Patent Publication Number: US-2019195106-A1

Title: Systems and methods for air assisted injection of a reductant into an aftertreatment system

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/609,712, filed Dec. 22, 2017, the entire disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to aftertreatment systems for use with internal combustion (IC) engines. 
     BACKGROUND 
     Exhaust aftertreatment systems are used to receive and treat exhaust gas generated by IC engines. Generally, exhaust gas aftertreatment systems comprise any of several different components to reduce the levels of harmful exhaust emissions present in the exhaust gas. For example, certain exhaust gas aftertreatment systems for diesel-powered IC engines comprise a selective catalytic reduction (SCR) system, including a catalyst formulated to convert NO x  (NO and NO 2  in some fraction) into harmless nitrogen gas (N 2 ) and water vapor (H 2 O) in the presence of ammonia (NH 3 ). Generally, in such aftertreatment systems, an exhaust reductant (e.g., a diesel exhaust fluid such as urea) is injected into the SCR system to provide a source of ammonia and mixed with the exhaust gas to partially reduce the NO x  gases. The reduction byproducts of the exhaust gas are then fluidly communicated to the catalyst included in the SCR system to decompose substantially all of the NO x  gases into relatively harmless byproducts that are expelled out of the aftertreatment system. 
     Aftertreatment systems generally include a reductant insertion assembly for inserting a reductant into the SCR system. Some reductant insertion assemblies use air provided by an air supply system to assist in insertion of the reductant into the SCR system, i.e., provide air-assisted insertion of the reductant. Such air supply systems generally include a compressor and an external air source (e.g., an air tank) to provide air-assisted insertion of the reductant. Furthermore, such air supply systems may also require a dedicated energy source, a filtration system, and/or an oil separation system. These requirements increase the complexity of such reductant insertion assemblies and therefore increase manufacturing and maintenance costs. 
     SUMMARY 
     Embodiments described herein relate generally to systems and methods for providing air-assisted reductant insertion in an aftertreatment system, and in particular to a reductant insertion assembly that includes an injector positioned on a SCR system for inserting a reductant therein. A portion of compressed air from an outlet of a compressor included in a turbocharger of the aftertreatment system is rerouted to the injector and used in air-assisted insertion of the reductant into the SCR system. 
     In one embodiment, an aftertreatment system structured to decompose constituents of an exhaust produced by an engine having a turbocharger including a turbine and a compressor coupled thereto, includes: a selective catalytic reduction system; an injector fluidly coupled to the selective catalytic reduction system and structured to selectively insert a reductant into the selective catalytic reduction system an intake conduit fluidly coupled to a compressor outlet of the compressor and structured to deliver a compressed air from the compressor to the engine; and an air delivery line fluidly coupling the intake conduit to the injector, the air delivery line being structured to deliver a portion of the compressed air to the injector so as to facilitate air-assisted insertion of the reductant by the injector. 
     In another embodiment, an aftertreatment system for an internal combustion engine includes a turbocharger, an intake conduit, an intake manifold, an air delivery line, and a housing. The turbocharger includes a compressor and a turbine. The compressor is configured to receive air from an air source. The turbine is configured to receive exhaust from the internal combustion engine. The intake conduit is configured to receive compressed air from compressor. The intake manifold is configured to receive a first portion of the compressed air from the intake conduit and to provide the first portion of the compressed air to the internal combustion engine. The air delivery line is configured to receive a second portion of the compressed air from the intake conduit separate from the intake manifold. The housing is configured to receive the second portion of compressed air from the air delivery line and to receive the exhaust from the turbine. 
     In yet another embodiment, an aftertreatment system for an internal combustion engine having a turbocharger with a compressor and a turbine, includes an intake conduit, an air delivery line, and a housing. The intake conduit is configured to receive compressed air. The air delivery line is coupled to the intake conduit and structured such that a first portion of the compressed air bypasses the air delivery line and a second portion of the compressed air is diverted into the air delivery line. The housing is structured to receive the second portion of compressed air from the air delivery line and to separately receive exhaust. 
     It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the subject matter disclosed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several implementations in accordance with the disclosure and are therefore not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings. 
         FIG. 1  is a schematic illustration of an aftertreatment system, according to an embodiment. 
         FIG. 2  is a flow diagram of an example method for air-assisted insertion of a reductant into a SCR system, according to an embodiment. 
     
