Compressor cooling in a gas turbine engine
11060530 ยท 2021-07-13
Assignee
Inventors
Cpc classification
F04D29/584
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F04D29/582
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F05D2260/20
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
Y02T50/60
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
F04D29/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F01D5/084
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F01D5/085
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F05D2220/3216
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
Abstract
A gas turbine engine includes a combustion section and a compressor section, the compressor section including a high pressure compressor. The high pressure compressor includes an aft-most compressor stage and an upstream compressor stage, each of the aft-most compressor stage and the upstream compressor stage including a rotor disk. The gas turbine engine also includes a high pressure spool assembly, the high pressure spool assembly including a rotor disk, and an airflow member extending from the rotor disk of the high pressure spool assembly to the rotor disk of the upstream compressor stage of the high pressure compressor to define in part a compressor cooling air passage outward of the airflow member along a radial direction.
Claims
1. A gas turbine engine defining a radial direction and comprising: a combustion section; a compressor section comprising a high pressure compressor, the high pressure compressor comprising an aft-most compressor stage and an upstream compressor stage, each of the aft-most compressor stage and the upstream compressor stage comprising a rotor disk; a high pressure spool assembly, the high pressure spool assembly comprising a rotor disk; and an airflow member extending from the rotor disk of the high pressure spool assembly to the rotor disk of the upstream compressor stage of the high pressure compressor to define in part a compressor cooling air passage outward of the airflow member along the radial direction; and a plurality of cooling holes, wherein a cooling airflow originating from airflow downstream of the aft-most compressor stage and in fluid communication with an outlet guide vane passes through the cooling air passage and then through the cooling holes to provide cooling air to one or more components of the high pressure compressor.
2. The gas turbine engine of claim 1, wherein the rotor disk of the upstream compressor stage comprises a rotor bore, wherein the rotor disk of the high pressure spool assembly comprises a rotor bore, and wherein the airflow member extends from the rotor bore of the rotor disk of the high pressure spool assembly to the rotor bore of the rotor disk of the upstream compressor stage.
3. The gas turbine engine of claim 1, wherein the airflow member is positioned inward of the rotor disk of the aft-most compressor stage along the radial direction.
4. The gas turbine engine of claim 3, wherein the high pressure compressor further comprises an intermediate compressor stage located between the aft-most compressor stage and the upstream compressor stage, wherein the intermediate compressor stage comprises a rotor disk, and wherein the airflow member extends inward of the rotor disk of the intermediate compressor stage along the radial direction.
5. The gas turbine engine of claim 4, wherein the rotor disk of the intermediate compressor stage comprises a rotor bore, and wherein the airflow member comprises at least one of a metering feature or an airflow directing feature operable with the rotor bore of the rotor disk of the intermediate compressor stage to modify an airflow between the rotor bore of the rotor disk of the intermediate compressor stage and the airflow member.
6. The gas turbine engine of claim 1, wherein the high pressure spool assembly further comprises a cone arm extending from the rotor disk of the high pressure spool assembly to the rotor disk of the aft-most compressor stage of the high pressure compressor.
7. The gas turbine engine of claim 6, wherein the combustion section comprises the outlet guide vane located downstream of the high pressure compressor and an inner support arm supporting the outlet guide vane, wherein the inner support arm and the cone arm together define at least in part a forward seal cavity, wherein the gas turbine engine further comprises: a compressor cooling air system, wherein the compressor cooling air system is configured to provide compressor cooling air to the forward seal cavity, and wherein the high pressure spool assembly defines one or more airflow openings extending from the forward seal cavity to the compressor cooling air passage.
8. The gas turbine engine of claim 7, wherein the cone arm defines the one or more airflow openings extending from the forward seal cavity to the compressor cooling air passage.
9. The gas turbine engine of claim 7, wherein the combustion section comprises a compressor discharge pressure seal at least partially sealing off the forward seal cavity, and wherein at least a portion of the compressor discharge pressure seal is coupled to the high pressure spool assembly.
