Abstract:
The subject matter of this specification can be embodied in, among other things, a fuel pressure regulator system for regulating pressure through a fuel delivery path that includes a fuel pressure regulator valve in the fuel delivery path operable to selectively provide a restriction in the fuel delivery path in response to a reference fluid pressure, a reference fluid path comprising a first orifice, a second orifice and an outlet downstream of the first orifice, the reference fluid path coupled to the fuel pressure regulator valve intermediate the first and second orifices to supply the reference fluid pressure to the fuel pressure regulator valve, and a reference fluid valve upstream of the first orifice operable to selectively provide a restriction into the reference fluid path.

Description:
TECHNICAL FIELD 
       [0001]    The concepts herein relate to fluid pressure regulators and more particularly to fluid pressure regulators with damped regulation responses. 
       BACKGROUND 
       [0002]    Pressure regulators can maintain the pressure of fluid provided at the inlet of the pressure regulator above the pressure of a reference fluid. The reference fluid is also provided to the regulator. The upstream fluid can then be provided at the higher, regulated, pressure to other valves and equipment. 
         [0003]    Many pressure regulators use a loading element such as a spring to apply a force to a restricting element that limits the available flow area through the pressure regulator. The spring and restricting element combination gives a spring-mass system that can oscillate under varying combinations of upstream fluid pressure, downstream fluid pressure, and reference pressure inputs. 
       SUMMARY 
       [0004]    In general, this document describes fluid pressure regulators. 
         [0005]    In a first aspect, a fuel pressure regulator system for regulating pressure through a fuel delivery path includes a fuel pressure regulator valve in the fuel delivery path operable to selectively provide a restriction in the fuel delivery path in response to a reference fluid pressure, a reference fluid path comprising a first orifice, a second orifice and an outlet downstream of the first orifice, the reference fluid path coupled to the fuel pressure regulator valve intermediate the first and second orifices to supply the reference fluid pressure to the fuel pressure regulator valve, and a reference fluid valve upstream of the first orifice operable to selectively provide a restriction into the reference fluid path. 
         [0006]    Various implementations can include all, some, or none of the following features. The reference fluid valve can be operable in response to a control signal. The control signal can be indicative of a threshold speed of an engine, and the reference fluid valve can be operable to provide the restriction into the reference fluid path when the control signal indicates that the engine is operating below the threshold speed and remove the restriction into the reference fluid path when the control signal indicates that the engine is operating at or above the threshold speed. The reference fluid valve can be operable in response to the reference fluid pressure, the reference fluid valve providing the restriction into the reference fluid path when the reference fluid pressure is below a threshold pressure and removing the restriction into the reference fluid path when the reference fluid pressure is at or above the threshold pressure. The reference fluid pressure can be indicative of an operating speed of an engine, and the threshold pressure can be reflective of the threshold operating speed of the engine. 
         [0007]    In a second aspect, a method for regulating fuel pressure through a fuel delivery path includes providing a fuel pressure regulator valve in the fuel delivery path operable to selectively provide a restriction between a fuel inlet and a fuel outlet in the fuel delivery path in response to a reference fluid pressure, providing a reference fluid path comprising a first orifice, a second orifice and an outlet downstream of the first orifice, the reference fluid path coupled to the fuel pressure regulator valve intermediate the first and second orifices to supply the reference fluid pressure to the fuel pressure regulator valve. The method also includes providing a reference fluid valve upstream of the first orifice operable to selectively provide a restriction into the reference fluid path/providing a reference fluid at the reference fluid valve, providing a first control signal at the reference fluid valve, restricting by the reference fluid valve in response to the first control signal flow of the reference fluid, providing the reference fluid and a second control signal at the reference fluid valve, flowing, by the reference fluid valve in response to the second control signal, the reference fluid to the first orifice, restricting by the first orifice flow of the reference fluid to the reference fluid path, restricting by the second orifice flow of the reference fluid out of the reference fluid path wherein flow of the reference fluid into the reference fluid path and flow of the reference fluid out of the reference fluid path create the reference fluid pressure as a differential pressure in the reference fluid path, providing fuel to the fuel pressure regulator valve at the fuel inlet, and selectively providing, by the fuel pressure regulator valve and in proportion to the reference fluid pressure, the restriction between the fuel inlet and the fuel outlet in the fuel delivery path in response to the reference fluid pressure. 
