Patent Publication Number: US-2023135874-A1

Title: Variable turbine geometry component wear mitigation in radial turbomachines with divided volutes by aerodynamic force optimization at all vanes or only vane(s) adjacent to volute tongue(s)

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This disclosure claims priority pursuant to 35 U.S.C. 119(e) to U.S. Provisional Pat. Application No. 63/275711, filed Nov. 4, 2021, which application is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to an entryway system including a divided volute turbocharger having variable turbine geometry. 
     DESCRIPTION OF THE RELATED ART 
     Turbochargers receive exhaust gas from an internal combustion engine and deliver compressed air to the internal combustion engine. Turbochargers increase the power output of the internal combustion engine, lower fuel consumption of the internal combustion engine, and/or reduce emissions produced by the internal combustion engine. Delivery of compressed air to the internal combustion engine by the turbocharger allows the internal combustion engine to be smaller, yet able to develop the same or similar amount of horsepower as larger, naturally aspirated internal combustion engines. Having a smaller internal combustion engine for use in a vehicle reduces the mass and aerodynamic frontal area of the vehicle, which helps reduce fuel consumption of the internal combustion engine and improve fuel economy of the vehicle. 
     Some turbochargers include a turbine having a divided volute turbine housing, with the turbochargers therefore sometimes alternatively referred to as a divided volute turbocharger (or, when two volutes are utilized, a dual volute turbocharger). The volutes of a divided volute turbine housing are generally isolated from one another such that no mixing of exhaust gas occurs until after the exhaust gas passes the tongues of the respective volutes. The divided volute turbine housing includes a turbine inlet, a turbine outlet, and an interior volume. The turbine inlet is configured for attachment to an internal combustion engine (e.g., to an exhaust manifold or to a cylinder head of an internal combustion engine) and includes a plurality of inlet ports configured to be in fluid communication with exhaust paths of the internal combustion engine upon attachment. The interior volume of the turbine housing defines at least two divided volutes in fluid communication with the respective inlet ports for delivering exhaust gas from the internal combustion engine to a turbine wheel disposed in the interior volume. After energy is extracted from the exhaust gas by the turbine wheel, the exhaust gas exits the turbine housing via the turbine outlet. The volutes guide the exhaust gas from the exhaust manifold of the engine into an arcuate flow for distribution of exhaust around the circumference of the turbine wheel to rotate the turbine wheel. 
     Turbochargers also include a compressor. The compressor includes a compressor wheel coupled to the turbine wheel via a shaft. The compressor is powered by the rotation of the turbine wheel, which in turn drives a compressor wheel within a compressor housing of the compressor. 
     In multi-cylinder engines, cylinders fire in a specific order. For example, in an inline four-cylinder engine in which the cylinders are sequentially numbered 1 through 4, the firing order may be 1-3-4-2. A collection of cylinders may be grouped into a ‘bank’. In the above example, a first bank of cylinders would include cylinders 1 and 4 and a second bank of cylinders would include cylinders 2 and 3. In the case of a “V” engine, the banks of cylinders can be separated across the engine, and multiple cylinders may be firing at the same time. In the case of an inline engine, the banks of cylinders could simply be the front cylinders versus the back cylinders, or an alternate collection of cylinders as described above. Exhaust gas flow is not a smooth stream because exhaust gases exit each cylinder based on the engine’s firing sequence, resulting in intermittent exhaust gas pulses. The exhaust gas from each bank is conducted to the turbine housing in respective manifolds. The manifolds may be pipes and/or ducts attached to the internal combustion engine or may be integral to the internal combustion engine (e.g., manifold ducts cast into a cylinder head of the engine). By separating the exhaust gas streams, the “pulses” of pressure that occurs when the exhaust gas is released from the cylinder may be preserved through the volutes such that the pressure pulses impinge on the turbine wheel. The preservation of the pulses is typically desirable because the pressure pulse imparts momentum to the turbine wheel, thereby accelerating the turbine wheel faster and reducing turbo lag. Effective separation of the gas streams also reduces the instantaneous backpressure in the “non fired” volute. The term “fired” volute refers to the volute with the pressure pulse passing through it. This separation of pulse begins at the exhaust of each cylinder and is maintained in the exhaust manifold up to the turbine inlet (sometimes alternatively referred to as a turbine inlet scroll). In the region where the exhaust gases are admitted to the turbine housing, a separator wall between the respective volutes can help preserve the separation between exhaust gases from each cylinder or cylinder group, and thus maintain the pressure pulses. 
     To aid in directing and controlling the exhaust flow from the volute or divided volutes to the turbine wheel uniformly, a vane ring (sometimes alternatively referred to as a nozzle ring or vaned nozzle stator) with a plurality of vanes can be disposed on an annular disk in the turbine housing interior between the volutes and turbine wheel. These vanes can be fixed to the annular disk (sometimes alternatively referred to as a fixed nozzle ring or fixed vaned nozzle stator) or can be rotatably coupled to the annular disk (sometimes alternatively referred to as a variable nozzle ring or variable vaned nozzle stator) to create a variable turbine geometry (VTG). 
     Variable Turbine Geometry (VTG) nozzle rings in radial turbomachinery typically use a multitude of circumferentially equally spaced vanes to direct and control the flow into the turbine wheel. Furthermore spacers (or other mechanisms to space the upper and lower vane rings) are typically placed outside of the vane ring circle in order to minimize the flow disturbance. In a dual volute manifold, increased aerodynamic forces especially from pressure reversals through flow in each volute, lead to increased wear in the VTG components, particularly at vanes (and contacting components such as vane levers, an actuation ring, and vane rings) circumferentially positioned closest to the turbine housing tongues for each scroll. 
     SUMMARY OF THE DISCLOSURE AND ADVANTAGES 
     The subject disclosure provides for various design aspects in an entryway system manipulating the aerodynamic forces and/or subsequent mechanical loads in the VTG mechanism for managing the wear of VTG components. Such design modifications may include vane geometry optimization (shape, chord length, pivot axis location), asymmetric vane spacing, vane orientation and leading edge positioning of the vanes and alignment relative to the turbine tongue(s), vane fixation for vane(s) closest to the tongue(s), or geometry optimization of VTG spacers with anti-rotation features and combinations thereof. Each of these solutions can be applied individually or in combination in accordance with the required efficacy of wear mitigation for a specific turbine stage. 