10. The gas turbine engine of claim 1, wherein the airflow downstream of the aft-most compressor stage is airflow through a forward compressor discharge pressure seal cavity.
11. The gas turbine engine of claim 10, wherein the airflow member comprises a plurality of airflow features extending into the compressor cooling air cavity, and wherein the plurality of airflow features extend generally along an axial direction of the gas turbine engine.
12. The gas turbine engine of claim 1, wherein the airflow member extends continuously and directly from the rotor disk of the high pressure spool assembly to the rotor disk of the upstream compressor stage.
13. The gas turbine engine of claim 1, wherein the compressor section defines in part a core air flowpath through the gas turbine engine, wherein the rotor disk of the upstream compressor stage defines a cooling hole in airflow communication with the cooling air passage to provide a cooling airflow from the cooling air passage to one or more components of the upstream compressor stage exposed to the core air flowpath.
14. The gas turbine engine of claim 1, wherein the compressor section defines in part a core air flowpath through the gas turbine engine, wherein the aft-most compressor stage is stage N of the high pressure compressor, wherein the high pressure compressor further comprises a stage N1 having a rotor disk and located immediately upstream of the stage N, wherein the high pressure compressor further comprises a catenary arm extending from the rotor disk of the stage N to the rotor disk of the stage N1, and wherein the catenary arm, the rotor disk of the stage N1, or both defines a cooling hole to provide a cooling airflow from the cooling air passage to one or more components of the high pressure compressor exposed to the core air flowpath.
15. A gas turbine engine defining a radial direction and comprising: a combustion section; a compressor section comprising a high pressure compressor, the high pressure compressor comprising an aft-most compressor stage and an upstream compressor stage, each of the aft-most compressor stage and the upstream compressor stage comprising a rotor disk; a high pressure spool assembly, the high pressure spool assembly comprising a rotor disk; and an airflow member extending from the rotor disk of the high pressure spool assembly to the rotor disk of the upstream compressor stage of the high pressure compressor to define in part a compressor cooling air passage outward of the airflow member along the radial direction; wherein the high pressure spool assembly further comprises a cone arm extending from the rotor disk of the high pressure spool assembly to the rotor disk of the aft-most compressor stage of the high pressure compressor; wherein the combustion section comprises an outlet guide vane located downstream of the high pressure compressor and an inner support arm supporting the outlet guide vane, wherein the inner support arm and the cone arm together define at least in part a forward seal cavity, and wherein the gas turbine engine further comprises: a compressor cooling air system, the compressor cooling air system configured to provide compressor cooling air to the forward seal cavity, the high pressure spool assembly defining one or more airflow openings extending from the forward seal cavity to the compressor cooling air passage; and wherein the high pressure spool assembly comprises an airflow flange, wherein the airflow flange defines the one or more airflow openings such that the forward seal cavity is in airflow communication with the compressor cooling air passage through the airflow flange.
16. A cooling air passage assembly for a gas turbine engine comprising a high pressure compressor and a high pressure spool assembly, the high pressure compressor comprising an aft-most compressor stage and an upstream compressor stage, each of the aft-most compressor stage, the upstream compressor stage, and the high pressure spool assembly comprising a rotor disk, the cooling air passage assembly comprising: an airflow member extending from a first attachment end to a second attachment end, the first attachment end configured for attachment to the rotor disk of the upstream compressor stage of the high pressure compressor, and the second attachment end configured for attachment to the rotor disk of the high pressure spool assembly to define in part a compressor cooling air passage; an airflow flange comprising a plurality of apertures located downstream of the aft-most compressor stage and in fluid communication with both a forward compressor discharge pressure seal cavity and the cooling air passage.
17. The cooling air passage assembly of claim 16, wherein the airflow member comprises a plurality of airflow features configured to extend into the compressor cooling air cavity.
