Turbine bucket profile

The subject matter disclosed herein relates to turbomachines. More particularly, the subject matter disclosed herein relates to components within turbomachines such as gas and/or steam turbines.

Some aircraft and/or power plant systems, for example certain jet aircraft, nuclear, simple cycle and combined cycle power plant systems, employ turbines (also referred to as turbomachines) in their design and operation. Some of these turbines employ airfoils (e.g., turbine blades, blades, airfoils, etc.) which during operation are exposed to fluid flows. These airfoils are configured to aerodynamically interact with the fluid flows and generate energy (e.g., creating thrust, turning kinetic energy to mechanical energy, thermal energy to mechanical energy, etc.) from these fluid flows as part of power generation. As a result of this interaction and conversion, the aerodynamic characteristics and losses of these airfoils have an impact on system and turbine operation, performance, thrust, efficiency, and power.

Various embodiments of the invention include turbine buckets and systems employing such buckets. Various particular embodiments include a turbine bucket having: an airfoil having: a suction side; a pressure side opposing the suction side; a leading edge spanning between the pressure side and the suction side; and a trailing edge opposing the leading edge and spanning between the pressure side and the suction side; and a base connected with a first end of the airfoil along the suction side, pressure side, trailing edge and the leading edge, the base including a non-axisymmetric contour proximate a junction between the base and the airfoil.

A first aspect of the invention includes a turbine bucket having: an airfoil having: a suction side; a pressure side opposing the suction side; a leading edge spanning between the pressure side and the suction side; and a trailing edge opposing the leading edge and spanning between the pressure side and the suction side; and a base connected with a first end of the airfoil along the suction side, pressure side, trailing edge and the leading edge, the base including a non-axisymmetric contour proximate a junction between the base and the airfoil.

A second aspect of the invention includes a turbine rotor section including: a set of buckets, the set of buckets including at least one bucket having: an airfoil having: a suction side; a pressure side opposing the suction side; a leading edge spanning between the pressure side and the suction side; and a trailing edge opposing the leading edge and spanning between the pressure side and the suction side; and a base connected with a first end of the airfoil along the suction side, pressure side, trailing edge and the leading edge, the base including a non-axisymmetric contour proximate a junction between the base and the airfoil, wherein at least one of the suction side or the pressure side of the airfoil includes a nominal profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in TABLE I, wherein the Z coordinate values are non-dimensional values of from 0 to 1 convertible to Z distances by multiplying the Z values by an airfoil height expressed in units of distance, and wherein X and Y values connected by smooth continuing arcs define airfoil profile sections at each distance Z along the airfoil, the profile sections at the Z distances being joined smoothly with one another to form the airfoil profile, the X, Y, and Z distances being scalable as a function of the same constant or number to provide a scaled up or scaled down airfoil, wherein the Cartesian coordinate values have an origin at a root of the leading edge of the airfoil.

A third aspect of the invention includes a turbine bucket having: an airfoil having: a suction side; a pressure side opposing the suction side; a leading edge spanning between the pressure side and the suction side; and a trailing edge opposing the leading edge and spanning between the pressure side and the suction side; and a base connected with a first end of the airfoil along the suction side, pressure side, trailing edge and the leading edge, wherein at least one of the suction side or the pressure side of the airfoil includes a nominal profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in TABLE I, wherein the Z coordinate values are non-dimensional values of from 0 to 1 convertible to Z distances by multiplying the Z values by an airfoil height expressed in units of distance, and wherein X and Y values connected by smooth continuing arcs define airfoil profile sections at each distance Z along the airfoil, the profile sections at the Z distances being joined smoothly with one another to form the airfoil profile, the X, Y, and Z distances being scalable as a function of the same constant or number to provide a scaled up or scaled down airfoil, wherein the Cartesian coordinate values have an origin at a root of the leading edge of the airfoil.

These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which:

FIG. 1 shows a three-dimensional partial cut-away perspective view of a portion of a turbine according to an embodiment of the invention.

FIG. 2 shows a schematic three-dimensional depiction of a turbine bucket including an airfoil and a base according to various embodiments of the invention.

FIG. 3 shows an example contour plot of the base surface surrounding the airfoil of FIG. 2 according to various embodiments of the invention.

FIG. 4 shows a schematic three-dimensional depiction of a plurality of turbine buckets according to various embodiments of the invention.

FIG. 4A shows a schematic three-dimensional depiction of a turbine bucket including an airfoil and a base according to various embodiments of the invention.

