Patent Publication Number: US-9416670-B2

Title: Locking spacer assembly

Description:
FIELD OF THE INVENTION 
     The present invention generally involves a turbomachine. More specifically, the invention relates to locking spacer assemblies for securing rotor blades to a rotor disk of the turbomachine. 
     BACKGROUND OF THE INVENTION 
     Various turbomachines such as a gas turbine or steam turbine include a shaft, multiple rotor disks coupled to the shaft and various rotor blades mounted to the rotor disks. A conventional gas turbine includes a rotatable shaft with various rotor blades mounted to discs in the compressor and turbine sections thereof. Each rotor blade includes an airfoil over which pressurized air, combustion gases or other fluids such as steam flows, and a platform at the base of the airfoil that defines a radially inner boundary for the air or fluid flow. 
     The rotor blades are typically removable, and therefore include a suitable root portion such as a T-type root portion that is configured to engage a complementary attachment slot in the perimeter of the rotor disk. The root may either be an axial-entry root or a circumferential-entry root that engages with corresponding axial or circumferential slots formed in the disk perimeter. A typical root includes a neck of minimum cross sectional area and root protrusions that extend from the root into a pair of lateral recesses located within the attachment slot. 
     For circumferential roots, a single attachment slot is formed between forward and aft continuous circumferential posts or hoops that extend circumferentially around the entire perimeter of forward and aft faces of the rotor disk. The cross-sectional shape of the circumferential attachment slot includes lateral recesses defined by the forward and aft rotor disk posts or hoops that cooperate with the root protrusions of the rotor blades to radially retain the individual blades during turbine operation. 
     In the compressor section of a gas turbine, for example, rotor or compressor blades (specifically the root components) are inserted into and around the circumferential slot and rotated approximately ninety degrees to bring the root protrusions of the rotor blades into contact with the lateral recesses to define a complete stage of rotor blades around the circumference of the rotor disks. The rotor blades include platforms at the airfoil base that may be in abutting engagement around the slot. In other embodiments, spacers may be installed in the circumferential slot between adjacent rotor blade platforms. Once all of the blades (and spacers) have been installed, a final remaining space or spaces in the attachment slot is typically filled with a specifically designed spacer assembly, as generally known in the art. 
     A common technique used to facilitate the insertion of the final spacer assembly into the circumferential slot is to include a non-axi symmetric loading slot in the rotor disc. Various conventional spacer assemblies have been designed to eliminate the need for a loading slot in the rotor disk. However, these assemblies include complex devices. These conventional assemblies are generally difficult to assemble, costly to manufacture and may result in rotor imbalance. Accordingly, there is a need for an improved locking spacer assembly that is relatively easy to assemble within the final space between platforms of adjacent rotor blades of a turbomachine such as compressor and/or turbine rotor blades of a gas turbine. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     One embodiment of the present invention is a locking spacer assembly for insertion into a circumferential attachment slot between platforms of adjacent rotor blades. The locking spacer assembly includes a first end piece that is configured to fit into a space between platforms of the adjacent rotor blades. The first end piece comprises a platform portion and a root portion. The platform portion and the root portion define a first inner surface of the first end piece. The root portion defines a first projection and an opposing second projection of the first end piece. The first projection has an outer profile that is adapted to project into a first lateral recess of the attachment slot. The second projection has an outer profile that is adapted to project into a second lateral recess of the attachment slot. A second end piece is configured to fit between the first inner surface of the first end piece and a sidewall portion of the attachment slot. The second end piece includes a platform portion and a root portion. A borehole extends continuously through the first end piece and the second end piece and a fastener extends through the borehole. One end of the fastener is configured to engage with a sidewall portion of the attachment slot. 
