Patent Publication Number: US-2023160349-A1

Title: Hydraulically rate limited valve

Description:
BACKGROUND OF THE INVENTION 
     This application relates to a valve and an electromechanical interface device (EMID) for use with a variable pressure supply. 
     Valves are used in any number of applications. In one application a metering valve is incorporated into a fuel supply system for supplying fuel to a combustor nozzle on a gas turbine engine. 
     EMIDS, such as electrohydraulic servo valves (EHSV) are also used in many applications. In one application an EHSV is incorporated to control hydraulic fluid flow to control the position of a metering valve. 
     There are a number of challenges with providing adequate fluid flow across such valve under different conditions. 
     SUMMARY OF THE INVENTION 
     A fluid flow system includes a main valve having a spool, a first chamber, and a second chamber. A pressure difference between the first chamber and the second chamber is configured to move the spool to control fluid flow. An electromechanical interface device (EMID) is in fluid communication with at least one of the first and second chambers of the main valve. The EMID is configured to meter fluid from a first source and a second source to the at least one of the first chamber and the second chamber. The first source has a different pressure from the second source. A fixed orifice is arranged between the main valve and the EMID. 
     A fuel system for a gas turbine engine is also disclosed. 
     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows a fluid flow system according to an exemplary embodiment. 
         FIG.  2    shows an exemplary electrohydraulic servo valve (EHSV). 
         FIG.  3    shows another example fluid flow system having a single stage servo valve (SSSV). 
         FIG.  4 A  shows a detail of an example fixed orifice. 
         FIG.  4 B  shows a cross-sectional view of the example fixed orifice of  FIG.  4 A . 
         FIG.  5    shows an example fixed orifice. 
         FIG.  6    shows another example fixed orifice. 
     
    
    
     DETAILED DESCRIPTION 
     A fluid flow system  28  is illustrated in  FIG.  1   . The fluid flow system  28  may be used to meter fuel to a nozzle  26  on an engine  11 , for example. The engine  11  may be a gas turbine engine, for example. Gas turbine engines are known, and may generally include a fan section, a compressor section, a combustor section and a turbine section, among other components. The nozzle  26  may be a nozzle  26  into a combustor section. The fluid flow system  28  may be utilized for applications other than fuel supply. 
     The fluid flow system  28  generally includes an electromechanical interface device (EMID)  16  and a metering valve  22 . The EMID  16  may be an electrohydraulic servo valve (EHSV), torque motor, or other device, for example. The EMID  16  and metering valve  22  control fluid to the nozzle  26  from a variable pressure source. A first fluid source  10  and a second fluid source  12  are in communication with the EMID  16  and then the metering valve  22 . In some examples, fluid from the first fluid source  10  also flows to the metering valve  22  to be delivered to nozzle  26 . In one example, the first fluid source  10  is a high-pressure fluid source and the second fluid source  12  is a low-pressure fluid source. In some examples, a pump  13 ,  15  at each of the first and second fluid sources  10 ,  12 , respectively, supplies the fluid to the system  28 . In this embodiment each source  10  and  12  are fuel. 
     In some examples, additional fluid flow lines  23 ,  24  connect the first source  10  to the EMID  16  and the metering valve  22 . Fluid flow line  24  connects the first source  10  and the inlet port  27  of the metering valve  22 . Fluid flow line  23  connects the first source  10  and the EMID  16 . A fluid line  25  connects the metering valve  22  to the fuel nozzle  26 . 
     In this example, the EMID  16  is in fluid communication with the metering valve  22  via two fluid lines  18 ,  20 . The EMID  16  modulates fluid from the high-pressure source  10  and the low-pressure source  12  to achieve a pressure differential to the metering valve  22 . An electronic control  50 , shown schematically, selectively controls the EHSV  16 . 
     The first fluid line  18  is in communication with a first chamber  37  at a first end  40  of the metering valve  22 . The second fluid line  20  is in communication with a second chamber  34  at a second end  42  of the metering valve  22 . The metering valve  22  also includes a spool  38  arranged between the first and second chambers  37 ,  34 . An annulus  39  is defined about the spool  38 . The annulus  39  is in communication with an inlet port  27  and an outlet port  29 . A pressure difference between the first and second chambers  37 ,  34  moves the spool  38 , which meters fluid between the inlet and outlet ports  27 ,  29  by blocking portions of the inlet and/or outlet ports  27 ,  29 . The speed at which the spool  38  moves based on the pressure differences between the chambers  37 ,  34  is known as the slew rate. 