     The various modification of the various design modifications managing the wear of VTG components has been illustrated herein without significantly altering the benefits of the prior design of the entryway system in terms of the overall turbine stage efficiency, pulse capture and engine BSFC reduction, while these modifications are also believed to not otherwise significantly changing the maintained benefits for thermal management, engine braking, efficiency towards rated and transient response. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present disclosure will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG.  1    is a schematic representation of a system including a turbocharger having variable turbine geometry and having a dual volute turbine housing, turbine wheel disposed in the turbine housing; 
         FIG.  2    is an exploded view of a portion of a schematic representation of an internal combustion engine and a cross-sectional end view of the dual volute turbine housing of  FIG.  1    adapted for fluid communication with an internal combustion engine that also includes a portion of a vane ring having rotatable vanes disposed on an annular disk and aerodynamic spacers; 
         FIG.  3    is an end view of a baseline configuration of the vane ring and a portion of the dual volute turbine housing of  FIG.  1    that also includes a portion of a vane ring having equally spaced rotatable vanes defining a first and second set of vanes disposed on an annular disk and aerodynamic spacers and wherein that a lengthwise axis of a closest adjacent tongue vane of each of the first and second set of vanes is aligned with a corresponding tongue axis of one of the first and second tongues of the wall that divides the first and second volute in an open position; 
         FIG.  4    is an end view of a baseline configuration of the vane ring and a portion of the dual volute turbine housing of  FIG.  3    but wherein the annular disk has been clocked such that a lengthwise axis of a closest adjacent tongue vane of each of the first and second set of vanes is not aligned with a corresponding tongue axis of one of the first and second tongues of the wall that divides the first and second volute in an open position; 
         FIG.  5    is an end view of a baseline configuration of the vane ring and a portion of the dual volute turbine housing of  FIG.  3    but wherein the annular disk has been clocked and wherein the vanes have been assembled with asymmetric vane spacing; 
         FIG.  6    is an end view of a baseline configuration of the vane ring and a portion of the dual volute turbine housing of  FIG.  3    but wherein the first and second tongue vanes have been shortened to increase the clearance between the end of the respective first and second tongue and the corresponding one vane of the first and second sets of vanes; 
         FIG.  7 A  is a perspective view of one vane of either the first or second set of vanes used in  FIG.  3    but wherein the design of one or more vanes of the first and second sets of vanes has been redesigned in accordance with an exemplary embodiment to have a reduced vane length as compared to a corresponding one vane of either the first or second set of vanes used in  FIGS.  2  and  3   ; 
         FIG.  7 B  is a perspective view of one vane of either the first or second set of vanes used in  FIG.  3    but wherein the design of one or more vanes of the first and second sets of vanes has been redesigned in accordance with an exemplary embodiment to include an altered pivot location corresponding to the location of the first and second shafts of one vane of the first or second set of vanes as compared to a corresponding one vane of either the first or second set of vanes used in  FIGS.  2  and  3   ; 
         FIG.  7 C  is a perspective view of one vane of either the first or second set of vanes used in the baseline configuration of  FIG.  3    but wherein the design of one or more vanes of the first and second sets of vanes has been redesigned in accordance with an exemplary embodiment to include an air slot not included in a corresponding one vane of either the first or second set of vanes used in  FIGS.  2  and  3   ; 
         FIG.  8    is an end view of a baseline configuration of the vane ring and a portion of the dual volute turbine housing of  FIG.  3    but wherein the design of the baseline configuration has been altered in accordance with an exemplary embodiment to include two aerodynamics spacers that extend from each of the first and second tongues of the wall that divides the first and second volute in a manner such that a closest adjacent vane of each of the first and second set of vanes is not aligned along an axis with a corresponding one of the aerodynamic spacers extending from the first and second tongues of the wall; and 
         FIG.  9    is an end view of a baseline configuration of the vane ring and a portion of the dual volute turbine housing of  FIG.  3    in accordance with another exemplary embodiment but wherein one vane of each of the first and second set of vanes most adjacent to the respective first and second tongues of the wall that divides the first and second volute is fixed to the annular disk. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     With reference to the FIGS., wherein like numerals indicate like parts throughout the several views, a schematic representation of a system  30  (i.e., an entryway system  30 ) is shown in  FIG.  1   . The system  30  includes a turbocharger  32  having a turbine portion  33  for receiving exhaust gas from an internal combustion engine  34  and a compressor portion  35  for delivering compressed air to the internal combustion engine  34 . Although not required, the turbocharger  32  is typically used in passenger and commercial automotive applications. However, it is to be appreciated that the turbocharger  32  may be used in non-automotive applications such as heavy equipment applications, non-automotive diesel engine applications, non-automotive motor applications, and the like. 
     The turbine portion  33  includes a turbine housing  36  having an interior surface  38  defining the turbine housing interior  40 . The turbine housing interior  40  is adapted to receive a turbine wheel  42  having a plurality of turbine blades (not shown), typically a plurality of evenly spaced turbine blades. In addition, the turbocharger  32  typically includes a turbocharger shaft  44 , a compressor wheel  46 , a compressor housing  48 , and a bearing housing  50 . During operation of the turbocharger  32 , the turbine wheel  42  (and in particular the turbine blades of the turbine wheel  42 ) receives exhaust gas from the internal combustion engine  34  which causes the turbine wheel  42  to rotate. When present, the turbocharger shaft  44  is coupled to and rotatable by the turbine wheel  42 . When present, the compressor wheel  46  is disposed in the compressor housing  48 , is coupled to the turbocharger shaft  44 , and is rotatable by the turbocharger shaft  44  for delivering compressed air to the internal combustion engine  34 . The bearing housing  50  extends about the turbocharger shaft  44  between the turbine wheel  42  and the compressor wheel  46 . The turbocharger  32  also typically includes bearings  52  disposed about the turbocharger shaft  44  and in the bearing housing  50  for rotatably supporting the turbocharger shaft  44 . 
     The interior surface  38  of the turbine housing  36  also defines a plurality of volutes separated by walls, and hence the turbine housing  36  is defined as a divided volute turbine housing. In one exemplary embodiment, the divided volute turbine housing  36  is a dual volute turbine housing  36 , and hence the interior surface  38  defines a first volute  54  and a second volute  56  that are respectfully separated by a wall  60 . The wall  60  includes first and second tongues  61 ,  63  (see  FIGS.  3 - 9   ), which represent different portions of the wall  60  spaced from each other that separates portions of the first and second volutes  54 ,  56 . 
