Patent Application
20160186671
The subject matter disclosed herein relates to turbomachines, such as gas turbine engines. More particularly, the present disclosure relates to a fuel purge system for purging and cooling fuel (e.g., liquid fuel) from a turbomachine, such as a gas turbine engine.
Turbomachines often include combustors configured to combust fuel with an oxidant, such as air. One or more fuel manifolds and one or more fuel premixers (which may be parts of one or more fuel nozzles) are configured to distribute one or more types of fuel to each of the combustors. After delivery of fuel to the combustors, residual fuel may remain in the fuel manifolds and/or fuel premixers. For example, residual fuel may stick to internal walls or surfaces of the fuel premixers. Residual fuel may form deposits that could obstruct fuel flow through the premixers. Unfortunately, the residual fuel can cause clogging of the fuel premixers and/or manifolds, or passages extending between the fuel premixers and the manifolds.
Certain embodiments commensurate in scope with the present disclosure are summarized below. These embodiments are not intended to limit the scope of the disclosure, but rather these embodiments are intended only to provide a brief summary of possible forms of the disclosure. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
In a first embodiment, a system includes first fuel premixer configured to distribute a first fuel to a combustor and a purge system configured to purge the first fuel from the first fuel premixer. The purge system includes a discharge line configured to receive a flow of a purge mixture from the first fuel premixer. The purge system also includes an orifice coupled to the discharge line, where the orifice is configured to constrict the flow of the purge mixture. Further, the purge system includes an eductor having an interior, an opening, and an outlet, where the interior is fluidly coupled to the orifice, to the opening, and to the outlet, the purge mixture is configured to flow through the interior from the orifice to the outlet, the flow of the purge mixture through the orifice is configured to, by way of the Venturi effect, draw coolant into interior of the eductor through the opening, and the coolant drawn through the opening is configured to mix with the purge mixture.
In a second embodiment, a purge system for a turbomachine includes a discharge line configured to receive a flow of a purge mixture from a fuel premixer. The purge system also includes an orifice coupled to the discharge line, where the orifice is configured to constrict the flow of the purge mixture. The purge system also includes an eductor, where the eductor includes an interior fluidly coupled openings in the eductor, the orifice, and an outlet. The eductor includes the openings configured to receive a coolant. The eductor also includes the outlet. The purge mixture is configured to flow through the interior from the orifice to the outlet, and the flow of the purge mixture through the orifice is configured to, by way of the Venturi effect, draw the coolant into the eductor through the openings of the eductor.
In a third embodiment, a purge system for a turbomachine includes a discharge line having an orifice and configured to receive a purge mixture from a fuel premixer of the turbomachine, where the purge mixture includes a fuel and compressed air from a compressor of the turbomachine. The purge system also includes an eductor coupled to the discharge line, where the eductor includes at least one eductor opening for drawing in ambient air as the purge mixture flows through the orifice into the eductor.
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:
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
Present embodiments are directed to turbomachines and fuel purge systems for turbomachines, such as gas turbine engines. In particular, present embodiments are directed to a system for purging fuel (e.g., liquid fuel) from a fuel manifold or fuel premixer (or a passage extending between the fuel manifold and the fuel premixer) of a turbomachine, such as a gas turbine engine. For example, one or more combustors of the turbomachine combust one or more fuels with an oxidant, such as air or oxygen. A fuel manifold and one or more fuel premixers (which may be parts of fuel nozzles) deliver the fuel to the one or more combustors. For example, the fuel manifold distributes fuel to the fuel premixers, which may mix the fuel with air (e.g., oxygen). The fuel or fuel-air mixture reacts within the combustors to produce combustion products.
