Patent Publication Number: US-2013247995-A1

Title: Systems and Methods for a Control Valve

Description:
TECHNICAL FIELD 
     The invention relates generally to controlling flow, and more particularly to systems and methods for a flow control valve. 
     BACKGROUND OF THE INVENTION 
     Conventional flow control valves regulate flow using a variable area orifice that imposes a restriction on the fluid flow. An example conventional flow control valve is shown in  FIG. 1 . The pressure drop generated by this restriction is developed by accelerating the flowing fluid to high local velocities and then dissipating the resulting kinetic energy by means of turbulent dissipation. This physical mechanism, while effective in many applications, can result in significant durability and operability problems such as noise generation, vibration, and cavitation erosion in severe service applications where the requirement is to generate very large pressure drops or to discharge to pressures very close to the vapor pressure of the flowing fluid. An example graph illustrating the generated pressure drop along the flow path through the valve is also provided in  FIG. 1 . As shown, P 1  is the pressure upstream of the valve, P 2  is the pressure downstream of the valve, Pmin is the minimum pressure experienced by the flowing fluid within the valve, and Pv is the fluid vapor pressure. The figure illustrates that the acceleration of the fluid at high velocities through the narrow space between the plug and seat of the valve results in the fluid pressure at this location dropping below the discharged pressure (P 2 ), potentially resulting in cavitation. A class of control valves known as “severe service” valves attempts to address the problems resulting from the presence of locally high fluid velocities with valve designs that employ multiple orifices and passages in series and/or parallel with the goal of producing a desired pressure while simultaneously reducing the magnitude of the peak flow velocities within the valve. Examples of such valves can be found in U.S. Pat. Nos. RE32,197; 7,013,919; and 5,390,896. To avoid cavitation, some valves may also provide limited pressure drop, thereby limiting their utility. 
     SUMMARY OF THE INVENTION 
     Certain embodiments of the invention can provide systems and methods for a control valve. In one embodiment, a valve can be provided. The valve can include a flow restrictor portion operable to generate a pressure drop in a fluid flow by viscous dissipation; a throttle portion operable to change a flow rate of the fluid; and a guard portion operable to separate the flow restrictor portion from the throttle portion. 
     In one aspect of an embodiment, the valve can include a seal portion operable to decrease leakage between the throttle portion and the guard portion. 
     In one aspect of an embodiment, the flow restrictor portion can include a porous sleeve, the guard portion can include a perforated tube within the porous sleeve, and the throttle portion can include a piston within the perforated tube. 
     In one aspect of an embodiment, the flow restrictor portion can include at least one of: a porous media or a layered or stacked wire mesh or screen. Regardless of the construction, the flow restrictor portion may comprise a matrix of an indeterminately large number of randomly oriented passages in any series and/or parallel combination, which promote laminar flow and pressure drop through viscous dissipation. 
     In one aspect of an embodiment, the porous media of the flow restrictor portion may comprise a metal, plastic or ceramic, including one or more of stainless steel, brass, bronze, a porous metal, a porous plastic, or a porous ceramic. 
     In one aspect of an embodiment, the throttle portion can include at least one of the following: a translating piston, a sliding plate, a rotating cylinder, a rotating plate, a pivoting wall, or any suitable mechanism that can change the surface area of the restrictor portion exposed to the flow. 
     In one aspect of an embodiment, fluid flow can be reversed to flow in either direction through the valve. 
     In another embodiment, a method for controlling fluid flow can be provided. The method can include generating a pressure drop in the fluid flow by viscous dissipation within a valve comprising a throttle portion and a flow restrictor portion separated by a guard; and increasing or decreasing the flow rate of the fluid through a restrictor portion by adjusting the throttle portion. 
     In one aspect of an embodiment, a method can include reversing the fluid flow between the inlet and the outlet, wherein the fluid flows from the outlet to the inlet. 
     In one aspect of an embodiment, generating a pressure drop in the fluid flow by viscous dissipation can further include passing the fluid through a porous sleeve, wherein the fluid may also pass through one or more perforated tubes over which little to no pressure drop is generated. 
     In one aspect of an embodiment, controlling the flow rate of the fluid can include manipulating a throttle portion to vary the surface area of the restrictor exposed to the fluid flow. The throttle portion may be a piston or any other suitable device that can change the surface area of the flow restrictor exposed to the fluid flow. 