FIG. 5 shows a schematic block diagram illustrating portions of a multi-shaft combined cycle power plant system according to embodiments of the invention; and

FIG. 6 shows a schematic block diagram illustrating portions of a single-shaft combined cycle power plant system according to embodiments of the invention.

It is noted that the drawings of the invention are not necessarily to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. It is understood that elements similarly numbered between the FIGURES may be substantially similar as described with reference to one another. Further, in embodiments shown and described with reference to FIGS. 1-6 , like numbering may represent like elements. Redundant explanation of these elements has been omitted for clarity. Finally, it is understood that the components of FIGS. 1-6 and their accompanying descriptions may be applied to any embodiment described herein.

As noted herein, various aspects of the invention are directed toward turbine buckets. Particular aspects of the invention include turbine buckets having a base with a non-axisymmetric contour.

In contrast to conventional turbine buckets, aspects of the invention include a turbine bucket (e.g., a dynamic bucket for driving a turbine shaft) having a non-axisymmetric contour at its base. This non-axisymmetric contour can provide for enhanced performance, efficiency and/or durability of the bucket (and associated turbine stages and turbine machines) when compared with conventional buckets.

As used herein, the terms “axial” and/or “axially” refer to the relative position/direction of objects along axis A, which is substantially parallel to the axis of rotation of the turbomachine (in particular, the rotor section). As further used herein, the terms “radial” and/or “radially” refer to the relative position/direction of objects along axis (r), which is substantially perpendicular with axis A and intersects axis A at only one location. Additionally, the terms “circumferential” and/or “circumferentially” refer to the relative position/direction of objects along a circumference which surrounds axis A but does not intersect the axis A at any location. Further, the term leading edge refers to components and/or surfaces which are oriented upstream relative to the fluid flow of the system, and the term trailing edge refers to components and/or surfaces which are oriented downstream relative to the fluid flow of the system.

In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific embodiments in which the present teachings may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present teachings and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present teachings. The following description is, therefore, merely exemplary.

Referring to the drawings, FIG. 1 shows a perspective partial cut-away illustration of a turbine 10 (e.g., a gas or steam turbine) according to various embodiments of the invention. Turbine 10 includes a rotor 12 that includes a rotating shaft 14 and a plurality of axially spaced rotor wheels 18 . A plurality of rotating buckets 20 (dynamic buckets) are mechanically coupled to each rotor wheel 18 . More specifically, buckets 20 are arranged in rows that extend circumferentially around each rotor wheel 18 . A static nozzle section 21 is shown including a plurality of stationary nozzles 22 circumferentially around shaft 14 , and nozzles 22 are axially positioned between adjacent rows of buckets 20 . Stationary nozzles 22 cooperate with buckets 20 to form a stage of turbine 10 , and to define a portion of a flow path through turbine 10 . As shown, static nozzle section 21 at least partially surrounds rotor 12 (shown in this cut-away view). It is understood that turbine 10 shown is a dual-flow turbine 10 that includes an axially centered inlet mouth which feeds two sets of turbine stages. It is understood that turbine 10 may be a single-flow turbine that includes a single inlet which feeds one set or turbine stages. It is understood that various teachings can be applied to axial turbines, e.g., axial inlet gas turbines that inlet a combustion gas from a first axial end and outlet that combustion gas to a second axial end after the gas has performed mechanical work on the turbine.

Returning to FIG. 1 , in operation, gas 24 enters an inlet 26 of turbine 10 and is channeled through stationary nozzles 22 . Nozzles 22 direct gas 24 against blades 20 . Gas 24 passes through the remaining stages imparting a force on buckets 20 causing shaft 14 to rotate. At least one end of turbine 10 may extend axially away from rotating shaft 12 and may be attached to a load or machinery (not shown) such as, but not limited to, a generator, and/or another turbine.

In one embodiment, turbine 10 may include five stages. The five stages are referred to as L 0 , L 1 , L 2 , L 3 and L 4 . Stage L 4 is the first stage and is the smallest (in a radial direction) of the five stages. Stage L 3 is the second stage and is the next stage in an axial direction. Stage L 2 is the third stage and is shown in the middle of the five stages. Stage L 1 is the fourth and next-to-last stage. Stage L 0 is the last stage and is the largest (in a radial direction). It is to be understood that five stages are shown as one example only, and each turbine may have more or less than five stages. Also, as will be described herein, the teachings of the invention do not require a multiple stage turbine. In another embodiment, turbine 10 may comprise an aircraft engine used to produce thrust.