In some embodiments, one or more fuel premixers distribute a pilot fuel to the combustors for an ignition portion (and/or startup portion) of the combustion process (e.g., while the gas turbine is in startup mode). Then, fuel premixers distribute a burn fuel to continue the combustion process (e.g., to transition the gas turbine from the startup mode to a steady state mode). The pilot fuel and the burn fuel may be different, and each fuel may be configured to enhance efficiency of their respective portions of the combustion process (e.g., startup and steady state modes of the gas turbine). In some embodiments, a first fuel manifold may distribute the pilot fuel to the fuel premixers, and a second fuel manifold may distribute the burn fuel to the fuel premixers. In other embodiments, a single type of fuel may be used for the duration of the combustion process. In either configuration, it may be desirable to purge residual fuel in the fuel manifold, fuel premixers, or fuel passageways extending between the fuel manifold and fuel premixers after delivering the fuel to the combustors, such as during shut down or maintenance intervals, or when the portions of the gas turbine directed to delivering fuel are not being used (e.g., after transition from startup to steady state) but still during operation of the gas turbine. Purging the fuel from the fuel manifolds, the fuel premixers, and/or passages or conduits between the fuel manifolds and fuel premixers may reduce or eliminate residual fuel that may block portions of the fuel manifold, fuel premixers, or fuel passages/conduits. Additionally, or in the alternate, residual fuel may coke (e.g., form deposits) within the fuel manifolds, fuel premixers, or fuel passages, which may reduce an efficiency of the gas turbine engine. Purging the fuel may reduce or eliminate coking of fuel in the fuel manifolds or fuel premixers.
In accordance with present embodiments, a purge system is configured to purge the fuel from the fuel manifolds and/or fuel premixers coupled to the fuel manifolds via the fuel passageways. For simplicity, embodiments of the purge system described with reference to the figures will be referred to as a purge system for purging fuel from the fuel premixers, in particular. However, it should be noted that the purge system may also purge fuel from the one or more fuel manifolds (or mini-manifolds thereof), fuel conduits (e.g., passageways), or a combination thereof. For example, each fuel manifold (e.g., for each type of fuel) may include an annular ring configured to distribute fuel to each fuel premixer coupled to the annular ring, where each fuel premixer or nozzle associated with each fuel premixer injects the fuel (and air) into a corresponding one of the combustors. In certain types of dual fuel systems, a different manifold may distribute a different type of fuel to the same fuel premixers. Alternatively, each fuel manifold may distribute its respective type of fuel to a different fuel premixer for each combustor. In general, presently disclosure purge systems may be capable of purging fuel from any fuel manifold and any fuel premixer of any turbomachine, for example, a gas turbine engine.
The purge system, in accordance with present embodiments, may include a purge mechanism configured to route a fluid (e.g., compressed air) through, for example, the fuel premixers. Further, the purge system may include a purge segment that is a bi-directional flow segment of a fuel passageway or conduit that couples between and routes fuel between the fuel manifold and the fuel premixers. Thus, when the fuel manifold delivers fuel to the fuel premixer, the bi-directional purge segment enables the fuel to travel through the bi-directional purge segment to the premixer. When fuel and/or other fluid (e.g., compressed air) is being purged from the fuel premixer, the bi-directional purge segment enables the fuel and/or air to travel through the bi-directional purge segment of the fuel passageway toward the manifold. A juncture in the fuel passageway (e.g., at an end of the bi-directional purge segment) may include a valve or some other flow regulation device that enables the purged fuel and/or air to be routed to a discharge line coupled to the fuel passageway at the juncture.
The purged fuel and air may travel through the discharge line toward an eductor of the purge system, where the eductor is coupled to the discharge line. For example, the discharge line may include an orifice at an end of the discharge line proximate to the eductor, where the orifice is disposed in an inside of the eductor. The orifice generates a pressure drop within the eductor as the purged fuel and compressed fluid (e.g., compressed air) flows through the orifice. The pressure drop may enable ambient air (or some other cooling fluid, such as nitrogen) to be drawn into the eductor through an eductor opening of the eductor. The cooling fluid is configured to mix with the mixture of compressed air and purged fuel, cooling the mixture, which may be hot and otherwise susceptible to combustion. In other words, the cooling fluid (e.g., ambient air or nitrogen) being drawn into the eductor is configured to cool the mixture of compressed air discharge and purged fuel to reduce or negate a susceptibility of the mixture combusting. The mixture of compressed air, purged fuel, and ambient air or nitrogen is routed to a drain pan via a drain line or to a separator that separates and vents and non-fuel contents in the mixture before delivering the fuel contents to the drain pan. In some embodiments, cooling the compressed air and purged fuel with ambient air or nitrogen drawn through the eductor enables the elimination of traditional heat transfer equipment (e.g., heat exchangers, coolers, flame arrestors), thereby reducing the footprint and cost of the purge system.