     For ease of description herein after, the turbocharger  32  will be further explained as including a dual volute turbine housing  36 . However, embodiments of turbine housings having additional numbers of volutes (e.g., three volutes or four volutes) are within the scope described herein. 
     The first and second volutes  54 ,  56  are each in fluid communication with the internal combustion engine  34  and the turbine housing interior  40  for delivering exhaust gas from the internal combustion engine  34  to the turbine housing interior  40 . As also shown in  FIG.  1   , the interior surface  38  also defines a turbine housing outlet  58 . The turbine housing outlet  58  is in fluid communication with the turbine housing interior  40  for discharging exhaust gas from the turbine housing interior  40 . In addition, the inner surface  38  also defines a wastegate (not shown) fluidically coupling each or either of the first and second volutes  54 ,  56  to the turbine housing outlet  58 . The turbine housing  36  may be comprised of any suitable metal. Typically, the turbine housing  36  is comprised of iron or a steel alloy. 
     In certain embodiments, as also shown in  FIG.  1   , the system  30  also includes a controller  146  that is coupled to turbocharger  32  and/or to the internal combustion engine  34  that controls the various other components of the turbocharger  32  and/or internal combustion engine  34 . The controller  146  may include one or more processors, or microprocessors, for processing instructions stored in memory  150  to control various functions on the turbocharger  32  related to the introduction of the exhaust gas within the turbine housing interior  40  through the first and second volutes  54 ,  56 . Such instructions may be any of the functions, algorithms or techniques described herein performed by the controller  146 . Additionally, or alternatively, the controller  146  may include one or more microcontrollers, field programmable gate arrays, systems on a chip, discrete circuitry, and/or other suitable hardware, software, or firmware that is capable of carrying out the functions described herein. In some embodiments, the controller  146  is an engine control unit (ECU) that controls the various other components of the turbocharger  32  and/or internal combustion engine  34 . In embodiments where the controller  146  is the engine control unit, the controller  146  is separate from the turbocharger  32 . In other words, the controller  146  is a separate component that is not included on or in the turbocharger  32 . In other embodiments, the controller  146  is discrete from the ECU. For example, the controller  146  may be included on or in the turbocharger  32 . In other words, the controller  146  is a component included on or in the turbocharger  32 . With reference to  FIG.  1   , the system  30  may include the turbocharger  32 , the internal combustion engine  34 , and the controller  146 . Typically, the system  30  also includes at least one sensor  148 . 
     While not illustrated in  FIG.  1   , the internal combustion engine  34  includes a plurality of cylinders. For example, the internal combustion engine  34  may include two cylinders, four cylinders, six cylinders, eight cylinders, or more cylinders. The internal combustion engine  34  may also include an odd number of cylinders (e.g., three cylinders or five cylinders). The internal combustion engine  34  may have a V-engine configuration, a flat/boxer engine configuration, a W-engine configuration, an inline engine configuration, and the like. In the illustrated embodiment, the internal combustion engine  34  has an inline engine configuration. The internal combustion engine  34  includes a first group of cylinders and a second group of cylinders, with the first and second groups of cylinders each typically including half of the cylinders that are included in the internal combustion engine  34 . The first and second groups of cylinders produce exhaust gas in a series of pulses corresponding to an exhaust stroke of each of the first and second groups of cylinders. Timing of the exhaust strokes of the cylinders is such that pulses of exhaust gas are alternately emitted from the first group of cylinders and the second group of cylinders. The area of the first volute  54 , in combination with the produced gas from the exhaust stroke of the first set of cylinders, defines a first volute flow parameter. Similarly, the corresponding area of the second volute  56 , in combination with the produced gas from the exhaust stroke of the second set of cylinders, defines a second volute flow parameter. The volute flow parameter δ for a volute (such as the first and second volute flow parameter of the respective first and second volute  54 ,  56  (as provided herein)) is calculated by the equation: 
     
       
         
           
             δ 
             = 
             
               
                 
                   m 
                   ˙ 
                 
                 
                   T 
                 
               
               P 
             
           
         
       
     
      wherein m is the mass flow through the volute, T is the exhaust gas temperature at the inlet of the volute, and P is the exhaust gas pressure at the inlet of the volute. Typically, the volute flow parameter δ is measure for each respective exhaust stroke of the respective one of the first and second set of cylinders. 
     As noted above typically the first group of cylinders are in fluid communication with the first volute  54  and the second group of cylinders are in communication with the second volute  56 . In this manner, pulses of exhaust gas from the first and second groups of cylinders flow through the first and second volutes  54 ,  56 , respectively, and to the turbine housing interior  40 , where the pulses of exhaust gas rotate the turbine wheel  42 . The respective pulses of exhaust gas flowing through the first volute  54  from the first group of cylinders (typically measured for each exhaust stroke) and area of the first volute  54  define a first volute flow parameter, while the respective pulses of exhaust gas flowing through the second volute  56  from the second group of cylinders (again typically measured for each exhaust stroke) and area of the second volute  56  define a second volute flow parameter. Owing to the difference in sizes of the areas of the first and second volutes  54 ,  56 , the first and second volute flow parameters are generally different from one another. 
     In addition to the turbocharger  32 , as also shown in  FIG.  2   , the entryway system  30  also includes a vane ring  100  (also referred to as a VTG cartridge or Vane Pack Assembly) disposed in the turbine housing interior  40  between the first and second volutes  54 ,  56  and around the turbine wheel  42 , with the vane ring having plurality of vanes, shown as first and second set of vanes  130  and  140 , rotatably disposed to the vane ring  100  in an asymmetric vane pattern. The entryway system  30  also includes a plurality of spacers  400  disposed in a spaced apart manner on the vane ring  100 , with the vanes on the vane ring  100  and spacers  400  functioning to control the flow of exhaust gas flowing from the one or more volutes  54 ,  56  to the turbine wheel  42 . In particular, the spacers  400  function to minimize flow disturbance of exhaust gas flowing from the one or more volutes  54 ,  56  to the turbine wheel  42 . 
