Abstract:
A turbine blade can include a root configured to connect to a turbine and supporting an airfoil configured to extend into a flowpath of the turbine. The airfoil can include a tip disposed substantially opposite the root and a first tip fillet disposed proximate the tip that can extend substantially perpendicular to a local flow direction at points along a surface of the turbine blade over the extremity of the first tip fillet. The tip fillet can enhance performance of the turbine by beneficially altering flow through a stage in which the blade is included.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to turbine components for aircraft and power generation applications, and, more specifically, to turbine components including an airfoil portion having a tip fillet, the tip fillet increasing a thickness of the airfoil proximate a tip of the airfoil span. 
         [0002]    Some aircraft and/or power plant systems, for example certain jet aircraft, nuclear, simple cycle and combined cycle power plant systems, employ turbines in their design and operation. Some of these turbines include one or more stages of buckets which during operation are exposed to fluid flows. Each bucket can include a base supporting a respective airfoil (e.g., turbine blade, blade, etc.) configured to aerodynamically interact with and extract work from fluid flow (e.g., creating thrust, driving machinery, converting thermal energy to mechanical energy, etc.) as part of, for example, power generation. As a result of this interaction and conversion, the aerodynamic characteristics and losses of these airfoils have an impact on system and turbine operation, performance, thrust, efficiency, and power at each stage. 
         [0003]    In these systems, a source of aerodynamic loss and inefficiency can include overtip leakage, particularly in unshrouded gas turbine blades. During operation, portions of the fluid flow may leak over a tip of the airfoil (e.g., between a blade tip and flowpath sidewall of the turbine, through the blade clearance gap, etc.) and form a vortex on a suction side of the airfoil. This leakage and subsequent vortex formation on the suction side may cause a pressure gradient to form across the tip and/or through the blade clearance gap, thereby impacting the fluid flow and efficiency of the system and airfoil, and hindering device performance. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    A turbine component including a tip fillet on a radial end (e.g., tip) of an airfoil is disclosed. 
         [0005]    An embodiment of the invention disclosed herein can take the form of a turbine blade having a root configured to connect to a turbine and an airfoil connected to the root and configured to extend into a flowpath of the turbine. The airfoil can include a tip disposed substantially opposite the root, as well as a first tip fillet disposed on the tip and extending substantially away from a first surface of the turbine blade. 
         [0006]    Another embodiment of the invention disclosed herein can be implemented in a turbine component that can include a root configured to connect to a turbine and a blade disposed on the root and configured to extend into a turbine flowpath. The blade can have an airfoil shape and can include a tip. A tip fillet can be connected to the tip and can extend from a surface of the turbine component. 
         [0007]    An additional embodiment of the invention disclosed herein can take the form of a turbine having a nozzle including a casing and at least one blade, a rotor including a hub and at least one blade, and a working fluid passage including a first portion substantially surrounded by the nozzle casing and a second portion substantially surrounding the rotor hub. Each blade can include a root configured to connect to one of the nozzle casing or the rotor hub, as well as an airfoil connected to the root and configured to extend into the working fluid passage of the turbine. The airfoil can have a tip disposed substantially opposite the root, and a first tip fillet can be disposed on the tip. The tip fillet can extend from a surface of the turbine component in a direction substantially perpendicular to a local flow direction at points along a surface of the turbine component over the extremity of the first tip fillet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    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: 
           [0009]      FIG. 1  shows a three-dimensional partial cut-away perspective view of a portion of a turbine according to an embodiment of the invention; 
           [0010]      FIG. 2  shows a turbine component in accordance with embodiments of the invention; 
           [0011]      FIG. 3  shows a tip portion of a turbine component in accordance with embodiments of the invention; 
           [0012]      FIG. 4  shows an airfoil including a tip fillet in accordance with embodiments of the invention; 
           [0013]      FIG. 5  shows a graphical representation of an airfoil thickness function according to an embodiment; 
           [0014]      FIG. 6  shows a graphical representation of a tip fillet thickness function according to an embodiment; 
           [0015]      FIG. 7  shows a side view of a turbine airfoil including a tip fillet according to an embodiment; 
           [0016]      FIG. 8  shows a cross sectional view of the turbine airfoil of  FIG. 7  along view line A-A; 
           [0017]      FIG. 9  shows a cross sectional view of the turbine airfoil of  FIG. 7  along view line B-B; 
           [0018]      FIG. 10  shows a cross sectional view of the turbine airfoil of  FIG. 7  along view line C-C; 
           [0019]      FIG. 11  shows a side view of a turbine airfoil including a one-sided tip fillet according to an embodiment; 
           [0020]      FIG. 12  shows a side view of a turbine airfoil including a set of tip fillets according to an embodiment; 
           [0021]      FIG. 13  shows a schematic block diagram illustrating portions of a combined cycle power plant system according to embodiments of the invention; and 
           [0022]      FIG. 14  shows a schematic block diagram illustrating portions of a single-shaft combined cycle power plant system according to embodiments of the invention. 
