Patent Application
20140116660
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 an acceptably 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 to enhance the integrity of coatings deposited over the channels.
It would therefore be desirable to form micro-channels in a hot gas path component with relatively narrower openings.
One aspect of the present invention resides in a method of fabricating a component, where the component includes a substrate having an outer surface and an inner surface, where the inner surface defines at least one interior space. The fabrication method includes forming at least one groove in the outer surface of the substrate. Each groove extends at least partially along the outer surface of the substrate and has an asymmetric cross-section. The fabrication method further includes forming at least one access hole in the substrate, where each access hole connects the respective groove in fluid communication with the respective interior space and disposing a coating over at least a portion of the surface of the substrate, such that the groove(s) and the coating together define one or more channels for cooling the component.
Another aspect of the invention resides in a method of fabricating a component, where the component includes a substrate having an outer surface and an inner surface, where the inner surface defines at least one interior space. The fabrication method includes disposing a structural coating on the outer surface of the substrate, and forming at least one groove at least partially in the structural coating. Each groove extends at least partially along the outer surface of the structural coating and has an asymmetric cross-section. The fabrication method further includes forming at least one access hole in the substrate. Each access hole connects the groove in fluid communication with the respective interior space. The fabrication method further includes disposing a coating over at least a portion of the surface of the structural coating, such that the groove(s) and the coating together define one or more channels for cooling the component.
Yet another aspect of the invention resides in a component that includes a substrate having an outer surface and an inner surface, where the inner surface defines at least one interior space. At least one groove extends at least partially along the outer surface of the substrate and has an asymmetric cross-section. At least one access hole is formed in the substrate and connects each groove in fluid communication with the respective interior space. At least one coating is disposed over at least a portion of the surface of the substrate, such that the groove(s) and the coating together define one or more 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 flow of high temperature 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 turbine 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 flow of high temperature 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, as required to achieve the desired efficiency, performance and/or life of the system 10, a cooling system for the hot gas path component 100 is needed.
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 fabrication 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 a/., “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)A1-(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/or Mo3Si second phases. For other configurations, the substrate material comprises a ceramic matrix composite (CMC), such as a silicon carbide (SiC) matrix reinforced with SiC fibers. For other configurations the substrate material comprises a TiAl-based intermetallic compound.
Referring now to
As indicated in
The interior access holes 140 supplying the respective grooves may be drilled either as a straight hole of constant cross section, a shaped hole (elliptical etc.), or a converging or diverging hole. Methods for forming the access holes are provided in commonly assigned U.S. patent application Ser. No. 13/210,697, Ronald S. Bunker et al., “Components with cooling channels and methods of manufacture,” which is incorporated by reference herein in its entirety. For particular processes, the access hole(s) 140 may be formed using abrasive liquid jet, which is described in detail below.
Referring now to
Non-limiting examples of a structural coating deposited using ion plasma deposition are described in U.S. Pat. No. 5,626,462, Jackson et a/., “Double-wall airfoil”. For certain hot gas path components 100, the structural coating 54 comprises a nickel-based or cobalt-based alloy, and more particularly comprises a superalloy or a (Ni,Co)CrAlY alloy. 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 U.S. Pat. No. 5,626,462. Additionally, for superalloys the structural coating 54 may comprise compositions based on the γ′-Ni3Al family of alloys.
More generally, the structural coating composition will be dictated by the composition of the underlying substrate. For example, for CMC substrates, such as a silicon carbide (SiC) matrix reinforced with SiC fibers, the structural coating will typically include silicon.
For other process configurations, the 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, entrapment plating, and electroplating.
As indicated, for example, in
For particular configurations, the structural coating 54 and additional coating 150 have a combined 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 layer(s) may be deposited using a variety of techniques. Example deposition techniques for forming structural coatings are provided above. In addition to structural coatings, bond coatings, TBCs and oxidation-resistant coatings may also be deposited using the above-noted techniques.
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 thermal 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 particular processes, the coating 150 is applied at an angle of incidence that is approximately normal to the outer surface 112 of the substrate 110. See, for example,
Similarly, for the process shown in
As noted above, a number of techniques may be used to form the grooves 132. For the exemplary process shown in
Example abrasive liquid jet drilling processes and systems are provided 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. As explained in U.S. patent application Ser. No. 12/790,675, the abrasive liquid jet process typically utilizes a high-velocity stream of abrasive particles (e.g., abrasive “grit”), suspended in a stream of high pressure water. The pressure of the liquid may vary considerably, but is often in the range of about 35-620 MPa. A number of abrasive materials can be used, such as garnet, aluminum oxide, silicon carbide, and glass beads. Beneficially, the capability of abrasive liquid jet machining techniques facilitates the removal of material in stages to varying depths and with control over the shape of the machined features. This allows the interior access holes 140 that supply the channel to be drilled either as a straight hole of constant cross section, a shaped hole (e.g., elliptical), or a converging or diverging hole (not shown).