     The vane ring  100  includes an annular disk  101  disposed in the turbine housing interior  40  between the divided first and second volutes  54 ,  56  and the turbine wheel  42 . In certain embodiments, the vane ring  100  includes two spaced apart annular disks  101 A,  101 B (the annular disk  101 A may sometimes referred to as a first annular disk  101 A or lower vane ring (LVR)  101 A, while disk  101 B may sometimes referred to as a second annular disk  101 B or upper vane ring (UVR)  101 B), which the plurality of vanes  130 ,  140  rotatably disposed between the vane rings  100 A,  100 B in the afore-mentioned vane pattern. The vane ring  100  includes the plurality of vanes  130 ,  140  (shown as first and set of vanes  130  and  140  in  FIGS.  2 - 9   ) rotatably disposed to the vane ring  100  in a prespecified vane pattern. In these embodiments, the spacers  400  also function to provide an axial separation function between the first and second annular disks  101 A,  101 B, and thereby maintain clearance between the annular disks101A,  101 B and the vanes  130 ,  140 . 
     Each of the annular disks  101 A and  101 B includes a vane ring surface  102  which includes an inner vane ring surface  102 A and an opposing outer vane ring surface  102 B extending between an inner circumferential edge  104  and an outer circumferential edge  106 . The inner circumferential edge  104  defines a circular orifice for receiving the turbine wheel  42  of the turbocharger  32 . In particular, the vane ring  100  is disposed in the turbine housing  36  with the first and second tongue  61 ,  63  each separately terminating at a position adjacent to the outer circumferential ring  106 . 
     Each of the annular disks  101 A and  101 B also defines a plurality of first openings  107  within the inner vane ring surface  102 A between the inner circumferential edge  104  and an outer circumferential edge  106 , with the number of openings  107  corresponding to the number of the plurality of vanes  130 ,  140  and configured to receive a shaft  139 ,  149  of a respective one of the plurality of vanes  130 ,  140 , as will be explained further below. The openings  107  therefore further define the vane pivot point (VPP) of the respective one vane of the plurality of vanes  130 ,  140  disposed therein. In  FIG.  2    that includes the first and second annular disks  101 A,  101 B, the plurality of openings  107  in at least one the first and second annular disks  101 A,  101 B extend from the inner vane ring surface  102 A to the outer vane ring surface  102 B such that the entirety of the second shafts  137 ,  147  extends through the opening  107  of the second annular disk  101 B and such that the vane levers  153  are positioned within the turbine housing interior  40  between the outer vane ring surface  102 B of the second annular disk  101 B and the turbine housing  36 . 
     As also shown in  FIG.  2   , a vane lever  153  is coupled, and preferably fixed via riveting or welding, to the second shafts  137 ,  147  of the vanes  130 ,  140  and also includes a flange portion  159 . The vane levers  153  are configured to rotate each of the vanes  130  and  140  in a coordinated manner about their respective vane pivot point (VPP) between a closed position and an open position and through one or more intermediate positions, as will be explained further below. An adjustment ring  199  is retained between the vane levers  153  and the second annular disk  101 B, with the flange portion  159  of each of the vane levers  153  disposed within an opening in the adjustment ring  199 . An assembly  203  including a pin  205  and block  207  is affixed to the adjustment ring  199 , such as by riveting or welding, with a pivot having a pivot shaft (not shown) connecting the assembly  203 . The pivot shaft is rotated by a linkage (not shown) connected to an actuator (not shown). The actuator rotates the linkage on the basis of a particular engine operating condition to adjust the flow of exhaust gas through the vanes  130 ,  140 . In particular, the actuator rotates the linkage, which rotates the pivot shaft and adjustment ring  199  through the assembly  203 . The rotation of the adjustment ring  199  causes the adjustment ring  199  to contact the flange portion  159  of the vane levers  153  and rotates the vane levers  153  in response, which in turn causes the coupled vanes  130 ,  140  to move between the closed and open positions and through one or more intermediate positions to adjust the flow of exhaust gas through the vanes  130 ,  140  on the basis of an engine operating condition, such as engine speed. The closed position, as defined below, is a position in which the pulses of gas from the respective volutes  54 ,  56  through the respective vanes  130 ,  140  is minimized, while conversely the open position is a position in which the pulses of gas from the respective volutes  54 ,  56  through the respective vanes  130 ,  140  is maximized. Intermediate positions are therefore positions in which the pulses of gas from the respective volutes  54 ,  56  through the respective vanes  130 ,  140  are between a minimum and maximum value. 
     Referring now to  FIG.  3   , which generally represents one configuration of vanes  130 ,  140  for the entryway system  30  in a baseline configuration, the first set of vanes  130  (i.e., a first set of at least two vanes  130 ) are rotatably disposed in a spaced apart manner from one another on the vane ring surface  102  such that the first set of vanes  130  are positioned downstream of the first volute  54 . Still further, the second set of vanes  140  are rotatably disposed in a spaced apart manner from one another such that the second set of vanes  140  (i.e., a second set of at least two vanes  140 ) are positioned downstream of the second volute  56 . Each of the vanes  130 ,  140  are rotatable along the vane ring surface  102 , and in particular are rotatable along the inner vane ring surface  102 A of a respective annular ring  101 A,  101 B about a vane pivot axis between a closed position and an open position and through one or more intermediate positions between the closed and open position. The vane pivot axis, as defined herein, extends in a direction normal to a plane defining the vane ring surface  102  of the vane ring  100 . 
     Still further, in the embodiment illustrated in  FIG.  3   , the first set of vanes  130  includes six vanes  130  positioned adjacent to one another of the vane ring surface  102  around the vane ring  100 , while the second set of vanes  140  includes five vanes  140  positioned adjacent to one another of the vane ring surface  102  around the vane ring  100 . Accordingly, there are a total of eleven vanes  130 ,  140  on the vane ring  102  in the embodiment of  FIG.  3   , which provide exhaust flow to the turbine wheel  42  having a total of eleven equally spaced turbine blades  45 . While the embodiments provided herein include eleven vanes  130 ,  140  and eleven turbine blades  45 , alternative relative amounts of vanes and blades are contemplated, preferably wherein the number of vanes  130 ,  140  is an odd number, such as a prime number (such as, for example, in  FIG.  2    which illustrates thirteen vanes  130 ,  140 ). In addition, each of the vanes  130  and  140  includes a vane blade  131  or  141  each having a respective inner surface  131 A,  141 A and an opposing outer surface  131 B,  141 B with each of the vanes  130 ,  140  extending in length between a leading edge  132 ,  142  and a trailing edge  134 ,  144  and extending in width between the inner surface  131 A,  141 A and the opposing outer surface  131 B,  141 B. 