Turning now to the drawings and referring first to
The illustrated gas turbine engine 10 includes, among other features, fuel premixers 12, fuel manifolds 13, and combustors 16. The gas turbine engine 10 may be a dual fuel gas turbine engine 10, where multiple fuel manifolds 13 supply, via fuel passageways 14, various types of fuel 15 to the fuel premixers 12. For simplicity, only one fuel manifold 13 and fuel supply 15 (and associated fuel passageways 14) is shown, but it should be understood that the illustrated gas turbine engine 10 may include multiple manifolds 13, each being configured to deliver a different type of fuel 15 through respective fuel passageways 14 to the premixers 12. For example, one type of fuel may be used for ignition (e.g., during a startup mode) and another type of fuel may be used for steady state operation of the gas turbine engine 10.
As depicted, the fuel premixers 12 route the fuel 15 (or, in the illustrated embodiment, an air-fuel mixture 18) into the combustors 16. For example, the fuel premixers 12 may initially route a mixture 18 of pilot fuel and air into the combustors 16 to start the combustion process (e.g., for an ignition process and/or startup mode), in accordance with the description above. The fuel premixers 12 may then route a mixture 18 of burn fuel and compressed air into the combustors 16 to continue the combustion process (e.g., for a burn process).
In some embodiments, as described above, the fuel premixers 12 mix the fuel 15 (e.g., received from the fuel passageways 14 extending between the fuel manifold 13 and the premixers 12) with compressed air to form an air-fuel mixture 18 for delivery to the combustors 16. The air-fuel mixture 18 may include the pilot fuel or the burn fuel, depending on the stage of combustion (e.g., ignition process or burn process). The combustors 16 may then combust the mixture 18 to generate combustion products, which are passed to a turbine 20. The combustion products expand through blades or stages of the turbine 20, causing the blades of the turbine 20 to rotate. A coupling between the blades of the turbine 20 and a shaft 22 of the gas turbine engine 10 will cause the shaft 22 to rotate with the blades. The shaft 22 is also coupled to several other components throughout the gas turbine engine 10, as illustrated, such that rotation of the shaft 22 causes rotation of the components coupled to the shaft 22. For example, the illustrated shaft 22 is drivingly coupled to a compressor 24 (which may supply the air for the air-fuel mixture 18) and a load 26. As appreciated, the load 26 may be any suitable device that may generate power via the rotational output of the gas turbine engine 10, such as an electrical generator of a power generation plant or a vehicle.
An air supply 28 may provide air to an air intake 30, which then routes the air into the compressor 24. Indeed, in some embodiments, the air supply 28 may be ambient air surrounding the gas turbine engine 10. Additionally, or in the alternate, the air supply 28 may be an oxidant, such as oxygen. The compressor 24 includes a plurality of blades drivingly coupled to the shaft 22. When the shaft 22 rotates as a result of the expansion of the exhaust gases (e.g., combustion products) within the turbine 20, the shaft 22 causes the blades of the compressor 24 to rotate, which compresses the air supplied to the compressor 24 by the air intake 30 to generate compressed air. The compressed air is routed to the fuel premixers 12 for mixing with the fuel to generate the air-fuel mixture 18, which is then routed to the combustors 16. For example, the fuel premixers 12 may mix the compressed air from the compressor 24 and the fuel 15 from one of the fuel manifolds 13 to produce the air/fuel mixture 18, as previously described. After passing through the turbine 20, the exhaust gases exit the system at an exhaust outlet 34.
