The disclosure relates generally to turbine components, and more particularly, to a turbine blade tip cooling system including a tip rail cooling insert.
In a gas turbine system, it is well known that air is pressurized in a compressor and used to combust a fuel in a combustor to generate a flow of hot combustion gases, whereupon such gases flow downstream through one or more turbines so that energy can be extracted therefrom. In accordance with such a turbine, generally, rows of circumferentially spaced turbine blades extend radially outwardly from a supporting rotor disk. Each blade typically includes a dovetail that permits assembly and disassembly of the blade in a corresponding dovetail slot in the rotor disk, as well as an airfoil that extends radially outwardly from the dovetail.
The airfoil has a generally concave pressure side wall and generally convex suction side wall extending axially between corresponding leading and trailing edges and radially between a root and a tip. It will be understood that the blade tip is spaced closely to a radially outer turbine shroud for minimizing leakage therebetween of the combustion gases flowing downstream between the turbine blades. Maximum efficiency of the system is obtained by minimizing the tip clearance or gap such that leakage is prevented, but this strategy is limited somewhat by the different thermal and mechanical expansion and contraction rates between the turbine blades and the turbine shroud and the motivation to avoid an undesirable scenario of having excessive tip rub against the shroud during operation.
In addition, because turbine blades are bathed in hot combustion gases, effective cooling is required for ensuring a useful part life. Typically, the blade airfoils are hollow and disposed in fluid communication with the compressor so that a portion of pressurized air bled therefrom is received for use in cooling the airfoils, as a coolant. Airfoil cooling is quite sophisticated and may be employed using various forms of internal cooling channels and features, as well as cooling holes through the outer rail surfaces of the airfoil for discharging the coolant. Nevertheless, airfoil tips are particularly difficult to cool since they are located directly adjacent to the turbine shroud and are heated by the hot combustion gases that flow through the tip gap. Accordingly, a portion of the air channeled inside the airfoil of the blade is typically discharged through the tip for the cooling thereof.
It will be appreciated that conventional blade tips include several different geometries and configurations that are meant to prevent leakage and increase cooling effectiveness. Conventional blade tips, however, all have certain shortcomings, including a general failure to adequately reduce leakage and/or allow for efficient tip cooling that minimizes the use of efficiency-robbing compressor bypass air. One approach, referred to as a “squealer tip” arrangement, provides a radially extending rail that may rub against the tip shroud. The rail reduces leakage and therefore increases the efficiency of turbine engines.
However, the rail of the squealer tip is subjected to a high heat load and is difficult to effectively cool—it is frequently one of the hottest regions in the blade. Tip rail impingement cooling delivers coolant through the top of the rail, and has been demonstrated to be an effective method of rail cooling. However, there are numerous challenges associated with exhausting a coolant through the top of the rail. For example, backflow pressure margin requirements are difficult to satisfy with this arrangement (especially on the pressure side wall, where there are holes connected to low and high pressure regions—the top and pressure side walls of the rail, respectively). Hence, it is a challenge to create losses in the tip passage to back-pressure the coolant flow, and at the same time, sufficiently cool the rail, since losses reduce the amount of coolant used in this region. Further, the outlet holes must exhibit rub tolerance yet provide sufficient cooling to the rails. For example, the outlet holes must be tolerant of tip rub but also sufficiently large that dust cannot clog them. It is also desirable to maintain the cooling after tip wear, e.g., by exposing supplemental cooling channels.
Ideally, the rail cooling passages are also capable of formation using additive manufacturing, which presents further challenges. Additive manufacturing (AM) includes a wide variety of processes of producing a component through the successive layering of material rather than the removal of material. As such, additive manufacturing can create complex geometries without the use of any sort of tools, molds or fixtures, and with little or no waste material. Instead of machining components from solid billets of material, much of which is cut away and discarded, the only material used in additive manufacturing is what is required to shape the component. With regard to tip rail cooling passages, conventional circular cooling holes within the rail are very difficult to build using additive manufacturing (perpendicular to the nominal build direction) and can severely deform or collapse during manufacture.
Another challenge with tip cooling is accommodating the different temperatures observed in different areas of the tip rail. For example, the rail in the pressure side wall and aft region of the suction side wall are typically hotter than other areas. Another challenge is providing cooling in used turbine blades that did not initially include tip cooling passages.
