Abstract:
A turbine and method of operating a turbine includes a housing having an inlet, a volute and an outlet. The inlet is coupled to the volute through a primary fluid path and a secondary fluid path. The turbine further includes an impeller rotatably coupled to the housing and a hydraulically actuated valve assembly disposed within the secondary fluid path selectively communicating fluid from the inlet to the volute. The turbine includes a hydraulic actuator coupled to the valve assembly moving the valve assembly from a first position communicating fluid from the inlet into the volute to a second position blocking flow from the inlet to the volute.

Description:
RELATED APPLICATION 
       [0001]    This application is a non-provisional application of provisional application 61/968,581, filed Mar. 21, 2014, the disclosure of which is incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates generally to turbines, and, more specifically, to a method and system for controlling an amount of fluid in a control cavity using a hydraulically controlled secondary valve. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Turbochargers are used for many applications. A turbocharger includes a pump portion and a turbine portion. Turbochargers are used for recovering energy from a pressurized stream of fluid. Excessive pressure in the turbine portion is used to drive the pump portion. One use for a turbocharger is recovering energy from a brine outlet of a reverse osmosis membrane assembly. 
         [0005]    Reverse osmosis systems operate in a wide range of operating conditions for any given flow while seeking to maintain a high level of performance. Various turbine configurations are known for improving levels of performance for the turbine. 
         [0006]    In one known turbine, single volute nozzle volute systems use a valve stem to allow bypass fluid from the turbine inlet to the impeller. Some improvement in performance is achieved. A valve is used to control the amount of fluid in the bypass. Manually controlled valves require a person to physically move the control wheel using high torque. This is not practical especially in systems with multiple stages. Electrically controlled valves can be automated. However, due to the high torque involved in turning the valves, the systems for rotating the valves are expensive. 
       SUMMARY 
       [0007]    The present disclosure provides a turbine design that allows for controlling an amount of fluid entering a control volume using a hydraulically controlled valve in a bypass path. 
         [0008]    In one aspect of the disclosure, a turbine includes a housing having an inlet, a volute and an outlet. The inlet is coupled to the volute through a primary fluid path and a secondary fluid path. The turbine further includes an impeller rotatably coupled to the housing, and a hydraulically actuated valve assembly disposed within the secondary fluid path selectively communicating fluid from the inlet to the volute. The turbine includes a hydraulic actuator coupled to the valve assembly moving the valve assembly from a first position communicating fluid from the inlet into the volute to a second position blocking flow from the inlet to the volute. 
         [0009]    In another aspect of the disclosure, method of operating a turbine includes communicating fluid from an inlet of the turbine to a volute through a primary fluid path and selectively communicating fluid from the inlet of the turbine to the volute through a secondary path fluid path through a hydraulically controlled valve assembly. The hydraulically controlled valve assembly comprises a housing and a piston head defining a control cavity and a valve stem having a valve head thereon. The method further comprises communicating fluid to the control cavity, moving the valve head relative to a valve seat, and changing an amount of fluid flowing though the primary fluid path to the volute in response to communicating fluid to the control cavity. 
         [0010]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0011]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0012]      FIG. 1A  is a block diagrammatic view of a reverse osmosis system that includes a turbocharger. 
           [0013]      FIG. 1B  is a block diagrammatic view of the turbocharger of  FIG. 1A . 
           [0014]      FIG. 1C  is a block diagrammatic view of a turbocharger and motor assembly referred to as a HEMI. 
           [0015]      FIG. 2A  is a perspective view of the hydraulic valve assembly on a turbocharger according to the present disclosure. 
           [0016]      FIG. 2B  is an exploded view of the of the hydraulic valve assembly of the turbocharger according to the present disclosure. 
           [0017]      FIG. 3  is a cutaway perspective view of the turbocharger and valve assembly. 
           [0018]      FIG. 4  is a cutaway view of the hydraulic valve assembly according to the present disclosure. 
           [0019]      FIG. 5A  is a schematic view of a control circuit for control of the hydraulically actuated valve assembly in a closed position. 
           [0020]      FIG. 5B  is a schematic view of a control circuit for control of the hydraulically actuated valve assembly in an open position. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0022]    The present disclosure improves the hydraulic range of a turbine by allowing a variable amount of fluid to be communicated to the volute. The turbine has a primary fluid path and a secondary fluid path for communicating fluid from the inlet to the volute. The primary path is always open. As will be described below, a hydraulically actuated valve is attached to the turbine housing and opens and closes (including positions therebetween) a secondary fluid path from the inlet to the volute 
         [0023]    The turbocharger described below may be used for various types of systems, including a reverse osmosis system. Non-hydraulic applications such as natural gas processing are also possible. Further, the valves used in the turbocharger may be controlled based upon various process parameters. 
