Abstract:
Systems and devices configured to cool turbine components in a turbine by passing a cooling flow through the turbine component via a cooling passage with a variable diameter are disclosed. In one embodiment, a turbine component includes: at least one elongated cooling passage extending from a root of the bucket to a tip of the bucket, wherein the elongated cooling passage has a variable diameter along a length of the bucket.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to cooling passages in turbine components, more specifically, to turbine nozzles, shrouds, and/or buckets having shaped tube electrochemical machined (STEM) cooling holes with a varying diameter (e.g., a convergent shape, a divergent shape, etc.) therein. 
         [0002]    In some turbines (e.g., gas turbines), efficiencies are directly proportional to the temperature of turbine gases flowing along the hot gas path and driving the turbine blades. These gas turbines typically have operating temperatures on the order of approximately 2700 degrees Fahrenheit (1482 degrees Celsius), a temperature which may stress and/or damage turbine components (e.g., turbine buckets, shrouds, nozzles, etc.). To withstand these high temperatures, the components are manufactured from advanced materials and typically include smooth bore cooling passages with a constant diameter for flowing a cooling medium, typically compressor discharge air, through the buckets. These passages also typically extend from the radially inner bucket root to the radially outer bucket tip with a consistent diameter. 
         [0003]    Many power generation turbine buckets use Shaped Tube Electrochemical Machining (STEM) drilled circular round holes to form the radial cooling flow passages inside the turbine airfoils. STEM is used for non-contact drilling of small, deep holes in electrically conductive materials, with high aspect ratios (e.g., a ratio of the length or depth of the hole to the largest lateral dimension (e.g., diameter of the hole), which in certain specific applications can be as small as a few millimeters) such as 300:1. The STEM process removes stock by electrolytic dissolution, utilizing a flow of electric current between an electrode and the workpiece through an electrolyte flowing in the intervening space to form the radial cooling flow passages. 
         [0004]    While smooth-bore passages have been utilized, turbulence promoters, (e.g., turbulators), are also used in many gas turbine buckets to enhance the internal heat transfer coefficient. This heat transfer enhancement may increase the heat transfer coefficient to more than two times greater than smooth-bore passages for the same cooling flow rate. Turbulators conventionally comprise internal ridges or roughened surfaces along the interior surfaces of the cooling passages. However, formation of these smooth-bore passages and/or turbulators may be limited by wall thickness requirements within the turbine bucket, particularly in proximity to a tip and/or trailing edge of the turbine bucket which typically has very small/thin dimensions. These limitations result in the smooth-bore passages having a small diameter near root sections of the turbine bucket so as to meet wall thickness requirements in the tip. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    Turbine components (e.g., turbine nozzles, shrouds, and/or buckets) having shaped tube electrochemical machined (STEM) cooling holes with a varying diameter (e.g., a convergent shape, a divergent shape, etc.) are disclosed. 
         [0006]    A first aspect of the invention includes: a turbine component including: at least one elongated cooling passage extending from a root of the bucket to a tip of the bucket, wherein the elongated cooling passage has a variable diameter along a length of the bucket. 
         [0007]    A second aspect of the invention includes: turbine bucket including: a root configured to connect to a turbine; a base disposed on the root and configured to extend into a turbine flowpath, the base having an airfoil shape and including a tip; and at least one elongated cooling passage formed in the root and the base, the at least one elongated cooling pass including: a first section disposed proximate the root and including an aperture at a terminus of the at least one elongated cooling passage, the first section extending into the base, and a second section fluidly connected to the first section and disposed proximate the tip, wherein a second diameter of the second section is smaller than a first diameter of the first section. 
         [0008]    A third aspect of the invention includes: a turbine including: a stator; a working fluid passage substantially surrounded by the stator; a rotor disposed radially inboard of the stator and in the working fluid passage; and a turbine bucket connected to the rotor, the turbine bucket including: at least one elongated cooling passage extending from a root of the turbine bucket to a tip of the turbine bucket, wherein the elongated cooling passage has a variable diameter along a length of the turbine bucket. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which: 
           [0010]      FIG. 1  shows a turbine component in accordance with embodiments of the invention; 
           [0011]      FIG. 2  shows a turbine component in accordance with embodiments of the invention; 
           [0012]      FIG. 3  shows a cooling passage in accordance with embodiments of the invention; 
           [0013]      FIG. 4  shows a cooling passage in accordance with embodiments of the invention; 
           [0014]      FIG. 5  shows a cooling passage in accordance with embodiments of the invention; 
           [0015]      FIG. 6  shows a cooling passage in accordance with embodiments of the invention; 
           [0016]      FIG. 7  shows a cooling passage in accordance with embodiments of the invention; 
           [0017]      FIG. 8  shows a cross sectional view of a cooling passage in accordance with embodiments of the invention; 
           [0018]      FIG. 9  shows a cross sectional view of a cooling passage in accordance with embodiments of the invention; 
           [0019]      FIG. 10  shows a cross sectional view of a cooling passage in accordance with embodiments of the invention; 
           [0020]      FIG. 11  shows a schematic block diagram illustrating portions of a combined cycle power plant system according to embodiments of the invention; and 
           [0021]      FIG. 12  shows a schematic block diagram illustrating portions of a single-shaft combined cycle power plant system according to embodiments of the invention. 