18. The cooling air passage assembly of claim 17, wherein the plurality of airflow features extend generally along an axial direction of the gas turbine engine when the cooling air passage is installed in the gas turbine engine.
19. The cooling air passage assembly of claim 16, wherein the airflow member extends continuously from the first attachment end to the second attachment end.
20. The cooling air passage assembly of claim 16, further comprising: a metering feature extending from the airflow member for metering an airflow over the airflow member.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended Figs., in which:
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DETAILED DESCRIPTION
(10) Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention.
(11) As used herein, the terms first, second, and third may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.
(12) The terms forward and aft refer to relative positions within a gas turbine engine or vehicle, and refer to the normal operational attitude of the gas turbine engine or vehicle. For example, with regard to a gas turbine engine, forward refers to a position closer to an engine inlet and aft refers to a position closer to an engine nozzle or exhaust.
(13) The terms upstream and downstream refer to the relative direction with respect to fluid flow in a fluid pathway. For example, upstream refers to the direction from which the fluid flows, and downstream refers to the direction to which the fluid flows.
(14) The terms coupled, fixed, attached to, and the like refer to both direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching through one or more intermediate components or features, unless otherwise specified herein.
(15) The singular forms a, an, and the include plural references unless the context clearly dictates otherwise.
(16) Approximating language, as used herein throughout the specification and claims, is 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, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. For example, the approximating language may refer to being within a 10 percent margin.
(17) Here and throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.
(18) Referring now to the drawings, wherein identical numerals indicate the same elements throughout the Figs.,
(19) The exemplary turbomachine 16 depicted generally includes a substantially tubular outer casing 18 that defines an annular inlet 20. The outer casing 18 encases, in serial flow relationship, a compressor section including a booster or low pressure (LP) compressor 22 and a high pressure (HP) compressor 24; a combustion section 26; a turbine section including a high pressure (HP) turbine 28 and a low pressure (LP) turbine 30; and a jet exhaust nozzle section 32. The compressor section, combustion section 26, turbine section, and exhaust nozzle section 32 together define at least in part a core air flowpath 37 through the turbomachine 16. A high pressure (HP) shaft or spool 34 (or rather a high pressure spool assembly, as described below) drivingly connects the HP turbine 28 to the HP compressor 24. A low pressure (LP) shaft or spool 36 drivingly connects the LP turbine 30 to the LP compressor 22.
(20) For the embodiment depicted, the fan section 14 includes a variable pitch fan 38 having a plurality of fan blades 40 coupled to a disk 42 in a spaced apart manner. As depicted, the fan blades 40 extend outwardly from disk 42 generally along the radial direction R. Each fan blade 40 is rotatable relative to the disk 42 about a pitch axis P by virtue of the fan blades 40 being operatively coupled to a suitable actuation member 44 configured to collectively vary the pitch of the fan blades 40 in unison. The fan blades 40, disk 42, and actuation member 44 are together rotatable about the longitudinal axis 12 by LP shaft 36 across a power gear box 46. The power gear box 46 includes a plurality of gears for stepping down the rotational speed of the LP shaft 36 to a more efficient rotational fan speed.
(21) Referring still to the exemplary embodiment of
(22) During operation of the turbofan engine 10, a volume of air 58 enters the turbofan 10 through an associated inlet 60 of the nacelle 50 and/or fan section 14. As the volume of air 58 passes across the fan blades 40, a first portion of the air 58 as indicated by arrows 62 is directed or routed into the bypass airflow passage 56 and a second portion of the air 58 as indicated by arrow 64 is directed or routed into the LP compressor 22. The ratio between the first portion of air 62 and the second portion of air 64 is commonly known as a bypass ratio. The pressure of the second portion of air 64 is then increased as it is routed through the high pressure (HP) compressor 24 and into the combustion section 26, where it is mixed with fuel and burned to provide combustion gases 66. Subsequently, the combustion gases 66 are routed through the HP turbine 28 and the LP turbine 30, where a portion of thermal and/or kinetic energy from the combustion gases 66 is extracted.