       FIG.  3    illustrates a baseline configuration of the annular disk  101  of the vane ring  100  with rotatable vanes  130 ,  140  rotatably disposed thereon for use in the entryway system  30  of  FIG.  1    in which the first and second volutes  54 ,  56  are configured with first and second volute  54 ,  56  separation, with each volute  54 ,  56  having an identical respective (minimum) cross-sectional area defined as the volute throat, just upstream of the interface with the vane ring  100 , alternatively referred to as identical critical throat areas at the interface with the vane ring  100 . The positioning of the first and second tongues  61 ,  63  are configured wherein a first tongue clocking angle between the first and second tongues  61 ,  63  corresponding to the first arcuate region  105  is less than 180 degrees (see  FIG.  3   ), while a second tongue clocking angle between the between the first and second tongues  61 ,  63  corresponding to the second arcuate region  115  (also see  FIG.  3   ) is greater than 180 degrees, with the total combined degrees of the first and second clocking angles equals 360 degrees. In further embodiments, the positioning of the first and second tongues  61 ,  63  are configured wherein a first tongue clocking angle between the first and second tongues  61 ,  63  corresponding to the first arcuate region  105  is greater than 180 degrees (see  FIG.  3   ), while a second tongue clocking angle between the between the first and second tongues  61 ,  63  corresponding to the second arcuate region  115  (also see  FIG.  3   ) is less than 180 degrees, with the total combined degrees of the first and second clocking angles equals 360 degrees. In still further embodiments, the first and second clocking angles may each be 180 degrees, but wherein there is a degree of asymmetry in the vane configuration of the vanes  130 ,  140 , such as through asymmetric vane spacing. 
     In  FIG.  3   , the entryway system  30  having a baseline configuration is configured wherein each of the respective vanes  130 ,  140  is the same, with each of the respective vane pivot points (VPP) of the respective vanes  130 ,  140  (corresponding an axis defined by the length of the first shaft  133 ,  143  and an opposing second shaft  137 ,  147  of the respective vanes  130 ,  140  and corresponding to the openings  107  in the annular disk  101 A) being located along the same circumferential vane pitch circle radii from a center rotation axis with each of the first shaft  133 ,  143  and an opposing second shaft  137 ,  147  of the respective vanes  130 ,  140  located in certain embodiments approximately midway between the inner circumferential edge  104  and the outer circumferential edge  106 , although in other embodiments the position may be closer to or further from the inner circumferential edge  104 . Still further, the vane spacing (β) of each of the respective eleven vanes  130 ,  140 , as shown in  FIG.  3   , corresponds to an equiangular vane spacing angle (β) of about 32.7 degrees. 
     In certain embodiments, the second shaft  137  is an extension of the first shaft  133 , and the second shaft  147  is an extension of the first shaft  141 . In still further embodiments, the second shaft  137  is an extension of and integrally formed with the first shaft  133 , and the second shaft  147  is an extension of and integrally formed with the first shaft  141 . In these embodiments, the first and second shaft  133 ,  137  of vane  130  may simply referred to as a shaft  139  of vane  130 , while the first and second shaft  143 ,  147  of vane  140  may simply referred to as shaft  149  of vane  140 . 
     Still further, in the baseline configuration of  FIG.  3   , the virtual extension of an extended length of one vane  130 A (i.e., an aligned one vane  130 A, also referred to as a tongue vane  130 A or first tongue vane  130 A) of the first set of vanes  130 , defining by a vane axis  230 A or first vane axis  230 A, is aligned along a first tongue axis  213  defined by a virtual extended length of the first tongue  61 , while the virtual extension of an extended length of one vane  140 A (i.e., an aligned one vane  140 A, also referred to as a tongue vane  140 A or second tongue vane  140 A) of the second set of vanes  140 , defining a vane axis  240 A or second vane axis  240 A, is aligned along a second tongue axis  211  defined by a virtual extended length of the second tongue  63  when the tongue vanes  130 A,  140 A are in an open position. The length of a respective vane  130 ,  140  (including the length of the respective tongue vane  130 A,  140 A), is the distance between a leading edge  132 ,  142  and a trailing edge  134 ,  144  of each respective vane  130 ,  140 . When the respective axis  213 ,  230 A along the tongue vane  130 A and first tongue  61  are collinear or generally parallel to one another and close to collinear, the axis  230 A of the tongue vane  130 A is defined herein to be aligned along the axis  213  with the first tongue  61 . Similarly, when the respective axis  240 A along the tongue vane  140 A and the axis  211  along the second tongue  63  are collinear or generally parallel to one another and close to collinear, the axis  240 A of the tongue vane  140 A is defined herein to be aligned along the axis  211  with the second tongue  63 . 
     Still further, in the baseline configuration of  FIG.  3   , the length of the tongues  61 ,  63  extends all the way to the outer diameter  106  of the vane ring  100 , and as illustrated to the outer diameter of each of the respective annular disks  101 A,  101 B. Accordingly, in the baseline configuration of  FIG.  3   , when the vanes  130 ,  140  are positioned in the closed position, the pulses of exhaust gas from the cylinders via the respective volute  54 ,  56  through the respective vanes  130 ,  140  to the turbine wheel  42  can be precisely controlled in order to optimize turbine stage efficiency, pulse capture and engine BSFC reduction while maintaining benefits for thermal management, engine braking, and efficiency towards rated and transient response. Notably, there is minimal leakage of exhaust gas between the aligned one vane  130 A and the first tongue  61 , and between the aligned one vane  140 A and the second tongue  63 . 
     However, while providing these benefits, the baseline configuration of  FIG.  3    exhibited wear in various VTG components, and in particular to the vane levers  153  associated with the vanes  130 ,  140  adjacent to the tongues  61 ,  63  of the wall  60 , the adjustment ring  199 , and the annular disk  101 A,  101 B of the vane ring  100 . This increased wear is believed to be attributed in part, and in certain embodiments in a significant part, due to increased aerodynamic forces of the pulses of exhaust gas and mechanical loads in the VTG mechanism for the entryway system  30 , especially from pressure reversals through flow in each volute  54 ,  56 , which leads to the afore-mentioned wear in the various VTG components described immediately above. 
