Abstract:
A method for regulating gas turbine engine fluid flow may include the steps of providing a flow tube having an open valve, a first bend and a second bend, flowing fluid through the flow tube, actuating a piston so that the piston moves in the axial direction, and closing the valve due to the axial movement of the piston.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The exemplary embodiments relate generally to gas turbine engines and more particularly, to valve assemblies used to regulate fluid flow for gas turbine engines. 
         [0002]    Gas turbine engines typically include a compressor, a combustor, and at least one turbine. The compressor may compress air, which may be mixed with fuel and channeled to the combustor. The mixture may then be ignited for generating hot combustion gases, and the combustion gases may be channeled to the turbine. The turbine may extract energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator. 
         [0003]    Gas turbine engines typically include an engine casing that extends circumferentially around the compressor and turbine. Within at least some known engines, a plurality of ducts and valves coupled to an exterior surface of the casing are used to channel fluid flow from one area of the engine for use within another area of the engine or for exhausting overboard. For example, such ducts and valves may form a portion of an environmental control system (ECS). 
         [0004]    At least some known valve assemblies are used to control fluid flow that is at a high temperature and/or high pressure. Such valve assemblies include a substantially cylindrical valve body that is coupled between adjacent sections of ducting. The valve body includes a valve sealing mechanism that is selectively positionable to control fluid flow through the valve. More specifically, at least some known valves include a piston/cylinder arrangement that is positioned external to the valve body and is coupled to the valve sealing mechanism to provide the motive force necessary to selectively position the valve sealing mechanism. 
         [0005]    Because the piston/cylinder arrangement is offset from the main valve body, a center of gravity of the valve assembly is typically displaced a distance from a centerline axis of the valve body. Such an eccentric center of gravity may induce bending stresses into the valve assembly, adjoining tubing, and supporting brackets during engine operation. Depending on the application, the physical size and weight of the piston/cylinder arrangement may also present difficulties during the duct routing phase of the engine design. 
         [0006]    Some known valve assemblies have attempted to overcome these issues by including a bend in the ducting leading to the valve sealing mechanism. The intent of this change was to orient the valve sealing mechanism to be perpendicular to the piston and to orient the force transfer pins to be perpendicular to the piston travel direction. However, this design requires the use of a wishbone arrangement intermediate between the piston and the valve sealing mechanism. The wishbone could cause vibration modes with resultant unacceptable linkage wear issues or part stresses. The wishbone also included slots for the connection pins, which could allow dirt and moisture to enter the actuator cavity. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    In one exemplary embodiment, a method for regulating gas turbine engine fluid flow may include the steps of providing a flow tube having an open valve, a first bend and a second bend, flowing fluid through the flow tube, actuating a piston so that the piston moves in the axial direction, and closing the valve due to the axial movement of the piston. 
         [0008]    In another exemplary embodiment, a method for regulating gas turbine engine fluid flow may include the steps of providing a flow tube having an axis and a valve, the valve having an axle that is parallel to the axis and offset from a plane parallel to the axle and passing through the axis, flowing fluid through the flow tube, actuating a piston so that the piston moves in the axial direction, rotating the axle due to the axial movement of the piston, and changing the position of the valve due to the rotation of the axle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a bottom view of an exemplary gas turbine engine. 
           [0010]      FIG. 2  is a perspective view of one exemplary embodiment of a valve assembly. 
           [0011]      FIG. 3  is an exploded perspective view of the outer part of one exemplary embodiment of a valve assembly. 
           [0012]      FIG. 4  is an exploded perspective view of the inner part of one exemplary embodiment of a valve assembly. 
           [0013]      FIG. 5  is a side view of one exemplary embodiment of a valve assembly. 
           [0014]      FIG. 6  is a cross sectional view of one exemplary embodiment of a valve assembly taken along sectional line  6 - 6  in  FIG. 5 . 
           [0015]      FIG. 7  is a flow chart illustrating one exemplary embodiment of a method for regulating fluid flow. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]      FIG. 1  is a bottom view of a gas turbine engine  100  having a plurality of ducts  102  that may include one or more valve assemblies  104 . The engine  100  includes a compressor  106 , a combustor  108 , and a turbine  110 . The engine  100  may also include an additional turbine  112  and a fan assembly  114 , shown in phantom. In one exemplary embodiment, the ducts  102  and valve assemblies  104  may form a portion of a transient bleed system  116 . More specifically, the ducts  102  and valve assemblies  104  facilitate channeling and controlling, respectively, fluid flow at a high temperature, and/or at a high pressure, from one area of the engine  100  for use in another area. For example, in one exemplary embodiment, fluid flowing through the ducts  102  and valve assemblies  104  has an operating temperature that is greater than 800° F. and/or an operating pressure of greater than 300 PSI. 
         [0017]    Referring now to  FIGS. 2-6 , the valve assembly  104  may include a first body  118  that may partially or completely surround a second body  120 . The first body  118  and second body  120  may be annular structures for housing and supporting the components of the valve assembly  104 . A flow tube  122  may be supported within the second body  120  by a support  124 . The first body  118 , second body  120  and flow tube  122  may be any diameters known in the art and may be the same diameter throughout or change at a point or points along their lengths. The support  124  may be any structure known in the art that will allow the flow tube  122  to expand and contract due to changes in temperature and pressure of the fluid flowing through the flow tube  122  and to support vibration induced loads. In one exemplary embodiment, the support  124  is a formed piece of sheet metal that may be attached to the second body  120  at a first end  126  and the flow tube  122  at a second end  127 . In one exemplary embodiment, the support  124  may be formed as two or more pieces, where one is attached at the inlet side of the second body  120  and one is attached at the outlet side of the second body  120 . 