Turning to FIG. 2 , a schematic three-dimensional depiction of a turbine bucket (or simply, bucket) 200 is shown according to various embodiments. Bucket 200 is a rotatable (dynamic) bucket which is part of a set of buckets circumferentially dispersed about a rotor shaft in a stage of a turbine (e.g., turbine 10 ). That is, during operation of a turbine (e.g., turbine 10 ), bucket 200 will rotate about axis A as a working fluid (e.g., gas or steam) is directed across the bucket's airfoil, initiating rotation of a rotor shaft (e.g., shaft 14 ). It is understood that bucket 200 is configured to couple (mechanically couple via fasteners, welds, slot/grooves, etc.) with a plurality of similar or distinct buckets (e.g., buckets 200 or other buckets) to form an set of buckets in a stage of the turbine.

Returning to FIG. 2 , turbine bucket 200 can include an airfoil 202 having a suction side 204 (obstructed in this view), and a pressure side 206 opposing suction side 204 . Bucket 200 can also include a leading edge 208 spanning between pressure side 206 and suction side 204 , and a trailing edge 210 opposing leading edge 208 and spanning between pressure side 206 and suction side 204 .

As shown, bucket 200 can also include a base 212 connected with airfoil 202 . Base 212 can be connected with airfoil 202 along suction side 204 , pressure side 206 , trailing edge 210 and leading edge 208 . In various embodiments, bucket 200 includes a fillet 214 proximate a first end 215 of airfoil 202 , fillet 214 connecting airfoil 202 and base 212 . Fillet 214 can include a weld or braze fillet, which may be formed via conventional MIG welding, TIG welding, brazing, etc. Fillet 214 can include such forms as integral to the investment casting process or definition. As is known in the art, base 212 is designed to fit into a mating slot in the turbine rotor shaft (e.g., shaft 14 ) and mate with adjacent base components of other buckets 200 . The base 212 is designed to be located radially inboard of airfoil 202

As described herein, and in contrast to conventional turbine buckets, turbine bucket 200 can include a base 212 with a non-axisymmetric contour 218 proximate a junction 220 between base 212 and airfoil 202 . That is, bucket 200 includes a base 212 with a contour 218 proximate junction 220 between base 212 and airfoil 202 that improves the flow area around airfoil 202 when compared with conventional buckets.

In various embodiments, contour 218 allows for more efficient fluid flow across airfoil 202 than conventional buckets, allowing for fewer heat-related failures, and improving the efficiency of fluid flow within a turbine utilizing such a bucket 200 .

With reference to FIG. 1 , in various embodiments, bucket 200 can include a first stage bucket (L 4 ) or second stage bucket (L 3 ). In particular embodiments, bucket 200 is a second stage bucket (L 3 ), and the improved flow profile across airfoil 200 and base 212 interface allows that first stage bucket (L 4 ) to withstand the high-heat gas entering turbine 10 at that first stage. In various embodiments, turbine 10 can include a set of buckets 200 in only first stage (L 4 ) of turbine 10 , or in only first stage (L 4 ) and second stage (L 3 ) of turbine 10 .

According to various embodiments, non-axisymmetric contour 218 includes a first surface 222 along base 212 on suction side 204 of leading edge 208 , and a second surface 224 along base 212 on pressure side 206 of leading edge 208 . Second surface 224 and first surface 222 can have distinct slopes, e.g., distinct radial v. circumferential ratios. In various embodiments, first surface 222 has a distinct profile from second surface 224 . In some cases, the distinct profile includes distinct base features (e.g., bump(s), trough(s), etc.) in first surface 222 as compared with second surface 224 (having its own endwall features (e.g., bump(s), trough(s), etc.). In some cases, second surface 224 has a substantially flat, or unsloped gradient, and first surface 222 has a gradient distinct from the gradient of the second surface, e.g., a gradient that is positive or negative, but not equal to zero.

According to various particular embodiments, first surface 222 has a first length L 1 measured from a junction 228 of suction side 204 and leading edge 208 of airfoil 202 along base 212 to an outer edge 230 of base 212 . In these embodiments, second surface 224 has a second length L 2 measured from a junction 232 of pressure side 206 and leading edge 208 of airfoil 202 along base 212 to an inner edge 234 of base 212 . In various embodiments, the first length L 1 is distinct from the second length L 2 , and in particular embodiments, second length L 2 is greater than first length L 1 .

Turning to FIG. 3 , a radial contour map of a portion of bucket 200 (excluding the base 212 ) is shown according to various embodiments. As can be seen in this example radial contour map, the contour 218 (shown in two parts as a leading edge pressure side feature 218 A and a leading edge suction side feature 218 B) can aid in improving aerodynamic efficiency proximate leading edge 208 of bucket 200 . The radial contour map also shows a passage trough 250 on suction side 204 of bucket 200 .