       
    
    
       [0022]    It is noted that the drawings of the invention are not necessarily to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. It is understood that elements similarly numbered between the FIGURES may be substantially similar as described with reference to one another. Further, in embodiments shown and described with reference to  FIGS. 1-12 , like numbering may represent like elements. Redundant explanation of these elements has been omitted for clarity. Finally, it is understood that the components of  FIGS. 1-12  and their accompanying descriptions may be applied to any embodiment described herein. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Aspects of the invention provide for turbine components (e.g., nozzles, shrouds, buckets, etc.) having STEM shaped cooling passages with a varying diameter (e.g., convergent, divergent, etc.). 
         [0024]    As noted herein, cooling passages through turbine components are conventionally cylindrical passageways with a substantially constant diameter from root to tip. The diameter of the coolant passages is constant and is therefore limited by the thinnest part of the turbine component (e.g., the blade tip, the trailing edge, the nozzle trailing edge, etc.). 
         [0025]    In contrast to conventional approaches, aspects of the invention include a turbine component (e.g., turbine bucket, turbine nozzle, nozzle trailing edge, shroud, etc.) having cooling passages with a varying diameter (e.g., a cooling passage which has a first diameter in one portion of the turbine bucket which varies in dimensional size from a second diameter of the cooling passage in a second portion of the turbine bucket, convergent cooling passages, divergent cooling passages, etc.). In an embodiment, the cooling passage diameter may decrease/diminish (e.g., gradually, telescopically, stepwise, etc.) across a length of the cooling passage in a convergent manner. In one embodiment, the varying diameter of the cooling passage has a larger dimension proximate a root of a turbine component (e.g., bucket) relative to a diameter of the cooling passage proximate a tip of the turbine bucket (e.g., a small diameter cooling passage proximate the tip of the turbine bucket which has an increasingly larger diameter as the cooling passage extends through mid and lower points of an airfoil span of the turbine bucket). The thickness/diameter of the cooling passage may be greater at the turbine bucket root where a cooling fluid flow may be introduced, this thickness increasing the sectional area proximate the root and increasing flow of the cooling fluid there through. In an embodiment, the cooling passage may include an aperture (e.g., metering feature) through the nozzle trailing edge configured to manipulate/control characteristics of a cooling flow through the cooling passage. 
         [0026]    Turning to  FIG. 1 , a turbine bucket  100  is shown including a set of cooling passages  110  in accordance with embodiments. Turbine bucket  100  includes a base (e.g., an airfoil)  130  connected to a root  120  which is configured to connect to a turbine system. In an embodiment, set of cooling passages  110  may be formed/shaped through shaped tube electrochemical machining (STEM). Set of cooling passages  110  extend substantially radially from root  120  toward a tip  132  of base  130 . Base  130  is shaped as an airfoil and includes a trailing edge  134  with a relatively thin thickness. Set of cooling passages  110  may enable a cooling flow  70  to pass through turbine component  100  and may include a varying diameter (e.g., convergent, divergent, etc.). In one embodiment, a diameter of set of cooling passages  110  may vary in proportion/relation to a thickness of turbine bucket  100 . Cooling passages  110  are defined by an interior surface of turbine bucket  100  and may include an aperture  118  which allows cooling flow  70  to enter a flow path of a turbine. 
         [0027]    As used herein, the terms “axial” and/or “axially” refer to the relative position/direction of objects along axis A, which is substantially perpendicular to the axis of rotation of the turbomachine (in particular, the rotor section). As further used herein, the terms “radial” and/or “radially” refer to the relative position/direction of objects along axis (r), which is substantially perpendicular with axis A and intersects axis A at only one location. Additionally, the terms “circumferential” and/or “circumferentially” refer to the relative position/direction of objects along a circumference which surrounds axis A but does not intersect the axis A at any location. 