     In the exemplary embodiments of the subject application disclosed herein in  FIGS.  4 - 9   , various methods of manipulating the aerodynamic forces and/or subsequent mechanical loads in the VTG mechanism of the entryway system  30  are provided that include individual or various combinations of vane geometry, vane fixation, vane spacing, spacer geometry, vane to tongue relationship, and/or vane to housing relationship. By manipulating the aerodynamic forces and/or subsequent mechanical loads in the VTG mechanism, VTG component wear can be mitigated during normal usage of vehicles or components of engines. 
     In each of these alternative embodiments of  FIGS.  4 - 9   , modifications of one or more components of the VTG mechanism, or the location of these components, of the baseline configuration of  FIG.  3    are provided that do not significantly impact the performance characteristics of the modified entryway system  30  in terms of optimized turbine stage efficiency, pulse capture and engine BSFC reduction as compared to the baseline configuration of  FIG.  3   , all while maintaining benefits for thermal management, engine braking, and efficiency towards rated and transient response similar to that of  FIG.  3   . Notably, however, each of the alternative embodiments reduces the aerodynamic forces and/or subsequent mechanical loads in the VTG mechanism of the entryway system  30  and thereby reduce or mitigate the wear on the VTG components that may occur in the baseline configuration of  FIG.  3   . 
     In one exemplary embodiment, as illustrated in  FIG.  4   , the location of the vanes  130  are configured such that the respective closest one vane  130 B, also referred to as the first tongue vane  130 B, of the first set of vanes  130  is adjacent to the first tongue  61 , but wherein the first tongue vane axis  230 B (defined by the extended virtual length of the first tongue vane  130 B) is not aligned along the first tongue axis  211  when the first tongue vane  130 B is in the open position. In addition, the location of the vanes  140  are configured such that the respective closest one vane  140 B, as referred to as the second tongue vane  140 B, of the second set of vanes  140  is adjacent to the second tongue  63 , but wherein the virtual extended length of the second tongue vane  140 B, which defines a second tongue vane axis  240 B, is not aligned along a second tongue axis  213  when the second tongue vane  140 B in the open position. In  FIG.  4   , and corresponding to the definition of adjacent to as provided herein, the respective tongue vanes  130 B,  140 B represent the closest adjacent vane  130 ,  140  of each of the first and second set of vanes  130 ,  140  to the respective tongue  61 ,  63 , This alternation of the location of the respective tongue vanes  130 B,  140 B from the baseline configuration in  FIG.  3    (which include the adjacent tongue vanes  130 A,  140 A which define respective tongue axes  230 A,  240 A and which are aligned with the respective tongue axes  211 ,  213  when the adjacent tongue vanes  130 A,  140 A are in the open position) allows a small portion of leakage of exhaust gas between the first tongue vane  130 B and the first tongue  61 , and between the second tongue vane  140 B and the second tongue  63  in any relative vane position (i.e., open, closed, or in an intermediate position), and in particular in the open vane position. This small leakage of exhaust gas between the adjacent vane  130 B,  140 B and the respective tongue vane  61 ,  63  lessens the aerodynamic forces and mechanical loads applied onto the respective vanes  130 ,  130 B  140 ,  140 B in the closed position or in any van position, which in turn lessens the mechanical loads and wear of the components that are impacted by the forces applied to the vanes  130 B,  140 B as compared with the baseline configuration in  FIG.  3    with aligned vanes  130 A,  140 A. For example, less wear was exhibited over the same testing cycle on the vane levers  153  that were coupled to the respective vanes  130 B,  140 B, as well as wear on the adjustment ring  199  adjacent to the location of these vane levers  153 , as compared to vanes  130 A,  140 A. in the baseline configuration of  FIG.  3   . In the particular embodiment of  FIG.  4   , the entirety of the vane ring  100  and vanes  130 ,  140  are clocked (i.e., pivoted) relative to the baseline configuration of  FIG.  3   , and hence each of the respective vanes  130 ,  140 ,  130 B,  140 B, are clocked/pivoted while maintaining the respective spacing of the vanes  130 ,  140  on the vane ring  100 . 
     In another exemplary embodiment, as illustrated in  FIG.  5   , in addition to adjusting the location of the vanes  130 ,  130 B,  140 ,  140 B as in  FIG.  4    by clocking as described above to create the leakage gaps between the adjacent vanes  130 B,  140 B and the respective tongue vanes  61 ,  63 , an asymmetric spacing between adjacent vanes  130 ,  130 B,  140 ,  140 B is also provided. For example, as shown in  FIG.  5   , the adjacent spacing between two adjacent vanes  140  and  140 B was β′, while the spacing between adjacent vanes  140 B and  130  was increased to β″. Accordingly, during a closed condition, leakage of exhaust gas between the vane  140 B and the adjacent vane  130  of the first set of vanes  130 , or between adjacent vanes  140  and  140 B of the second set of vanes  140  can also occur, small leakage of exhaust gas, which lessens the aerodynamic forces and mechanical loads applied onto the respective vanes  130 ,  130 B,  140 ,  140 B in the closed position and provides similar wear reduction in the VTG components as in  FIG.  4   . 
     In another exemplary embodiment, as illustrated in  FIG.  6   , as opposed to manipulating the vanes  130 ,  130 B,  140 ,  140 B as in  FIGS.  4  and  5   , the length one or both of the respective tongues  61 ,  63  is shortened such that it does not extend to the outer circumference  106  of the vane ring  100  (or either of the annular rings  101 A,  101 B). Accordingly, in the closed position, a gap  425 ,  435  still exists between the respective vanes  130 A,  140 A and the respective tongues  61 ,  63 . This alternation of the location of the tongues  61 ,  63  away from the respective aligned vanes  130 A,  140 A allows a small portion of leakage of exhaust gas between the adjacent tongue vane  130 A and the first tongue  61 , and between the adjacent tongue vane  140 A and the second tongue  63 , in any vane position through the respective gaps  425 ,  435 . This small leakage of exhaust gas through the respective gaps  425 ,  435  is believed to lessen the aerodynamic forces and mechanical loads applied onto the respective vanes  130 ,  130 A,  140 ,  140 A in any vane position in the same manner described above in  FIG.  4    as compared with the baseline configuration in  FIG.  3   , which in turn is believed to lessen the mechanical loads and wear of the components that are impacted by the forces applied to the vanes  130 ,  130 A,  140 ,  140 A in  FIG.  4    as compared with the baseline configuration in  FIG.  3   . 