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 (
In addition, the step of forming the groove 132 may further include performing at least one additional pass, where the abrasive liquid jet 160 is directed toward a base 134 of the groove 132 at one or more angles between the lateral angle and a direction 52 substantially normal to the outer surface 112 of the substrate 110, such that material is removed from the base 134 of the groove 132. It should be noted that as used here “base” is the lower portion of the groove, and includes the end portion 137 of the groove, where the two sides of the groove come together. For these asymmetric grooves, the base will typically be curved, at least in part, and will not be purely flat. See for example,
Previous micro-channel cooling strategies have focused on the creation of essentially symmetric channel shaping where the interior shape or volume is mirror-imaged about the channel centerline. Symmetry provides a natural means for the balancing of flow and thermal effects. Symmetry may never be fully achieved, but within reasonable tolerances of machine accuracy and method, prior channels may be deemed symmetric.
The asymmetric channels of the present invention provide machining and coating integrity benefits, as described in further detail herein. However, the decreased opening width will also lead to a lesser channel volume unless compensated for by other changes such as depth or shaping. Such shaping changes will also accommodate desired local stress concentration factor reductions.
The specific geometry of the groove will vary based on the specific application. However, for certain configurations the base 134 of a groove 132 is at least two times wider than the top 146 of the respective groove 132. For particular configurations, the base 134 is at least 3 times wider than the top 146 of the respective groove 132, and more particularly, is in a range of about 3-4 times wider than the top 146 of the respective groove 132.
For specific configurations, a first wall 138 of a respective groove 132 is oriented at an angle φ in a range of about 10-80 degrees relative to a surface normal 52. See, for example,
In addition to forming grooves with an asymmetric cross-section in the substrate, as discussed above, grooves with asymmetric cross-sections may also be formed, at least partially in a structural coating. This alternative method of fabricating a component 100 is described with reference to
Beneficially, by so favoring one side of the geometry, the tool used in the machining process need only be angled in one direction from the normal rather than in opposite directions, thereby decreasing the resultant opening width of the channel. As the opening width of the channel is a key dimension in determining the integrity of the coatings applied over the channels, this reduced opening width may result in improved coating integrity over the channels. Additionally, when additional surface treatment is performed, such as peening, the initially smaller channel opening will be closed down relatively more, since only the one side of the channel (angled side) will be affected to any significant degree, more so as the angle of wall 138 is increased. Surface treatment of components with micro-channel cooling is described in commonly assigned U.S. patent applications Ser. No. 13/242,179, Ronald Scott Bunker et al., entitled “Components with cooling channels and methods of manufacture,” and Ser. No. 13/595,120, “Components with cooling channels and methods of manufacture,” both of which US Patent Applications are incorporated herein in their entirety.
Referring now to
Referring now to
As indicated in
Example techniques for depositing the coating are described above. For particular processes, the coating 150 is applied at an angle of incidence that is approximately normal to the outer surface 112 of the substrate 110. See, for example,
Similarly, for the process shown in
The grooves with asymmetric cross-sections may be formed partially or entirely within the structural coating 54. For the exemplary configuration shown in
The grooves 132 formed at least partially in the structural coating 54 may have the same geometries described above for the grooves formed in the substrate. For example, for particular configurations, a first wall 138 of a respective groove 132 may be oriented at an angle φ in a range of about 10-80 degrees relative to a surface normal 52. See, for example,
A component 100 embodiment of the invention is described with reference to
As indicated in
The coating may completely or only partially cover the grooves 132. For the configuration shown in
As noted above, depending on the specific configuration, the grooves may be located entirely within the substrate, entirely within the structural coating, or partially in the structural coating and extending into the substrate. For the configuration shown in
Various geometries for the grooves 132 with asymmetric cross-sections are described above. For example, for particular configurations, the base 134 of a respective groove 132 is at least 2 times wider than the top 146 of the respective groove 132. As noted above, the “base” is the lower portion of the groove, and includes the end portion 137 of the groove, where the two sides of the groove come together. For these asymmetric grooves, the base will typically be curved, at least in part, and will not be entirely flat. More particularly, the base 134 is at least 3 times wider than the top 146 of the respective groove 132, and still more particularly, is in a range of about 3-4 times wider than the top 146 of the respective groove 132.
The walls 138, 139 may be angled in a number of different orientations. Particular configurations are described above with reference to
Beneficially, incorporation of the above described asymmetric cooling channels serves to promote decreased channel openings for better coating durability, and to allow more flexibility in machining of channels on three-dimensional and spatially restricted surfaces. Commercially, this facilitates the use of more efficient designs with fewer compromises impacting performance and cost.
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.