As previously described, residual fuel may be left in the fuel manifolds 13 or the fuel premixers 12 after the fuel 15 is delivered to the combustors 16. For example, in dual fuel systems, the pilot fuel may be delivered to the combustors 16 via the fuel premixers 12. It may be beneficial to clear the fuel premixers 12 of the residual fuel left in the fuel premixers 12 after fuel delivery is complete, before combustion occurs in the combustor 16, or before burn fuel is routed from a different (or the same) fuel manifold 13 to the fuel premixers 12, as previously described, for delivery to the combustors 16. Thus, in accordance with the present disclosure, the gas turbine engine 10 includes a purge system 40 configured to purge residual fuel from the fuel premixers 12 to a drain pan 42, such that the residual fuel may be removed from the gas turbine engine 10. In some embodiments, the contents of the drain pan 42 (e.g., purged fuel) may be used for other purposes or reused in the gas turbine engine 10.
In the illustrated embodiment, the product purge system 40 includes bi-directional purge segments 44 (e.g., of the fuel passageways 14), discharge lines 50 extending from the bi-directional purge segments 44 at junctures 47 in the fuel passageways 14, and an eductor 46 configured to receive the discharge line(s) 50. In the illustrated embodiment, each bi-directional purge segment 44 (e.g., of the corresponding fuel passageway 14) is configured to route, during fuel delivery, fuel 15 from the fuel manifold 13 to the fuel premixer 12 in a first direction. Each bi-directional purge segment 44 (e.g., of the corresponding fuel passageway 14) is also configured to receive, during fuel purge, purged fuel 15 and air from the fuel premixer 12 in a second direction opposite to the first direction. For example, as previously described, fuel purge mode may be utilized between startup (e.g., ignition) mode and steady state mode of the gas turbine engine 10, or at any other desirable time. During fuel purge mode, compressed air from the compressor 24 may be routed through the fuel premixers 12 to purge residual fuel from the premixers 12 and into the bi-directional purge segments 44. Junctures 47 may include flow regulation devices (e.g., valves) configured to direct the purged fuel 15 and compressed air into the discharge lines 50. Additionally, or in the alternate, flow regulation devices 48 disposed on the discharge lines 50 downstream of the junctures 47 may be configured to enable the purged fuel 15 and/or air to enter and/or travel through the discharge lines 50. In other words, the portion of compressed air supplied by the compressor 24 is configured to urge residual fuel through (and out of) the fuel premixers 12, through the bi-directional purge segments 44 of the fuel passageways 14, and into the discharge line 50 (e.g., via flow regulation at the junctures 47 or via the flow regulation devices 48). Thus, the purge system 40 may purge the fuel premixers 12 and portions of the fuel passageways 14 (e.g., conduits, hoses, etc.). It should be noted that the flow regulation devices 48 may be valves configured to selectively restrict flow (e.g., to increase pressure) into and through the discharge lines 50, or the flow regulation devices 48 may be compressors or other devices configured to draw a pressure down relative to the fuel passageways 14 or bi-directional flow segments 44 thereof. Flow regulation devices at the junctures 47 may operate to enable or disable fluid communication between the bi-directional purge segment 44 and the fuel manifold 13 to disable or enable, respectively, fuel purge.
It should be noted that, in some embodiments, mini-manifolds may be disposed upstream of the fuel premixers 12, and may also be purged by the purge system 40. Further still, in some embodiments, the bi-directional purge segment 44 of the fuel passageway 14 may extend the entire length of the passageway 14 between the fuel manifold 13 and the fuel premixer 12, enabling purging of the entire fuel passageway 14 and, in some embodiments, the fuel manifold 13 itself. The presently disclosed purge system 40 is configured to purge residual fuel in any portion or component of the fuel manifolds 13, the fuel premixers 12, and/or the fuel passageways 14. Indeed, in some embodiments, the purge system 40 may additionally purge residual, unburned fuel (and/or other residual matter, such as flash residue, pollutants, etc.) from the combustors 16. Further, one of ordinary skill in the art would recognize that presently disclosed embodiments of the purge system 40 may be employed in a dual fuel gas turbine engine 10 or a single fuel gas turbine engine 10, as fuel manifolds 13 and fuel premixers 12 may be susceptible to coking of residual fuel in either configuration.