    
    
     Reference is made to the accompanying drawings throughout the following detailed description. In the drawings, similar symbols typically identify similar components unless context dictates otherwise. The illustrative implementations described in the detailed description, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure. 
     DETAILED DESCRIPTION 
     Embodiments described herein relate generally to systems and methods for providing air-assisted reductant insertion in an aftertreatment system, and in particular to a reductant insertion assembly that includes an injector positioned on a SCR system for inserting a reductant therein. A portion of compressed air from an outlet of a compressor included in a turbocharger of the aftertreatment system is rerouted to the injector and used in air-assisted insertion of the reductant into the SCR system. 
     Aftertreatment systems generally include a reductant insertion assembly for inserting a reductant into the SCR system. Some reductant insertion assemblies use air provided by an air supply system to assist in insertion of the reductant into the SCR system, i.e., provide air-assisted insertion of the reductant. For example, air may be mixed with the reductant, or air pulses may be used to insert the reductant. Such air supply systems generally include a compressor and an external air source (e.g., an air tank) to provide air-assisted insertion of the reductant. Furthermore, such air supply systems may also require a dedicated energy source, a filtration and/or an oil separation system. This increases the complexity of such reductant insertion assemblies and increases manufacturing, as well as maintenance costs. 
     Various embodiments of the systems and methods described herein may provide benefits including, for example: (1) using a portion of compressed air from an outlet of a compressor included in an aftertreatment system, thereby eliminating the use of a dedicated air source or supply; (2) eliminating the use of a dedicated energy source, filtration and/or oil separation system; and (3) reducing energy consumption, manufacturing costs as well as maintenance costs. 
       FIG. 1  is a schematic illustration of an aftertreatment system  100 , according to an embodiment. The aftertreatment system  100  is configured to receive an exhaust gas (e.g., a diesel exhaust gas, etc.) from an engine  10  and reduce constituents of the exhaust gas such as, for example, NO x  gases, CO, hydrocarbons, etc. The aftertreatment system  100  may comprise a reductant storage tank  110 , a reductant insertion assembly  120 , a turbocharger  130  and a SCR system  150 . 
     The engine  10  may include a diesel engine, a gasoline engine, a biodiesel engine, a natural gas engine, a dual fuel engine, or any other suitable engine that burns a fuel to produce energy and generates an exhaust gas. The engine  10  comprises a plurality of engine cylinders  12 . While shown as including four engine cylinders  12 , in other embodiments, the engine  10  may include any number of engine cylinders, for example 6, 8, 10, 12, 14, 16, 18, 20 or even more. 
     An intake manifold  20  is fluidly coupled to the engine  10  via a plurality of intake manifold conduits  22 . The intake manifold  20  is structured to receive air from a compressor  134  of the turbocharger  130 , described below in further detail, and communicate the air to each of the engine cylinders  12  via the corresponding intake manifold conduit  22 . Furthermore, an exhaust manifold  30  is fluidly coupled to the engine  10  via a plurality of exhaust manifold conduits  32 . The exhaust manifold  30  is structured to receive the exhaust gas from each of the engine cylinders  12  via the corresponding exhaust manifold conduit  32  and communicate the exhaust gas to the SCR system  150  via the turbocharger  130 . 
     The SCR system  150  is positioned downstream of the turbocharger  130  and comprises a housing  152  defining an internal volume within which at least one catalyst  154  is positioned. The housing  152  may be formed from a rigid, heat-resistant and corrosion-resistant material, for example stainless steel, iron, aluminum, metal, ceramic, or any other suitable material. The housing  152  may have any suitable cross-section, for example circular, square, rectangular, oval, elliptical, polygonal, or any other suitable shape. 
     In some embodiments, the SCR system  150  may comprise a selective catalytic reduction filter (SCRF) system, or any other aftertreatment component, configured to decompose constituents of the exhaust gas (e.g., NO x  gases such as such nitrous oxide, nitric oxide, nitrogen dioxide, etc.), flowing through the aftertreatment system  100  in the presence of a reductant, as described herein. 
     Although  FIG. 1  shows only the catalyst  154  positioned within the internal volume defined by the housing  152 , in other embodiments, a plurality of aftertreatment components may be positioned within the internal volume defined by the housing  152  in addition to the SCR system  150 . Such aftertreatment components may comprise, for example, filters (e.g., particulate matter filters, catalyzed filters, etc.), oxidation catalysts (e.g., carbon monoxide, hydrocarbons and/or ammonia oxidation catalysts), mixers, baffle plates, heaters (e.g., regenerative heaters coupled to the SCR system  150 ) or any other suitable aftertreatment component. 