     In one aspect of an embodiment, the porous media may comprise a metal, plastic, or ceramic, including one or more of stainless steel, brass, bronze, a porous metal, a porous plastic, or a porous ceramic. 
     In one aspect of an embodiment, controlling the flow rate of the fluid can include manipulating at least one of the following: a translating piston, a sliding plate, a rotating cylinder, a rotating plate, a pivoting wall, or a mechanism which changes the flow area. 
     In another embodiment, a system for controlling fluid flow can be provided. The system can include at least one of the following: a storage tank, a pipe, a hose, a pump, or a valve. The valve can include a flow restrictor portion operable to generate a pressure drop in the fluid flow by viscous dissipation; a throttle portion operable to change a flow rate of the fluid through the restrictor portion; and a guard portion operable to separate the flow restrictor portion from the throttle portion. 
     In one aspect of an embodiment, the guard portion can include a perforated tube, the restrictor portion can include a porous sleeve adjacent to the perforated tube, and a throttle portion can include a piston within the perforated tube. 
     In one aspect of an embodiment, the restrictor portion can include at least one of a porous media, a layered, a stacked wire mesh, or a screen. Regardless of the construction, the flow restriction may comprise a matrix of an indeterminately large number of randomly oriented passages in series and/or parallel, which may promote laminar flow and pressure drop through viscous dissipation. 
     In one aspect of an embodiment, the porous media may comprise a metal, plastic, or ceramic, including one or more of stainless steel, brass, bronze, a porous metal, a porous plastic, or a porous ceramic. 
     In one aspect of an embodiment, the actuator portion can include at least one of the following: a translating piston, a sliding plate, a rotating cylinder, a rotating plate, a pivoting wall, or any suitable mechanism that can change the surface area of the restrictor exposed to the flow. 
     Other systems, methods, apparatuses, features, and aspects according to various embodiments of the invention will become apparent with respect to the remainder of this document. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Having thus described embodiments of the invention in general terms, reference will now be made to the accompanying drawings, which are not drawn to scale, and wherein: 
         FIG. 1  illustrates one embodiment of a conventional valve and an associated pressure drop profile and velocity drop profile. 
         FIG. 2  illustrates a schematic block diagram of an example system and valve in accordance with an embodiment of the invention. 
         FIG. 3  illustrates a schematic view of an example valve in accordance with an embodiment of the invention. 
         FIG. 4  illustrates a schematic view of an example valve and pressure drop profile in accordance with an embodiment of the invention. 
         FIGS. 5A-5D  illustrate schematic views of another example valve in accordance with an embodiment of the invention. 
         FIG. 6  illustrates a flow diagram of an example method for operating a valve in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Embodiments of the invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention. Like numbers refer to like elements throughout. 
     As used herein, the term “viscous dissipation” can refer to the dissipation of energy within a boundary layer between a body and a fluid, or in a fluid medium. 
     Certain embodiments of the invention generally provide for systems, methods, and apparatuses for a flow control valve. The valve design described herein with respect to embodiments of the invention can minimize or otherwise eliminate relatively high fluid velocities and associated problems found in conventional and existing severe service valve designs. A valve according to an embodiment of the invention can employ a porous media restrictor to generate a flow-controlling pressure drop by means of viscous dissipation rather than the high fluid velocity turbulent dissipation mechanism employed in conventional valve designs. By placing a porous media restrictor in series with a minimally restrictive orifice or orifices (also referred to herein as a guard or guard portion) in the valve flow passage, the presence of high velocity and turbulent flow about the orifice can be minimized or otherwise eliminated, and the pressure drop is instead controlled by viscous dissipation in the micro-passages within the porous media and not the guard. That is, the random and arbitrary passages in the porous media provide long (relative to diameter) convoluted passages that operate to generate pressure drop while limiting fluid flow velocity within the restrictor. This results in primarily laminar flow, which generates pressure drop by viscous dissipation. 
     Protecting the porous media restrictor may be the guard, which may be interposed between the porous media restrictor and an adjustable throttle, and may include a seal to minimize, if not prevent, leakage between the throttle and the restrictor. In this manner, the turbulent dissipation of relatively high fluid velocity in the prior art valves can be minimized or otherwise eliminated. A function of the guard is to separate the surface of the restrictor from the moving throttle thereby protecting it from damage induced by sliding contact between the restrictor and the throttle. 