         [0008]    Various implementations can include some, all, or none of the following features. The first control signal can be indicative of an engine running below a threshold speed, and the second control signal can be indicative of the engine running at or above a threshold speed. The first control signal can be a first pressure of the reference fluid, and the second control signal can be a second pressure of the reference fluid. At least one of the first control signal and the second control signal can be an electrical command from the engine. 
         [0009]    The systems and techniques described here may provide one or more of the following advantages. First, a system can provide damping of the pressure regulator that is independent of amplitude by using a flowing orifice damping arrangement. Second, the system can provide two different reference pressure levels by turning off the flowing orifice damping arrangement. Third, the system can reduce the size and/or weight of a fluid pump used to supply a reference and inlet fluid to the system. 
         [0010]    The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0011]      FIGS. 1 and 2  are schematic diagrams of fluid pressure regulators with orifice damping. 
           [0012]      FIG. 3  is a schematic diagram of an example fluid pressure regulator that implements orifice damping with switching. 
           [0013]      FIGS. 4 and 5  are schematic diagrams of an example fluid delivery system that includes an example fluid pressure regulator with damping. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    This document describes systems and techniques for regulating fluid pressure with a damped response. Pressure regulators generally use a loading element such as a spring to apply a force to a restricting element that limits the area available for flow of fluid through the pressure regulator. The regulated pressure is set by a reference pressure input that is additive to the force applied by the loading element. The loading and restricting elements, however, can oscillate under varying combinations of upstream fluid pressures, downstream fluid pressures, and reference pressure inputs. Two damping schemes used for pressure regulator systems include laminar damping and orifice damping. Laminar damping is proportional to valve velocity, but can be sensitive to temperature when the viscosity of the fluid being regulated is highly temperature dependent. Due to this temperature sensitivity, laminar damping is not typically implemented on pressure regulators that must operate over a wide temperature range. 
         [0015]      FIG. 1  is schematic diagram of a fluid pressure regulator  100  that uses non-flowing orifice damping. A fluid with a pressure to be regulated is provided at an input  105  of a valve  110 . A spring  120  urges the valve  110  toward a position that restricts or blocks fluid flow between the inlet  105  and the outlet  115 . 
         [0016]    A control fluid is provided as a reference pressure at an input  130 . In general, as flow at the inlet  105  decreases the reference pressure  130  is added to the bias force of the spring  120  to urge the valve  110  toward a position that restricts fluid flow between the inlet  105  and the outlet  115 . Reducing the allowable flow area as flow level decreases maintains the inlet  105  pressure level. Likewise, the valve  110  moves toward a less restrictive position as flow level increases. Overall, the inlet  105  pressure level remains at approximately a fixed amount above the reference  130  pressure level regardless of the amount of flow through the valve. 
         [0017]    The valve  110  and spring  120  combination gives a spring-mass system that is prone to being unstable without damping. The pressure regulator  100  includes a non-flowing orifice  140  that provides damping by restricting the flow of control fluid in and out of the valve  110 . 
         [0018]    Non-flowing orifice damping, as implemented by the pressure regulator  100 , is substantially temperature insensitive (e.g., good), but is proportional to the square of valve velocity (e.g., bad). As a result, the non-flowing orifice  140  provides little or no damping when the valve  110  is stationary, and overdamps the valve  110  during large disturbances (e.g., when flow through the valve rapidly changes). To offset the over-damping problem, a collection of check valves  150  are positioned in parallel with the non-flowing orifice  140 . The check valves  150  shunt the orifice  140  during large, fast transients exhibited at the valve  110 . 
