Patent Application
20130078418
The invention relates generally to gas turbine engines, and, more specifically, to micro-channel cooling therein.
In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases. Energy is extracted from the gases in a high pressure turbine (HPT), which powers the compressor, and in a low pressure turbine (LPT), which powers a fan in a turbofan aircraft engine application, or powers an external shaft for marine and industrial applications.
Engine efficiency increases with temperature of combustion gases. However, the combustion gases heat the various components along their flowpath, which in turn requires cooling thereof to achieve a long engine lifetime. Typically, the hot gas path components are cooled by bleeding air from the compressor. This cooling process reduces engine efficiency, as the bled air is not used in the combustion process.
Gas turbine engine cooling art is mature and includes numerous patents for various aspects of cooling circuits and features in the various hot gas path components. For example, the combustor includes radially outer and inner liners, which require cooling during operation. Turbine nozzles include hollow vanes supported between outer and inner bands, which also require cooling. Turbine rotor blades are hollow and typically include cooling circuits therein, with the blades being surrounded by turbine shrouds, which also require cooling. The hot combustion gases are discharged through an exhaust which may also be lined, and suitably cooled.
In all of these exemplary gas turbine engine components, thin walls of high strength superalloy metals are typically used to reduce component weight and minimize the need for cooling thereof. Various cooling circuits and features are tailored for these individual components in their corresponding environments in the engine. For example, a series of internal cooling passages, or serpentines, may be formed in a hot gas path component. A cooling fluid may be provided to the serpentines from a plenum, and the cooling fluid may flow through the passages, cooling the hot gas path component substrate and any associated coatings. However, this cooling strategy typically results in comparatively low heat transfer rates and non-uniform component temperature profiles.
Micro-channel cooling has the potential to significantly reduce cooling requirements by placing the cooling as close as possible to the heated region, thus reducing the temperature difference between the hot side and cold side of the main load bearing substrate material for a given heat transfer rate. For certain applications, it is desirable to form channels with narrow openings (relative to the hydraulic diameter of the channel), so that the coating will more easily bridge the channel. For example, it has recently been proposed to machine micro-channels using an abrasive liquid jet. However, it may be challenging to form a sufficiently narrow channel top (restricted opening) in some instances because when the size of the liquid jet nozzle orifice is below about 10 mils (0.0254 mm), the abrasive particles may clog the nozzle, possibly leading to loss of dimensional tolerances, machining flaws, or loss of machine operability.
It would therefore be desirable to form channels with reduced openings (relative to the hydraulic diameter of the channel) to facilitate the application of bridging coatings across the channel openings.
One aspect of the present invention resides in a manufacturing method that includes forming one or more grooves in a component that comprises a substrate with an outer surface. The substrate has at least one interior space. Each groove extends at least partially along the substrate and has a base and a top. The manufacturing method further includes processing an intermediate surface of the component to plastically deform the surface adjacent at least one edge of a respective groove, such that the distance across the top of the groove is reduced.
Another aspect of the present invention resides in a manufacturing method that includes forming one or more grooves in a component that comprises a substrate with an outer surface. The substrate has at least one interior space. Each groove extends at least partially along the substrate and has a base and a top. The manufacturing method further includes processing an intermediate surface of the component to plastically facet the intermediate surface in the vicinity of the groove.
Yet another aspect of the present invention resides in a component that includes a substrate comprising an outer surface and an inner surface, where the inner surface defines at least one hollow, interior space. The component defines one or more grooves. Each groove extends at least partially along the substrate and has a base and a top, and each groove narrows at the respective top thereof, such that each groove comprises a re-entrant shaped groove. An intermediate surface of the component is faceted in the vicinity of the respective groove. One or more access holes are formed through the base of a respective groove, to connect the groove in fluid communication with the respective hollow interior space. The component further includes at least one coating disposed over at least a portion of the surface of the substrate. The groove(s) and the coating together define one or more re-entrant shaped channels for cooling the component.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The modifier “about” used in connection with a quantity is inclusive of the stated value, and has the meaning dictated by context, (e.g., includes the degree of error associated with measurement of the particular quantity). In addition, the term “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.
Moreover, in this specification, the suffix “(s)” is usually intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., “the passage hole” may include one or more passage holes, unless otherwise specified). Reference throughout the specification to “one embodiment,” “another embodiment,” “an embodiment,” and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. Similarly, reference to “a particular configuration” means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the configuration is included in at least one configuration described herein, and may or may not be present in other configurations. In addition, it is to be understood that the described inventive features may be combined in any suitable manner in the various embodiments and configurations.