     Another embodiment of the present invention is a rotor assembly. The rotor assembly comprises a rotor disk having a forward post and an aft post. The forward and the aft posts at least partially define a continuous circumferentially extending attachment slot. The rotor assembly further includes a plurality of rotor blades. Each of the plurality of rotor blades extends from one of a plurality of platforms. Each of the plurality of platforms is secured to the attachment slot by an inwardly extending root. A locking spacer assembly is disposed in a space between at least two of the plurality of platforms. The locking spacer assembly comprises a first end piece that is configured to fit into a space between platforms of the adjacent rotor blades. The first end piece includes a platform portion and a root portion. The platform portion and the root portion define a first inner surface. The root portion defines a first projection and an opposing second projection. The first projection has an outer profile that is adapted to project into a first lateral recess of the attachment slot. The second projection has an outer profile that is adapted to project into a second lateral recess of the attachment slot. A second end piece is configured to fit between the first inner surface of the first end piece and a sidewall portion of the attachment slot. The second end piece includes a platform portion and a root portion. A borehole extends continuously through the first end piece and the second end piece and a fastener extends through the borehole such that one end of the fastener engages with a sidewall portion of the attachment slot. 
     Another embodiment of the present invention is a turbomachine. The turbomachine includes a compressor, a combustor and a turbine. At least one of the compressor or the turbine comprises a rotor disk having forward and aft posts. The forward and aft posts at least partially define a continuous circumferentially extending attachment slot. The turbomachine further includes a plurality of rotor blades. Each of the rotor blades extends from a corresponding one platform of a plurality of platforms. Each of the plurality of platforms is secured to the attachment slot by an inwardly extending root. A locking spacer assembly is disposed in a space between at least two of the plurality of platforms. The locking spacer assembly comprises a first end piece that is configured to fit into a space between platforms of the adjacent rotor blades. The first end piece comprises a platform portion and a root portion. The platform portion and the root portion define a first inner surface and the root portion defines a first projection and an opposing second projection. The first projection has an outer profile that is adapted to project into a first lateral recess of the attachment slot. The second projection has an outer profile that is adapted to project into a second lateral recess of the attachment slot. A second end piece is configured to fit between the first inner surface of the first end piece and a sidewall portion of the attachment slot. The second end piece includes a platform portion and a root portion. A borehole extends continuously through the first end piece and the second end piece and a fastener extends through the borehole such that one end of the fastener engages with a sidewall portion of the attachment slot. 
     Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
         FIG. 1  is a functional diagram of an exemplary gas turbine within the scope of the present invention; 
         FIG. 2  is a partial sectional view of an embodiment of a root and attachment slot configuration for circumferential entry rotor blades; 
         FIG. 3  is a partial perspective view of an exemplary rotor disk including final or load-in spaces into which a locking spacer assembly may be inserted; 
         FIG. 4  is a top view of a portion of the rotor disk as shown in  FIG. 3 , according to one embodiment of the present invention; 
         FIG. 5  is a is an exploded view of the components of an embodiment of the locking spacer assembly in accordance with various aspects of the present invention; 
         FIG. 6  is a side view of a locking spacer assembly according to one embodiment of the present invention; 
         FIG. 7  is a top view of the locking spacer assembly as shown in  FIG. 5 , according to one embodiment of the present invention; 
         FIG. 8  is a top view of the locking spacer assembly as shown in  FIG. 5 , according to one embodiment of the present invention; 
         FIG. 9  is a top view of the locking spacer assembly as shown in  FIG. 5 , according to one embodiment of the present invention; and 
         FIG. 10 ,  FIG. 11 ,  FIG. 12 ,  FIG. 13  and  FIG. 14  are sequential assembly views of a locking spacer assembly according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. 
     As used herein, the terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. The term “radially” refers to the relative direction in a plane that is substantially perpendicular to an axial centerline of a particular component, and the term “axially” refers to the relative direction in a plane that is substantially parallel to an axial centerline of a particular component. 
     Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Although exemplary embodiments of the present invention will be described generally in the context of a gas turbine for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present invention may be applied to any turbomachine having a shaft and rotating blades coupled to the shaft such as a steam turbine or the like, and are not limited to a gas turbine unless specifically recited in the claims. 
     Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,  FIG. 1  provides a functional diagram of one embodiment of a turbomachine, in this case an exemplary gas turbine  10  which may incorporate various embodiments of the present invention. It should be understood that the present disclosure is not limited to gas turbines, and rather that steam turbines or any other suitable turbomachines are within the scope and spirit of the present disclosure. As shown, the gas turbine  10  generally includes a compressor section  12  including a compressor  14  disposed at an upstream end of the gas turbine  10 , a combustion section  16  having at least one combustor  18  downstream from the compressor  14 , and a turbine section  20  including a turbine  22  that is downstream from the combustion section  14 . A shaft  24  extends along an axial centerline  26  of the gas turbine  10  at least partially through the compressor  14  and/or the turbine  22 . In particular configurations, the shaft  24  may comprise of a plurality of individual shafts. 
