Abstract:
A fuel system including a fuel pump metering unit (FPMU) for delivering fuel to an engine manifold with an ecology valve for draining and storing fuel from the engine manifold. The ecology valve includes a housing having a piston dividing the housing into a first side in fluid communication with an output of the FPMU and a second side in fluid communication with the engine manifold. An assembly connected between the FPMU and engine manifold selectively creates a pressure differential across the first and second side of the housing when the FPMU delivers fuel to the engine manifold. In a run position, the piston moves to decrease a volume within the housing interior as a result of the pressure differential. In a drain position, the piston moves to increase the housing volume within the interior and thereby pull and store fuel from the engine manifold.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The subject invention is directed to an ecology system for draining fuel from the manifold of a gas turbine engine and more particularly, to an ecology system for draining and storing liquid fuel from the manifold in a self-contained manner. 
         [0003]    2. Background of the Related Art 
         [0004]    Manifold draining systems are useful in aerospace applications where gas turbine engines are used. If the fuel is allowed to remain in the engine manifold after shutdown, the fuel may collect to create a hot start or coke from heat exposure. To avoid these problems, several systems have been developed. 
         [0005]    In a traditional system, a separate tank is used to collect fuel from the manifold by actuating a solenoid valve. Other systems also send the manifold fuel back to the fuel tanks by an alternative flowpath. In either case, the fuel system is closed such that the volume pulled back out of the manifold must be absorbed or stored some where in the fuel system. Utilization of separate/external means to store the volume of manifold fuel is particularly undesirable to manage as is inclusion of alternative flowpaths and devices like the aforementioned solenoid. 
         [0006]    Examples of ecology systems for fuel systems are disclosed in: U.S. Pat. No. 5,809,771 to Wernberg issued on Sep. 22, 1998; U.S. Pat. No. 6,314,998 to Futa, Jr. et al. issued on Nov. 13, 2001; U.S. Pat. No. 6,385,962 to Futa, Jr. et al. issued on May 14, 2002; and U.S. Pat. No. 6,751,939 to Futa, Jr. et al. issued on Jun. 22, 2004, the disclosures of which are herein incorporated by reference in their entirety. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the above, it would be desirable to provide an ecology valve for a fuel system that has a simple, efficient and reliable design for draining the engine manifold and storing the drained volume of fuel. The subject technology discloses an ecology valve that has differential volume depending upon the position of a piston within the ecology valve, thus additional return lines or external storage can be eliminated. The ecology valve moves to an increased storage volume position after engine shutdown to drain the engine manifold, and restores the fuel to the nozzles at the next start by returning to a run position with reduced storage volume. The subject technology is also suitable for use as a modification of existing equipment and systems. 
         [0008]    In one embodiment, the subject technology is directed to an ecology valve for draining and storing fuel from a manifold of a gas turbine engine. The ecology valve includes a housing defining: an interior; a first port in fluid communication with a fuel pump metering unit (FPMU) for receiving fuel output from the FPMU; and a second port in fluid communication with the manifold. A piston is mounted for sliding movement within the interior between a run position and a drain position. In the run position, the interior contains a first volume of fuel. In the drain position, the interior contains a second volume of fuel, the second volume being greater than the first volume. A spring is coupled between the housing and the piston to normally bias the piston in the drain position. The subject technology may also utilize at least one sealing o-ring mounted in an opening of the housing for sealing the shaft during movement between the run and drain positions such that in the drain position, the shaft extends at least partially out of the opening so that the second volume is greater than the first volume. 
         [0009]    Another embodiment of the subject technology is a fuel system with a fuel pump metering unit (FPMU) for delivering fuel to an engine manifold. The fuel system includes an ecology valve for draining and storing fuel from the engine manifold. The ecology valve includes a housing having a piston dividing the housing into a first side in fluid communication with an output of the FPMU and a second side in fluid communication with the engine manifold. An assembly connects between the FPMU and engine manifold for selectively creating a pressure differential across the first and second side of the housing when the FPMU delivers fuel to the engine manifold. In a run position, the piston moves to decrease a volume within the interior as a result of the pressure differential, and in a drain position, the piston moves to increase the volume within the interior and thereby pull and store fuel from the engine manifold. 
         [0010]    The assembly may be a muscles valve, a flow divider, a pressurizing valve, a fixed orifice, and the like. The assembly may also be integral to the FPMU. Preferably, in the drain position, the shaft extends at least partially out of the opening and the head portion defines a passage for fuel flow between sides of the housing. The fuel system may also include a restrictor between the housing and the engine manifold. 