     Use of a porous media restrictor can also minimize or otherwise eliminate the complex fabrication methods required to produce conventional multi-orificed severe service valves. Flow control can be accomplished by mechanically varying the size and/or number of orifices in the porous media of the restrictor element. One feature of certain system and valve embodiments is the placement of a guard element having minimally restrictive orifices in series with the porous media. In certain embodiments, the orifices of the guard may be sized sufficiently large with respect to the orifices of the porous media restrictor so that the guard has little to no effect on the fluid flow through the valve. To control flow through the valve, the orifices of the porous media restrictor may be blocked or partially blocked with a moving mechanical element, such as a throttle. The guard element can be disposed at least partially between the blocking element that is the throttle and the porous media restrictor to minimize or otherwise eliminate the potential for contact between the throttle and the porous media of the restrictor that could damage the porous media surface and damage the valve or otherwise render the valve inoperable. 
     The system and valve design described herein with respect to embodiments of the invention can improve the series and parallel orifice concepts seen in conventional severe service valve designs by employing a novel porous media restrictor which can include a very large number of random and arbitrary orifices. Use of a porous media restrictor can minimize or otherwise eliminate the relatively complex fabrication methods sometimes required to produce conventional multi-orifice severe service valves while simultaneously improving the multi-orifice concept from a finite number of orifices to an essentially infinite number. In this manner, the locally high velocities responsible for certain problems encountered in conventional severe service valves can be reduced or otherwise eliminated. 
       FIG. 2  illustrates an example system and valve in accordance with an embodiment of the invention. In the example shown, the system  200  can include a valve  202  in communication with a pump  204  and a storage tank  206 . The valve  202  can be connected to the pump  204  via an inlet pipe  208 , and can be further connected to the storage tank  206  via an outlet pipe  210 . In a closed loop system, a return line  211  also connects the pump  204  and the storage tank  206 . Generally, fluid flow through the valve  202  can be facilitated by the valve  202  in a first direction  212  from the pump  204  towards the storage tank  206 . The return line  211  returns the fluid to the pump  204 . In certain instances, fluid flow through the valve  202  can be in a second direction  214  from the storage tank  206  towards the pump  204 , returning via return line  211 . The instances of reverse fluid flow through the valve  202  may be useful for cleaning the valve  202  or otherwise clearing any prior fluid or debris in the valve  202 . In any instance, flow control between the pump  204  and the storage tank  206  can be controlled by the valve  202 . Alternatively, by way of example, the valve  202  can be located on return line  211 , thereby illustrating that the valve can be disposed at either the inlet or discharge of pump  204 , and may be desired. 
     In this embodiment, the system  200  can also include a microprocessor  216  and a memory  218  for storing one or more computer-executable instructions for controlling the system  200  and/or valve  202 . 
     Other system embodiments in accordance with the invention can include fewer or greater numbers of components and may incorporate some or all of the functionalities described with respect to the system and valve components shown in  FIG. 2 . 
       FIG. 3  illustrates a schematic view of an example valve in accordance with an embodiment of the invention. In this embodiment, a valve  300  can include a flow restrictor portion  302 , a throttle portion  304 , and a guard portion  306 . The flow restrictor portion  302  can be operable to generate a pressure drop in a fluid flow, such as  308 , by viscous dissipation, or at least predominantly viscous dissipation. Further, the throttle portion  304  can be operable to change a flow rate of the fluid flow  308 . In addition, the guard portion  306  can be operable to separate the flow restrictor portion  302  from the throttle portion  304 . Relative to the flow restrictor portion  302 , the guard portion  306  produces negligible pressure drop, but provides tight clearances between the flow restrictor portion  302  and the throttle portion  304 , thereby controlling leakage through the valve while simultaneously protecting the flow restrictor portion  302  from contact by the throttle portion  304 . Generally, the valve  300  can control the fluid flow  308  in either direction  310 ,  312 , as may be imposed by other components in the system that define a pressure gradient across the valve. Similar to certain instances described above in  FIG. 2 , the fluid flow through the valve  300  may be reversed for cleaning the valve  300  or otherwise clearing any prior fluid or debris in the valve  300 . 