With reference to FIG. 2 and FIG. 3 , according to various particular embodiments, non-axisymmetric contour 218 includes at least one bump (thickened area) 260 and a passage trough 250 on suction side 204 of bucket 200 . In particular embodiments, leading edge pressure side feature 218 A can include at least one bump (thickened area) 260 , and leading edge suction side feature 218 B can include at least one bump (thickened area) 260 . It is understood that according to various embodiments, bump (thickened area) 260 along the leading edge pressure side 218 A can be thicker than bump 260 along leading edge suction side 218 B (extending a greater distance toward the opposite base 212 from second surface 224 than bump 260 extends toward the opposite endwall from first surface 222 ).

In various particular embodiments, each bump (thickened area) 260 can have an apex at approximately 0-5 percent of axial chord length L A (along axis A) of endwall 212 . In some particular cases, each thickened area 260 can have an approximately 0-10 percent pitch from the suction side 204 .

In various particular embodiments, at least one bump 260 (within 218 A) can have an apex at approximately 75% of the axial chord length from suction side 204 (+/−10%). In these cases, bump 260 can have an approximately 0-10% pitch as measured from suction side 204 .

In various embodiments, passage trough 250 includes a depression having an apex at approximately 15-20% of the chord length of suction side 204 (+/−10%). In this case, the depression in pressure trough 250 can have a 20-25% pitch as measured from suction side 204 .

It is understood that in various embodiments, other apex locations and pitches are possible, and those values given herein are merely illustrative of several of the many possible embodiments in accordance with the disclosure.

With reference to FIGS. 4 and 4A (and continuing reference to FIGS. 2-3 ), in various embodiments, airfoil 202 may have an airfoil shape at 5-15% of span S to fit airfoil 202 on a straight platform 246 of base 212 . A straight platform 246 refers to a platform 246 having a suction side edge 240 and pressure side edge 242 that are aligned with an axis of dovetail 248 . In various particular embodiments, bucket 200 may have an airfoil shape at 10% of span S to fit airfoil 202 on a straight platform 246 of base 212 . In various particular embodiments, bucket 200 may have an airfoil shape near fillet 214 that includes a tucked high “C” region 244 . The high “C” region refers to the bulge of suction side 204 of airfoil 202 . A tucked high “C” region 244 refers to a region of suction side 204 having a reduced bulge. In various particular embodiments, tucked high “C” region 244 near fillet 214 may cause increased cantilever of airfoil 202 at 10-15% span S. In various particular embodiments, tucked high “C” region 244 near fillet 214 may increase the size of airfoil 202 that is able to fit on straight platform 246 .

In various embodiments, an outermost tip 217 of airfoil 202 may have a reduced thickness to improve flex. The reduced thickness of outermost tip 217 of airfoil 202 may also improve blade vibrations, or 2-stripe behavior of airfoil 202 . In various embodiments, a reduced thickness of outermost tip 217 of airfoil 202 may raise the natural frequency of bucket 200 . Raising the natural frequency of bucket 200 may make bucket 200 less affected by vibrations of any upstream or neighboring nozzles, or other components of turbine 10 . Further, raising the natural frequency of bucket 200 may reduce the risk of vibrations in bucket 200 .

With reference to FIG. 4 (and continuing reference to FIGS. 2-3 ), a plurality of points 270 - 278 along span S, including root 215 and tip 217 , can correspond to Z coordinate values of chord lines, and a cross section of airfoil 202 at each point can be described by a respective set of X and Y coordinates. For example, 100 points can be listed for each cross section 270 - 278 , though it should be apparent that more or fewer points can be used for each cross section, and more or fewer cross sections can be used, as may be desired and/or appropriate. The X, Y, and Z coordinate values in TABLE I have been expressed in normalized or non-dimensionalized form in values of from 0 to 1, but it should be apparent that any or all of the coordinate values could instead be expressed in distance units so long as the proportions are maintained. To convert an X, Y or Z value of TABLE I to a respective X, Y or Z coordinate value in units of distance, such as inches or meters, the non-dimensional X, Y or Z value given in TABLE I can be multiplied by an airfoil height of airfoil 202 in such units of distance. By connecting the X and Y values with smooth continuing arcs, each profile cross section at each distance Z can be fixed, and the airfoil profiles of the various surface locations between the distances Z can be determined by smoothly connecting adjacent profile sections to one another, thus forming the airfoil profile.

The values in TABLE I are generated and shown to four decimal places for determining the profile of a nominal airfoil 202 at ambient, non-operating, or non-hot conditions, and do not take any coatings or fillets into account, though embodiments could account for other conditions, coatings, and/or fillets. To allow for typical manufacturing tolerances and/or coating thicknesses, ±values can be added to the values listed in TABLE I, particularly to the X and Y values therein. For example, a tolerance of about 10-20 percent of a thickness of the trailing edge in a direction normal to any surface location along the airfoil profile can define an airfoil profile envelope for a bucket airfoil design at cold or room temperature. In other words, a distance of about 10-20 percent of a thickness of the trailing edge in a direction normal to any surface location along the airfoil profile can define a range of variation between measured points on an actual airfoil surface and ideal positions of those points, particularly at a cold or room temperature, as embodied by the invention. The bucket airfoil design, as embodied by the invention, is robust to this range of variation without impairment of mechanical and aerodynamic functions. Likewise, the profile and/or design can be scaled up or down, such as geometrically, without impairment of operation, and such scaling can be facilitated by use of normalized coordinate values, i.e. multiplying the normalized values by a scaling factor, or a larger or smaller number of distance units than might have originally been used. For example, the values in TABLE I, particularly the X and Y values, could be multiplied by a scaling factor of 2, 0.5, or any other desired scaling factor. In various embodiments, the X, Y, and Z distances are scalable as a function of the same constant or number to provide a scaled up or scaled down airfoil. Alternatively, the values could be multiplied by a larger or smaller desired span. As referenced herein, the origin of the X, Y, Z coordinate system is the root of the leading edge (junction 232 ) of airfoil 202 .

According to various embodiments, and as a result of endwall contour 218 , a region of a passage trough 250 between two airfoils 202 proximate endwall 212 can be affected. For example, a bottom edge of a passage trough 250 between a pair of buckets 200 can vary radially, whereas an endwall without a contour would leave a bottom edge of such a throat as at least a straight line, if not a substantially constant radial distance.

Turning to FIG. 5 , a schematic view of portions of a multi-shaft combined cycle power plant 900 is shown. Combined cycle power plant 900 may include, for example, a gas turbine 980 operably connected to a generator 970 . Generator 970 and gas turbine 980 may be mechanically coupled by a shaft 915 , which may transfer energy between a drive shaft (not shown) of gas turbine 980 and generator 970 . Also shown in FIG. 5 is a heat exchanger 986 operably connected to gas turbine 980 and a steam turbine 992 . Heat exchanger 986 may be fluidly connected to both gas turbine 980 and a steam turbine 992 via conventional conduits (numbering omitted). Gas turbine 980 and/or steam turbine 992 may include one or more buckets 200 as shown and described with reference to FIG. 2 and/or other embodiments described herein. Heat exchanger 986 may be a conventional heat recovery steam generator (HRSG), such as those used in conventional combined cycle power systems. As is known in the art of power generation, HRSG 986 may use hot exhaust from gas turbine 980 , combined with a water supply, to create steam which is fed to steam turbine 992 . Steam turbine 992 may optionally be coupled to a second generator system 970 (via a second shaft 915 ). It is understood that generators 970 and shafts 915 may be of any size or type known in the art and may differ depending upon their application or the system to which they are connected. Common numbering of the generators and shafts is for clarity and does not necessarily suggest these generators or shafts are identical. In another embodiment, shown in FIG. 5 , a single shaft combined cycle power plant 990 may include a single generator 970 coupled to both gas turbine 980 and steam turbine 992 via a single shaft 915 . Steam turbine 992 and/or gas turbine 980 may include one or more buckets 200 shown and described with reference to FIG. 2 and/or other embodiments described herein.

The apparatus and devices of the present disclosure are not limited to any one particular engine, turbine, jet engine, generator, power generation system or other system, and may be used with other aircraft systems, power generation systems and/or systems (e.g., combined cycle, simple cycle, nuclear reactor, etc.). Additionally, the apparatus of the present invention may be used with other systems not described herein that may benefit from the increased reduced tip leakage and increased efficiency of the apparatus and devices described herein.

In various embodiments, components described as being “coupled” to one another can be joined along one or more interfaces. In some embodiments, these interfaces can include junctions between distinct components, and in other cases, these interfaces can include a solidly and/or integrally formed interconnection. That is, in some cases, components that are “coupled” to one another can be simultaneously formed to define a single continuous member. However, in other embodiments, these coupled components can be formed as separate members and be subsequently joined through known processes (e.g., fastening, ultrasonic welding, bonding).

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The foregoing description of various aspects of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to an individual in the art are included within the scope of the invention as defined by the accompanying claims.

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 languages of the claims.