Captured compliant coil seal

A combustor seal system for a gas turbine engine is provided that includes a rear inner discharge nozzle (RIDN) configured to engage a liner of a combustor. The system further includes a nozzle guide vane (NGV) positioned adjacent the RIDN. The NGV and the RIDN together define a cavity. The system further includes a seal in contact with the RIDN and positioned in the cavity. The seal curves along a surface of the cavity and contacts the RIDN at a first point and a second point in the cavity. The seal contacts the NGV at a third point.

TECHNICAL FIELD

This disclosure relates to combustor systems and, in particular, to combustor seal systems.

BACKGROUND

Present combustor sealing systems suffer from a variety of drawbacks, limitations, and disadvantages. Accordingly, there is a need for inventive systems, methods, components, and apparatuses described herein.

DETAILED DESCRIPTION

In one example, a combustor seal system for a gas turbine engine is provided that includes a rear inner discharge nozzle (RIDN) configured to engage a liner of a combustor. The system further includes a nozzle guide vane (NGV) positioned adjacent the RIDN. The NGV and the RIDN together define a cavity. The system further includes a seal in contact with the RIDN and positioned in the cavity. The seal curves along a surface of the cavity and contacts the RIDN at a first point and a second point in the cavity. The seal contacts the NGV at a third point.

In another example, a combustor seal assembly for a gas turbine engine is provided that includes a seal comprising a first end, a second end, and a seal body extending between the first end and the second end. The assembly further includes a rear inner discharge nozzle (RIDN) comprising an upstream portion and a downstream portion relative to a primary flow path of the gas turbine engine. The assembly further includes a nozzle guide vane (NGV). The NGV is positioned adjacent the RIDN, the RIDN and the NGV together defining a cavity. The seal is positioned in the cavity. The seal curves along a surface of the cavity. The seal contacts the upstream portion of the RIDN at a first point and a second point, and the seal contacts the NGV at a third point.

In yet another example, a method of assembly of a combustor seal system is provided. A rear inner discharge nozzle (RIDN) is provided, the RIDN comprising an upstream portion and a downstream portion relative to a primary flow path of a gas turbine engine. A seal is positioned on the RIDN, the seal comprising a first end, a second end, and a seal body extending between the first end and the second end. A nozzle guide vane (NGV) and the RIDN are positioned adjacent to each other, the RIDN and the NGV together defining a cavity. The seal is positioned in the cavity and curves along a surface of the cavity. The seal contacts the upstream portion of the RIDN at a first point and a second point. The seal contacts the NGV at a third point.

One interesting feature of the systems and methods described herein may be to limit or prevent cooling fluid, such as air, from flowing into a combustion chamber. Such systems and methods include a rear inner discharge nozzle, a nozzle guide vane, and a seal positioned to prevent airflow between the rear inner discharge nozzle and the nozzle guide vane. Because the rear inner discharge nozzle and the nozzle guide vane often move with respect to each other, conventional seals are often exposed to wear from rubbing. Additionally, conventional systems require multiple sealing pieces, which increase the number of potential failure points and the number of potential air leakage points.

FIG. 1is a cross-sectional view of a portion of gas turbine engine100. In some examples, the gas turbine engine100may supply power to and/or provide propulsion of an aircraft. Examples of the aircraft may include a helicopter, an airplane, an unmanned space vehicle, a fixed wing vehicle, a variable wing vehicle, a rotary wing vehicle, an unmanned combat aerial vehicle, a tailless aircraft, a hover craft, and any other airborne and/or extraterrestrial (spacecraft) vehicle. Alternatively or in addition, the gas turbine engine100may be utilized in a configuration unrelated to an aircraft such as, for example, an industrial application, an energy application, a power plant, a pumping set, a marine application (for example, for naval propulsion), a weapon system, a security system, a perimeter defense or security system.

The gas turbine engine100may take a variety of forms in various embodiments. Though depicted as an axial flow engine, in some forms the gas turbine engine100may have multiple spools and/or may be a centrifugal or mixed centrifugal/axial flow engine. In some forms, the gas turbine engine100may be a turboprop, a turbofan, or a turboshaft engine. Furthermore, the gas turbine engine100may be an adaptive cycle and/or variable cycle engine. Other variations are also contemplated.