     In still other exemplary embodiments, as illustrated in  FIGS.  7 A,  7 B, and  7 C  for use in altering the baseline configuration of the entryway system  30  of  FIG.  3    or for use in the configurations of the entryway system of  FIGS.  4  and  5   , various modifications are made to one or more of the vanes  130 ,  140  themselves that allow for exhaust gas leakage either between the vanes  130 ,  140  or through the vanes  130 ,  140  when the vanes are rotated to a closed position. 
     Referring first to  FIG.  7 A , another exemplary embodiment is illustrated in which one or both of the leading edge  132 ,  142  and the trailing edge  134 ,  144  of the vane blade  131 ,  141  of one or more of the vanes  130 ,  140  (i.e., the distance between the leading edge  132 ,  142  and a pivot point PP (i.e., a pivot axis PP), or the trailing edge trailing edge  134 ,  144  and the pivot point PP, or both) is altered as compared to the baseline configuration as illustrated in  FIG.  3   . More in particular, the distance between the leading edge  132 ,  142  and its pivot point PP of its respective shaft  139 ,  149  of the vane blade  131 ,  141  of one or more of the respective vanes  130 ,  140 , and/or the distance between the trailing edge  134 ,  144  and its pivot point PP respective shaft  139 ,  149  of the vane blade  131 ,  141  of one or more of the respective vanes  130 ,  140 , is shortened as compared to the baseline configuration of  FIG.  3   . As illustrated in  FIG.  7 A , the original leading edge  132 ,  142  and the trailing edge  134 ,  144  of the vane blade  131 ,  141  as in  FIG.  3    are respectively shown in phantom lines, while the newer leading edge  132 ′,  142 ′ and the trailing edge  134 ′,  144 ′ of the respective vane blade  131 ,  141  in accordance with the exemplary embodiment of  FIG.  7 A  are illustrated in solid lines. 
     This shortening of the vane blade  131 ,  141  of one or more of the respective vanes  130 ,  140  allows a small portion of leakage of exhaust gas between any pair of adjacent vane blades (i.e., between adjacent vane blades  131  of the first set of vanes  130 ; adjacent vane blades  141  of the second set of vanes  140 , and/or between adjacent vane blades  131  and  141  of a respective pair of vanes  130  and  140 ) when the vanes  130 ,  140  are rotated about the new pivot point PP’ to the closed position (i.e., a leakage gap (a representative leakage gap  215  is shown in phantom in  FIG.   3    with the vane  130  altered as in  FIG.  7    - although this gap  215  is not actually present in the configuration of  FIG.  3    which illustrates equal length vanes  130 ,  140  that close in a manner wherein leakage gaps are not present but is merely representative of where such a gap would be in the configuration of  FIG.  7   ) is created between the newer leading edge  132 ′,  142 ′ and the adjacent trailing edge  134 ,  144  or  134 ′,  144 ′ of a respective pair of adjacent vane blades  131 ,  131  of a pair of vanes  130 ,  130 ; a respective pair of adjacent vane blades  141 ,  141  of a respective pair of vanes  140 ,  140 ; or a respective pair of vane blades  131 ,  141  of a respective pair of vanes  130 ,  140 ; when rotated to the closed position). Similar to the embodiments of  FIGS.  4 - 6   , this leakage gap  215  lessens the mechanical loads and wear of the VTG components that are impacted by the aerodynamic forces applied to the vanes  130 ,  140 . 
     Referring next to  FIG.  7 B , yet another exemplary embodiment is illustrated in which the relative location of the shafts  139 ,  149  on one or both of the vane blades  131 ,  141  of the baseline configuration as illustrated in  FIG.  3    are shifted to a new position (identified as  133 ′,  137 ′,  143 ′,  147 ′ in phantom in  FIG.  7 B ) relative to their respective leading edge  132 ,  142  and trailing edge  134 ,  144  of the respective vane blade  131 ,  141  but wherein the overall length of the vane blades  131 ,  141  of the baseline configuration as illustrated in  FIG.  3    between the respective leading edge  132 ,  142  and trailing edge  134 ,  144  remains constant. This shifting changes the pivot point PP of the respective vane  130 ,  140  of the baseline configuration of  FIG.  3    to pivot point PP’ (also shown by arrow PP’ in phantom in  FIG.  7 B ), which changes the pressure profile applied to the vanes  130 ,  140  which can change the aerodynamic forces and mechanical loads applied onto the respective vanes  130 A,  140 A in any vane position to mitigate the mechanical loads and wear of the components that are impacted by the forces applied to the vanes  130 ,  140  in a manner similar to allowing leakage as in  FIGS.  4 - 6  and  7 A . 
     In certain embodiments, the shifting is such that a first distance, defined as the distance between the respective leading edge  132 ,  142  of one vane  130 ,  140  and the pivot point PP, is less than a second distance defined between the respective leading edge  132 ′,  142 ′ and the new pivot point PP’ of the same, but modified, one vane  130 ,  140  (and wherein a first distance between the respective trailing edge  134 ,  144  of one vane  130 ,  140  and the pivot point PP, is greater than a second distance defined between the respective trailing edge  134 ′,  144 ′ and the new pivot point PP’ of the same, but modified, one vane  130 ,  140 ). 
     In still another alternative (not shown), the shifting could be in the opposite direction, in which the shifting is such that a first distance, defined as the distance between the respective leading edge  132 ,  142  of one vane  130 ,  140  and the pivot point PP, is greater than a second distance defined between the respective leading edge  132 ′,  142 ′ and the new pivot point PP’ of the same, but modified, one vane  130 ,  140  (and wherein a first distance between the respective trailing edge  134 ,  144  of one vane  130 ,  140  and the pivot point PP, is less than a second distance defined between the respective trailing edge  134 ′,  144 ′ and the new pivot point PP’ of the same, but modified, one vane  130 ,  140 ). 
     In still further related embodiments, vane blades  130 ,  140  are also contemplated having a combination of attributes of  FIG.  7 A  and/or 7B. In particular, in one exemplary embodiment one but less than all of the vane blade  130  or  140  may be shortened as in  FIG.  7 A , while another one but less than all of the vane blade  130  or  140  may be shifted as in  FIG.  7 B . In still further exemplary embodiments, one or more but less than all of the vanes  130  or  140  may be shortened and shifted. 