         [0011]    Still another embodiment of the subject technology is directed to a method for draining fuel from an engine manifold including the steps of delivering fuel to the engine manifold, coupling an ecology valve to the engine manifold, creating an increase in a volume in the ecology valve during shutdown of delivery of the fuel such that the ecology valve pulls fuel from the engine manifold, and storing the drained fuel in the increased volume. 
         [0012]    The method may also include the steps of restarting delivery of fuel to the engine manifold, and creating a decrease in the volume to redeliver the drained fuel to the engine manifold. The ecology valve includes a housing having a piston that moves between a drain position at least partially outside the housing to create the increase and a run position substantially within the housing to create the decrease. Preferably, the method includes the steps of normally biasing the piston into the drain position, creating a pressure differential across the piston when delivering fuel to the engine manifold to move the piston into the run position, and providing a passage through the piston for fuel flow. 
         [0013]    It should be appreciated that the present invention can be implemented and utilized in numerous ways, including without limitation as a process, an apparatus, a system, a device, and a method for applications now known and later developed. These and other unique features of the system disclosed herein will become more readily apparent from the following description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    So that those having ordinary skill in the art to which the subject invention appertains will more readily understand how to make and use the same, reference may be had to the following figures. 
           [0015]      FIG. 1  is a schematic cross-sectional representation of a portion of a fuel system having an ecology valve constructed in accordance with the subject technology shown in the running or fuel delivery position. 
           [0016]      FIG. 2  is a schematic cross-sectional representation of the portion of the fuel system of  FIG. 1  and shown in the shutdown or no fuel delivery position. 
           [0017]      FIG. 3  is a schematic cross-sectional representation of a portion of another fuel system having another ecology valve constructed in accordance with the subject technology shown in the prestart/drained position. 
           [0018]      FIG. 4  is a schematic cross-sectional representation of the portion of the fuel system of  FIG. 3  shown in a start position. 
           [0019]      FIG. 5  is a schematic cross-sectional representation of the portion of the fuel system of  FIG. 3  shown in the run position. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    The present disclosure overcomes many of the prior art problems associated with removing fuel from engine manifolds and the like. The advantages, and other features of the technology disclosed herein, will become more readily apparent to those having ordinary skill in the art from the following detailed description of certain preferred embodiments taken in conjunction with the drawings which set forth representative embodiments of the present invention and wherein like reference numerals identify similar structural elements. 
         [0021]    All relative descriptions herein such as left, right, up, and down are with reference to the Figures, and not meant in a limiting sense. Unless otherwise specified, the illustrated embodiments can be understood as providing exemplary features of varying detail of certain embodiments, and therefore, unless otherwise specified, features, components, modules, elements, and/or aspects of the illustrations can be otherwise substituted, combined, interconnected, sequenced, separated, interchanged, positioned, and/or rearranged without materially departing from the disclosed systems or methods. 
         [0022]    Additionally, the shapes and sizes of components are also exemplary and can be altered without materially affecting or limiting the disclosed technology. For clarity throughout the following description, arrows are shown within the flowpaths or lines of fuel systems to indicate the direction in which the fuel flows and an annotated letter “P” is shown to indicate a pressure at certain locations at various times in the fuel delivery cycle. Additionally, for clarity common items such as filters have not been included in the Figures. 
       First Embodiments 
       [0023]    Referring now to  FIGS. 1 and 2 , there are illustrated schematic cross-sectional representations of a portion of a fuel system  10  having an ecology valve  20  in accordance with the subject invention. The fuel system  10  pumps fuel from a fuel tank (not shown) to an engine manifold (not shown). Upon engine shutdown, the ecology valve  20  drains the engine manifold and stores the drained volume of fuel for subsequent redelivery upon engine start up. 
         [0024]    The fuel system  10  includes a fuel pump and metering unit (FPMU) pressure valve  12  among other components not shown to filter and control delivery of high pressure fuel. The FPMU pressure valve  12  acts as a check valve to help maintain pressure downstream thereof at pressure P 1 . The fuel flows from the FPMU pressure valve  12  to a muscles valve  30 , which creates a pressure differential. The muscles valve  30  creates a pressure differential from the input pressure at P 1  to the output pressure P 3  with pressure P 3  being lower than pressure P 1  when fuel flows to the engine. It should be appreciated by those of ordinary skill in the art that other types of devices for creating pressure differentials such as flow dividers, fixed orifices, and other valves like pressurizing valves, similarly and differently arranged would perform this same function and are, therefore, considered design choices well within the scope of the subject technology. 