(23) The combustion gases 66 are then routed through the jet exhaust nozzle section 32 of the turbomachine 16 to provide propulsive thrust. Simultaneously, the pressure of the first portion of air 62 is substantially increased as the first portion of air 62 is routed through the bypass airflow passage 56 before it is exhausted from a fan nozzle exhaust section 76 of the turbofan 10, also providing propulsive thrust.
(24) Moreover, as is depicted schematically, the exemplary turbofan engine 10 further includes various accessory systems to aid in the operation of the turbofan engine 10. For example, the exemplary turbofan engine 10 further includes a compressor cooling air system 80 for providing cooled air to one or more components of the HP compressor 24. The compressor cooling air system 80 will be described in greater detail below.
(25) It should be appreciated, however, that the exemplary turbofan engine 10 depicted in
(26) Referring now to
(27) Referring first to the HP compressor 24, the HP compressor 24 generally includes a plurality of stages. For example, the HP compressor 24 generally includes an aft-most compressor stage 100 and an upstream compressor stage 102. The upstream compressor stage 102 may be immediately upstream of the aft-most compressor stage 100, or alternatively, such as in the embodiment depicted, may be positioned further upstream of the aft-most compressor stage 100. More particularly, for the exemplary embodiment depicted, the HP compressor 24 further includes an intermediate compressor stage 104 located between the aft-most compressor stage 100 and the upstream compressor stage 102 (i.e. forward of the aft-most compressor stage 100 and aft of the upstream compressor stage 102).
(28) Each of the compressor stages 100, 102, 104 may also be referred to relative to the total number, N, of compressor stages of the HP compressor 24. For example, the aft-most compressor stage 100 may also be referred to as stage N, the intermediate compressor stage 104 may also be referred to as stage N1, and the upstream compressor stage 102 may also be referred to as stage N2.
(29) Moreover, it will be appreciated that each of the various stages of the HP compressor 24 generally includes a plurality of compressor rotor blades 106 and a rotor disk 108. Each of the plurality of compressor rotor blades 106 of a given stage are coupled to the respective rotor disk 108, such that the plurality of compressor rotor blades 106 and rotor disk 108 rotate together during operation. As will be discussed in greater detail below, each of the rotor disks 108 generally includes an attachment portion 110, a rotor web 112, and a rotor bore 114. The attachment portion 110 it is, for the embodiment shown, a circumferential slot, such as a circumferential dovetail slot, for receiving a correspondingly shaped portion of a base 116 of the respective compressor rotor blades 106. However, in other exemplary embodiments, any other suitable configuration may be provided for attaching the plurality of compressor rotor blades 106 of a given stage to a rotor disk 108 of such stage. For example, in other exemplary embodiments, the attachment portion 110 of the rotor disk 108 may define one or more axial slots, or alternatively, the compressor rotor blades and rotor disk 108 may be formed together as a blisk.
(30) Referring still to
(31) For the embodiment depicted, each of the stages of the HP compressor 24 further comprises a plurality of compressor stator vanes 120. In such a manner, the HP compressor 24 includes a row of compressor stator vanes 120 positioned between adjacent rows of compressor rotor blades 106. The compressor stator vanes 120 are operable to modify an airflow through a portion of the core air flowpath 37 defined at least in part by the HP compressor 24. Each of the compressor stator vanes 120 depicted generally defines an inner end 122 along the radial direction R and includes a seal member 124 at the inner end 122.
(32) Accordingly, it will be appreciated that the HP compressor 24 is configured to form a seal between rotating components and stationary components between adjacent stages. More specifically, for the embodiment shown, each of the catenary arms 118 between rotor disks 108 of adjacent stages of the HP compressor 24 includes seal teeth 126 operable with respective seal members 124 at the inner ends 122 of the compressor stator vanes 120 to form a seal therebetween. Such may increase an efficiency of the HP compressor 24 by preventing relatively high pressure air at an upstream end of the compressor stator vane 120 from flowing around the inner end 122 to a relatively low pressure location at a downstream end of the compressor state vane 120.