Continuing with
To enable the above described Venturi effect, the eductor 46 (or the discharge line 50 extending up to and, in some embodiments, into the eductor 46) includes an orifice through which the flow of the mixture passes (e.g., where the orifice enables a converging section upstream or as part of the orifice, a throat at the orifice, and a diverging section downstream of the orifice). The orifice may generate a pressure drop as the mixture flows through the orifice (e.g., within or immediately adjacent the eductor 46), such that the pressure drop draws ambient air or nitrogen into the eductor 46 through the eductor opening 56 and increases a velocity of the mixture as it passes through the orifice. The ambient air or nitrogen mixes with the mixture of compressed air discharge and purged fuel, thereby cooling the mixture. The cooled mixture (e.g., including the ambient air or nitrogen) flows out of the eductor 46 and toward and into the drain pan 42. However, in some embodiments, a separator 41 may be disposed between the eductor 46 and the drain pan 42, and may be configured to separate the purged fuel from any other contents (e.g., compressed air and/or contaminants), such that the drain pan 42 only receives the purged fuel.
It should be noted, however, that the coolant drawn into the eductor 46 through the eductor opening 56 may not be ambient air. For example, a nitrogen tank (or some other coolant tank) may be coupled with the eductor opening 56, such that nitrogen (or some other coolant) is drawn into the eductor 46 via the above-described Venturi effect. Further, it should be noted that, in the illustrated embodiment, only one purge system 40 associated with one fuel manifold 13 is shown. However, as previously described, the gas turbine engine 10 may include multiple fuel manifolds 13 (e.g., 2, 3, 4, or more fuel manifolds 13), each being configured to supply a different type of fuel to the fuel premixers 12 (and, thus the combustors 16) depending on a stage or mode of operation of the gas turbine engine 10. In such embodiments, each fuel manifold 13 may include its own purge system 40, e.g., the gas turbine engine 10 may include three fuel manifolds 13 and three purge systems 40.
Turning now to
As the mixture 70 passes through the orifice 72 and enters into the interior 76 of the eductor 46, the mixture 70 continues to flow in direction 55 toward an outlet 78 of the eductor 46. The mixture 70 may be biased toward the outlet 78 via gravity or, in the illustrated embodiment, via acceleration of the mixture 70 as the mixture 70 passes through the orifice 72 of the discharge line 50. However, gravity and inertia may also promote continued (or accelerated) flow of the mixture 70 toward the outlet 78 of the eductor 46.
It should be noted that the illustrated orifice 72 is a portion of the discharge line 50 extending into the eductor 46. However, in some embodiments, the discharge line 50 may coupled to the eductor 46, where the eductor 46 includes an internal flow path on the inside of the eductor 46 that couples to the discharge line 50 and includes the orifice 72. In either configuration, the mixture 70 flows into the eductor 46 and through the orifice 72, which generates the pressure drop as described above.
As the mixture 70 flows toward the outlet 78 of the eductor 46, fluid or coolant 79 (e.g., ambient air, nitrogen, etc.) is drawn into the eductor 46 through the opening 56 in the eductor 46 from the environment 58. It should be noted, however, that a different type of coolant 79 may be drawn in to the eductor 46 from a different source. For example, a coolant source (e.g., nitrogen tank) may be coupled to the opening 56, where the coolant 79 (e.g., nitrogen) is drawn in from the coolant source (e.g., nitrogen tank).
In the illustrated embodiment, the opening 56 is disposed upstream of the orifice 72 of the discharge line 50 (relative to direction 55). The coolant 79 is drawn into the eductor 46 through the opening 56 in the eductor 46 via the flow of the mixture 70 through the orifice 72. For example, a pressure drop is generated proximate to the end 74 (e.g., within the interior 76 of the eductor 46) of the discharge line 50 via the orifice 72 of the discharge line 50. To balance the pressure differential, coolant 79 from the environment 58 (or coolant source) is automatically drawn into the eductor 76 through the opening 56. The coolant 79 is drawn into a flow path of the mixture 70, such that the coolant 79 mixes with the mixture 70. The coolant 79 cools the mixture 70 as the mixture 70 travels toward the outlet 78 of the eductor 46 and into a drain line 80 of the purge system 40. The cooled mixture 70 is routed in direction 55 through the drain line 80 toward the separator 41, which separates the fuel from any other contents of the cooled mixture 70 (e.g., air). Residual contents (e.g., not the purged fuel) is vented via vent 84, and the purged fuel is routed to the drain pan 42 downstream of the separator 41 for storage or for reuse.