     An inlet conduit  151  is fluidly coupled to an inlet of the housing  152  and structured to receive exhaust gas from the engine  10 . The inlet conduit  151  communicates the exhaust gas to an internal volume defined by the housing  152 . Furthermore, an outlet conduit  153  may be coupled to an outlet of the housing  152  and structured to expel treated exhaust gas into the environment. One or more sensors may be positioned in the inlet conduit  151 . Such sensors may include a NO x  sensor, for example a physical or virtual NO x  sensor, configured to determine an amount of NO x  gases included in the exhaust gas being emitted by the engine  10 . 
     In other embodiments, an oxygen sensor, an ammonia sensor, a temperature sensor, a pressure sensor, or any other sensor may also be positioned in the inlet conduit  151  so as to determine one or more operational parameters of the exhaust gas flowing through the aftertreatment system  100 . One or more sensors may also be positioned in the outlet conduit  153 . The one or more sensors may comprise a second NO x  sensor configured to determine an amount of NO x  gases expelled into the environment after passing through the SCR system  150 , and/or a particulate matter sensor. 
     The catalyst  154  is formulated to decompose constituents of an exhaust gas, for example NO x  gases, flowing through the aftertreatment system  100 . The catalyst  154  is formulated to selectively decompose constituents of the exhaust gas. Any suitable catalyst can be used such as, for example, platinum, palladium, rhodium, cerium, iron, manganese, copper, vanadium based catalyst, any other suitable catalyst, or a combination thereof. The catalyst  154  can be disposed on a suitable substrate such as, for example, a ceramic (e.g., cordierite) or metallic (e.g., kanthal) monolith core which can, for example, define a honeycomb structure. A washcoat can also be used as a carrier material for the catalyst  154 . Such washcoat materials may comprise, for example, aluminum oxide, titanium dioxide, silicon dioxide, any other suitable washcoat material, or a combination thereof. The exhaust gas (e.g., diesel exhaust gas) can flow over and/or about the catalyst  154  such that any NO x  gases included in the exhaust gas are further reduced to yield an exhaust gas which is substantially free of NO x  gases. 
     An injector  122  may be positioned on a sidewall of housing  152  and is in fluid communication with the internal volume of the housing  152 , for example via a reductant insertion port defined on a sidewall of the housing  152 . In various embodiments, the injector  122  may comprise a dosing lance. The injector  122  is configured to selectively insert a reductant into the internal volume defined by the housing  152 . The injector  122  may also include a nozzle  124  structured to shear the reductant into droplets so as to deliver the reductant as a mist, a stream, a jet or as a conical spray cone into the SCR system  150 . Furthermore, the injector  122  may be configured to insert the reductant droplets as a steady state stream, or in a pulsed or transient sequence. 
     Furthermore, the injector  122  is structured to receive air, as described herein so as to provide air-assisted insertion of the reductant into the SCR system  150 . For example, the injector  122  may also comprise a blending chamber structured to receive pressurized reductant from a metering valve at a controllable rate. The blending chamber may also be structured to receive air, for example from the compressor  134  as described herein, so as to deliver a combined flow of the air and the reductant to the SCR system  150  through the nozzle  124 . 
     The aftertreatment system  100  may also include a reductant storage tank  110  and a reductant insertion assembly  120 . The reductant storage tank  110  is structured to store the reductant. The reductant is formulated to facilitate decomposition of the constituents of the exhaust gas (e.g., NO x  gases included in the exhaust gas). Any suitable reductant can be used. In some embodiments, the exhaust gas comprises a diesel exhaust gas and the reductant comprises a diesel exhaust fluid. For example, the diesel exhaust fluid may comprise urea, an aqueous solution of urea, or any other fluid that comprises ammonia, by-products, or any other suitable diesel exhaust fluid (e.g., the diesel exhaust fluid marketed under the name) ADBLUE®). In particular embodiments, the reductant comprises an aqueous urea solution having a particular ratio of urea to water. For example, the reductant may comprise an aqueous urea solution including 32.5% by volume of urea and 67.5% by volume of deionized water. In other embodiments, the reductant may include 40% by volume of urea and 60% by volume of deionized water. 
     A reductant insertion assembly  120  is fluidly coupled to the reductant storage tank  110 . The reductant insertion assembly  120  is configured to selectively provide the reductant to the injector  122  from the reductant storage tank  110 . The reductant insertion assembly  120  may comprise one or more pumps having filter screens (e.g., to prevent solid particles of the reductant or contaminants from flowing into the pump) and/or valves (e.g., check valves) positioned upstream thereof to receive reductant from the reductant storage tank  110 . In some embodiments, the pump may comprise a diaphragm pump but any other suitable pump may be used such as, for example, a centrifugal pump, a suction pump, etc. 