       
    
    
       [0023]    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. 1-14 , 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. 1-14  and their accompanying descriptions may be applied to any embodiment described herein. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Aspects of the invention provide for a turbine component including a tip fillet on a portion of an airfoil section, the tip fillet increasing a thickness of the airfoil proximate a radial extent of the airfoil. 
         [0025]    In contrast to conventional approaches, aspects of the invention include a turbine component (e.g., turbine blade, turbine nozzle, blade, etc.) having a tip fillet disposed on a portion of the turbine component and configured to reduce tip leakage. In an embodiment, the tip fillet extends from a surface of the turbine component in a direction substantially perpendicular to a local flow direction at points along the surface of the turbine component over the extremity of the tip fillet. The tip fillet may overhang the blade/airfoil and/or a tip vortex location of the turbine component, the tip vortex forming during operation/exposure of the turbine component to a fluid flow. The tip fillet can reduce tip vortex formation and tip leakage, thereby inhibiting formation of a pressure gradient across a tip of the airfoil and assisting with improvement of aerodynamic performance. 
         [0026]    As used herein, the terms “axial” and/or “axially” refer to the relative position/direction of objects along axis A, which is substantially parallel 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. Further, the term “leading edge” refers to components and/or surfaces which are oriented upstream relative to the fluid flow of the system, and the term “trailing edge” refers to components and/or surfaces which are oriented downstream relative to the fluid flow of the system. 
         [0027]    Turning to the FIGURES, embodiments of systems and devices are shown, which can be configured to reduce tip leakage losses in a turbine by providing a tip fillet disposed proximate a radial extent/tip of a turbine component. Each of the components in the FIGURES may be connected via conventional means, e.g., via a common conduit or other known means as is indicated in  FIGS. 1-14 . Referring to the drawings,  FIG. 1  shows a perspective partial cut-away illustration of a gas or steam turbine  10 . Turbine  10  includes a rotor  12  that includes a rotating shaft  14  and a plurality of axially spaced rotor wheels  18 . A plurality of rotating blades or buckets  20  are mechanically coupled to each rotor wheel  18 . More specifically, buckets  20  are arranged in rows that extend circumferentially around each rotor wheel  18 . A nozzle  21  can include a plurality of stationary blades or vanes  22  that can extend circumferentially around shaft  14 , and the vanes are axially positioned between adjacent rows of buckets  20 . Stationary vanes  22  cooperate with buckets  20  to form a stage and to define a portion of a flow path through turbine  10 . For example, each vane  22  can extend radially inward into the flow path from a root attached to a casing or the like of a nozzle  21  to a radially inward tip, while each bucket  20  can extend radially outward into the flow path from a root attached to a hub or the like of a rotor wheel  18  to a radially outward tip. 
         [0028]    In operation, gas  24  enters an inlet  26  of turbine  10  and is channeled through stationary vanes  22 . Vanes  22  direct gas  24  against blades  20 . Gas  24  passes through the remaining stages imparting a force on buckets  20  causing shaft  14  to rotate. At least one end of turbine  10  may extend axially away from rotating shaft  12  and may be attached to a load or machinery (not shown) such as, but not limited to, a generator, and/or another turbine, such as might be used in aviation and/or other applications. 