         [0019]      FIG. 2  is schematic diagram of a prior art fluid pressure regulator  200  that uses flowing orifice damping. A fluid with a pressure to be regulated is provided at an input  205  of a valve  210 . A spring  220  urges the valve  210  toward a position that restricts or blocks fluid flow between the inlet  205  and the outlet  215 . 
         [0020]    A control fluid is provided as a reference pressure at an input  230 . The control fluid flows from the input  230  to an input flowing orifice  240  and an output flowing orifice  250  connected in series with the input orifice  240 . A differential pressure is developed in a fluid pathway  260  that fluidically connects the input flowing orifice  240  and the output flowing orifice  250 . 
         [0021]    The valve  210  is responsive to changes in flow through it. In general, as the flow at inlet  205  decreases pressure within the fluid pathway  260  is added to the bias force of the spring  220  to urge the valve  210  toward a position that restricts fluid flow between the inlet  205  and the outlet  215 . Reducing the allowable flow area as flow level decreases maintains the inlet  205  pressure level. The inlet  205  pressure level remains at an approximately fixed level above the pathway  260  value even though flow through the valve varies. 
         [0022]    Flowing orifice damping, as implemented in the pressure regulator  200 , is substantially temperature insensitive (e.g., good) and tends to be proportional to the velocity of the valve  210  (e.g., good) rather than to the square of valve velocity. As such, the flowing orifices  240  and  250  provide damping at both low and high valve velocities, and the damping is less amplitude dependent as compared to the non-flowing orifice  140 . Flowing orifice embodiments, however, result in internal leakage that can have adverse performance impacts on upstream and/or downstream systems. 
         [0023]      FIG. 3  is a schematic diagram of an example fluid pressure regulator  300  that implements orifice damping with switching. In general, the pressure regulator  300  implements a flowing orifice design while eliminating the adverse consequence of internal leakage. In some implementations, the pressure regulator  300  may be a component within a system for regulating fuel flow to an aircraft engine. 
         [0024]    A fluid with a pressure to be regulated is provided at an input  305  of a valve  310 . A spring  320  urges the valve  310  toward a position that restricts or blocks fluid flow between the inlet  305  and the outlet  315 . 
         [0025]    The valve  310  is responsive to changes in flow through it. In general, as flow at inlet  305  decreases the pressure within fluid pathway  360  is added to the bias force of the spring  320  to urge the valve  310  toward a position that restricts fluid flow between the inlet  305  and the outlet  315 . Reducing the allowable flow area as flow level decreases maintains the inlet  305  pressure level. The inlet  305  pressure level remains at an approximately fixed level above the pathway  360  value even though flow through the valve varies A control fluid is provided at a reference pressure to an adjustment input  330 . The control fluid flows from the adjustment input  330  to a bypass valve  370  which is biased by a spring  380 . When the bypass valve  370  is open, the control fluid is allowed to flow to an input flowing orifice  340  and an output flowing orifice  350  connected in series with the input orifice  340 . A differential pressure is developed in a fluid pathway  360  that fluidically connects the input flowing orifice  340  and the output flowing orifice  350 . When the bypass valve  370  is closed, the control fluid is blocked from flowing to the input flowing orifice  340 . 
         [0026]    The flowing damping orifice configuration of the valve  310  provides dynamic benefits, however in some implementations the leakage flow consumed by the combination of the input flowing orifice  340  and the output flowing orifice  350  may not always be beneficial, e.g., at engine start in engine fuel pressure regulator applications. In engine fuel pressure control implementations, at engine start speed, engine speed is low, which can result in low pump flow. The bypass valve  370  can be responsive to this low pump flow, and can position itself near a closed stop, blocking flow to the input flowing orifice. As engine speed increases, so too does pump flow, which can reposition the bypass valve  370  to a more open position that permits excess pump fluid flow through the bypass valve  370 . 
