cylinder  20  can have a leading edge  26  and a trailing edge  28 . Support struts  24  can connect between the exhaust cylinder  20  and a shaft bearing (not shown) provided within an inner diffuser case  30 , which can support the internal shaft (not shown) of the engine. Passages  27  can be provided in the exhaust diffuser  22  to allow the struts  24  to pass therethrough. Those portions of each support strut  24  that extend within the path of the exhaust gas E (that is, in the space between the exhaust diffuser  22  and the housing  30 ) can be protected by a heat shield  25 . The heat shields  25  can connect between the exhaust diffuser  22  and the shaft bearing housing  30 . The support struts  24  can extend through the heat shields  25 . 
     The interface  10  according to aspects of the invention can include a plurality of connecting members that operatively connect the exhaust cylinder  20  and the exhaust diffuser  22 , while permitting relative radial motion of these components, which may arise due to differing rates of thermal expansion, among other things. Each connecting member can have a first end and a second end. According to aspects of the invention, at least a portion of the first and second ends of each connecting member can be pivotable. It should be noted that the term “pivotable” as used herein includes but is not limited to two dimensional pivoting motion. The term “pivotable” can further include three dimensional pivoting motion as well as other non-pivoting motion. For instance, at least a portion of the first and second ends of each connecting member can be at least partially spherically pivotable, allowing multi-directional pivoting motion as well as rotation about an axis. In such case, the range of motion of the first and second ends can be similar to at least a part of the range of motion of a ball and socket type joint. In another embodiment, at least a portion of the first and second ends of each connecting member can be substantially radially pivotable; that is, at least a portion of each of the first and second ends can, at a minimum, pivot and/or rotate substantially about an axis that is substantially in the radial direction. 
     As will be described in more detail below, the first end of each connecting member can be connected to the exhaust cylinder  20 , preferably at or near the trailing edge  28 . In one embodiment, the first end of the connecting member can be connected to a platform (not shown) jutting from the trailing edge  28  of the exhaust cylinder  20 . Each connecting member can further be connected at its second end to the exhaust diffuser  22 . 
     The connecting members can support the weight of the exhaust diffuser  22 . In one embodiment, the connecting members can be the sole support of the exhaust diffuser  22 . In addition, the connecting members can substantially axially fix the exhaust diffuser  22  relative to the exhaust cylinder  20 . Further, the connecting members can otherwise substantially retain the exhaust diffuser  22  in place, preventing undesired motion of the exhaust diffuser  22  such as vertical movement or tipping. Ideally, the connecting members can substantially maintain the substantially coaxial relationship between the exhaust diffuser  22  and the exhaust cylinder  20 . 
     There can be any quantity of connecting members. In one embodiment, the interface  10  can include twenty-four connecting members. The connecting members can be arrayed about the interface  10  in various ways. For example, the connecting members can be provided about the interface  10  at substantially regular intervals. However, other arrangements including irregular intervals are possible. 
     The connecting members can also be positioned in various ways. For example, the connecting members can be provided in pairs. In each pair, the connecting members can be angled relative to one another. Such an arrangement can minimize relative circumferential movement between the exhaust diffuser  22  and the exhaust cylinder  20 , which may occur due to twisting or torquing. In one embodiment, there can be at least four pairs of connecting members provided about the interface, and, preferably, the connecting member pairs are substantially equally spaced. 
     In one embodiment, a pair of the connecting members can be angled from about 25 degrees to about 165 degrees in relation to one another. More specifically, the connecting members can be angled from about 60 degrees to about 120 degrees relative to each another. In one embodiment, a pair of the connecting members can be positioned at substantially 90 degrees relative to each other. The angle between one pair of connecting members can be substantially the same for each pair of connecting members about the interface  10 . However, at least one pair of connecting members can be positioned at a different relative angle from the other pairs. 
     The connecting members can be any of a number of devices. In one embodiment, the connecting members can be tie rods  40 . An example of a tie rod  40  according to aspects of the invention is shown in  FIG. 3 . The tie rod  40  can generally include a first end  42 , a rod link  58 , and a second end  44 . As will be explained in more detail below, at least a portion of the first and second ends  42 ,  44  of the tie rod  40  can be radially pivotable. The tie rods  40  can be made of almost any material, but it is preferred if the tie rods  40  are made of a heat resistant material, such as, for example, 300 series stainless steel or other material having sufficient heat resistance and strength to maintain the connection between two turbine engine components. 