     In one embodiment, a valve such as  300  can include a seal portion  314  operable to decrease leakage between the throttle portion  304  and the guard portion  306 . The seal portion  314  can be a gasket or other device which permits the throttle portion  304  to move with respect to the guard portion  306 , and minimizes any leakage between the throttle portion  304  and the guard portion  306 . Depending on the valve design, the seal portion  314  can be a stepped seal, a sliding contact seal, a piston ring seal, a face seal or any other suitable design to minimize leakage through the clearance between the throttle portion  304  and the flow restrictor portion  302 . 
     As previously discussed, the guard portion  306  may protect the flow restrictor portion  302  from the throttle portion  304  and/or the seal portion  314 . For example, if the flow restrictor portion  302  includes a sintered porous material, then contact with the throttle portion  304  and/or the seal portion  314  may damage the flow restrictor portion  302  by sealing pore entrances, and thus, interfering with valve function. 
     In one embodiment, a flow restrictor portion such as  302  can include at least one of a porous media or a layered or stacked wire mesh or screen. Materials suitable for the flow restrictor portion  302  include metal, plastic, or ceramic, such as stainless steel, brass, bronze, a porous metal, a porous plastic, or a porous ceramic. 
     In one embodiment, a throttle portion such as  304  can include at least one of the following: a translating piston, a sliding plate, a rotating cylinder, a rotating plate, a pivoting wall, or a mechanism which changes the flow area. 
     Other system embodiments in accordance with the invention can include fewer or greater numbers of components and may incorporate some or all of the functionalities described with respect to the system and valve components shown in  FIG. 3 . 
       FIG. 4  illustrates a schematic view of an example valve and pressure drop profile in accordance with an embodiment of the invention, and  FIGS. 5A-5D  illustrate schematic views of another example valve in accordance with an embodiment of the invention. The valve designs shown in FIGS.  4  and  5 A- 5 D may be in-tank, piston-in-sleeve arrangements. The valves  400 ,  500  in FIGS.  4  and  5 A- 5 D can include a porous sleeve assembly  402 ,  502 , a flow control piston  404 ,  504 , and an actuator  406 ,  506 , and can operate in a similar manner to the embodiments shown in  FIGS. 2 and 3 . The valve pressure and velocity profiles in  FIG. 4  illustrate the elimination of the high internal valve velocity and associated local pressure minimum found in certain prior art valves as illustrated in  FIG. 1 . The region of pressure in the prior art valve of  FIG. 1 , which falls below the valve discharge pressure (P 2 ) and the associated high velocity, have been eliminated in the embodiment of the invention illustrated in  FIG. 1 . This is possible, at least in part, because the invention employs the porous restrictor element  402  to render pressure drop in the valve by viscous dissipation rather than accelerating the fluid to high velocity and generating pressure drop through turbulent dissipation, as in the prior art. 
     In the embodiments shown in  FIGS. 5A-5D , the porous sleeve assembly  502  can be a cylindrically-shaped device and can include a guard  508  (e.g., the inner tube) made from a perforated metal and a restrictor  510  (e.g., the outer tube) made from a sintered porous media. For example, the restrictor  510  can be approximately 36 inches (0.92 m) in length, and about 3.5 inches (8.89 cm) with a wall thickness of about 0.2 inch (5.1 mm). The sintered porous media can have pores of approximately 20 microns (0.020 mm) in diameter. Similar to the flow restrictor portion  302  described in  FIG. 3 , the restrictor  510  of the porous sleeve assembly  502  can include at least one of a porous media or a layered or stacked wire mesh or screen. Materials suitable for the restrictor portion include metal, plastic or ceramic, such as stainless steel, brass, bronze, a porous metal, a porous plastic, or a porous ceramic. If desired, to tailor the pressure drop characteristic as a function of valve position, the restrictor may have a wall thickness that varies in a linear or nonlinear fashion along its length, as illustrated by restrictors  530  and  528  in the embodiments of  FIG. 5C . 
     The guard  508  of  FIGS. 5A-5D  can be a relatively thick wall perforated tube wrapped by the restrictor  510  and comprising a porous medium such as a sintered metal or screen. Preferably, the perforations of the guard  508  are materially larger than the passages in the porous restrictor  510  so the inner tube imposes little to no restriction on the flow, that is, unless such restriction is desired. By way of example only, the guard  508  can be a perforated metal tube approximately 36 inches (0.92 m) in length, about 3.0 inches (7.62 cm) ID with a wall thickness of about 0.25 inch (6.35 cm), and approximately 50% open area. If flow restriction is desired in the guard  508 , then the thickness of the guard tube wall and/or the size of its openings may be sized to provide the desired flow restriction. 