         [0029]    In the example shown in  FIG. 1 , turbine  10  can include five stages identified as a first stage L 4 , a second stage L 3 , a third stage L 2 , a fourth stage L 1 , and a fifth stage L 0 , which is also the last stage. Each stage has a respective radius, with first stage L 4  having the smallest radius of the five stages and each subsequent stage having a larger radius, with fifth stage L 0  having a largest radius of the five stages. While five stages are shown in  FIG. 1 , this simply a non-limiting example, and the teachings herein can be applied to turbines having more or fewer stages, including a turbine with a single stage. In addition, while the example shown in  FIG. 1  is stationary, the teachings herein can be applied to any suitable turbine, including turbines used in aircraft engines, and may also be applied to compressors. 
         [0030]    Turning to  FIG. 2 , a turbine component  200  (e.g., a turbine blade, a blade, a bucket, a vane, etc.) is shown including an airfoil  220  with a tip fillet  210  in accordance with embodiments of the invention. In an embodiment, tip fillet  210  is disposed proximate a tip  202  of turbine component  200  and extends/protrudes from a first flow surface  206  of turbine component  200 . Tip fillet  210  may extend across a width of turbine component  200  and may substantially overhang portions of the blade/airfoil between tip  202  and a root  208  of turbine component  200 . In one embodiment, tip fillet  210  may have a concave shape and/or may flare out from first flow surface  206 . In another embodiment, tip fillet  210  may have a linear shape or a convex shape. Where turbine component  200  includes a dynamic blade or bucket, airfoil  220  may extend outboard or radially outward from root  208  to tip  202 , root  208  being attached, for example, to a casing or the like of a nozzle  21  of turbine  10 . Where turbine component  200  includes a stationary blade or vane, airfoil  220  may extend inboard or radially inward from root  208  to tip  202 , root  208  being attached, for example, to a hub of a rotor  18  of turbine  10 . In either case, tip fillet  210  may extend substantially into a fluid path  70  from a suction side of airfoil  220  and/or substantially perpendicular to direction of fluid flow  70  so as to overhang a location of a tip vortex  240  (shown in phantom). In one embodiment, tip fillet  210  may extend from a leading edge of airfoil  220  substantially into fluid flow  70 . In another embodiment, tip fillet  210  may extend in a direction substantially perpendicular to the direction of fluid flow  70  from a pressure side of airfoil  220 . First flow surface  206  may be a suction side of turbine component  200  relative to the direction of fluid flow  70  in turbine  100  (shown in  FIG. 1 ). In one embodiment, tip fillet  210  may increase a cross-sectional dimension (e.g., thickness) of turbine component  200  relative to an adjacent cross sectional portion of turbine component  200  (as shown in  FIGS. 5 and 6 ). In one embodiment, tip fillet  210  may be formed as a portion of turbine component  200  (e.g., shaped from a single piece of stock material, formed as a uniform body, etc.). In another embodiment, tip fillet  210  may be connected (e.g., bolted, welded, etc.) to tip  202  of airfoil  220 . As is discussed herein, airfoil  220  and tip fillet  210  may be used in an aircraft engine, a power generation turbine, etc. 
         [0031]    Turning to  FIG. 3 , a portion of a turbine blade  300  with a tip  302  including a set of tip fillets  310  is shown in accordance with embodiments. Set of tip fillets  310  include a first tip fillet  312  disposed on a first flow surface  306  of turbine blade  300 , and a second tip fillet  314  disposed on a second flow surface  308  of turbine blade  300 . In an embodiment, first flow surface  306  may be a suction side of turbine component  300  relative to fluid flow  70 , and second flow surface  308  may be a pressure side of turbine component  300  relative to fluid flow  70 . In an embodiment, at least one of first tip fillet  312  and second tip fillet  314  may have a substantially concave shape. In one embodiment, first tip fillet  312  may extend over a location of tip vortex  340  (shown in phantom) formed during operation/exposure to fluid flow  70 . 
         [0032]    Turning to  FIG. 4 , a portion of a turbine blade  400  including a tip fillet  420  is shown in accordance with embodiments. Tip fillet  420  may be disposed on a second surface  408  of turbine blade  400  and may extend from a pressure side of turbine blade  400  and/or into fluid flow  70 . In an embodiment, second surface  408  may be a pressure side of turbine blade  400 . 