(33) Furthermore, as will be appreciated, the HP compressor 24 is driven through a high pressure spool assembly 128 (the high pressure spool assembly 128 depicted as, and described above with reference to, numeral 34 in
(34) Referring still to
(35) As will also be appreciated, the combustion section 26 further includes a plurality of fuel-air mixers 156 configured to mix the compressed air within the forward combustion cavity 148 with fuel and provide such fuel-air mixture to a combustion chamber 158 to generate combustion gases.
(36) Furthermore, as briefly noted above with reference to
(37) Moreover, as is depicted, the inner OGV support arm 152 and cone arm 130 of the high pressure spool assembly 128 together define at least in part a forward seal cavity, or more particularly for the embodiment depicted, a forward compressor discharge pressure (CDP) seal cavity 166. The inner OGV support arm 152 defines one or more openings 168 allowing for a flow of the compressor cooling air 164 therethrough to the forward CDP seal cavity 166. As will be discussed in greater detail below, the compressor cooling air 164 provided to the CDP seal cavity 166 will subsequently be used to cool at least one or more components of the HP compressor 24.
(38) Notably, positioned within the forward CDP seal cavity 166 is a CDP seal 170. The CDP seal 170 generally includes a stationary seal member 172 coupled to the inner OGV support arm 152 and a rotating seal tooth assembly 174. At least a portion of the CDP seal 170 is coupled to the high pressure spool assembly 128, or more specifically, the rotating seal tooth assembly 174 is coupled to the high pressure spool assembly 128. More specifically, still, the rotating seal tooth assembly 174 is coupled to the high pressure spool assembly 128 at the joint 142. The rotating seal tooth assembly 174 is configured to form a seal with the stationary seal number 172 to meter an amount of airflow from the forward CDP seal cavity 166 that is allowed aft to the turbine section.
(39) Referring still to
(40) More particularly, referring now to
(41) As may be seen in
(42) Further, as is depicted in
(43) Notably, by utilizing the airflow flange 182 to provide the compressor cooling air 164 to the cooling air passage 180, the compressor cooling air 164 flowing therethrough may also be rotated in the circumferential direction C during operation by virtue of the rotation of the airflow flange 182 and apertures 194 therein. Such may prevent the compressor cooling air 164 from unnecessarily heating up when reaching the cooling air cavity 180.
(44) Referring back to
(45) It will be appreciated, however, that the airflow member 200 depicted in
(46) Further, as is depicted, the HP compressor 24 includes features for providing the compressor cooling air 164 provided to the cooling air passage 180 through the joint 142 to one or more components of the HP compressor 24 exposed to the core air flowpath 37. More specifically, as shown, the catenary arm 118 extending between the rotor disks 108 of the aft-most compressor stage and intermediate compressor stage 104, the catenary arm 118 extending between the rotor disks 108 of the intermediate compressor stage 104 and the upstream compressor stage 102, the rotor disk 108 of the upstream compressor stage 102, the rotor disk 108 of the intermediate compressor stage 104, or a plurality of these components define one or more cooling holes 202 to allow compressor cooling air 164 from the cooling air passage 180 to one or more components of the HP compressor 24 exposed to the core air flowpath 37 to cool the one or more components of the HP compressor 24 exposed to the core air flowpath 37. Notably, as used herein, the term exposed to the core air flowpath 37 generally refers to such component being in contact with an airflow through the core air flowpath 37.