         [0025]    The ecology valve  20  is connected to both sides of the muscles valve  30 . The ecology valve  20  has a housing  21  defining an interior  22  with inlets  23   a ,  23   b . Inlet  23   a  is connected to the outlet of the FPMU pressure valve  12  (i.e., pressure P 1 ) by line  14  whereas inlet  23   b  is connected to the outlet of the muscles valve  30  (i.e., pressure P 3 ). The interior  22  slidably receives a piston  24  having a shaft  25   a  terminating in a head  25   b . Two o-rings  26   a ,  26   b  seal the shaft  25   a  to maintain the fuel system  10  closed. 
         [0026]    The piston head  25   b  divides the interior  22  into two parts or sides, the left part at pressure P 2  and the right part at pressure P 3 . A spring  27  biases the piston  24  to the left but when the pressure P 2  on the left of the piston head  25   b  exceeds the pressure P 3  on the right of the piston head  25   b , the piston head  25   b  is forced against a shoulder  28  formed in the housing  21 , which is the running position as shown in  FIG. 1 . The piston head  25   b  also forms a passage  29  between the left and right sides of the interior  22  to allow fuel to flow there through. The passage  29  may include a restrictor  29   a  to limit the flow there through. A second optional restrictor  29   b  may be included adjacent the inlet  23   b  to help damp the effect of pressure changes on the piston  24 . 
         [0027]    The muscles valve  30  also includes a housing  31  defining an interior  32  with an inlet  33   a  and outlet  33   b . The inlet  33   a  is connected to the outlet of the FPMU pressure valve  12  (i.e., pressure P 1 ) and the outlet  33   b  feeds the engine manifold at pressure P 3 . The muscles valve interior  32  also slidably receives a piston  34  having a shaft  35   a  terminating in a head  35   b . The piston  34  also defines a central flowpath  36  for fuel through the muscles valve  30  when in the running position as shown in  FIG. 1 . The piston  34  has a valve portion  36   a  that can close the flowpath when in the shutdown position as shown in  FIG. 2 . 
         [0028]    The piston head  35   b  is normally biased downward by a spring  37  into the drained or shutdown position shown in  FIG. 2 . During shutdown, the spring  37  forces the piston  34  downward so that the valve portion  36   a  seals against the housing  31  stopping flow. When fuel flows in the running position of  FIG. 1 , the piston head  35  overcomes the force of the spring  37  and moves upward. Throughout the fuel system  10 , springs are sized as a function of the product of piston area and fuel pressure as would be appreciated by those of ordinary skill in the art and therefore not further described herein. 
       In Operation 
       [0029]    Referring now to  FIG. 1 , the ecology valve  20  and the muscle valve  30  are shown in a steady-state running position with the FPMU (not shown) delivering fuel to the engine manifold and, thereby, opening the muscles valve  30 . The muscles valve  30  creates a pressure differential so that pressure P 3  is less than pressure P 2 . The pressure differential is sufficient so that the spring force in the ecology valve  20  is overcome by the piston  24 , which is moved all the way to the right in a reduced volume position. 
         [0030]    Upon shutdown of fuel delivery, the check valve  12  prevents return flow to the FPMU so that the fuel system  10  shown has pressure equalize under the lack of flow (e.g., pressure P 1 =P 2 =P 3 ). Once pressure equalizes, the springs  27 ,  37  in the valves  20 ,  30 , respectively, drive the pistons  24 ,  34  to the drained position shown in  FIG. 2 . In the ecology valve  20 , the piston shaft  25   a  moves outside the housing  21 . The optional restrictor  29   b  damps the movement of the piston  24  within the ecology valve housing  21 . 
         [0031]    As the piston shaft  25   a  is no longer within the interior  22  of the ecology valve  20 , additional volume within the interior  22  is created. The volume increase pulls fuel from the engine manifold into the interior  22  to empty the engine manifold. In the event that the muscles valve  30  is closed before draining is completed, the passage  29  allows fluid transfer across the piston head  25   b . The amount of fuel drawn from the engine manifold can be specifically determined by the size and travel of the piston  24  in the ecology valve  20 . The volume of fuel pulled from the engine manifold remains in the ecology valve  20  until start up. 