         [0033]    Turning to  FIG. 5 , a two-dimensional graphical representation  500  of an embodiment of a conventional airfoil thickness function  570  is shown. Graphical representation  500  includes an x-axis  560  representing increments of an airfoil thickness dimension and a y-axis  562  representing increments of a percent radial span of the airfoil, with 0% representing a location proximate the root of the airfoil and 100% representing a location proximate a tip of the airfoil. As can be seen in  FIG. 5 , as a percentage of the radial span of the airfoil increases (e.g., extends from the root to the tip) from about 0% radial span to about 90% radial span, the airfoil thickness may decrease (e.g., taper, reduce in thickness, etc.). However, contrary to conventional implementations, between about 90% and about 100% of the percent of the radial span the airfoil thickness may increase as a result of a tip fillet (e.g., tip fillet  210 ) as indicated by a tip fillet curve/function  572  (shown in phantom). This local change in the airfoil thickness provided by tip fillet  210  near tip  202  of the airfoil may reduce tip leakage and improve turbine efficiency. 
         [0034]    Turning to  FIG. 6 , a two-dimensional graphical representation  600  of an embodiment of a conventional airfoil thickness slope function  670  is shown. Graphical representation  600  includes an x-axis  660  representing increments of an airfoil thickness slope and a y-axis  662  representing increments of a percent radial span of the airfoil, with 0% representing a location proximate the root of the airfoil and 100% representing a location proximate a tip of the airfoil. Thickness slope may represent a rate of change in airfoil section thickness at any chordwise location per unit radial height and/or span. As such, a thickness slope function can reflect changes in both a pressure side and a suction side of airfoil  220 . 
         [0035]    As can be seen in  FIG. 6 , a typical airfoil can have a substantially constant, negative thickness slope over substantially its entire span as represented by curve  670 , indicative of a taper of the airfoil from root to tip. In embodiments, however, tip fillet  210  can result in and/or be defined at least in part by a change in thickness slope, which is illustrated by example curve  672 . More specifically, thickness slope can begin to increase at at least about 75% radial span, such as at at least about 80% radial span. In addition, thickness slope can continue to increase from at least about 80% radial span to about 100% radial span. Further, since in the example shown thickness slope can increase from at least about 80% radial span to about 100% radial span, the thickness of airfoil  220  can increase at a higher rate toward 100% radial span. Thus, as can be seen in  FIG. 6 , taper of airfoil  220  slows beginning at at least about 80% radial span (i.e., where slope begins to increase) until the thickness slope becomes positive at at least about 90% radial span, such as at at least about 95% radial span, at which point the airfoil thickness begins to increase. In an embodiment, tip fillet  210  may be construed to begin where thickness slope becomes positive, such as at at least about 95% of the radial span of the airfoil, which can also represent a point of minimum airfoil thickness, though in another embodiment, tip fillet  210  may be construed to begin where thickness slope begins to increase, such as at at least about 80% radial span. Tip fillet  210  may thicken or widen at an increasing rate between at least about 95% radial span and about 100% radial span (e.g., tip  202 ) so as to flare into an end wall or the like, and a profile of one or both of the suction side and the pressure side of airfoil  220  can change to effect a change in thickness slope according to embodiments. 
         [0036]    In one embodiment, thickness slope may be calculated by Equation (1) shown below, where rad is the spanwise position of the first airfoil section, chd is the chordwise position of the first airfoil section where the airfoil thickness is to be measured, and delta_rad is a small change in span. The thickness slope can be calculated based on two measurements of airfoil thickness which are close together in span (e.g., separated by delta_rad) and can be evaluated via equation 1 as follows: 
         [0000]      Thickness slope=(airfoil thickness ( rad, chd )−airfoil thickness ( rad -delta_ rad, chd )/delta —   rad )  (Eq. 1)
 
         [0037]    It should be noted that the thickness slope function shown in  FIG. 6  is an example according to the teachings herein and is thus not limiting embodiments of the invention disclosed herein. As indicated above, a profile of one or both of the suction side and the pressure side of airfoil  220  can be varied to implement embodiments. In addition, while embodiments have been described in the context of a tip fillet of a rotor blade, it should be recognized that the teachings herein can be applied to implement a tip fillet of a stator blade, recognizing that in the case of a stator blade, radial span for the purposes of embodiments can increase from an outer extremity of a stator blade to an inner extremity of a stator blade. 
