Abstract:
A method for plugging a turbine wheel hole in a turbine wheel. The method may include the steps of: 1) obtaining a turbine wheel hole plug that includes an approximate cylindrical body, a first flange at a first end of the body, and a hollow cylinder at the second end of the body, wherein the body, the first flange and the hollow cylinder are sized such that: a) the cylindrical body fits snuggly into the turbine wheel hole; b) the first flange comprises a diameter that is greater than the diameter of the turbine wheel hole; and c) the hollow cylinder protrudes from one end of the turbine wheel hole when the turbine wheel hole plug is inserted into the other end of the turbine wheel hole until the first flange abuts the turbine wheel; 2) positioning the turbine wheel hole plug into the turbine wheel hole; and 3) deforming the hollow cylinder so that the hollow cylinder flares outward.

Description:
BACKGROUND OF THE INVENTION 
     This present application relates generally to systems and apparatus for modifying turbine wheel holes. More specifically, but not by way of limitation, the present application relates to systems and apparatus for enhancing turbine performance by reducing or plugging turbine wheel holes. 
     Turbine wheel holes are common in the turbine industry. Generally, these holes are defined through turbine wheels, which connect the turbine buckets or blades to the rotor. Turbine wheel holes allow the passage of a secondary flow of working fluid through the turbine wheels. This flow path may be provided for several reasons. First, for example, turbine wheel holes allow the leakage of secondary flow through the turbine wheel so to prevent reentry of the working fluid back into the primary flow path, which may cause inefficient flow patterns. In addition, wheel holes may be used to reduce the pressure drop across a turbine stage or to reduce axial pressure on the turbine wheel, which under certain operating conditions may be preferred or necessary. Generally, turbine wheel holes may measure approximately 0.5 to 3.0 inches in diameter and, when present, a turbine wheel may have approximately 3 to 15 wheel holes defined through its axial thickness. 
     Often, it becomes desirable to cover, plug, block or partially block turbine wheel holes. Depending on certain operating conditions, it may be preferable to completely block turbine wheel holes so that no flow is allowed to pass therethrough, or it may be preferable to partially block turbine wheel holes, i.e., reducing the diameter of the wheel hole, so that a decreased amount of flow is allowed to pass therethrough. The reasons for blocking or reducing turbine wheel holes may be several. Many times, plugging the turbine wheel holes is done during the process of refurbishing older turbine engines. The plugging is done to improve the efficiency of the engine. However, processes, systems and/or apparatus currently used for plugging turbine wheel holes are overly complex, time consuming and expensive. Thus, there is a need for improved methods, systems and/or apparatus for plugging turbine wheel holes in an efficient and cost effective manner. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present application thus describes a method for plugging a turbine wheel hole in a turbine wheel. The method may include the steps of: 1) obtaining a turbine wheel hole plug that includes an approximate cylindrical body, a first flange at a first end of the body, and a hollow cylinder at the second end of the body, wherein the body, the first flange and the hollow cylinder are sized such that: a) the cylindrical body fits snuggly into the turbine wheel hole; b) the first flange comprises a diameter that is greater than the diameter of the turbine wheel hole; and c) the hollow cylinder protrudes from one end of the turbine wheel hole when the turbine wheel hole plug is inserted into the other end of the turbine wheel hole until the first flange abuts the turbine wheel; 2) positioning the turbine wheel hole plug into the turbine wheel hole; and 3) deforming the hollow cylinder so that the hollow cylinder flares outward. 
     The present application further describes another method for plugging a turbine wheel hole in a turbine wheel. This method may include the steps of: 1) obtaining a turbine wheel hole plug that includes an approximate cylindrical body, a first flange at a first end of the body, and a hollow cylinder at the second end of the body, wherein the body, the first flange and the hollow cylinder are sized such that: a) the cylindrical body fits snuggly into the turbine wheel hole; b) the first flange comprises a diameter that is greater than the diameter of the turbine wheel hole; and c) the hollow cylinder protrudes from one end of the turbine wheel hole when the turbine wheel hole plug is inserted into the other end of the turbine wheel hole until the first flange abuts the turbine wheel; 2) positioning the turbine wheel hole plug into the turbine wheel hole such that the first flange abuts the turbine wheel; 3) using means for securing the axial position of the first flange so that the first flange is secured against the turbine wheel hole; and 4) pushing a cone into the hollow cylinder so that the hollow cylinder spreads outward. 