The gas turbine system 10 may include a number of hot gas path components 100. A hot gas path component is any component of the system 10 that is at least partially exposed to a high temperature flow of gas through the system 10. For example, bucket assemblies (also known as blades or blade assemblies), nozzle assemblies (also known as vanes or vane assemblies), shroud assemblies, transition pieces, retaining rings, and compressor exhaust components are all hot gas path components. However, it should be understood that the hot gas path component 100 of the present invention is not limited to the above examples, but may be any component that is at least partially exposed to a high temperature flow of gas. Further, it should be understood that the hot gas path component 100 of the present disclosure is not limited to components in gas turbine systems 10, but may be any piece of machinery or component thereof that may be exposed to high temperature flows.
When a hot gas path component 100 is exposed to a hot gas flow, the hot gas path component 100 is heated by the hot gas flow and may reach a temperature at which the hot gas path component 100 is substantially degraded or fails. Thus, in order to allow system 10 to operate with hot gas flow at a high temperature, increasing the efficiency, performance and/or life of the system 10, a cooling system for the hot gas path component 100 is required.
In general, the cooling system of the present disclosure includes a series of small channels, or micro-channels, formed in the surface of the hot gas path component 100. For industrial sized power generating turbine components, “small” or “micro” channel dimensions would encompass approximate depths and widths in the range of 0.25 mm to 1.5 mm, while for aviation sized turbine components channel dimensions would encompass approximate depths and widths in the range of 0.1 mm to 0.5 mm. The hot gas path component may be provided with a protective coating. A cooling fluid may be provided to the channels from a plenum, and the cooling fluid may flow through the channels, cooling the hot gas path component.
A manufacturing method is described with reference to
The substrate 110 is typically cast prior to forming the groove(s) 132. As discussed in U.S. Pat. No. 5,626,462, Melvin R. Jackson et al.,“Double-wall airfoil,” which is incorporated herein in its entirety, substrate 110 may be formed from any suitable material. Depending on the intended application for component 100, this could include Ni-base, Co-base and Fe-base superalloys. The Ni-base superalloys may be those containing both γ and γ′ phases, particularly those Ni-base superalloys containing both γ and γ′ phases wherein the γ′ phase occupies at least 40% by volume of the superalloy. Such alloys are known to be advantageous because of a combination of desirable properties including high temperature strength and high temperature creep resistance. The substrate material may also comprise a NiAl intermetallic alloy, as these alloys are also known to possess a combination of superior properties including high temperature strength and high temperature creep resistance that are advantageous for use in turbine engine applications used for aircraft. In the case of Nb-base alloys, coated Nb-base alloys having superior oxidation resistance will be preferred, particularly those alloys comprising Nb-(27-40)Ti-(4.5-10.5)Al-(4.5-7.9)Cr-(1.5-5.5)Hf-(0-6)V, where the composition ranges are in atom per cent. The substrate material may also comprise a Nb-base alloy that contains at least one secondary phase, such as a Nb-containing intermetallic compound comprising a silicide, carbide or boride. Such alloys are composites of a ductile phase (i.e., the Nb-base alloy) and a strengthening phase (i.e., a Nb-containing intermetallic compound). For other arrangements, the substrate material comprises a molybdenum based alloy, such as alloys based on molybdenum (solid solution) with Mo5SiB2 and Mo3Si second phases. For other configurations, the substrate material comprises a ceramic matrix composite, such as a silicon carbide (SiC) matrix reinforced with SiC fibers. For other configurations the substrate material comprises a TiAl-based intermetallic compound.
For the example process shown in
The grooves 132 may be formed using a variety of techniques. Example techniques for forming the groove(s) 132 include abrasive liquid jet, plunge electrochemical machining (ECM), electric discharge machining (EDM) with a spinning electrode (milling EDM), and laser machining. Example laser machining techniques are described in commonly assigned, U.S. patent application Ser. No. 12/697,005, “Process and system for forming shaped air holes” filed Jan. 29, 2010, which is incorporated by reference herein in its entirety. Example EDM techniques are described in commonly assigned U.S. patent application Ser. No. 12/790,675, “Articles which include chevron film cooling holes, and related processes,” filed May 28, 2010, which is incorporated by reference herein in its entirety.
For particular processes, the grooves are formed using an abrasive liquid jet 160 (
In addition, and as explained in U.S. patent application Ser. No. 12/790,675, the water jet system can include a multi-axis computer numerically controlled (CNC) unit 210 (
Referring now to
For particular processes, the intermediate surface 112, 55 of the component 100 is processed by shot peening. In addition, shot peening typically introduces a number of surface irregularities in the intermediate surface 112, 55 of the component 100. Beneficially, the surface irregularities may aid in the bridging of coatings deposited over the surface, and especially coatings deposited using ion plasma deposition, electron beam physical vapor deposition, and sputtering.
For other processes, the intermediate surface 112, 55 of the component 100 is processed by burnishing the intermediate surface 112, 55. A variety of burnishing techniques may be employed, depending on the material being surface treated and on the desired deformation. Non-limiting examples of burnishing techniques include plastically massaging the intermediate surface of the component, for example using rollers, pins, or balls, and low plasticity burnishing.