The gas turbine engine100may include an intake section (not shown), a compressor section102, a combustion section104, a turbine section106, and an exhaust section (not shown). During operation of the gas turbine engine100, fluid received from the intake section, such as air, may be compressed within the compressor section102. The compressed fluid may then be mixed with fuel and the mixture may be burned in the combustion section104. The combustion section104may include any suitable fuel injection and combustion mechanisms. The hot, high pressure fluid may then pass through the turbine section106to extract energy from the fluid and cause a turbine shaft of a turbine in the turbine section106to rotate, which in turn drives the compressor section102. Discharge fluid may exit the exhaust section.

The combustor section104includes a combustor108, which defines a combustion chamber110. The combustor108and a combustion rear inner casing112define a second chamber114, which may contain some of the compressed fluid received from the compressor section102. The gas turbine engine100may include a system200for sealing the combustor108of the gas turbine engine100positioned between the combustion section104and the turbine section106. The system200may prevent or limit the flow of fluid from the second chamber114to the combustion chamber110.

FIG. 2illustrates in more detail the circled region labelled R inFIG. 1. In particular,FIG. 2illustrates a cross-sectional view of a first example of the system200for sealing the combustor108of the gas turbine engine100. The example of the system200illustrated inFIG. 2includes a rear inner discharge nozzle (RIDN)202, a nozzle guide vane (NGV)204, and a seal206. The RIDN202may include an upstream portion208relative to a primary flow path224of the gas turbine engine100and a downstream portion210relative to the primary flow path224of the gas turbine engine100. The upstream portion208may be positioned to engage a liner212of the combustor108. The NGV204may be positioned adjacent to the downstream portion210of the RIDN202, where the NGV204and the RIDN202together define a cavity216. The seal206is positioned in the cavity216, and the seal206curves along a surface217of the cavity216. In the first example, the seal206contacts the RIDN202at a first point218and a second point220, and the seal contacts the NGV204at a third point222. In other examples, the seal206may contact each of the RIDN202and the NGV204in two or more points, respectively.

The liner212of the combustor108may be any wall that houses combustion of the gas turbine engine. In the first example, as shown inFIG. 2, the liner212may be a double-walled liner having an inner wall214and an outer wall215. The inner wall214and the outer wall215may be segmented. As shown inFIG. 2, multiple segments of the inner wall214may be staggered with respect to multiple segments of the outer wall215. The inner wall214may include clearance between each segment, and the outer wall215may also include clearance between each segment. Alternatively or in addition, there may be clearance between the inner wall214and the outer wall215allowing cooling fluid, such as air, to flow through the liner212. In the first example, the liner212may also include an inner end wall226positioned at the downstream end of the liner212. In another example, the inner wall214and/or the outer wall215may be unsegmented pieces. In yet another example, the liner212may include only a single wall, which may be segmented or unsegmented.

The NGV204may be any annular structure positioned to guide fluid, such as air, from the combustor107toward the turbine section106of the gas turbine engine100. In one example, the NGV204may include an inner platform228, an outer platform (not shown), and a stator231extending between the inner platform228and the outer platform. The inner platform228of the NGV204may include an inner upstream edge232relative to the primary flow path224of the gas turbine engine100. In the first example, the third point222may be positioned on the inner upstream edge232of the NGV204. In other examples, the third point222may be positioned along alternate portions of the inner platform.

The RIDN202may be any annular sealing structure positioned to add radial and axial support to the liner212and the NGV204. The RIDN202may extend across a gap between an inner end wall226of the liner212and the inner platform228of the NGV204. In one example, as shown inFIG. 2, the RIDN202may include a groove230in the upstream portion208for receiving the inner end wall226. In other examples, the groove230may be configured to receive any portion of the liner212. The downstream portion210of the RIDN202may include a projection that extends toward a midline of the combustion chamber110. The projection includes a first side242facing upstream, a second side244facing toward the midline of the combustion chamber110, and a third side246facing downstream. As shown inFIG. 2, the downstream portion210of the RIDN202may include a tang234. The tang234may assist in positioning the seal206in the RIDN202and the NGV204. In some examples, the RIDN202may include other positioning features. In other examples, the RIDN202may not include the tang234or other positioning features. The RIDN202may be configured to allow both the liner212and the NGV204to move axially and radially relative to the RIDN202. Alternatively or in addition, the RIDN202may be configured to move axially and radially with respect the liner212and/or the NGV204.