     These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a schematic line drawing illustrating a cross-sectional view of several stages in an exemplary turbine in which an embodiment of the present invention may be used. 
         FIG. 2  is a cross-sectional view of a turbine wheel hole plug according to an exemplary embodiment of the present invention. 
         FIG. 3  is a cross-sectional view of a turbine wheel hole plug according to an alternative exemplary embodiment of the present invention. 
         FIG. 4  is a cross-sectional view demonstrating an exemplary installment method of a turbine wheel hole plug according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     Referring now to the figures, where the various numbers represent like parts throughout the several views,  FIG. 1  illustrates a cross-sectional view of several stages in an exemplary turbine  100  in which an embodiment of the present invention may be used. The turbine  100  may be a steam turbine, though the invention disclosed herein is not limited to steam turbine applications and may be used on other turbines, such as gas turbines. As shown, the several stages of the turbine  100  may include alternating stationary and rotating components. The stationary components generally are known as diaphragms  104 . The rotating components are known as buckets or blades  108 . A flow of working fluid is directed by the diaphragms  104  onto the blades  108 , causing the blades  108  to rotate. The blades  108  maybe connected by turbine wheels  112  to a rotor  116 . The rotating blades  108  thusly convert the energy of the expanding working fluid into the mechanical energy of the rotating rotor  116 , which may then be coupled to an external load, such as a generator to generate power. Turbine wheel holes  120  may be defined through the turbine wheels  112 . Generally, turbine wheel holes may measure approximately 0.5 to 3.0 inches in diameter and, when present, a turbine wheel may have approximately 3 to 15 wheel holes defined through its axial thickness. 
     A main or primary flow path, which is indicated by arrows  124 , is the flow path of the working fluid that is directed through the stationary diaphragms  104  and through the rotating blades  108 . A secondary flow path, which is indicated by arrows  128 , also may be defined. The secondary flow path  128  generally is much smaller in volume than the main flow path  124 . The secondary flow path  128  is directed in an inward radial direction to a shaft seal  132 . The shaft seal  132  creates a seal that limits the amount of working fluid that travels along the route of the secondary flow path  128 . As one of ordinary skill in the art will appreciate, working fluid that bypasses the main flow path  124  (and thus bypasses the blades  108 ) decreases the efficiency of the turbine  100  because no work is extracted from it. The working fluid that does travel through the shaft seal  132  then generally travels in an outward radial direction until reaching one of the turbine wheel holes  120 . The secondary flow then passes through the turbine wheel  112  via the turbine wheel holes  120  and continues toward the next shaft seal  132 . The secondary flow path  128  then similarly traverses the next stage of the turbine  100 , as illustrated. 
     As described above, leakage through the turbine wheel holes  120  may be advantageous under certain operating conditions. For example, the turbine wheel holes  120   3 may allow leakage of the secondary flow through the turbine wheel so to prevent reentry of the secondary flow back into the primary flow path, which may cause inefficient flow patterns in the primary flow. In addition, turbine wheel holes  120  may be provided to reduce the pressure drop across the turbine wheel  112 , which under certain conditions, may be necessary. However, blocking, plugging or reducing turbine wheel holes  120  may become desirable, such as, for example, when an older turbine is being updated or refurbished and an increase in operating efficiency is desired. 