     The pump may be configured to pressurize the reductant so as to provide the reductant to the injector  122  at a predetermined pressure. Screens, check valves, pulsation dampers, or other structures may also be positioned downstream of the pump to provide the reductant to the injector  122 . In various embodiments, the reductant insertion assembly  120  may also comprise a bypass line structured to provide a return path of the reductant from the pump to the reductant storage tank  110   
     A valve (e.g., an orifice valve) may be provided in the bypass line. The valve may be structured to allow the reductant to pass therethrough to the reductant storage tank  110  if an operating pressure of the reductant generated by the pump exceeds a predetermined pressure so as to prevent over pressurizing of the pump, the reductant delivery lines, or other components of the reductant insertion assembly  120 . In some embodiments, the bypass line may be configured to allow the return of the reductant to the reductant storage tank  110  during purging of the reductant insertion assembly  120  (e.g., after the engine  10  is shut off). 
     The turbocharger  130  is positioned upstream of the SCR system  150  and downstream of the exhaust manifold  30 . The turbocharger  130  comprises a turbine  132  and the compressor  134  operably coupled to the turbine  132  via a shaft  136 . A turbine inlet  133  of the turbine  132  is fluidly coupled to the exhaust manifold  30  via an exhaust conduit  131 , and structured to receive the exhaust gas therefrom. The exhaust gas drives the turbine  132  and thereby the compressor  134  via the shaft  136 . The inlet conduit  151  is also fluidly coupled to the turbine  132  and communicates the exhaust gas therefrom to the SCR system  150 . 
     The compressor  134  is fluidly coupled to an air inlet conduit  162  and configured to receive air therefrom. An air filter  160  may be positioned upstream of the air inlet conduit  162  and structured to remove particles such as, for example dust, soot, carbon, inorganic particles, etc. from the air communicated to the compressor  134 . Driving of the compressor  134  by the turbine  132  may generate negative pressure in the air inlet conduit  162  which draws air into the compressor  134 . The compressor  134  is structured to compress the air so as to produce compressed air at a first pressure. The first pressure may be less than 1 bar. 
     An intake conduit  138  is fluidly coupled to a compressor outlet  135  of the compressor  134  and structured to deliver the compressed air from the compressor  134  to the engine  10  via the intake manifold  20 . An air delivery line  144  fluidly couples the intake conduit  138  to the injector  122 . The air delivery line  144  is structured to deliver a portion of the compressed air to the injector  122  so as to facilitate air-assisted insertion of the reductant by the injector  122  into the SCR system  150 . Expanding further, the air delivery line  144  includes a sideline (e.g., a small tube, hose or conduit) which draws the first portion of the compressed air from the intake conduit  138  and delivers to the injector  122 . 
     In various embodiments, the portion of the compressed air may have a volume in a range of 0.01-8% (e.g., 0.01%, 0.02%, 1%, 1.1%, 7.9%, 7.99%, or 8% inclusive of all ranges and values therebetween) of a total volume of the compressed air flowing through the intake conduit  138 . In one embodiment, where the first pressure is greater than 2.5 bar, the portion of the compressed air may have a volume of less than 1% of the total volume of the compressed air flowing through the intake conduit  138 . 
     In some embodiments, the portion of the compressed air may have a volume in a range of 0.5-8% (e.g., 0.5%, 1%, 1.5%, 7%, 7.5%, or 8% inclusive of all ranges and values therebetween) of a total volume of the compressed air flowing through the intake conduit  138 . In some embodiments, the portion of the compressed air may have a volume in a range of 4-8% (e.g., 4%, 5%, 6%, 7%, or 8% inclusive of all ranges and values therebetween) of the total volume of the compressed air flowing through the intake conduit  138 . In some embodiments, the air delivery line  144  may be fluidly coupled to any portion of the turbocharger  130 , for example the turbine  132  (e.g., the turbine inlet  133  of the turbine  132 ) or the compressor  132  and configured to receive the air therefrom. 
     In some embodiments, the air delivery line  144  delivers the compressed air at the first pressure to the injector  122 . In such embodiments, the first pressure may be sufficient for the injector  122  to provide air-assisted reductant insertion into the SCR system  150 . Furthermore, the nozzle  124  may be structured to shear the reductant into reductant droplets using the compressed air at the first pressure. 
     In other embodiments, a booster pump  146  (e.g., a positive displacement pump, a centrifugal pump, a rotary lobe pump, a progressive cavity pump, a rotary gear pump, a piston pump, a diaphragm pump, a screw pump, a gear pump, a hydraulic pump, etc.) may be positioned in the air delivery line  144  upstream of the injector  122 . The booster pump  146  may be configured to pressurize the portion of the compressed air so as to generate pressurized air having a second pressure greater than the first pressure, and deliver the pressurized air to the injector  122 . In particular embodiments, the second pressure may be in a range of 1-3 bar (e.g., 1 bar, 1.5 bar, 2 bar, 2.5 bar or 3 bar inclusive of all ranges and values therebetween), and may correspond to a designed pressure of the injector  122 . Moreover, the nozzle  124  may be structured to shear the reductant into reductant droplets using the pressurized air at the second pressure. 