     Referring next to  FIG.  7 C , still yet another exemplary embodiment is illustrated in which a slot opening  230  is defined through one or more of the vanes  130 ,  140  between the inner surface  131 A,  141 A and the outer surface  131 B,  141 B (with the distance  140  between the inner surface  131 A,  141 A and the outer surface  131 B,  141 B as defined as the width of the respective vane  130 ,  140 ) in a location between the respective leading edge  132 ,  142  and trailing edge  134 ,  144 . This slot opening  230  functions as a leakage path for exhaust gas through the vanes  130 ,  140  when the vanes  130 ,  140  in any vane position, including a closed position. Similar to the embodiments of  FIGS.  4 - 6   , this leakage through the slot  230  lessens the mechanical loads and wear of the VTG components that are impacted by the aerodynamic forces applied to the vanes  130 ,  140 . 
     In still a further related embodiment to  FIGS.  7 A- 7 C , a vane configuration can be presented in which one or more of the first and second set of vanes  130 ,  140  includes a combination of the features of  FIG.  7 A  and  FIG.  7 B , alone or in combination with the features of  FIG.  7 C . By way of example, one vane  130  and  140  of either or each of the first and second set of vanes  130 ,  140  could be shortened as described and illustrated above in  FIG.  7 A , whereas another vane  130  and/or  140  or wherein the same vane  130  and/or  140  of each of the first and second set of vanes could have a shifted pivot point PP as described and illustrated above in  FIG.  7 B , and where any one of the vanes  130 ,  140  in this alternative configuration includes the slot opening  230  as described and illustrated above in  FIG.  7 C . 
     In yet another exemplary embodiment, as illustrated in  FIG.  8   , typically used in conjunction with the alternative vane  130 ,  140  arrangement of  FIG.  5    in which the adjacent vane  130 B,  140 B is not aligned along an axis with the respective tongue  61 ,  63  (as also shown in  FIG.  4   ) and in which asymmetric vane spacing is utilized, a first one  400 A of the plurality of spacers  400  is positioned adjacent to the first tongue  61  of the wall  60 , while a second one  400 B of the plurality of spacers is positioned adjacent to the second tongue  63  of the wall  60 . The term “adjacent to”, as defined herein with respect to the relationship of the first one  400 A and second one  400 B of the spacers  400 , refers to the positioning of the respective first one  400 A or second one  400 B of the spacers circumferentially outward of the vanes  130 A,  140 A and along a radial line (RL) extending from the axis of rotation of the turbine wheel  42  to the respective first or second tongue  61 ,  63 . The respective first one  400 A or second one  400 B may be positioned adjacent to the outer circumferential ring  106  such that the respective first one  400 A or second one  400 B of the spacers  400  is aligned and generally flush to the respective first or second tongue  61 ,  63 , or may be positioned slightly inward of the outer circumferential ring  106  so that a small gap may exist between the respective first one  400 A or second one  400 B of the spacers  400  and the respective first or second tongue  61 ,  63 . In addition, the respective circumferentially inward most portion of the respective first one  400 A or second one  400 B are generally spaced circumferentially outward a sufficient distance from a respective adjacent one of the vanes  130 A,  140 B to allow the vane  130 A,  140 B to rotate between the open and closed position. 
     In addition to assisting in adjusting the flow of exhaust gas entering from the respective first or second volute  54 ,  56  prior to being received by the turbine blades of the turbine wheel  42 , the first one  400 A and second one  400 B of the spacers  400  function to reduce scroll to scroll leakage that occurs between one of the vanes  130 A,  140 A and one of the respective tongues  61 ,  63  during operation of the entryway system  30  in each of the intermediate positions and open position as compared with entryway systems that do not include such spacers  400 A,  400 B. However, because the first one  400 A and the second one  400 B of the spacers  400  do not contact the respective vanes  130 A or  140 A in the closed position, a small portion of leakage of exhaust gas between the vane  130 A and the first one  400 A spacer, and between the vane  140 A and the second one spacer  400 B in any vane position. This leakage of exhaust gas lessens the aerodynamic forces and mechanical loads applied onto the respective vanes  130 A,  140 A in the closed position in the same manner described above in  FIG.  4   , which in turn lessens the mechanical loads and wear of the components that are impacted by the forces applied to the vanes  130 A,  140 A. 
     In yet a still further embodiment, as illustrated in  FIG.  9   , the adjacent vanes  130 A and/or  140 A may be fixed vanes, referred to by reference numbers  130 A′,  140 A′, as opposed to rotating vanes  130 A,  140 A as in the baseline configuration of  FIG.  3   . In this embodiment, the remainder of the first set of vanes  130  and second set of vanes  140  remain as rotatable vanes  130 ,  140 . These fixed vanes  130 A′,  140 A′ are welded or otherwise secured to the annular ring  101 A, and thus do not rotate in conjunction with the rotation of the remainder of the first set of vanes  130  and second set of vanes  140  between the open and closed position. As such, when the first set of vanes  130  and second set of vanes  140  are rotated to the closed position, a gap still exists between the respective fixed vanes  130 A′,  140 A′ and the respective tongues  61 ,  63 . This allows a small portion of leakage of exhaust gas between the fixed vane  130 A and the first tongue  61 , and between the vane  140 A and the second tongue  63  in any vane position. Still further, a small portion of leakage of exhaust gas also occurs between the fixed vane  130 A′ or  140 A′ and adjacent respective ones of the first and second set of vanes  130 ,  140 . These paths of leakage all individually lessens the mechanical loads and wear of the components that are impacted by the forces applied to the fixed vanes  130 A′,  140 A′ and other vanes  130 ,  140  during usage. 
     In still further embodiments, any combination of the features of the embodiments of  FIGS.  4 - 9    may be used in combination with each other, which combines the features to create varying alternative paths of leakage that all individually or in combination lessen the mechanical loads and wear of the components that are impacted by the forces applied to the vanes  130 ,  140  (movable or fixed) during usage as compared to those provided in the baseline configuration of  FIG.  3   . 
     The disclosure has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present disclosure are possible in light of the above teachings, and the disclosure may be practiced otherwise than as specifically described.