         [0024]    Referring now to  FIG. 1A , a reverse osmosis system  10  that includes a turbocharger  12  is set forth. In this example, feed fluid from an input manifold  14  is communicated through a high pressure pump  16  which in turn is communicated to a membrane housing  18  through the turbocharger  12 . The membrane housing  18  includes a reverse osmosis membrane  20  that is used to generate fresh water from sea water. Fresh water is generated at the permeate output  22  of the membrane housing. A brine stream from the membrane housing is directed to an inlet  24  of the turbocharger  12  through a brine control valve  25  selectively communicates the fluid from the turbocharger  12  to the membrane housing  18 . The turbocharger  12  uses the energy from the high pressure brine stream to increase feed fluid pressure. The pressurized feed fluid from the high pressure pump  16  is received through a pump input  26 . The turbocharger  12  increases the pressure of the feed fluid and increases the pressure of the feed fluid at the pump output  28 . Waste from the turbocharger  12  is discharged at a lower pressure through the turbocharger outlet  30 . Although one specific example of a reverse osmosis system  10  is illustrated, various examples for reverse osmosis systems will be evident to those skilled in the art. By providing the turbocharger  12 , the required pressure from the high pressure pump is reduced and the overall energy consumed by the system is also reduced as compared to a system without the turbocharger  12 . 
         [0025]    Referring now to  FIG. 1B , the turbocharger  12  is illustrated in further detail. The turbocharger  12  includes a turbine portion  40  and a pump portion  42 . The turbine portion  40  recovers energy from the high pressure stream by rotating and ultimately rotating the components within the pump portion  42 . The pump is used to increase the pressure of fluid to the input of the membrane housing  18 . 
         [0026]    Referring now to  FIG. 1C , the turbocharger  12  may also be incorporated into a system that includes a common shaft  50  that extends not only through the pump and turbine portion illustrated in  FIG. 1B  but extends to a motor  52 . The motor  52  includes a controller  54  the addition of the motor  52  allows the turbocharger to act as a pump when desired. The controller  54  may be used to drive the motor  52 . The controller  54  may be referred to as a variable frequency device. The motor  52  may also act as a generator to recover the excess power generated. 
         [0027]    Referring now to  FIGS. 2A and 2B , an assembled view and an exploded view of a turbocharger  12  is illustrated. In this example, the turbine portion  40  and a pump portion  42  having a common shaft  50  therebetween (as denoted by the dotted line). The turbine portion  40  includes a turbine housing assembly  202  and a hydraulically controlled valve assembly  204 . The turbine housing assembly  202  includes the brine stream the inlet  24 . The turbine outlet  30  is not illustrated in the perspective of  FIG. 2A . 
         [0028]    The hydraulically controlled valve assembly  204  has a piston housing  206  coupled to the turbine housing assembly  202  and an end cap  208 . Fasteners  209  may be used to secure the end cap  208  to the piston housing  206 . 
         [0029]    The hydraulically controlled valve assembly  204  has a linear guide  210  that is in physical communication with a position sensor  212  and which extends through the end cap  208 . The linear guide  210  is movable in a direction parallel with the direction of movement of a piston head  216  and valve stem  218  that is coupled thereto. The linear guide  210  may extend into the hydraulically controlled valve assembly  204  a varying amount. 
         [0030]    The position sensor  212  may be coupled to the housing  202  with a holder  214 . The position sensor  212  may be various types of sensors used to determine the relative position of the linear guide  210 . The position sensor  212  generates a position signal corresponding to the linear position. The position sensor  212  may, for example, be formed of a linear potentiometer that changes an output signal or voltage based upon the position of the linear guide  210 . The position sensor  212  may also be a linear encoder that provides the relative position of the linear guide  210  to a controller as described below. The position sensor  212  may also be comprised of a limit switch if exact positions of the system are not required. Details of the movement of the linear guide  210  and the position sensor  212  will be described in more detail below. 
         [0031]    The valve stem  218  is coupled to the piston head  216  and moves together therewith during use. The housing comprises a valve guide  220 . The valve guide  220  may be integrally formed with the piston housing  206 . The valve guide  220  positions the valve stem  218  so that the valve head  222  is positioned in the desired position relative to a valve seat as is described below. 
         [0032]    Referring now to  FIG. 3 , an end view of the turbine assembly  200  illustrating the turbine housing assembly  202 , the volute  232 , the hydraulically controlled valve assembly  204  and the inlet  24  are set forth in an assembled manner. The hydraulically controlled valve assembly  204  is set forth without the position sensor  212 , guide  210  and the holder  214  for simplicity. 
         [0033]    The shaft  50  is coupled to and rotates with a turbine impeller  228 . The shaft  50  represents the axis of rotation of the impeller  228 . The shaft  50  may extend out of the turbine housing  202  into the pump portion  42  of the turbocharger as described above. The impeller  228  has impeller vanes  234  that are used to receive pressurized fluid and rotate the shaft  50 . 
         [0034]    The housing  202  has a primary fluid path  240  from the turbine inlet  24  to the volute  232 . The primary fluid path  240  has a fixed width to allow fluid to pass therethrough. The primary fluid path  240  does not change. That is, fluid is always communicating therethrough during operation. A secondary fluid path  242  also communicates fluid from the inlet  24  to the volute  232 . The secondary fluid path  242  has the hydraulic actuated valve assembly  204  disposed therein. The hydraulically controlled valve assembly  204  is used to selectively move between an opened and closed position in the secondary fluid path  242 . Thus, the valve assembly  204  may be partially opened or closed. The hydraulically controlled valve assembly  204  is illustrated in an open position. However, as the valve stem  218  moves, the valve head  222  contacts the valve seat  252 . The valve seat  252  may be formed as part of the housing  202 . 