         [0032]    Still referring to  FIGS. 1 and 2 , upon start up, the FPMU sends fuel through the check valve  12 . Upon reaching a certain predetermined pressure value, the muscle valve  30  opens and flow passes to the engine manifold. As noted above, when the muscle valve  30  opens, the muscle valve  30  creates a pressure differential across the ecology valve  20  (e.g., pressure P 2 &gt;P 3 ) to drive the piston  24  to the right as shown in  FIG. 1 . As the piston  24  drives right, the shaft  25   a  reenters the housing  21  to reduce the volume of the interior  22  and send the fuel volume drained from the engine manifold back into the fuel system  10  for delivery to the engine manifold. The cycling between the positions shown in  FIGS. 1 and 2  repeats as the engine starts and stops to desirably maintain the engine manifold drained during shutdown. As can be seen, the ecology valve  20  functions to both drain the engine manifold and store the drained volume of fuel within the closed system to advantageously remove the need for undesirable separate storage and/or return drain lines. 
       Alternative Embodiments 
       [0033]    Referring now to  FIG. 3 , a schematic cross-sectional representation of a portion of another fuel system  110  having an ecology valve  120  constructed in accordance with the subject technology is shown with the ecology valve  120  in the prestart/drained position. In the prestart position, the fuel system  110  is not operational in that the FPMU is not delivering fuel, the engine manifold has been drained, and the moving components are in a steady-state. As will be appreciated by those of ordinary skill in the pertinent art, the fuel system  110  utilizes similar principles to the fuel system  10  described above. Accordingly, like reference numerals preceded by the numeral “1” are used to indicate like elements. The primary difference of the fuel system  110  in comparison to the fuel system  10  is the use of a flow divider  130  instead of a muscles valve to create a pressure differential across the ecology valve  120 . 
         [0034]    The flow divider  130  includes a housing  131  having a spool  132  slidably mounted in the housing  131  for smooth movement. A spring  137  biases the spool  132 . Although not explicitly shown, the housing  131  defines an inlet and two outlets, which are represented by flow arrows in subsequent figures. One of ordinary skill in the art would be able to make and use the subject technology even though the inlet, the outlets and associated flowpaths are not explicitly shown. 
         [0035]    In the prestart position, the pressure has equalized within the ecology valve  120  and the flow divider  130  so that the spring  127  has pushed the ecology valve piston  124  to the left and the flow divider spring  137  has pushed the spool  132  upwards. With the piston  124  to the left, a portion of the shaft  125  has extended out of the housing  121  to increase the ecology valve housing volume for storage of fuel drained from the engine manifold. With the spool  132  upward, the spool  132  has a valve seal  135  against a housing seat  136  to close off flow from the FPMU. The arrows “e” also represent two flowpaths established from the engine manifold so that the fuel therein can drain into the ecology valve  120  as described below. 
         [0036]    Referring now to  FIG. 4 , a schematic cross-sectional representation of a portion of the fuel system  110  is shown in a start mode position. To enter start mode, the FPMU begins sending fuel to the engine manifold. As the pressure rises in the fuel system  110 , the spool  132  overcomes the force of spring  137  to move downward and open a primary flowpath to the engine manifold as represented by the arrows “a”. Initially, the ecology valve spring  127  provides sufficient force to maintain the piston  124  to the left (e.g., in the non-operational position) as shown. 
         [0037]    Referring now to  FIG. 5 , a schematic cross-sectional representation of the fuel system  110  is shown in the run position. As the fuel system comes up to pressure, additional fuel flow (denoted as arrows “b”) to the ecology valve  120  from the FPMU creates pressure P 2  on the left side of the piston  124  whereas the flow divider  130  creates a lower pressure P 3  on the right side of the piston  124  within the housing  121 . The pressure differential on the piston  124  overcomes the force of spring  127  and the piston  124  moves to the right. The piston shaft  125   a  moving into the interior  122  reduces the volume therein such that a specific volume of fuel (denoted as flowpath arrow “c”) will flow from the interior  122  and through the spool  132  to the engine manifold. The main delivery of the fuel to the engine manifold is by the flowpath denoted by arrows “d”. It is envisioned that during steady-state running, the only fuel delivered to the engine manifold travels along flowpath arrows “d”. 
         [0038]    Referring again to  FIG. 3 , upon shutdown, the fuel system  110  moves into the drained position shown. Similar to above, the fuel system is closed so that equalization to residual pressure occurs. With no pressure differential across the ecology valve piston  124 , the piston  124  moves left and a portion of the shaft  125   a  extends out of the housing  121  to increase the ecology valve interior volume. The volume increase creates a pull or drain on the engine manifold along the flowpaths denoted by arrows “e”. Hence again, the ecology valve  120  drains fuel from the engine manifold and stores the drained fuel. 
         [0039]    While the subject invention has been described with respect to preferred embodiments, those skilled in the art will readily appreciate that various changes and/or modifications can be made to the invention without departing from the spirit or scope of the invention as defined by the appended claims.