In some embodiments, the purge system 40 includes additional features. For example, in the illustrated embodiment in
Turning now to
Focusing first on the embodiment of the purge system 40 shown in
The illustrated orifice 72 is configured to restrict a cross-sectional width of the flow path through which the mixture 70 (e.g., of compressed air and purged fuel) travels. The illustrated eductor 46 also includes orifice openings 104 directly downstream of the orifice 72, where the orifice openings 104 are configured to further restrict the flow path through which the mixture 70 travels. In other words, the orifice openings 104 increase the pressure differential (e.g., pressure drop, static pressure drop, static pressure differential) between the interior 76 and the environment 58 generated by the flow of the mixture 70 through the orifice 72. As the mixture 70 accelerates through the orifice 72 and the orifice openings 104 via the static pressure drop, coolant 79 is drawn into the interior 76 of the eductor 46 through the multiple openings 56 disposed through the surface 102 of the eductor 46, via the Venturi effect as previously described. The air drawn in through the openings 56 cools the mixture 70 as the mixture 70 travels into and through the drain line 80 toward the drain pan 42.
As indicated above,
It should be noted that, in other embodiments, the eductor 46 may include more than four openings 56 or less than four openings 56. For example, the eductor 46 may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more openings 56. The eductor 46 also include more than four orifice openings 104 or less than four orifice openings 104. For example, the eductor 46 may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more orifice openings 104. Further, the eductor 46 may include a greater number of openings 56 than orifice openings 104. Alternatively, the eductor 46 may include fewer openings 56 than orifice openings 104. Furthermore, depending on the embodiment, the openings 56 may or may not be aligned with the orifice openings 104. The number of openings 56 and orifice openings 104, their positions relative to each other, and the geometry of the openings 56 and orifice openings 104 may vary depending on the amount of ambient air needed to be drawn into the eductor 46 to cool the mixture 70 (e.g., of compressed air discharge and fuel) passing through the eductor 46. For example, a cross-sectional front view of another embodiment of the eductor 46 is shown in
Turning now to
In accordance with the present disclosure, embodiments are directed to a purge system for purging fuel from a fuel premixer, manifold, or conduits of a turbomachine. The purge system includes an eductor configured to draw in ambient air or nitrogen for cooling a mixture of the fuel, and a compressed air flow configured to clear the fuel from the premixers (or manifolds, conduits, passageways, or other equipment). The ambient air or nitrogen cools the mixture before the mixture is delivered to a separator and/or drain pan (where the drain pan may receive only purged fuel from the mixture), thereby reducing a risk of the mixture igniting or combusting before or after delivery to the drain pan. Disclosed embodiments of the product purge system reduce cost associated with manufacturing, storage, and operation of equipment used in traditional mechanisms.
It should be noted that the particular pressures, temperatures, and flow rates of the various flows of fluids described above may vary depending on the type, size, orientation, application, and/or function of the turbomachine. For example, the pressure of the mixture flowing into the eductor (which may be a function of the pressure of the compressed air discharge used to purge the fuel from the fuel manifold) may be in the range of approximately 50 to 500 pounds per square inch absolute (psia), 150 to 400 psia, or 250 to 300 psia. The temperature of the mixture flowing into the eductor may be in the range or approximately 400 to 850 degrees Fahrenheit (F), 500 to 750 degrees F., or 600 to 650 degrees F. The flow rate of the mixture flowing into the eductor may range from 0.08 pounds per second (lbs/sec) to 0.30 lbs/sec, 0.15 lbs/sec to 0.23 lbs/sec, or 0.18 to 0.20 lbs/sec. The max temperature of the mixture (or fuel) flowing into the drain line may be in the range of approximately 130 to 150 degrees F., 135 to 145 degrees F., or 138 to 142 degrees F.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