       FIG. 2  is a cross-sectional view of a turbine wheel hole plug  140  according to an exemplary embodiment of the present invention. The turbine wheel hole plug  140  may be shaped and sized such that it corresponds to the size and shape of the turbine wheel hole  120  it is meant to plug. As used herein, “to plug” a hole shall be interpreted to mean either blocking the entirety or a portion of the hole. The turbine wheel hole plug  140  may have a body  142 . In most cases, because turbine wheel holes  120  generally have a circular cross-section, the turbine wheel hole plug  140  will have a cylindrical body  142 , as illustrated. Of course, if the turbine wheel hole  120  is a different shape, other shapes and configurations for the turbine wheel hole plug  140  are possible. The cylindrical body  142  of the turbine wheel hole plug  140  may be sized such that it fits relatively snuggly into the turbine wheel hole  120 , i.e., the diameter of the cylindrical body  142  is only slight smaller than the diameter of the turbine wheel hole  120 . 
     At one end of the cylindrical body  142  of the turbine wheel hole plug  140 , a first flange or upstream flange  144  may be formed, as illustrated in  FIG. 2 . The upstream flange  144  may take many forms, but in the case of a cylindrical body  142 , it may take a cylindrical shape also, as illustrated. The upstream flange  144  may have a diameter greater than the cylindrical body  142  and greater than the diameter of the turbine wheel hole  120  such that the upstream flange  144  provides a “stop” when the body  142  is fully inserted in the hole  120 . 
     The other end of the cylindrical body  142  may be a threaded extension  152 , as illustrated in  FIG. 2 . The length of the turbine wheel hole plug  140  may be such so that when inserted into the turbine wheel hole  120  the threaded extension  152  protrudes out of the other end of the turbine wheel hole  120 , as illustrated. The turbine wheel hole plug  140  also may include a second or downstream flange  148 . In some embodiments, the downstream flange  148  may be detachably fixed to the cylindrical body  142 . As the embodiment of  FIG. 2  illustrates, the downstream flange  148  may screw onto the threaded extension  152 . That is, the downstream flange  148  may be a cylindrical ring that is threaded along an inner surface such that it may be screwed onto the threaded extension  152  of the cylindrical body  142 . Of course, other attachment methods may be used. 
     As already described, depending on the certain conditions, it may be preferable to completely block the turbine wheel hole  120  so that substantially no flow is allowed to pass through it, or it may be preferable to partially block the turbine wheel hole  120 , reducing its diameter so that a decreased amount of flow is allowed to pass through it. If it is desired that the turbine wheel hole  120  may be completely blocked, the cylindrical body  142  may be formed so that it is solid or forms a solid surface in the turbine wheel hole  120  that blocks substantially all of the secondary flow from traveling though the turbine wheel hole  120 . (Note that insubstantial amounts of the secondary flow may still pass through the wheel hole  120  even when “completely blocked” via the small areas that may remain between the turbine wheel hole plug  140  and the turbine wheel hole  120 .) 
     If, on the other hand, it is desired to reduce the amount of secondary flow moving through the turbine wheel hole  120  and not completely block it, the cylindrical body  142  may have a bore hole  156  (the diameter of which is indicated in  FIG. 2  by the dashed lines). The bore hole  156  may be of any configuration that allows the desired amount of secondary flow through the turbine wheel hole  120 . As shown in  FIG. 2  and as used in many preferred embodiments, the bore hole  156  may be cylindrical in shape. The diameter of the bore hole  156  may be made smaller or larger depending on the amount of secondary flow that is desired to pass therethrough. Note that the first flange  144  is described as being fixed and upstream (in relation to the direction of the steam flow) of the second flange  148 . This is exemplary of a preferred embodiment only. The first flange  144  and the second flange  148  may be reversed in relation to which is upstream and which is downstream, and still function effectively. Further, in some embodiments, both of the first flange  144  and the second flange  148  may be detachably fixed to the body  142 . The components of the turbine wheel hole plug  140  may be made out of any suitable material that is able to withstand the environment of the turbine, such as stainless steel. 
     In use, the turbine wheel hole plug  140  may be installed in a turbine wheel hole  120  so that a preferred amount of working fluid is allowed through the turbine wheel hole  120 . The turbine wheel hole plug  140  may be conveniently installed by inserting the body  142  through the turbine wheel hole  120  until the first flange  144  abuts the turbine wheel  112 . As already described, the turbine wheel hole plug  140  preferably may be oriented such that the first flange  144  is upstream of the second flange  148 . As described, this orientation may be reversed if desired. Once the body  142  is installed in the turbine wheel hole  120 , the turbine wheel hole plug  140  may be fixed in place by securing the second flange  148 , which, as described, may be done by screwing the second flange  148  on the treaded extension  152 . The bore hole  156 , if present, may be sized to a predetermined diameter such that in use a desired amount of working fluid is allowed to pass through the turbine wheel hole  120 . 
       FIG. 3  is a cross-sectional view of a turbine wheel hole plug  160  according to an alternative embodiment of the present invention. Similar to the above described turbine wheel hole plug  140 , the turbine wheel hole plug  160  may be shaped and sized such that it corresponds to the size and shape of the turbine wheel hole  120  that it is meant to plug. The turbine wheel hole plug  160  may have a body  162 . In most cases, because turbine wheel holes  120  generally have a circular cross-section, the turbine wheel hole plug  160  will have a cylindrical body  162 , as illustrated. Of course, if the turbine wheel hole  120  is a different shape, other shapes and configurations of the turbine wheel hole plug  160  are possible. The cylindrical body  162  of the turbine wheel hole plug  160  may be sized such that it fits relatively snuggly into the turbine wheel hole  120 . 
     In some embodiments and as shown in  FIG. 3 , the cylindrical body  162  of the turbine wheel hole plug  160  may have: 1) a flow determining portion  163 , which will determine the amount of flow allowed through the turbine wheel hole  120  once the turbine wheel hole plug  160  is installed; and 2) a hollow portion  164 , as illustrated in  FIG. 3 . The ratio of the flow determining portion  163  to hollow portion  164  may be approximately equal, as shown. Note that other configurations may be possible, such as a body  162  composed completely of the flow determining portion  163  or bodies  162  with differing ratios of flow determining portions  163  to hollow portions  164 . As one of ordinary skill in the art will appreciate, having some portion of the body  162  be hollow may reduce material costs. Note that the option of having a portion of the body be hollow also may be used with the first embodiment described above. 
     Like the first embodiment described above, the first flange or upstream flange  144  may be defined at one end of the cylindrical body  162 , as illustrated in  FIG. 3 . The upstream flange  144  may also have a cylindrical shape, though other configurations are possible. The upstream flange  144  may have a diameter greater than the cylindrical body  162  and greater than the diameter of the turbine wheel hole  120  such that the upstream flange  144  provides a “stop” when the body  142  is fully inserted in the hole  120 . 
     At the other end of the cylindrical body  162  a flared flange  166  may be formed. As illustrated in  FIG. 3 , the flared flange  166  may flare in an outward direction from the turbine wheel hole  120  such that it may be conical shaped. More specifically, the flared flange  166  may be shaped like the section of a cone or bell. The diameter of the flared flange  166  at its termination point may be greater than the diameter of the turbine wheel hole  120 . Thusly, the outward flare of the flared flange  166  may secure the turbine wheel hole plug  160  in place, i.e., so that the body  162  is restrained from moving axially. 
     As already described, depending on the certain operating conditions, it may be preferable to completely block the turbine wheel hole  120  so that no flow is allowed to pass therethrough, or it may be preferable to partially block the turbine wheel hole  120  so that the diameter of the wheel hole  120  is reduced so that a decreased amount of flow is allowed to pass therethrough. If it is desired that the turbine wheel hole  120  be completely blocked, the flow determining portion  163  of the cylindrical body  162  may be solid (i.e., have a solid face) so that it blocks substantially all of the secondary flow from traveling though the turbine wheel hole  120 . (Note that insubstantial amounts of the secondary flow may still pass through the wheel hole  120  even when “completely blocked” via the small areas that may remain between the turbine wheel hole plug  140  and the turbine wheel hole  120 .) 