     In still other embodiments, a flow valve  148  may be positioned in the air delivery line  144  upstream of the booster pump  146 . The flow valve  148  may include a check valve, a butterfly valve, a disc valve, a clapper valve, a diaphragm valve or any other suitable valve structured to control a flow rate of the portion of the compressed air to the injector  122 . 
     In this manner, the aftertreatment system  100  uses a portion of the compressed air provided by the compressor  134  of the turbocharger  130  for air-assisted insertion of the reductant through the injector  122  into the SCR system  150 . This eliminates the use of a separate air supply system for providing air to the injector  122 , thereby reducing energy consumption, manufacturing costs, and/or maintenance costs. 
     While  FIG. 1  shows the aftertreatment system  100  as including a single intake conduit  138 , in other embodiments, the aftertreatment system  100  or any other aftertreatment system described herein may include a plurality of intake conduits (e.g., the intake conduit  138 ), and a plurality of exhaust conduits fluidly coupled to the intake manifold  20  and the exhaust manifold  30 , respectively. An SCR system (e.g., the SCR system  150 ) may be fluidly coupled to each of the exhaust conduits, and an injector (e.g., the injector  122 ) may be fluidly coupled to each of the plurality of SCR systems or otherwise, the plurality of exhaust conduits. Furthermore, each of the plurality of exhaust conduits may have a turbocharger, (e.g., the turbocharger  130 ) including the turbine and the compressor, fluidly coupled to a corresponding exhaust conduit. In such embodiments, the aftertreatment system  100  may include a plurality of air delivery lines (e.g., the air delivery lines  144 ) fluidly coupling a respective intake conduit to a corresponding injector so as to provide air assisted insertion thereto, as previously described herein. Furthermore, a booster pump (e.g., the booster pump  146 ) and/or a flow valve (e.g., the flow valve  148 ) may be provided in each of the plurality of air delivery lines. 
       FIG. 2  is a schematic flow diagram of an example method  200  for providing air-assisted insertion of a reductant into an SCR system (e.g., the SCR system  150 ) of an aftertreatment system (e.g., the aftertreatment system  100 ), according to an embodiment. The aftertreatment system  100  also includes a turbocharger (e.g., the turbocharger  130 ) comprising a turbine (e.g., the turbine  132 ) and a compressor (e.g., the compressor  134 ). The compressor is operably coupled to the turbine via a shaft (e.g., the shaft  136 ). 
     The method  200  comprises communicating an exhaust gas from an exhaust manifold of an engine to the turbine so as to drive the compressor, at  202 . For example, the exhaust gas is communicated from the exhaust manifold  30  fluidly coupled to the engine  10 , to the turbine  132  via the exhaust conduit  131 . The exhaust gas drives the turbine  132  and thereby the compressor  134  via the shaft  136 . The compressor  134  may receive air from the air inlet conduit  162  (e.g., after passing through the air filter  160 ) and compress the air so as to generate compressed air. 
     The compressed air is communicated from the compressor to an intake manifold of the engine via an intake conduit, at  204 . For example, the compressed air from the compressor  134  is communicated to the intake manifold  20  via the intake conduit  138 . A portion of the compressed air is communicated to an air delivery line fluidly coupling the intake conduit to an injector fluidly coupled to the SCR system, at  206 . For example, the portion of the compressed air is communicated to the air delivery line  144  fluidly coupled at one end to the intake conduit  138 , and at an opposite end to the injector  122 . 
     In some embodiments, the method  200  also includes pressurizing the portion of the compressed air so as to produce pressurized air, at  208 . For example, the booster pump  146  may be positioned in the air delivery line  144 , and structured to pressurize the portion of the compressed air so as to generate the pressurized air. The pressurized air is delivered to the injector  122  via the air delivery line  144 . A reductant mixed with the portion of the compressed air is communicated into the SCR system via the injector, at  210 . For example, the injector  122  inserts the reductant mixed with the portion of the compressed air or the pressurized air into the SCR system  150 , thereby providing air-assisted insertion of the reductant into the SCR system  150 . 
     Experimental Results 
     A ⅜ inch air delivery line was used to fluidly couple an air intake conduit to an injector. A booster pump was used to pump compressed air at various air pressures to the injector via the air delivery line. The injector included a nozzle having a SU46 body and a SU29 orifice. Table 1 shows results of air flow and reductant insertion rates at various air pressures, as well as the profile of a DEF spray produced by the nozzle. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Air flow rates, DEF insertion rates and DEF spray profiles produce 
               