The seal206may be any curved and/or coiled device positioned to prevent a flow of air between the RIDN202and the NGV204. The seal206may be a coil seal. The seal206may be configured to prevent or limit the flow of air between the combustion chamber110and the second chamber114. In the example shown inFIG. 2, the seal206includes a first end236, a second end238, and a seal body240extending between the first end236and the second end238, the seal body240curving along the surface217of the cavity216. In the first example, the first end236may be positioned adjacent the first point218. In other examples, the seal body240may extend along the RIDN202downstream of the first point218. The seal206may be configured to bend causing a distance between the second end238and the first point218to change. In the first example, the seal206may be fixed to the RIDN202at the first point218. In other examples, the seal206may be fixed at the first point218, the second point220, the third point222, or any other point. The seal206may extend radially from the first point218, the second point220, and the third point220, contacting the RIDN202and the NGV204along an entire length of the seal206. The seal206may fixed to the RIDN202by brazing or any other type of fastening. In still other examples, the seal206may not be fixed to any point of the RIDN202or the NGV204.

The tang234may extend downstream from the third side246of the RIDN202. The tang234may include a first edge248extending from the third side246and a second edge250extending from the first edge248. The second edge250may extend towards the NGV204. In one example, the RIDN202and the tang234may be one continuous piece. In other examples the RIDN202and the tang234may be separate pieces coupled together.

During operation of the system200, fluid, such as air flows in the direction of the primary flow path224from the compressor section102, through the combustion section104, toward the turbine section106. In some examples, there may be a pressure differential between the combustion chamber110and the second chamber114, where the combustion chamber110has a lower pressure than the second chamber114. Because of the pressure differential between the combustion chamber110and the second chamber114, the fluid is urged from the second chamber114toward the combustion chamber110. The fluid may flow along the RIDN202and/or the NGV204toward the cavity216. The fluid may contact the seal206, causing the seal206to press against the RIDN202and the NGV204at the first point218, the second point220, and the third point222, and preventing or limiting the fluid from flowing into the combustion chamber110. An increase in fluid pressure against the seal206may cause the distance between the second end238and the first point218to increase. A decrease in fluid pressure against the seal206may cause the distance between the second end238and the first point218to decrease.

The seal206may expand and/or contract as the RIDN202moves axially and/or radially with respect to the NGV204. Alternatively or in addition, the seal206may expand and/or contract as the NGV204moves axially and/or radially with respect to the RIDN202.

FIG. 3illustrates an example of the system200in which the inner upstream edge232of the NGV204comprises at least one flat section300. Two of the flat sections300are shown inFIG. 3. The flat section300may be any flat surface formed in the NGV204, such as a cord of an arc. In some examples, as shown inFIG. 3, the inner upstream edge232may include multiple flat sections300. In other examples, the inner upstream edge232may include only one flat section300.

In the example shown inFIG. 3, the seal206includes a first portion302and a second portion304. The first portion302may curve along the surface217of the cavity216from the second end238to the first point218. In some examples, the second portion304may extend along the first side242, the second side244, and the third side246. The seal206may be affixed to the RIDN202at, for example, a point on the first side242, the second side244, and/or the third side246. In other examples, the seal206may extend along the surface217of the cavity216from the second end238and along the first side242and then terminate. Alternatively, the seal206may extend further still along the second side244of the downstream portion210of the RIDN202and terminate.

As shown inFIG. 3, the seal206may also include at least one slot306at the second end238. The slot306may be any gap formed in the seal body240that allows the seal206to bend and accommodate curved geometries of the RIDN202and the NGV204. The slots may be positioned perpendicular to the inner upstream edge232of the NGV204, extending upstream of the NGV204. The seal206may extend along the inner upstream edge232. The slot306may be positioned along the inner upstream edge232between two of the flat sections310that are adjacent to each other.

FIG. 4illustrates an example of the system200that includes a flap seal400, a spring402, an attachment pin404, and the seal206. The spring402may be positioned downstream of the flap seal400, and the attachment pin404may extend through the spring402and the flap seal400, coupling the spring402and the flap seal400to the NGV204.