     The first end  42  of the tie rod  40  can include a first connection assembly  46 . The first connection assembly  46  can include a bearing housing  52  with a channeled pivot bearing  66 ( a ) contained therein. The bearing housing  52  and the pivot bearing  66 ( a ) can move relative to each other. In one embodiment, the bearing housing  52  and the pivot bearing  66 ( a ) can be adapted to allow at least partial spherical movement relative to each other. The first connection assembly  46  can include any other means that can permit a radially pivotable attachment between the first end  42  of the tie rod  40  and the turbine engine component to which it is attached. The first connection assembly  46  can be connected to the rod link  58  in various manners. In one embodiment, the first connection assembly  46  can be connected to the rod link  58  by threaded engagement. To that end, the first connection assembly  46  can include external threads  56 , and the rod link  58  can provide complementary internal threads  62 ( a ). 
     The second end  44  of the tie rod  40  can include a second connection assembly  48 . The second connection assembly  48  can include a bearing housing  72  with a channeled pivot bearing  66 ( b ) contained therein. The bearing housing  72  and the pivot bearing  66 ( b ) can move relative to each other. Preferably, the bearing housing  72  and the pivot bearing  66 ( b ) can be adapted to allow at least partial spherical movement relative to each other. The second connection assembly  48  can provide any other means that can provide a radially pivotal attachment between the second end  44  of the tie rod  40  and a turbine engine component to which it is attached. The second connection assembly  48  can be connected to the rod link  58  in various manners. In one embodiment, the second connection assembly  48  can be connected to the rod link  58  by threaded engagement. In such case, the second connection assembly  48  can include external threads  76 , and complementary internal threads  62 ( b ) can be provided in the rod link  58 . In one embodiment, the external threads  76  on the second connection assembly  48  can be opposite to the external threads  56  on the first connection assembly  46 . 
     To facilitate installation, it is preferred if the overall length of the tie rod  40  is adjustable. In the context of the tie rod  40  shown in  FIG. 3 , it will be appreciated that adjustment of the length of the tie rod  40  can be achieved by increasing or decreasing the amount of threaded engagement between the first and second connection assemblies  46 ,  48  and the rod link  58 . 
     Once the desired length is achieved, the tie rod  40  can be configured to secure the position and affix the length of the tie rod  40 . In one embodiment, the tie rod  40  can include jam nuts  78 ( a ),  78 ( b ). One of the jam nuts  78 ( a ) can engage a portion of the first connection assembly  46 , such as external threads  56 . Similarly, the other jam nut  78 ( b ) can engage a portion of the second connection assembly  48 , such as external threads  76 . When the desired length is achieved, the jam nuts  78 ( a ),  78 ( b ) can be tightened against the rod link  58  to minimize or prevent any undesired change in position of the tie rod assembly  40 . Naturally, the jam nuts  78 ( a ),  78 ( b ) can be loosened to permit allow adjustment of the length of the tie rod  40 . 
     The first and second ends  42 ,  44  of each tie rod  40  can be connected to the exhaust cylinder  20  and the exhaust diffuser  22  in various ways. The exhaust cylinder  20  and the exhaust diffuser  22  can be adapted as needed to facilitate such operative connection. For example, as shown in  FIG. 2 , a plurality of mounting posts  80  can be disposed about the periphery of the trailing edge  28  of the exhaust cylinder  20 , and a plurality of mounting posts  82  can be disposed about the periphery of the exhaust diffuser  22 . The mounting posts  80 ,  82  can be affixed to and extend outward from the exhaust cylinder  20  and exhaust diffuser  22 , respectively. In one embodiment, the mounting posts  80 ,  82  can extend substantially radially outward from the exhaust cylinder  20  and exhaust diffuser  22 , respectively. The mounting posts  80 ,  82  can be threaded or unthreaded. The mounting posts  80 ,  82  can be bolts, studs or any other structure to which the ends  42 ,  44  of the tie rods  40  can connect. 