     Hydraulic control of a metering valve  22  through an EMID  16  is dependent upon the pressure within the system  28 . Thus, for a given fluid supply, the slew rate of the metering valve  22  will increase as the pressure differential between lines  18  and  20  is increased. The EHSV  16  controls the pressure acting on either end of the metering valve  22  to achieve a desired position for spool  38 . 
     As the pressure changes between the chambers  37 ,  34  the slew rate may increase. It is undesirable for the slew rate to exceed a predetermined threshold. To prevent the pressure differences that cause a slew rate above the predetermined threshold, fixed orifices  19  and  20  may be arranged between the EMID  16  and the metering valve  22 . 
     In this example, a first fixed orifice  19  is arranged along the first fluid line  18  and a second fixed orifice  21  is arranged along the second fluid line  20 . The fixed orifices  19 ,  21  are arranged between the EMID  16  and metering valve  22  to limit the flow rate of fuel to the metering valve  22 . The fixed rate orifices  19 ,  21  are sized to maintain the flow of fluid within a predetermined pressure range. For example, there may be a predetermined threshold flow rate that is a maximum flow rate and the orifices  19 ,  21  are sized to ensure the pressure difference between the first chamber  37  and the second chamber  34  remains below the predetermined threshold. This maintains the slew rate below the predetermined maximum. 
     While this application specifically discloses a metering valve in a fuel system, other valves for controlling fluid flow in other applications may benefit from the teachings of this disclosure. 
       FIG.  2    shows an example EMID  16 . In this example, the EMID  16  is an electrohydraulic servo valve (EHSV). The EHSV  16  has two stages including a torque motor  30  and a hydraulic mechanism  300  used to drive a spool  55  of a spool valve  41 . The torque motor  30  controls the flow of hydraulic fluid which drives the hydraulic mechanism  300  and the spool  55 . The torque motor  30  includes an armature  32  and magnetic coils  36 . The armature  32  is positioned by the magnetic force from the energized coils  36  to provide a supply pressure  35  to position the hydraulic mechanism  300 . The hydraulic mechanism  300  attached to the torque motor  30  may be a jet type, or any other type of hydraulic mechanism. 
     The spool  55  has a right spool valve land  58  and a left spool valve land  56  on a spool  55 . The right spool valve land  58  controls communication with the second fluid line  20  and the left spool valve land  56  controls communication with the first fluid line  18 . The spool  55  moves in response to fluid pressure in a left spool chamber  52  and a right spool chamber  54 . End lands  57  provide reaction surfaces for fluid in chambers  52  and  54 . Source  10  is directed into chambers between end lands  57  and each of lands  56  and  58 . Source  12  is directed into a chamber between lands  56  and  58 . Electronic control  50  positions spool  55  such that a desired mix from sources  10  and  12  passes into lines  18  and  20 , to in turn achieve a desired position of the spool  38  in metering valve  22 . This provides a desired flow of fuel through metering valve. 
       FIG.  3    illustrates another example of a fluid flow system  128 . To the extent not otherwise described or shown, the fluid flow system  128  corresponds to the fluid flow system  28  of  FIGS.  1  and  2   , with like parts having reference numerals pre-appended with a “ 1 .” The EMID  116  in the system  128  is a single stage servo valve (SSSV)  116 . The SSSV  116  is in communication with a high pressure source  110  and a low pressure source  112 . The SSSV  116  includes a flapper  133  that moves in response to current through a torque motor  130 . Fluid flowing through the flapper  133  flows from the fluid sources  110 ,  112  to the first fluid line  118  and then to the metering valve  122 . Electronic control  150  controls the torque motor  130  to achieve a desired mix between lines  110  and  112  into line  118 . 
     The fluid line  118  connects the SSSV  116  to a first chamber  137  of the metering valve  122 . A second chamber  134  is in communication with the second fluid source  112 . A third chamber  135  is in communication with source  112 . A fluid pressure difference between the first and third chambers  134 ,  135  in combination, acts against a mixed flow from line  118  in chamber  137 . This moves the spool  138  to modulate fluid flowing to the nozzle  136  through line  126 . As spool  138  moves an annulus  139  selectively controls flow between inlet line  124 , from source  110 , and to outlet line  126 . Control  150  controls the mixed pressure on line  118  to position spool  138 . 