     If, on the other hand, it is desired to reduce the amount of secondary flow moving through the turbine wheel hole  120  and not completely block it, the flow determining portion  163  of the body  162  may have a bore hole  156  (the diameter of which is indicated in  FIG. 3  by the dashed lines). The bore hole  156  may be of any configuration that allows the desired amount of secondary flow through the turbine wheel hole  120 . As shown in  FIG. 3  and as used in many preferred embodiments, the bore hole  156  may be cylindrical in shape. The diameter of the bore hole  156  may be made smaller or larger depending on the amount of secondary flow that is desired to pass therethrough. Note that the first flange  144  is described as being upstream (in relation to the direction of the steam flow) of the flared flange  166 . This is exemplary of a preferred embodiment only. The first flange  144  and the flared flange  148  may be reversed in relation to which is in the upstream and which is downstream and still function effectively. The components of the turbine wheel hole plug  160  may be made out of any suitable material that is able to withstand the environment of the turbine, such as stainless steel. 
     In use, the turbine wheel hole plug  160  may be conveniently installed in a turbine wheel hole  120  so that a preferred amount of working fluid is allowed through the turbine wheel  120 .  FIG. 4  illustrates an efficient method of installing the turbine wheel hole plug  160  pursuant to an exemplary embodiment of the present invention. As illustrated, the turbine wheel hole plug  160  may be inserted into the turbine wheel hole  120 . The turbine wheel hole plug  160  may be oriented such that its first flange or upstream flange  144  is in the upstream position, though, as stated, turbine wheel hole plug  160  also may function in the reverse orientation. Before installation, the flared flange  166  may be in a pre-installation unflared form  172 , as illustrated in  FIG. 4 . In the unflared form  172 , the flared flange  166  may not be flared outward, i.e., in the unflared form  172 , the flared flange  166  forms a cylinder that is in line with the cylinder defined by the body  162 . In the unflared form, the turbine wheel hole plug  162  may be inserted through the turbine wheel hole  120  so that the turbine wheel hole plug  160  may be positioned properly. In the proper position, the turbine wheel hole plug  160  is pushed into the turbine wheel hole  120  until the first or upstream flange  144  abuts the turbine wheel  112 . 
     Once this is complete, a wedge block  176  may be placed into the position shown in  FIG. 4 . That is, the wedge block  176  is positioned so that it holds the turbine wheel hole plug  160  in a fixed installed position i.e., so that the first or upstream flange  144  remains abutted against the turbine wheel  112 . The wedge block  176  may do this by being wedged between the first or upstream flange  144  and the turbine wheel  112  of a neighboring turbine stage. The wedge block  176  may be a block or other object (such as an adjustable threaded spacer) that is able to rigidly hold the turbine wheel hole plug  160  in place. 
     Once the turbine wheel hole plug  160  is secured in place by the wedge block  176 , the flared flange  166  may be created by deforming the unflared form  172 . This may be accomplished by forcing a cone  178  into the unflared form  172 . As the cone  178  is pushed against the unflared form  172  it forces the unflared form  172  to flare outward. Thusly, the flared flange  166  is created. The turbine wheel hole plug  160  becomes axially locked into position by the upstream flange  144  and the flared flange  166 . As shown, the cone  178  may be pushed into the unflared form  172  using a hydraulic jack  180 . Other methods also may be used. While the hydraulic jack  180  is used to push the cone  178  into the unflared form  172 , the hydraulic jack  180  may be secured into position by placing it against a neighboring turbine wheel  112 , as illustrated in  FIG. 4 . 
     Depending on whether it is desired that all of the flow be blocked or just a partial amount of the flow, the bore hole  156  may or may not be present in the turbine wheel hole plug  160 . If it is present, the bore hole  156  may be sized to a predetermined diameter such that, in use, a desired amount of working fluid is allowed to pass through the turbine wheel hole  120 . 
     From the above description of preferred embodiments of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.