     Multiple rotor wheels or disks  28  are disposed coaxially along the shaft  24  within the compressor  14  and/or the turbine  22 . Each rotor disk  28  is configured to receive a plurality of radially extending rotor blades  30  that are circumferentially spaced around and removably fixed to the rotor disk  28 . The rotor blades  30  may be configured for use within the compressor  14  such as a compressor rotor blade  32  or for use within the turbine  22  such as a turbine bucket or turbine rotor blade  34 . Each blade  30  has a longitudinal centerline axis  36  and includes an airfoil portion  38  having a leading edge  40  and a trailing edge  42 . 
     In operation, a working fluid  44  such as air is routed into the compressor  14  where it is progressively compressed in part by the compressor rotor blades  32  as it is routed towards the combustion section  16 . A compressed working fluid  46  flows from the compressor  14  and is supplied to the combustion section  16 . The compressed working fluid  46  is distributed to each of the combustors  18  where it is mixed with a fuel to provide a combustible mixture. The combustible mixture is burned to produce combustion gases  48  at a relatively high temperature and high velocity. The combustion gases  48  are routed through the turbine  22  where thermal and kinetic energy is transferred to the turbine rotor blades  34 , thereby causing the shaft  24  to rotate. In particular applications, the shaft  24  is coupled to a generator (not shown) to produce electricity. 
       FIG. 2  is an enlarged cross section view of a portion of an exemplary rotor disk  28  including an exemplary rotor blade  30  having a T-type root and attachment slot configuration. As shown in  FIG. 2 , each rotor blade  30  also may include a platform  50  that provides a portion of a radially inner boundary for airflow, combustion gas flow or other fluid flow such as steam over the airfoils  38  during operation of the gas turbine  10 . In addition, each rotor blade  30  includes an integral root portion  52  that extends radially inward from the platform  50 . The root portion  52  slides into and along a circumferentially extending attachment slot  54  at least partially defined by forward and aft hoop or post components  56  of the rotor disk  28 , as is generally known in the art. In the alternative, the circumferentially extending attachment slot  54  may be machined, cast or otherwise defined by the rotor disk  28 . 
     The root portion  52  may include protrusions  58  that are received into lateral recesses  60  defined within the attachment slot  54  and at least partially defined by recessed wall portions  62  of the post components  56 . The post components  56  and/or the rotor disk  28  may further define sidewall portions  64  of the attachment slot  54 . It should be readily appreciated that the configuration of the root portion  52  and attachment slot  54  provided in  FIG. 2  is for illustrative purposes only, and that the root and slot configuration may vary widely within the scope and spirit of the present subject matter. 
       FIG. 3  is a partial perspective view of a portion of an exemplary rotor disk  28 , and particularly illustrates a plurality of the rotor blades  30  configured in an attachment slot  54  ( FIG. 2 ) between the forward and aft post components  56  of the rotor disk  28 . As shown in  FIG. 3 , each of the rotor blades  30  includes a platform  50 . Conventional spacers  66  are disposed between the platforms  50  of adjacent rotor blades  30 , as is generally known in the art. 
       FIG. 4  is a top view of a portion of the rotor disk  28  as shown in  FIG. 3 , according to one embodiment of the present invention. As shown in  FIG. 3 , one or more final or load-in spaces  68 , having a circumferential width  70 , are defined between adjacent rotor blade  30  platforms  50 . The final or load-in spaces  68  are generally used to insert the rotor blades  30  into the attachment slot  54  during assembly and/or disassembly of the rotor blades  30  to the rotor disk  28 . In particular embodiments, as shown in  FIG. 4 , the final or load-in spaces  68  can be filled by various embodiments of a locking spacer assembly  100  which is described in greater detail below. 
     It should be appreciated that in particular embodiments, the locking spacer assembly  100  can be used to fill the final spaces  68  between platforms  50  of adjacent rotor blades  30  including the compressor rotor blades  32  located within the compressor  14  and/or the turbine rotor blades  34  located within the turbine  22 . As such, the locking spacer assembly  100  will be generally described below as being installed between platforms  50  of adjacent rotor blades  30 , wherein the platforms  50  may be part of a compressor rotor blade  32  or a turbine rotor blade  34  so as to fully encompass both applications. 