     An orifice  119  arranged along the first fluid line  118  between the SSSV  116  and the metering valve  122  limits the pressure of fluid flowing into the first chamber  137 . The fixed orifice  119  limits the slew rate of the metering valve  122  by preventing large pressure differences between the chambers  134 / 135  and  137 . 
     In the event of a failure of the EMID  16 ,  116 , it is possible high pressure fluid only may be directed to one side of either metering valve  22 ,  122 , causing a high slew rate. A high slew rate of the metering valve  22 ,  122  would be undesirable. The fixed orifices  19 ,  21 ,  119  arranged between the EMID  16 ,  116  and the metering valve  22 ,  122  help to ensure the metering valve  22 ,  122  is not exposed to fluid pressure differentials above a predetermined threshold. 
       FIG.  4 A  shows an example orifice  19 . Although the example orifice  19  is shown, this description may also apply to the orifice  21  in  FIG.  1    and orifice  119  in  FIG.  3   . In this example, the orifice  19  is arranged along a pipe  51  and maintains valve slew rates at the metering valve  22  below a predetermined threshold. The orifice  19  has an inner diameter  44  that is smaller than a nominal diameter  46  of the pipe  51 . 
     As shown in  FIG.  4 B , the orifice  19  extends inward of the pipe  51  and is symmetric about the longitudinal axis  48  of the pipe  51 . In other words, the orifice  19  extends into the pipe  51  about a circumference of the pipe  51 . This configuration limits the slew rates during a failed EMID  16  condition by limiting the pressure of fluid flowing to the metering valve. Although a particular orifice  19  is shown, other orifice configurations may be used. The diameters  44 ,  46  may be selected based on a particular application to maintain the slew rate below a predetermined threshold. 
       FIG.  5    shows another example orifice  170 . The orifice  170  is arranged within a housing  66 . In this example, a first screen  60  and a second screen  64  are arranged on opposite sides of restriction  144 . The screens  60 ,  64  protect the restriction  144  from debris in the fluid. 
       FIG.  6    shows another example orifice  219 . The orifice  219  includes a housing  70 . A first screen  68  and a second screen  72  are arranged on opposite sides of the restriction  244 . 
     The disclosed system eliminates concerns about undesirably high slew rates with a simple construction using fixed orifices to maintain the valve slew rates within a safe range. 
     This arrangement limits the slew rates when the EMID fails. This arrangement may reduce cost and weight and improve reliability of the fuel metering system. 
     While this disclosure specifically describes a metering valve in a fuel supply, it could be used in other applications. As examples, it could be used with actuators for other functions on an engine, such as for variable vane stator actuators, pneumatic valves, bleed valves, or other applications. 
     A fluid flow system under this disclosure could be said to include a metering valve having a spool, a first chamber, and a second chamber. A pressure difference between the first chamber and the second chamber is configured to move the spool to meter a fluid. The metering valve is in fluid communication with a use. An electromechanical meter interface device (EMID) is in fluid communication with at least one of the first and second chambers of the metering valve. The EMID is configured to meter fluid from a first source and a second source to at least one of the first chamber and the second chamber. The first source has a different pressure from the second source. At least one fixed orifice is arranged between the metering valve and the EMID. 
     The first chamber may be in communication with the EMID via a first fluid line and the second chamber is in communication with the EMID via a second fluid line. The at least one fixed orifice includes a pair of fixed orifices, with one of the fixed orifices on the first fluid line and one on the second fluid line. 
     Alternatively, one of the first and second chambers may be is in fluid communication with the EMID via a first line, and the other of the first and second chambers is in fluid communication with one of the first and second sources without passing through the EMID, and the fixed orifice is on the first line. 
     A fluid flow system under this disclosure could also be said to include a metering means for metering fluid flow from a fluid source to a use. Control valve means direct a fluid source mixed from a first fluid source and a second fluid source through a first line to control a volume of fluid metered by the metering means. Fixed restriction means on the first line limit a pressure from the control valve means reaching the metering means. 
     The metering means may be a spool valve. The control valve means may be an electromechanical interface device and the fluid restrictions means may be a fixed orifice. 
     Although embodiments of this disclosure have been shown, a worker of ordinary skill in this art would recognize that modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure.