Patent Publication Number: US-8529194-B2

Title: Shank cavity and cooling hole

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to a turbine bucket with a shank cavity and a cooling hole. 
     In turbine engines, such as gas or steam turbine engines, a mixture of fuel and air are combusted within a combustor and the by products of that combustion are delivered to a turbine section downstream as high temperature fluids. These high temperature fluids aerodynamically interact with annular arrays of turbine blades at various stages and thereby produce power and/or electricity. 
     In some cases, the high temperature fluids may cause damage to the turbine blades by, for example, thermal degradation. As a result, it may be necessary to cool the turbine blades as a countermeasure. Unfortunately, providing coolant to the turbine blades can be operationally costly and may often require relatively complex fluid circuitry that is difficult to install and maintain. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a turbine bucket is provided and includes a shank defining a cavity therein, which is connectable with a rotor such that wheelspace air having an initial pressure is permitted to flow into the cavity and a platform coupled to the shank and defining a cooling hole therein, the shank and the platform each further defining the cavity and the cooling hole, respectively, such that the cavity and the cooling hole are fluidly communicative and such that the wheelspace air, which is permitted to flow into the cavity, is deliverable from the cavity to the cooling hole, and through the cooling hole at a second pressure, which is greater than the initial pressure. 
     According to another aspect of the invention, a turbine bucket is provided and includes a shank including a shank body defining a cavity therein, the shank body being connectable with a rotor such that wheelspace air having an initial pressure is permitted to flow into the cavity, a platform including a platform body coupled to the shank and defining a cooling hole therein, which is fluidly communicative with the cavity such that the wheelspace air, which is permitted to flow into the cavity, is deliverable from the cavity to the cooling hole and through the cooling hole at a second pressure greater than the initial pressure and an aft platform extending from the platform at which the cooling hole terminates such that the wheelspace air is exhaustible into at least one of a turbine flow path, which is defined substantially radially outwardly from the aft platform, and a trench cavity, which is defined substantially radially inwardly from the aft platform. 
     According to yet another aspect of the invention, a turbine bucket is provided and includes a shank defining a cavity therein, which is connectable with a rotor such that wheelspace air having an initial pressure is permitted to flow into the cavity, a platform coupled to the shank and defining a main cooling hole therein, which is fluidly communicative with the cavity, and tributary cooling holes therein, which are fluidly communicative with the main cooling hole, such that the wheelspace air, which is permitted to flow into the cavity, is deliverable from the cavity to the main cooling hole, through the main cooling hole and subsequently through the tributary cooling holes at a second pressure greater than the initial pressure and an aft platform extending from the platform at which the tributary cooling holes terminate such that the wheelspace air is exhaustible into at least one of a turbine flow path, which is defined substantially radially outwardly from the aft platform, and a trench cavity, which is defined substantially radially inwardly from the aft platform. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is an enlarged side sectional view of a portion of a turbine bucket; and 
         FIG. 2  is a side view of the turbine bucket of  FIG. 1 . 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 and 2 , a turbine bucket  10  is provided and includes a shank  20 , including a shank body  21 , a platform  30 , including a platform body  31 , and an aft platform  70 . The shank body  21  is formed to define a shank cavity  22  therein and has, in some embodiments, a radially inward section that is connectable with a dovetail assembly of a rotor. This connection permits wheelspace air  40  having an initial pressure to flow or leak into the shank cavity  22 . 
     The platform body  31  supports an airfoil  32  over which hot fluids and gases  33  flow and is integrally coupled to a radially outward portion of the shank body  21  and is formed to define a cooling hole with an inlet and a mid-section therein. The inlet is a main cooling hole  50  and the mid-section may include one or more tributary cooling holes  60 . Both the main cooling hole  50  and the tributary cooling holes  60  may be oriented at an oblique angel relative to a centerline  90  of the rotor. The main cooling hole  50  is fluidly communicative with the shank cavity  22  and the tributary cooling holes  60  are fluidly communicative with the main cooling hole  50 . As such, the wheelspace air  40  that is permitted to flow into the shank cavity  22  is deliverable from the shank cavity  22 , through the main cooling hole  50  and through the tributary cooling holes  60  at a second pressure that may be at least similar to or, in some cases, greater than the initial pressure. 
     The aft platform  70  extends axially from the main platform body  31  and includes a flow path facing surface  71  and a trench cavity facing surface  72 . The tributary cooling holes  60  may each terminate at the aft platform  70 . More particularly, a first group of the tributary cooling holes  60  may terminate at the flow path facing surface  71  and a second group of the tributary cooling holes  60  may terminate at the trench cavity facing surface  72 . In some embodiments, the first group of tributary cooling holes  60  may be circumferentially aligned with one another. Similarly, the second group of tributary cooling holes  60  may be circumferentially aligned with one another. 
     Where the tributary cooling holes  60  terminate at the flow path facing surface  71 , the wheelspace air  40  may flow over a portion of the flow path facing surface  71  and be exhaustible as first exhaust  401  into the turbine flow path  80 , which is defined substantially radially outwardly of the aft platform  70 . Conversely, where the tributary cooling holes  60  terminate at the trench cavity facing surface  72 , the wheelspace air  40  may impinge upon the trench cavity facing surface  72  and be exhaustible as second exhaust  402  into the trench cavity  81 , which is defined substantially radially inwardly of the aft platform  70 . 
     The wheelspace air  40  removes heat from the turbine bucket  10  at a variety of locations and in a variety of ways. For example, the wheelspace air  40  in the shank cavity  22 , the main cooling hole  50  and the tributary cooling holes  60  provide convective cooling while those portions of the shank body  21  and the platform body  31  proximate to the shank cavity  22 , the main cooling hole  50  and the tributary cooling holes  60  thereby experience conductive cooling. Similarly, the wheelspace air  40  that is output from the tributary cooling holes  60  into the turbine flow path  80  may flow over the flow path facing surface  71  to thereby provide film cooling to the flow path facing surface  71 . The wheelspace air  40  that is output from the tributary cooling holes  60  into the trench cavity  81  may impinge upon the trench cavity facing surface  72  to thereby provide impingement cooling to the trench cavity facing surface  72 . 
     The main cooling hole  50  has a width, W 1 , which is wider that the width, W 2 , of the tributary cooling holes  60 . As such, a pressure of the wheelspace air  40  flowing into the tributary cooling holes  60  may be maintained or increased from the initial pressure. In some embodiments, the pressure of the wheelspace air  40  may be further increased by an inflow of additional wheelspace air  41  and centrifugal force applied thereto during rotation of the turbine bucket  10  about the rotor. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.