       FIG. 5  is an exploded view of the components of a locking spacer assembly  100  herein referred to as “assembly  100 ” according to one embodiment of the present invention. As shown, the assembly  100  includes a first end piece  102 , a second end piece  104  and a fastener  106 . The first end piece  102  and the second end piece  104  are configured to fit into the final or load-in spaces  68  between the platforms  50  of adjacent rotor blades  30  ( FIG. 4 ). The end pieces  102 ,  104 , thus, have any dimensional configuration such that the width, length, thickness, or any other characteristics enables the end pieces  102 ,  104  to be inserted between the platforms  50 . For example, the end pieces  102 ,  104  may generally have a circumferential width  108  ( FIG. 4 ) in order to fit snugly between the platforms  50  of adjacent airfoils. 
     As shown in  FIG. 5 , the first end piece  102  comprises a platform portion  110  and a root portion  112 . The platform portion  110  generally has a radial height  114 , an axial length  116  and a circumferential width  118 . The root portion  112  extends radially inwardly from the platform portion  110 . The platform portion  110  and the root portion  112  define a first inner surface  120 . In one embodiment, the first inner surface  120  extends generally perpendicular to an axial plane that extends through the locker spacer assembly  100  and/or the first end piece  102 . 
     The root portion  112  defines a first projection  122  and an opposing second projection  124 . The first projection  122  has an outer profile that is adapted to project into a first lateral recess  126  of the attachment slot  54 . The second projection  124  has an outer profile that is adapted to project into a second lateral recess  128  of the attachment slot  54 . For example, the profile of the first and second projections  122 ,  124  may have a top portion that is substantially curved to mirror the curve of the forward and aft post  56 . Moreover, the profiles may include a bottom portion that extends outwardly at the corner formed between the post components  56  and the first and second lateral recesses  126 ,  128  to project into the illustrated t-type attachment slot  54 . 
     It should be readily appreciated that the first and second projections  122 ,  124  can have any desired profile and need not have the particular profile illustrated in  FIG. 5 . The profile of the first and second projections  122 ,  124  will depend in large part on the particular shape and configuration of the attachment slot  54 . 
     In particular embodiments, an arcuate groove  130  or other stress relief feature such as a blend or fillet is defined by the first end piece  102  proximate to a location where the first and/or second projections  122 ,  124  are defined or extend axially outward from the root portion  112  of the first end piece  102 . The arcuate groove  130  may be included to provide a point of low stress or a location for stress relief on the first end piece  102 . As illustrated, the arcuate groove  130  may be located on the root portion  112  at corners formed between the forward and aft post components  56  and the first and second lateral recesses  126 ,  128  respectfully. 
     The second end piece  104  is configured to fit between the first inner surface  120  of the first end piece  102  and one of the sidewall portions  64  of the attachment slot  54 . For example, the second end piece  102  may have an outer profile that is substantially curved to mirror the curve of the forward or aft post  56 . 
     The second end piece  104  comprises a platform portion  132  and a root portion  134 . The platform portion  132  generally has a radial height  136 , an axial length  138  and a circumferential width  140 . The circumferential widths  118 ,  140  of the platforms  110 ,  132  respectfully, generally define the circumferential width  108  ( FIG. 4 ) of the locker spacer assembly  100 . 
     As shown in  FIG. 5 , the root portion  134  extends radially inwardly from the platform portion  132 . The platform portion  132  and the root portion  134  define a second inner surface  142 . The second inner surface  142  is configured to mate with the first inner surface  120 . For example, the first and second inner surfaces  120 ,  142  may be flat or congruently curved or slotted. In one embodiment, the second inner surface  142  extends generally perpendicular to an axial plane that extends through the locker spacer assembly  100  and/or the second end piece  104 . In one embodiment, the first inner surface  130  and the second inner surface  142  generally face towards each other and are engaged when the first and second end pieces  102 ,  104  are inserted into the attachment slot  54 , as is generally illustrated in  FIG. 13 . 