         [0018]    The flow tube  122  may include an inlet portion  128  having an inlet  130  for receiving fluid flowing through the flow tube  122  and an outlet portion  132  having an outlet  133  for transferring fluid downstream of the flow tube  122 . A valve  134  is disposed within the flow tube  122 . The valve  134  may be any type of valve known in the art. In one exemplary embodiment, the valve  134  is a butterfly valve. The valve  134  may be selectively positionable between an open position, a closed position and anywhere therebetween. An axle  136  may connect the valve  134  to the flow tube  122  and selectively position the valve  134 . The axle  136  may pass through the valve  134  and connect to the flow tube  122  through a bearing assembly  138 . The axle  136  may be substantially perpendicular to the axis of the first body  118  and second body  120 . The axle  136  may also be offset from a plane that is parallel with the axle  136  and that passes through the center of the first body  118  and second body  120 . 
         [0019]    A piston assembly  140  may be used to actuate the axle  136  and valve  134 . A piston  142  may be disposed between the first body  118  and the second body  120 . A port  144  may be connected to the first body  118  for providing actuation fluid to the piston  142 . The port  144  may be positioned such that the pressure drop of the fluid may be minimized. A plurality of seals  146  may be disposed in proximity to the piston  142  for sealing an actuation cavity  148 . The actuation cavity  148  may fill with actuation fluid to actuate the valve  134 . The piston  142  may be connected to a piston rod  150 . A bushing  151  may be disposed around said piston rod  150 . The bushing  151  may guide and seal the piston rod  150 . A piston rod clevis  152  may be disposed on the piston rod  150  at the end opposite the piston  142 . The piston  142 , piston rod  150 , bushing  151  and piston rod clevis  152  may be arranged so as to be parallel to the axis of the first body  118  and second body  120 . A link arm  154  may be connected to the piston rod clevis  150  at one end by a pin  156  and to an axle crank arm  158  at another end by a pin  157 . The axle crank arm  158  may be connected to one end of the axle  136 . The axle crank arm  158  may be connected such that the axle  136  rotates when the axle crank arm  158  rotates. The piston assembly  140  may have a second piston rod  164  disposed 180 degrees from the piston rod  150  so as to balance the piston force around the piston  142 . The piston rod  164  may be connected to the piston  142  in an arrangement similar to that described above. A bushing  165 , a piston rod clevis  166 , a link arm  168  and an axle crank arm  170  may be associated with the piston rod  164 . The piston rods  150 ,  164  each may convert the rectilinear force of the piston  142  into rotary force at the axle  136 , causing the axle  136  to rotate, thus causing the valve  134  to open or close, depending on the movement of the piston  142 . 
         [0020]    The flow tube  122  may include a first bend  172  and a second bend  174 . The first bend  172  may allow the axle  136  to be positioned so that it is offset from a plane passing through the piston rods  150  and  164 . The second bend  174  may allow the valve  134  to be centered between the piston rods  150  and  164 . This may allow the axle crank arms  158  and  170  to be substantially aligned with the piston rods  150  and  164 . Such an arrangement may allow a direct connection between the axle  136  and piston rods  150 ,  164  without the need for a wishbone assembly. 
         [0021]    A sensor  176  may be disposed adjacent to the piston assembly  140 . The sensor  176  may be disposed such that it senses the position of the piston  142  in order to provide feedback to the engine on the position of the valve  134 . Any position sensor known in the art may be used. In one exemplary embodiment, a linear variable differential transformer (LVDT) may be used. The sensor  176  may be attached to the piston rod  150 ,  162  with an L-bracket  178 . It should be noted that any attachment arrangement may be used so long as the sensor can detect the position of the piston  142 . 
         [0022]    As shown in  FIG. 7 , during use, fluid may flow through the inlet  130  of the flow tube  122  at step  200 . The fluid may change direction within the flow tube  122  at the first bend  172  at step  202 . The fluid may change direction a second time within the flow tube  122  at the second bend  174  at step  204 . Actuation fluid may flow from the port  144  to the actuation cavity  148  at step  206 . Any actuation fluid known in the art may be used. At step  208 , the actuation fluid will cause the piston  142  to move axially towards the valve  134 . The piston rod  150 ,  164  and piston rod clevis  152 ,  166  will also move axially towards the valve  134  with the movement of the piston  142  at step  210 . The rectilinear force may further be transferred to the axle crank arm  158 ,  170  through the link arm  154 ,  168  at step  212 . The rectilinear force of the axle crank arm  158 ,  170  will be transferred to the axle  136  as rotary force, thereby causing the axle  136  and attached valve  134  to rotate at step  214 . The valve  134  may be actuated to change from open to closed, closed to open or somewhere in between. A second port  180  may provide actuation fluid to the actuation cavity  148 , causing the port  144  to act as an outlet, causing the valve  134  to close. The valve  134  may be actuated for a plurality of reasons, including, but not limited to, stall conditions, redistributing high-pressure flow to the aft part of the engine, lower inlet pressure to the combustor, engine anti-icing, wing anti-icing, controlling blade tip clearances, providing air to environmental control systems and/or auxiliary power units on the airplane or any combination thereof. The initial position may be either open or closed. Since the piston  142 , piston rod  150 , piston rod clevis  152 , link arm  154  and axle crank arm  158  are aligned axially, the force transferred to the axle and valve may be more direct and balanced, thus reducing the transient forces applied to the valve. 
         [0023]    This written description discloses exemplary embodiments, including the best mode, to enable any person skilled in the art to make and use the exemplary embodiments. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.