     In an embodiment shown in  FIG. 5D , the restrictor and guard of a porous sleeve assembly  532  may be disposed inside the throttle, which itself may take the form of a tube  534 . In this embodiment, the throttle forms the outer tube surrounding the restrictor by the guard, wherein the guard is disposed between the throttle and the restrictor. 
     In any instance, in the embodiment shown in  FIGS. 5A-5D , a combination of the guard and restrictor can facilitate a relatively tight radial clearance between the flow control piston throttle tube and the guard of the porous sleeve assembly  502  to control leakage flow while minimizing or otherwise preventing contact between the surface of the flow control piston and the porous media of the restrictor, which could result in closing some or all of the media pores and rendering the valve inoperable. 
     The porous medium of the restrictor may impose a flow-controlling pressure drop as illustrated, for example, by the pressure and velocity graphs  408  of  FIG. 4 , by providing predominantly viscous dissipation or a similar mechanism, which can minimize or otherwise eliminate relatively high fluid velocities responsible for the problems experienced in conventional control valves. The porous medium of the restrictor may also result in a low Reynolds number flow reducing, if not substantially eliminating, turbulent dissipation. The wrapped tube design can also facilitate flexibility in tailoring certain valve characteristics, such as pressure drop and flow capacity as a function of valve position, for a wide variety of applications. 
     One will recognize the ability to spatially vary the permeability of the porous sleeve assembly through simple modifications to its guard and/or restrictor components to tailor or otherwise define certain valve characteristics, such as pressure drop and flow capacity as a function of valve position, in accordance with embodiments of the invention. For example, the pore size of the sintered media used to form the restrictor and/or the radial thickness of the restrictor  510  may be varied along its length in a linear or nonlinear fashion, as illustrated in  FIG. 5C . 
     With reference to  FIG. 5A , the porous sleeve assembly  502  can be mounted inside a reservoir tank  512  between two tank wall flanges  514 ,  516 . Fluid can axially  518  (e.g., axial inlet flow) enter the porous sleeve assembly  502  of the valve  500  and can flow radially outward  520  (e.g., radial discharge flow) through the porous media of the restrictor of the porous sleeve assembly  502  into the reservoir tank  512 . The flow rate of the valve  500  can be controlled by varying the available flow area through the porous media of the restrictor by varying the position of the flow control piston  504 . The flow control piston  504  can be a sliding piston, which can slide or otherwise move with respect to and internal to the porous sleeve assembly  502 . 
     Similar to the throttle portion  304  described in  FIG. 3 , the flow control piston  504  can include at least one of the following: a translating piston, a sliding plate, a rotating cylinder, a rotating plate, a pivoting wall, or a mechanism which changes the flow area. 
     Other system and valve embodiments in accordance with the invention can include fewer or greater numbers of components and may incorporate some or all of the functionalities described with respect to the system and valve components shown in FIGS.  4  and  5 A- 5 D. 
     It will be appreciated that while the disclosure may in certain instances describe a valve or system with only a single flow restrictor portion, throttle portion, guard portion, and seal portion, there may be multiple flow restrictor portions, throttle portions, guard portions, and seal portions in certain system or valve embodiments without departing from example embodiments of the invention. 
     In certain embodiments, a microprocessor and/or computer can be in communication with any of the components of the systems and valves described with respect to  FIGS. 2-4 , and  5 A- 5 D. The microprocessor and/or computer can execute computer-executable program instructions stored in a computer-readable medium or memory, such as a random access memory (“RAM”), read-only memory (“ROM”), and/or a removable storage device, coupled to the processor  216  in  FIG. 2 . In one embodiment, a microprocessor and/or computer may include computer-executable program instructions stored in the memory or the microprocessor for monitoring and controlling one or more valve characteristics, such as pressure drop and flow capacity, of a valve, such as  202 ,  300 ,  400 ,  500  or a system, such as  200 . For example, a microprocessor such as  216  and/or a computer can be in communication with one or more sensors oriented at an inlet and outlet of a valve, such as  202  in  FIG. 2 . The microprocessor can include one or more instructions stored in memory  218 , and operable to control the valve  202  in response to one or more flow characteristics of the valve  202  or external commands provided by a user. In response to inlet flow and outlet flow characteristics of the valve  202 , the microprocessor  216  and/or the computer can manipulate certain components of the valve, such as a valve actuator and/or a flow control piston with respect to a porous sleeve assembly, to control one or more flow characteristics of the valve  202 . Other system and valve embodiments operating in conjunction with a microprocessor and/or computer can be implemented in accordance with embodiments of the invention. 