     As shown in  FIG. 5 , the first end piece  102  and the second end piece  104  at least partially define a borehole  144 . When assembled, the borehole  144  extends continuously through the first end piece  102  and the second end piece  104 . In one embodiment, the borehole  144  extends through the platform portion  110  of the first end piece  102  and the root portion  134  of the second end piece  104  at an angle determined with respect to a radial plane that extends through the spacer locker assembly  100  and that is generally perpendicular to an axial plane that extends through the locking spacer assembly  100 . 
     As shown in  FIG. 5 , the borehole  144  may extend through a side wall  146  of the root portion  134  of the second end piece  104 . In particular embodiments, the borehole  144  may be threaded in at least one of the first end piece  102  or the second end piece  104 . In one embodiment, the borehole  144  may include a counter bore  148  or step feature defined within the platform portion  110  of the first end piece  102 . 
     The fastener  106  may include any fastener such as a screw, bolt, pin or the like that extends through the borehole  144 . As shown in  FIG. 5 , an end  150  of the fastener  106  is configured to engage with one of the sidewall portions  64  of the attachment slot  54 . For example, as shown, the end  150  may be chamfered or otherwise shaped to engage the sidewall portion  64  of the attachment slot  54 . The fastener  106  may include threads  152  disposed along the shank of the fastener  106 . The threads  152  may be complementary to the threads defined within the first and/or second end pieces  102 ,  104 . 
       FIG. 6  provides a side view of the locking spacer assembly  100  according to one embodiment of the present invention. As shown, the first and second inner surfaces  120 ,  142  may be angled with respect to an axial plane that extends parallel to or along an axial centerline of the locking spacer assembly  100 . 
       FIG. 7 ,  FIG. 8  and  FIG. 9  provide top views of the locker spacer assembly  100  as shown in  FIG. 5 , according to various embodiments of the present invention. As shown in  FIGS. 7 and 9 , a recess  154  may be formed on the platform portion  132  of the second end piece  104 . In the alternative, as shown in  FIG. 8 , the recess  154  may be formed on the platform portion  110  of the first end piece  102 . The recess  154  may be configured to receive a complimentary collar  156  formed on the platform portion  110  of the first end piece  102  ( FIGS. 7 and 9 ) or on the platform portion  132  of the second end piece  104  ( FIG. 8 ) when the first end piece  102  and the second end piece  104  are installed into the attachment slot  54 . For example, the recess  154  and the collar  156  may be rectangular, trapezoidal, arcuate or any shape so as to create an interlocking action between the first and second end pieces  102 ,  104 . 
       FIG. 10 ,  FIG. 11 ,  FIG. 12 ,  FIG. 13  and  FIG. 14  are sequential assembly views of a locking spacer assembly  100  according to one embodiment of the present invention. As shown in  FIG. 10 , the first end piece  102  is rotated such that the second projection  124  extends within the second lateral recess  128  of the attachment slot  54 . As shown in  FIG. 11 , the first end piece  102  is then rotated such that platform portion  110  rests on the post component  56 . As shown in  FIG. 12 , the first end piece  102  is then positioned such that the first projection  122  extends within the first lateral recess  126  and the second projection  124  simultaneously extends within the second lateral recess  128  of the attachment slot  54 . 
     As further illustrated in  FIGS. 12 and 13 , the second end piece  104  is then inserted between the first inner surface  120  of the first end piece  102  and the sidewall portion  64  of the attachment slot  54  such that the first inner surface  120  and the second inner surface  142  are adjacent or facing each other. As shown in  FIG. 14 , the fastener  106  is inserted into the borehole  144  and turned, threaded, hammered or otherwise translated through the borehole  144  until the end  150  engages with a sidewall portion  64  of the attachment slot  54 . The fastener  106  causes a generally radial force  156  between the first and second projections  122 ,  124  and the corresponding recessed wall portion  62  of the attachment slot  54 , thereby locking the locking spacer assembly  100  into position and securing the plurality of rotor blades  30  to the rotor disk  28 . A second end of the fastener  106  may extend beyond the platform  110  after the fastener has engaged with the side wall portion  64 . However, the second end may be cut away to maintain a smooth surface along the platform  110 . In the alternative, the second end may be recessed within the counter bore  148 . It should be obvious to one of ordinary skill that disassembly of the locker spacer assembly  100  may be achieved by simply reversing the assembly steps described herein. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.