The distance across the top of the groove will vary based on the specific application. However, for certain configurations, the distance across the top 146 of the groove 132 is in a range of about 8-25 mil (0.2-0.6 mm) prior to processing the intermediate surface 112, 55 of the component 100, and the distance across the top 146 of the groove 132 is in a range of about 0-15 mil (0-0.4 mm) after the intermediate surface 112, 55 has been processed.
For particular processes, the step of processing the intermediate surface 112, 55 of the component 100 also facets the intermediate surface 112, 55 in the vicinity of the groove 132. As used herein, “faceting” should be understood to tilt the intermediate surface in the vicinity of the groove inward, as indicated, for example, in the circled regions in
The grooves 132 may be formed in the substrate 110 (
As indicated, for example, in
For particular configurations, the coating 150 has a thickness in the range of 0.1-2.0 millimeters, and more particularly, in the range of 0.2 to 1 millimeter, and still more particularly 0.2 to 0.5 millimeters for industrial components. For aviation components, this range is typically 0.1 to 0.25 millimeters. However, other thicknesses may be utilized depending on the requirements for a particular component 100.
The coating 150 comprises structural coating layers and may further include optional additional coating layer(s). The coating layer(s) may be deposited using a variety of techniques. For particular processes, the structural coating layer(s) are deposited by performing an ion plasma deposition (cathodic arc). Example ion plasma deposition apparatus and method are provided in commonly assigned, US Published Patent Application No. 10080138529, Weaver et al, “Method and apparatus for cathodic arc ion plasma deposition,” which is incorporated by reference herein in its entirety. Briefly, ion plasma deposition comprises placing a consumable cathode formed of a coating material into a vacuum environment within a vacuum chamber, providing a substrate 110 within the vacuum environment, supplying a current to the cathode to form a cathodic arc upon a cathode surface resulting in arc-induced erosion of coating material from the cathode surface, and depositing the coating material from the cathode upon the substrate surface 112.
Non-limiting examples of a coating deposited using ion plasma deposition include structural coatings, as well as bond coatings and oxidation-resistant coatings, as discussed in greater detail below with reference to U.S. Pat. No. 5,626,462, Jackson et al.,“Double-wall airfoil.” For certain hot gas path components 100, the structural coating comprises a nickel-based or cobalt-based alloy, and more particularly comprises a superalloy or a (Ni,Co)CrAlY alloy. For example, where the substrate material is a Ni-base superalloy containing both γ and γ′ phases, structural coating may comprise similar compositions of materials, as discussed in greater detail below with reference to U.S. Pat. No. 5,626,462.
For other process configurations, a structural coating is deposited by performing at least one of a thermal spray process and a cold spray process. For example, the thermal spray process may comprise combustion spraying or plasma spraying, the combustion spraying may comprise high velocity oxygen fuel spraying (HVOF) or high velocity air fuel spraying (HVAF), and the plasma spraying may comprise atmospheric (such as air or inert gas) plasma spray, or low pressure plasma spray (LPPS, which is also known as vacuum plasma spray or VPS). In one non-limiting example, a (Ni,Co)CrAlY coating is deposited by HVOF or HVAF. Other example techniques for depositing the structural coating include, without limitation, sputtering, electron beam physical vapor deposition, electroless plating, and electroplating.
For certain configurations, it is desirable to employ multiple deposition techniques for depositing structural and optional additional coating layers. For example, a first structural coating layer may be deposited using an ion plasma deposition, and a subsequently deposited layer and optional additional layers (not shown) may be deposited using other techniques, such as a combustion spray process or a plasma spray process. Depending on the materials used, the use of different deposition techniques for the coating layers may provide benefits in properties, such as, but not restricted to strain tolerance, strength, adhesion, and/or ductility.
For the particular process illustrated by
Beneficially, the above-described manufacturing method reduces the top surface opening size of the grooves. As reduced channel opening size markedly enhances the ability of coatings to bridge the opening directly (without the use of a sacrificial filler), machining specifications may be relaxed, such that, for example, relatively large abrasive liquid jet nozzles may be employed, reducing machining time and cost.
Another manufacturing method is described with reference to
As indicated, for example in
The manufacturing method typically further includes casting the substrate 110 prior to forming the groove(s) 132. As noted above, suitable techniques for forming the groove(s) include, without limitation, abrasive liquid jet, plunge electrochemical machining (ECM), electric discharge machining (EDM) with a spinning electrode (milling EDM), and laser machining.
Returning now to
For particular processes, the intermediate surface 112, 55 of the component 100 is shot peened. As indicated, for example in
As noted above, the grooves 132 may be formed in the substrate 110 or in an inner layer of a structural coating 54 (
A component 100 embodiment of the invention is described with reference to
For the example shown in
Although only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