     One skilled in the art may recognize the applicability of embodiments of the invention to other environments, contexts, and applications. One will appreciate that components of the system  200  and valves shown in and described with respect to  FIGS. 2-4  and  5 A- 5 D are provided by way of example only. Numerous other operating environments, system architectures, and apparatus configurations are possible. Accordingly, embodiments of the invention should not be construed as being limited to any particular operating environment, system architecture, or apparatus configuration. 
     Embodiments of a system, such as  200 , can facilitate providing a flow control valve. Improvements in providing a flow control valve, can be achieved by way of implementation of various embodiments of the system  200 , the valves described in  FIGS. 2-4 , and  5 A- 5 D and the methods described herein. Example methods and processes which can be implemented with the example system  200  and/or the valves described in  FIGS. 2-4 , and  5 A- 5 D are described by reference to  FIG. 6 . 
       FIG. 6  illustrates an example method for controlling fluid flow between an inlet and an outlet. The method  600  begins at block  602 , in which a pressure drop is generated in the fluid flow by viscous dissipation, that is, predominantly viscous dissipation because there may be some turbulent dissipation in any valve. This is done with a valve comprising a throttle and a flow restrictor separated by a guard in accordance with embodiments of the present invention. 
     In one aspect of one embodiment, generating a pressure drop in the fluid flow by viscous dissipation can include a fluid flowing through a portion of a porous tube. 
     Block  602  is followed by block  604 , in which the flow rate of the fluid between the inlet and the outlet is increased or decreased by adjusting the throttle to change the area of fluid flow exposed to the restrictor. 
     In one aspect of one embodiment, increasing or decreasing the flow rate of the fluid between the inlet and the outlet can include manipulating at least one of the following: a translating piston, a sliding plate, a rotating cylinder, a rotating plate, a pivoting wall, or a mechanism which changes the flow area. For example, increasing or decreasing the flow rate of the fluid between the inlet and the outlet can include manipulating a piston to change the area of the restrictor available for fluid flow. 
     The movement of the throttle is facilitated by the guard, which separates the throttle from the porous media restrictor. The guard protects the restrictor and provides a tight fit with the throttle to decrease leakage and prevent wear and/or damage to the restrictor. 
     Block  604  is followed by optional block  606 , in which the fluid flow between the inlet and the outlet is reversed, wherein the fluid flows from the outlet to the inlet, which is an optional step. 
     After optional block  606 , the method  600  can end. 
     Embodiments of the invention are described above with reference to block diagrams and flow diagrams of systems, methods, apparatuses, and computer program products. It will be understood that some or all of the blocks of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and flow diagrams, respectively, can be implemented by computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer such as a switch, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified in the flow diagram block or blocks. 
     These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means that implement the functions specified in the flow diagram block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational elements or steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide elements or steps for implementing the functions specified in the flow diagram block or blocks. 
     Accordingly, blocks of the block diagrams and flow diagrams may support combinations of means for performing the specified functions, combinations of elements for performing the specified functions, and program instruction means for performing the specified functions. It will also be understood that some or all of the blocks of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and flow diagrams, can be implemented by special purpose hardware-based computer systems that perform the specified functions, elements, or combinations of special purpose hardware and computer instructions. 
     Additionally, it is to be recognized that, while the invention has been described above in terms of one or more embodiments, it is not limited thereto. Various features and aspects of the above described invention may be used individually or jointly. Although the invention has been described in the context of its implementation in a particular environment and for particular purposes, its usefulness is not limited thereto, and the invention can be beneficially utilized in any number of environments and implementations. Furthermore, while the methods have been described as occurring in a specific sequence, it is appreciated that the order of performing the methods is not limited to that illustrated and described herein, and that not every element described and illustrated need be performed. Accordingly, the claims set forth below should be construed in view of the full breadth of the embodiments as disclosed herein.