         [0035]    Referring now to  FIG. 4 , details of the hydraulically controlled valve assembly  204  is set forth. In this example, the piston head  216  and the valve stem  218  moves in the direction indicated by the arrows  410 , which corresponds to the longitudinal axis of the valve assembly  204 . The linear guide  210  that moves the position sensor  212  also moves in the direction indicated by the arrows  410 . The linear guide  210  may have seals  412  that seal a control cavity  414  from the external environment to prevent leakage. The piston head  216  may also include seals  416 . The seals  416  may be referred to as piston rings. The seals  416  prevent fluid from within the control cavity  414  from leaking outside of the control cavity  414 . 
         [0036]    The piston head  216  divides the piston housing  206  into the control cavity  414  and a movement area  418  that allows the piston to travel back and forth and expand and contract the control cavity  414 . 
         [0037]    An inlet port  420  is used to provide a control fluid to the control cavity  414 . By providing a high pressure fluid to the control cavity  414 , the control cavity  414  is expanded and the piston head  216  is moved toward the valve seat  252 . When a low pressure fluid is provided to the control cavity  414 , the piston head  216  moves toward the inlet port  420 . This, in turn, moves the valve stem  218  and the valve head  222  away from the valve seat  252 . 
         [0038]    An exit port  422  is in fluid communication with the movement area  418 . The inlet port  420  allows any air to escape the volume between the piston head  216  and the other part of the piston housing  206 . 
         [0039]    In an alternative embodiment, the exit port  422  may be used to provide high pressure into the movement area  418  while the inlet portion  420  is used as an inlet port for the control cavity  414  which is exposed to a low pressure. In this manner, the piston head  216  may be forced toward the inlet  420 . 
         [0040]    A plurality of seals  424  may be used to seal the valve stem  218  within the valve guide  220 . The valve guide  220  may be sealed within the housing  202  with seals  426 . 
         [0041]    A control circuit  440  may be coupled to the inlet port  420 . As mentioned briefly above, the control circuit  440  may also be coupled to the exit port  420 . The control circuit  440  may be combination of valves that are electrically controlled to provide fluid paths to the control cavity  414  to control the movement of the piston head  216  and the valve stem  218  attached thereto. By controlling the movement of the valve stem  218 , the opening and closing of the hydraulically controlled valve assembly  204  is controlled. 
         [0042]    The valve head  222  may include an angular seal surface  426  that is used for engaging the seal seat  252  to form a seal therebetween. The seal prevents fluid flow through the secondary fluid path  242 . An angular surface  428  may couple the valve stem  218  to the seal surface. The valve head  222  may also include a flat surface  430 . In this example, the flat surface  430  is perpendicular to the longitudinal axis of the valve stem  218 . 
         [0043]    Referring now to  FIG. 5A , a simplified hydraulic control diagram is illustrated in which the control circuit  440  provides high pressure fluid to the control cavity  414 . In this example, the valve head  222  is shown in a closed position. That is, the fluid from the inlet  24  does not travel through secondary fluid path  242  to the volute  232 . In this example, valve  510  is in an open position to allow high pressure fluid from the high pressure source  508  into the control cavity  414  through the inlet port  420 . The low pressure valve  512  is in a closed position. The high pressure valve or the low pressure valve may be a normally open valve for failsafe operation. When the high pressure valve is a normally open valve, the system will close the valve assembly  204  upon loss of power or control. If the low pressure valve  512  is replaced with a normally open valve, the system will open the secondary fluid path  242  upon loss of system power or shutdown. The choice between which valve is normally open is based on design considerations. 
         [0044]    A controller  514  controls the operation of the valves  510 ,  512 . During operation, typically either the high pressure valve  510  or the low pressure valve  512  is open to allow a varying amount of fluid to pass though the valve assembly  204  and through the fluid path  242 . However, during a cleaning process or other type of process, both valves  510  and  512  may be opened. The controller  514  is in communication with a plurality of process sensors  520 . The process sensors  520  may include the position sensor illustrated above. Other types of sensors such as temperature sensors, flow sensors, flow rate sensors, or the like may be used by the controller  514  to determine whether to open or close the high pressure valve  510  or the low pressure valve  512  to change the amount of fluid passing through the fluid path  242 . It should be noted that both valves  510  and  512  may be closed when no change is desired in the position of the valve head  222  relative to the valve seat  252 . From an at-rest position, the piston head  216 , the valve stem  218  and valve head  222  may be moved by introducing high pressure fluid into the inlet port  420 . To move the piston head  216  and valve head  222  toward the valve seat  252 , low pressure may be exposed to the control cavity  414  through the low pressure valve  512 . 
         [0045]    Feedback control is achieved by periodically monitoring the process variables using the process sensors  520 . The controller  514 , in response to the process sensors  520 , open and close the appropriate valves  510 ,  512  to change the opening between the valve head  222  and the valve seat  252 . The process variables are described below: 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Loop Forever 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 E = (P − S) / S 
                 Calculate error percentage 
               