               
                 by the nozzle of the injector at various air pressures. 
               
            
           
           
               
               
               
               
            
               
                 Air 
                   
                   
                   
               
               
                 Pressure 
                 Air Flow [standard 
                 DEF Insertion Rate 
                 DEF Spray 
               
               
                 [bar] 
                 liters per minute] 
                 [milliliters per second] 
                 Profile 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 0.689 
                 98.1 
                 ~1 
                 Very fine mist 
               
               
                 2.068 
                 201.3 
                 8.7 
                 Mist with some 
               
               
                   
                   
                   
                 wall impacting 
               
               
                 2.896 
                 258.1 
                 ~8.5 
                 Some mist 
               
               
                   
               
            
           
         
       
     
     It should be noted that the term “example” as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such term is not intended to connote that such embodiments are necessarily extraordinary or superlative examples). 
     The terms “coupled” and the like as used herein mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. 
     It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements; values of parameters, mounting arrangements; use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Additionally, it should be understood that features from one embodiment disclosed herein may be combined with features of other embodiments disclosed herein as one of ordinary skill in the art would understand. Other substitutions, modifications, changes, and omissions may also be made in the design, operating conditions, and arrangement of the various exemplary embodiments without departing from the scope of the present application. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any embodiments or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular embodiments. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.