A first aspect of the disclosure provides a turbine blade tip cooling system, comprising: a turbine blade having a tip cavity, a tip rail surrounding at least a portion of the tip cavity and at least one internal cooling cavity; the tip rail having an inner rail surface, an outer rail surface, an end surface and at least one tip rail pocket open at the end surface and fluidly connected to the at least one internal cooling cavity that carries a coolant; and a tip rail cooling insert attached to the at least one tip rail pocket, the tip rail cooling insert having at least one insert cooling channel and a coolant collection plenum for directing coolant from the at least one internal cooling cavity to the at least one insert cooling channel.
A second aspect of the disclosure provides a method of cooling a turbine blade tip, comprising: providing a turbine blade having a tip cavity, a tip rail surrounding least a portion of the tip cavity and at least one internal cooling cavity configured to deliver a coolant, the tip rail having an inner rail surface, an outer rail surface and an end surface; forming a tip rail pocket in the end surface of the tip rail, the tip rail pocket including a tip pocket coolant opening in fluid communication with the at least one internal cooling cavity; forming a tip rail cooling insert having a coolant collection plenum configured for fluid communication with the tip pocket coolant opening and at least one insert cooling channel in fluid communication with the coolant collection plenum, the tip rail cooling insert being sized and shaped to engage in the tip rail pocket; and attaching the tip rail cooling insert to the tip rail pocket to fluidly connect the coolant collection plenum to the internal cooling cavity.
A third aspect provides a gas turbine having a rotating blade, the gas turbine comprising: a turbine blade having a tip cavity, a tip rail surrounding at least a portion of the tip cavity and at least one internal cooling cavity; the tip rail having an inner rail surface, an outer rail surface, an end surface and at least one tip rail pocket open at the end surface, the at least one tip rail pocket fluidly connected to the at least one internal cooling cavity; and a tip rail cooling insert attached to the at least one tip rail pocket, the tip rail cooling insert having at least one insert cooling channel and a coolant collection plenum for directing coolant from the at least one internal cooling cavity to the at least one insert cooling channel.
The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.
These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure, in which:
It is noted that the drawings of the disclosure are not necessarily to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.
As an initial matter, in order to clearly describe the current disclosure it will become necessary to select certain terminology when referring to and describing relevant machine components within a turbomachine system and relative to a turbine blade. When doing this, if possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single part.
In addition, several descriptive terms may be used regularly herein, and it should prove helpful to define these terms at the onset of this section. These terms and their definitions, unless stated otherwise, are as follows. As used herein, “downstream” and “upstream” are terms that indicate a direction relative to the flow of a working fluid, such as combustion gases through the turbine engine or, for example, the flow of air through the combustor or coolant through or by one of the turbine's components. The term “downstream” corresponds to the direction of flow of the fluid, and the term “upstream” refers to the direction opposite to the flow. The terms “forward” and “aft,” without any further specificity, refer to directions, with “forward” referring to an upstream portion of the part being referenced, i.e., closest to compressor, and “aft” referring to a downstream portion of the part being referenced, i.e., farthest from compressor. It is often required to describe parts that are at differing radial positions with regard to a center axis. The term “radial” refers to movement or position perpendicular to an axis. In cases such as this, if a first component resides closer to the axis than a second component, it will be stated herein that the first component is “radially inward” or “inboard” of the second component. If, on the other hand, the first component resides further from the axis than the second component, it may be stated herein that the first component is “radially outward” or “outboard” of the second component. The term “axial” refers to movement or position parallel to an axis. Finally, the term “circumferential” refers to movement or position around an axis. It will be appreciated that such terms may be applied in relation to the center axis of the turbine.
Where an element or layer is referred to as being “on,” “engaged to,” “disengaged from,” “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
As indicated above, embodiments of the disclosure provide a turbine blade tip cooling system for a turbine blade including a tip rail cooling insert. A turbine blade has a tip cavity, a tip rail surrounding at least a portion of the tip cavity and at least one internal cooling cavity, i.e., an internal cooling cavity carrying a coolant disposed within the airfoil. The tip cavity can be created by a tip plate and the tip rail. The tip rail has an inner rail surface, an outer rail surface, an end surface and at least one tip rail pocket open at the end surface. That is, the tip rail may include an inner rail surface defining a tip cavity therein, an outer rail surface and an end surface (e.g., a radially outward facing rail surface) between the inner rail surface and the outer rail surface. The tip rail extends radially from the tip plate. The tip rail pocket is fluidly connected to the at least one internal cooling cavity that carries a coolant. A tip rail cooling insert attaches to the at least one tip rail pocket, and has insert cooling channel(s) and a coolant collection plenum for directing coolant from the at least one internal cooling cavity to the insert cooling channel(s). Insert cooling channel(s) can take a variety of forms to provide a wide variety of desired cooling. The tip rail cooling insert allows for selectively placed cooling of the tip rail in used or new turbine blades. That is, tip rail cooling insert can deliver coolant to those areas of the tip and/or tip rail, e.g., the suction side, aft portion thereof, requiring additional cooling compared to other parts of the tip. The tip rail cooling insert may also improve cooling of the tip rail while metering coolant therethrough. The tip rail cooling insert may also address dust clogging.