(47) More specifically, for the embodiment depicted, each of the rotor disk 108 of the upstream compressor stage 102, the rotor disk 108 of the aft-most compressor stage 100, and the rotor disk 108 of the intermediate compressor stage 104 define cooling holes 202 to allow the compressor cooling air 164 from the cooling air passage 180 to the one or more components of the HP compressor 24 exposed to the core air flowpath 37 to cool the one or more components of the HP compressor 24 exposed core air flowpath 37. For the embodiment shown, the one or more components exposed to the core air flowpath 37 include the attachment portions 110 of the rotor disks 108, the seal teeth 126 of the catenary arms 118, etc.
(48) Notably, as mentioned above, the exemplary rotor disks 108 depicted are configured as circumferential rotor disks, which may assist with dispersing the compressor cooling air 164 provided through the cooling holes 202. However, it should be appreciated that in other embodiments, the rotor disks 108 may instead be configured as axial disks (i.e., wherein the compressor rotor blades 106 are inserted generally along the axial direction A), or alternatively, may be configured as blisks (i.e., wherein the rotor disks 108 and airflow portion of the compressor rotor blades 106 are formed integrally of a single material), or in any other suitable manner. Further, in other exemplary embodiments, the cooling holes 202 may be defined in other locations and/or by other components to cool the one or more components of the HP compressor 24 exposed to the core air flowpath 37.
(49) Furthermore, referring still to
(50) Moreover, it will be appreciated that in other exemplary embodiments, the airflow member 200 may have any other suitable configuration. For example, referring now to
(51) For example, as is shown, the gas turbine engine 10 generally includes an airflow member 200 extending from a rotor disk 132 of a high pressure spool assembly 128 to a rotor disk 108 of an upstream compressor stage 102 of an HP compressor 24. In such a manner, the airflow member 200 defines a compressor cooling air passage 180 outward of the airflow member 200 along a radial direction R of the gas turbine engine 10. However, for the embodiment shown, the airflow member 200 further includes a plurality of airflow features 206 extending into the compressor cooling air passage 180. For example, the plurality of airflow features 206 extend, for the embodiment depicted, generally along an axial direction A of the gas turbine engine 10, e.g., inward of the rotor disk 108 of an aft-most compressor stage 100 of the HP compressor 24, and further, between the rotor disks 108 of the intermediate compressor stage 104 and upstream compressor stage 102. Notably, however, in other exemplary embodiments, the plurality of airflow features 206 may instead extend at any other suitable location along the airflow member 200.
(52) Referring now particularly to
(53) Furthermore, it will be appreciated that in still other exemplary embodiments, the gas turbine engine 10 may have any other suitable configuration. For example, in other exemplary embodiments, the compressor section, combustion section 26, and/or turbine section may include any other suitable configuration of compressor(s), turbine(s), combustor(s), support member(s), etc.
(54) Additionally, referring now to
(55) For example, as is depicted, the gas turbine engine 10 generally includes a compressor cooling air system 80. As with the embodiment above, for the embodiment of
(56) Additionally, as with the other embodiments described above, the high pressure spool assembly 128 defines one or more airflow openings 178 extending from the forward CDP seal cavity 166 to a compressor cooling air passage 180 defined at least in part by an airflow member 200 extending from a rotor disk 132 of the high pressure spool assembly 128 to a rotor disk 108 of an upstream compressor stage 102 of the HP compressor 24. By contrast, however, for the embodiment of
(57) It will be appreciated that including an airflow member in a gas turbine engine in accordance with one or more of the exemplary embodiments described herein may allow for an HP compressor of a compressor section of the gas turbine engine to reach higher pressures, leading to a higher overall pressure ratio of the compressor section, which in turn may result in an overall more efficient gas turbine engine. More specifically, inclusion of an airflow member in accordance with one or more embodiments of the present disclosure may allow for the gas turbine engine to duct the compressor cooling air to one or more compressor stages positioned forward of an aft-most compressor stage (e.g., an upstream compressor stage and/or an intermediate compressor stage), which may allow for these compressor stages to reach higher pressures without damaging the components exposed to such higher pressure air.
(58) 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 include 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.