     The first end  42  of the tie rod  40  can receive one of the mounting posts  80  on the exhaust cylinder  20 , and the second end  44  of the tie rod  40  can receive one of the diffuser mounting posts  82  on the exhaust diffuser  22 . In one embodiment, the pivot bearings  66 ( a ),  66 ( b ) housed in the respective bearing housings  52 ,  72  of the first connection assembly  46  and second radially pivotally connection assembly  48  can include channels  68 ( a ),  68 ( b ) for receiving and connecting to the mounting posts  80 ,  82 . 
     Once connected to the mounting posts  80 ,  82 , the ends  42 ,  44  of the tie rods  40  can be secured in place on the respective mounting posts  80 ,  82 . Securement can be achieved by, for example, a lug nut  84 , a friction fitting (not shown), or a weld (not shown). Alternative or additional securement devices can be used. For example, when lug nuts  84  are used, each lug nut  84  can be retained in place by a retainer  86 , such as, for example, a lock nut, a lock washer, a spring washer, a wedge-lock washer, a cotter pin, a split pin, a weld or an anti-rotation device to prevent undesired loosening of the lug nuts  84 . In one embodiment, the wedge-lock washers can be Nord-Lock washers, manufactured by Nord-Lock AB of Mattmar, Sweden. 
     Having described the individual components of the interface according to aspects of the invention, procedures for practicing aspects of the invention will now be described. It will be understood that the following explanations should not be construed as limiting and that any and all obvious variations are included. 
     During operation of a turbine engine, the exhaust gas E is axially passed through the exhaust cylinder  20  and exhaust diffuser  22 . The intense heat and pressure of the exhaust gas E causes the components to thermally expand in the radial direction. The exhaust diffuser  22 , due to its smaller size in relation to the exhaust cylinder  20 , is subjected to a faster rate of heat absorption and can expand at a rate higher than that of the exhaust cylinder  20 . 
     As the expansion occurs, the tie rods  40  disposed about the periphery of the interface  10  allow the exhaust diffuser  22  to expand radially while substantially restricting other movement of the exhaust diffuser  22 . For instance, as noted earlier, the tie rods  40  can maintain an axial connection between the exhaust cylinder  20  and the exhaust diffuser  22 . Further, relative circumferential movement between the exhaust cylinder  20  and the exhaust diffuser  22  can be minimized by positioning the tie rods  40  at angles in relation to one another. The tie rods  40  can also prevent other undesired movement of the exhaust diffuser  22 , such as vertical up and down motion and tipping. Ideally, the tie rods  40  maintain the substantially coaxial relationship of the exhaust cylinder  20  and the exhaust diffuser  22 . 
     Again, the differential rate of radial expansion of the exhaust cylinder  20  and the exhaust diffuser  22  can be accommodated by the pivotable ends  42 ,  44  of the tie rods  40 . For instance, as the exhaust diffuser  22  expands radially outward, the pivot bearing  66 ( b ) in the second connection assembly  48  can remain substantially fixed around the mounting post  82 . However, the bearing housing  72  can pivot relative to the mounting post  82 , which can extend radially from the exhaust diffuser  22 . The bearing housing  72  can also rotate relative to the mounting post  82 . Similar motions can occur at the connection between the first end  42  of the tie rod  40  and the exhaust cylinder  20 . Preferably, the pivotable ends  42 ,  44  of the tie rods  40  impart little or no bending loads on the exhaust cylinder  20  and the exhaust diffuser  22 . 
     An interface according to aspects of the invention can provide numerous advantages. For example, the interface can protect and maintain the integrity of the connection between the exhaust cylinder and exhaust diffuser. As a result, there can be a reduction in the occurrence of component failure and attendant downtime. In addition, the interface can facilitate the location of the diffuser during assembly. Further, the connecting members can be made at a relatively low cost and can be easily replaced if they require repair due to wear or abusive operation. 
     In as much as the proceeding disclosure presents the best mode devised by the inventors for practicing invention and is intended to enable one skilled and the pertinent art to carry it out, it is apparent that structures and methods incorporating modifications and variations will be obvious to those skilled in the art. For instance, it will be appreciated that the interface can be used in a gas turbine or other turbine engine, such as for example, a dual fuel turbine engine. As such, it should not be construed to be limited thereby but should included aforementioned obvious variations and be limited only by the spirit and scope of the following claims.