               
                   
                 If E &gt;1 then E = 1 
                 Limit error to range [−1 . . . 1] 
               
               
                   
                 If E &lt;−1 then E = −1 
               
               
                   
                 TO = K E T 
                 Compute valve open time 
               
               
                   
                 TC = T − TO 
                 Compute valve closed time 
               
               
                   
                 If E &gt; D 
                 Check for outside of deadband 
               
               
                   
                 Open V1 for time TO 
                 Open V1 to close primary fluid path 
               
               
                   
                 Close V1 for time TC 
               
               
                   
                 If E &lt; −D, 
                 Check for outside of deadband 
               
               
                   
                 Open V2 for time TO 
                 Open V2 to open primary fluid path 
               
               
                   
                 Close V2 for time TC 
               
               
                   
                   
               
               
                   
                 P—Process variable, measured value. 
               
               
                   
                 S—Set point for process. 
               
               
                   
                 E—Current error (percent). 
               
               
                   
                 K—Proportional gain (~1, tunable value). 
               
               
                   
                 D—Deadband in percent (typically 1%). 
               
               
                   
                 T—Update time period (typically 5 seconds). 
               
               
                   
                 TO—Valve open time period. 
               
               
                   
                 TC—Valve close time period. 
               
             
          
         
       
     
         [0046]    In the above algorithm the error percentage is calculated between a range of −1 and +1. The valve open time and the valve close time may be calculated using a proportional gain, a current error and an update. A deadband D may be compared to the current error. When the current error is outside of the deadband, the valve may be opened or closed. That is, when the error is greater than the deadband, valve  510  is opened to close the amount of the opening of valve assembly  204 . When the error is less than the negative deadband, then the valve  512  is opened so that the piston moves toward the control port. 
         [0047]    Referring now to  FIG. 5B , the piston  216  is illustrated toward the inlet port  420 . To move the piston  216  toward the inlet port  420  as compared to that in  FIG. 5A , the high pressure valve is  510  is closed and the low pressure valve  512  is opened. This causes the valve head  222  to be in an open position to allow flow through the valve. A plurality of valve head positions may be achievable between the valve head positions illustrated in  FIGS. 5A and 5B  so that the flow through the fluid path  242  may be varied. 
         [0048]    In both  FIGS. 5A and 5B  high pressure source  508  and the low pressure source  516  may be hydraulically coupled to the turbine portion. That is, the high pressure source  508  may be in fluidic communication with the turbine inlet  24  which is a high pressure source. The low pressure source  516  may be coupled to the turbine outlet  30  or even to the atmosphere. 
         [0049]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.