Certain embodiments of the tip rail cooling insert allow for additive manufacturing, among other manufacturing processes, as described herein. Additive manufacturing (AM) includes a wide variety of processes of producing a component through the successive layering of material rather than the removal of material. Additive manufacturing techniques typically include taking a three-dimensional computer aided design (CAD) file of the component to be formed, electronically slicing the component into layers, e.g., 18-102 micrometers thick, and creating a file with a two-dimensional image of each layer, including vectors, images or coordinates. The file may then be loaded into a preparation software system that interprets the file such that the component can be built by different types of additive manufacturing systems. In 3D printing, rapid prototyping (RP), and direct digital manufacturing (DDM) forms of additive manufacturing, material layers are selectively dispensed, sintered, formed, deposited, etc., to create the component. In metal powder additive manufacturing techniques, such as direct metal laser melting (DMLM) (also referred to as selective laser melting (SLM)), metal powder layers are sequentially melted together to form the component. More specifically, fine metal powder layers are sequentially melted after being uniformly distributed using an applicator on a metal powder bed. Each applicator includes an applicator element in the form of a lip, brush, blade or roller made of metal, plastic, ceramic, carbon fibers or rubber that spreads the metal powder evenly over the build platform. The metal powder bed can be moved in a vertical axis. The process takes place in a processing chamber having a precisely controlled atmosphere. Once each layer is created, each two-dimensional slice of the component geometry can be fused by selectively melting the metal powder. The melting may be performed by a high-powered melting beam, such as a 100 Watt ytterbium laser, to fully weld (melt) the metal powder to form a solid metal. The melting beam moves in the X-Y direction using scanning mirrors, and has an intensity sufficient to fully weld (melt) the metal powder to form a solid metal. The metal powder bed may be lowered for each subsequent two-dimensional layer, and the process repeats until the component is completely formed.
In one aspect, combustor 104 uses liquid and/or gas fuel, such as natural gas or a hydrogen rich synthetic gas, to run the engine. For example, fuel nozzles 110 are in fluid communication with an air supply and a fuel supply 112. Fuel nozzles 110 create an air-fuel mixture, and discharge the air-fuel mixture into combustor 104, thereby causing a combustion that creates a hot pressurized exhaust gas. Combustor 104 directs the hot pressurized gas through a transition piece into a turbine nozzle (or “stage one nozzle”), and other stages of buckets and nozzles causing turbine 106 rotation. The rotation of turbine 106 causes shaft 108 to rotate, thereby compressing the air as it flows into compressor 102. In an embodiment, hot gas path components, including, but not limited to, shrouds, diaphragms, nozzles, blades and transition pieces are located in turbine 106, where hot gas flow across the components causes creep, oxidation, wear and thermal fatigue of turbine parts. Controlling the temperature of the hot gas path components can reduce distress modes in the components. The efficiency of the gas turbine increases with an increase in firing temperature in turbine system 100. As the firing temperature increases, the hot gas path components need to be properly cooled to meet service life. Components with improved arrangements for cooling of regions proximate to the hot gas path and methods for making such components are discussed in detail herein. Although the following discussion primarily focuses on gas turbines, the concepts discussed are not limited to gas turbines.
Each turbine blade 115 generally includes a base 122 (also referred to as root or dovetail) which may have any conventional form, such as an axial dovetail configured for being mounted in a corresponding dovetail slot in the perimeter of rotor disk 117. A hollow airfoil 124 is integrally joined to base 122 and extends radially or longitudinally outwardly therefrom. Turbine blade 115 also includes an integral platform 126 disposed at the junction of airfoil 124 and base 122 for defining a portion of the radially inner flow path for combustion gases 116. It will be appreciated that turbine blade 115 may be formed in any conventional manner, and is typically a one-piece casting, an additively manufactured part, or an additively manufacturing tip joined to a cast blade base section. It will be seen that airfoil 124 preferably includes a generally concave pressure side wall 128 and a circumferentially or laterally opposite, generally convex suction side wall 130 extending axially between opposite leading and trailing edges 132 and 134, respectively. Side walls 128 and 130 also extend in the radial direction from platform 126 to a radially outer blade tip or, simply, tip 137.