         [0028]    Turning to  FIG. 2 , a portion of a rotor  10  is shown including a first wheel  12  and a second wheel  14 . Each of the wheels  12  and  14  carries a circumferential array of buckets  16  and  18 , respectively. Circumferential arrays of first and second-stage nozzle vanes  20  and  22  are also shown. It will be appreciated that the buckets  16  and  18  and nozzle vanes  20  and  22  lie in the working fluid flowpath  21  of the turbine. Nozzle vane  22  is carried by an inner shell  24  which disposes nozzle vanes  20  and  22  in the flowpath. The trailing edges of the nozzle vanes  20  and  22  are cooled by a flow of liquid (e.g., air, compressor discharge, etc.) into a trailing edge cavity  26  for flow through cooling passages  110  through the trailing edge tip  34  into the flowpath. In one embodiment, set of cooling passages  110  may extend to a nozzle trailing edge  34 , a diameter of the cooling passages  110  decreasing relative to a proximity to the trailing edge  34  (e.g., convergently, divergently, etc.). 
         [0029]    Turning to  FIG. 3 , a portion of a turbine component  200  is shown including a cooling passage  210  with a set of sections  220 ,  230 , and  240 , with varied diameter in accordance with embodiments of the invention. Cooling passage  210  is defined by an inner surface  280  of turbine component  200 . In an embodiment, cooling passage  210  includes a first section  220  fluidly connected to a second section  230  and a third section  240 . As can be seen, first section  220  may include a first diameter A, second section  230  may include a second diameter B, and/or third section  240  may include a third diameter C. In this embodiment, first section  220 , second section  230 , and third section  240  may form a step (e.g., incremental, tiered, telescoped, etc.) shaped cooling passage  210 , whereby a diameter of cooling passage  210  decreases incrementally/stepwise as cooling passage  210  extends (e.g., radially) through turbine component  200 . In one embodiment, cooling flow  70  may flow in a convergent direction through first section  220  to second section  230  and/or third section  240 . Diameter A of first section  220  may be greater than diameter B of second section  230 , and diameter B of second section  230  may be greater than diameter C of third section  240 . In one embodiment, inner surface  280  may have a substantially uniform material composition (e.g., metal, ceramic, etc.) throughout cooling passage  210 . In an embodiment, inner surface  280  comprises a machined surface of turbine component  200 . It is understood that while embodiments are described with reference to particular cooling passages, these embodiments may be combinable and/or applicable to any cooling passages described herein, including cooling passages  110 ,  210 ,  310 ,  410 , etc. 
         [0030]    Turning to  FIG. 4 , a portion of a turbine component  300  including a cooling passage  310  is shown in accordance with embodiments. Cooling passage  310  has a diameter D which varies gradually (e.g., from a dimension D 1 , D 2 , . . . D 1+N , etc.) in a convergent fashion from a base  302  of turbine component  300  toward a tip  304  of turbine component  300 . An interior surface of cooling passage  310  may be angled and have a substantially coned/frusto-conical shape. 
         [0031]    Turning to  FIG. 5 , a portion of a turbine component  400  including a cooling passage  410  is shown in accordance with embodiments. Cooling passage  410  may include a first section  420  with a substantially coned shape fluidly connected to a second section  430  with a reduced diameter ‘G.’ First section  420  may have a diameter E which gradually diminishes (e.g., from E 1 , to E 2 , to E 1+N ) between a root  402  of turbine component  400  and second section  430 . It is understood that the descriptions and/or combinations of cooling passage sections described herein are merely exemplary, and that any combination, modification, orientation, and/or arrangement of cooling passage sections may be included in accordance with embodiments. 
         [0032]    Turning to  FIG. 6 , a portion of a turbine component  500  including a cooling passage  510  is shown in accordance with embodiments. Cooling passage  510  may have a coned/frusto-conical shape and include a turbulator  550  disposed on a surface  518  of cooling passage  510 . Turbulator  550  may extend into a flow path of cooling flow  70  and may be configured to induce and/or enhance turbulent flow. In an embodiment, turbulator  550  may include a set of sections (e.g., rings, tabs, protrusions, etc.) disposed within cooling passage  510 . In an embodiment, the set of sections of turbulator  550  may be disposed at a proximity relative one another which is in a range of about 7 to about 13 times a relative protrusion height (e.g., how far each section protrudes into cooling passage  510 ) of each of the sections of turbulator  550 . In one embodiment, the set of sections may be disposed at a substantially regular interval relative to one another. In another embodiment, shown in  FIG. 7 , a portion of a turbine component  600  may include a cooling passage  610  as shown in accordance with embodiments. Cooling passage  610  may include a turbulator  650  disposed on a surface of cooling passage  610  with a substantially swirl shaped configuration. Turbulator  650  may include a first end  622  disposed proximate a root portion  612  of turbine component  600 , and second end  624  disposed proximate a tip portion  614  of turbine component  600 . Turbulator  650  may be disposed circumferentially about cooling passage  610  while extending radially outward through cooling passage  610 . In an embodiment, flow  70  may travel through cooling passage  610  in a divergent direction (e.g., from a first section of cooling passage  610  with a first diameter to a second section of cooling passage  610  with a second diameter which is greater than the first diameter) from tip portion  614  toward root portion  612 . It is understood that cooling flow  70  as described in embodiments herein may flow in any direction, and that the embodiments described herein are merely exemplary. 