         [0027]    The bypass valve  370  is responsive to an external signal. In some embodiments, the external signal can be the pressure of the end chambers  390  and  392 . For example, the bypass valve  370  may by urged closed by the spring  380  and pressure within an end chamber  390 , and may remain closed until the pressure of an end chamber  392  is sufficient to overcome the bias of the spring  380  and pressure within the end chamber  390 . In some embodiments, the external signal can be an electrical signal. For example, the valve  370  can be an electromechanical valve that is operable to selectively block or allow flow of the control fluid between the adjustment input  330  and the input flowing orifice  340  in response to an electrical signal. In some embodiments, the external signal can be a fluid signal. For example, the valve  370  can be an fluidically actuated valve that is operable to selectively block or allow flow of the control fluid between the adjustment input  330  and the input flowing orifice  340  in response to a fluid (e.g., hydraulic, pneumatic) signal that is separate from the control fluid. 
         [0028]    In aircraft applications, space and weight can be limited commodities. Use of the pressure regulator  100  of  FIG. 1  in such examples may allow high-frequency pressure oscillations in the fuel to go substantially undamped across the valve  110 . For example, the operation of fuel injectors downstream of the pressure regulator  100  may introduce oscillations that can back-propagate and cause problems with equipment upstream from the pressure regulator  100  (e.g., noisy sensor readings, damage to fuel pumps). In another example, oscillations introduced upstream of the pressure regulator  100  (e.g., by fuel pumps, vibration from the engine) can propagate to and interfere with the function of equipment downstream from the pressure regulator (e.g., fuel injectors). 
         [0029]    Use of the pressure regulator  200  of  FIG. 2  in such examples (e.g., aircraft engine systems) may increase the total weight of the engine system. For example, the flow of control fluid through the fluid pathway  260  may be dependent upon engine speed, such as by an engine-driven pump, and the input flowing orifice  240  and the output flowing orifice  250  may be selected to provide a desired pressure within the fluid pathway  260  at normal engine operating speeds. At idle engine speeds however, the flow provided through the fluid pathway  260  by such an engine speed-dependent pump can drop far enough to prevent the valve  210  from functioning as needed. This situation can be resolved by using a larger pump that is capable of providing sufficient flow at idle speeds, however such larger pumps are generally correspondingly larger, heavier, and/or more costly than pumps that can provide sufficient flow at normal engine speeds. 
         [0030]    By contrast, the pressure regulator  300  of  FIG. 3  avoids the need for larger pumps. At normal engine speeds, the valve  310  operates much like the valve  210 , and the pump used to supply control fluid to the adjustment input  330  can be sized to provide the desired flow at normal engine speeds. But unlike the pressure regulator  200 , the pressure regulator  300  includes the bypass valve  370  that can be activated at low engine speeds 
         [0031]      FIGS. 4 and 5  are schematic diagrams of an example fluid delivery system  400  that includes an example fluid pressure regulator with damping. The system  400  includes a bypass valve  410 , a metering valve  430 , and a pressurizing valve  450  (e.g., pressure regulator). In some implementations, the system  400  can regulate fuel flow to an aircraft engine. 
         [0032]    In general, a fluid  402  (e.g., fuel) is provided at a fluid inlet  404 . The fluid flows to a meter inlet  432  of the metering valve  430 , and out a meter outlet  434  to a pressurizing valve inlet  452  of the pressurizing valve  450 . The pressurizing valve  450  regulates the pressure of the fluid  402  at an outlet  452  in response to the pressure of a fluid  460  applied at an input  456 . 
         [0033]    In use, the bypass valve  410  maintains a substantially constant differential pressure across the metering window of the metering valve  430 . The metering valve  430  holds a metering port window that corresponds to the desired flow of the fluid  402  at the outlet  452  (e.g., a desired engine burn flow). The pressurizing valve  450  maintains at least a predetermined minimum fluidic pressure used to provide fluidic force margins for the metering valve  430  and internal or external actuation systems. 