Due to certain performance advantages, such as reduced leakage flow, blade tips 137 frequently include tip rail 150. Coinciding with pressure side wall 128 and suction side wall 130, tip rail 150 may be described as including a pressure side wall rail 152 and a suction side wall rail 154, respectively. Generally, pressure side wall rail 152 extends radially outwardly from tip plate 148 and extends from leading edge 132 to trailing edge 134 of airfoil 124. As illustrated, the path of pressure side wall rail 152 is adjacent to or near the outer radial edge of pressure side wall 128 (i.e., at or near the periphery of tip plate 148 such that it aligns with the outer radial edge of the pressure side wall 128). Similarly, as illustrated, suction side wall rail 154 extends radially outwardly from tip plate 148 and may extend from leading edge 132 to trailing edge 134 of airfoil 124. The path of suction side wall rail 154 is adjacent to or near the outer radial edge of suction side wall 130 (i.e., at or near the periphery of the tip plate 148 such that it aligns with the outer radial edge of the suction side wall 130). Both pressure side wall rail 152 and suction side wall rail 154 may be described as having an inner rail surface 157, an outer rail surface 159 and an end surface 160, e.g., radially outward facing rail surface, between inner rail surface 157 and outer rail surface 159. It should be understood though that rail(s) may not necessarily follow the pressure or suction side wall rails. That is, in alternative types of tips in which the present disclosure may be used, tip rails 150 may be moved away from the edges of tip plate 148 and may not extend to trailing edge 134.
Formed in this manner, it will be appreciated that tip rail 150 defines tip cavity 155 at tip 137 of turbine blade 115. As one of ordinary skill in the art will appreciate, tip 137 configured in this manner, i.e., one having this type of tip cavity 155, is often referred to as a “squealer tip” or a tip having a “squealer pocket or cavity.” The height and width of pressure side wall rail 152 and/or suction side wall rail 154 (and thus the depth of tip cavity 155) may be varied depending on best performance and the size of the overall turbine assembly. It will be appreciated that tip plate 148 forms the floor of tip cavity 155 (i.e., the inner radial boundary of the cavity), tip rail 150 forms the side walls of tip cavity 155, and tip cavity 155 remains open through an outer radial face, which, once installed within a turbine engine, is bordered closely by annular, stationary turbine shroud 120 (see
As understood in the art, tip rail 150 may have any of a variety of cooling passages (not shown) extending therethrough to cool the tip rail. Some outlets 162 of those cooling passages are shown, for example, in
With continuing reference to
As shown in
In one embodiment, as shown for example in
In another embodiment, as shown for example in the perspective view of
Returning to
Referring again to
Referring to
While each different embodiment shows insert cooling channel(s) 282 in a particular pattern, it is understood that patterns from the different embodiments can be intermixed. For example, of insert cooling channel(s) 282 in an insert 280 at least one could have a serpentine pattern, a crossing pattern and a helical pattern, and at least one other could have one of the other patterns. Some of the inserts 280 described herein must be additively manufactured; however, others can be formed using casting or a material removing technique, perhaps with electro-discharge machining (EDM), wire EDM and/or laser cutting to create certain features, e.g., channels 282, plenum 284, etc. While particular examples of insert cooling channel(s) 282 have been illustrated herein, it is understood that others are possible, and considered within the scope of the disclosure. Any of the variety of cooling channel arrangements described herein or otherwise available can include adaptive cooling channels, i.e., those allowing opening of other cooling channels when one is destroyed or clogged. In this fashion, insert cooling channel(s) 282 can form redistribution manifolds interconnecting any of a variety of branch cooling circuits for continued cooling operation during rubs that remove tip rail material or clog indiscriminate upper channels and/or exit apertures 286.
Embodiments of the disclosure provide improved and selectable blade tip cooling to reduce cooling flow requirements. The insert cooling channel(s) can take a variety of forms to provide a wide variety of desired cooling. The tip rail cooling insert allows for selectively placed cooling of the tip rail in used or new turbine blades. That is, tip rail cooling insert can deliver coolant to those areas of the tip and/or tip rail, e.g., the suction side, aft portion thereof, requiring additional cooling compared to other parts of the tip. The tip rail cooling insert may also improve cooling of the tip rail while metering coolant therethrough. The tip rail cooling insert may also address dust clogging. The airfoil 124, tip 137, 237, and insert 280 can be manufactured using any now known or later developed process such as casting and additive manufacturing. However, it is noted that many embodiments of insert 280 lend themselves especially to additive manufacture.
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. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. “Approximately” as applied to a particular value of a range applies to both values, and unless otherwise dependent on the precision of the instrument measuring the value, may indicate +/−10% of the stated value(s).
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
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