         [0038]    Turning to  FIGS. 7-10 , embodiments of portions of an airfoil  700  are shown in accordance with embodiments of the disclosure.  FIG. 7  shows a top view of portions of airfoil  700 .  FIG. 8  shows a cross-sectional view of portions of airfoil  700  along line A-A in  FIG. 7 ,  FIG. 9  shows a cross-sectional view of portions of airfoil  700  along line B-B in  FIG. 7 , and  FIG. 10  shows a cross-sectional view of portions of airfoil  700  along line C-C in  FIG. 7 . 
         [0039]    Referring to  FIG. 7 , a top view radially down of an embodiment of an airfoil  700  is shown in accordance with embodiments. Airfoil  700  includes a tip fillet  770  disposed on a suction side  752  and extending into the flow path. As can be seen, tip fillet  770  is disposed substantially perpendicular relative to a camber line  780  (shown in phantom) of airfoil  700  and increases the thickness of a cross sectional tip portion of airfoil  700  relative to the thickness of a nominal/standard airfoil section. 
         [0040]    As shown in  FIGS. 8-10 , tip fillet of  770  may have a varying thickness and/or shape relative to airfoil  700 . This shape and/or thickness of tip fillet  770  may depend on a location of a given section of tip fillet  770  on airfoil  700 . Turning to  FIG. 8 , a cross-sectional view of airfoil  700  along line A-A nearest a leading edge of airfoil  700  is shown according to embodiments. As can be seen, a first portion  774  of tip fillet  770  at this location on airfoil  700  proximate the leading edge has a thickness which is substantially smaller relative to a second portion  776  shown in  FIG. 9  which is located proximate a mid-point of airfoil  700  between the leading and trailing edges. Similarly, third portion  778  shown in  FIG. 10  and located proximate a trailing edge of airfoil  700  may have a smaller thickness than second portion  776 . It is understood that a thickness and/or shape of tip fillet  770  may vary across surface  752  and that while walls of airfoil  700  are indicated as substantially parallel in  FIGS. 7-10 , these embodiments are merely examples and that walls of airfoil  700  may take any shape and/or relation relative one another. 
         [0041]    Turning to  FIG. 11 , an airfoil  850  is shown including a single tip fillet  852  disposed on an airfoil  850  in accordance with embodiments. In an embodiment, a thickness of tip fillet  852  may increase relative to a proximity to a tip  854  of airfoil  850 . As can be seen, a rate of change of thickness ΔT may gradually increase across a rate of radial proximity AR to tip  854 . In another embodiment, shown in  FIG. 12 , airfoil  850  includes a first tip fillet  852  and a second tip fillet  856 . In an embodiment, a rate of change of thickness ΔT of airfoil  850  may be regulated by both first tip fillet  852  and second tip fillet  856 . In an embodiment, each of first tip fillet  852  and second tip fillet  856  may contribute to a relative thickness of airfoil  850  across a radial span portion R. In one embodiment, at a minimum radial span R, the effect of each tip fillet may be ΔT/2. In one embodiment, tip fillet  852  may include a linear shape, a concave shape, a convex shape, and/or a point of inflection shape. 
         [0042]    Embodiments of the invention can be used in aviation, power generation, and/or other applications and/or devices as may be desired and/or appropriate. For example,  FIG. 13  shows a schematic view of portions of a multi-shaft combined cycle power plant  900  in which embodiments can be used. 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. 13  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 tip fillet  210  of  FIG. 2  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. 14 , 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 tip fillet  210  of  FIG. 2  or other embodiments described herein. 
         [0043]    The apparatus and devices of the present disclosure are not limited to any one particular engine, turbine, jet engine, generator, power generation system or other system, and may be used with other aircraft systems, power generation systems and/or systems (e.g., combined cycle, simple cycle, nuclear reactor, etc.). Additionally, the apparatus of the present invention may be used with other systems not described herein that may benefit from the increased reduced tip leakage and increased efficiency of the apparatus and devices described herein. 
         [0044]    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 
         [0045]    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.