         [0034]    The bypass valve  410  includes a pressure switch  414  affixed to the bypass valve. The pressure switch  414  controls the flow of the fluid  460  from a switch inlet  416  to a switch outlet  418 , and on to a flowing damping orifice assembly  470  which includes a flowing inlet orifice  472  and a flowing outlet orifice  474 . The flowing damping orifice assembly  470  restricts the flow of the fluid  460  and dampens the response of the pressurizing valve  450 . In some embodiments, the flowing inlet orifice  472  can be the input flowing orifice  340  of  FIG. 3 , the flowing outlet orifice  474  can be the output flowing orifice  350 , and the fluid  460  can be the fluid  360 . 
         [0035]    In some implementations, the configuration shown in  FIG. 4  may be used in an engine fuel delivery application. Referring to  FIG. 4 , the bypass valve  410  is in a near closed position during engine start conditions. The pressure of the fluid  460  at the switch inlet  416  is isolated from the flowing damping orifice assembly  470 , resulting in no added fluid flow to support the damping arrangement. In this configuration, the pressure of the fluid  460  provided to the pressurizing valve  450  is the same as the pressure of the fluid  460  at an outlet  490 . Pressure at the outlet  490  approximates the pressure of the fluid  402  at a bypass valve outlet  420  of the bypass valve  410 . The setting of pressure level  452  is a function of preload provided by a spring  458  and pressure at the outlet  490 . 
         [0036]    In the example configuration of  FIG. 4 , bypass valve  410  and setting of the pressure switch  414  reduces or eliminated system leakage through the flowing damping orifice assembly  470 . In some implementations, the illustrated configuration can reduce pump flow demand at engine start conditions. 
         [0037]    Referring now to  FIG. 5 , the bypass valve  410  is shown in an open configuration. In some implementations, the example configuration of the system  400  may be used at idle engine speeds or higher. The fluid  460  is connected to the flowing damping orifice assembly  470 . The fluid  460  flows from the flowing inlet orifice  472  to the flowing outlet orifice  474  as a circuit flow  505 . The circuit flow  505  from the flowing inlet orifice  472  to the flowing outlet orifice  474  creates a differential fluid pressure  510  that is provided at the adjustment input  456 . The circuit flow  505  is supplied by pump flow to support the damping arrangement provided by the flowing damping orifice assembly  470 . In some implementations, aircraft engine systems have excess pump flow at idle engine speeds and above, which provide flow that meet or exceed the circuit flow  505 . 
         [0038]    In the present example, the pressure of the fluid  460  at the switch inlet  416  can be about 150 to 400 psid above the fluid pressure  510 . The setting of the pressurizing valve  450  is a function of preload of the spring  458  plus the fluid pressure  510  setting. In some embodiments, having a relatively high differential pressure between the fluid  402  at the inlet  404  and at the outlet  420  can be used in high actuation system pressure applications to reduce the size requirement for internal and external actuators. 
         [0039]    In some embodiments, the position of the switch  414  may be variable between its fully open and fully closed configurations. For example, the position of the bypass valve  410  at aircraft takeoff conditions can be similar to the position of the bypass valve  410  at aircraft engine start conditions, e.g., both conditions can result in positions of the bypass valve  410  near the full closed position. In some embodiments, analysis can be used during aircraft takeoff to determine that system pressure (e.g., the differential pressure between the fluid  402  at the fluid inlet  404  and at the bypass valve outlet  420 ) may be set via nozzle and/or compressor discharge pressure drops, and the pressurizing valve  450  can be fully open, in which case there may be no need for the flowing damping orifice assembly  470 , and closure of the switch  414  may be redundant. 
         [0040]    In some embodiments, the fluid  460  pressure can be equivalent to fluid pressure at the inlet  404 . In some embodiments, the fluid  460  can be replaced by a fluid (e.g., the fluid  402  at the inlet  404 ) that has passed through heaters and/or screens. The pressure of the heated and/or screened fluid can be nearly equivalent to the pressure of the fluid  402 . In still other embodiments, the fluid  460  can be replaced by a fluid that is supplied by an alternate pressure regulator having a pressure setting less than the pressure of the fluid at the inlet  404 . 
         [0041]    Although a few implementations have been described in detail above, other modifications are possible. For example, logic flows do not require the particular order described, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.