The flap seal400may be any structure extending between the downstream portion210of the RIDN202and the NGV204. The flap seal400may further prevent and/or limit the flow of air between the combustion chamber110and the second chamber114. The flap seal400may be positioned to contact the NGV204and a portion of the seal206extending along the third side246of the downstream portion210of the RIDN202. In some examples, as shown inFIG. 4, the seal206extends between the third side246of the of the RIDN202and the flap seal400, the flap seal400contacting both the seal206and the NGV204. In this example, the seal206may be configured to prevent and/or limit wear on the flap seal400. In other examples, the flap seal400may directly contact the RIDN202.

The spring402may be any device configured to keep the flap seal400in contact with the NGV204and the RIDN202. The spring402may be positioned between the flap seal400and a head406of the attachment pin404. The spring402may contact the flap seal400and the head406of the attachment pin404.

The attachment pin404may be any fastener configured to couple the spring402and the flap seal400to the NGV204. The attachment pin404may include the head406and shaft408extending upstream from head406and through the spring403and the flap seal400. In some examples, such as is shown inFIG. 4, the seal206extends along an entire length of the second edge250of the tang234. In this example, the seal206extends between and contacts the head406of the attachment pin404and the second edge250. In such an arrangement, the seal206may limit wear on the head406of the attachment pin404and/or the tang234. Even if the seal206wears, it may be more cost effective to replace the seal206than the attachment pin404. In other examples, where the seal206does not extend along the entire length of the second edge250, the head406may contact the second edge250of the tang234directly.

During operation of the system200, as the RIDN202and the NGV204move radially and/or axially, the spring402may apply a force to the flap seal400causing the flap seal400to keep constant contact with the RIDN202and the NGV204. If fluid moves into the cavity216through gaps between the flap seals400, or if the flap seal400otherwise fails, the seal206may expand and/or contract when contacted by the fluid, preventing and/or limiting a flow of the fluid into the combustion chamber110. Alternatively or in addition, as the RIDN202and NGV204move with respect to each other, the seal206may limit surface-to-surface wear of the flap seal400, the tang234, and the attachment pin404.

FIGS. 5 and 6illustrate an example of the system200shown inFIG. 4in which the seal206includes at least one tab500. The tab500may be any projection from the seal206configured to position the seal206on the RIDN202by engaging the RIDN202and/or the tang234. As shown inFIGS. 5 and 6, the tab500may extend radially outward from the seal206. The tab500may engage a side502of the tang234. In one example, as shown inFIG. 5, the tab500may extend along the first edge248of the tang234. In another example, as shown inFIG. 6, the tab may extend along the second edge250of the tang234. In other examples, the tab500may extend along and engage the first side242, the second side244, and/or the third side246of the RIDN202. Alternatively or in addition, the seal206may include multiple tabs500extending along opposite sides502of the tang234(not shown).

During operation, the tab500may help in the positioning of the seal206when the seal206is being attached to the RIDN202and/or the NGV204. In some examples, the tab500may add additional support to the seal206. In other examples, the tab may be removed after the seal206is attached to the RIDN202and/or the NGV.

FIGS. 7 and 8illustrate an example of the system200in which the seal206includes multiple expanded portions700and multiple contracted portions702, and the inner upstream edge232of the NGV204includes multiple channels704. Because the channels704are largely hidden from view inFIG. 7,FIG. 7illustrates a perspective view of the system200with the RIDN202removed. As shown inFIG. 7, each of the expanded portions700may be positioned to contact a respective channel704. Each of the contracted portions702may be positioned to contact a respective portion706of the inner upstream edge232that is between adjacent channels704. As shown inFIGS. 7 and 8, the expanded portions700and the contracted portions702may alternate position along the seal206. A respective slot306may be positioned between respective expanded portions700and contracted portions702.

As shown inFIG. 7, the NGV204may include multiple segments708coupled together. The RIDN202and the seal206may also include multiple segments. In some examples, as shown inFIG. 7, multiple segments708of the NGV204may be positioned adjacent one segment of the seal206. Alternatively or in addition, multiple segments708of the NGV204may be positioned adjacent one segment of the RIDN202. In other examples, the system200may include an equal number of segments of the RIDN202, segments of the seal206, and segments708of the NGV204.

As shown inFIG. 8, the system200may include an overlap plate800. The overlap plate800may be any sealing plate positioned to overlap two adjacent flap seals400. The overlap plate800may be positioned between the flap seal400and the spring402. The overlap plate800may be configured to seal a gap between two adjacent flap seals400(not shown).

In another example, an assembly may be provided including the RIDN202, the NGV204, and the seal206. The seal206may include the first end236, the second end238, and the seal body240extending between the first end236and the second end238. The RIDN202may include the upstream portion208and the downstream portion210relative to the primary flow path224of the gas turbine engine100. The NGV204may be positioned adjacent to the RIDN202. The RIDN202and the NGV204together may define the cavity216. The seal206may be positioned in the cavity216. The seal206may curve along the surface217of the cavity216. The seal206may contact the upstream portion208of the RIDN202at the first point218and the second point220, and the seal206contacts the NGV204the a third point222.

In yet another example, a method of assembly of the combustor seal system may be provide. The RIDN202is provided. The seal206may be positioned on the RIDN. The NGV204may be positioned adjacent to the RIDN202, the RIDN202and the NGV204together defining the cavity216. The seal206is positioned in the cavity216and curves along a surface217of the cavity216. The method may further include attaching the seal206at the first point218and/or the second point220. In some examples the attaching the seal206may include brazing, bolting, resistance welding, and/or tungsten inert gas (TIG) tack welding. Alternatively or in addition, the RIDN202may include a slot for receiving a fixed end of the seal206. In other examples the attaching the seal206may include attaching the seal206to the tang234. Alternatively or in addition, the tabs500may be provided to aid in the positioning of the seal206on the RIDN202during the attaching the seal206. In some examples, the method of assembly may include attaching the flap seal400, the spring402, and the overlap plate800to the NGV204with the attachment pin404. In other examples, the flap seal400, the spring402, the attachment pin404, and the overlap plate800may not be provided.

The system200may be implemented with additional, different, or fewer components. For example, the RIDN202may be in the shape of a bird mouth, a fish mouth, or any other shape configured to allow positioning of the RIDN202between the liner112and the NGV204. In other examples instead of the RIDN202, the system200may include a rear inner combustion liner (RICL) positioned adjacent to the NGV204. In some examples, the system200may include only the seal206the RIDN202, and the NGV204.

The seal206may comprise a material that is capable of withstanding high-temperatures, is resistant to wear, and has high ductility. The material may be a nickel alloy, such as a cobalt-nickel-chromium-tungsten alloy, or any other material having desirable creep capability, ductility, yield strength, temperature capability, wear properties, forming characteristics and cost.

A first aspect relates to a combustor seal system for a gas turbine engine, the system comprising: a rear inner discharge nozzle (RIDN) configured to engage a liner of a combustor; a nozzle guide vane (NGV) positioned adjacent the RIDN, wherein the NGV and the RIDN together define a cavity; and a seal in contact with the RIDN and positioned in the cavity, wherein the seal curves along a surface of the cavity and contacts the RIDN at a first point and a second point in the cavity, and the seal contacts the NGV at a third point.

A second aspect relates to the system of claim1, wherein the NGV comprises an inner upstream edge relative to a primary flow path of the gas turbine engine, wherein the seal extends along the inner upstream edge, and wherein the seal contacts the inner upstream edge of the NGV at the third point.

A third aspect relates to the system of any preceding aspect, wherein the inner upstream edge of the NGV comprises at least one flat section, wherein the seal comprises a plurality of slots, and wherein the slots are positioned adjacent opposite ends of the at least one flat section.

A fourth aspect relates to the system of any preceding aspect, wherein the inner upstream edge comprises a plurality of channels, wherein the seal comprises a plurality of contracted portions, a plurality of expanded portions, and a respective slot between each of the contracted and expanded portions, and wherein the expanded portions contact the channels.

A fifth aspect relates to the system of any preceding aspect, wherein the RIDN comprises an upstream portion and a downstream portion relative to a primary flow path of the gas turbine engine, wherein the downstream portion comprises a first side, a second side, and a third side, and wherein the seal extends along at least a portion of the first side, the second side, and the third side.

A sixth aspect relates to the system of any preceding aspect, wherein the RIDN further comprises a tang positioned downstream of the third side relative to the primary flow path of the gas turbine engine, the tang including a first edge extending away from the third side and a second edge extending from the first edge toward the NGV, wherein the seal extends along the first edge.

A seventh aspect relates to the system of any preceding aspect, wherein the seal comprises at least one tab extending radially outward from the seal along the first edge, and wherein the at least one tab extends along at least one side of the tang.

An eighth aspect relates to the system of any preceding aspect, wherein the seal extends along the second edge, wherein the seal comprises at least one tab extending radially outward from the seal along the second edge, and where the at least one tab extends along at least one side of the tang.

A ninth aspect relates to a combustor seal assembly for a gas turbine engine, the assembly comprising: a seal comprising a first end, a second end, and a seal body extending between the first end and the second end; a rear inner discharge nozzle (RIDN) comprising an upstream portion and a downstream portion relative to a primary flow path of the gas turbine engine; and a nozzle guide vane (NGV), wherein the NGV is positioned adjacent the RIDN, the RIDN and the NGV together defining a cavity, wherein the seal is positioned in the cavity, wherein the seal curves along a surface of the cavity, wherein the seal contacts the upstream portion of the RIDN at a first point and a second point, and the seal contacts the NGV at a third point.

A tenth aspect relates to the assembly of aspect nine, wherein the seal body is configured to bend, causing a distance between the second end of the seal and the first point to change.

An eleventh aspect relates to the assembly of any preceding aspects, wherein the seal body comprises a first portion, wherein the first portion is curved.

A twelfth aspect relates to the assembly of any preceding aspect, wherein the seal body further comprises a second portion, wherein the second portion extends along the downstream portion of the RIDN.

A thirteenth aspect relates to the assembly of any preceding aspect, further comprising a flap seal and an attachment pin, wherein the flap seal is positioned between the downstream portion of the RIDN and the NGV, wherein the attachment pin couples the flap seal to the NGV, and wherein the flap seal contacts the NGV and the seal.

A fourteenth aspect relates to the assembly of any preceding aspect, wherein the downstream portion of the RIDN further comprises a tang positioned downstream of the attachment pin, wherein the seal extends along the tang, wherein the attachment pin contacts the seal.

A fifteenth aspect relates to the system of any preceding aspect, wherein the NGV comprises an inner upstream edge relative to the primary flow path of the gas turbine engine, wherein the inner upstream edge includes a plurality of flat sections, wherein the seal includes a plurality of slots, wherein a first slot of the plurality of slots is positioned adjacent a point between two adjacent flat sections of the plurality of flat sections and between, and wherein a second slot of the plurality of slots is positioned adjacent a point between two adjacent segments of the NGV.

A sixteenth aspect relates to a method of assembly of a combustor seal system, the method comprising: providing a rear inner discharge nozzle (RIDN), the RIDN comprising an upstream portion and a downstream portion relative to a primary flow path of a gas turbine engine; positioning a seal on the RIDN, the seal comprising a first end, a second end, and a seal body extending between the first end and the second end; and positioning a nozzle guide vane (NGV) and the RIDN adjacent to each other, the RIDN and the NGV together defining a cavity, wherein the seal is positioned in the cavity and curves along a surface of the cavity, wherein the seal contacts the upstream portion of the RIDN at a first point and a second point, and wherein the seal contacts the NGV at a third point.

A seventeenth aspect relates to the method of the sixteenth aspect, wherein the positioning the seal on the RIDN further comprises attaching the seal to the RIDN at the first point.

A eighteenth aspect relates to the method of any preceding aspect, wherein the downstream portion of the RIDN further comprises a tang, wherein the seal extends along the downstream portion of the RIDN, and wherein the positioning the seal on the RIDN further comprises attaching the seal to the downstream portion of the RIDN.

A nineteenth aspect relates to the method of any preceding aspect, further comprising providing a flap seal, an overlap seal and an attachment pin and attaching the flap seal and the overlap seal to the NGV with the attachment pin, wherein the seal extends along a portion of the tang between the tang and the attachment pin, wherein the flap seal contacts the NGV and the seal, wherein the flap seal includes a first flap seal segment and a second flap seal segment, and wherein the overlap seal is positioned to contact the first and second flap seal segments downstream of the flap seal.

A twentieth aspect relates to the method of any preceding aspect, wherein the seal comprises a tab extending from a downstream portion of the seal, wherein the tab contacts the tang, wherein the tabs are configured to hold the seal in place during the positioning of the seal on the RIDN.

In addition to the features mentioned in each of the independent aspects enumerated above, some examples may show, alone or in combination, the optional features mentioned in the dependent aspects and/or as disclosed in the description above and shown in the figures.