         [0033]    Turning to  FIG. 8 , a portion of a turbine component  700  including a cooling passage  710  is shown according to embodiments. In this embodiment, cooling passage  710  includes a first portion  714  which is fluidly connected to a metering feature  712 . Metering feature  712  includes an aperture  716  disposed at a terminus of cooling passage  710 . In an embodiment, a flow  70  (e.g., air) may travel axially (e.g., through a radial end of a bucket, through an axial end of a nozzle, etc.) through cooling passage  710 . Metering feature  712  may fluidly connect cooling passage  710  to a fluid passage of a turbine. In an embodiment, metering feature  712  and/or aperture  716  may be adjustable/variable in diameter. Metering feature  712  and/or aperture  716  may control/meter cooling flow  70  in and/or through cooling passage  710  and may be modified/machined by a technician to adjust flow characteristics through cooling passage  710  (e.g., during maintenance, diagnostics, testing, cold flows, etc.). In an embodiment, aperture  716  and/or metering feature  712  may be machined to tune cooling passage  710  to meet design/nominal amounts and flow results. In one embodiment, aperture  716  and/or metering feature  712  may be adjusted (e.g., increased, drilled out, etc,) during cold testing of the component to correct manufacturing irregularities/errors. 
         [0034]    In an embodiment, a technician may increase (e.g., drill, bore, STEM, etc.) a diameter of metering feature  712  and/or aperture  716  in order to adjust the heat transfer coefficient within cooling passage  710 . In another embodiment, shown in  FIG. 9 , a turbine component  800  may include a cooling passage  810  with a telescoping (e.g., incremental, stepped, etc.) shape and a metering feature  812 . Cooling passage  810  may include a first section  814  with a diameter which is greater than a diameter of a second section  818 . In an embodiment, cooling passage  810  may include a metering feature  812  which is fluidly connected to second section  818 . Metering feature  812  may include an aperture  816  and enable cooling flow  70  to enter and/or exit cooling passage  810 . In another embodiment, shown in  FIG. 10 , a turbine component  850  may include a cooling passage  870  with a substantially constant diameter and a set of turbulators  880  disposed on a surface thereof. Turbine component  850  may include a metering feature  874  with an aperture  878  configured to meter/control cooling flow  70  through cooling passage  870 . 
         [0035]    Turning to  FIG. 11 , a schematic view of portions of a multi-shaft combined cycle power plant  900  is shown. Combined cycle power plant  900  may include, for example, a gas turbine  980  operably connected to a generator  970 . Generator  970  and gas turbine  980  may be mechanically coupled by a shaft  915 , which may transfer energy between a drive shaft (not shown) of gas turbine  980  and generator  970 . Also shown in  FIG. 11  is a heat exchanger  986  operably connected to gas turbine  980  and a steam turbine  992 . Heat exchanger  986  may be fluidly connected to both gas turbine  980  and a steam turbine  992  via conventional conduits (numbering omitted). Gas turbine  980  and/or steam turbine  992  may include component  100  and/or set of cooling passages  110  of  FIG. 1  or other embodiments described herein. Heat exchanger  986  may be a conventional heat recovery steam generator (HRSG), such as those used in conventional combined cycle power systems. As is known in the art of power generation, HRSG  986  may use hot exhaust from gas turbine  980 , combined with a water supply, to create steam which is fed to steam turbine  992 . Steam turbine  992  may optionally be coupled to a second generator system  970  (via a second shaft  915 ). It is understood that generators  970  and shafts  915  may be of any size or type known in the art and may differ depending upon their application or the system to which they are connected. Common numbering of the generators and shafts is for clarity and does not necessarily suggest these generators or shafts are identical. In another embodiment, shown in  FIG. 12 , a single shaft combined cycle power plant  990  may include a single generator  970  coupled to both gas turbine  980  and steam turbine  992  via a single shaft  915 . Steam turbine  992  and/or gas turbine  980  may include set of cooling passages  110  of  FIG. 1  or other embodiments described herein. 
         [0036]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof 
         [0037]    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 have 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 languages of the claims.